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

Hong, Yongchun; Hensley, Alyssa; McEwen, Jean-Sabin

Catalytic fast pyrolysis is the most promising approach for biofuel production, due to its simple process and versatility to handle lignocellulosic biomass feedstocks with varying and complex compositions. Compared with in situ catalytic fast pyrolysis, ex situ catalytic pyrolysis has the flexibility of optimizing the pyrolysis step and catalytic process individually to improve the quality of pyrolysis oil (stability, oxygen content, acid number, etc.) and to maximize the carbon efficiency in the conversion of biomass to pyrolysis oil. Hydrodeoxygenation is one of the key catalytic functions in ex situ catalytic fast pyrolysis. Recently, Fe-based catalysts have been reported to exhibitmore » superior catalytic properties in hydrodeoxygenation of model compounds in pyrolysis oil, which potentially makes the ex situ pyrolysis of biomass commercially viable due to the abundance and low cost of Fe. Here, we briefly summarize the recent progress on Fe-based catalysts for hydrodeoxygenation of biomass, and provide perspectives on how to further improve Fe-based catalysts (activity and stability) for their potential applications in the emerging area of biomass conversion.« less

Homogeneous Molecular Catalysis of Electrochemical Reactions: Catalyst Benchmarking and Optimization Strategies.

PubMed

Costentin, Cyrille; Savéant, Jean-Michel

2017-06-21

Modern energy challenges currently trigger an intense interest in catalysis of redox reactions-electrochemical and photochemical-particularly those involving small molecules such as water, hydrogen, oxygen, proton, carbon dioxide. A continuously increasing number of molecular catalysts of these reactions, mostly transition metal complexes, have been proposed, rendering necessary procedures for their rational benchmarking and fueling the quest for leading principles that could inspire the design of improved catalysts. The search of "volcano plots" correlating catalysis kinetics to the stability of the key intermediate is a popular approach to the question in catalysis by surface-active sites, with as foremost example the electrochemical reduction of aqueous proton on metal surfaces. We discussed here for the first time, on theoretical and experimental grounds, the pertinence of such an approach in the field of molecular catalysis. This is the occasion to insist on the virtue of careful mechanism assignments. Particular emphasis is put on the interest of expressing the catalysts' intrinsic kinetic properties by means of catalytic Tafel plots, which relate kinetics and overpotential. We also underscore that the principle and strategies put forward for the catalytic activation of the above-mentioned small molecules are general as illustrated by catalytic applications out of this particular field.

Sol-gel (template) synthesis of macroporous Mo-based catalysts for hydrothermal oxidation of radionuclide-organic complexes

NASA Astrophysics Data System (ADS)

Papynov, E. K.; Palamarchuk, M. S.; Mayorov, V. Yu; Modin, E. B.; Portnyagin, A. S.; Sokol'nitskaya, T. A.; Belov, A. A.; Tananaev, I. G.; Avramenko, V. A.

2017-07-01

Molybdenum compounds are industrially demanding as heterogeneous catalysts for oxidation of various organic substances. Highly porous structure of molybdenum-containing catalysts avoids surface's colmatation and prevents blocking catalytic sites that makes these materials play a key role in processes of hydrothermal oxidation of radionuclide organic complexes. The study presents an original way of sol-gel synthesis of new macroporous molybdenum compounds using ;core-shell; colloid template (polymer latex) as poreforming agent. We have described three individual routs of template removal via thermal decomposition to obtain porous materials based on molybdenum compounds. Thermal treatment conditions (temperature, gaseous atmosphere) have been studied with respect to their influence on composition, structure and catalytic properties of synthesized molybdenum systems. The optimal way to synthesis of crystal molybdenum (VI) oxide with ordered porous structure (mean pore size 100-160 nm) has been suggested. Catalytic properties of macroporous molybdenum materials have been investigated in the process of liquid phase and hydrothermal oxidation of such organic substances thiazine and stable Co-EDTA complex. It was shown that macroporous molybdenum oxides could be applied as prospective catalysts for hydrothermal oxidation of organic radionuclide complexes during the processing of radioactive waste.

An optimization study of PtSn/C catalysts applied to direct ethanol fuel cell: Effect of the preparation method on the electrocatalytic activity of the catalysts

NASA Astrophysics Data System (ADS)

Almeida, T. S.; Palma, L. M.; Leonello, P. H.; Morais, C.; Kokoh, K. B.; De Andrade, A. R.

2012-10-01

The aim of this work was to perform a systematic study of the parameters that can influence the composition, morphology, and catalytic activity of PtSn/C nanoparticles and compare two different methods of nanocatalyst preparation, namely microwave-assisted heating (MW) and thermal decomposition of polymeric precursors (DPP). An investigation of the effects of the reducing and stabilizing agents on the catalytic activity and morphology of Pt75Sn25/C catalysts prepared by microwave-assisted heating was undertaken for optimization purposes. The effect of short-chain alcohols such as ethanol, ethylene glycol, and propylene glycol as reducing agents was evaluated, and the use of sodium acetate and citric acid as stabilizing agents for the MW procedure was examined. Catalysts obtained from propylene glycol displayed higher catalytic activity compared with catalysts prepared in ethylene glycol. Introduction of sodium acetate enhanced the catalytic activity, but this beneficial effect was observed until a critical acetate concentration was reached. Optimization of the MW synthesis allowed for the preparation of highly dispersed catalysts with average sizes lying between 2.0 and 5.0 nm. Comparison of the best catalyst prepared by MW with a catalyst of similar composition prepared by the polymeric precursors method showed that the catalytic activity of the material can be improved when a proper condition for catalyst preparation is achieved.

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

Interplay between the spin-selection rule and frontier orbital theory in O2 activation and CO oxidation by single-atom-sized catalysts on TiO2(110).

PubMed

Li, Shunfang; Zhao, Xingju; Shi, Jinlei; Jia, Yu; Guo, Zhengxiao; Cho, Jun-Hyung; Gao, Yanfei; Zhang, Zhenyu

2016-09-28

Exploration of the catalytic activity of low-dimensional transition metal (TM) or noble metal catalysts is a vital subject of modern materials science because of their instrumental role in numerous industrial applications. Recent experimental advances have demonstrated the utilization of single atoms on different substrates as effective catalysts, which exhibit amazing catalytic properties such as more efficient catalytic performance and higher selectivity in chemical reactions as compared to their nanostructured counterparts; however, the underlying microscopic mechanisms operative in these single atom catalysts still remain elusive. Based on first-principles calculations, herein, we present a comparative study of the key kinetic rate processes involved in CO oxidation using a monomer or dimer of two representative TMs (Pd and Ni) on defective TiO2(110) substrates (TMn@TiO2(110), n = 1, 2) to elucidate the underlying mechanism of single-atom catalysis. We reveal that the O2 activation rates of the single atom TM catalysts deposited on TiO2(110) are governed cooperatively by the classic spin-selection rule and the well-known frontier orbital theory (or generalized d-band picture) that emphasizes the energy gap between the frontier orbitals of the TM catalysts and O2 molecule. We further illuminate that the subsequent CO oxidation reactions proceed via the Langmuir-Hinshelwood mechanism with contrasting reaction barriers for the Pd monomer and dimer catalysts. These findings not only provide an explanation for existing observations of distinctly different catalytic activities of Pd@TiO2(110) and Pd2@TiO2(110) [Kaden et al., Science, 2009, 326, 826-829] but also shed new insights into future utilization and optimization of single-atom catalysis.

Enhancement of Treatment Efficiency of Recalcitrant Wastewater Containing Textile Dyes Using a Newly Developed Iron Zeolite Socony Mobil-5 Heterogeneous Catalyst

PubMed Central

Ahmad, Mushtaq; Asghar, Anam; Abdul Raman, Abdul Aziz; Wan Daud, Wan Mohd Ashri

2015-01-01

Fenton oxidation, an advanced oxidation process, is an efficient method for the treatment of recalcitrant wastewaters. Unfortunately, it utilizes H2O2 and iron-based homogeneous catalysts, which lead to the formation of high volumes of sludge and secondary pollutants. To overcome these problems, an alternate option is the usage of heterogeneous catalyst. In this study, a heterogeneous catalyst was developed to provide an alternative solution for homogeneous Fenton oxidation. Iron Zeolite Socony Mobile-5 (Fe-ZSM-5) was synthesized using a new two-step process. Next, the catalyst was characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, fourier transform infrared spectroscopy, and Brunauer-Emmett-Teller analysis and tested against a model wastewater containing the azo dye Acid Blue 113. Results showed that the loading of iron particles reduced the surface area of the catalyst from 293.59 to 243.93 m2/g; meanwhile, the average particle size of the loaded material was 12.29 nm. Furthermore, efficiency of the developed catalyst was evaluated by performing heterogeneous Fenton oxidation. Taguchi method was coupled with principal component analysis in order to assess and optimize mineralization efficiency. Experimental results showed that under optimized conditions, over 99.7% degradation and 77% mineralization was obtained, with a 90% reduction in the consumption of the developed catalyst. Furthermore, the developed catalyst was stable and reusable, with less than 2% leaching observed under optimized conditions. Thus, the present study proved that newly developed catalyst has enhanced the oxidation process and reduced the chemicals consumption. PMID:26517827

Enhancement of Treatment Efficiency of Recalcitrant Wastewater Containing Textile Dyes Using a Newly Developed Iron Zeolite Socony Mobil-5 Heterogeneous Catalyst.

PubMed

Ahmad, Mushtaq; Asghar, Anam; Abdul Raman, Abdul Aziz; Wan Daud, Wan Mohd Ashri

2015-01-01

Fenton oxidation, an advanced oxidation process, is an efficient method for the treatment of recalcitrant wastewaters. Unfortunately, it utilizes H2O2 and iron-based homogeneous catalysts, which lead to the formation of high volumes of sludge and secondary pollutants. To overcome these problems, an alternate option is the usage of heterogeneous catalyst. In this study, a heterogeneous catalyst was developed to provide an alternative solution for homogeneous Fenton oxidation. Iron Zeolite Socony Mobile-5 (Fe-ZSM-5) was synthesized using a new two-step process. Next, the catalyst was characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, fourier transform infrared spectroscopy, and Brunauer-Emmett-Teller analysis and tested against a model wastewater containing the azo dye Acid Blue 113. Results showed that the loading of iron particles reduced the surface area of the catalyst from 293.59 to 243.93 m2/g; meanwhile, the average particle size of the loaded material was 12.29 nm. Furthermore, efficiency of the developed catalyst was evaluated by performing heterogeneous Fenton oxidation. Taguchi method was coupled with principal component analysis in order to assess and optimize mineralization efficiency. Experimental results showed that under optimized conditions, over 99.7% degradation and 77% mineralization was obtained, with a 90% reduction in the consumption of the developed catalyst. Furthermore, the developed catalyst was stable and reusable, with less than 2% leaching observed under optimized conditions. Thus, the present study proved that newly developed catalyst has enhanced the oxidation process and reduced the chemicals consumption.

HARNESSING THE CHEMISTRY OF CO2

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

Louie, Janis

2010-05-11

Our research program is broadly focused on activating CO{sub 2} through the use of organic and organometallic based catalysts. Some of our methods have centered on annulation reactions of unsaturated hydrocarbons (and carbonyl substrates) to provide a diverse array of carbocycles and heterocycles. We use a combination of catalyst discovery and optimization in conjunction with classical physical organic chemistry to elucidate the key mechanistic features of the cycloaddition reactions such that the next big advances in catalyst development can be made. Key to all of our cycloaddition reactions is the use of a sterically hindered, electron donating N heterocyclic carbenemore » (NHC) ligand, namely IPr (or SIPr), in conjunction with a low valent nickel pre-catalyst. The efficacy of this ligand is two-fold: (1) the high {delta}-donating ability of the NHC increases the nucleophilicity of the metal center which thereby facilitates interaction with the electrophilic carbonyl and (2) the steric hindrance prevents an otherwise competitive side reaction involving only the alkyne substrate. Such a system has allowed for the facile cycloaddition to prepare highly functionalized pyrones, pyridones, pyrans, as well as novel carbocycles. Importantly, all reactions proceed under extremely mild conditions (room temperature, atmospheric pressures, and short reaction times), require only catalytic amounts of Ni/NHC and readily available starting materials, and afford annulated products in excellent yields. Our current focus revolves around understanding the fundamental processes that govern these cycloadditions such that the next big advance in the cyclization chemistry of CO{sub 2} can be made. Concurrent to our annulation chemistry is our investigation of the potential for imidazolylidenes to function as thermally-actuated CO{sub 2} sequestering and delivery agents.« less

Pt/SnO2-based CO-oxidation catalysts for CO2 lasers

NASA Technical Reports Server (NTRS)

Upchurch, Billy T.; Schryer, David R.; Hess, Robert V.; Brown, Kenneth G.; Van Norman, John D.

1990-01-01

The activity of Pt/SnO2-based CO-oxidation catalysts has been maximized by optimizing pretreatment conditions and catalyst formulation. The role of H2O in activating these catalysts and of CO2 retention in deactivating them has been determined as has the interaction of these catalysts with rare-isotope C(0-18) and (O-18)2.

Alkene metathesis: the search for better catalysts.

PubMed

Deshmukh, Prashant H; Blechert, Siegfried

2007-06-28

Alkene metathesis catalyst development has made significant progress over recent years. Research in metathesis catalyst design has endeavoured to tackle three key issues: those of (i) catalyst efficiency and activity, (ii) substrate scope and selectivity--particularly stereoselective metathesis reactions--and (iii) the minimization of metal impurities and catalyst recycling. This article describes a brief history of metathesis catalyst development, followed by a survey of more recent research, with a particular emphasis on ruthenium catalysts.

Combinatorial Optimization of Heterogeneous Catalysts Used in the Growth of Carbon Nanotubes

NASA Technical Reports Server (NTRS)

Cassell, Alan M.; Verma, Sunita; Delzeit, Lance; Meyyappan, M.; Han, Jie

2000-01-01

Libraries of liquid-phase catalyst precursor solutions were printed onto iridium-coated silicon substrates and evaluated for their effectiveness in catalyzing the growth of multi-walled carbon nanotubes (MWNTs) by chemical vapor deposition (CVD). The catalyst precursor solutions were composed of inorganic salts and a removable tri-block copolymer (EO)20(PO)70(EO)20 (EO = ethylene oxide, PO = propylene oxide) structure-directing agent (SDA), dissolved in ethanol/methanol mixtures. Sample libraries were quickly assayed using scanning electron microscopy after CVD growth to identify active catalysts and CVD conditions. Composition libraries and focus libraries were then constructed around the active spots identified in the discovery libraries to understand how catalyst precursor composition affects the yield, density, and quality of the nanotubes. Successful implementation of combinatorial optimization methods in the development of highly active, carbon nanotube catalysts is demonstrated, as well as the identification of catalyst formulations that lead to varying densities and shapes of aligned nanotube towers.

Membrane-electrode structures for molecular catalysts for use in fuel cells and other electrochemical devices

DOEpatents

Kerr, John B.; Zhu, Xiaobing; Hwang, Gi Suk; Martin, Zulima; He, Qinggang; Driscoll, Peter; Weber, Adam; Clark, Kyle

2016-09-27

Water soluble catalysts, (M)meso-tetra(N-Methyl-4-Pyridyl)Porphinepentachloride (M=Fe, Co, Mn & Cu), have been incorporated into the polymer binder of oxygen reduction cathodes in membrane electrode assemblies used in PEM fuel cells and found to support encouragingly high current densities. The voltages achieved are low compared to commercial platinum catalysts but entirely consistent with the behavior observed in electroanalytical measurements of the homogeneous catalysts. A model of the dynamics of the electrode action has been developed and validated and this allows the MEA electrodes to be optimized for any chemistry that has been demonstrated in solution. It has been shown that improvements to the performance will come from modifications to the structure of the catalyst combined with optimization of the electrode structure and a well-founded pathway to practical non-platinum group metal catalysts exists.

Morphology controlled synthesis of 2-D Ni-Ni3S2 and Ni3S2 nanostructures on Ni foam towards oxygen evolution reaction

NASA Astrophysics Data System (ADS)

Chaudhari, Nitin Kaduba; Oh, Aram; Sa, Young Jin; Jin, Haneul; Baik, Hionsuck; Kim, Sang Gu; Lee, Suk Joong; Joo, Sang Hoon; Lee, Kwangyeol

2017-03-01

Catalysts for oxygen evolution reactions (OER) are at the heart of key renewable energy technologies, and development of non-precious metal catalysts with high activity and stability remain a great challenge in this field. Among various material candidates, metal sulfides are receiving increasing attention. While morphology-dependent catalytic performances are well established in noble metal-based catalysts, relatively little is known for the morphology‒catalytic performance relationship in metal sulfide catalysts. In this study, uniform spider web-like Ni nanosheets-Ni3S2 and honeycomb-like Ni3S2 structures are deposited on nickel foam (Ni3S2/NF) by a facile one-step hydrothermal synthetic route. When used as an oxygen evolution electrode, the spider web-like Ni-Ni3S2/NF with the large exposed surface area shown excellent catalytic activity and stability with an overpotential of 310 mV to achieve at 10 mA/cm2 and a Tafel slope of 63 mV/dec in alkaline media, which is superior to the honeycomb-like structure without Ni nanosheet. The low Tafel slope of the spider web-like Ni-Ni3S2/NF represents one of the best OER kinetics among nickel sulfide-based OER catalysts. The results point to the fact that performance of the metal sulfide electrocatalysts might be fine-tuned and optimized with morphological controls.

New catalysts for coal liquefaction and new nanocrystalline catalysts synthesis methods

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

Linehan, J.C.; Matson, D.W.; Darab, J.G.

1994-09-01

The use of coal as a source of transportation fuel is currently economically unfavorable due to an abundant world petroleum supply and the relatively high cost of coal liquefaction. Consequently, a reduction in the cost of coal liquefaction, for example by using less and/or less costly catalysts or lower liquefaction temperatures, must be accomplished if coal is to play an significant role as a source of liquid feedstock for the petrochemical industry. The authors and others have investigated the applicability of using inexpensive iron-based catalysts in place of more costly and environmentally hazardous metal catalysts for direct coal liquefaction. Iron-basedmore » catalysts can be effective in liquefying coal and in promoting carbon-carbon bond cleavage in model compounds. The authors have been involved in an ongoing effort to develop and optimize iron-based powders for use in coal liquefaction and related petrochemical applications. Research efforts in this area have been directed at three general areas. The authors have explored ways to optimize the effectiveness of catalyst precursor species through use of nanocrystalline materials and/or finely divided powders. In this effort, the authors have developed two new nanophase material production techniques, Modified Reverse Micelle (MRM) and the Rapid Thermal Decomposition of precursors in Solution (RTDS). A second effort has been aimed at optimizing the effectiveness of catalysts by variations in other factors. To this, the authors have investigated the effect that the crystalline phase has on the capacity of iron-based oxide and oxyhydroxide powders to be effectively converted to an active catalyst phase under liquefaction conditions. And finally, the authors have developed methods to produce active catalyst precursor powders in quantities sufficient for pilot-scale testing. Major results in these three areas are summarized.« less

First-Principles Mechanistic Analysis of Dimethyl Ether Electro-Oxidation on Monometallic Single-Crystal Surfaces

DOE PAGES

Herron, Jeffrey A.; Ferrin, Peter; Mavrikakis, Manos

2014-08-27

Dimethyl ether is an attractive alternative to petroleum fuels due to its physical properties, comparable energy density to methanol and ethanol, and minimal deleterious environmental/toxicological effects. For direct fuel cells, it has a number of advantages over other prominent fuels, including easier storage with respect to hydrogen, lower toxicity and crossover when compared to methanol, and more facile complete oxidation as compared to ethanol (which includes a relatively difficult to break C–C bond). However, the dimethyl ether electro-oxidation reaction is poorly understood, hindering the development of improved electrocatalysts. Using periodic, self-consistent (PW91-GGA) density functional theory calculations, we evaluate the thermochemistrymore » of dimethyl ether (DME) electro-oxidation, at the elementary step level, on 12 model, closed-packed facets of pure transition metals: Au, Ag, Cu, Pt, Pd, Ni, Ir, Rh, Co, Os, Ru, and Re. From the calculated thermochemistry, we determine the most probable reaction paths on each of these surfaces, focusing on Pt as a model system. Our results predict two key electro-oxidation peaks. At lower potentials, there is a peak corresponding to partial oxidation of DME to CO (and other surface poisoning species) or complete oxidation to CO 2 via formic acid as a key intermediate. A second, higher-potential peak is due to complete oxidation of adsorbed CO (and other surface poisoning species) to CO 2. Assuming the catalysts remain in their metallic state during the DME electro-oxidation process, our results suggest that the onset potential of the surfaces increases in the order Cu < Ni < Os < Rh < Ir < Co < Ru < Pt < Ag < Pd < Re < Au. Using our results, we construct a theoretical phase diagram showing predicted catalyst activity based on two key reactivity descriptors, the free energies of adsorbed CO and OH. Here, we compare all results to methanol electro-oxidation to understand key mechanistic differences and their impacts on optimal catalyst design for direct DME fuel cells.« less

Application of Metal Catalysts for High Selectivity of Glycerol Conversion to Alcohols

DOT National Transportation Integrated Search

2010-11-01

The objective of this project is to determine the applicability of metal-based catalysts and optimize the process conditions for thermochemically producing primary alcohols. Metal catalysts were evaluated for their selectivities for producing alcohol...

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.

Fast Optimization of LiMgMnOx/La2O3 Catalysts for the Oxidative Coupling of Methane.

PubMed

Li, Zhinian; He, Lei; Wang, Shenliang; Yi, Wuzhong; Zou, Shihui; Xiao, Liping; Fan, Jie

2017-01-09

The development of efficient catalyst for oxidative coupling of methane (OCM) reaction represents a grand challenge in direct conversion of methane into other useful products. Here, we reported that a newly developed combinatorial approach can be used for ultrafast optimization of La 2 O 3 -based multicomponent metal oxide catalysts in OCM reaction. This new approach integrated inkjet printing assisted synthesis (IJP-A) with multidimensional group testing strategy (m-GT) tactfully takes the place of conventionally high-throughput synthesis-and-screen experiment. Just within a week, 2048 formulated LiMgMnO x -La 2 O 3 catalysts in a 64·8·8·8·8 = 262 144 compositional space were fabricated by IJP-A in a four-round synthesis-and-screen process, and an optimized formulation has been successfully identified through only 4·8 = 32 times of tests via m-GT screening strategy. The screening process identifies the most promising ternary composition region is Li 0-0.48 Mg 0-6.54 Mn 0-0.62 -La 100 O x with an external C 2 yield of 10.87% at 700 °C. The yield of C 2 is two times as high as the pure nano-La 2 O 3 . The good performance of the optimized catalyst formulation has been validated by the manual preparation, which further prove the effectiveness of the new combinatorial methodology in fast discovery of heterogeneous catalyst.

Tethered catalysts for the hydration of carbon dioxide

DOEpatents

Valdez, Carlos A; Satcher, Jr., Joe H; Aines, Roger D; Wong, Sergio E; Baker, Sarah E; Lightstone, Felice C; Stolaroff, Joshuah K

2014-11-04

A system is provided that substantially increases the efficiency of CO.sub.2 capture and removal by positioning a catalyst within an optimal distance from the air-liquid interface. The catalyst is positioned within the layer determined to be the highest concentration of carbon dioxide. A hydrophobic tether is attached to the catalyst and the hydrophobic tether modulates the position of the catalyst within the liquid layer containing the highest concentration of carbon dioxide.

Promotion of redox and stability features of doped Ce-W-Ti for NH3-SCR reaction over a wide temperature range

NASA Astrophysics Data System (ADS)

Zhao, Kun; Han, Weiliang; Lu, Gongxuan; Lu, Jiangyin; Tang, Zhicheng; Zhen, Xinping

2016-08-01

In this study, transition metals Co, Mn, and Cu were introduced into a Ce-W-Ti catalyst to promote low-temperature catalytic activity. Among these metal-modified M/Ce-W-Ti catalysts (M represents Co, Mn, or Cu), the Cu/Ce-W-Ti catalyst with an optimized Cu content of 5 wt.% exhibited more than 90% conversion of nitrogen oxide (NOx) in the selective catalytic reduction by NH3 over a wide temperature range (260-400 °C). This catalyst likewise exhibited higher resistance to SO2 gas and water vapor under severe test conditions. On the basis of the characterization results by powder X-ray diffraction and X-ray photoelectron spectroscopy, we concluded that the superior catalytic properties of the Cu/Ce-W-Ti catalyst could be attributed to the highly dispersed Cu species, which increased the contents of Ce3+ species and adsorbed oxygen species in the catalysts. In addition, the NH3 temperature-programmed desorption results demonstrated that the Cu species doped into the Ce-W-Ti catalysts optimized surface acid content.

Application of Mössbauer spectroscopy in industrial heterogeneous catalysis: effect of oxidant on FePO4 material phase transformations in direct methanol synthesis from methane

NASA Astrophysics Data System (ADS)

Dasireddy, Venkata D. B. C.; Khan, Faiza B.; Hanzel, Darko; Bharuth-Ram, Krish; Likozar, Blaž

2017-11-01

The effect of the FePO4 material phase transformation in the direct selective oxidation of methane to methanol was studied using various oxidants, i.e. O2, H2O and N2O. The phases of the heterogeneous catalyst applied, before and after the reactions, were characterized by M¨ossbauer spectroscopy. The main reaction products were methanol, carbon monoxide and carbon dioxide, whereas formaldehyde was produced in rather minute amounts. The Mössbauer spectra showed the change of the initial catalyst material, FePO4 (tridymite-like phase (tdm)), to the reduced metal form, iron(II) pyrophosphate, Fe2P2O7, and thereafter, the material phase change was governed by the oxidation with individual oxidizing species.Mössbauer spectroscopy measurements applied along with X-ray diffraction (XRD) studies on fresh, reduced and spent catalytic materials demonstrated a transformation of the catalyst to a mixture of phases which depended on operating process conditions. Generally, activity was low and should be a subject of further material optimization and engineering, while the selectivity towards methanol at low temperatures applied was adequate. The proceeding redox mechanism should thus play a key role in catalytic material design, while the advantage of iron-based heterogeneous catalysts primarily lies in them being comparably inexpensive and comprising non-critical raw materials only.

Optimization of levulinic acid from lignocellulosic biomass using a new hybrid catalyst.

PubMed

Ya'aini, Nazlina; Amin, Nor Aishah Saidina; Asmadi, Mohd

2012-07-01

Conversion of glucose, empty fruit bunch (efb) and kenaf to levulinic acid over a new hybrid catalyst has been investigated in this study. The characterization and catalytic performance results revealed that the physico-chemical properties of the new hybrid catalyst comprised of chromium chloride and HY zeolite increased the levulinic acid production from glucose compared to the parent catalysts. Optimization of the glucose conversion process using two level full factorial designs (2(3)) with two center points reported 55.2% of levulinic acid yield at 145.2 °C, 146.7 min and 12.0% of reaction temperature, reaction time and catalyst loading, respectively. Subsequently, the potential of efb and kenaf for producing levulinic acid at the optimum conditions was established after 53.2% and 66.1% of efficiencies were reported. The observation suggests that the hybrid catalyst has a potential to be used in biomass conversion to levulinic acid. Copyright © 2012 Elsevier Ltd. All rights reserved.

Reactivity improvement of cellulolytic enzyme lignin via mild hydrothermal modification.

PubMed

Ma, Zhuoming; Tang, Jiafa; Li, Shujun; Suo, Enxiang

2017-12-01

Isolated by the cellulolytic enzyme lignin (CEL) process, water-alcohol (1:1, v/v) was introduced as co-solvent in the process of the hydrothermal treatment. The modification parameters such as reaction temperature and time, solid-to-liquid ratio, and catalysts (NaOH and NaOAlO 2 ) have been investigated in terms of the specific lignin properties, such as the phenolic hydroxyl content (OH phen ), DPPH free radical scavenging rate, and formaldehyde value. The CELs were also characterized by GPC, FT-IR and 1 H NMR spectroscopy, and Py-GC/MS. The key data are under optimal lignin modification conditions (solid-to-liquid ratio of 1:10 (w/v) and a temperature of 250°C for 60min) are: OH phen content: 2.50mmol/g; half maximal inhibitory concentration (IC 50 ) towards DPPH free radicals: 88.2mg/L; formaldehyde value: 446.9g/kg). Both base catalysts decrease the residue rate, but phenol reactivities of the products were also detracted. Py-GC/MS results revealed that modified lignin had a higher phenolic composition than the CEL did, especially the modified lignin without catalyst (ML), which represented 74.51% phenolic content. Copyright © 2017. Published by Elsevier Inc.

Experimental research of technology activating catalysts for SCR DeNOx in boiler

NASA Astrophysics Data System (ADS)

Zeng, Xi; Yang, Zhengde; Li, Yan; Chen, Donglin

2018-01-01

In order to improve activity of the catalysts used in SCR DeNOx system of flue gas, a series of catalysts activated by different activating liquids under varied conditions in boiler directly were conducted. Then these catalysts were characterized by SEM, FT-IR and BET technology. And NO conversions of the activated catalysts were studied and compared with that of inactivated catalyst. The above experiment shows that NO conversion of the activated catalyst can be up to 99%, which 30% higher than that of inactivated catalyst, so activity of catalysts were improved greatly. Furthermore, optimal activating liquid labeled L2 and effective technology parameters were gained in the experiment.

A Mössbauer spectroscopic study of an industrial catalyst for dehydrogenation of etylbenzene to styrene

NASA Astrophysics Data System (ADS)

Jiang, K. Y.; Fan, Q.; Zhao, Z. J.; Mao, L. S.; Yang, X. L.

2006-01-01

Iron oxide catalyst with spinel structure used for dehydrogenation of ethylbenzene is one kind of important catalyst in petrochemical industry. In this work several series of industrial catalyst were prepared with different components and different manufacturing processes. Mössbauer Spectroscopy has been used to determine the optimal components and the better manufacturing process for spinel structure formation. The results may prove useful for producing the industrial dehydrogenation catalyst with better catalytic property.

Rational assignment of key motifs for function guides in silico enzyme identification.

PubMed

Höhne, Matthias; Schätzle, Sebastian; Jochens, Helge; Robins, Karen; Bornscheuer, Uwe T

2010-11-01

Biocatalysis has emerged as a powerful alternative to traditional chemistry, especially for asymmetric synthesis. One key requirement during process development is the discovery of a biocatalyst with an appropriate enantiopreference and enantioselectivity, which can be achieved, for instance, by protein engineering or screening of metagenome libraries. We have developed an in silico strategy for a sequence-based prediction of substrate specificity and enantiopreference. First, we used rational protein design to predict key amino acid substitutions that indicate the desired activity. Then, we searched protein databases for proteins already carrying these mutations instead of constructing the corresponding mutants in the laboratory. This methodology exploits the fact that naturally evolved proteins have undergone selection over millions of years, which has resulted in highly optimized catalysts. Using this in silico approach, we have discovered 17 (R)-selective amine transaminases, which catalyzed the synthesis of several (R)-amines with excellent optical purity up to >99% enantiomeric excess.

Enhanced Performance of non-PGM Catalysts in Air Operated PEM-Fuel Cells

DOE PAGES

Barkholtz, Heather M.; Chong, Lina; Kaiser, Zachary Brian; ...

2016-10-13

Here a non-platinum group metal (non-PGM) oxygen reduction catalyst was prepared from “support-free” zeolitic imidazolate framework (ZIF) precursor and tested in the proton exchange membrane fuel cell with air as the cathode feed. The iron nitrogen and carbon composite (FeeNeC) based catalyst has high specific surface area decorated uniformly with active sites, which redefines the triple phase boundary (TPB) and requires re-optimization of the cathodic membrane electrode fabrication to ensure efficient mass and charge transports to the catalyst surface. This study reports an effort in optimizing catalytic ink formulation for the membrane electrode preparation and its impact to the fuelmore » cell performance under air. Through optimization, the fuel cell areal current density as high as 115.2 mA/cm 2 at 0.8 V or 147.6 mA/cm 2 at 0.8 V iR-free has been achieved under one bar air. We also investigated impacts on fuel cell internal impedance and the water formation.« less

A study on experimental characteristic of microwave-assisted pyrolysis of microalgae.

PubMed

Hu, Zhifeng; Ma, Xiaoqian; Chen, Chunxiang

2012-03-01

The microwave-assisted pyrolysis of Chlorella vulgaris was carried out under different microwave power levels, catalysts and contents of activated carbon and solid residue. The products, pyrolysis temperature and temperature rising rate were analyzed in order to obtain the optimal conditions. The results indicated that the higher the microwave power level was, the higher the maximum temperature rising rate and pyrolysis temperature were. The maximum bio-oil yield (35.83 wt.%) and gas yield (52.37%) were achieved under the microwave power of 1500 W and 2250 W, respectively. And 2250 W was the optimal power to obtain bio-fuel product. High microwave power level and catalyst can enhance the production of gas. Catalysts can promote the pyrolysis of C. vulgaris, and activated carbon was the best among the tested catalysts followed by the solid residue. The optimal content of activated carbon is 5% with the maximum bio-fuel yield of 87.47%. Copyright © 2011 Elsevier Ltd. All rights reserved.

Novel process and catalytic materials for converting CO2 and H2 containing mixtures to liquid fuels and chemicals.

PubMed

Meiri, Nora; Dinburg, Yakov; Amoyal, Meital; Koukouliev, Viatcheslav; Nehemya, Roxana Vidruk; Landau, Miron V; Herskowitz, Moti

2015-01-01

Carbon dioxide and water are renewable and the most abundant feedstocks for the production of chemicals and fungible fuels. However, the current technologies for production of hydrogen from water are not competitive. Therefore, reacting carbon dioxide with hydrogen is not economically viable in the near future. Other alternatives include natural gas, biogas or biomass for the production of carbon dioxide, hydrogen and carbon monoxide mixtures that react to yield chemicals and fungible fuels. The latter process requires a high performance catalyst that enhances the reverse water-gas-shift (RWGS) reaction and Fischer-Tropsch synthesis (FTS) to higher hydrocarbons combined with an optimal reactor system. Important aspects of a novel catalyst, based on a Fe spinel and three-reactor system developed for this purpose published in our recent paper and patent, were investigated in this study. Potassium was found to be a key promoter that improves the reaction rates of the RWGS and FTS and increases the selectivity of higher hydrocarbons while producing mostly olefins. It changed the texture of the catalyst, stabilized the Fe-Al-O spinel, thus preventing decomposition into Fe3O4 and Al2O3. Potassium also increased the content of Fe5C2 while shifting Fe in the oxide and carbide phases to a more reduced state. In addition, it increased the relative exposure of carbide iron on the catalysts surface, the CO2 adsorption and the adsorption strength. A detailed kinetic model of the RWGS, FTS and methanation reactions was developed for the Fe spinel catalyst based on extensive experimental data measured over a range of operating conditions. Significant oligomerization activity of the catalyst was found. Testing the pelletized catalyst with CO2, CO and H2 mixtures over a range of operating conditions demonstrated its high productivity to higher hydrocarbons. The composition of the liquid (C5+) was found to be a function of the potassium content and the composition of the feedstock.

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.

A Study of Iron-Nitrogen-Carbon Fuel Cell Catalysts: Chemistry - Nanostructure - Performance

NASA Astrophysics Data System (ADS)

Workman, Michael J., Jr.

Fuel cells have the potential to be a pollution-free, low-cost, and energy efficient alternative to the internal combustion engine for transportation and small-scale stationary power applications. The current state of fuel cell technology has already achieved two of these three lofty goals. The remaining barrier to wide-scale deployment is the high cost, which is primarily caused by dependence on large amounts of platinum to catalyze the energy conversion reactions. To overcome this barrier and facilitate the integration of fuel cells into mainstream applications, research into a new class of catalyst materials that do not require platinum is needed. There has been a significant amount of research effort directed toward the development of platinum-group metal free (PGM-free) catalysts, yet there is a lack of consensus on both the engineering parameters necessary to improve the technology and the fundamental science that would facilitate rational design. I have engaged in research on PGM-free catalysts based on inexpensive and abundant reagents, specifically: nicarbazin and iron. Catalysts made from these precursors have previously proven to be among the best PGM-free catalysts, but their continued advancement suffered from the same lack of understanding that besets all catalysts in this class. The work I have performed address both engineering concerns and fundamental underlying principles. I present results demonstrating correlations between physical structure, chemical speciation, and synthesis parameters, as well as addressing active site chemistry and likely locations. My research presented herein introduces new morphology analysis techniques and elucidates several key structure-to-property characteristics of catalysts derived from iron and nicarbazin. I discuss the development and application of a new length-scale specific surface analysis technique that allows for analysis of well-defined size ranges from a few nm to several microns. The existing technique of focused ion beam tomography is modified and optimized for platinum-group metal free catalyst layers, facilitating direct observation of catalyst integration into catalyst layers. I present evidence supporting the hypothesis that atomically dispersed iron coordinated with nitrogen are the dominant active sites in these catalysts. Further, that the concentration of surface oxides in the carbon structure, which can be directly influenced by synthesis parameters, correlates with both the concentration of active sites in the material and with fuel cell performance. Catalyst performance is hindered by the addition of carbon nanotubes and by the presence of metallic iron. Evidence consistent with the catalytic active sites residing in the graphitic plane is also presented.

Enhancement of biodiesel production from marine alga, Scenedesmus sp. through in situ transesterification process associated with acidic catalyst.

PubMed

Kim, Ga Vin; Choi, Woonyong; Kang, Dohyung; Lee, Shinyoung; Lee, Hyeonyong

2014-01-01

The aim of this study was to increase the yield of biodiesel produced by Scenedesmus sp. through in situ transesterification by optimizing various process parameters. Based on the orthogonal matrix analysis for the acidic catalyst, the effects of the factors decreased in the order of reaction temperature (47.5%) > solvent quantity (26.7%) > reaction time (17.5%) > catalyst amount (8.3%). Based on a Taguchi analysis, the effects of the factors decreased in the order of solvent ratio (34.36%) > catalyst (28.62%) > time (19.72%) > temperature (17.32%). The overall biodiesel production appeared to be better using NaOH as an alkaline catalyst rather than using H2SO4 in an acidic process, at 55.07 ± 2.18% (based on lipid weight) versus 48.41 ± 0.21%. However, in considering the purified biodiesel, it was found that the acidic catalyst was approximately 2.5 times more efficient than the alkaline catalyst under the following optimal conditions: temperature of 70 °C (level 2), reaction time of 10 hrs (level 2), catalyst amount of 5% (level 3), and biomass to solvent ratio of 1 : 15 (level 2), respectively. These results clearly demonstrated that the acidic solvent, which combined oil extraction with in situ transesterification, was an effective catalyst for the production of high-quantity, high-quality biodiesel from a Scenedesmus sp.

Enhancement of Biodiesel Production from Marine Alga, Scenedesmus sp. through In Situ Transesterification Process Associated with Acidic Catalyst

PubMed Central

Kim, Ga Vin; Choi, WoonYong; Kang, DoHyung; Lee, ShinYoung; Lee, HyeonYong

2014-01-01

The aim of this study was to increase the yield of biodiesel produced by Scenedesmus sp. through in situ transesterification by optimizing various process parameters. Based on the orthogonal matrix analysis for the acidic catalyst, the effects of the factors decreased in the order of reaction temperature (47.5%) > solvent quantity (26.7%) > reaction time (17.5%) > catalyst amount (8.3%). Based on a Taguchi analysis, the effects of the factors decreased in the order of solvent ratio (34.36%) > catalyst (28.62%) > time (19.72%) > temperature (17.32%). The overall biodiesel production appeared to be better using NaOH as an alkaline catalyst rather than using H2SO4 in an acidic process, at 55.07 ± 2.18% (based on lipid weight) versus 48.41 ± 0.21%. However, in considering the purified biodiesel, it was found that the acidic catalyst was approximately 2.5 times more efficient than the alkaline catalyst under the following optimal conditions: temperature of 70°C (level 2), reaction time of 10 hrs (level 2), catalyst amount of 5% (level 3), and biomass to solvent ratio of 1 : 15 (level 2), respectively. These results clearly demonstrated that the acidic solvent, which combined oil extraction with in situ transesterification, was an effective catalyst for the production of high-quantity, high-quality biodiesel from a Scenedesmus sp. PMID:24689039

Identification of optimal solar fuel electrocatalysts via high throughput in situ optical measurements

DOE PAGES

Shinde, Aniketa; Guevarra, Dan; Haber, Joel A.; ...

2014-10-21

For many solar fuel generator designs involve illumination of a photoabsorber stack coated with a catalyst for the oxygen evolution reaction (OER). In this design, impinging light must pass through the catalyst layer before reaching the photoabsorber(s), and thus optical transmission is an important function of the OER catalyst layer. Many oxide catalysts, such as those containing elements Ni and Co, form oxide or oxyhydroxide phases in alkaline solution at operational potentials that differ from the phases observed in ambient conditions. To characterize the transparency of such catalysts during OER operation, 1031 unique compositions containing the elements Ni, Co, Ce,more » La, and Fe were prepared by a high throughput inkjet printing technique. Moreover, the catalytic current of each composition was recorded at an OER overpotential of 0.33 V with simultaneous measurement of the spectral transmission. By combining the optical and catalytic properties, the combined catalyst efficiency was calculated to identify the optimal catalysts for solar fuel applications within the material library. Our measurements required development of a new high throughput instrument with integrated electrochemistry and spectroscopy measurements, which enables various spectroelectrochemistry experiments.« less

Reaction kinetics of free fatty acids esterification in palm fatty acid distillate using coconut shell biochar sulfonated catalyst

NASA Astrophysics Data System (ADS)

Hidayat, Arif; Rochmadi, Wijaya, Karna; Budiman, Arief

2015-12-01

Recently, a new strategy of preparing novel carbon-based solid acids has been developed. In this research, the esterification reactions of Palm Fatty Acid Distillate (PFAD) with methanol, using coconut shell biochar sulfonated catalyst from biomass wastes as catalyst, were studied. In this study, the coconut shell biochar sulfonated catalysts were synthesized by sulfonating the coconut shell biochar using concentrated H2SO4. The kinetics of free fatty acid (FFA) esterification in PFAD using a coconut shell biochar sulfonated catalyst was also studied. The effects of the mass ratio of catalyst to oil (1-10%), the molar ratio of methanol to oil (6:1-12:1), and the reaction temperature (40-60°C) were studied for the conversion of PFAD to optimize the reaction conditions. The results showed that the optimal conditions were an methanol to PFAD molar ratio of 12:1, the amount of catalyst of 10%w, and reaction temperature of 60°C. The proposed kinetic model shows a reversible second order reaction and represents all the experimental data satisfactorily, providing deeper insight into the kinetics of the reaction.

Materials and characterization techniques for high-temperature polymer electrolyte membrane fuel cells.

PubMed

Zeis, Roswitha

2015-01-01

The performance of high-temperature polymer electrolyte membrane fuel cells (HT-PEMFC) is critically dependent on the selection of materials and optimization of individual components. A conventional high-temperature membrane electrode assembly (HT-MEA) primarily consists of a polybenzimidazole (PBI)-type membrane containing phosphoric acid and two gas diffusion electrodes (GDE), the anode and the cathode, attached to the two surfaces of the membrane. This review article provides a survey on the materials implemented in state-of-the-art HT-MEAs. These materials must meet extremely demanding requirements because of the severe operating conditions of HT-PEMFCs. They need to be electrochemically and thermally stable in highly acidic environment. The polymer membranes should exhibit high proton conductivity in low-hydration and even anhydrous states. Of special concern for phosphoric-acid-doped PBI-type membranes is the acid loss and management during operation. The slow oxygen reduction reaction in HT-PEMFCs remains a challenge. Phosphoric acid tends to adsorb onto the surface of the platinum catalyst and therefore hampers the reaction kinetics. Additionally, the binder material plays a key role in regulating the hydrophobicity and hydrophilicity of the catalyst layer. Subsequently, the binder controls the electrode-membrane interface that establishes the triple phase boundary between proton conductive electrolyte, electron conductive catalyst, and reactant gases. Moreover, the elevated operating temperatures promote carbon corrosion and therefore degrade the integrity of the catalyst support. These are only some examples how materials properties affect the stability and performance of HT-PEMFCs. For this reason, materials characterization techniques for HT-PEMFCs, either in situ or ex situ, are highly beneficial. Significant progress has recently been made in this field, which enables us to gain a better understanding of underlying processes occurring during fuel cell operation. Various novel tools for characterizing and diagnosing HT-PEMFCs and key components are presented in this review, including FTIR and Raman spectroscopy, confocal Raman microscopy, synchrotron X-ray imaging, X-ray microtomography, and atomic force microscopy.

Materials and characterization techniques for high-temperature polymer electrolyte membrane fuel cells

PubMed Central

2015-01-01

Summary The performance of high-temperature polymer electrolyte membrane fuel cells (HT-PEMFC) is critically dependent on the selection of materials and optimization of individual components. A conventional high-temperature membrane electrode assembly (HT-MEA) primarily consists of a polybenzimidazole (PBI)-type membrane containing phosphoric acid and two gas diffusion electrodes (GDE), the anode and the cathode, attached to the two surfaces of the membrane. This review article provides a survey on the materials implemented in state-of-the-art HT-MEAs. These materials must meet extremely demanding requirements because of the severe operating conditions of HT-PEMFCs. They need to be electrochemically and thermally stable in highly acidic environment. The polymer membranes should exhibit high proton conductivity in low-hydration and even anhydrous states. Of special concern for phosphoric-acid-doped PBI-type membranes is the acid loss and management during operation. The slow oxygen reduction reaction in HT-PEMFCs remains a challenge. Phosphoric acid tends to adsorb onto the surface of the platinum catalyst and therefore hampers the reaction kinetics. Additionally, the binder material plays a key role in regulating the hydrophobicity and hydrophilicity of the catalyst layer. Subsequently, the binder controls the electrode–membrane interface that establishes the triple phase boundary between proton conductive electrolyte, electron conductive catalyst, and reactant gases. Moreover, the elevated operating temperatures promote carbon corrosion and therefore degrade the integrity of the catalyst support. These are only some examples how materials properties affect the stability and performance of HT-PEMFCs. For this reason, materials characterization techniques for HT-PEMFCs, either in situ or ex situ, are highly beneficial. Significant progress has recently been made in this field, which enables us to gain a better understanding of underlying processes occurring during fuel cell operation. Various novel tools for characterizing and diagnosing HT-PEMFCs and key components are presented in this review, including FTIR and Raman spectroscopy, confocal Raman microscopy, synchrotron X-ray imaging, X-ray microtomography, and atomic force microscopy. PMID:25671153

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.

The Catalytic Asymmetric Intramolecular Stetter Reaction

PubMed Central

de Alaniz, Javier Read; Rovis, Tomislav

2010-01-01

This account chronicles our efforts at the development of a catalytic asymmetric Stetter reaction using chiral triazolium salts as small molecule organic catalysts. Advances in the mechanistically related azolium-catalyzed asymmetric benzoin reaction are discussed, particularly as they apply to catalyst design. A chronological treatise of reaction discovery, catalyst optimization and reactivity extension follows. PMID:20585467

Photocatalytic degradation of pentachlorophenol by visible light Ν-F-TiO₂ in the presence of oxalate ions: optimization, modeling, and scavenging studies.

PubMed

Antonopoulou, M; Konstantinou, I

2015-06-01

The efficiency of heterogeneous photocatalysis using N-F-TiO2 as photocatalyst to degrade a priority pollutant, pentachlorophenol (PCP), in the presence of oxalates (OA) was investigated in detail. Response surface methodology was used to optimize the effect of three variables (catalyst concentration, OA/PCP ratio, and pH) on the photocatalytic degradation of pentachlorophenol. A quadratic model was established as a functional relationship between three independent variables and the degradation efficiency of PCP. The results of model fitting and statistical analysis demonstrated that the pH played a key role in the degradation of PCP. Within the studied experimental ranges, the optimum conditions for maximum PCP degradation efficiency (97.5 %) were: catalyst concentration 600 mg L(-1), OA/PCP ratio 2, and pH 10. The contribution of HO(·), O2 (·-), and e(-) produced during the photocatalytic treatment was investigated with the addition of scavengers. The photocatalytic degradation was essentially proceeded through an oxidative mechanism at both acid and alkaline pH values by HO(.) and O2 (·-) radicals attack. It was found that O2 (·-) were the major reactive species involved in PCP degradation in pH 4 and HO(·) in pH 10.

Rotating packed bed reactor for enzymatic synthesis of biodiesel.

PubMed

Xu, Juntao; Liu, Changsheng; Wang, Meng; Shao, Lei; Deng, Li; Nie, Kaili; Wang, Fang

2017-01-01

The aim of the present work was to study the applicability of rotating packed bed (RPB) for biodiesel through the biocatalytic method. In this research, the RPB facilitated a more homogeneous mixture of substrates due to its higher mass transfer efficiency and better micromixing environment. This was superior to the traditional continuous stirred tank reactor (CSTR) system. Candida sp. 99-125 lipase was used without any organic solvent or additive, and demonstrated a significant catalyst efficiency. The key factors, such as the high gravity factor (β), pattern of the catalyst and methanol-FFA molar ratio etc. were investigated. Under the optimal conditions, the hydrolysis yield of fatty acids was 97.0% after 24h and the esterification yield of biodiesel was 96.0% 6h later. The esterifying yield didn't have an obvious decline in the fifth batch. Consequently, the RPB is an attractive and effective reactor for enzymatic synthesis. Copyright © 2016 Elsevier Ltd. All rights reserved.

Hydrolysis of cellulose catalyzed by quaternary ammonium perrhenates in 1-allyl-3-methylimidazolium chloride.

PubMed

Wang, Jingyun; Zhou, Mingdong; Yuan, Yuguo; Zhang, Quan; Fang, Xiangchen; Zang, Shuliang

2015-12-01

Quaternary ammonium perrhenates were applied as catalyst to promote the hydrolysis of cellulose in 1-allyl-3-methylimidazolium chloride ([Amim]Cl). The quaternary ammonium perrhenates displayed good catalytic performance for cellulose hydrolysis. Water was also proven to be effective to promote cellulose hydrolysis. Accordingly, 97% of total reduced sugar (TRS) and 42% of glucose yields could be obtained under the condition of using 5mol% of tetramethyl ammonium perrhenate as catalyst, 70μL of water, ca. 0.6mmol of microcrystalline cellulose (MCC) and 2.0g of [Amim]Cl as solvent under microwave irradiation for 30min at 150°C (optimal conditions). The influence of quaternary ammonium cation on the efficiency of cellulose hydrolysis was examined based on different cation structures of perrhenates. The mechanism on perrhenate catalyzed cellulose hydrolysis is also discussed, whereas hydrogen bonding between ReO4 anion and hydroxyl groups of cellulose is assumed to be the key step for depolymerization of cellulose. Copyright © 2015. Published by Elsevier Ltd.

Efficient Nitrogen Fixation via a Redox-Flexible Single-Iron Site with Reverse-Dative Iron → Boron σ Bonding.

PubMed

Lu, Jun-Bo; Ma, Xue-Lu; Wang, Jia-Qi; Liu, Jin-Cheng; Xiao, Hai; Li, Jun

2018-05-10

Model systems of the FeMo cofactor of nitrogenase have been explored extensively in catalysis to gain insights into their ability for nitrogen fixation that is of vital importance to the human society. Here we investigate the trigonal pyramidal borane-ligand Fe complex by first-principles calculations, and find that the variation of oxidation state of Fe along the reaction path correlates with that of the reverse-dative Fe → B bonding. The redox-flexibility of the reverse-dative Fe → B bonding helps to provide an electron reservoir that buffers and stabilizes the evolution of Fe oxidation state, which is essential for forming the key intermediates of N 2 activation. Our work provides insights for understanding and optimizing homogeneous and surface single-atom catalysts with reverse-dative donating ligands for efficient dinitrogen fixation. The extension of this kind of molecular catalytic active center to heterogeneous catalysts with surface single-clusters is also discussed.

Recent advances in efficient long-life, eye-safe solid state and CO2 lasers for laser radar applications

NASA Technical Reports Server (NTRS)

Hess, R. V.; Buoncristiani, A. M.; Brockman, P.; Bair, C. H.; Schryer, D. R.; Upchurch, B. T.; Wood, G. M.

1989-01-01

The key problems in the development of eye-safe solid-state lasers are discussed, taking into account the energy transfer mechanisms between the complicated energy level manifolds of the Tm, Ho, Er ion dopants in hosts with decreasing crystal fields such as YAG or YLF. Optimization of energy transfer for efficient lasing through choice of dopant concentration, power density, crystal field and temperature is addressed. The tailoring of energy transfer times to provide efficient energy extraction for short pulses used in DIAL and Doppler lidar is considered. Recent advances in Pt/SnO2 oxide catalysts and other noble metal/metal oxide combinations for CO2 lasers are discussed. Emphasis is given to the dramatic effects of small quantities of H2O vapor for increasing the activity and lifetime of Pt/SnO2 catalysts and to increased lifetime operation with rare isotope (C-12)(O-18)2 lasing mixtures.

Efficient dehydration of 6-gingerol to 6-shogaol catalyzed by an acidic ionic liquid under ultrasound irradiation.

PubMed

Kou, Xingran; Li, Xingze; Rahman, Md Ramim Tanver; Yan, Minming; Huang, Huanhuan; Wang, Hongxin; Su, Yihai

2017-01-15

6-Gingerol and 6-shogaol are the main bioactive compounds in ginger. Although 6-shogaol has more and better bioactivities than its precursor 6-gingerol, the low content of 6-shogaol in ginger restricts its bioactive effects in functional foods. The traditional preparation methods of 6-shogaol are defective because of the environmental hazards and low efficiency of the processes. In this study, an efficient, easy and eco-friendly dehydration conversion of 6-gingerol to 6-shogaol is presented using an acidic ionic liquid 1-butyl-3-methylimidazolium hydrosulfate ([Bmim]HSO4) under ultrasound irradiation. The key parameters, including reaction temperature, reaction time, mass ratio of catalyst to substrate and ultrasonic power in each reaction process, were investigated. The yield of 6-shogaol reached as high as 97.16% under optimized condition. The catalyst could be separated from the reaction mixture and reused five times with only a slight loss of activity. Copyright © 2016 Elsevier Ltd. All rights reserved.

ECUT: Energy Conversion and utilization Technologies program biocatalysis research activity. Generation of chemical intermediates by catalytic oxidative decarboxylation of dilute organic acids

NASA Technical Reports Server (NTRS)

Distefano, S.; Gupta, A.; Ingham, J. D.

1983-01-01

A rhodium-based catalyst was prepared and preliminary experiments were completed where the catalyst appeared to decarboxylate dilute acids at concentrations of 1 to 10 vol%. Electron spin resonance spectroscoy was used to characterize the catalyst as a first step leading toward modeling and optimization of rhodium catalysts. Also, a hybrid chemical/biological process for the production of hydrocarbons has been assessed. These types of catalysts could greatly increase energy efficiency of this process.

Optimization of esterification of dicarboxylic acids and 2-ethyl-1-hexanol

NASA Astrophysics Data System (ADS)

Jafri, Nur Hafifah Nahdirah; Othman, Nor Hamidah Abu; Salimon, Jumat

2018-04-01

Dicarboxylate ester has the potential alternative as plasticizer which environmentally friendly in polymeric formulation especially for poly (vinyl chloride) (PVC). Dicarboxylate ester compounds were synthesized via esterification between dicarboxylic acid and 2-ethyl-1-hexanol by using sulfuric acid as catalyst. The effects of reaction parameters were studied by optimizing temperature, mole ratio of reactants, amount of catalyst and reaction to obtain highest ester conversion. The optimum results showed dicarboxylic acid successfully converted to the dicarboxylate ester at parameters; 4 hours; 120 °C; catalyst amount: 2% w/w of diacid; and mole ratio: 1:2.5. Functional group analysis was conducted by using ATR-FTIR spectroscopy.

Direct 17O dynamic nuclear polarization of single-site heterogeneous catalysts

DOE PAGES

Perras, Frédéric A.; Boteju, Kasuni C.; Slowing, Igor I.; ...

2018-03-13

In this work, we utilize direct 17O DNP for the characterization of non-protonated oxygens in heterogeneous catalysts. The optimal sample preparation and population transfer approach for 17O direct DNP experiments performed on silica surfaces is determined and applied to the characterization of Zr- and Y-based mesoporous silica-supported single-site catalysts.

Highly active non-PGM catalysts prepared from metal organic frameworks

DOE PAGES

Barkholtz, Heather M.; Chong, Lina; Kaiser, Zachary B.; ...

2015-06-11

Finding inexpensive alternatives to platinum group metals (PGMs) is essential for reducing the cost of proton exchange membrane fuel cells (PEMFCs). Numerous materials have been investigated as potential replacements of Pt, of which the transition metal and nitrogen-doped carbon composites (TM/N x/C) prepared from iron doped zeolitic imidazolate frameworks (ZIFs) are among the most active ones in catalyzing the oxygen reduction reaction based on recent studies. In this report, we demonstrate that the catalytic activity of ZIF-based TM/N x/C composites can be substantially improved through optimization of synthesis and post-treatment processing conditions. Ultimately, oxygen reduction reaction (ORR) electrocatalytic activity mustmore » be demonstrated in membrane-electrode assemblies (MEAs) of fuel cells. The process of preparing MEAs using ZIF-based non-PGM electrocatalysts involves many additional factors which may influence the overall catalytic activity at the fuel cell level. Evaluation of parameters such as catalyst loading and perfluorosulfonic acid ionomer to catalyst ratio were optimized. Our overall efforts to optimize both the catalyst and MEA construction process have yielded impressive ORR activity when tested in a fuel cell system.« less

Investigating catalyst coated membrane equilibration time for polymer electrolyte membrane fuel cell manufacturing

NASA Astrophysics Data System (ADS)

Cote, Philippe

Mercedes-Benz Canada Inc., Fuel Cell Division, manufactures polymer electrolyte membrane fuel cell stacks for use in vehicles. The manufacturing line is being optimized for efficiency and quality control, in order to uphold the high standards of Mercedes-Benz Inc. vehicles. In an operating polymer electrolyte membrane fuel cell, the catalyst coated membrane facilitates the electrochemical reaction that generates electricity. This research examines the equilibration of catalyst coated membrane rolls to controlled temperature and humidity conditions, before they are used in the manufacturing of polymer electrolyte membrane fuel cells. Equilibration involves allowing the water content in the catalyst coated membrane to stabilize at the controlled conditions, in order to reduce mechanical stress in the material for better manufacturability. Initial equilibration measurements were conducted on discrete catalyst coated membrane samples using novel electronic conductivity measurements of the catalyst layer, and compared to ionic conductivity measurements of the membrane. Electronic conductivity measurements are easier to implement in the manufacturing environment than the more complex ionic conductivity measurements. When testing discrete catalyst coated membrane samples in an environmental chamber, the equilibration trends for the measured ionic and electronic conductivity signals were similar enough to permit us to adapt the electronic conductivity measurements for catalyst coated membrane in roll form. Equilibration measurements of catalyst coated membrane rolls were optimized to achieve a robust and repeatable procedure which could be used in the manufacturing environment at Mercedes-Benz Canada Inc., Fuel Cell Division.

A Mössbauer spectroscopic study of an industrial catalyst for dehydrogenation of etylbenzene to styrene

NASA Astrophysics Data System (ADS)

Jiang, K. Y.; Fan, Q.; Zhao, Z. J.; Mao, L. S.; Yang, X. L.

Iron oxide catalyst with spinel structure used for dehydrogenation of ethylbenzene is one kind of importantcatalyst in petrochemical industry. In this work several series of industrial catalyst were prepared with differentcomponents and differentmanufacturing processes. Mössbauer Spectroscopy has been used to determine the optimal components and the better manufacturing process for spinel structure formation. The results may prove useful for producing the industrial dehydrogenation catalyst with better catalytic property.

Nanoporous carbon for electric double layer supercapacitor electrodes

NASA Astrophysics Data System (ADS)

Garcia, Betzaida Batalla

The subject of this study is the synthesis, characterization, chemical composition, and tuning of the porous structure of organic and carbon cryogels for electrochemical applications, particularly supercapacitors. Alternate methods such as an improved synthesis using a reactive catalyst, surface chemical modifications and an electrochemical characterization that takes into account the pore morphology are discussed. Impedance spectroscopy, complex capacitance and power were used to identify key energy losses in the capacitor; an optimal pore size of ca. 2 nm and other features were found. Also, synthesis modification and surface chemistry were used to improve the chemistry and structure of the electrodes reducing metal impurities and removing detrimental functional groups. First, carbon cryogels produced without metal ion impurities were synthesized using hexamine (an amine base catalyst), resorcinol, furaldehyde and solvent mixtures. These metal ion free amine-catalyzed gels also produced strong cryogels that can be machined. The carbon cryogels produced using the amine catalyst have cycle stability performances that exceed that of commercial samples. Carbon cryogels were also doped using ammonia borane to promote boron and nitrogen esters and improved the capacitance up to 30% due to faradaic reactions. Furthermore, nitrogen esters were also introduced into the carbon (via pyrolysis of hexamine) with yields of up to 14 at%. These new esters have low content of oxygen and increased the capacitance up to 50%.

Direct amidation of carboxylic acids catalyzed by ortho-iodo arylboronic acids: catalyst optimization, scope, and preliminary mechanistic study supporting a peculiar halogen acceleration effect.

PubMed

Gernigon, Nicolas; Al-Zoubi, Raed M; Hall, Dennis G

2012-10-05

The importance of amides as a component of biomolecules and synthetic products motivates the development of catalytic, direct amidation methods employing free carboxylic acids and amines that circumvent the need for stoichiometric activation or coupling reagents. ortho-Iodophenylboronic acid 4a has recently been shown to catalyze direct amidation reactions at room temperature in the presence of 4A molecular sieves as dehydrating agent. Herein, the arene core of ortho-iodoarylboronic acid catalysts has been optimized with regards to the electronic effects of ring substitution. Contrary to the expectation, it was found that electron-donating substituents are preferable, in particular, an alkoxy substituent positioned para to the iodide. The optimal new catalyst, 5-methoxy-2-iodophenylboronic acid (MIBA, 4f), was demonstrated to be kinetically more active than the parent des-methoxy catalyst 4a, providing higher yields of amide products in shorter reaction times under mild conditions at ambient temperature. Catalyst 4f is recyclable and promotes the formation of amides from aliphatic carboxylic acids and amines, and from heteroaromatic carboxylic acids and other functionalized substrates containing moieties like a free phenol, indole and pyridine. Mechanistic studies demonstrated the essential role of molecular sieves in this complex amidation process. The effect of substrate stoichiometry, concentration, and measurement of the catalyst order led to a possible catalytic cycle based on the presumed formation of an acylborate intermediate. The need for an electronically enriched ortho-iodo substituent in catalyst 4f supports a recent theoretical study (Marcelli, T. Angew. Chem. Int. Ed.2010, 49, 6840-6843) with a purported role for the iodide as a hydrogen-bond acceptor in the orthoaminal transition state.

Optimizing Binding Energies of Key Intermediates for CO 2 Hydrogenation to Methanol over Oxide-Supported Copper

DOE PAGES

None, None

2016-08-29

Rational optimization of catalytic performance has been one of the major challenges in catalysis. We report a bottom-up study on the ability of TiO 2 and ZrO 2 to optimize the CO 2 conversion to methanol on Cu, using combined density functional theory (DFT) calculations, kinetic Monte Carlo (KMC) simulations, in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) measurements, and steady-state flow reactor tests. Furthermore, the theoretical results from DFT and KMC agree with in situ DRIFTS measurements, showing that both TiO 2 and ZrO 2 help to promote methanol synthesis on Cu via carboxyl intermediates and the reversemore » water–gas-shift (RWGS) pathway; the formate intermediates, on the other hand, likely act as a spectator eventually. The origin of the superior promoting effect of ZrO 2 is associated with the fine-tuning capability of reduced Zr 3+ at the interface, being able to bind the key reaction intermediates, e.g. *CO 2, *CO, *HCO, and *H 2CO, moderately to facilitate methanol formation. Our study demonstrates the importance of synergy between theory and experiments to elucidate the complex reaction mechanisms of CO 2 hydrogenation for the realization of a better catalyst by design.« less

Supported Dendrimer-Encapsulated Metal Clusters: Toward Heterogenizing Homogeneous Catalysts

DOE PAGES

Ye, Rong; Zhukhovitskiy, Aleksandr V.; Deraedt, Christophe V.; ...

2017-07-13

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 optimizemore » and expand the scope of their reactivity and selectivity. Ongoing efforts in our laboratories 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., π-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 PhICl 2) or reduced (e.g., with H 2) 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. Here in this Account, we will briefly introduce metal clusters and describe the synthesis and characterizations of supported DEMCs. We will present the catalysis studies of supported DEMCs in both the batch and flow modes. Lastly, we will summarize the current state of heterogenizing homogeneous catalysis and provide future directions for this area of research.« less

Bioinspired organocatalytic aerobic C-H oxidation of amines with an ortho-quinone catalyst.

PubMed

Qin, Yan; Zhang, Long; Lv, Jian; Luo, Sanzhong; Cheng, Jin-Pei

2015-03-20

A simple bioinspired ortho-quinone catalyst for the aerobic oxidative dehydrogenation of amines to imines is reported. Without any metal cocatalysts, the identified optimal ortho-quinone catalyst enables the oxidations of α-branched primary amines and cyclic secondary amines. Mechanistic studies have disclosed the origins of different performances of ortho-quinone vs para-quinone in biomimetic amine oxidations.

Optimizing C–C Coupling on Oxide-Derived Copper Catalysts for Electrochemical CO 2 Reduction

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

Lum, Yanwei; Yue, Binbin; Lobaccaro, Peter

Here, copper electrodes, prepared by reduction of oxidized metallic copper, have been reported to exhibit higher activity for the electrochemical reduction of CO 2 and better selectivity toward C 2 and C 3 (C 2+) products than metallic copper that has not been preoxidized. We report here an investigation of the effects of four different preparations of oxide-derived electrocatalysts on their activity and selectivity for CO 2 reduction, with particular attention given to the selectivity to C 2+ products. All catalysts were tested for CO 2 reduction in 0.1 M KHCO 3 and 0.1 M CsHCO 3 at applied voltagesmore » in the range from –0.7 to –1.0 V vs RHE. The best performing oxide-derived catalysts show up to ~70% selectivity to C 2+ products and only ~3% selectivity to C 1 products at –1.0 V vs RHE when CsHCO 3 is used as the electrolyte. In contrast, the selectivity to C 2+ products decreases to ~56% for the same catalysts tested in KHCO 3. By studying all catalysts under identical conditions, the key factors affecting product selectivity could be discerned. These efforts reveal that the surface area of the oxide-derived layer is a critical parameter affecting selectivity. A high selectivity to C 2+ products is attained at an overpotential of –1 V vs RHE by operating at a current density sufficiently high to achieve a moderately high pH near the catalyst surface but not so high as to cause a significant reduction in the local concentration of CO 2. On the basis of recent theoretical studies, a high pH suppresses the formation of C 1 relative to C 2+ products. At the same time, however, a high local CO 2 concentration is necessary for the formation of C 2+ products.« less

Optimizing C–C Coupling on Oxide-Derived Copper Catalysts for Electrochemical CO 2 Reduction

DOE PAGES

Lum, Yanwei; Yue, Binbin; Lobaccaro, Peter; ...

