Silicene Catalyzed Reduction of Nitrobenzene to Aniline: a Computational Study

NASA Astrophysics Data System (ADS)

Morrissey, Christopher; He, Haiying

The reduction of nitrobenzene to aniline has a broad range of applications in the production of rubbers, dyes, agrochemicals, and pharmaceuticals. Currently, use of metal catalysts is the most popular method of performing this reaction on a large scale. These metal catalysts usually require high-temperature and/or high-pressure reaction conditions, and produce hazardous chemicals. This has led to a call for more environmentally friendly nonmetal catalysts. Recent studies suggest that silicene, the recently discovered silicon counterpart of graphene, could potentially work as a nonmetal catalyst due to its unique electronic property and strong interactions with molecules containing nitrogen and oxygen. In this computational study, we have investigated the plausibility of using silicene as a catalyst for the reduction of nitrobenzene. Possible reaction mechanisms will be discussed with a highlight of the difference between silicene and metal catalysts. . All calculations were performed in the framework of density functional theory.

Cyclic alkyl amino carbene (CAAC) ruthenium complexes as remarkably active catalysts for ethenolysis

DOE PAGES

Marx, Vanessa M.; Sullivan, Alexandra H.; Melaimi, Mohand; ...

2014-12-17

In this paper, an expanded family of ruthenium-based metathesis catalysts bearing cyclic alkyl amino carbene (CAAC) ligands was prepared. These catalysts exhibited exceptional activity in the ethenolysis of the seed-oil derivative methyl oleate. In many cases, catalyst turnover numbers (TONs) of more than 100,000 were achieved, at a catalyst loading of only 3 ppm. Remarkably, the most active catalyst system was able to achieve a TON of 340 000, at a catalyst loading of only 1 ppm. Finally, this is the first time a series of metathesis catalysts has exhibited such high performance in cross-metathesis reactions employing ethylene gas, withmore » activities sufficient to render ethenolysis applicable to the industrial-scale production of linear α-olefins (LAOs) and other terminal-olefin products.« less

Co-Production of Electricity and Hydrogen Using a Novel Iron-based Catalyst

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hilaly, Ahmad; Georgas, Adam; Leboreiro, Jose

2011-09-30

The primary objective of this project was to develop a hydrogen production technology for gasification applications based on a circulating fluid-bed reactor and an attrition resistant iron catalyst. The work towards achieving this objective consisted of three key activities: Development of an iron-based catalyst suitable for a circulating fluid-bed reactor; Design, construction, and operation of a bench-scale circulating fluid-bed reactor system for hydrogen production; Techno-economic analysis of the steam-iron and the pressure swing adsorption hydrogen production processes. This report describes the work completed in each of these activities during this project. The catalyst development and testing program prepared and iron-basedmore » catalysts using different support and promoters to identify catalysts that had sufficient activity for cyclic reduction with syngas and steam oxidation and attrition resistance to enable use in a circulating fluid-bed reactor system. The best performing catalyst from this catalyst development program was produced by a commercial catalyst toll manufacturer to support the bench-scale testing activities. The reactor testing systems used during material development evaluated catalysts in a single fluid-bed reactor by cycling between reduction with syngas and oxidation with steam. The prototype SIP reactor system (PSRS) consisted of two circulating fluid-bed reactors with the iron catalyst being transferred between the two reactors. This design enabled demonstration of the technical feasibility of the combination of the circulating fluid-bed reactor system and the iron-based catalyst for commercial hydrogen production. The specific activities associated with this bench-scale circulating fluid-bed reactor systems that were completed in this project included design, construction, commissioning, and operation. The experimental portion of this project focused on technical demonstration of the performance of an iron-based catalyst and a circulating fluid-bed reactor system for hydrogen production. Although a technology can be technically feasible, successful commercial deployment also requires that a technology offer an economic advantage over existing commercial technologies. To effective estimate the economics of this steam-iron process, a techno-economic analysis of this steam iron process and a commercial pressure swing adsorption process were completed. The results from this analysis described in this report show the economic potential of the steam iron process for integration with a gasification plant for coproduction of hydrogen and electricity.« less

Durability of template-free Fe-N-C foams for electrochemical oxygen reduction in alkaline solution

NASA Astrophysics Data System (ADS)

Mufundirwa, Albert; Harrington, George F.; Smid, Břetislav; Cunning, Benjamin V.; Sasaki, Kazunari; Lyth, Stephen M.

2018-01-01

Due to the high cost and limited availability of platinum, the development of non-platinum-group metals (non-PGM) catalysts is of paramount importance. A promising alternative to Pt are Fe-N-C-based materials. Here we present the synthesis, characterization and electrochemistry of a template-free nitrogen-doped carbon foam, impregnated with iron. This low-cost and gram-scale method results in materials with micron-scale pore size and large surface area (1600 m2g-1). When applied as an oxygen reduction reaction (ORR) electrocatalyst in alkaline solution, the Fe-N-C foams display extremely high initial activity, slightly out-performing commercially available non-PGM catalysts (NCP-2000, Pajarito Powder). The load-cycle durability in alkaline solution is investigated, and the performance steadily degrades over 60,000 potential cycles, whilst the commercial catalyst is remarkably stable. The post-operation catalyst microstructure is elucidated by transmission electron microscopy (TEM), to provide insight into the degradation processes. The resulting images suggest that potential cycling leads to leaching of atomically dispersed Fe-N2/4 sites in all the catalysts, whereas encapsulated iron nanoparticles are protected.

Critical advancements in achieving high power and stable nonprecious metal catalyst–based MEAs for real-world proton exchange membrane fuel cell applications

PubMed Central

Zhou, Yingjie; Bai, Kyoung

2018-01-01

Despite great progress in the development of nonprecious metal catalysts (NPMCs) over the past several decades, the performance and stability of these promising catalysts have not yet achieved commercial readiness for proton exchange membrane fuel cells (PEMFCs). Through rational design of the cathode catalyst layer (CCL), we demonstrate the highest reported performance for an NPMC-based membrane electrode assembly (MEA), achieving a peak power of 570 mW/cm2 under air. This record performance is achieved using a precommercial catalyst for which nearly all pores are <3 nm in diameter, challenging previous beliefs regarding the need for larger catalyst pores to achieve high current densities. This advance is achieved at industrially relevant scales (50 cm2 MEA) using a precommercial NPMC. In situ electrochemical analysis of the CCLs is also used to help gain insight into the degradation mechanism observed during galvanostatic testing. Overall, the performance of this NPMC-based MEA has achieved commercial readiness and will be introduced into an NPMC-based product for portable power applications. PMID:29582018

Final Project Report: Development of Micro-Structural Mitigation Strategies for PEM Fuel Cells: Morphological Simulations and Experimental Approaches

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wessel, Silvia; Harvey, David

2013-06-28

The durability of PEM fuel cells is a primary requirement for large scale commercialization of these power systems in transportation and stationary market applications that target operational lifetimes of 5,000 hours and 40,000 hours by 2015, respectively. Key degradation modes contributing to fuel cell lifetime limitations have been largely associated with the platinum-based cathode catalyst layer. Furthermore, as fuel cells are driven to low cost materials and lower catalyst loadings in order to meet the cost targets for commercialization, the catalyst durability has become even more important. While over the past few years significant progress has been made in identifyingmore » the underlying causes of fuel cell degradation and key parameters that greatly influence the degradation rates, many gaps with respect to knowledge of the driving mechanisms still exist; in particular, the acceleration of the mechanisms due to different structural compositions and under different fuel cell conditions remains an area not well understood. The focus of this project was to address catalyst durability by using a dual path approach that coupled an extensive range of experimental analysis and testing with a multi-scale modeling approach. With this, the major technical areas/issues of catalyst and catalyst layer performance and durability that were addressed are: 1. Catalyst and catalyst layer degradation mechanisms (Pt dissolution, agglomeration, Pt loss, e.g. Pt in the membrane, carbon oxidation and/or corrosion). a. Driving force for the different degradation mechanisms. b. Relationships between MEA performance, catalyst and catalyst layer degradation and operational conditions, catalyst layer composition, and structure. 2. Materials properties a. Changes in catalyst, catalyst layer, and MEA materials properties due to degradation. 3. Catalyst performance a. Relationships between catalyst structural changes and performance. b. Stability of the three-phase boundary and its effect on performance/catalyst degradation. The key accomplishments of this project are: • The development of a molecular-dynamics based description of the carbon supported-Pt and ionomer system • The development of a composition-based, 1D-statistical Unit Cell Performance model • A modified and improved multi-pathway ORR model • An extension of the existing micro-structural catalyst model to transient operation • The coupling of a Pt Dissolution model to the modified ORR pathway model • The Development A Semi-empirical carbon corrosion model • The integration and release of an open-source forward predictive MEA performance and degradation model • Completion of correlations of BOT (beginning of test) and EOT (end of test) performance loss breakdown with cathode catalyst layer composition, morphology, material properties, and operational conditions • Catalyst layer durability windows and design curves • A design flow path of interactions from materials properties and catalyst layer effective properties to performance loss breakdown for virgin and degraded catalyst layers In order to ensure the best possible user experience we will perform a staged release of the software leading up to the webinar scheduled in October 2013. The release schedule will be as follows (please note that the manual will be released with the beta release as direct support is provided in Stage 1): • Stage 0 - Internal Ballard Release o Cross check of compilation and installation to ensure machine independence o Implement code on portable virtual machine to allow for non-UNIX use (pending) • Stage 1 - Alpha Release o The model code will be made available via a GIT, sourceforge, or other repository (under discussion at Ballard) for download and installation by a small pre-selected group of users o Users will be given three weeks to install, apply, and evaluate features of the code, providing feedback on issues or software bugs that require correction prior to beta release • Stage 2 - Beta Release o The model code repository is opened to the general public on a beta release concept, with a mechanism for bug tracking and feedback from a large user group o Code will be tracked and patched for any discovered bugs or relevant feedback from the user community, upon the completion of three months without a major bug submission the code will be moved to a full version release • Stage 3 - Full Version Release o Code is version to revision 1.0 and that version is frozen in development/patching« less

Nanocarbon/oxide composite catalysts for bifunctional oxygen reduction and evolution in reversible alkaline fuel cells: A mini review

NASA Astrophysics Data System (ADS)

Chen, Mengjie; Wang, Lei; Yang, Haipeng; Zhao, Shuai; Xu, Hui; Wu, Gang

2018-01-01

A reversible fuel cell (RFC), which integrates a fuel cell with an electrolyzer, is similar to a rechargeable battery. This technology lies on high-performance bifunctional catalysts for the oxygen reduction reaction (ORR) in the fuel cell mode and the oxygen evolution reaction (OER) in the electrolyzer mode. Current catalysts are platinum group metals (PGM) such as Pt and Ir, which are expensive and scarce. Therefore, it is highly desirable to develop PGM-free catalysts for large-scale application of RFCs. In this mini review, we discussed the most promising nanocarbon/oxide composite catalysts for ORR/OER bifunctional catalysis in alkaline media, which is mainly based on our recent progress. Starting with the effectiveness of selected oxides and nanocarbons in terms of their activity and stability, we outlined synthetic methods and the resulting structures and morphologies of catalysts to provide a correlation between synthesis, structure, and property. A special emphasis is put on understanding of the possible synergistic effect between oxide and nanocarbon for enhanced performance. Finally, a few nanocomposite catalysts are discussed as typical examples to elucidate the rules of designing highly active and durable bifunctional catalysts for RFC applications.

Flowthrough Reductive Catalytic Fractionation of Biomass

DOE Office of Scientific and Technical Information (OSTI.GOV)

Anderson, Eric M.; Stone, Michael L.; Katahira, Rui

2017-11-01

Reductive catalytic fractionation (RCF) has emerged as a leading biomass fractionation and lignin valorization strategy. Here, flowthrough reactors were used to investigate RCF of poplar. Most RCF studies to date have been conducted in batch, but a flow-based process enables the acquisition of intrinsic kinetic and mechanistic data essential to accelerate the design, optimization, and scale-up of RCF processes. Time-resolved product distributions and yields obtained from experiments with different catalyst loadings were used to identify and deconvolute events during solvolysis and hydrogenolysis. Multi-bed RCF experiments provided unique insights into catalyst deactivation, showing that leaching, sintering, and surface poisoning are causesmore » for decreased catalyst performance. The onset of catalyst deactivation resulted in higher concentrations of unsaturated lignin intermediates and increased occurrence of repolymerization reactions, producing high-molecular-weight species. Overall, this study demonstrates the concept of flowthrough RCF, which will be vital for realistic scale-up of this promising approach.« less

High-Performance Core–Shell Catalyst with Nitride Nanoparticles as a Core: Well-Defined Titanium Copper Nitride Coated with an Atomic Pt Layer for the Oxygen Reduction Reaction

DOE PAGES

Tian, Xinlong; Tang, Haibo; Luo, Junming; ...

2017-04-25

A class of core–shell structured low-platinum catalysts with well-dispersed inexpensive titanium copper nitride nanoparticles as cores and atomic platinum layers as shells exhibiting high activity and stability for the oxygen reduction reaction is successfully developed. In using nitrided carbon nanotubes (NCNTs) as the support greatly improved the morphology and dispersion of the nitride nanoparticles, resulting in significant enhancement of the performance of the catalyst. The optimized catalyst, Ti 0.9Cu 0.1N@Pt/NCNTs, has a Pt mass activity 5 times higher than that of commercial Pt/C, comparable to that of core–shell catalysts with precious metal nanoparticles as the core, and much higher thanmore » that the latter if we take into account the mass activity of all platinum group metals. Furthermore, only a minimal loss of activity can be observed after 10000 potential cycles, demonstrating the catalyst’s high stability. After durability testing, atomic-scale elemental mapping confirmed that the core–shell structure of the catalyst remained intact. This approach may open a pathway for the design and preparation of high-performance inexpensive core–shell catalysts for a wide range of applications in energy conversion processes.« less

High-Performance Core–Shell Catalyst with Nitride Nanoparticles as a Core: Well-Defined Titanium Copper Nitride Coated with an Atomic Pt Layer for the Oxygen Reduction Reaction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tian, Xinlong; Tang, Haibo; Luo, Junming

A class of core–shell structured low-platinum catalysts with well-dispersed inexpensive titanium copper nitride nanoparticles as cores and atomic platinum layers as shells exhibiting high activity and stability for the oxygen reduction reaction is successfully developed. In using nitrided carbon nanotubes (NCNTs) as the support greatly improved the morphology and dispersion of the nitride nanoparticles, resulting in significant enhancement of the performance of the catalyst. The optimized catalyst, Ti 0.9Cu 0.1N@Pt/NCNTs, has a Pt mass activity 5 times higher than that of commercial Pt/C, comparable to that of core–shell catalysts with precious metal nanoparticles as the core, and much higher thanmore » that the latter if we take into account the mass activity of all platinum group metals. Furthermore, only a minimal loss of activity can be observed after 10000 potential cycles, demonstrating the catalyst’s high stability. After durability testing, atomic-scale elemental mapping confirmed that the core–shell structure of the catalyst remained intact. This approach may open a pathway for the design and preparation of high-performance inexpensive core–shell catalysts for a wide range of applications in energy conversion processes.« less

Bench-Scale Monolith Autothermal Reformer Catalyst Screening Evaluations in a Micro-Reactor With Jet-A Fuel

NASA Technical Reports Server (NTRS)

Tomsik, Thomas M.; Yen, Judy C.H.; Budge, John R.

2006-01-01

Solid oxide fuel cell systems used in the aerospace or commercial aviation environment require a compact, light-weight and highly durable catalytic fuel processor. The fuel processing method considered here is an autothermal reforming (ATR) step. The ATR converts Jet-A fuel by a reaction with steam and air forming hydrogen (H2) and carbon monoxide (CO) to be used for production of electrical power in the fuel cell. This paper addresses the first phase of an experimental catalyst screening study, looking at the relative effectiveness of several monolith catalyst types when operating with untreated Jet-A fuel. Six monolith catalyst materials were selected for preliminary evaluation and experimental bench-scale screening in a small 0.05 kWe micro-reactor test apparatus. These tests were conducted to assess relative catalyst performance under atmospheric pressure ATR conditions and processing Jet-A fuel at a steam-to-carbon ratio of 3.5, a value higher than anticipated to be run in an optimized system. The average reformer efficiencies for the six catalysts tested ranged from 75 to 83 percent at a constant gas-hourly space velocity of 12,000 hr 1. The corresponding hydrocarbon conversion efficiency varied from 86 to 95 percent during experiments run at reaction temperatures between 750 to 830 C. Based on the results of the short-duration 100 hr tests reported herein, two of the highest performing catalysts were selected for further evaluation in a follow-on 1000 hr life durability study in Phase II.

Alternative Fuel Research in Fischer-Tropsch Synthesis

NASA Technical Reports Server (NTRS)

Surgenor, Angela D.; Klettlinger, Jennifer L.; Yen, Chia H.; Nakley, Leah M.

2011-01-01

NASA Glenn Research Center has recently constructed an Alternative Fuels Laboratory which is solely being used to perform Fischer-Tropsch (F-T) reactor studies, novel catalyst development and thermal stability experiments. Facility systems have demonstrated reliability and consistency for continuous and safe operations in Fischer-Tropsch synthesis. The purpose of this test facility is to conduct bench scale Fischer-Tropsch (F-T) catalyst screening experiments while focusing on reducing energy inputs, reducing CO2 emissions and increasing product yields within the F-T process. Fischer-Tropsch synthesis is considered a gas to liquid process which reacts syn-gas (a gaseous mixture of hydrogen and carbon monoxide), over the surface of a catalyst material which is then converted into liquids of various hydrocarbon chain length and product distributions1. These hydrocarbons can then be further processed into higher quality liquid fuels such as gasoline and diesel. The experiments performed in this laboratory will enable the investigation of F-T reaction kinetics to focus on newly formulated catalysts, improved process conditions and enhanced catalyst activation methods. Currently the facility has the capability of performing three simultaneous reactor screening tests, along with a fourth fixed-bed reactor used solely for cobalt catalyst activation.

Characterization of three-way automotive catalysts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kenik, E.A.; More, K.L.; LaBarge, W.

1997-04-01

The CRADA between Delphi Automotive Systems (Delphi; formerly General Motors - AC Delco, Systems) and Lockheed Martin Energy Research (LMER) on automotive catalysts was completed at the end of FY96, after a ten month, no-cost extension. The CRADA was aimed at improved performance and lifetime of noble metal based three-way-catalysts (TWC), which are the primary catalytic system for automotive emission control systems. While these TWC can meet the currently required emission standards, higher than optimum noble metal loadings are often required to meet lifetime requirements. In addition, more stringent emission standards will be imposed in the near future, demanding improvedmore » performance and service life from these catalysts. Understanding the changes of TWC conversion efficiency with ageing is a critical need in improving these catalysts. Initially in a fresh catalyst, the active material is often distributed on a very fine scale, approaching single atoms or small atomic clusters. As such, a wide range of analytical techniques have been employed to provide high spatial resolution characterization of the evolving state of the catalytic material.« less

Liquid-Phase Catalytic Transfer Hydrogenation of Furfural over Homogeneous Lewis Acid-Ru/C Catalysts.

PubMed

Panagiotopoulou, Paraskevi; Martin, Nickolas; Vlachos, Dionisios G

2015-06-22

The catalytic performance of homogeneous Lewis acid catalysts and their interaction with Ru/C catalyst are studied in the catalytic transfer hydrogenation of furfural by using 2-propanol as a solvent and hydrogen donor. We find that Lewis acid catalysts hydrogenate the furfural to furfuryl alcohol, which is then etherified with 2-propanol. The catalytic activity is correlated with an empirical scale of Lewis acid strength and exhibits a volcano behavior. Lanthanides are the most active, with DyCl3 giving complete furfural conversion and a 97 % yield of furfuryl alcohol at 180 °C after 3 h. The combination of Lewis acid and Ru/C catalysts results in synergy for the stronger Lewis acid catalysts, with a significant increase in the furfural conversion and methyl furan yield. Optimum results are obtained by using Ru/C combined with VCl3 , AlCl3 , SnCl4 , YbCl3 , and RuCl3 . Our results indicate that the combination of Lewis acid/metal catalysts is a general strategy for performing tandem reactions in the upgrade of furans. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Full Scale Alternative Catalyst Testing for Bosch Reactor Optimization

NASA Technical Reports Server (NTRS)

Barton, Katherine; Abney, Morgan B.

2011-01-01

Current air revitalization technology onboard the International Space Station (ISS) cannot provide complete closure of the oxygen and hydrogen loops. This makes re-supply necessary, which is possible for missions in low Earth orbit (LEO) like the ISS, but unviable for long term space missions outside LEO. In comparison, Bosch technology reduces carbon dioxide with hydrogen, traditionally over a steel wool catalyst, to create water and solid carbon. The Bosch product water can then be fed to the oxygen generation assembly to produce oxygen for crew members and hydrogen necessary to reduce more carbon dioxide. Bosch technology can achieve complete oxygen loop closure, but has many undesirable factors that result in a high energy, mass, and volume system. Finding a different catalyst with an equal reaction rate at lower temperatures with less catalyst mass and longer lifespan would make a Bosch flight system more feasible. Developmental testing of alternative catalysts for the Bosch has been performed using the Horizontal Bosch Test Stand. Nickel foam, nickel shavings, and cobalt shavings were tested at 500 C and compared to the original catalyst, steel wool. This paper presents data and analysis on the performance of each catalyst tested at comparable temperatures and recycle flow rates.

In-situ upgrading of biomass pyrolysis vapors: catalyst screening on a fixed bed reactor.

PubMed

Stefanidis, S D; Kalogiannis, K G; Iliopoulou, E F; Lappas, A A; Pilavachi, P A

2011-09-01

In-situ catalytic upgrading of biomass fast pyrolysis vapors was performed in a fixed bed bench-scale reactor at 500°C, for catalyst screening purposes. The catalytic materials tested include a commercial equilibrium FCC catalyst (E-cat), various commercial ZSM-5 formulations, magnesium oxide and alumina materials with varying specific surface areas, nickel monoxide, zirconia/titania, tetragonal zirconia, titania and silica alumina. The bio-oil was characterized measuring its water content, the carbon-hydrogen-oxygen (by difference) content and the chemical composition of its organic fraction. Each catalytic material displayed different catalytic effects. High surface area alumina catalysts displayed the highest selectivity towards hydrocarbons, yielding however low organic liquid products. Zirconia/titania exhibited good selectivity towards desired compounds, yielding higher organic liquid product than the alumina catalysts. The ZSM-5 formulation with the highest surface area displayed the most balanced performance having a moderate selectivity towards hydrocarbons, reducing undesirable compounds and producing organic liquid products at acceptable yields. Copyright © 2011 Elsevier Ltd. All rights reserved.

In-Situ through-Plane Measurements of Ionic Potential Distributions in Non-Precious Metal Catalyst Electrode for PEFC

DOE PAGES

Komini Babu, S.; Chung, H. T.; Zelenay, P.; ...

2015-09-14

This manuscript presents micro-scale experimental diagnostics and nano-scale resolution X-ray imaging applied to the study of proton conduction in non-precious metal catalyst (NPMC) fuel cell cathodes. NPMC’s have the potential to reduce the cost of the fuel cell for multiple applications. But, NPMC electrodes are inherently thick compared to the convention Pt/C electrode due to the lower volumetric activity. Thus, the electric potential drop through the Nafion across the electrode thickness can yield significant performance loss. Ionomer distributions in the NPMC electrodes with different ionomer loading are extracted from morphological data using nanoscale X-ray computed tomography (nano-XCT) imaging of themore » cathode. Microstructured electrode scaffold (MES) diagnostics are used to measure the electrolyte potential at discrete points across the thickness of the catalyst layer. When using that apparatus, the electrolyte potential drop, the through-thickness reaction distribution, and the proton conductivity are measured and correlated with the corresponding Nafion morphology and cell performance.« less

Development of a Stochastically-driven, Forward Predictive Performance Model for PEMFCs

NASA Astrophysics Data System (ADS)

Harvey, David Benjamin Paul

A one-dimensional multi-scale coupled, transient, and mechanistic performance model for a PEMFC membrane electrode assembly has been developed. The model explicitly includes each of the 5 layers within a membrane electrode assembly and solves for the transport of charge, heat, mass, species, dissolved water, and liquid water. Key features of the model include the use of a multi-step implementation of the HOR reaction on the anode, agglomerate catalyst sub-models for both the anode and cathode catalyst layers, a unique approach that links the composition of the catalyst layer to key properties within the agglomerate model and the implementation of a stochastic input-based approach for component material properties. The model employs a new methodology for validation using statistically varying input parameters and statistically-based experimental performance data; this model represents the first stochastic input driven unit cell performance model. The stochastic input driven performance model was used to identify optimal ionomer content within the cathode catalyst layer, demonstrate the role of material variation in potential low performing MEA materials, provide explanation for the performance of low-Pt loaded MEAs, and investigate the validity of transient-sweep experimental diagnostic methods.

Technology development for iron Fischer-Tropsch catalysts. Technical progress report No. 8, July 1, 1992--September 30, 1992

DOE Office of Scientific and Technical Information (OSTI.GOV)

Frame, R.R.; Gala, H.B.

1992-12-31

The objectives of this contract are to develop a technology for the production of active and stable iron Fischer-Tropsch catalysts for use in slurry-phase synthesis reactors and to develop a scaleup procedure for large-scale synthesis of such catalysts for process development and long-term testing in slurry bubble-column reactors. With a feed containing hydrogen and carbon monoxide in the molar ratio of 0.5 to 1.0 to the slurry bubble-column reactor, the catalyst performance target is 88% CO + H{sub 2} conversion at a minimum space velocity of 2.4 NL/hr/gFe. The desired sum of methane and ethane selectivities is no more thanmore » 4%, and the conversion loss per week is not to exceed 1%. Contract Tasks are as follows: 1.0--Catalyst development, 1.1--Technology assessment, 1.2--Precipitated catalyst preparation method development, 1.3--Novel catalyst preparation methods investigation, 1.4--Catalyst pretreatment, 1.5--Catalyst characterization, 2.0--Catalyst testing, 3.0--Catalyst aging studies, and 4.0--Preliminary design and cost estimate of a catalyst synthesis facility. This paper reports progress made on Task 1.« less

Platinum Nanoparticle Decorated SiO2 Microfibers as Catalysts for Micro Unmanned Underwater Vehicle Propulsion.

PubMed

Chen, Bolin; Garland, Nathaniel T; Geder, Jason; Pruessner, Marius; Mootz, Eric; Cargill, Allison; Leners, Anne; Vokshi, Granit; Davis, Jacob; Burns, Wyatt; Daniele, Michael A; Kogot, Josh; Medintz, Igor L; Claussen, Jonathan C

2016-11-16

Micro unmanned underwater vehicles (UUVs) need to house propulsion mechanisms that are small in size but sufficiently powerful to deliver on-demand acceleration for tight radius turns, burst-driven docking maneuvers, and low-speed course corrections. Recently, small-scale hydrogen peroxide (H 2 O 2 ) propulsion mechanisms have shown great promise in delivering pulsatile thrust for such acceleration needs. However, the need for robust, high surface area nanocatalysts that can be manufactured on a large scale for integration into micro UUV reaction chambers is still needed. In this report, a thermal/electrical insulator, silicon oxide (SiO 2 ) microfibers, is used as a support for platinum nanoparticle (PtNP) catalysts. The mercapto-silanization of the SiO 2 microfibers enables strong covalent attachment with PtNPs, and the resultant PtNP-SiO 2 fibers act as a robust, high surface area catalyst for H 2 O 2 decomposition. The PtNP-SiO 2 catalysts are fitted inside a micro UUV reaction chamber for vehicular propulsion; the catalysts can propel a micro UUV for 5.9 m at a velocity of 1.18 m/s with 50 mL of 50% (w/w) H 2 O 2 . The concomitance of facile fabrication, economic and scalable processing, and high performance-including a reduction in H 2 O 2 decomposition activation energy of 40-50% over conventional material catalysts-paves the way for using these nanostructured microfibers in modern, small-scale underwater vehicle propulsion systems.

Performance enhancement of iron-chromium redox flow batteries by employing interdigitated flow fields

NASA Astrophysics Data System (ADS)

Zeng, Y. K.; Zhou, X. L.; Zeng, L.; Yan, X. H.; Zhao, T. S.

2016-09-01

The catalyst for the negative electrode of iron-chromium redox flow batteries (ICRFBs) is commonly prepared by adding a small amount of Bi3+ ions in the electrolyte and synchronously electrodepositing metallic particles onto the electrode surface at the beginning of charge process. Achieving a uniform catalyst distribution in the porous electrode, which is closely related to the flow field design, is critically important to improve the ICRFB performance. In this work, the effects of flow field designs on catalyst electrodeposition and battery performance are investigated. It is found that compared to the serpentine flow field (SFF) design, the interdigitated flow field (IFF) forces the electrolyte through the porous electrode between the neighboring channels and enhances species transport during the processes of both the catalyst electrodeposition and iron/chromium redox reactions, thus enabling a more uniform catalyst distribution and higher mass transport limitation. It is further demonstrated that the energy efficiency of the ICRFB with the IFF reaches 80.7% at a high current density (320 mA cm-2), which is 8.2% higher than that of the ICRFB with the SFF. With such a high performance and intrinsically low-cost active materials, the ICRFB with the IFF offers a great promise for large-scale energy storage.

Modeling Hierarchical Non-Precious Metal Catalyst Cathodes for PEFCs Using Multi-Scale X-ray CT Imaging

DOE PAGES

Komini Babu, S.; Chung, H. T.; Wu, G.; ...

2014-08-18

This paper reports the development of a model for simulating polymer electrolyte fuel cells (PEFCs) with non-precious metal catalyst (NPMC) cathodes. NPMCs present an opportunity to dramatically reduce the cost of PEFC electrodes by removing the costly Pt catalyst. To address the significant transport losses in thick NPMC cathodes (ca. >60 µm), we developed a hierarchical electrode model that resolves the unique structure of the NPMCs we studied. A unique feature of the approach is the integration of the model with morphology data extracted from nano-scale resolution X-ray computed tomography (nano-CT) imaging of the electrodes. A notable finding is themore » impact of the liquid water accumulation in the electrode and the significant performance improvement possible if electrode flooding is mitigated.« less

Dual redox catalysts for oxygen reduction and evolution reactions: towards a redox flow Li-O2 battery.

PubMed

Zhu, Yun Guang; Jia, Chuankun; Yang, Jing; Pan, Feng; Huang, Qizhao; Wang, Qing

2015-06-11

A redox flow lithium-oxygen battery (RFLOB) by using soluble redox catalysts with good performance was demonstrated for large-scale energy storage. The new device enables the reversible formation and decomposition of Li2O2 via redox targeting reactions in a gas diffusion tank, spatially separated from the electrode, which obviates the passivation and pore clogging of the cathode.

Nano-structured manganese oxide as a cathodic catalyst for enhanced oxygen reduction in a microbial fuel cell fed with a synthetic wastewater.

PubMed

Liu, Xian-Wei; Sun, Xue-Fei; Huang, Yu-Xi; Sheng, Guo-Ping; Zhou, Kang; Zeng, Raymond J; Dong, Fang; Wang, Shu-Guang; Xu, An-Wu; Tong, Zhong-Hua; Yu, Han-Qing

2010-10-01

Microbial fuel cells (MFCs) provide new opportunities for the simultaneous wastewater treatment and electricity generation. Enhanced oxygen reduction capacity of cost-effective metal-based catalysts in an air cathode is essential for the scale-up and commercialization of MFCs in the field of wastewater treatment. We demonstrated that a nano-structured MnO(x) material, prepared by an electrochemically deposition method, could be an effective catalyst for oxygen reduction in an MFC to generate electricity with the maximum power density of 772.8 mW/m(3) and remove organics when the MFC was fed with an acetate-laden synthetic wastewater. The nano-structured MnO(x) with the controllable size and morphology could be readily obtained with the electrochemical deposition method. Both morphology and manganese oxidation state of the nano-scale catalyst were largely dependent on the electrochemical preparation process, and they governed its catalytic activity and the cathodic oxygen reduction performance of the MFC accordingly. Furthermore, cyclic voltammetry (CV) performed on each nano-structured material suggests that the MnO(x) nanorods had an electrochemical activity towards oxygen reduction reaction via a four-electron pathway in a neutral pH solution. This work provides useful information on the facile preparation of cost-effective cathodic catalysts in a controllable way for the single-chamber air-cathode MFC for wastewater treatment. Copyright © 2010 Elsevier Ltd. All rights reserved.

Technology development for iron Fischer-Tropsch catalysts

DOE Office of Scientific and Technical Information (OSTI.GOV)

O`Brien, R.J.; Raje, A.; Keogh, R.A.

1995-12-31

The objective of this research project is to develop the technology for the production of physically robust iron-based Fischer-Tropsch catalysts that have suitable activity, selectivity and stability to be used in the slurry phase synthesis reactor development. The catalysts that are developed shall be suitable for testing in the Advanced Fuels Development Facility at LaPorte, Texas, to produce either low-or high-alpha product distributions. Previous work by the offeror has produced a catalyst formulation that is 1.5 times as active as the {open_quotes}standard-catalyst{close_quotes} developed by German workers for slurry phase synthesis. In parallel, work will be conducted to design a high-alphamore » iron catalyst this is suitable for slurry phase synthesis. Studies will be conducted to define the chemical phases present at various stages of the pretreatment and synthesis stages and to define the course of these changes. The oxidation/reduction cycles that are anticipated to occur in large, commercial reactors will be studied at the laboratory scale. Catalyst performance will be determined for catalysts synthesized in this program for activity, selectivity and aging characteristics.« less

Advanced gasifier and water gas shift technologies for low cost coal conversion to high hydrogen syngas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kramer, Andrew Kramer

The Gas Technology Institute (GTI) and team members RTI International (RTI), Coanda Research and Development, and Nexant, are developing and maturing a portfolio of technologies to meet the United States Department of Energy (DOE) goals for lowering the cost of producing high hydrogen syngas from coal for use in carbon capture power and coal-to-liquids/chemicals. This project matured an advanced pilot-scale gasifier, with scalable and commercially traceable components, to readiness for use in a first-of-a-kind commercially-relevant demonstration plant on the scale of 500-1,000 tons per day (TPD). This was accomplished through cold flow simulation of the gasifier quench zone transition regionmore » at Coanda and through an extensive hotfire gasifier test program on highly reactive coal and high ash/high ash fusion temperature coals at GTI. RTI matured an advanced water gas shift process and catalyst to readiness for testing at pilot plant scale through catalyst development and testing, and development of a preliminary design basis for a pilot scale reactor demonstrating the catalyst. A techno-economic analysis was performed by Nexant to assess the potential benefits of the gasifier and catalyst technologies in the context of power production and methanol production. This analysis showed an 18%reduction in cost of power and a 19%reduction in cost of methanol relative to DOE reference baseline cases.« less

Novel chemistries and materials for grid-scale energy storage: Quinones and halogen catalysis

NASA Astrophysics Data System (ADS)

Huskinson, Brian Thomas

In this work I describe various approaches to electrochemical energy storage at the grid-scale. Chapter 1 provides an introduction to energy storage and an overview of the history and development of flow batteries. Chapter 2 describes work on the hydrogen-chlorine regenerative fuel cell, detailing its development and the record-breaking performance of the device. Chapter 3 dives into catalyst materials for such a fuel cell, focusing on ruthenium oxide based alloys to be used as chlorine redox catalysts. Chapter 4 introduces and details the development of a performance model for a hydrogen-bromine cell. Chapter 5 delves into the more recent work I have done, switching to applications of quinone chemistries in flow batteries. It focuses on the pairing of one particular quinone (2,7-anthraquinone disulfonic acid) with bromine, and highlights the promising performance characteristics of a device based on this type of chemistry.

Unraveling micro- and nanoscale degradation processes during operation of high-temperature polymer-electrolyte-membrane fuel cells

NASA Astrophysics Data System (ADS)

Hengge, K.; Heinzl, C.; Perchthaler, M.; Varley, D.; Lochner, T.; Scheu, C.

2017-10-01

The work in hand presents an electron microscopy based in-depth study of micro- and nanoscale degradation processes that take place during the operation of high-temperature polymer-electrolyte-membrane fuel cells (HT-PEMFCs). Carbon supported Pt particles were used as cathodic catalyst material and the bimetallic, carbon supported Pt/Ru system was applied as anode. As membrane, cross-linked polybenzimidazole was used. Scanning electron microscopy analysis of cross-sections of as-prepared and long-term operated membrane-electrode-assemblies revealed insight into micrometer scale degradation processes: operation-caused catalyst redistribution and thinning of the membrane and electrodes. Transmission electron microscopy investigations were performed to unravel the nanometer scale phenomena: a band of Pt and Pt/Ru nanoparticles was detected in the membrane adjacent to the cathode catalyst layer. Quantification of the elemental composition of several individual nanoparticles and the overall band area revealed that they stem from both anode and cathode catalyst layers. The results presented do not demonstrate any catastrophic failure but rather intermediate states during fuel cell operation and indications to proceed with targeted HT-PEMFC optimization.

[Removal Characteristics of Elemental Mercury by Mn-Ce/molecular Sieve].

PubMed

Tan, Zeng-qiang; Niu, Guo-ping; Chen, Xiao-wen; An, Zhen

2015-06-01

The impregnation method was used to support molecular sieve with active manganese and cerium components to obtain a composite molecular sieve catalyst. The mercury removal performance of the catalyst was studied with a bench-scale setup. XPS analysis was used to characterize the sample before and after the modification in order to study the changes in the active components of the catalyst prepared. The results showed that the catalyst carrying manganese and cerium components had higher oxidation ability of elemental mercury in the temperature range of 300 degrees C - 450 degrees C, especially at 450 degrees C, the oxidation efficiency of elemental mercury was kept above 80%. The catalyst had more functional groups that were conducive to the oxidation of elemental mercury, and the mercury removal mainly depended on the chemical adsorption. The SO2 and NO in flue gas could inhibit the oxidation of elemental mercury to certain extent.

Scaling-Relation-Based Analysis of Bifunctional Catalysis: The Case for Homogeneous Bimetallic Alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Andersen, Mie; Medford, Andrew J.; Norskov, Jens K.

Here, we present a generic analysis of the implications of energetic scaling relations on the possibilities for bifunctional gains at homogeneous bimetallic alloy catalysts. Such catalysts exhibit a large number of interface sites, where second-order reaction steps can involve intermediates adsorbed at different active sites. Using different types of model reaction schemes, we show that such site-coupling reaction steps can provide bifunctional gains that allow for a bimetallic catalyst composed of two individually poor catalyst materials to approach the activity of the optimal monomaterial catalyst. However, bifunctional gains cannot result in activities higher than the activity peak of the monomaterialmore » volcano curve as long as both sites obey similar scaling relations, as is generally the case for bimetallic catalysts. These scaling-relation-imposed limitations could be overcome by combining different classes of materials such as metals and oxides.« less

Scaling-Relation-Based Analysis of Bifunctional Catalysis: The Case for Homogeneous Bimetallic Alloys

DOE PAGES

Andersen, Mie; Medford, Andrew J.; Norskov, Jens K.; ...

2017-04-14

Here, we present a generic analysis of the implications of energetic scaling relations on the possibilities for bifunctional gains at homogeneous bimetallic alloy catalysts. Such catalysts exhibit a large number of interface sites, where second-order reaction steps can involve intermediates adsorbed at different active sites. Using different types of model reaction schemes, we show that such site-coupling reaction steps can provide bifunctional gains that allow for a bimetallic catalyst composed of two individually poor catalyst materials to approach the activity of the optimal monomaterial catalyst. However, bifunctional gains cannot result in activities higher than the activity peak of the monomaterialmore » volcano curve as long as both sites obey similar scaling relations, as is generally the case for bimetallic catalysts. These scaling-relation-imposed limitations could be overcome by combining different classes of materials such as metals and oxides.« less

A novel iron (Ⅱ) polyphthalocyanine catalyst assembled on graphene with significantly enhanced performance for oxygen reduction reaction in alkaline medium

NASA Astrophysics Data System (ADS)

Lin, Lin; Li, Meng; Jiang, Liqing; Li, Yongfeng; Liu, Dajun; He, Xingquan; Cui, Lili

2014-12-01

To realize the large-scale commercial application of direct methanol fuel cells (DMFCs), the catalysts for oxygen reduction reaction (ORR) are the crucial obstacle. Here, an efficient non-noble-metal catalyst for ORR, denoted FePPc/PSS-Gr, has been obtained by anchoring p-phenyl-bis(3,4-dicyanophenyl) ether iron(Ⅱ) polyphthalocyanine (FePPc) on poly(sodium-p-styrenesulfonate) (PSS) modified graphene (PSS-Gr) through a solvothermally assisted π-π assembling approach. The Ultraviolet-visible (UV-vis) spectroscopy, Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) results reveal the π-π interaction between FePPc and PSS-Gr. The rotating disk electrode (RDE) and rotating ring disk electrode (RRDE) measurements show that the proposed catalyst possesses an excellent catalytic performance towards ORR comparable with the commercial Pt/C catalyst in alkaline medium, such as high onset potential (-0.08 V vs. SCE), half-wave potential (-0.19 V vs. SCE), better tolerance to methanol crossover, excellent stability (81.1%, retention after 10,000 s) and an efficient four-electron pathway. The enhanced electrocatalytic performance could be chiefly attributed to its large electrochemically accessible surface area, fast electron transfer rate of PSS-Gr, in particular, the synergistic effect between the FePPc moieties and the PSS-Gr sheets.

A General Small-Scale Reactor To Enable Standardization and Acceleration of Photocatalytic Reactions.

PubMed

Le, Chi Chip; Wismer, Michael K; Shi, Zhi-Cai; Zhang, Rui; Conway, Donald V; Li, Guoqing; Vachal, Petr; Davies, Ian W; MacMillan, David W C

2017-06-28

Photocatalysis for organic synthesis has experienced an exponential growth in the past 10 years. However, the variety of experimental procedures that have been reported to perform photon-based catalyst excitation has hampered the establishment of general protocols to convert visible light into chemical energy. To address this issue, we have designed an integrated photoreactor for enhanced photon capture and catalyst excitation. Moreover, the evaluation of this new reactor in eight photocatalytic transformations that are widely employed in medicinal chemistry settings has confirmed significant performance advantages of this optimized design while enabling a standardized protocol.

Catalysis on Single Supported Atoms

DOE Office of Scientific and Technical Information (OSTI.GOV)

DeBusk, Melanie Moses; Narula, Chaitanya Kumar

2015-01-01

The highly successful application of supported metals as heterogeneous catalysts in automotive catalysts, fuel cells, and other multitudes of industrial processes have led to extensive efforts to understand catalyst behavior at the nano-scale. Recent discovery of simple wet methods to prepare single supported atoms, the smallest nano-catalyst, has allowed for experimental validation of catalytic activity of a variety of catalysts and potential for large scale production for such catalysts for industrial processes. In this chapter, we summarize the synthetic and structural aspects of single supported atoms. We also present proposed mechanisms for the activity of single supported catalysts where conventionalmore » mechanisms cannot operate due to lack of M-M bonds in the catalysts.« less

Monolithic Hydrogen Peroxide Catalyst Bed Development

NASA Technical Reports Server (NTRS)

Ponzo, J. B.

2003-01-01

With recent increased industry and government interest in rocket grade hydrogen peroxide as a viable propellant, significant effort has been expended to improve on earlier developments. This effort has been predominately centered in improving heterogeneous. typically catalyst beds; and homogeneous catalysts, which are typically solutions of catalytic substances. Heterogeneous catalyst beds have traditionally consisted of compressed wire screens plated with a catalytic substance, usually silver, and were used m many RCS applications (X-1, Mercury, and Centaur for example). Aerojet has devised a heterogeneous catalyst design that is monolithic (single piece), extremely compact, and has pressure drops equal to or less than traditional screen beds. The design consists of a bonded stack of very thin, photoetched metal plates, silver coated. This design leads to a high surface area per unit volume and precise flow area, resulting in high, stable, and repeatable performance. Very high throughputs have been demonstrated with 90% hydrogen peroxide. (0.60 lbm/s/sq in at 1775-175 psia) with no flooding of the catalyst bed. Bed life of over 900 seconds has also been demonstrated at throughputs of 0.60 lbm/s/sq in across varying chamber pressures. The monolithic design also exhibits good starting performance, short break-in periods, and will easily scale to various sizes.

Low-Energy, Low-Cost Production of Ethylene by Low- Temperature Oxidative Coupling of Methane

DOE Office of Scientific and Technical Information (OSTI.GOV)

Radaelli, Guido; Chachra, Gaurav; Jonnavittula, Divya

In this project, we develop a catalytic process technology for distributed small-scale production of ethylene by oxidative coupling of methane at low temperatures using an advanced catalyst. The Low Temperature Oxidative Coupling of Methane (LT-OCM) catalyst system is enabled by a novel chemical catalyst and process pioneered by Siluria, at private expense, over the last six years. Herein, we develop the LT-OCM catalyst system for distributed small-scale production of ethylene by identifying and addressing necessary process schemes, unit operations and process parameters that limit the economic viability and mass penetration of this technology to manufacture ethylene at small-scales. The outputmore » of this program is process concepts for small-scale LT-OCM catalyst based ethylene production, lab-scale verification of the novel unit operations adopted in the proposed concept, and an analysis to validate the feasibility of the proposed concepts.« less

Surface faceting and elemental diffusion behaviour at atomic scale for alloy nanoparticles during in situ annealing

PubMed Central

Chi, Miaofang; Wang, Chao; Lei, Yinkai; Wang, Guofeng; Li, Dongguo; More, Karren L.; Lupini, Andrew; Allard, Lawrence F.; Markovic, Nenad M.; Stamenkovic, Vojislav R.

2015-01-01

The catalytic performance of nanoparticles is primarily determined by the precise nature of the surface and near-surface atomic configurations, which can be tailored by post-synthesis annealing effectively and straightforwardly. Understanding the complete dynamic response of surface structure and chemistry to thermal treatments at the atomic scale is imperative for the rational design of catalyst nanoparticles. Here, by tracking the same individual Pt3Co nanoparticles during in situ annealing in a scanning transmission electron microscope, we directly discern five distinct stages of surface elemental rearrangements in Pt3Co nanoparticles at the atomic scale: initial random (alloy) elemental distribution; surface platinum-skin-layer formation; nucleation of structurally ordered domains; ordered framework development and, finally, initiation of amorphization. Furthermore, a comprehensive interplay among phase evolution, surface faceting and elemental inter-diffusion is revealed, and supported by atomistic simulations. This work may pave the way towards designing catalysts through post-synthesis annealing for optimized catalytic performance. PMID:26576477

Surface faceting and elemental diffusion behaviour at atomic scale for alloy nanoparticles during in situ annealing

DOE PAGES

Chi, Miaofang; Wang, Chao; Lei, Yinkai; ...

2015-11-18

The catalytic performance of nanoparticles is primarily determined by the precise nature of the surface and near-surface atomic configurations, which can be tailored by post-synthesis annealing effectively and straightforwardly. Understanding the complete dynamic response of surface structure and chemistry to thermal treatments at the atomic scale is imperative for the rational design of catalyst nanoparticles. Here, by tracking the same individual Pt 3Co nanoparticles during in situ annealing in a scanning transmission electron microscope, we directly discern five distinct stages of surface elemental rearrangements in Pt 3Co nanoparticles at the atomic scale: initial random (alloy) elemental distribution; surface platinum-skin-layer formation;more » nucleation of structurally ordered domains; ordered framework development and, finally, initiation of amorphization. Furthermore, a comprehensive interplay among phase evolution, surface faceting and elemental inter-diffusion is revealed, and supported by atomistic simulations. In conlcusion, this work may pave the way towards designing catalysts through post-synthesis annealing for optimized catalytic performance.« less

Development of a reactor with carbon catalysts for modular-scale, low-cost electrochemical generation of H 2O 2

DOE PAGES

Chen, Zhihua; Chen, Shucheng; Siahrostami, Samira; ...

2017-03-01

The development of small-scale, decentralized reactors for H 2O 2 production that can couple to renewable energy sources would be of great benefit, particularly for water purification in the developing world. Herein, we describe our efforts to develop electrochemical reactors for H 2O 2 generation with high Faradaic efficiencies of >90%, requiring cell voltages of only ~1.6 V. The reactor employs a carbon-based catalyst that demonstrates excellent performance for H 2O 2 production under alkaline conditions, as demonstrated by fundamental studies involving rotating-ring disk electrode methods. Finally, the low-cost, membrane-free reactor design represents a step towards a continuous, modular-scale, de-centralizedmore » production of H 2O 2.« less

Technology development for cobalt F-T catalysts. Quarterly technical progress report number 10, January 1--March 31, 1995

DOE Office of Scientific and Technical Information (OSTI.GOV)

Singleton, A.H.

1995-06-28

The goal of this project is the development of a commercially-viable, cobalt-based Fischer-Tropsch (F-T) catalyst for use in a slurry bubble column reactor. The major objectives of this work are (1) to develop a cobalt-based F-T catalyst with low (< 5%) methane selectivity, (2) to develop a cobalt-based F-T catalyst with water-gas shift activity, and (3) to combine both these improvements into one catalyst. The project consists of five major tasks: catalyst development; catalyst testing; catalyst reproducibility tests; catalyst aging tests; and preliminary design and cost estimate for a demonstrate scale catalyst production facility. Technical accomplishments during this reporting periodmore » include the following. It appears that the higher activity obtained for the catalysts prepared using an organic solution and reduced directly without prior calcination was the result of higher dispersions obtained under such pretreatment. A Ru-promoted Co catalyst on alumina with 30% Co loading exhibited a 4-fold increase in dispersion and a 2-fold increase in activity in the fixed-bed reactor from that obtained with the non-promoted catalyst. Several reactor runs have again focused on pushing conversion to higher levels. The maximum conversion obtained has been 49.7% with 26g catalyst. Further investigations of the effect of reaction temperature on the performance of Co catalysts during F-T synthesis were started using a low activity catalyst and one of the most active catalysts. The three 1 kg catalyst batches prepared by Calsicat for the reproducibility and aging studies were tested in both the fixed-bed and slurry bubble column reactors under the standard reaction conditions. The effects of adding various promoters to some cobalt catalysts have also been addressed. Results are presented and discussed.« less

Mars Atmospheric Conversion to Methane and Water: An Engineering Model of the Sabatier Reactor with Characterization of Ru/Al2O3 for Long Duration Use on Mars

NASA Technical Reports Server (NTRS)

Meier, Anne J.; Shah, Malay; Petersen, Elspeth; Hintze, Paul; Muscatello, Tony

2017-01-01

The Atmospheric Processing Module (APM) is a Mars In-Situ Resource Utilization (ISRU) technology designed to demonstrate conversion of the Martian atmosphere into methane and water. The Martian atmosphere consists of approximately 95 carbon dioxide (CO2) and residual argon and nitrogen. APM utilizes cryocoolers for CO2 acquisition from a simulated Martian atmosphere and pressure. The captured CO2 is sublimated and pressurized as a feedstock into the Sabatier reactor, which converts CO2 and hydrogen to methane and water. The Sabatier reaction occurs over a packed bed reactor filled with Ru/Al2O3 pellets. The long duration use of the APM system and catalyst was investigated for future scaling and failure limits. Failure of the catalyst was detected by gas chromatography and temperature sensors on the system. Following this, characterization and experimentation with the catalyst was carried out with analysis including x-ray photoelectron spectroscopy and scanning electron microscopy with elemental dispersive spectroscopy. This paper will discuss results of the catalyst performance, the overall APM Sabatier approach, as well as intrinsic catalyst considerations of the Sabatier reactor performance incorporated into a chemical model.

Pilot plant operation of a nonadiabatic methanation reactor. [15 refs. ; Raney nickel catalyst

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schehl, R.R.; Pennline, H.W.; Strakey, J.P.

The design and operation of a pilot plant scale hybrid methanation reactor is discussed. The hybrid methanator, utilizing a finned, Raney nickel coated insert, consolidates features of the tube-wall and hot-gas-recycle methanation reactors. Data are presented from four tests lasting from 3/sup 1///sub 2/ weeks to three months. Topics discussed include conversion, product yields, catalyst properties, and reactor temperature profiles. A one-dimensional mathematical model capable of explaining reactor performance trends is employed.

Shining X-rays on catalysts at work

NASA Astrophysics Data System (ADS)

Grunwaldt, J.-D.

2009-11-01

Structure-performance relationships gained by studying catalysts at work are considered the key to further development of catalysts underlined here by a brief overview on our research in this area. The partial oxidation of methane to hydrogen and carbon monoxide over Pt- and Rh-based catalysts and the total combustion of hydrocarbons demonstrate the importance of structural identification of catalysts in its working state and the measurement of the catalytic performance at the same time. Moreover, proper cell design is a key both here and in liquid phase reactions including preparation or high pressure reactions. In several cases structural changes during preparation, activation and reaction occur on a subminute scale or the catalyst structure varies inside a reactor as a result of temperature or concentration gradients. This, additionally, requires time and spatial resolution. Examples from time-resolved QEXAFS studies during the partial oxidation of methane over Pt- and Rh-based catalysts demonstrate some of the recent developments of the technique (use not only of Si(111) but also Si(311) crystals, angular encoder, full EXAFS spectra at subsecond recording time, and modulation excitation spectroscopy). In order to obtain spectroscopic information on the oxidation state inside a microreactor, scanning and full field X-ray microscopy with X-ray absorption spectroscopic contrast were achieved under reaction conditions. If a microbeam is applied, fast scanning techniques like QEXAFS are required. In this way, even X-ray absorption spectroscopic tomographic images of a slice of a microreactor were obtained. The studies were recently extended to spatiotemporal studies that give important insight into the dynamics of the catalyst structure in a spatial manner with subsecond time-resolution.

Effect of the thickness of the anode electrode catalyst layers on the performance in direct methanol fuel cells

NASA Astrophysics Data System (ADS)

Glass, Dean E.; Olah, George A.; Prakash, G. K. Surya

2017-06-01

For the large scale fuel cell manufacture, the catalyst loading and layer thickness are critical factors affecting the performance and cost of membrane electrode assemblies (MEAs). The influence of catalyst layer thicknesses at the anode of a PEM based direct methanol fuel cell (DMFC) has been investigated. Catalysts were applied with the drawdown method with varied thicknesses ranging from 1 mil to 8 mils (1 mil = 25.4 μm) with a Pt/Ru anode loading of 0.25 mg cm-2 to 2.0 mg cm-2. The MEAs with the thicker individual layers (8 mils and 4 mils) performed better overall compared to the those with the thinner layers (1 mil and painted). The peak power densities for the different loading levels followed an exponential decrease of Pt/Ru utilization at the higher loading levels. The highest power density achieved was 49 mW cm-2 with the 4 mil layers at 2.0 mg cm-2 catalyst loading whereas the highest normalized power density was 116 mW mg-1 with the 8 mil layers at 0.25 mg cm-2 loading. The 8 mil drawdowns displayed a 50% and 23% increase in normalized power density compared to the 1 mil drawdowns at 0.25 mg cm-2 and 0.5 mg cm-2 loadings, respectively.

In situ Generated Ruthenium Catalyst Systems Bearing Diverse N-Heterocyclic Carbene Precursors for Atom-Economic Amide Synthesis from Alcohols and Amines.

PubMed

Cheng, Hua; Xiong, Mao-Qian; Cheng, Chuan-Xiang; Wang, Hua-Jing; Lu, Qiang; Liu, Hong-Fu; Yao, Fu-Bin; Chen, Cheng; Verpoort, Francis

2018-02-16

The transition-metal-catalyzed direct synthesis of amides from alcohols and amines is herein demonstrated as a highly environmentally benign and atom-economic process. Among various catalyst systems, in situ generated N-heterocyclic carbene (NHC)-based ruthenium (Ru) halide catalyst systems have been proven to be active for this transformation. However, these existing catalyst systems usually require an additional ligand to achieve satisfactory results. In this work, through extensive screening of a diverse variety of NHC precursors, we discovered an active in situ catalyst system for efficient amide synthesis without any additional ligand. Notably, this catalyst system was found to be insensitive to the electronic effects of the substrates, and various electron-deficient substrates, which were not highly reactive with our previous catalyst systems, could be employed to afford the corresponding amides efficiently. Furthermore, mechanistic investigations were performed to provide a rationale for the high activity of the optimized catalyst system. NMR-scale reactions indicated that the rapid formation of a Ru hydride intermediate (signal at δ=-7.8 ppm in the 1 H NMR spectrum) after the addition of the alcohol substrate should be pivotal in establishing the high catalyst activity. Besides, HRMS analysis provided possible structures of the in situ generated catalyst system. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Demonstration of Selective Catalytic Reduction (SCR) technology for the control of nitrogen oxide (NO sub x ) emissions from high-sulfur coal-fired boilers: Innovative Clean Coal Technology (ICCT)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

1992-05-01

The objective of this project is to demonstrate and evaluate commercially available Selective Catalytic Reduction (SCR) catalysts from US, Japanese and European catalyst suppliers on a high-sulfur US coal-fired boiler. SCR is a post-combustion nitrogen oxide (NO{sub x}) control technology that involves injecting ammonia into the flue gas generated from coal combustion in an electric utility boiler. The flue gas containing ammonia is then passed through a reactor that contains a specialized catalyst. In the presence of the catalyst, the amonia reacts with NO{sub x} to convert it to nitrogen and water vapor. Although SCR is widely practiced in Japanmore » and Europe, there are numerous technical uncertainties associated with applying SCR to US coals. These uncertainties include: (1) potential catalyst deactivation due to poisoning by trace metal species present in US coals that are not present in other fuels. (2) performance of the technology and effects on the balance-of-plant equipment in the presence of high amounts of SO, and SO{sub 3}. (3) performance of a wide variety of SCR catalyst compositions, geometries and methods of manufacture under typical high-sulfur coal-fired utility operating conditions. These uncertainties will be explored by constructing a series of small-scale SCR reactors and simultaneously exposing different SCR catalysts to flue gas derived from the combustion of high sulfur US coal. The demonstration will be performed at Gulf Power Company's Plant Crist Unit No. 5 (75 MW capacity) near Pensacola, Florida. The project will be funded by the US Department of Energy (DOE), Southern Company Services, Inc. (SCS on behalf of the entire Southern electric system), and the Electric Power Research Institute.« less

Ultrathin Wall (1 nm) and Superlong Pt Nanotubes with Enhanced Oxygen Reduction Reaction Performance.

PubMed

Tao, Lu; Yu, Dan; Zhou, Junshuang; Lu, Xiong; Yang, Yunxia; Gao, Faming

2018-05-01

The synthesis of Pt nanotubes catalysts remains a substantial challenge, especially for those with both sub-nanometer wall thickness and micrometer-scale length characteristics. Combining techniques of insulin fibril template with Pd nanowire template, numerous Pt nanotubes with diameter of 5.5 nm, tube-length of several micrometers, and ultrathin wall thickness of 1 nm are assembled. These tubular catalysts with both open ends deliver electrochemical active surface area (ECSA) of 91.43 m 2 g pt -1 which results from multiple Pt atoms exposed on the inner and outer surfaces that doubled Pt atoms can participate in catalytic reactions, further with enhanced electrocatalytic performance for oxygen reduction reaction (ORR). The ultrafine Pt nanotubes represent a class of hollow nanostructure with increased Pt-utilization and large ECSA, which is regarded as a type of cost-effective catalysts for ORR. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ionita, G.; Stefanescu, I.

The nature and performance of our patented catalysts, with platinum on carbon and polytetrafluorethylene [Pt/C/PTFE] and platinum on styrenedivynilbenzene and polystyrene [Pt/STB/PS], used in a water-hydrogen isotope exchange process are presented. The behaviour of the two catalysts in tritiated water was tested by determining their physical and structural characteristics as well as the catalytic activity before and after immersion in tritiated water. The test results emphasized that the two catalysts are highly active in the hydrogen - water vapor (H{sub 2(g)}-H{sub 2}O{sub (v)}) isotopic exchange and highly stable to tritium radiation. It was discovered that Pt/SDB/PS catalyst proved to bemore » quite unstable in the hydrogen- water vapor - water (H{sub 2(g)}-H{sub 2}O{sub (v)}-H{sub 2}O{sub (1)}) isotopic exchange, while the Pt/C/PTFE catalyst was highly stable. Thus, the Pt/C/PTFE catalyst was chosen for hydrogen isotope separation by liquid hydrogen cryogenic distillation combined with water - hydrogen isotopic exchange in a demonstration scale plant. 5 refs., 8 figs., 2 tabs.« less

The Dependence of CNT Aerogel Synthesis on Sulfur-driven Catalyst Nucleation Processes and a Critical Catalyst Particle Mass Concentration.

PubMed

Hoecker, Christian; Smail, Fiona; Pick, Martin; Weller, Lee; Boies, Adam M

2017-11-06

The floating catalyst chemical vapor deposition (FC-CVD) process permits macro-scale assembly of nanoscale materials, enabling continuous production of carbon nanotube (CNT) aerogels. Despite the intensive research in the field, fundamental uncertainties remain regarding how catalyst particle dynamics within the system influence the CNT aerogel formation, thus limiting effective scale-up. While aerogel formation in FC-CVD reactors requires a catalyst (typically iron, Fe) and a promotor (typically sulfur, S), their synergistic roles are not fully understood. This paper presents a paradigm shift in the understanding of the role of S in the process with new experimental studies identifying that S lowers the nucleation barrier of the catalyst nanoparticles. Furthermore, CNT aerogel formation requires a critical threshold of Fe x C y  > 160 mg/m 3 , but is surprisingly independent of the initial catalyst diameter or number concentration. The robustness of the critical catalyst mass concentration principle is proved further by producing CNTs using alternative catalyst systems; Fe nanoparticles from a plasma spark generator and cobaltocene and nickelocene precursors. This finding provides evidence that low-cost and high throughput CNT aerogel routes may be achieved by decoupled and enhanced catalyst production and control, opening up new possibilities for large-scale CNT synthesis.

N-doped carbon nanomaterials are durable catalysts for oxygen reduction reaction in acidic fuel cells

PubMed Central

Shui, Jianglan; Wang, Min; Du, Feng; Dai, Liming

2015-01-01

The availability of low-cost, efficient, and durable catalysts for oxygen reduction reaction (ORR) is a prerequisite for commercialization of the fuel cell technology. Along with intensive research efforts of more than half a century in developing nonprecious metal catalysts (NPMCs) to replace the expensive and scarce platinum-based catalysts, a new class of carbon-based, low-cost, metal-free ORR catalysts was demonstrated to show superior ORR performance to commercial platinum catalysts, particularly in alkaline electrolytes. However, their large-scale practical application in more popular acidic polymer electrolyte membrane (PEM) fuel cells remained elusive because they are often found to be less effective in acidic electrolytes, and no attempt has been made for a single PEM cell test. We demonstrated that rationally designed, metal-free, nitrogen-doped carbon nanotubes and their graphene composites exhibited significantly better long-term operational stabilities and comparable gravimetric power densities with respect to the best NPMC in acidic PEM cells. This work represents a major breakthrough in removing the bottlenecks to translate low-cost, metal-free, carbon-based ORR catalysts to commercial reality, and opens avenues for clean energy generation from affordable and durable fuel cells. PMID:26601132

N-doped carbon nanomaterials are durable catalysts for oxygen reduction reaction in acidic fuel cells.

PubMed

Shui, Jianglan; Wang, Min; Du, Feng; Dai, Liming

2015-02-01

The availability of low-cost, efficient, and durable catalysts for oxygen reduction reaction (ORR) is a prerequisite for commercialization of the fuel cell technology. Along with intensive research efforts of more than half a century in developing nonprecious metal catalysts (NPMCs) to replace the expensive and scarce platinum-based catalysts, a new class of carbon-based, low-cost, metal-free ORR catalysts was demonstrated to show superior ORR performance to commercial platinum catalysts, particularly in alkaline electrolytes. However, their large-scale practical application in more popular acidic polymer electrolyte membrane (PEM) fuel cells remained elusive because they are often found to be less effective in acidic electrolytes, and no attempt has been made for a single PEM cell test. We demonstrated that rationally designed, metal-free, nitrogen-doped carbon nanotubes and their graphene composites exhibited significantly better long-term operational stabilities and comparable gravimetric power densities with respect to the best NPMC in acidic PEM cells. This work represents a major breakthrough in removing the bottlenecks to translate low-cost, metal-free, carbon-based ORR catalysts to commercial reality, and opens avenues for clean energy generation from affordable and durable fuel cells.

Biodiesel synthesis by TiO2-ZnO mixed oxide nanocatalyst catalyzed palm oil transesterification process.

PubMed

Madhuvilakku, Rajesh; Piraman, Shakkthivel

2013-12-01

Biodiesel is a promising alternating environmentally benign fuel to mineral diesel. For the development of easier transesterification process, stable and active heterogeneous mixed metal oxide of TiO2-ZnO and ZnO nanocatalysts were synthesized and exploited for the palm oil transesterification process. The synthesized catalysts were characterized by XRD, FT-IR, and FE-SEM studies for their structural and morphological characteristics. It was found that TiO2-ZnO nanocatalyst exhibits good catalytic activity and the catalytic performance was greatly depends on (i) catalyst concentration (ii) methanol to oil molar ratio (iii) reaction temperature and (iv) reaction time. A highest 98% of conversion was obtained at the optimum reaction parameters with 200 mg of catalyst loading and the biodiesel was analyzed by TLC and (1)H NMR techniques. The TiO2-ZnO nanocatalyst shows good catalytic performance over the ZnO catalyst, which could be a potential candidate for the large-scale biodiesel production from palm oil at the reduced temperature and time. Copyright © 2013. Published by Elsevier Ltd.

Fe3-xCuxO4 as highly active heterogeneous Fenton-like catalysts toward elemental mercury removal.

PubMed

Zhou, Changsong; Sun, Lushi; Zhang, Anchao; Wu, Xiaofeng; Ma, Chuan; Su, Sheng; Hu, Song; Xiang, Jun

2015-04-01

A series of novel spinel Fe3-xCuxO4 (0

Mechanistic insights into heterogeneous methane activation

DOE PAGES

Latimer, Allegra A.; Aljama, Hassan; Kakekhani, Arvin; ...

2017-01-11

While natural gas is an abundant chemical fuel, its low volumetric energy density has prompted a search for catalysts able to transform methane into more useful chemicals. This search has often been aided through the use of transition state (TS) scaling relationships, which estimate methane activation TS energies as a linear function of a more easily calculated descriptor, such as final state energy, thus avoiding tedious TS energy calculations. It has been shown that methane can be activated via a radical or surface-stabilized pathway, both of which possess a unique TS scaling relationship. Herein, we present a simple model tomore » aid in the prediction of methane activation barriers on heterogeneous catalysts. Analogous to the universal radical TS scaling relationship introduced in a previous publication, we show that a universal TS scaling relationship that transcends catalysts classes also seems to exist for surface-stabilized methane activation if the relevant final state energy is used. We demonstrate that this scaling relationship holds for several reducible and irreducible oxides, promoted metals, and sulfides. By combining the universal scaling relationships for both radical and surface-stabilized methane activation pathways, we show that catalyst reactivity must be considered in addition to catalyst geometry to obtain an accurate estimation for the TS energy. Here, this model can yield fast and accurate predictions of methane activation barriers on a wide range of catalysts, thus accelerating the discovery of more active catalysts for methane conversion.« less

Mechanistic insights into heterogeneous methane activation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Latimer, Allegra A.; Aljama, Hassan; Kakekhani, Arvin

While natural gas is an abundant chemical fuel, its low volumetric energy density has prompted a search for catalysts able to transform methane into more useful chemicals. This search has often been aided through the use of transition state (TS) scaling relationships, which estimate methane activation TS energies as a linear function of a more easily calculated descriptor, such as final state energy, thus avoiding tedious TS energy calculations. It has been shown that methane can be activated via a radical or surface-stabilized pathway, both of which possess a unique TS scaling relationship. Herein, we present a simple model tomore » aid in the prediction of methane activation barriers on heterogeneous catalysts. Analogous to the universal radical TS scaling relationship introduced in a previous publication, we show that a universal TS scaling relationship that transcends catalysts classes also seems to exist for surface-stabilized methane activation if the relevant final state energy is used. We demonstrate that this scaling relationship holds for several reducible and irreducible oxides, promoted metals, and sulfides. By combining the universal scaling relationships for both radical and surface-stabilized methane activation pathways, we show that catalyst reactivity must be considered in addition to catalyst geometry to obtain an accurate estimation for the TS energy. Here, this model can yield fast and accurate predictions of methane activation barriers on a wide range of catalysts, thus accelerating the discovery of more active catalysts for methane conversion.« less

A carbon-supported copper complex of 3,5-diamino-1,2,4-triazole as a cathode catalyst for alkaline fuel cell applications.

PubMed

Brushett, Fikile R; Thorum, Matthew S; Lioutas, Nicholas S; Naughton, Matthew S; Tornow, Claire; Jhong, Huei-Ru Molly; Gewirth, Andrew A; Kenis, Paul J A

2010-09-08

The performance of a novel carbon-supported copper complex of 3,5-diamino-1,2,4-triazole (Cu-tri/C) is investigated as a cathode material using an alkaline microfluidic H(2)/O(2) fuel cell. The absolute Cu-tri/C cathode performance is comparable to that of a Pt/C cathode. Furthermore, at a commercially relevant potential, the measured mass activity of an unoptimized Cu-tri/C-based cathode was significantly greater than that of similar Pt/C- and Ag/C-based cathodes. Accelerated cathode durability studies suggested multiple degradation regimes at various time scales. Further enhancements in performance and durability may be realized by optimizing catalyst and electrode preparation procedures.

Furfural production using ionic liquids: A review.

PubMed

Peleteiro, Susana; Rivas, Sandra; Alonso, José Luis; Santos, Valentín; Parajó, Juan Carlos

2016-02-01

Furfural, a platform chemical with a bright future, is commercially obtained by acidic processing of xylan-containing biomass in aqueous media. Ionic liquids (ILs) can be employed in processed for furfural manufacture as additives, as catalysts and/or as reaction media. Depending on the IL utilized, externally added catalysts (usually, Lewis acids, Brönsted acids and/or solid acid catalysts) can be necessary to achieve high reaction yields. Oppositely, acidic ionic liquids (AILs) can perform as both solvents and catalysts, enabling the direct conversion of suitable substrates (pentoses, pentosans or xylan-containing biomass) into furfural. Operating in IL-containing media, the furfural yields can be improved when the product is continuously removed along the reaction (for example, by stripping or extraction), to avoid unwanted side-reactions leading to furfural consumption. These topics are reviewed, as well as the major challenges involved in the large scale utilization of ILs for furfural production. Copyright © 2015 Elsevier Ltd. All rights reserved.

Kinetics studies of d-glucose hydrogenation over activated charcoal supported platinum catalyst

NASA Astrophysics Data System (ADS)

Ahmed, Muthanna J.

2012-02-01

The kinetics of the catalytic hydrogenation of d-glucose to produce d-sorbitol was studied in a three-phase laboratory scale reactor. The hydrogenation reactions were performed on activated charcoal supported platinum catalyst in the temperature range 25-65°C and in a constant pressure of 1 atm. The kinetic data were modeled by zero, first and second-order reaction equations. In the operating regimes studied, the results show that the hydrogenation reaction was of a first order with respect to d-glucose concentration. Also the activation energy of the reaction was determined, and found to be 12.33 kJ mole-1. A set of experiment was carried out to test the deactivation of the catalyst, and the results show that the deactivation is slow with the ability of using the catalyst for several times with a small decrease in product yield.

Catalyst Residence Time Distributions in Riser Reactors for Catalytic Fast Pyrolysis. Part 2: Pilot-Scale Simulations and Operational Parameter Study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Foust, Thomas D.; Ziegler, Jack L.; Pannala, Sreekanth

2017-02-21

Here, wsing the validated simulation model developed in part one of this study for biomass catalytic fast pyrolysis (CFP), we assess the functional utility of using this validated model to assist in the development of CFP processes in fluidized catalytic cracking (FCC) reactors to a commercially viable state. Specifically, we examine the effects of mass flow rates, boundary conditions (BCs), pyrolysis vapor molecular weight variation, and the impact of the chemical cracking kinetics on the catalyst residence times. The factors that had the largest impact on the catalyst residence time included the feed stock molecular weight and the degree ofmore » chemical cracking as controlled by the catalyst activity. Lastly, because FCC reactors have primarily been developed and utilized for petroleum cracking, we perform a comparison analysis of CFP with petroleum and show the operating regimes are fundamentally different.« less

Effect of deposition rate on melting point of copper film catalyst substrate at atomic scale

NASA Astrophysics Data System (ADS)

Marimpul, Rinaldo; Syuhada, Ibnu; Rosikhin, Ahmad; Winata, Toto

2018-03-01

Annealing process of copper film catalyst substrate was studied by molcular dynamics simulation. This copper film catalyst substrate was produced using thermal evaporation method. The annealing process was limited in nanosecond order to observe the mechanism at atomic scale. We found that deposition rate parameter affected the melting point of catalyst substrate. The change of crystalline structure of copper atoms was observed before it had been already at melting point. The optimum annealing temperature was obtained to get the highest percentage of fcc structure on copper film catalyst substrate.

Study of the Influence of Key Process Parameters on Furfural Production.

PubMed

Fele Žilnik, Ljudmila; Grilc, Viktor; Mirt, Ivan; Cerovečki, Željko

2016-01-01

The present work reports the influence of key process variables on the furfural formation from leached chestnut-wood chips in a pressurized reactor. Effect of temperature, pressure, type and concentration of the catalyst solution, the steam flow rate or stripping module, the moisture content of the wood particles and geometric characteristics such as size and type of the reactor, particle size and bed height were considered systematically. One stage process was only taken into consideration. Lab-scale and pilot-scale studies were performed. The results of the non-catalysed laboratory experiments were compared with an actual non-catalysed (auto-catalysed) industrial process and with experiments on the pilot scale, the latter with 28% higher furfural yield compared to the others. Application of sulphuric acid as catalyst, in an amount of 0.03-0.05 g (H2SO4 100%)/g d.m. (dry material), enables a higher production of furfural at lower temperature and pressure of steam in a shorter reaction time. Pilot scale catalysed experiments have revealed very good performance for furfural formation under less severe operating conditions, with a maximum furfural yield as much as 88% of the theoretical value.

Attrition of precipitated iron Fischer-Tropsch catalysts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Datye, A.K.; Reardon, J.; Hanprasopwattana, A.

1996-12-31

Precipitated Iron catalysts used in slurry phase bubble column reactors are known to undergo attrition during use. The attrition reduces the lifetime of the catalyst as well as causing problems in separating the product liquids from the catalyst. In this study, the authors have investigated the underlying mechanisms that lead to attrition in precipitated iron catalysts. They have discovered that attrition takes place on two length scales. On the macro scale, attrition is caused by the break-up of the weak agglomerates that constitute this catalyst into individual crystallites. Addition of binders such as kaolin does not help significantly in strengtheningmore » the catalyst particles. In addition, there is a second process leading to nanoscale attrition that is caused by the break-up of individual iron oxide crystallites into nano particles of iron carbide as the catalyst is activated for reaction. Design of attrition resistant F-T catalysts must consider these two modes of catalyst attrition. Preliminary work in the laboratory directed at improving the attrition resistance of precipitated iron catalysts will also be described in this paper.« less

Attrition and carbon formation on iron catalysts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kohler, S.D.; Harrington, M.S.; Jackson, N.B.

1994-08-01

A serious engineering problem that needs to be addressed in the scale-up of slurry-phase, Fischer-Tropsch reactors is attrition of the precipitated iron catalyst. Attrition, which can break down the catalyst into particles too small to filter, results from both mechanical and chemical forces. This study examines the chemical causes of attrition in iron catalysts. A bench-scale, slurry-phase CSTR is used to simulate operating conditions that lead to attrition of the catalyst. The average particle size and size distribution of the catalyst samples are used to determine the effect of slurry temperature, reducing gas, gas flow rate and time upon attritionmore » of the catalyst. Carbon deposition, a possible contributing factor to attrition, has been examined using gravimetric analysis and TEM. Conditions affecting the rate of carbon deposition have been compared to those leading to attrition of the precipitated iron catalyst.« less

Development of modified FT (MFT) process

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jinglai Zhou; Zhixin Zhang; Wenjie Shen

1995-12-31

Two-Stage Modified FT (MFT) process has been developed for producing high-octane gasoline from coal-based syngas. The main R&D are focused on the development of catalysts and technologies process. Duration tests were finished in the single-tube reactor, pilot plant (100T/Y), and industrial demonstration plant (2000T/Y). A series of satisfactory results has been obtained in terms of operating reliability of equipments, performance of catalysts, purification of coal - based syngas, optimum operating conditions, properties of gasoline and economics etc. Further scaling - up commercial plant is being considered.

A Simple Primary Amine Catalyst for Enantioselective α-Hydroxylations and α-Fluorinations of Branched Aldehydes.

PubMed

Witten, Michael R; Jacobsen, Eric N

2015-06-05

A new primary amine catalyst for the asymmetric α-hydroxylation and α-fluorination of α-branched aldehydes is described. The products of the title transformations are generated in excellent yields with high enantioselectivities. Both processes can be performed within short reaction times and on gram scale. The similarity in results obtained in both reactions, combined with computational evidence, implies a common basis for stereoinduction and the possibility of a general catalytic mechanism for α-functionalizations. Promising initial results in α-amination and α-chlorination reactions support this hypothesis.

ZnO/perovskite core–shell nanorod array based monolithic catalysts with enhanced propane oxidation and material utilization efficiency at low temperature

DOE PAGES

Wang, Sibo; Ren, Zheng; Song, Wenqiao; ...

2015-04-24

Here, a hydrothermal strategy combined with colloidal deposition synthesis was successfully used to grow ZnO/perovskite (LaBO 3, B=Mn, Co, Ni) core-shell nanorod arrays within three dimensional (3-D) honeycomb cordierite substrates. A facile sonication assisted colloidal wash coating process is able to coat a uniformly dispersed perovskite nanoparticles onto the large scale ZnO nanorod arrays rooted on the channel surfaces of the 3D cordierite substrate achieved by hydrothermal synthesis. Compared to traditional wash-coated perovskite catalysts, an enhanced catalytic performance was observed for propane oxidation with 25°C lower light-off temperature than wash-coated perovskite catalyst of similar LaMnO 3 loading (4.3mg). Temperature programmedmore » reduction and desorption under H 2 and O 2 atmosphere, respectively, were used to study the reducibility and oxygen activity of these core-shell nanorod arrays based monolithic catalysts, revealing a catalytic activity sequence of LaCoO 3>LaMnO 3>La 2NiO 4 at the initial stage of catalytic reaction. The good dispersion and size control in La-based perovskite nanoparticles and their interfaces to ZnO nanorod arrays support may contribute to the enhancement of catalytic performance. Lastly, this work may provide a new type of Pt-group metals (PGM) free catalysts with improved catalytic performance for hydrocarbon oxidations at low temperatures.« less

Transitioning Rationally Designed Catalytic Materials to Real 'Working' Catalysts Produced at Commercial Scale: Nanoparticle Materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schaidle, Joshua A.; Habas, Susan E.; Baddour, Frederick G.

Catalyst design, from idea to commercialization, requires multi-disciplinary scientific and engineering research and development over 10-20 year time periods. Historically, the identification of new or improved catalyst materials has largely been an empirical trial-and-error process. However, advances in computational capabilities (new tools and increased processing power) coupled with new synthetic techniques have started to yield rationally-designed catalysts with controlled nano-structures and tailored properties. This technological advancement represents an opportunity to accelerate the catalyst development timeline and to deliver new materials that outperform existing industrial catalysts or enable new applications, once a number of unique challenges associated with the scale-up ofmore » nano-structured materials are overcome.« less

First principle chemical kinetics in zeolites: the methanol-to-olefin process as a case study.

PubMed

Van Speybroeck, Veronique; De Wispelaere, Kristof; Van der Mynsbrugge, Jeroen; Vandichel, Matthias; Hemelsoet, Karen; Waroquier, Michel

2014-11-07

To optimally design next generation catalysts a thorough understanding of the chemical phenomena at the molecular scale is a prerequisite. Apart from qualitative knowledge on the reaction mechanism, it is also essential to be able to predict accurate rate constants. Molecular modeling has become a ubiquitous tool within the field of heterogeneous catalysis. Herein, we review current computational procedures to determine chemical kinetics from first principles, thus by using no experimental input and by modeling the catalyst and reacting species at the molecular level. Therefore, we use the methanol-to-olefin (MTO) process as a case study to illustrate the various theoretical concepts. This process is a showcase example where rational design of the catalyst was for a long time performed on the basis of trial and error, due to insufficient knowledge of the mechanism. For theoreticians the MTO process is particularly challenging as the catalyst has an inherent supramolecular nature, for which not only the Brønsted acidic site is important but also organic species, trapped in the zeolite pores, must be essentially present during active catalyst operation. All these aspects give rise to specific challenges for theoretical modeling. It is shown that present computational techniques have matured to a level where accurate enthalpy barriers and rate constants can be predicted for reactions occurring at a single active site. The comparison with experimental data such as apparent kinetic data for well-defined elementary reactions has become feasible as current computational techniques also allow predicting adsorption enthalpies with reasonable accuracy. Real catalysts are truly heterogeneous in a space- and time-like manner. Future theory developments should focus on extending our view towards phenomena occurring at longer length and time scales and integrating information from various scales towards a unified understanding of the catalyst. Within this respect molecular dynamics methods complemented with additional techniques to simulate rare events are now gradually making their entrance within zeolite catalysis. Recent applications have already given a flavor of the benefit of such techniques to simulate chemical reactions in complex molecular environments.

Intermetallic nickel silicide nanocatalyst—A non-noble metal–based general hydrogenation catalyst

PubMed Central

Pohl, Marga-Martina; Agapova, Anastasiya

2018-01-01

Hydrogenation reactions are essential processes in the chemical industry, giving access to a variety of valuable compounds including fine chemicals, agrochemicals, and pharmachemicals. On an industrial scale, hydrogenations are typically performed with precious metal catalysts or with base metal catalysts, such as Raney nickel, which requires special handling due to its pyrophoric nature. We report a stable and highly active intermetallic nickel silicide catalyst that can be used for hydrogenations of a wide range of unsaturated compounds. The catalyst is prepared via a straightforward procedure using SiO2 as the silicon atom source. The process involves thermal reduction of Si–O bonds in the presence of Ni nanoparticles at temperatures below 1000°C. The presence of silicon as a secondary component in the nickel metal lattice plays the key role in its properties and is of crucial importance for improved catalytic activity. This novel catalyst allows for efficient reduction of nitroarenes, carbonyls, nitriles, N-containing heterocycles, and unsaturated carbon–carbon bonds. Moreover, the reported catalyst can be used for oxidation reactions in the presence of molecular oxygen and is capable of promoting acceptorless dehydrogenation of unsaturated N-containing heterocycles, opening avenues for H2 storage in organic compounds. The generality of the nickel silicide catalyst is demonstrated in the hydrogenation of over a hundred of structurally diverse unsaturated compounds. The wide application scope and high catalytic activity of this novel catalyst make it a nice alternative to known general hydrogenation catalysts, such as Raney nickel and noble metal–based catalysts. PMID:29888329

Intermetallic nickel silicide nanocatalyst-A non-noble metal-based general hydrogenation catalyst.

PubMed

Ryabchuk, Pavel; Agostini, Giovanni; Pohl, Marga-Martina; Lund, Henrik; Agapova, Anastasiya; Junge, Henrik; Junge, Kathrin; Beller, Matthias

2018-06-01

Hydrogenation reactions are essential processes in the chemical industry, giving access to a variety of valuable compounds including fine chemicals, agrochemicals, and pharmachemicals. On an industrial scale, hydrogenations are typically performed with precious metal catalysts or with base metal catalysts, such as Raney nickel, which requires special handling due to its pyrophoric nature. We report a stable and highly active intermetallic nickel silicide catalyst that can be used for hydrogenations of a wide range of unsaturated compounds. The catalyst is prepared via a straightforward procedure using SiO 2 as the silicon atom source. The process involves thermal reduction of Si-O bonds in the presence of Ni nanoparticles at temperatures below 1000°C. The presence of silicon as a secondary component in the nickel metal lattice plays the key role in its properties and is of crucial importance for improved catalytic activity. This novel catalyst allows for efficient reduction of nitroarenes, carbonyls, nitriles, N-containing heterocycles, and unsaturated carbon-carbon bonds. Moreover, the reported catalyst can be used for oxidation reactions in the presence of molecular oxygen and is capable of promoting acceptorless dehydrogenation of unsaturated N-containing heterocycles, opening avenues for H 2 storage in organic compounds. The generality of the nickel silicide catalyst is demonstrated in the hydrogenation of over a hundred of structurally diverse unsaturated compounds. The wide application scope and high catalytic activity of this novel catalyst make it a nice alternative to known general hydrogenation catalysts, such as Raney nickel and noble metal-based catalysts.

Theoretical Heterogeneous Catalysis: Scaling Relationships and Computational Catalyst Design.

PubMed

Greeley, Jeffrey

2016-06-07

Scaling relationships are theoretical constructs that relate the binding energies of a wide variety of catalytic intermediates across a range of catalyst surfaces. Such relationships are ultimately derived from bond order conservation principles that were first introduced several decades ago. Through the growing power of computational surface science and catalysis, these concepts and their applications have recently begun to have a major impact in studies of catalytic reactivity and heterogeneous catalyst design. In this review, the detailed theory behind scaling relationships is discussed, and the existence of these relationships for catalytic materials ranging from pure metal to oxide surfaces, for numerous classes of molecules, and for a variety of catalytic surface structures is described. The use of the relationships to understand and elucidate reactivity trends across wide classes of catalytic surfaces and, in some cases, to predict optimal catalysts for certain chemical reactions, is explored. Finally, the observation that, in spite of the tremendous power of scaling relationships, their very existence places limits on the maximum rates that may be obtained for the catalyst classes in question is discussed, and promising strategies are explored to overcome these limitations to usher in a new era of theory-driven catalyst design.

Steam reforming of commercial ultra-low sulphur diesel

NASA Astrophysics Data System (ADS)

Boon, Jurriaan; van Dijk, Eric; de Munck, Sander; van den Brink, Ruud

Two main routes for small-scale diesel steam reforming exist: low-temperature pre-reforming followed by well-established methane steam reforming on the one hand and direct steam reforming on the other hand. Tests with commercial catalysts and commercially obtained diesel fuels are presented for both processes. The fuels contained up to 6.5 ppmw sulphur and up to 4.5 vol.% of biomass-derived fatty acid methyl ester (FAME). Pre-reforming sulphur-free diesel at around 475 °C has been tested with a commercial nickel catalyst for 118 h without observing catalyst deactivation, at steam-to-carbon ratios as low as 2.6. Direct steam reforming at temperatures up to 800 °C has been tested with a commercial precious metal catalyst for a total of 1190 h with two catalyst batches at steam-to-carbon ratios as low as 2.5. Deactivation was neither observed with lower steam-to-carbon ratios nor for increasing sulphur concentration. The importance of good fuel evaporation and mixing for correct testing of catalysts is illustrated. Diesel containing biodiesel components resulted in poor spray quality, hence poor mixing and evaporation upstream, eventually causing decreasing catalyst performance. The feasibility of direct high temperature steam reforming of commercial low-sulphur diesel has been demonstrated.

Enhancing Zeolite Performance by Catalyst Shaping in a Mesoscale Continuous-Flow Diels-Alder Process.

PubMed

Seghers, Sofie; Lefevere, Jasper; Mullens, Steven; De Vylder, Anton; Thybaut, Joris W; Stevens, Christian V

2018-03-26

In contrast to most lab-scale batch procedures, a continuous-flow implementation requires a thorough consideration of the solid catalyst design. In a previous study, irregular zeolite pellets were applied in a miniaturized continuous-flow reactor for the Diels-Alder reaction in the construction of norbornene scaffolds. After having faced the challenges of continuous operation, the aim of this study is to exploit catalyst structuring. To this end, microspheres with high uniformity and various sphere diameters were synthesized according to the vibrational droplet coagulation method. The influence of the use of these novel zeolite shapes in a mesoscale continuous-flow Diels-Alder process of cyclopentadiene and methyl acrylate is discussed. An impressive enhancement of catalyst lifetime is demonstrated, as even after a doubled process time of 14 h, the microspheres still exceeded the conversion after 7 h when using zeolite pellets by 30 %. A dual reason is found for this beneficial impact of catalyst shaping. The significant improvement in catalyst longevity can be attributed to the interplay of the chemical composition and the porosity structure of the microspheres. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Cl-Assisted Large Scale Synthesis of Cm-Scale Buckypapers of Fe₃C-Filled Carbon Nanotubes with Pseudo-Capacitor Properties: The Key Role of SBA-16 Catalyst Support as Synthesis Promoter.

PubMed

Boi, Filippo S; He, Yi; Wen, Jiqiu; Wang, Shanling; Yan, Kai; Zhang, Jingdong; Medranda, Daniel; Borowiec, Joanna; Corrias, Anna

2017-10-23

We show a novel chemical vapour deposition (CVD) approach, in which the large-scale fabrication of ferromagnetically-filled cm-scale buckypapers is achieved through the deposition of a mesoporous supported catalyst (SBA-16) on a silicon substrate. We demonstrate that SBA-16 has the crucial role of promoting the growth of carbon nanotubes (CNTs) on a horizontal plane with random orientation rather than in a vertical direction, therefore allowing a facile fabrication of cm-scale CNTs buckypapers free from the onion-crust by-product observed on the buckypaper-surface in previous reports. The morphology and composition of the obtained CNTs-buckypapers are analyzed in detail by scanning electron microscopy (SEM), Energy Dispersive X-ray (EDX), transmission electron microscopy (TEM), high resolution TEM (HRTEM), and thermogravimetric analysis (TGA), while structural analysis is performed by Rietveld Refinement of XRD data. The room temperature magnetic properties of the produced buckypapers are also investigated and reveal the presence of a high coercivity of 650 Oe. Additionally, the electrochemical performances of these buckypapers are demonstrated and reveal a behavior that is compatible with that of a pseudo-capacitor (resistive-capacitor) with better performances than those presented in other previously studied layered-buckypapers of Fe-filled CNTs, obtained by pyrolysis of dichlorobenzene-ferrocene mixtures. These measurements indicate that these materials show promise for applications in energy storage systems as flexible electrodes.

Bioleaching of nickel from spent petroleum catalyst using Acidithiobacillus thiooxidans DSM- 11478.

PubMed

Sharma, Mohita; Bisht, Varsha; Singh, Bina; Jain, Pratiksha; Mandal, Ajoy K; Lal, Banwari; Sarma, Priyangshu M

2015-06-01

The present work deals with optimization of culture conditions and process parameters for bioleaching of spent petroleum catalyst collected from a petroleum refinery. The efficacy of Ni bioleaching from spent petroleum catalyst was determined using pure culture of Acidithiobacillus thiooxidans DSM- 11478. The culture conditions of pH, temperature and headspace volume to media volume ratio were optimized. EDX analysis was done to confirm the presence of Ni in the spent catalyst after roasting it to decoke its surface. The optimum temperature for A. thiooxidans DSM-11478 growth was found to be 32 degrees C. The enhanced recovery of nickel at very low pH was attributed to the higher acidic strength of sulfuric acid produced in the culture medium by the bacterium. During the bioleaching process, 89% of the Ni present in the catalyst waste could be successfully recovered in optimized conditions. This environment friendly bioleaching process proved efficient than the chemical method. Taking leads from the lab scale results, bioleaching in larger volumes (1, 5 and 10 L) was also performed to provide guidelines for taking up this technology for in situ industrial waste management.

Novel Solar Photocatalytic Reactor for Wastewater Treatment

NASA Astrophysics Data System (ADS)

Sutisna; Rokhmat, M.; Wibowo, E.; Murniati, R.; Khairurrijal; Abdullah, M.

2017-07-01

A new solar photocatalytic reactor (photoreactor) using TiO2 nanoparticles coated onto plastic granules has been designed. Catalyst granules are placed into the cavity of a reactor panel made of glass. A pump is used to circulate wastewater in the photoreactor. Methylene blue (MB) dissolved in water was chosen as the wastewater model. The performance of the photoreactor was evaluated based on changes in MB concentration with respect to time. The photoreactor showed a good performance by degrading 10 L of MB solution up to 96.54% after 48 h of solar irradiation. The photoreactor was scaled up by enlarging the panel area to twice its original size. The increase in the surface area of the reactor panel and therefore of the mass of catalyst granules and reactor volume led to a three-fold increase of the photodegradation rate. In addition, the MB degradation kinetics were also studied. Data analysis confirmed the applicability of the pseudo-first-order Langmuir-Hinshelwood model. The proposed photoreactor has great potential for use in large-scale wastewater treatment.

A porous proton-relaying metal-organic framework material that accelerates electrochemical hydrogen evolution

DOE PAGES

Hod, Idan; Deria, Pravas; Bury, Wojciech; ...

2015-09-14

The availability of efficient hydrogen evolution reaction (HER) catalysts is of high importance for solar fuel technologies aimed at reducing future carbon emissions. Even though Pt electrodes are excellent HER electrocatalysts, commercialization of large-scale hydrogen production technology requires finding an equally efficient, low-cost, earth-abundant alternative. Here, high porosity, metal-organic framework (MOF) films have been used as scaffolds for the deposition of a Ni-S electrocatalyst. Compared with an MOF-free Ni-S, the resulting hybrid materials exhibit significantly enhanced performance for HER from aqueous acid, decreasing the kinetic overpotential by more than 200 mV at a benchmark current density of 10 mA cm −2. In conclusion,more » although the initial aim was to improve electrocatalytic activity by greatly boosting the active area of the Ni-S catalyst, the performance enhancements instead were found to arise primarily from the ability of the proton-conductive MOF to favourably modify the immediate chemical environment of the sulfide-based catalyst.« less

A porous proton-relaying metal-organic framework material that accelerates electrochemical hydrogen evolution

PubMed Central

Hod, Idan; Deria, Pravas; Bury, Wojciech; Mondloch, Joseph E.; Kung, Chung-Wei; So, Monica; Sampson, Matthew D.; Peters, Aaron W.; Kubiak, Cliff P.; Farha, Omar K.; Hupp, Joseph T.

2015-01-01

The availability of efficient hydrogen evolution reaction (HER) catalysts is of high importance for solar fuel technologies aimed at reducing future carbon emissions. Even though Pt electrodes are excellent HER electrocatalysts, commercialization of large-scale hydrogen production technology requires finding an equally efficient, low-cost, earth-abundant alternative. Here, high porosity, metal-organic framework (MOF) films have been used as scaffolds for the deposition of a Ni-S electrocatalyst. Compared with an MOF-free Ni-S, the resulting hybrid materials exhibit significantly enhanced performance for HER from aqueous acid, decreasing the kinetic overpotential by more than 200 mV at a benchmark current density of 10 mA cm−2. Although the initial aim was to improve electrocatalytic activity by greatly boosting the active area of the Ni-S catalyst, the performance enhancements instead were found to arise primarily from the ability of the proton-conductive MOF to favourably modify the immediate chemical environment of the sulfide-based catalyst. PMID:26365764

Mild Deoxygenation of Aromatic Ketones and Aldehydes over Pd/C Using Polymethylhydrosiloxane as the Reducing Agent**

PubMed Central

Volkov, Alexey; Gustafson, Karl P J; Tai, Cheuk-Wai; Verho, Oscar; Bäckvall, Jan-E; Adolfsson, Hans

2015-01-01

Herein, a practical and mild method for the deoxygenation of a wide range of benzylic aldehydes and ketones is described, which utilizes heterogeneous Pd/C as the catalyst together with the green hydride source, polymethylhydrosiloxane. The developed catalytic protocol is scalable and robust, as exemplified by the deoxygenation of ethyl vanillin, which was performed on a 30 mmol scale in an open-to-air setup using only 0.085 mol % Pd/C catalyst to furnish the corresponding deoxygenated product in 93 % yield within 3 hours at room temperature. Furthermore, the Pd/C catalyst was shown to be recyclable up to 6 times without any observable decrease in efficiency and it exhibited low metal leaching under the reaction conditions. PMID:25728614

Demonstration of Selective Catalytic Reduction (SCR) technology for the control of nitrogen oxide (NO{sub x}) emissions from high-sulfur coal-fired boilers: Innovative Clean Coal Technology (ICCT). Quarterly report No. 7, January--March 1992

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

1992-05-01

The objective of this project is to demonstrate and evaluate commercially available Selective Catalytic Reduction (SCR) catalysts from US, Japanese and European catalyst suppliers on a high-sulfur US coal-fired boiler. SCR is a post-combustion nitrogen oxide (NO{sub x}) control technology that involves injecting ammonia into the flue gas generated from coal combustion in an electric utility boiler. The flue gas containing ammonia is then passed through a reactor that contains a specialized catalyst. In the presence of the catalyst, the amonia reacts with NO{sub x} to convert it to nitrogen and water vapor. Although SCR is widely practiced in Japanmore » and Europe, there are numerous technical uncertainties associated with applying SCR to US coals. These uncertainties include: (1) potential catalyst deactivation due to poisoning by trace metal species present in US coals that are not present in other fuels. (2) performance of the technology and effects on the balance-of-plant equipment in the presence of high amounts of SO, and SO{sub 3}. (3) performance of a wide variety of SCR catalyst compositions, geometries and methods of manufacture under typical high-sulfur coal-fired utility operating conditions. These uncertainties will be explored by constructing a series of small-scale SCR reactors and simultaneously exposing different SCR catalysts to flue gas derived from the combustion of high sulfur US coal. The demonstration will be performed at Gulf Power Company`s Plant Crist Unit No. 5 (75 MW capacity) near Pensacola, Florida. The project will be funded by the US Department of Energy (DOE), Southern Company Services, Inc. (SCS on behalf of the entire Southern electric system), and the Electric Power Research Institute.« less

The economic production of alcohol fuels from coal-derived synthesis gas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kugler, E.L.; Dadyburjor, D.B.; Yang, R.Y.K.

1995-12-31

The objectives of this project are to discover, (1) study and evaluate novel heterogeneous catalytic systems for the production of oxygenated fuel enhancers from synthesis gas. Specifically, alternative methods of preparing catalysts are to be investigated, and novel catalysts, including sulfur-tolerant ones, are to be pursued. (Task 1); (2) explore, analytically and on the bench scale, novel reactor and process concepts for use in converting syngas to liquid fuel products. (Task 1); (3) simulate by computer the most energy efficient and economically efficient process for converting coal to energy, with primary focus on converting syngas to fuel alcohols. (Task 2);more » (4) develop on the bench scale the best holistic combination of chemistry, catalyst, reactor and total process configuration integrated with the overall coal conversion process to achieve economic optimization for the conversion of syngas to liquid products within the framework of achieving the maximum cost effective transformation of coal to energy equivalents. (Tasks 1 and 2); and (5) evaluate the combustion, emission and performance characteristics of fuel alcohols and blends of alcohols with petroleum-based fuels. (Task 2)« less

Resolving Electrode Morphology’s Impact on Platinum Group Metal-Free Cathode Performance Using Nano-CT of 3D Hierarchical Pore and Ionomer Distribution

DOE Office of Scientific and Technical Information (OSTI.GOV)

Komini Babu, Siddharth; Chung, Hoon T.; Zelenay, Piotr

This paper reports on the characterization of polymer electrolyte fuel cell (PEFC) cathodes featuring a platinum group metal-free (PGM-free) catalyst using nano-scale resolution X-ray computed tomography (nano-CT) and morphological analysis. PGM-free PEFC cathodes have gained significant interest in the past decade since they have the potential to dramatically reduce PEFC costs by eliminating the large platinum (Pt) raw material cost. However, several challenges remain before they are commercially viable. Since these catalysts have lower volumetric activity, the PGM-free cathodes are thicker and are subject to increased gas and proton transport resistances that reduce the performance. To better understand the efficacymore » of the catalyst and improve electrode performance, a detailed understanding the correlation between electrode fabrication, morphology, and performance is crucial. In this work, the pore/solid structure and the ionomer distribution was resolved in three dimensions (3D) using nano-CT for three PGM-free electrodes of varying Nafion® loading. The associated transport properties were evaluated from pore/particlescale simulations within the nano-CT imaged structure. These characterizations are then used to elucidate the microstructural origins of the dramatic changes in fuel cell performance with varying Nafion® ionomer loading. We show that this is primarily a result of distinct changes in ionomer’s spatial distribution. The significant impact of electrode morphology on performance highlights the importance of PGM-free electrode development in concert with efforts to improve catalyst activity and durability.« less

Resolving Electrode Morphology’s Impact on Platinum Group Metal-Free Cathode Performance Using Nano-CT of 3D Hierarchical Pore and Ionomer Distribution

DOE PAGES

Komini Babu, Siddharth; Chung, Hoon T.; Zelenay, Piotr; ...

2016-11-02

This paper reports on the characterization of polymer electrolyte fuel cell (PEFC) cathodes featuring a platinum group metal-free (PGM-free) catalyst using nano-scale resolution X-ray computed tomography (nano-CT) and morphological analysis. PGM-free PEFC cathodes have gained significant interest in the past decade since they have the potential to dramatically reduce PEFC costs by eliminating the large platinum (Pt) raw material cost. However, several challenges remain before they are commercially viable. Since these catalysts have lower volumetric activity, the PGM-free cathodes are thicker and are subject to increased gas and proton transport resistances that reduce the performance. To better understand the efficacymore » of the catalyst and improve electrode performance, a detailed understanding the correlation between electrode fabrication, morphology, and performance is crucial. In this work, the pore/solid structure and the ionomer distribution was resolved in three dimensions (3D) using nano-CT for three PGM-free electrodes of varying Nafion® loading. The associated transport properties were evaluated from pore/particlescale simulations within the nano-CT imaged structure. These characterizations are then used to elucidate the microstructural origins of the dramatic changes in fuel cell performance with varying Nafion® ionomer loading. We show that this is primarily a result of distinct changes in ionomer’s spatial distribution. The significant impact of electrode morphology on performance highlights the importance of PGM-free electrode development in concert with efforts to improve catalyst activity and durability.« less

Indirect Liquefaction of Coal-Biomass Mixture for Production of Jet Fuel with High Productivity and Selectivity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gangwal, Santosh K; McCabe, Kevin

Coal to liquids (CTL) and coal-biomass to liquids (CBTL) processes were advanced by testing and demonstrating Southern Research’s sulfur tolerant nickel-based reforming catalyst and Chevron’s highly selective and active cobalt-zeolite hybrid Fischer-Tropsch (FT) catalyst to clean, upgrade and convert syngas predominantly to jet fuel range hydrocarbon liquids, thereby minimizing expensive cleanup and wax upgrading operations. The National Carbon Capture Center (NCCC) operated by Southern Company (SC) at Wilsonville, Alabama served as the host site for the gasifier slip-stream and simulated syngas testing/demonstration. Reformer testing was performed to (1) reform tar and light hydrocarbons, (2) decompose ammonia in the presence H2S,more » and (3) deliver the required H2 to CO ratio for FT synthesis. FT Testing was performed to produce a product primarily containing C5-C20 liquid hydrocarbons and no C21+ waxy hydrocarbons with productivity greater than 0.7 gC5+/g catalyst/h, and at least 70% diesel and jet fuel range (C8-C20) hydrocarbon selectivity in the liquid product. A novel heat-exchange reactor system was employed to enable the use of the highly active FT catalyst and larger diameter reactors that results in cost reduction for commercial systems. Following laboratory development and testing, SR’s laboratory reformer was modified to operate in a Class 1 Div. 2 environment, installed at NCCC, and successfully tested for 125 hours using raw syngas. The catalyst demonstrated near equilibrium reforming (~90%) of methane and complete reforming/decomposition of tar and ammonia in the presence of up to 380 ppm H2S. For FT synthesis, SR modified and utilized a bench scale skid mounted FT reactor system (SR-CBTL test rig) that was fully integrated with a slip stream from SC/NCCC’s transport gasifier (TRIG). The test-rig developed in a previous project (DE-FE0010231) was modified to receive up to 7.5 lb/h raw syngas augmented with bottled syngas to adjust the H2/CO molar ratio to 2, clean it to cobalt FT catalyst specifications, and produce liquid FT products at the design capacity of up to 6 L/day. Promising Chevron catalyst candidates in the size range from 70-200 μm were loaded onto SR’s 2-inch ID and 4-inch ID bench-scale reactors utilizing IntraMicron’s micro-fiber entrapped catalyst (MFEC) heat exchange reactor technology. During 2 test campaigns, the FT reactors were successfully demonstrated at NCCC using syngas for ~420 hours. The catalyst did not experience deactivation during the tests. SR’s thermo-syphon heat removal system maintained reactor operating temperature along the axis to within ±4 °C. The experiments gave a steady catalyst productivity of 0.7-0.8 g/g catalyst/h, liquid hydrocarbon selectivity of ~75%, and diesel and jet fuel range hydrocarbon selectivity in the liquid product as high as 85% depending on process conditions. A preliminary techno-economic evaluation showed that the SR technology-based 50,000 bpd plant had a 10 % lower total plant cost compared to a conventional slurry reactor based plant. Furthermore, because of the modular nature of the SR technology, it was shown that the total plant cost advantage increases to >35 % as the plant is scaled down to 1000 bpd.« less

Innovative Clean Coal Technology (ICCT). Demonstration of Selective Catalytic Reduction (SCR) technology for the control of nitrogen oxide (NO{sub x}) emissions from high-sulfur coal-fired boilers: Volume 1. Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

NONE

1996-10-01

The objective of this project is to demonstrate and evaluate commercially available Selective Catalytic Reduction (SCR) catalysts from U.S., Japanese and European catalyst suppliers on a high-sulfur U.S. coal-fired boiler. SCR is a post-combustion nitrogen oxide (NO.) control technology that involves injecting ammonia into the flue gas generated from coal combustion in an electric utility boiler. The flue gas containing ammonia is then passed through a reactor that contains a specialized catalyst. In the presence of the catalyst, the ammonia reacts with NO. to convert it to nitrogen and water vapor. Although SCR is widely practiced in Japan and Europemore » on gas-, oil-, and low-sulfur coal- fired boilers, there are several technical uncertainties associated with applying SCR to U.S. coals. These uncertainties include: 1) potential catalyst deactivation due to poisoning by trace metal species present in U.S. coals that are not present in other fuels. 2) performance of the technology and effects on the balance-of- plant equipment in the presence of high amounts of SO{sub 2} and SO{sub 3}. 3) performance of a wide variety of SCR catalyst compositions, geometries and methods of manufacturer under typical high-sulfur coal-fired utility operating conditions. These uncertainties were explored by operating nine small-scale SCR reactors and simultaneously exposing different SCR catalysts to flue gas derived from the combustion of high sulfur U.S. coal. In addition, the test facility operating experience provided a basis for an economic study investigating the implementation of SCR technology.« less

Nano-Array Integrated Structured Catalysts: A New Paradigm upon Conventional Wash-Coated Monolithic Catalysts?

DOE PAGES

Weng, Junfei; Lu, Xingxu; Gao, Pu-Xian

2017-08-28

The monolithic catalyst, namely the structured catalyst, is one of the important categories of catalysts used in various fields, especially in catalytic exhaust after-treatment. Despite its successful application in conventional wash-coated catalysts in both mobile and stationary catalytic converters, washcoat-based technologies are facing multi-fold challenges, including: (1) high Pt-group metals (PGM) material loading being required, driving the market prices; (2) less-than ideal distribution of washcoats in typically square-shaped channels associated with pressure drop sacrifice; and (3) far from clear correlations between macroscopic washcoat structures and their catalytic performance. To tackle these challenges, the well-defined nanostructure array (nano-array)-integrated structured catalysts whichmore » we invented and developed recently have been proven to be a promising class of cost-effective and efficient devices that may complement or substitute wash-coated catalysts. This new type of structured catalysts is composed of honeycomb-structured monoliths, whose channel surfaces are grown in situ with a nano-array forest made of traditional binary transition metal oxide support such as Al 2O 3, CeO 2, Co 3O 4, MnO 2, TiO 2, and ZnO, or newer support materials including perovskite-type ABO3 structures, for example LaMnO 3, LaCoO 3, LaNiO, and LaFeO 3. The integration strategy parts from the traditional washcoat technique. Instead, an in situ nanomaterial assembly method is utilized, such as a hydro (solva-) thermal synthesis approach, in order to create sound structure robustness, and increase ease and complex-shaped substrate adaptability. Specifically, the critical fabrication procedures for nano-array structured catalysts include deposition of seeding layer, in situ growth of nano-array, and loading of catalytic materials. The generic methodology utilization in both the magnetic stirring batch process and continuous flow reactor synthesis offers the nano-array catalysts with great potential to be scaled up readily and cost-effectively. The tunability of the structure and catalytic performance could be achieved through morphology and geometry adjustment and guest atoms and defect manipulation, as well as composite nano-array catalyst manufacture. Excellent stabilities under various conditions were also present compared to conventional wash-coated catalysts.« less

Nano-Array Integrated Structured Catalysts: A New Paradigm upon Conventional Wash-Coated Monolithic Catalysts?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Weng, Junfei; Lu, Xingxu; Gao, Pu-Xian

The monolithic catalyst, namely the structured catalyst, is one of the important categories of catalysts used in various fields, especially in catalytic exhaust after-treatment. Despite its successful application in conventional wash-coated catalysts in both mobile and stationary catalytic converters, washcoat-based technologies are facing multi-fold challenges, including: (1) high Pt-group metals (PGM) material loading being required, driving the market prices; (2) less-than ideal distribution of washcoats in typically square-shaped channels associated with pressure drop sacrifice; and (3) far from clear correlations between macroscopic washcoat structures and their catalytic performance. To tackle these challenges, the well-defined nanostructure array (nano-array)-integrated structured catalysts whichmore » we invented and developed recently have been proven to be a promising class of cost-effective and efficient devices that may complement or substitute wash-coated catalysts. This new type of structured catalysts is composed of honeycomb-structured monoliths, whose channel surfaces are grown in situ with a nano-array forest made of traditional binary transition metal oxide support such as Al 2O 3, CeO 2, Co 3O 4, MnO 2, TiO 2, and ZnO, or newer support materials including perovskite-type ABO3 structures, for example LaMnO 3, LaCoO 3, LaNiO, and LaFeO 3. The integration strategy parts from the traditional washcoat technique. Instead, an in situ nanomaterial assembly method is utilized, such as a hydro (solva-) thermal synthesis approach, in order to create sound structure robustness, and increase ease and complex-shaped substrate adaptability. Specifically, the critical fabrication procedures for nano-array structured catalysts include deposition of seeding layer, in situ growth of nano-array, and loading of catalytic materials. The generic methodology utilization in both the magnetic stirring batch process and continuous flow reactor synthesis offers the nano-array catalysts with great potential to be scaled up readily and cost-effectively. The tunability of the structure and catalytic performance could be achieved through morphology and geometry adjustment and guest atoms and defect manipulation, as well as composite nano-array catalyst manufacture. Excellent stabilities under various conditions were also present compared to conventional wash-coated catalysts.« less

A Simple Primary Amine Catalyst for Enantioselective α-Hydroxylations and α-Fluorinations of Branched Aldehydes

PubMed Central

Witten, Michael R.; Jacobsen, Eric N.

2016-01-01

A new primary amine catalyst for the asymmetric α-hydroxylation and α-fluorination of α-branched aldehydes is described. The products of the title transformations are generated in excellent yields and with high enantioselectivities. Both processes can be performed within short reaction times and on gram scale. The similarity in the results obtained in both reactions, combined with computational evidence, implies a common basis for stereoinduction and the possibility of a general catalytic mechanism for α-functionalizations. Promising initial results in α-amination and α-chlorination reactions support this hypothesis. PMID:25952578

Direct evidence of atomic-scale structural fluctuations in catalyst nanoparticles.

PubMed

Lin, Pin Ann; Gomez-Ballesteros, Jose L; Burgos, Juan C; Balbuena, Perla B; Natarajan, Bharath; Sharma, Renu

2017-05-01

Rational catalyst design requires an atomic scale mechanistic understanding of the chemical pathways involved in the catalytic process. A heterogeneous catalyst typically works by adsorbing reactants onto its surface, where the energies for specific bonds to dissociate and/or combine with other species (to form desired intermediate or final products) are lower. Here, using the catalytic growth of single-walled carbon nanotubes (SWCNTs) as a prototype reaction, we show that the chemical pathway may in-fact involve the entire catalyst particle, and can proceed via the fluctuations in the formation and decomposition of metastable phases in the particle interior. We record in situ and at atomic resolution, the dynamic phase transformations occurring in a Cobalt catalyst nanoparticle during SWCNT growth, using a state-of-the-art environmental transmission electron microscope (ETEM). The fluctuations in catalyst carbon content are quantified by the automated, atomic-scale structural analysis of the time-resolved ETEM images and correlated with the SWCNT growth rate. We find the fluctuations in the carbon concentration in the catalyst nanoparticle and the fluctuations in nanotube growth rates to be of complementary character. These findings are successfully explained by reactive molecular dynamics (RMD) simulations that track the spatial and temporal evolution of the distribution of carbon atoms within and on the surface of the catalyst particle. We anticipate that our approach combining real-time, atomic-resolution image analysis and molecular dynamics simulations will facilitate catalyst design, improving reaction efficiencies and selectivity towards the growth of desired structure.

Subnanometer Molybdenum Sulfide on Carbon Nanotubes as a Highly Active and Stable Electrocatalyst for Hydrogen Evolution Reaction.

PubMed

Li, Ping; Yang, Zhi; Shen, Juanxia; Nie, Huagui; Cai, Qiran; Li, Luhua; Ge, Mengzhan; Gu, Cancan; Chen, Xi'an; Yang, Keqin; Zhang, Lijie; Chen, Ying; Huang, Shaoming

2016-02-10

Electrochemically splitting water for hydrogen evolution reaction (HER) has been viewed as a promising approach to produce renewable and clean hydrogen energy. However, searching for cheap and efficient HER electrocatalysts to replace the currently used Pt-based catalysts remains an urgent task. Herein, we develop a one-step carbon nanotube (CNT) assisted synthesis strategy with CNTs' strong adsorbability to mediate the growth of subnanometer-sized MoS(x) on CNTs. The subnanometer MoS(x)-CNT hybrids achieve a low overpotential of 106 mV at 10 mA cm(-2), a small Tafel slope of 37 mV per decade, and an unprecedentedly high turnover frequency value of 18.84 s(-1) at η = 200 mV among all reported non-Pt catalysts in acidic conditions. The superior performance of the hybrid catalysts benefits from the presence of a higher number of active sites and the abundant exposure of unsaturated S atoms rooted in the subnanometer structure, demonstrating a new class of subnanometer-scale catalysts.

Molecular-beam, mass-spectrometric studies of wood vapor and model compounds over HZSM-5 catalyst

NASA Astrophysics Data System (ADS)

Evans, Robert J.; Milne, Thomas A.

1987-11-01

The use of molecular beam mass spectrometry (MBMS) for the real time screening of wood pyrolysis product conversion over Mobil's HZSM-5 catalyst allows the evaluation of the performance of different catalysts, reaction conditions and feedstocks. This information can help guide more extensive testing at the bench scale level and provide insight into the chemistry of conversion. The following conclusions can be drawn from the work to date: (1) there can be no breakthrough of primary wood vapor organics until the weight of wood/weight of the catalyst is 1; (2) there are few intermediates from wood on the way to alkenes, light aromatics, and naphthalenes; (3) the light aromatics/alkenes ration is 1 for the nonoptimized conditions studied to date; (4) much of the oxygen is favorably rejected as CO and CO sub 2; (5) the coke yield is about 10 percent in these experiments; and (6) methanol is a poor model for wood because the mechanism of hydrocarbon formation is apparently different.

Aerosol processing: a wind of innovation in the field of advanced heterogeneous catalysts.

PubMed

Debecker, Damien P; Le Bras, Solène; Boissière, Cédric; Chaumonnot, Alexandra; Sanchez, Clément

2018-06-05

Aerosol processing is long known and implemented industrially to obtain various types of divided materials and nanomaterials. The atomisation of a liquid solution or suspension produces a mist of aerosol droplets which can then be transformed via a diversity of processes including spray-drying, spray pyrolysis, flame spray pyrolysis, thermal decomposition, micronisation, gas atomisation, etc. The attractive technical features of these aerosol processes make them highly interesting for the continuous, large scale, and tailored production of heterogeneous catalysts. Indeed, during aerosol processing, each liquid droplet undergoes well-controlled physical and chemical transformations, allowing for example to dry and aggregate pre-existing solid particles or to synthesise new micro- or nanoparticles from mixtures of molecular or colloidal precursors. In the last two decades, more advanced reactive aerosol processes have emerged as innovative means to synthesise tailored-made nanomaterials with tunable surface properties, textures, compositions, etc. In particular, the "aerosol-assisted sol-gel" process (AASG) has demonstrated tremendous potential for the preparation of high-performance heterogeneous catalysts. The method is mainly based on the low-cost, scalable, and environmentally benign sol-gel chemistry process, often coupled with the evaporation-induced self-assembly (EISA) concept. It allows producing micronic or submicronic, inorganic or hybrid organic-inorganic particles bearing tuneable and calibrated porous structures at different scales. In addition, pre-formed nanoparticles can be easily incorporated or formed in a "one-pot" bottom-up approach within the porous inorganic or hybrid spheres produced by such spray drying method. Thus, multifunctional catalysts with tailored catalytic activities can be prepared in a relatively simple way. This account is an overview of aerosol processed heterogeneous catalysts which demonstrated interesting performance in various relevant chemical reactions like isomerisation, hydrogenation, olefin metathesis, pollutant total oxidation, selective oxidation, CO2 methanation, etc. A short survey of patents and industrial applications is also presented. Our objective is to demonstrate the tremendous possibilities offered by the coupling between bottom up synthesis routes and these aerosol processing technologies which will most probably represent a major route of innovation in the mushrooming field of catalyst preparation research.

Tuning the surface properties of novel ternary iron(III) fluoride-based catalysts using the template effect of the matrix.

PubMed

Guo, Ying; Lippitz, Andreas; Saftien, Paul; Unger, Wolfgang E S; Kemnitz, Erhard

2015-03-21

Sol-gel prepared ternary FeF3-MgF2 materials have become promising heterogeneous catalysts due to their porosity and surface Lewis/Brønsted acidity (bi-acidity). Despite the good catalytic performance, nanoscopic characterisations of this type of material are still missing and the key factors controlling the surface properties have not yet been identified, impeding both a better understanding and further development of ternary fluoride catalysts. In this study, we characterised the interaction between the bi-acidic component (FeF3) and the matrix (MgF2) on the nano-scale. For the first time, the formation pathway of FeF3-MgF2 was profiled and the template effect of MgF2 during the synthesis process was discovered. Based on these new insights two novel materials, FeF3-CaF2 and FeF3-SrF2, were established, revealing that with decreasing the atomic numbers (from Sr to Mg), the ternary fluorides exhibited increasing surface acidity and surface area but decreasing pore size. These systematic changes gave rise to a panel of catalysts with tuneable surface and bulk properties either by changing the matrix alkaline earth metal fluoride or by adjusting their ratios to Fe or both. The template effect of the alkaline earth metal fluoride matrix was identified as the most probable key factor determining the surface properties and further influencing the catalytic performance in ternary fluoride based catalysts, and paves the way to targeted design of next-generation catalysts with tunable properties.

Identification of a Catalytically Highly Active Surface Phase for CO Oxidation over PtRh Nanoparticles under Operando Reaction Conditions

NASA Astrophysics Data System (ADS)

Hejral, U.; Franz, D.; Volkov, S.; Francoual, S.; Strempfer, J.; Stierle, A.

2018-03-01

Pt-Rh alloy nanoparticles on oxide supports are widely employed in heterogeneous catalysis with applications ranging from automotive exhaust control to energy conversion. To improve catalyst performance, an atomic-scale correlation of the nanoparticle surface structure with its catalytic activity under industrially relevant operando conditions is essential. Here, we present x-ray diffraction data sensitive to the nanoparticle surface structure combined with in situ mass spectrometry during near ambient pressure CO oxidation. We identify the formation of ultrathin surface oxides by detecting x-ray diffraction signals from particular nanoparticle facets and correlate their evolution with the sample's enhanced catalytic activity. Our approach opens the door for an in-depth characterization of well-defined, oxide-supported nanoparticle based catalysts under operando conditions with unprecedented atomic-scale resolution.

Highly efficient nonprecious metal catalyst prepared with metal–organic framework in a continuous carbon nanofibrous network

PubMed Central

Shui, Jianglan; Chen, Chen; Grabstanowicz, Lauren; Zhao, Dan; Liu, Di-Jia

2015-01-01

Fuel cell vehicles, the only all-electric technology with a demonstrated >300 miles per fill travel range, use Pt as the electrode catalyst. The high price of Pt creates a major cost barrier for large-scale implementation of polymer electrolyte membrane fuel cells. Nonprecious metal catalysts (NPMCs) represent attractive low-cost alternatives. However, a significantly lower turnover frequency at the individual catalytic site renders the traditional carbon-supported NPMCs inadequate in reaching the desired performance afforded by Pt. Unconventional catalyst design aiming at maximizing the active site density at much improved mass and charge transports is essential for the next-generation NPMC. We report here a method of preparing highly efficient, nanofibrous NPMC for cathodic oxygen reduction reaction by electrospinning a polymer solution containing ferrous organometallics and zeolitic imidazolate framework followed by thermal activation. The catalyst offers a carbon nanonetwork architecture made of microporous nanofibers decorated by uniformly distributed high-density active sites. In a single-cell test, the membrane electrode containing such a catalyst delivered unprecedented volumetric activities of 3.3 A⋅cm−3 at 0.9 V or 450 A⋅cm−3 extrapolated at 0.8 V, representing the highest reported value in the literature. Improved fuel cell durability was also observed. PMID:26261338

Highly efficient nonprecious metal catalyst prepared with metal–organic framework in a continuous carbon nanofibrous network

DOE PAGES

Shui, Jianglan; Chen, Chen; Grabstanowicz, Lauren; ...

2015-08-25

Fuel cell vehicles, the only all-electric technology with a demonstrated >300 miles per fill travel range, use Pt as the electrode catalyst. The high price of Pt creates a major cost barrier for large-scale implementation of polymer electrolyte membrane fuel cells. Nonprecious metal catalysts (NPMCs) represent attractive low-cost alternatives. However, a significantly lower turnover frequency at the individual catalytic site renders the traditional carbon-supported NPMCs inadequate in reaching the desired performance afforded by Pt. Unconventional catalyst design aiming at maximizing the active site density at much improved mass and charge transports is essential for the next-generation NPMC. We report heremore » a method of preparing highly efficient, nanofibrous NPMC for cathodic oxygen reduction reaction by electrospinning a polymer solution containing ferrous organometallics and zeolitic imidazolate framework followed by thermal activation. The catalyst offers a carbon nanonetwork architecture made of microporous nanofibers decorated by uniformly distributed high-density active sites. In a single-cell test, the membrane electrode containing such a catalyst delivered unprecedented volumetric activities of 3.3 A∙cm -3 at 0.9 V or 450 A∙cm -3 extrapolated at 0.8 V, representing the highest reported value in the literature. Improved fuel cell durability was also observed.« less

Highly efficient nonprecious metal catalyst prepared with metal-organic framework in a continuous carbon nanofibrous network.

PubMed

Shui, Jianglan; Chen, Chen; Grabstanowicz, Lauren; Zhao, Dan; Liu, Di-Jia

2015-08-25

Fuel cell vehicles, the only all-electric technology with a demonstrated >300 miles per fill travel range, use Pt as the electrode catalyst. The high price of Pt creates a major cost barrier for large-scale implementation of polymer electrolyte membrane fuel cells. Nonprecious metal catalysts (NPMCs) represent attractive low-cost alternatives. However, a significantly lower turnover frequency at the individual catalytic site renders the traditional carbon-supported NPMCs inadequate in reaching the desired performance afforded by Pt. Unconventional catalyst design aiming at maximizing the active site density at much improved mass and charge transports is essential for the next-generation NPMC. We report here a method of preparing highly efficient, nanofibrous NPMC for cathodic oxygen reduction reaction by electrospinning a polymer solution containing ferrous organometallics and zeolitic imidazolate framework followed by thermal activation. The catalyst offers a carbon nanonetwork architecture made of microporous nanofibers decorated by uniformly distributed high-density active sites. In a single-cell test, the membrane electrode containing such a catalyst delivered unprecedented volumetric activities of 3.3 A ⋅ cm(-3) at 0.9 V or 450 A ⋅ cm(-3) extrapolated at 0.8 V, representing the highest reported value in the literature. Improved fuel cell durability was also observed.

Melamine-Schiff base/manganese complex with denritic structure: An efficient catalyst for oxidation of alcohols and one-pot synthesis of nitriles.

PubMed

Kazemnejadi, Milad; Nikookar, Mahsa; Mohammadi, Mohammad; Shakeri, Alireza; Esmaeilpour, Mohsen

2018-05-18

Efficient and selective oxidation of alcohol to the corresponding carbonyl and/or nitrile was carried out by a new water-soluble melamine-based dendritic Mn(III) complex (Melamine-Mn (III)-Schiff base complex) in the presence of 2,4,6-trichloro-1,3,5-triazine (TCT) and O 2 at room temperature. Also, the oxidation of amine to the corresponding nitrile with high selectivity and conversion was performed at room temperature using the current method and high amounts of turnover frequencies (TOFs) were obtained for reactions. This system was also applicable for direct preparation of oxime through oxidation of alcohol. The catalyst was characterized by Fourier-transform infrared (FTIR), ultraviolet-visible (UV-Vis), thermogravimetric analysis (TGA), energy-dispersive X-ray (EDX), X-ray photoelectron spectroscopy (XPS), CHN and inductively coupled plasma (ICP) analyses. Also, oxidation/reduction behavior of the catalyst was studied by cyclic voltammetry (CV). Moreover, chemoselectivity of the catalyst was discussed with various combinations. The water-soluble catalyst could be recycled from the reaction mixture and reused for several times with a very low losing in efficiency. The recovered catalyst was also investigated with various analyses. Finally, gram scale preparation of nitrile was evaluated by present method. Copyright © 2018 Elsevier Inc. All rights reserved.

CO{sub 2} Reuse in Petrochemical Facilities

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jason Trembly; Brian Turk; Maruthi Pavani

2010-12-31

To address public concerns regarding the consequences of climate change from anthropogenic carbon dioxide (CO{sub 2}) emissions, the U.S. Department of Energy's National Energy Technology Laboratory (DOE/NETL) is actively funding a CO{sub 2} management program to develop technologies capable of mitigating CO{sub 2} emissions from power plant and industrial facilities. Over the past decade, this program has focused on reducing the costs of carbon capture and storage technologies. Recently, DOE/NETL launched an alternative CO{sub 2} mitigation program focused on beneficial CO{sub 2} reuse to support the development of technologies that mitigate emissions by converting CO{sub 2} into valuable chemicals andmore » fuels. RTI, with DOE/NETL support, has been developing an innovative beneficial CO{sub 2} reuse process for converting CO{sub 2} into substitute natural gas (SNG) by using by-product hydrogen (H{sub 2)-containing fuel gas from petrochemical facilities. This process leveraged commercial reactor technology currently used in fluid catalytic crackers in petroleum refining and a novel nickel (Ni)-based catalyst developed by RTI. The goal was to generate an SNG product that meets the pipeline specifications for natural gas, making the SNG product completely compatible with the existing natural gas infrastructure. RTI's technology development efforts focused on demonstrating the technical feasibility of this novel CO{sub 2} reuse process and obtaining the necessary engineering information to design a pilot demonstration unit for converting about 4 tons per day (tons/day) of CO{sub 2} into SNG at a suitable host site. This final report describes the results of the Phase I catalyst and process development efforts. The methanation activity of several commercial fixed-bed catalysts was evaluated under fluidized-bed conditions in a bench-scale reactor to identify catalyst performance targets. RTI developed two fluidizable Ni-based catalyst formulations (Cat-1 and Cat-3) that demonstrated equal or better performance than that of commercial methanation catalysts. The Cat-1 and Cat-3 formulations were successfully scaled up using commercial manufacturing equipment at the Sud-Chemie Inc. pilot-plant facility in Louisville, KY. Pilot transport reactor testing with RTI's Cat-1 formulation at Kellog Brown & Root's Technology Center demonstrated the ability of the process to achieve high single-pass CO{sub 2} conversion. Using information acquired from bench- and pilot-scale testing, a basic engineering design package was prepared for a 4-ton/day CO{sub 2} pilot demonstration unit, including process and instrumentation diagrams, equipment list, control philosophy, and preliminary cost estimate.« less

Biosynthesis of Pd-Au alloys on carbon fiber paper: Towards an eco-friendly solution for catalysts fabrication

NASA Astrophysics Data System (ADS)

Zhuang, Zechao; Wang, Feifeng; Naidu, Ravendra; Chen, Zuliang

2015-09-01

Bimetallic nanomaterials with enhanced activity and stability have been extensively studied as emerging catalysts for hydrogen evolution reaction (HER). Expensive and environmentally unfriendly chemical synthesis routes inhibit their large-scale applications. In this work, we developed a facile and green synthesis of Pd-Au alloy nanoparticles (NPs) dispersed on carbon fiber paper (CFP) by plant-mediated bioreduction coupled with self-assembly. Engineering the morphology and composition of bimetallic catalysts synthesized by plant extracts on complex substrate is achieved. The resulting NPs are uniform in shape and have a spherical morphology with an average diameter of ∼180 nm, in which the molar ratio of Au/Pd is near 75:25 and the catalysts loading is about 0.5 mg cm-2. The Pd-Au/CFP hybrid electrode exhibits an excellent HER performance with a Tafel slope of 47 mV dec-1 and an exchange current density of 0.256 mA cm-2. Electrochemical stability tests through long-term potential cycles and potentiostatic electrolysis further confirm the high durability of the electrode. This development offers an efficient and eco-friendly catalysts synthesis route for constructing water-splitting cells and other electrocatalytic devices.

Highly efficient Cu-decorated iron oxide nanocatalyst for low pressure CO 2 conversion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Halder, Avik; Kilianová, Martina; Yang, Bing

We report a nanoparticulate iron oxide based catalyst for CO2 conversion with high efficiency at low pressures and on the effect of the presence of copper on the catalyst's restructuring and its catalytic performance. In situ X-ray scattering reveals the restructuring of the catalyst at the nanometer scale. In situ X-ray absorption near edge structure (XANES) shows the evolution of the composition and oxidation state of the iron and copper components under reaction conditions along with the promotional effect of copper on the chemical transformation of the iron component. X-ray diffraction (XRD), XANES and Raman spectroscopy proved that the startingmore » nano catalyst is composed of iron oxides differing in chemical nature (alpha-Fe2O3, Fe3O4, FeO(OH)) and dimensionality, while the catalyst after CO2 conversion was identified as a mixture of alpha-Fe, Fe3C, and traces of Fe5C2. The significant increase of the rate CO2 is turned over in the presence of copper nanoparticles indicates that Cu nanoparticles activate hydrogen, which after spilling over to the neighbouring iron sites, facilitate a more efficient conversion of carbon dioxide.« less

Microgravity Effects on Chronoamperometric Ammonia Oxidation Reaction at Platinum Nanoparticles on Modified Mesoporous Carbon Supports

NASA Astrophysics Data System (ADS)

Poventud-Estrada, Carlos M.; Acevedo, Raúl; Morales, Camila; Betancourt, Luis; Diaz, Diana C.; Rodriguez, Manuel A.; Larios, Eduardo; José-Yacaman, Miguel; Nicolau, Eduardo; Flynn, Michael; Cabrera, Carlos R.

2017-10-01

The effect of microgravity on the electrochemical oxidation of ammonia at platinum nanoparticles supported on modified mesoporous carbons (MPC) with three different pore diameters (64, 100, and 137 Å) was studied via the chronoamperometric technique in a half-cell. The catalysts were prepared by a H2 reductive process of PtCl6^{4-} in presence of the mesoporous carbon support materials. A microgravity environment was obtained with an average gravity of less than 0.02 g created aboard an airplane performing parabolic maneuvers. Results show the chronoamperommetry of the ammonia oxidation reaction in 1.0 M NH4OH at 0.60 V vs. RHE under microgravity conditions. The current density, in all three catalysts, decreased while in microgravity conditions when compared to ground based experiments. Under microgravity, all three catalysts yielded a decrease in ammonia oxidation reaction current density between 25 to 63% versus terrestrial experimental results, in time scales between 1 and 15 s. The Pt catalyst prepared with mesoporous carbon of 137 Å porous showed the smallest changes, between 25 to 48%. Nanostructuring catalyst materials have an effect on the level of current density decrease under microgravity conditions.

Bond Strength and Reactivity Scales for Lewis Superacid Adducts: A Comparative Study with In(OTf)3 and Al(OTf)3.

PubMed

Compain, Guillaume; Sikk, Lauri; Massi, Lionel; Gal, Jean-François; Duñach, Elisabet

2017-03-17

Metal triflates, often called Lewis superacids, are potent catalysts for organic synthesis. However, the reactivity of a given Lewis superacid toward a given base is difficult to anticipate. A systematic screening of catalysts is often necessary when developing synthetic methodologies. Presented herein is the development of quantitative reactivity and bond strength scales by using mass spectrometry (MS). By applying a collision-induced dissociation (CID) technique to the adducts formed between Lewis superacids Al(OTf) 3 or In(OTf) 3 with a series of amides bases, including monodentate and bidentate ligands, different dissociation pathways were observed. Quantitative relative energy scales were established by performing energy-resolved mass spectrometry (ERMS) analysis on the adducts. ERMS of the adducts affords a bond strength scale when the fragmentation leads to the loss of a ligand, and reactivity scales when the dissociation leads to the C-F bond activation of one triflate anion or the deprotonation of the ligand. Al(OTf) 3 was found to bind stronger to amides than In(OTf) 3 and to provide the most reactive adducts. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Oxidation catalyst

DOEpatents

Ceyer, Sylvia T.; Lahr, David L.

2010-11-09

The present invention generally relates to catalyst systems and methods for oxidation of carbon monoxide. The invention involves catalyst compositions which may be advantageously altered by, for example, modification of the catalyst surface to enhance catalyst performance. Catalyst systems of the present invention may be capable of performing the oxidation of carbon monoxide at relatively lower temperatures (e.g., 200 K and below) and at relatively higher reaction rates than known catalysts. Additionally, catalyst systems disclosed herein may be substantially lower in cost than current commercial catalysts. Such catalyst systems may be useful in, for example, catalytic converters, fuel cells, sensors, and the like.

Metal-Organic Framework-Derived Reduced Graphene Oxide-Supported ZnO/ZnCo2O4/C Hollow Nanocages as Cathode Catalysts for Aluminum-O2 Batteries.

PubMed

Liu, Yisi; Jiang, Hao; Hao, Jiayu; Liu, Yulong; Shen, Haibo; Li, Wenzhang; Li, Jie

2017-09-20

Aluminum-air battery is a promising candidate for large-scale energy applications because of its low cost and high energy density. Remarkably, tremendous efforts have been concentrated on developing efficient and stable cathode electrocatalysts toward the oxygen reduction reaction. In this work, a hydrothermal-calcination approach was utilized to prepare novel reduced graphene oxide (rGO)-supported hollow ZnO/ZnCo 2 O 4 nanoparticle-embedded carbon nanocages (ZnO/ZnCo 2 O 4 /C@rGO) using a zeolitic imidazolate framework (ZIF-67)/graphene oxide/zinc nitrate composite as the precursor. The ZnO/ZnCo 2 O 4 /C@rGO hybrid exhibits remarkable electrocatalytic performance for oxygen reduction reaction under alkaline conditions and superior stability and methanol tolerance to those of the commercial Pt/C catalyst. Furthermore, novel and simple Al-air coin cells were first fabricated using the hybrid materials as cathode catalysts under ambient air conditions to further investigate their catalytic performance. The coin cell with the ZnO/ZnCo 2 O 4 /C@rGO cathode catalyst displays a higher open circuit voltage and discharge voltage and more sluggish potential drop than those of the cell with the ZnO/ZnCo 2 O 4 /C cathode catalyst, which confirms that rGO can enhance the electrocatalytic activity and stability of the catalyst system. The excellent electrocatalytic performance of the ZnO/ZnCo 2 O 4 /C@rGO hybrid is attributed to the prominent conductivity and high specific surface area resulting from rGO, the more accessible catalytic active sites induced by the unique porous hollow nanocage structure, and synergic covalent coupling between rGO sheets and ZnO/ZnCo 2 O 4 /C nanocages.

Ethanesulfonic acid-based esterification of industrial acidic crude palm oil for biodiesel production.

PubMed

Hayyan, Adeeb; Mjalli, Farouq S; Hashim, Mohd Ali; Hayyan, Maan; AlNashef, Inas M; Al-Zahrani, Saeed M; Al-Saadi, Mohammed A

2011-10-01

An industrial grade acidic crude palm oil (ACPO) pre-treatment process was carried out using ethanesulfonic acid (ESA) as a catalyst in the esterification reaction. ESA was used in different dosages to reduce free fatty acid (FFA) to a minimum level for the second stage of biodiesel production via alkaline transesterification reaction. Different process operating conditions were optimized such as ESA dosage (0.25-3.5% wt/wt), methanol to ACPO molar ratio (1:1-20:1), reaction temperature (40-70 °C), and reaction time (3-150 min). This study revealed the potential use of abundant quantities of ACPO from oil palm mills for biodiesel production. The lab scale results showed the effectiveness of the pre-treatment process using ESA catalyst. Three consecutive catalyst recycling runs were achieved without significant degradation in its performance. Second and third reuse runs needed more reaction time to achieve the target level of FFA content. Esterification and transesterification using ESA and KOH respectively is proposed for biodiesel industrial scale production. The produced biodiesel meets the international standards specifications for biodiesel fuel (EN 14214 and ASTM D6751). Copyright © 2011 Elsevier Ltd. All rights reserved.

High-indexed Pt 3Ni alloy tetrahexahedral nanoframes evolved through preferential CO etching

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Chenyu; Zhang, Lihua; Yang, Hongzhou

2017-03-07

Here, chemically controlling crystal structures in nanoscale is challenging, yet provides an effective way to improve catalytic performances. Pt-based nanoframes are a new class of nanomaterials that have great potential as high-performance catalysts. To date, these nanoframes are formed through acid etching in aqueous solutions, which demands long reaction time and often yields ill-defined surface structures. Herein we demonstrate a robust and unprecedented protocol for facile development of high-performance nanoframe catalysts using size and crystallographic facet-controlled PtNi 4 tetrahexahedral nanocrystals prepared through a colloidal synthesis approach as precursors. This new protocol employs the Mond process to preferentially dealloy nickel componentmore » in the <100> direction through carbon monoxide etching of carbon-supported PtNi 4 tetrahexahedral nanocrystals at an elevated temperature. The resultant Pt 3Ni alloy tetrahexahedral nanoframes possess an open, stable, and high-indexed microstructure, containing a segregated Pt thin layer strained to the Pt–Ni alloy surfaces and featuring a down-shift d-band center as revealed by the density functional theory calculations. These nanoframes exhibit much improved catalytic performance, such as high stability under prolonged electrochemical potential cycles, promoting direct electro-oxidation of formic acid to carbon dioxide and enhancing oxygen reduction reaction activities. Because carbon monoxide can be generated from the carbon support through thermal annealing in air, a common process for pretreating supported catalysts, the developed approach can be easily adopted for preparing industrial scale catalysts that are made of Pt–Ni and other alloy nanoframes.« less

Quantitative elemental imaging of heterogeneous catalysts using laser-induced breakdown spectroscopy

NASA Astrophysics Data System (ADS)

Trichard, F.; Sorbier, L.; Moncayo, S.; Blouët, Y.; Lienemann, C.-P.; Motto-Ros, V.

2017-07-01

Currently, the use of catalysis is widespread in almost all industrial processes; its use improves productivity, synthesis yields and waste treatment as well as decreases energy costs. The increasingly stringent requirements, in terms of reaction selectivity and environmental standards, impose progressively increasing accuracy and control of operations. Meanwhile, the development of characterization techniques has been challenging, and the techniques often require equipment with high complexity. In this paper, we demonstrate a novel elemental approach for performing quantitative space-resolved analysis with ppm-scale quantification limits and μm-scale resolution. This approach, based on laser-induced breakdown spectroscopy (LIBS), is distinguished by its simplicity, all-optical design, and speed of operation. This work analyzes palladium-based porous alumina catalysts, which are commonly used in the selective hydrogenation process, using the LIBS method. We report an exhaustive study of the quantification capability of LIBS and its ability to perform imaging measurements over a large dynamic range, typically from a few ppm to wt%. These results offer new insight into the use of LIBS-based imaging in the industry and paves the way for innumerable applications.

Catalysts Based on Earth-Abundant Metals for Visible Light-Driven Water Oxidation Reaction.

PubMed

Lin, Junqi; Han, Qing; Ding, Yong

2018-06-04

Exploration of water oxidation catalyst (WOC) with excellent performance is the key for the overall water splitting reaction, which is a feasible strategy to convert solar energy to chemical energy. Although some compounds composed of noble metals, mainly Ru and Ir, have been reported to catalyze water oxidation with high efficiency, catalysts based on low-cost and earth-abundant transition metals are essential for realizing economical and large-scale light-driven water splitting. Various WOCs containing earth-abundant metals (mainly Mn, Fe, Co, Ni, Cu) have been utilized for visible light-driven water oxidation in recent years. In this Personal Account, we summarize our recent developments in WOCs based on earth-abundant transition metals including polyoxometalates (POMs), metal oxides or bimetal oxides, and metal complexes containing multidentate ligand scaffolds for visible light-driven water oxidation reaction. © 2018 The Chemical Society of Japan & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Highly Efficient Catalytic Cyclic Carbonate Formation by Pyridyl Salicylimines.

PubMed

Subramanian, Saravanan; Park, Joonho; Byun, Jeehye; Jung, Yousung; Yavuz, Cafer T

2018-03-21

Cyclic carbonates as industrial commodities offer a viable nonredox carbon dioxide fixation, and suitable heterogeneous catalysts are vital for their widespread implementation. Here, we report a highly efficient heterogeneous catalyst for CO 2 addition to epoxides based on a newly identified active catalytic pocket consisting of pyridine, imine, and phenol moieties. The polymeric, metal-free catalyst derived from this active site converts less-reactive styrene oxide under atmospheric pressure in quantitative yield and selectivity to the corresponding carbonate. The catalyst does not need additives, solvents, metals, or co-catalysts, can be reused at least 10 cycles without the loss of activity, and scaled up easily to a kilogram scale. Density functional theory calculations reveal that the nucleophilicity of pyridine base gets stronger due to the conjugated imines and H-bonding from phenol accelerates the reaction forward by stabilizing the intermediate.

Adsorptive removal of catalyst poisons from coal gas for methanol synthesis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bhatt, B.L.; Golden, T.C.; Hsiung, T.H.

1991-12-01

As an integral part of the liquid-phase methanol (LPMEOH) process development program, the present study evaluated adsorptive schemes to remove traces of catalyst poisons such as iron carbonyl, carbonyl sulfide, and hydrogen sulfide from coal gas on a pilot scale. Tests were conducted with coal gas from the Cool Water gasification plant at Daggett, California. Iron carbonyl, carbonyl sulfide, and hydrogen sulfide were effectively removed from the coal gas. The adsorption capacities of Linde H-Y zeolite and Calgon BPL carbon for Fe(CO){sub 5} compared well with previous bench-scale results at similar CO{sub 2} partial pressure. Adsorption of COS by Calgonmore » FCA carbon appeared to be chemical and nonregenerable by thermal treatment in nitrogen. A Cu/Zn catalyst removed H{sub 2}S very effectively. With the adsorption system on-line, a methanol catalyst showed stable activity during 120 h operation, demonstrating the feasibility of adsorptive removal of trace catalyst poisons from the synthesis gas. Mass transfer coefficients were estimated for Fe(CO){sub 5} and COS removal which can be directly used for design and scale up.« less

EVALUATION OF SCR CATALYSTS FOR COMBINED CONTROL OF NOX AND MERCURY

EPA Science Inventory

The report documents two-task, bench- and pilot-scale research on the effect of selective catalytic reduction (SCR) catalysts on mercury speciation in Illinois and Powder River Basin (PRB) coal combustion flue gases. In task I, a bench-scale reactor was used to study the oxidatio...

High-Flux, High Performance H2O2 Catalyst Bed for ISTAR

NASA Technical Reports Server (NTRS)

Ponzo, J.

2005-01-01

On NASA's ISTAR RBCC program packaging and performance requirements exceeded traditional H2O2 catalyst bed capabilities. Aerojet refined a high performance, monolithic 90% H202 catalyst bed previously developed and demonstrated. This approach to catalyst bed design and fabrication was an enabling technology to the ISTAR tri-fluid engine. The catalyst bed demonstrated 55 starts at throughputs greater than 0.60 lbm/s/sq in for a duration of over 900 seconds in a physical envelope approximately 114 of traditional designs. The catalyst bed uses photoetched plates of metal bonded into a single piece monolithic structure. The precise control of the geometry and complete mixing results in repeatable, quick starting, high performing catalyst bed. Three different beds were designed and tested, with the best performing bed used for tri-fluid engine testing.

Effect of fly ash on catalytic removal of gaseous dioxins over V{sub 2}O{sub 5}-WO{sub 3} catalyst of a sinter plant

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shu Hao Chang; Kai Hsien Chi; Chi Wei Young

2009-10-01

A PCDD/F (polychlorinated dibenzo-p-dioxin and dibenzofuran)-containing gas stream generating system was developed to investigate the efficiency and effectiveness of V{sub 2}O{sub 5}-WO{sub 3} catalyst for PCDD/F destruction. Catalytic decomposition of PCDD/Fs (simulated gas streams) was evaluated with lab-scale pelletized and plate-type catalyst based on V{sub 2}O{sub 5}-WO{sub 3}/TiO{sub 2} at controlled temperature, space velocity, and inlet PCDD/F concentration. Due to the lower porosity of the pelletized catalyst, PCDD/F destruction efficiencies reach 72.9-83.2% for different levels of inlet PCDD/F concentrations (1.08-3.04 ng-TEQ/Nm{sup 3}) of the gas stream (space velocity: 5000 h-1). As the surface area is increased from 287 m{sup 2}/m{supmore » 3} (plate-type A) to 550 m{sup 2}/m{sup 3} (plate-type B), the PCDD/F destruction achieved with plate-type catalyst increases from 76.0% to 85.3% at 320{sup o}C (space velocity: 5000 h{sup -1}). In addition, the results of pilot-scale experiment (real flue gases of a sinter plant) indicate that relatively lower PCDD/F destruction efficiencies (62.1-65.7%) were achieved with the plate-type B catalyst as the solid-phase PCDD/F and fly ash passed through the reactor (space velocity: 5000 h{sup -1}). Overall, the lab-scale and pilot-scale experiments indicate that PCDD/F destructions achieved with pelletized and plate-type catalysts strongly depend on the operating temperature of the catalyst. The results also indicate that the presence of fly ash lowers PCDD/F destruction due to significant PCDD/F formation via de novo synthesis at 320{sup o}C. 20 refs., 5 figs., 3 tabs.« less

Pt-Ni and Pt-Co Catalyst Synthesis Route for Fuel Cell Applications

NASA Technical Reports Server (NTRS)

Firdosy, Samad A.; Ravi, Vilupanur A.; Valdez, Thomas I.; Kisor, Adam; Narayan, Sri R.

2013-01-01

Oxygen reduction reactions (ORRs) at the cathode are the rate-limiting step in fuel cell performance. The ORR is 100 times slower than the corresponding hydrogen oxidation at the anode. Speeding up the reaction at the cathode will improve fuel cell efficiency. The cathode material is generally Pt powder painted onto a substrate (e.g., graphite paper). Recent efforts in the fuel cell area have focused on replacing Pt with Pt-X alloys (where X = Co, Ni, Zr, etc.) in order to (a) reduce cost, and (b) increase ORR rates. One of these strategies is to increase ORR rates by reducing the powder size, which would result in an increase in the surface area, thereby facilitating faster reaction rates. In this work, a process has been developed that creates Pt-Ni or Pt-Co alloys that are finely divided (on the nano scale) and provide equivalent performance at lower Pt loadings. Lower Pt loadings will translate to lower cost. Precursor salts of the metals are dissolved in water and mixed. Next, the salt mixtures are dried on a hot plate. Finally, the dried salt mixture is heattreated in a furnace under flowing reducing gas. The catalyst powder is then used to fabricate a membrane electrode assembly (MEA) for electrochemical performance testing. The Pt- Co catalyst-based MEA showed comparable performance to an MEA fabri cated using a standard Pt black fuel cell catalyst. The main objective of this program has been to increase the overall efficiencies of fuel cell systems to support power for manned lunar bases. This work may also have an impact on terrestrial programs, possibly to support the effort to develop a carbon-free energy source. This catalyst can be used to fabricate high-efficiency fuel cell units that can be used in space as regenerative fuel cell systems, and terrestrially as primary fuel cells. Terrestrially, this technology will become increasingly important when transition to a hydrogen economy occurs.

Linear scaling relationships and volcano plots in homogeneous catalysis - revisiting the Suzuki reaction.

PubMed

Busch, Michael; Wodrich, Matthew D; Corminboeuf, Clémence

2015-12-01

Linear free energy scaling relationships and volcano plots are common tools used to identify potential heterogeneous catalysts for myriad applications. Despite the striking simplicity and predictive power of volcano plots, they remain unknown in homogeneous catalysis. Here, we construct volcano plots to analyze a prototypical reaction from homogeneous catalysis, the Suzuki cross-coupling of olefins. Volcano plots succeed both in discriminating amongst different catalysts and reproducing experimentally known trends, which serves as validation of the model for this proof-of-principle example. These findings indicate that the combination of linear scaling relationships and volcano plots could serve as a valuable methodology for identifying homogeneous catalysts possessing a desired activity through a priori computational screening.

Microwave assisted synthesis of biarlys by Csbnd C coupling reactions with a new chitosan supported Pd(II) catalyst

NASA Astrophysics Data System (ADS)

Baran, Talat; Menteş, Ayfer

2016-10-01

In this study a new type chitosan-based support has been produced for Pd(II) catalyst and its catalytic performance in Suzuki Csbnd C reactions has been studied under microwave irradiation without using any solvent. The chemical identification of the catalyst was performed using TG/DTG, FTIR, UV-Vis ICP-OES, SEM/EDAX, 13C NMR, molar conductivity, XRD and magnetic moment techniques. The performance of this new Pd(II) catalyst was studied in Suzuki Csbnd C reactions. The Pd(II) catalyst exhibited a good catalytic performance in very short time (4 min) by giving high TONs and TOFs with low amount of the catalyst (0.015 mol%). The catalyst also had reusability and did not lose its activity until six runs.

An Exploration of Geometric and Electronic Effects in Metal Nanoparticle Catalysts

NASA Astrophysics Data System (ADS)

Childers, David

The goal of this thesis is to investigate the influence geometric and electronic effects on metal nanoparticle catalysis. There are three main methods which alter a catalyst's properties: changing support material, changing nanoparticle size and alloying a second metal. This work will focus on the latter two methods using Pt-group metals and alloys. Platinum and palladium were chosen as the active metals due to a large amount of industry significance and prior literature to draw upon. Neopentane conversion and propane dehydrogenation were the two probe reactions used to evaluate these catalysts mainly due to their relative simplicity and ease of operation on a laboratory scale. The effect of particle size was studied with Pt and Pd monometallic catalysts using neopentane hydrogenolysis/isomerization as the probe reaction. Particle size studies have been done previously using this reaction so there is literature data to compare this study's results. This data will also be used as comparison for the bimetallic studies conducted later so that particle size effects can be accounted for when attempting to determine the effect of alloying a second metal. Bimetallic catalysts have several different possible structures depending on a number of factors from the identity of the two metals to the synthesis procedure. Homogeneous, core-shell and intermetallic alloys are the three structures evaluated in this work. Determining the surface composition of a homogeneous alloy can be difficult especially if both metals adsorb CO. PtPd homogeneous alloys were used to evaluate the ability of EXAFS to give information about surface composition using CO adsorption. These catalysts were also tested using neopentane conversion to evaluate changes in catalytic performance. Core-shell catalysts can also exhibit unique properties although it is not clear whether the identity of the core metal is relevant or if surface changes are most important to changing catalytic behavior. PdAu catalysts were synthesized with varying Pd loadings to determine if the Au-rich core would continue to influence neopentane conversion performance with increasing Pd layers on the surface of the nanoparticle. Finally, intermetallic alloys have produced some very interesting literature results and can drastically alter catalyst surface structure. PdZn showed the potential to improve neopentane isomerization selectivity past that of Pt based on calculated electronic properties. Two PdZn catalysts with different loadings were synthesized to evaluate the electronic and geometric effects using both neopentane conversion and propane dehydrogenation.

Fe3O4@MOF core-shell magnetic microspheres as excellent catalysts for the Claisen-Schmidt condensation reaction

NASA Astrophysics Data System (ADS)

Ke, Fei; Qiu, Ling-Guang; Zhu, Junfa

2014-01-01

Separation and recycling of catalysts after catalytic reactions are critically required to reduce the cost of catalysts as well as to avoid the generation of waste in industrial applications. In this work, we present a facile fabrication and characterization of a novel type of MOF-based porous catalyst, namely, Fe3O4@MIL-100(Fe) core-shell magnetic microspheres. It has been shown that these catalysts not only exhibit high catalytic activities for the Claisen-Schmidt condensation reactions under environmentally friendly conditions, but remarkably, they can be easily separated and recycled without significant loss of catalytic efficiency after being used for many times. Therefore, compared to other reported catalysts used in the Claisen-Schmidt condensation reactions, these catalysts are green, cheap and more suitable for large scale industrial applications.Separation and recycling of catalysts after catalytic reactions are critically required to reduce the cost of catalysts as well as to avoid the generation of waste in industrial applications. In this work, we present a facile fabrication and characterization of a novel type of MOF-based porous catalyst, namely, Fe3O4@MIL-100(Fe) core-shell magnetic microspheres. It has been shown that these catalysts not only exhibit high catalytic activities for the Claisen-Schmidt condensation reactions under environmentally friendly conditions, but remarkably, they can be easily separated and recycled without significant loss of catalytic efficiency after being used for many times. Therefore, compared to other reported catalysts used in the Claisen-Schmidt condensation reactions, these catalysts are green, cheap and more suitable for large scale industrial applications. Electronic supplementary information (ESI) available: SEM and TEM images, and GC-MS spectra for chalcones. See DOI: 10.1039/c3nr05051c

Fabrication Method for Laboratory-Scale High-Performance Membrane Electrode Assemblies for Fuel Cells.

PubMed

Sassin, Megan B; Garsany, Yannick; Gould, Benjamin D; Swider-Lyons, Karen E

2017-01-03

Custom catalyst-coated membranes (CCMs) and membrane electrode assemblies (MEAs) are necessary for the evaluation of advanced electrocatalysts, gas diffusion media (GDM), ionomers, polymer electrolyte membranes (PEMs), and electrode structures designed for use in next-generation fuel cells, electrolyzers, or flow batteries. This Feature provides a reliable and reproducible fabrication protocol for laboratory scale (10 cm 2 ) fuel cells based on ultrasonic spray deposition of a standard Pt/carbon electrocatalyst directly onto a perfluorosulfonic acid PEM.

Power generation in microbial fuel cells using platinum group metal-free cathode catalyst: Effect of the catalyst loading on performance and costs

NASA Astrophysics Data System (ADS)

Santoro, Carlo; Kodali, Mounika; Herrera, Sergio; Serov, Alexey; Ieropoulos, Ioannis; Atanassov, Plamen

2018-02-01

Platinum group metal-free (PGM-free) catalyst with different loadings was investigated in air breathing electrodes microbial fuel cells (MFCs). Firstly, the electrocatalytic activity towards oxygen reduction reaction (ORR) of the catalyst was investigated by rotating ring disk electrode (RRDE) setup with different catalyst loadings. The results showed that higher loading led to an increased in the half wave potential and the limiting current and to a further decrease in the peroxide production. The electrons transferred also slightly increased with the catalyst loading up to the value of ≈3.75. This variation probably indicates that the catalyst investigated follow a 2x2e- transfer mechanism. The catalyst was integrated within activated carbon pellet-like air-breathing cathode in eight different loadings varying between 0.1 mgcm-2 and 10 mgcm-2. Performance were enhanced gradually with the increase in catalyst content. Power densities varied between 90 ± 9 μWcm-2 and 262 ± 4 μWcm-2 with catalyst loading of 0.1 mgcm-2 and 10 mgcm-2 respectively. Cost assessments related to the catalyst performance are presented. An increase in catalyst utilization led to an increase in power generated with a substantial increase in the whole costs. Also a decrease in performance due to cathode/catalyst deterioration over time led to a further increase in the costs.