2017-07-06

Here, copper electrodes, prepared by reduction of oxidized metallic copper, have been reported to exhibit higher activity for the electrochemical reduction of CO 2 and better selectivity toward C 2 and C 3 (C 2+) products than metallic copper that has not been preoxidized. We report here an investigation of the effects of four different preparations of oxide-derived electrocatalysts on their activity and selectivity for CO 2 reduction, with particular attention given to the selectivity to C 2+ products. All catalysts were tested for CO 2 reduction in 0.1 M KHCO 3 and 0.1 M CsHCO 3 at applied voltagesmore » in the range from –0.7 to –1.0 V vs RHE. The best performing oxide-derived catalysts show up to ~70% selectivity to C 2+ products and only ~3% selectivity to C 1 products at –1.0 V vs RHE when CsHCO 3 is used as the electrolyte. In contrast, the selectivity to C 2+ products decreases to ~56% for the same catalysts tested in KHCO 3. By studying all catalysts under identical conditions, the key factors affecting product selectivity could be discerned. These efforts reveal that the surface area of the oxide-derived layer is a critical parameter affecting selectivity. A high selectivity to C 2+ products is attained at an overpotential of –1 V vs RHE by operating at a current density sufficiently high to achieve a moderately high pH near the catalyst surface but not so high as to cause a significant reduction in the local concentration of CO 2. On the basis of recent theoretical studies, a high pH suppresses the formation of C 1 relative to C 2+ products. At the same time, however, a high local CO 2 concentration is necessary for the formation of C 2+ products.« less

Semiconductor-Electrocatalyst Interfaces: Theory, Experiment, and Applications in Photoelectrochemical Water Splitting.

PubMed

Nellist, Michael R; Laskowski, Forrest A L; Lin, Fuding; Mills, Thomas J; Boettcher, Shannon W

2016-04-19

Light-absorbing semiconductor electrodes coated with electrocatalysts are key components of photoelectrochemical energy conversion and storage systems. Efforts to optimize these systems have been slowed by an inadequate understanding of the semiconductor-electrocatalyst (sem|cat) interface. The sem|cat interface is important because it separates and collects photoexcited charge carriers from the semiconductor. The photovoltage generated by the interface drives "uphill" photochemical reactions, such as water splitting to form hydrogen fuel. Here we describe efforts to understand the microscopic processes and materials parameters governing interfacial electron transfer between light-absorbing semiconductors, electrocatalysts, and solution. We highlight the properties of transition-metal oxyhydroxide electrocatalysts, such as Ni(Fe)OOH, because they are the fastest oxygen-evolution catalysts known in alkaline media and are (typically) permeable to electrolyte. We describe the physics that govern the charge-transfer kinetics for different interface types, and show how numerical simulations can explain the response of composite systems. Emphasis is placed on "limiting" behavior. Electrocatalysts that are permeable to electrolyte form "adaptive" junctions where the interface energetics change during operation as charge accumulates in the catalyst, but is screened locally by electrolyte ions. Electrocatalysts that are dense, and thus impermeable to electrolyte, form buried junctions where the interface physics are unchanged during operation. Experiments to directly measure the interface behavior and test the theory/simulations are challenging because conventional photoelectrochemical techniques do not measure the electrocatalyst potential during operation. We developed dual-working-electrode (DWE) photoelectrochemistry to address this limitation. A second electrode is attached to the catalyst layer to sense or control current/voltage independent from that of the semiconductor back ohmic contact. Consistent with simulations, electrolyte-permeable, redox-active catalysts such as Ni(Fe)OOH form "adaptive" junctions where the effective barrier height for electron exchange depends on the potential of the catalyst. This is in contrast to sem|cat interfaces with dense electrolyte-impermeable catalysts, such as nanocrystalline IrOx, that behave like solid-state buried (Schottky-like) junctions. These results elucidate a design principle for catalyzed photoelectrodes. The buried heterojunctions formed by dense catalysts are often limited by Fermi-level pinning and low photovoltages. Catalysts deposited by "soft" methods, such as electrodeposition, form adaptive junctions that tend to provide larger photovoltages and efficiencies. We also preview efforts to improve theory/simulations to account for the presence of surface states and discuss the prospect of carrier-selective catalyst contacts.

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%.

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

Ye, Rong; Zhukhovitskiy, Aleksandr V.; Deraedt, Christophe V.

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 optimizemore » and expand the scope of their reactivity and selectivity. Ongoing efforts in our laboratories 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., π-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 PhICl 2) or reduced (e.g., with H 2) 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. Here in this Account, we will briefly introduce metal clusters and describe the synthesis and characterizations of supported DEMCs. We will present the catalysis studies of supported DEMCs in both the batch and flow modes. Lastly, we will summarize the current state of heterogenizing homogeneous catalysis and provide future directions for this area of research.« less

Esterification free fatty acid in sludge palm oil using ZrO2/SO42- - rice husk ash catalyst

NASA Astrophysics Data System (ADS)

Hidayat, Arif; Sutrisno, Bachrun

2017-05-01

Indonesia, as one of the biggest palm oil producers and exporters in the world, is producing large amounts of low-grade oil such as sludge palm oil (SPO) from palm oil industries. The use of SPO can lower the cost of biodiesel production significantly, which makes SPO a highly potential alternative feedstock for biodiesel production. In this paper, the esterification of free fatty acid on sludge palm oil was studied using rice husk ash as heterogeneous solid catalysts. Heterogeneous solid catalysts offer significant advantages of eliminating separation, corrosion, toxicity and environmental problems. In this paper the esterification of SPO, a by-product from palm oil industry, in the presence of modified rice husk ash catalysts was studied. The rice husk ash catalysts were synthesized by impregnating of Zirconia (Zr) on rice husk ash followed by sulfonation. The rice husk ash catalysts were characterized by using different techniques, such as FT-IR, XRD, and porous analysis. The effects of the mass ratio of catalyst to oil (1 - 10%), the molar ratio of methanol to oil (4:1 - 10:1), and the reaction temperature (40 - 60°C) were studied for the conversion of free fatty acids (FFAs) to optimize the reaction conditions. The results showed that the optimal conditions were an methanol to oil molar ratio of 10:1, the amount of catalyst of 10%w, and reaction temperature of 60°C.

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.

Film fabrication of Fe or Fe3O4 nanoparticles mixed with palmitic acid for vertically aligned carbon nanotube growth using Langmuir-Blodgett technique

NASA Astrophysics Data System (ADS)

Nakamura, Kentaro; Kuriyama, Naoki; Takagiwa, Shota; Sato, Taiga; Kushida, Masahito

2016-03-01

Vertically aligned carbon nanotubes (VA-CNTs) were studied as a new catalyst support for polymer electrolyte fuel cells (PEFCs). Controlling the number density and the diameter of VA-CNTs may be necessary to optimize PEFC performance. As the catalyst for CNT growth, we fabricated Fe or Fe3O4 nanoparticle (NP) films by the Langmuir-Blodgett (LB) technique. The catalyst Fe or Fe3O4 NPs were widely separated by mixing with filler molecules [palmitic acid (C16)]. The number density of VA-CNTs was controlled by varying the ratio of catalyst NPs to C16 filler molecules. The VA-CNTs were synthesized from the catalyst NP-C16 LB films by thermal chemical vapor deposition (CVD) using acetylene gas as the carbon source. The developing solvents used in the LB technique and the hydrogen reduction conditions of CVD were optimized to improve the VA-CNT growth rate. We demonstrate that the proposed method can independently control both the density and the diameter of VA-CNTs.

Production of sugars and levulinic acid from marine biomass Gelidium amansii.

PubMed

Jeong, Gwi-Taek; Park, Don-Hee

2010-05-01

This study focused on optimization of reaction conditions for formation of sugars and levulinic acid from marine algal biomass Gelidium amansii using acid catalyst and by using statistical approach. By this approach, optimal conditions for production of sugars and levulinic acid were found as follows: glucose (reaction temperature of 139.4 degrees C, reaction time of 15.0 min, and catalyst concentration of 3.0%), galactose (108.2 degrees C, 45.0 min, and 3.0%), and levulinic acid (160.0 degrees C, 43.1 min, and 3.0%). While trying to optimize the conditions for the production of glucose and galactose, levulinic acid production was found to be minimum. Similarly, the production of glucose and galactose were found to be minimum while optimizing the conditions for the production of levulinic acid. In addition, optimized production of glucose required a higher reaction temperature and shorter reaction time than that of galactose. Levulinic acid was formed at a high reaction temperature, long reaction time, and high catalyst concentration. The combined results of this study may provide useful information to develop more economical and efficient systems for production of sugars and chemicals from marine biomass.

Extraction of caustic potash from spent tea for biodiesel Production

NASA Astrophysics Data System (ADS)

Sulaiman, Sarina; Faiz Che Fisol, Ahmad; Sharikh, Atikah Mohamed; Noraini Jimat, Dzun; Jamal, Parveen

2018-01-01

Biodiesel is an alternative to non-renewable fossil fuels due to its low gas emission and economical value. This study aims to extract caustic potash (KOH) from spent tea and to optimize the transesterfication process based on parameters such as amount of catalyst, reaction temperature and methanol to oil ratio. The spent tea was first dried at 60°C prior to calcination at 600°C for two hours. Caustic Potash were extracted from the calcined spent tea. The transesterification process was done based on Design of Experiments (DOE) to study the effects of amount of catalyst ranging from 0.5 wt % to 2.5 wt %, reaction temperature from 55°C to 65°C and methanol to oil ratio from 6:1 to 12:1 at a constant agitation rate of 300 rpm for three hours. The calcined spent tea produced was recorded the highest at 54.3 wt % and the extracted catalyst was 2.4 wt %. The optimized biodiesel yield recorded was 56.95% at the optimal conditions of 2.5 wt % amount of catalyst, 65°C reaction temperature and 9:1 methanol to oil ratio.

BBD Optimization of K-ZnO Catalyst Modification Process for Heterogeneous Transesterification of Rice Bran Oil to Biodiesel

NASA Astrophysics Data System (ADS)

Kabo, K. S.; Yacob, A. R.; Bakar, W. A. W. A.; Buang, N. A.; Bello, A. M.; Ruskam, A.

2016-07-01

Environmentally benign zinc oxide (ZnO) was modified with 0-15% (wt.) potassium through wet impregnation and used in transesterification of rice bran oil (RBO) to form biodiesel. The catalyst was characterized by X-Ray powder Diffraction (XRD), its basic sites determined by back titration and Response Surface Methodology (RSM) Box-Behnken Design (BBD) was used to optimize the modification process variables on the basic sites of the catalyst. The transesterification product, biodiesel was analyzed by Nuclear Magnetic Resonance (NMR) spectroscopy. The result reveals K-modified ZnO with highly increased basic sites. Quadratic model with high regression R2 = 0.9995 was obtained from the ANOVA of modification process, optimization at maximum basic sites criterion gave optimum modification conditions of K-loading = 8.5% (wt.), calcination temperature = 480 oC and time = 4 hours with response and basic sites = 8.14 mmol/g which is in close agreement with the experimental value of 7.64 mmol/g. The catalyst was used and a value of 95.53% biodiesel conversion was obtained and effect of potassium leaching was not significant in the process

Lagrangian Approach to Jet Mixing and Optimization of the Reactor for Production of Carbon Nanotubes

NASA Technical Reports Server (NTRS)

Povitsky, Alex; Salas, Manuel D.

2001-01-01

This study was motivated by an attempt to optimize the High Pressure carbon oxide (HiPco) process for the production of carbon nanotubes from gaseous carbon oxide, The goal is to achieve rapid and uniform heating of catalyst particles by an optimal arrangement of jets. A mixed Eulerian and Lagrangian approach is implemented to track the temperature of catalyst particles along their trajectories as a function of time. The FLUENT CFD software with second-order upwind approximation of convective terms and an algebraic multigrid-based solver is used. The poor performance of the original reactor configuration is explained in terms of features of particle trajectories. The trajectories most exposed to the hot jets appear to be the most problematic for heating because they either bend towards the cold jet interior or rotate upwind of the mixing zone. To reduce undesirable slow and/or oscillatory heating of catalyst particles, a reactor configuration with three central jets is proposed and the optimal location of the central and peripheral nozzles is determined.

Promoted Iron Nanocrystals Obtained via Ligand Exchange as Active and Selective Catalysts for Synthesis Gas Conversion

PubMed Central

2017-01-01

Colloidal synthesis routes have been recently used to fabricate heterogeneous catalysts with more controllable and homogeneous properties. Herein a method was developed to modify the surface composition of colloidal nanocrystal catalysts and to purposely introduce specific atoms via ligands and change the catalyst reactivity. Organic ligands adsorbed on the surface of iron oxide catalysts were exchanged with inorganic species such as Na2S, not only to provide an active surface but also to introduce controlled amounts of Na and S acting as promoters for the catalytic process. The catalyst composition was optimized for the Fischer–Tropsch direct conversion of synthesis gas into lower olefins. At industrially relevant conditions, these nanocrystal-based catalysts with controlled composition were more active, selective, and stable than catalysts with similar composition but synthesized using conventional methods, possibly due to their homogeneity of properties and synergic interaction of iron and promoters. PMID:28824820

A molecule-like PtAu24(SC6H13)18 nanocluster as an electrocatalyst for hydrogen production

PubMed Central

Kwak, Kyuju; Choi, Woojun; Tang, Qing; Kim, Minseok; Lee, Yongjin; Jiang, De-en; Lee, Dongil

2017-01-01

The theoretically predicted volcano plot for hydrogen production shows the best catalyst as the one that ensures that the hydrogen binding step is thermodynamically neutral. However, the experimental realization of this concept has suffered from the inherent surface heterogeneity of solid catalysts. It is even more challenging for molecular catalysts because of their complex chemical environment. Here, we report that the thermoneutral catalyst can be prepared by simple doping of a platinum atom into a molecule-like gold nanocluster. The catalytic activity of the resulting bimetallic nanocluster, PtAu24(SC6H13)18, for the hydrogen production is found to be significantly higher than reported catalysts. It is even better than the benchmarking platinum catalyst. The molecule-like bimetallic nanocluster represents a class of catalysts that bridge homogeneous and heterogeneous catalysis and may provide a platform for the discovery of finely optimized catalysts. PMID:28281526

Optimizing the deposition of hydrogen evolution sites on suspended semiconductor particles using on-line photocatalytic reforming of aqueous methanol solutions.

PubMed

Busser, G Wilma; Mei, Bastian; Muhler, Martin

2012-11-01

The deposition of hydrogen evolution sites on photocatalysts is a crucial step in the multistep process of synthesizing a catalyst that is active for overall photocatalytic water splitting. An alternative approach to conventional photodeposition was developed, applying the photocatalytic reforming of aqueous methanol solutions to deposit metal particles on semiconductor materials such as Ga₂O₃ and (Ga₀.₆ Zn₀.₄)(N₀.₆O₀.₄). The method allows optimizing the loading of the co-catalysts based on the stepwise addition of their precursors and the continuous online monitoring of the evolved hydrogen. Moreover, a synergetic effect between different co-catalysts can be directly established. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

O-nitroso aldol synthesis: Catalytic enantioselective route to α-aminooxy carbonyl compounds via enamine intermediate

PubMed Central

Momiyama, Norie; Torii, Hiromi; Saito, Susumu; Yamamoto, Hisashi

2004-01-01

The approach using pyrrolidine enamine as substrate has been studied for this synthesis, and an important catalyst structural feature has been developed. After survey of pyrrolidine-based Brønsted acid catalyst, tetrazole catalyst (3f) was found to be optimal in synthesis of aminooxy carbonyl compounds in high yields, with complete enantioselectivity not only for aldehydes but also for ketones. PMID:15067138

Water Oxidation Mechanisms of Metal Oxide Catalysts by Vibrational Spectroscopy of Transient Intermediates.

PubMed

Zhang, Miao; Frei, Heinz

2017-05-05

Water oxidation is an essential reaction of an artificial photosystem for solar fuel generation because it provides electrons needed to reduce carbon dioxide or protons to a fuel. Earth-abundant metal oxides are among the most attractive catalytic materials for this reaction because of their robustness and scalability, but their efficiency poses a challenge. Knowledge of catalytic surface intermediates gained by vibrational spectroscopy under reaction conditions plays a key role in uncovering kinetic bottlenecks and provides a basis for catalyst design improvements. Recent dynamic infrared and Raman studies reveal the molecular identity of transient surface intermediates of water oxidation on metal oxides. Combined with ultrafast infrared observations of how charges are delivered to active sites of the metal oxide catalyst and drive the multielectron reaction, spectroscopic advances are poised to play a key role in accelerating progress toward improved catalysts for artificial photosynthesis.

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.

Effect of H2O2 injection patterns on catalyst bed characteristics

NASA Astrophysics Data System (ADS)

Kang, Hongjae; Lee, Dahae; Kang, Shinjae; Kwon, Sejin

2017-01-01

The decomposition process of hydrogen peroxide can be applied to a bipropellant thruster, as well as to monopropellant thruster. To provide a framework for the optimal design of the injector and catalyst bed depending on a type of thruster, this research scrutinizes the effect of injection patterns of the propellant on the performance of the catalyst bed. A showerhead injector and impinging jet injector were tested with a 50 N monopropellant thruster. Manganese oxide/γ-alumina catalyst and manganese oxide/lanthanum-doped alumina catalyst were prepared and tested. The showerhead injector provided a fast response time, suitable for pulse mode operation. The impinging jet injector mitigated the performance instability and catalyst attrition that is favorable for large scale bipropellant thrusters. The design of a dual catalyst bed was conceptually proposed based on the data obtained from firing tests.

Abstract - Cooperative Research and Development Agreement between Penn State University and National Energy Technology Laboratory

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

Hickner, Michael A.; Matranga, Christopher S.

This project will use bipolar membranes to produce efficient vapor-phase electrolysis cells for splitting CO 2 to CO and oxygen. CO is a valuable chemical feedstock that can be combined catalytically with hydrogen in the Fischer-Tropsch process to make liquid fuels. CO is arguably the best target for CO 2 reduction since, as a gaseous product, it is easily collected and is relatively immune to membrane crossover losses. The keys to success in this project are to design and synthesize hydrophilic, low resistance bipolar membranes and to create optimized electrode/catalyst/ electrolyte architectures based on these new membranes and advanced catalystsmore » in order to achieve high current density at low overpotentials for CO 2 conversion. High current density is key to achieving industrially-relevant throughput for the process and low overpotentials maintain high overall efficiency for the process.« less

Different routes to methanol: Inelastic neutron scattering spectroscopy of adsorbates on supported copper catalysts

DOE PAGES

Kandemir, Timur; Friedrich, Matthias; Parker, Stewart F.; ...

2016-04-14

We have investigated methanol synthesis with model supported copper catalysts, Cu/ZnO and Cu/MgO, using CO/H 2 and CO 2/H 2 as feedstocks. Under CO/H 2 both catalysts show chemisorbed methoxy as a stable intermediate, the Cu/MgO catalyst also shows hydroxyls on the support. Under CO 2/H 2 the catalysts behave differently, in that formate is also seen on the catalyst. For the Cu/ZnO catalyst hydroxyls are present on the metal whereas for the Cu/MgO hydroxyls are found on the support. Furthermore, these results are consistent with a recently published model for methanol synthesis and highlight the key role of ZnOmore » in the process.« less

Balancing activity, stability and conductivity of nanoporous core-shell iridium/iridium oxide oxygen evolution catalysts

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

Kim, Yong-Tae; Lopes, Pietro Papa; Park, Shin-Ae

The selection of oxide materials for catalyzing the Oxygen Evolution Reaction in acid-based electrolyzers must be guided by the proper balance between activity, stability and conductivity – a challenging mission of great importance for delivering affordable and environmentally friendly hydrogen. Here we report that the highly conductive nanoporous architecture of an iridium oxide shell on a metallic iridium core, formed through the fast dealloying of osmium from an Ir25Os75 alloy, exhibits an exceptional balance between oxygen evolution activity and stability as quantified by the Activity-Stability FactorASF. Based on this metric, the nanoporous Ir/IrO2 morphology of dealloyed Ir25Os75 shows a factormore » of ~30 improvement ASFrelative to conventional Ir-based oxide materials and a ~8 times improvement over dealloyed Ir25Os75 nanoparticles due to optimized stability and conductivity, respectively. We propose that the Activity-Stability FactorASF is the key “metric” for determining the technological relevance of oxide-based anodic water electrolyzer catalysts.« less

Three-Dimensional Networks of S-Doped Fe/N/C with Hierarchical Porosity for Efficient Oxygen Reduction in Polymer Electrolyte Membrane Fuel Cells.

PubMed

Wu, Yi-Jin; Wang, Yu-Cheng; Wang, Rui-Xiang; Zhang, Peng-Fang; Yang, Xiao-Dong; Yang, Hui-Juan; Li, Jun-Tao; Zhou, Yao; Zhou, Zhi-You; Sun, Shi-Gang

2018-05-02

Reasonable design and synthesis of Fe/N/C-based catalysts is one of the most promising way for developing precious metal-free oxygen reduction reaction (ORR) catalysts in acidic mediums. Herein, we developed a highly active metal-organic framework-derived S-doped Fe/N/C catalyst [S-Fe/Z8/2-aminothiazole (2-AT)] prepared by thermal treatment. The S-Fe/Z8/2-AT catalyst with uniform S-doping possesses a three-dimensional macro-meso-micro hierarchically porous structure. Moreover, the chemical composition and structural features have been well-optimized and characterized for such S-Fe/Z8/2-AT catalysts; and their formation mechanism was also revealed. Significantly, applying the optimal S-Fe/Z8/2-AT catalysts into electrocatalytic test exhibits remarkable ORR catalytic activity with a half-wave potential of 0.82 V (vs reversible hydrogen electrode) and a mass activity of 18.3 A g -1 at 0.8 V in 0.1 M H 2 SO 4 solution; the polymer electrolyte membrane fuel cell test also confirmed their excellent catalytic activity, which gives a maximal power density as high as 800 mW cm -2 at 1 bar. A series of designed experiments disclosed that the favorable structural merits and desirable chemical compositions of S-Fe/Z8/2-AT catalysts are critical factors for efficient electrocatalytic performance. The work provides a new approach to open an avenue for accurately controlling the composition and structure of Fe/N/C catalysts with highly activity for ORR.

Fabrication of solar light induced Fe-TiO{sub 2} immobilized on glass-fiber and application for phenol photocatalytic degradation

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

Lin, Shaohua, E-mail: linsh75@163.com; Zhang, Xiwang; Sun, Qinju

2013-11-15

Graphical abstract: - Highlights: • Fe-doped TiO{sub 2} immobilized on glass-fiber net were prepared by sol–gel method. • Fe inhibited the phase transition of TiO{sub 2} from anatase to rutile. • The optimal Fe doping dose was around 0.005 wt%. • The optimal calcination temperature was around 600 °C. - Abstract: Iron-doped anatase titanium dioxide catalysts coated on glass-fiber were successfully synthesized by a dip-coating sol–gel method. The prepared catalysts were characterized by scanning electron microscopy (SEM) with energy dispersive X-ray (EDX) analysis, X-ray diffraction (XRD), UV-Vis diffuse reflectance spectroscopy to understand the synthesis mechanism, and their photocatalytic activities weremore » evaluated by photodegradation of phenol under simulated solar irradiation. EDX analysis confirmed the existence of iron in the immobilized catalysts. XRD suggested that the phase transition of the catalysts from anatase to rutile were restrained, and almost pure anatase TiO{sub 2} could retain even the calcination temperature reached 800 °C. The UV-Vis diffuse reflectance spectroscopy of the catalysts showed a red shift and increased photoabsorbance in the visible range for all the doped samples. Iron loading and calcination temperature have obvious influences on photocatalytic activity. In this study, the optimal doping dose and calcination temperature were around 0.005 wt% and 600 °C, respectively.« less

Design and Stereoselective Preparation of a New Class of Chiral Olefin Metathesis Catalysts and Application to Enantioselective Synthesis of Quebrachamine: Catalyst Development Inspired by Natural Product Synthesis

PubMed Central

Sattely, Elizabeth S.; Meek, Simon J.; Malcolmson, Steven J.; Schrock, Richard R.; Hoveyda, Amir H.

2010-01-01

A total synthesis of the Aspidosperma alkaloid quebrachamine in racemic form is first described. A key catalytic ring-closing metathesis of an achiral triene is used to establish the all-carbon quaternary stereogenic center and the tetracyclic structure of the natural product; the catalytic transformation proceeds with reasonable efficiency through the use of existing achiral Ru or Mo catalysts. Ru- or Mo-based chiral olefin metathesis catalysts have proven to be inefficient and entirely nonselective in cases where the desired product is observed. In the present study, the synthesis route thus serves as a platform for the discovery of new olefin metathesis catalysts that allow for efficient completion of an enantioselective synthesis of quebrachamine. Accordingly, on the basis of mechanistic principles, stereogenic-at-Mo complexes bearing only monodentate ligands have been designed. The new catalysts provide significantly higher levels of activity than observed with the previously reported Ru- or Mo-based complexes. Enantiomerically enriched chiral alkylidenes are generated through diastereoselective reactions involving achiral Mo-based bispyrrolides and enantiomerically pure silyl-protected binaphthols. Such chiral catalysts initiate the key enantioselective ring-closing metathesis step in the total synthesis of quebrachamine efficiently (1 mol % loading, 22 °C, 1 h, >98% conversion, 84% yield) and with high selectivity (98:2 er, 96% ee). PMID:19113867

Alkaline in situ transesterification of Aurantiochytrium sp. KRS 101 using potassium carbonate.

PubMed

Sung, Mina; Han, Jong-In

2016-04-01

The aims of this work were to evaluate K2CO3 as a potent alkaline catalyst for in situ transesterification of Aurantiochytrium sp. KRS 101, one step process in which oil extraction and conversion take place together. This K2CO3-based in situ transesterification was optimized in terms of recovery yield of fatty acid methyl esters (FAMEs) by way of varying biomass concentration, reaction temperature, reaction time, and catalyst concentration. The optimal condition was achieved at 50g/L of biomass concentration and 1% of K2CO3 in the methanol, 25°C of reaction temperature, and 5min of reaction time, resulting in the FAME recovery yield over 90%. It was found that K2CO3 performed better than any other tested catalysts including acids, supporting the notion that K2CO3 is a promising catalyst, especially for in situ transesterification. Copyright © 2016. Published by Elsevier Ltd.

Quantifying ligand effects in high-oxidation-state metal catalysis

NASA Astrophysics Data System (ADS)

Billow, Brennan S.; McDaniel, Tanner J.; Odom, Aaron L.

2017-09-01

Catalysis by high-valent metals such as titanium(IV) impacts our lives daily through reactions like olefin polymerization. In any catalysis, optimization involves a careful choice of not just the metal but also the ancillary ligands. Because these choices dramatically impact the electronic structure of the system and, in turn, catalyst performance, new tools for catalyst development are needed. Understanding ancillary ligand effects is arguably one of the most critical aspects of catalyst optimization and, while parameters for phosphines have been used for decades with low-valent systems, a comparable system does not exist for high-valent metals. A new electronic parameter for ligand donation, derived from experiments on a high-valent chromium species, is now available. Here, we show that the new parameters enable quantitative determination of ancillary ligand effects on catalysis rate and, in some cases, even provide mechanistic information. Analysing reactions in this way can be used to design better catalyst architectures and paves the way for the use of such parameters in a host of high-valent processes.

The degradation of wheat straw lignin

NASA Astrophysics Data System (ADS)

Liang, Jiaqi

2017-03-01

Lignin is a kind of formed by polymerization of aromatic alcohol, prices are lower and sources of renewable resources. Using lignin as raw material, through the push to resolve together preparation phenolic high value-added fine chemicals alkanes and aromatic hydrocarbons, such as the high grade biofuels, can partly replace fossil fuels as raw material to the production process, biomass resources is an important part of the comprehensive utilization of effective components. In lignin push solve clustering method, catalytic hydrogenolysis can directly to the lignin into liquid fuels, low oxygen content in the use of biofuels shows great potential. In this paper, through the optimization of the reaction time, reaction temperature, catalyst type and solvent type, dosage of catalyst, etc factors, determines the alcoholysis - hydrogen solution two-step degradation of lignin, the optimal process conditions: lignin alcoholysis under 50% methanol and NaOH catalyst in the solution, the lignin in methanol solution and 50% hydrogen solution under the Pd/C catalyst. In this process, the degradation of lignin yield can reach 42%.

Optimization of sodium loading on zeolite support for catalyzed transesterification of triolein with methanol.

PubMed

Wang, Yu-Yuan; Chou, Hsin-Yu; Chen, Bing-Hung; Lee, Duu-Jong

2013-10-01

Optimization of sodium loading on zeolite HY for catalyzed transesterification of triolein in excess methanol to biodiesel was studied. Zeolite HY catalyst was activated by loading sodium ions to their surface via an ion-exchange method. The effects of ion-exchange process parameters, including the temperature, the process time, the pH value, as well as concentrations and sources of Na(+) cations (NaOH, NaCl and Na2SO4), on the conversion yield of triolein to biodiesel were investigated. Most of these Na(+)-activated zeolite HY catalysts could really facilitate the catalyzed transesterification reaction of triolein to biodiesel at a lower temperature near 65°C. Consequently, a high conversion yield of triglycerides to biodiesel at 97.3% was obtained at 65°C. Moreover, the durability of zeolite catalysts was examined as well. Catalytic performance tests of these zeolite catalysts in transesterification did not show a significant decrease in catalysis at least for three batch cycles. Copyright © 2013 Elsevier Ltd. All rights reserved.

Hierarchically porous carbons with optimized nitrogen doping as highly active electrocatalysts for oxygen reduction

NASA Astrophysics Data System (ADS)

Liang, Hai-Wei; Zhuang, Xiaodong; Brüller, Sebastian; Feng, Xinliang; Müllen, Klaus

2014-09-01

Development of efficient, low-cost and stable electrocatalysts as the alternative to platinum for the oxygen reduction reaction is of significance for many important electrochemical devices, such as fuel cells, metal-air batteries and chlor-alkali electrolysers. Here we report a highly active nitrogen-doped, carbon-based, metal-free oxygen reduction reaction electrocatalyst, prepared by a hard-templating synthesis, for which nitrogen-enriched aromatic polymers and colloidal silica are used as precursor and template, respectively, followed by ammonia activation. Our protocol allows for the simultaneous optimization of both porous structures and surface functionalities of nitrogen-doped carbons. Accordingly, the prepared catalysts show the highest oxygen reduction reaction activity (half-wave potential of 0.85 V versus reversible hydrogen electrode with a low loading of 0.1 mg cm-2) in alkaline media among all reported metal-free catalysts. Significantly, when used for constructing the air electrode of zinc-air battery, our metal-free catalyst outperforms the state-of the-art platinum-based catalyst.

Highly recoverable pyridinium-tagged Hoveyda-Grubbs pre-catalyst for olefin metathesis. Design of the boomerang ligand toward the optimal compromise between activity and reusability.

PubMed

Rix, Diane; Caïjo, Fréderic; Laurent, Isabelle; Gulajski, Lukasz; Grela, Karol; Mauduit, Marc

2007-09-28

Whereas the boomerang ligand of Hoveyda-Grubbs pre-catalysts can be modified by attachment of a pyridinium tag to its benzylidene moiety, a precise adjustment of the length of the spacer allows the optimum balance to be reached between the activity of the catalyst and its recoverability, exceeding 98% after 6 catalytic runs in the best case.

Ultraefficient homogeneous catalyst for the CO2-to-CO electrochemical conversion.

PubMed

Costentin, Cyrille; Passard, Guillaume; Robert, Marc; Savéant, Jean-Michel

2014-10-21

A very efficient electrogenerated Fe(0) porphyrin catalyst was obtained by substituting in tetraphenylporphyrin two of the opposite phenyl rings by ortho-, ortho'-phenol groups while the other two are perfluorinated. It proves to be an excellent catalyst of the CO2-to-CO conversion as to selectivity (the CO faradaic yield is nearly quantitative), overpotential, and turnover frequency. Benchmarking with other catalysts, through catalytic Tafel plots, shows that it is the most efficient, to the best of our knowledge, homogeneous molecular catalyst of the CO2-to-CO conversion at present. Comparison with another Fe(0) tetraphenylporphyrin bearing eight ortho-, ortho'-phenol functionalities launches a general strategy where changes in substituents will be designed so as to optimize the operational combination of all catalyst elements of merit.

Single Turnover at Molecular Polymerization Catalysts Reveals Spatiotemporally Resolved Reactions.

PubMed

Easter, Quinn T; Blum, Suzanne A

2017-10-23

Multiple active individual molecular ruthenium catalysts have been pinpointed within growing polynorbornene, thereby revealing information on the reaction dynamics and location that is unavailable through traditional ensemble experiments. This is the first single-turnover imaging of a molecular catalyst by fluorescence microscopy and allows detection of individual monomer reactions at an industrially important molecular ruthenium ring-opening metathesis polymerization (ROMP) catalyst under synthetically relevant conditions (e.g. unmodified industrial catalyst, ambient pressure, condensed phase, ca. 0.03 m monomer). These results further establish the key fundamentals of this imaging technique for characterizing the reactivity and location of active molecular catalysts even when they are the minor components. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Optimization of Acid Orange 7 Degradation in Heterogeneous Fenton-like Reaction Using Fe3-xCoxO4 Catalyst

NASA Astrophysics Data System (ADS)

Ibrahim, M. Z.; Alrozi, R.; Zubir, N. A.; Bashah, N. A.; Ali, S. A. Md; Ibrahim, N.

2018-05-01

The oxidation process such as heterogeneous Fenton and/or Fenton-like reactions is considered as an effective and efficient method for treatment of dye degradation. In this study, the degradation of Acid Orange 7 (AO7) was investigated by using Fe3-xCoxO4 as a heterogeneous Fenton-like catalyst. Response surface methodology (RSM) was used to optimize the operational parameters condition and the interaction of two or more parameters. The parameter studies were catalyst dosage (X1 ), pH (X2 ) and H2O2 concentration (X3 ) towards AO7 degradation. Based on analysis of variance (ANOVA), the derived quadratic polynomial model was significant whereby the predicted values matched the experimental values with regression coefficient of R2 = 0.9399. The optimum condition for AO7 degradation was obtained at catalyst dosage of 0.84 g/L, pH of 3 and H2O2 concentration of 46.70 mM which resulted in 86.30% removal of AO7 dye. These findings present new insights into the influence of operational parameters in the heterogeneous Fenton-like oxidation of AO7 using Fe3-xCoxO4 catalyst.

Sulfate radical degradation of acetaminophen by novel iron-copper bimetallic oxidation catalyzed by persulfate: Mechanism and degradation pathways

NASA Astrophysics Data System (ADS)

Zhang, Yuanchun; Zhang, Qian; Hong, Junming

2017-11-01

A novel iron coupled copper oxidate (Fe2O3@Cu2O) catalyst was synthesized to activate persulfate (PS) for acetaminophen (APAP) degradation. The catalysts were characterized via field-emission scanning electron microscopy and energy-dispersive X-ray spectrometry. The effects of the catalyst, PS concentration, catalyst dosage, initial pH, dissolved oxygen were analyzed for treatment optimization. Results indicated that Fe2O3@Cu2O achieved higher efficiency in APAP degradation than Fe2O3/PS and Cu2O/PS systems. The optimal removal efficiency of APAP (90%) was achieved within 40 min with 0.6 g/L PS and 0.3 g/L catalyst. To clarify the mechanism for APAP degradation, intermediates were analyzed with gas chromatography-mass spectrometry. Three possible degradation pathways were identified. During reaction, Cu(I) was found to react with Fe(III) to generate Fe(II), which is the most active phase for PS activation. Through the use of methanol and tert-butyl alcohol (TBA) as radical trappers, SO4rad - was identified as the main radical species that is generated during oxidation.

Predicting the amount of coke deposition on catalyst pellets through image analysis and soft computing

NASA Astrophysics Data System (ADS)

Zhang, Jingqiong; Zhang, Wenbiao; He, Yuting; Yan, Yong

2016-11-01

The amount of coke deposition on catalyst pellets is one of the most important indexes of catalytic property and service life. As a result, it is essential to measure this and analyze the active state of the catalysts during a continuous production process. This paper proposes a new method to predict the amount of coke deposition on catalyst pellets based on image analysis and soft computing. An image acquisition system consisting of a flatbed scanner and an opaque cover is used to obtain catalyst images. After imaging processing and feature extraction, twelve effective features are selected and two best feature sets are determined by the prediction tests. A neural network optimized by a particle swarm optimization algorithm is used to establish the prediction model of the coke amount based on various datasets. The root mean square error of the prediction values are all below 0.021 and the coefficient of determination R 2, for the model, are all above 78.71%. Therefore, a feasible, effective and precise method is demonstrated, which may be applied to realize the real-time measurement of coke deposition based on on-line sampling and fast image analysis.

Nano-catalysts: Key to the Greener Pathways Leading to Sustainability

EPA Science Inventory

Synthetic processes using alternative energy input in combination with nano-catalysts shorten the reaction time that eliminate or minimize side product formation. This concept is already finding acceptance in the syntheses of pharmaceuticals, fine chemicals, and polymers and may ...

Biodiesel production from palm oil using calcined waste animal bone as catalyst.

PubMed

Obadiah, Asir; Swaroopa, Gnanadurai Ajji; Kumar, Samuel Vasanth; Jeganathan, Kenthorai Raman; Ramasubbu, Alagunambi

2012-07-01

Waste animal bones was employed as a cost effective catalyst for the transesterification of palm oil. The catalyst was calcined at different temperatures to transform the calcium phosphate in the bones to hydroxyapatite and 800 °C was found to give the best yield of biodiesel. The catalyst was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive spectrometry (EDS) and Fourier transform infrared spectrometry (FT-IR). Under the optimal reaction conditions of 20 wt.% of catalyst, 1:18 oil to methanol molar ratio, 200 rpm of stirring of reactants and at a temperature of 65 °C, the methyl ester conversion was 96.78% and it was achieved in 4h. The catalyst performed equally well as the laboratory-grade CaO. Animal bone is therefore a useful raw material for the production of a cheap catalyst for transesterification. Copyright © 2012 Elsevier Ltd. All rights reserved.

Pd and polyaniline nanocomposite on carbon fiber paper as an efficient direct formic acid fuel cell anode

NASA Astrophysics Data System (ADS)

Pandey, Rakesh K.

2018-03-01

Direct formic acid fuel cells are advantageous as portable power generating devices. In the present work, an anode catalyst for direct formic acid fuel cell (DFAFC) is presented which has good catalytic activity for formic acid oxidation. The catalyst is composed of Pd and conducting polymer polyaniline (Pd-PANI) nanocomposite. The catalyst was prepared by using a single step galvanostatic electrochemical deposition method. The Pd-PANI catalyst was electrodeposited at different time durations and a comparison of the catalytic activity at each deposition time was carried out and optimized.

Selective One-Pot Production of High-Grade Diesel-Range Alkanes from Furfural and 2-Methylfuran over Pd/NbOPO4.

PubMed

Xia, Qineng; Xia, Yinjiang; Xi, Jinxu; Liu, Xiaohui; Zhang, Yongguang; Guo, Yong; Wang, Yanqin

2017-02-22

A one-pot method for the selective production of high-grade diesel-range alkanes from biomass-derived furfural and 2-methylfuran (2-MF) was developed by combining the hydroxyalkylation/alkylation (HAA) condensation of furfural with 2-MF and the subsequent hydrodeoxygenation (HDO) over a multifunctional Pd/NbOPO 4 catalyst. The effects of various reaction conditions as well as a variety of solid-acid catalysts and metal-loaded NbOPO 4 catalysts were systematically investigated to optimize the reaction conditions for both reactions. Under the optimal reaction conditions up to 89.1 % total yield of diesel-range alkanes was obtained from furfural and 2-MF by this one-pot method. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Radiation absorption and optimization of solar photocatalytic reactors for environmental applications.

PubMed

Colina-Márquez, Jose; Machuca-Martínez, Fiderman; Li Puma, Gianluca

2010-07-01

This study provides a systematic and quantitative approach to the analysis and optimization of solar photocatalytic reactors utilized in environmental applications such as pollutant remediation and conversion of biomass (waste) to hydrogen. Ray tracing technique was coupled with the six-flux absorption scattering model (SFM) to analyze the complex radiation field in solar compound parabolic collectors (CPC) and tubular photoreactors. The absorption of solar radiation represented by the spatial distribution of the local volumetric rate of photon absorption (LVRPA) depends strongly on catalyst loading and geometry. The total radiation absorbed in the reactors, the volumetric rate of absorption (VRPA), was analyzed as a function of the optical properties (scattering albedo) of the photocatalyst. The VRPA reached maxima at specific catalyst concentrations in close agreement with literature experimental studies. The CPC has on average 70% higher photon absorption efficiency than a tubular reactor and requires 39% less catalyst to operate under optimum conditions. The "apparent optical thickness" is proposed as a new dimensionless parameter for optimization of CPC and tubular reactors. It removes the dependence of the optimum catalyst concentration on tube diameter and photocatalyst scattering albedo. For titanium dioxide (TiO(2)) Degussa P25, maximum photon absorption occurs at apparent optical thicknesses of 7.78 for CPC and 12.97 for tubular reactors.

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

Perras, Frédéric A.; Boteju, Kasuni C.; Slowing, Igor I.

In this work, we utilize direct 17O DNP for the characterization of non-protonated oxygens in heterogeneous catalysts. The optimal sample preparation and population transfer approach for 17O direct DNP experiments performed on silica surfaces is determined and applied to the characterization of Zr- and Y-based mesoporous silica-supported single-site catalysts.

Superstructure-based Design and Optimization of Batch Biodiesel Production Using Heterogeneous Catalysts

NASA Astrophysics Data System (ADS)

Nuh, M. Z.; Nasir, N. F.

2017-08-01

Biodiesel as a fuel comprised of mono alkyl esters of long chain fatty acids derived from renewable lipid feedstock, such as vegetable oil and animal fat. Biodiesel production is complex process which need systematic design and optimization. However, no case study using the process system engineering (PSE) elements which are superstructure optimization of batch process, it involves complex problems and uses mixed-integer nonlinear programming (MINLP). The PSE offers a solution to complex engineering system by enabling the use of viable tools and techniques to better manage and comprehend the complexity of the system. This study is aimed to apply the PSE tools for the simulation of biodiesel process and optimization and to develop mathematical models for component of the plant for case A, B, C by using published kinetic data. Secondly, to determine economic analysis for biodiesel production, focusing on heterogeneous catalyst. Finally, the objective of this study is to develop the superstructure for biodiesel production by using heterogeneous catalyst. The mathematical models are developed by the superstructure and solving the resulting mixed integer non-linear model and estimation economic analysis by using MATLAB software. The results of the optimization process with the objective function of minimizing the annual production cost by batch process from case C is 23.2587 million USD. Overall, the implementation a study of process system engineering (PSE) has optimized the process of modelling, design and cost estimation. By optimizing the process, it results in solving the complex production and processing of biodiesel by batch.

Nitrogen-doped three-dimensional graphene-supported platinum catalysts for polymer electrolyte membrane fuel cells application

NASA Astrophysics Data System (ADS)

Chu, Fuqiang; Li, Xingxing; Yuan, Wensen; Zhu, Huanhuan; Qin, Yong; Zhang, Shuai; Yuan, Ningyi; Lin, Bencai; Ding, Jianning

Catalysts are a key component of polymer electrolyte membrane fuel cells (PEMFCs). In this work, nitrogen-doped three-dimensional graphene-supported platinum (Pt-3DNG) catalysts are successfully prepared and characterized. SEM and TEM images show the Pt nanoparticles are uniformly dispersed in the sheets of nitrogen-doped 3DNG. Compared with that of the commercial Pt/C catalysts, Pt-3DNG show much better oxygen reduction reaction (ORR) activity and cycling stability, and the reduction in limit current density after 1000 cycles is only about 1.6% for the Pt-3DNG catalysts, whereas 7.2% for the commercial Pt/C catalysts. The single cell using Pt-3DNG catalysts in both the anode and the cathode show a higher peak power density (21.47mW cm-2) than that using commercial Pt/C catalysts (20.17mW cm-2) under the same conditions. These properties make this type of catalyst suitable for the application in PEMFCs.

Heterogeneous electro-Fenton catalyst for 1-butylpyridinium chloride degradation.

PubMed

Meijide, Jessica; Pazos, Marta; Sanromán, Maria Ángeles

2017-10-15

The application of the electro-Fenton process for organic compound mineralisation has been widely reported over the past years. However, operational problems related to the use of soluble iron salt as a homogeneous catalyst involve the development of novel catalysts that are able to operate in a wide pH range. For this purpose, polyvinyl alcohol-alginate beads, containing goethite as iron, were synthesised and evaluated as heterogeneous electro-Fenton catalyst for 1-butylpyridinium chloride mineralisation. The influence of catalyst dosage and pH solution on ionic liquid degradation was analysed, achieving almost total oxidation after 60 min under optimal conditions (2 g/L catalyst concentration and pH 3). The results showed good catalyst stability and reusability, although its effectiveness decreases slightly after three successive cycles. Furthermore, a plausible mineralisation pathway was proposed based on the oxidation byproducts determined by chromatographic techniques. Finally, the Microtox® test revealed notable detoxification after treatment which demonstrates high catalyst ability for pyridinium-based ionic liquid degradation by the electro-Fenton process.

Preparation and characterization of CuO catalyst for the thermolysis treatment of distillery wastewater.

PubMed

Sharma, Deepak; Prajapati, Abhinesh Kumar; Choudhary, Rumi; Kaushal, Rajesh Kumar; Pal, Dharm; Sawarkar, Ashish N

2017-08-16

CuO catalyst was prepared from copper sulfate by alkali precipitation method followed by drying and calcination. Characterization of CuO catalyst using X-ray diffraction, Brunauer-Emmett-Teller, and Barrett-Joyner-Halenda surface area analysis envisaged the effectiveness of CuO as a catalyst for the treatment of biodigester effluent (BDE) emanated from distilleries. The catalytic thermolysis is an efficient advance treatment method for distillery biodigester effluent (BDE). CT treatment of BDE was carried out in a 0.5 dm 3 thermolytic batch reactor using CuO as a catalyst at different pH (1-9), temperatures (80-110°C), and catalyst loadings (1-4 kg/m 3 ). With CuO catalyst, a temperature of 110°C, catalyst loading of 4 kg/m 3 , and pH of 2 was found to be optimal, providing a maximum reduction in chemical oxygen demand of 65%. The settling characteristics at different temperatures of CT-treated sludge were also presented.

On the suitability of different representations of solid catalysts for combinatorial library design by genetic algorithms.

PubMed

Gobin, Oliver C; Schüth, Ferdi

2008-01-01

Genetic algorithms are widely used to solve and optimize combinatorial problems and are more often applied for library design in combinatorial chemistry. Because of their flexibility, however, their implementation can be challenging. In this study, the influence of the representation of solid catalysts on the performance of genetic algorithms was systematically investigated on the basis of a new, constrained, multiobjective, combinatorial test problem with properties common to problems in combinatorial materials science. Constraints were satisfied by penalty functions, repair algorithms, or special representations. The tests were performed using three state-of-the-art evolutionary multiobjective algorithms by performing 100 optimization runs for each algorithm and test case. Experimental data obtained during the optimization of a noble metal-free solid catalyst system active in the selective catalytic reduction of nitric oxide with propene was used to build up a predictive model to validate the results of the theoretical test problem. A significant influence of the representation on the optimization performance was observed. Binary encodings were found to be the preferred encoding in most of the cases, and depending on the experimental test unit, repair algorithms or penalty functions performed best.

Final report for project "Next-Generation Semiconductors for Solar Photoelectrolysis"

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

Khalifah, Peter

2016-09-15

In this paper, effective methods have been developed for preparing high-quality LaTiO 2N films on conductive La 5Ti 5O 17 substrates that can serve as photoanodes for photoelectrochemical water oxidation. One paper has been written by the post-doc who completed this comprehensive, interdisciplinary study, and it is presently being finalized for submission. Our approach to this system integrates expertise that we have developed in single crystal growth, thin film growth, and thin film post-processing. Through this work, LTON films have been fully optimized for light harvesting, as their band gap is optimally matched with the incident solar spectrum and themore » film thicknesses have been optimized based on the absolute absorption coefficients that we have measured for this system. The next step is to optimize the co-catalyst functionalization and the solution conditions to maximize the catalytic activity for water oxidation. Since the preliminary tests described here were done without a water oxidation co-catalyst, and since good water oxidation catalysts have previously been identified based on studies of powder samples, this next step is highly likely to be successful.« less

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.

TAILORING CATALYSTS FOR HYDRODECHLORINATING CHLORINATED HYDROCARBON CONTAMINANTS IN GROUNDWATER. (R825689C078)

EPA Science Inventory

Abstract

A palladium-on-zeolite catalyst has been optimized for treating groundwater contaminated with halogenated hydrocarbon compounds (HHCs) by hydrodechlorination with dissolved hydrogen. Aqueous sulfite was used as the model poison and the dechlorination of 1,2-di...

TAILORING CATALYSTS FOR HYDRODECHLORINATING CHLORINATED HYDROCARBON CONTAMINANTS IN GROUNDWATER. (R825689C093)

EPA Science Inventory

Abstract

A palladium-on-zeolite catalyst has been optimized for treating groundwater contaminated with halogenated hydrocarbon compounds (HHCs) by hydrodechlorination with dissolved hydrogen. Aqueous sulfite was used as the model poison and the dechlorination of 1,2-di...

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.

Optimization of operating parameters for gas-phase photocatalytic splitting of H2S by novel vermiculate packed tubular reactor.

PubMed

Preethi, V; Kanmani, S

2016-10-01

Hydrogen production by gas-phase photocatalytic splitting of Hydrogen Sulphide (H2S) was investigated on four semiconductor photocatalysts including CuGa1.6Fe0.4O2, ZnFe2O3, (CdS + ZnS)/Fe2O3 and Ce/TiO2. The CdS and ZnS coated core shell particles (CdS + ZnS)/Fe2O3 shows the highest rate of hydrogen (H2) production under optimized conditions. Packed bed tubular reactor was used to study the performance of prepared photocatalysts. Selection of the best packing material is a key for maximum removal efficiency. Cheap, lightweight and easily adsorbing vermiculate materials were used as a novel packing material and were found to be effective in splitting H2S. Effect of various operating parameters like flow rate, sulphide concentration, catalyst dosage, light irradiation were tested and optimized for maximum H2 conversion of 92% from industrial waste H2S. Copyright © 2016 Elsevier Ltd. All rights reserved.

Molecular water oxidation mechanisms followed by transition metals: state of the art.

PubMed

Sala, Xavier; Maji, Somnath; Bofill, Roger; García-Antón, Jordi; Escriche, Lluís; Llobet, Antoni

2014-02-18

One clean alternative to fossil fuels would be to split water using sunlight. However, to achieve this goal, researchers still need to fully understand and control several key chemical reactions. One of them is the catalytic oxidation of water to molecular oxygen, which also occurs at the oxygen evolving center of photosystem II in green plants and algae. Despite its importance for biology and renewable energy, the mechanism of this reaction is not fully understood. Transition metal water oxidation catalysts in homogeneous media offer a superb platform for researchers to investigate and extract the crucial information to describe the different steps involved in this complex reaction accurately. The mechanistic information extracted at a molecular level allows researchers to understand both the factors that govern this reaction and the ones that derail the system to cause decomposition. As a result, rugged and efficient water oxidation catalysts with potential technological applications can be developed. In this Account, we discuss the current mechanistic understanding of the water oxidation reaction catalyzed by transition metals in the homogeneous phase, based on work developed in our laboratories and complemented by research from other groups. Rather than reviewing all of the catalysts described to date, we focus systematically on the several key elements and their rationale from molecules studied in homogeneous media. We organize these catalysts based on how the crucial oxygen-oxygen bond step takes place, whether via a water nucleophilic attack or via the interaction of two M-O units, rather than based on the nuclearity of the water oxidation catalysts. Furthermore we have used DFT methodology to characterize key intermediates and transition states. The combination of both theory and experiments has allowed us to get a complete view of the water oxidation cycle for the different catalysts studied. Finally, we also describe the various deactivation pathways for these catalysts.

Electrocatalytic reduction of carbon dioxide on electrodeposited tin-based surfaces

NASA Astrophysics Data System (ADS)

Alba, Bianca Christina S.; Camayang, John Carl A.; Mopon, Marlon L.; del Rosario, Julie Anne D.

2017-08-01

The electrocatalytic reduction of carbon dioxide to small organic molecular compounds provides a means of generating alternative fuel source while suppressing climate change. Suitable catalysts, however, are necessary to optimize its reaction kinetics towards more valuable products. Consequently, in this study, electrodeposited Sn electrodes have been developed as catalysts for CO2 electroreduction. Deposition potential was varied to produce different Sn catalysts. SEM showed varying morphologies and increasing amount as the applied potential becomes more negative. Cyclic voltammetry and chronoamperometry showed that the activity and stability of the catalysts towards CO2 reduction depend on the morphology and presence of tin oxides. These results provide a better understanding on the performance of electrodeposited Sn-based surfaces as catalysts for CO2 reduction.

Membrane catalyst layer for fuel cells

DOEpatents

Wilson, Mahlon S.

1993-01-01

A gas reaction fuel cell incorporates a thin catalyst layer between a solid polymer electrolyte (SPE) membrane and a porous electrode backing. The catalyst layer is preferably less than about 10 .mu.m in thickness with a carbon supported platinum catalyst loading less than about 0.35 mgPt/cm.sup.2. The film is formed as an ink that is spread and cured on a film release blank. The cured film is then transferred to the SPE membrane and hot pressed into the surface to form a catalyst layer having a controlled thickness and catalyst distribution. Alternatively, the catalyst layer is formed by applying a Na.sup.+ form of a perfluorosulfonate ionomer directly to the membrane, drying the film at a high temperature, and then converting the film back to the protonated form of the ionomer. The layer has adequate gas permeability so that cell performance is not affected and has a density and particle distribution effective to optimize proton access to the catalyst and electronic continuity for electron flow from the half-cell reaction occurring at the catalyst.

ENHANCING THE STABILITY OF POROUS CATALYSTS WITH SUPERCRITICAL REACTION MEDIA. (R826034)

EPA Science Inventory

Adsorption/desorption and pore-transport are key parameters influencing the activity and product selectivity in porous catalysts. With conventional reaction media (gas or liquid phase), one of these parameters is generally favorable while the other is not. For instance, while ...

Hydrazine Catalyst Production: Sustaining S-405 Technology

NASA Technical Reports Server (NTRS)

Wucherer, E. J.; Cook, Timothy; Stiefel, Mark; Humphries, Randy, Jr.; Parker, Janet

2003-01-01

The development of the iridium-based Shell 405 catalyst for spontaneous decomposition of hydrazine was one of the key enabling technologies for today's spacecraft and launch vehicles. To ensure that this crucial technology was not lost when Shell elected to exit the business, Aerojet, supported by NASA, has developed a dedicated catalyst production facility that will supply catalyst for future spacecraft and launch vehicle requirements. We have undertaken a program to transfer catalyst production from Shell Chemical USA (Houston, TX) to Aerojet's Redmond, WA location. This technology transition was aided by Aerojet's 30 years of catalyst manufacturing experience and NASA diligence and support in sustaining essential technologies. The facility has produced and tested S-405 catalyst to existing Shell 405 specifications and standards. Our presentation will describe the technology transition effort including development of the manufacturing facility, capture of the manufacturing process, test equipment validation, initial batch build and final testing.

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.

1H MAS NMR (magic-angle spinning nuclear magnetic resonance) techniques for the quantitative determination of hydrogen types in solid catalysts and supports.

PubMed

Kennedy, Gordon J; Afeworki, Mobae; Calabro, David C; Chase, Clarence E; Smiley, Randolph J

2004-06-01

Distinct hydrogen species are present in important inorganic solids such as zeolites, silicoaluminophosphates (SAPOs), mesoporous materials, amorphous silicas, and aluminas. These H species include hydrogens associated with acidic sites such as Al(OH)Si, non-framework aluminum sites, silanols, and surface functionalities. Direct and quantitative methodology to identify, measure, and monitor these hydrogen species are key to monitoring catalyst activity, optimizing synthesis conditions, tracking post-synthesis structural modifications, and in the preparation of novel catalytic materials. Many workers have developed several techniques to address these issues, including 1H MAS NMR (magic-angle spinning nuclear magnetic resonance). 1H MAS NMR offers many potential advantages over other techniques, but care is needed in recognizing experimental limitations and developing sample handling and NMR methodology to obtain quantitatively reliable data. A simplified approach is described that permits vacuum dehydration of multiple samples simultaneously and directly in the MAS rotor without the need for epoxy, flame sealing, or extensive glovebox use. We have found that careful optimization of important NMR conditions, such as magnetic field homogeneity and magic angle setting are necessary to acquire quantitative, high-resolution spectra that accurately measure the concentrations of the different hydrogen species present. Details of this 1H MAS NMR methodology with representative applications to zeolites, SAPOs, M41S, and silicas as a function of synthesis conditions and post-synthesis treatments (i.e., steaming, thermal dehydroxylation, and functionalization) are presented.

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

Fundamentals of Hydrocarbon Upgrading to Liquid Fuels and Commodity Chemicals over Catalytic Metallic Nanoparticles

NASA Astrophysics Data System (ADS)

Chen, Tao

Promising new technologies for biomass conversion into fuels and chemical feedstocks rely on the production of bio-oils, which need to be upgraded in order to remove oxygen-containing hydrocarbons and water. A high oxygen concentration makes bio-oils acidic and corrosive, unstable during storage, and less energetically valuable per unit weight than petroleum-derived hydrocarbons. Although there are efficient processes for the production of bio-oils, there are no efficient technologies for their upgrading. Current technologies utilize traditional petroleum refining catalysts, which are not optimized for biomass processing. New upgrading technologies are, therefore, urgently needed for development of sustainable energy resources. Development of such new technologies, however, is severely hindered by a lack of fundamental understanding of how oxygen and oxygen-containing hydrocarbons derived from biomass interact with promising noble-metal catalysts. In this study, kinetic reaction measurements, catalyst characterization and quantum chemical calculations using density functional theory were combined for determining adsorption modes and reaction mechanisms of hydrocarbons in the presence of oxygen on surfaces of catalytic noble-metal nanoparticles. The results were used for developing improved catalyst formulations and optimization of reaction conditions. The addition of molybdenum to platinum catalysts was shown to improve catalytic activity, stability, and selectivity in hydrodeoxygenation of acetic acid, which served as a model biomass compound. The fundamental results that describe interactions of oxygen and hydrocarbons with noble-metal catalysts were extended to other reactions and fields of study: evaluation of the reaction mechanism for hydrogen peroxide decomposition, development of improved hydrogenation catalysts and determination of adsorption modes of a spectroscopic probe molecule.

Role of solid acid catalysts in bio diesel production.

PubMed

Shivayogimath, C B; Sunita, G; Manoj Kumar, B

2009-07-01

Biodiesel is gaining importance as an alternate source of attractive fuel because of depleting fossil fuel resources. It is produced by trans-esterification, in which oil or fat reacts with a monohydric alcohol in presence of a catalyst. In the present work, trans-esterification of sunflower oil with methanol is carried out by using zirconia supported isopoly and heteropoly tungstates (HPAs) as catalysts. Effects of reaction parameters, such as catalyst types and its concentration, molar ratio of sunflower oil to methanol, reaction temperature and time, have been optimized to get higher conversion of sunflower oil and the product distribution of fatty acid methyl esters (FAME) in the trans-esterfication reaction.

Performance comparison of protonic and sodium phosphomolybdovanadate polyoxoanion catholytes within a chemically regenerative redox cathode polymer electrolyte fuel cell

NASA Astrophysics Data System (ADS)

Ward, David B.; Gunn, Natasha L. O.; Uwigena, Nadine; Davies, Trevor J.

2018-01-01

The direct reduction of oxygen in conventional polymer electrolyte fuel cells (PEFCs) is seen by many researchers as a key challenge in PEFC development. Chemically regenerative redox cathode (CRRC) polymer electrolyte fuel cells offer an alternative approach via the indirect reduction of oxygen, improving durability and reducing cost. These systems substitute gaseous oxygen for a liquid catalyst that is reduced at the cathode then oxidised in a regeneration vessel via air bubbling. A key component of a CRRC system is the liquid catalyst or catholyte. To date, phosphomolybdovanadium polyoxometalates with empirical formula H3+nPVnMo12-nO40 have shown the most promise for CRRC PEFC systems. In this work, four catholyte formulations are studied and compared against each other. The catholytes vary in vanadium content, pH and counter ion, with empirical formulas H6PV3Mo9O40, H7PV4Mo8O40, Na3H3PV3Mo9O40 and Na4H3PV4Mo8O40. Thermodynamic properties, cell performance and regeneration rates are measured, generating new insights into how formulation chemistry affects the components of a CRRC system. The results include the best CRRC PEFC performance reported to date, with noticeable advantages over conventional PEFCs. The optimum catholyte formulation is then determined via steady state tests, the results of which will guide further optimization of the catholyte formulation.

Ultrasound assisted synthesis of iron doped TiO2 catalyst.

PubMed

Ambati, Rohini; Gogate, Parag R

2018-01-01

The present work deals with synthesis of Fe (III) doped TiO 2 catalyst using the ultrasound assisted approach and conventional sol-gel approach with an objective of establishing the process intensification benefits. Effect of operating parameters such as Fe doping, type of solvent, solvent to precursor ratio and initial temperature has been investigated to get the best catalyst with minimum particle size. Comparison of the catalysts obtained using the conventional and ultrasound assisted approach under the optimized conditions has been performed using the characterization techniques like DLS, XRD, BET, SEM, EDS, TEM, FTIR and UV-Vis band gap analysis. It was established that catalyst synthesized by ultrasound assisted approach under optimized conditions of 0.4mol% doping, irradiation time of 60min, propan-2-ol as the solvent with the solvent to precursor ratio as 10 and initial temperature of 30°C was the best one with minimum particle size as 99nm and surface area as 49.41m 2 /g. SEM analysis, XRD analysis as well as the TEM analysis also confirmed the superiority of the catalyst obtained using ultrasound assisted approach as compared to the conventional approach. EDS analysis also confirmed the presence of 4.05mol% of Fe element in the sample of 0.4mol% iron doped TiO 2 . UV-Vis band gap results showed the reduction in band gap from 3.2eV to 2.9eV. Photocatalytic experiments performed to check the activity also confirmed that ultrasonically synthesized Fe doped TiO 2 catalyst resulted in a higher degradation of Acid Blue 80 as 38% while the conventionally synthesized catalyst resulted in a degradation of 31.1%. Overall, the work has clearly established importance of ultrasound in giving better catalyst characteristics as well as activity for degradation of the Acid Blue 80 dye. Copyright © 2017 Elsevier B.V. All rights reserved.

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

New mechanistic insights regarding Pd/Cu catalysts for the Sonogashira reaction: HRMAS NMR studies of silica-immobilized systems.

PubMed

Posset, Tobias; Blümel, Janet

2006-07-05

The title technique, high-resolution magic angle spinning NMR of suspensions, constitutes a powerful new tool for investigating the structures and mobilities of immobilized species and, thus, for optimizing heterobimetallic catalyst systems, such as the Sonogashira coupling of terminal alkynes and aryl halides.

Optimization of Lactide synthesis from Lactic Acid in biorefinery of palm oil waste using Response Surface Methodology

NASA Astrophysics Data System (ADS)

Gozan, M.; Kamilah, F.; Whulanza, Y.; Rahmayetty

2018-03-01

Ring open polymerization is one of the production polylactic acid by formation of monomer before. Lactic acid is converted into lactide in two stages, polycondensation and depolymerization. Yield lactide will determine the molecular weight which produced. This study is to optimize the lactide production from lactic acid 90% by the variations of temperature (190-220°C), vacuum pressure (5-15 cmHg), and zinc acetate catalyst (0,3-0,6% w/w). As the temperature, vacuum pressure, and catalyst is increased, lactide that is produced also increases. Optimum condition of lactide production is obtained by Response surface methodology at the temperature 220°C, catalyst 0,45%w/w, and 10 cmHg in vacuum pressure. Equation or model from this study by using RSM is yield lactide = -258,75 + 7,79A + 2,90B + 3,51C + 0,48AB - 0,06AC – 3,97x10-3BC – 105,42A2 – 7,17B2– 0,10C2(A:catalyst; B:temperature; C:pressure).

Co-production of hydrogen and carbon nanotubes on nickel foam via methane catalytic decomposition

NASA Astrophysics Data System (ADS)

Ping, Dan; Wang, Chaoxian; Dong, Xinfa; Dong, Yingchao

2016-04-01

The co-production of COx-free hydrogen and carbon nanotubes (CNTs) was achieved on 3-dimensional (3D) macroporous nickel foam (NF) via methane catalytic decomposition (MCD) over nano-Ni catalysts using chemical vapor deposition (CVD) technique. By a simple coating of a NiO-Al2O3 binary mixture sol followed by a drying-calcination-reduction treatment, NF supported composite catalysts (denoted as NiyAlOx/NF) with Al2O3 transition-layer incorporated with well-dispersed nano-Ni catalysts were successfully prepared. The effects of Ni loading, calcination temperature and reaction temperature on the performance for simultaneous production of COx-free hydrogen and CNTs were investigated in detail. Catalysts before and after MCD were characterized by XRD, TPR, SEM, TEM, TG and Raman spectroscopy technology. Results show that increasing Ni loading, lowering calcination temperature and optimizing MCD reaction temperature resulted in high production efficiency of COx-free H2 and carbon, but broader diameter distribution of CNTs. Through detailed parameter optimization, the catalyst with a Ni/Al molar ratio of 0.1, calcination temperature of 550 °C and MCD temperature of 650 °C was favorable to simultaneously produce COx-free hydrogen with a growth rate as high as 10.3% and CNTs with uniform size on NF.

The utilization of leftover as acid catalyst to catalyse the transesterification and esterification reactions

NASA Astrophysics Data System (ADS)

Leung, K. K.; Yau, Y. H.

2017-08-01

Biodiesel (Fatty Acid Methyl Ester, FAME) is a green and renewable energy. It is carbon neutral and produces less air pollutants in combustion. In my project, the selected feedstock of biodiesel production is grease trap oil (GTO). It is extracted from restaurants, and needs pre-treatment. The triglycerides and free fatty acid (FFA) are the main components of GTO. Both triglycerides and free fatty acid can be converted to biodiesel (Fatty Acid Methyl Ester) by transesterification and esterification, through reaction with alcohol (methanol) and catalyst. In the processes, acidic catalyst is chosen to speed up the reactions. The catalyst used In the study, a heterogeneous solid acid is applied. It is waste cooked rice (WCR) collected from leftover. The WCR powder is pyrolysed in 400°C furnace 15 hours and blown with nitrogen gas (incomplete carbonization). The WCR black powder is then mixed with concentrated sulphuric acid and heat in 160°C furnace 15 hours and continuous blown with nitrogen gas (sulphonation). This heterogeneous solid acid is used in the both transesterification and esterification to produce FAME. Moreover, in the optimal reaction conditions, this catalyst offers a stable catalytic effect. After 20 times usage in optimal reaction condition, the catalytic activity remains unchanged.

Synthesis of Platinum-nickel Nanowires and Optimization for Oxygen Reduction Performance.