Amine-Functionalized Sugarcane Bagasse: A Renewable Catalyst for Efficient Continuous Flow Knoevenagel Condensation Reaction at Room Temperature.

PubMed

Qiao, Yanhui; Teng, Junjiang; Wang, Shuangfei; Ma, Hao

2017-12-24

A biomass-based catalyst with amine groups (-NH₂), viz., amine-functionalized sugarcane bagasse (SCB-NH₂), was prepared through the amination of sugarcane bagasse (SCB) in a two-step process. The physicochemical properties of the catalyst were characterized through FT-IR, elemental analysis, XRD, TG, and SEM-EDX techniques, which confirmed the -NH₂ group was grafted onto SCB successfully. The catalytic performance of SCB-NH₂ in Knoevenagel condensation reaction was tested in the batch and continuous flow reactions. Significantly, it was found that the catalytic performance of SCB-NH₂ is better in flow system than that in batch system. Moreover, the SCB-NH₂ presented an excellent catalytic activity and stability at the high flow rate. When the flow rate is at the 1.5 mL/min, no obvious deactivation was observed and the product yield and selectivity are more than 97% and 99% after 80 h of continuous reaction time, respectively. After the recovery of solvent from the resulting solution, a white solid was obtained as a target product. As a result, the SCB-NH₂ is a promising catalyst for the synthesis of fine chemicals by Knoevenagel condensation reaction in large scale, and the modification of the renewable SCB with -NH₂ group is a potential avenue for the preparation of amine-functionalized catalytic materials in industry.

Open-source FCPEM-Performance & Durability Model Consideration of Membrane Properties on Cathode Degradation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Knights, Shanna; Harvey, David

The durability of PEM fuel cells is a primary requirement for large scale commercialization of these power systems in transportation and stationary market applications which target operational lifetimes of 5,000 hours and 60,000 hours by 2020, respectively. Key degradation modes contributing to fuel cell lifetime limitations have been largely associated with the platinum-based cathode catalyst layer. Furthermore, as fuel cells are driven to low cost materials and lower catalyst loadings in order to meet the cost targets for commercialization, the catalyst durability has become even more important. While over the past few years significant progress has been made in identifyingmore » the underlying causes of fuel cell degradation and key parameters that greatly influence the degradation rates, many gaps with respect to knowledge of the driving mechanisms still exist; in particular, the acceleration of the mechanisms due to different membrane compositions remains an area not well understood. The focus of this project extension was to enhance the predictive capability of the PEM Fuel Cell Performance & Durability Model called FC-APOLLO (Application Package for Open-source Long Life Operation) by including interaction effects of membrane transport properties such as water transport, changes in proton conductivity, and overall water uptake/adsorption and the state of the catalyst layer local conditions to further understand the driving forces for platinum dissolution.« less

Post-formation copper-nitrogen species on carbon black: their chemical structures and active sites for oxygen reduction reaction.

PubMed

Xie, Xin; Liu, Jingjun; Li, Tuanfeng; Song, Ye; Wang, Feng

2018-05-16

Note that 3d transition metal and nitrogen co-doped carbon materials (TM-N-C) are considered as the most promising next-generation electrocatalysts alternative to precious Pt for oxygen reduction reaction (ORR). Herein, we have fabricated a Cu-N-C catalyst through directly grafting copper-nitrogen complexes composed by cuprous chloride and ammonia water onto the surface of an industrial carbon black at 500℃. In an alkaline environment, the synthesized catalyst exhibits excellent ORR catalytic activity, which is comparable to the state-of-the-art Pt/C catalyst but far exceeding that obtained by the original carbon. Moreover, the catalyst displays much better stability than the Pt/C. The enhanced ORR performance is proven to originate from the post-formation Cu(I)-N2 and Cu(II)-N4 sites at the carbon surface, as evidenced by X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS). The possible ORR process catalyzed by these Cu-Nx species is discussed at atomic level. This work provides a simple and fast synthesis strategy for efficient TM-N-C catalysts on a large scale for energy storage and conversion systems. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Gram-level synthesis of core-shell structured catalysts for the oxygen reduction reaction in proton exchange membrane fuel cells

NASA Astrophysics Data System (ADS)

Luo, Mingchuan; Wei, Lingli; Wang, Fanghui; Han, Kefei; Zhu, Hong

2014-12-01

Over the past decade, Pt based core-shell structured alloys have been studied extensively as oxygen reduction reaction (ORR) catalysts for proton exchange membrane fuel cells (PEMFCs) because of their distinctive electrochemical performance and low Pt loading. In this paper, a facile route based on microwave-assisted polyol method and chemical dealloying process is proposed to synthesize carbon supported core-shell structured nanoparticles (NPs) in gram-level for ORR electrocatalysis in PEMFCs. The obtained samples are characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), inductively coupled plasma atomic emission spectroscopy (ICP-AES), and X-ray photoelectron spectroscopy (XPS). These physical characterization indicate that the final synthesized NPs are highly dispersed on the carbon support, and in a core-shell structure with CuPt alloy as the core and Pt as the shell. Electrochemical measurements, conducted by cyclic voltammetry (CV) and rotating disk electrode (RDE) tests, show the core-shell structured catalyst exhibit a 3× increase in mass activity and a 2× increase in specific activity over the commercial Pt/C catalyst, respectively. These results demonstrate that this route can be a reliable way to synthesize low-Pt catalyst in large-scale for PEMFCs.

Efficient decomposition of formaldehyde at room temperature over Pt/honeycomb ceramics with ultra-low Pt content.

PubMed

Nie, Longhui; Zheng, Yingqiu; Yu, Jiaguo

2014-09-14

Pt/honeycomb ceramic (Pt/HC) catalysts with ultra-low Pt content (0.005-0.055 wt%) were for the first time prepared by an impregnation of honeycomb ceramics with Pt precursor and NaBH4-reduction combined method. The microstructures, morphologies and textural properties of the resulting samples were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), and transmission electron microscopy (TEM). The obtained Pt/HC catalysts were used for catalytic oxidative decomposition of formaldehyde (HCHO) at room temperature. It was found that the as-prepared Pt/HC catalysts can efficiently decompose HCHO in air into CO2 and H2O at room temperature. The catalytic activity of the Pt/HC catalysts increases with increasing the Pt loading in the range of 0.005-0.013 wt%, and the further increase of the Pt loading does not obviously improve catalytic activity. From the viewpoint of cost and catalytic performance, 0.013 wt% Pt loading is the optimal Pt loading amount, and the Pt/HC catalyst with 0.013 wt% Pt loading also exhibited good catalytic stability. Considering practical applications, this work will provide new insights into the low-cost and large-scale fabrication of advanced catalytic materials for indoor air purification.

Study on Endurance and Performance of Impregnated Ruthenium Catalyst for Thruster System.

PubMed

Kim, Jincheol; Kim, Taegyu

2018-02-01

Performance and endurance of the Ru catalyst were studied for nitrous oxide monopropellant thruster system. The thermal decomposition of N2O requires a considerably high temperature, which make it difficult to be utilized as a thruster propellant, while the propellant decomposition temperature can be reduced by using the catalyst through the decomposition reaction with the propellant. However, the catalyst used for the thruster was frequently exposed to high temperature and high-pressure environment. Therefore, the state change of the catalyst according to the thruster operation was analyzed. Characterization of catalyst used in the operation condition of the thruster was performed using FE-SEM and EDS. As a result, performance degradation was occurred due to the volatilization of Ru catalyst and reduction of the specific surface area according to the phase change of Al2O3.

Anh To | NREL

Science.gov Websites

pyrolysis vapors Catalytic depolymerization of biomass Process scale-up for catalyst synthesis and testing continuous flow reactors (gas & liquid phases) Catalyst synthesis: zeolites, supported metals, and

Catalytic Oxidation of Chlorobenzene over MnxCe1-xO2/HZSM-5 Catalysts: A Study with Practical Implications.

PubMed

Weng, Xiaole; Sun, Pengfei; Long, Yu; Meng, Qingjie; Wu, Zhongbiao

2017-07-18

Industrial-use catalysts usually encounter severe deactivation after long-term operation for catalytic oxidation of chlorinate volatile organic compounds (CVOCs), which becomes a "bottleneck" for large-scale application of catalytic combustion technology. In this work, typical acidic solid-supported catalysts of Mn x Ce 1-x O 2 /HZSM-5 were investigated for the catalytic oxidation of chlorobenzene (CB). The activation energy (E a ), Brønsted and Lewis acidities, CB adsorption and activation behaviors, long-term stabilities, and surficial accumulation compounds (after aging) were studied using a range of analytical techniques, including XPS, H 2 -TPR, pyridine-IR, DRIFT, and O 2 -TP-Ms. Experimental results revealed that the Brønsted/Lewis (B/L) ratio of Mn x Ce 1-x O 2 /HZSM-5 catalysts could be adjusted by ion exchange of H• (in HZSM-5) with Mn n+ (where the exchange with Ce 4+ did not distinctly affect the acidity); the long-term aged catalysts could accumulate ca. 14 organic compounds at surface, including highly toxic tetrachloromethane, trichloroethylene, tetrachloroethylene, o-dichlorobenzene, etc.; high humid operational environment could ensure a stable performance for Mn x Ce 1-x O 2 /HZSM-5 catalysts; this was due to the effective removal of Cl• and coke accumulations by H 2 O washing, and the distinct increase of Lewis acidity by the interaction of H 2 O with HZSM-5. This work gives an in-depth view into the CB oxidation over acidic solid-supported catalysts and could provide practical guidelines for the rational design of reliable catalysts for industrial applications.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Underwood, R.P.

As part of the DOE-sponsored contract Synthesis of Dimethyl Ether and Alternative Fuels in the Liquid Phase from Coal-Derived Syngas'' experimental evaluations of the one-step synthesis of alternative fuels were carried out. The objective of this work was to develop novel processes for converting coal-derived syngas to fuels or fuel additives. Building on a technology base acquired during the development of the Liquid Phase Methanol (LPMEOH) process, this work focused on the development of slurry reactor based processes. The experimental investigations, which involved bench-scale reactor studies, focused primarily on three areas: (1) One-step, slurry-phase syngas conversion to hydrocarbons or methanol/hydrocarbonmore » mixtures using a mixture of methanol synthesis catalyst and methanol conversion catalyst in the same slurry reactor. (2) Slurry-phase conversion of syngas to mixed alcohols using various catalysts. (3) One-step, slurry-phase syngas conversion to mixed ethers using a mixture of mixed alcohols synthesis catalyst and dehydration catalyst in the same slurry reactor. The experimental results indicate that, of the three types of processes investigated, slurry phase conversion of syngas to mixed alcohols shows the most promise for further process development. Evaluations of various mixed alcohols catalysts show that a cesium-promoted Cu/ZnO/Al[sub 2]O[sub 3] methanol synthesis catalyst, developed in Air Products' laboratories, has the highest performance in terms of rate and selectivity for C[sub 2+]-alcohols. In fact, once-through conversion at industrially practical reaction conditions yielded a mixed alcohols product potentially suitable for direct gasoline blending. Moreover, an additional attractive aspect of this catalyst is its high selectivity for branched alcohols, potential precursors to iso-olefins for use in etherification.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Underwood, R.P.

As part of the DOE-sponsored contract ``Synthesis of Dimethyl Ether and Alternative Fuels in the Liquid Phase from Coal-Derived Syngas`` experimental evaluations of the one-step synthesis of alternative fuels were carried out. The objective of this work was to develop novel processes for converting coal-derived syngas to fuels or fuel additives. Building on a technology base acquired during the development of the Liquid Phase Methanol (LPMEOH) process, this work focused on the development of slurry reactor based processes. The experimental investigations, which involved bench-scale reactor studies, focused primarily on three areas: (1) One-step, slurry-phase syngas conversion to hydrocarbons or methanol/hydrocarbonmore » mixtures using a mixture of methanol synthesis catalyst and methanol conversion catalyst in the same slurry reactor. (2) Slurry-phase conversion of syngas to mixed alcohols using various catalysts. (3) One-step, slurry-phase syngas conversion to mixed ethers using a mixture of mixed alcohols synthesis catalyst and dehydration catalyst in the same slurry reactor. The experimental results indicate that, of the three types of processes investigated, slurry phase conversion of syngas to mixed alcohols shows the most promise for further process development. Evaluations of various mixed alcohols catalysts show that a cesium-promoted Cu/ZnO/Al{sub 2}O{sub 3} methanol synthesis catalyst, developed in Air Products` laboratories, has the highest performance in terms of rate and selectivity for C{sub 2+}-alcohols. In fact, once-through conversion at industrially practical reaction conditions yielded a mixed alcohols product potentially suitable for direct gasoline blending. Moreover, an additional attractive aspect of this catalyst is its high selectivity for branched alcohols, potential precursors to iso-olefins for use in etherification.« less

Interfaces in Heterogeneous Catalysts: Advancing Mechanistic Understanding through Atomic-Scale Measurements.

PubMed

Gao, Wenpei; Hood, Zachary D; Chi, Miaofang

2017-04-18

Developing novel catalysts with high efficiency and selectivity is critical for enabling future clean energy conversion technologies. Interfaces in catalyst systems have long been considered the most critical factor in controlling catalytic reaction mechanisms. Interfaces include not only the catalyst surface but also interfaces within catalyst particles and those formed by constructing heterogeneous catalysts. The atomic and electronic structures of catalytic surfaces govern the kinetics of binding and release of reactant molecules from surface atoms. Interfaces within catalysts are introduced to enhance the intrinsic activity and stability of the catalyst by tuning the surface atomic and chemical structures. Examples include interfaces between the core and shell, twin or domain boundaries, or phase boundaries within single catalyst particles. In supported catalyst nanoparticles (NPs), the interface between the metallic NP and support serves as a critical tuning factor for enhancing catalytic activity. Surface electronic structure can be indirectly tuned and catalytically active sites can be increased through the use of supporting oxides. Tuning interfaces in catalyst systems has been identified as an important strategy in the design of novel catalysts. However, the governing principle of how interfaces contribute to catalyst behavior, especially in terms of interactions with intermediates and their stability during electrochemical operation, are largely unknown. This is mainly due to the evolving nature of such interfaces. Small changes in the structural and chemical configuration of these interfaces may result in altering the catalytic performance. These interfacial arrangements evolve continuously during synthesis, processing, use, and even static operation. A technique that can probe the local atomic and electronic interfacial structures with high precision while monitoring the dynamic interfacial behavior in situ is essential for elucidating the role of interfaces and providing deeper insight for fine-tuning and optimizing catalyst properties. Scanning transmission electron microscopy (STEM) has long been a primary characterization technique used for studying nanomaterials because of its exceptional imaging resolution and simultaneous chemical analysis. Over the past decade, advances in STEM, that is, the commercialization of both aberration correctors and monochromators, have significantly improved the spatial and energy resolution. Imaging atomic structures with subangstrom resolution and identifying chemical species with single-atom sensitivity are now routine for STEM. These advancements have greatly benefitted catalytic research. For example, the roles of lattice strain and surface elemental distribution and their effect on catalytic stability and reactivity have been well documented in bimetallic catalysts. In addition, three-dimensional atomic structures revealed by STEM tomography have been integrated in theoretical modeling for predictive catalyst NP design. Recent developments in stable electronic and mechanical devices have opened opportunities to monitor the evolution of catalysts in operando under synthesis and reaction conditions; high-speed direct electron detectors have achieved sub-millisecond time resolutions and allow for rapid structural and chemical changes to be captured. Investigations of catalysts using these latest microscopy techniques have provided new insights into atomic-level catalytic mechanisms. Further integration of new microscopy methods is expected to provide multidimensional descriptions of interfaces under relevant synthesis and reaction conditions. In this Account, we discuss recent insights on understanding catalyst activity, selectivity, and stability using advanced STEM techniques, with an emphasis on how critical interfaces dictate the performance of precious metal-based heterogeneous catalysts. The role of extended interfacial structures, including those between core and shell, between separate phases and twinned grains, between the catalyst surface and gas, and between metal and support are discussed. We also provide an outlook on how emerging electron microscopy techniques, such as vibrational spectroscopy and electron ptychography, will impact future catalysis research.

Cobalt-manganese-based spinels as multifunctional materials that unify catalytic water oxidation and oxygen reduction reactions.

PubMed

Menezes, Prashanth W; Indra, Arindam; Sahraie, Nastaran Ranjbar; Bergmann, Arno; Strasser, Peter; Driess, Matthias

2015-01-01

Recently, there has been much interest in the design and development of affordable and highly efficient oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) catalysts that can resolve the pivotal issues that concern solar fuels, fuel cells, and rechargeable metal-air batteries. Here we present the synthesis and application of porous CoMn2 O4 and MnCo2 O4 spinel microspheres as highly efficient multifunctional catalysts that unify the electrochemical OER with oxidant-driven and photocatalytic water oxidation as well as the ORR. The porous materials were prepared by the thermal degradation of the respective carbonate precursors at 400 °C. The as-prepared spinels display excellent performances in electrochemical OER for the cubic MnCo2 O4 phase in comparison to the tetragonal CoMn2 O4 material in an alkaline medium. Moreover, the oxidant-driven and photocatalytic water oxidations were performed and they exhibited a similar trend in activity to that of the electrochemical OER. Remarkably, the situation is reversed in ORR catalysis, that is, the oxygen reduction activity and stability of the tetragonal CoMn2 O4 catalyst outperformed that of cubic MnCo2 O4 and rivals that of benchmark Pt catalysts. The superior catalytic performance and the remarkable stability of the unifying materials are attributed to their unique porous and robust microspherical morphology and the intrinsic structural features of the spinels. Moreover, the facile access to these high-performance materials enables a reliable and cost-effective production on a large scale for industrial applications. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Novel anode catalyst for direct methanol fuel cells.

PubMed

Basri, S; Kamarudin, S K; Daud, W R W; Yaakob, Z; Kadhum, A A H

2014-01-01

PtRu catalyst is a promising anodic catalyst for direct methanol fuel cells (DMFCs) but the slow reaction kinetics reduce the performance of DMFCs. Therefore, this study attempts to improve the performance of PtRu catalysts by adding nickel (Ni) and iron (Fe). Multiwalled carbon nanotubes (MWCNTs) are used to increase the active area of the catalyst and to improve the catalyst performance. Electrochemical analysis techniques, such as energy dispersive X-ray spectrometry (EDX), X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and X-ray photoelectron spectroscopy (XPS), are used to characterize the kinetic parameters of the hybrid catalyst. Cyclic voltammetry (CV) is used to investigate the effects of adding Fe and Ni to the catalyst on the reaction kinetics. Additionally, chronoamperometry (CA) tests were conducted to study the long-term performance of the catalyst for catalyzing the methanol oxidation reaction (MOR). The binding energies of the reactants and products are compared to determine the kinetics and potential surface energy for methanol oxidation. The FESEM analysis results indicate that well-dispersed nanoscale (2-5 nm) PtRu particles are formed on the MWCNTs. Finally, PtRuFeNi/MWCNT improves the reaction kinetics of anode catalysts for DMFCs and obtains a mass current of 31 A g(-1) catalyst.

Novel Anode Catalyst for Direct Methanol Fuel Cells

PubMed Central

Basri, S.; Kamarudin, S. K.; Daud, W. R. W.; Yaakob, Z.; Kadhum, A. A. H.

2014-01-01

PtRu catalyst is a promising anodic catalyst for direct methanol fuel cells (DMFCs) but the slow reaction kinetics reduce the performance of DMFCs. Therefore, this study attempts to improve the performance of PtRu catalysts by adding nickel (Ni) and iron (Fe). Multiwalled carbon nanotubes (MWCNTs) are used to increase the active area of the catalyst and to improve the catalyst performance. Electrochemical analysis techniques, such as energy dispersive X-ray spectrometry (EDX), X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and X-ray photoelectron spectroscopy (XPS), are used to characterize the kinetic parameters of the hybrid catalyst. Cyclic voltammetry (CV) is used to investigate the effects of adding Fe and Ni to the catalyst on the reaction kinetics. Additionally, chronoamperometry (CA) tests were conducted to study the long-term performance of the catalyst for catalyzing the methanol oxidation reaction (MOR). The binding energies of the reactants and products are compared to determine the kinetics and potential surface energy for methanol oxidation. The FESEM analysis results indicate that well-dispersed nanoscale (2–5 nm) PtRu particles are formed on the MWCNTs. Finally, PtRuFeNi/MWCNT improves the reaction kinetics of anode catalysts for DMFCs and obtains a mass current of 31 A g−1 catalyst. PMID:24883406

Power generation in microbial fuel cells using platinum group metal-free cathode catalyst: Effect of the catalyst loading on performance and costs.

PubMed

Santoro, Carlo; Kodali, Mounika; Herrera, Sergio; Serov, Alexey; Ieropoulos, Ioannis; Atanassov, Plamen

2018-02-28

Platinum group metal-free (PGM-free) catalyst with different loadings was investigated in air breathing electrodes microbial fuel cells (MFCs). Firstly, the electrocatalytic activity towards oxygen reduction reaction (ORR) of the catalyst was investigated by rotating ring disk electrode (RRDE) setup with different catalyst loadings. The results showed that higher loading led to an increased in the half wave potential and the limiting current and to a further decrease in the peroxide production. The electrons transferred also slightly increased with the catalyst loading up to the value of ≈3.75. This variation probably indicates that the catalyst investigated follow a 2x2e - transfer mechanism. The catalyst was integrated within activated carbon pellet-like air-breathing cathode in eight different loadings varying between 0.1 mgcm -2 and 10 mgcm -2 . Performance were enhanced gradually with the increase in catalyst content. Power densities varied between 90 ± 9 μWcm -2 and 262 ± 4 μWcm -2 with catalyst loading of 0.1 mgcm -2 and 10 mgcm -2 respectively. Cost assessments related to the catalyst performance are presented. An increase in catalyst utilization led to an increase in power generated with a substantial increase in the whole costs. Also a decrease in performance due to cathode/catalyst deterioration over time led to a further increase in the costs.

PCDD/F adsorption and destruction in the flue gas streams of MWI and MSP via Cu and Fe catalysts supported on carbon.

PubMed

Chang, Shu Hao; Yeh, Jhy Wei; Chein, Hung Min; Hsu, Li Yeh; Chi, Kai Hsien; Chang, Moo Been

2008-08-01

Catalytic destruction has been applied to control polychlorinated dibenzo-p-dioxin and dibenzofuran (PCDD/Fs) emissions from different facilities. The cost of carbon-based catalysts is considerably lower than that of the metal oxide or zeolite-based catalysts used in the selective catalytic reduction (SCR) system. In this study, destruction and adsorption efficiencies of PCDD/Fs achieved with Cu/C and Fe/C catalysts from flue gas streams of a metal smelting plant (MSP) and a large-scale municipal waste incinerator (MWI), respectively, are evaluated via the pilot-scale catalytic reactor system (PCRS). The results indicate that Cu and Fe catalysts supported on carbon surface are capable of decomposing and adsorbing PCDD/ Fs from gas streams. In the testing sources of MSP and MWI, the PCDD/F removal efficiencies achieved with Cu/C catalyst at 250 degrees C reach 96%, however, the destruction efficiencies are negative (-1,390% and -112%, respectively) due to significant PCDD/F formation on catalyst promoted by copper. In addition, Fe/C catalyst is of higher removal and destruction efficiencies compared with Cu/C catalyst in both testing sources. The removal efficiencies of PCDD/Fs achieved with Fe/C catalyst are 97 and 94% for MSP and MWI, respectively, whereas the destruction efficiencies are both higher than 70%. Decrease of PCDD/F destruction efficiency and increase of adsorption efficiency with increasing chlorination of dioxin congeners is also observed in the test via three-layer Fe/C catalyst. Furthermore, the mass of 2,3,7,8-PCDD/Fs retained on catalyst decreases on the order of first to third layer of catalyst. Each gram Fe/C catalyst in first layer adsorbs 10.9, 6.91, and 3.04 ng 2,3,7,8-PCDD/Fs in 100 min testing duration as the operating temperature is controlled at 150, 200, and 250 degrees C, respectively.

In situ growth of NiFe alloy nanoparticles embedded into N-doped bamboo-like carbon nanotube as a bifunctional electrocatalyst for Zn-air battery.

PubMed

Bin, Duan; Yang, Beibei; Li, Chao; Liu, Yao; Zhang, Xiao; Wang, Yong-Gang; Xia, Yongyao

2018-06-26

Developing low-cost catalysts for electrochemical oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) with superior performance in alkaline solution is of significance for large-scale application in aqueous zinc-air batteries (ZABs). Herein, we describe in situ design of embedded NiFe nanoparticles into the N-doped bamboo-like carbon nanotube (NBCNT) with high catalytic performance and stability. The obtained NiFe@NBCNT hybrid exhibits a high electrochemical activity and stability with an unexpectedly low overpotential of ~195 mV for OER at 10 mA cm-2, and an onset potential at 1.03 V for ORR, superior to the state-of-the-art Pt/C and RuO2 catalysts. Additionally, compared to the mixture Pt/C and RuO2 cathode, the ZAB based on the NiFe@NBCNT cathode displays lower overpotential (0.80 V), higher stable round-trip efficiency (58.3%) and improved power density for 200 cycles at 10 mA cm-2. Apparently, the obtained results indicate that NiFe@NBCNT hybird is proven to be one of the best non-noble metal catalysts for achieving commercial implementation of rechargeable ZABs.

Large-scale synthesis of arrays of high-aspect-ratio rigid vertically aligned carbon nanofibres

NASA Astrophysics Data System (ADS)

Melechko, A. V.; McKnight, T. E.; Hensley, D. K.; Guillorn, M. A.; Borisevich, A. Y.; Merkulov, V. I.; Lowndes, D. H.; Simpson, M. L.

2003-09-01

We report on techniques for catalytic synthesis of rigid, high-aspect-ratio, vertically aligned carbon nanofibres by dc plasma enhanced chemical vapour deposition that are tailored for applications that require arrays of individual fibres that feature long fibre lengths (up to 20 µm) such as scanning probe microscopy, penetrant cell and tissue probing arrays and mechanical insertion approaches for gene delivery to cell cultures. We demonstrate that the definition of catalyst nanoparticles is the critical step that enables growth of individual, long-length fibres and discuss methods for catalyst particle preparation that allow the growth of individual isolated nanofibres from catalyst dots with diameters as large as 500 nm. This development enables photolithographic definition of catalyst and therefore the inexpensive, large-scale production of such arrays.

Development of dynamic kinetic resolution on large scale for (±)-1-phenylethylamine.

PubMed

Thalén, Lisa K; Bäckvall, Jan-E

2010-09-13

Candida antarctica lipase B (CALB) and racemization catalyst 4 were combined in the dynamic kinetic resolution (DKR) of (±)-1-phenylethylamine (1). Several reaction parameters have been investigated to modify the method for application on multigram scale. A comparison of isopropyl acetate and alkyl methoxyacetates as acyl donors was carried out. It was found that lower catalyst loadings could be used to obtain (R)-2-methoxy-N-(1-phenylethyl)acetamide (3) in good yield and high ee when alkyl methoxyacetates were used as acyl donors compared to when isopropyl acetate was used as the acyl donor. The catalyst loading could be decreased to 1.25 mol % Ru-catalyst 4 and 10 mg CALB per mmol 1 when alkyl methoxyacetates were used as the acyl donor.

Single Atomic Iron Catalysts for Oxygen Reduction in Acidic Media: Particle Size Control and Thermal Activation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Hanguang; Hwang, Sooyeon; Wang, Maoyu

It remains a grand challenge to replace platinum group metal (PGM) catalysts with earth-abundant materials for the oxygen reduction reaction (ORR) in acidic media, which is crucial for large-scale deployment of proton exchange membrane fuel cells (PEMFCs). Here, we report a high-performance atomic Fe catalyst derived from chemically Fe-doped zeolitic imidazolate frameworks (ZIFs) by directly bonding Fe ions to imidazolate ligands within 3D frameworks. Although the ZIF was identified as a promising precursor, the new synthetic chemistry enables the creation of well-dispersed atomic Fe sites embedded into porous carbon without the formation of aggregates. The size of catalyst particles ismore » tunable through synthesizing Fe-doped ZIF nanocrystal precursors in a wide range from 20 to 1000 nm followed by one-step thermal activation. Similar to Pt nanoparticles, the unique size control without altering chemical properties afforded by this approach is able to increase the number of PGM-free active sites. The best ORR activity is measured with the catalyst at a size of 50 nm. Further size reduction to 20 nm leads to significant particle agglomeration, thus decreasing the activity. Using the homogeneous atomic Fe model catalysts, we elucidated the active site formation process through correlating measured ORR activity with the change of chemical bonds in precursors during thermal activation up to 1100 °C. The critical temperature to form active sites is 800 °C, which is associated with a new Fe species with a reduced oxidation number (from Fe3+ to Fe2+) likely bonded with pyridinic N (FeN4) embedded into the carbon planes. Further increasing the temperature leads to continuously enhanced activity, linked to the rise of graphitic N and Fe–N species. The new atomic Fe catalyst has achieved respectable ORR activity in challenging acidic media (0.5 M H2SO4), showing a half-wave potential of 0.85 V vs RHE and leaving only a 30 mV gap with Pt/C (60 μgPt/cm2). Enhanced stability is attained with the same catalyst, which loses only 20 mV after 10 000 potential cycles (0.6–1.0 V) in O2 saturated acid. The high-performance atomic Fe PGM-free catalyst holds great promise as a replacement for Pt in future PEMFCs.« less

Single Atomic Iron Catalysts for Oxygen Reduction in Acidic Media: Particle Size Control and Thermal Activation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Hanguang; Hwang, Sooyeon; Wang, Maoyu

It remains a grand challenge to replace platinum group metal (PGM) catalysts with earth-abundant materials for the oxygen reduction reaction (ORR) in acidic media, which is crucial for large-scale deployment of proton exchange membrane fuel cells (PEMFCs). We report a high-performance atomic Fe catalyst derived from chemically Fe-doped zeolitic imidazolate frameworks (ZIFs) by directly bonding Fe ions to imidazolate ligands within 3D frameworks. Although the ZIF was identified as a promising precursor, the new synthetic chemistry enables the creation of well-dispersed atomic Fe sites embedded into porous carbon without the formation of aggregates. The size of catalyst particles is tunablemore » through synthesizing Fe-doped ZIF nanocrystal precursors in a wide range from 20 to 1000 nm followed by one-step thermal activation. Similar to Pt nanoparticles, the unique size control without altering chemical properties afforded by this approach is able to increase the number of PGM-free active sites. The best ORR activity is measured with the catalyst at a size of 50 nm. Further size reduction to 20 nm leads to significant particle agglomeration, thus decreasing the activity. In using the homogeneous atomic Fe model catalysts, we elucidated the active site formation process through correlating measured ORR activity with the change of chemical bonds in precursors during thermal activation up to 1100 °C. The critical temperature to form active sites is 800 °C, which is associated with a new Fe species with a reduced oxidation number (from Fe 3+ to Fe 2+) likely bonded with pyridinic N (FeN 4) embedded into the carbon planes. Further increasing the temperature leads to continuously enhanced activity, linked to the rise of graphitic N and Fe–N species. The new atomic Fe catalyst has achieved respectable ORR activity in challenging acidic media (0.5 M H 2SO 4), showing a half-wave potential of 0.85 V vs RHE and leaving only a 30 mV gap with Pt/C (60 μg Pt/cm 2). Finally, enhanced stability is attained with the same catalyst, which loses only 20 mV after 10 000 potential cycles (0.6–1.0 V) in O 2 saturated acid. The high-performance atomic Fe PGM-free catalyst holds great promise as a replacement for Pt in future PEMFCs.« less

Single Atomic Iron Catalysts for Oxygen Reduction in Acidic Media: Particle Size Control and Thermal Activation

DOE PAGES

Zhang, Hanguang; Hwang, Sooyeon; Wang, Maoyu; ...

2017-09-13

It remains a grand challenge to replace platinum group metal (PGM) catalysts with earth-abundant materials for the oxygen reduction reaction (ORR) in acidic media, which is crucial for large-scale deployment of proton exchange membrane fuel cells (PEMFCs). We report a high-performance atomic Fe catalyst derived from chemically Fe-doped zeolitic imidazolate frameworks (ZIFs) by directly bonding Fe ions to imidazolate ligands within 3D frameworks. Although the ZIF was identified as a promising precursor, the new synthetic chemistry enables the creation of well-dispersed atomic Fe sites embedded into porous carbon without the formation of aggregates. The size of catalyst particles is tunablemore » through synthesizing Fe-doped ZIF nanocrystal precursors in a wide range from 20 to 1000 nm followed by one-step thermal activation. Similar to Pt nanoparticles, the unique size control without altering chemical properties afforded by this approach is able to increase the number of PGM-free active sites. The best ORR activity is measured with the catalyst at a size of 50 nm. Further size reduction to 20 nm leads to significant particle agglomeration, thus decreasing the activity. In using the homogeneous atomic Fe model catalysts, we elucidated the active site formation process through correlating measured ORR activity with the change of chemical bonds in precursors during thermal activation up to 1100 °C. The critical temperature to form active sites is 800 °C, which is associated with a new Fe species with a reduced oxidation number (from Fe 3+ to Fe 2+) likely bonded with pyridinic N (FeN 4) embedded into the carbon planes. Further increasing the temperature leads to continuously enhanced activity, linked to the rise of graphitic N and Fe–N species. The new atomic Fe catalyst has achieved respectable ORR activity in challenging acidic media (0.5 M H 2SO 4), showing a half-wave potential of 0.85 V vs RHE and leaving only a 30 mV gap with Pt/C (60 μg Pt/cm 2). Finally, enhanced stability is attained with the same catalyst, which loses only 20 mV after 10 000 potential cycles (0.6–1.0 V) in O 2 saturated acid. The high-performance atomic Fe PGM-free catalyst holds great promise as a replacement for Pt in future PEMFCs.« less

High-Performance Carbon Dioxide Electrocatalytic Reduction by Easily Fabricated Large-Scale Silver Nanowire Arrays.

PubMed

Luan, Chuhao; Shao, Yang; Lu, Qi; Gao, Shenghan; Huang, Kai; Wu, Hui; Yao, Kefu

2018-05-30

An efficient and selective catalyst is in urgent need for carbon dioxide electroreduction and silver is one of the promising candidates with affordable costs. Here we fabricated large-scale vertically standing Ag nanowire arrays with high crystallinity and electrical conductivity as carbon dioxide electroreduction catalysts by a simple nanomolding method that was usually considered not feasible for metallic crystalline materials. A great enhancement of current densities and selectivity for CO at moderate potentials was achieved. The current density for CO ( j co ) of Ag nanowire array with 200 nm in diameter was more than 2500 times larger than that of Ag foil at an overpotential of 0.49 V with an efficiency over 90%. The origin of enhanced performances are attributed to greatly increased electrochemically active surface area (ECSA) and higher intrinsic activity compared to those of polycrystalline Ag foil. More low-coordinated sites on the nanowires which can stabilize the CO 2 intermediate better are responsible for the high intrinsic activity. In addition, the impact of surface morphology that induces limited mass transportation on reaction selectivity and efficiency of nanowire arrays with different diameters was also discussed.

Nano-array based monolithic catalysts: Concept, rational materials design and tunable catalytic performance

DOE PAGES

Ren, Zheng; Guo, Yanbing; Gao, Pu-Xian

2015-03-20

Monolithic catalysts, also known as structured catalysts, represent an important catalyst configuration widely used in automotive, chemical, and energy industries. However, several issues associated with washcoat based monolithic catalyst preparation are ever present, such as compromised materials utilization efficiency due to a less-than-ideal wash coating process, difficulty in precise and optimum microstructure control and lack of structure-property correlation. Here, in this mini-review, we introduce the concept of nano-array catalyst, a new type of monolithic catalyst featuring high catalyst utilization efficiency, good thermal/mechanical robustness, and catalytic performance tunability. A comprehensive overview is presented with detailed discussion of the strategies for nano-arraymore » catalyst preparation and rational catalytic activity adjustment enabled by the well-defined nano-array geometry. Specifically their scalable fabrication processes are reviewed in conjunction with discussion of their various catalytic oxidation reaction performances at low temperature. Finally, we hope this review will serve as a timely and useful research guide for rational design and utilization of the new type of monolithic catalysts.« less

Synthesis H-Zeolite catalyst by impregnation KI/KIO3 and performance test catalyst for biodiesel production

NASA Astrophysics Data System (ADS)

Widayat, W.; Rizky Wicaksono, Adit; Hakim Firdaus, Lukman; Okvitarini, Ndaru

2016-02-01

The objective of this research is to produce H-catalyst catalyst that was impregnated with KI/KIO3. The catalyst was analyzed about surface area, X-Ray Diffraction (XRD) and performance test of catalyst for biodiesel production. An H-Zeolite catalyst was synthesized from natural zeolite with chemical treatment processing, impregnation KI/KIO3 and physical treatment. The results shows that the surface area of the catalyst by 27.236 m2/g at a concentration of 5% KI. XRD analysis shows peak 2-θ at 23.627o indicating that KI was impregnated on H-zeolite catalyst. The catalyst was tested in production of biodiesel using palm oil with conventional methods for 3 hour at temperature of 70-80 oC. The result for conversion Fatty Acid Methyl Ester (FAME) reached maximum value on 87.91% under production process using catalyst 5% KIO3-H zeolite.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vardon, Derek R.; Settle, Amy E.; Vorotnikov, Vassili

Succinic acid is a biomass-derived platform chemical that can be catalytically converted in the aqueous phase to 1,4-butanediol (BDO), a prevalent building block used in the polymer and chemical industries. Despite significant interest, limited work has been reported regarding sustained catalyst performance and stability under continuous aqueous-phase process conditions. As such, this work examines Ru-Sn on activated carbon (AC) for the aqueous-phase conversion of succinic acid to BDO under batch and flow reactor conditions. Initially, powder Ru-Sn catalysts were screened to determine the most effective bimetallic ratio and provide a comparison to other monometallic (Pd, Pt, Ru) and bimetallic (Pt-Sn,more » Pd-Re) catalysts. Batch reactor tests determined that a ~1:1 metal weight ratio of Ru to Sn was effective for producing BDO in high yields, with complete conversion resulting in 82% molar yield. Characterization of the fresh Ru-Sn catalyst suggests that the sequential loading method results in Ru sites that are colocated and surface-enriched with Sn. Postbatch reaction characterization confirmed stable Ru-Sn material properties; however, upon a transition to continuous conditions, significant Ru-Sn/AC deactivation occurred due to stainless steel leaching of Ni that resulted in Ru-Sn metal crystallite restructuring to form discrete Ni-Sn sites. Computational modeling confirmed favorable energetics for Ru-Sn segregation and Ni-Sn formation at submonolayer Sn incorporation. To address stainless steel leaching, reactor walls were treated with an inert silica coating by chemical vapor deposition. With leaching reduced, stable Ru-Sn/AC performance was observed that resulted in a molar yield of 71% BDO and 15% tetrahydrofuran for 96 h of time on stream. Postreaction catalyst characterization confirmed low levels of Ni and Cr deposition, although early-stage islanding of Ni-Sn will likely be problematic for industrially relevant time scales (i.e., thousands of hours). Overall, these results (i) demonstrate the performance of Ru-Sn/AC for aqueous phase succinic acid reduction, (ii) provide insight into the Ru-Sn bimetallic structure and deactivation in the presence of leached Ni, and (iii) underscore the importance of compatible reactor metallurgy and durable catalysts.« less

Mathematical modeling of methyl ester concentration distribution in a continuous membrane tubular reactor and comparison with conventional tubular reactor

NASA Astrophysics Data System (ADS)

Talaghat, M. R.; Jokar, S. M.; Modarres, E.

2017-10-01

The reduction of fossil fuel resources and environmental issues made researchers find alternative fuels include biodiesels. One of the most widely used methods for production of biodiesel on a commercial scale is transesterification method. In this work, the biodiesel production by a transesterification method was modeled. Sodium hydroxide was considered as a catalyst to produce biodiesel from canola oil and methanol in a continuous tubular ceramic membranes reactor. As the Biodiesel production reaction from triglycerides is an equilibrium reaction, the reaction rate constants depend on temperature and related linearly to catalyst concentration. By using the mass balance for a membrane tubular reactor and considering the variation of raw materials and products concentration with time, the set of governing equations were solved by numerical methods. The results clearly show the superiority of membrane reactor than conventional tubular reactors. Afterward, the influences of molar ratio of alcohol to oil, weight percentage of the catalyst, and residence time on the performance of biodiesel production reactor were investigated.

Structural analysis of nickel doped cerium oxide catalysts for fuel reforming in solid oxide fuel cells

NASA Astrophysics Data System (ADS)

Cavendish, Rio

As world energy demands increase, research into more efficient energy production methods has become imperative. Heterogeneous catalysis and nanoscience are used to promote chemical transformations important for energy production. These concepts are important in solid oxide fuel cells (SOFCs) which have attracted attention because of their potential to provide an efficient and environmentally favorable power generation system. The SOFC is also fuel-flexible with the ability to run directly on many fuels other than hydrogen. Internal fuel reforming directly in the anode of the SOFC would greatly reduce the cost and complexity of the device. Methane is the simplest hydrocarbon and a main component in natural gas, making it useful when testing catalysts on the laboratory scale. Nickel (Ni) and gadolinium (Gd) doped ceria (CeO 2) catalysts for potential use in the SOFC anode were synthesized with a spray drying method and tested for catalytic performance using partial oxidation of methane and steam reforming. The relationships between catalytic performance and structure were then investigated using X-ray diffraction, transmission electron microscopy, and environmental transmission electron microscopy. The possibility of solid solutions, segregated phases, and surface layers of Ni were explored. Results for a 10 at.% Ni in CeO2 catalyst reveal a poor catalytic behavior while a 20 at.% Ni in CeO2 catalyst is shown to have superior activity. The inclusion of both 10 at.% Gd and 10 at.% Ni in CeO2 enhances the catalytic performance. Analysis of the presence of Ni in all 3 samples reveals Ni heterogeneity and little evidence for extensive solid solution doping. Ni is found in small domains throughout CeO2 particles. In the 20 at.% Ni sample a segregated, catalytically active NiO phase is observed. Overall, it is found that significant interaction between Ni and CeO2 occurs that could affect the synthesis and functionality of the SOFC anode.

Effect of polymer binders in anode catalyst layer on performance of alkaline direct ethanol fuel cells

NASA Astrophysics Data System (ADS)

Li, Y. S.; Zhao, T. S.; Liang, Z. X.

In preparing low-temperature fuel cell electrodes, a polymer binder is essential to bind discrete catalyst particles to form a porous catalyst layer that simultaneously facilitates the transfer of ions, electrons, and reactants/products. For two types of polymer binder, namely, an A3-an anion conducting ionomer and a PTFE-a neutral polymer, an investigation is made of the effect of the content of each binder in the anode catalyst layer on the performance of an alkaline direct ethanol fuel cell (DEFC) with an anion-exchange membrane and non-platinum (non-Pt) catalysts. Experiments are performed by feeding either ethanol (C 2H 5OH) solution or ethanol-potassium hydroxide (C 2H 5OH-KOH) solution. The experimental results for the case of feeding C 2H 5OH solution without added KOH indicate that the cell performance varies with the A3 ionomer content in the anode catalyst layer, and a content of 10 wt.% exhibits the best performance. When feeding C 2H 5OH-KOH solution, the results show that: (i) in the region of low current density, the best performance is achieved for a membrane electrode assembly without any binder in the anode catalyst layer; (ii) in the region of high current density, the performance is improved with incorporation of PTFE binder in the anode catalyst layer; (iii) the PTFE binder yields better performance than does the A3 binder.

Catalyst and electrode research for phosphoric acid fuel cells

NASA Technical Reports Server (NTRS)

Antoine, A. C.; King, R. B.

1987-01-01

An account is given of the development status of phosphoric acid fuel cells' high performance catalyst and electrode materials. Binary alloys have been identified which outperform the baseline platinum catalyst; it has also become apparent that pressurized operation is required to reach the desired efficiencies, calling in turn for the use of graphitized carbon blacks in the role of catalyst supports. Efforts to improve cell performance and reduce catalyst costs have led to the investigation of a class of organometallic cathode catalysts represented by the tetraazaannulenes, and a mixed catalyst which is a mixture of carbons catalyzed with an organometallic and a noble metal.

Graphitized Carbon: A Promising Stable Cathode Catalyst Support Material for Long Term PEMFC Applications.

PubMed

Mohanta, Paritosh Kumar; Regnet, Fabian; Jörissen, Ludwig

2018-05-28

Stability of cathode catalyst support material is one of the big challenges of polymer electrolyte membrane fuel cells (PEMFC) for long term applications. Traditional carbon black (CB) supports are not stable enough to prevent oxidation to CO₂ under fuel cell operating conditions. The feasibility of a graphitized carbon (GC) as a cathode catalyst support for low temperature PEMFC is investigated herein. GC and CB supported Pt electrocatalysts were prepared via an already developed polyol process. The physical characterization of the prepared catalysts was performed using transmission electron microscope (TEM), X-ray Powder Diffraction (XRD) and inductively coupled plasma optical emission spectrometry (ICP-OES) analysis, and their electrochemical characterizations were conducted via cyclic voltammetry(CV), rotating disk electrode (RDE) and potential cycling, and eventually, the catalysts were processed using membrane electrode assemblies (MEA) for single cell performance tests. Electrochemical impedance spectroscopy (EIS) and scanning electrochemical microscopy (SEM) have been used as MEA diagonostic tools. GC showed superior stability over CB in acid electrolyte under potential conditions. Single cell MEA performance of the GC-supported catalyst is comparable with the CB-supported catalyst. A correlation of MEA performance of the supported catalysts of different Brunauer⁻Emmett⁻Teller (BET) surface areas with the ionomer content was also established. GC was identified as a promising candidate for catalyst support in terms of both of the stability and the performance of fuel cell.

Platinum assisted by carbon quantum dots for methanol electro-oxidation

NASA Astrophysics Data System (ADS)

Pan, Dan; Li, Xingwei; Zhang, Aofeng

2018-01-01

Various types of fuel cells as clean and portable power sources show a great attraction, especially direct methanol fuel cell (DMFC) having high energy density, low operating temperature and convenient fuel storage. However, the preparation of low-cost Pt-based catalysts with satisfactory catalytic performance still faces many challenges for its commercialization on large scale. Here, Pt catalysts assisted by carbon quantum dots (CQDs) are reported. The synergistic effect of carbon quantum dots and Pt metals is similar to a bi-component catalyst, such as PtRu. First, carbon quantum dots derived from Vulcan XC-72 carbon black are synthesized by mixed acid etching. Then, carbon black (Vulcan XC-72) is soaked in carbon quantum dots solution for several days to obtain carbon black modified by carbon quantum dots (XC-72-CQDs). Finally, Pt catalysts are supported on XC-72-CQDs (Pt/XC-72-CQDs) through a simple chemical reduction method. For methanol electro-oxidation reaction, the catalytic performance of Pt/XC-72-CQDs is compared with commercial PtRu/C (30% Pt + 15% Ru). Results show that a typical product (Pt/XC-72-CQDs5) exhibits a better catalytic activity than PtRu/C. In cyclic voltammetry test, the specific activity of Pt/XC-72-CQDs5 is 1.06 mA cm-2 Pt and 477.6 mA mg-1 Pt, while that of PtRu/C is 0.77 mA cm-2 Pt and 280.6 mA mg-1 Pt.

Discerning the Location and Nature of Coke Deposition from Surface to Bulk of Spent Zeolite Catalysts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Devaraj, Arun; Vijayakumar, Murugesan; Bao, Jie

The nanoscale compositional mapping of fresh HZSM-5 catalyst synthesized using hydrothermal process as well as after just steaming and after ethanol conversion reaction for 72 hours at realistic catalytic conditions was investigated using atom probe tomography. Atom probe tomography permitted direct atomic scale imaging of non-uniform distribution of Al within the HZSM-5 as well as for the first time image the hydrocarbon coking after ethanol reaction. Clear evidences for existence of multiple C-H molecular species which appear to aggregate as clusters within the pores of spent HZSM-5 catalyst materials is provided. These results provide evidence for the ability of atommore » probe tomography, a powerful 3D characterization tool in interrogating the atomic scale chemistry of zeolite catalyst materials at industrially relevant catalytic conditions.« less

Synthesis of CaO-CeO2 catalysts by soft template method for biodiesel production

NASA Astrophysics Data System (ADS)

Zheng, Y. C.; Yu, X. H.; Yang, J.

2017-06-01

Biodiesel has recently gained extensive attention. Catalysts play an important role in producing biodiesel by transesterification reaction. In this study, CaO-CeO2 catalysts are developed as the solid base catalyst. Using PDMS-PEO as a structure-directing agent, the prepared CaO-CeO2 catalysts have a three-dimensional interconnected porous structure, which benefits the transesterification reaction. While the added Ce slightly decreases the catalytic activity, the stability of the catalyst shows remarkable improvement. Considering the catalytic activity and stability, the best catalyst is determined to be catalyst 0.15-1073 (Ce/Ca molar ratio of 0.15 and calcination temperature of 1073 K). Under optimum reaction conditions, the biodiesel yield reaches to 97.5% and metal leaching is 117.7 ppm. For catalyst 0.15-1073 regenerated after four reaction cycles, the biodiesel yield is 94.1%. The results reveal that the CaO-CeO2 catalyst has good potential for application in large-scale biodiesel production in the future.

Understanding low temperature oxidation activity of nanoarray-based monolithic catalysts: from performance observation to structural and chemical insights

DOE PAGES

Du, Shoucheng; Tang, Wenxiang; Guo, Yanbing; ...

2016-12-30

Monolithic catalysts have been widely used in automotive, chemical, and energy relevant industries. Nano-array based monolithic catalysts have been developed, demonstrating high catalyst utilization efficiency and good thermal/mechanical robustness. Compared with the conventional wash-coat based monolithic catalysts, they have shown advances in precise and optimum microstructure control and feasibility in correlating materials structure with properties. Recently, the nano-array based monolithic catalysts have been studied for low temperature oxidation of automotive engine exhaust and exhibited interesting and promising catalytic activities. Here, this review focuses on discussing the key catalyst structural parameters that affect the catalytic performance from the following aspects, (1)more » geometric shape and crystal planes, (2) guest atom doping and defects, (3) array size and size-assisted active species loading, and (4) the synergy effect of metal oxide in composite nano-arrays. Prior to the discussion, an overview of the current status of synthesis and development of the nano-array based monolithic catalysts is introduced. The performance of these materials in low temperature simulated engine exhaust oxidation is also demonstrated. Finally, we hope this review will elucidate the science and chemistry behind the good oxidation performance of the nanoarray- based monolithic catalysts, and serve as a timely and useful research guide for rational design and further improvement of the nano-array based monolithic catalysts for automobile emission control.« less

Understanding low temperature oxidation activity of nanoarray-based monolithic catalysts: from performance observation to structural and chemical insights

DOE Office of Scientific and Technical Information (OSTI.GOV)

Du, Shoucheng; Tang, Wenxiang; Guo, Yanbing

Monolithic catalysts have been widely used in automotive, chemical, and energy relevant industries. Nano-array based monolithic catalysts have been developed, demonstrating high catalyst utilization efficiency and good thermal/mechanical robustness. Compared with the conventional wash-coat based monolithic catalysts, they have shown advances in precise and optimum microstructure control and feasibility in correlating materials structure with properties. Recently, the nano-array based monolithic catalysts have been studied for low temperature oxidation of automotive engine exhaust and exhibited interesting and promising catalytic activities. Here, this review focuses on discussing the key catalyst structural parameters that affect the catalytic performance from the following aspects, (1)more » geometric shape and crystal planes, (2) guest atom doping and defects, (3) array size and size-assisted active species loading, and (4) the synergy effect of metal oxide in composite nano-arrays. Prior to the discussion, an overview of the current status of synthesis and development of the nano-array based monolithic catalysts is introduced. The performance of these materials in low temperature simulated engine exhaust oxidation is also demonstrated. Finally, we hope this review will elucidate the science and chemistry behind the good oxidation performance of the nanoarray- based monolithic catalysts, and serve as a timely and useful research guide for rational design and further improvement of the nano-array based monolithic catalysts for automobile emission control.« less

NOVEL RU-NI-S ELECTRODE CATALYST FOR PEMFC

EPA Science Inventory

The expected results from this project include:

• a new formula and preparation procedures for Ru-Ni-S catalyst;
• demonstration of CO and S tolerance of the new catalyst;
• a small size PEMFC with Ru-Ni-S catalyst and good performance; an...

• Electrochemical performance and durability of carbon supported Pt catalyst in contact with aqueous and polymeric proton conductors.

  PubMed

  Andersen, Shuang Ma; Skou, Eivind

  2014-10-08

  Significant differences in catalyst performance and durability are often observed between the use of a liquid electrolyte (e.g., sulfuric acid), and a solid polymer electrolyte (e.g., Nafion). To understand this phenomenon, we studied the electrochemical behavior of a commercially available carbon supported platinum catalyst in four different electrode structures: catalyst powder (CP), catalyst ionomer electrode (CIE), half membrane electrode assembly (HMEA), and full membrane electrode assembly (FMEA) in both ex situ and in situ experiments under a simulated start/stop cycle. We found that the catalyst performance and stability are very much influenced by the presence of the Nafion ionomers. The proton conducting phase provided by the ionomer and the self-assembled electrode structure render the catalysts a higher utilization and better stability. This is probably due to an enhanced dispersion, an improved proton-catalyst interface, the restriction of catalyst particle aggregation, and the improved stability of the ionomer phase especially after the lamination. Therefore, an innovative electrode HMEA design for ex-situ catalyst characterization is proposed. The electrode structure is identical to the one used in a real fuel cell, where the protons transport takes place solely through solid state proton conducting phase.

• Core-shell rhodium sulfide catalyst for hydrogen evolution reaction / hydrogen oxidation reaction in hydrogen-bromine reversible fuel cell

  NASA Astrophysics Data System (ADS)

  Li, Yuanchao; Nguyen, Trung Van

  2018-04-01

  Synthesis and characterization of high electrochemical active surface area (ECSA) core-shell RhxSy catalysts for hydrogen evolution oxidation (HER)/hydrogen oxidation reaction (HOR) in H2-Br2 fuel cell are discussed. Catalysts with RhxSy as shell and different percentages (5%, 10%, and 20%) of platinum on carbon as core materials are synthesized. Cyclic voltammetry is used to evaluate the Pt-equivalent mass specific ECSA and durability of these catalysts. Transmission electron microscopy (TEM), X-ray Photoelectron spectroscopy (XPS) and Energy-dispersive X-ray spectroscopy (EDX) techniques are utilized to characterize the bulk and surface compositions and to confirm the core-shell structure of the catalysts, respectively. Cycling test and polarization curve measurements in the H2-Br2 fuel cell are used to assess the catalyst stability and performance in a fuel cell. The results show that the catalysts with core-shell structure have higher mass specific ECSA (50 m2 gm-Rh-1) compared to a commercial catalyst (RhxSy/C catalyst from BASF, 6.9 m2 gm-Rh-1). It also shows better HOR/HER performance in the fuel cell. Compared to the platinum catalyst, the core-shell catalysts show more stable performance in the fuel cell cycling test.

Creative musical expression as a catalyst for quality-of-life improvement in inner-city adolescents placed in a court-referred residential treatment program.

PubMed

Bittman, Barry; Dickson, Larry; Coddington, Kim

2009-01-01

Obstacles to effectively rehabilitate inner-city adolescents in staff-secure residential treatment centers should not be underestimated. Effective evidence-based protocols are lacking to help juveniles who are often angry, detached, frustrated, and in direct conflict with their peers. Facing a myriad of issues ranging from youth delinquency offenses to trauma, abuse, drug/alcohol use, peer pressure/gang-related activities, lack of structure in home environments, mental health diagnoses, and cognitive functioning difficulties, these adolescents present extraordinary challenges to an over-stressed juvenile justice system. A randomized controlled crossover study is utilized to comprehensively evaluate the effectiveness of a novel creative musical expression protocol as a catalyst for nonverbal and verbal disclosure leading to improvements in quality of life for inner-city youth in a court-referred residential treatment program. A total of 52 (30 females and 22 males) African-American, Asian, Caucasian, and Puerto Rican subjects ranging in age from 12 to 18 (mean age 14.5) completed the study. Dependent variable measures included the Child and Adolescent Functional Assessment Scale (CAFAS), the Adolescent Psychopathology Scale (APS), the Adolescent Anger Rating Scale (AARS), the Reynolds Adolescent Depression Scale, 2nd edition (RADS 2), and the Adolescent Visual-Analog Recreational Music Making Assessment (A-VARMMA). Statistically significant (experimental vs control) improvements in multiple parameters include school/work role performance, total depression, anhedonia/negative affect, negative self-evaluation, and instrumental anger. In addition, extended impact (experimental vs control) is characterized by statistically significant improvements 6 weeks after completion of the protocol, for school/work role performance, behavior toward others, anhedonia/negative affect, total anger, instrumental anger, anger, and interpersonal problems. The primary limitations of this study include an extended follow-up period of only 6 weeks post completion of the protocol, and the inability to blind the counselors performing standardized assessments. This study is the first of its kind to test a replicable creative musical expression protocol as a catalyst for nonverbal and verbal disclosure leading to improved quality of life for inner-city youth in a court-referred residential treatment program. With substantial potential for widespread dissemination, this innovative protocol for adolescents can be readily utilized by behavioral health professionals without prior musical experience.

Synthesis of Millimeter-Scale Carbon Nanotube Arrays and Their Applications on Electrochemical Supercapacitors

NASA Astrophysics Data System (ADS)

Cui, Xinwei

This research is aimed at synthesizing millimeter-scale carbon nanotube arrays (CNTA) by conventional chemical vapor deposition (CCVD) and water-assisted chemical vapor deposition (WACVD) methods, and exploring their application as catalyst supports for electrochemical supercapacitors. The growth mechanism and growth kinetics of CNTA under different conditions were systematically investigated to understand the relationship among physical characteristics of catalyst particles, growth parameters, and carbon nanotube (CNT) structures within CNTAs. Multiwalled CNT (MWCNT) array growth demonstrates lengthening and thickening stages in CCVD and WACVD. In CCVD, the lengthening and thickening were found to be competitive. By investigating catalyst particles after different pretreatment conditions, it has been found that inter-particle spacing plays a significant role in influencing CNTA height, CNT diameter and wall number. In WACVD, a long linear lengthening stage has been found. CNT wall number remains constant and catalysts preserve the activity in this stage, while MWCNTs thicken substantially and catalysts deactivate following the previously proposed radioactive decay model in the thickening stage of WACVD. Water was also shown to preserve the catalyst activity by significantly inhibiting catalyst-induced and gas phase-induced thickening processes in WACVD. Mn3O4 nanoparticles were successfully deposited and uniformly distributed within millimeter-long CNTAs by dip-casting method from non-aqueous solutions. After modification with Mn3O4 nanoparticles, CNTAs have been changed from hydrophobic to hydrophilic without their alignment and integrity being destroyed. The hydrophilic Mn 3O4/CNTA composite electrodes present ideal capacitive behavior with high reversibility. This opens up a new route of utilizing ultra-long CNTAs, based on which a scalable and cost-effective method was developed to fabricate composite electrodes using millimeter-long CNTAs. To improve the performance of the composites, epsilon-MnO2 nanorods were anodically pulse-electrodeposited within hydrophilic 0.5 mm-thick Mn 3O4 decorated CNTAs. The maximum gravimetric capacitance for the MnO2 nanorods/CNTA composite electrode was found to be 185 F/g, and that for epsilon-MnO2 nanorods was determined to be 221 F/g. After electrodeposition, the area-normalized capacitance and volumetric capacitance values were increased by a factor of 3, and an extremely high area-normalized capacitance of 1.80 F/cm2 was also achieved for the MnO2 nanorods/CNTA composite.

An experimental study of catalytic and non-catalytic reaction in heat recirculating reactors and applications to power generation

NASA Astrophysics Data System (ADS)

Ahn, Jeongmin

An experimental study of the performance of a Swiss roll heat exchanger and reactor was conducted, with emphasis on the extinction limits and comparison of results with and without Pt catalyst. At Re<40, the catalyst was required to sustain reaction; with the catalyst self-sustaining reaction could be obtained at Re less than 1. Both lean and rich extinction limits were extended with the catalyst, though rich limits were extended much further. At low Re, the lean extinction limit was rich of stoichiometric and rich limit had equivalence ratios 80 in some cases. Non-catalytic reaction generally occurred in a flameless mode near the center of the reactor. With or without catalyst, for sufficiently robust conditions, a visible flame would propagate out of the center, but this flame could only be re-centered with catalyst. Gas chromatography indicated that at low Re, CO and non-C3 H8 hydrocarbons did not form. For higher Re, catalytic limits were slightly broader but had much lower limit temperatures. At sufficiently high Re, catalytic and gas-phase limits merged. Experiments with titanium Swiss rolls have demonstrated reducing wall thermal conductivity and thickness leads to lower heat losses and therefore increases operating temperatures and extends flammability limits. By use of Pt catalysts, reaction of propane-air mixtures at temperatures 54°C was sustained. Such low temperatures suggest that polymers may be employed as a reactor material. A polyimide reactor was built and survived prolonged testing at temperatures up to 500°C. Polymer reactors may prove more practical for microscale devices due to their lower thermal conductivity and ease of manufacturing. Since the ultimate goal of current efforts is to develop combustion driven power generation devices at MEMS like scales, a thermally self-sustaining miniature power generation device was developed utilizing a single-chamber solid-oxide-fuel-cell (SOFC) placed in a Swiss roll. With the single-chamber design, fuel/oxygen crossover due to cracking of seals via thermal cycling is irrelevant and coking on the anode is practically eliminated. SOFC power densities up to 420mW/cm2 were observed at low Re. These results suggest that single-chamber SOFC's integrated with heat-recirculating reactors may be a viable approach for small-scale power generation devices.

Applications of Neutron Scattering in the Chemical Industry: Proton Dynamics of Highly Dispersed Materials, Characterization of Fuel Cell Catalysts, and Catalysts from Large-Scale Chemical Processes

NASA Astrophysics Data System (ADS)

Albers, Peter W.; Parker, Stewart F.

The attractiveness of neutron scattering techniques for the detailed characterization of materials of high degrees of dispersity and structural complexity as encountered in the chemical industry is discussed. Neutron scattering picks up where other analytical methods leave off because of the physico-chemical properties of finely divided products and materials whose absorption behavior toward electromagnetic radiation and electrical conductivity causes serious problems. This is demonstrated by presenting typical applications from large-scale production technology and industrial catalysis. These include the determination of the proton-related surface chemistry of advanced materials that are used as reinforcing fillers in the manufacture of tires, where interrelations between surface chemistry, rheological properties, improved safety, and significant reduction of fuel consumption are the focus of recent developments. Neutron scattering allows surface science studies of the dissociative adsorption of hydrogen on nanodispersed, supported precious metal particles of fuel cell catalysts under in situ loading at realistic gas pressures of about 1 bar. Insight into the occupation of catalytically relevant surface sites provides valuable information about the catalyst in the working state and supplies essential scientific input for tailoring better catalysts by technologists. The impact of deactivation phenomena on industrial catalysts by coke deposition, chemical transformation of carbonaceous deposits, and other processes in catalytic hydrogenation processes that result in significant shortening of the time of useful operation in large-scale plants can often be traced back in detail to surface or bulk properties of catalysts or materials of catalytic relevance. A better understanding of avoidable or unavoidable aspects of catalyst deactivation phenomena under certain in-process conditions and the development of effective means for reducing deactivation leads to more energy-efficient and, therefore, environmentally friendly processes and helps to save valuable resources. Even small or gradual improvements in all these fields are of considerable economic impact.

Efficient low-temperature soot combustion by bimetallic Ag-Cu/SBA-15 catalysts.

PubMed

Wen, Zhaojun; Duan, Xinping; Hu, Menglin; Cao, Yanning; Ye, Linmin; Jiang, Lilong; Yuan, Youzhu

2018-02-01

In this study, the effects of copper (Cu) additive on the catalytic performance of Ag/SBA-15 in complete soot combustion were investigated. The soot combustion performance of bimetallic Ag-Cu/SBA-15 catalysts was higher than that of monometallic Ag and Cu catalysts. The optimum catalytic performance was acquired with the 5Ag 1 -Cu 0.1 /SBA-15 catalyst, on which the soot combustion starts at T ig =225°C with a T 50 =285°C. The temperature for 50% of soot combustion was lower than that of conventional Ag-based catalysts to more than 50°C (Aneggi et al., 2009). Physicochemical characterizations of the catalysts indicated that addition of Cu into Ag could form smaller bimetallic Ag-Cu nanolloy particles, downsizing the mean particle size from 3.7nm in monometallic catalyst to 2.6nm in bimetallic Ag-Cu catalyst. Further experiments revealed that Ag and Cu species elicited synergistic effects, subsequently increasing the content of surface active oxygen species. As a result, the structure modifications of Ag by the addition of Cu strongly intensified the catalytic performance. Copyright © 2017. Published by Elsevier B.V.

Pore-scale study of effects of macroscopic pores and their distributions on reactive transport in hierarchical porous media

DOE PAGES

Chen, Li; Zhang, Ruiyuan; Min, Ting; ...

2018-05-19

For applications of reactive transport in porous media, optimal porous structures should possess both high surface area for reactive sites loading and low mass transport resistance. Hierarchical porous media with a combination of pores at different scales are designed for this purpose. In this paper, using the lattice Boltzmann method, pore-scale numerical studies are conducted to investigate diffusion-reaction processes in 2D hierarchical porous media generated by self-developed reconstruction scheme. Complex interactions between porous structures and reactive transport are revealed under different conditions. Simulation results show that adding macropores can greatly enhance the mass transport, but at the same time reducemore » the reactive surface, leading to complex change trend of the total reaction rate. Effects of gradient distribution of macropores within the porous medium are also investigated. It is found that a front-loose, back-tight (FLBT) hierarchical structure is desirable for enhancing mass transport, increasing total reaction rate, and improving catalyst utilization. Finally, on the whole, from the viewpoint of reducing cost and improving material performance, hierarchical porous structures, especially gradient structures with the size of macropores gradually decreasing along the transport direction, are desirable for catalyst application.« less

Pore-scale study of effects of macroscopic pores and their distributions on reactive transport in hierarchical porous media

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Li; Zhang, Ruiyuan; Min, Ting

For applications of reactive transport in porous media, optimal porous structures should possess both high surface area for reactive sites loading and low mass transport resistance. Hierarchical porous media with a combination of pores at different scales are designed for this purpose. In this paper, using the lattice Boltzmann method, pore-scale numerical studies are conducted to investigate diffusion-reaction processes in 2D hierarchical porous media generated by self-developed reconstruction scheme. Complex interactions between porous structures and reactive transport are revealed under different conditions. Simulation results show that adding macropores can greatly enhance the mass transport, but at the same time reducemore » the reactive surface, leading to complex change trend of the total reaction rate. Effects of gradient distribution of macropores within the porous medium are also investigated. It is found that a front-loose, back-tight (FLBT) hierarchical structure is desirable for enhancing mass transport, increasing total reaction rate, and improving catalyst utilization. Finally, on the whole, from the viewpoint of reducing cost and improving material performance, hierarchical porous structures, especially gradient structures with the size of macropores gradually decreasing along the transport direction, are desirable for catalyst application.« less

Stability of High-Performance Pt-Based Catalysts for Oxygen Reduction Reactions.

PubMed

Lin, Rui; Cai, Xin; Zeng, Hao; Yu, Zhuoping

2018-04-01

Due to their environmental sustainability and high efficiency, proton-exchange-membrane fuel cells (PEMFCs) are expected to be an essential type of energy source for electric vehicles, energy generation, and the space industry in the coming decades. Here, the recent developments regarding shape-controlled nanostructure catalysts are reviewed, with a focus on the stability of high-performance Pt-based catalysts and related mechanisms. The catalysts, which possess great activity, are still far from meeting the requirements of their applications, due to stability issues, especially in membrane electrode assemblies (MEAs). Thus, solutions toward the comprehensive performance of Pt-based catalysts are discussed here. The research trends and related theories that can promote the application of Pt-based catalysts are also provided. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Nano-Engineered Catalysts for Direct Methanol Fuel Cells

NASA Technical Reports Server (NTRS)

Myung, Nosang; Narayanan, Sekharipuram; Wiberg, Dean

2008-01-01

Nano-engineered catalysts, and a method of fabricating them, have been developed in a continuing effort to improve the performances of direct methanol fuel cells as candidate power sources to supplant primary and secondary batteries in a variety of portable electronic products. In order to realize the potential for high energy densities (as much as 1.5 W h/g) of direct methanol fuel cells, it will be necessary to optimize the chemical compositions and geometric configurations of catalyst layers and electrode structures. High performance can be achieved when catalyst particles and electrode structures have the necessary small feature sizes (typically of the order of nanometers), large surface areas, optimal metal compositions, high porosity, and hydrophobicity. The present method involves electrodeposition of one or more catalytic metal(s) or a catalytic-metal/polytetrafluoroethylene nanocomposite on an alumina nanotemplate. The alumina nanotemplate is then dissolved, leaving the desired metal or metal/polytetrafluoroethylene-composite catalyst layer. Unlike some prior methods of making fine metal catalysts, this method does not involve processing at elevated temperature; all processing can be done at room temperature. In addition, this method involves fewer steps and is more amenable to scaling up for mass production. Alumina nanotemplates are porous alumina membranes that have been fabricated, variously, by anodizing either pure aluminum or aluminum that has been deposited on silicon by electronbeam evaporation. The diameters of the pores (7 to 300 nm), areal densities of pores (as much as 7 x 10(exp 10)sq cm), and lengths of pores (up to about 100 nm) can be tailored by selection of fabrication conditions. In a given case, the catalytic metal, catalytic metal alloy, or catalytic metal/ polytetrafluoroethylene composite is electrodeposited in the pores of the alumina nanotemplate. The dimensions of the pores, together with the electrodeposition conditions, determine the sizes and surface areas of the catalytic particles. Hence, the small features and large surface areas of the porosity translate to the desired small particle size and large surface area of the catalyst (see figure). When polytetrafluoroethylene is included, it is for the purpose of imparting hydrophobicity in order to prevent water from impeding the desired diffusion of gases through the catalyst layer. To incorporate polytetrafluoroethylene into a catalytic-metal/polytetrafluoroethylene nanocomposite, one suspends polytetrafluoroethylene nanoparticles in the electrodeposition solution. The polytetrafluoroethylene content can be varied to obtain the desired degree of hydrophobicity and permeability by gas.

Enhanced MEA Performance for PEMFCs under Low Relative Humidity and Low Oxygen Content Conditions via Catalyst Functionalization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xin, Le; Yang, Fan; Xie, Jian

2017-01-01

This work demonstrates that functionalizing annealed-Pt/Ketjen black EC300j (a-Pt/KB) and dealloyed-PtNi/Ketjen black EC300j (d-PtNi/KB) catalysts using p-phenyl sulfonic acid can effectively enhance performance in the membrane electrode assemblies (MEAs) of proton exchange membrane fuel cells (PEMFCs). The functionalization increased the size of both Pt and PtNi catalyst particles and resulted in the further leaching of Ni from the PtNi catalyst while promoting the formation of nanoporous PtNi nanoparticles. The size of the SO3H-Pt/KB and SO3H-PtNi/KB carbon-based aggregates decreased dramatically, leading to the formation of catalyst layers with narrower pore size distributions.MEA tests highlighted the benefits of the surface functionalization, inmore » which the cells with SO3H-Pt/KB and SO3H-PtNi/KB cathode catalysts showed superior high current density performance under reduced RH conditions, in comparison with cells containing annealed Pt/KB (a-Pt/KB) and de-alloyed PtNi/KB (d-PtNi/KB) catalysts. The performance improvement was particularly evident when using reactant gases with low relative humidity, indicating that the hydrophilic functional groups on the carbon improved the water retention in the cathode catalyst layer. These results show a new avenue for enhancing catalyst performance for the next generation of catalytic materials for PEMFCs.« less

Understanding trends in C-H bond activation in heterogeneous catalysis.

PubMed

Latimer, Allegra A; Kulkarni, Ambarish R; Aljama, Hassan; Montoya, Joseph H; Yoo, Jong Suk; Tsai, Charlie; Abild-Pedersen, Frank; Studt, Felix; Nørskov, Jens K

2017-02-01

While the search for catalysts capable of directly converting methane to higher value commodity chemicals and liquid fuels has been active for over a century, a viable industrial process for selective methane activation has yet to be developed. Electronic structure calculations are playing an increasingly relevant role in this search, but large-scale materials screening efforts are hindered by computationally expensive transition state barrier calculations. The purpose of the present letter is twofold. First, we show that, for the wide range of catalysts that proceed via a radical intermediate, a unifying framework for predicting C-H activation barriers using a single universal descriptor can be established. Second, we combine this scaling approach with a thermodynamic analysis of active site formation to provide a map of methane activation rates. Our model successfully rationalizes the available empirical data and lays the foundation for future catalyst design strategies that transcend different catalyst classes.

Understanding trends in C–H bond activation in heterogeneous catalysis

DOE PAGES

Latimer, Allegra A.; Kulkarni, Ambarish R.; Aljama, Hassan; ...

2016-10-10

While the search for catalysts capable of directly converting methane to higher value commodity chemicals and liquid fuels has been active for over a century, a viable industrial process for selective methane activation has yet to be developed1. Electronic structure calculations are playing an increasingly relevant role in this search, but large-scale materials screening efforts are hindered by computationally expensive transition state barrier calculations. The purpose of the present letter is twofold. First, we show that, for the wide range of catalysts that proceed via a radical intermediate, a unifying framework for predicting C–H activation barriers using a single universalmore » descriptor can be established. Second, we combine this scaling approach with a thermodynamic analysis of active site formation to provide a map of methane activation rates. Lastly, our model successfully rationalizes the available empirical data and lays the foundation for future catalyst design strategies that transcend different catalyst classes.« less

Understanding trends in C-H bond activation in heterogeneous catalysis

NASA Astrophysics Data System (ADS)

Latimer, Allegra A.; Kulkarni, Ambarish R.; Aljama, Hassan; Montoya, Joseph H.; Yoo, Jong Suk; Tsai, Charlie; Abild-Pedersen, Frank; Studt, Felix; Nørskov, Jens K.

2017-02-01

While the search for catalysts capable of directly converting methane to higher value commodity chemicals and liquid fuels has been active for over a century, a viable industrial process for selective methane activation has yet to be developed. Electronic structure calculations are playing an increasingly relevant role in this search, but large-scale materials screening efforts are hindered by computationally expensive transition state barrier calculations. The purpose of the present letter is twofold. First, we show that, for the wide range of catalysts that proceed via a radical intermediate, a unifying framework for predicting C-H activation barriers using a single universal descriptor can be established. Second, we combine this scaling approach with a thermodynamic analysis of active site formation to provide a map of methane activation rates. Our model successfully rationalizes the available empirical data and lays the foundation for future catalyst design strategies that transcend different catalyst classes.

Catalytic Production of Ethanol from Biomass-Derived Synthesis Gas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Trewyn, Brian G.; Smith, Ryan G.

2016-06-01

Heterogeneous catalysts have been developed for the conversion of biomass-derived synthetic gas (syngas) to ethanol. The objectives of this project were to develop a clean synthesis gas from biomass and develop robust catalysts with high selectivity and lifetime for C 2 oxygenate production from biomass-derived syngas and surrogate syngas. During the timeframe for this project, we have made research progress on the four tasks: (1) Produce clean bio-oil generated from biomass, such as corn stover or switchgrass, by using fast pyrolysis system, (2) Produce clean, high pressure synthetic gas (syngas: carbon monoxide, CO, and hydrogen, H 2) from bio-oil generatedmore » from biomass by gasification, (3) Develop and characterize mesoporous mixed oxide-supported metal catalysts for the selective production of ethanol and other alcohols, such as butanol, from synthesis gas, and (4) Design and build a laboratory scale synthesis gas to ethanol reactor system evaluation of the process. In this final report, detailed explanations of the research challenges associated with this project are given. Progress of the syngas production from various biomass feedstocks and catalyst synthesis for upgrading the syngas to C 2-oxygenates is included. Reaction properties of the catalyst systems under different reaction conditions and different reactor set-ups are also presented and discussed. Specifically, the development and application of mesoporous silica and mesoporous carbon supports with rhodium nanoparticle catalysts and rhodium nanoparticle with manganese catalysts are described along with the significant material characterizations we completed. In addition to the synthesis and characterization, we described the activity and selectivity of catalysts in our micro-tubular reactor (small scale) and fixed bed reactor (larger scale). After years of hard work, we are proud of the work done on this project, and do believe that this work will provide a solid foundation for the future production of syngas from biomass and the development of heterogeneous catalysts for the syngas to C 2-oxygenate process and for the commercialization of this process. Potential future directions for this research are also discussed within the report.« less

Hydrophobic and hydrophilic nanosheet catalysts with high catalytic activity and recycling stability through control of the outermost ligand

NASA Astrophysics Data System (ADS)

Ko, Younji; Kim, Donghee; Kwon, Cheong Hoon; Cho, Jinhan

2018-04-01

In this study, we introduce hydrophobic and hydrophilic graphene oxide nanosheet (GON) catalysts prepared by consecutive ligand replacement of hydrophobically stabilized magnetic and catalytic nanoparticles (NPs); it exhibits high catalytic activity, fast magnetic response, and good dispersion in both nonpolar and aqueous media, allowing high loading amount of magnetic and catalytic NPs onto GON sheets. More specifically, these GON catalysts showed a high product yield of 66-99% and notable recyclability (93% of the initial product yield after 10 reaction cycles) in a Suzuki-Miyaura reaction in nonpolar media, outperforming the performance of the conventional hydrophilic GON catalysts. Additional coating of a hydrophilic layer onto GON catalysts also showed the notable performance (product yield ∼99%) in catalytic reactions performed in aqueous media. Given that ligand-controlled catalytic NPs adsorbed onto 2D nanosheets can be used as hydrophobic and hydrophilic stabilizers as well as catalysts, our approach can provide a tool for developing and designing 2D-nanosheet catalysts with high performance in nonpolar and polar media.

Reactor for tracking catalyst nanoparticles in liquid at high temperature under a high-pressure gas phase with X-ray absorption spectroscopy.

PubMed

Nguyen, Luan; Tao, Franklin Feng

2018-02-01

Structure of catalyst nanoparticles dispersed in liquid phase at high temperature under gas phase of reactant(s) at higher pressure (≥5 bars) is important for fundamental understanding of catalytic reactions performed on these catalyst nanoparticles. Most structural characterizations of a catalyst performing catalysis in liquid at high temperature under gas phase at high pressure were performed in an ex situ condition in terms of characterizations before or after catalysis since, from technical point of view, access to the catalyst nanoparticles during catalysis in liquid phase at high temperature under high pressure reactant gas is challenging. Here we designed a reactor which allows us to perform structural characterization using X-ray absorption spectroscopy including X-ray absorption near edge structure spectroscopy and extended X-ray absorption fine structure spectroscopy to study catalyst nanoparticles under harsh catalysis conditions in terms of liquid up to 350 °C under gas phase with a pressure up to 50 bars. This reactor remains nanoparticles of a catalyst homogeneously dispersed in liquid during catalysis and X-ray absorption spectroscopy characterization.

Linear scaling relationships and volcano plots in homogeneous catalysis – revisiting the Suzuki reaction† †Electronic supplementary information (ESI) available: Detailed derivation of the linear scaling relationships and construction of the volcano plots as well as comparisons of computed values using PBE0-dDsC and M06 functionals is included. See DOI: 10.1039/c5sc02910d Click here for additional data file.

PubMed Central

Busch, Michael; Wodrich, Matthew D.

2015-01-01

Linear free energy scaling relationships and volcano plots are common tools used to identify potential heterogeneous catalysts for myriad applications. Despite the striking simplicity and predictive power of volcano plots, they remain unknown in homogeneous catalysis. Here, we construct volcano plots to analyze a prototypical reaction from homogeneous catalysis, the Suzuki cross-coupling of olefins. Volcano plots succeed both in discriminating amongst different catalysts and reproducing experimentally known trends, which serves as validation of the model for this proof-of-principle example. These findings indicate that the combination of linear scaling relationships and volcano plots could serve as a valuable methodology for identifying homogeneous catalysts possessing a desired activity through a priori computational screening. PMID:28757966

40 CFR 63.4363 - How do I establish the add-on control device operating limits during the performance test?

Code of Federal Regulations, 2010 CFR

2010-07-01

... performance test, you must monitor and record the temperature at the inlet to the catalyst bed and the temperature difference across the catalyst bed at least once every 15 minutes during each of the three test... temperature at the inlet to the catalyst bed and the average temperature difference across the catalyst bed...

Rambutan-like CNT-Al2O3 scaffolds for high-performance cathode catalyst layers of polymer electrolyte fuel cells

NASA Astrophysics Data System (ADS)

Chang, KwangHyun; Cho, Seonghun; Lim, Eun Ja; Park, Seok-Hee; Yim, Sung-Dae

2018-03-01

Rambutan-like CNT-Al2O3 scaffolds are introduced as a potential candidate for CNT-based catalyst supports to overcome the CNT issues, such as the easy bundling in catalyst ink and the poor pore structure of the CNT-based catalyst layers, and to achieve high MEA performance in PEFCs. Non-porous α-phase Al2O3 balls are introduced to enable the growth of multiwalled CNTs, and Pt nanoparticles are loaded onto the CNT surfaces. In a half-cell, the Pt/CNT-Al2O3 catalyst shows much higher durability than those of a commercial Pt/C catalyst even though it shows lower oxygen reduction reaction (ORR) activity than Pt/C. After using the decal process for MEA formation, the Pt/CNT-Al2O3 shows comparable initial performance characteristics to Pt/C, overcoming the lower ORR activity, mainly due to the facile oxygen transport in the cathode catalyst layers fabricated with the CNT-Al2O3 scaffolds. The Pt/CNT-Al2O3 also exhibits much higher durability against carbon corrosion than Pt/C owing to the durable characteristics of CNTs. Systematic analysis of single cell performance for both initial and after degradation is provided to understand the origin of the high initial performance and durable behavior of Pt/CNT-Al2O3-based catalyst layers. This will provide insights into the design of electrocatalysts for high-performance MEAs in PEFCs.

Synthesis of Pt/rGO catalysts with two different reducing agents and their methanol electrooxidation activity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vu, Thu Ha Thi, E-mail: ptntd2004@yahoo.fr; Tran, Thanh Thuy Thi, E-mail: tranthithanhthuygl@gmail.com; Le, Hong Ngan Thi

2016-01-15

Highlights: • Pt/rGO catalysts were successfully synthesized using either NaBH{sub 4} or ethylene glycol. • Synthesis using NaBH{sub 4} could improve electrocatalytic towards methanol oxidation of Pt/rGO catalyst. • 40%Pt/rGO synthesized using NaBH{sub 4} showed the best electrocatalytic performance. - Abstract: The synthesis processes of Platinum (Pt) on reduced graphene oxide (rGO) catalysts from graphene oxide (GO) using two reducing agents including sodium borohydride and ethylene glycol is reported. Structure and morphology of Pt/rGO catalysts are characterized by X-ray powder diffraction, transmission electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy. Electrocatalytic methanol oxidation properties of these catalysts are evaluated bymore » cyclic voltammetry and chronoamperometry. The results show that catalyst synthesized using sodium borohydride has a higher metallic Pt content and an improved catalytic performance in comparison to catalyst synthesized using ethylene glycol. Moreover, effect of Pt loading amount on electrocatalytic methanol oxidation performance of catalysts synthesized using sodium borohydride is systematically investigated. The optimal Pt loading amount on graphene is determined to be 40%.« less

Homogeneously Dispersed Co9S8 Anchored on Nitrogen and Sulfur Co-Doped Carbon Derived from Soybean as Bifunctional Oxygen Electrocatalysts and Supercapacitors.

PubMed

Xiao, Zhen; Xiao, Guozheng; Shi, Minhao; Zhu, Ying

2018-05-16

Developing low-cost and highly active multifunctional electrocatalysts to replace noble metal catalysts is crucial for the commercialization of future clean energy technology. Herein, homogeneous Co 9 S 8 nanoparticles anchored on nitrogen and sulfur co-doped porous carbon nanomaterials (CoS@NSCs) are fabricated by pyrolysis of natural soybean treated with cobalt nitrate. The unique porous structures of the soybean are utilized to provide space for the oxidation and complexation reactions for cobalt compounds, thus leading to in situ generation of homogenously dispersed cobalt sulfide nanoparticles that anchored on the N,S co-doped carbon framework. Because of the coupling effect of cobalt sulfide and doping heteroatoms, CoS@NSC-800 not only displays excellent electrocatalytic performances with low overpotential and high current density toward both oxygen reduction reaction and oxygen evolution reaction comparable to the commercial Pt/C catalyst and IrO 2 catalyst, but also might be a promising candidate for high-performance supercapacitors. The method for the preparation of the multifunctional hybrids is simple but effective for the formation of uniformly distributed metal sulfide nanoparticles anchored on carbon materials, therefore providing a new perspective for the design and synthesis of multifunctional electrocatalysts for electrochemical energy conversion and storage at a large scale.

Fabrication of polymer electrolyte membrane fuel cell MEAs utilizing inkjet print technology

NASA Astrophysics Data System (ADS)

Towne, Silas; Viswanathan, Vish; Holbery, James; Rieke, Peter

Utilizing drop-on-demand technology, we have successfully fabricated hydrogen-air polymer electrolyte membrane fuel cells (PEMFC), demonstrated some of the processing advantages of this technology and have demonstrated that the performance is comparable to conventionally fabricated membrane electrode assemblies (MEAs). Commercial desktop inkjet printers were used to deposit the active catalyst electrode layer directly from print cartridges onto Nafion ® polymer membranes in the hydrogen form. The layers were well-adhered and withstood simple tape peel, bending and abrasion tests and did so without any post-deposition hot press step. The elimination of this processing step suggests that inkjet-based fabrication or similar processing technologies may provide a route to less expensive large-scale fabrication of PEMFCs. When tested in our experimental apparatus, open circuit voltages up to 0.87 V and power densities of up to 155 mW cm -2 were obtained with a catalyst loading of 0.20 mg Pt cm -2. A commercially available membrane under identical, albeit not optimized test conditions, showed about 7% greater power density. The objective of this work was to demonstrate some of the processing advantages of drop-on-demand technology for fabrication of MEAs. It remains to be determined if inkjet fabrication offers performance advantages or leads to more efficient utilization of expensive catalyst materials.

Turning Biodiesel Waste Glycerol into 1,3-Propanediol: Catalytic Performance of Sulphuric acid-Activated Montmorillonite Supported Platinum Catalysts in Glycerol Hydrogenolysis.

PubMed

Samudrala, Shanthi Priya; Kandasamy, Shalini; Bhattacharya, Sankar

2018-05-10

Direct C-O hydrogenolysis of bioglycerine to produce 1,3-propanediol selectively is a vital technology that can expand the scope of biodiesel industry and green chemical production from biomass. Herein we report sulphuric acid-activated montmorillonite clay supported platinum nanoparticles as highly effective solid acid catalysts for the selective production of 1,3-propanediol from glycerol. The catalytic performances of the catalysts were investigated in the hydrogenolysis of glycerol with a fixed bed reactor under ambient pressure. The results were found promising and showed that the activation of montmorillonite by sulphuric acid incorporated Brønsted acidity in the catalyst and significantly improved the selectivity to 1,3-propanediol. The catalytic performance of different platinum loaded catalysts was examined and 2 wt% Pt/S-MMT catalyst presented superior activity among others validating 62% 1,3-propanediol selectivity at 94% glycerol conversion. The catalytic activity of 2Pt/S-MMT was systematically investigated under varying reaction parameters including reaction temperature, hydrogen flow rate, glycerol concentration, weight hourly space velocity, and contact time to derive the optimum conditions for the reaction. The catalyst stability, reusability and structure-activity correlation were also elucidated. The high performance of the catalyst could be ascribed to well disperse Pt nanoparticles immobilized on acid-activated montmorillonite, wider pore-structure and appropriate acid sites of the catalyst.

KF-loaded mesoporous Mg-Fe bi-metal oxides: high performance transesterification catalysts for biodiesel production.

PubMed

Tao, Guiju; Hua, Zile; Gao, Zhe; Zhu, Yan; Zhu, Yan; Chen, Yu; Shu, Zhu; Zhang, Lingxia; Shi, Jianlin

2013-09-21

Using newly developed mesoporous Mg-Fe bi-metal oxides as supports, a novel kind of high performance transesterification catalysts for biodiesel production has been synthesized. More importantly, the impregnation solvent was for the first time found to substantially affect the structures and catalytic performances of the resultant transesterification catalysts.

Computationally Probing the Performance of Hybrid, Heterogeneous, and Homogeneous Iridium-Based Catalysts for Water Oxidation

DOE Office of Scientific and Technical Information (OSTI.GOV)

García-Melchor, Max; Vilella, Laia; López, Núria

2016-04-29

An attractive strategy to improve the performance of water oxidation catalysts would be to anchor a homogeneous molecular catalyst on a heterogeneous solid surface to create a hybrid catalyst. The idea of this combined system is to take advantage of the individual properties of each of the two catalyst components. We use Density Functional Theory to determine the stability and activity of a model hybrid water oxidation catalyst consisting of a dimeric Ir complex attached on the IrO 2(110) surface through two oxygen atoms. We find that homogeneous catalysts can be bound to its matrix oxide without losing significant activity.more » Hence, designing hybrid systems that benefit from both the high tunability of activity of homogeneous catalysts and the stability of heterogeneous systems seems feasible.« less

Copper(I)/TEMPO Catalyzed Aerobic Oxidation of Primary Alcohols to Aldehydes with Ambient Air

PubMed Central

Hoover, Jessica M.; Steves, Janelle E.; Stahl, Shannon S.

2012-01-01

This protocol describes a practical laboratory-scale method for aerobic oxidation of primary alcohols to aldehydes, using a chemoselective CuI/TEMPO catalyst system. The catalyst is prepared in situ from commercially available reagents, and the reactions are performed in a common organic solvent (acetonitrile) with ambient air as the oxidant. Three different reaction conditions and three procedures for the isolation and purification of the aldehyde product are presented. The oxidations of eight different alcohols, described here, include representative examples of each reaction condition and purification method. Reaction times vary from 20 min to 24 h, depending on the alcohol, while the purification methods each take about 2 h. The total time necessary for the complete protocol ranges from 3 – 26 h. PMID:22635108

Develop and test fuel cell powered on-site integrated total energy systems. Phase 3: Full-scale power plant development

NASA Technical Reports Server (NTRS)

1981-01-01

A schematic and physical layout is given for the 5kW integrated system and the development status of individual components is described. The results of using a one dimensional mathematical model of the 5kW reformer are presented. Plans for a single-tube reformer test unit for the acquisition of temperature profile data are described. Tentative specifications for a 50kW dc-to-ac inverter are listed. Performance data are given on two 3-cell stacks incorporating semiautomatic acid replenishment systems and improved electrocatalysts. A qualification test on methanol/steam reforming catalyst T2107RS is reported, including a portion in which the catalyst was deliberately poisoned with 800 ppm ethanol in the feed.

AO13. High energy, low methane syngas from low-rank coals for coal-to-liquids production

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lucero, Andrew; Goyal, Amit; McCabe, Kevin

2015-06-30

An experimental program was undertaken to develop and demonstrate novel steam reforming catalysts for converting tars, C2+ hydrocarbons, and methane under high temperature and sulfur environments at lab scale. Several catalysts were developed and synthesized along with some catalysts based on recipes found in the literature. Of these, two had good resistance at 90 ppm H 2S with one almost not affected at all. Higher concentrations of H 2S did affect methane conversion across the catalyst, but performance was fairly stable for up to 200 hours. Based on the results of the experimental program, a techno-economic analysis was developed formore » IGCC and CTL applications and compared to DOE reference cases to examine the effects of the new technology. In the IGCC cases, the reformer/POX system produces nearly the same amount of electricity for nearly the same cost, however, the reformers/POX case sequesters a higher percentage of the carbon when compared to IGCC alone. For the CTL case the economics of the new process were nearly identical to the CTL case, but due to improved yields, the greenhouse gas emissions for a given production of fuels was approximately 50% less than the baseline case.« less

Development of Molecular Catalysts to Bridge the Gap between Heterogeneous and Homogeneous Catalysts

NASA Astrophysics Data System (ADS)

Ye, Rong

Catalysts, heterogeneous, homogeneous, and enzymatic, are comprised of nanometer-sized inorganic and/or organic components. They share molecular factors including charge, coordination, interatomic distance, bonding, and orientation of catalytically active atoms. By controlling the governing catalytic components and molecular factors, catalytic processes of a multichannel and multiproduct nature could be run in all three catalytic platforms to create unique end-products. Unifying the fields of catalysis is the key to achieving the goal of 100% selectivity in catalysis. Recyclable catalysts, especially those that display selective reactivity, are vital for the development of sustainable chemical processes. Among available catalyst platforms, heterogeneous catalysts are particularly well-disposed toward separation from the reaction mixture via filtration methods, which renders them readily recyclable. Furthermore, heterogeneous catalysts offer numerous handles - some without homogeneous analogues - for performance and selectivity optimization. These handles include nanoparticle size, pore profile of porous supports, surface ligands and interface with oxide supports, and flow rate through a solid catalyst bed. Despite these available handles, however, conventional heterogeneous catalysts are themselves often structurally heterogeneous compared to homogeneous catalysts, which complicates efforts to optimize and expand the scope of their reactivity and selectivity. Ongoing efforts are aimed to address the above challenge by heterogenizing homogeneous catalysts, which can be defined as the modification of homogeneous catalysts to render them in a separable (solid) phase from the starting materials and products. Specifically, we grow the small nanoclusters in dendrimers, a class of uniform polymers with the connectivity of fractal trees and generally radial symmetry. Thanks to their dense multivalency, shape persistence and structural uniformity, dendrimers have proven to be versatile scaffolds for the synthesis and stabilization of small nanoclusters. Then these dendrimer-encapsulated metal clusters (DEMCs) are adsorbed onto mesoporous silica. Through this method, we have achieved selective transformations that had been challenging to accomplish in a heterogeneous setting, e.g. pi-bond activation and aldol reactions. Extensive investigation into the catalytic systems under reaction conditions allowed us to correlate the structural features (e.g. oxidation states) of the catalysts and their activity. Moreover, we have demonstrated that supported DEMCs are also excellent catalysts for typical heterogeneous reactions, including hydrogenation and alkane isomerization. Critically, these investigations also confirmed that the supported DEMCs are heterogeneous and stable against leaching. Catalysts optimization is achieved through the modulation of various parameters. The clusters are oxidized (e.g., with PhICl2) or reduced (e.g., with H2) in situ. Changing the dendrimer properties (e.g., generation, terminal functional groups) is analogous to ligand modification in homogeneous catalysts, which affect both catalytic activity and selectivity. Similarly, pore size of the support is another factor in determining product distribution. In a flow reactor, the flow rate is adjusted to control the residence time of the starting material and intermediates, and thus the final product selectivity. Our approach to heterogeneous catalysis affords various advantages: (1) the catalyst system can tap into the reactivity typical to homogeneous catalysts, which conventional heterogeneous catalysts could not achieve; (2) unlike most homogeneous catalysts with comparable performance, the heterogenized homogeneous catalysts can be recycled; (3) improved activity or selectivity compared to conventional homogeneous catalysts is possible because of uniquely heterogeneous parameters for optimization. While localized surface plasmon resonance (LSPR) provides a powerful platform for nanoparticle catalysis, our studies suggest that in some cases interband transitions should be considered as an alternative mechanism of light-driven nanoparticle catalysis. The benefits already demonstrated by plasmonic nanostructures as catalysts provided the impetus for examining complementary activation modes based on the metal nanoparticle itself. Leveraging these transitions has the potential to provide a means to highly active catalysis modes that would otherwise be challenging to access. For example, for the preparation of highly active metal catalysts on a subnanosized scale is challenging, thus limiting their exploitation and study in catalysis. Our work suggests a novel and facile strategy for the formation of highly active gold nanocluster catalysts by light illumination of the interband transitions in the presence of the appropriate substrate.

ECUT: Energy Conversion and Utilization Technologies program. Heterogeneous catalysis modeling program concept

NASA Technical Reports Server (NTRS)

Voecks, G. E.

1983-01-01

Insufficient theoretical definition of heterogeneous catalysts is the major difficulty confronting industrial suppliers who seek catalyst systems which are more active, selective, and stable than those currently available. In contrast, progress was made in tailoring homogeneous catalysts to specific reactions because more is known about the reaction intermediates promoted and/or stabilized by these catalysts during the course of reaction. However, modeling heterogeneous catalysts on a microscopic scale requires compiling and verifying complex information on reaction intermediates and pathways. This can be achieved by adapting homogeneous catalyzed reaction intermediate species, applying theoretical quantum chemistry and computer technology, and developing a better understanding of heterogeneous catalyst system environments. Research in microscopic reaction modeling is now at a stage where computer modeling, supported by physical experimental verification, could provide information about the dynamics of the reactions that will lead to designing supported catalysts with improved selectivity and stability.

Porous metallosilicates for heterogeneous, liquid-phase catalysis: perspectives and pertaining challenges

PubMed Central

Padovan, Daniele; Tarantino, Giulia

2018-01-01

Porous silicates containing dilute amounts of tri-, tetra- and penta-valent metal sites, such as TS-1, Sn-β and Fe-ZSM-5, have recently emerged as state of the art catalysts for a variety of sustainable chemical transformations. In contrast with their aluminosilicate cousins, which are widely employed throughout the refinery industry for gas-phase catalytic transformations, such metallosilicates have exhibited unprecedented levels of performance for a variety of liquid-phase catalytic processes, including the conversion of biomass to chemicals, and sustainable oxidation technologies with H2O2. However, despite their unique levels of performance for these new types of chemical transformations, increased utilization of these promising materials is complicated by several factors. For example, their utilization in a liquid, and often polar, medium hinders process intensification (scale-up, catalyst deactivation). Moreover, such materials do not generally exhibit the active-site homogeneity of conventional aluminosilicates, and they typically possess a wide variety of active-site ensembles, only some of which may be directly involved in the catalytic chemistry of interest. Consequently, mechanistic understanding of these catalysts remains relatively low, and competitive reactions are commonly observed. Accordingly, unified approaches towards developing more active, selective and stable porous metallosilicates have not yet been achieved. Drawing on some of the most recent literature in the field, the purpose of this mini review is both to highlight the breakthroughs made with regard to the use of porous metallosilicates as heterogeneous catalysts for liquid-phase processing, and to highlight the pertaining challenges that we, and others, aim to overcome during the forthcoming years. PMID:29515849

Porous metallosilicates for heterogeneous, liquid-phase catalysis: perspectives and pertaining challenges

NASA Astrophysics Data System (ADS)

Hammond, Ceri; Padovan, Daniele; Tarantino, Giulia

2018-02-01

Porous silicates containing dilute amounts of tri-, tetra- and penta-valent metal sites, such as TS-1, Sn-β and Fe-ZSM-5, have recently emerged as state of the art catalysts for a variety of sustainable chemical transformations. In contrast with their aluminosilicate cousins, which are widely employed throughout the refinery industry for gas-phase catalytic transformations, such metallosilicates have exhibited unprecedented levels of performance for a variety of liquid-phase catalytic processes, including the conversion of biomass to chemicals, and sustainable oxidation technologies with H2O2. However, despite their unique levels of performance for these new types of chemical transformations, increased utilization of these promising materials is complicated by several factors. For example, their utilization in a liquid, and often polar, medium hinders process intensification (scale-up, catalyst deactivation). Moreover, such materials do not generally exhibit the active-site homogeneity of conventional aluminosilicates, and they typically possess a wide variety of active-site ensembles, only some of which may be directly involved in the catalytic chemistry of interest. Consequently, mechanistic understanding of these catalysts remains relatively low, and competitive reactions are commonly observed. Accordingly, unified approaches towards developing more active, selective and stable porous metallosilicates have not yet been achieved. Drawing on some of the most recent literature in the field, the purpose of this mini review is both to highlight the breakthroughs made with regard to the use of porous metallosilicates as heterogeneous catalysts for liquid-phase processing, and to highlight the pertaining challenges that we, and others, aim to overcome during the forthcoming years.

Morphological effect of BiVO4 catalysts on degradation of aqueous paracetamol under visible light irradiation.

PubMed

Hu, Changying; Xu, Jie; Zhu, Yaqi; Chen, Acong; Bian, Zhaoyong; Wang, Hui

2016-09-01

Morphological effect of bismuth vanadate (BiVO4) on visible light-driven catalytic degradation of aqueous paracetamol was carefully investigated using four monoclinic BiVO4 catalysts. The catalysts with different morphologies were controllably prepared by a hydrothermal method without any additions. The prepared catalysts were fully characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and UV-Vis diffuse reflectance spectroscopy (DRS). Under the visible light irradiation, these catalysts with different morphology were investigated to degrade aqueous paracetamol contaminant. The degradation effects were evaluated based on the catalyst morphology, solution pH, initial paracetamol concentration, and catalyst dosage. Cube-like BiVO4 powders exhibited excellent photocatalytic performance. The optimal photocatalytic performance of the cube-like BiVO4 in degrading paracetamol was achieved.

Effect of Graphitic Content on Carbon Supported Catalyst Performance

DOE Office of Scientific and Technical Information (OSTI.GOV)

Patel, Anant; Artyushkova, Kateryna; Atanassov, Plamen

2011-07-01

The effect of graphitic content on carbon supported platinum catalysts was investigated in order to investigate its influence on catalyst performance. Four catalysts of varying surface areas and graphitic content were analyzed using XPS, HREELS, and tested using RDE experiments. The catalysts were also heat treated at 150oC and 100%RH as means to uniformly age them. The heat treated samples were analyzed using the same methods to determine what changes had occurred due to this aging process. When compared to the BOL catalysts, heat treated catalysts displayed increased graphitic carbon and platinum metalic content, however they also showed depressed catalyticmore » activity. The primary cause is still under investigation, though it is believed to be related to loss of amorphous carbon content.« less

Dehydration of glycerol over niobia-supported silicotungstic acid catalysts.

PubMed

Lee, Young Yi; Ok, Hye Jeong; Moon, Dong Ju; Kim, Jong Ho; Park, Nam Cook; Kim, Young Chul

2013-01-01

Liquid-phase dehydration of glycerol to acrolein over nanosized niobia-supported silicotungstic acid catalysts was performed to investigate the effect of the silicotungstic acid loading on the catalytic performance of the catalysts. The catalysts were prepared by following an impregnation method with different HSiW loadings in the range of 10-50 wt%. The prepared catalysts were characterized by N2 physisorption, XRD, FT-IR, TPD of ammonia, and TGA. Dehydration of glycerol was conducted in an autoclave reactor under the conditions of controlled reaction temperatures under corresponding pressure. Increasing HSiW loading rapidly increased the acidity of HSiW/Nb205 catalyst and rate of glycerol conversion, but acrolein selectivity decreased due to enhanced deactivation of the catalyst by carbon deposit. Consequently, it was confirmed that catalytic activity for the dehydration of glycerol to acrolein was dependant on the acidity of catalyst and can be controlled by HSiW loading.

Durability testing at 5 atmospheres of advanced catalysts and catalyst supports for gas turbine engine combustors

NASA Technical Reports Server (NTRS)

Olson, B. A.; Lee, H. C.; Osgerby, I. T.; Heck, R. M.; Hess, H.

1980-01-01

The durability of CATCOM catalysts and catalyst supports was experimentally demonstrated in a combustion environment under simulated gas turbine engine combustor operating conditions. A test of 1000 hours duration was completed with one catalyst using no. 2 diesel fuel and operating at catalytically-supported thermal combustion conditions. The performance of the catalyst was determined by monitoring emissions throughout the test, and by examining the physical condition of the catalyst core at the conclusion of the test. Tests were performed periodically to determine changes in catalytic activity of the catalyst core. Detailed parametric studies were also run at the beginning and end of the durability test, using no. 2 fuel oil. Initial and final emissions for the 1000 hours test respectively were: unburned hydrocarbons (C3 vppm):0, 146, carbon monoxide (vppm):30, 2420; nitrogen oxides (vppm):5.7, 5.6.

Failure analysis of fuel cell electrodes using three-dimensional multi-length scale X-ray computed tomography

NASA Astrophysics Data System (ADS)

Pokhrel, A.; El Hannach, M.; Orfino, F. P.; Dutta, M.; Kjeang, E.

2016-10-01

X-ray computed tomography (XCT), a non-destructive technique, is proposed for three-dimensional, multi-length scale characterization of complex failure modes in fuel cell electrodes. Comparative tomography data sets are acquired for a conditioned beginning of life (BOL) and a degraded end of life (EOL) membrane electrode assembly subjected to cathode degradation by voltage cycling. Micro length scale analysis shows a five-fold increase in crack size and 57% thickness reduction in the EOL cathode catalyst layer, indicating widespread action of carbon corrosion. Complementary nano length scale analysis shows a significant reduction in porosity, increased pore size, and dramatically reduced effective diffusivity within the remaining porous structure of the catalyst layer at EOL. Collapsing of the structure is evident from the combination of thinning and reduced porosity, as uniquely determined by the multi-length scale approach. Additionally, a novel image processing based technique developed for nano scale segregation of pore, ionomer, and Pt/C dominated voxels shows an increase in ionomer volume fraction, Pt/C agglomerates, and severe carbon corrosion at the catalyst layer/membrane interface at EOL. In summary, XCT based multi-length scale analysis enables detailed information needed for comprehensive understanding of the complex failure modes observed in fuel cell electrodes.

Technology for advanced liquefaction processes: Coal/waste coprocessing studies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cugini, A.V.; Rothenberger, K.S.; Ciocco, M.V.

1995-12-31

The efforts in this project are directed toward three areas: (1) novel catalyst (supported and unsupported) research and development, (2) study and optimization of major operating parameters (specifically pressure), and (3) coal/waste coprocessing. The novel catalyst research and development activity has involved testing supported catalysts, dispersed catalysts, and use of catalyst testing units to investigate the effects of operating parameters (the second area) with both supported and unsupported catalysts. Several supported catalysts were tested in a simulated first stage coal liquefaction application at 404{degrees}C during this performance period. A Ni-Mo hydrous titanate catalyst on an Amocat support prepared by Sandiamore » National laboratories was tested. Other baseline experiments using AO-60 and Amocat, both Ni-Mo/Al{sub 2}O{sub 3} supported catalysts, were also made. These experiments were short duration (approximately 12 days) and monitored the initial activity of the catalysts. The results of these tests indicate that the Sandia catalyst performed as well as the commercially prepared catalysts. Future tests are planned with other Sandia preparations. The dispersed catalysts tested include sulfated iron oxide, Bayferrox iron oxide (iron oxide from Miles, Inc.), and Bailey iron oxide (micronized iron oxide from Bailey, Inc.). The effects of space velocity, temperature, and solvent-to-coal ratio on coal liquefaction activity with the dispersed catalysts were investigated. A comparison of the coal liquefaction activity of these catalysts relative to iron catalysts tested earlier, including FeOOH-impregnated coal, was made. These studies are discussed.« less

Ru-Sn/AC for the Aqueous-Phase Reduction of Succinic Acid to 1,4-Butanediol under Continuous Process Conditions

DOE PAGES

Vardon, Derek R.; Settle, Amy E.; Vorotnikov, Vassili; ...

2017-08-18

Succinic acid is a biomass-derived platform chemical that can be catalytically converted in the aqueous phase to 1,4-butanediol (BDO), a prevalent building block used in the polymer and chemical industries. Despite significant interest, limited work has been reported regarding sustained catalyst performance and stability under continuous aqueous-phase process conditions. As such, this work examines Ru-Sn on activated carbon (AC) for the aqueous-phase conversion of succinic acid to BDO under batch and flow reactor conditions. Initially, powder Ru-Sn catalysts were screened to determine the most effective bimetallic ratio and provide a comparison to other monometallic (Pd, Pt, Ru) and bimetallic (Pt-Sn,more » Pd-Re) catalysts. Batch reactor tests determined that a ~1:1 metal weight ratio of Ru to Sn was effective for producing BDO in high yields, with complete conversion resulting in 82% molar yield. Characterization of the fresh Ru-Sn catalyst suggests that the sequential loading method results in Ru sites that are colocated and surface-enriched with Sn. Postbatch reaction characterization confirmed stable Ru-Sn material properties; however, upon a transition to continuous conditions, significant Ru-Sn/AC deactivation occurred due to stainless steel leaching of Ni that resulted in Ru-Sn metal crystallite restructuring to form discrete Ni-Sn sites. Computational modeling confirmed favorable energetics for Ru-Sn segregation and Ni-Sn formation at submonolayer Sn incorporation. To address stainless steel leaching, reactor walls were treated with an inert silica coating by chemical vapor deposition. With leaching reduced, stable Ru-Sn/AC performance was observed that resulted in a molar yield of 71% BDO and 15% tetrahydrofuran for 96 h of time on stream. Postreaction catalyst characterization confirmed low levels of Ni and Cr deposition, although early-stage islanding of Ni-Sn will likely be problematic for industrially relevant time scales (i.e., thousands of hours). Overall, these results (i) demonstrate the performance of Ru-Sn/AC for aqueous phase succinic acid reduction, (ii) provide insight into the Ru-Sn bimetallic structure and deactivation in the presence of leached Ni, and (iii) underscore the importance of compatible reactor metallurgy and durable catalysts.« less

Bimetallic platinum group metal-free catalysts for high power generating microbial fuel cells

NASA Astrophysics Data System (ADS)

Kodali, Mounika; Santoro, Carlo; Herrera, Sergio; Serov, Alexey; Atanassov, Plamen

2017-10-01

M1-M2-N-C bimetallic catalysts with M1 as Fe and Co and M2 as Fe, Co, Ni and Mn were synthesized and investigated as cathode catalysts for oxygen reduction reaction (ORR). The catalysts were prepared by Sacrificial Support Method in which silica was the template and aminoantipyrine (AAPyr) was the organic precursor. The electro-catalytic properties of these catalysts were investigated by using rotating ring disk (RRDE) electrode setup in neutral electrolyte. Fe-Mn-AAPyr outperformed Fe-AAPyr that showed higher performances compared to Fe-Co-AAPyr and Fe-Ni-AAPyr in terms of half-wave potential. In parallel, Fe-Co-AAPyr, Co-Mn-AAPyr and Co-Ni-AAPyr outperformed Co-AAPyr. The presence of Co within the catalyst contributed to high peroxide production not desired for efficient ORR. The catalytic capability of the catalysts integrated in air-breathing cathode was also verified. It was found that Co-based catalysts showed an improvement in performance by the addition of second metal compared to simple Co- AAPyr. Fe-based bimetallic materials didn't show improvement compared to Fe-AAPyr with the exception of Fe-Mn-AAPyr catalyst that had the highest performance recorded in this study with maximum power density of 221.8 ± 6.6 μWcm-2. Activated carbon (AC) was used as control and had the lowest performances in RRDE and achieved only 95.6 ± 5.8 μWcm-2 when tested in MFC.

Organometallic catalysts for primary phosphoric acid fuel cells

NASA Technical Reports Server (NTRS)

Walsh, Fraser

1987-01-01

A continuing effort by the U.S. Department of Energy to improve the competitiveness of the phosphoric acid fuel cell by improving cell performance and/or reducing cell cost is discussed. Cathode improvement, both in performance and cost, available through the use of a class of organometallic cathode catalysts, the tetraazaannulenes (TAAs), was investigated. A new mixed catalyst was identified which provides improved cathode performance without the need for the use of a noble metal. This mixed catalyst was tested under load for 1000 hr. in full cell at 160 to 200 C in phosphoric acid H3PO4, and was shown to provide stable performance. The mixed catalyst contains an organometallic to catalyze electroreduction of oxygen to hydrogen peroxide and a metal to catalyze further electroreduction of the hydrogen peroxide to water. Cathodes containing an exemplar mixed catalyst (e.g., Co bisphenyl TAA/Mn) operate at approximately 650 mV vs DHE in 160 C, 85% H3PO4 with oxygen as reactant. In developing this mixed catalyst, a broad spectrum of TAAs were prepared, tested in half-cell and in a rotating ring-disk electrode system. TAAs found to facilitate the production of hydrogen peroxide in electroreduction were shown to be preferred TAAs for use in the mixed catalyst. Manganese (Mn) was identified as a preferred metal because it is capable of catalyzing hydrogen peroxide electroreduction, is lower in cost and is of less strategic importance than platinum, the cathode catalyst normally used in the fuel cell.

Low-Temperature CO-Oxidation Catalysts for Long-Life CO2 Lasers

NASA Technical Reports Server (NTRS)

Schryer, David R. (Editor); Hoflund, Gar B. (Editor)

1990-01-01

Low-temperature CO-oxidation catalysts are necessary for closed-cycle pulsed CO2 lasers as well as for other applications, including air purification. The papers presented in this volume discuss several such catalysts, including information on catalyst preparation, techniques for enhancing catalyst performance, laboratory and laser test results, and mechanistic considerations.

Impact of Contaminants Present in Coal-Biomass Derived Synthesis Gas on Water-gas Shift and Fischer-Tropsch Synthesis Catalysts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alptekin, Gokhan

2013-02-15

Co-gasification of biomass and coal in large-scale, Integrated Gasification Combined Cycle (IGCC) plants increases the efficiency and reduces the environmental impact of making synthesis gas ("syngas") that can be used in Coal-Biomass-to-Liquids (CBTL) processes for producing transportation fuels. However, the water-gas shift (WGS) and Fischer-Tropsch synthesis (FTS) catalysts used in these processes may be poisoned by multiple contaminants found in coal-biomass derived syngas; sulfur species, trace toxic metals, halides, nitrogen species, the vapors of alkali metals and their salts (e.g., KCl and NaCl), ammonia, and phosphorous. Thus, it is essential to develop a fundamental understanding of poisoning/inhibition mechanisms before investingmore » in the development of any costly mitigation technologies. We therefore investigated the impact of potential contaminants (H 2S, NH 3, HCN, AsH 3, PH 3, HCl, NaCl, KCl, AS 3, NH 4NO 3, NH 4OH, KNO 3, HBr, HF, and HNO 3) on the performance and lifetime of commercially available and generic (prepared in-house) WGS and FT catalysts.« less

Liquid phase fluid dynamic (methanol) run in the LaPorte alternative fuels development unit

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bharat L. Bhatt

1997-05-01

A fluid dynamic study was successfully completed in a bubble column at DOE's Alternative Fuels Development Unit (AFDU) in LaPorte, Texas. Significant fluid dynamic information was gathered at pilot scale during three weeks of Liquid Phase Methanol (LPMEOJP) operations in June 1995. In addition to the usual nuclear density and temperature measurements, unique differential pressure data were collected using Sandia's high-speed data acquisition system to gain insight on flow regime characteristics and bubble size distribution. Statistical analysis of the fluctuations in the pressure data suggests that the column was being operated in the churn turbulent regime at most of themore » velocities considered. Dynamic gas disengagement experiments showed a different behavior than seen in low-pressure, cold-flow work. Operation with a superficial gas velocity of 1.2 ft/sec was achieved during this run, with stable fluid dynamics and catalyst performance. Improvements included for catalyst activation in the design of the Clean Coal III LPMEOH{trademark} plant at Kingsport, Tennessee, were also confirmed. In addition, an alternate catalyst was demonstrated for LPMEOH{trademark}.« less

Mild deoxygenation of aromatic ketones and aldehydes over Pd/C using polymethylhydrosiloxane as the reducing agent.

PubMed

Volkov, Alexey; Gustafson, Karl P J; Tai, Cheuk-Wai; Verho, Oscar; Bäckvall, Jan-E; Adolfsson, Hans

2015-04-20

Herein, a practical and mild method for the deoxygenation of a wide range of benzylic aldehydes and ketones is described, which utilizes heterogeneous Pd/C as the catalyst together with the green hydride source, polymethylhydrosiloxane. The developed catalytic protocol is scalable and robust, as exemplified by the deoxygenation of ethyl vanillin, which was performed on a 30 mmol scale in an open-to-air setup using only 0.085 mol % Pd/C catalyst to furnish the corresponding deoxygenated product in 93 % yield within 3 hours at room temperature. Furthermore, the Pd/C catalyst was shown to be recyclable up to 6 times without any observable decrease in efficiency and it exhibited low metal leaching under the reaction conditions. © 2015 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA. This is an open access article under the terms of the Creative Commons Attribution Non-Commercial NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.

TiO2 Nanotube-Carbon (TNT-C) as Support for Pt-based Catalyst for High Methanol Oxidation Reaction in Direct Methanol Fuel Cell.

PubMed

Abdullah, M; Kamarudin, S K; Shyuan, L K

2016-12-01

In this study, TiO 2 nanotubes (TNTs) were synthesized via a hydrothermal method using highly concentrated NaOH solutions varying from 6 to 12 M at 180 °C for 48 h. The effects of the NaOH concentration and the TNT crystal structure on the performance for methanol oxidation were investigated to determine the best catalyst support for Pt-based catalysts. The results showed that TNTs produced with 10 M NaOH exhibited a length and a diameter of 550 and 70 nm, respectively; these TNTs showed the best nanotube structure and were further used as catalyst supports for a Pt-based catalyst in a direct methanol fuel cell. The synthesized TNT and Pt-based catalysts were analysed by FESEM, TEM, BET, EDX, XRD and FTIR. The electrochemical performance of the catalysts was investigated using cyclic voltammetry (CV) and chronoamperometric (CA) analysis to further understand the methanol oxidation in the direct methanol fuel cell (DMFC). Finally, the result proves that Pt-Ru/TNT-C catalyst shows high performance in methanol oxidation as the highest current density achieved at 3.3 mA/cm 2 (normalised by electrochemically active surface area) and high catalyst tolerance towards poisoning species was established.

3D Polymer Hydrogel for High-Performance Atomic Fe and Mn Catalysts for Oxygen Reduction in Challenging Acids

NASA Astrophysics Data System (ADS)

Qiao, Zhi

Current platinum group metal (PGM)-free carbon nanocomposite catalysts for the oxygen reduction reaction (ORR) in acidic electrolyte often suffer from rapid degradation associated with carbon corrosion due to the use of large amount of the amorphoous carbon black supports. Here, we developed a new concept of using freestanding 3D hydrogel to design support-free Fe-N-C catalysts. A 3D polyaniline (PANI)-based hydrogel approach was used for preparing a new type of single atomic iron site-rich catalyst, which has exhibited exceptionally enhanced activity and stability compared to conventional Fe-N-C catalysts supported on amorphous carbon blacks. The achieved performance metric on the hydrogel PANI-Fe catalysts is one of the best ever reported PGM-free catalysts, reaching a half-wave potential up to 0.83 V vs. RHE and only leaving 30 mV gap with Pt/C catalysts (60mugPt/cm 2) in challenging acidic media. Remarkable ORR stability was accomplished as well on the same catalyst evidenced by using harsh potential cycling tests. The well dispersion of atomic iron into partially graphitized carbon, featured with dominance of micropores and porous network structures, is capable of accommodating increased number of active sites, strengthening local bonding among iron, nitrogen and carbon, and facilitating mass transfer. On the other hand, in order to decrease the produced Fenton reagent, which will oxidize the proton exchange membrane and ionomer in membrane electrode assembly (MEA), we produce Mn-based catalysts by this novel hydrogel method. This is the first time that Mn-based catalysts can show such outstanding performance in acid media, whose half-wave potential is up to 0.80 V vs. RHE. The work related to the performance improvement is still in processing. We believe the 3D polymer hydrogel approach would be a new pathway to advance PGM-free catalysts.

Visible-Light-Responsive Photocatalysis: Ag-Doped TiO2 Catalyst Development and Reactor Design Testing

NASA Technical Reports Server (NTRS)

Coutts, Janelle L.; Hintze, Paul E.; Meier, Anne; Shah, Malay G.; Devor, Robert W.; Surma, Jan M.; Maloney, Phillip R.; Bauer, Brint M.; Mazyck, David W.

2016-01-01

In recent years, the alteration of titanium dioxide to become visible-light-responsive (VLR) has been a major focus in the field of photocatalysis. Currently, bare titanium dioxide requires ultraviolet light for activation due to its band gap energy of 3.2 eV. Hg-vapor fluorescent light sources are used in photocatalytic oxidation (PCO) reactors to provide adequate levels of ultraviolet light for catalyst activation; these mercury-containing lamps, however, hinder the use of this PCO technology in a spaceflight environment due to concerns over crew Hg exposure. VLR-TiO2 would allow for use of ambient visible solar radiation or highly efficient visible wavelength LEDs, both of which would make PCO approaches more efficient, flexible, economical, and safe. Over the past three years, Kennedy Space Center has developed a VLR Ag-doped TiO2 catalyst with a band gap of 2.72 eV and promising photocatalytic activity. Catalyst immobilization techniques, including incorporation of the catalyst into a sorbent material, were examined. Extensive modeling of a reactor test bed mimicking air duct work with throughput similar to that seen on the International Space Station was completed to determine optimal reactor design. A bench-scale reactor with the novel catalyst and high-efficiency blue LEDs was challenged with several common volatile organic compounds (VOCs) found in ISS cabin air to evaluate the system's ability to perform high-throughput trace contaminant removal. The ultimate goal for this testing was to determine if the unit would be useful in pre-heat exchanger operations to lessen condensed VOCs in recovered water thus lowering the burden of VOC removal for water purification systems.

Durability testing at one atmosphere of advanced catalysts and catalyst supports for automotive gas turbine engine combustors, part 1

NASA Technical Reports Server (NTRS)

Heck, R. M.; Chang, M.; Hess, H.; Carrubba, R.

1977-01-01

The durability of catalysts and catalyst supports in a combustion environment was experimentally demonstrated. A test of 1000 hours duration was completed with two catalysts, using diesel fuel and operating at catalytically supported thermal combustion conditions. The performance of the catalysts was determined by monitoring emissions throughout the test, and by examining the physical condition of the catalyst core at the conclusion of the test. The test catalysts proved to be capable of low emissions operation after 1000 hours diesel aging, with no apparent physical degradation of the catalyst support.

Poisoning of a Silica-Supported Cobalt Catalyst due to Presence of Sulfur Impurities in Syngas during Fischer–Tropsch Synthesis: Effects of Chelating Agent

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bambal, Ashish S.; Guggilla, Vidya S.; Kugler, Edwin L.

2014-04-09

The effects of sulfur impurities on the performance of cobalt-based Fischer–Tropsch catalysts are evaluated under industrially relevant operating conditions of temperature, pressure, and impurity levels. Chelating agents (CAs) were used to modify the SiO 2 support, and the performances of the CA-modified catalysts are compared with conventional Co/SiO 2 catalysts. For both the Co/SiO 2 and CA-modified catalysts, the presence of sulfur in the inlet syngas results in a notable drop in the CO conversion, an undesired shift in the hydrocarbon selectivity toward short-chain hydrocarbons, more olefins in the products, and lower product yields. In the post-poisoning stage, i.e., aftermore » termination of sulfur introduction in the inlet syngas, the CA-modified catalysts recover activity and selectivity (to some extent at least), whereas such trends are not observed for the base-case, i.e., unmodified Co/SiO 2 catalyst. Finally, the improved performance of the CA-modified catalysts in the presence of sulfur is attributed to higher densities of active sites.« less

Study of superhydrophobic electrosprayed catalyst layers using a localized reference electrode technique

NASA Astrophysics Data System (ADS)

Chaparro, A. M.; Ferreira-Aparicio, P.; Folgado, M. A.; Brightman, E.; Hinds, G.

2016-09-01

The performance of electrosprayed cathode catalyst layers in a polymer electrolyte membrane fuel cell (PEMFC) is studied using a localized reference electrode technique. Single cells with an electrosprayed cathode catalyst layer show an increase of >20% in maximum power density under standard testing conditions, compared with identical cells assembled with a conventional, state-of-the-art, gas diffusion cathode. When operated at high current density (1.2 A cm-2) the electrosprayed catalyst layers show more homogeneous distribution of the localized cathode potential, with a standard deviation from inlet to outlet of <50 mV, compared with 79 mV for the conventional gas diffusion cathode. Higher performance and homogeneity of cell response is attributed to the superhydrophobic nature of the macroporous electrosprayed catalyst layer structure, which enhances the rate of expulsion of liquid water from the cathode. On the other hand, at low current densities (<0.5 A cm-2), the electrosprayed layers exhibit more heterogeneous distribution of cathode potential than the conventional cathodes; this behavior is attributed to less favorable kinetics for oxygen reduction in very hydrophobic catalyst layers. The optimum performance may be obtained with electrosprayed catalyst layers employing a high Pt/C catalyst ratio.

Catalyst recycling via specific non-covalent adsorption on modified silicas.

PubMed

Kluwer, Alexander M; Simons, Chretien; Knijnenburg, Quinten; van der Vlugt, Jarl Ivar; de Bruin, Bas; Reek, Joost N H

2013-03-14

This article describes a new strategy for the recycling of a homogeneous hydroformylation catalyst, by selective adsorption of the catalyst to tailor-made supports after a batchwise reaction. The separation of the catalyst from the product mixture is based on selective non-covalent supramolecular interactions between a ligand and the support. Changing the solvent releases the active catalyst back into the reactor and allows a subsequent batch reaction with the recycled active catalyst. For this purpose, the bidentate NixantPhos ligand has been equipped with a pyridine group. The corresponding rhodium pre-catalyst [Rh(Nix-py)(acac)] (acac = acetylacetonate) forms a very selective, active and highly stable catalyst, and able to reach a turnover number (TON) of 170 000 in a single run (reaction performed in nearly neat 1-octene, S/C ratio of 200 000, at 140 °C, 20 bars syngas pressure). Various commercially available supports have been explored in binding studies and recycling experiments. The end-capped silica-alumina performs the best so far with respect to ligand-adsorbing properties for the current purpose. Although this system has not been fully optimized, four recycling runs could be performed successfully.

Catalytic ignition model in a monolithic reactor with in-depth reaction

NASA Technical Reports Server (NTRS)

Tien, Ta-Ching; Tien, James S.

1990-01-01

Two transient models have been developed to study the catalytic ignition in a monolithic catalytic reactor. The special feature in these models is the inclusion of thermal and species structures in the porous catalytic layer. There are many time scales involved in the catalytic ignition problem, and these two models are developed with different time scales. In the full transient model, the equations are non-dimensionalized by the shortest time scale (mass diffusion across the catalytic layer). It is therefore accurate but is computationally costly. In the energy-integral model, only the slowest process (solid heat-up) is taken as nonsteady. It is approximate but computationally efficient. In the computations performed, the catalyst is platinum and the reactants are rich mixtures of hydrogen and oxygen. One-step global chemical reaction rates are used for both gas-phase homogeneous reaction and catalytic heterogeneous reaction. The computed results reveal the transient ignition processes in detail, including the structure variation with time in the reactive catalytic layer. An ignition map using reactor length and catalyst loading is constructed. The comparison of computed results between the two transient models verifies the applicability of the energy-integral model when the time is greater than the second largest time scale of the system. It also suggests that a proper combined use of the two models can catch all the transient phenomena while minimizing the computational cost.

Atomic Scale Structure-Chemistry Relationships at Oxide Catalyst Surfaces and Interfaces

NASA Astrophysics Data System (ADS)

McBriarty, Martin E.

Oxide catalysts are integral to chemical production, fuel refining, and the removal of environmental pollutants. However, the atomic-scale phenomena which lead to the useful reactive properties of catalyst materials are not sufficiently understood. In this work, the tools of surface and interface science and electronic structure theory are applied to investigate the structure and chemical properties of catalytically active particles and ultrathin films supported on oxide single crystals. These studies focus on structure-property relationships in vanadium oxide, tungsten oxide, and mixed V-W oxides on the surfaces of alpha-Al2O3 and alpha-Fe2O 3 (0001)-oriented single crystal substrates, two materials with nearly identical crystal structures but drastically different chemical properties. In situ synchrotron X-ray standing wave (XSW) measurements are sensitive to changes in the atomic-scale geometry of single crystal model catalyst surfaces through chemical reaction cycles, while X-ray photoelectron spectroscopy (XPS) reveals corresponding chemical changes. Experimental results agree with theoretical calculations of surface structures, allowing for detailed electronic structure investigations and predictions of surface chemical phenomena. The surface configurations and oxidation states of V and W are found to depend on the coverage of each, and reversible structural shifts accompany chemical state changes through reduction-oxidation cycles. Substrate-dependent effects suggest how the choice of oxide support material may affect catalytic behavior. Additionally, the structure and chemistry of W deposited on alpha-Fe 2O3 nanopowders is studied using X-ray absorption fine structure (XAFS) measurements in an attempt to bridge single crystal surface studies with real catalysts. These investigations of catalytically active material surfaces can inform the rational design of new catalysts for more efficient and sustainable chemistry.

Effect of calcination temperature of a copper ferrite synthesized by a sol-gel method on its structural characteristics and performance as Fenton catalyst to remove gallic acid from water.

PubMed

López-Ramón, María V; Álvarez, Miguel A; Moreno-Castilla, Carlos; Fontecha-Cámara, María A; Yebra-Rodríguez, África; Bailón-García, Esther

2018-02-01

A copper ferrite synthesized by a sol-gel combustion method was calcined at different temperatures up to 800°C, determining changes in its structural characteristics and magnetic measurements and studying its catalytic performance in gallic acid removal by Fenton reaction. The main objective was to study the effect of the calcination temperature of copper ferrite on its crystalline phase formation and transformation, activity and metal ion leaching. The cubic-to-tetragonal transformation of the spinel occurred via its reaction with the CuO phase, displacing Fe 3+ ions in B (octahedral) sites out of the spinel structure by the following reaction: 2Fe 3+ B +3CuO→Fe 2 O 3 +3Cu 2+ B . The catalysts showed superparamagnetic or substantial superparamagnetic behaviour. At higher calcination temperatures, catalyst activity was lower, and Cu ion leaching was markedly decreased. There was no Fe ion leaching with any catalyst. The as-prepared catalyst showed better catalytic performance than a commercial copper ferrite. Leached Cu ions acted as homogeneous catalysts, and their contribution to the overall removal mechanism was examined. Cu 2 O present in the as-prepared catalysts made only a small contribution to their activity. Finally, the reutilization of various catalysts was studied by performing different catalytic cycles. Copyright © 2017 Elsevier Inc. All rights reserved.

Hydrogen production by steam reforming of liquefied natural gas over a nickel catalyst supported on mesoporous alumina xerogel

NASA Astrophysics Data System (ADS)

Seo, Jeong Gil; Youn, Min Hye; Cho, Kyung Min; Park, Sunyoung; Song, In Kyu

Mesoporous alumina xerogel (A-SG) is prepared by a sol-gel method for use as a support for a nickel catalyst. The Ni/A-SG catalyst is then prepared by an impregnation method, and is applied to hydrogen production by steam reforming of liquefied natural gas (LNG). The effect of the mesoporous alumina xerogel support on the catalytic performance of Ni/A-SG catalyst is investigated. For the purpose of comparison, a nickel catalyst supported on commercial alumina (A-C) is also prepared by an impregnation method (Ni/A-C). Both the hydroxyl-rich surface and the electron-deficient sites of the A-SG support enhance the dispersion of the nickel species on the support during the calcination step. The formation of the surface nickel aluminate phase in the Ni/A-SG catalyst remarkably increases the reducibility and stability of the catalyst. Furthermore, the high-surface area and the well-developed mesoporosity of the Ni/A-SG catalyst enhance the gasification of surface hydrocarbons that are adsorbed in the reaction. In the steam reforming of LNG, the Ni/A-SG catalyst exhibits a better catalytic performance than the Ni/A-C catalyst in terms of LNG conversion and hydrogen production. Moreover, the Ni/A-SG catalyst shows strong resistance toward catalyst deactivation.

ENVIRONMENTAL TECHNOLOGY VERIFICATION, TEST REPORT OF MOBILE SOURCE EMISSIONS CONTROL DEVICES/CLEAN DIESEL TECHNOLOGIES FUEL BORNE CATALYST WITH CLEANAIR SYSTEM'S DIESEL OXIDATION CATALYST

EPA Science Inventory

The Environmental Technology Verification report discusses the technology and performance of the Fuel-Borne Catalyst with CleanAir System's Diesel Oxidation Catalyst manufactured by Clean Diesel Technologies, Inc. The technology is a fuel-borne catalyst used in ultra low sulfur d...

Magnetic solid base catalyst CaO/CoFe2O4 for biodiesel production: Influence of basicity and wettability of the catalyst in catalytic performance

NASA Astrophysics Data System (ADS)

Zhang, Pingbo; Han, Qiuju; Fan, Mingming; Jiang, Pingping

2014-10-01

A novel magnetic solid base catalyst CaO/CoFe2O4 was successfully prepared with CoFe2O4 synthesized by hydrothermal method as the magnetic core and applied to the transesterification of soybean oil for the production of biodiesel. The magnetic solid base catalysts were characterized by a series of techniques including CO2-TPD, powder XRD, TGA, TEM and the contact angle measurement of the water droplet. It was demonstrated that CaO/CoFe2O4 has stronger magnetic strength indicating perfect utility for repeated use and better basic strength. Compared with CaO/ZnFe2O4 and CaO/MnFe2O4, solid base catalyst CaO/CoFe2O4 has better catalytic performance, weaker hydroscopicity and stronger wettability, demonstrating that catalytic performance was relative to both basicity of catalyst and the full contact between the catalyst and the reactants, but the latter was a main factor in the catalytic system.

Chiral catalysts immobilized on achiral polymers: effect of the polymer support on the performance of the catalyst.

PubMed

Altava, Belén; Burguete, M Isabel; García-Verdugo, Eduardo; Luis, Santiago V

2018-04-23

Positive effects of the polymeric support on the performance of supported chiral catalysts, in terms of activity, stability and selectivity-enantioselectivity, have been reported when the support is properly selected and optimized opening the way to the design of more efficient catalytic systems.

Continuous preparation of carbon-nanotube-supported platinum catalysts in a flow reactor directly heated by electric current

PubMed Central

dos Santos, Antonio Rodolfo; Kunz, Ulrich; Turek, Thomas

2011-01-01

Summary In this contribution we present for the first time a continuous process for the production of highly active Pt catalysts supported by carbon nanotubes by use of an electrically heated tubular reactor. The synthesized catalysts show a high degree of dispersion and narrow distributions of cluster sizes. In comparison to catalysts synthesized by the conventional oil-bath method a significantly higher electrocatalytic activity was reached, which can be attributed to the higher metal loading and smaller and more uniformly distributed Pt particles on the carbon support. Our approach introduces a simple, time-saving and cost-efficient method for fuel cell catalyst preparation in a flow reactor which could be used at a large scale. PMID:22043252

Sub-nanometer surface chemistry and orbital hybridization in lanthanum-doped ceria nano-catalysts revealed by 3D electron microscopy.

PubMed

Collins, Sean M; Fernandez-Garcia, Susana; Calvino, José J; Midgley, Paul A

2017-07-14

Surface chemical composition, electronic structure, and bonding characteristics determine catalytic activity but are not resolved for individual catalyst particles by conventional spectroscopy. In particular, the nano-scale three-dimensional distribution of aliovalent lanthanide dopants in ceria catalysts and their effect on the surface electronic structure remains unclear. Here, we reveal the surface segregation of dopant cations and oxygen vacancies and observe bonding changes in lanthanum-doped ceria catalyst particle aggregates with sub-nanometer precision using a new model-based spectroscopic tomography approach. These findings refine our understanding of the spatially varying electronic structure and bonding in ceria-based nanoparticle aggregates with aliovalent cation concentrations and identify new strategies for advancing high efficiency doped ceria nano-catalysts.

Warm Cleanup of Coal-Derived Syngas: Multicontaminant Removal Process Demonstration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Spies, Kurt A.; Rainbolt, James E.; Li, Xiaohong S.

Warm cleanup of coal- or biomass-derived syngas requires sorbent and catalytic beds to protect downstream processes and catalysts from fouling. Sulfur is particularly harmful because even parts-per-million amounts are sufficient to poison downstream synthesis catalysts. Zinc oxide (ZnO) is a conventional sorbent for sulfur removal; however, its operational performance using real gasifier-derived syngas and in an integrated warm cleanup process is not well reported. In this paper, we report the optimal temperature for bulk desulfurization to be 450oC, while removal of sulfur to parts-per-billion levels requires a lower temperature of approximately 350oC. Under these conditions, we found that sulfur inmore » the form of both hydrogen sulfide and carbonyl sulfide could be absorbed equally well using ZnO. For long-term operation, sorbent regeneration is desirable to minimize process costs. Over the course of five sulfidation and regeneration cycles, a ZnO bed lost about a third of its initial sulfur capacity, however sorbent capacity stabilized. Here, we also demonstrate, at the bench-scale, a process and materials used for warm cleanup of coal-derived syngas using five operations: 1) Na2CO3 for HCl removal, 2) regenerable ZnO beds for bulk sulfur removal, 3) a second ZnO bed for trace sulfur removal, 4) a Ni-Cu/C sorbent for multi-contaminant inorganic removal, and 5) a Ir-Ni/MgAl2O4 catalyst employed for ammonia decomposition and tar and light hydrocarbon steam reforming. Syngas cleanup was demonstrated through successful long-term performance of a poison-sensitive, Cu-based, water-gas-shift catalyst placed downstream of the cleanup process train. The tar reformer is an important and necessary operation with this particular gasification system; its inclusion was the difference between deactivating the water-gas catalyst with carbon deposition and successful 100-hour testing using 1 LPM of coal-derived syngas.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

The objective of the contract is to consolidate the advances made during the previous contract in the conversion of syngas to motor fuels using Molecular Sieve-containing catalysts and to demonstrate the practical utility and economic value of the new catalyst/process systems with appropriate laboratory runs. Work on the program is divided into the following six tasks: (1) preparation of a detailed work plan covering the entire performance of the contract; (2) preliminary techno-economic assessment of the UCC catalyst/process system; (3) optimization of the most promising catalyst developed under prior contract; (4) optimization of the UCC catalyst system in a mannermore » that will give it the longest possible service life; (5) optimization of a UCC process/catalyst system based upon a tubular reactor with a recycle loop containing the most promising catalyst developed under Tasks 3 and 4 studies; and (6) economic evaluation of the optimal performance found under Task 5 for the UCC process/catalyst system. Progress reports are presented for tasks 2 through 5. 232 figs., 19 tabs.« less

The Experimental Measurement of Local and Bulk Oxygen Transport Resistances in the Catalyst Layer of Proton Exchange Membrane Fuel Cells.

PubMed

Wang, Chao; Cheng, Xiaojing; Lu, Jiabin; Shen, Shuiyun; Yan, Xiaohui; Yin, Jiewei; Wei, Guanghua; Zhang, Junliang

2017-12-07

Remarkable progress has been made in reducing the cathodic Pt loading of PEMFCs; however, a huge performance loss appears at high current densities, indicating the existence of a large oxygen transport resistance associated with the ultralow Pt loading catalyst layer. To reduce the Pt loading without sacrificing cell performance, it is essential to illuminate the oxygen transport mechanism in the catalyst layer. Toward this goal, an experimental approach to measure the oxygen transport resistance in catalyst layers is proposed and realized for the first time in this study. The measuring approach involves a dual-layer catalyst layer design, which consists of a dummy catalyst layer and a practical catalyst layer, followed by changing the thickness of dummy layer to respectively quantify the local and bulk resistances via limiting current measurements combined with linear extrapolation. The experimental results clearly reveal that the local resistance dominates the total resistance in the catalyst layer.

Methanol Steam Reforming Promoted by Molten Salt-Modified Platinum on Alumina Catalysts

PubMed Central

Kusche, Matthias; Agel, Friederike; Ní Bhriain, Nollaig; Kaftan, Andre; Laurin, Mathias; Libuda, Jörg; Wasserscheid, Peter

2014-01-01

We herein describe a straight forward procedure to increase the performance of platinum-on-alumina catalysts in methanol steam reforming by applying an alkali hydroxide coating according to the “solid catalyst with ionic liquid layer” (SCILL) approach. We demonstrate by diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and temperature-programmed desorption (TPD) studies that potassium doping plays an important role in the catalyst activation. Moreover, the hygroscopic nature and the basicity of the salt modification contribute to the considerable enhancement in catalytic performance. During reaction, a partly liquid film of alkali hydroxides/carbonates forms on the catalyst/alumina surface, thus significantly enhancing the availability of water at the catalytically active sites. Too high catalyst pore fillings with salt introduce a considerable mass transfer barrier into the system as indicated by kinetic studies. Thus, the optimum interplay between beneficial catalyst modification and detrimental mass transfer effects had to be identified and was found on the applied platinum-on-alumina catalyst at KOH loadings around 7.5 mass %. PMID:25124120

Design of a new reactor-like high temperature near ambient pressure scanning tunneling microscope for catalysis studies.

PubMed

Tao, Franklin Feng; Nguyen, Luan; Zhang, Shiran

2013-03-01

Here, we present the design of a new reactor-like high-temperature near ambient pressure scanning tunneling microscope (HT-NAP-STM) for catalysis studies. This HT-NAP-STM was designed for exploration of structures of catalyst surfaces at atomic scale during catalysis or under reaction conditions. In this HT-NAP-STM, the minimized reactor with a volume of reactant gases of ∼10 ml is thermally isolated from the STM room through a shielding dome installed between the reactor and STM room. An aperture on the dome was made to allow tip to approach to or retract from a catalyst surface in the reactor. This dome minimizes thermal diffusion from hot gas of the reactor to the STM room and thus remains STM head at a constant temperature near to room temperature, allowing observation of surface structures at atomic scale under reaction conditions or during catalysis with minimized thermal drift. The integrated quadrupole mass spectrometer can simultaneously measure products during visualization of surface structure of a catalyst. This synergy allows building an intrinsic correlation between surface structure and its catalytic performance. This correlation offers important insights for understanding of catalysis. Tests were done on graphite in ambient environment, Pt(111) in CO, graphene on Ru(0001) in UHV at high temperature and gaseous environment at high temperature. Atom-resolved surface structure of graphene on Ru(0001) at 500 K in a gaseous environment of 25 Torr was identified.

High-performance oxygen reduction catalysts in both alkaline and acidic fuel cells based on pre-treating carbon material and iron precursor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Song, Ping; Barkholtz, Heather M.; Wang, Ying

We demonstrate a new and simple method for pre-treating the carbon material and iron precursor to prepare oxygen reduction reaction (ORR) catalysts, which can produce super-high performance and stability in alkaline solution, with high performance in acid solution. This strategy using cheap materials is simply controllable. Moreover, it has achieved smaller uniform nanoparticles to exhibit high stability, and the synergetic effect of Fe and N offered much higher performance in ORR than commercial Pt/C, with high maximum power density in alkaline and acid fuel cell test. So it can make this kind of catalysts be the most promising alternatives ofmore » Pt-based catalysts with best performance/price.« less

Ultra-high-performance core–shell structured Ru@Pt/C catalyst prepared by a facile pulse electrochemical deposition method

DOE PAGES

Chen, Dan; Li, Yuexia; Liao, Shijun; ...

2015-08-03

Core–shell structured catalysts, made by placing either a monolayer or a thin layer of a noble metal on relatively cheap core-metal nanoparticles, are fascinating and promising fuel cell catalysts due to their high utilization of noble metals. Here, we report our development of a core–shell structured catalyst, Ru@Pt/C, generated by a novel and facile pulse electrochemical deposition (PED) approach. We demonstrate that compared with a commercial Pt/C catalyst, this novel catalyst achieves over four times higher mass activity towards the anodic oxidation of methanol, and 3.6 times higher mass activity towards the cathodic reduction of oxygen. Importantly, we find thatmore » the intrinsic activity of Pt in this Ru@Pt/C catalyst is doubled due to the formation of the core–shell structure. The catalyst also shows superior stability: even after 2000 scans, it still retains up to 90% of the peak current. As a result, our findings demonstrate that this novel PED approach is a promising method for preparing high-performance core–shell catalysts for fuel cell applications.« less

Hydrogen Generation from Biomass-Derived Surgar Alcohols via the Aqueous-Phase Carbohydrate Reforming (ACR) Process

DOE Office of Scientific and Technical Information (OSTI.GOV)

Randy Cortright

2006-06-30

This project involved the investigation and development of catalysts and reactor systems that will be cost-effective to generate hydrogen from potential sorbitol streams. The intention was to identify the required catalysts and reactors systems as well as the design, construction, and operation of a 300 grams per hour hydrogen system. Virent was able to accomplish this objective with a system that generates 2.2 kgs an hour of gas containing both hydrogen and alkanes that relied directly on the work performed under this grant. This system, funded in part by the local Madison utility, Madison, Gas & Electric (MGE), is describedmore » further in the report. The design and development of this system should provide the necessary scale-up information for the generation of hydrogen from corn-derived sorbitol.« less

Fabrication and electrical characterization of silicon nanowires based resistors

NASA Astrophysics Data System (ADS)

Ni, L.; Demami, F.; Rogel, R.; Salaün, A. C.; Pichon, L.

2009-11-01

Silicon nanowires (SiNWs) are synthesized via the Vapor-Liquid-Solid (VLS) mechanism using gold (Au) as metal catalyst and silane (SiH4) as precursor gas. Au nanoparticles are employed as liquid droplets catalysis during the SiNWs growth performed in a hot wall LPCVD reactor at 480°C and 40 Pa. SiNWs local synthesis at micron scale is demonstrated using classical optical photolithography process. SiNWs grow with high density anchored at the dedicated catalyst islands. This resulting network is used to interconnect two heavily doped polysilicon interdigitated electrodes leading to the formation of electrical resistors in a coplanar structure. Current-voltage (I-V) characteristics highlight a symmetric shape. The temperature dependence of the electrical resistance is activated, with activation energy of 0.47 eV at temperatures greater than 300K.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

The objective of the contract is to consolidate the advances made during the previous contract in the conversion of syngas to motor fuels using Molecular Sieve-containing catalysts and to demonstrate the practical utility and economic value of the new catalyst/process systems with appropriate laboratory runs. Work on the program is divided into the following six tasks: (1) preparation of a detailed work plan covering the entire performance of the contract; (2) preliminary techno-economic assessment of the UCC catalyst/process system; (3) optimization of the most promising catalysts developed under prior contract; (4) optimization of the UCC catalyst system in a mannermore » that will give it the longest possible service life; (5) optimization of a UCC process/catalyst system based upon a tubular reactor with a recycle loop; and (6) economic evaluation of the optimal performance found under Task 5 for the UCC process/catalyst system. Accomplishments are reported for Tasks 2 through 5.« less

Catalyst and process development for synthesis gas conversion to isobutylene. Quarterly report, October 1, 1992--December 31, 1992

DOE Office of Scientific and Technical Information (OSTI.GOV)

Anthony, R.G.; Akgerman, A.

1993-02-01

The objectives of this project are to develop a new catalyst, the kinetics for this catalyst, reactor models for trickle bed, slurry and fixed bed reactors, and simulate the performance of fixed bed trickle flow reactors, slurry flow reactors, and fixed bed gas phase reactors for conversion of a hydrogen lean synthesis gas to isobutylene. The goals for the quarter include: (1) Conduct experiments using a trickle bed reactor to determine the effect of reactor type on the product distribution. (2) Use spherical pellets of silica as a support for zirconia for the purpose of increasing surface, area and performancemore » of the catalysts. (3) Conduct exploratory experiments to determine the effect of super critical drying of the catalyst on the catalyst surface area and performance. (4) Prepare a ceria/zirconia catalyst by the precipitation method.« less

Experimental study of isopropanol dehydrogenation over amorphous alloy raney nickel catalysts

NASA Astrophysics Data System (ADS)

Xin, Fang; Xu, Min; Li, Xun-Feng; Huai, Xiu-Lan

2013-12-01

The dehydrogenation reaction of isopropanol occurring at low temperature is of great industrial importance. It is a key procedure in isopropanol/acetone/hydrogen chemical heat pump system. An experimental investigation was performed to study the behavior of the liquid phase dehydrogenation of isopropanol over amorphous alloy Raney nickel catalysts. Un-promoted and promoted catalysts were used and their performances were compared under various catalyst amounts, acetone content in the reactant and reaction temperature ranging from 348 K to 355 K. It is found that there exists an optimum catalyst concentration which is about 0.34 g in 300 ml isopropanol. The temperature has evident effect on the reaction. The presence of activities of Fe-promoted catalyst decrease slightly compared to the un-promoted catalyst when the temperature are 348 K and 351 K. Besides, the reaction rate decreases almost linearly with the increase of acetone volume fraction in the reactant.

Hydrothermal Synthesis of Platinum-Group-Metal-Free Catalysts: Structural Elucidation and Oxygen Reduction Catalysis

DOE PAGES

Gokhale, Rohan; Tsui, Lok-Kun; Roach, Kristin; ...

2017-12-07

In this paper, a hydrothermal approach to generate a platinum-group-metal-free (PGM-free) Fe-N-C catalyst for the oxygen reduction reaction (ORR) is introduced. The process involves partial carbonization by hydrothermal means followed by thermal treatment to obtain the final catalysts. Detailed X-ray scattering analysis of the glucose-imidazole catalysts (termed as GLU-IMID-C catalysts), obtained for the first time with the use of CarbonXS GUI program, reveals the presence of face-centered cubic (FCC) iron nanoparticles embedded in partially graphitic carbon in all catalyst variations. We also report the physical characterization of these catalysts by using X-ray photoelectron spectroscopy, Brunauer-Emmett-Teller surface area analysis, and transmissionmore » electron microscopy. The electrocatalytic behavior of the catalysts towards oxygen reduction is studied separately in acidic and alkaline electrolytes by rotating ring disk electrode measurements. The catalysts exhibit high ORR activity in acidic (0.5 M H 2SO 4) and alkaline (0.1 M KOH) electrolytes. Lastly, a precursor structure-performance relationship of these catalysts and their performance trends in both electrolytes has been discussed in this work.« less

Hydrothermal Synthesis of Platinum-Group-Metal-Free Catalysts: Structural Elucidation and Oxygen Reduction Catalysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gokhale, Rohan; Tsui, Lok-Kun; Roach, Kristin

In this paper, a hydrothermal approach to generate a platinum-group-metal-free (PGM-free) Fe-N-C catalyst for the oxygen reduction reaction (ORR) is introduced. The process involves partial carbonization by hydrothermal means followed by thermal treatment to obtain the final catalysts. Detailed X-ray scattering analysis of the glucose-imidazole catalysts (termed as GLU-IMID-C catalysts), obtained for the first time with the use of CarbonXS GUI program, reveals the presence of face-centered cubic (FCC) iron nanoparticles embedded in partially graphitic carbon in all catalyst variations. We also report the physical characterization of these catalysts by using X-ray photoelectron spectroscopy, Brunauer-Emmett-Teller surface area analysis, and transmissionmore » electron microscopy. The electrocatalytic behavior of the catalysts towards oxygen reduction is studied separately in acidic and alkaline electrolytes by rotating ring disk electrode measurements. The catalysts exhibit high ORR activity in acidic (0.5 M H 2SO 4) and alkaline (0.1 M KOH) electrolytes. Lastly, a precursor structure-performance relationship of these catalysts and their performance trends in both electrolytes has been discussed in this work.« less

Development of attrition resistant iron-based Fischer-Tropsch catalysts

DOE Office of Scientific and Technical Information (OSTI.GOV)

NONE

2000-09-20

The Fischer-Tropsch (F-T) reaction provides a way of converting coal-derived synthesis gas (CO+H{sub 2}) to liquid fuels. Since the reaction is highly exothermic, one of the major problems in control of the reaction is heat removal. Recent work has shown that the use of slurry bubble column reactors (SBCRs) can largely solve this problem. The use of iron-based catalysts is attractive not only due to their low cost and ready availability, but also due to their high water-gas shift activity which makes it possible to use these catalysts with low H{sub 2}/CO ratios. However, a serious problem with use ofmore » Fe catalysts in a SBCR is their tendency to undergo attrition. This can cause fouling/plugging of downstream filters and equipment, makes the separation of catalyst from the oil/wax product very difficult if not impossible, and results a steady loss of catalyst from the reactor. The objective of this research is to develop robust iron-based Fischer-Tropsch catalysts that have suitable activity, selectivity and stability to be used in the slurry bubble column reactor. Specifically we aim to develop to: (1) improve the performance and preparation procedure of the high activity, high attrition resistant, high alpha iron-based catalysts synthesized at Hampton University (2) seek improvements in the catalyst performance through variations in process conditions, pretreatment procedures and/or modifications in catalyst preparation steps and (3) investigate the performance in a slurry reactor. The effort during the reporting period has been devoted to effects of pretreating procedures, using H{sub 2}, CO and syngas (H{sub 2}/CO = 0.67) as reductants, on the performance (activity, selectivity and stability with time) of a precipitated iron catalyst (100Fe/5Cu/4.2K/10SiO{sub 2} on a mass basis ) during F-T synthesis were studied in a fixed-bed reactor.« less

The influences of microwave irradiation and polyol precursor pH on Cu/AC catalyst and its CO oxidation performance

NASA Astrophysics Data System (ADS)

Chuang, Kui-Hao; Shih, Kaimin; Wey, Ming-Yen

2012-10-01

This study evaluated the effects of microwave irradiation parameters and the pH of the polyol precursor on the morphological features and catalytic performances of Cu/activated carbon (AC) catalysts. Experimental results of carbon monoxide (CO) oxidation indicated that the highest catalytic activity is achieved when the Cu/AC catalyst is prepared with microwave irradiation at 700 W for 60 s. Scanning electron microscopy revealed the presence of beneficial small copper aciculae on the Cu/AC catalyst under such a microwave irradiation scheme. Further investigation of operational parameters found that the performance of Cu/AC catalysts is enhanced by adopting a pH = 12 polyol precursor solution. With the observation that small cube copper ( 16 nm) aggregates form when a pH = 12 polyol precursor solution is used, this study also demonstrated the importance of controlling the morphology of metal nanoparticles on Cu/AC catalysts when using the microwave-assisted polyol method.

40 CFR Table 6 to Subpart Zzzz of... - Continuous Compliance With Emission Limitations, and Other Requirements

Code of Federal Regulations, 2014 CFR

2014-07-01

... >500 HP located at a major source of HAP a. Reduce CO emissions and using an oxidation catalyst, and... not using an oxidation catalyst, and using a CPMS i. Conducting semiannual performance tests for CO to... RICE exhaust and using oxidation catalyst or NSCR i. Conducting semiannual performance tests for...

40 CFR Table 6 to Subpart Zzzz of... - Continuous Compliance With Emission Limitations, and Other Requirements

Code of Federal Regulations, 2013 CFR

2013-07-01

... >500 HP located at a major source of HAP a. Reduce CO emissions and using an oxidation catalyst, and... not using an oxidation catalyst, and using a CPMS i. Conducting semiannual performance tests for CO to... RICE exhaust and using oxidation catalyst or NSCR i. Conducting semiannual performance tests for...

Self-assembled air-stable magnesium hydride embedded in 3-D activated carbon for reversible hydrogen storage.

PubMed

Shinde, S S; Kim, Dong-Hyung; Yu, Jin-Young; Lee, Jung-Ho

2017-06-01

The rational design of stable, inexpensive catalysts with excellent hydrogen dynamics and sorption characteristics under realistic environments for reversible hydrogen storage remains a great challenge. Here, we present a simple and scalable strategy to fabricate a monodispersed, air-stable, magnesium hydride embedded in three-dimensional activated carbon with periodic synchronization of transition metals (MHCH). The high surface area, homogeneous distribution of MgH 2 nanoparticles, excellent thermal stability, high energy density, steric confinement by carbon, and robust architecture of the catalyst resulted in a noticeable enhancement of the hydrogen storage performance. The resulting MHCH-5 exhibited outstanding hydrogen storage performance, better than that of most reported Mg-based hydrides, with a high storage density of 6.63 wt% H 2 , a rapid kinetics loading in <5 min at 180 °C, superior reversibility, and excellent long-term cycling stability over ∼435 h. The significant reduction of the enthalpy and activation energy observed in the MHCH-5 demonstrated enhancement of the kinetics of de-/hydrogenation compared to that of commercial MgH 2 . The origin of the intrinsic hydrogen thermodynamics was elucidated via solid state 1 H NMR. This work presents a readily scaled-up strategy towards the design of realistic catalysts with superior functionality and stability for applications in reversible hydrogen storage, lithium ion batteries, and fuel cells.