PubMed

Alia, Shaun M; Pivovar, Bryan S

2018-04-27

Platinum-nickel (Pt-Ni) nanowires were developed as fuel cell electrocatalysts, and were optimized for the performance and durability in the oxygen reduction reaction. Spontaneous galvanic displacement was used to deposit Pt layers onto Ni nanowire substrates. The synthesis approach produced catalysts with high specific activities and high Pt surface areas. Hydrogen annealing improved Pt and Ni mixing and specific activity. Acid leaching was used to preferentially remove Ni near the nanowire surface, and oxygen annealing was used to stabilize near-surface Ni, improving durability and minimizing Ni dissolution. These protocols detail the optimization of each post-synthesis processing step, including hydrogen annealing to 250 °C, exposure to 0.1 M nitric acid, and oxygen annealing to 175 °C. Through these steps, Pt-Ni nanowires produced increased activities more than an order of magnitude than Pt nanoparticles, while offering significant durability improvements. The presented protocols are based on Pt-Ni systems in the development of fuel cell catalysts. These techniques have also been used for a variety of metal combinations, and can be applied to develop catalysts for a number of electrochemical processes.

Direct synthesis of ethanol from dimethyl ether and syngas over combined H-Mordenite and Cu/ZnO catalysts.

PubMed

Li, Xingang; San, Xiaoguang; Zhang, Yi; Ichii, Takashi; Meng, Ming; Tan, Yisheng; Tsubaki, Noritatsu

2010-10-25

Ethanol was directly synthesized from dimethyl ether (DME) and syngas with the combined H-Mordenite and Cu/ZnO catalysts that were separately loaded in a dual-catalyst bed reactor. Methyl acetate (MA) was formed by DME carbonylation over the H-Mordenite catalyst. Thereafter, ethanol and methanol were produced by MA hydrogenation over the Cu/ZnO catalyst. With the reactant gas containing 1.0% DME, the optimized temperature for the reaction was at 493 K to reach 100% conversion. In the products, the yield of methanol and ethanol could reach 46.3% and 42.2%, respectively, with a small amount of MA, ethyl acetate, and CO(2). This process is environmentally friendly as the main byproduct methanol can be recycled to DME by a dehydration reaction. In contrast, for the physically mixed catalysts, the low conversion of DME and high selectivity of methanol were observed.

Subeutectic Synthesis of Epitaxial Si-NWs with Diverse Catalysts Using a Novel Si Precursor

PubMed Central

2010-01-01

The applicability of a novel silicon precursor with respect to reasonable nanowire (NW) growth rates, feasibility of epitaxial NW growth and versatility with respect to diverse catalysts was investigated. Epitaxial growth of Si-NWs was achieved using octochlorotrisilane (OCTS) as Si precursor and Au as catalyst. In contrast to the synthesis approach with SiCl4 as precursor, OCTS provides Si without the addition of H2. By optimizing the growth conditions, effective NW synthesis is shown for alternative catalysts, in particular, Cu, Ag, Ni, and Pt with the latter two being compatible to complementary metal-oxide-semiconductor technology. As for these catalysts, the growth temperatures are lower than the lowest liquid eutectic; we suggest that the catalyst particle is in the solid state during NW growth and that a solid-phase diffusion process, either in the bulk, on the surface, or both, must be responsible for NW nucleation. PMID:20843058

Boron and oxygen-codoped porous carbon as efficient oxygen reduction catalysts

NASA Astrophysics Data System (ADS)

Lei, Zhidan; Chen, Hongbiao; Yang, Mei; Yang, Duanguang; Li, Huaming

2017-12-01

A low-cost boron- and oxygen-codoped porous carbon electrocatalyst towards oxygen reduction reaction (ORR) has been fabricated by a facile one-step pyrolysis approach, while a boron- and oxygen-rich polymer network was used as precursor. The boron- and oxygen-codoped carbon catalyst with high ORR electrocatalytic activity is comparable to that of Pt/C and is superior to that of catalysts doped solely with boron atoms or with oxygen atoms. Furthermore, the optimized boron- and oxygen-codoped carbon catalyst possesses excellent methanol tolerance and long-term durability in alkaline media. The high electrocatalytic activity of the dual-doped carbon catalysts can be attributed to the synergistic effects of high surface area, predominant mesostructure, abundant active oxygen-containing groups, and effective boron doping. The present results show that this boron- and oxygen-codoping strategy could be as a promising way for the preparation of highly efficient ORR catalysts.

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

Studies of long-life pulsed CO2 laser with Pt/SnO2 catalyst

NASA Technical Reports Server (NTRS)

Sidney, Barry D.

1987-01-01

Closed-cycle CO2 laser testing with and without a catalyst and with and without CO addition indicate that a catalyst is necessary for long-term operation. Initial results indicate that CO addition with a catalyst may prove optimal, but a precise gas mix has not yet been determined. A long-term run of 10 to the 6th power pulses using 1.3% added CO and a 2% Pt on SnO2 catalyst yields an efficiency of about 95% of open-cycle steady-state power. A simple mathematical analysis yields results which may be sufficient for determining optimum running conditions. Future plans call for testing various catalysts in the laser and longer tests, 10 to the 7th power pulses. A Gas Chromatograph will be installed to measure gas species concentration and the analysis will be slightly modified to include neglected but possibly important parameters.

Aromatics and phenols from catalytic pyrolysis of Douglas fir pellets in microwave with ZSM-5 as a catalyst

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

Wang, Lu; Lei, Hanwu; Ren, Shoujie

Microwave assisted catalytic pyrolysis was investigated to convert Douglas fir pellets to bio-oils by a ZSM-5 Zeolite catalyst. A central composite experimental design (CCD) was used to optimize the catalytic pyrolysis process. The effects of reaction time, temperature and catalyst to biomass ratio on the bio-oil, syngas, and biochar yields were determined. GC/MS analysis results showed that the bio-oil contained a series of important and useful chemical compounds. Phenols, guaiacols, and aromatic hydrocarbons were the most abundant compounds which were about 50-82 % in bio-oil depending on the pyrolysis conditions. Comparison between the bio-oils from microwave pyrolysis with and withoutmore » catalyst showed that the catalyst increased the content of aromatic hydrocarbons and phenols. A reaction pathway was proposed for microwave assisted catalyst pyrolysis of Douglas fir pellets.« less

Catalyst-induced growth of carbon nanotubes on tips of cantilevers and nanowires

DOEpatents

Lee, James Weifu; Lowndes, Douglas H.; Merkulov, Vladimir I.; Eres, Gyula; Wei, Yayi; Greenbaum, Elias; Lee, Ida

2004-06-29

A method is described for catalyst-induced growth of carbon nanotubes, nanofibers, and other nanostructures on the tips of nanowires, cantilevers, conductive micro/nanometer structures, wafers and the like. The method can be used for production of carbon nanotube-anchored cantilevers that can significantly improve the performance of scaning probe microscopy (AFM, EFM etc). The invention can also be used in many other processes of micro and/or nanofabrication with carbon nanotubes/fibers. Key elements of this invention include: (1) Proper selection of a metal catalyst and programmable pulsed electrolytic deposition of the desired specific catalyst precisely at the tip of a substrate, (2) Catalyst-induced growth of carbon nanotubes/fibers at the catalyst-deposited tips, (3) Control of carbon nanotube/fiber growth pattern by manipulation of tip shape and growth conditions, and (4) Automation for mass production.

Oxidation of methane over palladium catalysts: effect of the support.

PubMed

Escandón, Lara S; Ordóñez, Salvador; Vega, Aurelio; Díez, Fernando V

2005-01-01

This work is focused on the deep catalytic oxidation of methane over supported palladium catalysts. The influences of the metal loading, oxidation state of palladium, nature of supports, presence of promoters in the supports (for zirconia-based supports), and thermal stability have been studied experimentally. Catalysts were prepared by incipient wetness of commercially available supports with aqueous solutions of palladium nitrate. For gamma-alumina support, it was observed that the optimal amount of palladium is between 0.5% and 2%, with higher amounts leading to a loss in specific activity. Concerning the oxidation state of the catalyst, it is concluded that for all the supports tested in the present work, a reduction of the catalyst is not needed, yielding the same conversion at steady state catalysts reduced and oxidised. The thermal stability of various supported catalysts were also studied, zirconia supports being the most active. These supports, specially Y-modified zirconia support, do not suffer appreciable deactivation below 500 degrees C.

Visible-light photo-Fenton oxidation of phenol with rGO-α-FeOOH supported on Al-doped mesoporous silica (MCM-41) at neutral pH: Performance and optimization of the catalyst.

PubMed

Wang, Ying; Liang, Mingxing; Fang, Jiasheng; Fu, Jun; Chen, Xiaochun

2017-09-01

In this study, α-FeOOH on reduced graphene oxide (rGO-α-FeOOH) supported on an Al-doped MCM-41 catalyst (RFAM) was optimized for the visible-light photo-Fenton oxidation of phenol at neutral pH. The stability of the catalysts, effect of bubbling aeration, and degradation intermediates were investigated. Results indicated that RFAM with a large Brunauer-Emmett-Teller (BET) area and mesoporous structure displayed excellent catalytic activity for the visible-light-driven (VLD) photo-Fenton process. Phenol degradation was well described by a pseudo-first-order reaction kinetics model. Raman analysis demonstrated that an rGO-α-FeOOH (RF) composite is formed during the ferrous-ion-induced self-assembly process. Al-MCM-41 could uniformly disperse RF nanosheets and promote the mobility and diffusion of matter. The activity of the main catalyst α-FeOOH was enhanced after the incorporation of rGO nanosheets. The α-FeOOH crystal in RFAM showed catalytic activity superior to those of Fe 3 O 4 and Fe 2 O 3 . The RFAM catalyst, with an optimal GO-Fe 2+ mass ratio of 2.33, exhibited a larger BET area, pore size, and pore volume, and thus exhibited high performance and energy utilization efficiency in the VLD photo-Fenton reaction with remarkable stability. Bubbling N 2 inhibited catalytic performance, while bubbling O 2 or air only slightly accelerated the phenol degradation. Visible light played an important role in accelerating the formation of reactive oxygen species (·OH) for the highly efficient phenol degradation. Analysis of degradation intermediates indicated a high phenol mineralization level and the formation of low-molecular-weight organic acids. This work would be helpful in providing an insight into a new type of catalyst assembly and a possible route to a promising heterogeneous catalyst applicable in the visible light photo-Fenton process for effective wastewater remediation at neutral pH. Copyright © 2017. Published by Elsevier Ltd.

Polymer-Supported Raney Nickel Catalysts for Sustainable Reduction Reactions.

PubMed

Jiang, Haibin; Lu, Shuliang; Zhang, Xiaohong; Dai, Wei; Qiao, Jinliang

2016-06-25

Green is the future of chemistry. Catalysts with high selectivity are the key to green chemistry. Polymer-supported Raney catalysts have been found to have outstanding performance in the clean preparation of some chemicals. For example, a polyamide 6-supported Raney nickel catalyst provided a 100.0% conversion of n-butyraldehyde without producing any detectable n-butyl ether, the main byproduct in industry, and eliminated the two main byproducts (isopropyl ether and methyl-iso-butylcarbinol) in the hydrogenation of acetone to isopropanol. Meanwhile, a model for how the polymer support brought about the elimination of byproducts is proposed and confirmed. In this account the preparation and applications of polymer-supported Raney catalysts along with the corresponding models will be reviewed.

Study of catalysis for solid oxide fuel cells and direct methanol fuel cells

NASA Astrophysics Data System (ADS)

Jiang, Xirong

Fuel cells offer the enticing promise of cleaner electricity with lower environmental impact than traditional energy conversion technologies. Driven by the interest in power sources for portable electronics, and distributed generation and automotive propulsion markets, active development efforts in the technologies of both solid oxide fuel cell (SOFC) and direct methanol fuel cell (DMFC) devices have achieved significant progress. However, current catalysts for fuel cells are either of low catalytic activity or extremely expensive, presenting a key barrier toward the widespread commercialization of fuel cell devices. In this thesis work, atomic layer deposition (ALD), a novel thin film deposition technique, was employed to apply catalytic Pt to SOFC, and investigate both Pt skin catalysts and Pt-Ru catalysts for methanol oxidation, a very important reaction for DMFC, to increase the activity and utilization levels of the catalysts while simultaneously reducing the catalyst loading. For SOFCs, we explored the use of ALD for the fabrication of electrode components, including an ultra-thin Pt film for use as the electrocatalyst, and a Pt mesh structure for a current collector for SOFCs, aiming for precise control over the catalyst loading and catalyst geometry, and enhancement in the current collect efficiency. We choose Pt since it has high chemical stability and excellent catalytic activity for the O2 reduction reaction and the H2 oxidation reaction even at low operating temperatures. Working SOFC fuel cells were fabricated with ALD-deposited Pt thin films as an electrode/catalyst layer. The measured fuel cell performance reveals that comparable peak power densities were achieved for ALD-deposited Pt anodes with only one-fifth of the Pt loading relative to a DC-sputtered counterpart. In addition to the continuous electrocatalyst layer, a micro-patterned Pt structure was developed via the technique of area selective ALD. By coating yttria-stabilized zirconia, a typical solid oxide electrolyte, with patterned (octadecyltrichlorosilane) ODTS self-assembled monolayers (SAMs), Pt thin films were grown selectively on the SAM-free surface regions. Features with sizes as small as 2 mum were deposited by this combined ALD-muCP method. The micro-patterned Pt structure deposited by area selective ALD was applied to SOFCs as a current collector grid/patterned catalyst. An improvement in the fuel cell performance by a factor of 10 was observed using the Pt current collector grids/patterned catalyst integrated onto cathodic La0.6Sr 0.4Co0.2Fe0.8O3-delta. For possible catalytic anodes in DMFCs employing a 1:1 stoichiometric methanol-water reforming mixture, two strategies were employed in this thesis. One approach is to fabricate skin catalysts, where ALD Pt films of various thicknesses were used to coat sputtered Ru films forming Pt skin catalysts for study of methanol oxidation. Another strategy is to replace or alloy Pt with Ru; for this effort, both dc-sputtering and atomic layer deposition were employed to fabricate Pt-Ru catalysts of various Ru contents. The electrochemical behavior of all of the Pt skin catalysts, the DC co-sputtered Pt-Ru catalysts and the ALD co-deposited Pt-Ru catalysts were evaluated at room temperature for methanol oxidation using cyclic voltammetry and chronoamperometry in highly concentrated 16.6 M MeOH, which corresponds to the stoichiometric fuel that will be employed in next generation DMFCs that are designed to minimize or eliminate methanol crossover. The catalytic activity of sputtered Ru catalysts toward methanol oxidation is strongly enhanced by the ALD Pt overlayer, with such skin layer catalysts displaying superior catalytic activity over pure Pt. For both the DC co-sputtered catalysts and ALD co-deposited catalysts, the electrochemical studies illustrate that the optimal stoichiometry ratio for Pt to Ru is approximately 1:1, which is in good agreement with most literature.

Degradation of cationic red GTL by catalytic wet air oxidation over Mo-Zn-Al-O catalyst under room temperature and atmospheric pressure.

PubMed

Xu, Yin; Li, Xiaoyi; Cheng, Xiang; Sun, Dezhi; Wang, Xueye

2012-03-06

To overcome the drawback of catalytic wet air oxidation (CWAO) with high temperature and high pressure, the catalytic activity of Mo-Zn-Al-O catalyst for degradation of cationic red GTL under room temperature and atmospheric pressure was investigated. Mo-Zn-Al-O catalyst was prepared by coprecipitation and impregnation. XRD, TG-DTG, and XPS were used to characterize the resulting sample. Central composition design using response surface methodology was employed to optimize correlation of factors on the decolorization of cationic red GTL. The results show that the optimal conditions of pH value, initial concentration of dye and catalyst dosage were found to be 4.0, 85 mg/L and 2.72 g/L, respectively, for maximum decolorization of 80.1% and TOC removal of 50.9%. Furthermore, the reaction on the Mo-Zn-Al-O catalyst and degradation mechanism of cationic red GTL was studied by Electron spin resonance (ESR) and GC-MS technique. The possible reaction mechanism was that the Mo-Zn-Al-O catalyst can efficiently react with adsorbed oxygen/H(2)O to produce ·OH and (1)O(2) and finally induce the degradation of cationic red GTL. GC-MS analysis of the degradation products indicates that cationic red GTL was initiated by the cleavage of -N ═ N- and the intermediates were further oxidized by ·OH or (1)O(2).

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

Co3O4/MnO2/Hierarchically Porous Carbon as Superior Bifunctional Electrodes for Liquid and All-Solid-State Rechargeable Zinc-Air Batteries.

PubMed

Li, Xuemei; Dong, Fang; Xu, Nengneng; Zhang, Tao; Li, Kaixi; Qiao, Jinli

2018-05-09

The design of efficient, durable, and affordable catalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is very indispensable in liquid-type and flexible all-solid-state zinc-air batteries. Herein, we present a high-performance bifunctional catalyst with cobalt and manganese oxides supported on porous carbon (Co 3 O 4 /MnO 2 /PQ-7). The optimized Co 3 O 4 /MnO 2 /PQ-7 exhibited a comparable ORR performance with commercial Pt/C and a more superior OER performance than all of the other prepared catalysts, including commercial Pt/C. When applied to practical aqueous (6.0 M KOH) zinc-air batteries, the Co 3 O 4 /MnO 2 /porous carbon hybrid catalysts exhibited exceptional performance, such as a maximum discharge peak power density as high as 257 mW cm -2 and the most stable charge-discharge durability over 50 h with negligible deactivation to date. More importantly, a series of flexible all-solid-state zinc-air batteries can be fabricated by the Co 3 O 4 /MnO 2 /porous carbon with a layer-by-layer method. The optimal catalyst (Co 3 O 4 /MnO 2 /PQ-7) exhibited an excellent peak power density of 45 mW cm -2 . The discharge potentials almost remained unchanged for 6 h at 5 mA cm -2 and possessed a long cycle life (2.5 h@5 mA cm -2 ). These results make the optimized Co 3 O 4 /MnO 2 /PQ-7 a promising cathode candidate for both liquid-type and flexible all-solid-state zinc-air batteries.

First Novozym 435 lipase-catalyzed Morita-Baylis-Hillman reaction in the presence of amides.

PubMed

Tian, Xuemei; Zhang, Suoqin; Zheng, Liangyu

2016-03-01

The first Novozym 435 lipase-catalyzed Morita-Baylis-Hillman (MBH) reaction with amides as co-catalyst was realized. Results showed that neither Novozym 435 nor amide can independently catalyze the reaction. This co-catalytic system that used a catalytic amount of Novozym 435 with a corresponding amount of amide was established and optimized. The MBH reaction strongly depended on the structure of aldehyde substrate, amide co-catalyst, and reaction additives. The optimized reaction yield (43.4%) was achieved in the Novozym 435-catalyzed MBH reaction of 2, 4-dinitrobenzaldehyde and cyclohexenone with isonicotinamide as co-catalyst and β-cyclodextrin as additive only in 2 days. Although enantioselectivity of Novozym 435 was not found, the results were still significant because an MBH reaction using lipase as biocatalyst was realized for the first time. Copyright © 2015 Elsevier Inc. All rights reserved.

Heptanuclear CoII5CoIII2 Cluster as Efficient Water Oxidation Catalyst.

PubMed

Xu, Jia-Heng; Guo, Ling-Yu; Su, Hai-Feng; Gao, Xiang; Wu, Xiao-Fan; Wang, Wen-Guang; Tung, Chen-Ho; Sun, Di

2017-02-06

Inspired by the transition-metal-oxo cubical Mn 4 CaO 5 in photosystem II, we herein report a disc-like heptanuclear mixed-valent cobalt cluster, [Co II 5 Co III 2 (mdea) 4 (N 3 ) 2 (CH 3 CN) 6 (OH) 2 (H 2 O) 2 ·4ClO 4 ] (1, H 2 mdea = N-methyldiethanolamine), for photocatalytic oxygen evolution. The topology of the Co 7 core resembles a small piece of cobaltate protected by terminal H 2 O, N 3 - , CH 3 CN, and multidentate N-methyldiethanolamine at the periphery. Under the optimal photocatalytic conditions, 1 exhibits water oxidation activity with a turnover number (TON) of 210 and a turnover frequency (TOF initial ) of 0.23 s -1 . Importantly, electrospray mass spectrometry (ESI-MS) was used to not only identify the possible main active species in the water oxidation reaction but also monitor the evolutions of oxidation states of cobalt during the photocatalytic reactions. These results shed light on the design concept of new water oxidation catalysts and mechanism-related issues such as the key active intermediate and oxidation state evolution in the oxygen evolution process. The magnetic properties of 1 were also discussed in detail.

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

NONE

The objective of Task I is to prepare and evaluate catalysts and to develop efficient reactor systems for the selective conversion of hydrogen-lean synthesis gas to alcohol fuel extenders and octane enhancers. In Task 1, during this reporting period, we encountered and solved a problem in the analysis of the reaction products containing a small amount of heavy components. Subsequently, we continued with the major thrusts of the program. We analyzed the results from our preliminary studies on the packed-bed membrane reactor using the BASF methanol synthesis catalyst. We developed a quantitative model to describe the performance of the reactor.more » The effect of varying permeances and the effect of catalyst aging are being incorporated into the model. Secondly, we resumed our more- detailed parametric studies on selected non-sulfide Mo-based catalysts. Finally, we continue with the analysis of data from the kinetic study of a sulfided carbon-supported potassium-doped molybdenum-cobalt catalyst in the Rotoberty reactor. We have completed catalyst screening at UCC. The complete characterization of selected catalysts has been started. In Task 2, the fuel blends of alcohol and unleaded test gas 96 (UTG 96) have been made and tests have been completed. The testing includes knock resistance tests and emissions tests. Emissions tests were conducted when the engine was optimized for the particular blend being tested (i.e. where the engine produced the most power when running on the blend in question). The data shows that the presence of alcohol in the fuel increases the fuel`s ability to resist knock. Because of this, when the engine was optimized for use with alcohol blends, the engine produced more power and lower emission rates.« less

Ir catalysts: Preventing CH3COOH formation in ethanol oxidation

NASA Astrophysics Data System (ADS)

Miao, Bei; Wu, Zhipeng; Xu, Han; Zhang, Minhua; Chen, Yifei; Wang, Lichang

2017-11-01

Current catalysts used for ethanol oxidation reaction (EOR) cannot effectively prevent CH3COOH formation, and thus become a major hindrance for direct ethanol fuel cell applications. We report an Ir catalyst that shows great promise for a complete EOR based on density functional theory calculations using PBE functional. The reaction barrier on Ir(1 0 0) was found to be 2.10 eV for CH3COOH formation, which is much higher than currently used Pd and Pt, and 0.57 eV for Csbnd C bond cleavage in CHCO species, which are comparable to Pd and Pt. The result suggests future directions for studying optimal complete EOR catalysts.

Evaluation of the Optimum Composition of Low-Temperature Fuel Cell Electrocatalysts for Methanol Oxidation by Combinatorial Screening.

PubMed

Antolini, Ermete

2017-02-13

Combinatorial chemistry and high-throughput screening represent an innovative and rapid tool to prepare and evaluate a large number of new materials, saving time and expense for research and development. Considering that the activity and selectivity of catalysts depend on complex kinetic phenomena, making their development largely empirical in practice, they are prime candidates for combinatorial discovery and optimization. This review presents an overview of recent results of combinatorial screening of low-temperature fuel cell electrocatalysts for methanol oxidation. Optimum catalyst compositions obtained by combinatorial screening were compared with those of bulk catalysts, and the effect of the library geometry on the screening of catalyst composition is highlighted.

Optimizing Metalloporphyrin-Catalyzed Reduction Reactions for In Situ Remediation of DOE Contaminants

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

Schlautman, Mark A.

2013-07-14

Past activities have resulted in a legacy of contaminated soil and groundwater at Department of Energy facilities nationwide. Uranium and chromium are among the most frequently encountered and highest-priority metal and radionuclide contaminants at DOE installations. Abiotic chemical reduction of uranium and chromium at contaminated DOE sites can be beneficial because the reduced metal species are less soluble in water, less mobile in the environment, and less toxic to humans and ecosystems. Although direct biological reduction has been reported for U(VI) and Cr(VI) in laboratory studies and at some field sites, the reactions can sometimes be slow or even inhibitedmore » due to unfavorable environmental conditions. One promising approach for the in-situ remediation of DOE contaminants is to develop electron shuttle catalysts that can be delivered precisely to the specific subsurface locations where contaminants reside. Previous research has shown that reduction of oxidized organic and inorganic contaminants often can be catalyzed by electron shuttle systems. Metalloporphyrins and their derivatives are well known electron shuttles for many biogeochemical systems, and thus were selected to study their catalytic capabilities for the reduction of chromium and uranium in the presence of reducing agents. Zero valent iron (ZVI) was chosen as the primary electron donor in most experimental systems. Research proceeded in three phases and the key findings of each phase are reported here. Phase I examined Cr(VI) reduction and utilized micro- and nano-sized ZVI as the electron donors. Electron shuttle catalysts tested were cobalt- and iron-containing metalloporphyrins and Vitamin B12. To aid in the recycle and reuse of the nano-sized ZVI and soluble catalysts, sol-gels and calcium-alginate gel beads were tested as immobilization/support matrices. Although the nano-sized ZVI could be incorporated within the alginate gel beads, preliminary attempts to trap it in sol-gels were not successful. Conversely, the water-soluble catalysts could be trapped within sol-gel matrices but they tended to leach out of the alginate gel beads during use. In general, immobilization of the nano-sized ZVI in gel beads and of the catalysts in sol-gels tended to result in slower rates of Cr(VI) reduction, but these effects could be overcome to some extent by using higher reactant/catalyst concentrations. In addition, the lowering of their effectiveness would likely be offset by the benefits obtained when recycling and reusing the materials because they were immobilized. Addition of the catalytic electron shuttles will be most useful when the micro-sized or nano-sized ZVI becomes less reactive with reaction time. Continued work in Phase II in the area of nano-sized ZVI immobilization led to procedures that were successful in incorporating the iron particles in sol-gel matrices. The water-soluble reductants sodium dithionite and L-ascorbic acid were also tested, but their use appeared to lead to formation of complexes with the uranyl cation which limited their effectiveness. Also, although the sol-gel supported nano-sized ZVI showed some promise at reducing uranium, the fluoride used in the sol-gel synthesis protocol appeared to lead to formation of uranyl-fluoride complexes that were less reactive. Because hexavalent chromium is an anion which does not form complexes with fluoride, it was used to demonstrate the intrinsic reactivity of the sol-gel immobilized nano-sized ZVI. Consistent with our observations in Phase I, the sol-gel matrix once again slowed down the reduction reaction but the expected benefits of recycle/reuse should outweigh this adverse effect. The major emphasis in Phase III of this study was to simultaneously incorporate nano-sized ZVI and water-soluble catalysts in the same sol-gel matrix. The catalysts utilized were cobalt complexes of uroporphyrin and protoporphyrin and Cr(VI) reduction was used to test the efficacy of the combined "catalyst + reductant" sol-gel matrix. When enough catalyst was added to the sol-gels, enhancement of the Cr(VI) reduction reaction was observed. At the lowest levels of catalyst addition, however, the rates of Cr(VI) reduction were similar to those systems which only used sol-gel immobilized nano-sized ZVI without any catalyst present. These findings suggest future areas of research that should be pursued to further optimize abiotic reduction reactions of metals with combined "catalyst + reductant" matrices.« less

Can a book of charts catalyze improvements in quality? Views of a healthcare alchemist.

PubMed

Watson, Diane E

2012-01-01

This commentary reviews international evidence about the impact of public reporting on better care and outcomes, outlines conditions under which publicly available performance information can become a potent catalyst to precipitate improvements in quality and the optimal conditions in healthcare systems to ensure that such a catalyst results in a desirable reaction.

Mentoring for Talent Development, Creativity, Social Skills, and Insider Knowledge: The APA Catalyst Program

ERIC Educational Resources Information Center

Subotnik, Rena F.; Edmiston, Ashley M.; Cook, Lucas; Ross, Michael D.

2010-01-01

The mentoring component of the American Psychological Association Catalyst Program, and the Pinnacle Model upon which it was built, was derived from Bloom's (1985) model of talent development. According to Bloom and his associates, optimal instruction for talent development takes place in three stages. During the first stage, young people are…

Metal-catalyst-free carbohydrazide fuel cells with three-dimensional graphene anodes.

PubMed

Qi, Ji; Benipal, Neeva; Wang, Hui; Chadderdon, David J; Jiang, Yibo; Wei, Wei; Hu, Yun Hang; Li, Wenzhen

2015-04-13

As a potential solution to concerns on sustainable energy, the wide spread commercialization of fuel cell has long been hindered by limited reserves and relatively high costs of metal catalysts. 3D graphene, a carbon-only catalyst prepared by reduction of carbon monoxide with lithium oxide, is found to electrochemically catalyze carbohydrazide oxidation reaction efficiently. A prototype of a completely metal-catalyst-free anion exchange membrane fuel cell (AEMFC) with a 3D graphene anode catalyst and an N-doped CNT (N-CNT) cathode catalyst generate a peak power density of 24.9 mW cm(-2) . The average number of electrons electrochemically extracted from one carbohydrazide molecule is 4.9, indicating the existence of CN bond activation, which is a key factor contributing to high fuel utilization efficiency. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effect of Electric Discharge on Properties of Nano-Particulate Catalyst for Plasma-Catalysis.

PubMed

Lee, Chung Jun; Kim, Jip; Kim, Taegyu

2016-02-01

Heterogeneous catalytic processes have been used to produce hydrogen from hydrocarbons. However, high reforming temperature caused serious catalyst deteriorations and low energy efficiency. Recently, a plasma-catalyst hybrid process was used to reduce the reforming temperature and to improve the stability and durability of reforming catalysts. Effect of electric discharges on properties of nanoparticulate catalysts for plasma-catalysis was investigated in the present study. Catalyst-bed porosity was varied by packing catalyst beads with the different size in a reactor. Discharge power and onset voltage of the plasma were measured as the catalyst-bed porosity was varied. The effect of discharge voltage, frequency and voltage waveforms such as the sine, pulse and square was investigated. We found that the optimal porosity of the catalyst-bed exists to maximize the electric discharge. At a low porosity, the electric discharge was unstable to be sustained because the space between catalysts got narrow nearly close to the sheath region. On the other hand, at a high porosity, the electric discharge became weak because the plasma was not sufficient to interact with the surface of catalysts. The discharge power increased as the discharge voltage and frequency increased. The square waveform was more efficient than the sine and pulse one. At a high porosity, however, the effect of the voltage waveform was not considerable because the space between catalysts was too large for plasma to interact with the surface of catalysts.

Advancing Fenton and photo-Fenton water treatment through the catalyst design.

PubMed

Vorontsov, Alexander V

2018-04-20

The review is devoted to modern Fenton, photo-Fenton, as well as Fenton-like and photo-Fenton-like reactions with participation of iron species in liquid phase and as heterogeneous catalysts. Mechanisms of these reactions were considered that include hydroxyl radical and oxoferryl species as the reactive intermediates. The barriers in the way of application of these reactions to wastewater treatment were discussed. The following fundamental problems need further research efforts: inclusion of more mechanism steps and quantum calculations of all rate constants lacking in the literature, checking the outer sphere electron transfer contribution, determination of the causes for the key changes in the homogeneous Fenton reaction mechanism with a change in the reagents concentration. The key advances for Fenton reactions implementation for the water treatment are related to tremendous hydrodynamical effects on the catalytic activity, design of ligands for high rate and completeness of mineralization in short time, and design of highly active heterogeneous catalysts. While both homogeneous and heterogeneous Fenton and photo-Fenton systems are open for further improvements, heterogeneous photo-Fenton systems are most promising for practical applications because of the inherent higher catalyst stability. Modern methods of quantum chemistry are expected to play a continuously increasing role in development of such catalysts. Copyright © 2018 Elsevier B.V. All rights reserved.

Investigating Catalyst–Support Interactions To Improve the Hydrogen Evolution Reaction Activity of Thiomolybdate [Mo 3 S 13 ] 2– Nanoclusters

DOE PAGES

Hellstern, Thomas R.; Kibsgaard, Jakob; Tsai, Charlie; ...

2017-09-22

Molybdenum sulfides have been identified as promising materials for catalyzing the hydrogen evolution reaction (HER) in acid, with active edge sites that exhibit some of the highest turnover frequencies among nonpreciousmetal catalysts. The thiomolybdate [Mo 3S 13] 2- nanocluster catalyst contains a structural motif that resembles the active site of MoS 2 and has been reported to be among the most active forms of molybdenum sulfide. Herein, we improve the activity of the [Mo 3S 13] 2- catalysts through catalyst-support interactions. We synthesize [Mo 3S 13] 2- on gold, silver, glassy carbon, and copper supports to demonstrate the ability tomore » tune the hydrogen binding energy of [Mo 3S 13] 2- using catalyst-support electronic interactions and optimize HER activity.« less

Investigating Catalyst–Support Interactions To Improve the Hydrogen Evolution Reaction Activity of Thiomolybdate [Mo 3 S 13 ] 2– Nanoclusters

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

Hellstern, Thomas R.; Kibsgaard, Jakob; Tsai, Charlie

Molybdenum sulfides have been identified as promising materials for catalyzing the hydrogen evolution reaction (HER) in acid, with active edge sites that exhibit some of the highest turnover frequencies among nonpreciousmetal catalysts. The thiomolybdate [Mo 3S 13] 2- nanocluster catalyst contains a structural motif that resembles the active site of MoS 2 and has been reported to be among the most active forms of molybdenum sulfide. Herein, we improve the activity of the [Mo 3S 13] 2- catalysts through catalyst-support interactions. We synthesize [Mo 3S 13] 2- on gold, silver, glassy carbon, and copper supports to demonstrate the ability tomore » tune the hydrogen binding energy of [Mo 3S 13] 2- using catalyst-support electronic interactions and optimize HER activity.« less

Application of solid-acid catalyst and marine macro-algae Gracilaria verrucosa to production of fermentable sugars.

PubMed

Jeong, Gwi-Taek; Kim, Sung-Koo; Park, Don-Hee

2015-04-01

In this study, the hydrolysis of marine macro-algae Gracilaria verrucosa with a solid-acid catalyst was investigated. To optimize the hydrolysis, four reaction factors, including liquid-to-solid ratio, catalyst loading, reaction temperature, and reaction time, were investigated. In the results, the highest total reducing sugar (TRS) yield, 61 g/L (51.9%), was obtained under the following conditions: 1:7.5 solid-to-liquid ratio, 15% (w/v) catalyst loading, 140 °C reaction temperature, and 150 min reaction time. Under these conditions, 10.7 g/L of 5-HMF and 2.5 g/L of levulinic acid (LA) were generated. The application of solid-acid catalyst and marine macro-algae resources shows a very high potential for production of fermentable sugars. Copyright © 2015 Elsevier Ltd. All rights reserved.

Process economics and safety considerations for the oxidative dehydrogenation of ethane using the M1 catalyst

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

Baroi, Chinmoy; Gaffney, Anne M.; Fushimi, Rebecca

Olefins or unsaturated hydrocarbons play a vital role as feedstock for many industrially significant processes. Ethylene is the simplest olefin and a key raw material for consumer products. Oxidative Dehydrogenation (ODH) is one of the most promising new routes for ethylene production that can offer a significant advantage in energy efficiency over the conventional steam pyrolysis process. This study is focused on the ODH chemistry using the mixed metal oxide MoVTeNbOx catalysts, generally referred to as M1 for the key phase known to be active for dehydrogenation. Using performance results from the patent literature a series of process simulations weremore » conducted to evaluate the effect of feed composition on operating costs, profitability and process safety. The key results of this study indicate that the ODH reaction can be made safer and more profitable without use of an inert diluent and furthermore by replacing O2 with CO2 as an oxidant. Modifications of the M1 catalyst composition in order to adopt these changes are discussed.« less

A palladium-doped ceria@carbon core-sheath nanowire network: a promising catalyst support for alcohol electrooxidation reactions

NASA Astrophysics Data System (ADS)

Tan, Qiang; Du, Chunyu; Sun, Yongrong; Du, Lei; Yin, Geping; Gao, Yunzhi

2015-08-01

A novel palladium-doped ceria and carbon core-sheath nanowire network (Pd-CeO2@C CSNWN) is synthesized by a template-free and surfactant-free solvothermal process, followed by high temperature carbonization. This hierarchical network serves as a new class of catalyst support to enhance the activity and durability of noble metal catalysts for alcohol oxidation reactions. Its supported Pd nanoparticles, Pd/(Pd-CeO2@C CSNWN), exhibit >9 fold increase in activity toward the ethanol oxidation over the state-of-the-art Pd/C catalyst, which is the highest among the reported Pd systems. Moreover, stability tests show a virtually unchanged activity after 1000 cycles. The high activity is mainly attributed to the superior oxygen-species releasing capability of Pd-doped CeO2 nanowires by accelerating the removal of the poisoning intermediate. The unique interconnected one-dimensional core-sheath structure is revealed to facilitate immobilization of the metal catalysts, leading to the improved durability. This core-sheath nanowire network opens up a new strategy for catalyst performance optimization for next-generation fuel cells.A novel palladium-doped ceria and carbon core-sheath nanowire network (Pd-CeO2@C CSNWN) is synthesized by a template-free and surfactant-free solvothermal process, followed by high temperature carbonization. This hierarchical network serves as a new class of catalyst support to enhance the activity and durability of noble metal catalysts for alcohol oxidation reactions. Its supported Pd nanoparticles, Pd/(Pd-CeO2@C CSNWN), exhibit >9 fold increase in activity toward the ethanol oxidation over the state-of-the-art Pd/C catalyst, which is the highest among the reported Pd systems. Moreover, stability tests show a virtually unchanged activity after 1000 cycles. The high activity is mainly attributed to the superior oxygen-species releasing capability of Pd-doped CeO2 nanowires by accelerating the removal of the poisoning intermediate. The unique interconnected one-dimensional core-sheath structure is revealed to facilitate immobilization of the metal catalysts, leading to the improved durability. This core-sheath nanowire network opens up a new strategy for catalyst performance optimization for next-generation fuel cells. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr03023d

Cobalt–iron nano catalysts supported on TiO{sub 2}–SiO{sub 2}: Characterization and catalytic performance in Fischer–Tropsch synthesis

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

Feyzi, Mostafa, E-mail: Dalahoo2011@yahoo.com; Yaghobi, Nakisa; Eslamimanesh, Vahid

2015-12-15

Graphical abstract: The Co–Fe/TiO{sub 2}–SiO{sub 2} catalysts were prepared. The prepared catalysts were tested for light olefins and C{sub 5}–C{sub 12} production. The best operational conditions are 250 °C, H{sub 2}/CO = 1/1 under 5 bar pressure. - Highlights: • The TiO{sub 2}–SiO{sub 2} supported cobalt–iron catalysts were prepared via sol–gel method. • The best operational conditions were 250 °C, GHSV = 2000 h{sup −1}, H{sub 2}/CO = 1/1 and 5 bar. • The (Co/Fe)/TiO{sub 2}–SiO{sub 2} is efficient catalyst for light olefins and C{sub 5}–C{sub 12} production. - Abstract: A series of Co–Fe catalysts supported on TiO{sub 2}–SiO{sub 2}more » were prepared by the sol–gel method. This research investigated the effects of (Co/Fe) wt.%, the solution pH, different Co/Fe molar ratio, calcination conditions and different promoters on the catalytic performance of cobalt–iron catalysts for the Fisher–Tropsch synthesis (FTS). It was found that the catalyst containing 35 wt.% (Co–Fe)/TiO{sub 2}–SiO{sub 2} (Co/Fe molar ratio is 80/20) promoted with 1.5 wt.% Cu and calcined in air atmosphere at 600 °C for 7 h with a heating rate of 3 °C min{sup −1} is an optimal nano catalyst for converting synthesis gas to light olefins and C{sub 5}–C{sub 12} hydrocarbons. The effects of operational conditions such as the H{sub 2}/CO ratio, gas hourly space velocity (GHSV), different reaction temperature, and reaction pressure were investigated. The results showed that the best operational conditions for optimal nano catalyst are 250 °C, GHSV = 2000 h{sup −1}, H{sub 2}/CO molar ratio 1/1 under 5 bar total pressure. Catalysts and precursors were characterized by, X-ray diffraction (XRD), scanning electron microcopy (SEM), thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC), temperature program reduction (TPR) and N{sub 2} adsorption–desorption measurements.« less

A systematic study on photocatalysis of antipyrine: Catalyst characterization, parameter optimization, reaction mechanism a toxicity evolution to plankton.

PubMed

Gong, Han; Chu, Wei; Chen, Meijuan; Wang, Qinxing

2017-04-01

The toxicity of antipyrine (AP) in the photodegradation using UV/CoFe 2 O 4 /TiO 2 was investigated by analyzing the characteristic of the catalyst, the effect of parameters (light source wavelength, catalyst dose, pH and initial AP concentration), the reaction mechanism (the organic intermediates, TOC reduction and inorganic ions release) and the newly proposed low-dosage-high-effective radical reaction approach. The catalyst shows the optimal removal efficiency under the conditions of wavelength at 350 nm, the catalyst dose at 0.5 g/L, and pH value at 5.5. Ten organic intermediates were identified, and five of them were newly reported in AP treatment process. Hydroxylation, demethylation and the cleavage of the pentacyclic ring were included in the decomposition pathways. The ring opening was certified by the 45% TOC reduction and 60% ammonia release during the process. The parent compound AP and its degradation products show positive effects on the growth of the algae. However, acute toxicity of AP was detected on brine shrimps Artemia salina. The toxicity was eliminated gradually with the decomposition of AP and the generation of the byproducts. The results indicate that the photocatalysis process is effective in AP removal, TOC reduction and toxicity elimination. Copyright © 2017 Elsevier Ltd. All rights reserved.

Evolution of Active Sites in Pt-Based Nanoalloy Catalysts for the Oxidation of Carbonaceous Species by Combined in Situ Infrared Spectroscopy and Total X-ray Scattering.

PubMed

Petkov, Valeri; Maswadeh, Yazan; Lu, Aolin; Shan, Shiyao; Kareem, Haval; Zhao, Yinguang; Luo, Jin; Zhong, Chuan-Jian; Beyer, Kevin; Chapman, Karena

2018-04-04

We present results from combined in situ infrared spectroscopy and total X-ray scattering studies on the evolution of catalytically active sites in exemplary binary and ternary Pt-based nanoalloys during a sequence of CO oxidation-reactivation-CO oxidation reactions. We find that when within a particular compositional range, the fresh nanoalloys may exhibit high catalytic activity for low-temperature CO oxidation. Using surface-specific atomic pair distribution functions (PDFs) extracted from the in situ total X-ray scattering data, we find that, regardless of their chemical composition and initial catalytic activity, the fresh nanoalloys suffer a significant surface structural disorder during CO oxidation. Upon reactivation in oxygen atmosphere, the surface of used nanoalloy catalysts both partially oxidizes and orders. Remarkably, it largely retains its structural state when the nanoalloys are reused as CO oxidation catalysts. The seemingly inverse structural changes of studied nanoalloy catalysts occurring under CO oxidation and reactivation conditions affect the active sites on their surface significantly. In particular, through different mechanisms, both appear to reduce the CO binding strength to the nanoalloy's surface and thus increase the catalytic stability of the nanoalloys. The findings provide clues for further optimization of nanoalloy catalysts for the oxidation of carbonaceous species through optimizing their composition, activation, and reactivation. Besides, the findings demonstrate the usefulness of combined in situ infrared spectroscopy and total X-ray scattering coupled to surface-specific atomic PDF analysis to the ongoing effort to produce advanced catalysts for environmentally and technologically important applications.

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

In situ TPR XANES study of the partial oxidation of methane using a Ni-substituted hexaaluminate catalyst

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

Kugler, E.L.; Gardner, T.H.; Campos, Andrew

2008-04-01

Metallic Ni formation near the mirror cation site, Ba in this study, is believed to cause the partial oxidation activity observed in Ni-substituted hexaaluminate catalysts. The BaNi1.0Al11.6O19-d catalyst was prepared by coprecipitation with nitrate salt precursors; following the coprecipitation procedure, the catalyst was calcined at 1400°C to create the hexaaluminate structure. TPR XANES in fluorescence was used to probe the local structure of the BaNi1.0Al11.6O19-d catalyst to determine whether metallic nickel forms at different temperatures: 825°C, 875°C, 925°C. The XANES results indicate that the Ni in the hexaaluminate catalyst only reduces if the temperature is maintained at 925°C. Once themore » metallic state is formed, the oxidation state is stable; even in the POX environment. Future work using a theoretical approach to the XANES data using FEFF 8.4 gives information on the interactions between Ni and Ba, which will be used to further optimize the catalyst.« less

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.

Microstructural observation of fuel cell catalyst inks by Cryo-SEM and Cryo-TEM.

PubMed

Shimanuki, Junichi; Takahashi, Shinichi; Tohma, Hajime; Ohma, Atsushi; Ishihara, Ayumi; Ito, Yoshiko; Nishino, Yuri; Miyazawa, Atsuo

2017-06-01

In order to improve the electricity generation performance of fuel cell electric vehicles, it is necessary to optimize the microstructure of the catalyst layer of a polymer electrolyte fuel cell. The catalyst layer is formed by a wet coating process using catalyst inks. Therefore, it is very important to observe the microstructure of the catalyst ink. In this study, the morphology of carbon-supported platinum (Pt/C) particles in catalyst inks with a different solvent composition was investigated by cryogenic scanning electron microscopy (cryo-SEM). In addition, the morphology of the ionomer, which presumably influences the formation of agglomerated Pt/C particles in a catalyst ink, was investigated by cryogenic transmission electron microscopy (cryo-TEM). The results of a cryo-SEM observation revealed that the agglomerated Pt/C particles tended to become coarser with a higher 1-propanol (NPA) weight fraction. The results of a cryo-TEM observation indicated that the actual ionomer dispersion in a catalyst ink formed a network structure different from that of the ionomer in the solvent. © The Author 2017. Published by Oxford University Press on behalf of The Japanese Society of Microscopy. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Selective Hydrodeoxygenation of 5-Hydroxymethylfurfural to 2,5-Dimethylfuran over Heterogeneous Iron Catalysts.

PubMed

Li, Jiang; Liu, Jun-Ling; Liu, He-Yang; Xu, Guang-Yue; Zhang, Jun-Jie; Liu, Jia-Xing; Zhou, Guang-Lin; Li, Qin; Xu, Zhi-Hao; Fu, Yao

2017-04-10

This work provided the first example of selective hydrodeoxygenation of 5-hydroxymethylfurfural (HMF) to 2,5-dimethylfuran (DMF) over heterogeneous Fe catalysts. A catalyst prepared by the pyrolysis of an Fe-phenanthroline complex on activated carbon at 800 °C was demonstrated to be the most active heterogeneous Fe catalyst. Under the optimal reaction conditions, complete conversion of HMF was achieved with 86.2 % selectivity to DMF. The reaction pathway was investigated thoroughly, and the hydrogenation of the C=O bond in HMF was demonstrated to be the rate-determining step during the hydrodeoxygenation, which could be accelerated greatly by using alcohol solvents as additional H-donors. The excellent stability of the Fe catalyst, which was probably a result of the well-preserved active species and the pore structure of the Fe catalyst in the presence of H 2 , was demonstrated in batch and continuous flow fixed-bed reactors. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

The catalyst layer and its dimensionality - A look into its ingredients and how to characterize their effects

NASA Astrophysics Data System (ADS)

Zamel, Nada

2016-03-01

Development of polymer electrolyte membrane (PEM) fuel cells throughout the years is established through its component optimization. This is especially true of its catalyst layer, where structuring of the layer has led to many breakthroughs. The catalyst layer acts as the heart of the cell, where it controls the half-cell reactions and their products. The complex nature of various transport phenomena simultaneously taking place in the layer requires the layer to be heterogeneous in structure. Hence, a delicate balance of the layer's ingredients, coupled with the understanding of the ingredients' interaction, is required. State-of-the-art catalyst layers are composed of a catalyst, its support, a solvent and a binder. Changes in the morphology, structure or material of any of these components ultimately affects the layer's activity and durability. In this review paper, we provide an overview of the various works tailored to understand how each component in the catalyst's ink affects the stability and life-time of the layer.

Catalyst evaluation for oxygen reduction reaction in concentrated phosphoric acid at elevated temperatures

NASA Astrophysics Data System (ADS)

Hu, Yang; Jiang, Yiliang; Jensen, Jens Oluf; Cleemann, Lars N.; Li, Qingfeng

2018-01-01

Phosphoric acid is the common electrolyte for high-temperature polymer electrolyte fuel cells (HT-PEMFCs) that have advantages such as enhanced CO tolerance and simplified heat and water management. The currently used rotating disk electrode technique is limited to tests in dilute solutions at low temperatures and hence is not suitable for catalyst evaluation for HT-PEMFCs. In this study, we have designed and constructed a half-cell setup to measure the intrinsic activities of catalysts towards the oxygen reduction reaction (ORR) in conditions close to HT-PEMFC cathodes. By optimization of the hydrophobic characteristics of electrodes and the catalyst layer thickness, ORR activities of typical Pt/C catalysts are successfully measured in concentrated phosphoric acid at temperatures above 100 °C. In terms of mass-specific activities, the catalyst exhibits about two times higher activity in the half-cell electrode than that observed in fuel cells, indicating the feasibility of the technique as well as the potential for further improvement of fuel cell electrode performance.

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.

Enhanced furfural production from raw corn stover employing a novel heterogeneous acid catalyst.

PubMed

Li, Wenzhi; Zhu, Yuanshuai; Lu, Yijuan; Liu, Qiyu; Guan, Shennan; Chang, Hou-Min; Jameel, Hasan; Ma, Longlong

2017-12-01

With the aim to enhance the direct conversion of raw corn stover into furfural, a promising approach was proposed employing a novel heterogeneous strong acid catalyst (SC-CaC t -700) in different solvents. The novel catalyst was characterized by elemental analysis, N 2 adsorption-desorption, FT-IR, XPS, TEM and SEM. The developed catalytic system demonstrated superior efficacy for furfural production from raw corn stover. The effects of reaction temperature, residence time, catalyst loading, substrate concentration and solvent were investigated and optimized. 93% furfural yield was obtained from 150mg corn stover at 200°C in 100min using 45mg catalyst in γ-valerolactone (GVL). In comparison, 51.5% furfural yield was achieved in aqueous media under the same conditions (200°C, 5h, and 45mg catalyst), which is of great industrial interest. Furfural was obtained from both hemicelluloses and cellulose in corn stover, which demonstrated a promising routine to make the full use of biomass. Copyright © 2017 Elsevier Ltd. All rights reserved.

A novel nano-Ni/SiO2 catalyst for hydrogen production from steam reforming of ethanol.

PubMed

Wu, Chunfei; Williams, Paul T

2010-08-01

Catalytic steam reforming of ethanol has been regarded as a promising way to produce hydrogen. However, catalytic deactivation is a key problem in the process. In this paper, a novel nano-Ni/SiO2 catalyst was prepared by a simple sol-gel method and compared to catalysts prepared by an impregnation method in relation to the steam reforming ethanol process. Good Ni dispersion and high BET surface areas (>700 m2 g(-1)) were obtained for sol-gel catalysts, whereas only 1 m2 g(-1) surface area was obtained for the Ni/SiO2 impregnation catalyst. The results of catalytic steam reforming of ethanol showed that about twice of the hydrogen production was produced with the Ni/SiO2 catalyst prepared by sol-gel (around 0.2 g h(-1)) compared with that prepared by impregnation (around 0.1 g h(-1)). The analysis of the used catalysts showed that 10Ni/SiO2-B and 20Ni/SiO2-B presented the highest stability, while other catalysts were fragmented into small pieces after the reforming process, especially the catalysts prepared by impregnation. A novel catalyst has been produced that has been shown to be effective in the production of hydrogen from the steam reforming of ethanol.

Industrial wastewater advanced treatment via catalytic ozonation with an Fe-based catalyst.

PubMed

Li, Xufang; Chen, Weiyu; Ma, Luming; Wang, Hongwu; Fan, Jinhong

2018-03-01

An Fe-based catalyst was used as a heterogeneous catalyst for the ozonation of industrial wastewater, and key operational parameters (pH and catalyst dosage) were studied. The results indicated that the Fe-based catalyst significantly improved the mineralization of organic pollutants in wastewater. TOC (total organic carbon) removal was high, at 78.7%, with a catalyst concentration of 200 g/L, but only 31.6% with ozonation alone. The Fe-based catalyst significantly promoted ozone decomposition by 70% in aqueous solution. Hydroxyl radicals (·OH) were confirmed to be existed directly via EPR (electron paramagnetic resonance) experiments, and ·OH were verified to account for about 34.4% of TOC removal with NaHCO 3 as a radical scavenger. Through characterization by SEM-EDS (field emission scanning electron microscope with energy-dispersive spectrometer), XRD (X-ray powder diffraction) and XPS (X-ray photoelectron spectroscopy), it was deduced that FeOOH on the surface of the catalyst was the dominant contributor to the catalytic efficiency. The catalyst was certified as having good stability and excellent reusability based on 50 successive operations and could be used as a filler simultaneously. Thereby, it is a promising catalyst for practical industrial wastewater advanced treatment. Copyright © 2017 Elsevier Ltd. All rights reserved.

Synthesis of Platinum-nickel Nanowires and Optimization for Oxygen Reduction Performance

DOE PAGES

Alia, Shaun M.; Pivovar, Bryan S.

2018-01-01

Platinum-nickel (Pt-Ni) nanowires were developed as fuel cell electrocatalysts, and were optimized for the performance and durability in the oxygen reduction reaction. Spontaneous galvanic displacement was used to deposit Pt layers onto Ni nanowire substrates. The synthesis approach produced catalysts with high specific activities and high Pt surface areas. Hydrogen annealing improved Pt and Ni mixing and specific activity. Acid leaching was used to preferentially remove Ni near the nanowire surface, and oxygen annealing was used to stabilize near-surface Ni, improving durability and minimizing Ni dissolution. These protocols detail the optimization of each post-synthesis processing step, including hydrogen annealing tomore » 250 degrees C, exposure to 0.1 M nitric acid, and oxygen annealing to 175 degrees C. Through these steps, Pt-Ni nanowires produced increased activities more than an order of magnitude than Pt nanoparticles, while offering significant durability improvements. The presented protocols are based on Pt-Ni systems in the development of fuel cell catalysts. Furthermore, these techniques have also been used for a variety of metal combinations, and can be applied to develop catalysts for a number of electrochemical processes.« less

Synthesis of Platinum-nickel Nanowires and Optimization for Oxygen Reduction Performance

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

Alia, Shaun M.; Pivovar, Bryan S.

Platinum-nickel (Pt-Ni) nanowires were developed as fuel cell electrocatalysts, and were optimized for the performance and durability in the oxygen reduction reaction. Spontaneous galvanic displacement was used to deposit Pt layers onto Ni nanowire substrates. The synthesis approach produced catalysts with high specific activities and high Pt surface areas. Hydrogen annealing improved Pt and Ni mixing and specific activity. Acid leaching was used to preferentially remove Ni near the nanowire surface, and oxygen annealing was used to stabilize near-surface Ni, improving durability and minimizing Ni dissolution. These protocols detail the optimization of each post-synthesis processing step, including hydrogen annealing tomore » 250 degrees C, exposure to 0.1 M nitric acid, and oxygen annealing to 175 degrees C. Through these steps, Pt-Ni nanowires produced increased activities more than an order of magnitude than Pt nanoparticles, while offering significant durability improvements. The presented protocols are based on Pt-Ni systems in the development of fuel cell catalysts. Furthermore, these techniques have also been used for a variety of metal combinations, and can be applied to develop catalysts for a number of electrochemical processes.« less

Development of a ruthenium/phosphite catalyst system for domino hydroformylation-reduction of olefins with carbon dioxide.

PubMed

Liu, Qiang; Wu, Lipeng; Fleischer, Ivana; Selent, Detlef; Franke, Robert; Jackstell, Ralf; Beller, Matthias

2014-06-02

An efficient domino ruthenium-catalyzed reverse water-gas-shift (RWGS)-hydroformylation-reduction reaction of olefins to alcohols is reported. Key to success is the use of specific bulky phosphite ligands and triruthenium dodecacarbonyl as the catalyst. Compared to the known ruthenium/chloride system, the new catalyst allows for a more efficient hydrohydroxymethylation of terminal and internal olefins with carbon dioxide at lower temperature. Unwanted hydrogenation of the substrate is prevented. Preliminary mechanism investigations uncovered the homogeneous nature of the active catalyst and the influence of the ligand and additive in individual steps of the reaction sequence. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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+.

Synthesis and Characterization of AlCl3 Impregnated Molybdenum Oxide as Heterogeneous Nano-Catalyst for the Friedel-Crafts Acylation Reaction in Ambient Condition.

PubMed

Jadhav, Arvind H; Chinnappan, Amutha; Hiremath, Vishwanath; Seo, Jeong Gil

2015-10-01

Aluminum trichloride (AlCl3) impregnated molybdenum oxide heterogeneous nano-catalyst was prepared by using simple impregnation method. The prepared heterogeneous catalyst was characterized by powder X-ray diffraction, FT-IR spectroscopy, solid-state NMR spectroscopy, SEM imaging, and EDX mapping. The catalytic activity of this protocol was evaluated as heterogeneous catalyst for the Friedel-Crafts acylation reaction at room temperature. The impregnated MoO4(AlCl2)2 catalyst showed tremendous catalytic activity in Friedel-Crafts acylation reaction under solvent-free and mild reaction condition. As a result, 84.0% yield of acyl product with 100% consumption of reactants in 18 h reaction time at room temperature was achieved. The effects of different solvents system with MoO4(AlCl2)2 catalyst in acylation reaction was also investigated. By using optimized reaction condition various acylated derivatives were prepared. In addition, the catalyst was separated by simple filtration process after the reaction and reused several times. Therefore, heterogeneous MoO4(AlCl2)2 catalyst was found environmentally benign catalyst, very convenient, high yielding, and clean method for the Friedel-Crafts acylation reaction under solvent-free and ambient reaction condition.

Catalyst system and process for benzyl ether fragmentation and coal liquefaction

DOEpatents

Zoeller, Joseph Robert

1998-04-28

Dibenzyl ether can be readily cleaved to form primarily benzaldehyde and toluene as products, along with minor amounts of bibenzyl and benzyl benzoate, in the presence of a catalyst system comprising a Group 6 metal, preferably molybdenum, a salt, and an organic halide. Although useful synthetically for the cleavage of benzyl ethers, this cleavage also represents a key model reaction for the liquefaction of coal; thus this catalyst system and process should be useful in coal liquefaction with the advantage of operating at significantly lower temperatures and pressures.

Catalysts for CO2/epoxide ring-opening copolymerization

PubMed Central

Trott, G.; Saini, P. K.; Williams, C. K.

2016-01-01

This article summarizes and reviews recent progress in the development of catalysts for the ring-opening copolymerization of carbon dioxide and epoxides. The copolymerization is an interesting method to add value to carbon dioxide, including from waste sources, and to reduce pollution associated with commodity polymer manufacture. The selection of the catalyst is of critical importance to control the composition, properties and applications of the resultant polymers. This review highlights and exemplifies some key recent findings and hypotheses, in particular using examples drawn from our own research. PMID:26755758

Diaminophosphine oxide ligand enabled asymmetric nickel-catalyzed hydrocarbamoylations of alkenes.

PubMed

Donets, Pavel A; Cramer, Nicolai

2013-08-14

Chiral trivalent phosphorus species are the dominant class of ligands and the key controlling element in asymmetric homogeneous transition-metal catalysis. Here, novel chiral diaminophosphine oxide ligands are described. The arising catalyst system with nickel(0) and trimethylaluminum efficiently activates formamide C-H bonds under mild conditions providing pyrrolidones via intramolecular hydrocarbamoylation in a highly enantioselective manner with as little as 0.25% mol catalyst loading. Mechanistically, the secondary phosphine oxides behave as bridging ligands for the nickel center and the Lewis acidic organoaluminum center to give a heterobimetallic catalyst with superior reactivity.

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

The Effect of K and Acidity of NiW-Loaded HY Zeolite Catalyst for Selective Ring Opening of 1-Methylnaphthalene.

PubMed

Lee, You-Jin; Kim, Eun-Sang; Kim, Jeong-Rang; Kim, Joo-Wan; Kim, Tae-Wan; Chae, Ho-Jeong; Kim, Chul-Ung; Lee, Chang-Ha; Jeong, Soon-Yong

2016-05-01

Bi-functional catalysts were prepared using HY zeolites with various SiO2/Al2O3 ratios for acidic function, NiW for metallic function, and K for acidity control. 1-Methylnaphthalene was selected as a model compound for multi-ring aromatics in heavy oil, and its selective ring opening reaction was investigated using the prepared bi-functional catalysts with different levels of acidity in a fixed bed reactor system. In NiW/HY catalysts without K addition, the acidity decreased with the SiO2/Al2O3 mole ratio of the HY zeolite. Ni1.1W1.1/HY(12) catalyst showed the highest acidity but slightly lower yields for the selective ring opening than Ni1.1W1.1/HY(30) catalyst. The acidity of the catalyst seemed to play an important role as the active site for the selective ring opening of 1-methylnaphthalene but there should be some optimum catalyst acidity for the reaction. Catalyst acidity could be controlled between Ni1.1W1.1/HY(12) and Ni1.1W1.1/HY(30) by adding a moderate amount of K to Ni1.1W1.1/HY(12) catalyst. K0.3Ni1.1W1.1/HY(12) catalyst should have the optimum acidity for the selective ring opening. The addition of a moderate amount of K to the NiW/HY catalyst must improve the catalytic performance due to the optimization of catalyst acidity.

Synthesis of fatty acid methyl ester from palm oil (Elaeis guineensis) with Ky(MgCa)2xO3 as heterogeneous catalyst.

PubMed

Olutoye, M A; Lee, S C; Hameed, B H

2011-12-01

Fatty acid methyl esters (FAME) were produced from palm oil using eggshell modified with magnesium and potassium nitrates to form a composite, low-cost heterogeneous catalyst for transesterification. The catalyst, prepared by the combination of impregnation/co-precipitation was calcined at 830 °C for 4 h. Transesterification was conducted at a constant temperature of 65 °C in a batch reactor. Design of experiment (DOE) was used to optimize the reaction parameters, and the conditions that gave highest yield of FAME (85.8%) was 5.35 wt.% catalyst loading at 4.5 h with 16:1 methanol/oil molar ratio. The results revealed that eggshell, a solid waste, can be utilized as low-cost catalyst after modification with magnesium and potassium nitrates for biodiesel production. Copyright © 2011 Elsevier Ltd. All rights reserved.

High-throughput investigation of catalysts for JP-8 fuel cracking to liquefied petroleum gas.

PubMed

Bedenbaugh, John E; Kim, Sungtak; Sasmaz, Erdem; Lauterbach, Jochen

2013-09-09

Portable power technologies for military applications necessitate the production of fuels similar to LPG from existing feedstocks. Catalytic cracking of military jet fuel to form a mixture of C₂-C₄ hydrocarbons was investigated using high-throughput experimentation. Cracking experiments were performed in a gas-phase, 16-sample high-throughput reactor. Zeolite ZSM-5 catalysts with low Si/Al ratios (≤25) demonstrated the highest production of C₂-C₄ hydrocarbons at moderate reaction temperatures (623-823 K). ZSM-5 catalysts were optimized for JP-8 cracking activity to LPG through varying reaction temperature and framework Si/Al ratio. The reducing atmosphere required during catalytic cracking resulted in coking of the catalyst and a commensurate decrease in conversion rate. Rare earth metal promoters for ZSM-5 catalysts were screened to reduce coking deactivation rates, while noble metal promoters reduced onset temperatures for coke burnoff regeneration.

Chiral poly-rare earth metal complexes in asymmetric catalysis

PubMed Central

Shibasaki, Masakatsu

2006-01-01

Asymmetric catalysis is a powerful component of modern synthetic organic chemistry. To further broaden the scope and utility of asymmetric catalysis, new basic concepts for the design of asymmetric catalysts are crucial. Because most chemical reactions involve bond-formation between two substrates or moieties, high enantioselectivity and catalyst activity should be realized if an asymmetric catalyst can activate two reacting substrates simultaneously at defined positions. Thus, we proposed the concept of bifunctional asymmetric catalysis, which led us to the design of new asymmetric catalysts containing two functionalities (e.g. a Lewis acid and a Brønsted base or a Lewis acid and a Lewis base). These catalysts demonstrated broad reaction applicability with excellent substrate generality. Using our catalytic asymmetric reactions as keys steps, efficient total syntheses of pharmaceuticals and their biologically active lead natural products were achieved. PMID:25792774

Bimetallic cooperative effect on O-O bond formation: copper polypyridyl complexes as water oxidation catalyst.

PubMed

Su, Xiao-Jun; Zheng, Chu; Hu, Qin-Qin; Du, Hao-Yi; Liao, Rong-Zhen; Zhang, Ming-Tian

2018-06-13

The performance of water oxidation catalysis by a Cu-based polypyridyl complex, [CuII(TPA)(OH2)]2+ (1H; TPA = tris-(pyridylmethyl)amine), has been investigated in neutral aqueous solution by electrochemical methods. Compared with our previously reported binuclear catalyst, [(BPMAN)(CuII)2(μ-OH)]3+ (2; BPMAN = 2,7-[bis(2-pyridylmethyl)aminomethyl]-1,8-naphthyridine), mononuclear catalyst 1 has a higher overpotential and lower catalytic activity toward water oxidation under the same conditions. Experimental results revealed that the O-O bond formation occurred via a water nucleophilic attack mechanism in which formal CuIV(O) is proposed as a key intermediate for the mononuclear catalyst 1H. In contrast, for the binuclear catalyst, O-O bond formation was facilitated by bimetallic cooperation between the two CuIII centers.

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.

Calcium oxide supported gold nanoparticles as catalysts for the selective epoxidation of styrene by t-butyl hydroperoxide.

PubMed

Dumbre, Deepa K; Choudhary, Vasant R; Patil, Nilesh S; Uphade, Balu S; Bhargava, Suresh K

2014-02-01

Gold nanoparticles are deposited on basic CaO supports as catalysts for the selective conversion of styrene into styrene oxide. Synthetic methods, gold loading and calcination temperatures are varied to permit an understanding of their influence on gold nanoparticle size, the presence of cationic gold species and the nature of interaction between the gold nanoparticles and the CaO support. Based on these studies, optimal conditions are designed to make the Au/CaO catalyst efficient for the selective epoxidation of styrene. Copyright © 2013 Elsevier Inc. All rights reserved.

Process for hydrogenating coal and coal solvents

DOEpatents

Tarrer, Arthur R.; Shridharani, Ketan G.

1983-01-01

A novel process is described for the hydrogenation of coal by the hydrogenation of a solvent for the coal in which the hydrogenation of the coal solvent is conducted in the presence of a solvent hydrogenation catalyst of increased activity, wherein the hydrogenation catalyst is produced by reacting ferric oxide with hydrogen sulfide at a temperature range of 260.degree. C. to 315.degree. C. in an inert atmosphere to produce an iron sulfide hydrogenation catalyst for the solvent. Optimally, the reaction temperature is 275.degree. C. Alternately, the reaction can be conducted in a hydrogen atmosphere at 350.degree. C.

Graphene as a thin-film catalyst booster: graphene-catalyst interface plays a critical role.

PubMed

Chae, Sieun; Jin Choi, Won; Sang Chae, Soo; Jang, Seunghun; Chang, Hyunju; Lee, Tae Il; Kim, Youn Sang; Lee, Jeong-O

2017-12-08

Due to its extreme thinness, graphene can transmit some surface properties of its underlying substrate, a phenomenon referred to as graphene transparency. Here we demonstrate the application of the transparency of graphene as a protector of thin-film catalysts and a booster of their catalytic efficiency. The photocatalytic degradation of dye molecules by ZnO thin films was chosen as a model system. A ZnO thin film coated with monolayer graphene showed greater catalytic efficiency and long-term stability than did bare ZnO. Interestingly, we found the catalytic efficiency of the graphene-coated ZnO thin film to depend critically on the nature of the bottom ZnO layer; graphene transferred to a relatively rough, sputter-coated ZnO thin film showed rather poor catalytic degradation of the dye molecules while a smooth sol-gel-synthesized ZnO covered with monolayer graphene showed enhanced catalytic degradation. Based on a systematic investigation of the interface between graphene and ZnO thin films, we concluded the transparency of graphene to be critically dependent on its interface with a supporting substrate. Graphene supported on an atomically flat substrate was found to efficiently transmit the properties of the substrate, but graphene suspended on a substrate with a rough nanoscale topography was completely opaque to the substrate properties. Our experimental observations revealed the morphology of the substrate to be a key factor affecting the transparency of graphene, and should be taken into account in order to optimally apply graphene as a protector of catalytic thin films and a booster of their catalysis.

The Functionality of Surface Hydroxy Groups on the Selectivity and Activity of Carbon Dioxide Reduction over Cuprous Oxide in Aqueous Solutions.

PubMed

Yang, Piaoping; Zhao, Zhi-Jian; Chang, Xiaoxia; Mu, Rentao; Zha, Shenjun; Zhang, Gong; Gong, Jinlong

2018-06-25

Carbon dioxide (CO 2 ) reduction in aqueous solutions is an attractive strategy for carbon capture and utilization. Cuprous oxide (Cu 2 O) is a promising catalyst for CO 2 reduction as it can convert CO 2 into valuable hydrocarbons and suppress the side hydrogen evolution reaction (HER). However, the nature of the active sites in Cu 2 O remains under debate because of the complex surface structure of Cu 2 O under reducing conditions, leading to limited guidance in designing improved Cu 2 O catalysts. This paper describes the functionality of surface-bonded hydroxy groups on partially reduced Cu 2 O(111) for the CO 2 reduction reaction (CO 2 RR) by combined density functional theory (DFT) calculations and experimental studies. We find that the surface hydroxy groups play a crucial role in the CO 2 RR and HER, and a moderate coverage of hydroxy groups is optimal for promotion of the CO 2 RR and suppression of the HER simultaneously. Electronic structure analysis indicates that the charge transfer from hydroxy groups to coordination-unsaturated Cu (Cu CUS ) sites stabilizes surface-adsorbed COOH*, which is a key intermediate during the CO 2 RR. Moreover, the CO 2 RR was evaluated over Cu 2 O octahedral catalysts with {111} facets and different surface coverages of hydroxy groups, which demonstrates that Cu 2 O octahedra with moderate coverage of hydroxy groups can indeed enhance the CO 2 RR and suppress the HER. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

ZnO/La 2O 2CO 3 layered composite: A new heterogeneous catalyst for the efficient ultra-fast microwave biofuel production

DOE PAGES

Jin, Lei; Zhang, Yashan; Dombrowski, James; ...

2011-01-21

The search for solid state materials with high catalytic activities and with no leaching into the reaction medium is one of the key steps toward reducing the cost of producing biodiesel. We report a high biodiesel yield (>95%) in less than 5 min under mild reaction conditions (<100°C) on a ZnO/La₂O₂CO₃ heterogeneous catalyst, showing no catalyst leaching into the reaction medium. The ZnO/La₂O₂CO₃ catalyst is prepared by a co-precipitation method and characterized by X-ray diffraction (XRD), thermogravimetric analyses (TGA), transmission electron microscopy (SEM), and transmission electron microscopy (TEM). The fatty acid methyl ester (FAME) yields as function of different amountsmore » of catalyst was also investigated. Less than 1.0 wt.% catalyst can be used in the reaction to get higher than a 95% FAME yield under mild reaction conditions. The catalytic performance is maintained after storing the catalyst in Ar for a month and no catalyst leaching into the products was found based on XRF analysis. The catalyst has a higher reaction rate than the homogeneous KOH catalyst with the assistance of microwave irradiation. All of these results promote the industrial application of the synthesized ZnO/La₂O₂CO₃ as an ideal catalyst for fast biodiesel production, avoiding many of the issues found in both commercial and independently published catalysts.« less

System Engineering Concept Demonstration, Effort Summary. Volume 1

DTIC Science & Technology

1992-12-01

involve only the system software, user frameworks and user tools. U •User Tool....s , Catalyst oExternal 00 Computer Framwork P OSystems • •~ Sysytem...analysis, synthesis, optimization, conceptual design of Catalyst. The paper discusses the definition, design, test, and evaluation; operational concept...This approach will allow system engineering The conceptual requirements for the Process Model practitioners to recognize and tailor the model. This

Optimization and fabrication of porous carbon electrodes for Fe/Cr redox flow cells

NASA Technical Reports Server (NTRS)

Jalan, V.; Morriseau, B.; Swette, L.

1982-01-01

Negative electrode development for the NASA chromous/ferric Redox battery is reported. The effects of substrate material, gold/lead catalyst composition and loading, and catalyzation procedures on the performance of the chromium electrode were investigated. Three alternative catalyst systems were also examined, and 1/3 square foot size electrodes were fabricated and delivered to NASA at the conclusion of the program.

Fischer-Tropsch Cobalt Catalyst Activation and Handling Through Wax Enclosure Methods

NASA Technical Reports Server (NTRS)

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

2016-01-01

Fischer-Tropsch (F-T) synthesis is considered a gas to liquid process which converts syn-gas, a gaseous mixture of hydrogen and carbon monoxide, into liquids of various hydrocarbon chain length and product distributions. Cobalt based catalysts are used in F-T synthesis and are the focus of this paper. One key concern with handling cobalt based catalysts is that the active form of catalyst is in a reduced state, metallic cobalt, which oxidizes readily in air. In laboratory experiments, the precursor cobalt oxide catalyst is activated in a fixed bed at 350 ?C then transferred into a continuous stirred tank reactor (CSTR) with inert gas. NASA has developed a process which involves the enclosure of active cobalt catalyst in a wax mold to prevent oxidation during storage and handling. This improved method allows for precise catalyst loading and delivery into a CSTR. Preliminary results indicate similar activity levels in the F-T reaction in comparison to the direct injection method. The work in this paper was supported by the NASA Fundamental Aeronautics Subsonics Fixed Wing Project.

A highly active and stable IrO x/SrIrO 3 catalyst for the oxygen evolution reaction

DOE PAGES

Seitz, Linsey C.; Dickens, Colin F.; Nishio, Kazunori; ...

2016-09-02

Oxygen electrochemistry plays a key role in renewable energy technologies such as fuel cells and electrolyzers, but the slow kinetics of the oxygen evolution reaction (OER) limit the performance and commercialization of such devices. Here we report an iridium oxide/strontium iridium oxide (IrO x/SrIrO 3) catalyst formed during electrochemical testing by strontium leaching from surface layers of thin films of SrIrO 3. This catalyst has demonstrated specific activity at 10 milliamps per square centimeter of oxide catalyst (OER current normalized to catalyst surface area), with only 270 to 290 millivolts of overpotential for 30 hours of continuous testing in acidicmore » electrolyte. Here, density functional theory calculations suggest the formation of highly active surface layers during strontium leaching with IrO 3 or anatase IrO 2 motifs. The IrO x/SrIrO 3 catalyst outperforms known IrO x and ruthenium oxide (RuO x) systems, the only other OER catalysts that have reasonable activity in acidic electrolyte.« less

A highly active and stable IrOx/SrIrO3 catalyst for the oxygen evolution reaction.

PubMed

Seitz, Linsey C; Dickens, Colin F; Nishio, Kazunori; Hikita, Yasuyuki; Montoya, Joseph; Doyle, Andrew; Kirk, Charlotte; Vojvodic, Aleksandra; Hwang, Harold Y; Norskov, Jens K; Jaramillo, Thomas F

2016-09-02

Oxygen electrochemistry plays a key role in renewable energy technologies such as fuel cells and electrolyzers, but the slow kinetics of the oxygen evolution reaction (OER) limit the performance and commercialization of such devices. Here we report an iridium oxide/strontium iridium oxide (IrO x /SrIrO 3 ) catalyst formed during electrochemical testing by strontium leaching from surface layers of thin films of SrIrO 3 This catalyst has demonstrated specific activity at 10 milliamps per square centimeter of oxide catalyst (OER current normalized to catalyst surface area), with only 270 to 290 millivolts of overpotential for 30 hours of continuous testing in acidic electrolyte. Density functional theory calculations suggest the formation of highly active surface layers during strontium leaching with IrO 3 or anatase IrO 2 motifs. The IrO x /SrIrO 3 catalyst outperforms known IrO x and ruthenium oxide (RuO x ) systems, the only other OER catalysts that have reasonable activity in acidic electrolyte. Copyright © 2016, American Association for the Advancement of Science.

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

Challenging nickel-catalysed amine arylations enabled by tailored ancillary ligand design

PubMed Central

Lavoie, Christopher M.; MacQueen, Preston M.; Rotta-Loria, Nicolas L.; Sawatzky, Ryan S.; Borzenko, Andrey; Chisholm, Alicia J.; Hargreaves, Breanna K. V.; McDonald, Robert; Ferguson, Michael J.; Stradiotto, Mark

2016-01-01

Palladium-catalysed C(sp2)–N cross-coupling (that is, Buchwald–Hartwig amination) is employed widely in synthetic chemistry, including in the pharmaceutical industry, for the synthesis of (hetero)aniline derivatives. However, the cost and relative scarcity of palladium provides motivation for the development of alternative, more Earth-abundant catalysts for such transformations. Here we disclose an operationally simple and air-stable ligand/nickel(II) pre-catalyst that accommodates the broadest combination of C(sp2)–N coupling partners reported to date for any single nickel catalyst, without the need for a precious-metal co-catalyst. Key to the unprecedented performance of this pre-catalyst is the application of the new, sterically demanding yet electron-poor bisphosphine PAd-DalPhos. Featured are the first reports of nickel-catalysed room temperature reactions involving challenging primary alkylamine and ammonia reaction partners employing an unprecedented scope of electrophiles, including transformations involving sought-after (hetero)aryl mesylates for which no capable catalyst system is known. PMID:27004442

Highly porous non-precious bimetallic electrocatalysts for efficient hydrogen evolution

DOE PAGES

Lu, Qi; Hutchings, Gregory S.; Yu, Weiting; ...

2015-03-16

One of the key components of carbon dioxide-free hydrogen production is a robust and efficient non-precious metal catalyst for the hydrogen evolution reaction. We report that a hierarchical nanoporous copper-titanium bimetallic electrocatalyst is able to produce hydrogen from water under a mild overpotential at more than twice the rate of state-of-the- art carbon-supported platinum catalyst. Although both copper and titanium are known to be poor hydrogen evolution catalysts, the combination of these two elements creates unique copper-copper-titanium hollow sites, which have a hydrogen-binding energy very similar to that of platinum, resulting in an exceptional hydrogen evolution activity. Moreover, the hierarchicalmore » porosity of the nanoporous-copper titanium catalyst also contributes to its high hydrogen evolution activity, because it provides a large-surface area for electrocatalytic hydrogen evolution, and improves the mass transport properties. Moreover, the catalyst is self-supported, eliminating the overpotential associated with the catalyst/support interface.« less

Activation of surface lattice oxygen in single-atom Pt/CeO 2 for low-temperature CO oxidation

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

Nie, Lei; Mei, Donghai; Xiong, Haifeng

While single-atom catalysts can provide high catalytic activity and selectivity, application in industrial catalysts demands long term performance and the ability to regenerate the catalysts. We have investigated the factors that lead to improved catalytic activity of a Pt/CeO2 catalyst for low temperature CO oxidation. Single-atom Pt/CeO2 becomes active for CO oxidation under lean condition only at elevated temperatures, because CO is strongly bound to ionic Pt sites. Reducing the catalyst, even under mild conditions, leads to onset of CO oxidation activity even at room temperature. This high activity state involves the transformation of mononuclear Pt species to sub-nanometer sizedmore » Pt particles. Under oxidizing conditions, the Pt can be restored to its stable, single-atom state. The key to facile regeneration is the ability to create mobile Pt species and suitable trapping sites on the support, making this a prototypical catalyst system for industrial application of single-atom catalysis.« less

Adsorbate-mediated strong metal–support interactions in oxide-supported Rh catalysts

DOE PAGES

Matsubu, John C.; Zhang, Shuyi; DeRita, Leo; ...

2016-09-19

The optimization of supported metal catalysts predominantly focuses on engineering the metal site, for which physical insights based on extensive theoretical and experimental contributions have enabled the rational design of active sites. Although it is well known that supports can influence the catalytic properties of metals, insights into how metal–support interactions can be exploited to optimize metal active-site properties are lacking. Here in this paper, we utilize in situ spectroscopy and microscopy to identify and characterize a support effect in oxide-supported heterogeneous Rh catalysts. This effect is characterized by strongly bound adsorbates (HCO x) on reducible oxide supports (TiO 2more » and Nb 2O 5) that induce oxygen-vacancy formation in the support and cause HCO x-functionalized encapsulation of Rh nanoparticles by the support. The encapsulation layer is permeable to reactants, stable under the reaction conditions and strongly influences the catalytic properties of Rh, which enables rational and dynamic tuning of CO 2-reduction selectivity.« less

Synthesis of carbon nanotubes via Fe-catalyzed pyrolysis of phenolic resin

NASA Astrophysics Data System (ADS)

Wang, Junkai; Deng, Xiangong; Zhang, Haijun; Zhang, Yuanzhuo; Duan, Hongjuan; Lu, Lilin; Song, Jianbo; Tian, Liang; Song, Shupeng; Zhang, Shaowei

2017-02-01

Carbon nanotubes (CNTs) with 40-100 nm in diameter and tens of micrometers in length were prepared via catalytic pyrolysis of phenol resin in Ar at 673-1273 K using ferric nitrate as a catalyst precursor. Structure and morphology of pyrolyzed resin were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy. Ferric nitrate was transformed to Fe3O4 at 673 K, and to metallic Fe and FexC carbide at 873-1273 K. The optimal weight ratio of Fe catalyst to phenol resin for growing CNTs was 1.00 wt%, and the optimal temperature was 1073 K. In addition, use of a high pressure increased the yield of CNTs. Density functional theory (DFT) calculations suggest that Fe catalysts facilitate the CNTs growth by increasing the bond length and weakening the bond strength in C2H4 via donating electrons to the C atoms in it.

Unsupported Pt-Ni Aerogels with Enhanced High Current Performance and Durability in Fuel Cell Cathodes.

PubMed

Henning, Sebastian; Ishikawa, Hiroshi; Kühn, Laura; Herranz, Juan; Müller, Elisabeth; Eychmüller, Alexander; Schmidt, Thomas J

2017-08-28

Highly active and durable oxygen reduction catalysts are needed to reduce the costs and enhance the service life of polymer electrolyte fuel cells (PEFCs). This can be accomplished by alloying Pt with a transition metal (for example Ni) and by eliminating the corrodible, carbon-based catalyst support. However, materials combining both approaches have seldom been implemented in PEFC cathodes. In this work, an unsupported Pt-Ni alloy nanochain ensemble (aerogel) demonstrates high current PEFC performance commensurate with that of a carbon-supported benchmark (Pt/C) following optimization of the aerogel's catalyst layer (CL) structure. The latter is accomplished using a soluble filler to shift the CL's pore size distribution towards larger pores which improves reactant and product transport. Chiefly, the optimized PEFC aerogel cathodes display a circa 2.5-fold larger surface-specific ORR activity than Pt/C and maintain 90 % of the initial activity after an accelerated stress test (vs. 40 % for Pt/C). © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Comparison of sulfuric and hydrochloric acids as catalysts in hydrolysis of Kappaphycus alvarezii (cottonii).

PubMed

Meinita, Maria Dyah Nur; Hong, Yong-Ki; Jeong, Gwi-Taek

2012-01-01

In this study, hydrolysis of marine algal biomass Kappaphhycus alvarezii using two different acid catalysts was examined with the goal of identifying optimal reaction conditions for the formation of sugars and by-products. K. alvarezii were hydrolyzed by autoclave using sulfuric acid or hydrochloric acid as catalyst with different acid concentrations (0.1-1.0 M), substrate concentrations (1.0-13.5%), hydrolysis time (10-90 min) and hydrolysis temperatures (100-130 (°)C). A difference in galactose, glucose, reducing sugar and total sugar content was observed under the different hydrolysis conditions. Different by-product compounds such as 5-hydroxymethylfurfural and levulinic acid were also observed under the different reaction conditions. The optimal conditions for hydrolysis were achieved at a sulfuric acid concentration, temperature and reaction time of 0.2 M, 130 °C and 15 min, respectively. These results may provide useful information for the development of more efficient systems for biofuel production from marine biomass.

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.

Minimizing Isolate Catalyst Motion in Metal-Assisted Chemical Etching for Deep Trenching of Silicon Nanohole Array.

PubMed

Kong, Lingyu; Zhao, Yunshan; Dasgupta, Binayak; Ren, Yi; Hippalgaonkar, Kedar; Li, Xiuling; Chim, Wai Kin; Chiam, Sing Yang

2017-06-21

The instability of isolate catalysts during metal-assisted chemical etching is a major hindrance to achieve high aspect ratio structures in the vertical and directional etching of silicon (Si). In this work, we discussed and showed how isolate catalyst motion can be influenced and controlled by the semiconductor doping type and the oxidant concentration ratio. We propose that the triggering event in deviating isolate catalyst motion is brought about by unequal etch rates across the isolate catalyst. This triggering event is indirectly affected by the oxidant concentration ratio through the etching rates. While the triggering events are stochastic, the doping concentration of silicon offers a good control in minimizing isolate catalyst motion. The doping concentration affects the porosity at the etching front, and this directly affects the van der Waals (vdWs) forces between the metal catalyst and Si during etching. A reduction in the vdWs forces resulted in a lower bending torque that can prevent the straying of the isolate catalyst from its directional etching, in the event of unequal etch rates. The key understandings in isolate catalyst motion derived from this work allowed us to demonstrate the fabrication of large area and uniformly ordered sub-500 nm nanoholes array with an unprecedented high aspect ratio of ∼12.

Hydrophilic TiO2 porous spheres anchored on hydrophobic polypropylene membrane for wettability induced high photodegrading activities.

PubMed

Niu, Fang; Zhang, Le-Sheng; Chen, Chao-Qiu; Li, Wei; Li, Lin; Song, Wei-Guo; Jiang, Lei

2010-08-01

TiO(2) porous nanospheres on polypropylene (PP) films (TiO(2)/PP composite) are produced at ambient temperature. Particle/pore size match up is the key anchoring point to overcome the low affinity between hydrophilic materials and hydrophobic materials. With the hydrophilic TiO(2) catalyst evenly dispersed on a hydrophobic surface, the aqueous solution will selectively skip the substrate and wet the catalysts. Such a wettability-induced smart system maximizes the degrading activity of the TiO(2) catalyst. In photodegrading reactions, the resulting TiO(2)/PP composite film exhibits a 10 times higher activity in flow-type setup than the same TiO(2) catalyst in a traditional batch-type setup.

The synthesis of new oxazoline-containing bifunctional catalysts and their application in the addition of diethylzinc to aldehydes.

PubMed

Coeffard, Vincent; Müller-Bunz, Helge; Guiry, Patrick J

2009-04-21

The straightforward preparation of new modular oxazoline-containing bifunctional catalysts is reported employing a microwave-assisted Buchwald-Hartwig aryl amination as the key step. Covalent attachment of 2-(o-aminophenyl)oxazolines and pyridine derivatives generated in good-to-high yields a series of ligands in two or three steps in which each part was altered independently to tune the activity and the selectivity of the corresponding catalysts. These catalysts prepared in situ were subsequently applied in the asymmetric addition of diethylzinc to various aldehydes, producing the corresponding alcohols with enantioselectivities of up to 68%. A transition state model, based on relevant X-ray crystal structures, has also been proposed to explain the observed stereoselectivities.

Heterojunction-Assisted Co3 S4 @Co3 O4 Core-Shell Octahedrons for Supercapacitors and Both Oxygen and Carbon Dioxide Reduction Reactions.

PubMed

Yan, Yibo; Li, Kaixin; Chen, Xiaoping; Yang, Yanhui; Lee, Jong-Min

2017-12-01

Expedition of electron transfer efficiency and optimization of surface reactant adsorption products desorption processes are two main challenges for developing non-noble catalysts in the oxygen reduction reaction (ORR) and CO 2 reduction reaction (CRR). A heterojunction prototype on Co 3 S 4 @Co 3 O 4 core-shell octahedron structure is established via hydrothermal lattice anion exchange protocol to implement the electroreduction of oxygen and carbon dioxide with high performance. The synergistic bifunctional catalyst consists of p-type Co 3 O 4 core and n-type Co 3 S 4 shell, which afford high surface electron density along with high capacitance without sacrificing mechanical robustness. A four electron ORR process, identical to the Pt catalyzed ORR, is validated using the core-shell octahedron catalyst. The synergistic interaction between cobalt sulfide and cobalt oxide bicatalyst reduces the activation energy to convert CO 2 into adsorbed intermediates and hereby enables CRR to run at a low overpotential, with formate as the highly selective main product at a high faraday efficiency of 85.3%. The remarkable performance can be ascribed to the synergistic coupling effect of the structured co-catalysts; heterojunction structure expedites the electron transfer efficiency and optimizes surface reactant adsorption product desorption processes, which also provide theoretical and pragmatic guideline for catalyst development and mechanism explorations. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Room-temperature CO Thermoelectric Gas Sensor based on Au/Co3O4 Catalyst Tablet.

PubMed

Sun, L; Luan, W L; Wang, T C; Su, W X; Zhang, L X

2017-02-17

A carbon monoxide (CO) thermoelectric (TE) gas sensor was fabricated by affixing a Au/Co 3 O 4 catalyst tablet on a TE film layer. The Au/Co 3 O 4 catalyst tablet was prepared by a co-precipitation and tablet compression method and its possible catalytic mechanism was discussed by means of x-ray diffraction, field emission scanning electron microscopy, high resolution transmission electron microscopy, x-ray photoelectron spectroscopy, temperature-programmed reduction of hydrogen, Fourier transform infrared spectroscopy and Brunauer-Emmett-Teller analysis. The optimal catalyst, with a Au content of 10 wt%, was obtained at a calcination temperature between 200 and 300 °C. The small size of the Au nanoparticles, high specific surface, the existence of Co 3+ and water-derived species contributed to  high catalytic activity. Based on the optimal Au/Co 3 O 4 catalyst tablet, the CO TE gas sensor worked at room temperature and showed a response voltage signal (ΔV) of 23 mV, high selectivity among hydrogen and methane, high stability, and a fast response time of 106 s for 30 000 ppm CO/air. In addition, a CO concentration in the range of 5000-30 000 ppm could obviously be detected and exhibited a linear relationship with ΔV. The CO TE gas sensor provides a promising option for the detection of CO gas at room temperature.

The effect of clay catalyst on the chemical composition of bio-oil obtained by co-pyrolysis of cellulose and polyethylene

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

Solak, Agnieszka; Rutkowski, Piotr, E-mail: piotr.rutkowski@pwr.wroc.pl

2014-02-15

Highlights: • Non-catalytic and catalytic fast pyrolysis of cellulose/polyethylene blend was carried out in a laboratory scale reactor. • Optimization of process temperature was done. • Optimization of clay catalyst type and amount for co-pyrolysis of cellulose and polyethylene was done. • The product yields and the chemical composition of bio-oil was investigated. - Abstract: Cellulose/polyethylene (CPE) mixture 3:1, w/w with and without three clay catalysts (K10 – montmorillonite K10, KSF – montmorillonite KSF, B – Bentonite) addition were subjected to pyrolysis at temperatures 400, 450 and 500 °C with heating rate of 100 °C/s to produce bio-oil with highmore » yield. The pyrolytic oil yield was in the range of 41.3–79.5 wt% depending on the temperature, the type and the amount of catalyst. The non-catalytic fast pyrolysis at 500 °C gives the highest yield of bio-oil (79.5 wt%). The higher temperature of catalytic pyrolysis of cellulose/polyethylene mixture the higher yield of bio-oil is. Contrarily, increasing amount of montmorillonite results in significant, almost linear decrease in bio-oil yield followed by a significant increase of gas yield. The addition of clay catalysts to CPE mixture has a various influence on the distribution of bio-oil components. The addition of montmorillonite K10 to cellulose/polyethylene mixture promotes the deepest conversion of polyethylene and cellulose. Additionally, more saturated than unsaturated hydrocarbons are present in resultant bio-oils. The proportion of liquid hydrocarbons is the highest when a montmorillonite K10 is acting as a catalyst.« less

Sequential-Optimization-Based Framework for Robust Modeling and Design of Heterogeneous Catalytic Systems

DOE PAGES

Rangarajan, Srinivas; Maravelias, Christos T.; Mavrikakis, Manos

2017-11-09

Here, we present a general optimization-based framework for (i) ab initio and experimental data driven mechanistic modeling and (ii) optimal catalyst design of heterogeneous catalytic systems. Both cases are formulated as a nonlinear optimization problem that is subject to a mean-field microkinetic model and thermodynamic consistency requirements as constraints, for which we seek sparse solutions through a ridge (L 2 regularization) penalty. The solution procedure involves an iterative sequence of forward simulation of the differential algebraic equations pertaining to the microkinetic model using a numerical tool capable of handling stiff systems, sensitivity calculations using linear algebra, and gradient-based nonlinear optimization.more » A multistart approach is used to explore the solution space, and a hierarchical clustering procedure is implemented for statistically classifying potentially competing solutions. An example of methanol synthesis through hydrogenation of CO and CO 2 on a Cu-based catalyst is used to illustrate the framework. The framework is fast, is robust, and can be used to comprehensively explore the model solution and design space of any heterogeneous catalytic system.« less

Sequential-Optimization-Based Framework for Robust Modeling and Design of Heterogeneous Catalytic Systems

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

Rangarajan, Srinivas; Maravelias, Christos T.; Mavrikakis, Manos

Here, we present a general optimization-based framework for (i) ab initio and experimental data driven mechanistic modeling and (ii) optimal catalyst design of heterogeneous catalytic systems. Both cases are formulated as a nonlinear optimization problem that is subject to a mean-field microkinetic model and thermodynamic consistency requirements as constraints, for which we seek sparse solutions through a ridge (L 2 regularization) penalty. The solution procedure involves an iterative sequence of forward simulation of the differential algebraic equations pertaining to the microkinetic model using a numerical tool capable of handling stiff systems, sensitivity calculations using linear algebra, and gradient-based nonlinear optimization.more » A multistart approach is used to explore the solution space, and a hierarchical clustering procedure is implemented for statistically classifying potentially competing solutions. An example of methanol synthesis through hydrogenation of CO and CO 2 on a Cu-based catalyst is used to illustrate the framework. The framework is fast, is robust, and can be used to comprehensively explore the model solution and design space of any heterogeneous catalytic system.« less

Life Support Catalyst Regeneration Using Ionic Liquids and In Situ Resources

NASA Technical Reports Server (NTRS)

Abney, Morgan B.; Karr, Laurel J.; Paley, Mark S.; Donovan, David N.; Kramer, Teersa J.

2016-01-01

Oxygen recovery from metabolic carbon dioxide is an enabling capability for long-duration manned space flight. Complete recovery of oxygen (100%) involves the production of solid carbon. Catalytic approaches for this purpose, such as Bosch technology, have been limited in trade analyses due in part to the mass penalty for high catalyst resupply caused by carbon fouling of the iron or nickel catalyst. In an effort to mitigate this challenge, several technology approaches have been proposed. These approaches have included methods to prolong the life of the catalysts by increasing the total carbon mass loading per mass catalyst, methods for simplified catalyst introduction and removal to limit the resupply container mass, methods of using in situ resources, and methods to regenerate catalyst material. Research and development into these methods is ongoing, but only use of in situ resources and/or complete regeneration of catalyst material has the potential to entirely eliminate the need for resupply. The use of ionic liquids provides an opportunity to combine these methods in a technology approach designed to eliminate the need for resupply of oxygen recovery catalyst. Here we describe the results of an initial feasibility study using ionic liquids and in situ resources for life support catalyst regeneration, we discuss the key challenges with the approach, and we propose future efforts to advance the technology.

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

Controlling Catalyst Bulk Reservoir Effects for Monolayer Hexagonal Boron Nitride CVD.

PubMed

Caneva, Sabina; Weatherup, Robert S; Bayer, Bernhard C; Blume, Raoul; Cabrero-Vilatela, Andrea; Braeuninger-Weimer, Philipp; Martin, Marie-Blandine; Wang, Ruizhi; Baehtz, Carsten; Schloegl, Robert; Meyer, Jannik C; Hofmann, Stephan

2016-02-10

Highly controlled Fe-catalyzed growth of monolayer hexagonal boron nitride (h-BN) films is demonstrated by the dissolution of nitrogen into the catalyst bulk via NH3 exposure prior to the actual growth step. This "pre-filling" of the catalyst bulk reservoir allows us to control and limit the uptake of B and N species during borazine exposure and thereby to control the incubation time and h-BN growth kinetics while also limiting the contribution of uncontrolled precipitation-driven h-BN growth during cooling. Using in situ X-ray diffraction and in situ X-ray photoelectron spectroscopy combined with systematic growth calibrations, we develop an understanding and framework for engineering the catalyst bulk reservoir to optimize the growth process, which is also relevant to other 2D materials and their heterostructures.

Boron- and Nitrogen-Substituted Graphene Nanoribbons as Efficient Catalysts for Oxygen Reduction Reaction

DOE PAGES

Gong, Yongji; Fei, Huilong; Zou, Xiaolong; ...

2015-02-02

Here, we show that nanoribbons of boron- and nitrogen-substituted graphene can be used as efficient electrocatalysts for the oxygen reduction reaction (ORR). Optimally doped graphene nanoribbons made into three-dimensional porous constructs exhibit the highest onset and half-wave potentials among the reported metal-free catalysts for this reaction and show superior performance compared to commercial Pt/C catalyst. Moreover, this catalyst possesses high kinetic current density and four-electron transfer pathway with low hydrogen peroxide yield during the reaction. Finally, first-principles calculations suggest that such excellent electrocatalytic properties originate from the abundant edges of boron- and nitrogen-codoped graphene nanoribbons, which significantly reduce the energymore » barriers of the rate-determining steps of the ORR reaction.« less

Synthesis, characterization and application of a nano-manganese-catalyst as an efficient solid catalyst for solvent free selective oxidation of ethylbenzene, cyclohexene, and benzylalcohol

NASA Astrophysics Data System (ADS)

Habibi, Davood; Faraji, Ali Reza

2013-07-01

The object of this study is to synthesize the heterogeneous Mn-nano-catalyst (MNC) which has been covalently anchored on a modified nanoscaleSiO2/Al2O3, and characterized by FT-IR, UV-Vis, CHN elemental analysis, EDS, TEM, and EDX. The method is efficient for the highly selective oxidation of ethylbenzene, cyclohexene, and benzylalcohol without the need to any solvents, using tert-butyl hydroperoxide (TBHP) as an oxidant. Oxidation of ethylbenzene, cyclohexene, and benzylalcohol gave acetophenone, 2-cyclohexene-1-one and benzaldehyde, respectively, as major products. Reaction conditions have been optimized by considering the effect of various factors such as reaction time, amounts of substrates and oxidant, Mn-nano-catalyst and application of various solvents.

Molecular catalysis science: Perspective on unifying the fields of catalysis.

PubMed

Ye, Rong; Hurlburt, Tyler J; Sabyrov, Kairat; Alayoglu, Selim; Somorjai, Gabor A

2016-05-10

Colloidal chemistry is used to control the size, shape, morphology, and composition of metal nanoparticles. Model catalysts as such are applied to catalytic transformations in the three types of catalysts: heterogeneous, homogeneous, and enzymatic. Real-time dynamics of oxidation state, coordination, and bonding of nanoparticle catalysts are put under the microscope using surface techniques such as sum-frequency generation vibrational spectroscopy and ambient pressure X-ray photoelectron spectroscopy under catalytically relevant conditions. It was demonstrated that catalytic behavior and trends are strongly tied to oxidation state, the coordination number and crystallographic orientation of metal sites, and bonding and orientation of surface adsorbates. It was also found that catalytic performance can be tuned by carefully designing and fabricating catalysts from the bottom up. Homogeneous and heterogeneous catalysts, and likely enzymes, behave similarly at the molecular level. Unifying the fields of catalysis is the key to achieving the goal of 100% selectivity in catalysis.

Molecular catalysis science: Perspective on unifying the fields of catalysis

PubMed Central

Ye, Rong; Hurlburt, Tyler J.; Sabyrov, Kairat; Alayoglu, Selim; Somorjai, Gabor A.

2016-01-01

Colloidal chemistry is used to control the size, shape, morphology, and composition of metal nanoparticles. Model catalysts as such are applied to catalytic transformations in the three types of catalysts: heterogeneous, homogeneous, and enzymatic. Real-time dynamics of oxidation state, coordination, and bonding of nanoparticle catalysts are put under the microscope using surface techniques such as sum-frequency generation vibrational spectroscopy and ambient pressure X-ray photoelectron spectroscopy under catalytically relevant conditions. It was demonstrated that catalytic behavior and trends are strongly tied to oxidation state, the coordination number and crystallographic orientation of metal sites, and bonding and orientation of surface adsorbates. It was also found that catalytic performance can be tuned by carefully designing and fabricating catalysts from the bottom up. Homogeneous and heterogeneous catalysts, and likely enzymes, behave similarly at the molecular level. Unifying the fields of catalysis is the key to achieving the goal of 100% selectivity in catalysis. PMID:27114536

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

Ye, Rong; Hurlburt, Tyler J.; Sabyrov, Kairat

Colloidal chemistry is used to control the size, shape, morphology, and composition of metal nanoparticles. Model catalysts as such are applied to catalytic transformations in the three types of catalysts: heterogeneous, homogeneous, and enzymatic. Real-time dynamics of oxidation state, coordination, and bonding of nanoparticle catalysts are put under the microscope using surface techniques such as sumfrequency generation vibrational spectroscopy and ambient pressure X-ray photoelectron spectroscopy under catalytically relevant conditions. It was demonstrated that catalytic behavior and trends are strongly tied to oxidation state, the coordination number and crystallographic orientation of metal sites, and bonding and orientation of surface adsorbates. Itmore » was also found that catalytic performance can be tuned by carefully designing and fabricating catalysts from the bottom up. Homogeneous and h eterogeneous catalysts, and likely enzymes, behave similarly at the molecular level. Finally, unifying the fields of catalysis is the key to achieving the goal of 100% selectivity in catalysis.« 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

Au and Pt nanoparticle supported catalysts tailored for H-2 production: From models to powder catalysts

DOE PAGES

T. D. Nguyen-Phan; Baber, A. E.; Rodriguez, J. A.; ...

2015-12-10

The use of metal nanoparticles (NPs), including Au and Pt, supported over oxides has been pivotal, and is ever increasing in enabling catalytic reactions which target the production of hydrogen. We review here the most recent works pertaining to the fundamental understanding of the structure, morphology, growth, characterization, and intrinsic phenomenological properties of Au– and Pt– based catalysts that influence the reactivity and selectivity to target hydrogen production. We draw on surface science and theoretical methods of model and powder catalysts using high resolution imaging, spectroscopy, scattering experiments, and theoretical studies. Based on these insights we identify key aspects ofmore » studies of supported metal nanoparticle (NP) catalysts for several reactions. The main focus of this review is on the intersection of catalytic chemistry related to the water-gas shift (WGS), oxygenate steam reforming (OSR), and solarassisted reactions (SAR).« less

Biodiesel production from municipal secondary sludge.

PubMed

Kumar, Manish; Ghosh, Pooja; Khosla, Khushboo; Thakur, Indu Shekhar

2016-09-01

In the present study, feasibility of biodiesel production from freeze dried sewage sludge was studied and its yield was enhanced by optimization of the in situ transesterification conditions (temperature, catalyst and concentration of sludge solids). Optimized conditions (45°C, 5% catalyst and 0.16g/mL sludge solids) resulted in a 20.76±0.04% biodiesel yield. The purity of biodiesel was ascertained by GC-MS, FT-IR and NMR ((1)H and (13)C) spectroscopy. The biodiesel profile obtained revealed the predominance of methyl esters of fatty acids such as oleic, palmitic, myristic, stearic, lauric, palmitoleic and linoleic acids indicating potential use of sludge as a biodiesel feedstock. Copyright © 2016 Elsevier Ltd. All rights reserved.

Biodiesel production from multi feedstock as feed with direct ultrasound assisted

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

Widayat, E-mail: yayat-99@yahoo.com; Center of Biomass and Renewable Energy; Satriadi, H.

The objective of this study was to optimize of ratio oil type, ratio oil to methanol and catalyst concentration. The optimization was used Central Composite Design (CCD). Biodiesel was produced with multi stock oil as feed and conducted in direct ultrasonic radiation. Biosonic equiped with ultrasonic generator with a frequency of 28 kHz. Biodiesel produced at a pressure of 1 atm, reaction time of 60 min and temperature 60 ° C. The optimum conditions of volume ratio for Palm and Coconut oil 4:1, KOH catalyst concentration 0.3% and methanol to oil mole ratio 7:1. Biodiesel yield was determined under thismore » condition and obtained 81.105%.« less

Biodiesel production from multi feedstock as feed with direct ultrasound assisted

NASA Astrophysics Data System (ADS)

Widayat, Satriadi, H.; Nafiega, N. Favian; Dipo, Rheza; Okvitarini, Alimin, A. J.; Ali, Mas Fawzi Mohd

2015-12-01

The objective of this study was to optimize of ratio oil type, ratio oil to methanol and catalyst concentration. The optimization was used Central Composite Design (CCD). Biodiesel was produced with multi stock oil as feed and conducted in direct ultrasonic radiation. Biosonic equiped with ultrasonic generator with a frequency of 28 kHz. Biodiesel produced at a pressure of 1 atm, reaction time of 60 min and temperature 60 ° C. The optimum conditions of volume ratio for Palm and Coconut oil 4:1, KOH catalyst concentration 0.3% and methanol to oil mole ratio 7:1. Biodiesel yield was determined under this condition and obtained 81.105%.

Hybrid Mo-CT nanowires as highly efficient catalysts for direct dehydrogenation of isobutane.

PubMed

Mu, Jiali; Shi, Junjun; France, Liam John; Wu, Yongshan; Zeng, Qiang; Liu, Baoan; Jiang, Lilong; Long, Jinxing; Li, Xuehui

2018-06-20

Direct dehydrogenation of isobutane to isobutene has drawn extensive attention for synthesizing various chemicals. The Mo-based catalysts hold promise as an alternative to the toxic CrOx- and scarce Pt-based catalysts. However, the low activity and rapid deactivation of the Mo-based catalysts greatly hinder their practical applications. Herein, we demonstrate a feasible approach towards the development of efficient and non-noble metal dehydrogenation catalysts basing on Mo-CT hybrid nanowires calcined at different temperatures. In particular, the optimal Mo-C700 catalyst exhibits isobutane consumption rate of 3.9 mmol g-1 h-1, and isobutene selectivity of 73% with production rate of 2.8 mmol g-1 h-1. The catalyst maintained 90% of its initial activity after 50 h of reaction. Extensive characterizations reveal that such prominent performance is well-correlated with the adsorption abilities of isobutane and isobutene, and the formation of η-MoC species. By contrast, the generation of β-Mo2C crystalline phase during long-term reaction causes minor decline in activity. Compared to MoO2 and β-Mo2C, η-MoC plays a role more likely in suppressing the cracking reaction. This work demonstrates a feasible approach towards the development of efficient and non-noble metal dehydrogenation catalysts.

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.

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.

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.

Catalyst and Fuel Interactions to Optimize Endothermic Cooling

DTIC Science & Technology

2016-08-30

research , special, group study, etc. 3. DATES COVERED. Indicate the time during which the work was performed and the report was written, e.g., Jun 1997...information from the experimental measurements. In close collaboration with experimental group of Anderson, we completed theoretical studies on the effect...observed shifts. 3. Methane Activation by Controlling s- and d-states in Iron-based Single Site Catalysts In a recent experimental finding Guo et

One-pot synthesis of a PtPd dendritic nanocube cage superstructure on graphenes as advanced catalysts for oxygen reduction

NASA Astrophysics Data System (ADS)

Zheng, Yuanyuan; Qiao, Junhua; Yuan, Junhua; Shen, Jianfeng; Wang, Ai-Jun; Gong, Peijun

2018-03-01

How to use Pt economically and efficiently in the oxygen reduction reaction (ORR) is of theoretical and practical significance for the industrialization of the proton-exchange membrane fuel cells. In order to minimize Pt consumption and optimize the ORR performance, the ORR catalysts are recommended to be designed as a porous nanostructure. Herein, we report a one-pot solvothermal strategy to prepare PtPd dendritic nanocube cages via a galvanic replacement mechanism triggered by an I- ion. These PtPd alloy crystals are nanoporous, and uniformly dispersed on reduced graphene oxides (RGOs). The size of the PtPd dendritic nanocube cages can be easily tuned from 20-80 nm by controlling their composition. Their composition is optimized to be 1:5 Pt/Pd atomic ratio for these RGO-supported PtPd dendritic nanocages. This catalyst shows superior ORR performance with a specific activity of 2.01 mA cm-2 and a mass activity of 4.45 A mg-1 Pt, far above those for Pt/C catalysts (0.288 mA cm-2 for specific activity, and 0.21 A mg-1 Pt for mass activity). In addition to ORR activity, it also exhibits robust durability with almost negligible decay in ORR mass activity after 10 000 voltammetric cycling.

Finding Furfural Hydrogenation Catalysts via Predictive Modelling

PubMed Central

Strassberger, Zea; Mooijman, Maurice; Ruijter, Eelco; Alberts, Albert H; Maldonado, Ana G; Orru, Romano V A; Rothenberg, Gadi

2010-01-01

Abstract We combine multicomponent reactions, catalytic performance studies and predictive modelling to find transfer hydrogenation catalysts. An initial set of 18 ruthenium-carbene complexes were synthesized and screened in the transfer hydrogenation of furfural to furfurol with isopropyl alcohol complexes gave varied yields, from 62% up to >99.9%, with no obvious structure/activity correlations. Control experiments proved that the carbene ligand remains coordinated to the ruthenium centre throughout the reaction. Deuterium-labelling studies showed a secondary isotope effect (kH:kD=1.5). Further mechanistic studies showed that this transfer hydrogenation follows the so-called monohydride pathway. Using these data, we built a predictive model for 13 of the catalysts, based on 2D and 3D molecular descriptors. We tested and validated the model using the remaining five catalysts (cross-validation, R2=0.913). Then, with this model, the conversion and selectivity were predicted for four completely new ruthenium-carbene complexes. These four catalysts were then synthesized and tested. The results were within 3% of the model’s predictions, demonstrating the validity and value of predictive modelling in catalyst optimization. PMID:23193388

Catalytic Formylation of Primary and Secondary Amines with CO2 and H2 Using Abundant-Metal Catalysts.

PubMed

Affan, Mohammad A; Jessop, Philip G

2017-06-19

Catalytic hydrogenation of CO 2 is an efficient and selective way to prepare formic acid derivatives, but most of the highly active catalysts used for this purpose require precious metals. In this study, in situ abundant-metal complexes have been evaluated as potential catalysts for CO 2 hydrogenation to prepare formamides, including N-formylmorpholine, 2-ethylhexylformamide, and dimethylformamide, from the corresponding amines. From these initial screening results, the most active catalysts for these reactions were found to be MX 2 /dmpe in situ catalysts (M = Fe(II), Ni(II); X = Cl - , CH 3 CO 2 - , acac - ; dmpe = 1,2-bis(dimethylphosphino)ethane) in DMSO. The optimal reaction conditions were found to be 100-135 °C and a total pressure of 100 bar. Morpholine was formylated with a TON value of up to 18000, which is the highest TON for the hydrogenation of CO 2 to formamides using any abundant-metal-phosphine complex. With an appropriate selection of catalyst and reaction conditions, >90-98% conversion of amine to formamide could be achieved.

A palladium-doped ceria@carbon core-sheath nanowire network: a promising catalyst support for alcohol electrooxidation reactions.

PubMed

Tan, Qiang; Du, Chunyu; Sun, Yongrong; Du, Lei; Yin, Geping; Gao, Yunzhi

2015-08-28

A novel palladium-doped ceria and carbon core-sheath nanowire network (Pd-CeO2@C CSNWN) is synthesized by a template-free and surfactant-free solvothermal process, followed by high temperature carbonization. This hierarchical network serves as a new class of catalyst support to enhance the activity and durability of noble metal catalysts for alcohol oxidation reactions. Its supported Pd nanoparticles, Pd/(Pd-CeO2@C CSNWN), exhibit >9 fold increase in activity toward the ethanol oxidation over the state-of-the-art Pd/C catalyst, which is the highest among the reported Pd systems. Moreover, stability tests show a virtually unchanged activity after 1000 cycles. The high activity is mainly attributed to the superior oxygen-species releasing capability of Pd-doped CeO2 nanowires by accelerating the removal of the poisoning intermediate. The unique interconnected one-dimensional core-sheath structure is revealed to facilitate immobilization of the metal catalysts, leading to the improved durability. This core-sheath nanowire network opens up a new strategy for catalyst performance optimization for next-generation fuel cells.

Degradation of sulfamethazine using Fe3O4-Mn3O4/reduced graphene oxide hybrid as Fenton-like catalyst.

PubMed

Wan, Zhong; Wang, Jianlong

2017-02-15

In this paper, Fe 3 O 4 -Mn 3 O 4 /reduced graphene oxide (RGO) hybrid was synthesized through polyol process and impregnation method and used as heterogeneous Fenton-like catalyst for degradation of sulfamethazine (SMT) in aqueous solution. The hybrid catalyst had higher catalytic efficiency compared with Fe 3 O 4 -Mn 3 O 4 and Mn 3 O 4 as catalyst for degradation of SMT . The effects of pH value, H 2 O 2 concentration, catalyst dosage, initial SMT concentration and temperature on SMT degradation were investigated. The removal efficiency of SMT was about 98% at following optimal conditions: pH=3, T=35°C, Fe 3 O 4 /Mn 3 O 4 -RGO composites=0.5g/L, H 2 O 2 =6mM. The inhibitor experiments indicated that the main active species was hydroxyl radicals (·OH) on catalyst surface. At last, the possible catalytic mechanism was proposed. Copyright © 2016 Elsevier B.V. All rights reserved.

Development of membrane electrode assembly for high temperature proton exchange membrane fuel cell by catalyst coating membrane method

NASA Astrophysics Data System (ADS)

Liang, Huagen; Su, Huaneng; Pollet, Bruno G.; Pasupathi, Sivakumar

2015-08-01

Membrane electrode assembly (MEA), which contains cathode and anode catalytic layer, gas diffusion layers (GDL) and electrolyte membrane, is the key unit of a PEMFC. An attempt to develop MEA for ABPBI membrane based high temperature (HT) PEMFC is conducted in this work by catalyst coating membrane (CCM) method. The structure and performance of the MEA are examined by scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS) and I-V curve. Effects of the CCM preparation method, Pt loading and binder type are investigated for the optimization of the single cell performance. Under 160 °C and atmospheric pressure, the peak power density of the MEA, with Pt loading of 0.5 mg cm-2 and 0.3 mg cm-2 for the cathode and the anode, can reach 277 mW cm-2, while a current density of 620 A cm-2 is delivered at the working voltage of 0.4 V. The MEA prepared by CCM method shows good stability operating in a short term durability test: the cell voltage maintained at ∼0.45 V without obvious drop when operated at a constant current density of 300 mA cm-2 and 160 °C under ambient pressure for 140 h.

Optimization of Synthesis Conditions of Carbon Nanotubes via Ultrasonic-Assisted Floating Catalyst Deposition Using Response Surface Methodology

PubMed Central

Mohammadian, Narges; Ghoreishi, Seyyed M.; Hafeziyeh, Samira; Saeidi, Samrand; Dionysiou, Dionysios D.

2018-01-01

The growing use of carbon nanotubes (CNTs) in a plethora of applications has provided to us a motivation to investigate CNT synthesis by new methods. In this study, ultrasonic-assisted chemical vapor deposition (CVD) method was employed to synthesize CNTs. The difficulty of controlling the size of clusters and achieving uniform distribution—the major problem in previous methods—was solved by using ultrasonic bath and dissolving ferrocene in xylene outside the reactor. The operating conditions were optimized using a rotatable central composite design (CCD), which helped optimize the operating conditions of the method. Response surface methodology (RSM) was used to analyze these experiments. Using statistical software was very effective, considering that it decreased the number of experiments needed to achieve the optimum conditions. Synthesis of CNTs was studied as a function of three independent parameters viz. hydrogen flow rate (120–280 cm3/min), catalyst concentration (2–6 wt %), and synthesis temperature (800–1200 °C). Optimum conditions for the synthesis of CNTs were found to be 3.78 wt %, 184 cm3/min, and 976 °C for catalyst concentration, hydrogen flow rate, and synthesis temperature, respectively. Under these conditions, Raman spectrum indicates high values of (IG/ID), which means high-quality CNTs. PMID:29747451

Ozone assisted oxidation of gaseous PCDD/Fs over CNTs-containing composite catalysts at low temperature.

PubMed

Wang, Qiulin; Tang, Minghui; Peng, Yaqi; Du, Cuicui; Lu, Shengyong

2018-05-01

Ozone assisted carbon nanotubes (CNTs) supported vanadium oxide/titanium dioxide (V/Ti-CNTs) or vanadium oxide-manganese oxide/titanium dioxide (V-Mn/Ti-CNTs) catalysts towards gaseous PCDD/Fs (polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans) catalytic oxidations at low temperature (150 °C) were investigated. The removal efficiency (RE) and decomposition efficiency (DE) of PCDD/Fs achieved with V-Mn/Ti-CNTs alone were 95% and 45% at 150 °C under a space velocity (SV) of 14000 h -1 ; yet, these values reached 99% and 91% when catalyst and low concentration (50 ppm) ozone were used in combined. The ozone promotion effect on catalytic activity was further enhanced with the addition of manganese oxide (MnO x ) and CNTs. Adding MnO x and CNTs in V/Ti catalysts facilitated the ozone decomposition (creating more active species on catalyst surface), thus, improved ozone utilization (demanding relatively lower ozone addition concentration). On the other hand, this study threw light upon ozone promotion mechanism based on the comparison of catalyst properties (i.e. components, surface area, surface acidity, redox ability and oxidation state) before and after ozone treatment. The experimental results indicate that a synergistic effect exists between catalyst and ozone: ozone is captured and decomposed on catalyst surface; meanwhile, the catalyst properties are changed by ozone in return. Reactive oxygen species from ozone decomposition and the accompanied catalyst properties optimization are crucial reasons for catalyst activation at low temperature. Copyright © 2018 Elsevier Ltd. All rights reserved.

Carbohydrates as efficient catalysts for the hydration of α-amino nitriles.

PubMed

Chitale, Sampada; Derasp, Joshua S; Hussain, Bashir; Tanveer, Kashif; Beauchemin, André M

2016-11-01

Directed hydration of α-amino nitriles was achieved under mild conditions using simple carbohydrates as catalysts exploiting temporary intramolecularity. A broadly applicable procedure using both formaldehyde and NaOH as catalysts efficiently hydrated a variety of primary and secondary susbtrates, and allowed the hydration of enantiopure substrates to proceed without racemization. This work also provides a rare comparison of the catalytic activity of carbohydrates, and shows that the simple aldehydes at the basis of chemical evolution are efficient organocatalysts mimicking the function of hydratase enzymes. Optimal catalytic efficiency was observed with destabilized aldehydes, and with difficult substrates only simple carbohydrates such as formaldehyde and glycolaldehyde proved reliable.

Isomerization of glucose into fructose by environmentally friendly Fe/β zeolite catalysts.

PubMed

Xu, Siquan; Zhang, Lei; Xiao, Kehao; Xia, Haian

2017-06-29

Herein, the environmentally friendly Fe/β zeolite for glucose isomerization to fructose in aqueous media was reported for the first time. The effects of various reaction conditions including reaction temperature, reaction time, catalyst dosage, etc. on the isomerization reaction over Fe/β zeolite were studied in detail. Under the optimized conditions, yield of fructose higher than 20% were obtained. Moreover, the Fe/β zeolite catalysts were stable and remained constant catalytic activity after five consecutive runs. The possible active Fe species for isomerization of glucose in Fe/β zeolite is also discussed. Copyright © 2017 Elsevier Ltd. All rights reserved.

Mn-Catalyzed Highly Efficient Aerobic Oxidative Hydroxyazidation of Olefins: A Direct Approach to β-Azido Alcohols.

PubMed

Sun, Xiang; Li, Xinyao; Song, Song; Zhu, Yuchao; Liang, Yu-Feng; Jiao, Ning

2015-05-13

An efficient Mn-catalyzed aerobic oxidative hydroxyazidation of olefins for synthesis of β-azido alcohols has been developed. The aerobic oxidative generation of azido radical employing air as the terminal oxidant is disclosed as the key process for this transformation. The reaction is appreciated by its broad substrate scope, inexpensive Mn-catalyst, high efficiency, easy operation under air, and mild conditions at room temperature. This chemistry provides a novel approach to high value-added β-azido alcohols, which are useful precursors of aziridines, β-amino alcohols, and other important N- and O-containing heterocyclic compounds. This chemistry also provides an unexpected approach to azido substituted cyclic peroxy alcohol esters. A DFT calculation indicates that Mn catalyst plays key dual roles as an efficient catalyst for the generation of azido radical and a stabilizer for peroxyl radical intermediate. Further calculation reasonably explains the proposed mechanism for the control of C-C bond cleavage or for the formation of β-azido alcohols.

Catalytic Transfer Hydrogenation of Furfural to Furfuryl Alcohol over Nitrogen-Doped Carbon-Supported Iron Catalysts.

PubMed

Li, Jiang; Liu, Jun-Ling; Zhou, Hong-Jun; Fu, Yao

2016-06-08

Iron-based heterogeneous catalysts, which were generally prepared by pyrolysis of iron complexes on supports at elevated temperature, were found to be capable of catalyzing the transfer hydrogenation of furfural (FF) to furfuryl alcohol (FFA). The effects of metal precursor, nitrogen precursor, pyrolysis temperature, and support on catalytic performance were examined thoroughly, and a comprehensive study of the reaction parameters was also performed. The highest selectivity of FFA reached 83.0 % with a FF conversion of 91.6 % under the optimal reaction condition. Catalyst characterization suggested that iron cations coordinated by pyridinic nitrogen functionalities were responsible for the enhanced catalytic activity. The iron catalyst could be recycled without significant loss of catalytic activity for five runs, and the destruction of the nitrogen-iron species, the presence of crystallized Fe2 O3 phase, and the pore structure change were the main reasons for catalyst deactivation. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

An economically viable synthesis of biodiesel from a crude Millettia pinnata oil of Jharkhand, India as feedstock and crab shell derived catalyst.

PubMed

Madhu, Devarapaga; Chavan, Supriya B; Singh, Veena; Singh, Bhaskar; Sharma, Yogesh C

2016-08-01

Biodiesel has emerged as a prominent source to replace petroleum diesel. The cost incurred in the production of biodiesel is higher than that for refining of crude oil to obtain mineral diesel. The heterogeneous catalyst was prepared from crab shells by calcining the crushed mass at 800°C. The solid waste catalyst was characterized with XRD, XPS, BET, SEM-EDS, and FT-IR. Millettia pinnata (karanja) oil extracted from its seeds was used as a feedstock for the synthesis of biodiesel. Biodiesel was synthesized through esterification followed by transesterification in a two-step process. Characterization of biodiesel was done using proton NMR spectroscopy. Reaction parameters such as reaction time, reaction temperature, concentration of catalyst and stirrer speed were optimized. Reusability of catalyst was checked and found that there was no loss of catalytic activity up to five times. Copyright © 2016. Published by Elsevier Ltd.

A facile self-assembly approach to prepare palladium/carbon nanotubes catalyst for the electro-oxidation of ethanol

NASA Astrophysics Data System (ADS)

Wen, Cuilian; Zhang, Xinyuan; Wei, Ying; Zhang, Teng; Chen, Changxin

2018-02-01

A facile self-assembly approach is reported to prepare palladium/carbon nanotubes (Pd/CNTs) catalyst for the electro-oxidation of ethanol. In this method, the Pd-oleate/CNTs was decomposed into the Pd/CNTs at an optimal temperature of 195 °C in air, in which no inert gas is needed for the thermal decomposition process due to the low temperature used and the decomposed products are also environmental friendly. The prepared Pd/CNTs catalyst has a high metallic Pd0 content and the Pd particles in the catalyst are disperse, uniform-sized with an average size of ˜2.1 nm, and evenly distributed on the CNTs. By employing our strategy, the problems including the exfoliation of the metal particles from the CNTs and the aggregation of the metal particles can be solved. Comparing with the commercial Pd/C one, the prepared Pd/CNTs catalyst exhibits a much higher electrochemical activity and stability for the electro-oxidation of ethanol in the direct ethanol fuel cells.

Pt/Mo 2C/C-cp as a highly active and stable catalyst for ethanol electrooxidation

DOE PAGES

Lin, Lili; Sheng, Wenchao; Yao, Siyu; ...

2017-02-09

Here, a Pt/Mo 2C/C-cp electrocatalyst with optimized Pt-Mo 2C chemical bonding is synthesized and evaluated for the ethanol oxidation reaction (EOR). The chemical bonding of Mo 2C to Pt particles renders exceptional EOR activity at low potentials, which is 15 and 2.5 times higher than Pt/C and commercial 40% PtRu/C, respectively, at 0.6 V (vs. RHE). The stability of the Pt/Mo 2C/C-cp electrocatalyst is comparable to the commercial 40% PtRu/C catalyst. CO stripping test demonstrates the existence of highly active sites for CO oxidation on the Pt/Mo 2C/C-cp catalyst. In-situ infrared spectroscopic studies of EOR reveal that the excellent anti-poisoningmore » ability of the Pt/Mo 2C/C-cp catalyst is related to the relatively weak binding of carbonyl intermediates over the Pt/Mo 2C/C-cp catalysts.« less

Pt/Mo 2C/C-cp as a highly active and stable catalyst for ethanol electrooxidation

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

Lin, Lili; Sheng, Wenchao; Yao, Siyu

Here, a Pt/Mo 2C/C-cp electrocatalyst with optimized Pt-Mo 2C chemical bonding is synthesized and evaluated for the ethanol oxidation reaction (EOR). The chemical bonding of Mo 2C to Pt particles renders exceptional EOR activity at low potentials, which is 15 and 2.5 times higher than Pt/C and commercial 40% PtRu/C, respectively, at 0.6 V (vs. RHE). The stability of the Pt/Mo 2C/C-cp electrocatalyst is comparable to the commercial 40% PtRu/C catalyst. CO stripping test demonstrates the existence of highly active sites for CO oxidation on the Pt/Mo 2C/C-cp catalyst. In-situ infrared spectroscopic studies of EOR reveal that the excellent anti-poisoningmore » ability of the Pt/Mo 2C/C-cp catalyst is related to the relatively weak binding of carbonyl intermediates over the Pt/Mo 2C/C-cp catalysts.« less

Nanoporous Cu–Al–Co Alloys for Selective Furfural Hydrodeoxygenation to 2-Methylfuran

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

Hutchings, Gregory S.; Luc, Wesley; Lu, Qi

By finding new catalysts for selective and efficient conversion of biomass-derived products to industrially relevant chemicals and fuels, a transition from fossil fuel feedstocks may be achieved. Furfural (C 5H 4O 2) is a platform chemical which may be converted to multiple heterocyclic and ring-opening products, but to date there have been few catalysts which enable selective hydrodeoxygenation to 2-methylfuran (2-MF, C 5H 6O). Here, we present a self-supported nanoporous Cu–Al–Co ternary alloy catalyst with high furfural HDO activity toward 2-MF, achieving up to 66.0% selectivity and 98.2% overall conversion at 513 K with only a ~5 atomic % Comore » composition. Some further analysis over multiple temperature conditions and nominal Co concentrations was performed to examine optimal conditions and tune catalyst performance, and operando X-ray absorption spectroscopy experiments were conducted to elucidate the structure of the catalyst in the reaction environment.« less

Transesterification of edible, non-edible and used cooking oils for biodiesel production using calcined layered double hydroxides as reusable base catalysts.

PubMed

Sankaranarayanan, Sivashunmugam; Antonyraj, Churchil A; Kannan, S

2012-04-01

Fatty acid methyl esters (FAME) were produced from edible, non-edible and used cooking oils with different fatty acid contents by transesterification with methanol using calcined layered double hydroxides (LDHs) as solid base catalysts. Among the catalysts, calcined CaAl2-LDH (hydrocalumite) showed the highest activity with >90% yield of FAME using low methanol:oil molar ratio (<6:1) at 65 °C in 5 h. The activity of the catalyst was attributed to its high basicity as supported by Hammett studies and CO(2)-TPD measurements. The catalyst was successfully reused in up to four cycles. Some of the properties such as density, viscosity, neutralization number and glycerol content of the obtained biodiesel matched well with the standard DIN values. It is concluded that a scalable heterogeneously catalyzed process for production of biodiesel in high yields from a wide variety of triglyceride oils including used oils is possible using optimized conditions. Copyright © 2012 Elsevier Ltd. All rights reserved.

Characteristics of Subfreezing Operation of Polymer Electrolyte Membrane Fuel Cells

NASA Astrophysics Data System (ADS)

Mishler, Jeffrey Harris

Polymer Electrolyte Membrane (PEM) Fuel Cells are capable of high efficiency operation, and are free of NOx, SOx, and CO2 emissions when using hydrogen fuel, and ideally suited for use in transportation applications due to their high power density and low operating temperatures. However, under subfreezing conditions which may be encountered during winter seasons in some areas, product water will freeze within the membrane, cathode side catalyst layer and gas diffusion media, leading to voltage loss and operation failure. Experiments were undertaken in order to characterize the amount and location of water during fuel cell operation. First, in-situ neutron radiography was undertaken on the fuel cells at a normal operating temperature for various operating current densities, inlet relative humidities, and diffusion media hydrophobicities. It was found that more hydrophobic cathode microporous layer (MPL) or hydrophilic anode MPL may result in a larger amount of water transporting back to the anode. The water profiles along the channels were measured and the point of liquid water emergence, where two phase flow begins, was compared to previous models. Secondly, under subfreezing temperatures, neutron imaging showed that water ice product accumulates because of lack of a water removal mechanism. Water was observed under both the lands and channels, and increased almost linearly with time. It is found that most ice exists in the cathode side. With evidence from experimental observation, a cold start model was developed and explained, following existing approaches in the literature. Three stages of cold start are explained: membrane saturation, ice storage in catalyst layer pores, and then ice melting. The voltage losses due to temperature change, increased transport resistance, and reduced electrochemical surface area. The ionic conductivity of the membrane at subfreezing temperatures was modeled. Voltage evolution over time for isothermal cold starts was predicted and validated against experimental data. The ice coverage coefficient was shown to be a key variable in matching with experimental data. From model analysis, it appears that the coulombs of charge passed before operation failure is an important parameter characterizing PEM fuel cell cold start. To investigate the coulombs of charge and its determining factors, PEM fuel cells were constructed to measure the effects of membrane configuration (thickness and initial state), catalyst layer configuration (thickness and ionomer-carbon ratio), current density, and temperature on the quantity. It was found that subfreezing temperature, ionomer-catalyst ratio, and catalyst-layer thickness significantly affect the amount of charge transferred before operational failure, whereas the membrane thickness and initial hydration level have limited effect for the considered cases. In addition, degradation of the catalyst layer was observed and quantified. These results improve the fundamental understanding of characteristics of subfreezing operation and thus are valuable for automobile applications of PEM fuel cells. The model directly relates the material properties to voltage loss, and predicts voltage evolution, thus providing a way for material optimization and diagnostics. Additionally, insights into component design and operating conditions can be used to better optimize the fuel cell for cold start-up of the vehicle.

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.

Hydrodeoxygenation of water-insoluble bio-oil to alkanes using a highly dispersed Pd-Mo catalyst.

PubMed

Duan, Haohong; Dong, Juncai; Gu, Xianrui; Peng, Yung-Kang; Chen, Wenxing; Issariyakul, Titipong; Myers, William K; Li, Meng-Jung; Yi, Ni; Kilpatrick, Alexander F R; Wang, Yu; Zheng, Xusheng; Ji, Shufang; Wang, Qian; Feng, Junting; Chen, Dongliang; Li, Yadong; Buffet, Jean-Charles; Liu, Haichao; Tsang, Shik Chi Edman; O'Hare, Dermot

2017-09-19

Bio-oil, produced by the destructive distillation of cheap and renewable lignocellulosic biomass, contains high energy density oligomers in the water-insoluble fraction that can be utilized for diesel and valuable fine chemicals productions. Here, we show an efficient hydrodeoxygenation catalyst that combines highly dispersed palladium and ultrafine molybdenum phosphate nanoparticles on silica. Using phenol as a model substrate this catalyst is 100% effective and 97.5% selective for hydrodeoxygenation to cyclohexane under mild conditions in a batch reaction; this catalyst also demonstrates regeneration ability in long-term continuous flow tests. Detailed investigations into the nature of the catalyst show that it combines hydrogenation activity of Pd and high density of both Brønsted and Lewis acid sites; we believe these are key features for efficient catalytic hydrodeoxygenation behavior. Using a wood and bark-derived feedstock, this catalyst performs hydrodeoxygenation of lignin, cellulose, and hemicellulose-derived oligomers into liquid alkanes with high efficiency and yield.Bio-oil is a potential major source of renewable fuels and chemicals. Here, the authors report a palladium-molybdenum mixed catalyst for the selective hydrodeoxygenation of water-insoluble bio-oil to mixtures of alkanes with high carbon yield.

Solid-State Water Electrolysis with an Alkaline Membrane

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

Leng, YJ; Chen, G; Mendoza, AJ

2012-06-06

We report high-performance, durable alkaline membrane water electrolysis in a solid-state cell. An anion exchange membrane (AEM) and catalyst layer ionomer for hydroxide ion conduction were used without the addition of liquid electrolyte. At 50 degrees C, an AEM electrolysis cell using iridium oxide as the anode catalyst and Pt black as the cathode catalyst exhibited a current density of 399 mA/cm(2) at 1.80 V. We found that the durability of the AEM-based electrolysis cell could be improved by incorporating a highly durable ionomer in the catalyst layer and optimizing the water feed configuration. We demonstrated an AEM-based electrolysis cellmore » with a lifetime of > 535 h. These first-time results of water electrolysis in a solid-state membrane cell are promising for low-cost, scalable hydrogen production.« less

Study of KOH/Al2O3 as heterogeneous catalyst for biodiesel production via in situ transesterification from microalgae.