Modeling Electrochemical Performance of the Hierarchical Morphology of Precious Group Metal-free Cathode for Polymer Electrolyte Fuel Cell

DOE PAGES

Komini Babu, Siddharth; Chung, Hoon Taek; Zelenay, Piotr; ...

2017-08-04

Here, this paper presents a two-dimensional (2D) computational model of a polymer electrolyte fuel cell (PEFC) with a platinum group metal-free (PGM-free) catalyst cathode that can significantly reduce PEFC costs by eliminating the need for expensive platinum catalysts. Due to their comparatively low volumetric activity, PGM-free cathodes are an order of magnitude thicker than their Pt-based counterpart. The resulting need for greater electrode thickness to achieve sufficient power density requires careful attention to the transport losses across the thicker cathodes. The presented model is used to correlate the composition and morphology of the cathode to PEFC performance. The model ismore » a complete cell, continuum model that includes an advanced agglomerate model for a microstructurally consistent representation of the cathode. A unique feature of the approach is the integration of morphology and transport parameter statistics extracted from nano-scale resolution X-ray computed tomography (nano-CT) imaging of PGM-free cathodes. The model was validated with experimental results of PGM-free cathodes with varying Nafion loading. Lastly, our key findings are a need for increased cathode hydrophobicity and increased ionomer conductivity through either reduced tortuosity or increased bulk conductivity. We further use the model to evaluate targets for the volumetric activity and active site density for future catalysts.« less

Modeling Electrochemical Performance of the Hierarchical Morphology of Precious Group Metal-free Cathode for Polymer Electrolyte Fuel Cell

DOE Office of Scientific and Technical Information (OSTI.GOV)

Komini Babu, Siddharth; Chung, Hoon Taek; Zelenay, Piotr

Here, this paper presents a two-dimensional (2D) computational model of a polymer electrolyte fuel cell (PEFC) with a platinum group metal-free (PGM-free) catalyst cathode that can significantly reduce PEFC costs by eliminating the need for expensive platinum catalysts. Due to their comparatively low volumetric activity, PGM-free cathodes are an order of magnitude thicker than their Pt-based counterpart. The resulting need for greater electrode thickness to achieve sufficient power density requires careful attention to the transport losses across the thicker cathodes. The presented model is used to correlate the composition and morphology of the cathode to PEFC performance. The model ismore » a complete cell, continuum model that includes an advanced agglomerate model for a microstructurally consistent representation of the cathode. A unique feature of the approach is the integration of morphology and transport parameter statistics extracted from nano-scale resolution X-ray computed tomography (nano-CT) imaging of PGM-free cathodes. The model was validated with experimental results of PGM-free cathodes with varying Nafion loading. Lastly, our key findings are a need for increased cathode hydrophobicity and increased ionomer conductivity through either reduced tortuosity or increased bulk conductivity. We further use the model to evaluate targets for the volumetric activity and active site density for future catalysts.« less

Thermally stable single-atom platinum-on-ceria catalysts via atom trapping

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jones, John; Xiong, Haifeng; DelaRiva, Andrew

2016-07-08

Catalysts based on single atoms of scarce precious metals can lead to more efficient use through enhanced reactivity and selectivity. However, single atoms on catalyst supports can be mobile and aggregate into nanoparticles when heated at elevated temperatures. High temperatures are detrimental to catalyst performance unless these mobile atoms can be trapped. We used ceria powders having similar surface areas but different exposed surface facets. When mixed with a platinum/ aluminum oxide catalyst and aged in air at 800°C, the platinum transferred to the ceria and was trapped. Polyhedral ceria and nanorods were more effective than ceria cubes at anchoringmore » the platinum. Performing synthesis at high temperatures ensures that only the most stable binding sites are occupied, yielding a sinter-resistant, atomically dispersed catalyst.« less

Enhanced performance of a novel anodic PdAu/VGCNF catalyst for electro-oxidation in a glycerol fuel cell.

PubMed

Yahya, N; Kamarudin, S K; Karim, N A; Masdar, M S; Loh, K S

2017-11-25

This study presents a novel anodic PdAu/VGCNF catalyst for electro-oxidation in a glycerol fuel cell. The reaction conditions are critical issues affecting the glycerol electro-oxidation performance. This study presents the effects of catalyst loading, temperature, and electrolyte concentration. The glycerol oxidation performance of the PdAu/VGCNF catalyst on the anode side is tested via cyclic voltammetry with a 3 mm 2 active area. The morphology and physical properties of the catalyst are examined using X-ray diffraction (XRD), field emission scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) spectroscopy. Then, optimization is carried out using the response surface method with central composite experimental design. The current density is experimentally obtained as a response variable from a set of experimental laboratory tests. The catalyst loading, temperature, and NaOH concentration are taken as independent parameters, which were evaluated previously in the screening experiments. The highest current density of 158.34 mAcm -2 is obtained under the optimal conditions of 3.0 M NaOH concentration, 60 °C temperature and 12 wt.% catalyst loading. These results prove that PdAu-VGCNF is a potential anodic catalyst for glycerol fuel cells.

Options and processes for spent catalyst handling and utilization.

PubMed

Marafi, M; Stanislaus, A

2003-07-18

The quantity of spent hydroprocessing catalysts discarded as solid wastes in the petroleum refining industries has increased remarkably in recent years due to a rapid growth in the hydroprocessing capacity to meet the rising demand for low-sulfur fuels. Due to their toxic nature, spent hydroprocessing catalysts have been branded as hazardous wastes, and the refiners are experiencing pressure from environmental authorities to handle them safely. Several alternative methods such as reclamation of metals, rejuvenation and reuse, disposal in landfills and preparation of useful materials using spent catalysts as raw materials are available to deal with the spent catalyst problem. The technical feasibility as well as the environmental and economic aspects of these options are reviewed. In addition, details of two bench-scale processes, one for rejuvenation of spent hydroprocessing catalysts, and the other for producing non-leachable synthetic aggregate materials that were developed in this laboratory, are presented in this paper.

Hydrodesulfurization reactions of atmospheric gas oil over CoMo/alumina-aluminum borate catalysts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chiuping Li; Jungchung Wu; Yuwen Chen

1993-08-01

A precipitation technique at constant pH value was used to prepare a series of alumina-aluminum borates (AABs) with various Al/B atomic ratios. These materials were used as the supports of Co-Mo catalysts. Hydrodesulfurization (HDS) of Kuwait atmospheric gas (AGO) oil was carried out over these presulfided catalysts in a bench-scale trickle bed reactor at 400 psi and 340 C. All CoMo/AAB catalysts are much more active than the conventional CoMo/Al[sub 2]O[sub 3] catalyst on HDS reactions. A correlation exists between the acidity and the HDS activity of the catalysts. The high activities of the CoMo/AAB catalysts can be rationalized onmore » the presence of boron. On one hand, it can increase the metal dispersions and hydrogenation capabilities. On the other hand, it can enhance the acidities and cracking abilities of the catalysts. The desulfurization data can be fitted with a pseudo-second-order rate equation. The activation energy for desulfurization is found to be 26 kcal/mol.« less

Ship-in-a-bottle catalysts

DOEpatents

Haw, James F.; Song, Weiguo

2006-07-18

In accordance with the present invention there is provided a novel catalyst system in which the catalytic structure is tailormade at the nanometer scale using the invention's novel ship-in-a-bottle synthesis techniques. The invention describes modified forms of solid catalysts for use in heterogeneous catalysis that have a microporous structure defined by nanocages. Examples include zeolites, SAPOs, and analogous materials that have the controlled pore dimensions and hydrothermal stability required for many industrial processes. The invention provides for modification of these catalysts using reagents that are small enough to pass through the windows used to access the cages. The small reagents are then reacted to form larger molecules in the cages.

Method of depositing a catalyst on a fuel cell electrode

DOEpatents

Dearnaley, Geoffrey; Arps, James H.

2000-01-01

Fuel cell electrodes comprising a minimal load of catalyst having maximum catalytic activity and a method of forming such fuel cell electrodes. The method comprises vaporizing a catalyst, preferably platinum, in a vacuum to form a catalyst vapor. A catalytically effective amount of the catalyst vapor is deposited onto a carbon catalyst support on the fuel cell electrode. The electrode preferably is carbon cloth. The method reduces the amount of catalyst needed for a high performance fuel cell electrode to about 0.3 mg/cm.sup.2 or less.

From fundamental studies of reactivity on single crystals to the design of catalysts

NASA Astrophysics Data System (ADS)

H. Larsen, Jane; Chorkendorff, Ib

One of the prominent arguments for performing surface science studies have for many years been to improve and design new and better catalysts. Although surface science has provided the fundamental framework and tools for understanding heterogeneous catalysis until now there have been extremely few examples of actually designing new catalysts based solely on surface science studies. In this review, we shall demonstrate how a close collaboration between different fundamental disciplines like structural-, theoretical-and reactivity-studies of surfaces as well as a strong interaction with industry can have strong synergetic effects and how this was used to develop a new catalyst. As so often before the studies reviewed here were not initiated with the objective to solve a specific problem, but realizing that a new class of very stable two-dimensional alloys could be synthesized from otherwise immiscible metals made it possible to present a new solution to a specific problem in the industrial catalysis relating to methane activation in the steam reforming process. Methane is the main constituent of natural gas and it is an extremely important raw material for many large scale chemical processes such as production of hydrogen, ammonia, and methanol. In the steam reforming process methane and water are converted into a mixture of mainly hydrogen and carbon monoxide, the so-called synthesis gas. Industrially the steam reforming process usually takes place over a catalyst containing small nickel crystallites highly dispersed on a porous support material like aluminum/magnesium oxides in order to achieve a high active metal area. There is a general consensus that the rate limiting step of this process is the dissociative sticking of methane on the nickel surface. Driven by the desire to understand this step and hopefully be able to manipulate the reactivity, a large number of investigations of the methane/nickel interaction have been performed using nickel single crystals as model catalysts. The process has been investigated, both under thermal conditions and by using supersonic molecular beams elucidating the dynamical aspects of the interaction. The results obtained will be reviewed both with respect to the clean and modified nickel surfaces. Especially the two-dimensional gold-nickel alloy system will be considered since the fundamental results here have lead to the invention of a new nickel based catalyst, which is much more resistant to carbon formation than the conventional nickel catalysts. This may be one of the first examples of how fundamental research can lead to the invention of new catalysts. Other overlayer/alloy combinations, their stability, and reactivity are briefly discussed with respect to manipulation of the surface reactivity towards methane.

Reformer Fuel Injector

NASA Technical Reports Server (NTRS)

Suder, Jennifer L.

2004-01-01

Today's form of jet engine power comes from what is called a gas turbine engine. This engine is on average 14% efficient and emits great quantities of green house gas carbon dioxide and air pollutants, Le. nitrogen oxides and sulfur oxides. The alternate method being researched involves a reformer and a solid oxide fuel cell (SOFC). Reformers are becoming a popular area of research within the industry scale. NASA Glenn Research Center's approach is based on modifying the large aspects of industry reforming processes into a smaller jet fuel reformer. This process must not only be scaled down in size, but also decrease in weight and increase in efficiency. In comparison to today's method, the Jet A fuel reformer will be more efficient as well as reduce the amount of air pollutants discharged. The intent is to develop a 10kW process that can be used to satisfy the needs of commercial jet engines. Presently, commercial jets use Jet-A fuel, which is a kerosene based hydrocarbon fuel. Hydrocarbon fuels cannot be directly fed into a SOFC for the reason that the high temperature causes it to decompose into solid carbon and Hz. A reforming process converts fuel into hydrogen and supplies it to a fuel cell for power, as well as eliminating sulfur compounds. The SOFC produces electricity by converting H2 and CO2. The reformer contains a catalyst which is used to speed up the reaction rate and overall conversion. An outside company will perform a catalyst screening with our baseline Jet-A fuel to determine the most durable catalyst for this application. Our project team is focusing on the overall research of the reforming process. Eventually we will do a component evaluation on the different reformer designs and catalysts. The current status of the project is the completion of buildup in the test rig and check outs on all equipment and electronic signals to our data system. The objective is to test various reformer designs and catalysts in our test rig to determine the most efficient configuration to incorporate into the specific compact jet he1 reformer test rig. Additional information is included in the original extended abstract.

Platinum and palladium nano-structured catalysts for polymer electrolyte fuel cells and direct methanol fuel cells.

PubMed

Long, Nguyen Viet; Thi, Cao Minh; Yong, Yang; Nogami, Masayuki; Ohtaki, Michitaka

2013-07-01

In this review, we present the synthesis and characterization of Pt, Pd, Pt based bimetallic and multi-metallic nanoparticles with mixture, alloy and core-shell structure for nano-catalysis, energy conversion, and fuel cells. Here, Pt and Pd nanoparticles with modified nanostructures can be controllably synthesized via chemistry and physics for their uses as electro-catalysts. The cheap base metal catalysts can be studied in the relationship of crystal structure, size, morphology, shape, and composition for new catalysts with low cost. Thus, Pt based alloy and core-shell catalysts can be prepared with the thin Pt and Pt-Pd shell, which are proposed in low and high temperature proton exchange membrane fuel cells (PEMFCs), and direct methanol fuel cells (DMFCs). We also present the survey of the preparation of Pt and Pd based catalysts for the better catalytic activity, high durability, and stability. The structural transformations, quantum-size effects, and characterization of Pt and Pd based catalysts in the size ranges of 30 nm (1-30 nm) are presented in electro-catalysis. In the size range of 10 nm (1-10 nm), the pure Pt catalyst shows very large surface area for electro-catalysis. To achieve homogeneous size distribution, the shaped synthesis of the polyhedral Pt nanoparticles is presented. The new concept of shaping specific shapes and morphologies in the entire nano-scale from nano to micro, such as polyhedral, cube, octahedra, tetrahedra, bar, rod, and others of the nanoparticles is proposed, especially for noble and cheap metals. The uniform Pt based nanosystems of surface structure, internal structure, shape, and morphology in the nanosized ranges are very crucial to next fuel cells. Finally, the modifications of Pt and Pd based catalysts of alloy, core-shell, and mixture structures lead to find high catalytic activity, durability, and stability for nano-catalysis, energy conversion, fuel cells, especially the next large-scale commercialization of next PEMFCs, and DMFCs.

MERCURY OXIDATION PROMOTED BY A SELECTIVE CATALYTIC REDUCTION CATALYST UNDER SIMULATED POWDER RIVER BASIN COAL COMBUSTION CONDITIONS

EPA Science Inventory

A bench-scale reactor consisting of a natural gas burner and an electrically heated reactor housing a selective catalytic reduction (SCR) catalyst was constructed for studying elemental mercury oxidation under SCR conditions. A low sulfur Power River Basin (PRB) coal combustion ...

Tin-containing zeolites are highly active catalysts for the isomerization of glucose in water.

PubMed

Moliner, Manuel; Román-Leshkov, Yuriy; Davis, Mark E

2010-04-06

The isomerization of glucose into fructose is a large-scale reaction for the production of high-fructose corn syrup (HFCS; reaction performed by enzyme catalysts) and recently is being considered as an intermediate step in the possible route of biomass to fuels and chemicals. Here, it is shown that a large-pore zeolite that contains tin (Sn-Beta) is able to isomerize glucose to fructose in aqueous media with high activity and selectivity. Specifically, a 10% (wt/wt) glucose solution containing a catalytic amount of Sn-Beta (150 Sn:glucose molar ratio) gives product yields of approximately 46% (wt/wt) glucose, 31% (wt/wt) fructose, and 9% (wt/wt) mannose after 30 min and 12 min of reaction at 383 K and 413 K, respectively. This reactivity is achieved also when a 45 wt% glucose solution is used. The properties of the large-pore zeolite greatly influence the reaction behavior because the reaction does not proceed with a medium-pore zeolite, and the isomerization activity is considerably lower when the metal centers are incorporated in ordered mesoporous silica (MCM-41). The Sn-Beta catalyst can be used for multiple cycles, and the reaction stops when the solid is removed, clearly indicating that the catalysis is occurring heterogeneously. Most importantly, the Sn-Beta catalyst is able to perform the isomerization reaction in highly acidic, aqueous environments with equivalent activity and product distribution as in media without added acid. This enables Sn-Beta to couple isomerizations with other acid-catalyzed reactions, including hydrolysis/isomerization or isomerization/dehydration reaction sequences [starch to fructose and glucose to 5-hydroxymethylfurfural (HMF) demonstrated here].

Tin-containing zeolites are highly active catalysts for the isomerization of glucose in water

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moliner, Manuel; Roman-Leshkov, Yuriy; Davis, Mark E.

The isomerization of glucose into fructose is a large-scale reaction for the production of high-fructose corn syrup (HFCS; reaction performed by enzyme catalysts) and recently is being considered as an intermediate step in the possible route of biomass to fuels and chemicals. Here, it is shown that a large-pore zeolite that contains tin (Sn-Beta) is able to isomerize glucose to fructose in aqueous media with high activity and selectivity. Specifically, a 10% (wt/wt) glucose solution containing a catalytic amount of Sn-Beta (1:50 Sn:glucose molar ratio) gives product yields of approximately 46% (wt/wt) glucose, 31% (wt/wt) fructose, and 9% (wt/wt) mannosemore » after 30 min and 12 min of reaction at 383 K and 413 K, respectively. This reactivity is achieved also when a 45 wt% glucose solution is used. The properties of the large-pore zeolite greatly influence the reaction behavior because the reaction does not proceed with a medium-pore zeolite, and the isomerization activity is considerably lower when the metal centers are incorporated in ordered mesoporous silica (MCM-41). The Sn-Beta catalyst can be used for multiple cycles, and the reaction stops when the solid is removed, clearly indicating that the catalysis is occurring heterogeneously. Most importantly, the Sn-Beta catalyst is able to perform the isomerization reaction in highly acidic, aqueous environments with equivalent activity and product distribution as in media without added acid. This enables Sn-Beta to couple isomerizations with other acid-catalyzed reactions, including hydrolysis/isomerization or isomerization/dehydration reaction sequences [starch to fructose and glucose to 5-hydroxymethylfurfural (HMF) demonstrated here].« less

40 CFR 57.302 - Performance level of interim constant controls.

Code of Federal Regulations, 2010 CFR

2010-07-01

... limitation shall take into account unavoidable catalyst deterioration in sulfuric acid plants, but may prescribe the frequency of catalyst screening or replacement. The NSO shall also prohibit the smelter owner... completely fill all available catalyst bed stages with sufficient catalyst; (iii) Inability of the gas pre...

One-Step Facile Synthesis of Cobalt Phosphides for Hydrogen Evolution Reaction Catalysts in Acidic and Alkaline Medium.

PubMed

Sumboja, Afriyanti; An, Tao; Goh, Hai Yang; Lübke, Mechthild; Howard, Dougal Peter; Xu, Yijie; Handoko, Albertus Denny; Zong, Yun; Liu, Zhaolin

2018-05-09

Catalysts for hydrogen evolution reaction are in demand to realize the efficient conversion of hydrogen via water electrolysis. In this work, cobalt phosphides were prepared using a one-step, scalable, and direct gas-solid phosphidation of commercially available cobalt salts. It was found that the effectiveness of the phosphidation reaction was closely related to the state of cobalt precursors at the reaction temperature. For instance, a high yield of cobalt phosphides obtained from the phosphidation of cobalt(II) acetate was related to the good stability of cobalt salt at the phosphidation temperature. On the other hand, easily oxidizable salts (e.g., cobalt(II) acetylacetonate) tended to produce a low amount of cobalt phosphides and a large content of metallic cobalt. The as-synthesized cobalt phosphides were in nanostructures with large catalytic surface areas. The catalyst prepared from phosphidation of cobalt(II) acetate exhibited an improved catalytic activity as compared to its counterpart derived from phosphidation of cobalt(II) acetylacetonate, showing an overpotential of 160 and 175 mV in acidic and alkaline electrolytes, respectively. Both catalysts also displayed an enhanced long-term stability, especially in the alkaline electrolyte. This study illustrates the direct phosphidation behavior of cobalt salts, which serve as a good vantage point in realizing the large-scale synthesis of transition-metal phosphides for high-performance electrocatalysts.

The Role of Non-Conventional Supports for Single-Atom Platinum-Based Catalysts in Fuel-Cell Technology: A Theoretical Surface Science Approach

DTIC Science & Technology

2013-02-05

could be a promising catalyst for PEM fuel cells. Introduction: Proton exchange membrane fuel cells ( PEMFCs ) have found wide potential...Unfortunately, due to their high cost and low lifespan, wide-scale commercialization of PEMFCs has been greatly impeded and much effort has been made to...lower its cost as well as to improve its durability over time. In an attempt to alleviate the high-cost associated with conventional PEMFC catalysts

Refining of Military Jet Fuels from Shale Oil. Volume I. Part II. Preparation of Laboratory-Scale Fuel Samples.

DTIC Science & Technology

1982-03-01

ON SPEC Meeting Specifications *1 OXY Test Series on In Situ Shale Oil P Pressure (P + N) Paraffins and Naphthenes PHO Test Series on Above-Ground...material, the crude shale is heated and processed through caustic desalt- ing similar to conventional technology. The desalted oil is mixed with recycle...with hot regenerated catalyst. Spent catalyst and oil vapors are disengaqed by -.eans of high temperature cyclones. The spent catalyst first passes

On the Preparation and Testing of Fuel Cell Catalysts Using the Thin Film Rotating Disk Electrode Method.

PubMed

Inaba, Masanori; Quinson, Jonathan; Bucher, Jan Rudolf; Arenz, Matthias

2018-03-16

We present a step-by-step tutorial to prepare proton exchange membrane fuel cell (PEMFC) catalysts, consisting of Pt nanoparticles (NPs) supported on a high surface area carbon, and to test their performance in thin film rotating disk electrode (TF-RDE) measurements. The TF-RDE methodology is widely used for catalyst screening; nevertheless, the measured performance sometimes considerably differs among research groups. These uncertainties impede the advancement of new catalyst materials and, consequently, several authors discussed possible best practice methods and the importance of benchmarking. The visual tutorial highlights possible pitfalls in the TF-RDE testing of Pt/C catalysts. A synthesis and testing protocol to assess standard Pt/C catalysts is introduced that can be used together with polycrystalline Pt disks as benchmark catalysts. In particular, this study highlights how the properties of the catalyst film on the glassy carbon (GC) electrode influence the measured performance in TF-RDE testing. To obtain thin, homogeneous catalyst films, not only the catalyst preparation, but also the ink deposition and drying procedures are essential. It is demonstrated that an adjustment of the ink's pH might be necessary, and how simple control measurements can be used to check film quality. Once reproducible TF-RDE measurements are obtained, determining the Pt loading on the catalyst support (expressed as Pt wt%) and the electrochemical surface area is necessary to normalize the determined reaction rates to either surface area or Pt mass. For the surface area determination, so-called CO stripping, or the determination of the hydrogen underpotential deposition (Hupd) charge, are standard. For the determination of the Pt loading, a straightforward and cheap procedure using digestion in aqua regia with subsequent conversion of Pt(IV) to Pt(II) and UV-vis measurements is introduced.

On the Preparation and Testing of Fuel Cell Catalysts Using the Thin Film Rotating Disk Electrode Method

PubMed Central

Inaba, Masanori; Quinson, Jonathan; Bucher, Jan Rudolf; Arenz, Matthias

2018-01-01

We present a step-by-step tutorial to prepare proton exchange membrane fuel cell (PEMFC) catalysts, consisting of Pt nanoparticles (NPs) supported on a high surface area carbon, and to test their performance in thin film rotating disk electrode (TF-RDE) measurements. The TF-RDE methodology is widely used for catalyst screening; nevertheless, the measured performance sometimes considerably differs among research groups. These uncertainties impede the advancement of new catalyst materials and, consequently, several authors discussed possible best practice methods and the importance of benchmarking. The visual tutorial highlights possible pitfalls in the TF-RDE testing of Pt/C catalysts. A synthesis and testing protocol to assess standard Pt/C catalysts is introduced that can be used together with polycrystalline Pt disks as benchmark catalysts. In particular, this study highlights how the properties of the catalyst film on the glassy carbon (GC) electrode influence the measured performance in TF-RDE testing. To obtain thin, homogeneous catalyst films, not only the catalyst preparation, but also the ink deposition and drying procedures are essential. It is demonstrated that an adjustment of the ink's pH might be necessary, and how simple control measurements can be used to check film quality. Once reproducible TF-RDE measurements are obtained, determining the Pt loading on the catalyst support (expressed as Pt wt%) and the electrochemical surface area is necessary to normalize the determined reaction rates to either surface area or Pt mass. For the surface area determination, so-called CO stripping, or the determination of the hydrogen underpotential deposition (Hupd) charge, are standard. For the determination of the Pt loading, a straightforward and cheap procedure using digestion in aqua regia with subsequent conversion of Pt(IV) to Pt(II) and UV-vis measurements is introduced. PMID:29608166

Manganese-cerium oxide catalysts prepared by non-thermal plasma for NO oxidation: Effect of O2 in discharge atmosphere

NASA Astrophysics Data System (ADS)

Liu, Lu; Zheng, Chenghang; Wu, Shenghao; Gao, Xiang; Ni, Mingjiang; Cen, Kefa

2017-09-01

Non-thermal plasma with different O2 concentration in discharge atmosphere was applied to synthesize manganese and cerium mixed-oxides catalysts, which were compared in NO oxidation activity. Discharge atmosphere displayed a crucial influence on the performance of the catalysts prepared by plasma. Relatively low O2 concentration in discharge atmosphere allows synthesizing manganese-cerium oxides catalysts in a moderate environment and therefore is favorable for better physicochemical properties which lead to superior catalytic behavior. The best catalyst was obtained by treatment with 10% O2/N2 plasma and presented over 80% NO conversion in the temperature range of 275-325 °C, whereas catalyst prepared in pure O2 discharge atmosphere had the same activity with a catalyst prepared by calcinations. A correlation between the surface properties of the plasma prepared catalysts and its catalytic activity in NO oxidation is proposed. The amount of the surface adsorbed oxygen has an obvious linear correlation with the amount of Ce3+, the H2 consumption at low temperatures and the catalytic performance. The superior catalytic performance is mainly attributed to the stronger interaction between manganese oxides and ceria, and the formation of poorly crystallized Mn-O-Ce phase in the catalyst which resulted from the slow decomposition of nitrates and organics during plasma treatment. Catalysts prepared in relatively low O2 concentration have large specific surface area and is abundant in Ce3+ species and active oxygen species. The study suggests that plasma treatment with proper discharge gas components is a promising method to prepare effective manganese- cerium oxides catalyst for NO oxidation.

Performance comparison of low-temperature direct alcohol fuel cells with different anode catalysts

NASA Astrophysics Data System (ADS)

Zhou, W. J.; Zhou, B.; Li, W. Z.; Zhou, Z. H.; Song, S. Q.; Sun, G. Q.; Xin, Q.; Douvartzides, S.; Goula, M.; Tsiakaras, P.

Low-temperature polymer electrolyte membrane fuel cells directly fed by methanol and ethanol were investigated employing carbon supported Pt, PtSn and PtRu as anode catalysts, respectively. Employing Pt/C as anode catalyst, both direct methanol fuel cell (DMFC) and direct ethanol fuel cell (DEFC) showed poor performances even in presence of high Pt loading on anode. It was found that the addition of Ru or Sn to the Pt dramatically enhances the electro-oxidation of both methanol and ethanol. It was also found that the single cell adopting PtRu/C as anode shows better DMFC performance, while PtSn/C catalyst shows better DEFC performance. The single fuel cell using PtSn/C as anode catalyst at 90 °C shows similar power densities whenever fueled by methanol or ethanol. The cyclic voltammetry (CV) and single fuel cell tests indicated that PtRu is more suitable for DMFC while PtSn is more suitable for DEFC.

Performance of (CoPC)n catalyst in active lithium-thionyl chloride cells

NASA Technical Reports Server (NTRS)

Shah, Pinakin M.

1990-01-01

An experimental study was conducted with anode limited D size cells to characterize the performance of an active lithium-thionyl chloride (Li/SOCl2) system using the polymeric cobalt phthalocyanine, (CoPC)n, catalyst in carbon cathodes. The author describes the results of this experiment with respect to initial voltage delays, operating voltages, and capacities. The effectiveness of the preconditioning methods evolved to alleviate passivation effects on storage are also discussed. The results clearly demonstrated the superior high rate capability of cells with the catalyst. The catalyst did not adversely impact the performance of cells after active storage for up to 6 months, while retaining its beneficial influences.

Catalytic combustion of methane over commercial catalysts in presence of ammonia and hydrogen sulphide.

PubMed

Hurtado, Paloma; Ordóñez, Salvador; Vega, Aurelio; Díez, Fernando V

2004-05-01

The performance of different commercially available catalysts (supported Pd, Pt, Rh, bimetallic Pd-Pt, and Cr-Cu-Ti oxide catalyst) for the oxidation of methane, alone and in presence of ammonia and hydrogen sulphide is studied in this work. Catalysts performance was evaluated both in terms of activity and resistance to poisoning. The main conclusions are that supported Pd and Rh, present the highest activities for methane oxidation, both alone and in presence of ammonia, whereas they are severely poisoned in presence of H2S. Pt and Cr-Cu-Ti are less active but more sulphur resistant, but their activity is lower than the residual activity of sulphur-deactivated Pd and Rh catalysts. The Pd-Pt catalyst exhibits low activity and it is quickly deactivated in presence of hydrogen sulphide.

Selective liquid phase oxidation of benzyl alcohol to benzaldehyde by tert-butyl hydroperoxide over γ-Al2O3 supported copper and gold nanoparticles

NASA Astrophysics Data System (ADS)

Ndolomingo, Matumuene Joe; Meijboom, Reinout

2017-03-01

Benzyl alcohol oxidation to benzaldehyde was performed by tert-butyl hydroperoxide (TBHP) in the absence of any solvent using γ-Al2O3 supported copper and gold nanoparticles. Li2O and ionic liquids were used as additive and stabilizers for the synthesis of the catalysts. The physico-chemical properties of the catalysts were characterized by atomic absorption spectroscopy (AAS), X-ray diffraction spectroscopy (XRD), N2 absorption/desorption (BET), transmission electron microscopy (TEM), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and temperature programmed reduction (TPR), whereas, the oxidation reaction was followed by gas chromatography with a flame ionization detector (GC-FID). The as prepared catalysts exhibited good catalytic performance in terms of conversion and selectivity towards benzaldehyde. The performance of the Au-based catalysts is significantly higher than that of the Cu-based catalysts. For both Cu and Au catalysts, the conversion of benzyl alcohol increased as the reaction proceeds, while the selectivity for benzaldehyde decreased. Moreover, the catalysts can be easily recycled and reused with neither significant loss of activity nor selectivity. A kinetic study for the Cu and Au-catalyzed oxidation of benzyl alcohol to benzyldehyde is reported. The rate at which the oxidation of benzyl alcohol is occurring as a function of catalyst and oxidant amounts was investigated, with the apparent rate constant, kapp being proportional to the amount of nano catalyst and oxygen present in the system.

Nitrogen-Coordinated Single Cobalt Atom Catalysts for Oxygen Reduction in Proton Exchange Membrane Fuel Cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Xiao Xia; Cullen, David A.; Pan, Yung-Tin

Due to the Fenton reaction, the presence of Fe and peroxide in electrodes generates free radicals causing serious degradation of the organic ionomer and the membrane. Pt-free and Fe-free cathode catalysts therefore are urgently needed for durable and inexpensive proton exchange membrane fuel cells (PEMFCs). In this paper, a high-performance nitrogen-coordinated single Co atom catalyst is derived from Co-doped metal-organic frameworks (MOFs) through a one-step thermal activation. Aberration-corrected electron microscopy combined with X-ray absorption spectroscopy virtually verifies the CoN 4 coordination at an atomic level in the catalysts. Through investigating effects of Co doping contents and thermal activation temperature, anmore » atomically Co site dispersed catalyst with optimal chemical and structural properties has achieved respectable activity and stability for the oxygen reduction reaction (ORR) in challenging acidic media (e.g., half-wave potential of 0.80 V vs reversible hydrogen electrode (RHE). The performance is comparable to Fe-based catalysts and 60 mV lower than Pt/C -60 μg Pt cm -2). Fuel cell tests confirm that catalyst activity and stability can translate to high-performance cathodes in PEMFCs. Finally, the remarkably enhanced ORR performance is attributed to the presence of well-dispersed CoN 4 active sites embedded in 3D porous MOF-derived carbon particles, omitting any inactive Co aggregates.« less

Nitrogen-Coordinated Single Cobalt Atom Catalysts for Oxygen Reduction in Proton Exchange Membrane Fuel Cells

DOE PAGES

Wang, Xiao Xia; Cullen, David A.; Pan, Yung-Tin; ...

2018-01-24

Due to the Fenton reaction, the presence of Fe and peroxide in electrodes generates free radicals causing serious degradation of the organic ionomer and the membrane. Pt-free and Fe-free cathode catalysts therefore are urgently needed for durable and inexpensive proton exchange membrane fuel cells (PEMFCs). In this paper, a high-performance nitrogen-coordinated single Co atom catalyst is derived from Co-doped metal-organic frameworks (MOFs) through a one-step thermal activation. Aberration-corrected electron microscopy combined with X-ray absorption spectroscopy virtually verifies the CoN 4 coordination at an atomic level in the catalysts. Through investigating effects of Co doping contents and thermal activation temperature, anmore » atomically Co site dispersed catalyst with optimal chemical and structural properties has achieved respectable activity and stability for the oxygen reduction reaction (ORR) in challenging acidic media (e.g., half-wave potential of 0.80 V vs reversible hydrogen electrode (RHE). The performance is comparable to Fe-based catalysts and 60 mV lower than Pt/C -60 μg Pt cm -2). Fuel cell tests confirm that catalyst activity and stability can translate to high-performance cathodes in PEMFCs. Finally, the remarkably enhanced ORR performance is attributed to the presence of well-dispersed CoN 4 active sites embedded in 3D porous MOF-derived carbon particles, omitting any inactive Co aggregates.« less

Nitrogen-Coordinated Single Cobalt Atom Catalysts for Oxygen Reduction in Proton Exchange Membrane Fuel Cells.

PubMed

Wang, Xiao Xia; Cullen, David A; Pan, Yung-Tin; Hwang, Sooyeon; Wang, Maoyu; Feng, Zhenxing; Wang, Jingyun; Engelhard, Mark H; Zhang, Hanguang; He, Yanghua; Shao, Yuyan; Su, Dong; More, Karren L; Spendelow, Jacob S; Wu, Gang

2018-03-01

Due to the Fenton reaction, the presence of Fe and peroxide in electrodes generates free radicals causing serious degradation of the organic ionomer and the membrane. Pt-free and Fe-free cathode catalysts therefore are urgently needed for durable and inexpensive proton exchange membrane fuel cells (PEMFCs). Herein, a high-performance nitrogen-coordinated single Co atom catalyst is derived from Co-doped metal-organic frameworks (MOFs) through a one-step thermal activation. Aberration-corrected electron microscopy combined with X-ray absorption spectroscopy virtually verifies the CoN 4 coordination at an atomic level in the catalysts. Through investigating effects of Co doping contents and thermal activation temperature, an atomically Co site dispersed catalyst with optimal chemical and structural properties has achieved respectable activity and stability for the oxygen reduction reaction (ORR) in challenging acidic media (e.g., half-wave potential of 0.80 V vs reversible hydrogen electrode (RHE). The performance is comparable to Fe-based catalysts and 60 mV lower than Pt/C -60 μg Pt cm -2 ). Fuel cell tests confirm that catalyst activity and stability can translate to high-performance cathodes in PEMFCs. The remarkably enhanced ORR performance is attributed to the presence of well-dispersed CoN 4 active sites embedded in 3D porous MOF-derived carbon particles, omitting any inactive Co aggregates. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

An Investigation of Methyl Viologen Functionalized Reduced Graphene Oxide: Chitosan as a Support for Pt Nanoparticles Towards Ethanol Electrooxidation

NASA Astrophysics Data System (ADS)

Ekrami-Kakhki, Mehri-Saddat; Farzaneh, Nahid; Abbasi, Sedigheh; Beitollahi, Hadi; Ekrami-Kakhki, Seyed Ali

2018-05-01

In this research, graphene oxide was prepared by a modified Hummers' method, and then functionalized with 1, 1'-dimethyl-4, 4'-bipyridinium dichloride (MV), and chitosan (CH) to get a MV-RGO-CH support. Pt nanoparticles were prepared on this support to get Pt/MV-RGO-CH catalyst. The morphology and microstructure of Pt/MV-RGO-CH catalyst were characterized with transmission electron microscopy image and X-ray diffraction analysis. The electrocatalytic activity of the prepared catalyst towards ethanol oxidation was investigated by carbon monoxide stripping voltammetry, cyclic voltammetry, and electrochemical impedance spectroscopy techniques. The effects of some experimental parameters such as scan rate, ethanol concentration, and temperature were investigated for ethanol electrooxidation at Pt/MV-RGO-CH catalyst. Durability of the catalyst was also investigated. The electrocatalytic performance of Pt/MV-RGO-CH catalyst for ethanol oxidation was compared with those of Pt/CH and Pt/MV-RGO catalysts. The higher electrocatalytic performance of Pt/MV-RGO-CH than Pt/CH and Pt/MV-RGO catalysts towards ethanol electrooxidation indicated that Pt/MV-RGO-CH could be a promising catalyst for application in direct ethanol fuel cells.

A novel multi-functional magnetic Fe-Ti-V spinel catalyst for elemental mercury capture and callback from flue gas.

PubMed

Yang, Shijian; Guo, Yongfu; Yan, Naiqiang; Wu, Daqing; He, Hongping; Xie, Jiangkun; Qu, Zan; Yang, Chen; Jia, Jinping

2010-11-28

A novel magnetic Fe-Ti-V spinel catalyst showed an excellent performance for elemental mercury capture at 100 °C, and the formed HgO can be catalytically decomposed by the catalyst at 300 °C to reclaim elemental mercury and regenerate the catalyst.

High performance, high durability non-precious metal fuel cell catalysts

DOEpatents

Wood, Thomas E.; Atanasoski, Radoslav; Schmoeckel, Alison K.

2016-03-15

This invention relates to non-precious metal fuel cell cathode catalysts, fuel cells that contain these catalysts, and methods of making the same. The fuel cell cathode catalysts are highly nitrogenated carbon materials that can contain a transition metal. The highly nitrogenated carbon materials can be supported on a nanoparticle substrate.

An Overview of Recent Development in Composite Catalysts from Porous Materials for Various Reactions and Processes

PubMed Central

Xie, Zaiku; Liu, Zhicheng; Wang, Yangdong; Yang, Qihua; Xu, Longya; Ding, Weiping

2010-01-01

Catalysts are important to the chemical industry and environmental remediation due to their effective conversion of one chemical into another. Among them, composite catalysts have attracted continuous attention during the past decades. Nowadays, composite catalysts are being used more and more to meet the practical catalytic performance requirements in the chemical industry of high activity, high selectivity and good stability. In this paper, we reviewed our recent work on development of composite catalysts, mainly focusing on the composite catalysts obtained from porous materials such as zeolites, mesoporous materials, carbon nanotubes (CNT), etc. Six types of porous composite catalysts are discussed, including amorphous oxide modified zeolite composite catalysts, zeolite composites prepared by co-crystallization or overgrowth, hierarchical porous catalysts, host-guest porous composites, inorganic and organic mesoporous composite catalysts, and polymer/CNT composite catalysts. PMID:20559508

Preparation and catalytic performance of copper-containing magnetic catalysts for degradation of azo dye (direct violet).

PubMed

Duan, Qiannan; Lee, Jianchao; Chen, Han; Zheng, Yunyun

2017-12-01

A novel magnetically separable magnetic activated carbon supporting-copper (MCAC) catalyst for catalytic wet peroxide oxidation (CWPO) was prepared by chemical impregnation. The prepared samples were characterized by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) method, and scanning electron microscopy (SEM) equipped with energy dispersive spectrometry (EDS). The catalytic performance of the catalysts was evaluated by direct violet (D-BL) degradation in CWPO experiments. The influence of preparative and operational parameters (dipping conditions, calcination temperature, catalyst loading H 2 O 2 dosage, pH, reaction temperature, additive salt ions and initial D-BL concentration) on degradation performance of CWPO process was investigated. The resulting MCAC catalyst showed higher reusability in direct violet oxidation than the magnetic activated carbon (MAC). Besides, dynamic tests also showed the maximal degradation rate reached 90.16% and its general decoloring ability of MCAC was 34 mg g -1 for aqueous D-BL.

Toluene decomposition performance and NOx by-product formation during a DBD-catalyst process.

PubMed

Guo, Yufang; Liao, Xiaobin; Fu, Mingli; Huang, Haibao; Ye, Daiqi

2015-02-01

Characteristics of toluene decomposition and formation of nitrogen oxide (NOx) by-products were investigated in a dielectric barrier discharge (DBD) reactor with/without catalyst at room temperature and atmospheric pressure. Four kinds of metal oxides, i.e., manganese oxide (MnOx), iron oxide (FeOx), cobalt oxide (CoOx) and copper oxide (CuO), supported on Al2O3/nickel foam, were used as catalysts. It was found that introducing catalysts could improve toluene removal efficiency, promote decomposition of by-product ozone and enhance CO2 selectivity. In addition, NOx was suppressed with the decrease of specific energy density (SED) and the increase of humidity, gas flow rate and toluene concentration, or catalyst introduction. Among the four kinds of catalysts, the CuO catalyst showed the best performance in NOx suppression. The MnOx catalyst exhibited the lowest concentration of O3 and highest CO2 selectivity but the highest concentration of NOx. A possible pathway for NOx production in DBD was discussed. The contributions of oxygen active species and hydroxyl radicals are dominant in NOx suppression. Copyright © 2014. Published by Elsevier B.V.

Methanol steam reforming promoted by molten salt-modified platinum on alumina catalysts.

PubMed

Kusche, Matthias; Agel, Friederike; Ní Bhriain, Nollaig; Kaftan, Andre; Laurin, Mathias; Libuda, Jörg; Wasserscheid, Peter

2014-09-01

We herein describe a straight forward procedure to increase the performance of platinum-on-alumina catalysts in methanol steam reforming by applying an alkali hydroxide coating according to the "solid catalyst with ionic liquid layer" (SCILL) approach. We demonstrate by diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and temperature-programmed desorption (TPD) studies that potassium doping plays an important role in the catalyst activation. Moreover, the hygroscopic nature and the basicity of the salt modification contribute to the considerable enhancement in catalytic performance. During reaction, a partly liquid film of alkali hydroxides/carbonates forms on the catalyst/alumina surface, thus significantly enhancing the availability of water at the catalytically active sites. Too high catalyst pore fillings with salt introduce a considerable mass transfer barrier into the system as indicated by kinetic studies. Thus, the optimum interplay between beneficial catalyst modification and detrimental mass transfer effects had to be identified and was found on the applied platinum-on-alumina catalyst at KOH loadings around 7.5 mass%. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Novel methods of stabilization of Raney-Nickel catalyst for fuel-cell electrodes

NASA Astrophysics Data System (ADS)

Al-Saleh, M. A.; Sleem-Ur-Rahman; Kareemuddin, S. M. M. J.; Al-Zakri, A. S.

Two new methods of stabilizing Raney-Nickel (Raney-Ni) catalyst for making fuel-cell anodes were studied. In the first method, the catalyst was oxidized with aqueous H 2O 2 solution, while in the second, oxygen/air (O 2/air) was used in a slurry reactor. Effects of different concentrations of H 2O 2 (5-25 wt.%) and different pressures (10-20 psig) of gas were investigated. The stabilized catalyst was characterized using BET surface area, scanning electron microscopy (SEM) and X-ray diffraction (XRD). The catalyst was used in fuel-cell anodes and the electrochemical performance was determined in an alkaline half-cell. The results were compared with electrodes prepared using conventionally stabilized catalysts. The hydrogen peroxide-treated catalyst has higher BET surface area and produces electrodes with lower polarization. In addition to this, H 2O 2 treatment is convenient, fast and needs simple equipment which involves no instrumentation. Use of oxygen in a slurry reactor to stabilize the catalyst is also convenient but electrode performance is relatively poor.

Fly ash zeolite catalyst support for Fischer-Tropsch synthesis

NASA Astrophysics Data System (ADS)

Campen, Adam

This dissertation research aimed at evaluating a fly ash zeolite (FAZ) catalyst support for use in heterogeneous catalytic processes. Gas phase Fischer-Tropsch Synthesis (FTS) over a fixed-bed of the prepared catalyst/FAZ support was identified as an appropriate process for evaluation, by comparison with commercial catalyst supports (silica, alumina, and 13X). Fly ash, obtained from the Wabash River Generating Station, was first characterized using XRD, SEM/EDS, particle size, and nitrogen sorption techniques. Then, a parametric study of a two-step alkali fusion/hydrothermal treatment process for converting fly ash to zeolite frameworks was performed by varying the alkali fusion agent, agent:flyash ratio, fusion temperature, fused ash/water solution, aging time, and crystallization time. The optimal conditions for each were determined to be NaOH, 1.4 g NaOH: 1 g fly ash, 550 °C, 200 g/L, 12 hours, and 48 hours. This robust process was applied to the fly ash to obtain a faujasitic zeolite structure with increased crystallinity (40 %) and surface area (434 m2/g). Following the modification of fly ash to FAZ, ion exchange of H+ for Na+ and cobalt incipient wetness impregnation were used to prepare a FTS catalyst. FTS was performed on the catalysts at 250--300 °C, 300 psi, and with a syngas ratio H2:CO = 2. The HFAZ catalyst support loaded with 11 wt% cobalt resulted in a 75 % carbon selectivity for C5 -- C18 hydrocarbons, while methane and carbon dioxide were limited to 13 and 1 %, respectively. Catalyst characterization was performed by XRD, N2 sorption, TPR, and oxygen pulse titration to provide insight to the behavior of each catalyst. Overall, the HFAZ compared well with silica and 13X supports, and far exceeded the performance of the alumina support under the tested conditions. The successful completion of this research could add value to an underutilized waste product of coal combustion, in the form of catalyst supports in heterogeneous catalytic processes.

Tuning Catalytic Performance through a Single or Sequential Post-Synthesis Reaction(s) in a Gas Phase

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shan, Junjun; Zhang, Shiran; Choksi, Tej

2016-12-05

Catalytic performance of a bimetallic catalyst is determined by geometric structure and electronic state of the surface or even the near-surface region of the catalyst. Here we report that single and sequential postsynthesis reactions of an as-synthesized bimetallic nanoparticle catalyst in one or more gas phases can tailor surface chemistry and structure of the catalyst in a gas phase, by which catalytic performance of this bimetallic catalyst can be tuned. Pt–Cu regular nanocube (Pt–Cu RNC) and concave nanocube (Pt–Cu CNC) are chosen as models of bimetallic catalysts. Surface chemistry and catalyst structure under different reaction conditions and during catalysis weremore » explored in gas phase of one or two reactants with ambient-pressure X-ray photoelectron spectroscopy (AP-XPS) and extended X-ray absorption fine structure (EXAFS) spectroscopy. The newly formed surface structures of Pt–Cu RNC and Pt–Cu CNC catalysts strongly depend on the reactive gas(es) used in the postsynthesis reaction(s). A reaction of Pt–Cu RNC-as synthesized with H2 at 200 °C generates a near-surface alloy consisting of a Pt skin layer, a Cu-rich subsurface, and a Pt-rich deep layer. This near-surface alloy of Pt–Cu RNC-as synthesized-H2 exhibits a much higher catalytic activity in CO oxidation in terms of a low activation barrier of 39 ± 4 kJ/mol in contrast to 128 ± 7 kJ/mol of Pt–Cu RNC-as synthesized. Here the significant decrease of activation barrier demonstrates a method to tune catalytic performances of as-synthesized bimetallic catalysts. A further reaction of Pt–Cu RNC-as synthesized-H2 with CO forms a Pt–Cu alloy surface, which exhibits quite different catalytic performance in CO oxidation. It suggests the capability of generating a different surface by using another gas. The capability of tuning surface chemistry and structure of bimetallic catalysts was also demonstrated in restructuring of Pt–Cu CNC-as synthesized.« less

The oxidation of copper catalysts during ethylene epoxidation.

PubMed

Greiner, M T; Jones, T E; Johnson, B E; Rocha, T C R; Wang, Z J; Armbrüster, M; Willinger, M; Knop-Gericke, A; Schlögl, R

2015-10-14

The oxidation of copper catalysts during ethylene epoxidation was characterized using in situ photoemission spectroscopy and electron microscopy. Gas chromatography, proton-transfer reaction mass spectrometry and electron-ionization mass spectrometry were used to characterize the catalytic properties of the oxidized copper. We find that copper corrodes during epoxidation in a 1 : 1 mixture of oxygen and ethylene. The catalyst corrosion passes through several stages, beginning with the formation of an O-terminated surface, followed by the formation of Cu2O scale and eventually a CuO scale. The oxidized catalyst exhibits measurable activity for ethylene epoxidation, but with a low selectivity of <3%. Tests on pure Cu2O and CuO powders confirm that the oxides intrinsically exhibit partial-oxidation activity. Cu2O was found to form acetaldehyde and ethylene epoxide in roughly equal amounts (1.0% and 1.2% respectively), while CuO was found to form much less ethyl aldehyde than ethylene epoxide (0.1% and 1.0%, respectively). Metallic copper catalysts were examined in extreme dilute-O2 epoxidation conditions to try and keep the catalyst from oxidizing during the reaction. It was found that in feed of 1 part O2 to 2500 parts C2H4 (PO2 = 1.2 × 10(-4) mbar) the copper surface becomes O-terminated. The O-terminated surface was found to exhibit partial-oxidation selectivity similar to that of Cu2O. With increasing O2 concentration (>8/2500) Cu2O forms and eventually covers the surface.

Need for optimizing catalyst loading for achieving affordable microbial fuel cells.

PubMed

Singh, Inderjeet; Chandra, Amreesh

2013-08-01

Microbial fuel cell (MFC) technology is a promising technology for electricity production together with simultaneous water treatment. Catalysts play an important role in deciding the MFC performance. In most reports, effect of catalyst - both type and quantity is not optimized. In this paper, synthesis of nanorods of MnO2-catalyst particles for application in Pt-free MFCs is reported. The effect of catalyst loading i.e., weight ratio, with respect to conducting element and binder has been optimized by employing large number of combinations. Using simple theoretical model, it is shown that too high (or low) concentration of catalysts result in loss of MFC performance. The operation of MFC has been investigated using domestic wastewater as source of bio-waste for obtaining real world situation. Maximum power density of ∼61 mW/m(2) was obtained when weight ratio of catalyst and conducting species was 1:1. Suitable reasons are given to explain the outcomes. Copyright © 2013 Elsevier Ltd. All rights reserved.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

The objective of the contract is to consolidate the advances made during the previous contract in the conversion of syngas to motor fuels using Molecular Sieve-containing catalysts and to demonstrate the practical utility and economic value of the new catalyst/process systems with appropriate laboratory runs. Work on the program is divided into the following six tasks: (1) preparation of a detailed work plan covering the entire performance of the contract; (2) techno-economic studies that will supplement those that are presently being carried out by MITRE; (3) optimization of the most promising catalysts developed under prior contract; (4) optimization of themore » UCC catalyst system in a manner that will give it the longest possible service life; (5) optimization of a UCC process/catalyst system based upon a tubular reactor with a recycle loop containing the most promising catalyst developed under Tasks 3 and 4 studies; and (6) economic evaluation of the optimal performance found under Task 5 for the UCC process/catalyst system. Progress reports are presented for Tasks 1, 3, 4, and 5.« less

Immobilization of molecular catalysts in supported ionic liquid phases.

PubMed

Van Doorslaer, Charlie; Wahlen, Joos; Mertens, Pascal; Binnemans, Koen; De Vos, Dirk

2010-09-28

In a supported ionic liquid phase (SILP) catalyst system, an ionic liquid (IL) film is immobilized on a high-surface area porous solid and a homogeneous catalyst is dissolved in this supported IL layer, thereby combining the attractive features of homogeneous catalysts with the benefits of heterogeneous catalysts. In this review reliable strategies for the immobilization of molecular catalysts in SILPs are surveyed. In the first part, general aspects concerning the application of SILP catalysts are presented, focusing on the type of catalyst, support, ionic liquid and reaction conditions. Secondly, organic reactions in which SILP technology is applied to improve the performance of homogeneous transition-metal catalysts are presented: hydroformylation, metathesis reactions, carbonylation, hydrogenation, hydroamination, coupling reactions and asymmetric reactions.

Scaled up Fabrication of High-Throughout SWNT Nanoelectronics and Nanosensor Devices

DTIC Science & Technology

2007-04-20

copolymer, polystyrene-block-ferrocenylethylmethylsilane (PS-b- PFEMS ) as the polymer-based catalyst for optimized SWNT growth. Spin coating a dilute...solution of 1 wt % PS-b- PFEMS in toluene provides uniform ~ 100nm thick films of the catalyst. In order to get well-separated individual SWNT or SWNT rope

Environmental implications of iron fuel borne catalysts and their effects on diesel particulate formation and composition

EPA Science Inventory

Metal fuel borne catalysts can be used with diesel fuels to effectively reduce engine out particle mass emissions. Mixed with the fuel, the metals become incorporated as nanometer-scale occlusions with soot during its formation and are available to promote in-cylinder soot oxida...

Moisture condensation behavior of hierarchically carbon nanotube-grafted carbon nanofibers.

PubMed

Park, Kyu-Min; Lee, Byoung-Sun; Youk, Ji Ho; Lee, Jinyong; Yu, Woong-Reol

2013-11-13

Hierarchical micro/nanosurfaces with nanoscale roughness on microscale uneven substrates have been the subject of much recent research interest because of phenomena such as superhydrophobicity. However, an understanding of the effect of the difference in the scale of the hierarchical entities, i.e., nanoscale roughness on microscale uneven substrates as opposed to nanoscale roughness on (a larger) nanoscale uneven surface, is still lacking. In this study, we investigated the effect of the difference in scale between the nano- and microscale features. We fabricated carbon nanotube-grafted carbon nanofibers (CNFs) by dispersing a catalyst precursor in poly (acrylonitrile) (PAN) solution, electrospinning the PAN/catalyst precursor solution, carbonization of electrospun PAN nanofibers, and direct growth of carbon nanotubes (CNTs) on the CNFs. We investigated the relationships between the catalyst concentrations, the size of catalyst nanoparticles on CNFs, and the sizes of CNFs and CNTs. Interestingly, the hydrophobic behavior of micro/nano and nano/nano hierarchical surfaces with water droplets was similar; however a significant difference in the water condensation behavior was observed. Water condensed into smaller droplets on the nano/nano hierarchical surface, causing it to dry much faster.

The leguminous species Anthyllis vulneraria as a Zn-hyperaccumulator and eco-Zn catalyst resources.

PubMed

Grison, Claire M; Mazel, Marine; Sellini, Amandine; Escande, Vincent; Biton, Jacques; Grison, Claude

2015-04-01

Anthyllis vulneraria was highlighted here as a Zn-hyperaccumulator for the development of a pilot phytoextraction process in the mine site of Les Avinières in the district of Saint-Laurent-Le-Minier. A. vulneraria appeared to hyperaccumulate the highest concentration of Zn in shoots with a better metal selectivity relative to Cd and Pb than the reference Zn-hyperaccumulator Noccea caerulescens. A bigger biomass production associated to a higher Zn concentration conducted A. vulneraria to the highest total zinc gain per hectare per year. As a legume, A. vulneraria was infected by rhizobia symbionts. Inoculation of A. vulneraria seeds showed a positive impact on Zn hyperaccumulation. A large-scale culture process of symbiotic rhizobia of A. vulneraria was investigated and optimized to allow large-scale inoculation process. Contaminated shoots of A. vulneraria were not considered as wastes and were recovered as Eco-Zn catalyst in particular, examples of organic synthesis, electrophilic aromatic substitution. Eco-Zn catalyst was much more efficient than conventional catalysts and allowed greener chemical processes.

Catalysts at work: From integral to spatially resolved X-ray absorption spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Grunwaldt, Jan-Dierk; Kimmerle, Bertram; Baiker, Alfons

2009-09-25

Spectroscopic studies on heterogeneous catalysts have mostly been done in an integral mode. However, in many cases spatial variations in catalyst structure can occur, e.g. during impregnation of pre-shaped particles, during reaction in a catalytic reactor, or in microstructured reactors as the present overview shows. Therefore, spatially resolved molecular information on a microscale is required for a comprehensive understanding of theses systems, partly in ex situ studies, partly under stationary reaction conditions and in some cases even under dynamic reaction conditions. Among the different available techniques, X-ray absorption spectroscopy (XAS) is a well-suited tool for this purpose as the differentmore » selected examples highlight. Two different techniques, scanning and full-field X-ray microscopy/tomography, are described and compared. At first, the tomographic structure of impregnated alumina pellets is presented using full-field transmission microtomography and compared to the results obtained with a scanning X-ray microbeam technique to analyse the catalyst bed inside a catalytic quartz glass reactor. On the other hand, by using XAS in scanning microtomography, the structure and the distribution of Cu(0), Cu(I), Cu(II) species in a Cu/ZnO catalyst loaded in a quartz capillary microreactor could be reconstructed quantitatively on a virtual section through the reactor. An illustrating example for spatially resolved XAS under reaction conditions is the partial oxidation of methane over noble metal-based catalysts. In order to obtain spectroscopic information on the spatial variation of the oxidation state of the catalyst inside the reactor XAS spectra were recorded by scanning with a micro-focussed beam along the catalyst bed. Alternatively, full-field transmission imaging was used to efficiently determine the distribution of the oxidation state of a catalyst inside a reactor under reaction conditions. The new technical approaches together with quantitative data analysis and an appropriate in situ catalytic experiment allowed drawing important conclusions on the reaction mechanism, and the analytical strategy might be similarly applied in other case studies. The corresponding temperature profiles and the catalytic performance were measured by means of an IR-camera and mass spectrometric analysis. In a more advanced experiment the ignition process of the partial oxidation of methane was followed in a spatiotemporal manner which demonstrates that spatially resolved spectroscopic information can even be obtained in the subsecond scale.« less

Effect of Particle Size and Operating Conditions on Pt 3Co PEMFC Cathode Catalyst Durability

DOE PAGES

Gummalla, Mallika; Ball, Sarah; Condit, David; ...

2015-05-29

The initial performance and decay trends of polymer electrolyte membrane fuel cells (PEMFC) cathodes with Pt 3Co catalysts of three mean particle sizes (4.9 nm, 8.1 nm, and 14.8 nm) with identical Pt loadings are compared. Even though the cathode based on 4.9 nm catalyst exhibited the highest initial electrochemical surface area (ECA) and mass activity, the cathode based on 8.1 nm catalyst showed better initial performance at high currents. Owing to the low mass activity of the large particles, the initial performance of the 14.8 nm Pt3Co-based electrode was the lowest. The performance decay rate of the electrodes withmore » the smallest Pt 3Co particle size was the highest and that of the largest Pt 3Co particle size was lowest. Interestingly, with increasing number of decay cycles (0.6 to 1.0 V, 50 mV/s), the relative improvement in performance of the cathode based on 8.1 nm Pt 3Co over the 4.9 nm Pt 3Co increased, owing to better stability of the 8.1 nm catalyst. The electron microprobe analysis (EMPA) of the decayed membrane-electrode assembly (MEA) showed that the amount of Co in the membrane was lower for the larger particles, and the platinum loss into the membrane also decreased with increasing particle size. This suggests that the higher initial performance at high currents with 8.1 nm Pt 3Co could be due to lower contamination of the ionomer in the electrode. Furthermore, lower loss of Co from the catalyst with increased particle size could be one of the factors contributing to the stability of ECA and mass activity of electrodes with larger cathode catalyst particles. To delineate the impact of particle size and alloy effects, these results are compared with prior work from our research group on size effects of pure platinum catalysts. The impact of PEMFC operating conditions, including upper potential, relative humidity, and temperature on the alloy catalyst decay trends, along with the EMPA analysis of the decayed MEAs, are reported.« less

Fuel processing in integrated micro-structured heat-exchanger reactors

NASA Astrophysics Data System (ADS)

Kolb, G.; Schürer, J.; Tiemann, D.; Wichert, M.; Zapf, R.; Hessel, V.; Löwe, H.

Micro-structured fuel processors are under development at IMM for different fuels such as methanol, ethanol, propane/butane (LPG), gasoline and diesel. The target application are mobile, portable and small scale stationary auxiliary power units (APU) based upon fuel cell technology. The key feature of the systems is an integrated plate heat-exchanger technology which allows for the thermal integration of several functions in a single device. Steam reforming may be coupled with catalytic combustion in separate flow paths of a heat-exchanger. Reactors and complete fuel processors are tested up to the size range of 5 kW power output of a corresponding fuel cell. On top of reactor and system prototyping and testing, catalyst coatings are under development at IMM for numerous reactions such as steam reforming of LPG, ethanol and methanol, catalytic combustion of LPG and methanol, and for CO clean-up reactions, namely water-gas shift, methanation and the preferential oxidation of carbon monoxide. These catalysts are investigated in specially developed testing reactors. In selected cases 1000 h stability testing is performed on catalyst coatings at weight hourly space velocities, which are sufficiently high to meet the demands of future fuel processing reactors.

Defining a Materials Database for the Design of Copper Binary Alloy Catalysts for Electrochemical CO2 Conversion.

PubMed

Lee, Chan Woo; Yang, Ki Dong; Nam, Dae-Hyun; Jang, Jun Ho; Cho, Nam Heon; Im, Sang Won; Nam, Ki Tae

2018-01-24

While Cu electrodes are a versatile material in the electrochemical production of desired hydrocarbon fuels, Cu binary alloy electrodes are recently proposed to further tune reaction directionality and, more importantly, overcome the intrinsic limitation of scaling relations. Despite encouraging empirical demonstrations of various Cu-based metal alloy systems, the underlying principles of their outstanding performance are not fully addressed. In particular, possible phase segregation with concurrent composition changes, which is widely observed in the field of metallurgy, is not at all considered. Moreover, surface-exposed metals can easily form oxide species, which is another pivotal factor that determines overall catalytic properties. Here, the understanding of Cu binary alloy catalysts for CO 2 reduction and recent progress in this field are discussed. From the viewpoint of the thermodynamic stability of the alloy system and elemental mixing, possible microstructures and naturally generated surface oxide species are proposed. These basic principles of material science can help to predict and understand metal alloy structure and, moreover, act as an inspiration for the development of new binary alloy catalysts to further improve CO 2 conversion and, ultimately, achieve a carbon-neutral cycle. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Efficient solar-to-fuels production from a hybrid microbial-water-splitting catalyst system.

PubMed

Torella, Joseph P; Gagliardi, Christopher J; Chen, Janice S; Bediako, D Kwabena; Colón, Brendan; Way, Jeffery C; Silver, Pamela A; Nocera, Daniel G

2015-02-24

Photovoltaic cells have considerable potential to satisfy future renewable-energy needs, but efficient and scalable methods of storing the intermittent electricity they produce are required for the large-scale implementation of solar energy. Current solar-to-fuels storage cycles based on water splitting produce hydrogen and oxygen, which are attractive fuels in principle but confront practical limitations from the current energy infrastructure that is based on liquid fuels. In this work, we report the development of a scalable, integrated bioelectrochemical system in which the bacterium Ralstonia eutropha is used to efficiently convert CO2, along with H2 and O2 produced from water splitting, into biomass and fusel alcohols. Water-splitting catalysis was performed using catalysts that are made of earth-abundant metals and enable low overpotential water splitting. In this integrated setup, equivalent solar-to-biomass yields of up to 3.2% of the thermodynamic maximum exceed that of most terrestrial plants. Moreover, engineering of R. eutropha enabled production of the fusel alcohol isopropanol at up to 216 mg/L, the highest bioelectrochemical fuel yield yet reported by >300%. This work demonstrates that catalysts of biotic and abiotic origin can be interfaced to achieve challenging chemical energy-to-fuels transformations.

Chitosan-microreactor: a versatile approach for heterogeneous organic synthesis in microfluidics.

PubMed

Basavaraju, K C; Sharma, Siddharth; Singh, Ajay K; Im, Do Jin; Kim, Dong-Pyo

2014-07-01

Microreactors have been proven to be efficient tools for a variety of homogeneous organic transformations due to their mixing efficiency, which results in very fast reactions, better heat and mass transfer, and simple scale-up. However, in heterogeneous catalytic reactions each catalyst needs an individual substrate as support. Herein, a versatile approach to immobilize metal catalysts on chitosan as a common substrate is presented. Chitosan, accommodating many metal catalysts, is grafted onto the microchannel surface as nanobrush. The versatility, catalytic efficiency, and stability/durability of the microreactor are demonstrated for a number of organic transformations involving various metal compounds as catalysts. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

From bio-mineralisation to fuel cells: biomanufacture of Pt and Pd nanocrystals for fuel cell electrode catalyst.

PubMed

Yong, P; Paterson-Beedle, M; Mikheenko, I P; Macaskie, L E

2007-04-01

Biosynthesis of nano-scale platinum and palladium was achieved via enzymatically-mediated deposition of metal ions from solution. The bio-accumulated Pt(0) and Pd(0) crystals were dried, applied onto carbon paper and tested as anodes in a polymer electrolyte membrane (PEM) fuel cell for power production. Up to 100% and 81% of the maximum power generation was achieved by the bio-Pt and bio-Pd catalysts, respectively, compared to commercial fuel cell grade Pt catalyst. Hence, biomineralisation could pave the way for economical production of fuel cell catalysts since previous studies have shown that precious metals can be biorecovered from wastes into catalytically active bionanomaterials.

Atomic cobalt on nitrogen-doped graphene for hydrogen generation

PubMed Central

Fei, Huilong; Dong, Juncai; Arellano-Jiménez, M. Josefina; Ye, Gonglan; Dong Kim, Nam; Samuel, Errol L.G.; Peng, Zhiwei; Zhu, Zhuan; Qin, Fan; Bao, Jiming; Yacaman, Miguel Jose; Ajayan, Pulickel M.; Chen, Dongliang; Tour, James M.

2015-01-01

Reduction of water to hydrogen through electrocatalysis holds great promise for clean energy, but its large-scale application relies on the development of inexpensive and efficient catalysts to replace precious platinum catalysts. Here we report an electrocatalyst for hydrogen generation based on very small amounts of cobalt dispersed as individual atoms on nitrogen-doped graphene. This catalyst is robust and highly active in aqueous media with very low overpotentials (30 mV). A variety of analytical techniques and electrochemical measurements suggest that the catalytically active sites are associated with the metal centres coordinated to nitrogen. This unusual atomic constitution of supported metals is suggestive of a new approach to preparing extremely efficient single-atom catalysts. PMID:26487368

Non-metal doped TiO2 nanotube arrays for high efficiency photocatalytic decomposition of organic species in water

NASA Astrophysics Data System (ADS)

Szkoda, Mariusz; Siuzdak, Katarzyna; Lisowska-Oleksiak, Anna

2016-10-01

Titanium dioxide is a well-known photoactive semiconductor with a variety of possible applications. The procedure of pollutant degradation is mainly performed using TiO2 powder suspension. It can also be exploited an immobilized catalyst on a solid support. Morphology and chemical doping have a great influence on TiO2 activity under illumination. Here we compare photoactivity of titania nanotube arrays doped with non-metal atoms: nitrogen, iodine and boron applied for photodegradation of organic dye - methylene blue and terephtalic acid. The doped samples act as a much better photocatalyst in the degradation process of methylene blue and lead to the formation of much higher amount of hydroxyl radicals (•OH) than undoped TiO2 nanotube arrays. The use of a catalyst active under solar light illumination in the form of thin films on a stable substrate can be scaled up for an industrial application.

Novel bufferless photosynthetic microbial fuel cell (PMFCs) for enhanced electrochemical performance.

PubMed

Wang, Chin-Tsan; Huang, Yan-Sian; Sangeetha, Thangavel; Chen, Yen-Ming; Chong, Wen-Tong; Ong, Hwai-Chyuan; Zhao, Feng; Yan, Wei-Mon

2018-05-01

Photosynthetic microbial fuel cells (PMFCs) are novel bioelectrochemical transducers that employ microalgae to generate oxygen, organic metabolites and electrons. Conventional PMFCs employ non-eco-friendly membranes, catalysts and phosphate buffer solution. Eliminating the membrane, buffer and catalyst can make the MFC a practical possibility. Therefore, single chambered (SPMFC) were constructed and operated at different recirculation flow rates (0, 40 and 240 ml/min) under bufferless conditions. Furthermore, maximum power density of 4.06 mW/m 2 , current density of 46.34 mA/m 2 and open circuit potential of 0.43 V and low internal resistance of 611.8 Ω were obtained at 40 ml/min. Based on the results it was decided that SPMFC was better for operation at 40 ml/min. Therefore, these findings provided progressive insights for future pilot and industrial scale studies of PMFCs. Copyright © 2018 Elsevier Ltd. All rights reserved.

Heavily Graphitic-Nitrogen Self-doped High-porosity Carbon for the Electrocatalysis of Oxygen Reduction Reaction

NASA Astrophysics Data System (ADS)

Feng, Tong; Liao, Wenli; Li, Zhongbin; Sun, Lingtao; Shi, Dongping; Guo, Chaozhong; Huang, Yu; Wang, Yi; Cheng, Jing; Li, Yanrong; Diao, Qizhi

2017-11-01

Large-scale production of active and stable porous carbon catalysts for oxygen reduction reaction (ORR) from protein-rich biomass became a hot topic in fuel cell technology. Here, we report a facile strategy for synthesis of nitrogen-doped porous nanocarbons by means of a simple two-step pyrolysis process combined with the activation of zinc chloride and acid-treatment process, in which kidney bean via low-temperature carbonization was preferentially adopted as the only carbon-nitrogen sources. The results show that this carbon material exhibits excellent ORR electrocatalytic activity, and higher durability and methanol-tolerant property compared to the state-of-the-art Pt/C catalyst for the ORR, which can be mainly attributed to high graphitic-nitrogen content, high specific surface area, and porous characteristics. Our results can encourage the synthesis of high-performance carbon-based ORR electrocatalysts derived from widely-existed natural biomass.

A multiscale physical model for the transient analysis of PEM water electrolyzer anodes.

PubMed

Oliveira, Luiz Fernando L; Laref, Slimane; Mayousse, Eric; Jallut, Christian; Franco, Alejandro A

2012-08-07

Polymer electrolyte membrane water electrolyzers (PEMWEs) are electrochemical devices that can be used for the production of hydrogen. In a PEMWE the anode is the most complex electrode to study due to the high overpotential of the oxygen evolution reaction (OER), not widely understood. A physical bottom-up multi-scale transient model describing the operation of a PEMWE anode is proposed here. This model includes a detailed description of the elementary OER kinetics in the anode, a description of the non-equilibrium behavior of the nanoscale catalyst-electrolyte interface, and a microstructural-resolved description of the transport of charges and O(2) at the micro and mesoscales along the whole anode. The impact of different catalyst materials on the performance of the PEMWE anode, and a study of sensitivity to the operation conditions are evaluated from numerical simulations and the results are discussed in comparison with experimental data.

Multifunctional nanostructured electrocatalysts for energy conversion and storage: current status and perspectives.

PubMed

Ghosh, Srabanti; Basu, Rajendra N

2018-06-21

Electrocatalytic oxygen reduction reaction (ORR), oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) have attracted widespread attention because of their important role in the application of various energy storage and conversion devices, such as fuel cells, metal-air batteries and water splitting devices. However, the sluggish kinetics of the HER/OER/ORR and their dependency on expensive noble metal catalysts (e.g., Pt) obstruct their large-scale application. Hence, the development of efficient and robust bifunctional or trifunctional electrocatalysts in nanodimension for both oxygen reduction/evolution and hydrogen evolution reactions is highly desired and challenging for their commercialization in renewable energy technologies. This review describes some recent developments in the discovery of bifunctional or trifunctional nanostructured catalysts with improved performances for application in rechargeable metal-air batteries and fuel cells. The role of the electronic structure and surface redox chemistry of nanocatalysts in the improvement of their performance for the ORR/OER/HER under an alkaline medium is highlighted and the associated reaction mechanisms developed in the recent literature are also summarized.

First Attempt of Glycidol-to-Monoalkyl Glyceryl Ethers Conversion by Acid Heterogeneous Catalysis: Synthesis and Simplified Sustainability Assessment.

PubMed

Ricciardi, Maria; Passarini, Fabrizio; Capacchione, Carmine; Proto, Antonio; Barrault, Joel; Cucciniello, Raffaele; Cespi, Daniele

2018-04-14

The selective preparation of monoalkylglyceryl ethers (MAGEs) is a task for researchers owing to their broad range of applications. In this work, green feedstocks such as glycidol and alcohols were used to prepare MAGEs under mild reaction conditions (80 °C, 3 h, 0.5 mol % catalyst) in the presence of acid heterogeneous catalysts. Nafion shows the best performances in terms of conversion and selectivity to MAGES and also high stability. A comparison of the environmental performances with the most consolidated pathway from glycerol has shown that the usage of glycidol (recovered as a value-added product from Epicerol process) and Nafion leads to a lower impact on ecosystems. In addition, results achieved from a simplified socio-economic analysis show that the innovative route here proposed has potential (at the laboratory scale) of enhancing potential gains and of reducing the social implications resulting from externalities associated with environmental impacts (e.g., CO 2 equivalents). © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Multifunctional Co₀.₈₅Se/graphene hybrid nanosheets: controlled synthesis and enhanced performances for the oxygen reduction reaction and decomposition of hydrazine hydrate.

PubMed

Zhang, Lin-fei; Zhang, Chun-yang

2014-01-01

Ultrathin nanosheets possess novel electronic structures and physical properties as compared with their corresponding bulk samples. However, the controlled synthesis of ultrathin monolayer nanosheets still remains a great challenge due to the lack of an intrinsic driving force for anisotropic growth of two-dimensional (2D) structures. Here we demonstrate, for the first time to our knowledge, the in situ synthesis of large-scale ultrathin single-crystalline Co₀.₈₅Se nanosheets on graphene oxide (GO) sheets, with a thickness of 3 nm. Owing to the synergetic chemical coupling effects between GO and Co₀.₈₅Se, the Co₀.₈₅Se/graphene hybrid nanosheets exhibit the highest catalytic performance among the available cobalt chalcogenide-based catalysts for the oxygen reduction reaction (ORR). Moreover, Co₀.₈₅Se/graphene hybrid nanosheets can catalyze the decomposition of hydrazine hydrate rapidly, with 97% of hydrazine hydrate being degraded in 12 min and the degradation rate remaining constant over 10 consecutive cycles, thus having great potential as long-term catalysts in wastewater treatment.

Catalyst Development for Hydrogen Peroxide Rocket Engines

NASA Technical Reports Server (NTRS)

Morlan, P. W.; Wu, P.-K.; Ruttle, D. W.; Fuller, R. P.; Nejad, A. S.; Anderson, W. E.

1999-01-01

The development of various catalysts of hydrogen peroxide was conducted for the applications of liquid rocket engines. The catalyst development includes silver screen technology, solid catalyst technology, and homogeneous catalyst technology. The silver screen technology development was performed with 85% (by weight) hydrogen peroxide. The results of this investigation were used as the basis for the catalyst design of a pressure-fed liquid-fueled upper stage engine. Both silver-plated nickel 200 screens and pure silver screens were used as the active metal catalyst during the investigation, The data indicate that a high decomposition efficiency (greater than 90%) of 85% hydrogen peroxide can be achieved at a bed loading of 0.5 lbm/sq in/sec with both pure silver and silver plated screens. Samarium oxide coating, however, was found to retard the decomposition process and the catalyst bed was flooded at lower bed loading. A throughput of 200 lbm of hydrogen peroxide (1000 second run time) was tested to evaluate the catalyst aging issue and performance degradation was observed starting at approximately 400 seconds. Catalyst beds of 3.5 inch in diameter was fabricated using the same configuration for a 1,000-lbf rocket engine. High decomposition efficiency was obtained with a low pressure drop across the bed. Solid catalyst using precious metal was also developed for the decomposition of hydrogen peroxide from 85% to 98% by weight. Preliminary results show that the catalyst has a strong reactivity even after 15 minutes of peroxide decomposition. The development effort also includes the homogeneous catalyst technology. Various non-toxic catalysts were evaluated with 98% peroxide and hydrocarbon fuels. The results of open cup drop tests indicate an ignition delay around 11 ms.

Design and assembly of a catalyst bed gas generator for the catalytic decomposition of high concentration hydrogen peroxide propellants and the catalytic combustion of hydrocarbon/air mixtures

NASA Technical Reports Server (NTRS)

Lohner, Kevin A. (Inventor); Mays, Jeffrey A. (Inventor); Sevener, Kathleen M. (Inventor)

2004-01-01

A method for designing and assembling a high performance catalyst bed gas generator for use in decomposing propellants, particularly hydrogen peroxide propellants, for use in target, space, and on-orbit propulsion systems and low-emission terrestrial power and gas generation. The gas generator utilizes a sectioned catalyst bed system, and incorporates a robust, high temperature mixed metal oxide catalyst. The gas generator requires no special preheat apparatus or special sequencing to meet start-up requirements, enabling a fast overall response time. The high performance catalyst bed gas generator system has consistently demonstrated high decomposition efficiency, extremely low decomposition roughness, and long operating life on multiple test articles.

Ce-Sn binary oxide catalyst for the selective catalytic reduction of NOx by NH3

NASA Astrophysics Data System (ADS)

Liu, Zhiming; Feng, Xu; Zhou, Zizheng; Feng, Yongjun; Li, Junhua

2018-01-01

Ce-Sn binary oxide catalysts prepared by the hydrothermal method have been investigated for the selective catalytic reduction (SCR) of NOx with NH3. Compared with pure CeO2 and SnO2, Ce-Sn binary oxide catalyst showed significantly higher NH3-SCR activity. Moreover, Ce-Sn catalyst showed high resistance against H2O and SO2. The high catalytic performance of Ce-Sn binary oxide is attributed to the synergetic effect between Ce and Sn species, which not only enhances the redox property of the catalyst but also increases the Lewis acidity, thus promoting the adsorption and activation of NH3 species, which contributes to improving the NH3-SCR performance.

Studies of Heterogenous Palladium and Related Catalysts for Aerobic Oxidation of Primary Alcohols

NASA Astrophysics Data System (ADS)

Ahmed, Maaz S.

Development of aerobic oxidation methods is of critical importance for the advancement of green chemistry, where the only byproduct produced is water. Recent work by our lab has produced an efficient Pd based heterogenous catalyst capable of preforming the aerobic oxidation of a wide spectrum of alcohols to either carboxylic acid or methyl ester. The well-defined catalyst PdBi 0.35Te0.23/C (PBT/C) catalyst has been shown to can perform the aerobic oxidation of alcohols to carboxylic acids in basic conditions. Additionally, we explored this catalyst for a wide range of alcohols and probed the nature of the selectivity of PBT/C for methyl esterification over other side products. Finally, means by which the catalyst operates with respect to oxidation states of the three components, Pd, Bi, and Te, was probed. Carboxylic acids are an important functional group due to their prevalence in various pharmaceutically active agents, agrochemicals, and commodity scale chemicals. The well-defined catalyst PBT/C catalyst was discovered to be effective for the oxidation of a wide spectrum of alcohols to carboxylic acid. The demonstrated substrate scope and functional group tolerance are the widest reported for an aerobic heterogeneous catalyst. Additionally, the catalyst has been implemented in a packed bed reactor with quantitative yield of benzoic acid maintained throughout a two-day run. Biomass derived 5-(hydroxymethyl)furfural (HMF) is also oxidized to 2,5-furandicarboxylic acid (FDCA) in high yield. Exploration of PBT/C for the oxidative methyl esterification was found to exhibit exquisite selectivity for the initial oxidation of primary alcohol instead of methanol, which is the bulk solvent. We explored this selectivity and conclude that it results from various substrate-surface interactions, which are not attainable by methanol. The primary alcohol can outcompete the methanol for binding on the catalyst surface through various interactions between the side chain of the alcohol solvent and the surface of the catalyst: (listed in order of strength) lone pair-surface (heterocyclic primary alcohols) > pi-surface (aryl primary alcohols) > van der Waals-surface (alkyl primary alcohols). These interactions were previously underappreciated in condensed phase heterogeneously catalyzed aerobic oxidations. Bi and Te serve as synergistic promoters that enhance both the rate and yield of the reactions relative to reactions employing Pd alone or Pd in combination with Bi or with Te as the sole promoter. We report X-ray absorption spectroscopic studies of the heterogenous catalyst. These methods show that the promoters undergo oxidation in preference to Pd, maintaining the Pd surface in the active metallic state and preventing inhibition by surface Pd-oxide formation. The data also suggest formation of a Pd-Te alloy phase that modifies the electronic properties of the Pd catalyst. Collectively, these results provide valuable insights into the synergistic benefits of multiple promoters in heterogeneous catalytic oxidation reactions.

Effect of preparation method and CuO promotion in the conversion of ethanol into 1,3-butadiene over SiO₂-MgO catalysts.

PubMed

Angelici, Carlo; Velthoen, Marjolein E Z; Weckhuysen, Bert M; Bruijnincx, Pieter C A

2014-09-01

Silica-magnesia (Si/Mg=1:1) catalysts were studied in the one-pot conversion of ethanol to butadiene. The catalyst synthesis method was found to greatly influence morphology and performance, with materials prepared through wet-kneading performing best both in terms of ethanol conversion and butadiene yield. Detailed characterization of the catalysts synthesized through co-precipitation or wet-kneading allowed correlation of activity and selectivity with morphology, textural properties, crystallinity, and acidity/basicity. The higher yields achieved with the wet-kneaded catalysts were attributed to a morphology consisting of SiO2 spheres embedded in a thin layer of MgO. The particle size of the SiO2 catalysts also influenced performance, with catalysts with smaller SiO2 spheres showing higher activity. Temperature-programmed desorption (TPD) measurements showed that best butadiene yields were obtained with SiO2-MgO catalysts characterized by an intermediate amount of acidic and basic sites. A Hammett indicator study showed the catalysts' pK(a) value to be inversely correlated with the amount of dehydration by-products formed. Butadiene yields could be further improved by the addition of 1 wt% of CuO as promoter to give butadiene yields and selectivities as high as 40% and 53%, respectively. The copper promoter boosts the production of the acetaldehyde intermediate changing the rate-determining step of the process. TEM-energy-dispersive X-ray (EDX) analyses showed CuO to be present on both the SiO2 and MgO components. UV/Vis spectra of promoted catalysts in turn pointed at the presence of cluster-like CuO species, which are proposed to be responsible for the increased butadiene production. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Highly Durable Supportless Pt Hollow Spheres Designed for Enhanced Oxygen Transport in Cathode Catalyst Layers of Proton Exchange Membrane Fuel Cells.

PubMed

Dogan, Didem C; Cho, Seonghun; Hwang, Sun-Mi; Kim, Young-Min; Guim, Hwanuk; Yang, Tae-Hyun; Park, Seok-Hee; Park, Gu-Gon; Yim, Sung-Dae

2016-10-10

Supportless Pt catalysts have several advantages over conventional carbon-supported Pt catalysts in that they are not susceptible to carbon corrosion. However, the need for high Pt loadings in membrane electrode assemblies (MEAs) to achieve state-of-the-art fuel cell performance has limited their application in proton exchange membrane fuel cells. Herein, we report a new approach to the design of a supportless Pt catalyst in terms of catalyst layer architecture, which is crucial for fuel cell performance as it affects water management and oxygen transport in the catalyst layers. Large Pt hollow spheres (PtHSs) 100 nm in size were designed and prepared using a carbon template method. Despite their large size, the unique structure of the PtHSs, which are composed of a thin-layered shell of Pt nanoparticles (ca. 7 nm thick), exhibited a high surface area comparable to that of commercial Pt black (PtB). The PtHS structure also exhibited twice the durability of PtB after 2000 potential cycles (0-1.3 V, 50 mV/s). A MEA fabricated with PtHSs showed significant improvement in fuel cell performance compared to PtB-based MEAs at high current densities (>800 mA/cm 2 ). This was mainly due to the 2.7 times lower mass transport resistance in the PtHS-based catalyst layers compared to that in PtB, owing to the formation of macropores between the PtHSs and high porosity (90%) in the PtHS catalyst layers. The present study demonstrates a successful example of catalyst design in terms of catalyst layer architecture, which may be applied to a real fuel cell system.

Catalytic fast pyrolysis of white oak wood in-situ using a bubbling fluidized bed reactor

USDA-ARS?s Scientific Manuscript database

Catalytic fast pyrolysis was performed on white oak wood using two zeolite-type catalysts as bed material in a bubbling fluidized bed reactor. The two catalysts chosen, based on a previous screening study, were Ca2+ exchanged Y54 (Ca-Y54) and a proprietary ß-zeolite type catalyst (catalyst M) both ...

Nitrogen-doped Carbon Derived from ZIF-8 as a High-performance Metal-free Catalyst for Acetylene Hydrochlorination

NASA Astrophysics Data System (ADS)

Chao, Songlin; Zou, Fang; Wan, Fanfan; Dong, Xiaobin; Wang, Yanlin; Wang, Yuxuan; Guan, Qingxin; Wang, Guichang; Li, Wei

2017-01-01

Acetylene hydrochlorination is a major industrial technology for manufacturing vinyl chloride monomer in regions with abundant coal resources; however, it is plagued by the use of mercury(II) chloride catalyst. The development of a nonmercury catalyst has been extensively explored. Herein, we report a N-doped carbon catalyst derived from ZIF-8 with both high activity and quite good stability. The acetylene conversion reached 92% and decreased slightly during a 200 h test at 220 °C and atmospheric pressure. Experimental studies and theoretical calculations indicate that C atoms adjacent to the pyridinic N are the active sites, and coke deposition covering pyridinic N is the main reason for catalyst deactivation. The performance of those N-doped carbons makes it possible for practical applications with further effort. Furthermore, the result also provides guidance for designing metal-free catalysts for similar reactions.

New insides in the characterization of HDS industrial catalysts by HAADF-STEM

NASA Astrophysics Data System (ADS)

Del Angel, Paz; Ponce, Arturo; Arellano, Josefina; Yacaman, Miguel J.; Hernandez-Pichardo, Martha; Montoya, J. Ascencion; Escobar, Jose

2015-03-01

Hydrodesulfurization (HDS) catalysts are of great importance in the petroleum industry. Transition metal sulphides catalysts of Ni(Co)Mo(W)/Al2O3 are widely used for hydrotreating reactions, like hydrodenitrogenation and HDS. One of the main issue in these catalysts is to understand the mechanism of the reaction, where MoS2 plays the most important role in the catalytic activity. We studied an industrial NiMo/Alumina sulfide catalyst highly active by using aberration-corrected HAADF-STEM techniques. The used catalysts was a state-of- the art commercial nickel-molybdenum alumina-supported formulation, including organic agent modifier. This type of material belongs to a novel family of catalysts specially designed for ultra-low sulfur production from straight-run gas oil (SRGO), cycle oil, coker gas oil, or their combinations at operating conditions of commercial interest in hydrotreating units at industrial scale. Aberration corrected HAADF-STEM allowed to observe the nanostructure and location of MoS2 and his interaction with the alumina. The results indicate that the MoS2 is highly dispersed on the alumina, however the location of Ni is one of the task of this kind of catalyst.

Enhanced low-temperature NH3-SCR performance of MnOx/CeO2 catalysts by optimal solvent effect

NASA Astrophysics Data System (ADS)

Yao, Xiaojiang; Kong, Tingting; Chen, Li; Ding, Shimin; Yang, Fumo; Dong, Lin

2017-10-01

A series of MnOx/CeO2 catalysts were prepared by modulating the solvents (deionized water (DW), anhydrous ethanol (AE), acetic acid (AA), and oxalic acid (OA) solution) with the purpose of improving the low-temperature NH3-SCR performance, broadening the operating temperature window, and enhancing the H2O + SO2 resistance. The synthesized catalysts were characterized by means of N2-physisorption, XRD, EDS mapping, Raman, XPS, H2-TPR, NH3-TPD, and in situ DRIFTS technologies. Furthermore, the catalytic performance and H2O + SO2 resistance were evaluated by NH3-SCR model reaction. The obtained results indicate that MnOx/CeO2 catalyst prepared with oxalic acid solution as a solvent exhibits the best catalytic performance among these catalysts, which shows above 80% NO conversion during a wide operating temperature range of 100-250 °C and good H2O + SO2 resistance for low-temperature NH3-SCR reaction. This is related to that oxalic acid solution can promote the dispersion of MnOx and enhance the electron interaction between MnOx and CeO2, which are beneficial to improving the physicochemical property of MnOx/CeO2 catalyst, and further lead to the enhancement of catalytic performance and good H2O + SO2 resistance.

Reduction Reaction Activity on Pt-Monolayer-Shell PdIr/Ni-core Catalysts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Song, Liang; Vukmirovic, Miomir B.; Adzic, Radoslav R.

Platinum monolayer oxygen reduction reaction catalysts present promising way of reducing the Pt content without scarifying its fuel cell performance. We present a facile way of preparing Pt monolayer shell PdIr-based core catalysts, which showed much higher activity for oxygen reduction reaction than that of TKK 46.6% Pt/C catalyst. Among tested samples, PtMLPd2Ir/Ni/C performs the best with Pt and Platinum Group Metal mass activity around 9 and 0.25 times higher of that of TKK 46.6% Pt/C. In addition, accelerated aging test indicates its excellent durability.

Reduction Reaction Activity on Pt-Monolayer-Shell PdIr/Ni-core Catalysts

DOE PAGES

Song, Liang; Vukmirovic, Miomir B.; Adzic, Radoslav R.

2018-05-14

Platinum monolayer oxygen reduction reaction catalysts present promising way of reducing the Pt content without scarifying its fuel cell performance. We present a facile way of preparing Pt monolayer shell PdIr-based core catalysts, which showed much higher activity for oxygen reduction reaction than that of TKK 46.6% Pt/C catalyst. Among tested samples, PtMLPd2Ir/Ni/C performs the best with Pt and Platinum Group Metal mass activity around 9 and 0.25 times higher of that of TKK 46.6% Pt/C. In addition, accelerated aging test indicates its excellent durability.

Rapid Catalyst Screening by a Continuous-Flow Microreactor Interfaced with Ultra High Pressure Liquid Chromatography

PubMed Central

Fang, Hui; Xiao, Qing; Wu, Fanghui; Floreancig, Paul E.; Weber, Stephen G.

2010-01-01

A high-throughput screening system for homogeneous catalyst discovery has been developed by integrating a continuous-flow capillary-based microreactor with ultra-high pressure liquid chromatography (UHPLC) for fast online analysis. Reactions are conducted in distinct and stable zones in a flow stream that allows for time and temperature regulation. UHPLC detection at high temperature allows high throughput online determination of substrate, product, and byproduct concentrations. We evaluated the efficacies of a series of soluble acid catalysts for an intramolecular Friedel-Crafts addition into an acyliminium ion intermediate within one day and with minimal material investment. The effects of catalyst loading, reaction time, and reaction temperature were also screened. This system exhibited high reproducibility for high-throughput catalyst screening and allowed several acid catalysts for the reaction to be identified. Major side products from the reactions were determined through off-line mass spectrometric detection. Er(OTf)3, the catalyst that showed optimal efficiency in the screening, was shown to be effective at promoting the cyclization reaction on a preparative scale. PMID:20666502

Pt-based Bi-metallic Monolith Catalysts for Partial Upgrading of Microalgae Oil

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lawal, Adeniyi; Manganaro, James; Goodall, Brian

Valicor’s proprietary wet extraction process in conjunction with thermochemical pre-treatment was performed on algal biomass from two different algae strains, Nannochloropsis Salina (N.S.) and Chlorella to produce algae oils. Polar lipids such as phospholipids were hydrolyzed, and metals and metalloids, known catalyst poisons, were separated into the aqueous phase, creating an attractive “pre-refined” oil for hydrodeoxygenation (HDO) upgrading by Stevens. Oil content and oil extraction efficiency of approximately 30 and 90% respectively were achieved. At Stevens, we formulated a Pt-based bi-metallic catalyst which was demonstrated to be effective in the hydro-treating of the algae oils to produce ‘green’ diesel. Themore » bi-metallic catalyst was wash-coated on a monolith, and in conjunction with a high throughput high pressure (pilot plant) reactor system, was used in hydrotreating algae oils from N.S. and Chlorella. Mixtures of these algae oils and refinery light atmospheric gas oil (LAGO) supplied by our petroleum refiner partner, Marathon Petroleum Corporation, were co-processed in the pilot plant reactor system using the Pt-based bi-metallic monolith catalyst. A 26 wt% N.S. algae oil/74 wt % LAGO mixture hydrotreated in the reactor system was subjected to the ASTM D975 Diesel Fuel Specification Test and it met all the important requirements, including a cetane index of 50.5. An elemental oxygen analysis performed by an independent and reputable lab reported an oxygen content of trace to none found. The successful co-processing of a mixture of algae oil and LAGO will enable integration of algae oil as a refinery feedstock which is one of the goals of DOE-BETO. We have presented experimental data that show that our precious metal-based catalysts consume less hydrogen than the conventional hydrotreating catalyst NiMo Precious metal catalysts favor the hydrodecarbonylation/hydrodecarboxylation route of HDO over the dehydration route preferred by base metal catalysts, and consumes less hydrogen, if methanation can be mitigated. Our methanation data on Pt and Rh indicate effective suppression of methanation. Our data also show that our catalysts are less susceptible to coking; and unlike NiMo and CoMo, precious metal catalysts are not deactivated by water, a by-product of HDO of algae oil. Finally, our catalysts do not need to be sulfided to be active. A rigorous techno-economic analysis of our process for commercial scale production of 10,000 barrels per day of hydrotreated algae oil, with nutraceuticals co-product claiming only 0.05% of the raw algae oil, indicates an estimated plant gate price of ~$10/gal. Sensitivity analysis shows that critical parameters affecting sale price include (1) algae doubling time (2) biomass oil content (3) CAPEX, and (4) moisture content of post extracted algae residue. Modest improvements in these areas will result in enhanced and competitive economics. Based on a life cycle assessment for greenhouse gas emission, we found that if algae oil replaced 10% of the US consumption, this would result in a CO2e reduction of 210,000 tons per day. Improving the drying process for animal feed by 50% would result in further significant reduction in CO2e.« less

Influence of Alumina Binder Content on Catalytic Performance of Ni/HZSM-5 for Hydrodeoxygenation of Cyclohexanone

PubMed Central

Kong, Xiangjin; Liu, Junhai

2014-01-01

The influence of the amount of alumina binders on the catalytic performance of Ni/HZSM-5 for hydrodeoxygenation of cyclohexanone was investigated in a fixed-bed reactor. N2 sorption, X-ray diffraction, H2-chemisorption and temperature-programmed desorption of ammonia were used to characterize the catalysts. It can be observed that the Ni/HZSM-5 catalyst bound with 30 wt.% alumina binder exhibited the best catalytic performance. The high catalytic performance may be due to relatively good Ni metal dispersion, moderate mesoporosity, and proper acidity of the catalyst. PMID:25009974

Influence of alumina binder content on catalytic performance of Ni/HZSM-5 for hydrodeoxygenation of cyclohexanone.

PubMed

Kong, Xiangjin; Liu, Junhai

2014-01-01

The influence of the amount of alumina binders on the catalytic performance of Ni/HZSM-5 for hydrodeoxygenation of cyclohexanone was investigated in a fixed-bed reactor. N2 sorption, X-ray diffraction, H2-chemisorption and temperature-programmed desorption of ammonia were used to characterize the catalysts. It can be observed that the Ni/HZSM-5 catalyst bound with 30 wt.% alumina binder exhibited the best catalytic performance. The high catalytic performance may be due to relatively good Ni metal dispersion, moderate mesoporosity, and proper acidity of the catalyst.

Sulfur poisoning of CeO[subscript 2]-Al[subscript 2]O[subscript 3]-supported mono- and bi-metallic Ni and Rh catalysts in steam reforming of liquid hydrocarbons at low and high temperatures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xie, Chao; Chen, Yongsheng; Li, Yan

2010-12-01

In order to develop a better understanding on sulfur poisoning of reforming catalysts in fuel processing for hydrogen production, steam reforming of liquid hydrocarbons was performed over CeO{sub 2}-Al{sub 2}O{sub 3} supported monometallic Ni and Rh and bimetallic Rh-Ni catalysts at 550 and 800 C. XANES was used to identify the sulfur species in the used catalysts and to study their impacts on the metal surface properties probed by XPS. It was found that both monometallic catalysts rapidly deactivated at 550 C, and showed poor sulfur tolerance. Although ineffective for the Ni catalyst, increasing the temperature to 800 C dramaticallymore » improved the sulfur tolerance of the Rh catalyst. XANES revealed that metal sulfide and organic sulfide are the dominant sulfur species on the used Ni catalyst, while sulfonate and sulfate predominate on the used Rh catalyst. The presence of sulfur induced severe carbon deposition on the Ni catalyst at 800 C. The superior sulfur tolerance of the Rh catalyst at 800 C may be associated with its capability in sulfur oxidation. It is likely that the formation of the oxygen-shielded sulfur structure of sulfonate and sulfate can suppress the poisoning impact of sulfur on Rh by inhibiting direct rhodium-sulfur interaction. Moreover, XPS indicated that the metal surface properties of the Rh catalysts after the reaction without and with sulfur at 800 C are similar, suggesting that sulfur poisoning on Rh was mitigated under the high-temperature condition. Although the Rh-Ni catalyst exhibited better sulfur tolerance than the monometallic catalysts at 550 C, its catalytic performance was inferior compared with the Rh catalyst in the sulfur-containing reaction at 800 C probably due to the severe carbon deposition on the bimetallic catalyst.« less

Heterogeneous Electrocatalyst of Palladium-Cobalt-Phosphorus on Carbon Support for Oxygen Reduction Reaction in High Temperature Proton Exchange Membrane Fuel Cells.

PubMed

You, Dae Jong; Pak, Chanho; Jin, Seon-Ah; Lee, Kang Hee; Kwon, Kyungjung; Choi, Kyoung Hwan; Heo, Pil Won; Jang, Hongchul; Kim, Jun Young; Kim, Ji Man

2016-05-01

Palladium-cobalt-phosphorus (PdCoP) catalysts supported on carbon (Ketjen Black) were investigated as a cathode catalyst for oxygen reduction reaction (ORR) in high temperature proton exchange membrane fuel cells (HT-PEMFCs). The PdCoP catalyst was synthesized via a modified polyol process in teflon-sealed reactor by microwave-heating. From X-ray diffraction and transmission electron microscopic analysis, the PdCoP catalyst exhibits a face-centered cubic structure, similar to palladium (Pd), which is attributed to form a good solid solution of Co atoms and P atoms in the Pd lattice. The PdCoP nanoparticles with average diameter of 2.3 nm were uniformly distributed on the carbon support. The electrochemical surface area (ECSA) and ORR activity of PdP, PdCo and PdCoP catalysts were measured using a rotating disk electrode technique with cyclic voltammetry and the linear sweep method. The PdCoP catalysts showed the highest performances for ECSA and ORR, which might be attributed both to formation of small nanoparticle by phosphorus atom and to change in lattice constant of Pd by cobalt atom. Furthermore, The HT-PEMFCs single cell performance employing PdCoP catalyst exhibited an enhanced cell performance compared to a single cell using the PdP and PdCo catalysts. This result indicates the importance of electric and geometric control of Pd alloy nanoparticles that can improve the catalytic activity. This synergistic combination of Co and P with Pd could provide the direction of development of non-Pt catalyst for fuel cell system.

Catalyst-free dehydrative α-alkylation of ketones with alcohols: green and selective autocatalyzed synthesis of alcohols and ketones.

PubMed

Xu, Qing; Chen, Jianhui; Tian, Haiwen; Yuan, Xueqin; Li, Shuangyan; Zhou, Chongkuan; Liu, Jianping

2014-01-03

Direct dehydrative α-alkylation reactions of ketones with alcohols are now realized under simple, practical, and green conditions without using external catalysts. These catalyst-free autocatalyzed alkylation methods can efficiently afford useful alkylated ketone or alcohol products in a one-pot manner and on a large scale by CC bond formation of the in situ generated intermediates with subsequent controllable and selective Meerwein-Pondorf-Verley-Oppenauer-type redox processes. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Integrated process and dual-function catalyst for olefin epoxidation

DOEpatents

Zhou, Bing; Rueter, Michael

2003-01-01

The invention discloses a dual-functional catalyst composition and an integrated process for production of olefin epoxides including propylene oxide by catalytic reaction of hydrogen peroxide from hydrogen and oxygen with olefin feeds such as propylene. The epoxides and hydrogen peroxide are preferably produced simultaneously in situ. The dual-functional catalyst comprises noble metal crystallites with dimensions on the nanometer scale (on the order of <1 nm to 10 nm), specially dispersed on titanium silicalite substrate particles. The dual functional catalyst catalyzes both the direct reaction of hydrogen and oxygen to generate hydrogen peroxide intermediate on the noble metal catalyst surface and the reaction of the hydrogen peroxide intermediate with the propylene feed to generate propylene oxide product. Combining both these functions in a single catalyst provides a very efficient integrated process operable below the flammability limits of hydrogen and highly selective for the production of hydrogen peroxide to produce olefin oxides such as propylene oxide without formation of undesired co-products.

Impact of initial catalyst form on the 3D structure and performance of ball-milled Ni-catalyzed MgH 2 for hydrogen storage

DOE Office of Scientific and Technical Information (OSTI.GOV)

House, Stephen D.; Vajo, John J.; Ren, Chai

Although it has been shown that the hydrogen storage kinetics of metal hydrides can be significantly improved by the addition of transition metal-based catalysts, relatively little attention has been paid to the impact that the form in which these catalysts are introduced during synthesis has on the resulting structure and how this alters performance. Two mixtures of MgH 2 doped with Ni were prepared via high-energy ball-milling under identical conditions, one using a pure Ni nanopowder catalyst and the other using anhydrous NiCl 2. The resulting Ni catalyst particles of the NiCl 2-doped material were 10-100 times smaller, as wellmore » as more uniform in size and shape. Electron tomography revealed that the additive form also altered its incorporation and 3D spatial distribution, with Ni particles limited to the outer surface in the NiCl 2-doped case. The significantly lower desorption performance measured in the NiCl 2-doped material is attributed to regions of MgCl 2 acting as barriers between the MgH 2 and Ni, hindering the ability of the latter to effectively catalyze the reactions. Finally, this work demonstrates the hazards in assuming different catalyst forms produce similar final structures and highlights the potential of catalyst form as a synthesis tool for optimizing the material structure and performance.« less

Catalytic dehydrogenation of isobutane in the presence of hydrogen over Cs-modified Ni2P supported on active carbon

NASA Astrophysics Data System (ADS)

Xu, Yanli; Sang, Huanxin; Wang, Kang; Wang, Xitao

2014-10-01

In this article, an environmentally friendly non-noble-metal class of Cs-Ni2P/active carbon (AC) catalyst was prepared and demonstrated to exhibit enhanced catalytic performance in isobutane dehydrogenation. The results of activity tests reveal that Ni/AC catalyst was highly active for isobutane cracking, which led to the formation of abundant methane and coke. After the introduction of phosphorus through impregnation with ammonium di-hydrogen phosphate and H2-temperature programmed reduction, undesired cracking reactions were effectively inhibited, and the selectivity to isobutene and stability of catalyst increased remarkably. The characterization results indicate that, after the addition of phosphorous, the improvement of dehydrogenation selectivity is ascribed to the partial positive charges carried on Ni surface in Ni2P particles, which decreases the strength of Nisbnd C bond between Ni and carbonium-ion intermediates and the possibility of excessive dehydrogenation. In addition, Cs-modified Ni2P/AC catalysts display much higher catalytic performance as compared to Ni2P/AC catalyst. Cs-Ni2P-6.5 catalyst has the highest catalytic performance, and the selectivity to isobutene higher than 93% can be obtained even after 4 h reaction. The enhancement in catalytic performance of the Cs-modified catalysts is mainly attributed to the function of Cs to improve the dispersion of Ni2P particles, transfer electron from Cs to Ni, and decrease acid site number and strength.

Impact of initial catalyst form on the 3D structure and performance of ball-milled Ni-catalyzed MgH 2 for hydrogen storage

DOE PAGES

House, Stephen D.; Vajo, John J.; Ren, Chai; ...

2017-02-24

Although it has been shown that the hydrogen storage kinetics of metal hydrides can be significantly improved by the addition of transition metal-based catalysts, relatively little attention has been paid to the impact that the form in which these catalysts are introduced during synthesis has on the resulting structure and how this alters performance. Two mixtures of MgH 2 doped with Ni were prepared via high-energy ball-milling under identical conditions, one using a pure Ni nanopowder catalyst and the other using anhydrous NiCl 2. The resulting Ni catalyst particles of the NiCl 2-doped material were 10-100 times smaller, as wellmore » as more uniform in size and shape. Electron tomography revealed that the additive form also altered its incorporation and 3D spatial distribution, with Ni particles limited to the outer surface in the NiCl 2-doped case. The significantly lower desorption performance measured in the NiCl 2-doped material is attributed to regions of MgCl 2 acting as barriers between the MgH 2 and Ni, hindering the ability of the latter to effectively catalyze the reactions. Finally, this work demonstrates the hazards in assuming different catalyst forms produce similar final structures and highlights the potential of catalyst form as a synthesis tool for optimizing the material structure and performance.« less

Study on the mechanism of a manganese-based catalyst for catalytic NOX flue gas denitration

NASA Astrophysics Data System (ADS)

Zhang, Lei; Wen, Xin; Lei, Zhang; Gao, Long; Sha, Xiangling; Ma, Zhenhua; He, Huibin; Wang, Yusu; Jia, Yang; Li, Yonghui

2018-04-01

Manganese-based bimetallic catalysts were prepared with self-made pyrolysis coke as carrier and its denitration performance of low-temperature SCR (selective catalyst reduction) was studied. The effects of different metal species, calcination temperature, calcination time and the metal load quantity on the denitration performance of the catalyst were studied by orthogonal test. The denitration mechanism of the catalyst was analyzed by XRD (X-ray diffraction), SEM (scanning electron microscope), BET test and transient test. The experiments show that: * The denitration efficiency of Mn-based bimetallic catalysts mainly relates to the metal type, the metal load quantity and the catalyst adjuvant type. * The optimal catalyst preparation conditions are as follows: the load quantity of monometallic MnO2 is 10%, calcined at 300°C for 4h, and then loaded with 8% CeO2, calcined at 350°Cfor 3h. * The denitration mechanism of manganese-based bimetallic oxide catalysts is stated as: NH3 is firstly adsorbed by B acid center Mn-OH which nears Mn4+==O to form NH4+, NH4+ was then attacked by the gas phase NO to form N2, H2O and Mn3+-OH. Finally, Mn3+-OH was oxidized by O2 to regenerate Mn4+.

Novel synthesis of highly durable and active Pt catalyst encapsulated in nitrogen containing carbon for polymer electrolyte membrane fuel cell

NASA Astrophysics Data System (ADS)

Lee, Hyunjoon; Sung, Yung-Eun; Choi, Insoo; Lim, Taeho; Kwon, Oh Joong

2017-09-01

Novel synthesis of a Pt catalyst encapsulated in a N-containing carbon layer for use in a polymer electrolyte membrane fuel cell is described in this study. A Pt-aniline complex, formed by mixing Pt precursor and aniline monomer, was used as the source of Pt, C, and N. Heat treatment of the Pt-aniline complex with carbon black yielded 5 nm Pt nanoparticles encapsulated by a N-containing carbon layer originating from aniline carbonization. The synthesized Pt catalyst exhibited higher mass specific activity to oxygen reduction reaction than that shown by conventional Pt/C catalyst because pyridinic N with graphitic carbon in the carbon layer provided active sites for oxygen reduction reaction in addition to those provided by Pt. In single cell testing, initial performance of the synthesized catalyst was limited because the thick catalyst layer increased resistance related to mass transfer. However, it was observed that the carbon layer successfully prevented Pt nanoparticles from growing via agglomeration and Ostwald ripening under fuel cell operation, thereby improving durability. Furthermore, a mass specific performance of the synthesized catalyst higher than that of a conventional Pt/C catalyst was achieved by modifying the synthesized catalyst's layer thickness.

Understanding the Oxygen Evolution Reaction Mechanism on CoO x using Operando Ambient-Pressure X-ray Photoelectron Spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Favaro, Marco; Yang, Jinhui; Nappini, Silvia

Photoelectrochemical water splitting is a promising approach for renewable production of hydrogen from solar energy and requires interfacing advanced water-splitting catalysts with semiconductors. Understanding the mechanism of function of such electrocatalysts at the atomic scale and under realistic working conditions is a challenging, yet important, task for advancing efficient and stable function. This is particularly true for the case of oxygen evolution catalysts and, here, we study a highly active Co 3O 4/Co(OH) 2 biphasic electrocatalyst on Si by means of operando ambient-pressure X-ray photoelectron spectroscopy performed at the solid/liquid electrified interface. Spectral simulation and multiplet fitting reveal that themore » catalyst undergoes chemical-structural transformations as a function of the applied anodic potential, with complete conversion of the Co(OH) 2 and partial conversion of the spinel Co 3O 4 phases to CoO(OH) under precatalytic electrochemical conditions. Furthermore, we observe new spectral features in both Co 2p and O 1s core-level regions to emerge under oxygen evolution reaction conditions on CoO(OH). The operando photoelectron spectra support assignment of these newly observed features to highly active Co 4+ centers under catalytic conditions. Comparison of these results to those from a pure phase spinel Co 3O 4 catalyst supports this interpretation and reveals that the presence of Co(OH) 2 enhances catalytic activity by promoting transformations to CoO(OH). The direct investigation of electrified interfaces presented in this work can be extended to different materials under realistic catalytic conditions, thereby providing a powerful tool for mechanism discovery and an enabling capability for catalyst design.« less

Understanding the Oxygen Evolution Reaction Mechanism on CoO x using Operando Ambient-Pressure X-ray Photoelectron Spectroscopy

DOE PAGES

Favaro, Marco; Yang, Jinhui; Nappini, Silvia; ...

2017-06-09

Photoelectrochemical water splitting is a promising approach for renewable production of hydrogen from solar energy and requires interfacing advanced water-splitting catalysts with semiconductors. Understanding the mechanism of function of such electrocatalysts at the atomic scale and under realistic working conditions is a challenging, yet important, task for advancing efficient and stable function. This is particularly true for the case of oxygen evolution catalysts and, here, we study a highly active Co 3O 4/Co(OH) 2 biphasic electrocatalyst on Si by means of operando ambient-pressure X-ray photoelectron spectroscopy performed at the solid/liquid electrified interface. Spectral simulation and multiplet fitting reveal that themore » catalyst undergoes chemical-structural transformations as a function of the applied anodic potential, with complete conversion of the Co(OH) 2 and partial conversion of the spinel Co 3O 4 phases to CoO(OH) under precatalytic electrochemical conditions. Furthermore, we observe new spectral features in both Co 2p and O 1s core-level regions to emerge under oxygen evolution reaction conditions on CoO(OH). The operando photoelectron spectra support assignment of these newly observed features to highly active Co 4+ centers under catalytic conditions. Comparison of these results to those from a pure phase spinel Co 3O 4 catalyst supports this interpretation and reveals that the presence of Co(OH) 2 enhances catalytic activity by promoting transformations to CoO(OH). The direct investigation of electrified interfaces presented in this work can be extended to different materials under realistic catalytic conditions, thereby providing a powerful tool for mechanism discovery and an enabling capability for catalyst design.« less

Hard and soft X-ray microscopy and tomography in catalysis: bridging the different time and length scales.

PubMed

Grunwaldt, Jan-Dierk; Schroer, Christian G

2010-12-01

X-ray microscopic techniques are excellent and presently emerging techniques for chemical imaging of heterogeneous catalysts. Spatially resolved studies in heterogeneous catalysis require the understanding of both the macro and the microstructure, since both have decisive influence on the final performance of the industrially applied catalysts. A particularly important aspect is the study of the catalysts during their preparation, activation and under operating conditions, where X-rays have an inherent advantage due to their good penetration length especially in the hard X-ray regime. Whereas reaction cell design for hard X-rays is straightforward, recently smart in situ cells have also been reported for the soft X-ray regime. In the first part of the tutorial review, the constraints from a catalysis view are outlined, then the scanning and full-field X-ray microscopy as well as coherent X-ray diffraction imaging techniques are described together with the challenging design of suitable environmental cells. Selected examples demonstrate the application of X-ray microscopy and tomography to monitor structural gradients in catalytic reactors and catalyst preparation with micrometre resolution but also the possibility to follow structural changes in the sub-100 nm regime. Moreover, the potential of the new synchrotron radiation sources with higher brilliance, recent milestones in focusing of hard X-rays as well as spatiotemporal studies are highlighted. The tutorial review concludes with a view on future developments in the field of X-ray microscopy that will have strong impact on the understanding of catalysts in the future and should be combined with in situ electron microscopic studies on the nanoscale and other spectroscopic studies like microRaman, microIR and microUV-vis on the macroscale.

SELECTIVE HYDROGENATION OF MALEIC ANHYDRIDE TO Y-BUTYROLACTONE OVER PD/AL(2)O(3) CATALYST USING SUPERCRITICAL CO(2) AS SOLVENT

EPA Science Inventory

A selective hydrogenation of maleic anhydride to either y-butyrolactone or succinic anhydride over simple Pd/Al(2)O(3) catalyst under supercritical CO(2) medium is described for the first time which has considerable promise for obht lab-scale as well as industrial selective hydro...

PILOT-SCALE STUDY OF THE EFFECT OF SELECTIVE CATALYTIC REDUCTION CATALYST ON MERCURY SPECIATION IN ILLINOIS AND POWDER RIVER BASIN COAL COMBUSTION FLUE GASES

EPA Science Inventory

A study was conducted to investigate the effect of selective catalytic reduction (SCR) catalyst on mercury (Hg) speciation in bituminous and subbituminous coal combustion flue gases. Three different Illinois Basin bituminous coals (from high to low sulfur and chlorine) and one Po...

250-W RF-excited slab CO2 lasers using gold catalyst

NASA Astrophysics Data System (ADS)

Kyun, V. V.; Samorodov, V. G.; Shishkanov, E. F.

2003-11-01

The investigations and constructions of compact RF-excitation CO2 lasers with slab discharge channel geometry and unstable-waveguide resonators are described. The output average power scale up to 260 W from electrode area of 198 cm2 have been obtained in sealed-off mode because use a catalyst effect in discharge volume.

Understanding the performance and mechanism of Mg-containing oxides as support catalysts in the thermal dry reforming of methane.

PubMed

Khairudin, Nor Fazila; Sukri, Mohd Farid Fahmi; Khavarian, Mehrnoush; Mohamed, Abdul Rahman

2018-01-01

Dry reforming of methane (DRM) is one of the more promising methods for syngas (synthetic gas) production and co-utilization of methane and carbon dioxide, which are the main greenhouse gases. Magnesium is commonly applied in a Ni-based catalyst in DRM to improve catalyst performance and inhibit carbon deposition. The aim of this review is to gain better insight into recent developments on the use of Mg as a support or promoter for DRM catalysts. Its high basicity and high thermal stability make Mg suitable for introduction into the highly endothermic reaction of DRM. The introduction of Mg as a support or promoter for Ni-based catalysts allows for good metal dispersion on the catalyst surface, which consequently facilitates high catalytic activity and low catalyst deactivation. The mechanism of DRM and carbon formation and reduction are reviewed. This work further explores how different constraints, such as the synthesis method, metal loading, pretreatment, and operating conditions, influence the dry reforming reactions and product yields. In this review, different strategies for enhancing catalytic activity and the effect of metal dispersion on Mg-containing oxide catalysts are highlighted.

Understanding the performance and mechanism of Mg-containing oxides as support catalysts in the thermal dry reforming of methane

PubMed Central

Khairudin, Nor Fazila; Sukri, Mohd Farid Fahmi; Khavarian, Mehrnoush

2018-01-01

Dry reforming of methane (DRM) is one of the more promising methods for syngas (synthetic gas) production and co-utilization of methane and carbon dioxide, which are the main greenhouse gases. Magnesium is commonly applied in a Ni-based catalyst in DRM to improve catalyst performance and inhibit carbon deposition. The aim of this review is to gain better insight into recent developments on the use of Mg as a support or promoter for DRM catalysts. Its high basicity and high thermal stability make Mg suitable for introduction into the highly endothermic reaction of DRM. The introduction of Mg as a support or promoter for Ni-based catalysts allows for good metal dispersion on the catalyst surface, which consequently facilitates high catalytic activity and low catalyst deactivation. The mechanism of DRM and carbon formation and reduction are reviewed. This work further explores how different constraints, such as the synthesis method, metal loading, pretreatment, and operating conditions, influence the dry reforming reactions and product yields. In this review, different strategies for enhancing catalytic activity and the effect of metal dispersion on Mg-containing oxide catalysts are highlighted. PMID:29719767

DEVELOPMENT OF ATTRITION RESISTANT IRON-BASED FISCHER-TROPSCH CATALYSTS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Adeyinka A. Adeyiga

2001-09-01

The Fischer-Tropsch (F-T) reaction provides a way of converting coal-derived synthesis gas (CO+H{sub 2}) to liquid fuels. Since the reaction is highly exothermic, one of the major problems in control of the reaction is heat removal. Recent work has shown that the use of slurry bubble column reactors (SBCRs) can largely solve this problem. The use of iron-based catalysts is attractive not only due to their low cost and ready availability, but also due to their high water-gas shift activity which makes it possible to use these catalysts with low H{sub 2}/CO ratios. However, a serious problem with use ofmore » Fe catalysts in a SBCR is their tendency to undergo attrition. This can cause fouling/plugging of downstream filters and equipment, makes the separation of catalyst from the oil/wax product very difficult if not impossible, and results in a steady loss of catalyst from the reactor. Recently, fundamental understanding of physical attrition is being addressed by incorporating suitable binders into the catalyst recipe. This has resulted in the preparation of a spray dried Fe-based catalyst having aps of 70 mm with high attrition resistance. This Fe-based attrition resistant, active and selective catalyst gave 95% CO conversion through 125 hours of testing in a fixed-bed at 270 C, 1.48 MPa, H{sub 2}/CO=0.67 and 2.0 NL/g-cat/h with C{sub 5}{sup +} selectivity of >78% and methane selectivity of <5%. However, further development of the catalyst is needed to address the chemical attrition due to phase changes that any Fe-catalyst goes through potentially causing internal stresses within the particle and resulting in weakening, spalling or cracking. The objective of this research is to develop robust iron-based Fischer-Tropsch catalysts that have suitable activity, selectivity and stability to be used in the slurry bubble column reactor. Specifically we aim to develop to: (i) improve the performance and preparation procedure of the high activity, high attrition resistant, high alpha iron-based catalysts synthesized at Hampton University, (ii) seek improvements in the catalyst performance through variations in process conditions, pretreatment procedures and/or modifications in catalyst preparation steps and (iii) investigate the performance in a slurry reactor. The effort during the reporting period has been devoted to attrition study of the iron-based catalysts. Precipitated silica appeared to decrease attrition resistance of spray-dried iron FT catalysts. It was found that the catalyst with precipitated silica content at around 12wt% showed the lowest attrition resistance. The results of net change in volume moment and catalyst morphology showed supporting evidences to the attrition results. Catalysts with low attrition resistance generated more fines loss, had higher net change in volume moment and showed more breakage of particles. BET surface area and pore volume of this catalyst series fluctuated; therefore no conclusion can be drawn from the data obtained. However, catalyst with no precipitated silica showed the lowest in BET surface area and pore volume, as expected. Addition of precipitated silica to the catalysts had no effect to the phase changes of iron that could have significant influence to catalyst attrition. The presence of precipitated silica is needed for enhancing catalyst surface area; however, the amount of silica added should be compromising with attrition resistance of catalysts.« less

Bifunctional catalysts for upgrading of biomass-derived oxygenates: A review

DOE PAGES

Robinson, Allison M.; Hensley, Jesse E.; Medlin, J. Will

2016-06-21

Deoxygenation is an important reaction in the conversion of biomass-derived oxygenates to fuels and chemicals. A key route for biomass refining involves the production of pyrolysis oil through rapid heating of the raw biomass feedstock. Pyrolysis oil as produced is highly oxygenated, so the feasibility of this approach depends in large part on the ability to selectively deoxygenate pyrolysis oil components to create a stream of high-value finished products. Identification of catalytic materials that are active and selective for deoxygenation of pyrolysis oil components has therefore represented a major research area. One catalyst is rarely capable of performing the differentmore » types of elementary reaction steps required to deoxygenate biomass-derived compounds. For this reason, considerable attention has been placed on bifunctional catalysts, where two different active materials are used to provide catalytic sites for diverse reaction steps. Here, we review recent trends in the development of catalysts, with a focus on catalysts for which a bifunctional effect has been proposed. We summarize recent studies of hydrodeoxygenation (HDO) of pyrolysis oil and model compounds for a range of materials, including supported metal and bimetallic catalysts as well as transition-metal oxides, sulfides, carbides, nitrides, and phosphides. Particular emphasis is placed on how catalyst structure can be related to performance via molecular-level mechanisms. Finally, these studies demonstrate the importance of catalyst bifunctionality, with each class of materials requiring hydrogenation and C-O scission sites to perform HDO at reasonable rates.« less

Nitrogen-based catalysts for the electrochemical reduction of CO2 to CO.

PubMed

Tornow, Claire E; Thorson, Michael R; Ma, Sichao; Gewirth, Andrew A; Kenis, Paul J A

2012-12-05

The synthesis and application of carbon-supported, nitrogen-based organometallic silver catalysts for the reduction of CO(2) is studied using an electrochemical flow reactor. Their performance toward the selective formation of CO is similar to the performance achieved when using Ag as the catalyst, but comparatively at much lower silver loading. Faradaic efficiencies of the organometallic catalyst are higher than 90%, which are comparable to those of Ag. Furthermore, with the addition of an amine ligand to Ag/C, the partial current density for CO increases significantly, suggesting a possible co-catalyst mechanism. Additional improvements in activity and selectivity may be achieved as greater insight is obtained on the mechanism of CO(2) reduction and on how these complexes assemble on the carbon support.

'Design of CO-O2 recombination catalysts for closed-cycle CO2 lasers'

NASA Technical Reports Server (NTRS)

Guinn, K.; Goldblum, S.; Noskowski, E.; Herz, R.

1989-01-01

Pulsed CO2 lasers have many applications in aeronautics, space research, weather monitoring and other areas. Full exploitation of the potential of these lasers is hampered by the dissociation of CO2 that occurs during laser operation. The development of closed-cycle CO2 lasers requires active CO-O2 recombination (CO oxidation) catalysts and design methods for implementation of catalysts inside lasers. This paper will discuss the performance criteria and constraints involved in the design of monolith catalyst configurations for use in a closed-cycle laser and will present a design study performed with a computerized design program that had been written. Trade-offs between catalyst activity and dimensions, flow channel dimensions, pressure drop, O2 conversion and other variables will be discussed.

Epoxidation catalyst and process

DOEpatents

Linic, Suljo; Christopher, Phillip

2010-10-26

Disclosed herein is a catalytic method of converting alkenes to epoxides. This method generally includes reacting alkenes with oxygen in the presence of a specific silver catalyst under conditions suitable to produce a yield of the epoxides. The specific silver catalyst is a silver nanocrystal having a plurality of surface planes, a substantial portion of which is defined by Miller indices of (100). The reaction is performed by charging a suitable reactor with this silver catalyst and then feeding the reactants to the reactor under conditions to carry out the reaction. The reaction may be performed in batch, or as a continuous process that employs a recycle of any unreacted alkenes. The specific silver catalyst has unexpectedly high selectivity for epoxide products. Consequently, this general method (and its various embodiments) will result in extraordinarily high epoxide yields heretofore unattainable.

Engineering New Catalysts for In-Process Elimination of Tars

DOE Office of Scientific and Technical Information (OSTI.GOV)

Felix, Larry G.

2012-09-30

The key objective of this project was to develop a new and more efficient methodology for engineering and economically producing optimized robust catalysts for the reduction or elimination of tars in biomass gasification. Whereas current catalyst technology typically disposes thin layers of catalytically-active material onto rigid supports via wet chemistry-based methods, this project investigated novel thermal methods for directly incorporating catalytically active materials onto robust supports as well as novel approaches for incorporating catalytically active materials on and/or within an otherwise inert refractory support material which is then subsequently formed and processed to create a catalytically-active material on all exposedmore » surfaces. Specifically, the focus of this engineered catalyst development was on materials which were derived from, or otherwise related to, olivine-like minerals, due to the inherent attrition resistance and moderate catalytic properties exhibited by natural olivine when used in a fluidized bed biomass gasifier. Task 1 of this project successfully demonstrated the direct thermal impregnation of catalytically-active materials onto an olivine substrate, with the production of a Ni-olivine catalyst. Nickel and nickel oxide were thermally impregnated onto an olivine substrate and when reduced were shown to demonstrate improved catalytic activity over the baseline olivine material and equal the tar-decomposing performance of Ni-olivine catalysts prepared by conventional wet impregnation. Task 2 involved coordination with our subcontracted project partners to further develop and characterize catalyst formulations and to optimize activity and production methods. Within this task, several significant new materials were developed. NexTech Materials developed a sintered ceramic nickel-magnesium-silicate catalyst that demonstrated superb catalytic activity and high resistance to deactivation by H2S. Alfred University developed both supported and integrated (bulk) catalysts via a glass-ceramic processing route which were shown to exhibit excellent catalytic activity and superior resistance to attrition deactivation. With the discovery of these active, robust, glass-based catalysts, and with the permission of the project officer, the investigation of waste-based materials as originally proposed for Task 3 and pilot-scale testing proposed in Task 5 were deferred indefinitely in favor of further investigation of the glass-ceramic based catalyst materials. This choice was justified in part because during FY 2006 and through FY 2007, funding restrictions imposed by congressional budget choices significantly reduced funding for DOE biomass-related projects. Funding for this project was limited to what had been authorized which slowed the pace of project work at GTI so that our project partners could continue in their work. Thereafter, project work was allowed to resume and with restored funding, the project continued and concentrated on the development and testing of glass-ceramic catalysts in bulk or supported formats. Work concluded with a final development devoted to increasing the surface area of glass-ceramic catalysts in the form of microspheres. Following that development, project reporting was completed and the project was concluded.« less

Solar photocatalytic disinfection with immobilised TiO(2) at pilot-plant scale.

PubMed

Sordo, Carlos; Van Grieken, Rafael; Marugán, Javier; Fernández-Ibáñez, Pilar

2010-01-01

The photocatalytic disinfection efficiency has been investigated for two immobilized TiO(2) catalytic systems (wall reactor and fixed-bed reactor) in a solar pilot plant. Their performances have been compared with the use of a slurry reactor and the solar disinfection without catalyst. The use of photocatalytic TiO(2) wall reactors does no show clear benefits over the solar disinfection process in the absence of catalyst. The reason is that the efficiency of the solar disinfection is so high that the presence of titania in the reactor wall reduces the global efficiency due to the competition for the absorption of photons. As expected, the maximum efficiency was shown by the slurry TiO(2) reactor, due to the optimum contact between bacteria and catalyst. However, it is noticeable that the use of the fixed-bed reactor leads to inactivation rate quite close to that of the slurry, requiring comparable accumulated solar energy of about 6 kJ L(-1) to achieve a 6-log decrease in the concentration of viable bacteria and allowing a total disinfection of the water (below the detection limit of 1 CFU mL(-1)). Not only the high titania surface area of this configuration is responsible for the bacteria inactivation but the important contribution of the mechanical stress has to be considered. The main advantage of the fixed-bed TiO(2) catalyst is the outstanding stability, without deactivation effects after ten reaction cycles, being readily applicable for continuous water treatment systems.

Treatment of emerging contaminants in wastewater treatment plants (WWTP) effluents by solar photocatalysis using low TiO2 concentrations.

PubMed

Prieto-Rodriguez, L; Miralles-Cuevas, S; Oller, I; Agüera, A; Li Puma, G; Malato, S

2012-04-15

The optimal photocatalyst concentration for industrial wastewater treatment in current photoreactor designs is several hundreds of milligrams per liter. However, the elimination of emerging contaminants (ECs), which are present at extremely low concentrations in waste water treatment plants (WWTP) effluents might be accomplished at much lower catalyst (TiO(2)) concentrations. One of the main drawbacks of reducing catalyst loading below the optimum is the loss of useful photons which instead are transmitted through the TiO(2) suspension without being absorbed by the catalyst. Accordingly, in this work, laboratory and solar pilot-scale experiments were performed with real WWTP effluents to evaluate the kinetics of photocatalytic degradation of 52 emerging contaminants under realistic (ppb) concentrations. The analysis of the samples was accomplished by solid phase extraction (SPE) followed by liquid chromatography-mass spectrometry (LC-MS). In view of the results, low concentrations of TiO(2) of the order of tens of milligrams per liter were found to be insufficient for the degradation of the ECs in photoreactors with a short light-path length (29 cm). However, it was established that solar reactors of diameters of several hundreds of millimetres could be used for the efficient removal of ECs from WWTP effluents. The results presented show a general methodology for selecting the most efficient reactor diameter on the basis of the desired catalyst concentration. Copyright © 2011 Elsevier B.V. All rights reserved.

Realization of Both High-Performance and Enhanced Durability of Fuel Cells: Pt-Exoskeleton Structure Electrocatalysts.

PubMed

Kim, Ok-Hee; Cho, Yoon-Hwan; Jeon, Tae-Yeol; Kim, Jung Won; Cho, Yong-Hun; Sung, Yung-Eun

2015-07-01

Core-shell structure nanoparticles have been the subject of many studies over the past few years and continue to be studied as electrocatalysts for fuel cells. Therefore, many excellent core-shell catalysts have been fabricated, but few studies have reported the real application of these catalysts in a practical device actual application. In this paper, we demonstrate the use of platinum (Pt)-exoskeleton structure nanoparticles as cathode catalysts with high stability and remarkable Pt mass activity and report the outstanding performance of these materials when used in membrane-electrode assemblies (MEAs) within a polymer electrolyte membrane fuel cell. The stability and degradation characteristics of these materials were also investigated in single cells in an accelerated degradation test using load cycling, which is similar to the drive cycle of a polymer electrolyte membrane fuel cell used in vehicles. The MEAs with Pt-exoskeleton structure catalysts showed enhanced performance throughout the single cell test and exhibited improved degradation ability that differed from that of a commercial Pt/C catalyst.

Nickel supported on nitrogen-doped carbon nanotubes as hydrogen oxidation reaction catalyst in alkaline electrolyte

DOE PAGES

Zhuang, Zhongbin; Giles, Stephen A.; Zheng, Jie; ...

2016-01-14

The development of a low-cost, high-performance platinum-group-metal-free hydroxide exchange membrane fuel cell is hindered by the lack of a hydrogen oxidation reaction catalyst at the anode. Here we report that a composite catalyst, nickel nanoparticles supported on nitrogen-doped carbon nanotubes, has hydrogen oxidation activity similar to platinum-group metals in alkaline electrolyte. Although nitrogen-doped carbon nanotubes are a very poor hydrogen oxidation catalyst, as a support, it increases the catalytic performance of nickel nanoparticles by a factor of 33 (mass activity) or 21 (exchange current density) relative to unsupported nickel nanoparticles. Density functional theory calculations indicate that the nitrogen-doped support stabilizesmore » the nanoparticle against reconstruction, while nitrogen located at the edge of the nanoparticle tunes local adsorption sites by affecting the d-orbitals of nickel. Here, owing to its high activity and low cost, our catalyst shows significant potential for use in low-cost, high-performance fuel cells.« less

Nickel supported on nitrogen-doped carbon nanotubes as hydrogen oxidation reaction catalyst in alkaline electrolyte

PubMed Central

Zhuang, Zhongbin; Giles, Stephen A.; Zheng, Jie; Jenness, Glen R.; Caratzoulas, Stavros; Vlachos, Dionisios G.; Yan, Yushan

2016-01-01

The development of a low-cost, high-performance platinum-group-metal-free hydroxide exchange membrane fuel cell is hindered by the lack of a hydrogen oxidation reaction catalyst at the anode. Here we report that a composite catalyst, nickel nanoparticles supported on nitrogen-doped carbon nanotubes, has hydrogen oxidation activity similar to platinum-group metals in alkaline electrolyte. Although nitrogen-doped carbon nanotubes are a very poor hydrogen oxidation catalyst, as a support, it increases the catalytic performance of nickel nanoparticles by a factor of 33 (mass activity) or 21 (exchange current density) relative to unsupported nickel nanoparticles. Density functional theory calculations indicate that the nitrogen-doped support stabilizes the nanoparticle against reconstruction, while nitrogen located at the edge of the nanoparticle tunes local adsorption sites by affecting the d-orbitals of nickel. Owing to its high activity and low cost, our catalyst shows significant potential for use in low-cost, high-performance fuel cells. PMID:26762466

METHOD OF PURIFYING CATALYSTS

DOEpatents

Joris, G.G.

1958-09-01

It has been fuund that the presence of chlorine as an impurity adversely affects the performance of finely divided platinum catalysts such as are used in the isotopic exchange process for the production of beavy water. This chlorine impurity may be removed from these catalysts by treating the catalyst at an elevated temperature with dry hydrogen and then with wet hydrogen, having a hydrogen-water vapor volume of about 8: 1. This alternate treatment by dry hydrogen and wet hydrogen is continued until the chlorine is largely removed from the catalyst.

Carbon nanocages: a new support material for Pt catalyst with remarkably high durability.

PubMed

Wang, Xiao Xia; Tan, Zhe Hua; Zeng, Min; Wang, Jian Nong

2014-03-24

Low durability is the major challenge hindering the large-scale implementation of proton exchange membrane fuel cell (PEMFC) technology, and corrosion of carbon support materials of current catalysts is the main cause. Here, we describe the finding of remarkably high durability with the use of a novel support material. This material is based on hollow carbon nanocages developed with a high degree of graphitization and concurrent nitrogen doping for oxidation resistance enhancement, uniform deposition of fine Pt particles, and strong Pt-support interaction. Accelerated degradation testing shows that such designed catalyst possesses a superior electrochemical activity and long-term stability for both hydrogen oxidation and oxygen reduction relative to industry benchmarks of current catalysts. Further testing under conditions of practical fuel cell operation reveals almost no degradation over long-term cycling. Such a catalyst of high activity, particularly, high durability, opens the door for the next-generation PEMFC for "real world" application.

Development of inexpensive metal macrocyclic complexes for use in fuel cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Doddapaneni, N.; Ingersoll, D.; Kosek, J.A.

Several metal macrocyclic complexes were synthesized for use as catalysts in fuel cells. An initial evaluation of their ability to catalyze the fuel cell reactions were completed. Based on this initial evaluation, one metal macrocyclic catalyst was selected and long-term stability testing in a fuel cell was initiated. The fuel cell employing this catalyst was operated continuously for one year with little signs of catalyst degradation. The effect of synthetic reformates on the performance of the catalyst in the fuel cell environment also demonstrated high tolerance of this catalyst for common contaminants and poisons.

The role of support morphology on the performance of Cu/ZnO-catalyst for hydrogenation of CO{sub 2} to methanol

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tasfy, Sara Faiz Hanna, E-mail: miss25208@gmail.com; Zabidi, Noor Asmawati Mohd, E-mail: noorasmawati-mzabidi@petronas.com.my; Shaharun, Maizatul Shima, E-mail: maizats@petronas.com.my

The effects of SBA-15 support morphology on the activity of Cu/ZnO catalyst in the hydrogenation of CO{sub 2} to methanol was investigated. In the hydrogenation of CO{sub 2} to methanol at 210°C, 2.25 MPa, H{sub 2}/CO{sub 2} ratio of three remarkable difference was obtained using Cu/ZnO catalyst supported on SBA-15 with different morphology. The catalysts were characterized using N{sub 2}-adsorption, field emission scanning microscopy (FESEM/EDX), transmission electron microscopy (HRTEM), and temperature-programmed reduction (TPR). Characterization of the catalyst showed that support morphology, surface area, metals dispersion, and reducibility influenced the catalytic performance. On the fiber-shaped SBA-15, copper dispersion was 29 % whereasmore » on the spherical-shaped SBA-15, the dispersion was 20 %. The experimental results showed that the catalyst supported over fiber-shaped SBA-15 exhibit higher CO{sub 2} conversion (13.96 %) and methanol selectivity (91.32 %) compare to catalyst supported over spherical-shaped SBA-15.« less

Preparation and characterizaton of CaO nanoparticle for biodiesel production

NASA Astrophysics Data System (ADS)

Gupta, Jharna; Agarwal, Madhu

2016-04-01

Nanoparticle of CaO from calcium Nitrate (CaO/CaN) and Snail shell (CaO/SS) are successfully synthesized by method as described in the literature and used as an active and stable catalyst for the biodiesel production. These catalysts are characterized by Fourier-transform infrared spectra (FT-IR), X-ray diffraction (XRD), and thermal gravimetric analysis (TGA). The average crystalline size in nanometer was also calculated by Debye-Scherrer equation. The performance of the CaO/CaN and CaO/SS were tested for their catalytic activity via transesterification process and it was found that biodiesel yield has been increased from 93 to 96%. The optimum conditions for the highest yield were 8wt% catalyst loading, 65°C temperature, 12:1 methanol/oil molar ratio, and 6 h for reaction time. The nano catalyst from snail shell exhibits excellent catalytic activity and stability for the transesterification reaction, which suggested that this catalyst would be potentially used as a solid base nano catalyst for biodiesel production. In order to examine the reusability of catalyst developed from snail shell, five transesterification reaction cycles were also performed.

Effect of alkaline earth metals on the liquid-phase hydrogenation of hydroquinone over Ru-based catalysts

NASA Astrophysics Data System (ADS)

Li, Hongwei; Ji, Dong; Li, Yu; Liang, Yalan; Li, Gui Xian

2015-12-01

A series of Ru-based catalysts modified by alkaline earth metals were prepared by the impregnation-precipitation method and characterized using transmission electron microscopy, X-ray diffraction, ICP optical emission spectroscopy, Infrared Spectroscopy of adsorbed pyridine analysis and surface area analysis. The performance of the catalysts was measured via liquid-phase hydroquinone hydrogenation reaction. Results show that the Ru-Sr/NaY catalyst has the best activity and selectivity among those Ru-based catalysts. The conversion of hydroquinone and the selectivity to 1,4-cyclohexanediol reached up to 99.6% and 89.6% at optimum reaction condition (700 r/min, 423 K and 5 MPa pressure of H2 in 3 h). This may be attributed to the fact that the right amount of Strontium is beneficial to the good dispersion of the ruthenium nanoclusters on the surface of NaY and modify the acidic properties of the catalyst. Moreover, IR of adsorbed pyridine analysis suggested the proper ratio of L/B acid of the catalysts played an important role in the performance of the hydroquinone hydrogenation reaction.

Regeneration of LOHC dehydrogenation catalysts: In-situ IR spectroscopy on single crystals, model catalysts, and real catalysts from UHV to near ambient pressure

NASA Astrophysics Data System (ADS)

Amende, Max; Kaftan, Andre; Bachmann, Philipp; Brehmer, Richard; Preuster, Patrick; Koch, Marcus; Wasserscheid, Peter; Libuda, Jörg

2016-01-01

The Liquid Organic Hydrogen Carrier (LOHC) concept offers an efficient route to store hydrogen using organic compounds that are reversibly hydrogenated and dehydrogenated. One important challenge towards application of the LOHC technology at a larger scale is to minimize degradation of Pt-based dehydrogenation catalysts during long-term operation. Herein, we investigate the regeneration of Pt/alumina catalysts poisoned by LOHC degradation. We combine ultrahigh vacuum (UHV) studies on Pt(111), investigations on well-defined Pt/Al2O3 model catalysts, and near-ambient pressure (NAP) measurements on real core⿿shell Pt/Al2O3 catalyst pellets. The catalysts were purposely poisoned by reaction with the LOHC perhydro-dibenzyltoluene (H18-MSH) and with dicyclohexylmethane (DCHM) as a simpler model compound. We focus on oxidative regeneration under conditions that may be applied in real dehydrogenation reactors. The degree of poisoning and regeneration under oxidative reaction conditions was quantified using CO as a probe molecule and measured by infrared reflection-absorption spectroscopy (IRAS) and diffuse reflectance Fourier transform IR spectroscopy (DRIFTS) for planar model systems and real catalysts, respectively. We find that regeneration strongly depends on the composition of the catalyst surface. While the clean surface of a poisoned Pt(111) single crystal is fully restored upon thermal treatment in oxygen up to 700 K, contaminated Pt/Al2O3 model catalyst and core⿿shell pellet were only partially restored under the applied reaction conditions. Whereas partial regeneration on facet-like sites on supported catalysts is more facile than on Pt(111), carbonaceous deposits adsorbed at low-coordinated defect sites impede full regeneration of the Pt/Al2O3 catalysts.

Recent progress in solution plasma-synthesized-carbon-supported catalysts for energy conversion systems

NASA Astrophysics Data System (ADS)

Lun Li, Oi; Lee, Hoonseung; Ishizaki, Takahiro

2018-01-01

Carbon-based materials have been widely utilized as the electrode materials in energy conversion and storage technologies, such as fuel cells and metal-air batteries. In these systems, the oxygen reduction reaction is an important step that determines the overall performance. A novel synthesis route, named the solution plasma process, has been recently utilized to synthesize various types of metal-based and heteroatom-doped carbon catalysts. In this review, we summarize cutting-edge technologies involving the synthesis and modeling of carbon-supported catalysts synthesized via solution plasma process, followed by current progress on the electrocatalytic performance of these catalysts. This review provides the fundamental and state-of-the-art performance of solution-plasma-synthesized electrode materials, as well as the remaining scientific and technological challenges for this process.

Development of Ultra-Low Platinum Alloy Cathode Catalysts for PEM Fuel Cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Popov, Branko N.; Weidner, John

2016-01-07

The goal of this project is to synthesize a low cost PEM fuel cell cathode catalyst and support with optimized average mass activity, stability of mass activity, initial high current density performance under H 2/air (power density), and catalyst and support stability able to meet 2017 DOE targets for electrocatalysts for transportation applications. Pt*/ACCS-2 catalyst was synthesized according to a novel methodology developed at USC through: (i) surface modification, (ii) metal catalyzed pyrolysis and (iii) chemical leaching to remove excess meal used to dope the support. Pt* stands for suppressed platinum catalyst synthesized with Co doped platinum. The procedure resultsmore » in increasing carbon graphitization, inclusion of cobalt in the bulk and formation of non-metallic active sites on the carbon surface. Catalytic activity of the support shows an onset potential of 0.86 V for the oxygen reduction reaction (ORR) with well-defined kinetic and mass transfer regions and 2.5% H 2O 2 production. Pt*/ACCS-2 catalyst durability under 0.6-1.0 V potential cycling and support stability under 1.0-1.5 V potential cycling was evaluated. The results indicated excellent catalyst and support performance under simulated start-up/shut down operating conditions (1.0 – 1.5 V, 5000 cycles) which satisfy DOE 2017 catalyst and support durability and activity. The 30% Pt*/ACCS-2 catalyst showed high initial mass activity of 0.34 A/mg PGM at 0.9 ViR-free and loss of mass activity of 45% after 30,000 cycles (0.6-1.0 V). The catalyst performance under H 2-air fuel cell operating conditions showed only 24 mV (iR-free) loss at 0.8 A/cm 2 with an ECSA loss of 42% after 30,000 cycles (0.6-1.0 V). The support stability under 1.0-1.5 V potential cycling showed mass activity loss of 50% and potential loss of 8 mV (iR-free) at 1.5 A/cm 2. The ECSA loss was 22% after 5,000 cycles. Furthermore, the Pt*/ACCS-2 catalyst showed an initial power density (rated) of 0.174 g PGM/kW. Excellent activity and stability of the catalyst are due to synergistic effect of the catalytic activity and stability of ACCS-2, its enhanced hydrophobicity as well as activity of compressive Pt* lattice catalysts. For the first time, we report a carbon based support which is stable under simulated start-up/shut down operating conditions. Five 25cm 2 MEA’s were fabricated at USC using Pt*/ACCS-2 cathode catalyst for independent evaluation at National Renewable Energy. In the Final NREL report they summarize their results as follow: (1) Initial ORR activity and performance of the USC MEA’s Pt*/ACCS-2 under oxygen air, evaluated at NREL were comparable to that measured and reported by USC in their report: (2) Cyclic durability studies indicate that Pt*/ACCS-2 catalysts has minimal losses in activity and performant under 1-1.5 V potential cycling indicating a robust corrosion resistant support.« less

Effects of the Acrylic Polyol Structure and the Selectivity of the Employed Catalyst on the Performance of Two-Component Aqueous Polyurethane Coatings

PubMed Central

Cakic, Suzana; Lacnjevac, Caslav; Stamenkovic, Jakov; Ristic, Nikola; Takic, Ljiljana; Barac, Miroljub; Gligoric, Miladin

2007-01-01

Two kinds of aqueous acrylic polyols (single step and multi step synthesis type) have been investigated for their performance in the two-component aqueous polyurethane application, by using more selective catalysts. The aliphatic polyfunctional isocyanates based on hexamethylen diisocyanates have been employed as suitable hardeners. The complex of zirconium, commercially known as K-KAT®XC-6212, and manganese (III) complexes with mixed ligands based on the derivative of maleic acid have been used as catalysts in this study. Both of the aqueous polyols give good results, in terms of application and hardness, when elevated temperatures and more selective catalysts are applied. A more selective catalyst promotes the reaction between the isocyanate and polyol component. This increases the percentage of urethane bonds and the degree of hardness in the films formed from the two components of aqueous polyurethane lacquers. The polyol based on the single step synthesis route is favourable concerning potlife and hardness. The obtained results show that the performance of the two-component aqueous polyurethane coatings depends on the polymer structure of the polyols as well as on the selectivity of the employed catalyst.

Dependence of crystal size on the catalytic performance of a porous coordination polymer.

PubMed

Kiyonaga, Tomokazu; Higuchi, Masakazu; Kajiwara, Takashi; Takashima, Yohei; Duan, Jingui; Nagashima, Kazuro; Kitagawa, Susumu

2015-02-14

Submicrosized MOF-76(Yb) exhibits a higher catalytic performance for esterification than microsized MOF-76(Yb). Control of the crystal size of porous heterogeneous catalysts, such as PCP/MOFs, offers a promising approach to fabricating high-performance catalysts based on accessibility to the internal catalytic sites.

Development of advanced fuel cell system, phase 2

NASA Technical Reports Server (NTRS)

Handley, L. M.; Meyer, A. P.; Bell, W. F.

1973-01-01

A multiple task research and development program was performed to improve the weight, life, and performance characteristics of hydrogen-oxygen alkaline fuel cells for advanced power systems. Development and characterization of a very stable gold alloy catalyst was continued from Phase I of the program. A polymer material for fabrication of cell structural components was identified and its long term compatibility with the fuel cell environment was demonstrated in cell tests. Full scale partial cell stacks, with advanced design closed cycle evaporative coolers, were tested. The characteristics demonstrated in these tests verified the feasibility of developing the engineering model system concept into an advanced lightweight long life powerplant.

Achieving significantly enhanced visible-light photocatalytic efficiency using a polyelectrolyte: the composites of exfoliated titania nanosheets, graphene, and poly(diallyl-dimethyl-ammonium chloride)

NASA Astrophysics Data System (ADS)

Zhang, Qian; An, Qi; Luan, Xinglong; Huang, Hongwei; Li, Xiaowei; Meng, Zilin; Tong, Wangshu; Chen, Xiaodong; Chu, Paul K.; Zhang, Yihe

2015-08-01

A high-performance visible-light-active photocatalyst is prepared using the polyelectrolyte/exfoliated titania nanosheet/graphene oxide (GO) precursor by flocculation followed by calcination. The polyelectrolyte poly(diallyl-dimethyl-ammonium chloride) serves not only as an effective binder to precipitate GO and titania nanosheets, but also boosts the overall performance of the catalyst significantly. Unlike most titania nanosheet-based catalysts reported in the literature, the composite absorbs light in the UV-Vis-NIR range. Its decomposition rate of methylene blue is 98% under visible light. This novel strategy of using a polymer to enhance the catalytic performance of titania nanosheet-based catalysts affords immense potential in designing and fabricating next-generation photocatalysts with high efficiency.A high-performance visible-light-active photocatalyst is prepared using the polyelectrolyte/exfoliated titania nanosheet/graphene oxide (GO) precursor by flocculation followed by calcination. The polyelectrolyte poly(diallyl-dimethyl-ammonium chloride) serves not only as an effective binder to precipitate GO and titania nanosheets, but also boosts the overall performance of the catalyst significantly. Unlike most titania nanosheet-based catalysts reported in the literature, the composite absorbs light in the UV-Vis-NIR range. Its decomposition rate of methylene blue is 98% under visible light. This novel strategy of using a polymer to enhance the catalytic performance of titania nanosheet-based catalysts affords immense potential in designing and fabricating next-generation photocatalysts with high efficiency. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr03256c

Porous Ni-Mn oxide nanosheets in situ formed on nickel foam as 3D hierarchical monolith de-NOx catalysts

NASA Astrophysics Data System (ADS)

Cai, Sixiang; Zhang, Dengsong; Shi, Liyi; Xu, Jing; Zhang, Lei; Huang, Lei; Li, Hongrui; Zhang, Jianping

2014-06-01

In this work, we successfully in situ decorated nickel foam with porous Ni-Mn oxide nanosheets (3DH-NM/NF) as 3D hierarchical monolith de-NOx catalysts via a simple hydrothermal reaction and calcination process. The catalysts were carefully examined by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, elemental mapping, X-ray photoelectron spectroscopy, H2 temperature-programmed reduction and NH3 temperature-programmed desorption measurements. The results indicated that the nanosheets are composed of a Ni6Mn1O8 spinel and the metal species are uniformly dispersed in bi-metal oxides. As a result, the strong synergistic effects between the Mn and Ni species have been observed. The active oxygen species, reducible species and acidity are enhanced by the in situ formation of the nanosheets on the surface of nickel foam. These desirable features of 3DH-NM/NF catalysts bring about the excellent de-NOx performance. Moreover, the 3DH-NM/NF catalysts also present good stability and H2O resistance. Based on these favorable properties, 3DH-NM/NF could be considered as a promising candidate for the monolith de-NOx catalysts.In this work, we successfully in situ decorated nickel foam with porous Ni-Mn oxide nanosheets (3DH-NM/NF) as 3D hierarchical monolith de-NOx catalysts via a simple hydrothermal reaction and calcination process. The catalysts were carefully examined by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, elemental mapping, X-ray photoelectron spectroscopy, H2 temperature-programmed reduction and NH3 temperature-programmed desorption measurements. The results indicated that the nanosheets are composed of a Ni6Mn1O8 spinel and the metal species are uniformly dispersed in bi-metal oxides. As a result, the strong synergistic effects between the Mn and Ni species have been observed. The active oxygen species, reducible species and acidity are enhanced by the in situ formation of the nanosheets on the surface of nickel foam. These desirable features of 3DH-NM/NF catalysts bring about the excellent de-NOx performance. Moreover, the 3DH-NM/NF catalysts also present good stability and H2O resistance. Based on these favorable properties, 3DH-NM/NF could be considered as a promising candidate for the monolith de-NOx catalysts. Electronic supplementary information (ESI) available: Experimental details and catalytic performance of the NM/cordierite catalysts, SEM image and EDX analysis of the NF and 3DH-N/NF catalysts, N2 selectivity and catalytic performance under different gas hourly space velocities of the 3DH-NM/NF catalysts. See DOI: 10.1039/c4nr00475b

Efficiency of bimetallic PtPd on polydopamine modified on various carbon supports for alcohol oxidations

NASA Astrophysics Data System (ADS)

Pinithchaisakula, A.; Ounnunkad, K.; Themsirimongkon, S.; Promsawan, N.; Waenkaew, P.; Saipanya, S.

2017-02-01

In this work, the preparation, characterization, and electrocatalytic analysis of the catalysts on various carbon substrates for direct alcohol fuel cells were studied. Selected carbons were modified with/without polydopamine (labelled as PDA-C and C) and further metal electrodeposited incorporated onto the glassy carbon (labelled as 5Pt1Pd/PDA-C and 5Pt1Pd/C). Four various carbon materials were used e.g. graphite (G), carbon nanotube (CNT), graphene (GP) and graphene oxide (GO) and the carbons were modified with PDA denoted as PDA-G, PDA-CNT, PDA-GP and PDA-GO, respectively. The transmission electron microscopy (TEM) and scanning electron microscopy (SEM) experimental observation showed narrow size distribution of metal anchored on the PDA-C and C materials. Chemical compositions and oxidation states of the catalysts were determined by X-ray photoelectron spectroscopy (XPS) and energy-dispersive X-ray spectroscopy (EDX). The catalytic performances for small organic electro-oxidation (e.g. methanol and ethanol) were measured by cyclic voltammetry (CV). Among different PDA-C and C catalysts, monometallic Pt showed less activity than the bimetallic catalysts. Among catalysts with PDA, the 5Pt1Pd/PDA-GO catalyst facilitated methanol and ethanol oxidations with high oxidation currents and If/Ib value and stability with low potentials while among catalysts without PDA, the 5Pt1Pd/CNT provides highest activity and stability. It was found that the catalysts with PDA provided high activity and stability than the catalysts without PDA. The improved catalytic performance of the prepared catalysts could be related to the higher active surface area from polymer modification and bimetallic catalyst system in the catalyst composites.

Hydrogen production by steam reforming of liquefied natural gas (LNG) over nickel catalysts supported on cationic surfactant-templated mesoporous aluminas

NASA Astrophysics Data System (ADS)

Seo, Jeong Gil; Youn, Min Hye; Park, Sunyoung; Jung, Ji Chul; Kim, Pil; Chung, Jin Suk; Song, In Kyu

Two types of mesoporous γ-aluminas (denoted as A-A and A-S) are prepared by a hydrothermal method under different basic conditions using cationic surfactant (cetyltrimethylammonium bromide, CTAB) as a templating agent. A-A and A-S are synthesized in a medium of ammonia solution and sodium hydroxide solution, respectively. Ni/γ-Al 2O 3 catalysts (Ni/A-A and Ni/A-S) are then prepared by an impregnation method, and are applied to hydrogen production by steam reforming of liquefied natural gas (LNG). The effect of a mesoporous γ-Al 2O 3 support on the catalytic performance of Ni/γ-Al 2O 3 is investigated. The identity of basic solution strongly affects the physical properties of the A-A and A-S supports. The high surface-area of the mesoporous γ-aluminas and the strong metal-support interaction of supported catalysts greatly enhance the dispersion of nickel species on the catalyst surface. The well-developed mesopores of the Ni/A-A and Ni/A-S catalysts prohibit the polymerization of carbon species on the catalyst surface during the reaction. In the steam reforming of LNG, both Ni/A-A and Ni/A-S catalysts give better catalytic performance than the nickel catalyst supported on commercial γ-Al 2O 3 (Ni/A-C). In addition, the Ni/A-A catalyst is superior to the Ni/A-S catalyst. The relatively strong metal-support interaction of Ni/A-A catalyst effectively suppresses the sintering of metallic nickel and the carbon deposition in the steam reforming of LNG. The large pores of the Ni/A-A catalyst also play an important role in enhancing internal mass transfer during the reaction.