PubMed

Ma, Guixia; Hu, Wenrong; Pei, Haiyan; Jiang, Liqun; Ji, Yan; Mu, Ruimin

2015-01-01

Heterogeneous KOH/Al2O3 catalysts, synthesized by the wet impregnation method with different KOH loadings (20-40 wt%) and calcination temperatures from 400°C to 800°C, were used to produce biodiesel from Chlorella vulgaris biomass by in situ transesterification. The highest yield of biodiesel of 89.53±1.58% was achieved at calcination temperature of 700°C for 2 h and 35 wt% loading of KOH, and at the optimal reaction condition of 10 wt% of catalyst content, 8 mL/g of methanol to biomass ratio and at 60°C for 5 h. The characteristics of the catalysts were analysed by X-ray diffraction, scanning electron microscopy and Brunauer-Emmett-Teller.

Catalytic ignition of hydrogen and oxygen propellants

NASA Technical Reports Server (NTRS)

Zurawski, Robert L.; Green, James M.

1988-01-01

An experimental program was conducted to evaluate the catalytic ignition of gaseous hydrogen and oxygen propellants. Shell 405 granular catalyst and a monolithic sponge catalyst were tested. Mixture ratio, mass flow rate, propellant temperature, and back pressure were varied parametrically in testing to determine the operational limits of the catalytic igniter. The test results show that the gaseous hydrogen and oxygen propellant combination can be ignited catalytically using Shell 405 catalyst over a wide range of mixture ratios, mass flow rates, and propellant injection temperatures. These operating conditions must be optimized to ensure reliable ignition for an extended period of time. A cyclic life of nearly 2000, 2 sec pulses at nominal operating conditions was demonstrated with the catalytic igniter. The results of the experimental program and the established operational limits for a catalytic igniter using the Shell 405 catalysts are presented.

Catalytic ignition of hydrogen and oxygen propellants

NASA Technical Reports Server (NTRS)

Zurawski, Robert L.; Green, James M.

1988-01-01

An experimental program was conducted to evaluate the catalytic ignition of gaseous hydrogen and oxygen propellants. Shell 405 granular catalyst and a monolithic sponge catalyst were tested. Mixture ratio, mass flow rate, propellant temperature, and back pressure were varied parametrically in testing to determine the operational limits of the catalytic igniter. The test results show that the gaseous hydrogen and oxygen propellant combination can be ignited catalytically using Shell 405 catalyst over a wide range of mixture ratios, mass flow rates, and propellant injection temperatures. These operating conditions must be optimized to ensure reliable ignition for an extended period of time. A cyclic life of nearly 2000, 2 sec pulses at nominal operating conditions was demonstrated with the catalytic igniter. The results of the experimental program and the established operational limits for a catalytic igniter using the Shell 405 catalyst are presented.

Design and use of nanostructured single-site heterogeneous catalysts for the selective transformation of fine chemicals.

PubMed

Dal Santo, Vladimiro; Liguori, Francesca; Pirovano, Claudio; Guidotti, Matteo

2010-05-26

Nanostructured single-site heterogeneous catalysts possess the advantages of classical solid catalysts, in terms of easy recovery and recycling, together with a defined tailored chemical and steric environment around the catalytically active metal site. The use of inorganic oxide supports with selected shape and porosity at a nanometric level may have a relevant impact on the regio- and stereochemistry of the catalytic reaction. Analogously, by choosing the optimal preparation techniques to obtain spatially isolated and well-characterised active sites, it is possible to achieve performances that are comparable to (or, in the most favourable cases, better than) those obtained with homogeneous systems. Such catalysts are therefore particularly suitable for the transformation of highly-functionalised fine chemicals and some relevant examples where high chemo-, regio- and stereoselectivity are crucial will be described.

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

Yung, M. M.; Cheah, S.; Kuhn, J. N.

The production of biofuels can proceed via a biomass gasification to produce syngas, which can then undergo catalytic conditioning and reforming reactions prior to being sent to a fuel synthesis reactor. Catalysts used for biomass conditioning are plagued by short lifetimes which are a result of, among other things, poisoning. Syngas produced from biomass gasification may contain between 30-300 ppm H2S, depending on the feedstock and gasification conditions, and H2S is a key catalyst poison. In order to overcome catalyst poisoning, either an H2S-tolerant catalyst or an efficient regeneration protocol should be employed. In this study, sulfur K-edge X-ray absorptionmore » near edge spectroscopy (XANES) was used to monitor sulfur species on spent catalyst samples and the transformation of these species from sulfides to sulfates during steam and air regeneration on a Ni/Mg/K/Al2O3 catalyst used to condition biomass-derived syngas. Additionally, nickel K-edge EXAFS and XANES are used to examine the state of nickel species on the catalysts. Post-reaction samples showed the presence of sulfides on the H2S-poisoned nickel catalyst and although some gaseous sulfur species were observed to leave the catalyst bed during regeneration, sulfur remained on the catalyst and a transformation from sulfides to sulfates was observed. The subsequent H2 reduction led to a partial reduction of sulfates back to sulfides. A proposed reaction sequence is presented and recommended regeneration strategies are discussed.« less

Beneficial Role of Copper in the Enhancement of Durability of Ordered Intermetallic PtFeCu Catalyst for Electrocatalytic Oxygen Reduction.

PubMed

Arumugam, Balamurugan; Tamaki, Takanori; Yamaguchi, Takeo

2015-08-05

Design of Pt alloy catalysts with enhanced activity and durability is a key challenge for polymer electrolyte membrane fuel cells. In the present work, we compare the durability of the ordered intermetallic face-centered tetragonal (fct) PtFeCu catalyst for the oxygen reduction reaction (ORR) relative to its counterpart bimetallic catalysts, i.e., the ordered intermetallic fct-PtFe catalyst and the commercial catalyst from Tanaka Kikinzoku Kogyo, TKK-PtC. Although both fct catalysts initially exhibited an ordered structure and mass activity approximately 2.5 times higher than that of TKK-Pt/C, the presence of Cu at the ordered intermetallic fct-PtFeCu catalyst led to a significant enhancement in durability compared to that of the ordered intermetallic fct-PtFe catalyst. The ordered intermetallic fct-PtFeCu catalyst retained more than 70% of its mass activity and electrochemically active surface area (ECSA) over 10 000 durability cycles carried out at 60 °C. In contrast, the ordered intermetallic fct-PtFe catalyst maintained only about 40% of its activity. The temperature of the durability experiment is also shown to be important: the catalyst was more severely degraded at 60 °C than at room temperature. To obtain insight into the observed enhancement in durability of fct-PtFeCu catalyst, a postmortem analysis of the ordered intermetallic fct-PtFeCu catalyst was carried out using scanning transmission electron microscopy-energy dispersive X-ray spectroscopy (STEM-EDX) line scan. The STEM-EDX line scans of the ordered intermetallic fct-PtFeCu catalyst over 10 000 durability cycles showed a smaller degree of Fe and Cu dissolution from the catalyst. Conversely, large dissolution of Fe was identified in the ordered intermetallic fct-PtFe catalyst, indicating a lesser retention of Fe that causes the destruction of ordered structure and gives rise to poor durability. The enhancement in the durability of the ordered intermetallic fct-PtFeCu catalyst is ascribed to the synergistic effects of Cu presence and the ordered structure of catalyst.

Varied morphology carbon nanotubes and method for their manufacture

DOEpatents

Li, Wenzhi; Wen, Jian Guo; Ren, Zhi Feng

2007-01-02

The present invention describes the preparation of carbon nanotubes of varied morphology, catalyst materials for their synthesis. The present invention also describes reactor apparatus and methods of optimizing and controlling process parameters for the manufacture carbon nanotubes with pre-determined morphologies in relatively high purity and in high yields. In particular, the present invention provides methods for the preparation of non-aligned carbon nanotubes with controllable morphologies, catalyst materials and methods for their manufacture.

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.

Artificial Metalloenzymes Based on the Biotin-Streptavidin Technology: Challenges and Opportunities.

PubMed

Heinisch, Tillmann; Ward, Thomas R

2016-09-20

The biotin-streptavidin technology offers an attractive means to engineer artificial metalloenzymes (ArMs). Initiated over 50 years ago by Bayer and Wilchek, the biotin-(strept)avidin techonology relies on the exquisite supramolecular affinity of either avidin or streptavidin for biotin. This versatile tool, commonly referred to as "molecular velcro", allows nearly irreversible anchoring of biotinylated probes within a (strept)avidin host protein. Building upon a visionary publication by Whitesides from 1978, several groups have been exploiting this technology to create artificial metalloenzymes. For this purpose, a biotinylated organometallic catalyst is introduced within (strept)avidin to afford a hybrid catalyst that combines features reminiscent of both enzymes and organometallic catalysts. Importantly, ArMs can be optimized by chemogenetic means. Combining a small collection of biotinylated organometallic catalysts with streptavidin mutants allows generation of significant diversity, thus allowing optimization of the catalytic performance of ArMs. Pursuing this strategy, the following reactions have been implemented: hydrogenation, alcohol oxidation, sulfoxidation, dihydroxylation, allylic alkylation, transfer hydrogenation, Suzuki cross-coupling, C-H activation, and metathesis. In this Account, we summarize our efforts in the latter four reactions. X-ray analysis of various ArMs based on the biotin-streptavidin technology reveals the versatility and commensurability of the biotin-binding vestibule to accommodate and interact with transition states of the scrutinized organometallic transformations. In particular, streptavidin residues at positions 112 and 121 recurrently lie in close proximity to the biotinylated metal cofactor. This observation led us to develop a streamlined 24-well plate streptavidin production and screening platform to optimize the performance of ArMs. To date, most of the efforts in the field of ArMs have focused on the use of purified protein samples. This seriously limits the throughput of the optimization process. With the ultimate goal of complementing natural enzymes in the context of synthetic and chemical biology, we outline the milestones required to ultimately implement ArMs within a cellular environment. Indeed, we believe that ArMs may allow signficant expansion of the natural enzymes' toolbox to access new-to-nature reactivities in vivo. With this ambitious goal in mind, we report on our efforts to (i) activate the biotinylated catalyst precursor upon incorporation within streptavidin, (ii) minimize the effect of the cellular environment on the ArM's performance, and (iii) demonstrate the compatibility of ArMs with natural enzymes in cascade reactions.

Construction of High Activity Titanium Dioxide Crystal Surface Heterostructures and Characterization of Its Basic Properties

NASA Astrophysics Data System (ADS)

Wang, Chunxiao; Li, DanQi; Shen, Tingting; Lu, Cheng; Sun, Jing; Wang, Xikui

2018-01-01

Heterogeneous photocatalytic materials, which combine the advantages of photocatalytic materials and heterojunction, have been developed rapidly in the field of environmental pollution control. In this paper, TiO2 surface heterojunction catalysts with different catalytic activity were prepared by controlling the amount of HF, and their XRD characterization was also carried out. In addition, the optimum amount of HF was determined by photocatalytic degradation of simulated dye wastewater by methylene blue solution. And the optimal amount of catalyst and the optimal pH reaction conditions for degradation experiments were used to screen the highly reactive titania surface heterojunction system and its optimum application conditions. It provides the possibility of application in the degradation of industrial wastewater and environmental treatment.

Production of Biodiesel by Esterification of Free Fatty Acid over Solid Catalyst from Biomass Waste

NASA Astrophysics Data System (ADS)

Mukti, N. I. F.; Sutrisno, B.; Hidayat, A.

2018-05-01

Recently, low cost feedstocks have been utilized to replace vegetable oils in order to improve the economic feasibility of biodiesel. The esterification of free fatty acid (FFA) on Palm Fatty Acid Distillate (PFAD) with methanol using solid catalyst generated from bagasse fly ash is a promising method to convert FFA into biodiesel. In this research, the esterification of FFA on PFAD using the sulfonated bagasse fly ash catalyst was studied. The performances of the catalysts were evaluated in terms of the reaction temperatures, the molar ratios of methanol to PFAD, and the catalyst loading. The effects of the mass ratio of catalyst to oil (1-10%), the molar ratio of methanol to oil (6:1-12:1), and the reaction temperature (40-60°C) were studied for the conversion of PFAD to optimize the reaction conditions. The results showed that the optimum conditions were methanol to PFAD molar ratio of 12:1, the amount of catalyst of 10%wt. of PFAD, and reaction temperature of 6°C. The reusability of the solid acid carbon catalysts was also studied in this work. The catalytic activity decreased up to 38% after third cycle. The significant decline in catalyst esterification activity was due to acid site leaching. The physico-characteristics and acid site densities were analyzed by Nitrogen gas adsorption, surface functional groups by Fourier transform infrared spectroscopy (FT-IR), elemental analysis using X-ray fluorescent (XRF), and acid-base back titration methods for determination of acid density.

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.

Molecular Transporters for Desalination Applications

DTIC Science & Technology

2014-08-02

Collaborative and commercially available state-of-the-art test  Zeolite template based synthesis II. Summary of key results and challenges For the...size setting CNT diameter. The tightest distribution of SWCNTs reported (Lu group, Duke Univ.) was achieved by loading catalyst into zeolite with the...pore size nominally acting to set the size of catalyst on the surface. However nano particles and CNTs grow on the surface of the zeolite , thus

Confirming the key role of Ar+ ion bombardment in the growth feature of nanostructured carbon materials by PECVD

NASA Astrophysics Data System (ADS)

Liu, Yulin; Lin, Jinghuang; Jia, Henan; Chen, Shulin; Qi, Junlei; Qu, Chaoqun; Cao, Jian; Feng, Jicai; Fei, Weidong

2017-11-01

In order to confirm the key role of Ar+ ion bombardment in the growth feature of nanostructured carbon materials (NCMs), here we report a novel strategy to create different Ar+ ion states in situ in plasma enhanced chemical vapor deposition (PECVD) by separating catalyst film from the substrate. Different bombardment environments on either side of the catalyst film were created simultaneously to achieve multi-layered structural NCMs. Results showed that Ar+ ion bombardment is crucial and complex for the growth of NCMs. Firstly, Ar+ ion bombardment has both positive and negative effects on carbon nanotubes (CNTs). On one hand, Ar+ ions can break up the graphic structure of CNTs and suppress thin CNT nucleation and growth. On the other hand, Ar+ ion bombardment can remove redundant carbon layers on the surface of large catalyst particles which is essential for thick CNTs. As a result, the diameter of the CNTs depends on the Ar+ ion state. As for vertically oriented few-layer graphene (VFG), Ar+ ions are essential and can even convert the CNTs into VFG. Therefore, by combining with the catalyst separation method, specific or multi-layered structural NCMs can be obtained by PECVD only by changing the intensity of Ar+ ion bombardment, and these special NCMs are promising in many fields.

Confirming the key role of Ar+ ion bombardment in the growth feature of nanostructured carbon materials by PECVD.

PubMed

Liu, Yulin; Lin, Jinghuang; Jia, Henan; Chen, Shulin; Qi, Junlei; Qu, Chaoqun; Cao, Jian; Feng, Jicai; Fei, Weidong

2017-11-24

In order to confirm the key role of Ar + ion bombardment in the growth feature of nanostructured carbon materials (NCMs), here we report a novel strategy to create different Ar + ion states in situ in plasma enhanced chemical vapor deposition (PECVD) by separating catalyst film from the substrate. Different bombardment environments on either side of the catalyst film were created simultaneously to achieve multi-layered structural NCMs. Results showed that Ar + ion bombardment is crucial and complex for the growth of NCMs. Firstly, Ar + ion bombardment has both positive and negative effects on carbon nanotubes (CNTs). On one hand, Ar + ions can break up the graphic structure of CNTs and suppress thin CNT nucleation and growth. On the other hand, Ar + ion bombardment can remove redundant carbon layers on the surface of large catalyst particles which is essential for thick CNTs. As a result, the diameter of the CNTs depends on the Ar + ion state. As for vertically oriented few-layer graphene (VFG), Ar + ions are essential and can even convert the CNTs into VFG. Therefore, by combining with the catalyst separation method, specific or multi-layered structural NCMs can be obtained by PECVD only by changing the intensity of Ar + ion bombardment, and these special NCMs are promising in many fields.

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

Exceptional oxygen reduction reaction activity and durability of platinum–nickel nanowires through synthesis and post-treatment optimization

DOE PAGES

Alia, Shaun M.; Ngo, Chilan; Shulda, Sarah; ...

2017-04-11

For the first time, extended nanostructured catalysts are demonstrated with both high specific activity (>6000 μA cm Pt –2 at 0.9 V) and high surface areas (>90 m 2 g Pt –1). Platinum–nickel (Pt—Ni) nanowires, synthesized by galvanic displacement, have previously produced surface areas in excess of 90 m 2 g Pt –1, a significant breakthrough in and of itself for extended surface catalysts. Unfortunately, these materials were limited in terms of their specific activity and durability upon exposure to relevant electrochemical test conditions. Through a series of optimized postsynthesis steps, significant improvements were made to the activity (3-fold increasemore » in specific activity), durability (21% mass activity loss reduced to 3%), and Ni leaching (reduced from 7 to 0.3%) of the Pt—Ni nanowires. Finally, these materials show more than a 10-fold improvement in mass activity compared to that of traditional carbon-supported Pt nanoparticle catalysts and offer significant promise as a new class of electrocatalysts in fuel cell applications.« less

Exceptional oxygen reduction reaction activity and durability of platinum–nickel nanowires through synthesis and post-treatment optimization

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

Alia, Shaun M.; Ngo, Chilan; Shulda, Sarah

For the first time, extended nanostructured catalysts are demonstrated with both high specific activity (>6000 μA cm Pt –2 at 0.9 V) and high surface areas (>90 m 2 g Pt –1). Platinum–nickel (Pt—Ni) nanowires, synthesized by galvanic displacement, have previously produced surface areas in excess of 90 m 2 g Pt –1, a significant breakthrough in and of itself for extended surface catalysts. Unfortunately, these materials were limited in terms of their specific activity and durability upon exposure to relevant electrochemical test conditions. Through a series of optimized postsynthesis steps, significant improvements were made to the activity (3-fold increasemore » in specific activity), durability (21% mass activity loss reduced to 3%), and Ni leaching (reduced from 7 to 0.3%) of the Pt—Ni nanowires. Finally, these materials show more than a 10-fold improvement in mass activity compared to that of traditional carbon-supported Pt nanoparticle catalysts and offer significant promise as a new class of electrocatalysts in fuel cell applications.« less

Heteroleptic Copper(I)-Based Complexes for Photocatalysis: Combinatorial Assembly, Discovery, and Optimization.

PubMed

Minozzi, Clémentine; Caron, Antoine; Grenier-Petel, Jean-Christophe; Santandrea, Jeffrey; Collins, Shawn K

2018-05-04

A library of 50 copper-based complexes derived from bisphosphines and diamines was prepared and evaluated in three mechanistically distinct photocatalytic reactions. In all cases, a copper-based catalyst was identified to afford high yields, where new heteroleptic complexes derived from the bisphosphine BINAP displayed high efficiency across all reaction types. Importantly, the evaluation of the library of copper complexes revealed that even when photophysical data is available, it is not always possible to predict which catalyst structure will be efficient or inefficient in a given process, emphasizing the advantages for catalyst structures with high modularity and structural variability. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Molecular catalysis science: Perspective on unifying the fields of catalysis

DOE PAGES

Ye, Rong; Hurlburt, Tyler J.; Sabyrov, Kairat; ...

2016-04-25

Colloidal chemistry is used to control the size, shape, morphology, and composition of metal nanoparticles. Model catalysts as such are applied to catalytic transformations in the three types of catalysts: heterogeneous, homogeneous, and enzymatic. Real-time dynamics of oxidation state, coordination, and bonding of nanoparticle catalysts are put under the microscope using surface techniques such as sumfrequency generation vibrational spectroscopy and ambient pressure X-ray photoelectron spectroscopy under catalytically relevant conditions. It was demonstrated that catalytic behavior and trends are strongly tied to oxidation state, the coordination number and crystallographic orientation of metal sites, and bonding and orientation of surface adsorbates. Itmore » was also found that catalytic performance can be tuned by carefully designing and fabricating catalysts from the bottom up. Homogeneous and h eterogeneous catalysts, and likely enzymes, behave similarly at the molecular level. Finally, unifying the fields of catalysis is the key to achieving the goal of 100% selectivity in catalysis.« less

Highly selective plasma-activated copper catalysts for carbon dioxide reduction to ethylene

DOE PAGES

Mistry, Hemma; Varela, Ana Sofia; Bonifacio, Cecile S.; ...

2016-06-30

There is an urgent need to develop technologies that use renewable energy to convert waste products such as carbon dioxide into hydrocarbon fuels. Carbon dioxide can be electrochemically reduced to hydrocarbons over copper catalysts, although higher efficiency is required. We have developed oxidized copper catalysts displaying lower overpotentials for carbon dioxide electroreduction and record selectivity towards ethylene (60%) through facile and tunable plasma treatments. Herein we provide insight into the improved performance of these catalysts by combining electrochemical measurements with microscopic and spectroscopic characterization techniques. Operando X-ray absorption spectroscopy and cross-sectional scanning transmission electron microscopy show that copper oxides aremore » surprisingly resistant to reduction and copper + species remain on the surface during the reaction. Furthermore, our results demonstrate that the roughness of oxide-derived copper catalysts plays only a partial role in determining the catalytic performance, while the presence of copper + is key for lowering the onset potential and enhancing ethylene selectivity.« less

One-pot aldol condensation and hydrodeoxygenation of biomass-derived carbonyl compounds for biodiesel synthesis.

PubMed

Faba, Laura; Díaz, Eva; Ordóñez, Salvador

2014-10-01

Integrating reaction steps is of key interest in the development of processes for transforming lignocellulosic materials into drop-in fuels. We propose a procedure for performing the aldol condensation (reaction between furfural and acetone is taken as model reaction) and the total hydrodeoxygenation of the resulting condensation adducts in one step, yielding n-alkanes. Different combinations of catalysts (bifunctional catalysts or mechanical mixtures), reaction conditions, and solvents (aqueous and organic) have been tested for performing these reactions in an isothermal batch reactor. The results suggest that the use of bifunctional catalysts and aqueous phase lead to an effective integration of both reactions. Therefore, selectivities to n-alkanes higher than 50% were obtained using this catalyst at typical hydrogenation conditions (T=493 K, P=4.5 MPa, 24 h reaction time). The use of organic solvent, carbonaceous supports, or mechanical mixtures of monofunctional catalysts leads to poorer results owing to side effects; mainly, hydrogenation of reactants and adsorption processes. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Efficient and Highly Selective Solvent-Free Oxidation of Primary Alcohols to Aldehydes Using Bucky Nanodiamond.

PubMed

Lin, Yangming; Wu, Kuang-Hsu Tim; Yu, Linhui; Heumann, Saskia; Su, Dang Sheng

2017-09-11

Selective oxidation of alcohols to aldehydes is widely applicable to the synthesis of various green chemicals. The poor chemoselectivity for complicated primary aldehydes over state-of-the-art metal-free or metal-based catalysts represents a major obstacle for industrial application. Bucky nanodiamond is a potential green catalyst that exhibits excellent chemoselectivity and cycling stability for the selective oxidation of primary alcohols in diverse structures (22 examples, including aromatic, substituted aromatic, unsaturated, heterocyclic, and linear chain alcohols) to their corresponding aldehydes. The results are comparable to reported transition-metal catalysts including conventional Pt/C and Ru/C catalysts for certain substrates under solvent-free conditions. The possible activation process of the oxidant and substrates by the surface oxygen groups and defect species are revealed with model catalysts, ex situ electrochemical measurements, and ex situ attenuated total reflectance. The zigzag edges of sp 2 carbon planes are shown to play a key role in these reactions. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

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.

Calculating the True and Observed Rates of Complex Heterogeneous Catalytic Reactions

NASA Astrophysics Data System (ADS)

Avetisov, A. K.; Zyskin, A. G.

2018-06-01

Equations of the theory of steady-state complex reactions are considered in matrix form. A set of stage stationarity equations is given, and an algorithm is described for deriving the canonic set of stationarity equations with appropriate corrections for the existence of fast stages in a mechanism. A formula for calculating the number of key compounds is presented. The applicability of the Gibbs rule to estimating the number of independent compounds in a complex reaction is analyzed. Some matrix equations relating the rates of dependent and key substances are derived. They are used as a basis to determine the general diffusion stoichiometry relationships between temperature, the concentrations of dependent reaction participants, and the concentrations of key reaction participants in a catalyst grain. An algorithm is described for calculating heat and mass transfer in a catalyst grain with respect to arbitrary complex heterogeneous catalytic reactions.

Use of Ceramic Material (cement Clinker) for the Production of Biodiesel

NASA Astrophysics Data System (ADS)

Soni, Sunny; Agarwal, Madhu

Biodiesel is a renewable liquid fuel made from natural, renewable biological sources such as edible and non edible oils. Over the last years, biodiesel has gained more market due to its benefits and because it appears as the natural substitute for diesel. Reasons for growing interest in biodiesel include its potential for reducing noxious emissions, potential contributions to rural economic development, as an additional demand center for agricultural commodities, and as a way to reduce reliance on foreign oil. Biodiesel was prepared from soybean oil by transesterification with methanol in the presence of cement clinker. Cement clinker was examined as a catalyst for a conversion of soybean oil to fatty acid methyl esters (FAMEs). It can be a promising heterogeneous catalyst for the production of biodiesel fuels from soybean oil because of high activity in the conversion and no leaching in the transesterification reaction. The reaction conditions were optimized. A study for optimizing the reaction parameters such as the reaction temperature, and reaction time, was carried out. The catalyst cement clinker composition was characterized by XRF. The results demonstrate that the cement clinker shows high catalytic performance & it was found that the yield of biodiesel can reach as high as 84.52% after 1 h reaction at 65°C, with a 6:1 molar ratio of methanol to oil, 21 wt% KOH/cement clinker as catalyst.

Iron-Induced Activation of Ordered Mesoporous Nickel Cobalt Oxide Electrocatalyst for the Oxygen Evolution Reaction.

PubMed

Deng, Xiaohui; Öztürk, Secil; Weidenthaler, Claudia; Tüysüz, Harun

2017-06-28

Herein, ordered mesoporous nickel cobalt oxides prepared by the nanocasting route are reported as highly active oxygen evolution reaction (OER) catalysts. By using the ordered mesoporous structure as a model system and afterward elevating the optimal catalysts composition, it is shown that, with a simple electrochemical activation step, the performance of nickel cobalt oxide can be significantly enhanced. The electrochemical impedance spectroscopy results indicated that charge transfer resistance increases for Co 3 O 4 spinel after an activation process, while this value drops for NiO and especially for CoNi mixed oxide significantly, which confirms the improvement of oxygen evolution kinetics. The catalyst with the optimal composition (Co/Ni 4/1) reaches a current density of 10 mA/cm 2 with an overpotential of a mere 336 mV and a Tafel slope of 36 mV/dec, outperforming benchmarked and other reported Ni/Co-based OER electrocatalysts. The catalyst also demonstrates outstanding durability for 14 h and maintained the ordered mesoporous structure. The cyclic voltammograms along with the electrochemical measurements in Fe-free KOH electrolyte suggest that the activity boost is attributed to the generation of surface Ni(OH) 2 species that incorporate Fe impurities from the electrolyte. The incorporation of Fe into the structure is also confirmed by inductively coupled plasma optical emission spectrometry.

Improved Electricity Generation by a Microbial Fuel Cell after Pretreatment of Ammonium and Nitrate in Livestock Wastewater with Microbubbles and a Catalyst.

PubMed

Jang, Jae Kyung; Kim, Taeyoung; Kang, Sukwon; Sung, Je Hoon; Kang, Youn Koo; Kim, Young Hwa

2016-11-28

Livestock wastewater containing high concentrations of ammonium and nitrate ions was pretreated with microbubbles and an Fe/MgO catalyst prior to its application in microbial fuel cells because high ion concentrations can interfere with current generation. Therefore, tests were designed to ascertain the effect of pretreatment on current generation. In initial tests, the optimal amount of catalyst was found to be 300 g/l. When 1,000 ml/min O₂ was used as the oxidant, the removal of ammonium- and nitrate-nitrogen was highest. After the operating parameters were optimized, the removal of ammonium and nitrate ions was quantified. The maximum ammonium removal was 32.8%, and nitrate was removed by up to 75.8% at a 500 g/l catalyst concentration over the course of the 2 h reaction time. The current was about 0.5 mA when livestock wastewater was used without pretreatment, whereas the current increased to 2.14 ± 0.08 mA when livestock wastewater was pretreated with the method described above. This finding demonstrates that a 4-fold increase in the current can be achieved when using pretreated livestock wastewater. The maximum power density and current density performance were 10.3 W/m³ and 67.5 A/m³, respectively, during the evaluation of the microbial fuel cells driven by pretreated livestock wastewater.

Silver-palladium catalysts for the direct synthesis of hydrogen peroxide

NASA Astrophysics Data System (ADS)

Khan, Zainab; Dummer, Nicholas F.; Edwards, Jennifer K.

2017-11-01

A series of bimetallic silver-palladium catalysts supported on titania were prepared by wet impregnation and assessed for the direct synthesis of hydrogen peroxide, and its subsequent side reactions. The addition of silver to a palladium catalyst was found to significantly decrease hydrogen peroxide productivity and hydrogenation, but crucially increase the rate of decomposition. The decomposition product, which is predominantly hydroxyl radicals, can be used to decrease bacterial colonies. The interaction between silver and palladium was characterized using scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy (XPS) and temperature programmed reduction (TPR). The results of the TPR and XPS indicated the formation of a silver-palladium alloy. The optimal 1% Ag-4% Pd/TiO2 bimetallic catalyst was able to produce approximately 200 ppm of H2O2 in 30 min. The findings demonstrate that AgPd/TiO2 catalysts are active for the synthesis of hydrogen peroxide and its subsequent decomposition to reactive oxygen species. The catalysts are promising for use in wastewater treatment as they combine the disinfectant properties of silver, hydrogen peroxide production and subsequent decomposition. This article is part of a discussion meeting issue 'Providing sustainable catalytic solutions for a rapidly changing world'.

Regenerable cobalt oxide loaded magnetosphere catalyst from fly ash for mercury removal in coal combustion flue gas.

PubMed

Yang, Jianping; Zhao, Yongchun; Zhang, Junying; Zheng, Chuguang

2014-12-16

To remove Hg(0) in coal combustion flue gas and eliminate secondary mercury pollution of the spent catalyst, a new regenerable magnetic catalyst based on cobalt oxide loaded magnetospheres from fly ash (Co-MF) was developed. The catalyst, with an optimal loading of 5.8% cobalt species, attained approximately 95% Hg(0) removal efficiency at 150 °C under simulated flue gas atmosphere. O2 could enhance the Hg(0) removal activity of magnetospheres catalyst via the Mars-Maessen mechanism. SO2 displayed an inhibitive effect on Hg(0) removal capacity. NO with lower concentration could promote the Hg(0) removal efficiency. However, when increasing the NO concentration to 300 ppm, a slightly inhibitive effect of NO was observed. In the presence of 10 ppm of HCl, greater than 95.5% Hg(0) removal efficiency was attained, which was attributed to the formation of active chlorine species on the surface. H2O presented a seriously inhibitive effect on Hg(0) removal efficiency. Repeated oxidation-regeneration cycles demonstrated that the spent Co-MF catalyst could be regenerated effectively via thermally treated at 400 °C for 2 h.

Direct production of biodiesel from high-acid value Jatropha oil with solid acid catalyst derived from lignin

PubMed Central

2011-01-01

Background Solid acid catalyst was prepared from Kraft lignin by chemical activation with phosphoric acid, pyrolysis and sulfuric acid. This catalyst had high acid density as characterized by scanning electron microscope (SEM), energy-dispersive x-ray spectrometry (EDX) and Brunauer, Emmett, and Teller (BET) method analyses. It was further used to catalyze the esterification of oleic acid and one-step conversion of non-pretreated Jatropha oil to biodiesel. The effects of catalyst loading, reaction temperature and oil-to-methanol molar ratio, on the catalytic activity of the esterification were investigated. Results The highest catalytic activity was achieved with a 96.1% esterification rate, and the catalyst can be reused three times with little deactivation under optimized conditions. Biodiesel production from Jatropha oil was studied under such conditions. It was found that 96.3% biodiesel yield from non-pretreated Jatropha oil with high-acid value (12.7 mg KOH/g) could be achieved. Conclusions The catalyst can be easily separated for reuse. This single-step process could be a potential route for biodiesel production from high-acid value oil by simplifying the procedure and reducing costs. PMID:22145867

Synthesis of solid catalyst from egg shell waste and clay for biodiesel production

NASA Astrophysics Data System (ADS)

Setiadji, S.; Sundari, C. D. D.; Munir, M.; Fitriyah, S.

2018-05-01

Until now, energy consumption in Indonesia is almost entirely fulfilled by fossil fuels, thus, its availability will be limited and continue to decrease. To overcome these problems, development and utilization of renewable energy are required, one of which is biodiesel. Biodiesel can be prepared through transesterification reaction of vegetable oil using catalyst. In this research, a solid catalyst for biodiesel synthesis was prepared from chicken egg shell waste and clay. Optimization of the transesterification reaction of coconut (Cocos nucifera) oil to obtain biodiesel was also carried out. The formation of CaO/kaolin catalyst was confirmed based on the results of XRD and SEM-EDS. This catalyst is suitable for biodiesel synthesis from vegetable oils with lower FFA (free fatty acid) levels, i.e. coconut oil with FFA level of 0.18%. Based on FTIR result, FFA level and flame tests, it was found that biodiesel was successfully formed. Synthesis of biodiesel has the optimum conditions on reaction time of 16 hours and temperature of 64 °C, with oil: methanol ratio of 1: 15 and CaO/kaolin catalyst concentration of 0.9% in a reflux system.

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.

Application of kaolin-based catalysts in biodiesel production via transesterification of vegetable oils in excess methanol.

PubMed

Dang, Tan Hiep; Chen, Bing-Hung; Lee, Duu-Jong

2013-10-01

Biodiesel production from transesterification of vegetable oils in excess methanol was performed by using as-prepared catalyst from low-cost kaolin clay. This effective heterogeneous catalyst was successfully prepared from natural kaolin firstly by dehydroxylation at 800°C for 10h and, subsequently, by NaOH-activation hydrothermally at 90°C for 24h and calcined again at 500°C for 6h. The as-obtained catalytic material was characterized with instruments, including FT-IR, XRD, SEM, and porosimeter (BET/BJH analysis). The as-prepared catalyst was advantageous not only for its easy preparation, but also for its cost-efficiency and superior catalysis in transesterification of vegetable oils in excess methanol to produce fatty acid methyl esters (FAMEs). Conversion efficiencies of soybean and palm oils to biodiesel over the as-prepared catalysts reached 97.0±3.0% and 95.4±3.7%, respectively, under optimal conditions. Activation energies of transesterification reactions of soybean and palm oils in excess methanol using these catalysts are 14.09 kJ/mol and 48.87 kJ/mol, respectively. Copyright © 2012 Elsevier Ltd. All rights reserved.

Real-space observation of strong metal-support interaction: state-of-the-art and what's the next.

PubMed

Shi, X Y; Zhang, W; Zhang, C; Zheng, W T; Chen, H; Qi, J G

2016-06-01

The real-space resolving of the encapsulated overlayer in the well-known model and industry catalysts, ascribed to the advent of dedicated transmission electron microscopy, enables us to probe novel nano/micro architecture chemistry for better application, revisiting our understanding of this key issue in heterogeneous catalysis. In this review, we summarize the latest progress of real-space observation of SMSI in several well-known systems mainly covered from the metal catalysts (mostly Pt) supported by the TiO2 , CeO2 and Fe3 O4 . As a comparison with the model catalyst Pt/Fe3 O4 , the industrial catalyst Cu/ZnO is also listed, followed with the suggested ongoing directions in the field. © 2015 The Authors Journal of Microscopy © 2015 Royal Microscopical Society.

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.

Fabrication and characterization of anode catalyst layers with structural variations for DMFC

NASA Astrophysics Data System (ADS)

Wang, Dazhi; Shi, Peng; Zhou, Peng; Mao, Qing; Liang, Junsheng; Wang, Suli; Li, Yang; Ren, Tongqun; Sun, Gongquan

2018-04-01

In this work, the electrohydrodynamic jet (E-Jet) Layer-by-Layer (LbL) deposition technique was employed to produce anode catalyst layer (CL) structure for direct methanol fuel cells (DMFC). The CLs with different thickness and porosity were fabricated with the control of the E-Jet deposition parameters. Then, the deposited anode CLs with structural variations were assembled to membrane electrode assemblies (MEAs). The results showed that the anode CL with higher porosity contributed higher dispersed catalyst, which further induced greater electrochemical active surface area (ESA) and higher performance. At optimized working condition the anode CL with high-dispersed catalyst of was produced using the E-Jet LbL deposition technique. It was observed that the peak power density is 72.8 mW cm‑2 for the cell having a porosity of 0.63, which has an increase of about 33% after modification of the CL structure.

Direct growth and patterning of multilayer graphene onto a targeted substrate without an external carbon source.

PubMed

Kang, Dongseok; Kim, Won-Jun; Lim, Jung Ah; Song, Yong-Won

2012-07-25

Using only a simple tube furnace, we demonstrate the synthesis of patterned graphene directly on a designed substrate without the need for an external carbon source. Carbon atoms are absorbed onto Ni evaporator sources as impurities, and incorporated into catalyst layers during the deposition. Heat treatment conditions were optimized so that the atoms diffused out along the grain boundaries to form nanocrystals at the catalyst-substrate interfaces. Graphene patterns were obtained under patterned catalysts, which restricted graphene formation to within patterned areas. The resultant multilayer graphene was characterized by Raman spectroscopy and transmission electron microscopy to verify the high crystallinity and two-dimensional nanomorphology. Finally, a metal-semiconductor diode with a catalyst-graphene contact structure were fabricated and characterized to assess the semiconducting properties of the graphene sheets with respect to the display of asymmetric current-voltage behavior.

A green recyclable SO(3)H-carbon catalyst derived from glycerol for the production of biodiesel from FFA-containing karanja (Pongamia glabra) oil in a single step.

PubMed

Prabhavathi Devi, B L A; Vijai Kumar Reddy, T; Vijaya Lakshmi, K; Prasad, R B N

2014-02-01

Simultaneous esterification and transesterification method is employed for the preparation of biodiesel from 7.5% free fatty acid (FFA) containing karanja (Pongamia glabra) oil using water resistant and reusable carbon-based solid acid catalyst derived from glycerol in a single step. The optimum reaction parameters for obtaining biodiesel in >99% yield by simultaneous esterification and transesterification are: methanol (1:45 mole ratio of oil), catalyst 20wt.% of oil, temperature 160°C and reaction time of 4h. After the reaction, the catalyst was easily recovered by filtration and reused for five times with out any deactivation under optimized conditions. This single-step process could be a potential route for biodiesel production from high FFA containing oils by simplifying the procedure and reducing costs and effluent generation. Copyright © 2013 Elsevier Ltd. All rights reserved.

Magnetic diatomite(Kieselguhr)/Fe2O3/TiO2 composite as an efficient photo-Fenton system for dye degradation

NASA Astrophysics Data System (ADS)

Barbosa, Isaltino A.; Zanatta, Lucas D.; Espimpolo, Daniela M.; da Silva, Douglas L.; Nascimento, Leandro F.; Zanardi, Fabrício B.; de Sousa Filho, Paulo C.; Serra, Osvaldo A.; Iamamoto, Yassuko

2017-10-01

We explored the potential use of diatomite/Fe2O3/TiO2 composites as catalysts for heterogeneous photo-Fenton degradation of methylene blue under neutral pH. Such system consists in magnetic solids synthesized by co-precipitation with Fe2+/Fe3+ in the presence of diatomite, followed by impregnation of TiO2. The results showed that the optimal amount of the catalyst was 2.0 g L-1, since aggregation phenomena become significant above this concentration, which decreases the photodegradation activity. The catalyst is highly efficient in the degradation of methylene blue and shows an easy recovery by an external magnetic field. This allows for an effective catalyst reuse without significant loss of activity in catalytic cycles, which is a highly interesting prospect for recyclable dye degradation systems.

Catalytic ignition of hydrogen/oxygen

NASA Technical Reports Server (NTRS)

Green, James M.; Zurawski, Robert L.

1988-01-01

An experimental program was conducted to evaluate the catalytic ignition of gaseous hydrogen and oxygen. Shell 405 granular catalyst and a unique monolithic sponge catalyst were tested. Mixture ratio, mass flow rate, propellant inlet temperature, and back pressure were varied parametrically in testing to determine the operational limits of a catalytic igniter. The test results showed that the gaseous hydrogen/oxygen propellant combination can be ignited catalytically using Shell 405 catalyst over a wide range of mixture ratios, mass flow rates, and propellant injection temperatures. These operating conditions must be optimized to ensure reliable ignition for an extended period of time. The results of the experimental program and the established operational limits for a catalytic igniter using both the granular and monolithic catalysts are presented. The capabilities of a facility constructed to conduct the igniter testing and the advantages of a catalytic igniter over other ignition systems for gaseous hydrogen and oxygen are also discussed.

A heterogeneous Pd-Bi/C catalyst in the synthesis of L-lyxose and L-ribose from naturally occurring D-sugars.

PubMed

Fan, Ao; Jaenicke, Stephan; Chuah, Gaik-Khuan

2011-10-26

A critical step in the synthesis of the rare sugars, L-lyxose and L-ribose, from the corresponding D-sugars is the oxidation to the lactone. Instead of conventional oxidizing agents like bromine or pyridinium dichromate, it was found that a heterogeneous catalyst, Pd-Bi/C, could be used for the direct oxidation with molecular oxygen. The composition of the catalyst was optimized and the best results were obtained with 5 : 1 atomic ratio of Pd : Bi. The overall yields of the five-step procedure to L-ribose and L-lyxose were 47% and 50%, respectively. The synthetic procedure is advantageous from the viewpoint of overall yield, reduced number of steps, and mild reaction conditions. Furthermore, the heterogeneous oxidation catalyst can be easily separated from the reaction mixture and reused with no loss of activity.

Pyrolysis of triglyceride materials for the production of renewable fuels and chemicals.

PubMed

Maher, K D; Bressler, D C

2007-09-01

Conversion of vegetable oils and animal fats composed predominantly of triglycerides using pyrolysis type reactions represents a promising option for the production of renewable fuels and chemicals. The purpose of this article was to collect and review literature on the thermo-chemical conversion of triglyceride based materials. The literature was divided and discussed as (1) direct thermal cracking and (2) combination of thermal and catalytic cracking. Typically, four main catalyst types are used including transition metal catalysts, molecular sieve type catalysts, activated alumina, and sodium carbonate. Reaction products are heavily dependant on the catalyst type and reaction conditions and can range from diesel like fractions to gasoline like fractions. Research in this area is not as advanced as bio-oil and bio-diesel research and there is opportunity for further study in the areas of reaction optimization, detailed characterization of products and properties, and scale-up.

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

Production of biodiesel from bioethanol and Brassica carinata oil: oxidation stability study.

PubMed

Bouaid, Abderrahim; Martinez, Mercedes; Aracil, Jose

2009-04-01

In the present work the synthesis from bioethanol and Brassica carinata, as alternative vegetable oil, using KOH as catalyst, has been developed and optimized by application of the factorial design and response surface methodology (RSM). Temperature and catalyst concentration were found to have significant influence on conversion. A second-order model was obtained to predict conversions as a function of temperature and catalyst concentration. The maximum yield of ester (98.04%) was obtained working with an initial concentration of catalyst (1.5%) and an operation temperature of (35 degrees C). Results show that the acid value, peroxide value, and viscosity, increased while the iodine value decreased with increasing storage time of the biodiesel sample. Fatty acid ethyl esters (biodiesel) from B. carinata oil were very stable because they did not demonstrate rapid increase in peroxide value, acid value, and viscosity with increasing storage time to a period of 12 months.

Catalytic Reforming of Lignin-Derived Bio-Oil Over a Nanoporous Molecular Sieve Silicoaluminophosphate-11.

PubMed

Park, Y K; Kang, Hyeon Koo; Jang, Hansaem; Suh, Dong Jin; Park, Sung Hoon

2016-05-01

Catalytic pyrolysis of lignin, a major constituent of biomass, was performed. A nanoporous molecular sieve silicoaluminophosphate-11 (SAPO-11) was selected as catalyst. Thermogravimetric analysis showed that 500 degrees C was the optimal pyrolysis temperature. Pyrolyzer-gas chromatography/mass spectroscopy was used to investigate the pyrolysis product distribution. Production of phenolics, the dominant product from the pyrolysis of lignin, was promoted by the increase in the catalyst dose. In particular, low-molecular-mass phenolics were produced more over SAPO-11, while high-molecular-mass phenolics and double-bond-containing phenolics were produced less. The fraction of aromatic compounds, including benzene, toluene, xylene, and ethylbenzene, was also increased by catalytic reforming. The catalytic effects were more pronounced when the catalyst/biomass ratio was increased. The enhanced production of aromatic compounds by an acidic catalyst obtained in this study is in good agreement with the results of previous studies.

The Bosch Process-Performance of a Developmental Reactor and Experimental Evaluation of Alternative Catalysts

NASA Technical Reports Server (NTRS)

Abney, Morgan B.; Mansell, J. Matthew

2010-01-01

Bosch-based reactors have been in development at NASA since the 1960's. Traditional operation involves the reduction of carbon dioxide with hydrogen over a steel wool catalyst to produce water and solid carbon. While the system is capable of completely closing the loop on oxygen and hydrogen for Atmosphere Revitalization, steel wool requires a reaction temperature of 650C or higher for optimum performance. The single pass efficiency of the reaction over steel wool has been shown to be less than 10% resulting in a high recycle stream. Finally, the formation of solid carbon on steel wool ultimately fouls the catalyst necessitating catalyst resupply. These factors result in high mass, volume and power demands for a Bosch system. Interplanetary transportation and surface exploration missions of the moon, Mars, and near-earth objects will require higher levels of loop closure than current technology cannot provide. A Bosch system can provide the level of loop closure necessary for these long-term missions if mass, volume, and power can be kept low. The keys to improving the Bosch system lie in reactor and catalyst development. In 2009, the National Aeronautics and Space Administration refurbished a circa 1980's developmental Bosch reactor and built a sub-scale Bosch Catalyst Test Stand for the purpose of reactor and catalyst development. This paper describes the baseline performance of two commercially available steel wool catalysts as compared to performance reported in the 1960's and 80's. Additionally, the results of sub-scale testing of alternative Bosch catalysts, including nickel- and cobalt-based catalysts, are discussed.

Continuous hydrogenation of ethyl levulinate to γ-valerolactone and 2-methyl tetrahydrofuran over alumina doped Cu/SiO2 catalyst: the potential of commercialization

NASA Astrophysics Data System (ADS)

Zheng, Junlin; Zhu, Junhua; Xu, Xuan; Wang, Wanmin; Li, Jiwen; Zhao, Yan; Tang, Kangjian; Song, Qi; Qi, Xiaolan; Kong, Dejin; Tang, Yi

2016-07-01

Hydrogenation of levulinic acid (LA) and its esters to produce γ-valerolactone (GVL) and 2-methyl tetrahydrofuran (2-MTHF) is a key step for the utilization of cellulose derived LA. Aiming to develop a commercially feasible base metal catalyst for the production of GVL from LA, with satisfactory activity, selectivity, and stability, Al2O3 doped Cu/SiO2 and Cu/SiO2 catalysts were fabricated by co-precipitation routes in parallel. The diverse physio-chemical properties of these two catalysts were characterized by XRD, TEM, dissociative N2O chemisorptions, and Py-IR methods. The catalytic properties of these two catalysts were systematically assessed in the continuous hydrogenation of ethyl levulinate (EL) in a fixed-bed reactor. The effect of acidic property of the SiO2 substrate on the catalytic properties was investigated. To justify the potential of its commercialization, significant attention was paid on the initial activity, proper operation window, by-products control, selectivity, and stability of the catalyst. The effect of reaction conditions, such as temperature and pressure, on the performance of the catalyst was also thoroughly studied. The development of alumina doped Cu/SiO2 catalyst strengthened the value-chain from cellulose to industrially important chemicals via LA and GVL.

Continuous hydrogenation of ethyl levulinate to γ-valerolactone and 2-methyl tetrahydrofuran over alumina doped Cu/SiO2 catalyst: the potential of commercialization

PubMed Central

Zheng, Junlin; Zhu, Junhua; Xu, Xuan; Wang, Wanmin; Li, Jiwen; Zhao, Yan; Tang, Kangjian; Song, Qi; Qi, Xiaolan; Kong, Dejin; Tang, Yi

2016-01-01

Hydrogenation of levulinic acid (LA) and its esters to produce γ-valerolactone (GVL) and 2-methyl tetrahydrofuran (2-MTHF) is a key step for the utilization of cellulose derived LA. Aiming to develop a commercially feasible base metal catalyst for the production of GVL from LA, with satisfactory activity, selectivity, and stability, Al2O3 doped Cu/SiO2 and Cu/SiO2 catalysts were fabricated by co-precipitation routes in parallel. The diverse physio-chemical properties of these two catalysts were characterized by XRD, TEM, dissociative N2O chemisorptions, and Py-IR methods. The catalytic properties of these two catalysts were systematically assessed in the continuous hydrogenation of ethyl levulinate (EL) in a fixed-bed reactor. The effect of acidic property of the SiO2 substrate on the catalytic properties was investigated. To justify the potential of its commercialization, significant attention was paid on the initial activity, proper operation window, by-products control, selectivity, and stability of the catalyst. The effect of reaction conditions, such as temperature and pressure, on the performance of the catalyst was also thoroughly studied. The development of alumina doped Cu/SiO2 catalyst strengthened the value-chain from cellulose to industrially important chemicals via LA and GVL. PMID:27377401

Attrition Resistant Iron-Based Catalysts For F-T SBCRs

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

Adeyinka A. Adeyiga

2006-01-31

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-(FE) 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 withmore » the use of 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. Under a previous Department of Energy (DOE)/University Research Grant (UCR) grant, Hampton University reported, for the first time, the development of demonstrably attrition-resistant Fe F-T synthesis catalysts having good activity, selectivity, and attrition resistance. These catalysts were prepared by spray drying Fe catalysts with potassium (K), copper (Cu), and silica (SiO{sub 2}) as promoters. SiO{sub 2} was also used as a binder for spray drying. These catalysts were tested for activity and selectivity in a laboratory-scale fixed-bed reactor. Fundamental understanding of attrition is being addressed by incorporating suitable binders into the catalyst recipe. This has resulted in the preparation of a spray dried HPR-43 catalyst having average particle size (aps) of 70 {micro}m with high attrition resistance. This HPR-43 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+} selectivity of >78% and methane selectivity of less than 5% at an {alpha} of 0.9. Research is proposed to enable further development and optimization of these catalysts by (1) better understanding the role and interrelationship of various catalyst composition and preparation parameters on attrition resistance, activity, and selectivity of these catalysts, (2) the presence of sulfide ions on a precipitated iron catalyst, and (3) the effect of water on sulfided iron F-T catalysts for its activity, selectivity, and attrition. Catalyst preparations will be based on spray drying. The research employed, among other measurements, attrition testing and F-T synthesis at high pressure. Catalyst activity and selectivity is evaluated using a small fixed-bed reactor and a continuous stirred tank reactor (CSTR). The catalysts were prepared by co-precipitation, followed by binder addition and spray drying at 250 C in a 1-m-diameter, 2-m-tall spray dryer. The binder silica content was varied from 0 to 20 wt%. The results show that the use of small amounts of precipitated SiO{sub 2} alone in spray-dried Fe catalysts can result in good attrition resistance. All catalysts investigated with SiO2 wt% {le} 12 produced fines less than 10 wt% during the jet cup attrition test, making them suitable for long-term use in a slurry bubble column reactor. Thus, concentration rather than the type of SiO{sub 2} incorporated into catalyst has a more critical impact on catalyst attrition resistance of spray-dried Fe catalysts. Lower amounts of SiO{sub 2} added to a catalyst give higher particle densities and therefore higher attrition resistances. In order to produce a suitable SBCR catalyst, however, the amount of SiO{sub 2} added has to be optimized to provide adequate surface area, particle density, and attrition resistance. Two of the catalysts with precipitated and binder silica were tested in Texas A&M University's CSTR (Autoclave Engineers). The two catalysts were also tested at The Center for Applied Energy Research in Lexington, Kentucky of the University of Kentucky. Spray-dried catalysts with compositions 100 Fe/5 Cu/4.2 K/11 (P) SiO{sub 2} and 100 Fe/5 Cu/4.2 K/1.1 (B) SiO{sub 2} have excellent selectivity characteristics (low methane and high C{sub 5+} yields), but their productivity and stability (deactivation rate) need to be improved. Mechanical integrity (attrition strength) of these two catalysts was markedly dependent upon their morphological features. The attrition strength of the catalyst made out of largely spherical particles (1.1 (B) SiO{sub 2}) was considerably higher than that of the catalyst consisting of irregularly shaped particles (11 (P) SiO{sub 2}).« less

Highly efficient hydrogenation of carbon dioxide to formate catalyzed by iridium(iii) complexes of imine-diphosphine ligands.

PubMed

Liu, Chong; Xie, Jian-Hua; Tian, Gui-Long; Li, Wei; Zhou, Qi-Lin

2015-05-01

A new iridium catalyst containing an imine-diphosphine ligand has been developed, which showed high efficiency for the hydrogenation of CO 2 to formate (yield up to 99%, TON up to 450 000). A possible catalytic mechanism is proposed, in which the imine group of the catalyst plays a key role in the cleavage of H 2 and the activation of CO 2 .

The production of high efficiency Ziegler-Natta catalyst with dual active sites nature using cyclohexyl chloride as promoter with super activity and produced superior polyethylene with controllable molecular weight distribution.

PubMed

Seifali Abbas-Abadi, Mehrdad

2017-01-01

In the previous studies, the several halocarbons (HC) were tested as promoters for a Ti-based Ziegler-Natta (ZN) catalyst at different polymerization conditions. The Results showed that chloro cyclohexane has the best operation in catalyst activity, polymer particle size growth, hydrogen responsibility and wax reduction too. For the first time in this study, the effect of Al/Ti ratio on the optimum HC/Ti ratio has been considered and the results showed that the optimum HC/Ti ratio depends on the Al/Ti ratio directly. In the optimum HC/Ti ratio, the catalyst activity and hydrogen responsibility ratio of the catalyst increase up to 125 and 55% respectively. The acceptable growth of polymer powder up to 46%, lower flow rate ratio (FRR) up to 19% and decrease of wax amount up to 12%, completed the promotion results. Furthermore, in the next part of this study and as key note, a little dose of halocarbon was used in the catalyst preparation to produce the special catalysts with dual active sites. In the catalyst preparation, the concentration of each active sites depends on the halocarbon amount and it can control the molecular weight distribution of the produced polyethylene; because each active sites have different response to hydrogen. The halocarbon based catalysts showed the remarkable effect on the catalyst activity, the molecular weight and especially molecular weight distribution (MWD). The flow rate ratio and MWD could be increased up to 77 and 88% respectively as the main result of halocarbon addition during the catalyst preparation.

The production of high efficiency Ziegler–Natta catalyst with dual active sites nature using cyclohexyl chloride as promoter with super activity and produced superior polyethylene with controllable molecular weight distribution

PubMed Central

Seifali Abbas-Abadi, Mehrdad

2017-01-01

Abstract In the previous studies, the several halocarbons (HC) were tested as promoters for a Ti-based Ziegler–Natta (ZN) catalyst at different polymerization conditions. The Results showed that chloro cyclohexane has the best operation in catalyst activity, polymer particle size growth, hydrogen responsibility and wax reduction too. For the first time in this study, the effect of Al/Ti ratio on the optimum HC/Ti ratio has been considered and the results showed that the optimum HC/Ti ratio depends on the Al/Ti ratio directly. In the optimum HC/Ti ratio, the catalyst activity and hydrogen responsibility ratio of the catalyst increase up to 125 and 55% respectively. The acceptable growth of polymer powder up to 46%, lower flow rate ratio (FRR) up to 19% and decrease of wax amount up to 12%, completed the promotion results. Furthermore, in the next part of this study and as key note, a little dose of halocarbon was used in the catalyst preparation to produce the special catalysts with dual active sites. In the catalyst preparation, the concentration of each active sites depends on the halocarbon amount and it can control the molecular weight distribution of the produced polyethylene; because each active sites have different response to hydrogen. The halocarbon based catalysts showed the remarkable effect on the catalyst activity, the molecular weight and especially molecular weight distribution (MWD). The flow rate ratio and MWD could be increased up to 77 and 88% respectively as the main result of halocarbon addition during the catalyst preparation. PMID:29491824

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

Benipal, Neeva; Qi, Ji; Dalian Univ. of Technology, Dalian

Electro-oxidation of alcohol is the key reaction occurring at the anode of a direct alcohol fuel cell (DAFC), in which both reaction kinetics (rate) and selectivity (to deep oxidation products) need improvement to obtain higher power density and fuel utilization for a more efficient DAFC. We recently found that a PdAg bimetallic nanoparticle catalyst is more efficient than Pd for alcohol oxidation: Pd can facilitate deprotonation of alcohol in a base electrolyte, while Ag can promote intermediate aldehyde oxidation and cleavage of C-single bondC bond of C 3 species to C 2 species. Furthermore, a combination of the two activemore » sites (Pd and Ag) with two different functions, can simultaneously improve the reaction rates and deeper oxidation products of alcohols. In this continuing work, Pd, Ag mono, and bimetallic nanoparticles supported on carbon nanotubes (Ag/CNT, Pd/CNT, Pd 1Ag 1/CNT, and Pd 1Ag 3/CNT) were prepared using an aqueous-phase reduction method; they served as working catalysts for studying electrocatalytic oxidation of glycerol in an anion-exchange membrane-based direct glycerol fuel cell. Combined XRD, TEM, and HAADF-STEM analyses performed to fully characterize as-prepared catalysts suggested that they have small particle sizes: 2.0 nm for Pd/CNT, 2.3 nm for PdAg/CNT, 2.4 nm for PdAg 3/CNT, and 13.9 nm for Ag/CNT. XPS further shows that alloying with Ag results in more metal state Pd presented on the surface, and this may be related to their higher direct glycerol fuel cell (DGFC) performances. Single DGFC performance and product analysis results show that PdAg bimetallic nanoparticles can not only improve the glycerol reaction rate so that higher power output can be achieved, but also facilitate deep oxidation of glycerol so that a higher faradaic efficiency and fuel utilization can be achieved along with optimal reaction conditions (increased base-to-fuel ratio). Half-cell electrocatalytic activity measurement and single fuel cell product analysis of different glycerol oxidation intermediates, including C 3: glycerate, tartronate, mesoxalate, and lactate; C 2: glycolate and oxalate, over PdAg/CNT catalyst was further conducted and produced deeper insight into the synergistic effects and reaction pathways of bimetallic PdAg catalysts in glycerol electrocatalytic oxidation.« less

Carbon nanotube supported PdAg nanoparticles for electrocatalytic oxidation of glycerol in anion exchange membrane fuel cells

DOE PAGES

Benipal, Neeva; Qi, Ji; Dalian Univ. of Technology, Dalian; ...

2017-03-10

Electro-oxidation of alcohol is the key reaction occurring at the anode of a direct alcohol fuel cell (DAFC), in which both reaction kinetics (rate) and selectivity (to deep oxidation products) need improvement to obtain higher power density and fuel utilization for a more efficient DAFC. We recently found that a PdAg bimetallic nanoparticle catalyst is more efficient than Pd for alcohol oxidation: Pd can facilitate deprotonation of alcohol in a base electrolyte, while Ag can promote intermediate aldehyde oxidation and cleavage of C-single bondC bond of C 3 species to C 2 species. Furthermore, a combination of the two activemore » sites (Pd and Ag) with two different functions, can simultaneously improve the reaction rates and deeper oxidation products of alcohols. In this continuing work, Pd, Ag mono, and bimetallic nanoparticles supported on carbon nanotubes (Ag/CNT, Pd/CNT, Pd 1Ag 1/CNT, and Pd 1Ag 3/CNT) were prepared using an aqueous-phase reduction method; they served as working catalysts for studying electrocatalytic oxidation of glycerol in an anion-exchange membrane-based direct glycerol fuel cell. Combined XRD, TEM, and HAADF-STEM analyses performed to fully characterize as-prepared catalysts suggested that they have small particle sizes: 2.0 nm for Pd/CNT, 2.3 nm for PdAg/CNT, 2.4 nm for PdAg 3/CNT, and 13.9 nm for Ag/CNT. XPS further shows that alloying with Ag results in more metal state Pd presented on the surface, and this may be related to their higher direct glycerol fuel cell (DGFC) performances. Single DGFC performance and product analysis results show that PdAg bimetallic nanoparticles can not only improve the glycerol reaction rate so that higher power output can be achieved, but also facilitate deep oxidation of glycerol so that a higher faradaic efficiency and fuel utilization can be achieved along with optimal reaction conditions (increased base-to-fuel ratio). Half-cell electrocatalytic activity measurement and single fuel cell product analysis of different glycerol oxidation intermediates, including C 3: glycerate, tartronate, mesoxalate, and lactate; C 2: glycolate and oxalate, over PdAg/CNT catalyst was further conducted and produced deeper insight into the synergistic effects and reaction pathways of bimetallic PdAg catalysts in glycerol electrocatalytic oxidation.« less

Rational approach to polymer-supported catalysts: synergy between catalytic reaction mechanism and polymer design.

PubMed

Madhavan, Nandita; Jones, Christopher W; Weck, Marcus

2008-09-01

Supported catalysis is emerging as a cornerstone of transition metal catalysis, as environmental awareness necessitates "green" methodologies and transition metal resources become scarcer and more expensive. Although these supported systems are quite useful, especially in their capacity for transition metal catalyst recycling and recovery, higher activity and selectivity have been elusive compared with nonsupported catalysts. This Account describes recent developments in polymer-supported metal-salen complexes, which often surpass nonsupported analogues in catalytic activity and selectivity, demonstrating the effectiveness of a systematic, logical approach to designing supported catalysts from a detailed understanding of the catalytic reaction mechanism. Over the past few decades, a large number of transition metal complex catalysts have been supported on a variety of materials ranging from polymers to mesoporous silica. In particular, soluble polymer supports are advantageous because of the development of controlled and living polymerization methods that are tolerant to a wide variety of functional groups, including controlled radical polymerizations and ring-opening metathesis polymerization. These methods allow for tuning the density and structure of the catalyst sites along the polymer chain, thereby enabling the development of structure-property relationships between a catalyst and its polymer support. The fine-tuning of the catalyst-support interface, in combination with a detailed understanding of catalytic reaction mechanisms, not only permits the generation of reusable and recyclable polymer-supported catalysts but also facilitates the design and realization of supported catalysts that are significantly more active and selective than their nonsupported counterparts. These superior supported catalysts are accessible through the optimization of four basic variables in their design: (i) polymer backbone rigidity, (ii) the nature of the linker, (iii) catalyst site density, and (iv) the nature of the catalyst attachment. Herein, we describe the design of polymer supports tuned to enhance the catalytic activity or decrease, or even eliminate, decomposition pathways of salen-based transition metal catalysts that follow either a monometallic or a bimetallic reaction mechanism. These findings result in the creation of some of the most active and selective salen catalysts in the literature.

Preparation and characterization of magnetic CsH{sub 2}PW{sub 12}O{sub 40}/Fe–SiO{sub 2} nanocatalysts for biodiesel production

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

Feyzi, Mostafa, E-mail: Dalahoo2011@yahoo.com; Nanoscience and Nanotechnology Research Center; Nourozi, Leila

Graphical abstract: In this study, a series of magnetic CsH{sub 2}PW{sub 12}O{sub 40}/Fe–SiO{sub 2} nanocatalysts were prepared and tested for biodiesel production. The best operational conditions were CH3OH/oil = 12/1 at 60 °C with mechanical stirring, the biodiesel yield reaches to 81% in 4 h. Also notably, recovery of the catalyst can be achieved easily with the help of an external magnet with no need for expensive ultracentrifugation. - Highlights: • Effects of preparation conditions for biodiesel production were studied. • The CsH{sub 2}PW{sub 12}O{sub 40}/Fe–SiO{sub 2} catalyst is efficient catalyst for biodiesel production. • The reaction conditions were foundmore » methanol/oil = 12/1, T = 60 °C. - Abstract: The magnetic CsH{sub 2}PW{sub 12}O{sub 40}/Fe–SiO{sub 2} nanocatalysts were prepared via combination of sol–gel and impregnation methods. The effects of different H{sub 3}PW{sub 12}O{sub 40}/(Fe–SiO{sub 2}) weight percentage, loading of Cs as a promotor and calcination conditions on the catalytic performance has been studied. It was found that the catalyst with H{sub 3}PW{sub 12}O{sub 40}/Fe–SiO{sub 2} = 4 wt.% and Cs = 2 wt.% is an optimal catalyst for biodiesel production. The activity of optimal catalyst was studied in different operational conditions. The best operational conditions were CH{sub 3}OH/oil = 12/1 at 60 °C with mechanical stirring rate of 500 rpm and the biodiesel yield reaches to 81% in 4 h. Characterization of catalysts was carried out by using scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform-infrared spectroscopy (FT-IR), vibrating sample magnetometry (VSM), N{sub 2} adsorption–desorption measurements methods, Thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC)« less

High-throughput heterogeneous catalyst research

NASA Astrophysics Data System (ADS)

Turner, Howard W.; Volpe, Anthony F., Jr.; Weinberg, W. H.

2009-06-01

With the discovery of abundant and low cost crude oil in the early 1900's came the need to create efficient conversion processes to produce low cost fuels and basic chemicals. Enormous investment over the last century has led to the development of a set of highly efficient catalytic processes which define the modern oil refinery and which produce most of the raw materials and fuels used in modern society. Process evolution and development has led to a refining infrastructure that is both dominated and enabled by modern heterogeneous catalyst technologies. Refineries and chemical manufacturers are currently under intense pressure to improve efficiency, adapt to increasingly disadvantaged feedstocks including biomass, lower their environmental footprint, and continue to deliver their products at low cost. This pressure creates a demand for new and more robust catalyst systems and processes that can accommodate them. Traditional methods of catalyst synthesis and testing are slow and inefficient, particularly in heterogeneous systems where the structure of the active sites is typically complex and the reaction mechanism is at best ill-defined. While theoretical modeling and a growing understanding of fundamental surface science help guide the chemist in designing and synthesizing targets, even in the most well understood areas of catalysis, the parameter space that one needs to explore experimentally is vast. The result is that the chemist using traditional methods must navigate a complex and unpredictable diversity space with a limited data set to make discoveries or to optimize known systems. We describe here a mature set of synthesis and screening technologies that together form a workflow that breaks this traditional paradigm and allows for rapid and efficient heterogeneous catalyst discovery and optimization. We exemplify the power of these new technologies by describing their use in the development and commercialization of a novel catalyst for the hydrodesulfurization of gasoline distillates having 50% more selectivity and 30% more activity for sulfur removal than the state-of-the-art commercial reference.

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.

Diethyl Ether Production during Catalytic Dehydration of Ethanol over Ru- and Pt- modified H-beta Zeolite Catalysts.

PubMed

Kamsuwan, Tanutporn; Praserthdam, Piyasan; Jongsomjit, Bunjerd

2017-01-01

In the present study, the catalytic dehydration of ethanol over H-beta zeolite (HBZ) catalyst with ruthenium (Ru-HBZ) and platinum (Pt-HBZ) modification was investigated. Upon the reaction temperature between 200 and 400°C, it revealed that ethanol conversion and ethylene selectivity increased with increasing temperature for both Ru and Pt modification. At lower temperature (200 to 250°C), diethyl ether (DEE) was the major product. It was found that Ru and Pt modification on HBZ catalyst can result in increased DEE yield at low reaction temperature due to increased ethanol conversion without a significant change in DEE selectivity. By comparing the DEE yield of all catalysts in this study, the Ru-HBZ catalyst apparently exhibited the highest DEE yield (ca. 47%) at 250°C. However, at temperature from 350 to 400°C, the effect of Ru and Pt was less pronounced on ethylene yield. With various characterization techniques, the effects of Ru and Pt modification on HBZ catalyst were elucidated. It revealed that Ru and Pt were present in the highly dispersed forms and well distributed in the catalyst granules. It appeared that the weak acid sites measured by NH 3 temperature-programmed desorption technique also decreased with Ru and Pt promotion. Thus, the increased DEE yields with the Ru and Pt modification can be attributed to the presence of optimal weak acid sites leading to increased intrinsic activity of the catalysts. It can be concluded that the modification of Ru and Pt on HBZ catalyst can improve the DEE yields by ca. 10%.

Effective rate constants for nanostructured heterogeneous catalysts

NASA Astrophysics Data System (ADS)

Hendy, Shaun; Gaston, Nicola; Zhang, Philip; Lund, Nat

2012-02-01

There is currently a high level of interest in the use of nanostructured materials for catalysis. For instance, gold, which is largely inert in the bulk, can exhibit strong catalytic activity when in nanoparticle form. With precious metal catalysts such as Pt and Pd in high demand, the use of these materials in nanoparticle form can also substantially reduce costs by exposure of more surface area for the same volume of material. When reactants are plentiful, the effective activity of a nanoparticulate catalyst will increase roughly with its surface area. However, under diffusion-limited conditions, the reactant must diffuse to active sites on the catalyst, so a high surface area and a high density of active sites may bring diminishing returns if reactant is consumed faster than it arrives. Here we apply a mathematical homogenisation approach to derive simple expressions for the effective reactivity of a nanostructured catalyst under diffusion limited conditions that relate the intrinsic rate constants of the surfaces presented by the catalyst to an effective rate constant. When highly active catalytic sites, such as step edges or other defects are present, we show that distinct limiting cases emerge depending on the degree of overlap of the reactant depletion zone about each site. In gases, the size of this depletion zone is approximately the mean free path, so the effective reactivity will depend on the structure of the catalyst on that scale. We discuss implications for the optimal design of nanoparticle catalysts.

Utilization of waste crab shell (Scylla serrata) as a catalyst in palm olein transesterification.

PubMed

Boey, Peng-Lim; Maniam, Gaanty Pragas; Hamid, Shafida Abd

2009-01-01

Aquaculture activity has increased the population of crab, hence increasing the generation of related wastes, particularly the shell. In addition, the number of molting process in crabs compounds further the amount of waste shell generated. As such, in the present work, the application of the waste crab shell as a source of CaO in transesterification of palm olein to biodiesel (methyl ester) was investigated. Preliminary XRD results revealed that thermally activated crab shell contains mainly CaO. Parametric study has been investigated and optimal conditions were found to be methanol/oil mass ratio, 0.5:1; catalyst amount, 4 wt. %; and reaction temperature, 338 K. As compared to laboratory CaO, the catalyst from waste crab shell performs well, thus creating another low-cost catalyst source for producing biodiesel as well as adding value to the waste crab shell. Reusability of crab shell CaO has also been studied and the outcome confirmed that the catalyst is capable to be reutilized up to 11 times, without any major deterioration.

Economical and green biodiesel production process using river snail shells-derived heterogeneous catalyst and co-solvent method.

PubMed

Roschat, Wuttichai; Siritanon, Theeranun; Kaewpuang, Teadkait; Yoosuk, Boonyawan; Promarak, Vinich

2016-06-01

River snail shells-derived CaO was used as a heterogeneous catalyst to synthesize biodiesel via transesterification of palm oil with methanol. The shell materials were calcined in air at 600-1000°C for 3h. Physicochemical properties of the resulting catalysts were characterized by TGA-DTG, XRD, SEM, BET, XRF, FT-IR and TPD. CaO catalyzed transesterification mechanism of palm oil into biodiesel was verified. The effects of adding a co-solvent on kinetic of the reaction and %FAME yield were investigated. %FAME yield of 98.5%±1.5 was achieved under the optimal conditions of catalyst/oil ratio of 5wt.%; methanol/oil molar ratio of 12:1; reaction temperature of 65°C; 10%v/v of THF in methanol and reaction time of 90min. The results ascertained that river snail shells is a novel raw material for preparation of CaO catalyst and the co-solvent method successfully decreases the reaction time and biodiesel production cost. Copyright © 2016 Elsevier Ltd. All rights reserved.

Ultrasonic-assisted production of biodiesel from transesterification of palm oil over ostrich eggshell-derived CaO catalysts.

PubMed

Chen, Guanyi; Shan, Rui; Shi, Jiafu; Yan, Beibei

2014-11-01

In this study, waste ostrich eggshell-derived calcium oxide (denoted as CaO(OE)) particles were synthesized and explored as cost-effective catalysts for the ultrasonic-assisted transesterification of palm oil. The physicochemical properties of the resultant catalysts were characterized by XRD, N2 adsorption, XRF and Hammett indicator, while the catalytic activity was evaluated through transesterification of palm oil with methanol under ultrasonic conditions. More specifically, the CaO(OE) showed comparable catalytic activity to the one derived from commercial calcium carbonate (denoted as CaO(Lab)). Moreover, under ultrasonic conditions, the catalytic activity of CaO(OE) could be enhanced significantly. The maximum yield of fatty acid methyl esters could reach 92.7% under the optimal condition of reaction time of 60 min with ultrasonic power of 60% (120 W), methanol-to-oil ratio of 9:1, and catalyst loading of 8 wt.%. The results indicated that the CaO(OE) catalysts showed good catalytic performance and reusability, and may potentially reduce the cost of biodiesel production. Copyright © 2014 Elsevier Ltd. All rights reserved.

Cu(3)(BTC)(2) as a viable heterogeneous solid catalyst for Friedel-Crafts alkylation of indoles with nitroalkenes.

PubMed

Nagaraj, Anbu; Amarajothi, Dhakshinamoorthy

2017-05-15

In the present work, Friedel-Crafts alkylation reaction of indole with β-nitrostyrene is examined using a readily available copper based metal-organic frameworks (MOFs) namely, Cu 3 (BTC) 2 (BTC: 1,3,5-benzenetricarboxylic acid) as solid catalyst under mild reaction conditions. Among the various catalysts screened for this reaction, Cu 3 (BTC) 2 exhibits higher activity under the optimized reaction conditions. Besides the absence of leaching of active sites, it is also observed that the catalyst can be reused for four cycles with a minimal decrease in its activity. Cu 3 (BTC) 2 is used as a catalyst to synthesise a series of heterocyclic compounds with different indole and β-nitrostyrene derivatives in moderate to high yields. The present catalytic system shows comparable activity against to recent reports but the advantage of Cu 3 (BTC) 2 is that it does not require any post-functionalization and above all it can be readily synthesised, thus contributing to the synthesis of heterocyclic compounds with high biological interest. Copyright © 2017 Elsevier Inc. All rights reserved.

Selective growth of chirality-enriched semiconducting carbon nanotubes by using bimetallic catalysts from salt precursors.

PubMed

Zhao, Xiulan; Yang, Feng; Chen, Junhan; Ding, Li; Liu, Xiyan; Yao, Fengrui; Li, Meihui; Zhang, Daqi; Zhang, Zeyao; Liu, Xu; Yang, Juan; Liu, Kaihui; Li, Yan

2018-04-19

Bimetallic catalysts play important roles in the selective growth of single-walled carbon nanotubes (SWNTs). Using the simple salts (NH4)6W7O24·6H2O and Co(CH3COO)2·4H2O as precursors, tungsten-cobalt catalysts were prepared. The catalysts were composed of W6Co7 intermetallic compounds and tungsten-dispersed cobalt. With the increase of the W/Co ratio in the precursors, the content of W6Co7 was increased. Because the W6Co7 intermetallic compound can enable the chirality specified growth of SWNTs, the selectivity of the resulting SWNTs is improved at a higher W/Co ratio. At a W/Co ratio of 6 : 4 and under optimized chemical vapor deposition conditions, we realized the direct growth of semiconducting SWNTs with the purity of ∼96%, in which ∼62% are (14, 4) tubes. Using salts as precursors to prepare tungsten-cobalt bimetallic catalysts is flexible and convenient. This offers an efficient pathway for the large-scale preparation of chirality enriched semiconducting SWNTs.

Selective preparation of zeolite X and A from flyash and its use as catalyst for biodiesel production.

PubMed

Volli, Vikranth; Purkait, M K

2015-10-30

This work discusses the utilization of flyash for synthesis of heterogeneous catalyst for transesterification. Different types of zeolites were synthesized from alkali fusion followed by hydrothermal treatment of coal flyash as source material. The synthesis conditions were optimized to obtain highly crystalline zeolite based on degree of crystallinity and cation exchange capacity (CEC). The effect of CEC, acid treatment, Si/Al ratio and calcination temperature (800, 900 and 1000 °C) on zeolite formation was also studied. Pure, single phase and highly crystalline zeolite was obtained at flyash/NaOH ratio (1:1.2), fusion temperature (550 °C), fusion time (1 h), hydrothermal temperature (110 °C) and hydrothermal time (12h). The synthesized zeolite was ion-exchanged with potassium and was used as catalyst for transesterification of mustard oil to obtain a maximum conversion of 84.6% with 5 wt% catalyst concentration, 12:1 methanol to oil molar ratio, reaction time of 7 h at 65 °C. The catalyst was reused for 3 times with marginal reduction in activity. Copyright © 2015 Elsevier B.V. All rights reserved.

Summary of engineering-scale experiments for the Solar Detoxification of Water project

NASA Astrophysics Data System (ADS)

Pacheco, J. E.; Yellowhorse, L.

1992-03-01

This report contains a summary of large-scale experiments conducted at Sandia National Laboratories under the Solar Detoxification of Water project. The objectives of the work performed were to determine the potential of using solar radiation to destroy organic contaminants in water by photocatalysis and to develop the process and improve its performance. For these experiments, we used parabolic troughs to focus sunlight onto glass pipes mounted at the trough's focus. Water spiked with a contaminant and containing suspended titanium dioxide catalyst was pumped through the illuminated glass pipe, activating the catalyst with the ultraviolet portion of the solar spectrum. The activated catalyst creates oxidizers that attack and destroy the organics. Included in this report are a summary and discussion of the implications of experiments conducted to determine: the effect of process kinetics on the destruction of chlorinated solvents (such as trichloroethylene, perchloroethylene, trichloroethane, methylene chloride, chloroform and carbon tetrachloride), the enhancement due to added hydrogen peroxide, the optimal catalyst loading, the effect of light intensity, the inhibition due to bicarbonates, and catalyst issues.

Production of biofuel from waste cooking palm oil using nanocrystalline zeolite as catalyst: process optimization studies.

PubMed

Taufiqurrahmi, Niken; Mohamed, Abdul Rahman; Bhatia, Subhash

2011-11-01

The catalytic cracking of waste cooking palm oil to biofuel was studied over different types of nano-crystalline zeolite catalysts in a fixed bed reactor. The effect of reaction temperature (400-500 °C), catalyst-to-oil ratio (6-14) and catalyst pore size of different nanocrystalline zeolites (0.54-0.80 nm) were studied over the conversion of waste cooking palm oil, yields of Organic Liquid Product (OLP) and gasoline fraction in the OLP following central composite design (CCD). The response surface methodology was used to determine the optimum value of the operating variables for maximum conversion as well as maximum yield of OLP and gasoline fraction, respectively. The optimum reaction temperature of 458 °C with oil/catalyst ratio=6 over the nanocrystalline zeolite Y with pore size of 0.67 nm gave 86.4 wt% oil conversion, 46.5 wt% OLP yield and 33.5 wt% gasoline fraction yield, respectively. The experimental results were in agreement with the simulated values within an experimental error of less than 5%. Copyright © 2011 Elsevier Ltd. All rights reserved.

Novel application of thermally expanded graphite as the support of catalysts for direct synthesis of DMC from CH3OH and CO2.

PubMed

Bian, J; Xiao, M; Wang, S J; Lu, Y X; Meng, Y Z

2009-06-01

Novel Cu-Ni bimetallic catalysts supported on thermally expanded graphite (TEG) were prepared as an example to show the particular characteristics of TEG as a carbon support material. The structures of TEG and the synthesized Cu-Ni/TEG catalysts were characterized using BET, FTIR, TG, SEM, TEM, XRD and TPR techniques. The catalytic activities of the prepared catalysts were investigated by performing micro-reaction in the direct synthesis of dimethyl carbonate (DMC) from CH3OH and CO2. The experimental results indicated that the prepared Cu-Ni/TEG catalysts exhibited highly catalytic activity. Under the optimal catalytic conditions at 100 degrees C and under 1.2 MPa, the highest conversion of CH3OH of 4.97% and high selectivity of DMC of 89.3% can be achieved. The highly catalytic activity of Cu-Ni/TEG in DMC synthesis can be attributed to the synergetic effects of metal Cu, Ni and Cu-Ni alloy in the activation of CH3OH and CO2 and the particular characteristics of TEG as a carbon support material.

Egg shell waste as heterogeneous nanocatalyst for biodiesel production: Optimized by response surface methodology.

PubMed

Pandit, Priti R; Fulekar, M H

2017-08-01

Worldwide consumption of hen eggs results in availability of large amount of discarded egg waste particularly egg shells. In the present study, the waste shells were utilized for the synthesis of highly active heterogeneous calcium oxide (CaO) nanocatalyst to transesterify dry biomass into methyl esters (biodiesel). The CaO nanocatalyst was synthesied by calcination-hydration-dehydration technique and fully characterized by infrared spectroscopy, X-ray powder diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), brunauer-emmett-teller (BET) elemental and thermogravimetric analysis. TEM image showed that the nano catalyst had spherical shape with average particle size of 75 nm. BET analysis indicated that the catalyst specific surface area was 16.4 m 2  g -1 with average pore diameter of 5.07 nm. The effect of nano CaO catalyst was investigated by direct transesterification of dry biomass into biodiesel along with other reaction parameters such as catalyst ratio, reaction time and stirring rate. The impact of the transesterification reaction parameters and microalgal biodiesel yield were analyzed by response surface methodology based on a full factorial, central composite design. The significance of the predicted mode was verified and 86.41% microalgal biodiesel yield was reported at optimal parameter conditions 1.7% (w/w), catalyst ratio, 3.6 h reaction time and stirring rate of 140.6 rpm. The biodiesel conversion was determined by 1 H nuclear magnetic resonance spectroscopy (NMR). The fuel properties of prepared biodiesel were found to be highly comply with the biodiesel standard ASTMD6751 and EN14214. Copyright © 2017 Elsevier Ltd. All rights reserved.

Tuning the redox potential of vitamin K3 derivatives by oxidative functionalization using a Ag(i)/GO catalyst.

PubMed

El-Hout, S I; Suzuki, H; El-Sheikh, S M; Hassan, H M A; Harraz, F A; Ibrahim, I A; El-Sharkawy, E A; Tsujimura, S; Holzinger, M; Nishina, Y

2017-08-03

We propose herein initial results to develop optimum redox mediators by the combination of computational simulation and catalytic functionalization of the core structure of vitamin K 3 . We aim to correlate the calculated energy value of the LUMO of different vitamin K 3 derivatives with their actual redox potential. For this, we optimized the catalytic alkylation of 1,4-naphthoquinones with a designed Ag(i)/GO catalyst and synthesized a series of molecules.

Enantioselective Organocatalytic α-Fluorination of Cyclic Ketones

PubMed Central

Kwiatkowski, Piotr; Beeson, Teresa D.; Conrad, Jay C.

2011-01-01

The first highly enantioselective α-fluorination of ketones using organocatalysis has been accomplished. The long-standing problem of enantioselective ketone α-fluorination via enamine activation has been overcome via high-throughput evaluation of a new library of amine catalysts. The optimal system, a primary amine functionalized Cinchona alkaloid, allows the direct and asymmetric α-fluorination of a variety of carbo- and heterocyclic substrates. Furthermore, this protocol also provides diastereo-, regio- and chemoselective catalyst control in fluorinations involving complex carbonyl systems. PMID:21247133

A Mixed-Ligand Chiral Rhodium(II) Catalyst Enables the Enantioselective Total Synthesis of Piperarborenine B.

PubMed

Panish, Robert A; Chintala, Srinivasa R; Fox, Joseph M

2016-04-11

A novel, mixed-ligand chiral rhodium(II) catalyst, Rh2(S-NTTL)3(dCPA), has enabled the first enantioselective total synthesis of the natural product piperarborenine B. A crystal structure of Rh2(S-NTTL)3(dCPA) reveals a "chiral crown" conformation with a bulky dicyclohexylphenyl acetate ligand and three N-naphthalimido groups oriented on the same face of the catalyst. The natural product was prepared on large scale using rhodium-catalyzed bicyclobutanation/ copper-catalyzed homoconjugate addition chemistry in the key step. The route proceeds in ten steps with an 8% overall yield and 92% ee. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

pH control of the structure, composition, and catalytic activity of sulfated zirconia

NASA Astrophysics Data System (ADS)

Ivanov, Vladimir K.; Baranchikov, Alexander Ye.; Kopitsa, Gennady P.; Lermontov, Sergey A.; Yurkova, Lyudmila L.; Gubanova, Nadezhda N.; Ivanova, Olga S.; Lermontov, Anatoly S.; Rumyantseva, Marina N.; Vasilyeva, Larisa P.; Sharp, Melissa; Pranzas, P. Klaus; Tretyakov, Yuri D.

2013-02-01

We report a detailed study of structural and chemical transformations of amorphous hydrous zirconia into sulfated zirconia-based superacid catalysts. Precipitation pH is shown to be the key factor governing structure, composition and properties of amorphous sulfated zirconia gels and nanocrystalline sulfated zirconia. Increase in precipitation pH leads to substantial increase of surface fractal dimension (up to ˜2.7) of amorphous sulfated zirconia gels, and consequently to increase in specific surface area (up to ˜80 m2/g) and simultaneously to decrease in sulfate content and total acidity of zirconia catalysts. Complete conversion of hexene-1 over as synthesized sulfated zirconia catalysts was observed even under ambient conditions.

Synthesis of acrylates and methacrylates from coal-derived syngas

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

Spivey, J.J.; Gogate, M.R.; Jang, B.W.L.

1995-12-31

Acrylates and methacrylates are among the most widely used chemical intermediates in the world. One of the key chemicals of this type is methyl methacrylate. Of the 4 billion pounds produced each year, roughly 85% is made using the acetone-cyanohydrin process, which requires handling of large quantities of hydrogen cyanide and produces ammonium sulfate wastes that pose an environmental disposal challenge. The U.S. Department of Energy and Eastman Chemical Company are sharing the cost of research to develop an alternative process for the synthesis of methyl methacrylate from syngas. Research Triangle Institute is focusing on the synthesis and testing ofmore » active catalysts for the condensation reactions, and Bechtel is analyzing the costs to determine the competitiveness of several process alternatives. Results thus far show that the catalysts for the condensation of formaldehyde and the propionate are key to selectively producing the desired product, methacrylic acid, with a high yield. These condensation catalysts have both acid and base functions and the strength and distribution of these acid-base sites controls the product selectivity and yield.« less

Electroremovable Traceless Hydrazides for Cobalt-Catalyzed Electro-Oxidative C-H/N-H Activation with Internal Alkynes.

PubMed

Mei, Ruhuai; Sauermann, Nicolas; Oliveira, João C A; Ackermann, Lutz

2018-06-27

Electrochemical oxidative C-H/N-H activations have been accomplished with a versatile cobalt catalyst in terms of [4 + 2] annulations of internal alkynes. The electro-oxidative C-H activation manifold proved viable with an undivided cell setup under exceedingly mild reaction conditions at room temperature using earth-abundant cobalt catalysts. The electrochemical cobalt catalysis prevents the use of transition metal oxidants in C-H activation catalysis, generating H 2 as the sole byproduct. Detailed mechanistic studies provided strong support for a facile C-H cobaltation by an initially formed cobalt(III) catalyst. The subsequent alkyne migratory insertion was interrogated by mass spectrometry and DFT calculations, providing strong support for a facile C-H activation and the formation of a key seven-membered cobalta(III) cycle in a regioselective fashion. Key to success for the unprecedented use of internal alkynes in electrochemical C-H/N-H activations was represented by the use of N-2-pyridylhydrazides, for which we developed a traceless electrocleavage strategy by electroreductive samarium catalysis at room temperature.

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

Cobalt-Catalyzed C(sp(2))-H Borylation: Mechanistic Insights Inspire Catalyst Design.

PubMed

Obligacion, Jennifer V; Semproni, Scott P; Pappas, Iraklis; Chirik, Paul J

2016-08-24

A comprehensive study into the mechanism of bis(phosphino)pyridine (PNP) cobalt-catalyzed C-H borylation of 2,6-lutidine using B2Pin2 (Pin = pinacolate) has been conducted. The experimentally observed rate law, deuterium kinetic isotope effects, and identification of the catalyst resting state support turnover limiting C-H activation from a fully characterized cobalt(I) boryl intermediate. Monitoring the catalytic reaction as a function of time revealed that borylation of the 4-position of the pincer in the cobalt catalyst was faster than arene borylation. Cyclic voltammetry established the electron withdrawing influence of 4-BPin, which slows the rate of C-H oxidative addition and hence overall catalytic turnover. This mechanistic insight inspired the next generation of 4-substituted PNP cobalt catalysts with electron donating and sterically blocking methyl and pyrrolidinyl substituents that exhibited increased activity for the C-H borylation of unactivated arenes. The rationally designed catalysts promote effective turnover with stoichiometric quantities of arene substrate and B2Pin2. Kinetic studies on the improved catalyst, 4-(H)2BPin, established a change in turnover limiting step from C-H oxidative addition to C-B reductive elimination. The iridium congener of the optimized cobalt catalyst, 6-(H)2BPin, was prepared and crystallographically characterized and proved inactive for C-H borylation, a result of the high kinetic barrier for reductive elimination from octahedral Ir(III) complexes.

Synthesis of TiO2-CNT hybrid nanocatalyst and its application in direct oxidation of H2S to S

NASA Astrophysics Data System (ADS)

Daraee, Maryam; Baniadam, Majid; Rashidi, Alimorad; Maghrebi, Morteza

2018-07-01

In this study, a TiO2-CNT hybrid catalyst has been synthesized and its catalytic activity in the oxidation of H2S to S has been investigated and compared with those of TiO2 nanoparticles and pyrolyzed TiO2-CNT hybrid (P-TiO2-CNT). The optimum catalyst amount was determined using central composite design (CCD) method. Catalysts were characterized by various analytical techniques. The H2S conversion, sulfur selectivity and yield at the optimal temperature of 200 °C and O2/H2S ratio of 0.5 were 98.3, 99.5 and 97%, respectively. TiO2-CNT16% catalyst has a higher surface area than TiO2 nanoparticles and P-TiO2-CNT. In addition, the former catalyst gives a high conversion of H2S and sulfur selectivity at 200 °C and O2/H2S ratio of 0.5 compared with the latter two catalysts. The superior conversion (over 10%) of TiO2-CNT16% hybrid compared to TiO2 nanoparticles can be attributed to the synergistic effects of TiO2 and CNT, the reduced band gap of TiO2-CNT16% hybrid and high specific surface area of the catalyst.

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.

Metal-organic frameworks: versatile heterogeneous catalysts for efficient catalytic organic transformations.

PubMed

Chughtai, Adeel H; Ahmad, Nazir; Younus, Hussein A; Laypkov, A; Verpoort, Francis

2015-10-07

Novel catalytic materials are highly demanded to perform a variety of catalytic organic reactions. MOFs combine the benefits of heterogeneous catalysis like easy post reaction separation, catalyst reusability, high stability and homogeneous catalysis such as high efficiency, selectivity, controllability and mild reaction conditions. The possible organization of active centers like metallic nodes, organic linkers, and their chemical synthetic functionalization on the nanoscale shows potential to build up MOFs particularly modified for catalytic challenges. In this review, we have summarized the recent research progress in heterogeneous catalysis by MOFs and their catalytic behavior in various organic reactions, highlighting the key features of MOFs as catalysts based on the active sites in the framework. Examples of their post functionalization, inclusion of active guest species and metal nanoparticles have been discussed. Finally, the use of MOFs as catalysts for asymmetric heterogeneous catalysis and stability of MOFs has been presented as separate sections.

Directing reaction pathways by catalyst active-site selection using self-assembled monolayers.

PubMed

Pang, Simon H; Schoenbaum, Carolyn A; Schwartz, Daniel K; Medlin, J Will

2013-01-01

One key route for controlling reaction selectivity in heterogeneous catalysis is to prepare catalysts that exhibit only specific types of sites required for desired product formation. Here we show that alkanethiolate self-assembled monolayers with varying surface densities can be used to tune selectivity to desired hydrogenation and hydrodeoxygenation products during the reaction of furfural on supported palladium catalysts. Vibrational spectroscopic studies demonstrate that the selectivity improvement is achieved by controlling the availability of specific sites for the hydrogenation of furfural on supported palladium catalysts through the selection of an appropriate alkanethiolate. Increasing self-assembled monolayer density by controlling the steric bulk of the organic tail ligand restricts adsorption on terrace sites and dramatically increases selectivity to desired products furfuryl alcohol and methylfuran. This technique of active-site selection simultaneously serves both to enhance selectivity and provide insight into the reaction mechanism.

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

Mistry, Hemma; Varela, Ana Sofia; Bonifacio, Cecile S.

There is an urgent need to develop technologies that use renewable energy to convert waste products such as carbon dioxide into hydrocarbon fuels. Carbon dioxide can be electrochemically reduced to hydrocarbons over copper catalysts, although higher efficiency is required. We have developed oxidized copper catalysts displaying lower overpotentials for carbon dioxide electroreduction and record selectivity towards ethylene (60%) through facile and tunable plasma treatments. Herein we provide insight into the improved performance of these catalysts by combining electrochemical measurements with microscopic and spectroscopic characterization techniques. Operando X-ray absorption spectroscopy and cross-sectional scanning transmission electron microscopy show that copper oxides aremore » surprisingly resistant to reduction and copper + species remain on the surface during the reaction. Furthermore, our results demonstrate that the roughness of oxide-derived copper catalysts plays only a partial role in determining the catalytic performance, while the presence of copper + is key for lowering the onset potential and enhancing ethylene selectivity.« less

Supramolecular water oxidation with Ru-bda-based catalysts.

PubMed

Richmond, Craig J; Matheu, Roc; Poater, Albert; Falivene, Laura; Benet-Buchholz, Jordi; Sala, Xavier; Cavallo, Luigi; Llobet, Antoni

2014-12-22

Extremely slow and extremely fast new water oxidation catalysts based on the Ru-bda (bda=2,2'-bipyridine-6,6'-dicarboxylate) systems are reported with turnover frequencies in the range of 1 and 900 cycles s(-1) , respectively. Detailed analyses of the main factors involved in the water oxidation reaction have been carried out and are based on a combination of reactivity tests, electrochemical experiments, and DFT calculations. These analyses give a convergent interpretation that generates a solid understanding of the main factors involved in the water oxidation reaction, which in turn allows the design of catalysts with very low energy barriers in all the steps involved in the water oxidation catalytic cycle. We show that for this type of system π-stacking interactions are the key factors that influence reactivity and by adequately controlling them we can generate exceptionally fast water oxidation catalysts. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Comparison of attrition test methods: ASTM standard fluidized bed vs jet cup

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

Zhao, R.; Goodwin, J.G. Jr.; Jothimurugesan, K.

2000-05-01

Attrition resistance is one of the key design parameters for catalysts used in fluidized-bed and slurry phase types of reactors. The ASTM fluidized-bed test has been one of the most commonly used attrition resistance evaluation methods; however, it requires the use of 50 g samples--a large amount for catalyst development studies. Recently a test using the jet cup requiring only 5 g samples has been proposed. In the present study, two series of spray-dried iron catalysts were evaluated using both the ASTM fluidized-bed test and a test based on the jet cup to determine this comparability. It is shown thatmore » the two tests give comparable results. This paper, by reporting a comparison of the jet-cup test with the ASTM standard, provides a basis for utilizing the more efficient jet cup with confidence in catalyst attrition studies.« less

Chiral 2-Aminobenzimidazole as Bifunctional Catalyst in the Asymmetric Electrophilic Amination of Unprotected 3-Substituted Oxindoles.

PubMed

Benavent, Llorenç; Baeza, Alejandro; Freckleton, Megan

2018-06-06

The use of readily available chiral trans -cyclohexanediamine-benzimidazole derivatives as bifunctional organocatalysts in the asymmetric electrophilic amination of unprotected 3-substituted oxindoles is presented. Different organocatalysts were evaluated; the most successful one contained a dimethylamino moiety ( 5 ). With this catalyst under optimized conditions, different oxindoles containing a wide variety of substituents at the 3-position were aminated in good yields and with good to excellent enantioselectivities using di- tert -butylazodicarboxylate as the aminating agent. The procedure proved to be also efficient for the amination of 3-substituted benzofuranones, although with moderate results. A bifunctional role of the catalyst, acting as Brønsted base and hydrogen bond donor, is proposed according to the experimental results observed.

Pyrolysis of de-oiled seed cake of Jatropha Curcas and catalytic steam reforming of pyrolytic bio-oil to hydrogen.

PubMed

Renny, Andrew; Santhosh, Viswanathan; Somkuwar, Nitin; Gokak, D T; Sharma, Pankaj; Bhargava, Sanjay

2016-11-01

The aim of this work was to study the pyrolysis of de-oiled seed cake of Jatropha Curcas and catalytic steam reforming of pyrolytic bio-oil to hydrogen. As per literature, presence of heavy nitrogenous and oxygenated compounds leads to catalyst deactivation. Here, an attempt has been made to tune pyrolytic reactions to optimize the N and O content of the pyrolytic bio-oil. Bio-oil conversion and hydrogen yield decreased as reaction progressed, which attributes to temporary loss of catalytic activity by blockage of catalyst pores by carbon deposition. Further, retention of steam reforming activity after repetitive steam activation suggests long-term catalyst usage. Copyright © 2016 Elsevier Ltd. All rights reserved.

Oxidation of benzyl alcohol by K2FeO4 to benzaldehyde over zeolites

NASA Astrophysics Data System (ADS)

Wang, Yuan-Yuan; Song, Hua; Song, Hua-Lin; Jin, Zai-Shun

2016-10-01

A novel and green procedure for benzaldehyde synthesis by potassium ferrate oxidation of benzyl alcohol employing zeolite catalysts was studied. The prepared oxidant was characterized by SEM and XRD. The catalytic activity of various solid catalysts was studied using benzyl alcohol as a model compound. USY was found to be a very efficient catalyst for this particular oxidation process. Benzaldehyde yields up to 96.0% could be obtained at the following optimal conditions: 0.2 mL of benzyl alcohol, 4 mmol of K2FeO4, 0.5 g of USY zeolite; 20 mL of cyclohexene, 0.3 mL of acetic acid (36 wt %), 30°C temperature, 4 h reaction time.

Photocatalytic water splitting—The untamed dream: A review of recent advances

DOE PAGES

Jafari, Tahereh; Moharreri, Ehsan; Amin, Alireza Shirazi; ...

2016-07-09

Here, photocatalytic water splitting using sunlight is a promising technology capable of providing high energy yield without pollutant byproducts. Herein, we review various aspects of this technology including chemical reactions, physiochemical conditions and photocatalyst types such as metal oxides, sulfides, nitrides, nanocomposites, and doped materials followed by recent advances in computational modeling of photoactive materials. As the best-known catalyst for photocatalytic hydrogen and oxygen evolution, TiO 2 is discussed in a separate section, along with its challenges such as the wide band gap, large overpotential for hydrogen evolution, and rapid recombination of produced electron-hole pairs. Various approaches are addressed tomore » overcome these shortcomings, such as doping with different elements, heterojunction catalysts, noble metal deposition, and surface modification. Development of a photocatalytic corrosion resistant, visible light absorbing, defect-tuned material with small particle size is the key to complete the sunlight to hydrogen cycle efficiently. Computational studies have opened new avenues to understand and predict the electronic density of states and band structure of advanced materials and could pave the way for the rational design of efficient photocatalysts for water splitting. Future directions are focused on developing innovative junction architectures, novel synthesis methods and optimizing the existing active materials to enhance charge transfer, visible light absorption, reducing the gas evolution overpotential and maintaining chemical and physical stability« less

Investigation of the spray characteristics for a secondary fuel injection nozzle using a digital image processing method

NASA Astrophysics Data System (ADS)

Jeong, Haeyoung; Lee, Kihyung; Ikeda, Yuji

2007-05-01

There are many ways to reduce diesel engine exhaust emissions. However, NOx emission is difficult to reduce because the hydrocarbon (HC) concentration in a diesel engine is not sufficient for NOx conversion. Therefore, in order to create stoichiometric conditions in the De-NOx catalyst, a secondary injection system is designed to inject liquid HC into the exhaust pipe. The atomization and distribution characteristics of the HC injected from a secondary injector are key technologies to obtain a high NOx conversion because inhomogeneous droplets of injected HC cause not only high fuel consumption but also deterioration of NOx emission. This paper describes the spray characteristics of a secondary injector including the spray angle, penetration length and breakup behaviour of the spray to optimize the reduction rate of the NOx catalyst. In this study, various optical diagnostics were applied to investigate these spray characteristics, the atomization mechanism and spray developing process. The visualization and image processing method for the spray pulsation were developed by high speed photography. The influence of the fuel supply pressure on the spray behaviour and a more detailed spray developing process have been analysed experimentally using image processing. Finally, the experimental results were used to correlate the spray structure to the injection system performance and to provide a design guide for a secondary injector nozzle.

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

Rapid and solvent-saving liquefaction of woody biomass using microwave-ultrasonic assisted technology.

PubMed

Lu, Zexiang; Wu, Zhengguo; Fan, Liwei; Zhang, Hui; Liao, Yiqiang; Zheng, Deyong; Wang, Siqun

2016-01-01

A novel process to rapidly liquefy sawdust using reduced quantities of solvent, was successfully carried out via microwave-ultrasonic assisted technology (MUAT) in a sulphuric acid/polyethylene glycol 400-glycerol catalytic system. The influences of some key parameters on the liquefaction yield were investigated. The results showed that compared with traditional liquefaction, the introduction of MUAT allowed the solvent dosage to be halved and shortened the liquefaction time from 60 to 20 min. The liquefaction yield reached 91% under the optimal conditions. However, the influence on the yield of some parameters such as catalyst concentration, was similar to that of traditional liquefaction, indicating that the application of MUAT possibly only intensified heat and mass transfer rather than altering either the degradation mechanism or pathway. The introduction of MUAT as a process intensification technology has good industrial application potential for woody biomass liquefaction. Copyright © 2015 Elsevier Ltd. All rights reserved.

Comparative study of UV/TiO2, UV/ZnO and photo-Fenton processes for the organic reactive dye degradation in aqueous solution.

PubMed

Peternel, Igor T; Koprivanac, Natalija; Bozić, Ana M Loncarić; Kusić, Hrvoje M

2007-09-05

In this study advanced oxidation processes (AOPs), UV/TiO(2), UV/ZnO and photo-Fenton, were applied in order to degrade C.I. Reactive Red 45 (RR45) dye in aqueous solution. The effects of key operating parameters, such as initial pH, catalyst and hydrogen peroxide dosage as well as the effect of initial dye concentration on decolorization and mineralization extents were studied. Primary objective was to determine the optimal conditions for each of the processes. The influence of added zeolite on the process efficiency was also studied. UV/vis spectrophotometric and total organic carbon (TOC) measurements were performed for determination of decolorization and mineralization extents. It has been found that photo-Fenton process was the most efficient with 74.2% TOC removal and complete color removal achieved after a 1h treatment.

"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.

Plasma-catalyst hybrid reactor with CeO2/γ-Al2O3 for benzene decomposition with synergetic effect and nano particle by-product reduction.

PubMed

Mao, Lingai; Chen, Zhizong; Wu, Xinyue; Tang, Xiujuan; Yao, Shuiliang; Zhang, Xuming; Jiang, Boqiong; Han, Jingyi; Wu, Zuliang; Lu, Hao; Nozaki, Tomohiro

2018-04-05

A dielectric barrier discharge (DBD) catalyst hybrid reactor with CeO 2 /γ-Al 2 O 3 catalyst balls was investigated for benzene decomposition at atmospheric pressure and 30 °C. At an energy density of 37-40 J/L, benzene decomposition was as high as 92.5% when using the hybrid reactor with 5.0wt%CeO 2 /γ-Al 2 O 3 ; while it was 10%-20% when using a normal DBD reactor without a catalyst. Benzene decomposition using the hybrid reactor was almost the same as that using an O 3 catalyst reactor with the same CeO 2 /γ-Al 2 O 3 catalyst, indicating that O 3 plays a key role in the benzene decomposition. Fourier transform infrared spectroscopy analysis showed that O 3 adsorption on CeO 2 /γ-Al 2 O 3 promotes the production of adsorbed O 2 - and O 2 2‒ , which contribute benzene decomposition over heterogeneous catalysts. Nano particles as by-products (phenol and 1,4-benzoquinone) from benzene decomposition can be significantly reduced using the CeO 2 /γ-Al 2 O 3 catalyst. H 2 O inhibits benzene decomposition; however, it improves CO 2 selectivity. The deactivated CeO 2 /γ-Al 2 O 3 catalyst can be regenerated by performing discharges at 100 °C and 192-204 J/L. The decomposition mechanism of benzene over CeO 2 /γ-Al 2 O 3 catalyst was proposed. Copyright © 2017 Elsevier B.V. All rights reserved.

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

Rabo, J.A.

Of the twelve catalysts tested in this quarter, none showed any significant effectiveness. The principal value of the quarter's work has been in whatever guidance may be derived from the negative findings, especially what they may tell us about the design parameters of a good catalyst. The most effective catalyst developed to date, Catalyst 6 (Run 11677-11) of the Third Annual Report, was composed of Co/Th/X/sub 4//UCC-103+UCC-101. This quarter's findings suggest three specifics of that catalyst which should prove useful in shaping further work. First, that the X/sub 4/ component is probably a key contributor to stability. Second, that themore » source of the X/sub 4/ is important; the X/sub 4/ must be free of known catalyst poisons, or have those poisons completely removed without impairing the cobalt Fischer-Tropsch activity. And third, that extra, physically mixed UCC-101 apparently contributes little if anything to stability. Eight of the twelve runs were devoted to tests of water gas shift catalysts in different formulations and methods of preparation, and under different operating conditions. Many attempts have been made to develop a copper-zinc water gas shift catalyst which will function effectively in combination with a Fischer-Tropsch catalyst and at the Fischer-Tropsch operating temperatures. The failure of these trials to date suggests that the water gas shift components may be deactivated by intermediates or products of Fischer-Tropsch synthesis. Yet attempts to isolate the water gas shift component from the Fischer-Tropsch products have been equally fruitless. 177 figs., 30 tabs.« 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

Novel utilization of waste marine sponge (Demospongiae) as a catalyst in ultrasound-assisted transesterification of waste cooking oil.

PubMed

Hindryawati, Noor; Maniam, Gaanty Pragas

2015-01-01

This study demonstrates the potential of Na-silica waste sponge as a source of low cost catalyst in the transesterification of waste cooking oil aided by ultrasound. In this work an environmentally friendly and efficient transesterification process using Na-loaded SiO2 from waste sponge skeletons as a solid catalyst is presented. The results showed that the methyl esters content of 98.4±0.4wt.% was obtainable in less than an hour (h) of reaction time at 55°C. Optimization of reaction parameters revealed that MeOH:oil, 9:1; catalyst, 3wt.% and reaction duration of 30min as optimum reaction conditions. The catalyst is able to tolerant free fatty acid and moisture content up to 6% and 8%, respectively. In addition, the catalyst can be reused for seven cycles while maintaining the methyl esters content at 86.3%. Ultrasound undoubtedly assisted in achieving this remarkable result in less than 1h reaction time. For the kinetics study at 50-60°C, a pseudo first order model was proposed, and the activation energy of the reaction is determined as 33.45kJ/mol using Arrhenius equation. Copyright © 2014 Elsevier B.V. All rights reserved.

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

NONE

During this time period, at WVU, the authors have obtained models for the kinetics of the HAS (higher alcohol synthesis) reaction over the Co-K-MoS{sub 2}/C catalyst. The Rotoberty reactor was then replaced in the reactor system by a plug-flow tubular reactor. Accordingly, the authors re-started the investigations on sulfide catalysts. The authors encountered and solved the leak problem from the sampling valve for the non-sulfided reactor system. They also modified the system to eliminate the condensation problem. Accordingly, they are continuing their kinetic studies on the reduced Mo-Ni-K/C catalysts. They have set up an apparatus for temperature-programmed reduction (TPR) studies,more » and have obtained some interesting results on TPR characterizations. At UCC, the complete characterization of selected catalysts has been started. The authors sent nine selected types of ZnO, Zn/CrO and Zn/Cr/MnO catalysts and supports for BET surface area, SEM, XRD and ICP. They also sent fresh and spent samples of the Engelhard Zn/CrO catalyst impregnated with 3 wt% potassium for ISS and XPS testing. In Task 2, work on the design and optimization portion of this task, as well as on the fuel testing, is completed. All funds have been expended and there are no personnel working on this project.« less

Ultrasound assisted transesterification of waste cooking oil using heterogeneous solid catalyst.

PubMed

Pukale, Dipak D; Maddikeri, Ganesh L; Gogate, Parag R; Pandit, Aniruddha B; Pratap, Amit P

2015-01-01

Transesterification based biodiesel production from waste cooking oil in the presence of heterogeneous solid catalyst has been investigated in the present work. The effect of different operating parameters such as type of catalyst, catalyst concentration, oil to methanol molar ratio and the reaction temperature on the progress of the reaction was studied. Some studies related to catalyst reusability have also been performed. The important physicochemical properties of the synthesized biodiesel have also been investigated. The results showed that tri-potassium phosphate exhibits high catalytic activity for the transesterification of waste cooking oil. Under the optimal conditions, viz. catalyst concentration of 3wt% K3PO4, oil to methanol molar ratio of 1:6 and temperature of 50°C, 92.0% of biodiesel yield was obtained in 90min of reaction time. Higher yield was obtained in the presence of ultrasound as compared to conventional approach under otherwise similar conditions, which can be attributed to the cavitational effects. Kinetic studies have been carried out to determine the rate constant at different operating temperatures. It was observed that the kinetic rate constant increased with an increase in the temperature and the activation energy was found to be 64.241kJ/mol. Copyright © 2014 Elsevier B.V. All rights reserved.

Enhancement of the electrooxidation of ethanol on Pt-Sn-P/C catalysts prepared by chemical deposition process

NASA Astrophysics Data System (ADS)

Xue, Xinzhong; Ge, Junjie; Tian, Tian; Liu, Changpeng; Xing, Wei; Lu, Tianhong

In this paper, five Pt 3Sn 1/C catalysts have been prepared using three different methods. It was found that phosphorus deposited on the surface of carbon with Pt and Sn when sodium hypophosphite was used as reducing agent by optimization of synthetic conditions such as pH in the synthetic solution and temperature. The deposition of phosphorus should be effective on the size reduction and markedly reduces PtSn nanoparticle size, and raise electrochemical active surface (EAS) area of catalyst and improve the catalytic performance. TEM images show PtSnP nanoparticles are highly dispersed on the carbon surface with average diameters of 2 nm. The optimum composition is Pt 3Sn 1P 2/C (note PtSn/C-3) catalyst in my work. With this composition, it shows very high activity for the electrooxidation of ethanol and exhibit enhanced performance compared with other two Pt 3Sn 1/C catalysts that prepared using ethylene glycol reduction method (note PtSn/C-EG) and borohydride reduction method (note PtSn/-B). The maximum power densities of direct ethanol fuel cell (DEFC) were 61 mW cm -2 that is 150 and 170% higher than that of the PtSn/C-EG and PtSn/C-B catalyst.

Novel Fast Pyrolysis/Catalytic Technology for the Production of Stable Upgraded Liquids

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

Oyama, Ted; Agblevor, Foster; Battaglia, Francine

The objective of the proposed research is the demonstration and development of a novel biomass pyrolysis technology for the production of a stable bio-oil. The approach is to carry out catalytic hydrodeoxygenation (HDO) and upgrading together with pyrolysis in a single fluidized bed reactor with a unique two-level design that permits the physical separation of the two processes. The hydrogen required for the HDO will be generated in the catalytic section by the water-gas shift reaction employing recycled CO produced from the pyrolysis reaction itself. Thus, the use of a reactive recycle stream is another innovation in this technology. Themore » catalysts will be designed in collaboration with BASF Catalysts LLC (formerly Engelhard Corporation), a leader in the manufacture of attrition-resistant cracking catalysts. The proposed work will include reactor modeling with state-of-the-art computational fluid dynamics in a supercomputer, and advanced kinetic analysis for optimization of bio-oil production. The stability of the bio-oil will be determined by viscosity, oxygen content, and acidity determinations in real and accelerated measurements. A multi-faceted team has been assembled to handle laboratory demonstration studies and computational analysis for optimization and scaleup.« less

Self-optimizing, highly surface-active layered metal dichalcogenide catalysts for hydrogen evolution

NASA Astrophysics Data System (ADS)

Liu, Yuanyue; Wu, Jingjie; Hackenberg, Ken P.; Zhang, Jing; Wang, Y. Morris; Yang, Yingchao; Keyshar, Kunttal; Gu, Jing; Ogitsu, Tadashi; Vajtai, Robert; Lou, Jun; Ajayan, Pulickel M.; Wood, Brandon C.; Yakobson, Boris I.

2017-09-01

Low-cost, layered transition-metal dichalcogenides (MX2) based on molybdenum and tungsten have attracted substantial interest as alternative catalysts for the hydrogen evolution reaction (HER). These materials have high intrinsic per-site HER activity; however, a significant challenge is the limited density of active sites, which are concentrated at the layer edges. Here we unravel electronic factors underlying catalytic activity on MX2 surfaces, and leverage the understanding to report group-5 MX2 (H-TaS2 and H-NbS2) electrocatalysts whose performance instead mainly derives from highly active basal-plane sites, as suggested by our first-principles calculations and performance comparisons with edge-active counterparts. Beyond high catalytic activity, they are found to exhibit an unusual ability to optimize their morphology for enhanced charge transfer and accessibility of active sites as the HER proceeds, offering a practical advantage for scalable processing. The catalysts reach 10 mA cm-2 current density at an overpotential of ˜50-60 mV with a loading of 10-55 μg cm-2, surpassing other reported MX2 candidates without any performance-enhancing additives.

Optimization of esterification of oleic acid and trimethylolpropane (TMP) and pentaerythritol (PE)

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

Mahmud, Hamizah Ammarah; Salimon, Jumat

Vegetable oil (VO) is the most potential alternative to replace mineral oil for lubricant due to better lubricating properties and great physicochemical properties. Chemical modification has to be done to overcome low temperature performance and low oxidation instability due to the presence of β-hydrogen atoms of glycerol molecule. The optimization of esterification of oleic acid and polyhydric alcohol with sulfuric acid catalyst was carried out to find the optimum conditions with the highest yield. Reeaction variables such as; molar ratio, temperature, duration and catalyst concentration. Two types of polyhydric alcohol have been used; TMP and PE. The optimum results showedmore » oleic acid successfully converted 91.2% ester TMP and 92.7% ester PE at duration: 5 hours (Ester TMP), 6 hours (Ester PE); temperature: 150°C (ester TMP), 180°C (Ester PE); catalyst concentration: 1.5% (w/w); and mol ratio: 3.9:1 (ester TMP), 4.9:1 (ester PE). From the data obtained, mole ratio showed most influenced factors to the increasing yields of ester conversions.. The TMP/PE ester was confirmed using gas chromatography (GC-FID), Fourier Transform Infrared Spectroscopy (FTIR) and Nuclear Magnetic Resonance (NMR)« less

Operando Synchrotron X-ray Powder Diffraction and Modulated-Excitation Infrared Spectroscopy Elucidate the CO2 Promotion on a Commercial Methanol Synthesis Catalyst.

PubMed

Martin, Oliver; Mondelli, Cecilia; Cervellino, Antonio; Ferri, Davide; Curulla-Ferré, Daniel; Pérez-Ramírez, Javier

2016-09-05

Optimal amounts of CO2 are added to syngas to boost the methanol synthesis rate on Cu-ZnO-Al2 O3 in the industrial process. The reason for CO2 promotion is not sufficiently understood at the particle level due to the catalyst complexity and the high demands of characterization under true reaction conditions. Herein, we applied operando synchrotron X-ray powder diffraction and modulated-excitation infrared spectroscopy on a commercial catalyst to gain insights into its morphology and surface chemistry. These studies unveiled that Cu and ZnO agglomerate and ZnO particles flatten under CO/H2 and/or CO2 /H2 . Under the optimal CO/CO2 /H2 mixture, sintering is prevented and ZnO crystals adopt an elongated shape due to the minimal presence of the H2 O byproduct, enhancing the water-gas shift activity and thus the methanol production. Our results provide a rationale to the CO2 promotion emphasizing the importance of advanced analytical methods to establish structure-performance relations in heterogeneous catalysis. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Synthesis and characterization of catalysts and electrocatalysts using combinatorial methods

NASA Astrophysics Data System (ADS)

Ramanathan, Ramnarayanan

This thesis documents attempts at solving three problems. Bead-based parallel synthetic and screening methods based on matrix algorithms were developed. The method was applied to search for new heterogeneous catalysts for dehydrogenation of methylcyclohexane. The most powerful use of the method to date was to optimize metal adsorption and evaluate catalysts as a function of incident energy, likely to be important in the future, should availability of energy be an optimization parameter. This work also highlighted the importance of order of addition of metal salts on catalytic activity and a portion of this work resulted in a patent with UOP LLC, Desplaines, Illinois. Combinatorial methods were also investigated as a tool to search for carbon-monoxide tolerant anode electrocatalysts and methanol tolerant cathode electrocatalysts, resulting in discovery of no new electrocatalysts. A physically intuitive scaling criterion was developed to analyze all experiments on electrocatalysts, providing insight for future experiments. We attempted to solve the CO poisoning problem in polymer electrolyte fuel cells using carbon molecular sieves as a separator. This approach was unsuccessful in solving the CO poisoning problem, possibly due to the tendency of the carbon molecular sieves to concentrate CO and CO 2 in pore walls.

The conversion of biomass to light olefins on Fe-modified ZSM-5 catalyst: Effect of pyrolysis parameters.

PubMed

Zhang, Shihong; Yang, Mingfa; Shao, Jingai; Yang, Haiping; Zeng, Kuo; Chen, Yingquan; Luo, Jun; Agblevor, Foster A; Chen, Hanping

2018-07-01

Light olefins are the key building blocks for the petrochemical industry. In this study, the effects of in-situ and ex-situ process, temperature, Fe loading, catalyst to feed ratio and gas flow rate on the olefins carbon yield and selectivity were explored. The results showed that Fe-modified ZSM-5 catalyst increased the olefins yield significantly, and the ex-situ process was much better than in-situ. With the increasing of temperature, Fe-loading amount, catalyst to feed ratio, and gas flow rate, the carbon yields of light olefins were firstly increased and further decreased. The maximum carbon yield of light olefins (6.98% C-mol) was obtained at the pyrolysis temperature of 600°C, catalyst to feed ratio of 2, gas flow rate of 100ml/min, and 3wt% Fe/ZSM-5 for cellulose. The selectivity of C 2 H 4 was more than 60% for all feedstock, and the total light olefins followed the decreasing order of cellulose, corn stalk, hemicelluloses and lignin. Copyright © 2018 Elsevier B.V. All rights reserved.

Nitrogen–doped graphitized carbon shell encapsulated NiFe nanoparticles: A highly durable oxygen evolution catalyst

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

Du, Lei; Luo, Langli; Feng, Zhenxing

Oxygen evolution reaction (OER) plays a crucial role in various energy conversion devices such as water electrolyzers and metal–air batteries. Precious metal catalysts such as Ir, Ru and their oxides are usually used for enhancing reaction kinetics but are limited by their scarce resource. The challenges associated with alternative non–precious metal catalysts such as transition metal oxides and (oxy)hydroxides etc. are their low electronic conductivity and durability. Herein, we report a highly active (360 mV overpotential at 10 mA cm–2GEO) and durable (no degradation after 20000 cycles) OER catalyst derived from bimetallic metal–organic frameworks (MOFs) precursors. This catalyst consists ofmore » NiFe nanoparticles encapsulated by nitrogen–doped graphitized carbon shells. The electron-donation/deviation from Fe and tuned electronic structure of metal cores by Ni are revealed to be primary contributors to the enhanced OER activity, whereas N concentration contributes negligibly. We further demonstrated that the structure and morphology of encapsulating carbon shells, which are the key factors influencing the durability, are facilely controlled by the chemical state of precursors.« less

Controlled growth of vertically aligned carbon nanotubes on metal substrates

NASA Astrophysics Data System (ADS)

Gao, Zhaoli

Carbon nanotube (CNT) is a fascinating material with extraordinary electrical thermal and mechanical properties. Growing vertically aligned CNT (VACNT) arrays on metal substrates is an important step in bringing CNT into practical applications such as thermal interface materials (TIMs) and microelectrodes. However, the growth process is challenging due to the difficulties in preventing catalyst diffusion and controlling catalyst dewetting on metal substrates with physical surface heterogeneity. In this work, the catalyst diffusion mechanism and catalyst dewetting theory were studied for the controlled growth of VACNTs on metal substrates. The diffusion time of the catalyst, the diffusion coefficients for the catalyst in the substrate materials and the number density of catalyst nanoparticles after dewetting are identified as the key parameters, based on which three strategies are developed. Firstly, a fast-heating catalyst pretreatment strategy was used, aiming at preserving the amount of catalyst prior to CNT growth by reducing the catalyst diffusion time. The catalyst lifetime is extended from half an hour to one hour on a patterned Al thin film and a VACNT height of 106 mum, about twenty fold of that reported in the literature, was attained. Secondly, a diffusion barrier layer strategy is employed for a reduction of catalyst diffusion into the substrate materials. Enhancement of VACNT growth on Cu substrates was achieved by adopting a conformal Al2O 3 diffusion barrier layer fabricated by a specially designed atomic layer deposition (ALD) system. Lastly, a novel catalyst glancing angle deposition (GLAD) strategy is performed to manipulate the morphology of a relatively thick catalyst on metal substrates with physical surface heterogeneity, aiming to obtain uniform and dense catalyst nanoparticles after dewetting in the pretreatment process for enhanced VACNT growth. We are able to control the VACNT growth conditions on metal substrates in terms of their distribution, heights and alignments. Catalyst loss is controlled by the catalyst diffusion time and catalyst diffusion coefficients. A shorter catalyst diffusion time and smaller diffusion coefficient enhance VACNT growth on metals due to reduced catalyst loss during the pretreatment process. The dewetting behaviors of the thin film catalysts are influenced by the physical surface heterogeneity of the substrates which leads to non-uniform growth of VACNTs. The GLAD process facilitates the deposition of a relatively thick catalyst layer for the creation of dense and uniform catalyst nanoparticles. Applications of VACNT-metal structures in TIMs and microelectrodes are demonstrated. The VACNT-TIMs fabricated on Al alloy substrates have a typical thermal contact resistivity of 17.1 mm2˙K/W and their effective application in high-brightness LED thermal management was demonstrated. Electrochemical characterization was carried out on VACNT microelectrodes for the development of high resolution retinal prostheses and a satisfactory electrochemical property was again demonstrated.

Microcombustor-thermoelectric power generator for 10-50 watt applications

NASA Astrophysics Data System (ADS)

Marshall, Daniel S.; Cho, Steve T.

2010-04-01

Fuel-based portable power systems, including combustion and fuel cell systems, take advantage of the 80x higher energy density of fuel over lithium battery technologies and offer the potential for much higher energy density power sources - especially for long-duration applications, such as unattended sensors. Miniaturization of fuel-based systems poses significant challenges, including processing of fuel in small channels, catalyst poisoning, and coke and soot formation. Recent advances in micro-miniature combustors in the 200Watt thermal range have enabled the development of small power sources that use the chemical energy of heavy fuel to drive thermal-to-electric converters for portable applications. CUBE Technology has developed compact Micro-Furnace combustors that efficiently deliver high-quality heat to optimized thermal-to-electric power converters, such as advanced thermoelectric power modules and Stirling motors, for portable power generation at the 10-50Watt scale. Key innovations include a compact gas-gas recuperator, innovative heavy fuel processing, coke- & soot-free operation, and combustor optimization for low balance-of-plant power use while operating at full throttle. This combustor enables the development of robust, high energy density, miniature power sources for portable applications.

Enzyme reactor design under thermal inactivation.

PubMed

Illanes, Andrés; Wilson, Lorena

2003-01-01

Temperature is a very relevant variable for any bioprocess. Temperature optimization of bioreactor operation is a key aspect for process economics. This is especially true for enzyme-catalyzed processes, because enzymes are complex, unstable catalysts whose technological potential relies on their operational stability. Enzyme reactor design is presented with a special emphasis on the effect of thermal inactivation. Enzyme thermal inactivation is a very complex process from a mechanistic point of view. However, for the purpose of enzyme reactor design, it has been oversimplified frequently, considering one-stage first-order kinetics of inactivation and data gathered under nonreactive conditions that poorly represent the actual conditions within the reactor. More complex mechanisms are frequent, especially in the case of immobilized enzymes, and most important is the effect of catalytic modulators (substrates and products) on enzyme stability under operation conditions. This review focuses primarily on reactor design and operation under modulated thermal inactivation. It also presents a scheme for bioreactor temperature optimization, based on validated temperature-explicit functions for all the kinetic and inactivation parameters involved. More conventional enzyme reactor design is presented merely as a background for the purpose of highlighting the need for a deeper insight into enzyme inactivation for proper bioreactor design.

Supported transition metal catalysts for para- to ortho-hydrogen conversion

NASA Technical Reports Server (NTRS)

Brooks, Christopher J.; Wang, Wei; Eyman, Darrell P.

1994-01-01

The main goal of this study was to develop and improve on existing catalysts for the conversion of ortho- to para-hydrogen. Starting with a commercially available Air Products nickel silicate, which had a beta value of 20, we were trying to synthesize catalysts that would be an improvement to AP. This was accomplished by preparing silicates with various metals as well as different preparation methods. We also prepared supported ruthenium catalysts by various techniques using several metal precursors to improve present technology. What was also found was that the activation conditions prior to catalytic testing was highly important for both the silicates and the supported ruthenium catalysts. While not the initial focus of the research, we made some interesting observations into the adsorption of H2 on ruthenium. This helped us to get a better understanding of how ortho- to para-H2 conversion takes place, and what features in a catalyst are important to optimize activity. Reactor design was the final area in which some interesting conclusions were drawn. As discussed earlier, the reactor catalyst bed must be constructed using straight 1/8 feet OD stainless steel tubing. It was determined that the use of 1/4 feet OD tubing caused two problems. First, the radius from the center of the bed to the wall was too great for thermal equilibrium. Since the reaction of ortho- to para-H2 is exothermic, the catalyst bed center was warmer than the edges. Second, the catalyst bed was too shallow using a 1/4 feet tube. This caused reactant blow-by which was thought to decrease the measured activity when the flow rate was increased. The 1/8 feet tube corrected both of these concerns.

Dual Layer Monolith ATR of Pyrolysis Oil for Distributed Synthesis Gas Production

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

Lawal, Adeniyi

We have successfully demonstrated a novel reactor technology, based on BASF dual layer monolith catalyst, for miniaturizing the autothermal reforming of pyrolysis oil to syngas, the second and most critical of the three steps for thermochemically converting biomass waste to liquid transportation fuel. The technology was applied to aged as well as fresh samples of pyrolysis oil derived from five different biomass feedstocks, namely switch-grass, sawdust, hardwood/softwood, golden rod and maple. Optimization of process conditions in conjunction with innovative reactor system design enabled the minimization of carbon deposit and control of the H2/CO ratio of the product gas. A comprehensivemore » techno-economic analysis of the integrated process using in part, experimental data from the project, indicates (1) net energy recovery of 49% accounting for all losses and external energy input, (2) weight of diesel oil produced as a percent of the biomass to be ~14%, and (3) for a demonstration size biomass to Fischer-Tropsch liquid plant of ~ 2000 daily barrels of diesel, the price of the diesel produced is ~$3.30 per gallon, ex. tax. However, the extension of catalyst life is critical to the realization of the projected economics. Catalyst deactivation was observed and the modes of deactivation, both reversible and irreversible were identified. An effective catalyst regeneration strategy was successfully demonstrated for reversible catalyst deactivation while a catalyst preservation strategy was proposed for preventing irreversible catalyst deactivation. Future work should therefore be focused on extending the catalyst life, and a successful demonstration of an extended (> 500 on-stream hours) catalyst life would affirm the commercial viability of the process.« less

Recent advances in automotive catalysis for NOx emission control by small-pore microporous materials

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

Beale, Andrew M.; Gao, Feng; Lezcano-Gonzalez, Ines

The ever increasing demand to develop highly fuel efficient engines coincides with the need to minimize air pollution originating from the exhaust gases of internal combustion engines. Dramatically improved fuel efficiency can be achieved at air-to-fuel ratios much higher than stoichiometric. In the presence of oxygen in large excess, however, traditional three-way catalysts are unable to reduce NOx. Among the number of lean-NOx reduction technologies, selective catalytic reduction (SCR) of NOx by NH3 over Cu- and Fe-ion exchanged zeolite catalysts has been extensively studied over the past 30+ years. Despite the significant advances in developing a viable practical zeolite-based catalystmore » for lean NOx reduction, the insufficient hydrothermal stabilities of the zeolite structures considered cast doubts about their real-world applicability. During the past decade a renewed interest in zeolite-based lean NOx reduction was spurred by the discovery of the very high activity of Cu-SSZ-13 (and the isostructural Cu-SAPO-34) in the NH3 SCR of NOx. These new, small-pore zeolite-based catalysts not only exhibited very high NOx conversion and N2 selectivity, but also exhibited exceptional high hydrothermal stability at high temperatures. In this review we summarize the key discoveries of the past ~5 years that lead to the introduction of these catalysts into practical application. The review first briefly discusses the structure and preparation of the CHA structure-based zeolite catalysts, and then summarizes the key learnings of the rather extensive (but not complete) characterisation work. Then we summarize the key findings of reaction kinetics studies, and provide some mechanistic details emerging from these investigations. At the end of the review we highlight some of the issues that are still need to be addressed in automotive exhaust control catalysis. Funding A.M.B. and I.L.G. would like to thank EPSRC for funding. F.G., C.H.F.P. and J.Sz. gratefully acknowledge financial support from the US Department of Energy (DOE), Office of Energy Efficiency and Renewable Energy, Vehicle Technologies Program.« less

Target-directed catalytic metallodrugs

PubMed Central

Joyner, J.C.; Cowan, J.A.

2013-01-01

Most drugs function by binding reversibly to specific biological targets, and therapeutic effects generally require saturation of these targets. One means of decreasing required drug concentrations is incorporation of reactive metal centers that elicit irreversible modification of targets. A common approach has been the design of artificial proteases/nucleases containing metal centers capable of hydrolyzing targeted proteins or nucleic acids. However, these hydrolytic catalysts typically provide relatively low rate constants for target inactivation. Recently, various catalysts were synthesized that use oxidative mechanisms to selectively cleave/inactivate therapeutic targets, including HIV RRE RNA or angiotensin converting enzyme (ACE). These oxidative mechanisms, which typically involve reactive oxygen species (ROS), provide access to comparatively high rate constants for target inactivation. Target-binding affinity, co-reactant selectivity, reduction potential, coordination unsaturation, ROS products (metal-associated vs metal-dissociated; hydroxyl vs superoxide), and multiple-turnover redox chemistry were studied for each catalyst, and these parameters were related to the efficiency, selectivity, and mechanism(s) of inactivation/cleavage of the corresponding target for each catalyst. Important factors for future oxidative catalyst development are 1) positioning of catalyst reduction potential and redox reactivity to match the physiological environment of use, 2) maintenance of catalyst stability by use of chelates with either high denticity or other means of stabilization, such as the square planar geometric stabilization of Ni- and Cu-ATCUN complexes, 3) optimal rate of inactivation of targets relative to the rate of generation of diffusible ROS, 4) targeting and linker domains that afford better control of catalyst orientation, and 5) general bio-availability and drug delivery requirements. PMID:23828584

Lanthanoid-free perovskite oxide catalyst for dehydrogenation of ethylbenzene working with redox mechanism.

PubMed

Watanabe, Ryo; Ikushima, Maiko; Mukawa, Kei; Sumomozawa, Fumitaka; Ogo, Shuhei; Sekine, Yasushi

2013-01-01

For the development of highly active and robust catalysts for dehydrogenation of ethylbenzene (EBDH) to produce styrene; an important monomer for polystyrene production, perovskite-type oxides were applied to the reaction. Controlling the mobility of lattice oxygen by changing the structure of Ba1 - x SrxFe y Mn1 - y O3 - δ (0 ≤ x ≤ 1, 0.2 ≤ y ≤ 0.8), perovskite catalyst showed higher activity and stability on EBDH. The optimized Ba/Sr and Fe/Mn molar ratios were 0.4/0.6 and 0.6/0.4, respectively. Comparison of the dehydrogenation activity of Ba0.4Sr0.6Fe0.6Mn0.4O3 - δ catalyst with that of an industrial potassium promoted iron (Fe-K) catalyst revealed that the Ba0.4Sr0.6Fe0.6Mn0.4O3 - δ catalyst showed higher initial activity than the industrial Fe-K oxide catalyst. Additionally, the Ba0.4Sr0.6Fe0.6Mn0.4O3 - δ catalyst showed high activity and stability under severe conditions, even at temperatures as low as 783 K, or at the low steam/EB ratio of 2, while, the Fe-K catalyst showed low activity in such conditions. Comparing reduction profiles of the Ba0.4Sr0.6Fe0.6Mn0.4O3 - δ and the Fe-K catalysts in a H2O/H2 atmosphere, reduction was suppressed by the presence of H2O over the Ba0.4Sr0.6Fe0.6Mn0.4O3 - δ catalyst while the Fe-K catalyst was reduced. In other words, Ba0.4Sr0.6Fe0.6Mn0.4O3 - δ catalyst had higher potential for activating the steam than the Fe-K catalyst. The lattice oxygen in perovskite-structure was consumed by H2, subsequently the consumed lattice oxygen was regenerated by H2O. So the catalytic performance of Ba0.4Sr0.6Fe0.6Mn0.4O3 - δ was superior to that of Fe-K catalyst thanks to the high redox property of the Ba0.4Sr0.6Fe0.6Mn0.4O3 - δ perovskite oxide.