Advanced Coal Liquefaction Research and Development Facility, Wilsonville, Alabama. Run 262 with Black Thunder subbituminous coal: Technical progress report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

This report presents the results of Run 262 performed at the Advanced Coal Liquefaction R&D Facility in Wilsonville, Alabama. The run started on July 10, 1991 and continued until September 30, 1991, operating in the Close-Coupled Integrated Two-Stage Liquefaction mode processing Black Thunder Mine subbituminous coal (Wyodak-Anderson seam from Wyoming Powder River Basin). A dispersed molybdenum catalyst was evaluated for its performance. The effect of the dispersed catalyst on eliminating solids buildup was also evaluated. Half volume reactors were used with supported Criterion 324 1/16`` catalyst in the second stage at a catalyst replacement rate of 3 lb/ton of MFmore » coal. The hybrid dispersed plus supported catalyst system was tested for the effect of space velocity, second stage temperature, and molybdenum concentration. The supported catalyst was removed from the second stage for one test period to see the performance of slurry reactors. Iron oxide was used as slurry catalyst at a rate of 2 wt % MF coal throughout the run (dimethyl disulfide (DMDS) was used as the sulfiding agent). The close-coupled reactor unit was on-stream for 1271.2 hours for an on-stream factor of 89.8% and the ROSE-SR unit was on-feed for 1101.6 hours for an on-stream factor of 90.3% for the entire run.« less

3D polymer hydrogel for high-performance atomic iron-rich catalysts for oxygen reduction in acidic media

DOE Office of Scientific and Technical Information (OSTI.GOV)

Qiao, Zhi; Zhang, Hanguang; Karakalos, Stavros

Current platinum group metal (PGM)-free carbon nanocomposite catalysts for the oxygen reduction reaction (ORR) in acidic electrolyte often suffer from rapid degradation associated with carbon corrosion due to the use of large amount of amorphoous carbon black supports. Here, we developed a new concept of using freestanding 3D hydrogel to design support-free Fe-N-C catalysts. A 3D polyaniline (PANI)-based hydrogel was used for preparing a new type of single atomic iron site-rich catalyst, which has exhibited exceptionally enhanced activity and stability compared to conventional Fe-N-C catalysts supported on amorphous carbon blacks. The achieved performance metric on the hydrogel PANI-Fe catalysts ismore » one of the best ever reported PGM-free catalysts, reaching a half-wave potential up to 0.83 V vs. RHE and only leaving 30 mV gap with Pt/C catalysts (60 μgPt/cm2) in challenging acidic media. Remarkable ORR stability was accomplished as well on the same catalyst evidenced by using harsh potential cycling tests. The well dispersion of atomic iron into partially graphitized carbon, featured with dominance of micropores and porous network structures, is capable of accommodating increased number of active sites, strengthening local bonding among iron, nitrogen and carbon, and facilitating mass transfer. The 3D polymer hydrogel approach would be a new pathway to advance PGM-free catalysts.« less

3D polymer hydrogel for high-performance atomic iron-rich catalysts for oxygen reduction in acidic media

DOE PAGES

Qiao, Zhi; Zhang, Hanguang; Karakalos, Stavros; ...

2017-08-03

Current platinum group metal (PGM)-free carbon nanocomposite catalysts for the oxygen reduction reaction (ORR) in acidic electrolyte often suffer from rapid degradation associated with carbon corrosion due to the use of large amount of amorphoous carbon black supports. Here, we developed a new concept of using freestanding 3D hydrogel to design support-free Fe-N-C catalysts. A 3D polyaniline (PANI)-based hydrogel was used for preparing a new type of single atomic iron site-rich catalyst, which has exhibited exceptionally enhanced activity and stability compared to conventional Fe-N-C catalysts supported on amorphous carbon blacks. The achieved performance metric on the hydrogel PANI-Fe catalysts ismore » one of the best ever reported PGM-free catalysts, reaching a half-wave potential up to 0.83 V vs. RHE and only leaving 30 mV gap with Pt/C catalysts (60 μgPt/cm2) in challenging acidic media. Remarkable ORR stability was accomplished as well on the same catalyst evidenced by using harsh potential cycling tests. The well dispersion of atomic iron into partially graphitized carbon, featured with dominance of micropores and porous network structures, is capable of accommodating increased number of active sites, strengthening local bonding among iron, nitrogen and carbon, and facilitating mass transfer. The 3D polymer hydrogel approach would be a new pathway to advance PGM-free catalysts.« less

Sustainability of the Catalytic Activity of a Silica-Titania Composite (STC) for Long-Term Indoor Air Quality Control

NASA Technical Reports Server (NTRS)

Coutts, Janelle L.; Levine, Lanfang H.; Richards, Jeffrey T.

2011-01-01

TiO2-assisted photocatalytic oxidation (PCO) is an emerging technology for indoor air quality control and is also being evaluated as an alternative trace contaminant control technology for crew habitats in space exploration. Though there exists a vast range of literature on the development of photocatalysts and associated reactor systems, including catalyst performance and performance-influencing factors, the critical question of whether photocatalysts can sustain their initial catalytic activity over an extended period of operation has not been adequately addressed. For a catalyst to effectively serve as an air quality control product, it must be rugged enough to withstand exposure to a multitude of low concentration volatile organic compounds (VOCs) over long periods of time with minimal loss of activity. The objective of this study was to determine the functional lifetime of a promising photocatalyst - the silica-titania composite (STC) from Sol Gel Solutions, LLC in a real-world scenario. A bench-scale STC-packed annular reactor under continuous irradiation by a UV-A fluorescent black-light blue lamp ((lambda)max = 365 nm) was exposed to laboratory air continuously at an apparent contact time of 0.27 sand challenged with a known concentration of ethanol periodically to assess any changes in catalytic activity. Laboratory air was also episodically spiked with halocarbons (e.g., octafluoropropane), organosulfur compounds (e.g., sulfur hexafluoride), and organosilicons (e.g., siloxanes) to simulate accidental releases or leaks of such VOCs. Total organic carbon (TOC) loading and contaminant profiles of the laboratory air were also monitored. Changes in STC photocatalytic performance were evaluated using the ethanol mineralization rate, mineralization efficiency, and oxidation intermediate (acetaldehyde) formation. Results provide insights to any potential catalyst poisoning by trace halocarbons and organosulfur compounds.

High-performance hydrogen fuel cell using nitrate reduction reaction on a non-precious catalyst.

PubMed

Han, Sang-Beom; Song, You-Jung; Lee, Young-Woo; Ko, A-Ra; Oh, Jae-Kyung; Park, Kyung-Won

2011-03-28

The H(2)-NO(3)(-) electrochemical cell using nitrate reduction on a non-precious cathode catalyst shows much improved efficiency despite ∼75% reduction of Pt metal loading as compared to typical PEMFCs using typical ORR on precious catalysts.

Catalytic wet air oxidation of aniline with nanocasted Mn-Ce-oxide catalyst.

PubMed

Levi, R; Milman, M; Landau, M V; Brenner, A; Herskowitz, M

2008-07-15

The catalytic wet air oxidation of aqueous solution containing 1000 ppm aniline was conducted in a trickle-bed reactor packed with a novel nanocasted Mn-Ce-oxide catalyst (surface area of 300 m2/g) prepared using SBA-15 silica as a hard template. A range of liquid hourly space velocities (5-20 h(-1)) and temperatures (110-140 degrees C) at 10 bar of oxygen were tested. The experiments were conducted to provide the intrinsic performance of the catalysts. Complete aniline conversion, 90% TOC conversion, and 80% nitrogen mineralization were achieved at 140 degrees C and 5 h(-1). Blank experiments yielded relatively low homogeneous aniline (<35%) and negligible TOC conversions. Fast deactivation of the catalysts was experienced due to leaching caused by complexation with aniline. Acidification of the solution with HCI (molar HCI to aniline ratio of 1.2) was necessary to avoid colloidization and leaching of the nanoparticulate catalyst components. The catalyst displayed stable performance for over 200 h on stream.

Progress in the Development of Oxygen Reduction Reaction Catalysts for Low-Temperature Fuel Cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Dongguo; Lv, Haifeng; Kang, Yijin

2016-04-06

In this paper, we present a brief summary on the most recent progress in the design of catalysts for electrochemical reduction of oxygen. The main challenge in the wide spread of fuel cell technology is to lower the content of, or even eliminate, Pt and other precious metals in catalysts without sacrificing their performance. Pt-based nanosized catalysts with novel and refined architectures continue to dominate in catalytic performance, and formation of Pt-skin-like surfaces is key to achieving the highest values in activity. Moreover, durability has also been improved in Pt-based systems with addition of Au, which plays an important rolemore » in stabilizing the Pt topmost layers against dissolution. However, various carbon-based materials without precious metal have shown improvement in activity and durability and have been explored to serve as catalyst supports. Finally, understanding how the doped elements interact with each other and/or carbon is challenging and necessary in the design of robust fuel cell catalysts.« less

Synthesis of fatty acid methyl ester from used vegetable cooking oil by solid reusable Mg 1-x Zn 1+x O2 catalyst.

PubMed

Olutoye, M A; Hameed, B H

2011-02-01

Fatty acid methyl ester was produced from used vegetable cooking oil using Mg(1-)(x) Zn(1+)(x)O(2) solid catalyst and the performance monitored in terms of ester content obtained. Used vegetable cooking oil was employed to reduce operation cost of biodiesel. The significant operating parameters which affect the overall yield of the process were studied. The highest ester content, 80%, was achieved with the catalyst during 4h 15 min reaction at 188°C with methanol to oil ratio of 9:1 and catalyst loading of 2.55 wt% oil. Also, transesterification of virgin oil gave higher yield with the heterogeneous catalyst and showed high selectivity towards ester production. The used vegetable cooking oil did not require any rigorous pretreatment. Catalyst stability was examined and there was no leaching of the active components, and its performance was as good at the fourth as at the first cycle. Copyright © 2010 Elsevier Ltd. All rights reserved.

Activity of Co-N multi walled carbon nanotubes electrocatalysts for oxygen reduction reaction in acid conditions

NASA Astrophysics Data System (ADS)

Osmieri, Luigi; Monteverde Videla, Alessandro H. A.; Specchia, Stefania

2015-03-01

Two catalysts are synthesized by wet impregnation of multi walled carbon nanotubes (MWCNT) with a complex formed between Co(II) ions and the nitrogen-containing molecule 2,4,6-tris(2-pyridyl)-1,3,5-triazine (TPTZ), followed by one or two identical heat treatments in N2 atmosphere at 800 °C for 3 h. Catalysts are fully characterized by FESEM, EDX, BET, XRD, FTIR, TGA, XPS analyses, and electrochemical techniques. The electrocatalytic activity towards oxygen reduction reaction (ORR) of the catalysts in acid conditions is assessed by means of a rotating disk electrode (RDE) apparatus and a specific type of cell equipped with a gas diffusion working electrode (GDE). In both testing approaches, the catalyst heat-treated twice (Co-N/MWCNT-2) exhibits higher electroactivity than the catalyst heat-treated once (Co-N/MWCNT-1). Chronoamperometries both in RDE and GDE cell are also performed, showing less electroactivity decay and better current performance for the catalyst heat-treated twice.

Synthesis of biodiesel from pongamia oil using heterogeneous ion-exchange resin catalyst.

PubMed

Jaya, N; Selvan, B Karpanai; Vennison, S John

2015-11-01

Biodiesel is a clean-burning renewable substitute fuel for petroleum. Biodiesel could be effectively produced by transesterification reaction of triglycerides of vegetable oils with short-chain alcohols in the presence of homogeneous or heterogeneous catalysts. Conventionally, biodiesel manufacturing processes employ strong acids or bases as catalysts. But, separation of the catalyst and the by-product glycerol from the product ester is too expensive to justify the product use as an automobile fuel. Hence heterogeneous catalysts are preferred. In this study, transesterification of pongamia oil with ethanol was performed using a solid ion-exchange resin catalyst. It is a macro porous strongly basic anion exchange resin. The process parameters affecting the ethyl ester yield were investigated. The reaction conditions were optimized for the maximum yield of fatty acid ethyl ester (FAEE) of pongamia oil. The properties of FAEE were compared with accepted standards of biodiesel. Engine performance was also studied with pongamia oil diesel blend and engine emission characteristics were observed. Copyright © 2015 Elsevier Inc. All rights reserved.

Two step esterification-transesterification process of wet greasy sewage sludge for biodiesel production.

PubMed

Urrutia, C; Sangaletti-Gerhard, N; Cea, M; Suazo, A; Aliberti, A; Navia, R

2016-01-01

Sewage sludge generated in municipal wastewater treatment plants was used as a feedstock for biodiesel production via esterification/transesterification in a two-step process. In the first esterification step, greasy and secondary sludge were tested using acid and enzymatic catalysts. The results indicate that both catalysts performed the esterification of free fatty acids (FFA) simultaneously with the transesterification of triacylglycerols (TAG). Acid catalyst demonstrated better performance in FFA esterification compared to TAG transesterification, while enzymatic catalyst showed the ability to first hydrolyze TAG in FFA, which were esterified to methyl esters. In addition, FAME concentration using greasy sludge were higher (63.9% and 58.7%), compared with those of secondary sludge (11% and 16%), using acid and enzymatic catalysts, respectively. Therefore, only greasy sludge was used in the second step of alkaline transesterification. The alkaline transesterification of the previously esterified greasy sludge reached a maximum FAME concentration of 65.4% when using acid catalyst. Copyright © 2015 Elsevier Ltd. All rights reserved.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tao, Franklin

Two main categories of heterogeneous catalysts are metal and metal oxide which catalyze 80% chemical reactions at solid-gas and solid-liquid interfaces. Metal oxide catalysts are much more complicated than metal catalysts. The reason is that the cations of the metal atoms could exhibit a few different oxidation states on surface of the same catalyst particle such as Co 3O 4 or change of their oxidation states under different reactive environments. For a metal catalyst, there is only one oxidation state typically. In addition, surface of a metal oxide can be terminated with multiple surface functionalities including O atoms with differentmore » binding configurations and OH group. For metal, only metal atoms are exposed typically. Obviously, the complication of surface chemistry and structure of a metal oxide makes studies of surface of an oxide catalyst very challenging. Due to the complication of surface of a meal oxide, the electronic and geometric structures of surface of a metal oxide and the exposed species have received enormous attention since oxide catalysts catalyze at least 1/3 chemical reactions in chemical and energy industries. Understanding of catalytic reactions on early transition metal oxide-based catalysts is fundamentally intriguing and of great practical interest in energy- and environment-related catalysis. Exploration of surface chemistry of oxide-based catalysts at molecular level during catalysis has remained challenging though it is critical in deeply understanding catalysis on oxide-based catalysts and developing oxide-based catalysts with high activity and selectivity. Thus, the overall objective of this project is to explore surface chemistry and structure of early transition metal oxide-based catalysts through in-situ characterization of surface of catalysts, measurements of catalytic performances, and then build an intrinsic correlation of surface chemistry and structure with their catalytic performances in a few important catalytic reactions, and essentially fundamentally understand catalytic mechanism. Furthermore, this correlation will guide the design of catalysts with high activity and selectivity.« less

Continuous bench-scale slurry catalyst testing direct coal liquefaction rawhide sub-bituminous coal

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bauman, R.F.; Coless, L.A.; Davis, S.M.

In 1992, the Department of Energy (DOE) sponsored research to demonstrate a dispersed catalyst system using a combination of molybdenum and iron precursors for direct coal liquefaction. This dispersed catalyst system was successfully demonstrated using Black Thunder sub-bituminous coal at Wilsonville, Alabama by Southern Electric International, Inc. The DOE sponsored research continues at Exxon Research and Development Laboratories (ERDL). A six month continuous bench-scale program using ERDL`s Recycle Coal Liquefaction Unit (RCLU) is planned, three months in 1994 and three months in 1995. The initial conditions in RCLU reflect experience gained from the Wilsonville facility in their Test Run 263.more » Rawhide sub-bituminous coal which is similar to the Black Thunder coal tested at Wilsonville was used as the feed coal. A slate of five dispersed catalysts for direct coal liquefaction of Rawhide sub-bituminous coal has been tested. Throughout the experiments, the molybdenum addition rate was held constant at 100 wppm while the iron oxide addition rate was varied from 0.25 to 1.0 weight percent (dry coal basis). This report covers the 1994 operations and accomplishments.« less

Continuous bench-scale slurry catalyst testing direct coal liquefaction of rawhide sub-bituminous coal

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bauman, R.F.; Coless, L.A.; Davis, S.M.

In 1992, the Department of Energy (DOE) sponsored research to demonstrate a dispersed catalyst system using a combination of molybdenum and iron precursors for direct coal liquefaction. This dispersed catalyst system was successfully demonstrated using Black Thunder sub-bituminous coal at Wilsonville, Alabama by Southern Electric International, Inc. The DOE sponsored research continues at Exxon Research and Development Laboratories (ERDL). A six month continuous bench-scale program using ERDL`s Recycle Coal Liquefaction Unit (RCLU) is planned, three months in 1994 and three months in 1995. The initial conditions in RCLU reflect experience gained from the Wilsonville facility in their Test Run 263.more » Rawhide sub-bituminous coal which is similar to the Black Thunder coal tested at Wilsonville was used as the feed coal. A slate of five dispersed catalysts for direct coal liquefaction of Rawhide sub-bituminous coal has been tested. Throughout the experiments, the molybdenum addition rate was held constant at 100 wppm while the iron oxide addition rate was varied from 0.25 to 1.0 weight percent (dry coal basis). This report covers the 1994 operations and accomplishments.« less

Development of highly active and stable hybrid cathode catalyst for PEMFCs

NASA Astrophysics Data System (ADS)

Jung, Won Suk

Polymer electrolyte membrane fuel cells (PEMFCs) are attractive power sources of the future for a variety of applications including portable electronics, stationary power, and automobile application. However, sluggish cathode kinetics, high Pt cost, and durability issues inhibit the commercialization of PEMFCs. To overcome these drawbacks, research has been focused on alloying Pt with transition metals since alloy catalysts show significantly improved catalytic properties like high activity, selectivity, and durability. However, Pt-alloy catalysts synthesized using the conventional impregnation method exhibit uneven particle size and poor particle distribution resulting in poor performance and/or durability in PEMFCs. In this dissertation, a novel catalyst synthesis methodology is developed and compared with catalysts prepared using impregnation method and commercial catalysts. Two approaches are investigated for the catalyst development. The catalyst durability was studied under U. S. DRIVE Fuel Cell Tech Team suggested protocols. In the first approach, the carbon composite catalyst (CCC) having active sites for oxygen reduction reaction (ORR) is employed as a support for the synthesis of Pt/CCC catalyst. The structural and electrochemical properties of Pt/CCC catalyst are investigated using high-resolution transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy, while RDE and fuel cell testing are carried out to study the electrochemical properties. The synergistic effect of CCC and Pt is confirmed by the observed high activity towards ORR for the Pt/CCC catalyst. The second approach is the synthesis of Co-doped hybrid cathode catalysts (Co-doped Pt/CCC) by diffusing the Co metal present within the CCC support into the Pt nanoparticles during heat-treatment. The optimized Co-doped Pt/CCC catalyst performed better than the commercial catalysts and the catalyst prepared using the impregnation method in PEMFCs and showed high stability under 30,000 potential cycles between 0.6 and 1.0 V. To further increase the stability of the catalyst at high potential cycles (1.0-1.5 V), high temperature treatment is used to obtain graphitized carbon having optimum BET surface area. The novel catalyst synthesis procedure developed in this study was successfully applied for the synthesis of Co-doped Pt catalysts supported on the graphitized carbon which showed high activity and enhanced stability at high potentials.

Bimetallic catalysts for continuous catalytic wet air oxidation of phenol.

PubMed

Fortuny, A; Bengoa, C; Font, J; Fabregat, A

1999-01-29

Catalytic wet oxidation has proved to be effective at eliminating hazardous organic compounds, such as phenol, from waste waters. However, the lack of active long-life oxidation catalysts which can perform in aqueous phase is its main drawback. This study explores the ability of bimetallic supported catalysts to oxidize aqueous phenol solutions using air as oxidant. Combinations of 2% of CoO, Fe2O3, MnO or ZnO with 10% CuO were supported on gamma-alumina by pore filling, calcined and later tested. The oxidation was carried out in a packed bed reactor operating in trickle flow regime at 140 degrees C and 900 kPa of oxygen partial pressure. Lifetime tests were conducted for 8 days. The pH of the feed solution was also varied. The results show that all the catalysts tested undergo severe deactivation during the first 2 days of operation. Later, the catalysts present steady activity until the end of the test. The highest residual phenol conversion was obtained for the ZnO-CuO, which was significantly higher than that obtained with the 10% CuO catalyst used as reference. The catalyst deactivation is related to the dissolution of the metal oxides from the catalyst surface due to the acidic reaction conditions. Generally, the performance of the catalysts was better when the pH of the feed solution was increased.

Graphene-derived Fe/Co-N-C catalyst in direct methanol fuel cells: Effects of the methanol concentration and ionomer content on cell performance

NASA Astrophysics Data System (ADS)

Park, Jong Cheol; Choi, Chang Hyuck

2017-08-01

Non-precious metal catalysts (typically Fe(Co)-N-C catalysts) have been widely investigated for use as cost-effective cathode materials in low temperature fuel cells. Despite the high oxygen reduction activity and methanol-tolerance of graphene-based Fe(Co)-N-C catalysts in an acidic medium, their use in direct methanol fuel cells (DMFCs) has not yet been successfully implemented, and only a few studies have investigated this topic. Herein, we synthesized a nano-sized graphene-derived Fe/Co-N-C catalyst by physical ball-milling and a subsequent chemical modification of the graphene oxide. Twelve membrane-electrode-assemblies are fabricated with various cathode compositions to determine the effects of the methanol concentration, ionomer (i.e. Nafion) content, and catalyst loading on the DMFC performance. The results show that a graphene-based catalyst is capable of tolerating a highly-concentrated methanol feed up to 10.0 M. The optimized electrode composition has an ionomer content and catalyst loading of 66.7 wt% and 5.0 mg cm-2, respectively. The highest maximum power density is ca. 32 mW cm-2 with a relatively low PtRu content (2 mgPtRu cm-2). This study overcomes the drawbacks of conventional graphene-based electrodes using a nano-sized graphene-based catalyst and further shows the feasibility of their potential applications in DMFC systems.

CeO2 nanocubes-graphene oxide as durable and highly active catalyst support for proton exchange membrane fuel cell

PubMed Central

Lei, M.; Wang, Z. B.; Li, J. S.; Tang, H. L.; Liu, W. J.; Wang, Y. G.

2014-01-01

Rapid degradation of cell performance still remains a significant challenge for proton exchange membrane fuel cell (PEMFC). In this work, we develop novel CeO2 nanocubes-graphene oxide nanocomposites as durable and highly active catalyst support for proton exchange membrane fuel cell. We show that the use of CeO2 as the radical scavenger in the catalysts remarkably improves the durability of the catalyst. The catalytic activity retention of Pt-graphene oxide-8 wt.% CeO2 nanocomposites reaches as high as 69% after 5000 CV-cycles at a high voltage range of 0.8–1.23 V, in contrast to 19% for that of the Pt-graphene oxide composites. The excellent durability of the Pt-CeO2 nanocubes-graphene oxide catalyst is attributed to the free radical scavenging activity of CeO2, which significantly slows down the chemical degradation of Nafion binder in catalytic layers, and then alleviates the decay of Pt catalysts, resulting in the excellent cycle life of Pt-CeO2-graphene oxide nanocomposite catalysts. Additionally, the performance of single cell assembled with Nafion 211 membrane and Pt-CeO2-graphene oxide catalysts with different CeO2 contents in the cathode as well as the Pt-C catalysts in the anode are also recorded and discussed in this study. PMID:25491655

Relationship between surface property and catalytic application of amorphous NiP/Hβ catalyst for n-hexane isomerization

NASA Astrophysics Data System (ADS)

Chen, Jinshe; Duan, Zunbin; Song, Zhaoyang; Zhu, Lijun; Zhou, Yulu; Xiang, Yuzhi; Xia, Daohong

2017-12-01

The amorphous NiP nanoparticles were synthesized and a novel amorphous NiP/Hβ catalyst was prepared successfully further. Due to the superior surface property of amorphous NiP/Hβ catalyst, it exhibited good catalytic application for n-hexane isomerization. The catalytic activity of amorphous NiP/Hβ catalyst was close to that of the prepared Pt/Hβ sample, and better than that of commercial catalyst and crystalline Ni2P/Hβ catalyst. What's more, the amorphous NiP/Hβ catalyst shows high resistance to different sulfur compounds and water on account of its unique surface property. The effect of loading amounts on surface property and catalytic performance was investigated, and the structure-function relationship among them was studied ulteriorly. The results demonstrate that loading amounts have effect on textural property and surface acid property, which further affect the catalytic performance. The 10 wt.% NiP/Hβ sample has appropriate pore structure and acid property with uniformly dispersed NiP nanoparticles on surface, which is helpful for providing suitable synergistic effect. The effects of reaction conditions on surface reactions and the mechanism for n-hexane isomerization were investigated further. Based on these results, the amorphous NiP/Hβ catalyst with superior surface property probably pavesa way to overcome the drawbacks of traditional noble metal catalyst, which shows good catalytic application prospects.

CeO2 nanocubes-graphene oxide as durable and highly active catalyst support for proton exchange membrane fuel cell.

PubMed

Lei, M; Wang, Z B; Li, J S; Tang, H L; Liu, W J; Wang, Y G

2014-12-10

Rapid degradation of cell performance still remains a significant challenge for proton exchange membrane fuel cell (PEMFC). In this work, we develop novel CeO2 nanocubes-graphene oxide nanocomposites as durable and highly active catalyst support for proton exchange membrane fuel cell. We show that the use of CeO2 as the radical scavenger in the catalysts remarkably improves the durability of the catalyst. The catalytic activity retention of Pt-graphene oxide-8 wt.% CeO2 nanocomposites reaches as high as 69% after 5000 CV-cycles at a high voltage range of 0.8-1.23 V, in contrast to 19% for that of the Pt-graphene oxide composites. The excellent durability of the Pt-CeO2 nanocubes-graphene oxide catalyst is attributed to the free radical scavenging activity of CeO2, which significantly slows down the chemical degradation of Nafion binder in catalytic layers, and then alleviates the decay of Pt catalysts, resulting in the excellent cycle life of Pt-CeO2-graphene oxide nanocomposite catalysts. Additionally, the performance of single cell assembled with Nafion 211 membrane and Pt-CeO2-graphene oxide catalysts with different CeO2 contents in the cathode as well as the Pt-C catalysts in the anode are also recorded and discussed in this study.

CeO2 nanocubes-graphene oxide as durable and highly active catalyst support for proton exchange membrane fuel cell

NASA Astrophysics Data System (ADS)

Lei, M.; Wang, Z. B.; Li, J. S.; Tang, H. L.; Liu, W. J.; Wang, Y. G.

2014-12-01

Rapid degradation of cell performance still remains a significant challenge for proton exchange membrane fuel cell (PEMFC). In this work, we develop novel CeO2 nanocubes-graphene oxide nanocomposites as durable and highly active catalyst support for proton exchange membrane fuel cell. We show that the use of CeO2 as the radical scavenger in the catalysts remarkably improves the durability of the catalyst. The catalytic activity retention of Pt-graphene oxide-8 wt.% CeO2 nanocomposites reaches as high as 69% after 5000 CV-cycles at a high voltage range of 0.8-1.23 V, in contrast to 19% for that of the Pt-graphene oxide composites. The excellent durability of the Pt-CeO2 nanocubes-graphene oxide catalyst is attributed to the free radical scavenging activity of CeO2, which significantly slows down the chemical degradation of Nafion binder in catalytic layers, and then alleviates the decay of Pt catalysts, resulting in the excellent cycle life of Pt-CeO2-graphene oxide nanocomposite catalysts. Additionally, the performance of single cell assembled with Nafion 211 membrane and Pt-CeO2-graphene oxide catalysts with different CeO2 contents in the cathode as well as the Pt-C catalysts in the anode are also recorded and discussed in this study.

Novel nanowire-structured polypyrrole-cobalt composite as efficient catalyst for oxygen reduction reaction

PubMed Central

Yuan, Xianxia; Li, Lin; Ma, Zhong; Yu, Xuebin; Wen, Xiufang; Ma, Zi-Feng; Zhang, Lei; Wilkinson, David P.; Zhang, Jiujun

2016-01-01

A novel nanowire-structured polypyrrole-cobalt composite, PPy-CTAB-Co, is successfully synthesized with a surfactant of cetyltrimethylammounium bromide (CTAB). As an electro-catalyst towards oxygen reduction reaction (ORR) in alkaline media, this PPy-CTAB-Co demonstrates a superior ORR performance when compared to that of granular PPy-Co catalyst and also a much better durability than the commercial 20 wt% Pt/C catalyst. Physiochemical characterization indicates that the enhanced ORR performance of the nanowire PPy-CTAB-Co can be attributed to the high quantity of Co-pyridinic-N groups as ORR active sites and its large specific surface area which allows to expose more active sites for facilitating oxygen reduction reaction. It is expected this PPy-CTAB-Co would be a good candidate for alkaline fuel cell cathode catalyst. PMID:26860889

Nano-Structured Bio-Inorganic Hybrid Material for High Performing Oxygen Reduction Catalyst.

PubMed

Jiang, Rongzhong; Tran, Dat T; McClure, Joshua P; Chu, Deryn

2015-08-26

In this study, we demonstrate a non-Pt nanostructured bioinorganic hybrid (BIH) catalyst for catalytic oxygen reduction in alkaline media. This catalyst was synthesized through biomaterial hemin, nanostructured Ag-Co alloy, and graphene nano platelets (GNP) by heat-treatment and ultrasonically processing. This hybrid catalyst has the advantages of the combined features of these bio and inorganic materials. A 10-fold improvement in catalytic activity (at 0.8 V vs RHE) is achieved in comparison of pure Ag nanoparticles (20-40 nm). The hybrid catalyst reaches 80% activity (at 0.8 V vs RHE) of the state-of-the-art catalyst (containing 40% Pt and 60% active carbon). Comparable catalytic stability for the hybrid catalyst with the Pt catalyst is observed by chronoamperometric experiment. The hybrid catalyst catalyzes 4-electron oxygen reduction to produce water with fast kinetic rate. The rate constant obtained from the hybrid catalyst (at 0.6 V vs RHE) is 4 times higher than that of pure Ag/GNP catalyst. A catalytic model is proposed to explain the oxygen reduction reaction at the BIH catalyst.

Method of performing sugar dehydration and catalyst treatment

DOEpatents

Hu, Jianli [Kennewick, WA; Holladay, Johnathan E [Kennewick, WA; Zhang, Xinjie [Burlington, MA; Wang, Yong [Richland, WA

2010-06-01

The invention includes a method of treating a solid acid catalyst. After exposing the catalyst to a mixture containing a sugar alcohol, the catalyst is washed with an organic solvent and is then exposed to a second reaction mixture. The invention includes a process for production of anhydrosugar alcohol. A solid acid catalyst is provided to convert sugar alcohol in a first sample to an anhydrosugar alcohol. The catalyst is then washed with an organic solvent and is subsequently utilized to expose a second sample. The invention includes a method for selective production of an anhydrosugar. A solid acid catalyst is provided within a reactor and anhydrosugar alcohol is formed by flowing a starting sugar alcohol into the reactor. The acid catalyst is then exposed to an organic solvent which allows a greater amount of additional anhydrosugar to be produced than would occur without exposing the acid catalyst to the organic solvent.

Relevance of the Interaction between the M-Phthalocyanines and Carbon Nanotubes in the Electroactivity toward ORR.

PubMed

González-Gaitán, Carolina; Ruiz-Rosas, Ramiro; Morallón, Emilia; Cazorla-Amorós, Diego

2017-10-31

In this work, the influence of the interaction between the iron and cobalt-phthalocyanines (FePc and CoPc) and carbon nanotubes (CNTs) used as support in the electroactivity toward oxygen reduction reaction (ORR) in alkaline media has been investigated. A series of thermal treatments were performed on these materials in order to modify the interaction between the CNTs and the phthalocyanines. The FePc-based catalysts showed the highest activity, with comparable performance to the state-of-the-art Pt-Vulcan catalyst. A heat treatment at 400 °C improved the activity of FePc-based catalysts, while the use of higher temperatures or oxidative atmosphere rendered the decomposition of the macrocyclic compound and consequently the loss of the electrochemical activity of the complex. CoPc-based catalysts performance was negatively affected for all of the tested treatments. Thermogravimetric analyses demonstrated that the FePc was stabilized when loaded onto CNTs, while CoPc did not show such a feature, pointing to a better interaction of the FePc instead of the CoPc. Interestingly, electrochemical measurements demonstrated an improvement of the electron transfer rate in thermally treated FePc-based catalysts. They also allowed us to assess that only 15% of the iron in the catalyst was available for direct electron transfer. This is the same iron amount that remains on the catalyst after a strong acid washing with concentrated HCl (ca. 0.3 wt %), which is enough to deliver a comparable ORR activity. Durability tests confirmed that the catalysts deactivation occurs at a slower rate in those catalysts where FePc is strongly attached to the CNT surface. Thus, the highest ORR activity seems to be provided by those FePc molecules that are strongly attached to the CNT surface, pointing out the relevance of the interaction between the support and the FePc in these catalysts.

Simulations of inorganic-bioorganic interfaces to discover new materials: insights, comparisons to experiment, challenges, and opportunities.

PubMed

Heinz, Hendrik; Ramezani-Dakhel, Hadi

2016-01-21

Natural and man-made materials often rely on functional interfaces between inorganic and organic compounds. Examples include skeletal tissues and biominerals, drug delivery systems, catalysts, sensors, separation media, energy conversion devices, and polymer nanocomposites. Current laboratory techniques are limited to monitor and manipulate assembly on the 1 to 100 nm scale, time-consuming, and costly. Computational methods have become increasingly reliable to understand materials assembly and performance. This review explores the merit of simulations in comparison to experiment at the 1 to 100 nm scale, including connections to smaller length scales of quantum mechanics and larger length scales of coarse-grain models. First, current simulation methods, advances in the understanding of chemical bonding, in the development of force fields, and in the development of chemically realistic models are described. Then, the recognition mechanisms of biomolecules on nanostructured metals, semimetals, oxides, phosphates, carbonates, sulfides, and other inorganic materials are explained, including extensive comparisons between modeling and laboratory measurements. Depending on the substrate, the role of soft epitaxial binding mechanisms, ion pairing, hydrogen bonds, hydrophobic interactions, and conformation effects is described. Applications of the knowledge from simulation to predict binding of ligands and drug molecules to the inorganic surfaces, crystal growth and shape development, catalyst performance, as well as electrical properties at interfaces are examined. The quality of estimates from molecular dynamics and Monte Carlo simulations is validated in comparison to measurements and design rules described where available. The review further describes applications of simulation methods to polymer composite materials, surface modification of nanofillers, and interfacial interactions in building materials. The complexity of functional multiphase materials creates opportunities to further develop accurate force fields, including reactive force fields, and chemically realistic surface models, to enable materials discovery at a million times lower computational cost compared to quantum mechanical methods. The impact of modeling and simulation could further be increased by the advancement of a uniform simulation platform for organic and inorganic compounds across the periodic table and new simulation methods to evaluate system performance in silico.

Catalytic wet oxidation of phenol in a trickle bed reactor over a Pt/TiO2 catalyst.

PubMed

Maugans, Clayton B; Akgerman, Aydin

2003-01-01

Catalytic wet oxidation of phenol was studied in a batch and a trickle bed reactor using 4.45% Pt/TiO2 catalyst in the temperature range 150-205 degrees C. Kinetic data were obtained from batch reactor studies and used to model the reaction kinetics for phenol disappearance and for total organic carbon disappearance. Trickle bed experiments were then performed to generate data from a heterogeneous flow reactor. Catalyst deactivation was observed in the trickle bed reactor, although the exact cause was not determined. Deactivation was observed to linearly increase with the cumulative amount of phenol that had passed over the catalyst bed. Trickle bed reactor modeling was performed using a three-phase heterogeneous model. Model parameters were determined from literature correlations, batch derived kinetic data, and trickle bed derived catalyst deactivation data. The model equations were solved using orthogonal collocations on finite elements. Trickle bed performance was successfully predicted using the batch derived kinetic model and the three-phase reactor model. Thus, using the kinetics determined from limited data in the batch mode, it is possible to predict continuous flow multiphase reactor performance.

Heterometallic metal-organic framework-templated synthesis of porous Co3O4/ZnO nanocage catalysts for the carbonylation of glycerol

NASA Astrophysics Data System (ADS)

Lü, Yinyun; Jiang, Yating; Zhou, Qi; Li, Yunmei; Chen, Luning; Kuang, Qin; Xie, Zhaoxiong; Zheng, Lansun

2017-12-01

The efficient synthesis of glycerol carbonate (GLC) has recently received great attention due to its significance in reducing excess glycerol in biodiesel production as well as its promising applications in several industrial fields. However, the achievement of high conversion and high selectivity of GLC from glycerol in heterogeneous catalytic processes remains a challenge due to the absence of high-performance solid catalysts. Herein, highly porous nanocage catalysts composed of well-mixed Co3O4 and ZnO nanocrystals were successfully fabricated via a facile heterometallic metal-organic framework (MOF)-templated synthetic route. Benefiting from a high porosity and the synergistic effect between Co3O4 and ZnO, the as-prepared composite catalysts exhibited a significantly enhanced production efficiency of GLC in the carbonylation reaction of glycerol with urea compared to the single-component counterparts. The yield of GLC over the Co50Zn50-350 catalyst reached 85.2%, with 93.3% conversion and near 91% GLC selectivity, and this catalytic performance was superior to that over most heterogeneous catalysts. More importantly, the proposed templated synthetic strategy of heterometallic MOFs facilitates the regulation of catalyst composition and surface structure and can therefore be potentially extended in the tailoring of other metal oxide composite catalysts.

Enhancement of Electrode Stability Using Platinum-Cobalt Nanocrystals on a Novel Composite SiCTiC Support.

PubMed

Millán, María; Zamora, Héctor; Rodrigo, Manuel A; Lobato, Justo

2017-02-22

PtCo alloy catalysts for high temperature PEMFCs (protonic exchange membrane fuel cells) were synthesized on a novel noncarbonaceous support (SiCTiC) using the impregnation method with NaBH 4 as the reducing agent at different synthesis temperatures to evaluate the effect of this variable on their physicochemical and electrochemical properties. The catalysts were characterized by inductively coupled plasma optical emission spectrometry, scanning electron microscopy-energy dispersive X-ray spectroscopy, X-ray diffraction, transmission electron microscope-energy dispersive X-ray,and temperature-programmed reduction. In addition, the electrochemical characterization (i.e., cyclic voltammetry, oxygen reduction reaction, and chronoamperometry) was carried out with a rotating disk electrode. For the cyclic voltammetry investigation, 400 cycles were performed in hot phosphoric acid and a half-cell to evaluate the stability of the synthesized catalysts. The catalyst synthesized on SiCTiC exhibited excellent durability compared to the catalyst synthesized on a Vulcan support. In addition, all synthesized catalysts exhibited better catalytic activity than that of the PtCo/C catalysts. The best results were observed for the catalyst synthesized at 80 °C due to its shorter Pt-Pt nearest-neighbor and higher alloy degree. Finally, a preliminary stability test was conducted in an HT-PEMFC, and promising results in terms of stability and performance were observed.

One-Pot Process for Hydrodeoxygenation of Lignin to Alkanes Using Ru-Based Bimetallic and Bifunctional Catalysts Supported on Zeolite Y

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Hongliang; Ruan, Hao; Feng, Maoqi

2017-03-16

The synthesis of high-efficiency and low-cost multifunctional catalysts for hydrodeoxygenation (HDO) of waste lignin into advanced biofuels is crucial for enhancing current biorefinery processes. Inexpensive transition metals, including Fe, Ni, Cu, Zn, were severally co-loaded with Ru on HY zeolite to form bimetallic and bifunctional catalysts. These catalysts were subsequently tested for HDO conversion of softwood lignin and several lignin model compounds. Results indicated that the inexpensive earth abundant metals could modulate the hydrogenolysis activity of Ru and decrease the yield of low molecular weight gaseous side-products. Among all the prepared catalysts, Ru-Cu/HY showed the best HDO performance, giving themore » highest selectivity to hydrocarbon products. The improved catalytic performance of Ru-Cu/HY was probably due to the following three factors: (1) high total and strong acid sites, (2) good dispersion of metal species and limited segregation, (3) high adsorption capacity for polar fractions, including hydroxyl groups and ether bonds. Moreover, all the bifunctional catalysts were proven to be superior over the combination catalysts of Ru/Al2O3 and HY zeolite, and this could be attributed to the “intimacy criterion”. The practical use of the designed catalysts would be promising in lignin valorization.« less

Highly selective oxidation of styrene to benzaldehyde over a tailor-made cobalt oxide encapsulated zeolite catalyst.

PubMed

Liu, Jiangyong; Wang, Zihao; Jian, Panming; Jian, Ruiqi

2018-05-01

A tailor-made catalyst with cobalt oxide particles encapsulated into ZSM-5 zeolites (Co 3 O 4 @HZSM-5) was prepared via a hydrothermal method with the conventional impregnated Co 3 O 4 /SiO 2 catalyst as the precursor and Si source. Various characterization results show that the Co 3 O 4 @HZSM-5 catalyst has well-organized structure with Co 3 O 4 particles compatibly encapsulated in the zeolite crystals. The Co 3 O 4 @HZSM-5 catalyst was employed as an efficient catalyst for the selective oxidation of styrene to benzaldehyde with hydrogen peroxide as a green and economic oxidant. The effect of various reaction conditions including reaction time, reaction temperature, different kinds of solvents, styrene/H 2 O 2 molar ratio and catalyst dosage on the catalytic performance were systematically investigated. Under the optimized reaction condition, the yield of benzaldehyde can achieve 78.9% with 96.8% styrene conversion and 81.5% benzaldehyde selectivity. Such an excellent catalytic performance can be attributed to the synergistic effect between the confined reaction environment and the proper acidic property. In addition, the reaction mechanism with Co 3 O 4 @HZSM-5 as the catalyst for the selective oxidation of styrene to benzaldehyde was reasonably proposed. Copyright © 2018 Elsevier Inc. All rights reserved.

Evaluation of the Effect of Water Vapor On the Performance of NASA's NMRO Catalysts for Carbon Monoxide Oxidation

NASA Technical Reports Server (NTRS)

Akyurtlu, Ates; Akyurtlu, Jale F.; Ammons, Vaughnery; Battle, Taikelia; Gay, Amy; Bray, Kyle; Washington, Boe; Schryer, David (Technical Monitor); Jordan, Jeff (Technical Monitor)

2002-01-01

The Noble Metal Reducible Oxide (NMRO) catalysts for the low temperature oxidation of carbon monoxide were developed by NASA for the reoxidation of carbon monoxide which forms by the dissociation of carbon dioxide during the operation of sealed carbon dioxide lasers. The NMRO catalyst, which consists of a noble metal in conjunction with a reducible metal oxide, was evaluated under conditions that will be encountered in a CO2 laser operation, namely temperatures in the range 298 to 373 K and no significant reaction gas components other than CO, CO2 and O2. The NMRO catalysts may have significant potential for spin-off applications such as the prevention of carbon monoxide build-up in closed spaces as in space vehicle cabins or submarines, and the elimination of the cold start-up problem of automobile exhaust catalysts. The most significant difference in the conditions of these possible future applications is the high moisture content of the gases to be processed. Lack of understanding of the effects of water vapor and high temperature on catalyst activity and operation for extended periods are currently the main stumbling blocks for the transfer of this NASA technology to be used for commercial purposes. In the original proposal the following objectives were stated: To obtain experimental data on the adsorption, desorption and reaction characteristics of CO and CO2 the catalysts under high moisture conditions; to collect evidence on the presence of carbonate and hydroxyl surface species and their involvement in the CO oxidation mechanism; and to model the reaction system using a Monte-Carlo simulation to gain insight on the various steps involved. After the work has commenced the NASA technical monitor Mr. David Scheyer informed us that there was increased interest in the possible use of the NMRO catalysts as automobile exhaust catalysts and therefore NASA wanted to know whether the catalysts can operate at high temperatures as well as with high moisture gases. At that meeting it was decided that investigation of the high temperature performance of the NMRO catalysts should be given priority and replace the Monte-Carlo simulation objective. As a result, the modified objectives of the investigation were taken as the investigation of the high-temperature activity of the NMRO catalysts, and the effect of water vapor on the performance of these catalysts.

Poisoning of a silica supported cobalt catalyst due to the presence of sulfur impurities in syngas during Fischer-Tropsch synthesis: Effect of chelating agent

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bambal, A.S.; Gardner, T.H.; Kugler, E.L.

2012-01-01

Sulfur compounds that are generally found in syngas derived from coal and biomass are a poison to Fischer-Tropsch (FT) catalysts. The presence of sulfur impurities in the ppm range can limit the life of a FT catalyst to a few hours or a few days. In this study, FT synthesis was carried out in a fixed-bed reactor at 230 °C, 20 bar, and 13,500 Ncm3/h/gcat for 72 h using syngas with H2/CO = 2.0. Cobalt-based catalysts were subjected to poisoning by 10 and 50 ppm sulfur in the syngas. The performance of FT catalyst was compared in context of syngasmore » conversion, product selectivities and yields, during the poisoning as well as post-poisoning stages. At both the impurity concentrations, the sulfur was noted to cause permanent loss in the activity, possibly by adsorbing irreversibly on the surface. The sulfur poison affects the hydrogenation and the chain-propagation ability of the catalysts, and shifts the product selectivity towards short-chain hydrocarbons with higher percentages of olefins. Additional diffusion limitations caused due to sulfur poisoning are thought to alter the product selectivity. The shifts in product selectivities suggest that the sulfur decreases the ability of the catalyst to form C-C bonds to produce longer-chain hydrocarbons. The selective blocking of sulfur is thought to affect the hydrogenation ability on the catalyst, resulting in more olefins in the product after sulfur poisoning. The sulfur poisoning on the cobalt catalyst is expected to cause an increase in the number of sites responsible for WGS or to influence the Boudouard reaction, resulting in a higher CO2 selectivity. Both the sites responsible for CO adsorptions as well as the sites for chain growth are poisoned during the poisoning. Additionally, the performance of a base-case cobalt catalyst is compared with that of catalysts modified by chelating agents (CAs). The superior performance of CA-modified catalysts during sulfur poisoning is attributed to the presence of smaller crystallite sizes and higher dispersions of cobalt on the support. Finally, the sulfur deactivation data is modeled by a simple kinetic expression to determine the deactivation constant, deactivation rates and half-life of the FT catalyst.« less

Magnetic silica supported palladium catalyst: synthesis of allyl aryl ethers in water

EPA Science Inventory

A simple and benign procedure for the synthesis of aryl allyl ethers has been developed using phenols, allyl acetates and magnetically recyclable silica supported palladium catalyst in water; performance of reaction in air and easy separation of the catalyst using an external mag...

40 CFR 1042.655 - Special certification provisions for-Category 3 engines with aftertreatment.

Code of Federal Regulations, 2010 CFR

2010-07-01

... demonstrating for certification that catalyst-equipped engines (or engines equipped with other aftertreatment... engine-out emissions comply with the Tier 2 standards. The catalyst material or other aftertreatment... points. This catalyst or aftertreatment testing may be performed on a benchscale. (c) Engineering...

Non-noble electrocatalysts for alkaline fuel cells

NASA Technical Reports Server (NTRS)

Sarangapani, S.; Lessner, P.; Manoukian, M.; Giner, J.

1989-01-01

Carbons activated with macrocyclics have attracted increasing attention as alternative electrocatalysts for oxygen reduction. Initial activity of these catalysts is good, but performance declines rapidly. Pyrolyzing the macrocyclic on the carbon support leads to enhanced stability and the catalysts retain good activity. The approach described is designed to develop bulk doped catalysts with similar structures to pyrolyzed macrocyclic catalysts. The transition metal and coordinated ligands are dispersed throughout the bulk of the conductive carbon skeleton. Two approaches to realizing this concept are being pursued, both involving the doping of carbon precursors. In one approach, the precursor is a solid phase carbon-containing ion-exchange resin. The precursor is doped with a transition metal and/or nitrogen, and the resulting mixture is pyrolyzed. In the other approach, the precursor is a gas-phase hydrocarbon. This is introduced with a transition metal species and nitrogen species into a reactor and pyrolyzed. Several studies have been conducted to determine if there is a synergistic effect between the transition metal and nitrogen and the effect of different methods of introducing the metal-nitrogen (M-N) coordination on performance. One approach was to introduce the metal and nitrogen separately, for example, by sequentially doping FeCl3 and NH4OH into the resin. Catalysts were prepared from an undoped ion-exchange resin, a resin doped only with N, a resin doped only with Fe, and a resin doped with both Fe and N. Introduction of nitrogen alone has no beneficial effect on the performance of the catalysts. The introduction of the Fe alone significantly improves the performance in both the high and low current density regions. When both Fe and N are introduced, the performance at lower current densities (catalytic activity) is increased beyond that of the Fe-doped carbon, but the performance at higher current densities is similar to the carbon containing only Fe. Catalysts prepared from resins-Fe(bipy)3SO4 precursors have performance that is only slightly less then CoTMPP adsorbed and pyroloyzed on Vulcan XC-72. Their performance is much better than carbons which have had the N and Fe introduced separately.

The use of catalyst to enhance the wet oxidation process.

PubMed

Maugans, C; Kumfer, B

2007-01-01

Wet oxidation tests were performed on two pure compound streams: acetic acid and ammonia; and on two wastewater streams: acrylic acid wastewater and sulphide laden spent caustic. Test results showed that Mn/Ce and Pt/TiO2 were effective catalysts that greatly enhanced acetic acid, ammonia and acrylic acid wastewater destruction. However, the Mn/Ce catalyst performance appears to be inhibited by concentrated salts dissolved in solution. This could limit the applicability of this catalyst for the treatment of brackish wastewaters. Zr, Ce and Ce nanoparticles were also shown to exhibit some catalytic activity, however not to the extent of the Mn/Ce and the Pt/TiO2.

Subnanometer Cobalt-Hydroxide-Anchored N-Doped Carbon Nanotube Forest for Bifunctional Oxygen Catalyst.

PubMed

Kim, Ji Eun; Lim, Joonwon; Lee, Gil Yong; Choi, Sun Hee; Maiti, Uday Narayan; Lee, Won Jun; Lee, Ho Jin; Kim, Sang Ouk

2016-01-27

Electrochemical oxygen redox reactions are the crucial elements for energy conversion and storage including fuel cells and metal air batteries. Despite tremendous research efforts, developing high-efficient, low-cost, and durable bifunctional oxygen catalysts remains a major challenge. We report a new class of hybrid material consisting of subnanometer thick amorphous cobalt hydroxide anchored on NCNT as a durable ORR/OER bifunctional catalyst. Although amorphous cobalt species-based catalysts are known as good OER catalysts, hybridizing with NCNT successfully enhanced ORR activity by promoting a 4e reduction pathway. Abundant charge carriers in amorphous cobalt hydroxide are found to trigger the superior OER activity with high current density and low Tafel slope as low as 36 mV/decade. A remarkably high OER turnover frequency (TOF) of 2.3 s(-1) at an overpotential of 300 mV was obtained, one of the highest values reported so far. Moreover, the catalytic activity was maintained over 120 h of cycling. The unique subnanometer scale morphology of amorphous hydroxide cobalt species along with intimate cobalt species-NCNT interaction minimizes the deactivation of catalyst during prolonged repeated cycles.

Removal of free fatty acid in Palm Fatty Acid Distillate using sulfonated carbon catalyst derived from biomass wastefor biodiesel production

NASA Astrophysics Data System (ADS)

Hidayat, Arif; Rochmadi; Wijaya, Karna; Budiman, Arief

2016-01-01

In this research, the esterification of PFAD using the sulfonatedcoconut shell biochar catalyst was studied. Carbon solid catalysts were prepared by a sulfonation of carbonized coconut shells. The performances of the catalysts were evaluated in terms of the reaction temperatures, the molar ratios of methanol to PFAD, the catalyst loading and the reaction times. The reusability of the solid acid carbon catalysts was also studied in this work. The results indicated that the FFA conversion was significantly increased with increasing catalyst loading and reaction times. It can be concluded that the optimal conditions were an PFAD to methanol molar ratio of 1:12, the amount of catalyst of 10%w, and reaction temperature of 60oC.At this optimum condition, the conversion to biodieselreached 88%.

Method of improving fuel cell performance by removing at least one metal oxide contaminant from a fuel cell electrode

DOEpatents

Kim, Yu Seung [Los Alamos, NM; Choi, Jong-Ho [Los Alamos, NM; Zelenay, Piotr [Los Alamos, NM

2009-08-18

A method of removing contaminants from a fuel cell catalyst electrode. The method includes providing a getter electrode and a fuel cell catalyst electrode having at least one contaminant to a bath and applying a voltage sufficient to drive the contaminant from the fuel cell catalyst electrode to the getter electrode. Methods of removing contaminants from a membrane electrode assembly of a fuel cell and of improving performance of a fuel cell are also provided.

Novel nano-semiconductor film layer supported nano-Pd Complex Nanostructured Catalyst Pd/Ⓕ-MeOx/AC for High Efficient Selective Hydrogenation of Phenol to Cyclohexanone.

PubMed

Si, Jiaqi; Ouyang, Wenbing; Zhang, Yanji; Xu, Wentao; Zhou, Jicheng

2017-04-28

Supported metal as a type of heterogeneous catalysts are the most widely used in industrial processes. High dispersion of the metal particles of supported catalyst is a key factor in determining the performance of such catalysts. Here we report a novel catalyst Pd/Ⓕ-MeO x /AC with complex nanostructured, Pd nanoparticles supported on the platelike nano-semiconductor film/activated carbon, prepared by the photocatalytic reduction method, which exhibited high efficient catalytic performance for selective hydrogenation of phenol to cyclohexanone. Conversion of phenol achieved up to more than 99% with a lower mole ratio (0.5%) of active components Pd and phenol within 2 h at 70 °C. The synergistic effect of metal nanoparticles and nano-semiconductors support layer and the greatly increasing of contact interface of nano-metal-semiconductors may be responsible for the high efficiency. This work provides a clear demonstration that complex nanostructured catalysts with nano-metal and nano-semiconductor film layer supported on high specific surface AC can yield enhanced catalytic activity and can afford promising approach for developing new supported catalyst.

Effects of K and Pt promoters on the performance of cobalt catalyst supported on CNTs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zabidi, Noor Asmawati Mohd, E-mail: noorasmawati-mzabidi@petronas.com.my; Ali, Sardar, E-mail: alikhan-635@yahoo.com; Subbarao, Duvvuri, E-mail: duvvuri-subbarao@petronas.com.my

2014-10-24

This paper presents a comparative study on the effects of incorporation of potassium (K) and platinum (Pt) as promoters on the physicochemical properties of cobalt catalyst. The catalyst was prepared by a wet impregnation method on a CNTs support. Samples were characterized using transmission electron microscopy (TEM), H{sub 2}-temperature-programmed reduction (TPR) and X-ray photoelectron spectroscopy (XPS) techniques. Fischer-Tropsch Synthesis (FTS) was carried out in a fixed-bed microreactor at 543 K and 1 atm, with H{sub 2}/CO = 2v/v and space velocity, SV of 12 L/g.h for 5 hours. The K-promoted and Pt-promoted Co catalysts have different physicochemical properties and catalytic performances comparedmore » to that of the un-promoted Co catalyst. XPS analysis revealed that K and Pt promoters induced electronic modifications as exhibited by the shifts in the Co binding energies. Incorporation of 0.06 wt% K and 0.06 wt% Pt in Co/CNTs catalyst resulted in an increase in the CO conversion and C{sub 5+} selectivity and a decrease in methane selectivity. Potassium was found to be a better promoter for Co/CNTs catalyst compared to platinum.« less

Effects of K and Pt promoters on the performance of cobalt catalyst supported on CNTs

NASA Astrophysics Data System (ADS)

Zabidi, Noor Asmawati Mohd; Ali, Sardar; Subbarao, Duvvuri

2014-10-01

This paper presents a comparative study on the effects of incorporation of potassium (K) and platinum (Pt) as promoters on the physicochemical properties of cobalt catalyst. The catalyst was prepared by a wet impregnation method on a CNTs support. Samples were characterized using transmission electron microscopy (TEM), H2-temperature-programmed reduction (TPR) and X-ray photoelectron spectroscopy (XPS) techniques. Fischer-Tropsch Synthesis (FTS) was carried out in a fixed-bed microreactor at 543 K and 1 atm, with H2/ CO = 2v / v and space velocity, SV of 12 L/g.h for 5 hours. The K-promoted and Pt-promoted Co catalysts have different physicochemical properties and catalytic performances compared to that of the un-promoted Co catalyst. XPS analysis revealed that K and Pt promoters induced electronic modifications as exhibited by the shifts in the Co binding energies. Incorporation of 0.06 wt% K and 0.06 wt% Pt in Co/CNTs catalyst resulted in an increase in the CO conversion and C5+ selectivity and a decrease in methane selectivity. Potassium was found to be a better promoter for Co/CNTs catalyst compared to platinum.

One-Pot Process for Hydrodeoxygenation of Lignin to Alkanes Using Ru-Based Bimetallic and Bifunctional Catalysts Supported on Zeolite Y.

PubMed

Wang, Hongliang; Ruan, Hao; Feng, Maoqi; Qin, Yuling; Job, Heather; Luo, Langli; Wang, Chongmin; Engelhard, Mark H; Kuhn, Erik; Chen, Xiaowen; Tucker, Melvin P; Yang, Bin

2017-04-22

The synthesis of high-efficiency and low-cost catalysts for hydrodeoxygenation (HDO) of waste lignin to advanced biofuels is crucial for enhancing current biorefinery processes. Inexpensive transition metals, including Fe, Ni, Cu, and Zn, were severally co-loaded with Ru on HY zeolite to form bimetallic and bifunctional catalysts. These catalysts were subsequently tested for HDO conversion of softwood lignin and several lignin model compounds. Results indicated that the inexpensive earth-abundant metals could modulate the hydrogenolysis activity of Ru and decrease the yield of low-molecular-weight gaseous products. Among these catalysts, Ru-Cu/HY showed the best HDO performance, affording the highest selectivity to hydrocarbon products. The improved catalytic performance of Ru-Cu/HY was probably a result of the following three factors: (1) high total and strong acid sites, (2) good dispersion of metal species and limited segregation, and (3) high adsorption capacity for polar fractions, including hydroxyl groups and ether bonds. Moreover, all bifunctional catalysts proved to be superior over the combination catalysts of Ru/Al 2 O 3 and HY zeolite. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Preparation and characterizaton of CaO nanoparticle for biodiesel production

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gupta, Jharna, E-mail: onlinejharna@gmail.com; Agarwal, Madhu, E-mail: madhunaresh@gmail.com

Nanoparticle of CaO from calcium Nitrate (CaO/CaN) and Snail shell (CaO/SS) are successfully synthesized by method as described in the literature and used as an active and stable catalyst for the biodiesel production. These catalysts are characterized by Fourier-transform infrared spectra (FT-IR), X-ray diffraction (XRD), and thermal gravimetric analysis (TGA). The average crystalline size in nanometer was also calculated by Debye–Scherrer equation. The performance of the CaO/CaN and CaO/SS were tested for their catalytic activity via transesterification process and it was found that biodiesel yield has been increased from 93 to 96%. The optimum conditions for the highest yield weremore » 8wt% catalyst loading, 65°C temperature, 12:1 methanol/oil molar ratio, and 6 h for reaction time. The nano catalyst from snail shell exhibits excellent catalytic activity and stability for the transesterification reaction, which suggested that this catalyst would be potentially used as a solid base nano catalyst for biodiesel production. In order to examine the reusability of catalyst developed from snail shell, five transesterification reaction cycles were also performed.« less

Electrical enhancement of direct methanol fuel cells by metal-plasma ion implantation Pt-Ru/C multilayer catalysts.

PubMed

Weng, Ko-Wei; Chen, Yung-Lin; Chen, Ya-Chi; Lin, Tai-Nan

2009-02-01

Direct methanol fuel cells (DMFC) have been widely studied owing to their simple cell configuration, high volume energy density, short start-up time, high operational reliability and other favorable characteristics. However, major limitations include high production cost, poisoning of the catalyst and methanol crossover. This study adopts a simple technique for preparing Pt-Ru/C multilayer catalysts, including magnetron sputtering (MS) and metal-plasma ion implantation (MPII). The Pt catalysts were sputtered onto the gas diffusion layer (GDL), followed by the implantation of Ru catalysts using MPII (at an accelerating voltage of 20 kV and an implantation dose of 1 x 10(16) ions/cm2). Pt-Ru is repeatedly processed to prepare Pt-Ru/C multilayer catalysts. The catalyst film structure and microstructure were analyzed by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and scanning electronic microscopy (SEM), respectively. The cell performance was tested using a potential stat/galvano-stat. The results reveal that the membrane electrode assembly (MEA) of four multilayer structures enhances the cell performance of DMFC. The measured power density is 2.2 mW/cm2 at a methanol concentration of 2 M, with an OCV of 0.493 V.

A new class of Cu/ZnO catalysts derived from zincian georgeite precursors prepared by co-precipitation† †Electronic supplementary information (ESI) available. See DOI: 10.1039/c6sc04130b Click here for additional data file.

PubMed Central

Smith, Paul J.; Kondrat, Simon A.; Chater, Philip A.; Yeo, Benjamin R.; Shaw, Greg M.; Lu, Li; Bartley, Jonathan K.; Taylor, Stuart H.; Spencer, Michael S.; Kiely, Christopher J.; Kelly, Gordon J.; Park, Colin W.

2017-01-01

Zincian georgeite, an amorphous copper–zinc hydroxycarbonate, has been prepared by co-precipitation using acetate salts and ammonium carbonate. Incorporation of zinc into the georgeite phase and mild ageing conditions inhibits crystallisation into zincian malachite or aurichalcite. This zincian georgeite precursor was used to prepare a Cu/ZnO catalyst, which exhibits a superior performance to a zincian malachite derived catalyst for methanol synthesis and the low temperature water–gas shift (LTS) reaction. Furthermore, the enhanced LTS activity and stability in comparison to that of a commercial Cu/ZnO/Al2O3 catalyst, indicates that the addition of alumina as a stabiliser may not be required for the zincian georgeite derived Cu/ZnO catalyst. The enhanced performance is partly attributed to the exclusion of alkali metals from the synthesis procedure, which are known to act as catalyst poisons. The effect of residual sodium on the microstructural properties of the catalyst precursor was investigated further from preparations using sodium carbonate. PMID:28451351

One-pot process for hydrodeoxygenation of lignin to alkanes using Ru-based bimetallic and bifunctional catalysts supported on zeolite Y

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Hongliang; Ruan, Hao; Feng, Maoqi

2017-02-22

Here, the synthesis of high-efficiency and low-cost catalysts for hydrodeoxygenation (HDO) of waste lignin to advanced biofuels is crucial for enhancing current biorefinery processes. Inexpensive transition metals, including Fe, Ni, Cu, and Zn, were severally co-loaded with Ru on HY zeolite to form bimetallic and bifunctional catalysts. These catalysts were subsequently tested for HDO conversion of softwood lignin and several lignin model compounds. Results indicated that the inexpensive earth-abundant metals could modulate the hydrogenolysis activity of Ru and decrease the yield of low-molecular-weight gaseous products. Among these catalysts, Ru-Cu/HY showed the best HDO performance, affording the highest selectivity to hydrocarbonmore » products. The improved catalytic performance of Ru-Cu/HY was probably a result of the following three factors: (1) high total and strong acid sites, (2) good dispersion of metal species and limited segregation, and (3) high adsorption capacity for polar fractions, including hydroxyl groups and ether bonds. Moreover, all bifunctional catalysts proved to be superior over the combination catalysts of Ru/Al 2O 3 and HY zeolite.« less

Efficient solar-to-fuels production from a hybrid microbial–water-splitting catalyst system

PubMed Central

Torella, Joseph P.; Gagliardi, Christopher J.; Chen, Janice S.; Bediako, D. Kwabena; Colón, Brendan; Way, Jeffery C.; Silver, Pamela A.; Nocera, Daniel G.

2015-01-01

Photovoltaic cells have considerable potential to satisfy future renewable-energy needs, but efficient and scalable methods of storing the intermittent electricity they produce are required for the large-scale implementation of solar energy. Current solar-to-fuels storage cycles based on water splitting produce hydrogen and oxygen, which are attractive fuels in principle but confront practical limitations from the current energy infrastructure that is based on liquid fuels. In this work, we report the development of a scalable, integrated bioelectrochemical system in which the bacterium Ralstonia eutropha is used to efficiently convert CO2, along with H2 and O2 produced from water splitting, into biomass and fusel alcohols. Water-splitting catalysis was performed using catalysts that are made of earth-abundant metals and enable low overpotential water splitting. In this integrated setup, equivalent solar-to-biomass yields of up to 3.2% of the thermodynamic maximum exceed that of most terrestrial plants. Moreover, engineering of R. eutropha enabled production of the fusel alcohol isopropanol at up to 216 mg/L, the highest bioelectrochemical fuel yield yet reported by >300%. This work demonstrates that catalysts of biotic and abiotic origin can be interfaced to achieve challenging chemical energy-to-fuels transformations. PMID:25675518

Integrated Biomass Gasification with Catalytic Partial Oxidation for Selective Tar Conversion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Lingzhi; Wei, Wei; Manke, Jeff

Biomass gasification is a flexible and efficient way of utilizing widely available domestic renewable resources. Syngas from biomass has the potential for biofuels production, which will enhance energy security and environmental benefits. Additionally, with the successful development of low Btu fuel engines (e.g. GE Jenbacher engines), syngas from biomass can be efficiently used for power/heat co-generation. However, biomass gasification has not been widely commercialized because of a number of technical/economic issues related to gasifier design and syngas cleanup. Biomass gasification, due to its scale limitation, cannot afford to use pure oxygen as the gasification agent that used in coal gasification.more » Because, it uses air instead of oxygen, the biomass gasification temperature is much lower than well-understood coal gasification. The low temperature leads to a lot of tar formation and the tar can gum up the downstream equipment. Thus, the biomass gasification tar removal is a critical technology challenge for all types of biomass gasifiers. This USDA/DOE funded program (award number: DE-FG36-O8GO18085) aims to develop an advanced catalytic tar conversion system that can economically and efficiently convert tar into useful light gases (such as syngas) for downstream fuel synthesis or power generation. This program has been executed by GE Global Research in Irvine, CA, in collaboration with Professor Lanny Schmidt's group at the University of Minnesota (UoMn). Biomass gasification produces a raw syngas stream containing H2, CO, CO2, H2O, CH4 and other hydrocarbons, tars, char, and ash. Tars are defined as organic compounds that are condensable at room temperature and are assumed to be largely aromatic. Downstream units in biomass gasification such as gas engine, turbine or fuel synthesis reactors require stringent control in syngas quality, especially tar content to avoid plugging (gum) of downstream equipment. Tar- and ash-free syngas streams are a critical requirement for commercial deployment of biomass-based power/heat co-generation and biofuels production. There are several commonly used syngas clean-up technologies: (1) Syngas cooling and water scrubbing has been commercially proven but efficiency is low and it is only effective at small scales. This route is accompanied with troublesome wastewater treatment. (2) The tar filtration method requires frequent filter replacement and solid residue treatment, leading to high operation and capital costs. (3) Thermal destruction typically operates at temperatures higher than 1000oC. It has slow kinetics and potential soot formation issues. The system is expensive and materials are not reliable at high temperatures. (4) In-bed cracking catalysts show rapid deactivation, with durability to be demonstrated. (5) External catalytic cracking or steam reforming has low thermal efficiency and is faced with problematic catalyst coking. Under this program, catalytic partial oxidation (CPO) is being evaluated for syngas tar clean-up in biomass gasification. The CPO reaction is exothermic, implying that no external heat is needed and the system is of high thermal efficiency. CPO is capable of processing large gas volume, indicating a very compact catalyst bed and a low reactor cost. Instead of traditional physical removal of tar, the CPO concept converts tar into useful light gases (eg. CO, H2, CH4). This eliminates waste treatment and disposal requirements. All those advantages make the CPO catalytic tar conversion system a viable solution for biomass gasification downstream gas clean-up. This program was conducted from October 1 2008 to February 28 2011 and divided into five major tasks. - Task A: Perform conceptual design and conduct preliminary system and economic analysis (Q1 2009 ~ Q2 2009) - Task B: Biomass gasification tests, product characterization, and CPO tar conversion catalyst preparation. This task will be conducted after completing process design and system economics analysis. Major milestones include identification of syngas cleaning requirements for proposed system design, identification and selection of tar compounds and 2 mixtures for use in CPO tests, and preparation of CPO catalysts for validation. (Q3 2009 ~ Q4 2009) - Task C: Test CPO with biomass gasification product gas. Optimize CPO performance with selected tar compounds. Optimize CPO performance with multi-component mixtures. Milestones include optimizing CPO catalysts design, collecting CPO experimental data for next stage kinetic modeling and understanding the effect of relative reactivities on ultimate tar conversion and syngas yields. (Q1 2010 ~ Q3 2010) - Task D: Develop tar CPO kinetic model with CPO kinetic model and modeling results as deliverables. (Q3 2010 ~ Q2 2011) - Task E: Project management and reporting. Milestone: Quarterly reports and presentations, final report, work presented at national technical conferences (Q1 2009 ~ Q2 2011) At the beginning of the program, IP landscaping was conducted to understand the operation of various types of biomass gasifiers, their unique syngas/tar compositions and potential tar mitigation options using the catalytic partial oxidation technology. A process simulation model was developed to quantify the system performance and economics impact of CPO tar removal technology. Biomass gasification product compositions used for performance evaluation tests were identified after literature review and system modeling. A reaction system for tar conversion tests was designed, constructed, with each individual component shaken-down in 2009. In parallel, University of Minnesota built a lab-scale unit and evaluated the tar removal performance using catalytic reforming. Benzene was used as the surrogate compound. The biomass gasification raw syngas composition was provided by GE through system studies. In 2010, GE selected different tar compounds and evaluated the tar removal effectiveness of the CPO catalyst. The catalytic performance was evaluated under different operating conditions, including catalyst geometry, S/C ratio, O/C ratio, GHSV, and N2 dilution. An understanding of how to optimize catalytic tar removal efficiency by varying operating conditions has been developed. GE collaborated with UoMn in examining inorganic impurities effects. Catalysts were pre-impregnated with inorganic impurities commonly present in biomass gasification syngas, including Si, Ca, Mg, Na, K, P and S. UoMn performed catalyst characterization and has acquired fundamental understandings of impurities effect on catalytic tar removal. Based on experimental data and the proposed reaction pathway, GE constructed a model to predict kinetic performance for biomass gasification tar cleanup process. Experimental data (eg. tar conversion, reactor inlet and outlet temperatures, product distribution) at different operating conditions were used to validate the model. A good fit between model predictions and experimental data was found. This model will be a valuable tool in designing the tar removal reactor and identifying appropriate operating conditions. We attended the 2011 DOE Biomass Program Thermochemical Platform Review held in Denver, CO from February 16 to 18 and received very positive comments from the review panel. Further, syngas utility and biomass to power/fuel companies expressed strong interest in our tar removal technology.« less

Activity and Stability of Dispersed Multi Metallic Pt-based Catalysts for CO Tolerance in Proton Exchange Membrane Fuel Cell Anodes.

PubMed

Hassan, Ayaz; Ticianelli, Edson A

2018-01-01

Studies aiming at improving the activity and stability of dispersed W and Mo containing Pt catalysts for the CO tolerance in proton exchange membrane fuel cell (PEMFC) anodes are revised for the following catalyst systems: (1) a carbon supported PtMo electrocatalyst submitted to heat treatments; (2) Pt and PtMo nanoparticles deposited on carbon-supported molybdenum carbides (Mo2C/C); (3) ternary and quaternary materials formed by PtMoFe/C, PtMoRu/C and PtMoRuFe/C and; (4) Pt nanoparticles supported on tungsten carbide/carbon catalysts and its parallel evaluation with carbon supported PtW catalyst. The heat-treated (600 oC) Pt-Mo/C catalyst showed higher hydrogen oxidation activity in the absence and in the presence of CO and better stability, compared to all other Mo-containing catalysts. PtMoRuFe, PtMoFe, PtMoRu supported on carbon and Pt supported on Mo2C/C exhibited similar CO tolerances but better stability, as compared to as-prepared PtMo supported on carbon. Among the tungsten-based catalysts, tungsten carbide supported Pt catalyst showed reasonable performance and reliable stability in comparison to simple carbon supported PtW catalyst, though an uneven level of catalytic activity towards H2 oxidation in presence of CO is observed for the former as compared to Mo containing catalyst. However, a small dissolution of Mo, Ru, Fe and W from the anodes and their migration toward cathodes during the cell operation is observed. These results indicate that the fuel cell performance and stability has been improved but not yet totally resolved.

Enhancing of catalytic properties of vanadia via surface doping with phosphorus using atomic layer deposition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Strempel, Verena E.; Naumann d'Alnoncourt, Raoul, E-mail: r.naumann@bascat.tu-berlin.de; Löffler, Daniel

2016-01-15

Atomic layer deposition is mainly used to deposit thin films on flat substrates. Here, the authors deposit a submonolayer of phosphorus on V{sub 2}O{sub 5} in the form of catalyst powder. The goal is to prepare a model catalyst related to the vanadyl pyrophosphate catalyst (VO){sub 2}P{sub 2}O{sub 7} industrially used for the oxidation of n-butane to maleic anhydride. The oxidation state of vanadium in vanadyl pyrophosphate is 4+. In literature, it was shown that the surface of vanadyl pyrophosphate contains V{sup 5+} and is enriched in phosphorus under reaction conditions. On account of this, V{sub 2}O{sub 5} with themore » oxidation state of 5+ for vanadium partially covered with phosphorus can be regarded as a suitable model catalyst. The catalytic performance of the model catalyst prepared via atomic layer deposition was measured and compared to the performance of catalysts prepared via incipient wetness impregnation and the original V{sub 2}O{sub 5} substrate. It could be clearly shown that the dedicated deposition of phosphorus by atomic layer deposition enhances the catalytic performance of V{sub 2}O{sub 5} by suppression of total oxidation reactions, thereby increasing the selectivity to maleic anhydride.« less

Tri-reforming of surrogate blogs over Ni/Mg/ceria-zirconia/alumina pellet catalysts

DOE PAGES

Zhao, Xianhui; Ngo, Huong T.; Walker, Devin M.; ...

2018-01-23

The performance of catalytic tri-reforming under industrially relevant situations (e.g., pellet catalysts, pressurized reactor) was investigated using surrogate biogas as the feedstock. Tri-reforming using Ni/Mg/Ce 0.6Zr 0.4O 2/Al 2O 3 pellet catalysts was studied in a bench scale fixed-bed reactor. The feed molar ratio for CH 4: CO 2: air was fixed as 1.0: 0.70: 0.95. The effects of temperature (800 – 860 °C), pressure (1 – 6 bar), and H 2O/CH 4 molar feed ratio (0.23 – 0.65) were examined. Pressure has substantial impact on the reaction and transport rates and equilibrium conversions, making it a key variable. Atmore » 860 °C, CO 2 conversion increased from 4 to 61% and H 2/CO molar ratio decreased from 2.0 to 1.1 as the pressure changed from 1 to 6 bar. CO 2 conversion and H 2/CO molar ratio were also influenced by the temperature and H 2O/CH 4 molar ratio. At 3 bar, CO 2 conversion varied between 4 and 43% and the H 2/CO molar ratio varied between 1.2 and 1.9 as the temperature changed from 800 to 860 °C. At 3 bar and 860 °C, CO 2 conversion decreased from 35 to 8% and H 2/CO molar ratio increased from 1.7 to 2.4 when the H 2O/CH 4 molar ratio was increased from 0.23 to 0.65. This work demonstrates that the tri-reforming technology is feasible for converting biogas under scaled-up conditions in a fixed-bed reactor.« less

Ambient temperature NO oxidation over Cr-based amorphous mixed oxide catalysts: effects from the second oxide components

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Aiyong; Lin, Bo; Zhang, Hanlei

2017-01-01

Three series of Cr-based mixed oxides (Cr-Co, Cr-Fe, and Cr-Ni oxides) with high specific surface areas and amorphous textures were synthesized using a novel sol-gel method. These mixed oxides, in comparison to their pure metal oxide (CrOx, Co3O4, FeOx and NiO) counterparts, display enhanced performance for catalytic oxidation of low-concentration NO at room temperature. The best performing catalysts achieve 100% NO conversion for ~30 h of operation at a high space velocity of 45,000 ml g-1 h-1. The amorphous structure was found to be critical for these catalysts to maintain high activity and durability. Control of Cr/M (M=Co, Fe andmore » Ni) molar ratio, nitrate precursor decomposition temperature and catalyst calcination temperature was key to the synthesis of these highly active catalysts.« less

Oxygen-reducing catalyst layer

DOEpatents

O'Brien, Dennis P [Maplewood, MN; Schmoeckel, Alison K [Stillwater, MN; Vernstrom, George D [Cottage Grove, MN; Atanasoski, Radoslav [Edina, MN; Wood, Thomas E [Stillwater, MN; Yang, Ruizhi [Halifax, CA; Easton, E Bradley [Halifax, CA; Dahn, Jeffrey R [Hubley, CA; O'Neill, David G [Lake Elmo, MN

2011-03-22

An oxygen-reducing catalyst layer, and a method of making the oxygen-reducing catalyst layer, where the oxygen-reducing catalyst layer includes a catalytic material film disposed on a substrate with the use of physical vapor deposition and thermal treatment. The catalytic material film includes a transition metal that is substantially free of platinum. At least one of the physical vapor deposition and the thermal treatment is performed in a processing environment comprising a nitrogen-containing gas.