Lanthanoid-free perovskite oxide catalyst for dehydrogenation of ethylbenzene working with redox mechanism

NASA Astrophysics Data System (ADS)

Watanabe, Ryo; Ikushima, Maiko; Mukawa, Kei; Sumomozawa, Fumitaka; Ogo, Shuhei; Sekine, Yasushi

2013-10-01

For the development of highly active and robust catalysts for dehydrogenation of ethylbenzene (EBDH) to produce styrene; an important monomer for polystyrene production, perovskite-type oxides were applied to the reaction. Controlling the mobility of lattice oxygen by changing the structure of Ba1-xSrxFeyMn1-yO3-d(0 ≤ x≤ 1, 0.2 ≤ y≤ 0.8), perovskite catalyst showed higher activity and stability on EBDH. The optimized Ba/Sr and Fe/Mn molar ratios were 0.4/0.6 and 0.6/0.4, respectively. Comparison of the dehydrogenation activity of Ba0.4Sr0.6Fe0.6Mn0.4O3-d catalyst with that of an industrial potassium promoted iron (Fe-K) catalyst revealed that the Ba0.4Sr0.6Fe0.6Mn0.4O3-d catalyst showed higher initial activity than the industrial Fe-K oxide catalyst. Additionally, the Ba0.4Sr0.6Fe0.6Mn0.4O3-d catalyst showed high activity and stability under severe conditions, even at temperatures as low as 783 K, or at the low steam/EB ratio of 2, while, the Fe-K catalyst showed low activity in such conditions. Comparing reduction profiles of the Ba0.4Sr0.6Fe0.6Mn0.4O3-d and the Fe-K catalysts in aH2O/H2 atmosphere, reduction was suppressed by the presence of H2O over the Ba0.4Sr0.6Fe0.6Mn0.4O3-d catalyst while the Fe-K catalyst was reduced. In other words, Ba0.4Sr0.6Fe0.6Mn0.4O3-d catalyst had higher potential for activating the steam than the Fe-K catalyst. The lattice oxygen in perovskite-structure was consumed by H2, subsequently the consumed lattice oxygen was regenerated by H2O. So the catalytic performance of Ba0.4Sr0.6Fe0.6Mn0.4O3-d was superior to that of Fe-K catalyst thanks to the high redox property of the Ba0.4Sr0.6Fe0.6Mn0.4O3-d perovskite oxide.

Precise localization of metal nanoparticles in dendrimer nanosnakes or inner periphery and consequences in catalysis

NASA Astrophysics Data System (ADS)

Liu, Xiang; Gregurec, Danijela; Irigoyen, Joseba; Martinez, Angel; Moya, Sergio; Ciganda, Roberto; Hermange, Philippe; Ruiz, Jaime; Astruc, Didier

2016-10-01

Understanding the relationship between the location of nanoparticles (NPs) in an organic matrix and their catalytic performances is essential for catalyst design. Here we show that catalytic activities of Au, Ag and CuNPs stabilized by dendrimers using coordination to intradendritic triazoles, galvanic replacement or stabilization outside dendrimers strongly depends on their location. AgNPs are found at the inner click dendrimer periphery, whereas CuNPs and AuNPs are encapsulated in click dendrimer nanosnakes. AuNPs and AgNPs formed by galvanic replacement are larger than precursors and only partly encapsulated. AuNPs are all the better 4-nitrophenol reduction catalysts as they are less sterically inhibited by the dendrimer interior, whereas on the contrary CuNPs are all the better alkyne azide cycloaddition catalysts as they are better protected from aerobic oxidation inside dendrimers. This work highlights the role of the location in macromolecules on the catalytic efficiency of metal nanoparticles and rationalizes optimization in catalyst engineering.

Evolution and enabling capabilities of spatially resolved techniques for the characterization of heterogeneously catalyzed reactions

DOE PAGES

Morgan, Kevin; Touitou, Jamal; Choi, Jae -Soon; ...

2016-01-15

The development and optimization of catalysts and catalytic processes requires knowledge of reaction kinetics and mechanisms. In traditional catalyst kinetic characterization, the gas composition is known at the inlet, and the exit flow is measured to determine changes in concentration. As such, the progression of the chemistry within the catalyst is not known. Technological advances in electromagnetic and physical probes have made visualizing the evolution of the chemistry within catalyst samples a reality, as part of a methodology commonly known as spatial resolution. Herein, we discuss and evaluate the development of spatially resolved techniques, including the evolutions and achievements ofmore » this growing area of catalytic research. The impact of such techniques is discussed in terms of the invasiveness of physical probes on catalytic systems, as well as how experimentally obtained spatial profiles can be used in conjunction with kinetic modeling. Moreover, some aims and aspirations for further evolution of spatially resolved techniques are considered.« less

Photocatalytic degradation of Maxilon C.I. basic dye using CS/CoFe2O4/GONCs as a heterogeneous photo-Fenton catalyst prepared by gamma irradiation.

PubMed

Al-Kahtani, Abdullah A; Abou Taleb, Manal F

2016-05-15

CS/CF/GONCs were synthesized via gamma irradiation cross-linking method with the aid of sonication. The nanocomposites exhibited a photo-Fenton catalytic feature for the degradation of Maxilon C.I. basic dye in aqueous medium using sunlight. The effects of pH, H2O2 concentration, and dosage of the catalyst, on the degradation rates of the dyes were examined. The optimal degradation rate was reached with 10mM H2O2 at pH 9.5. It was verified that the Maxilon C.I. basic dye degradation rate fits a pseudo-first-order kinetics for different initial concentrations of Maxilon C.I. dye. Fourth cyclic tests for Maxilon C.I. degradation showed that the magnetic catalyst was very stable, recoverable, highly active, and easy to separate using an external magnet. Hence, this magnetic catalyst has potential use in organic pollutant removal. Copyright © 2016 Elsevier B.V. All rights reserved.

Photocatalytic carbon dioxide reduction with rhodium-based catalysts in solution and heterogenized within metal-organic frameworks.

PubMed

Chambers, Matthew B; Wang, Xia; Elgrishi, Noémie; Hendon, Christopher H; Walsh, Aron; Bonnefoy, Jonathan; Canivet, Jérôme; Quadrelli, Elsje Alessandra; Farrusseng, David; Mellot-Draznieks, Caroline; Fontecave, Marc

2015-02-01

The first photosensitization of a rhodium-based catalytic system for CO2 reduction is reported, with formate as the sole carbon-containing product. Formate has wide industrial applications and is seen as valuable within fuel cell technologies as well as an interesting H2 -storage compound. Heterogenization of molecular rhodium catalysts is accomplished via the synthesis, post-synthetic linker exchange, and characterization of a new metal-organic framework (MOF) Cp*Rh@UiO-67. While the catalytic activities of the homogeneous and heterogeneous systems are found to be comparable, the MOF-based system is more stable and selective. Furthermore it can be recycled without loss of activity. For formate production, an optimal catalyst loading of ∼10 % molar Rh incorporation is determined. Increased incorporation of rhodium catalyst favors thermal decomposition of formate into H2 . There is no precedent for a MOF catalyzing the latter reaction so far. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Stable and Inert Cobalt Catalysts for Highly Selective and Practical Hydrogenation of C≡N and C═O Bonds.

PubMed

Chen, Feng; Topf, Christoph; Radnik, Jörg; Kreyenschulte, Carsten; Lund, Henrik; Schneider, Matthias; Surkus, Annette-Enrica; He, Lin; Junge, Kathrin; Beller, Matthias

2016-07-20

Novel heterogeneous cobalt-based catalysts have been prepared by pyrolysis of cobalt complexes with nitrogen ligands on different inorganic supports. The activity and selectivity of the resulting materials in the hydrogenation of nitriles and carbonyl compounds is strongly influenced by the modification of the support and the nitrogen-containing ligand. The optimal catalyst system ([Co(OAc)2/Phen@α-Al2O3]-800 = Cat. E) allows for efficient reduction of both aromatic and aliphatic nitriles including industrially relevant dinitriles to primary amines under mild conditions. The generality and practicability of this system is further demonstrated in the hydrogenation of diverse aliphatic, aromatic, and heterocyclic ketones as well as aldehydes, which are readily reduced to the corresponding alcohols.

E-Selective Semi-Hydrogenation of Alkynes by Heterobimetallic Catalysis.

PubMed

Karunananda, Malkanthi K; Mankad, Neal P

2015-11-25

A unique cooperative H2 activation reaction by heterobimetallic (NHC)M'-MCp(CO)2 complexes (NHC = N-heterocyclic carbene, M' = Cu or Ag, M = Fe or Ru) has been leveraged to develop a catalytic alkyne semi-hydrogenation transformation. The optimal Ag-Ru catalyst gives high selectivity for converting alkynes to E-alkenes, a rare selectivity mode for reduction reactions with H2. The transformation is tolerant of many reducible functional groups. Computational analysis of H2 activation thermodynamics guided rational catalyst development. Bimetallic alkyne hydrogenation and alkene isomerization mechanisms are proposed.

Comparative Study of the ORR Activity and Stability of Pt and PtM (M = Ni, Co, Cr, Pd) Supported on Polyaniline/Carbon Nanotubes in a PEM Fuel Cell.

PubMed

Kaewsai, Duanghathai; Hunsom, Mali

2018-05-04

The oxygen reduction reaction (ORR) activity and stability of platinum (Pt) and PtM (M = Ni, Co, Cr, Pd) supported on polyaniline/carbon nanotube (PtM/PANI-CNT) were explored and compared with the commercial Pt/C catalyst (ETEK). The Pt/PANI-CNT catalyst exhibited higher ORR activity and stability than the commercial Pt/C catalyst even though it had larger crystallite/particle sizes, lower catalyst dispersion and lower electrochemical surface area (ESA), probably because of its high electrical conductivity. The addition of second metal (M) enhanced the ORR activity and stability of the Pt/PANI-CNT catalyst, because the added M induced the formation of a PtM alloy and shifted the d -band center to downfield, leading to a weak chemical interaction between oxygenated species and the catalyst surface and, therefore, affected positively the catalytic activity. Among all the tested M, the addition of Cr was optimal. Although it improved the ORR activity of the Pt/PANI-CNT catalyst slightly less than that of Pd (around 4.98%) in low temperature (60 °C)/pressure (1 atm abs), it reduced the ESA loss by around 14.8% after 1000 cycles of repetitive cyclic voltammetry (CV). In addition, it is cheaper than Pd metal. Thus, Cr was recommended as the second metal to alloy with Pt on the PANI-CNT support.

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

Catalyst evaluation for high-purity H2 production by sorption-enhanced steam-methane reforming coupled to a Ca/Cu process

NASA Astrophysics Data System (ADS)

Navarro, M. V.; López, J. M.; García, T.; Grasa, G.; Murillo, R.

2017-09-01

The operational limits of a commercial nickel-based catalyst under the conditions of a sorption-enhanced steam-methane reforming process coupled to a Ca/Cu chemical loop are investigated for high-purity H2 production in a cyclic operation. The performance of the reforming catalyst is tested by means of a high number of oxidation-reduction-reforming cycles. After 100 oxidation-reduction cycles, this catalyst retains its exceptional reforming activity. The methane conversion values are close to the thermodynamic equilibrium under very demanding conditions: temperature between 500 °C - 700 °C and mass hourly space velocity of 8.8 kgCH4 h-1 kgcat-1. After 200 cycles, the sample shows reduction in its reforming activity in line with a lower dispersion of the Ni species. Sintering of Ni nanocrystals is evidenced during the oxidation-reduction multi-cycles. The performance of the catalyst after 200 oxidation-reduction cycles mixed with a CaO-based CO2 sorbent is studied under optimal conditions calculated for the sorption-enhanced reforming process coupled to a Ca/Cu cycle (temperature of 650 °C, steam/methane ratio of 4, sorbent/catalyst ratio of 4 and space velocity of 0.75 kgCH4 h-1 kgcat-1). Remarkably, an equilibrium value over 92 vol.% H2 concentration is achieved, highlighting this catalyst as a promising candidate for the next steps of the process development.

Heterogeneous catalytic process for alcohol fuels from syngas

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

Minahan, D.M.; Nagaki, D.A.

1995-12-31

This project is focused on the discovery and evaluation of novel heterogeneous catalyst for the production of oxygenated fuel enhancers from synthesis gas. Catalysts have been studied and optimized for the production of methanol and isobutanol mixtures which may be used for the downstream synthesis of MTBE or related oxygenates. Higher alcohols synthesis (HAS) from syngas was studied; the alcohols that are produced in this process may be used for the downstream synthesis of MTBE or related oxygenates. This work has resulted in the discovery of a catalyst system that is highly selective for isobutanol compared with the prior art.more » The catalysts operate at high temperature (400{degrees}C), and consist of a spinel oxide support (general formula AB{sub 2}O{sub 4}, where A=M{sup 2+} and B = M{sup 3+}), promoted with various other elements. These catalysts operate by what is believed to be an aldol condensation mechanism, giving a product mix of mainly methanol and isobutanol. In this study, the effect of product feed/recycle (methanol, ethanol. n-propanol, isopropanol, carbon dioxide and water) on the performance of 10-DAN-55 (spinel oxide based catalyst) at 400{degrees}C, 1000 psi, GHSV = 12,000 and syngas (H{sub 2}/CO) ratio = 1:2 (alcohol addition) and 1:1 (carbon dioxide and water addition) was studied. The effect of operation at high temperatures and pressures on the performance of an improved catalyst formulation was also examined.« less

Detailed surface reaction mechanism in a three-way catalyst.

PubMed

Chatterjee, D; Deutschmann, O; Warnatz, J

2001-01-01

Monolithic three-way catalysts are applied to reduce the emission of combustion engines. The design of such a catalytic converter is a complex process involving the optimization of different physical and chemical parameters (in the simplest case, e.g., length, cell densities or metal coverage of the catalyst). Numerical simulation can be used as an effective tool for the investigation of the catalytic properties of a catalytic converter and for the prediction of the performance of the catalyst. To attain this goal, a two-dimensional flow-field description is coupled with a detailed surface reaction model (gas-phase reactions can be neglected in three-way catalysts). This surface reaction mechanism (with C3H6 taken as representative of unburnt hydrocarbons) was developed using sub-mechanisms recently developed for hydrogen, carbon monoxide and methane oxidation, literature values for C3H6 oxidation, and estimates for the remaining unknown reactions. Results of the simulation of a monolithic single channel are used to validate the surface reaction mechanism. The performance of the catalyst was simulated under lean, nearly stoichiometric and rich conditions. For these characteristic conditions, the oxidation of propene and carbon monoxide and the reduction of NO on a typical Pt/Rh coated three-way catalyst were simulated as a function of temperature. The numerically predicted conversion data are compared with experimentally measured data. The simulation further reveals the coupling between chemical reactions and transport processes within the monolithic channel.

An efficient hybrid, nanostructured, epoxidation catalyst: titanium silsesquioxane-polystyrene copolymer supported on SBA-15.

PubMed

Zhang, Lei; Abbenhuis, Hendrikus C L; Gerritsen, Gijsbert; Bhriain, Nollaig Ní; Magusin, Pieter C M M; Mezari, Brahim; Han, Wei; van Santen, Rutger A; Yang, Qihua; Li, Can

2007-01-01

A novel interfacial hybrid epoxidation catalyst was designed with a new immobilization method for homogeneous catalysts by coating an inorganic support with an organic polymer film containing active sites. The titanium silsesquioxane (TiPOSS) complex, which contains a single-site titanium active center, was immobilized successfully by in-situ copolymerization on a mesoporous SBA-15-supported polystyrene polymer. The resulting hybrid materials exhibit attractive textural properties (highly ordered mesostructure, large specific surface area (>380 m2 g-1) and pore volume (>or==0.46 cm3 g-1)), and high activity in the epoxidation of alkenes. In the epoxidation of cyclooctene with tert-butyl hydrogen peroxide (TBHP), the hybrid catalysts have rate constants comparable with that of their homogeneous counterpart, and can be recycled at least seven times. They can also catalyze the epoxidation of cyclooctene with aqueous H2O2 as the oxidant. In two-phase reaction media, the catalysts show much higher activity than their homogeneous counterpart due to the hydrophobic environment around the active centers. They behave as interfacial catalysts due to their multifunctionality, that is, the hydrophobicity of polystyrene and the polyhedral oligomeric silsesquioxanes (POSS), and the hydrophilicity of the silica and the mesoporous structure. Combination of the immobilization of homogeneous catalysts on two conventional supports, inorganic solid and organic polymer, is demonstrated to achieve novel heterogeneous catalytic ensembles with the merits of attractive textural properties, tunable surface properties, and optimized environments around the active sites.

Comparative Study of the ORR Activity and Stability of Pt and PtM (M = Ni, Co, Cr, Pd) Supported on Polyaniline/Carbon Nanotubes in a PEM Fuel Cell

PubMed Central

Kaewsai, Duanghathai; Hunsom, Mali

2018-01-01

The oxygen reduction reaction (ORR) activity and stability of platinum (Pt) and PtM (M = Ni, Co, Cr, Pd) supported on polyaniline/carbon nanotube (PtM/PANI-CNT) were explored and compared with the commercial Pt/C catalyst (ETEK). The Pt/PANI-CNT catalyst exhibited higher ORR activity and stability than the commercial Pt/C catalyst even though it had larger crystallite/particle sizes, lower catalyst dispersion and lower electrochemical surface area (ESA), probably because of its high electrical conductivity. The addition of second metal (M) enhanced the ORR activity and stability of the Pt/PANI-CNT catalyst, because the added M induced the formation of a PtM alloy and shifted the d-band center to downfield, leading to a weak chemical interaction between oxygenated species and the catalyst surface and, therefore, affected positively the catalytic activity. Among all the tested M, the addition of Cr was optimal. Although it improved the ORR activity of the Pt/PANI-CNT catalyst slightly less than that of Pd (around 4.98%) in low temperature (60 °C)/pressure (1 atm abs), it reduced the ESA loss by around 14.8% after 1000 cycles of repetitive cyclic voltammetry (CV). In addition, it is cheaper than Pd metal. Thus, Cr was recommended as the second metal to alloy with Pt on the PANI-CNT support. PMID:29734719

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

NiFe(C2O4)x as a heterogeneous Fenton catalyst for removal of methyl orange.

PubMed

Liu, Yucan; Zhang, Guangming; Chong, Shan; Zhang, Nan; Chang, Huazhen; Huang, Ting; Fang, Shunyan

2017-05-01

This paper studies a heterogeneous Fenton catalyst NiFe(C 2 O 4 ) x , which showed better catalytic activity than Ni(C 2 O 4 ) x and better re-usability than Fe(C 2 O 4 ) x . The methyl orange removal efficiency was 98% in heterogeneous Fenton system using NiFe(C 2 O 4 ) x . The prepared NiFe(C 2 O 4 ) x had a laminated shape and the size was in the range of 2-4 μm, and Ni was doped into catalyst's structure successfully. The NiFe(C 2 O 4 ) x had a synergistic effect of catalyst of 24.7 for methyl orange removal, and the dope of Ni significantly reduced the leaching of Fe by 77%. The reaction factors and kinetics were investigated. Under the optimal conditions, 0.4 g/L of catalyst dose and 10 mmol/L of hydrogen peroxide concentration, 98% of methyl orange was removed within 20 min. Analysis showed that hydroxyl radicals and superoxide radicals participated in the reaction. With NiFe(C 2 O 4 ) x catalyst, the suitable pH range for heterogeneous Fenton system was wide from 3 to 10. The catalyst showed good efficiency after five times re-use. NiFe(C 2 O 4 ) x provided great potential in treatment of refractory wastewater with excellent property. Copyright © 2017 Elsevier Ltd. All rights reserved.

Catalytic pyrolysis of model compounds and waste cooking oil for production of light olefins over La/ZSM-5 catalysts

NASA Astrophysics Data System (ADS)

Li, F. W.; Ding, S. L.; Li, L.; Gao, C.; Zhong, Z.; Wang, S. X.; Li, Z. X.

2016-08-01

Waste cooking oil (WCO) and its model compounds (oleic acid and methyl laurate) are catalytically pyrolyzed in a fixed-bed reactor over La modified ZSM-5 catalysts (La/ZSM-5) aiming for production of C2-C4 light olefins. The LaO content in catalysts was set at 0, 2, 6, 10 and 14 wt%. The gas and liquid products are analyzed. The La/ZSM-5 catalyst with 6% LaO showed higher selectivity to light olefins when WCO and methyl laurate were pyrolyzed, and olefin content was 26% for WCO and 21% for methyl laurate. The catalyst with 10% LaO showed high selectivity to light olefins (28.5%) when oleic acid was pyrolyzed. The liquid products from WCO and model compounds mainly contain esters and aromatic hydrocarbons. More esters were observed in liquid products from methyl laurate and WCO pyrolysis, indicating that it is more difficult to pyrolyze esters and WCO than oleic acid. The coked catalysts were analyzed by temperature-programmed oxidation. The result shows that graphite is the main component of coke. The conversion of WCO to light olefins potentially provides an alternative and sustainable route for production of the key petrochemicals.

Level Alignment as Descriptor for Semiconductor/Catalyst Systems in Water Splitting: The Case of Hematite/Cobalt Hexacyanoferrate Photoanodes.

PubMed

Hegner, Franziska Simone; Cardenas-Morcoso, Drialys; Giménez, Sixto; López, Núria; Galan-Mascaros, Jose Ramon

2017-11-23

The realization of artificial photosynthesis may depend on the efficient integration of photoactive semiconductors and catalysts to promote photoelectrochemical water splitting. Many efforts are currently devoted to the processing of multicomponent anodes and cathodes in the search for appropriate synergy between light absorbers and active catalysts. No single material appears to combine both features. Many experimental parameters are key to achieve the needed synergy between both systems, without clear protocols for success. Herein, we show how computational chemistry can shed some light on this cumbersome problem. DFT calculations are useful to predict adequate energy-level alignment for thermodynamically favored hole transfer. As proof of concept, we experimentally confirmed the limited performance enhancement in hematite photoanodes decorated with cobalt hexacyanoferrate as a competent water-oxidation catalyst. Computational methods describe the misalignment of their energy levels, which is the origin of this mismatch. Photoelectrochemical studies indicate that the catalyst exclusively shifts the hematite surface state to lower potentials, which therefore reduces the onset for water oxidation. Although kinetics will still depend on interface architecture, our simple theoretical approach may identify and predict plausible semiconductor/catalyst combinations, which will speed up experimental work towards promising photoelectrocatalytic systems. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Thiolate-bridged dinuclear ruthenium and iron complexes as robust and efficient catalysts toward oxidation of molecular dihydrogen in protic solvents.

PubMed

Yuki, Masahiro; Sakata, Ken; Hirao, Yoshifumi; Nonoyama, Nobuaki; Nakajima, Kazunari; Nishibayashi, Yoshiaki

2015-04-01

Thiolate-bridged dinuclear ruthenium and iron complexes are found to work as efficient catalysts toward oxidation of molecular dihydrogen in protic solvents such as water and methanol under ambient reaction conditions. Heterolytic cleavage of the coordinated molecular dihydrogen at the dinuclear complexes and the sequential oxidation of the produced hydride complexes are involved as key steps to promote the present catalytic reaction. The catalytic activity of the dinuclear complexes toward the chemical oxidation of molecular dihydrogen achieves up to 10000 TON (turnover number), and electrooxidation of molecular dihydrogen proceeds quite rapidly. The result of the density functional theory (DFT) calculation on the reaction pathway indicates that a synergistic effect between the two ruthenium atoms plays an important role to realize the catalytic oxidation of molecular dihydrogen efficiently. The present dinuclear ruthenium complex is found to work as an efficient organometallic anode catalyst for the fuel cell. It is noteworthy that the present dinuclear complex worked not only as an effective catalyst toward chemical and electrochemical oxidation of molecular dihydrogen but also as a good anode catalyst for the fuel cell. We consider that the result described in this paper provides useful and valuable information to develop highly efficient and low-cost transition metal complexes as anode catalysts in the fuel cell.

Hierarchical Mesoporous NiO/MnO2@PANI Core-Shell Microspheres, Highly Efficient and Stable Bifunctional Electrocatalysts for Oxygen Evolution and Reduction Reactions.

PubMed

He, Junkai; Wang, Mingchao; Wang, Wenbo; Miao, Ran; Zhong, Wei; Chen, Sheng-Yu; Poges, Shannon; Jafari, Tahereh; Song, Wenqiao; Liu, Jiachen; Suib, Steven L

2017-12-13

We report on the new facile synthesis of mesoporous NiO/MnO 2 in one step by modifying inverse micelle templated UCT (University of Connecticut) methods. The catalyst shows excellent electrocatalytic activity and stability for both the oxygen evolution reaction (OER) and the oxygen reduction reaction (ORR) in alkaline media after further coating with polyaniline (PANI). For electrochemical performance, the optimized catalyst exhibits a potential gap, ΔE, of 0.75 V to achieve a current of 10 mA cm -2 for the OER and -3 mA cm -2 for the ORR in 0.1 M KOH solution. Extensive characterization methods were applied to investigate the structure-property of the catalyst for correlations with activity (e.g., XRD, BET, SEM, HRTEM, FIB-TEM, XPS, TGA, and Raman). The high electrocatalytic activity of the catalyst closely relates to the good electrical conductivity of PANI, accessible mesoporous structure, high surface area, as well as the synergistic effect of the specific core-shell structure. This work opens a new avenue for the rational design of core-shell structure catalysts for energy conversion and storage applications.

Systematic study on the discharge product of Pt-based lithium oxygen batteries

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

Wu, Feng; Xing, Yi; Bi, Xuanxuan

Lithium oxygen batteries have attracted much attention due to the high theoretical energy density. However, they suffer a large overpotential during oxygen evolution process and thus catalysts play a vital role in the reaction. Here, we systematically explored the influence of Pt-based nanoparticle catalysts on the discharge product Li 2O 2. Because of the superior electrical conductivity and the strong binding with oxygen, Pt-based nanoparticles serve as active sites which are favorable for the growth of toroidal Li 2O 2. We also found that the content and composition of Pt-based nanoparticle catalysts exert a significant influence on the electrochemical performancemore » of lithium oxygen batteries. The discharge products are composed of crystalline Li 2O 2 and oxygen-rich LiO 2 characterized by high-energy X-ray diffraction and Raman. Atomic force microscopy further provides detailed information of the particle size and surface roughness. The loading of Pt catalysts determines the phase and size of Li 2O 2 on the discharged electrode surface. This study will be beneficial for the optimization of Pt-based catalysts used in non-aqueous lithium oxygen batteries.« less

Hydrothermal conversion of N-acetyl-d-glucosamine to 5-hydroxymethylfurfural using ionic liquid as a recycled catalyst in a water-dimethyl sulfoxide mixture.

PubMed

Zang, Hongjun; Yu, Songbai; Yu, Pengfei; Ding, Hongying; Du, Yannan; Yang, Yuchan; Zhang, Yiwen

2017-04-10

Here, N-acetyl-d-glucosamine (GlcNAc), the monomer composing the second most abundant biopolymer, chitin, was efficiently converted into 5-hydroxymethylfurfural (5-HMF) using ionic liquid (IL) catalysts in a water/dimethyl sulfoxide (DMSO) mixture solvent. Various reaction parameters, including reaction temperature and time, DMSO/water mass ratios and catalyst dosage were optimized. A series of ILs with different structures were analyzed to explore their impact on GlcNAc conversion. The substrate scope was expanded from GlcNAc to d-glucosamine, chitin, chitosan and monosaccharides, although 5-HMF yields obtained from polymers and other monosaccharides were generally lower than those from GlcNAc. Moreover, the IL N-methylimidazolium hydrogen sulfate ([Hmim][HSO 4 ]) exhibited the best catalyst performance (64.6% yield) when GlcNAc was dehydrated in a DMSO/water mixture at 180 °C for 6 h without the addition of extra catalysts. To summarize, these results could provide knowledge essential to the production of valuable chemicals that are derived from renewable marine resources and benefit biofuel-related applications. Copyright © 2017 Elsevier Ltd. All rights reserved.

Systematic study on the discharge product of Pt-based lithium oxygen batteries

NASA Astrophysics Data System (ADS)

Wu, Feng; Xing, Yi; Bi, Xuanxuan; Yuan, Yifei; Wang, Hsien-Hau; Shahbazian-Yassar, Reza; Li, Li; Chen, Renjie; Lu, Jun; Amine, Khalil

2016-11-01

Lithium oxygen batteries have attracted much attention due to the high theoretical energy density. However, they suffer a large overpotential during oxygen evolution process and thus catalysts play a vital role in the reaction. Here, we systematically explored the influence of Pt-based nanoparticle catalysts on the discharge product Li2O2. Because of the superior electrical conductivity and the strong binding with oxygen, Pt-based nanoparticles serve as active sites which are favorable for the growth of toroidal Li2O2. We also found that the content and composition of Pt-based nanoparticle catalysts exert a significant influence on the electrochemical performance of lithium oxygen batteries. The discharge products are composed of crystalline Li2O2 and oxygen-rich LiO2 characterized by high-energy X-ray diffraction and Raman. Atomic force microscopy further provides detailed information of the particle size and surface roughness. The loading of Pt catalysts determines the phase and size of Li2O2 on the discharged electrode surface. This study will be beneficial for the optimization of Pt-based catalysts used in non-aqueous lithium oxygen batteries.

Metal-Organic Framework-Templated Porous Carbon for Highly Efficient Catalysis: The Critical Role of Pyrrolic Nitrogen Species.

PubMed

Huang, Gang; Yang, Li; Ma, Xiao; Jiang, Jun; Yu, Shu-Hong; Jiang, Hai-Long

2016-03-01

Metal-free catalysts are of great importance and alternative candidates to conventional metal-based catalysts for many reactions. Herein, several types of metal-organic frameworks have been exploited as templates/precursors to afford porous carbon materials with various nitrogen dopant forms and contents, degrees of graphitization, porosities, and surface areas. Amongst these materials, the PCN-224-templated porous carbon material optimized by pyrolysis at 700 °C (denoted as PCN-224-700) is composed of amorphous carbon coated with well-defined graphene layers, offering a high surface area, hierarchical pores, and high nitrogen content (mainly, pyrrolic nitrogen species). Remarkably, as a metal-free catalyst, PCN-224-700 exhibits a low activation energy and superior activity to most metallic catalysts in the catalytic reduction of 4-nitrophenol to 4-aminophenol. Theoretical investigations suggest that the content and type of the nitrogen dopant play crucial roles in determining the catalytic performance and that the pyrrolic nitrogen species makes the dominant contribution to this activity, which explains the excellent efficiency of the PCN-224-700 catalyst well. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Comparison of non-catalytic and catalytic fast pyrolysis of corncob in a fluidized bed reactor.

PubMed

Zhang, Huiyan; Xiao, Rui; Huang, He; Xiao, Gang

2009-02-01

Fast pyrolysis of corncob with and without catalyst was investigated in a fluidized bed to determine the effects of pyrolysis parameters (temperature, gas flow rate, static bed height and particle size) and a HZSM-5 zeolite catalyst on the product yields and the qualities of the liquid products. The result showed that the optimal conditions for liquid yield (56.8%) were a pyrolysis temperature of 550 degrees C, gas flow rate of 3.4 L/min, static bed height of 10 cm and particle size of 1.0-2.0mm. The presence of the catalyst increased the yields of non-condensable gas, water and coke, while decreased the liquid and char yields. The elemental analysis showed that more than 25% decrease in oxygen content of the collected liquid in the second condenser with HZSM-5 was observed compared with that without catalyst. The H/C, O/C molar ratios and the higher heating value of the oil fraction in the collected liquid with the catalyst were 1.511, 0.149 and 34.6 MJ/kg, respectively. It was indicated that the collected liquid in the second condenser had high qualities and might be used as transport oil.

Optimization of information content in a mass spectrometry based flow-chemistry system by investigating different ionization approaches.

PubMed

Martha, Cornelius T; Hoogendoorn, Jan-Carel; Irth, Hubertus; Niessen, Wilfried M A

2011-05-15

Current development in catalyst discovery includes combinatorial synthesis methods for the rapid generation of compound libraries combined with high-throughput performance-screening methods to determine the associated activities. Of these novel methodologies, mass spectrometry (MS) based flow chemistry methods are especially attractive due to the ability to combine sensitive detection of the formed reaction product with identification of introduced catalyst complexes. Recently, such a mass spectrometry based continuous-flow reaction detection system was utilized to screen silver-adducted ferrocenyl bidentate catalyst complexes for activity in a multicomponent synthesis of a substituted 2-imidazoline. Here, we determine the merits of different ionization approaches by studying the combination of sensitive detection of product formation in the continuous-flow system with the ability to simultaneous characterize the introduced [ferrocenyl bidentate+Ag](+) catalyst complexes. To this end, we study the ionization characteristics of electrospray ionization (ESI), atmospheric-pressure chemical ionization (APCI), no-discharge APCI, dual ESI/APCI, and dual APCI/no-discharge APCI. Finally, we investigated the application potential of the different ionization approaches by the investigation of ferrocenyl bidentate catalyst complex responses in different solvents. Copyright © 2011 Elsevier B.V. All rights reserved.

Atomic Scale Analysis of the Enhanced Electro- and Photo-Catalytic Activity in High-Index Faceted Porous NiO Nanowires

NASA Astrophysics Data System (ADS)

Shen, Meng; Han, Ali; Wang, Xijun; Ro, Yun Goo; Kargar, Alireza; Lin, Yue; Guo, Hua; Du, Pingwu; Jiang, Jun; Zhang, Jingyu; Dayeh, Shadi A.; Xiang, Bin

2015-02-01

Catalysts play a significant role in clean renewable hydrogen fuel generation through water splitting reaction as the surface of most semiconductors proper for water splitting has poor performance for hydrogen gas evolution. The catalytic performance strongly depends on the atomic arrangement at the surface, which necessitates the correlation of the surface structure to the catalytic activity in well-controlled catalyst surfaces. Herein, we report a novel catalytic performance of simple-synthesized porous NiO nanowires (NWs) as catalyst/co-catalyst for the hydrogen evolution reaction (HER). The correlation of catalytic activity and atomic/surface structure is investigated by detailed high resolution transmission electron microscopy (HRTEM) exhibiting a strong dependence of NiO NW photo- and electrocatalytic HER performance on the density of exposed high-index-facet (HIF) atoms, which corroborates with theoretical calculations. Significantly, the optimized porous NiO NWs offer long-term electrocatalytic stability of over one day and 45 times higher photocatalytic hydrogen production compared to commercial NiO nanoparticles. Our results open new perspectives in the search for the development of structurally stable and chemically active semiconductor-based catalysts for cost-effective and efficient hydrogen fuel production at large scale.

In Situ Graphene Growth Dynamics on Polycrystalline Catalyst Foils

PubMed Central

2016-01-01

The dynamics of graphene growth on polycrystalline Pt foils during chemical vapor deposition (CVD) are investigated using in situ scanning electron microscopy and complementary structural characterization of the catalyst with electron backscatter diffraction. A general growth model is outlined that considers precursor dissociation, mass transport, and attachment to the edge of a growing domain. We thereby analyze graphene growth dynamics at different length scales and reveal that the rate-limiting step varies throughout the process and across different regions of the catalyst surface, including different facets of an individual graphene domain. The facets that define the domain shapes lie normal to slow growth directions, which are determined by the interfacial mobility when attachment to domain edges is rate-limiting, as well as anisotropy in surface diffusion as diffusion becomes rate-limiting. Our observations and analysis thus reveal that the structure of CVD graphene films is intimately linked to that of the underlying polycrystalline catalyst, with both interfacial mobility and diffusional anisotropy depending on the presence of step edges and grain boundaries. The growth model developed serves as a general framework for understanding and optimizing the growth of 2D materials on polycrystalline catalysts. PMID:27576749

Graphene stabilized ultra-small CuNi nanocomposite with high activity and recyclability toward catalysing the reduction of aromatic nitro-compounds

NASA Astrophysics Data System (ADS)

Fang, Hao; Wen, Ming; Chen, Hanxing; Wu, Qingsheng; Li, Weiying

2015-12-01

Nowadays, it is of great significance and a challenge to design a noble-metal-free catalyst with high activity and a long lifetime for the reduction of aromatic nitro-compounds. Here, a 2D structured nanocomposite catalyst with graphene supported CuNi alloy nanoparticles (NPs) is prepared, and is promising for meeting the requirements of green chemistry. In this graphene/CuNi nanocomposite, the ultra-small CuNi nanoparticles (~2 nm) are evenly anchored on graphene sheets, which is not only a breakthrough in the structures, but also brings about an outstanding performance in activity and stability. Combined with a precise optimization of the alloy ratios, the reaction rate constant of graphene/Cu61Ni39 reached a high level of 0.13685 s-1, with a desirable selectivity as high as 99% for various aromatic nitro-compounds. What's more, the catalyst exhibited a unprecedented long lifetime because it could be recycled over 25 times without obvious performance decay or even a morphology change. This work showed the promise and great potential of noble-metal-free catalysts in green chemistry.Nowadays, it is of great significance and a challenge to design a noble-metal-free catalyst with high activity and a long lifetime for the reduction of aromatic nitro-compounds. Here, a 2D structured nanocomposite catalyst with graphene supported CuNi alloy nanoparticles (NPs) is prepared, and is promising for meeting the requirements of green chemistry. In this graphene/CuNi nanocomposite, the ultra-small CuNi nanoparticles (~2 nm) are evenly anchored on graphene sheets, which is not only a breakthrough in the structures, but also brings about an outstanding performance in activity and stability. Combined with a precise optimization of the alloy ratios, the reaction rate constant of graphene/Cu61Ni39 reached a high level of 0.13685 s-1, with a desirable selectivity as high as 99% for various aromatic nitro-compounds. What's more, the catalyst exhibited a unprecedented long lifetime because it could be recycled over 25 times without obvious performance decay or even a morphology change. This work showed the promise and great potential of noble-metal-free catalysts in green chemistry. Electronic supplementary information (ESI) available: Detailed SEM and TEM images, XRD patterns, XPS, EDS, Raman spectra, gas chromatograms, TG analyses, UV-vis spectra, and reaction rate constant tables. See DOI: 10.1039/c5nr05016b

Investigation of TiO2 based Mixed-metal Oxide Catalysts for the Production of Hydrogen

NASA Astrophysics Data System (ADS)

Luo, Si

Abstract of the Dissertation. Investigation of TiO2 based Mixed-metal Oxide Catalysts for the Production of Hydrogen. by. Si Luo. Doctor of Philosophy. in. Chemistry. Stony Brook University. 2017. The environmental impacts of fossil fuel consumption and the resulting global warming have attracted increasing attention to technologies and fuels that are both sustainable and renewable in the 21st century. To date, hydrogen has been proposed as an encouraging candidate of the next generation of chemical fuels, which meets all demands for carbon free and efficient chemistries that could be produced from a variety of sources. However, despite tremendous efforts, there is a clear need to develop new catalysts for the production of hydrogen through catalytic processes that are sustainable, such as in the photocatalytic splitting of water (PCS: H2O → H2 + 0.5O2) and the water-gas shift process (WGS: CO + H2O → H2 + CO2). This thesis is primarily motivated by this challenge and has focused on the photochemical and thermal production of H2 by the employment of novel TiO2 based catalysts. TiO2 is one of the most widely studied photocatalysts in all history, due to its relatively high activity, robust stability, safety and low cost. In this thesis, several TiO2-based mixed metal oxide nano catalysts (CeOx-TiO2, Ru-TiO2, Ga-TiO2) have been synthesized with carefully controlled morphology/structure and with inclusion of co-catalysts (Pt). These novel materials were comprehensively characterized to better understand their morphology, crystal structure, and electronic properties in an attempt to unravel phenomena responsible for high catalytic performance for the production of H2 from H2O. We have discovered the importance of low-dimensional metal oxide and interfacial stabilized nano-scaled mixed metal oxides for H2 production, while learning how best to tune such structure to optimize both thermal and photochemical conversion. Optimized structure and/or composition have been identified for TiO2 modified in different ways by another metal oxide (CeOx) or with dopants (Ga, Ru). In addition, we have also studied the water gas shift reaction on several TiO2 supported catalysts, where similar concepts can be applied. Advanced In situ characterization enabled the investigation of the catalyst structure, surface chemical intermediates and active species under reaction conditions. The influence of metal-oxide, oxide-oxide interactions has been further revealed for both the water-gas shift and the photocatalytic splitting of water.

Novel low-cost Fenton-like layered Fe-titanate catalyst: preparation, characterization and application for degradation of organic colorants.

PubMed

Chen, Yongzhou; Li, Nian; Zhang, Ye; Zhang, Lide

2014-05-15

Novel low-cost layered Fe-titanate catalyst for photo-Fenton degradation of organic contaminants was successfully developed by ion exchange of Fe(3+) with Na(+) layered nano Na-titanates which was prepared by alkali hydrothermal method. The as prepared materials were characterized by powder X-ray diffraction analysis (XRD), field emission scanning electron microscopy (FESEM) and energy-dispersive X-ray spectrometer (EDX). The catalytic activity of the Fe-titanate catalyst was evaluated by the decolorization of three different dyes (rhodamine 6G (R6G), methyl blue (MB), and methyl orange (MO)) under UV irradiation at room temperature. Effect of several important factors such as Fe loading in the catalyst, initial solution pH, catalyst dosage, H2O2 amount, and reaction time was systematically studied. It was found that the decolorization was very efficient for all three dyes. The efficiency reached 98% for R6G, 98.5% for MB, and 97% for MO, respectively, under optimal conditions. The oxidation process was quick, and only 15 min is needed for all three dyes. Moreover, the Fe-titanate catalyst could be used in a wider and near neutral pH range compared with classic Fenton systems which need to be operated at around pH 3.0. Kinetic analysis results showed that the oxidation kinetics was accurately represented by pseudo-first-order model. More importantly, the catalyst was very stable and could be reused for at least four cycles when operated under near neutral pH. The Fe leaching from the catalyst measured was almost negligible, which not only demonstrated the stability of the catalyst, but also avoided the formation of secondary Fe pollution. Therefore, the reported Fe-titanates are promising nanomaterials which can be used as Fenton like catalyst for the degradation of organic contaminant in wastewater. Crown Copyright © 2014. Published by Elsevier Inc. All rights reserved.

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 Product Selectivity for Aqueous CO2 Reduction with a Mn(bipyridine)-pyrene Catalyst Immobilized on a Carbon Nanotube Electrode

PubMed Central

2017-01-01

The development of high-performance electrocatalytic systems for the controlled reduction of CO2 to value-added chemicals is a key goal in emerging renewable energy technologies. The lack of selective and scalable catalysts in aqueous solution currently hampers the implementation of such a process. Here, the assembly of a [MnBr(2,2′-bipyridine)(CO)3] complex anchored to a carbon nanotube electrode via a pyrene unit is reported. Immobilization of the molecular catalyst allows electrocatalytic reduction of CO2 under fully aqueous conditions with a catalytic onset overpotential of η = 360 mV, and controlled potential electrolysis generated more than 1000 turnovers at η = 550 mV. The product selectivity can be tuned by alteration of the catalyst loading on the nanotube surface. CO was observed as the main product at high catalyst loadings, whereas formate was the dominant CO2 reduction product at low catalyst loadings. Using UV–vis and surface-sensitive IR spectroelectrochemical techniques, two different intermediates were identified as responsible for the change in selectivity of the heterogenized Mn catalyst. The formation of a dimeric Mn0 species at higher surface loading was shown to preferentially lead to CO formation, whereas at lower surface loading the electrochemical generation of a monomeric Mn-hydride is suggested to greatly enhance the production of formate. These results emphasize the advantages of integrating molecular catalysts onto electrode surfaces for enhancing catalytic activity while allowing excellent control and a deeper understanding of the catalytic mechanisms. PMID:28885841

Activating and optimizing MoS 2 basal planes for hydrogen evolution through the formation of strained sulphur vacancies

DOE PAGES

Li, Hong; Tsai, Charlie; Koh, Ai Leen; ...

2015-11-09

As a promising non-precious catalyst for the hydrogen evolution reaction, molybdenum disulphide (MoS 2) is known to contain active edge sites and an inert basal plane. Activating the MoS 2 basal plane could further enhance its HER activity but is not often a strategy for doing so. Herein, we report the first activation and optimization of the basal plane of monolayer 2H-MoS 2 for HER by introducing sulphur (S) vacancies and strain. Our theoretical and experimental results show that the S-vacancies are new catalytic sites in the basal plane, where gap states around the Fermi level allow hydrogen to bindmore » directly to exposed Mo atoms. The hydrogen adsorption free energy (ΔG H) can be further manipulated by straining the surface with S-vacancies, which fine-tunes the catalytic activity. Furthermore, proper combinations of S-vacancy and strain yield the optimal ΔG H = 0 eV, which allows us to achieve the highest intrinsic HER activity among molybdenum-sulphide-based catalysts.« less

Central composite design optimization of pilot plant fluidized-bed heterogeneous Fenton process for degradation of an azo dye.

PubMed

Aghdasinia, Hassan; Bagheri, Rasoul; Vahid, Behrouz; Khataee, Alireza

2016-11-01

Optimization of Acid Yellow 36 (AY36) degradation by heterogeneous Fenton process in a recirculated fluidized-bed reactor was studied using central composite design (CCD). Natural pyrite was applied as the catalyst characterized by X-ray diffraction and scanning electron microscopy. The CCD model was developed for the estimation of degradation efficiency as a function of independent operational parameters including hydrogen peroxide concentration (0.5-2.5 mmol/L), initial AY36 concentration (5-25 mg/L), pH (3-9) and catalyst dosage (0.4-1.2 mg/L). The obtained data from the model are in good agreement with the experimental data (R(2 )= 0.964). Moreover, this model is applicable not only to determine the optimized experimental conditions for maximum AY36 degradation, but also to find individual and interactive effects of the mentioned parameters. Finally, gas chromatography-mass spectroscopy (GC-MS) was utilized for the identification of some degradation intermediates and a plausible degradation pathway was proposed.

Platinum group metal-free electrocatalysts: Effects of synthesis on structure and performance in proton-exchange membrane fuel cell cathodes

NASA Astrophysics Data System (ADS)

Workman, Michael J.; Dzara, Michael; Ngo, Chilan; Pylypenko, Svitlana; Serov, Alexey; McKinney, Sam; Gordon, Jonathan; Atanassov, Plamen; Artyushkova, Kateryna

2017-04-01

Development of platinum group metal free catalysts for the oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs) requires understanding of the interactions between surface chemistry and performance, both of which are strongly dependent on synthesis conditions. To elucidate these complex relationships, a set of Fe-N-C catalysts derived from the same set of precursor materials is fabricated by varying several key synthetic parameters under controlled conditions. The results of physicochemical characterization are presented and compared with the results of rotating disk electrode (RDE) analysis and fuel cell testing. We find that electrochemical performance is strongly correlated with three key properties related to catalyst composition: concentrations of 1) atomically dispersed Fe species, 2) species in which N is bound to Fe, and 3) surface oxides. Not only are these factors related to performance, these types of chemical species are shown to correlate with each other. This study provides evidence supporting the role of iron coordinated with nitrogen as an active species for the ORR, and offers synthetic pathways to increase the density of atomically dispersed iron species and surface oxides for optimum performance.

Templated Synthesis of Single-Walled Carbon Nanotubes with Specific Structure.

PubMed

Yang, Feng; Wang, Xiao; Li, Meihui; Liu, Xiyan; Zhao, Xiulan; Zhang, Daqi; Zhang, Yan; Yang, Juan; Li, Yan

2016-04-19

Single-walled carbon nanotubes (SWNTs) have shown great potential in various applications attributed to their unique structure-dependent properties. Therefore, the controlled preparation of chemically and structurally pristine SWNTs is a crucial issue for their advanced applications (e.g., nanoelectronics) and has been a great challenge for two decades. Epitaxial growth from well-defined seeds has been shown to be a promising strategy to control the structure of SWNTs. Segments of carbon nanotubes, including short pipes from cutting of preformed nanotubes and caps from opening of fullerenes or cyclodehydrogenation of polycyclic hydrocarbon precursors, have been used as the seeds to grow SWNTs. Single-chirality SWNTs were obtained with both presorted chirality-pure SWNT segments and end caps obtained from polycyclic hydrocarbon molecules with designed structure. The main challenges of nanocarbon-segment-seeded processes are the stability of the seeds, yield, and efficiency. Catalyst-mediated SWNT growth is believed to be more efficient. The composition and morphology of the catalyst nanoparticles have been widely reported to affect the chirality distribution of SWNTs. However, chirality-specific SWNT growth is hard to achieve by alternating catalysts. The specificity of enzyme-catalyzed reactions brings us an awareness of the essentiality of a unique catalyst structure for the chirality-selective growth of SWNTs. Only catalysts with the desired atomic arrangements in their crystal planes can act as structural templates for chirality-specific growth of SWNTs. We have developed a new family of catalysts, tungsten-based intermetallic compounds, which have high melting points and very special crystal structures, to facilitate the growth of SWNTs with designed chirality. By the use of W6Co7 catalysts, (12,6) SWNTs were directly grown with purity higher than 92%. Both high-resolution transmission electron microscopy measurements and density functional theory simulations show that the selective growth of (12,6) tubes is due to a good structural match between the carbon atom arrangement around the nanotube circumference and the metal atom arrangement of (0 0 12) planes in the catalyst. Similarly, (16,0) SWNTs exhibit a good structural match to the (116) planes of the W6Co7 catalyst. By optimization of the chemical vapor deposition (CVD) conditions, zigzag (16,0) SWNTs, which are generally known as a kinetically unfavorable species in CVD growth, were obtained with a purity of ∼80%. Generally speaking, the chirality-specific growth of SWNTs is realized by the cooperation of two factors: the structural match between SWNTs and the catalysts makes the growth of SWNTs with specific chirality thermodynamically favorable, and further manipulation of the CVD conditions results in optimized growth kinetics for SWNTs with this designed chirality. We expect that this advanced epitaxial growth strategy will pave the way for the ultimate goal of chirality-specified growth of SWNTs and will also be applicable in the controlled preparation of other nanomaterials.

Charting the relationship between phase type-surface area-interactions between the constituent atoms and oxygen reduction activity of Pd–Cu nanocatalysts inside fuel cells by in operando high-energy X-ray diffraction

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

Maswadeh, Yazan; Shan, Shiyao; Prasai, Binay

The activity and stability of nanoalloy catalysts for chemical reactions driving devices for clean energy conversion, in particular the oxygen reduction reaction (ORR), depend critically on optimizing major structural characteristics of the nanoalloys, such as the phase composition, surface area and bonding interactions between the constituent atoms, for the harsh operating conditions inside the devices. The effort requires good knowledge of the potential effect of changes in these characteristics on the catalytic functionality of the nanoalloys and, hence, on the devices' performance. We present the results from an in operando high-energy X-ray diffraction (HE-XRD) study on the concurrent changes inmore » the structural characteristics and ORR activity of Pd–Cu nanoalloy catalysts as they function at the cathode of a proton exchange membrane fuel cell (PEMFC). We find that the as-prepared Pd–Cu nanoalloys with a chemical composition close to Pd1Cu1 are better ORR catalysts in comparison with Pd1Cu2, i.e. Pd-poor, and Pd3Cu1, i.e. Pd-rich, nanoalloys. Under operating conditions though, the former suffers a big loss in ORR activity appearing as a slow-mode oscillation in the current output of the PEMFC. Losses in ORR activity suffered by the latter also exhibit sudden drops and rises during the PEMFC operation. Through atomic pair distribution function (PDF) analysis of the in operando HE-XRD data, we identify the structural changes of Pd–Cu alloy NPs that are behind the peculiar decay of their ORR activity. The results uncover the instant link between the ever-adapting structural state of ORR nanocatalysts inside an operating PEMFC and the performance of the PEMFC. Besides, our results indicate that, among others, taking control over the intra-particle diffusion of metallic species in nanoalloy catalysts may improve the performance of PEMFCs significantly and, furthermore, in operando HE-XRD can be an effective tool to guide the effort. Finally, we argue that, though showing less optimal ORR activity in the as-prepared state, monophase Pd–Cu alloy catalysts with a composition ranging between Pd1Cu1 and Pd3Cu1 may deliver optimal performance inside operating PEMFCs.« less

Pt/glassy carbon model catalysts prepared from PS-b-P2VP micellar templates.

PubMed

Gu, Yunlong; St-Pierre, Jean; Ploehn, Harry J

2008-11-04

Poly(styrene)-block-poly(2-vinylpyridine) (PS-b-P2VP) diblock copolymer was used as a micellar template to fabricate arrays of Pt nanoparticles on mica and glassy carbon (GC) supports. Polymer micellar deposition yields Pt nanoparticles with tunable particle size and surface number density on both mica and GC. After deposition of precursor-loaded micelles onto GC, oxygen plasma etching removes the polymer shell, followed by thermal treatment with H2 gas to reduce the Pt. Etching conditions were optimized to maximize removal of the polymer while minimizing damage to the GC. Arrays of Pt nanoparticles with controlled size and surface number density can be prepared on mica (for particle size characterization) and GC to make Pt/GC model catalysts. These model catalysts were characterized by tapping mode atomic force microscopy, X-ray photoelectron spectroscopy, and cyclic voltammetry to measure activity for oxidation of carbon monoxide or methanol. Cyclic voltammetry results demonstrate the existence of a correlation between Pt particle size and electrocatalytic properties including onset potential, tolerance of carbonaceous adsorbates, and intrinsic activity (based on active Pt area from CO stripping voltammetry). Results obtained with Pt/GC model catalysts duplicate prior results obtained with Pt/porous carbon catalysts therefore validating the synthesis approach and offering a new, tunable platform to study catalyst structure and other effects such as aging on proton exchange membrane fuel cell (PEMFC) reactions.

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.

Reverse Micelle Synthesis and Characterization of Supported Pt/Ni Bimetallic Catalysts on gamma-Al2O3

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

B Cheney; J Lauterbach; J Chen

2011-12-31

Reverse micelle synthesis was used to improve the nanoparticle size uniformity of bimetallic Pt/Ni nanoparticles supported on {gamma}-Al{sub 2}O{sub 3}. Two impregnation methods were investigated to optimize the use of the micelle method: (1) step-impregnation, where Ni nanoparticles were chemically reduced in microemulsion and then supported, followed by Pt deposition using incipient wetness impregnation, and (2) co-impregnation, where Ni and Pt were chemically reduced simultaneously in microemulsion and then supported. Transmission electron microscopy (TEM) was used to characterize the particle size distribution. Atomic absorption spectroscopy (AAS) was used to perform elemental analysis of bimetallic catalysts. Extended X-ray absorption fine structuremore » (EXAFS) measurements were utilized to confirm the formation of the Pt-Ni bimetallic bond in the step-impregnated catalyst. CO pulse chemisorption and Fourier transform infrared spectroscopy (FTIR) studies of 1,3-butadiene hydrogenation in a batch reactor were performed to determine the catalytic activity. Step-impregnated Pt/Ni catalyst demonstrated enhanced hydrogenation activity over the parent monometallic Pt and Ni catalysts due to bimetallic bond formation. The catalyst synthesized using co-impregnation showed no enhanced activity, behaving similarly to monometallic Ni. Overall, our results indicate that reverse micelle synthesis combined with incipient wetness impregnation produced small, uniform nanoparticles with bimetallic bonds that enhanced hydrogenation activity.« less

Support effects in single atom iron catalysts on adsorption characteristics of toxic gases (NO2, NH3, SO3 and H2S)

NASA Astrophysics Data System (ADS)

Gao, Zhengyang; Yang, Weijie; Ding, Xunlei; Lv, Gang; Yan, Weiping

2018-04-01

The effects of support on gas adsorption is crucial for single atom catalysts design and optimization. To gain insight into support effects on gas adsorption characteristics, a comprehensive theoretical study was performed to investigate the adsorption characteristics of toxic gases (NO2, NH3, SO3 and H2S) by utilizing single atom iron catalysts with three graphene-based supports. The adsorption geometry, adsorption energy, electronic and magnetic properties of the adsorption system have been explored. Additionally, the support effects have been analyzed through d-band center and Fermi softness, and thermodynamic analysis has been performed to consider the effect of temperature on gas adsorption. The support effects have a remarkable influence on the adsorption characteristics of four types of toxic gases which is determined by the electronic structure of graphene-based support, and the electronic structure can be characterized by Fermi softness of catalysts. Fermi softness and uplift height of Fe atom could be good descriptors for the adsorption activity of single atom iron catalysts with graphene-based supports. The findings can lay a foundation for the further study of graphene-based support effects in single atom catalysts and provide a guideline for development and design of new graphene-based support materials utilizing the idea of Fermi softness.

Study on the treatment of 2-sec-butyl-4,6-dinitrophenol (DNBP) wastewater by ClO2 in the presence of aluminum oxide as catalyst.

PubMed

Wang, Hui-Long; Dong, Jing; Jiang, Wen-Feng

2010-11-15

The chlorine dioxide (ClO(2)) oxidative degradation of 2-sec-butyl-4,6-dinitrophenol (DNBP) in aqueous solution was studied in detail using Al(2)O(3) as a heterogeneous catalyst. The operating parameters such as the ClO(2) concentration, catalyst dosage, initial DNBP concentration, reaction time and pH were evaluated. Compared with the conventional ClO(2) oxidation process without the catalyst, the ClO(2) catalytic oxidation system could significantly enhance the degradation efficiency. Under the optimal condition (DNBP concentration 39 mg L(-1), ClO(2) concentration 0.355 g L(-1), reaction time 60 min, catalyst dosage 10.7 g L(-1) and pH 4.66), degradation efficiency approached 99.1%. The catalyst was used at least 8 cycles without any appreciable loss of activity. The kinetic studies revealed that the ClO(2) catalytic oxidation degradation of DNBP followed pseudo-first-order kinetics with respect to DNBP concentration. The ClO(2) catalytic oxidation process was found to be very effective in the decolorization and COD(Cr) reduction of real wastewater from DNBP manufacturing. Thus, this study showed potential application of ClO(2) catalytic oxidation process in degradation of organic contaminants and industrial effluents. Copyright © 2010 Elsevier B.V. All rights reserved.

Evaluation of Bosch-Based Systems Using Non-Traditional Catalysts at Reduced Temperatures

NASA Technical Reports Server (NTRS)

Abney, Morgan B.; Mansell, J. Matthew

2011-01-01

Oxygen and water resupply make open loop atmosphere revitalization (AR) systems unfavorable for long-term missions beyond low Earth orbit. Crucial to closing the AR loop are carbon dioxide reduction systems with low mass and volume, minimal power requirements, and minimal consumables. For this purpose, NASA is exploring using Bosch-based systems. The Bosch process is favorable over state-of-the-art Sabatier-based processes due to complete loop closure. However, traditional operation of the Bosch required high reaction temperatures, high recycle rates, and significant consumables in the form of catalyst resupply due to carbon fouling. A number of configurations have been proposed for next-generation Bosch systems. First, alternative catalysts (catalysts other than steel wool) can be used in a traditional single-stage Bosch reactor to improve reaction kinetics and increase carbon packing density. Second, the Bosch reactor may be split into separate stages wherein the first reactor stage is dedicated to carbon monoxide and water formation via the reverse water-gas shift reaction and the second reactor stage is dedicated to carbon formation. A series system will enable maximum efficiency of both steps of the Bosch reaction, resulting in optimized operation and maximum carbon formation rate. This paper details the results of testing of both single-stage and two-stage Bosch systems with alternative catalysts at reduced temperatures. These results are compared to a traditional Bosch system operated with a steel wool catalyst.

Vapor Phase Hydrogenolysis of Furanics Utilizing Reduced Cobalt Mixed Metal Oxide Catalysts

DOE PAGES

Sulmonetti, Taylor P.; Hu, Bo; Ifkovits, Zachary; ...

2017-03-21

Vapor phase hydrogenolysis of both furfuryl alcohol and furfural were investigated over reduced Co based mixed metal oxides derived from the calcination of a layered double hydroxide precursor. Although a reduced cobalt aluminate sample displays promising selectivity towards 2-methylfuran (2-MF) production, the addition of an Fe dopant into the oxide matrix significantly enhances the activity and selectivity per gram of catalyst. Approximately 82% 2-MF yield is achieved at high conversion when furfuryl alcohol is fed into the reactor at 180 °C over the reduced 3Co-0.25Fe-0.75Al catalyst. Based on structural characterization studies including TPR, XPS, and in-situ XAS it is suggestedmore » that Fe facilitates the reduction of Co, allowing for formation of more metallic species. Altogether, this study demonstrates that non-precious metal catalysts offer promise for the selective conversion of a key biomass oxygenate to a proposed fuel additive.« less

Deoxygenation of Palmitic and Lauric Acids over Pt/ZIF-67 Membrane/Zeolite 5A Bead Catalysts.

PubMed

Yang, Liqiu; Carreon, Moises A

2017-09-20

The deoxygenation of palmitic and lauric acids over 0.5 wt % Pt/ZIF-67 membrane/zeolite 5A bead catalysts is demonstrated. Almost complete conversion (% deoxygenation of ≥95%) of these two fatty acids was observed over both fresh and recycled catalyst after a 2 h reaction time. The catalysts displayed high selectivity to pentadecane and undecane via decarboxylation reaction pathway even at low 0.5 wt % Pt loading. Selectivity to pentadecane and undecane as high as ∼92% and ∼94% was observed under CO 2 atmosphere when palmitic and lauric acids were used respectively as reactants. Depending on the reaction gas atmosphere, two distinctive reaction pathways were observed: decarboxylation and hydrodeoxygenation. Specifically, it was found that decarboxylation reaction pathway was more favorable in the presence of helium and CO 2 , while hydrodeoxygenation pathway strongly competed against the decarboxylation pathway when hydrogen was employed during the deoxygenation reactions. Esters were identified as the key reaction intermediates leading to decarboxylation and hydrodeoxygenation pathways.

DeNOx active iron sites in iron loaded ZSM-5 - a multitechnique analysis of a complex heterogeneous catalyst based on Mössbauer spectroscopy

NASA Astrophysics Data System (ADS)

Padmalekha, K. G.; Huang, H.; Ellmers, I.; Pérez Vélez, R.; van Leusen, J.; Brückner, A.; Grünert, W.; Schünemann, V.

2017-11-01

Iron loaded zeolites like Fe-ZSM-5 are potent candidates for the catalytic abatement of nitrogen oxides from car exhaust, e.g. from Diesel engines. Recent problems in this field show that there is an urgent need in further improvement of such catalysts, for which a full analysis of Fe species present in them under different conditions is highly desirable. We have studied Fe-ZSM-5 catalysts prepared via solid-state ion exchange by using field dependent Mössbauer spectroscopy at low temperature in order to identify the different iron species present in this type of catalyst in the fresh state and after use in catalysis. Mössbauer spectroscopy proved to be the key technique for a full understanding of species structures, but due to the complexity of structures, guidance by parallel EPR experiments and control by SQUID magnetometry were essential to prove reliability of derived species distributions.

Effect and interaction study of acetamiprid photodegradation using experimental design.

PubMed

Tassalit, Djilali; Chekir, Nadia; Benhabiles, Ouassila; Mouzaoui, Oussama; Mahidine, Sarah; Merzouk, Nachida Kasbadji; Bentahar, Fatiha; Khalil, Abbas

2016-10-01

The methodology of experimental research was carried out using the MODDE 6.0 software to study the acetamiprid photodegradation depending on the operating parameters, such as the initial concentration of acetamiprid, concentration and type of the used catalyst and the initial pH of the medium. The results showed the importance of the pollutant concentration effect on the acetamiprid degradation rate. On the other hand, the amount and type of the used catalyst have a considerable influence on the elimination kinetics of this pollutant. The degradation of acetamiprid as an environmental pesticide pollutant via UV irradiation in the presence of titanium dioxide was assessed and optimized using response surface methodology with a D-optimal design. The acetamiprid degradation ratio was found to be sensitive to the different studied factors. The maximum value of discoloration under the optimum operating conditions was determined to be 99% after 300 min of UV irradiation.

Highly efficient hydrogen evolution based on Ni3S4@MoS2 hybrids supported on N-doped reduced graphene oxide

NASA Astrophysics Data System (ADS)

Xu, Xiaobing; Zhong, Wei; Wu, Liqian; Sun, Yuan; Wang, Tingting; Wang, Yuanqi; Du, Youwei

2018-01-01

Hydrogen evolution reaction (HER) through water splitting at low overpotential is an appealing technology to produce renewable energy, wherein the design of stable electrocatalysts is very critical. To achieve optimal electrochemical performance, a highly efficient and stable noble-metal-free HER catalyst is synthesized by means of a facile hydrothermal co-synthesis. It consists of Ni3S4 nanosheets and MoS2 nanolayers supported on N-doped reduced graphene oxide (Ni3S4/MoS2@N-rGO). The optimized sample provides a large amount of active sites that benefit electron transfer in 3D conductive networks. Thanks to the strong synergistic effect in the catalyst network, we achieved a low overpotential of 94 mV, a small Tafel slope of 56 mV/dec and remarkable durability in an acidic medium.

Preparation of Fe3O4/TiO2 magnetic mesoporous composites for photocatalytic degradation of organic pollutants.

PubMed

Zhang, Hongfeng; He, Xiu; Zhao, Weiwei; Peng, Yu; Sun, Donglan; Li, Hao; Wang, Xiaocong

2017-04-01

Fe 3 O 4 /TiO 2 magnetic mesoporous composites were synthesized through a sol-gel method with tetra-n-butyl titanate as precursor and surfactant P123 as template. The as-prepared Fe 3 O 4 /TiO 2 composites were characterized by X-ray diffraction, diffuse reflectance spectroscopy, nitrogen adsorption-desorption isotherm and pore size distribution. The as-synthesized products were applied as photocatalysis for the degradation of Acid Black ATT and tannery wastewater under UV lamp irradiation. Fe 3 O 4 /TiO 2 -8 composites containing Fe 3 O 4 of 8 wt% were selected as model catalysts. The optimal catalyst dosage was 3 g/L in this photocalytic system. The magnetic Fe 3 O 4 /TiO 2 composites possessed good photocatalytic stability and durability. This approach may provide a platform to prepare a magnetic composite to optimize the catalytic ability.

Development of a chemiluminescent and bioluminescent system for the detection of bacteria in wastewater effluent

NASA Technical Reports Server (NTRS)

Thomas, R. R.

1975-01-01

Automated chemiluminescent and bioluminescent sensors were developed for continuous monitoring of microbial levels in wastewater effluent. Development of the chemiluminescent system included optimization of reagent concentrations as well as two new techniques which will allow for increased sensitivity and specificity. The optimal reagent concentrations are 0.0025 M luminol and 0.0125 M sodium perborate in 0.75N sodium hydroxide before addition of sample. The methods developed to increase specificity include (1) extraction of porphyrins from bacteria collected in a filter using 0.1N NaOH - 50 percent Ethanol, and (2) use of the specific reaction rate characteristics for the different luminol catalysts. Since reaction times are different for each catalyst, the reaction can be made specific for bacteria by measuring only the light emission from the particular reaction time zone specific for bacteria. Developments of the bioluminescent firefly luciferase system were in the area of flow system design.

A Catalyst-Free Amination of Functional Organolithium Reagents by Flow Chemistry.

PubMed

Kim, Heejin; Yonekura, Yuya; Yoshida, Jun-Ichi

2018-04-03

Reported is the electrophilic amination of functional organolithium intermediates with well-designed aminating reagents under mild reaction conditions using flow microreactors. The aminating reagents were optimized to achieve efficient C-N bond formation without using any catalyst. The electrophilic amination reactions of functionalized aryllithiums were successfully conducted under mild reaction conditions, within 1 minute, by using flow microreactors. The aminating reagent was also prepared by the flow method. Based on stopped-flow NMR analysis, the reaction time for the preparation of the aminating reagent was quickly optimized without the necessity of work-up. Integrated one-flow synthesis consisting of the generation of an aryllithium, the preparation of an aminating reagent, and their combined reaction was successfully achieved to give the desired amine within 5 minutes of total reaction time. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Mechanistic Studies at the Interface Between Organometallic Chemistry and Homogeneous Catalysis

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

Casey, Charles P

Mechanistic Studies at the Interface Between Organometallic Chemistry and Homogeneous Catalysis Charles P. Casey, Principal Investigator Department of Chemistry, University of Wisconsin - Madison, Madison, Wisconsin 53706 Phone 608-262-0584 FAX: 608-262-7144 Email: casey@chem.wisc.edu http://www.chem.wisc.edu/main/people/faculty/casey.html Executive Summary. Our goal was to learn the intimate mechanistic details of reactions involved in homogeneous catalysis and to use the insight we gain to develop new and improved catalysts. Our work centered on the hydrogenation of polar functional groups such as aldehydes and ketones and on hydroformylation. Specifically, we concentrated on catalysts capable of simultaneously transferring hydride from a metal center and a proton frommore » an acidic oxygen or nitrogen center to an aldehyde or ketone. An economical iron based catalyst was developed and patented. Better understanding of fundamental organometallic reactions and catalytic processes enabled design of energy and material efficient chemical processes. Our work contributed to the development of catalysts for the selective and mild hydrogenation of ketones and aldehydes; this will provide a modern green alternative to reductions by LiAlH4 and NaBH4, which require extensive work-up procedures and produce waste streams. (C5R4OH)Ru(CO)2H Hydrogenation Catalysts. Youval Shvo described a remarkable catalytic system in which the key intermediate (C5R4OH)Ru(CO)2H (1) has an electronically coupled acidic OH unit and a hydridic RuH unit. Our efforts centered on understanding and improving upon this important catalyst for reduction of aldehydes and ketones. Our mechanistic studies established that the reduction of aldehydes by 1 to produce alcohols and a diruthenium bridging hydride species occurs much more rapidly than regeneration of the ruthenium hydride from the diruthenium bridging hydride species. Our mechanistic studies require simultaneous transfer of hydride from ruthenium to the aldehyde carbon and of a proton from the CpOH unit to the aldehyde oxygen and support reduction of the aldehyde without its prior coordination to ruthenium. Another important step in the catalysis is the regeneration of 1 from reaction of H2 with the stable diruthenium bridging hydride complex 2. Studies of the microscopic reverse of this process (hydrogen evolution from 1 which occurs at 80°C) in the presence of alcohol (the product of aldehyde hydrogenation) have shown that a dihydrogen complex is formed reversibly at a rate much faster than hydrogen evolution. Kinetic and theoretical studies in collaboration with Professor Qiang Cui of Wisconsin indicated an important role for alcohol in mediating transfer of hydrogen to ruthenium. One key to developing more active catalysts was to destabilize the bridging hydride intermediate 2 to prevent its formation or to speed its conversion to a reactive monohydride 1 by reaction with H2. We found several successful ways to destabilize the bridging hydride and to obtain more active catalysts. Most recently, we discovered related iron catalysts for hydrogenation that do not form dimers; the cost advantage of iron catalysts is spectacular. Iron Catalysts. In an exciting development, we found that a related iron complex is also a very active ketone hydrogenation catalyst. This hydrogenation catalyst shows high chemoselectivity for aldehydes, ketones, and imines and isolated C=C, CºC, C-X, -NO2, epoxides, and ester functions are unaffected by the hydrogenation conditions. Mechanistic studies have established a reversible hydrogen transfer step followed by rapid dihydrogen activation. The same iron complex also catalyzes transfer hydrogenation of ketones.« less

Efficient Electron Transfer across a ZnO-MoS2 -Reduced Graphene Oxide Heterojunction for Enhanced Sunlight-Driven Photocatalytic Hydrogen Evolution.

PubMed

Kumar, Suneel; Reddy, Nagappagari Lakshmana; Kushwaha, Himmat Singh; Kumar, Ashish; Shankar, Muthukonda Venkatakrishnan; Bhattacharyya, Kaustava; Halder, Aditi; Krishnan, Venkata

2017-09-22

The development of noble metal-free catalysts for hydrogen evolution is required for energy applications. In this regard, ternary heterojunction nanocomposites consisting of ZnO nanoparticles anchored on MoS 2 -RGO (RGO=reduced graphene oxide) nanosheets as heterogeneous catalysts show highly efficient photocatalytic H 2 evolution. In the photocatalytic process, the catalyst dispersed in an electrolytic solution (S 2- and SO 3 2- ions) exhibits an enhanced rate of H 2 evolution, and optimization experiments reveal that ZnO with 4.0 wt % of MoS 2 -RGO nanosheets gives the highest photocatalytic H 2 production of 28.616 mmol h -1  g cat -1 under sunlight irradiation; approximately 56 times higher than that on bare ZnO and several times higher than those of other ternary photocatalysts. The superior catalytic activity can be attributed to the in situ generation of ZnS, which leads to improved interfacial charge transfer to the MoS 2 cocatalyst and RGO, which has plenty of active sites available for photocatalytic reactions. Recycling experiments also proved the stability of the optimized photocatalyst. In addition, the ternary nanocomposite displayed multifunctional properties for hydrogen evolution activity under electrocatalytic and photoelectrocatalytic conditions owing to the high electrode-electrolyte contact area. Thus, the present work provides very useful insights for the development of inexpensive, multifunctional catalysts without noble metal loading to achieve a high rate of H 2 generation. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

XAS Study at Mo and Co K-Edges of the Sulfidation of a CoMo / Al2O3 Hydrotreating Catalyst

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

Pichon, C.; Gandubert, A. D.; Legens, C.

2007-02-02

Because of its impact on environment, the removal of sulfur is an indispensable step, called hydrotreatment, in the refining of petroleum. One of the most commonly used hydrotreating catalysts is CoMo-type catalyst which is composed of molybdenum disulfide slabs promoted by cobalt atoms (CoMoS phase) and well dispersed on a high specific area alumina. As far as the highest sulfur content allowed in gasoline and diesel is continually decreasing, more and more efficient and active hydrotreating catalysts are required. In order to optimize the reactivity of the CoMo-type catalyst in hydrotreatment, a better understanding of the processes used to producemore » the active phase (CoMoS slabs) of the catalyst is necessary. The study reported here deals with the sulfiding mechanism of the slabs and the influence of temperature on the phenomenon. Ex situ X-ray absorption spectroscopy (XANES and EXAFS) was used to study the evolution of the structure of CoMo-type catalyst sulfided at various temperatures (from 293 to 873 K). XAS analysis was performed at both molybdenum and cobalt K-edges to obtain a cross-characterization of the sulfidation of the slabs. It evidenced the formation of various compounds, including two molybdenum oxides, MoS3 (or MoS3-like compound) and Co9S8, at specific steps of the sulfiding process. It showed the role of intermediate played by MoS3 (or MoS3-like compound) during the formation of the slabs and the competition between the appearance of promoted slabs (CoMoS phase) and Co9S8. At last, it leaded to the proposal of a mechanism for the sulfidation of the catalyst.« less

Novel self-healing materials chemistries for targeted applications

NASA Astrophysics Data System (ADS)

Wilson, Gerald O.

Self-healing materials of the type developed by White and co-workers [1] were designed to autonomically heal themselves when damaged, thereby extending the lifetime of various applications in which such material systems are employed. The system was based on urea-formaldehyde microcapsules containing dicyclopentadiene (DCPD) and Grubbs' catalyst particles embedded together in an epoxy matrix. When a crack propagates through the material, it ruptures the microcapsules, releasing DCPD into the crack plane, where it comes in contact and reacts with the catalyst to initiate a ring opening metathesis polymerization (ROMP), bonding the crack and restoring structural continuity. The present work builds on this concept in several ways. Firstly, it expands the scope and versatility of the ROMP self-healing chemistry by incorporation into epoxy vinyl ester matrices. Major technical challenges in this application include protection of the catalyst from deactivation by aggressive curing agents, and optimization of the concentration of healing agents in the matrix. Secondly, new ruthenium catalysts are evaluated for application in ROMP-based self-healing materials. The use of alternative derivatives of Grubbs' catalyst gave rise to self-healing systems with improved healing efficiencies and thermal properties. Evaluation of the stability of these new catalysts to primary amine curing agents used in the curing of common epoxy matrices also led to the discovery and characterization of new ruthenium catalysts which exhibited ROMP initiation kinetics superior to those of first and second generation Grubbs' catalysts. Finally, free radical polymerization was evaluated for application in the development of bio-compatible self-healing materials. [1] White, S. R.; Sottos, N. R.; Geubelle, P. R.; Moore, J. S.; Kessler, M. R.; Sriram, S. R.; Brown, E. N.; Viswanathan, S. Nature 2001, 409, 794.

A new V-doped Bi2(O,S)3 oxysulfide catalyst for highly efficient catalytic reduction of 2-nitroaniline and organic dyes.

PubMed

Abay, Angaw Kelemework; Kuo, Dong-Hau; Chen, Xiaoyun; Saragih, Albert Daniel

2017-12-01

A new type of convenient, and environmentally friendly, Vanadium (V)-doped Bi 2 (O,S) 3 oxysulfide catalyst with different V contents was successfully synthesized via a simple and facile method. The obtained V-doped Bi 2 (O,S) 3 solid solution catalysts were fully characterized by conventional methods. The catalytic performance of the samples was tested by using the reduction of 2-nitroaniline (2-NA) in aqueous solution. The reduction/decolorization of methylene blue (MB) and rhodamine B (RhB) was also chosen to evaluate the universality of catalysts. It was observed that the introduction of V can improve the catalytic performance, and 20%V-Bi 2 (O,S) 3 was found to be the optimal V doping concentration for the reduction of 2-NA, MB, and RhB dyes. For comparative purposes, a related V-free Bi 2 (O, S) 3 oxysulfide material was synthesized and tested as the catalyst. The superior activity of V-doped Bi 2 (O,S) 3 over pure Bi 2 (O,S) 3 was ascribed mainly to an increase in active sites of the material and also due to the presence of synergistic effects. The presence of V 5+ as found from XPS analysis may interact with Bi atoms and enhancing the catalytic activity of the sample. In the catalytic reduction of 2-NA, MB and RhB, the obtained V-doped Bi 2 (O,S) 3 oxysulfide catalyst exhibited excellent catalytic activity as compared with other reported catalysts. Furthermore this highly efficient, low-cost and easily reusable V-doped Bi 2 (O,S) 3 catalyst is anticipated to be of great potential in catalysis in the future. Copyright © 2017 Elsevier Ltd. All rights reserved.

Design of Heterogeneous Hoveyda-Grubbs Second-Generation Catalyst-Lipase Conjugates.

PubMed

Neville, Anthony; Iniesta, Javier; Palomo, Jose M

2016-12-06

Heterogeneous catalysts have been synthesi zed by the conjugation of Hoveyda-Grubbs second-generation catalyst with a lipase. The catalytic properties of the organometallic compound in solution were firstly optimized, evaluating the activity of Ru in the ring-closing metathesis of diethyldiallymalonate at 25 °C at different solvents and in the presence of different additives. The best result was found using tetrahydrofuran as a solvent. Some additives such as phenylboronic acid or polyetheneglycol slightly improved the activity of the Ru catalyst whereas others, such as pyridine or dipeptides affected it negatively. The organometallic compound immobilized on functionalized-surface materials activated with boronic acid or epoxy groups (around 50-60 µg per mg support) and showed 50% conversion at 24 h in the ring-closing metathesis. Cross-linked enzyme aggregates (CLEA's) of the Hoveyda-Grubbs second-generation catalyst with Candida antarctica lipase (CAL-B) were prepared, although low Ru catalyst was found to be translated in low conversion. Therefore, a sol-gel preparation of the Hoveyda-Grubbs second-generation and CAL-B was performed. This catalyst exhibited good activity in the metathesis of diethyldiallymalonate in toluene and in aqueous media. Finally, a new sustainable approach was used by the conjugation lipase-Grubbs in solid phase in aqueous media. Two strategies were used: one using lipase previously covalently immobilized on an epoxy-Sepharose support (hydrophilic matrix) and then conjugated with grubbs; and in the second, the free lipase was incubated with organometallic in aqueous solution and then immobilized on epoxy-Sepharose. The different catalysts showed excellent conversion values in the ring-closing metathesis of diethyldiallymalonate in aqueous media at 25 °C.

Controllable cyanation of carbon-hydrogen bonds by zeolite crystals over manganese oxide catalyst

PubMed Central

Wang, Liang; Wang, Guoxiong; Zhang, Jian; Bian, Chaoqun; Meng, Xiangju; Xiao, Feng-Shou

2017-01-01

The synthesis of organic nitriles without using toxic cyanides is in great demand but challenging to make. Here we report an environmentally benign and cost-efficient synthesis of nitriles from the direct oxidative cyanation of primary carbon-hydrogen bonds with easily available molecular oxygen and urea. The key to this success is to design and synthesize manganese oxide catalysts fixed inside zeolite crystals, forming a manganese oxide catalyst with zeolite sheath (MnOx@S-1), which exhibits high selectivity for producing nitriles by efficiently facilitating the oxidative cyanation reaction and hindering the side hydration reaction. The work delineates a sustainable strategy for synthesizing nitriles while avoiding conventional toxic cyanide, which might open a new avenue for selective transformation of carbon-hydrogen bonds. PMID:28504259

Cooperative Light-Activated Iodine and Photoredox Catalysis for the Amination of Csp3 -H Bonds.

PubMed

Becker, Peter; Duhamel, Thomas; Stein, Christopher J; Reiher, Markus; Muñiz, Kilian

2017-06-26

An unprecedented method that makes use of the cooperative interplay between molecular iodine and photoredox catalysis has been developed for dual light-activated intramolecular benzylic C-H amination. Iodine serves as the catalyst for the formation of a new C-N bond by activating a remote Csp3 -H bond (1,5-HAT process) under visible-light irradiation while the organic photoredox catalyst TPT effects the reoxidation of the molecular iodine catalyst. To explain the compatibility of the two involved photochemical steps, the key N-I bond activation was elucidated by computational methods. The new cooperative catalysis has important implications for the combination of non-metallic main-group catalysis with photocatalysis. © 2017 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.

Ammonium-tungstate-promoted growth of boron nitride nanotubes

NASA Astrophysics Data System (ADS)

E, Songfeng; Li, Chaowei; Li, Taotao; Geng, Renjie; Li, Qiulong; Lu, Weibang; Yao, Yagang

2018-05-01

Ammonium tungstate ((NH4)10W12O41 · xH2O) is a kind of oxygen-containing ammonium salt. The following study proves that it can be successfully used as a metal oxide alternative to produce boron oxide (B2O2) by oxidizing boron (B) in a traditional boron oxide chemical vapor deposition (BOCVD) process. This special oxidant promotes the simplistic fabrication of boron nitride nanotubes (BNNTs) in a conventional horizontal tube furnace, an outcome which may have resulted from its strong oxidizability. The experimental results demonstrate that the mole ratio of B and (NH4)10W12O41 · xH2O is a key parameter in determining the formation, quality and quantity of BNNTs when stainless steel is employed as a catalyst. We also found that Mg(NO3)2 and MgO nanoparticles (NPs) can be used as catalysts to grow BNNTs with the same precursor. The BNNTs obtained from the Mg(NO3)2 catalyst were straighter than those obtained from the MgO NP catalyst. This could have been due to the different physical forms of the catalysts that were used.

Ammonium-tungstate-promoted growth of boron nitride nanotubes.

PubMed

E, Songfeng; Li, Chaowei; Li, Taotao; Geng, Renjie; Li, Qiulong; Lu, Weibang; Yao, Yagang

2018-05-11

Ammonium tungstate ((NH 4 ) 10 W 12 O 41  · xH 2 O) is a kind of oxygen-containing ammonium salt. The following study proves that it can be successfully used as a metal oxide alternative to produce boron oxide (B 2 O 2 ) by oxidizing boron (B) in a traditional boron oxide chemical vapor deposition (BOCVD) process. This special oxidant promotes the simplistic fabrication of boron nitride nanotubes (BNNTs) in a conventional horizontal tube furnace, an outcome which may have resulted from its strong oxidizability. The experimental results demonstrate that the mole ratio of B and (NH 4 ) 10 W 12 O 41  · xH 2 O is a key parameter in determining the formation, quality and quantity of BNNTs when stainless steel is employed as a catalyst. We also found that Mg(NO 3 ) 2 and MgO nanoparticles (NPs) can be used as catalysts to grow BNNTs with the same precursor. The BNNTs obtained from the Mg(NO 3 ) 2 catalyst were straighter than those obtained from the MgO NP catalyst. This could have been due to the different physical forms of the catalysts that were used.

Interdependency of Subsurface Carbon Distribution and Graphene–Catalyst Interaction

PubMed Central

2014-01-01

The dynamics of the graphene–catalyst interaction during chemical vapor deposition are investigated using in situ, time- and depth-resolved X-ray photoelectron spectroscopy, and complementary grand canonical Monte Carlo simulations coupled to a tight-binding model. We thereby reveal the interdependency of the distribution of carbon close to the catalyst surface and the strength of the graphene–catalyst interaction. The strong interaction of epitaxial graphene with Ni(111) causes a depletion of dissolved carbon close to the catalyst surface, which prevents additional layer formation leading to a self-limiting graphene growth behavior for low exposure pressures (10–6–10–3 mbar). A further hydrocarbon pressure increase (to ∼10–1 mbar) leads to weakening of the graphene–Ni(111) interaction accompanied by additional graphene layer formation, mediated by an increased concentration of near-surface dissolved carbon. We show that growth of more weakly adhered, rotated graphene on Ni(111) is linked to an initially higher level of near-surface carbon compared to the case of epitaxial graphene growth. The key implications of these results for graphene growth control and their relevance to carbon nanotube growth are highlighted in the context of existing literature. PMID:25188018

Determination of platinum in waste platinum-loaded carbon catalyst samples using microwave-assisted sample digestion and ICP-OES

NASA Astrophysics Data System (ADS)

Ma, Yinbiao; Wei, Xiaojuan

2017-04-01

A novel method for the determination of platinum in waste platinum-loaded carbon catalyst samples was established by inductively coupled plasma optical emission spectrometry after samples digested by microwave oven with aqua regia. Such experiment conditions were investigated as the influence of sample digestion methods, digestion time, digestion temperature and interfering ions on the determination. Under the optimized conditions, the linear range of calibration graph for Pt was 0 ˜ 200.00 mg L-1, and the recovery was 95.67% ˜ 104.29%. The relative standard deviation (RSDs) for Pt was 1.78 %. The proposed method was applied to determine the same samples with atomic absorption spectrometry with the results consistently, which is suitable for the determination of platinum in waste platinum-loaded carbon catalyst samples.

Mesoporous silica nanoparticle supported PdIr bimetal catalyst for selective hydrogenation, and the significant promotional effect of Ir

NASA Astrophysics Data System (ADS)

Yang, Hui; Huang, Chao; Yang, Fan; Yang, Xu; Du, Li; Liao, Shijun

2015-12-01

A mesoporous silica nanoparticle (MSN) supported bimetal catalyst, PdIr/MSN, was prepared by a facile impregnation and hydrogen reduction method. The strong promotional effect of Ir was observed and thoroughly investigated. At the optimal molar ratio of Ir to Pd (NIr/NPd = 0.1), the activity of PdIr0.1/MSN was up to eight times and 28 times higher than that of monometallic Pd/MSN and Ir/MSN, respectively. The catalysts were characterized comprehensively by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, and hydrogen temperature programmed reduction, which revealed that the promotional effect of Ir may be due to the enhanced dispersion of active components on the MSN, and to the intensified Pd-Ir electronic interaction caused by the addition of Ir.

Visible light photoreduction of CO.sub.2 using heterostructured catalysts

DOEpatents

Matranga, Christopher; Thompson, Robert L; Wang, Congjun

2015-03-24

The method provides for use of sensitized photocatalyst for the photocatalytic reduction of CO.sub.2 under visible light illumination. The photosensitized catalyst is comprised of a wide band gap semiconductor material, a transition metal co-catalyst, and a semiconductor sensitizer. The semiconductor sensitizer is photoexcited by visible light and forms a Type II band alignment with the wide band gap semiconductor material. The wide band gap semiconductor material and the semiconductor sensitizer may be a plurality of particles, and the particle diameters may be selected to accomplish desired band widths and optimize charge injection under visible light illumination by utilizing quantum size effects. In a particular embodiment, CO.sub.2 is reduced under visible light illumination using a CdSe/Pt/TiO2 sensitized photocatalyst with H.sub.2O as a hydrogen source.

Solar photodegradation of a textile azo dye using synthesized ZnO/Bentonite.

PubMed

Boutra, B; Trari, M

2017-03-01

The present work is devoted to the synthesis of a new photocatalyst ZnO (7.5%)/Bentonite prepared by impregnation method and its successful application for the degradation of Solophenyl Red 3BL (SR 3BL) under solar light (∼660 W/m 2 ). The X-ray diffraction (XRD) indicates mixed phases of the nanocomposite catalyst (ZnO/Bentonite), characterized by scanning electron microscopy, X-ray fluorescence and attenuated total reflection. The optical properties confirm the presence of the Wurtzite ZnO phase with an optical gap of 3.27 eV. The catalyst dose (0.25-1 gL -1 ), pH solution (2.5-11) and initial dye concentration (5-75 mg/L) are optimized. The optimal pH (∼6.7) is close to the natural environment. The photodegradation yield increases with decreasing the SR 3BL concentration. The equilibrium is reached within 160 min and the data are well fitted by the Langmuir-Hinshelwood model; the SR 3BL disappearance obeys to a first-order kinetic with an apparent rate constant of 10 - 2 mn - 1 . The best yield of SR 3BL photodegradation (92%) is achieved for a concentration of 5 mg/L and a catalyst dose of 0.75 gL -1 at free pH.

Improved capacitance characteristics of electrospun ACFs by pore size control and vanadium catalyst.

PubMed

Im, Ji Sun; Woo, Sang-Wook; Jung, Min-Jung; Lee, Young-Seak

2008-11-01

Nano-sized carbon fibers were prepared by using electrospinning, and their electrochemical properties were investigated as a possible electrode material for use as an electric double-layer capacitor (EDLC). To improve the electrode capacitance of EDLC, we implemented a three-step optimization. First, metal catalyst was introduced into the carbon fibers due to the excellent conductivity of metal. Vanadium pentoxide was used because it could be converted to vanadium for improved conductivity as the pore structure develops during the carbonization step. Vanadium catalyst was well dispersed in the carbon fibers, improving the capacitance of the electrode. Second, pore-size development was manipulated to obtain small mesopore sizes ranging from 2 to 5 nm. Through chemical activation, carbon fibers with controlled pore sizes were prepared with a high specific surface and pore volume, and their pore structure was investigated by using a BET apparatus. Finally, polyacrylonitrile was used as a carbon precursor to enrich for nitrogen content in the final product because nitrogen is known to improve electrode capacitance. Ultimately, the electrospun activated carbon fibers containing vanadium show improved functionality in charge/discharge, cyclic voltammetry, and specific capacitance compared with other samples because of an optimal combination of vanadium, nitrogen, and fixed pore structures.

Electrochemical transformation of trichloroethylene in aqueous solution by electrode polarity reversal.

PubMed

Rajic, Ljiljana; Fallahpour, Noushin; Yuan, Songhu; Alshawabkeh, Akram N

2014-12-15

Electrode polarity reversal is evaluated for electrochemical transformation of trichloroethylene (TCE) in aqueous solution using flow-through reactors with mixed metal oxide electrodes and Pd catalyst. The study tests the hypothesis that optimizing electrode polarity reversal will generate H2O2 in Pd presence in the system. The effect of polarity reversal frequency, duration of the polarity reversal intervals, current intensity and TCE concentration on TCE removal rate and removal mechanism were evaluated. TCE removal efficiencies under 6 cycles h(-1) were similar in the presence of Pd catalyst (50.3%) and without Pd catalyst (49.8%), indicating that Pd has limited impact on TCE degradation under these conditions. The overall removal efficacies after 60 min treatment under polarity reversal frequencies of 6, 10, 15, 30 and 90 cycles h(-1) were 50.3%, 56.3%, 69.3%, 34.7% and 23.4%, respectively. Increasing the frequency of polarity reversal increases TCE removal as long as sufficient charge is produced during each cycle for the reaction at the electrode. Electrode polarity reversal shifts oxidation/reduction and reduction/oxidation sequences in the system. The optimized polarity reversal frequency (15 cycles h(-1) at 60 mA) enables two reaction zones formation where reduction/oxidation occurs at each electrode surface. Published by Elsevier Ltd.

Performance of a passive direct ethanol fuel cell

NASA Astrophysics Data System (ADS)

Pereira, J. P.; Falcão, D. S.; Oliveira, V. B.; Pinto, A. M. F. R.

2014-06-01

Ethanol emerges as an attractive fuel since it is less toxic and has higher energy density than methanol and can be produced from biomass. Direct ethanol fuel cells (DEFCs) appear as a good choice for producing sustainable energy for portable applications. However, they are still far from attaining acceptable levels of power output, since their performance is affected by the slow electrochemical ethanol oxidation and water and ethanol crossover. In the present work, an experimental study on the performance of a passive DEFC is described. Tailored MEAs (membrane electrode assembly) with different catalyst loadings, anode diffusion layers and membranes were tested in order to select optimal working conditions at high ethanol concentrations and low ethanol crossover. The performance increased with an increase of membrane and anode diffusion layer thicknesses and anode catalyst loading. A maximum power density of 1.33 mW cm-2, was obtained using a Nafion 117 membrane, 4 mg cm-2 of Pt-Ru and 2 mg cm-2 of Pt on the anode and cathode catalyst layers, ELAT as anode diffusion layer, carbon cloth as cathode diffusion layer and an ethanol concentration of 2 M. As far as the authors are aware this is the first work reporting an experimental optimization of passive DEFCs.

Electrochemical transformation of trichloroethylene in aqueous solution by electrode polarity reversal

PubMed Central

Rajic, Ljiljana; Fallahpour, Noushin; Yuan, Songhu; Alshawabkeh, Akram N.

2014-01-01

Electrode polarity reversal is evaluated for electrochemical transformation of trichloroethylene (TCE) in aqueous solution using flow-through reactors with mixed metal oxide electrodes and Pd catalyst. The study tests the hypothesis that optimizing electrode polarity reversal will generate H2O2 in Pd presence in the system. The effect of polarity reversal frequency, duration of the polarity reversal intervals, current intensity and TCE concentration on TCE removal rate and removal mechanism were evaluated. TCE removal efficiencies under 6 cycles h−1 were similar in the presence of Pd catalyst (50.3%) and without Pd catalyst (49.8%), indicating that Pd has limited impact on TCE degradation under these conditions. The overall removal efficacies after 60 min treatment under polarity reversal frequencies of 6, 10, 15, 30 and 90 cycles h−1 were 50.3%, 56.3%, 69.3%, 34.7% and 23.4%, respectively. Increasing the frequency of polarity reversal increases TCE removal as long as sufficient charge is produced during each cycle for the reaction at the electrode. Electrode polarity reversal shifts oxidation/reduction and reduction/oxidation sequences in the system. The optimized polarity reversal frequency (15 cycles h−1 at 60 mA) enables two reaction zones formation where reduction/oxidation occurs at each electrode surface. PMID:25282093

Advancements in rationally designed PGM-free fuel cell catalysts derived from metal–organic frameworks

DOE PAGES

Barkholtz, Heather M.; Liu, Di -Jia

2016-11-14

Over the past several years, metal-organic framework (MOF)-derived platinum group metal free (PGM-free) electrocatalysts have gained considerable attention due to their high efficiency and low cost as potential replacement for platinum in catalyzing oxygen reduction reaction (ORR). In this review, we summarize the recent advancements in design, synthesis and characterization of MOF-derived ORR catalysts and their performances in acidic and alkaline media. As a result, we also discuss the key challenges such as durability and activity enhancement critical in moving forward this emerging electrocatalyst science.

Lanthanoid-free perovskite oxide catalyst for dehydrogenation of ethylbenzene working with redox mechanism

PubMed Central

Watanabe, Ryo; Ikushima, Maiko; Mukawa, Kei; Sumomozawa, Fumitaka; Ogo, Shuhei; Sekine, Yasushi

2013-01-01

For the development of highly active and robust catalysts for dehydrogenation of ethylbenzene (EBDH) to produce styrene; an important monomer for polystyrene production, perovskite-type oxides were applied to the reaction. Controlling the mobility of lattice oxygen by changing the structure of Ba1 − xSrxFeyMn1 − yO3 − δ (0 ≤ x ≤ 1, 0.2 ≤ y ≤ 0.8), perovskite catalyst showed higher activity and stability on EBDH. The optimized Ba/Sr and Fe/Mn molar ratios were 0.4/0.6 and 0.6/0.4, respectively. Comparison of the dehydrogenation activity of Ba0.4Sr0.6Fe0.6Mn0.4O3 − δ catalyst with that of an industrial potassium promoted iron (Fe–K) catalyst revealed that the Ba0.4Sr0.6Fe0.6Mn0.4O3 − δ catalyst showed higher initial activity than the industrial Fe–K oxide catalyst. Additionally, the Ba0.4Sr0.6Fe0.6Mn0.4O3 − δ catalyst showed high activity and stability under severe conditions, even at temperatures as low as 783 K, or at the low steam/EB ratio of 2, while, the Fe–K catalyst showed low activity in such conditions. Comparing reduction profiles of the Ba0.4Sr0.6Fe0.6Mn0.4O3 − δ and the Fe–K catalysts in a H2O/H2 atmosphere, reduction was suppressed by the presence of H2O over the Ba0.4Sr0.6Fe0.6Mn0.4O3 − δ catalyst while the Fe–K catalyst was reduced. In other words, Ba0.4Sr0.6Fe0.6Mn0.4O3 − δ catalyst had higher potential for activating the steam than the Fe–K catalyst. The lattice oxygen in perovskite-structure was consumed by H2, subsequently the consumed lattice oxygen was regenerated by H2O. So the catalytic performance of Ba0.4Sr0.6Fe0.6Mn0.4O3 − δ was superior to that of Fe–K catalyst thanks to the high redox property of the Ba0.4Sr0.6Fe0.6Mn0.4O3 − δ perovskite oxide. PMID:24790949

Copper slag as a catalyst for mercury oxidation in coal combustion flue gas.

PubMed

Li, Hailong; Zhang, Weilin; Wang, Jun; Yang, Zequn; Li, Liqing; Shih, Kaimin

2018-04-01

Copper slag is a byproduct of the pyrometallurgical smelting of copper concentrate. It was used in this study to catalyze elemental mercury (Hg 0 ) oxidation in simulated coal combustion flue gas. The copper slag exhibited excellent catalytic performance in Hg 0 oxidation at temperatures between 200 °C and 300 °C. At the most optimal temperature of 250 °C, a Hg 0 oxidation efficiency of 93.8% was achieved under simulated coal combustion flue gas with both a high Hg 0 concentration and a high gas hourly space velocity of 128,000 h -1 . Hydrogen chloride (HCl) was the flue gas component responsible for Hg 0 oxidation over the copper slag. The transition metal oxides, including iron oxides and copper oxide in the copper slag, exhibited significant catalytic activities in the surface-mediated oxidation of Hg 0 in the presence of HCl. It is proposed that the Hg 0 oxidation over the copper slag followed the Langmuir-Hinshelwood mechanism whereby reactive chlorine species that originated from HCl reacted with the physically adsorbed Hg 0 to form oxidized mercury. This study demonstrated the possibility of reusing copper slag as a catalyst for Hg 0 oxidation and revealed the mechanisms involved in the process and the key factors in the performance. This knowledge has fundamental importance in simultaneously reducing industrial waste and controlling mercury emissions from coal-fired power plants. Copyright © 2017 Elsevier Ltd. All rights reserved.

Trends in Selective Hydrogen Peroxide Production on Transition Metal Surfaces from First Principles

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

Rankin, Rees B.; Greeley, Jeffrey P.

2012-10-19

We present a comprehensive, Density Functional Theory-based analysis of the direct synthesis of hydrogen peroxide, H2O2, on twelve transition metal surfaces. We determine the full thermodynamics and selected kinetics of the reaction network on these metals, and we analyze these energetics with simple, microkinetically motivated rate theories to assess the activity and selectivity of hydrogen peroxide production on the surfaces of interest. By further exploiting Brønsted-Evans-Polanyi relationships and scaling relationships between the binding energies of different adsorbates, we express the results in the form of a two dimensional contour volcano plot, with the activity and selectivity being determined as functionsmore » of two independent descriptors, the atomic hydrogen and oxygen adsorption free energies. We identify both a region of maximum predicted catalytic activity, which is near Pt and Pd in descriptor space, and a region of selective hydrogen peroxide production, which includes Au. The optimal catalysts represent a compromise between activity and selectivity and are predicted to fall approximately between Au and Pd in descriptor space, providing a compact explanation for the experimentally known performance of Au-Pd alloys for hydrogen peroxide synthesis, and suggesting a target for future computational screening efforts to identify improved direct hydrogen peroxide synthesis catalysts. Related methods of combining activity and selectivity analysis into a single volcano plot may be applicable to, and useful for, other aqueous phase heterogeneous catalytic reactions where selectivity is a key catalytic criterion.« less

The Development of Multidimensional Analysis Tools for Asymmetric Catalysis and Beyond.

PubMed

Sigman, Matthew S; Harper, Kaid C; Bess, Elizabeth N; Milo, Anat

2016-06-21

In most modern organic chemistry reports, including many of ours, reaction optimization schemes are typically presented to showcase how reaction conditions have been tailored to augment the reaction's yield and selectivity. In asymmetric catalysis, this often involves evaluation of catalyst, solvent, reagent, and, sometimes, substrate features. Such an article will then detail the process's scope, which mainly focuses on its successes and briefly outlines the "limitations". These limitations or poorer-performing substrates are occasionally the result of obvious, significant changes to structure (e.g., a Lewis basic group binds to a catalyst), but frequently, a satisfying explanation for inferior performance is not clear. This is one of several reasons such results are not often reported. These apparent outliers are also commonplace in the evaluation of catalyst structure, although most of this information is placed in the Supporting Information. These practices are unfortunate because results that appear at first glance to be peculiar or poor are considerably more interesting than ones that follow obvious or intuitive trends. In other words, all of the data from an optimization campaign contain relevant information about the reaction under study, and the "outliers" may be the most revealing. Realizing the power of outliers as an entry point to entirely new reaction development is not unusual. Nevertheless, the concept that no data should be wasted when considering the underlying phenomena controlling the observations of a given reaction is at the heart of the strategy we describe in this Account. The idea that one can concurrently optimize a reaction to expose the structural features that control its outcomes would represent a transformative addition to the arsenal of catalyst development and, ultimately, de novo design. Herein we outline the development of a recently initiated program in our lab that unites optimization with mechanistic interrogation by correlating reaction outputs (e.g., electrochemical potential or enantio-, site, or chemoselectivity) with structural descriptors of the molecules involved. The ever-evolving inspiration for this program is rooted in outliers of classical linear free energy relationships. These outliers encouraged us to ask questions about the parameters themselves, suggest potential interactions at the source of the observed effects, and, of particular applicability, identify more sophisticated physical organic descriptors. Throughout this program, we have integrated techniques from disparate fields, including synthetic methodology development, mechanistic investigations, statistics, computational chemistry, and data science. The implementation of many of these strategies is described, and the resulting tools are illustrated in a wide range of case studies, which include data sets with simultaneous and multifaceted changes to the reagent, substrate, and catalyst structures. This tactic constitutes a modern approach to physical organic chemistry wherein no data are wasted and mechanistic hypotheses regarding sophisticated processes can be developed and probed.

Carbon Nanotubes by CVD and Applications

NASA Technical Reports Server (NTRS)

Cassell, Alan; Delzeit, Lance; Nguyen, Cattien; Stevens, Ramsey; Han, Jie; Meyyappan, M.; Arnold, James O. (Technical Monitor)

2001-01-01

Carbon nanotube (CNT) exhibits extraordinary mechanical and unique electronic properties and offers significant potential for structural, sensor, and nanoelectronics applications. An overview of CNT, growth methods, properties and applications is provided. Single-wall, and multi-wall CNTs have been grown by chemical vapor deposition. Catalyst development and optimization has been accomplished using combinatorial optimization methods. CNT has also been grown from the tips of silicon cantilevers for use in atomic force microscopy.

Role of Surface Chemistry on Catalyst/Ionomer Interactions for Transition Metal–Nitrogen–Carbon Electrocatalysts

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

Artyushkova, Kateryna; Workman, Michael J.; Matanovic, Ivana

The role of the interaction between doped carbon-based materials and ionic conductors is essential in multiple technologies, from fuel cells and energy storage devices to conductive polymer composites. In this paper, we report how the surface chemistry of transition metal–nitrogen–carbon (MNC) electrocatalysts affects catalyst–ionomer interaction and the resulting structure of cathodes. The cathode structure resulting from these interactions is directly related to the performance in membrane electrode assembly (MEA) fuel cells. To advance the development of platinum group metal (PGM)-free electrodes for the oxygen reduction reaction it is necessary to understand the structure of the catalyst layers with focus onmore » chemistry and distribution of active sites and ionomer morphology. To assess catalyst interaction with an ionomer, X-ray photoelectron spectroscopy is applied to study the chemistry of catalyst layers while density functional theory (DFT) is used to calculate adsorption energies of the ionomer side chain on different nitrogen species. We report that a high surface concentration of hydrogenated nitrogen at the surface of MNC catalysts causes inefficient ionomer morphology, while an abundance of surface oxides promotes both an efficient distribution of active sites and an optimal ionomer–catalyst interface. The critical role of protonation of nitrogen within catalytic layers in inhibiting proton transport during fuel cell operation is also suggested. As a result, this is the first report of the effect the surface chemistry of MNC catalysts, in the presence of the ionomer, has on the structure and performance of MEA electrodes.« less

Molecular system identification for enzyme directed evolution and design

NASA Astrophysics Data System (ADS)

Guan, Xiangying; Chakrabarti, Raj

2017-09-01

The rational design of chemical catalysts requires methods for the measurement of free energy differences in the catalytic mechanism for any given catalyst Hamiltonian. The scope of experimental learning algorithms that can be applied to catalyst design would also be expanded by the availability of such methods. Methods for catalyst characterization typically either estimate apparent kinetic parameters that do not necessarily correspond to free energy differences in the catalytic mechanism or measure individual free energy differences that are not sufficient for establishing the relationship between the potential energy surface and catalytic activity. Moreover, in order to enhance the duty cycle of catalyst design, statistically efficient methods for the estimation of the complete set of free energy differences relevant to the catalytic activity based on high-throughput measurements are preferred. In this paper, we present a theoretical and algorithmic system identification framework for the optimal estimation of free energy differences in solution phase catalysts, with a focus on one- and two-substrate enzymes. This framework, which can be automated using programmable logic, prescribes a choice of feasible experimental measurements and manipulated input variables that identify the complete set of free energy differences relevant to the catalytic activity and minimize the uncertainty in these free energy estimates for each successive Hamiltonian design. The framework also employs decision-theoretic logic to determine when model reduction can be applied to improve the duty cycle of high-throughput catalyst design. Automation of the algorithm using fluidic control systems is proposed, and applications of the framework to the problem of enzyme design are discussed.

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

Not Available

The LZ-105-6, a medium pore molecular sieve, similar in structure to ZSM-5, is the most active catalyst we have tested so far for the conversion of propylene. At optimal conditions, it converted 90% of the feed versus 63% found with UCC-104. However, the test carried out in the Berty reactor showed that this catalyst has inferior selectivity to C/sub 5//sup +/ (89%) relative to UCC-104 (96%). The lower C/sub 5//sup +/ yield with LZ-105 follows from the increased conversion of the propylene to saturated C/sub 3/-C/sub 4/ hydrocarbons. A Task 2 catalyst was prepared by the physical mixture of themore » reference Fischer-Tropsch catalyst used above and the large pore UCC-101. This catalyst, in contrast to the reference catalyst, did not produce the excess C/sub 20//sup +/ products. Here, the hydrocarbons were isomerized and the pour points of all condensed samples were below room temperature. Conditions were adjusted to obtain excellent selectivity to gasoline, 50 wt. %, and total motor fuel, 70 wt. %. The high selectivity was achieved with this catalyst, however, at a relatively low activity level. Importantly, the product distribution of two runs showed signs of a carbon number cut off (shape selective effect). Thus, this experiment demonstrated the efficiency of UCC-101 as SSC component in that it isomerized the hydrocarbons formed on the MC resulting in substantial improvement of the motor fuel products, and it also seemed to show a cut-off at the end of the motor fuel boiling range (C/sub 20/).« 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.

Role of Surface Chemistry on Catalyst/Ionomer Interactions for Transition Metal–Nitrogen–Carbon Electrocatalysts

DOE PAGES

Artyushkova, Kateryna; Workman, Michael J.; Matanovic, Ivana; ...

2017-12-18

The role of the interaction between doped carbon-based materials and ionic conductors is essential in multiple technologies, from fuel cells and energy storage devices to conductive polymer composites. In this paper, we report how the surface chemistry of transition metal–nitrogen–carbon (MNC) electrocatalysts affects catalyst–ionomer interaction and the resulting structure of cathodes. The cathode structure resulting from these interactions is directly related to the performance in membrane electrode assembly (MEA) fuel cells. To advance the development of platinum group metal (PGM)-free electrodes for the oxygen reduction reaction it is necessary to understand the structure of the catalyst layers with focus onmore » chemistry and distribution of active sites and ionomer morphology. To assess catalyst interaction with an ionomer, X-ray photoelectron spectroscopy is applied to study the chemistry of catalyst layers while density functional theory (DFT) is used to calculate adsorption energies of the ionomer side chain on different nitrogen species. We report that a high surface concentration of hydrogenated nitrogen at the surface of MNC catalysts causes inefficient ionomer morphology, while an abundance of surface oxides promotes both an efficient distribution of active sites and an optimal ionomer–catalyst interface. The critical role of protonation of nitrogen within catalytic layers in inhibiting proton transport during fuel cell operation is also suggested. As a result, this is the first report of the effect the surface chemistry of MNC catalysts, in the presence of the ionomer, has on the structure and performance of MEA electrodes.« less

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

Xing, Rong; Dagle, Vanessa Lebarbier; Flake, Matthew

In this study we examine feasibility for steam reforming the mixed oxygenate aqueous fraction derived from mildly hydrotreated fast pyrolysis bio-oils. Catalysts selective towards hydrogen formation and resistant to carbon formation utilizing feeds with relatively low steam-to-carbon (S/C) ratios are desired. Rh (5 wt%), Pt (5 wt%), Ru (5 wt%), Ir (5 wt%), Ni (15 wt%), and Co (15 wt%) metals supported on MgAl 2O 4 were evaluated for catalytic performance at 500°C and 1 atm using a complex feed mixture comprising of acids, polyols, cycloalkanes, and phenolic compounds. The Rh catalyst was found to be the most active andmore » resistant to carbon formation. The Ni and Co catalysts were found to be more active than the other noble metal catalysts investigated (Pt, Ru, and Ir). However, Ni was found to form significantly more carbon (coke) on the catalyst surface. Furthermore, Co was found to be the most selective towards H 2 formation. Evaluating the effect of temperature on stability for the Rh catalyst we found that catalyst stability was best when operated at 500°C as compared to the higher temperatures investigated (700, 800°C). When operating at 700°C significantly more graphitic formation was observed on the spent catalyst surface. Operating at 800°C resulted in reactor plugging as a result of thermal decomposition of the reactants. Thus, a concept analogous to the petroleum industries’ use of a pre-reformer, operated at approximately 500°C for steam reforming of the heavier naphtha components, followed by a high temperature methane reforming operated in the 600-850°C temperature range, could be applied in the case of steam reforming biomass derived oxygenates. Moreover, stability evaluations were performed over the Rh, Ni, and Co catalysts at 500°C and 1 atm, under similar initial conversions, reveal the Co catalyst to be the most stable and selective towards H 2 production. Conversion and selectivity to CH 4 over Co remained relatively stable at approximately 80% and 1.2%, respectively. By contrast, the Rh and Ni catalysts CH 4 selectivity’s were approximately 7-8%. Thus suggesting that a Co type catalyst may be more suitable for the steam reforming of biomass derived oxygenates as compared to the more conventional Ni and Rh type steam reforming catalysts. However, deposition of carbon on the surface was observed. High resolution TEM on the spent catalysts revealed the formation of graphitic carbon on the Rh catalyst, and filamentous carbon formation was observed on both the Ni and Co catalysts, albeit less pronounced on Co. Thus there is certainly opportunity for improvement in Co catalyst design and/or with process optimization.« less

Nitrogen–doped graphitized carbon shell encapsulated NiFe nanoparticles: A highly durable oxygen evolution catalyst

DOE PAGES

Du, Lei; Luo, Langli; Feng, Zhenxing; ...

2017-07-05

Oxygen evolution reaction (OER) plays a crucial role in various energy conversion devices such as water electrolyzers and metal–air batteries. Precious metal catalysts such as Ir, Ru and their oxides are usually used for enhancing reaction kinetics but are limited by their scarcity. The challenges associated with alternative non–precious metal catalysts such as transition metal oxides and (oxy)hydroxides are their low electronic conductivity and durability. The carbon encapsulating transition metal nanoparticles are expected to address these challenges. However, the relationship between precursor compositions and catalyst properties, and the intrinsic functions of each component has been rarely studied. In this paper,more » we report a highly durable (no degradation after 20,000 cycles) and highly active (360 mV overpotential at 10 mA cm –2 GEO) OER catalyst derived from bimetallic metal–organic frameworks (MOFs) precursors. This catalyst consists of NiFe nanoparticles encapsulated by nitrogen–doped graphitized carbon shells. The electron–donation/deviation from Fe and tuned lattice and electronic structures of metal cores by Ni are revealed to be primary contributors to the enhanced OER activity, whereas N concentration contributes negligibly. Finally, we further demonstrated that the structure and morphology of encapsulating carbon shells, which are the key factors influencing the durability, are facilely controlled by the chemical state of precursors.« less

Why Does Alkylation of the N-H Functionality within M/NH Bifunctional Noyori-Type Catalysts Lead to Turnover?

PubMed

Dub, Pavel A; Scott, Brian L; Gordon, John C

2017-01-25

Molecular metal/NH bifunctional Noyori-type catalysts are remarkable in that they are among the most efficient artificial catalysts developed to date for the hydrogenation of carbonyl functionalities (loadings up to ∼10 -5 mol %). In addition, these catalysts typically exhibit high C═O/C═C chemo- and enantioselectivities. This unique set of properties is traditionally associated with the operation of an unconventional mechanism for homogeneous catalysts in which the chelating ligand plays a key role in facilitating the catalytic reaction and enabling the aforementioned selectivities by delivering/accepting a proton (H + ) via its N-H bond cleavage/formation. A recently revised mechanism of the Noyori hydrogenation reaction (Dub, P. A. et al. J. Am. Chem. Soc. 2014, 136, 3505) suggests that the N-H bond is not cleaved but serves to stabilize the turnover-determining transition states (TDTSs) via strong N-H···O hydrogen-bonding interactions (HBIs). The present paper shows that this is consistent with the largely ignored experimental fact that alkylation of the N-H functionality within M/NH bifunctional Noyori-type catalysts leads to detrimental catalytic activity. The purpose of this work is to demonstrate that decreasing the strength of this HBI, ultimately to the limit of its complete absence, are conditions under which the same alkylation may lead to beneficial catalytic activity.

Ultrasmall PdmMn1-mOx binary alloyed nanoparticles on graphene catalysts for ethanol oxidation in alkaline media

NASA Astrophysics Data System (ADS)

Ahmed, Mohammad Shamsuddin; Park, Dongchul; Jeon, Seungwon

2016-03-01

A rare combination of graphene (G)-supported palladium and manganese in mixed-oxides binary alloyed catalysts (BACs) have been synthesized with the addition of Pd and Mn metals in various ratios (G/PdmMn1-mOx) through a facile wet-chemical method and employed as an efficient anode catalyst for ethanol oxidation reaction (EOR) in alkaline fuel cells. The as prepared G/PdmMn1-mOx BACs have been characterized by several instrumental techniques; the transmission electron microscopy images show that the ultrafine alloyed nanoparticles (NPs) are excellently monodispersed onto the G. The Pd and Mn in G/PdmMn1-mOx BACs have been alloyed homogeneously, and Mn presents in mixed-oxidized form that resulted by X-ray diffraction. The electrochemical performances, kinetics and stability of these catalysts toward EOR have been evaluated using cyclic voltammetry in 1 M KOH electrolyte. Among all G/PdmMn1-mOx BACs, the G/Pd0.5Mn0.5Ox catalyst has shown much superior mass activity and incredible stability than that of pure Pd catalysts (G/Pd1Mn0Ox, Pd/C and Pt/C). The well dispersion, ultrafine size of NPs and higher degree of alloying are the key factor for enhanced and stable EOR electrocatalysis on G/Pd0.5Mn0.5Ox.

Enhanced activity and stability of La-doped CeO2 monolithic catalysts for lean-oxygen methane combustion.

PubMed

Zhu, Wenjun; Jin, Jianhui; Chen, Xiao; Li, Chuang; Wang, Tonghua; Tsang, Chi-Wing; Liang, Changhai

2018-02-01

Effective utilization of coal bed methane is very significant for energy utilization and environment protection. Catalytic combustion of methane is a promising way to eliminate trace amounts of oxygen in the coal bed methane and the key to this technology is the development of high-efficiency catalysts. Herein, we report a series of Ce 1-x La x O 2-δ (x = 0-0.8) monolithic catalysts for the catalytic combustion of methane, which are prepared by citric acid method. The structural characterization shows that the substitution of La enhance the oxygen vacancy concentration and reducibility of the supports and promote the migration of the surface oxygen, as a result improve the catalytic activity of CeO 2 . M-Ce 0.8 La 0.2 O 2-δ (monolithic catalyst, Ce 0.8 La 0.2 O 2-δ coated on cordierite honeycomb) exhibits outstanding activity for methane combustion, and the temperature for 10 and 90% methane conversion are 495 and 580 °C, respectively. Additionally, Ce 0.8 La 0.2 O 2-δ monolithic catalyst presents excellent stability at high temperature. These Ce 1-x La x O 2-δ monolithic materials with a small amount of La incorporation therefore show promises as highly efficient solid solution catalysts for lean-oxygen methane combustion. Graphical abstract ᅟ.

Nitrogen–doped graphitized carbon shell encapsulated NiFe nanoparticles: A highly durable oxygen evolution catalyst

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

Du, Lei; Luo, Langli; Feng, Zhenxing

Oxygen evolution reaction (OER) plays a crucial role in various energy conversion devices such as water electrolyzers and metal–air batteries. Precious metal catalysts such as Ir, Ru and their oxides are usually used for enhancing reaction kinetics but are limited by their scarcity. The challenges associated with alternative non–precious metal catalysts such as transition metal oxides and (oxy)hydroxides are their low electronic conductivity and durability. The carbon encapsulating transition metal nanoparticles are expected to address these challenges. However, the relationship between precursor compositions and catalyst properties, and the intrinsic functions of each component has been rarely studied. In this paper,more » we report a highly durable (no degradation after 20,000 cycles) and highly active (360 mV overpotential at 10 mA cm –2 GEO) OER catalyst derived from bimetallic metal–organic frameworks (MOFs) precursors. This catalyst consists of NiFe nanoparticles encapsulated by nitrogen–doped graphitized carbon shells. The electron–donation/deviation from Fe and tuned lattice and electronic structures of metal cores by Ni are revealed to be primary contributors to the enhanced OER activity, whereas N concentration contributes negligibly. Finally, we further demonstrated that the structure and morphology of encapsulating carbon shells, which are the key factors influencing the durability, are facilely controlled by the chemical state of precursors.« less

Why Does Alkylation of the N–H Functionality within M/NH Bifunctional Noyori-Type Catalysts Lead to Turnover?

DOE PAGES

Dub, Pavel; Gordon, John Cameron; Scott, Brian Lindley

2017-01-25

Molecular metal/NH bifunctional Noyori-type catalysts are remarkable in that they are among the most efficient artificial catalysts developed to date for the hydrogenation of carbonyl functionalities (loadings up to ~10 –5 mol %). In addition, these catalysts typically exhibit high C$=$O/C$=$C chemo- and enantioselectivities. This unique set of properties is traditionally associated with the operation of an unconventional mechanism for homogeneous catalysts in which the chelating ligand plays a key role in facilitating the catalytic reaction and enabling the aforementioned selectivities by delivering/accepting a proton (H +) via its N–H bond cleavage/formation. A recently revised mechanism of the Noyori hydrogenationmore » reaction (Dub, P. A. et al. J. Am. Chem. Soc. 2014, 136, 3505) suggests that the N–H bond is not cleaved but serves to stabilize the turnover-determining transition states (TDTSs) via strong N–H···O hydrogen-bonding interactions (HBIs). Here, the present paper shows that this is consistent with the largely ignored experimental fact that alkylation of the N–H functionality within M/NH bifunctional Noyori-type catalysts leads to detrimental catalytic activity. Finally, the purpose of this work is to demonstrate that decreasing the strength of this HBI, ultimately to the limit of its complete absence, are conditions under which the same alkylation may lead to beneficial catalytic activity.« less

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.

Selective aerobic alcohol oxidation method for conversion of lignin into simple aromatic compounds

DOEpatents

Stahl, Shannon S; Rahimi, Alireza

2015-03-03

Described is a method to oxidize lignin or lignin sub-units. The method includes oxidation of secondary benzylic alcohol in the lignin or lignin sub-unit to a corresponding ketone in the presence of unprotected primarily aliphatic alcohol in the lignin or lignin sub-unit. The optimal catalyst system consists of HNO.sub.3 in combination with another Bronsted acid, in the absence of a metal-containing catalyst, thereby yielding a selectively oxidized lignin or lignin sub-unit. The method may be carried out in the presence or absence of additional reagents including TEMPO and TEMPO derivatives.

In situ observations of water production and distribution in an operating H2/O2 PEM fuel cell assembly using 1H NMR microscopy.

PubMed

Feindel, Kirk W; LaRocque, Logan P-A; Starke, Dieter; Bergens, Steven H; Wasylishen, Roderick E

2004-09-22

Proton NMR imaging was used to investigate in situ the distribution of water in a polymer electrolyte membrane fuel cell operating on H2 and O2. In a single experiment, water was monitored in the gas flow channels, the membrane electrode assembly, and in the membrane surrounding the catalysts. Radial gradient diffusion removes water from the catalysts into the surrounding membrane. This research demonstrates the strength of 1H NMR microscopy as an aid for designing fuel cells to optimize water management.

Structural rearrangement of mesostructured silica nanoparticles incorporated with ZnO catalyst and its photoactivity: Effect of alkaline aqueous electrolyte concentration

NASA Astrophysics Data System (ADS)

Jusoh, N. W. C.; Jalil, A. A.; Triwahyono, S.; Karim, A. H.; Salleh, N. F.; Annuar, N. H. R.; Jaafar, N. F.; Firmansyah, M. L.; Mukti, R. R.; Ali, M. W.

2015-03-01

ZnO-incorporated mesostructured silica nanoparticles (MSN) catalysts (ZM) were prepared by the introduction of Zn ions into the framework of MSN via a simple electrochemical system in the presence of various concentrations of NH4OH aqueous solution. The physicochemical properties of the catalysts were studied by XRD, 29Si MAS NMR, nitrogen adsorption-desorption, FE-SEM, TEM, FTIR, and photoluminescence spectroscopy. Characterization results demonstrated that the alkaline aqueous electrolyte simply generated abundant silanol groups on the surface of the catalysts as a consequence of desilication to form the hierarchical-like structure of the MSN. Subsequent restructuring of the silica network by the creation of oxygen vacancies and formation of Si-O-Zn during the electrolysis, as well as formation of new Si-O-Si bonds during calcination seemed to be the main factors that enhanced the catalytic performance of photodecolorization of methyl orange. A ZM prepared in the presence of 1.0 M NH4OH (ZM-1.0) was determined to be the most effective catalyst. The catalyst displays a higher first-order kinetics rate of 3.87 × 10-1 h-1 than unsupported ZnO (1.13 × 10-1 h-1) that prepared under the same conditions in the absence of MSN. The experiment on effect of scavengers showed that hydroxyl radicals generated from the three main sources; reduced O2 at the conduction band, decomposed water at the valence band and irradiated H2O2 in the solution, are key factors that influenced the reaction. It is also noted that the recycled ZM-1.0 catalyst maintained its activity up to five runs without serious catalyst deactivation.

Design of PdAg Hollow Nanoflowers through Galvanic Replacement and Their Application for Ethanol Electrooxidation.

PubMed

Bin, Duan; Yang, Beibei; Zhang, Ke; Wang, Caiqin; Wang, Jin; Zhong, Jiatai; Feng, Yue; Guo, Jun; Du, Yukou

2016-11-07

In this study, galvanic replacement provides a simple route for the synthesis of PdAg hollow nanoflower structures by using the Ag-seeds as sacrificial templates in the presence of l-ascorbic acid (reductant) and CTAC (capping agent). Transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and EDS mapping were used to characterize the as-prepared PdAg hollow nanoflower catalysts, where they were alloyed nanoflower structures with hollow interiors. By maneuvering the Pd/Ag ratio, we found that the as-prepared Pd 1 Ag 3 hollow nanoflower catalysts had the optimized performance for catalytic activity toward ethanol oxidation reaction. Moreover, these as-prepared PdAg hollow nanoflower catalysts exhibited noticeably higher electrocatalytic activity as compared to pure Pd and commercial Pd/C catalysts due to the alloyed Ag-Pd composition as well as the hollow nanoflower structures. It is anticipated that this work provides a rational design of other architecturally controlled bimetallic nanocrystals for application in fuel cells. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

A genetically optimized kinetic model for ethanol electro-oxidation on Pt-based binary catalysts used in direct ethanol fuel cells

NASA Astrophysics Data System (ADS)

Sánchez-Monreal, Juan; García-Salaberri, Pablo A.; Vera, Marcos

2017-09-01

A one-dimensional model is proposed for the anode of a liquid-feed direct ethanol fuel cell. The complex kinetics of the ethanol electro-oxidation reaction is described using a multi-step reaction mechanism that considers free and adsorbed intermediate species on Pt-based binary catalysts. The adsorbed species are modeled using coverage factors to account for the blockage of the active reaction sites on the catalyst surface. The reaction rates are described by Butler-Volmer equations that are coupled to a one-dimensional mass transport model, which incorporates the effect of ethanol and acetaldehyde crossover. The proposed kinetic model circumvents the acetaldehyde bottleneck effect observed in previous studies by incorporating CH3CHOHads among the adsorbed intermediates. A multi-objetive genetic algorithm is used to determine the reaction constants using anode polarization and product selectivity data obtained from the literature. By adjusting the reaction constants using the methodology developed here, different catalyst layers could be modeled and their selectivities could be successfully reproduced.

Seed-mediated synthesis of cross-linked Pt-NiO nanochains for methanol oxidation

NASA Astrophysics Data System (ADS)

Gu, Zhulan; Bin, Duan; Feng, Yue; Zhang, Ke; Wang, Jin; Yan, Bo; Li, Shumin; Xiong, Zhiping; Wang, Caiqin; Shiraishi, Yukihide; Du, Yukou

2017-07-01

A simple method was reported for employing NiO nanoparticles act as seeds and then different amounts of Pt2+ were reduced on the NiO nanoparticles, forming a cross-linked Pt-NiO nanocatalysts. These as-prepared catalysts were characterized using different physical-chemical techniques, including X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The results indicate that the morphology of the cross-linked Pt-NiO nanochain was successfully produced regardless of the molar ratio of Pt2+ to NiO precursors. The electrochemical characteristics of Pt-NiO nanochain catalysts were evaluated for the oxidation of methanol as a model reaction, which verify that the Pt-NiO catalysts show enhanced activity and high stability in comparison with the commercial Pt/C catalyst. The optimized ratio of Pt to NiO is 1:1, then tuned by simple adjusting the feed ratio of the precursors as well. The synthesized nanocatalysts will be found the great potential applications as electrocatalysts for fuel cells owe to their enhanced catalytic performance and long-term stability.

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.

Highly Dispersed Alloy Catalyst for Durability

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

Vivek S. Murthi; Izzo, Elise; Bi, Wu

2013-01-08

Achieving DOE's stated 5000-hr durability goal for light-duty vehicles by 2015 will require MEAs with characteristics that are beyond the current state of the art. Significant effort was placed on developing advanced durable cathode catalysts to arrive at the best possible electrode for high performance and durability, as well as developing manufacturing processes that yield significant cost benefit. Accordingly, the overall goal of this project was to develop and construct advanced MEAs that will improve performance and durability while reducing the cost of PEMFC stacks. The project, led by UTC Power, focused on developing new catalysts/supports and integrating them withmore » existing materials (membranes and gas diffusion layers (GDLs)) using state-of-the-art fabrication methods capable of meeting the durability requirements essential for automotive applications. Specifically, the project work aimed to lower platinum group metals (PGM) loading while increasing performance and durability. Appropriate catalysts and MEA configuration were down-selected that protects the membrane, and the layers were tailored to optimize the movements of reactants and product water through the cell to maximize performance while maintaining durability.« less

Bioprocess design guided by in situ substrate supply and product removal: process intensification for synthesis of (S)-1-(2-chlorophenyl)ethanol.

PubMed

Schmölzer, Katharina; Mädje, Katharina; Nidetzky, Bernd; Kratzer, Regina

2012-03-01

We report herein on bioprocess development guided by the hydrophobicities of substrate and product. Bioreductions of o-chloroacetophenone are severely limited by instability of the catalyst in the presence of aromatic substrate and (S)-1-(2-chlorophenyl)ethanol. In situ substrate supply and product removal was used to protect the utilized Escherichia coli whole cell catalyst based on Candida tenuis xylose reductase during the reaction. Further engineering at the levels of the catalyst and the reaction media was matched to low substrate concentrations in the aqueous phase. Productivities obtained in aqueous batch reductions were 21-fold improved by addition of 20% (v/v) hexane, NAD(+), expression engineering, cell permeabilization and pH optimization. Reduction of 300 mM substrate was accomplished in 97% yield and use of the co-solvent hexane in subsequent extraction steps led to 88% recovery. Product loss due to high catalyst loading was minimized by using the same extractant in bioreduction and product isolation. Copyright © 2012 Elsevier Ltd. All rights reserved.

Confined catalysis under two-dimensional materials

PubMed Central

Li, Haobo; Xiao, Jianping; Bao, Xinhe

2017-01-01

Confined microenvironments formed in heterogeneous catalysts have recently been recognized as equally important as catalytically active sites. Understanding the fundamentals of confined catalysis has become an important topic in heterogeneous catalysis. Well-defined 2D space between a catalyst surface and a 2D material overlayer provides an ideal microenvironment to explore the confined catalysis experimentally and theoretically. Using density functional theory calculations, we reveal that adsorption of atoms and molecules on a Pt(111) surface always has been weakened under monolayer graphene, which is attributed to the geometric constraint and confinement field in the 2D space between the graphene overlayer and the Pt(111) surface. A similar result has been found on Pt(110) and Pt(100) surfaces covered with graphene. The microenvironment created by coating a catalyst surface with 2D material overlayer can be used to modulate surface reactivity, which has been illustrated by optimizing oxygen reduction reaction activity on Pt(111) covered by various 2D materials. We demonstrate a concept of confined catalysis under 2D cover based on a weak van der Waals interaction between 2D material overlayers and underlying catalyst surfaces. PMID:28533413

Characterization of calcium oxide catalysts from natural sources and their application in the transesterification of sunflower oil.

PubMed

Correia, Leandro Marques; Saboya, Rosana Maria Alves; Campelo, Natália de Sousa; Cecilia, Juan Antonio; Rodríguez-Castellón, Enrique; Cavalcante, Célio Loureiro; Vieira, Rodrigo Silveira

2014-01-01

The catalytic activities of calcium oxide obtained from natural sources (crab shell and eggshell) were characterized and evaluated in the transesterification of vegetable oil. These catalysts are mainly composed of calcium carbonate, which is partially converted into CaO after calcination (900°C for 2h). The catalysts have some advantages, such as abundant occurrence, low cost, porous structure, and nontoxic. The materials were characterized by XRD, FTIR, TG/DTG, CO2-TPD, XPS, SEM, and BET methods. The thermal treatment produces small particles of CaCO3 and CaO that are responsible for the catalytic activity. The conversion from triglycerides to methyl ester was not observed in transesterification carried out using natural crab shell and eggshell. Under optimized reaction conditions, the conversions to YFAME using the calcined catalysts were: crab shell (83.10±0.27 wt.%) and eggshell (97.75±0.02 wt.%). These results, showed that these materials have promising viability in transesterification for biodiesel production. Copyright © 2013 Elsevier Ltd. All rights reserved.

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.

A Lewis acid β-diiminato-zinc-complex as all-rounder for co- and terpolymerisation of various epoxides with carbon dioxide.

PubMed

Reiter, M; Vagin, S; Kronast, A; Jandl, C; Rieger, B

2017-03-01

A β-diiminato-zinc-N(SiMe 3 ) 2 complex ( 1 ) was synthesised and fully characterised, including an X-ray diffraction study. The activity of catalyst 1 towards the coupling reaction of CO 2 and various epoxides, including propylene oxide (PO), cyclohexene oxide (CHO), styrene oxide (SO), limonene oxide (LO), octene oxide (OO) and epichlorohydrin (ECH), was investigated. Terpolymerisation of CO 2 , PO and LO, as well as CO 2 , CHO and PO, was successfully realised, resulting in polymers with adjustable glass transition temperatures and transparencies. Reaction conditions such as temperature, pressure and catalyst concentration were varied to find the optimal reaction values, especially regarding LO/CO 2 . In situ IR experiments hinted that at 60 °C and a critical LO concentration, polymerisation and depolymerisation are in an equilibrium (ceiling effect). Pressurising catalyst 1 with carbon dioxide resulted in a dimeric catalyst ( 2 ) with a OSiMe 3 group as a new initiator. Homopolymerisation of different epoxides was carried out in order to explain the reactivity concerning copolymerisation reaction of CO 2 and epoxides.

Alternative catalysts for low-temperature CO-oxidation

NASA Technical Reports Server (NTRS)

Gardner, Steven D.; Hoflund, Gar B.; Schryer, David R.; Schryer, Jacqueline; Upchurch, Billy T.; Brown, David R.

1990-01-01

MnO sub x, Ag/MnO sub x, Cu/MnO sub x, Pt/MnO sub x, Ru/MnO sub x, Au/CeO sub x, and Au/Fe2O3 were synthesized and tested for CO oxidation activity in low concentrations of stoichiometric CO and O2 at 30 to 75 C. Catalytic activity was measured for periods as long as 18000 minutes. At 75 deg Au/MnO sub x is most active sustaining nearly 100 percent CO conversion for 10000 minutes. It also retains high activity at 50 and 30 C with negligible decay in activity. A direct comparison between an unpretreated 10 percent Au/MnO sub x catalyst and an optimized 19.5 percent Pt/SnO sub 2 (pretreated) catalyst shows that the Au/MnO sub x catalyst exhibits much higher catalytic activity and far superior decay characteristics. Other catalysts including Au/CeO sub x and Au/Fe2O3 also perform well. The Cu/MnO sub x exhibits a high initial activity which decays rapidly. After the decay period the activity remains very stable making Cu/MnO sub x a potential candidate for long-term applications such as CO2 lasers in space.