Understanding of catalyst deactivation caused by sulfur poisoning and carbon deposition in steam reforming of liquid hydrocarbon fuels

NASA Astrophysics Data System (ADS)

Xie, Chao

2011-12-01

The present work was conducted to develop a better understanding on the catalyst deactivation in steam reforming of sulfur-containing liquid hydrocarbon fuels for hydrogen production. Steam reforming of Norpar13 (a liquid hydrocarbon fuel from Exxon Mobile) without and with sulfur was performed on various metal catalysts (Rh, Ru, Pt, Pd, and Ni) supported on different materials (Al2O3, CeO2, SiO2, MgO, and CeO2- Al2O3). A number of characterization techniques were applied to study the physicochemical properties of these catalysts before and after the reactions. Especially, X-ray absorption near edge structure (XANES) spectroscopy was intensively used to investigate the nature of sulfur and carbon species in the used catalysts to reveal the catalyst deactivation mechanism. Among the tested noble metal catalysts (Rh, Ru, Pt, and Pd), Rh catalyst is the most sulfur tolerant. Al2O3 and CeO2 are much better than SiO2 and MgO as the supports for the Rh catalyst to reform sulfur-containing hydrocarbons. The good sulfur tolerance of Rh/Al2O3 can be attributed to the acidic nature of the Al2O3 support and its small Rh crystallites (1-3 nm) as these characteristics facilitate the formation of electron-deficient Rh particles with high sulfur tolerance. The good catalytic performance of Rh/CeO2 in the presence of sulfur can be ascribed to the promotion effect of CeO2 on carbon gasification, which significantly reduced the carbon deposition on the Rh/CeO2catalyst. Steam reforming of Norpar13 in the absence and presence of sulfur was further carried out over CeO2-Al2O3 supported monometallic Ni and Rh and bimetallic Rh-Ni catalysts at 550 and 800 °C. Both monometallic catalysts rapidly deactivated at 550 °C, iv and showed poor sulfur tolerance. Although ineffective for the Ni catalyst, increasing the temperature to 800 °C dramatically improved the sulfur tolerance of the Rh catalyst. Sulfur K-edge XANES revealed that metal sulfide and organic sulfide are the dominant sulfur species on the used Ni catalyst, while sulfonate and sulfate predominate on the used Rh catalyst. The superior sulfur tolerance of the Rh/CeO2-Al2O3 catalyst at 800 °C may be associated with its capability in sulfur oxidation. It is very likely that the oxygenshielded sulfur structure of sulfonate and sulfate can suppress the poisoning impact of sulfur on Rh through inhibiting direct rhodium-sulfur interaction. Although the Rh-Ni catalyst exhibited better sulfur tolerance than the monometallic ones at 550 °C, its catalytic performance was inferior compared with the Rh catalyst in the sulfur-containing reaction at 800 °C probably due to the severe carbon deposition on the bimetallic catalyst. The last part of this work focuses on the influence of sulfur on the carbon deposition in steam reforming of liquid hydrocarbon fuels over CeO2-Al2O3 supported monometallic Ni and Rh catalysts at 800 ºC. Though abundant carbon deposits can accumulate on the pure CeO2-Al2O3 support due to fuel thermal cracking, the metal addition substantially mitigated the carbon deposition in the sulfur-free reaction. The presence of sulfur increased the carbon deposition on both catalysts, which has a much more significant impact for the Ni catalyst. Our results indicate that (I) the presence of sulfur can suppress carbon gasification and promote the formation of graphitic carbon on reforming catalysts, and (II) the Rh catalyst possesses stronger capability to maintain carbon gasification activity than the Ni catalyst in the presence of sulfur.

Bench-scale research in biomass liquefaction in support of the Albany, Oregon experimental facility

NASA Astrophysics Data System (ADS)

Elliott, D. C.

1981-03-01

The liquefaction of solid materials (wood, newsprint, animal manure) by beating to produce useful liquid fuels was investigated. Highlights of work performed include: (1) catalyst mechanism studies; (2) analytical reports on TR8 and TR9 product oils; (3) liquid chromatography/mass spectroscopy analysis of wood oil; (4) batch conversion tests on bottom material; (5) vapor pressure studies; and (6) product evaluation. It was confirmed that the key process parameters and the effects of varying operating conditions are in support of biomass liquefaction.

Homogeneous and heterogenized iridium water oxidation catalysts

NASA Astrophysics Data System (ADS)

Macchioni, Alceo

2014-10-01

The development of an efficient catalyst for the oxidative splitting of water into molecular oxygen, protons and electrons is of key importance for producing solar fuels through artificial photosynthesis. We are facing the problem by means of a rational approach aimed at understanding how catalytic performance may be optimized by the knowledge of the reaction mechanism of water oxidation and the fate of the catalytic site under the inevitably harsh oxidative conditions. For the purposes of our study we selected iridium water oxidation catalysts, exhibiting remarkable performance (TOF > 5 s-1 and TON > 20000). In particular, we recently focused our attention on [Cp*Ir(N,O)X] (N,O = 2-pyridincarboxylate; X = Cl or NO3) and [IrCl(Hedta)]Na water oxidation catalysts. The former exhibited a remarkable TOF whereas the latter showed a very high TON. Furthermore, [IrCl(Hedta)]Na was heterogenized onto TiO2 taking advantage of the presence of a dandling -COOH functionality. The heterogenized catalyst maintained approximately the same catalytic activity of the homogeneous analogous with the advantage that could be reused many times. Mechanistic studies were performed in order to shed some light on the rate-determining step and the transformation of catalysts when exposed to "oxidative stress". It was found that the last oxidative step, preceding oxygen liberation, is the rate-determining step when a small excess of sacrificial oxidant is used. In addition, several intermediates of the oxidative transformation of the catalyst were intercepted and characterized by NMR, X-Ray diffractometry and ESI-MS.

Palladium-atom catalyzed formic acid decomposition and the switch of reaction mechanism with temperature.

PubMed

He, Nan; Li, Zhen Hua

2016-04-21

Formic acid decomposition (FAD) reaction has been an innovative way for hydrogen energy. Noble metal catalysts, especially palladium-containing nanoparticles, supported or unsupported, perform well in this reaction. Herein, we considered the simplest model, wherein one Pd atom is used as the FAD catalyst. With high-level theoretical calculations of CCSD(T)/CBS quality, we investigated all possible FAD pathways. The results show that FAD catalyzed by one Pd atom follows a different mechanism compared with that catalyzed by surfaces or larger clusters. At the initial stage of the reaction, FAD follows a dehydration route and is quickly poisoned by CO due to the formation of very stable PdCO. PdCO then becomes the actual catalyst for FAD at temperatures approximately below 1050 K. Beyond 1050 K, there is a switch of catalyst from PdCO to Pd atom. The results also show that dehydration is always favoured over dehydrogenation on either the Pd-atom or PdCO catalyst. On the Pd-atom catalyst, neither dehydrogenation nor dehydration follows the formate mechanism. In contrast, on the PdCO catalyst, dehydrogenation follows the formate mechanism, whereas dehydration does not. We also systematically investigated the performance of 24 density functional theory methods. We found that the performance of the double hybrid mPW2PLYP functional is the best, followed by the B3LYP, B3PW91, N12SX, M11, and B2PLYP functionals.

Platinum clusters supported in zeolite LTL: Influence of catalyst morphology on performance in n-hexane reforming

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jentoft, R.E.; Gates, B.C.; Tsapatsis, M.

KLTL zeolite-supported platinum catalysts were synthesized from aqueous tetraammineplatinum(II) nitrate solutions and nonacidic KLTL zeolite crystallites, including some with dimensions as little as 300 x 500 {angstrom}. The zeolite crystallites had various morphologies, some being predominantly disk-shaped particles and some predominantly mosaics of rod-like domains with a range of c-dimension lengths. The activity and selectivity of each catalyst were evaluated for dehydrocyclization of n-hexane in the presence of H{sub 2} to form predominantly benzene at conversions of typically 45--90%. The data presented here provide a detailed characterization of the deactivation of such catalysts in the absence of sulfur. EXAFS datamore » show that the platinum in each catalyst was present in clusters of about 20 atoms each, on average. Electron micrographs show that the platinum clusters were nearly evenly dispersed on the surfaces of the zeolite crystallites, including the intracrystalline and extracrystalline surfaces. The catalytic performance was virtually independent of the zeolite channel length, but activity, selectivity, and resistance to deactivation were found to be correlated with the ratio of the surface area external to the crystallite domains to that within the intracrystalline pores. The catalyst performance is dependent on this ratio (which is related to the zeolite morphology) as follows: in comparison with the others, the catalysts with the relatively low fractions of platinum outside the intracrystalline pores are more active, more selective for benzene formation, and more resistant to deactivation.« less

Laboratory-scale photoredox catalysis using hydrated electrons sustainably generated with a single green laser.

PubMed

Naumann, Robert; Kerzig, Christoph; Goez, Martin

2017-11-01

The ruthenium-tris-bipyridyl dication as catalyst combined with the ascorbate dianion as bioavailable sacrificial donor provides the first regenerative source of hydrated electrons for chemical syntheses on millimolar scales. This electron generator is operated simply by illumination with a frequency-doubled Nd:YAG laser (532 nm) running at its normal repetition rate. Much more detailed information than by product studies alone was obtained by photokinetical characterization from submicroseconds (time-resolved laser flash photolysis) up to one hour (preparative photolysis). The experiments on short timescales established a reaction mechanism more complex than previously thought, and proved the catalytic action by unchanged concentration traces of the key transients over a number of flashes so large that the accumulated electron total surpassed the catalyst concentration many times. Preparative photolyses revealed that the sacrificial donor greatly enhances the catalyst stability through quenching the initial metal-to-ligand charge-transfer state before destructive dd states can be populated from it, such that the efficiency of this electron generator is no longer limited by catalyst decomposition but by electron scavenging by the accumulating oxidation products of the ascorbate. Applications covered dechlorinations of selected aliphatic and aromatic chlorides and the reduction of a model ketone. All these substrates are impervious to photoredox catalysts exhibiting lower reducing power than the hydrated electron, but the combination of an extremely negative standard potential and a long unquenched life allowed turnover numbers up to 1400 with our method.

Perspective: Size selected clusters for catalysis and electrochemistry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Halder, Avik; Curtiss, Larry A.; Fortunelli, Alessandro

We report that size-selected clusters containing a handful of atoms may possess noble catalytic properties different from nano-sized or bulk catalysts. Size- and composition-selected clusters can also serve as models of the catalytic active site, where an addition or removal of a single atom can have a dramatic effect on their activity and selectivity. In this Perspective, we provide an overview of studies performed under both ultra-high vacuum and realistic reaction conditions aimed at the interrogation, characterization and understanding of the performance of supported size-selected clusters in heterogeneous and electrochemical reactions, which address the effects of cluster size, cluster composition,more » cluster-support interactions and reaction conditions, the key parameters for the understanding and control of catalyst functionality. Computational modelling based on density functional theory sampling of local minima and energy barriers or ab initio Molecular Dynamics simulations is an integral part of this research by providing fundamental understanding of the catalytic processes at the atomic level, as well as by predicting new materials compositions which can be validated in experiments. Lastly, we discuss approaches which aim at the scale up of the production of well-defined clusters for use in real world applications.« less

Perspective: Size selected clusters for catalysis and electrochemistry

DOE PAGES

Halder, Avik; Curtiss, Larry A.; Fortunelli, Alessandro; ...

2018-03-15

We report that size-selected clusters containing a handful of atoms may possess noble catalytic properties different from nano-sized or bulk catalysts. Size- and composition-selected clusters can also serve as models of the catalytic active site, where an addition or removal of a single atom can have a dramatic effect on their activity and selectivity. In this Perspective, we provide an overview of studies performed under both ultra-high vacuum and realistic reaction conditions aimed at the interrogation, characterization and understanding of the performance of supported size-selected clusters in heterogeneous and electrochemical reactions, which address the effects of cluster size, cluster composition,more » cluster-support interactions and reaction conditions, the key parameters for the understanding and control of catalyst functionality. Computational modelling based on density functional theory sampling of local minima and energy barriers or ab initio Molecular Dynamics simulations is an integral part of this research by providing fundamental understanding of the catalytic processes at the atomic level, as well as by predicting new materials compositions which can be validated in experiments. Lastly, we discuss approaches which aim at the scale up of the production of well-defined clusters for use in real world applications.« less

Perspective: Size selected clusters for catalysis and electrochemistry

NASA Astrophysics Data System (ADS)

Halder, Avik; Curtiss, Larry A.; Fortunelli, Alessandro; Vajda, Stefan

2018-03-01

Size-selected clusters containing a handful of atoms may possess noble catalytic properties different from nano-sized or bulk catalysts. Size- and composition-selected clusters can also serve as models of the catalytic active site, where an addition or removal of a single atom can have a dramatic effect on their activity and selectivity. In this perspective, we provide an overview of studies performed under both ultra-high vacuum and realistic reaction conditions aimed at the interrogation, characterization, and understanding of the performance of supported size-selected clusters in heterogeneous and electrochemical reactions, which address the effects of cluster size, cluster composition, cluster-support interactions, and reaction conditions, the key parameters for the understanding and control of catalyst functionality. Computational modeling based on density functional theory sampling of local minima and energy barriers or ab initio molecular dynamics simulations is an integral part of this research by providing fundamental understanding of the catalytic processes at the atomic level, as well as by predicting new materials compositions which can be validated in experiments. Finally, we discuss approaches which aim at the scale up of the production of well-defined clusters for use in real world applications.

A comparative parametric study of a catalytic plate methane reformer coated with segmented and continuous layers of combustion catalyst for hydrogen production

NASA Astrophysics Data System (ADS)

Mundhwa, Mayur; Parmar, Rajesh D.; Thurgood, Christopher P.

2017-03-01

A parametric comparison study is carried out between segmented and conventional continuous layer configurations of the coated combustion-catalyst to investigate their influence on the performance of methane steam reforming (MSR) for hydrogen production in a catalytic plate reactor (CPR). MSR is simulated on one side of a thin plate over a continuous layer of nickel-alumina catalyst by implementing an experimentally validated surface microkinetic model. Required thermal energy for the MSR reaction is supplied by simulating catalytic methane combustion (CMC) on the opposite side of the plate over segmented and continuous layer of a platinum-alumina catalyst by implementing power law rate model. The simulation results of both coating configurations of the combustion-catalyst are compared using the following parameters: (1) co-flow and counter-flow modes between CMC and MSR, (2) gas hourly space velocity and (3) reforming-catalyst thickness. The study explains why CPR designed with the segmented combustion-catalyst and co-flow mode shows superior performance not only in terms of high hydrogen production but also in terms of minimizing the maximum reactor plate temperature and thermal hot-spots. The study shows that the segmented coating requires 7% to 8% less combustion-side feed flow and 70% less combustion-catalyst to produce the required flow of hydrogen (29.80 mol/h) on the reforming-side to feed a 1 kW fuel-cell compared to the conventional continuous coating of the combustion-catalyst.

Experimental Studies on the Hydrotreatment of Kraft Lignin to Aromatics and Alkylphenolics Using Economically Viable Fe-Based Catalysts

PubMed Central

2017-01-01

Limonite, a low-cost iron ore, was investigated as a potential hydrotreatment catalyst for kraft lignin without the use of an external solvent (batch reactor, initial H2 pressure of 100 bar, 4 h). The best results were obtained at 450 °C resulting in 34 wt % of liquefied kraft lignin (lignin oil) on lignin intake. The composition of the lignin oil was determined in detail (elemental composition, GC-MS, GC×GC-FID, and GPC). The total GC-detectable monomeric species amounts up to 31 wt % on lignin intake, indicating that 92 wt % of the products in the lignin oil are volatile and thus of low molecular weight. The lignin oil was rich in low-molecular-weight alkylphenolics (17 wt % on lignin) and aromatics (8 wt % on lignin). Performance of the limonite catalyst was compared to other Fe-based catalysts (goethite and iron disulfide) and limonite was shown to give the highest yields of alkylphenolics and aromatics. The limonite catalyst before and after reaction was characterized using XRD, TEM, and nitrogen physisorption to determine changes in structure during reaction. Catalyst recycling tests were performed and show that the catalyst is active after reuse, despite the fact that the morphology changed and that the surface area of the catalyst particles was decreased. Our results clearly reveal that cheap limonite catalysts have the potential to be used for the depolymerization/hydrodeoxygenation of kraft lignin for the production of valuable biobased phenolics and aromatics. PMID:28413733

Enhanced development of a catalyst chamber for the decomposition of up to 1.0 kg/s hydrogen peroxide

NASA Astrophysics Data System (ADS)

Božić, Ognjan; Porrmann, Dennis; Lancelle, Daniel; May, Stefan

2016-06-01

A new innovative hybrid rocket engine concept is developed within the AHRES program of the German Aerospace Center (DLR). This rocket engine based on hydroxyl-terminated polybutadiene (HTPB) with metallic additives as solid fuel and high test peroxide (HTP) as liquid oxidizer. Instead of a conventional ignition system, a catalyst chamber with a silver mesh catalyst is designed to decompose the HTP. The newly modified catalyst chamber is able to decompose up to 1.0 kg/s of 87.5 wt% HTP. Used as a monopropellant thruster, this equals an average thrust of 1600 N. The catalyst chamber is designed using the self-developed software tool SHAKIRA. The applied kinetic law, which determines catalytic decomposition of HTP within the catalyst chamber, is given and commented. Several calculations are carried out to determine the appropriate geometry for complete decomposition with a minimum of catalyst material. A number of tests under steady state conditions are carried out, using 87.5 wt% HTP with different flow rates and a constant amount of catalyst material. To verify the decomposition, the temperature is measured and compared with the theoretical prediction. The experimental results show good agreement with the results generated by the design tool. The developed catalyst chamber provides a simple, reliable ignition system for hybrid rocket propulsion systems based on hydrogen peroxide as oxidizer. This system is capable for multiple reignition. The developed hardware and software can be used to design full scale monopropellant thrusters based on HTP and catalyst chambers for hybrid rocket engines.

Capture and isotopic exchange method for water and hydrogen isotopes on zeolite catalysts up to technical scale for pre-study of processing highly tritiated water

DOE Office of Scientific and Technical Information (OSTI.GOV)

Michling, R.; Braun, A.; Cristescu, I.

2015-03-15

Highly tritiated water (HTW) may be generated at ITER by various processes and, due to the excessive radio toxicity, the self-radiolysis and the exceedingly corrosive property of HTW, a potential hazard is associated with its storage and process. Therefore, the capture and exchange method for HTW utilizing Molecular Sieve Beds (MSB) was investigated in view of adsorption capacity, isotopic exchange performance and process parameters. For the MSB, different types of zeolite were selected. All zeolite materials were additionally coated with platinum. The following work comprised the selection of the most efficient zeolite candidate based on detailed parametric studies during themore » H{sub 2}/D{sub 2}O laboratory scale exchange experiments (about 25 g zeolite per bed) at the Tritium Laboratory Karlsruhe (TLK). For the zeolite, characterization analytical techniques such as Infrared Spectroscopy, Thermogravimetry and online mass spectrometry were implemented. Followed by further investigation of the selected zeolite catalyst under full technical operation, a MSB (about 22 kg zeolite) was processed with hydrogen flow rates up to 60 mol*h{sup -1} and deuterated water loads up to 1.6 kg in view of later ITER processing of arising HTW. (authors)« less

Hydrogenation of artemisinin to dihydroartemisinin over heterogeneous metal catalysts

NASA Astrophysics Data System (ADS)

Kristiani, Anis; Pertiwi, Ralentri; Adilina, Indri Badria

2017-01-01

A series of heterogeneous metal catalysts of Ni, Pd, and Pt, both of synthesized and commercial catalysts were used for hydrogenation of artemisinin to dihydroartemisinin. Their catalytic properties were determsined by Surface Area Analyzer and Thermogravimetry Analyzer. The catalytic properties in various reaction conditions in terms of temperature, pressure, reaction time and reactant/catalyst ratio were also studied. The results catalytic activity tests showed that synthesized catalysts of Ni/zeolite, Ni-Sn/zeolite, Ni/bentonite and Ni-Sn/bentonite were not able to produced dihydroartemisinin and deoxyartemisinin was mainly formed. Meanwhile, commercial catalysts of Ni skeletal, Pd/activated charcoal and Pt/activated charcoal yielded the desired dihydroartemisinin product. Ni skeletal commercial catalyst gave the best performance of hydrogenation artemisinin to dihydroartemisinin in room temperature and low H2 pressure.

Chemical imaging of Fischer-Tropsch catalysts under operating conditions

PubMed Central

Price, Stephen W. T.; Martin, David J.; Parsons, Aaron D.; Sławiński, Wojciech A.; Vamvakeros, Antonios; Keylock, Stephen J.; Beale, Andrew M.; Mosselmans, J. Frederick W.

2017-01-01

Although we often understand empirically what constitutes an active catalyst, there is still much to be understood fundamentally about how catalytic performance is influenced by formulation. Catalysts are often designed to have a microstructure and nanostructure that can influence performance but that is rarely considered when correlating structure with function. Fischer-Tropsch synthesis (FTS) is a well-known and potentially sustainable technology for converting synthetic natural gas (“syngas”: CO + H2) into functional hydrocarbons, such as sulfur- and aromatic-free fuel and high-value wax products. FTS catalysts typically contain Co or Fe nanoparticles, which are often optimized in terms of size/composition for a particular catalytic performance. We use a novel, “multimodal” tomographic approach to studying active Co-based catalysts under operando conditions, revealing how a simple parameter, such as the order of addition of metal precursors and promoters, affects the spatial distribution of the elements as well as their physicochemical properties, that is, crystalline phase and crystallite size during catalyst activation and operation. We show in particular how the order of addition affects the crystallinity of the TiO2 anatase phase, which in turn leads to the formation of highly intergrown cubic close-packed/hexagonal close-packed Co nanoparticles that are very reactive, exhibiting high CO conversion. This work highlights the importance of operando microtomography to understand the evolution of chemical species and their spatial distribution before any concrete understanding of impact on catalytic performance can be realized. PMID:28345057

Stable hydrogen production from ethanol through steam reforming reaction over nickel-containing smectite-derived catalyst.

PubMed

Yoshida, Hiroshi; Yamaoka, Ryohei; Arai, Masahiko

2014-12-25

Hydrogen production through steam reforming of ethanol was investigated with conventional supported nickel catalysts and a Ni-containing smectite-derived catalyst. The former is initially active, but significant catalyst deactivation occurs during the reaction due to carbon deposition. Side reactions of the decomposition of CO and CH4 are the main reason for the catalyst deactivation, and these reactions can relatively be suppressed by the use of the Ni-containing smectite. The Ni-containing smectite-derived catalyst contains, after H2 reduction, stable and active Ni nanocrystallites, and as a result, it shows a stable and high catalytic performance for the steam reforming of ethanol, producing H2.

Stable Hydrogen Production from Ethanol through Steam Reforming Reaction over Nickel-Containing Smectite-Derived Catalyst

PubMed Central

Yoshida, Hiroshi; Yamaoka, Ryohei; Arai, Masahiko

2014-01-01

Hydrogen production through steam reforming of ethanol was investigated with conventional supported nickel catalysts and a Ni-containing smectite-derived catalyst. The former is initially active, but significant catalyst deactivation occurs during the reaction due to carbon deposition. Side reactions of the decomposition of CO and CH4 are the main reason for the catalyst deactivation, and these reactions can relatively be suppressed by the use of the Ni-containing smectite. The Ni-containing smectite-derived catalyst contains, after H2 reduction, stable and active Ni nanocrystallites, and as a result, it shows a stable and high catalytic performance for the steam reforming of ethanol, producing H2. PMID:25547495

A modified preparation procedure for carbon nanotube-confined Nd/Na heterobimetallic catalyst for anti-selective catalytic asymmetric nitroaldol reactions.

PubMed

Sureshkumar, Devarajulu; Hashimoto, Kazuki; Kumagai, Naoya; Shibasaki, Masakatsu

2013-11-15

A recyclable asymmetric metal-based catalyst is a rare entity among the vast collection of asymmetric catalysts developed so far. Recently we found that the combination of a self-assembling metal-based asymmetric catalyst and multiwalled carbon nanotubes (MWNTs) produced a highly active and recyclable catalyst in which the catalytically active metal complex was dispersed in the MWNT network. Herein we describe an improved preparation procedure and full details of a Nd/Na heterobimetallic complex confined in MWNTs. Facilitated self-assembly of the catalyst with MWNTs avoided the sacrificial use of excess chiral ligand for the formation of the heterobimetallic complex, improving the loading ratio of the catalyst components. Eighty-five percent of the catalyst components were incorporated onto MWNTs to produce the confined catalyst, which was a highly efficient and recyclable catalyst for the anti-selective asymmetric nitroaldol reaction. The requisite precautions for the catalyst preparation to elicit reproducible catalytic performance are summarized. Superior catalytic profiles over the prototype catalyst without MWNTs were revealed in the synthesis of optically active 1,2-nitroalkanols, which are key intermediates for the synthesis of therapeutics.

Forecasting the zeolite-containing catalyst activity in catalytic cracking technology taking into account the feedstock composition

NASA Astrophysics Data System (ADS)

Ivashkina, Elena; Nazarova, Galina; Shafran, Tatyana; Stebeneva, Valeriya

2017-08-01

The effect of the feedstock composition and the process conditions on the current catalyst activity in catalytic cracking technology using a mathematical model is performed in this research. The mathematical model takes into account the catalyst deactivation by coke for primary and secondary cracking reactions. The investigation results have shown that the feedstock has significant effect on the yield and the content of coke on the catalyst. Thus, the relative catalyst activity is significantly reduced by 7.5-10.7 %. With increasing the catalytic cracking temperature due to the catalyst flow temperature rising, the coke content and the yield per feedstock increase and the catalyst activity decreases by 5.3-7.7%. Rising the process temperature together with the catalyst circulation ratio contributes to increase of the coke yield per feedstock in the catalytic cracking and decrease of the coke content on the catalyst. It is connected with the catalyst flow rising to the riser and the contact time decreasing in the reaction zone. Also, the catalyst activity decreases in the range of 3.8-5.5% relatively to the regenerated catalyst activity (83 %).

Engineering the internal surfaces of three-dimensional nanoporous catalysts by surfactant-modified dealloying.

PubMed

Wang, Zhili; Liu, Pan; Han, Jiuhui; Cheng, Chun; Ning, Shoucong; Hirata, Akihiko; Fujita, Takeshi; Chen, Mingwei

2017-10-20

Tuning surface structures by bottom-up synthesis has been demonstrated as an effective strategy to improve the catalytic performances of nanoparticle catalysts. Nevertheless, the surface modification of three-dimensional nanoporous metals, fabricated by a top-down dealloying approach, has not been achieved despite great efforts devoted to improving the catalytic performance of three-dimensional nanoporous catalysts. Here we report a surfactant-modified dealloying method to tailor the surface structure of nanoporous gold for amplified electrocatalysis toward methanol oxidation and oxygen reduction reactions. With the assistance of surfactants, {111} or {100} faceted internal surfaces of nanoporous gold can be realized in a controllable manner by optimizing dealloying conditions. The surface modified nanoporous gold exhibits significantly enhanced electrocatalytic activities in comparison with conventional nanoporous gold. This study paves the way to develop high-performance three-dimensional nanoporous catalysts with a tunable surface structure by top-down dealloying for efficient chemical and electrochemical reactions.

Rapid synthesis of dendritic Pt/Pb nanoparticles and their electrocatalytic performance toward ethanol oxidation

NASA Astrophysics Data System (ADS)

Zhang, Ke; Xu, Hui; Yan, Bo; Wang, Jin; Gu, Zhulan; Du, Yukou

2017-12-01

This article reports a rapid synthetic method for the preparation of dendritic platinum-lead bimetallic catalysts by using an oil bath for 5 min in the presence of hexadecyltrimethylammonium chloride (CTAC) and ascorbic acid (AA). CTAC acts as a shape-direction agent, and AA acts as a reducing agent during the reaction process. A series of physical techniques are used to characterize the morphology, structure and electronic properties of the dendritic Pt/Pb nanoparticles, indicating the Pt/Pb dendrites are porous, highly alloying, and self-supported nanostructures. Various electrochemical techniques were also investigated the catalytic performance of the Pt/Pb catalysts toward the ethanol electrooxidation reaction. Cyclic voltammetry and chronoamperometry indicated that the synthesized dendritic Pt/Pb nanoparticles possessed much higher electrocatalytic performance than bulk Pt catalyst. This study may inspire the engineering of dendritic bimetallic catalysts, which are expected to have great potential applications in fuel cells.

High Coke-Resistance Pt/Mg1-xNixO Catalyst for Dry Reforming of Methane

PubMed Central

Al-Doghachi, Faris A. J.; Islam, Aminul; Zainal, Zulkarnain; Saiman, Mohd Izham; Embong, Zaidi; Taufiq-Yap, Yun Hin

2016-01-01

A highly active and stable nano structured Pt/Mg1-xNixO catalysts was developed by a simple co-precipitation method. The obtained Pt/Mg1-xNixO catalyst exhibited cubic structure nanocatalyst with a size of 50–80 nm and realized CH4 and CO2 conversions as high as 98% at 900°C with excellent stability in the dry reforming of methane. The characterization of catalyst was performed using various kinds of analytical techniques including XRD, BET, XRF, TPR-H2, TGA, TEM, FESEM, FT-IR, and XPS analyses. Characterization of spent catalyst further confirms that Pt/Mg1-xNixO catalyst has high coke-resistance for dry reforming. Thus, the catalyst demonstrated in this study, offers a promising catalyst for resolving the dilemma between dispersion and reducibility of supported metal, as well as activity and stability during high temperature reactions. PMID:26745623

Effect of Oxide Coating on Performance of Copper-Zinc Oxide-Based Catalyst for Methanol Synthesis via Hydrogenation of Carbon Dioxide.

PubMed

Umegaki, Tetsuo; Kojima, Yoshiyuki; Omata, Kohji

2015-11-16

The effect of oxide coating on the activity of a copper-zinc oxide-based catalyst for methanol synthesis via the hydrogenation of carbon dioxide was investigated. A commercial catalyst was coated with various oxides by a sol-gel method. The influence of the types of promoters used in the sol-gel reaction was investigated. Temperature-programmed reduction-thermogravimetric analysis revealed that the reduction peak assigned to the copper species in the oxide-coated catalysts prepared using ammonia shifts to lower temperatures than that of the pristine catalyst; in contrast, the reduction peak shifts to higher temperatures for the catalysts prepared using L(+)-arginine. These observations indicated that the copper species were weakly bonded with the oxide and were easily reduced by using ammonia. The catalysts prepared using ammonia show higher CO₂ conversion than the catalysts prepared using L(+)-arginine. Among the catalysts prepared using ammonia, the silica-coated catalyst displayed a high activity at high temperatures, while the zirconia-coated catalyst and titania-coated catalyst had high activity at low temperatures. At high temperature the conversion over the silica-coated catalyst does not significantly change with reaction temperature, while the conversion over the zirconia-coated catalyst and titania-coated catalyst decreases with reaction time. From the results of FTIR, the durability depends on hydrophilicity of the oxides.

Effect of Oxide Coating on Performance of Copper-Zinc Oxide-Based Catalyst for Methanol Synthesis via Hydrogenation of Carbon Dioxide

PubMed Central

Umegaki, Tetsuo; Kojima, Yoshiyuki; Omata, Kohji

2015-01-01

The effect of oxide coating on the activity of a copper-zinc oxide–based catalyst for methanol synthesis via the hydrogenation of carbon dioxide was investigated. A commercial catalyst was coated with various oxides by a sol-gel method. The influence of the types of promoters used in the sol-gel reaction was investigated. Temperature-programmed reduction-thermogravimetric analysis revealed that the reduction peak assigned to the copper species in the oxide-coated catalysts prepared using ammonia shifts to lower temperatures than that of the pristine catalyst; in contrast, the reduction peak shifts to higher temperatures for the catalysts prepared using L(+)-arginine. These observations indicated that the copper species were weakly bonded with the oxide and were easily reduced by using ammonia. The catalysts prepared using ammonia show higher CO2 conversion than the catalysts prepared using L(+)-arginine. Among the catalysts prepared using ammonia, the silica-coated catalyst displayed a high activity at high temperatures, while the zirconia-coated catalyst and titania-coated catalyst had high activity at low temperatures. At high temperature the conversion over the silica-coated catalyst does not significantly change with reaction temperature, while the conversion over the zirconia-coated catalyst and titania-coated catalyst decreases with reaction time. From the results of FTIR, the durability depends on hydrophilicity of the oxides. PMID:28793674

Discovery of true electrochemical reactions for ultrahigh catalyst mass activity in water splitting

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mo, Jingke; Kang, Zhenye; Retterer, Scott T.

Better understanding of true electrochemical reaction behaviors in electrochemical energy devices has long been desired. It has been assumed so far that the reactions occur across the entire catalyst layer (CL), which is designed and fabricated uniformly with catalysts, conductors of protons and electrons, and pathways for reactants and products. By introducing a state-of-the-art characterization system, a thin, highly tunable liquid/gas diffusion layer (LGDL), and an innovative design of electrochemical proton exchange membrane electrolyzer cells (PEMECs), the electrochemical reactions on both microspatial and microtemporal scales are revealed for the first time. Surprisingly, reactions occur only on the CL adjacent tomore » good electrical conductors. On the basis of these findings, new CL fabrications on the novel LGDLs exhibit more than 50 times higher mass activity than conventional catalyst-coated membranes in PEMECs. In conclusion, this discovery presents an opportunity to enhance the multiphase interfacial effects, maximizing the use of the catalysts and significantly reducing the cost of these devices.« less

Discovery of true electrochemical reactions for ultrahigh catalyst mass activity in water splitting

PubMed Central

Mo, Jingke; Kang, Zhenye; Retterer, Scott T.; Cullen, David A.; Toops, Todd J.; Green, Johney B.; Mench, Matthew M.; Zhang, Feng-Yuan

2016-01-01

Better understanding of true electrochemical reaction behaviors in electrochemical energy devices has long been desired. It has been assumed so far that the reactions occur across the entire catalyst layer (CL), which is designed and fabricated uniformly with catalysts, conductors of protons and electrons, and pathways for reactants and products. By introducing a state-of-the-art characterization system, a thin, highly tunable liquid/gas diffusion layer (LGDL), and an innovative design of electrochemical proton exchange membrane electrolyzer cells (PEMECs), the electrochemical reactions on both microspatial and microtemporal scales are revealed for the first time. Surprisingly, reactions occur only on the CL adjacent to good electrical conductors. On the basis of these findings, new CL fabrications on the novel LGDLs exhibit more than 50 times higher mass activity than conventional catalyst-coated membranes in PEMECs. This discovery presents an opportunity to enhance the multiphase interfacial effects, maximizing the use of the catalysts and significantly reducing the cost of these devices. PMID:28138516

Carbon nanocages: A new support material for Pt catalyst with remarkably high durability

PubMed Central

Wang, Xiao Xia; Tan, Zhe Hua; Zeng, Min; Wang, Jian Nong

2014-01-01

Low durability is the major challenge hindering the large-scale implementation of proton exchange membrane fuel cell (PEMFC) technology, and corrosion of carbon support materials of current catalysts is the main cause. Here, we describe the finding of remarkably high durability with the use of a novel support material. This material is based on hollow carbon nanocages developed with a high degree of graphitization and concurrent nitrogen doping for oxidation resistance enhancement, uniform deposition of fine Pt particles, and strong Pt-support interaction. Accelerated degradation testing shows that such designed catalyst possesses a superior electrochemical activity and long-term stability for both hydrogen oxidation and oxygen reduction relative to industry benchmarks of current catalysts. Further testing under conditions of practical fuel cell operation reveals almost no degradation over long-term cycling. Such a catalyst of high activity, particularly, high durability, opens the door for the next-generation PEMFC for “real world” application. PMID:24658614

Discovery of true electrochemical reactions for ultrahigh catalyst mass activity in water splitting

DOE PAGES

Mo, Jingke; Kang, Zhenye; Retterer, Scott T.; ...

2016-11-18

Better understanding of true electrochemical reaction behaviors in electrochemical energy devices has long been desired. It has been assumed so far that the reactions occur across the entire catalyst layer (CL), which is designed and fabricated uniformly with catalysts, conductors of protons and electrons, and pathways for reactants and products. By introducing a state-of-the-art characterization system, a thin, highly tunable liquid/gas diffusion layer (LGDL), and an innovative design of electrochemical proton exchange membrane electrolyzer cells (PEMECs), the electrochemical reactions on both microspatial and microtemporal scales are revealed for the first time. Surprisingly, reactions occur only on the CL adjacent tomore » good electrical conductors. On the basis of these findings, new CL fabrications on the novel LGDLs exhibit more than 50 times higher mass activity than conventional catalyst-coated membranes in PEMECs. In conclusion, this discovery presents an opportunity to enhance the multiphase interfacial effects, maximizing the use of the catalysts and significantly reducing the cost of these devices.« less

Synthesis and Characterization of Mixed-Conducting Corrosion Resistant Oxide Supports

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ramani, Vijay K.

An extensive search and evaluation of electrochemically stable catalyst supports (including metal oxides like RuO2-SiO2, RuO2-TiO2, and ITO was perfomed during the 4 years of the project. The suports were also catalyzed by deposition of Pt and tested for its performance and electrochemical stability in RDE and fuel cell experiments. For testing the electrochemical stability and fuel cell performance of the catalysts and supports, we have employed the protocols in use at the Department of Energy and Nissan Technological Center North America (NTCNA). The use of such procedures allows a precise and reproducible estimation of the performance and stability ofmore » the materials and permits comparisons among laboratories and DOE funded projects. RuO2-SiO2 catalyst supports showed no loss in surface area during start-stop stability tests that were performed by cycling the electrode potential between 0 V to 1.8 V for 1000 cycles. Catalyzed support (40% Pt/RuO2-SiO2; 1:1 mole ratio) were tested in a PEFC, resulting in a current density of 750 mA/cm2 at 0.6 Volts, and a maximum power density of 570 mW/cm2. Measurements were conducted at 80 ºC with 75% relative humidity of the inlet gases (H2/O2); Pt loadings were 0.4 mg/cm2 at the cathode and 0.2 mg/cm2 at the anode. Start-stop stability tests for support and catalyzed support performed in RDE and PEFC set-ups have confirmed RuO2-TiO2 support stability. The beginning of life performance was exactly equal to end of life performance (in an MEA that has been subjected to severe start-stop cycling for 10,000 start/stop cycles between 1 V to 1.5 V). This result was in sharp contrast to baseline Pt/C catalyst that showed significant performance deterioration after accelerated stability tests. The Pt/TRO showed minimal loss in performance upon exposure to start-stop cycles. The loss in cell voltage at 1 A/cm2 at 100% RH was almost 700 mV for Pt/C whereas it was only ca. 15 mV for Pt/TRO. 40% RH data (of inlet gases) revealed a similar trend in terms of stability – exceptional stability for Pt/TRO as opposed to very poor stability for Pt/HSAC. These observations were attributed to the much higher stability of the TRO support compared to Carbon. The carbon dioxide concentration in the cathode exit stream during the accelerated degradation test with Pt/TRO (start-stop protocol) was extremely low (between 3 to 10 ppm of CO2). In contrast, the CO2 emission levels from a conventional Pt/C catalyst were found to be approx. 200 ppm. This observation was a clear indicator that the main source of carbon being oxidized to carbon dioxide in an MEA was the carbon catalyst support, and not the gas diffusion layer or the graphite flow fields. Indium tin oxide (ITO) was also evaluated as a catalyst support for PEFCs. Pt/ITO was very stable under start-up/shutdown accelerated degradation protocol (RDE tests in perchloric acid). The ECSA change was less than 4% over 10,000 cycles. The load cycling accelerated protocol (from 0.6 to 0.95 V vs. RHE) resulted in a loss of approximately 34% of the initial ECSA after 10,000 cycles. However, fuel cell testing resulted in a very low performing catalyst. XPS spectroscopy was employed to investigate the changes in the catalysts occuring during fuel cell operation. It was observed a shift of In 3d5/2 and In 3d3/2 peaks towards higher binding energies. This can be explained by the formation of hydroxides or oxy-hydroxides in the surface of the catalyst. O1s spectrum for Pt/ITO catalyst after being operated in the fuel cell, also confirmed the formation of significant amounts of surface hydroxides (12 to 16%). The presence of surface hydroxides in the catalyst increased the electrode resistivity affecting fuel cell performance. NTCNA performed a detailed analysis of transport phenomena (reactants and products to/from the Pt active sites) in both commercial catalyst and Pt/RTO (in order to have a better understanding at the basic level). The proton resistance (Rionomer) in Pt/C and Pt/RTO cathode catalyst layers were 150 and 12 mΩ-cm2, respectively. Pt/RTO catalyst layer has about an order or magnitude lower proton transfer resistance than Pt/C catalyst layer. Since the ionomer/support ratio that was used in formulating the ink for both catalysts was the same (0.9), it is expected that the volumetric coverage of ionomer of both catalysts will be significantly different due to the disparity in the surface areas (Pt/C had ~ 800 m2/g, while Pt/RTO had ~ 50 m2/g). The differences in the ionomer volumetric coverage and the ionomer film thickness may explain the significantly higher proton conductivity in the Pt/RTO catalyst layer when compared to Pt/HSAC. It is therefore very important to optimize the ionomer loadings when synthesizing new catalyst supports (and never rely on values for carbon-based commercial catalysts). Finally, NTCNA has elaborated a cost model for non-carbon support materials considering their durability benefits. Material costs for production of Pt/ RuO2-TiO2 electrodes were compared to Pt/C. RuO2-TiO2 support was more expensive than carbon but the total material cost was still dominated by platinum cost. Though ruthenium is considered a precious metal, its cost is far less than platinum. It should also be noted that ruthenium only makes up 38% of the mass of the support, while the rest is inexpensive TiO2. After considering the durability advantages of Pt/RTO, cost model showed that even with almost double the Pt loading (0.35 vs 0.18 mgPt/cm2), Pt/RTO ($22.7/kWnet) is only slightly more expensive than Pt/C ($21.9/kWnet).« less

ENVIRONMENTAL TECHNOLOGY VERIFICATION, TEST REPORT OF MOBILE SOURCE EMISSIONS CONTROL DEVICES: CLEAN DIESEL TECHNOLOGIES FUEL-BORNE CATALYST WITH MITSUI/PUREARTH CATALYZED WIRE MESH FILTER

EPA Science Inventory

The Environmental Technology Verification report discusses the technology and performance of the Fuel-Borne Catalyst with Mitsui/PUREarth Catalyzed Wire Mesh Filter manufactured by Clean Diesel Technologies, Inc. The technology is a platinum/cerium fuel-borne catalyst in commerci...

40 CFR 60.584 - Monitoring of operations and recordkeeping requirements.

Code of Federal Regulations, 2010 CFR

2010-07-01

... the gas temperatures both upstream and downstream of the catalyst bed and shall comply with the... average gas temperature both upstream and downstream of the catalyst bed. After the performance test, the... average temperature of the gas stream before the catalyst bed is more than 28 °C below the average...

40 CFR 60.495 - Reporting and recordkeeping requirements.

Code of Federal Regulations, 2010 CFR

2010-07-01

... catalyst bed), the total mass of VOC per volume of coating solids before and after the incinerator, capture... device immediately before the catalyst bed is more than 28 °C below the average temperature of the device immediately before the catalyst bed during the most recent performance test at which destruction efficiency...

40 CFR 60.315 - Reporting and recordkeeping requirements.

Code of Federal Regulations, 2010 CFR

2010-07-01

... downstream of the catalyst bed), and (iv) A description of the method used to establish the amount of VOC's... the average temperature of the device immediately before the catalyst bed is more than 28 °C below the average temperature of the device immediately before the catalyst bed during the most recent performance...

hcp-Co nanowires grown on metallic foams as catalysts for the Fischer-Tropsch synthesis.

PubMed

Soulantica, Katerina; Harmel, Justine; Peres, Laurent; Estrader, Marta; Berliet, Adrien; Maury, Sylvie; Fécant, Antoine; Chaudret, Bruno; Serp, Philippe

2018-06-12

The possibility to control the structural characteristics of the active phase of supported catalysts offers the opportunity to improve catalyst performance, especially in structure sensitive catalytic reactions. In parallel, heat management is of critical importance for the catalytic performance in highly endo- or exothermic reactions. The Fisher-Tropsch synthesis (FTS) is a structure sensitive exothermic reaction, which enables catalytic transformation of syngas to high quality liquid fuels. We have elaborated monolithic cobalt based heterogeneous catalysts through a wet chemistry approach that allows control over nanocrystal shape and crystallographic phase, while at the same time enables heat management. Copper and nickel foams have been employed as supports for the epitaxial growth of hcp-Co nanowires, directly from a solution containing a coordination compound of cobalt and stabilizing ligands. The Co/Cufoam catalyst has been tested for the Fischer-Tropsch synthesis in fixed bed reactor, showing stability, and significantly superior activity and selectivity towards C5+ compared to a Co/SiO2-Al2O3 reference catalyst under the same conditions. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Hydrogen production from bio-fuels using precious metal catalysts

NASA Astrophysics Data System (ADS)

Pasel, Joachim; Wohlrab, Sebastian; Rotov, Mikhail; Löhken, Katrin; Peters, Ralf; Stolten, Detlef

2017-11-01

Fuel cell systems with integrated autothermal reforming unit require active and robust catalysts for H2 production. Thus, an experimental screening of catalysts for autothermal reforming of commercial biodiesel fuel was performed. Catalysts consisted of a monolithic cordierite substrate, an oxide support (γ-Al2O3) and Pt, Ru, Ni, PtRh and PtRu as active phase. Experiments were run by widely varying the O2/C and H2O/C molar ratios at different gas hourly space velocities. Fresh and aged catalysts were characterized by temperature programmed methods and thermogravimetry to find correlations with catalytic activity and stability.

Design of high-activity single-atom catalysts via n-p codoping

NASA Astrophysics Data System (ADS)

Wang, Xiaonan; Zhou, Haiyan; Zhang, Xiaoyang; Jia, Jianfeng; Wu, Haishun

2018-03-01

The large-scale synthesis of stable single-atom catalysts (SACs) in experiments remains a significant challenge due to high surface free energy of metal atom. Here, we propose a concise n-p codoping approach, and find it can not only disperse the relatively inexpensive metal, copper (Cu), onto boron (B)-doped graphene, but also result in high-activity SACs. We use CO oxidation on B/Cu codoped graphene as a prototype example, and demonstrate that: (1) a stable SAC can be formed by stronger electrostatic attraction between the metal atom (n-type Cu) and support (p-type B-doped graphene). (2) the energy barrier of the prototype CO oxidation on B/Cu codoped graphene is 0.536 eV by the Eley-Rideal mechanism. Further analysis shows that the spin selection rule can provide well theoretical insight into high activity of our suggested SAC. The concept of n-p codoping may lead to new strategy in large-scale synthesis of stable single-atom catalysts.

Relating structure and composition with accessibility of a single catalyst particle using correlative 3-dimensional micro-spectroscopy

DOE PAGES

Liu, Yijin; Meirer, Florian; Krest, Courtney M.; ...

2016-08-30

To understand how hierarchically structured functional materials operate, analytical tools are needed that can reveal small structural and chemical details in large sample volumes. Often, a single method alone is not sufficient to get a complete picture of processes happening at multiple length scales. Here we present a correlative approach combining three-dimensional X-ray imaging techniques at different length scales for the analysis of metal poisoning of an individual catalyst particle. The correlative nature of the data allowed establishing a macro-pore network model that interprets metal accumulations as a resistance to mass transport and can, by tuning the effect of metalmore » deposition, simulate the response of the network to a virtual ageing of the catalyst particle. In conclusion, the developed approach is generally applicable and provides an unprecedented view on dynamic changes in a material’s pore space, which is an essential factor in the rational design of functional porous materials.« less

Growth of carbon nanofibers on tipless cantilevers: process development and applications in scanning probe microscopy

NASA Astrophysics Data System (ADS)

Cui, Hongtao; Kalinin, Sergei; Yang, Xiaojing; Lowndes, Douglas

2005-03-01

Carbon nanofibers (CNFs) are grown on tipless cantilevers as probe tips for scanning probe microscopy. A catalyst dot pattern is formed on the surface of the tipless cantilever using electron beam lithography and CNF growth is performed in a direct-current plasma enhanced chemical vapor deposition reactor. Because the CNF is aligned with the electric field near the edge of the cantilever during growth, it is tilted with respect to the cantilever surface, which compensates partially for the probe tilt introduced when used in scanning probe microscopy. CNFs with different shapes and tip radii can be produced by variation of experimental conditions. The tip geometries of the CNF probes are defined by their catalyst particles, whose magnetic nature also imparts a capability for imaging magnetic samples. We have demonstrated their use in both atomic force and magnetic force surface imaging. These probe tips may provide information on magnetic phenomena at the nanometer scale in connection with the drive for ever-increasing storage density of magnetic hard disks.

Development of vanadium-phosphate catalysts for methanol production by selective oxidation of methane

DOE Office of Scientific and Technical Information (OSTI.GOV)

McCormick, R.L.

1995-12-31

The United States has vast natural gas reserves which could contribute significantly to our energy security if economical technologies for conversion to liquid fuels and chemicals were developed. Many of these reserves are small scale or in remote locations and of little value unless they can be transported to consumers. Transportation is economically performed via pipeline, but this route is usually unavailable in remote locations. Another option is to convert the methane in the gas to liquid hydrocarbons, such as methanol, which can easily and economically be transported by truck. Therefore, the conversion of methane to liquid hydrocarbons has themore » potential to decrease our dependence upon oil imports by opening new markets for natural gas and increasing its use in the transportation and chemical sectors of the economy. In this project, we are attempting to develop, and explore new catalysts capable of direct oxidation of methane to methanol. The specific objectives of this work are discussed.« less

Utilization of a by-product produced from oxidative desulfurization process over Cs-mesoporous silica catalysts.

PubMed

Kim, Hyeonjoo; Jeong, Kwang-Eun; Jeong, Soon-Yong; Park, Young-Kwon; Kim, Do Heui; Jeon, Jong-Ki

2011-02-01

We investigated the use of Cs-mesoporous silica catalysts to upgrade a by-product of oxidative desulfurization (ODS). Cs-mesoporous silica catalysts were characterized through N2 adsorption, XRD, CO2-temperature-programmed desorption, and XRF. Cs-mesoporous silica prepared by the direct incorporation method showed higher catalytic performance than a Cs/MCM-41 catalyst by impregnation method for the catalytic decomposition of sulfone compounds produced from ODS process.

Basic research on radiant burners. Semi-annual report, through July 1991

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sullivan, J.D.

1991-10-01

Basic performance characteristics of radiant burners are explored in the broad-based study combining theoretical modeling and experimental validation of predictions. The work included fabrication of catalyzed substrates and fibers; incorporation of the catalysts into burners; testing of catalysts; and investigation of new catalyst sources. The progress of the study is detailed and further plans are outlined. A report on the preparation of palladium catalysts by Andre Blaise Kooh is included in the appendix.

Rational Design of N- S- Fe- Doped Nanoporous Carbon Catalysts from Covalent Triazine Framework for High Efficient ORR.

PubMed

Zhu, Yuanzhi; Chen, Xifan; Liu, Jing; Zhang, Junfeng; Xu, Danyun; Peng, Wenchao; Li, Yang; Zhang, Guoliang; Zhang, Fengbao; Fan, Xiaobin

2018-05-15

Porous organic polymers (POFs) are promising precursors for developing high performance transition metal-nitrogen-carbon (M-N/C) catalysts towards ORR. But the rational design of POFs precursors remain a great challenge, because of the elusive structural association between the sacrificial POFs and the final M-N/C catalysts. Based on covalent triazine frameworks (CTFs), we developed a series of sulfur-doped Fe-N/C catalysts by selecting six different aromatic nitriles as building blocks. A new mixed solvent of molten FeCl3 and S was used for CTF polymerization, which benefit the formation of Fe-Nx site and make the subsequent pyrolysis process more convenient. Comprehensive study on these CTF-derived catalysts shows their ORR activities are not directly dependent on the theoretical N/C ratio of the building block, but closely correlated to the ratios of the nitrile group to benzene ring (Nnitrile/Nbenzene) and geometries of the building blocks. The high ratios of the Nnitrile/Nbenzene are crucial for ORR activity of the final catalysts due to the formation of more N-doped microporous and Fe-Nx sites in pyrolysis possess. The optimized catalyst shows high ORR performances in acid and superior ORR activity to the Pt/C catalysts under alkaline conditions. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Highly Effective Pt-Based Water-Gas Shift Catalysts by Surface Modification with Alkali Hydroxide Salts

DOE PAGES

Kusche, Matthias; Bustillo, Karen; Agel, Friederike; ...

2015-01-29

Here, we describe an economical and convenient method to improve the performance of Pt/alumina catalysts for the water–gas shift reaction through surface modification of the catalysts with alkali hydroxides according to the solid catalyst with ionic liquid layer approach. The results are in agreement with our findings reported earlier for methanol steam reforming. This report indicates that alkali doping of the catalyst plays an important role in the observed catalyst activation. In addition, the basic and hygroscopic nature of the salt coating contributes to a significant improvement in the performance of the catalyst. During the reaction, a partly liquid filmmore » of alkali hydroxide forms on the alumina surface, which increases the availability of H 2O at the catalytically active sites. Kinetic studies reveal a negligible effect of the KOH coating on the rate dependence of CO and H 2O partial pressures. In conclusion, TEM studies indicate an agglomeration of the active Pt clusters during catalyst preparation; restructuring of Pt nanoparticles occurs under reaction conditions, which leads to a highly active and stable system over 240h time on stream. Excessive pore fillings with KOH introduce a mass transfer barrier as indicated in a volcano-shaped curve of activity versus salt loading. The optimum KOH loading was found to be 7.5wt%.« less

New Method to Synthesize Highly Active and Durable Chemically Ordered fct-PtCo Cathode Catalyst for PEMFCs.

PubMed

Jung, Won Suk; Popov, Branko N

2017-07-19

In the bottom-up synthesis strategy performed in this study, the Co-catalyzed pyrolysis of chelate-complex and activated carbon black at high temperatures triggers the graphitization reaction which introduces Co particles in the N-doped graphitic carbon matrix and immobilizes N-modified active sites for the oxygen reduction reaction (ORR) on the carbon surface. In this study, the Co particles encapsulated within the N-doped graphitic carbon shell diffuse up to the Pt surface under the polymer protective layer and forms a chemically ordered face-centered tetragonal (fct) Pt-Co catalyst PtCo/CCCS catalyst as evidenced by structural and compositional studies. The fct-structured PtCo/CCCS at low-Pt loading (0.1 mg Pt cm -2 ) shows 6% higher power density than that of the state-of-the-art commercial Pt/C catalyst. After the MEA durability test of 30 000 potential cycles, the performance loss of the catalyst is negligible. The electrochemical surface area loss is less than 40%, while that of commercial Pt/C is nearly 80%. After the accelerated stress test, the uniform catalyst distribution is retained and the mean particle size increases approximate 1 nm. The results obtained in this study indicated that highly stable compositional and structural properties of chemically ordered PtCo/CCCS catalyst contribute to its exceptional catalyst durability.

Acidic Mesoporous Zeolite ZSM-5 Supported Cu Catalyst with Good Catalytic Performance in the Hydroxysulfurization of Styrenes with Disulfides.

PubMed

Hu, Jun; Zhu, Chaojie; Xia, Feifei; Fang, Zhongxue; Yang, Fengli; Weng, Jushi; Yao, Pengfei; Zheng, Chunzhi; Dong, Hai; Fu, Wenqian

2017-12-19

Development of highly active heterogeneous catalysts is an effective strategy for modern organic synthesis chemistry. In this work, acidic mesoporous zeolite ZSM-5 (HZSM-5-M), acidic-free mesoporous zeolite TS-1 (TS-1-M), and basic ETS-10 zeolite supported metal Cu catalysts were prepared to investigate their catalytic performances in the hydroxysulfurization of styrenes with diaryl disulfides. The effect of pore size and acidities of the supports, as well as the Cu species electronic properties of the catalysts on reaction activity were investigated. The results show that Cu⁺ and Cu 2+ binded on HZSM-5-M show the highest activity and product selectivity for the desired β -hydroxysulfides compounds.

Acidic Mesoporous Zeolite ZSM-5 Supported Cu Catalyst with Good Catalytic Performance in the Hydroxysulfurization of Styrenes with Disulfides

PubMed Central

Hu, Jun; Zhu, Chaojie; Xia, Feifei; Fang, Zhongxue; Yang, Fengli; Weng, Jushi; Yao, Pengfei; Zheng, Chunzhi; Dong, Hai; Fu, Wenqian

2017-01-01

Development of highly active heterogeneous catalysts is an effective strategy for modern organic synthesis chemistry. In this work, acidic mesoporous zeolite ZSM-5 (HZSM-5-M), acidic-free mesoporous zeolite TS-1 (TS-1-M), and basic ETS-10 zeolite supported metal Cu catalysts were prepared to investigate their catalytic performances in the hydroxysulfurization of styrenes with diaryl disulfides. The effect of pore size and acidities of the supports, as well as the Cu species electronic properties of the catalysts on reaction activity were investigated. The results show that Cu+ and Cu2+ binded on HZSM-5-M show the highest activity and product selectivity for the desired β-hydroxysulfides compounds. PMID:29257075

The catalytic activity of CoMo/USY on deoxygenation reaction of anisole in a batch reactor

NASA Astrophysics Data System (ADS)

Nugrahaningtyas, K. D.; Putri, I. F.; Heraldy, E.; Hidayat, Y.

2018-04-01

The catalytic hydrodeoxigenation of the bio oil model compounds (biomass pyrolysis results) typically uses sulphide catalysts. In this study, we studied the activity of non-sulphide catalyst, the effect of temperature and reaction time on anisole deoxygenation. The catalytic activity was performed in a batch reactor, using N2 gas at 1 bar of pressure. The product was analyzed by gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS). The result showed that the Co-Mo/USY catalyst perform a highest activity and produce pentamethylbenzene, an oxygen free products, when reaction time is 2 hours. The Co-Mo/USY catalysts has the value of the total yield of the product increased with time increase drastically.

A computer program for the design of optimum catalytic monoliths for CO2 lasers

NASA Technical Reports Server (NTRS)

Guinn, K.; Goldblum, S.; Noskowski, E.; Herz, R.

1990-01-01

Pulsed CO2 lasers have many applications in aeronautics, space research, weather monitoring and other areas. Full exploitation of the potential of these lasers is hampered by the dissociation of CO2 that occurs during laser operation. The development of closed-cycle CO2 lasers requires active CO-O2 recombination (CO oxidation) catalysts and design methods for implementation of catalysts inside lasers. The performance criteria and constraints involved in the design of catalyst configurations for use in a closed-cycle laser are discussed, and several design studies performed with a computerized design program that was written are presented. Trade-offs between catalyst activity and dimensions, flow channel dimensions, pressure drop, O2 conversion and other variables are discussed.

Large-scale synthesis of high-quality hexagonal boron nitride nanosheets for large-area graphene electronics.

PubMed

Lee, Kang Hyuck; Shin, Hyeon-Jin; Lee, Jinyeong; Lee, In-yeal; Kim, Gil-Ho; Choi, Jae-Young; Kim, Sang-Woo

2012-02-08

Hexagonal boron nitride (h-BN) has received a great deal of attention as a substrate material for high-performance graphene electronics because it has an atomically smooth surface, lattice constant similar to that of graphene, large optical phonon modes, and a large electrical band gap. Herein, we report the large-scale synthesis of high-quality h-BN nanosheets in a chemical vapor deposition (CVD) process by controlling the surface morphologies of the copper (Cu) catalysts. It was found that morphology control of the Cu foil is much critical for the formation of the pure h-BN nanosheets as well as the improvement of their crystallinity. For the first time, we demonstrate the performance enhancement of CVD-based graphene devices with large-scale h-BN nanosheets. The mobility of the graphene device on the h-BN nanosheets was increased 3 times compared to that without the h-BN nanosheets. The on-off ratio of the drain current is 2 times higher than that of the graphene device without h-BN. This work suggests that high-quality h-BN nanosheets based on CVD are very promising for high-performance large-area graphene electronics. © 2012 American Chemical Society

High-performance Fuel Cell with Stretched Catalyst-Coated Membrane: One-step Formation of Cracked Electrode.

PubMed

Kim, Sang Moon; Ahn, Chi-Yeong; Cho, Yong-Hun; Kim, Sungjun; Hwang, Wonchan; Jang, Segeun; Shin, Sungsoo; Lee, Gunhee; Sung, Yung-Eun; Choi, Mansoo

2016-05-23

We have achieved performance enhancement of polymer electrolyte membrane fuel cell (PEMFC) though crack generation on its electrodes. It is the first attempt to enhance the performance of PEMFC by using cracks which are generally considered as defects. The pre-defined, cracked electrode was generated by stretching a catalyst-coated Nafion membrane. With the strain-stress property of the membrane that is unique in the aspect of plastic deformation, membrane electrolyte assembly (MEA) was successfully incorporated into the fuel cell. Cracked electrodes with the variation of strain were investigated and electrochemically evaluated. Remarkably, mechanical stretching of catalyst-coated Nafion membrane led to a decrease in membrane resistance and an improvement in mass transport, which resulted in enhanced device performance.

Tungsten carbide/porous carbon composite as superior support for platinum catalyst toward methanol electro-oxidation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jiang, Liming; Fu, Honggang, E-mail: fuhg@vip.sina.com; Key Laboratory of Functional Inorganic Material Chemistry, Heilongjiang University, Harbin 150080

2014-01-01

Graphical abstract: The WC nanoparticles are well dispersed in the carbon matrix. The size of WC nanoparticles is about 30 nm. It can be concluded that tungsten carbide and carbon composite was successfully prepared by the present synthesis conditions. - Highlights: • The WC/PC composite with high specific surface area was prepared by a simple way. • The Pt/WC/PC catalyst has superior performance toward methanol electro-oxidation. • The current density for methanol electro-oxidation is as high as 595.93 A g{sup −1} Pt. • The Pt/WC/PC catalyst shows better durability and stronger CO electro-oxidation. • The performance of Pt/WC/PC is superiormore » to the commercial Pt/C (JM) catalyst. - Abstract: Tungsten carbide/porous carbon (WC/PC) composites have been successfully synthesized through a surfactant assisted evaporation-induced-assembly method, followed by a thermal treatment process. In particular, WC/PC-35-1000 composite with tungsten content of 35% synthesized at the carbonized temperature of 1000 °C, exhibited a specific surface area (S{sub BET}) of 457.92 m{sup 2} g{sup −1}. After loading Pt nanoparticles (NPs), the obtained Pt/WC/PC-35-1000 catalyst exhibits the highest unit mass electroactivity (595.93 A g{sup −1} Pt) toward methanol electro-oxidation, which is about 2.6 times as that of the commercial Pt/C (JM) catalyst. Furthermore, the Pt/WC/PC-35-1000 catalyst displays much stronger resistance to CO poisoning and better durability toward methanol electrooxidation compared with the commercial Pt/C (JM) catalyst. The high electrocatalytic activity, strong poison-resistivity and good stability of Pt/WC/PC-35-1000 catalyst are attributed to the porous structures and high specific surface area of WC/PC support could facilitate the rapid mass transportation. Moreover, synergistic effect between WC and Pt NPs is favorable to the higher catalytic performance.« less

Comparison of iridium- and ruthenium-based, Pt-surface-enriched, nanosize catalysts for the oxygen-reduction reaction

NASA Astrophysics Data System (ADS)

Kaplan, D.; Goor, M.; Alon, M.; Tsizin, S.; Burstein, L.; Rosenberg, Y.; Popov, I.; Peled, E.

2016-02-01

Pt-surface-enriched nanosize catalysts (Pt-SENS catalysts) with ruthenium and iridium cores, supported on XC72, were synthesized and characterized. The structure and composition of the catalysts are determined by Energy-Dispersive X-ray Spectroscopy (EDS), X-ray Photoelectron Spectroscopy (XPS), Scanning Transmission Electron Microscopy (STEM) and X-Ray Diffraction (XRD). Electrochemical characterization tests, including oxygen-reduction-catalysis activity and durability studies of catalysts are performed with the use of cyclic-voltammetry and rotating-disk-electrode (RDE) techniques at room temperature. The ORR activity of the homemade catalysts is also compared to ORR activity of commercial 50%Pt/C catalyst. It is determined that the Ir-based catalyst (Pt/Ir/XC72) shows higher ORR activity in terms of A g-1 of Pt (at 0.85 V vs. RHE) than the Ru-based catalyst (Pt/Ru/XC72) and the commercial 50%Pt/C. The Ru-based catalyst shows similar ORR activity in terms of A g-1 of Pt, to that of the commercial 50%Pt/C, but with much lower durability.

New insights into non-precious metal catalyst layer designs for proton exchange membrane fuel cells: Improving performance and stability

NASA Astrophysics Data System (ADS)

Banham, Dustin; Kishimoto, Takeaki; Sato, Tetsutaro; Kobayashi, Yoshikazu; Narizuka, Kumi; Ozaki, Jun-ichi; Zhou, Yingjie; Marquez, Emil; Bai, Kyoung; Ye, Siyu

2017-03-01

The activity of non-precious metal catalysts (NPMCs) has now reached a stage at which they can be considered as possible alternatives to Pt for some proton exchange membrane fuel cell (PEMFC) applications. However, despite significant efforts over the past 50 years on catalyst development, only limited studies have been performed on NPMC-based cathode catalyst layer (CCL) designs. In this work, an extensive ionomer study is performed to investigate the impact of ionomer equivalent weight on performance, which has uncovered two crucial findings. Firstly, it is demonstrated that beyond a critical CCL conductance, no further improvement in performance is observed. The procedure used to determine this critical conductance can be used by other researchers in this field to aid in their design of high performing NPMC-based CCLs. Secondly, it is shown that the stability of NPMC-based CCLs can be improved through the use of low equivalent weight ionomers. This represents a completely unexplored pathway for further stability improvements, and also provides new insights into the possible degradation mechanisms occurring in NPMC-based CCLs. These findings have broad implications on all future NPMC-based CCL designs.

Cobalt-Bridged Ionic Liquid Polymer on a Carbon Nanotube for Enhanced Oxygen Evolution Reaction Activity.

PubMed

Ding, Yuxiao; Klyushin, Alexander; Huang, Xing; Jones, Travis; Teschner, Detre; Girgsdies, Frank; Rodenas, Tania; Schlögl, Robert; Heumann, Saskia

2018-03-19

By taking inspiration from the catalytic properties of single-site catalysts and the enhancement of performance through ionic liquids on metal catalysts, we exploited a scalable way to place single cobalt ions on a carbon-nanotube surface bridged by polymerized ionic liquid. Single dispersed cobalt ions coordinated by ionic liquid are used as heterogeneous catalysts for the oxygen evolution reaction (OER). Performance data reveals high activity and stable operation without chemical instability. © 2017 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.

Small-Scale Coal-Biomass to Liquids Production Using Highly Selective Fischer-Tropsch Synthesis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gangwal, Santosh K.; McCabe, Kevin

2015-04-30

The research project advanced coal-to-liquids (CTL) and coal-biomass to liquids (CBTL) processes by testing and validating Chevron’s highly selective and active cobalt-zeolite hybrid Fischer-Tropsch (FT) catalyst to convert gasifier syngas predominantly to gasoline, jet fuel and diesel range hydrocarbon liquids, thereby eliminating expensive wax upgrading operations The National Carbon Capture Center (NCCC) operated by Southern Company (SC) at Wilsonville, Alabama served as the host site for the gasifier slip-stream testing/demonstration. Southern Research designed, installed and commissioned a bench scale skid mounted FT reactor system (SR-CBTL test rig) that was fully integrated with a slip stream from SC/NCCC’s transport integrated gasifiermore » (TRIG TM). The test-rig was designed to receive up to 5 lb/h raw syngas augmented with bottled syngas to adjust the H 2/CO molar ratio to 2, clean it to cobalt FT catalyst specifications, and produce liquid FT products at the design capacity of 2 to 4 L/day. It employed a 2-inch diameter boiling water jacketed fixed-bed heat-exchange FT reactor incorporating Chevron’s catalyst in Intramicron’s high thermal conductivity micro-fibrous entrapped catalyst (MFEC) packing to efficiently remove heat produced by the highly exothermic FT reaction.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ford, JP; Thapaliya, N; Kelly, MJ

Fatty acids (FAs) derived via thermal hydrolysis of food-grade lard and canola oil were deoxygenated in the liquid phase using a commercially available 5 wt % Pd/C catalyst. Online quadrupole mass spectrometry and gas chromatography were used to monitor the effluent gases from the semi-batch stirred autoclave reactors. Stearic, oleic, and palmitic acids were employed as model compounds. A catalyst lifetime exceeding 2200 turnovers for oleic acid deoxygenation was demonstrated at 300 degrees C and 15 atm under 10% H-2. The initial decarboxylation rate of palmitic acid under 5% H-2 decreases sharply with increasing initial concentration; in contrast, the initialmore » decarbonylation rate increases linearly, indicative of first-order kinetics. Scale-up of diesel-range hydrocarbon production was investigated by increasing the reactor vessel size, initial FA concentration, and FA/catalyst mass ratio. Lower CO2 selectivity and batch productivity were observed at the larger scales (600 and 5000 mL), primarily because of the higher initial FA concentration (67 wt %) employed. Because unsaturated FAs must be hydrogenated before deoxygenation can proceed at an appreciable rate, the additional batch time required for FA hydrogenation reduces the batch productivity for unsaturated feedstocks. Low-temperature hydrogenation of unsaturated feedstocks (using Pd/C or another less-expensive catalyst) prior to deoxygenation is recommended.« less

"Catalysis in a tea bag": synthesis, catalytic performance and recycling of dendrimer-immobilised bis- and trisoxazoline copper catalysts.

PubMed

Gaab, Manuela; Bellemin-Laponnaz, Stéphane; Gade, Lutz H

2009-01-01

Bis- and trisoxazolines (BOX and trisox), containing a linker unit in the ligand backbone that allows their covalent attachment to carbosilane dendrimers, have been employed as polyfunctional ligands for recyclable Cu(II) Lewis acid catalysts that were immobilised in a membrane bag. The oxazolines contained an alkynyl unit attached to their backbone that was deprotonated with LDA or BuLi and then reacted with the chlorosilyl termini of zeroth-, first- and second-generation carbosilane dendrimers in the presence of TlPF(6). The functionalised dendritic systems were subsequently separated from excess ligand by way of dialysis. The general catalytic potential of these systems was assessed by studying two benchmark reactions, the alpha-hydrazination of a beta-keto ester as well as the Henry reaction of 2-nitrobenzaldehyde with nitromethane. For both reactions the bisoxazoline-based catalysts displayed superior selectivity and, in particular, catalyst activity. The latter was interpreted as being due to the hindered decoordination of the third oxazoline unit, the key step in the generation of the active catalyst, in the immobilised trisox-copper complexes. Solutions of the second-generation dendrimer catalysts were placed in membrane bags, fabricated from commercially available dialysis membranes, with the purpose of catalyst recycling based on dialysis. Overall, the supported BOX catalyst gave good and highly reproducible results throughout the study, whereas the performance of the trisox dendrimer system decreased monotonically. The reason for the different behaviour is the markedly lower activity of trisox-based catalysts relative to those based on the BOX ligand. This necessitated an increased reaction time for each cycle of the trisox derivatives, resulting in higher levels of catalyst leaching, which was attributed to a modification of the structure of the membrane by its exposure to the solvent trifluoroethanol at 40 degrees C.

Data on calcium oxide and cow bone catalysts used for soybean biodiesel production.

PubMed

Ayodeji, Ayoola A; Blessing, Igho E; Sunday, Fayomi O

2018-06-01

Biodiesel was produced from soybean oil using calcium oxide and cow bone as heterogeneous catalysts, through transesterification process. The soybean oil used was characterized using gas chromatography mass spectrometer (GCMS) and the cow bone catalyst produced was characterized X-ray fluorescence (XRF) spectrometer. The effects of the variation of methanol/oil mole ratio, catalyst concentration and reaction temperature on biodiesel yield during the transesterification of soybean oil were investigated. Reaction time of 3 h and stirring rate of 500 rpm were kept constant. Using Response Optimizer (Minitab 17), the optimum conditions for biodiesel production were established. It was observed that the calcination of cow bone catalyst enhanced its conversion to apatite-CaOH. Also, the results obtained showed that the performance trends of calcined cow bone catalyst and the conventional CaO catalyst were similar.

Practical, economical, and eco-friendly starch-supported palladium catalyst for Suzuki coupling reactions.

PubMed

Baran, Talat

2017-06-15

In catalytic systems, the support materials need to be both eco friendly and low cost as well as having high thermal and chemical stability. In this paper, a novel starch supported palladium catalyst, which had these outstanding properties, was designed and its catalytic activity was evaluated in a Suzuki coupling reaction under microwave heating with solvent-free and mild reaction conditions. The starch supported catalyst gave remarkable reaction yields after only 5min as a result of the coupling reaction of the phenyl boronic acid with 23 different substrates, which are bearing aril bromide, iodide, and chloride. The longevity of the catalyst was also investigated, and the catalyst could be reused for 10 runs. The starch supported Pd(II) catalyst yielded remarkable TON (up to 25,000) and TOF (up to 312,500) values by using a simple, fast and eco-friendly method. In addition, the catalytic performance of the catalyst was tested against different commercial palladium catalysts, and the green starch supported catalyst had excellent selectivity. The catalytic tests showed that the novel starch based palladium catalyst proved to be an economical and practical catalyst for the synthesis of biaryl compounds. Copyright © 2017 Elsevier Inc. All rights reserved.

Methanol-Tolerant Platinum-Palladium Catalyst Supported on Nitrogen-Doped Carbon Nanofiber for High Concentration Direct Methanol Fuel Cells

PubMed Central

Kim, Jiyoung; Jang, Jin-Sung; Peck, Dong-Hyun; Lee, Byungrok; Yoon, Seong-Ho; Jung, Doo-Hwan

2016-01-01

Pt-Pd catalyst supported on nitrogen-doped carbon nanofiber (N-CNF) was prepared and evaluated as a cathode electrode of the direct methanol fuel cell (DMFC). The N-CNF, which was directly synthesized by the catalytic chemical vapor deposition from acetonitrile at 640 °C, was verified as having a change of electrochemical surface properties such as oxygen reduction reaction (ORR) activities and the electrochemical double layer compared with common carbon black (CB). To attain the competitive oxygen reduction reaction activity with methanol tolerance, the Pt and Pd metals were supported on the CB or the N-CNF. The physical and electrochemical characteristics of the N-CNF–supported Pt-Pd catalyst were examined and compared with catalyst supported on the CB. In addition, DMFC single cells using these catalysts as the cathode electrode were applied to obtain I-V polarization curves and constant current operating performances with high-concentration methanol as the fuel. Pt-Pd catalysts had obvious ORR activity even in the presence of methanol. The higher power density was obtained at all the methanol concentrations when it applied to the membrane electrode assembly (MEA) of the DMFC. When the N-CNF is used as the catalyst support material, a better performance with high-concentration methanol is expected. PMID:28335275

Synthesis of nanoporous CuO/TiO2/Pd-NiO composite catalysts by chemical dealloying and their performance for methanol and ethanol electro-oxidation

NASA Astrophysics Data System (ADS)

Niu, Mengying; Xu, Wence; Zhu, Shengli; Liang, Yanqin; Cui, Zhenduo; Yang, Xianjin; Inoue, Akihisa

2017-09-01

Nanoporous CuO/TiO2/Pd-NiO-x (x = 0, 1, 3, 5, 7 at%) catalysts have been synthesized by dealloying Cu-Ti-Pd-Ni alloy ribbons in acid solution. The nanoporous structure and chemical composition of the catalysts distribute uniformly. Based on the electrochemical active area (EASA), electrocatalytic activity and stability, the np-CuO/TiO2/Pd-NiO-3 catalyst possesses the best performance for methanol and ethanol electro-oxidation. For methanol and ethanol electro-oxidation, the anodic current densities in forward scan of the np-CuO/TiO2/Pd-NiO-3 catalyst are about 5.6 times and 2.1 times larger than that of the np-CuO/TiO2/Pd catalyst, respectively. The introduction of NiO provides more electrochemical active sites due to the improved geometrical and bifunctional mechanism. NiO promotes the adsorption of oxygen-containing species (OHads) on the catalyst surface, and electron effect between Pd and Ni is favorable for charge transfer. This accelerates the removal of intermediate products during the oxidation process. The electrocatalytic processes of methanol and ethanol oxidation in alkaline solution are controlled by both charge transfer and diffusion.

Methanol-Tolerant Platinum-Palladium Catalyst Supported on Nitrogen-Doped Carbon Nanofiber for High Concentration Direct Methanol Fuel Cells.

PubMed

Kim, Jiyoung; Jang, Jin-Sung; Peck, Dong-Hyun; Lee, Byungrok; Yoon, Seong-Ho; Jung, Doo-Hwan

2016-08-15

Pt-Pd catalyst supported on nitrogen-doped carbon nanofiber (N-CNF) was prepared and evaluated as a cathode electrode of the direct methanol fuel cell (DMFC). The N-CNF, which was directly synthesized by the catalytic chemical vapor deposition from acetonitrile at 640 °C, was verified as having a change of electrochemical surface properties such as oxygen reduction reaction (ORR) activities and the electrochemical double layer compared with common carbon black (CB). To attain the competitive oxygen reduction reaction activity with methanol tolerance, the Pt and Pd metals were supported on the CB or the N-CNF. The physical and electrochemical characteristics of the N-CNF-supported Pt-Pd catalyst were examined and compared with catalyst supported on the CB. In addition, DMFC single cells using these catalysts as the cathode electrode were applied to obtain I-V polarization curves and constant current operating performances with high-concentration methanol as the fuel. Pt-Pd catalysts had obvious ORR activity even in the presence of methanol. The higher power density was obtained at all the methanol concentrations when it applied to the membrane electrode assembly (MEA) of the DMFC. When the N-CNF is used as the catalyst support material, a better performance with high-concentration methanol is expected.

Performance of Ni/dolomite pellet catalyst on gas distribution from cassava rhizome gasification with a modular fixed-bed gasifier.

PubMed

Sricharoenchaikul, V; Atong, D; Sornkade, P; Nisamaneenate, J

2017-05-01

Thermal conversion of cassava rhizome was performed using a modular downdraft gasifier with the addition of Ni-based catalysts as promising tar eliminating and produced gas upgrading techniques. The activities of a synthesized 5% Ni/dolomite pellet catalyst prepared by impregnation method were investigated in a secondary reactor downstream of the gasifier. High reforming activity of the Ni/dolomite pellet catalyst on tar reduction was achieved. The conversion to H 2 and CO was improved via steam reforming of methane and char reaction with CO 2 . Moreover, the formation of CH 4 and C x H y was diminished through the tar or condensable hydrocarbon reformed on the catalyst surface. The carbon and hydrogen conversions of cassava rhizome with prepared catalyst were 83.79% and 61.78%, respectively, at an air flow rate of 1.98 m 3 /hr. At this condition, tar formation was low, while the lower heating value was 4.39 MJ/m 3 and H 2 to CO molar ratio was 1.22. Generally, the addition of a catalyst not only enhanced gas production, but also reduced tar and particulate matter generation; thus, its implementation should help lessen the pollution control requirement and cost of operation, while allowing higher quality fuel gas production.

Raney Ni-Sn catalyst for H2 production from biomass-derived hydrocarbons.

PubMed

Huber, G W; Shabaker, J W; Dumesic, J A

2003-06-27

Hydrogen (H2) was produced by aqueous-phase reforming of biomass-derived oxygenated hydrocarbons at temperatures near 500 kelvin over a tin-promoted Raney-nickel catalyst. The performance of this non-precious metal catalyst compares favorably with that of platinum-based catalysts for production of hydrogen from ethylene glycol, glycerol, and sorbitol. The addition of tin to nickel decreases the rate of methane formation from C-O bond cleavage while maintaining the high rates of C-C bond cleavage required for hydrogen formation.