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Sample records for fe-containing zeolite catalysts

  1. Zeolites for reforming catalysts

    SciTech Connect

    Kao, J.L.; Nadler, M.; Potter, M.J.; Martir, R.V.

    1991-01-22

    This patent describes a reforming catalyst exhibiting enhanced selectivity, activity, and activity maintenance. It comprises: zeolite crystals having a pH within the range of 9.4 to 10.0, wherein the pH is determined by measuring pH of supernatent liquid from a mixture of one part of the zeolite crystals with ten parts of dionized water by weight, and comprising exchangeable cations and at least one catalytically active metal selected from the group consisting of Group VII of the Periodic Table of Elements, tin and germanium. This patten also describes a process for treating zeolite to have a pH within a range effective in imparting enhanced activity, selectivity and activity maintenance to catalysts loaded onto the zeolite. The process comprising washing zeolite with an aqueous liquid in a manner so as to result with zeolite having a pH within the pH range of 9.4 to 10.0. The PH of supernatent liquid from a mixture of one part of the zeolite crystals with ten parts of dionized water by weight.

  2. Copper-containing zeolite catalysts

    DOEpatents

    Price, Geoffrey L.; Kanazirev, Vladislav

    1996-01-01

    A catalyst useful in the conversion of nitrogen oxides or in the synthesis of nitriles or imines from amines, formed by preparing an intimate mechanical mixture of a copper (II)-containing species, such as CuO or CuCl.sub.2, or elemental copper, with a zeolite having a pore mouth comprising 10 oxygen atoms, such as ZSM-5, converting the elemental copper or copper (II) to copper (I), and driving the copper (I) into the zeolite.

  3. Copper-containing zeolite catalysts

    DOEpatents

    Price, G.L.; Kanazirev, V.

    1996-12-10

    A catalyst useful in the conversion of nitrogen oxides or in the synthesis of nitriles or imines from amines, is formed by preparing an intimate mechanical mixture of a copper (II)-containing species, such as CuO or CuCl{sub 2}, or elemental copper, with a zeolite having a pore mouth comprising 10 oxygen atoms, such as ZSM-5, converting the elemental copper or copper (II) to copper (I), and driving the copper (I) into the zeolite.

  4. Dispersion enhanced metal/zeolite catalysts

    DOEpatents

    Sachtler, W.M.H.; Tzou, M.S.; Jiang, H.J.

    1987-03-31

    Dispersion stabilized zeolite supported metal catalysts are provided as bimetallic catalyst combinations. The catalyst metal is in a reduced zero valent form while the dispersion stabilizer metal is in an unreduced ionic form. Representative catalysts are prepared from platinum or nickel as the catalyst metal and iron or chromium dispersion stabilizer.

  5. Dispersion enhanced metal/zeolite catalysts

    DOEpatents

    Sachtler, Wolfgang M. H.; Tzou, Ming-Shin; Jiang, Hui-Jong

    1987-01-01

    Dispersion stabilized zeolite supported metal catalysts are provided as bimetallic catalyst combinations. The catalyst metal is in a reduced zero valent form while the dispersion stabilizer metal is in an unreduced ionic form. Representative catalysts are prepared from platinum or nickel as the catalyst metal and iron or chromium dispersion stabilizer.

  6. Catalytic reforming with improved zeolite catalysts

    SciTech Connect

    Chu, Y.F.

    1990-05-22

    This patent describes a method for reforming a naphtha. It comprises contacting the naphtha with a noble metal/alkali metal-containing zeolite naphtha reforming catalyst the catalyst containing from about 0.1--1.0 wt % of the noble metal and an amount of the alkali metal which exceeds the cationic exchange capacity of the zeolite, a pressure of from about 0 to about 2000 psig, a temperature of about 750{degrees} F. to about 1200{degrees} F., a hydrogen to hydrocarbon molar ratio of about 0.1 to 1 to about 15 to 1 and a weight hourly spaced velocity of about 0.5 to about 20, whereby naphtha reforming activity of the catalyst is enhanced by the zeolite resulting in significantly improved C{sub 4}{sup +} gasoline yields.

  7. Pf/Zeolite Catalyst for Tritium Stripping

    SciTech Connect

    Hsu, R.H.

    2001-03-26

    This report described promising hydrogen (protium and tritium) stripping results obtained with a Pd/zeolite catalyst at ambient temperature. Preliminary results show 90-99+ percent tritium stripping efficiency may be obtained, with even better performance expected as bed configuration and operating conditions are optimized. These results suggest that portable units with single beds of the Pd/zeolite catalyst may be utilized as ''catalytic absorbers'' to clean up both tritium gas and tritiated water. A cart-mounted prototype stripper utilizing this catalyst has been constructed for testing. This portable stripper has potential applications in maintenance-type jobs such as tritium line breaks. This catalyst can also potentially be utilized in an emergency stripper for the Replacement Tritium Facility.

  8. Bound zeolite catalyst and process for using the catalyst

    SciTech Connect

    Kao, J.L.; Poeppelmeier, K.R.; Funk, W.G.; Steger, J.J.; Fung, S.C.; Cross, V.R.

    1987-03-10

    A process is described for reforming naphtha. The process comprises (a) contacting the naphtha in the presence of hydrogen at elevated temperatures with a catalyst comprising a binder, a type L zeolite containing exchangeable cations of which at least 75% are selected from the group consisting of lithium, sodium, potassium, rubidium, cesium, calcium and barium, at least one Group VIII noble metal, the particles of which are well dispersed over the surface of the catalyst and at least 90% of the noble metal associated with the zeolite is in the form of particles having a diameter of less than about 7 A; and (b) recovering reformed product.

  9. Zeolites as catalysts in oil refining.

    PubMed

    Primo, Ana; Garcia, Hermenegildo

    2014-11-21

    Oil is nowadays the main energy source and this prevalent position most probably will continue in the next decades. This situation is largely due to the degree of maturity that has been achieved in oil refining and petrochemistry as a consequence of the large effort in research and innovation. The remarkable efficiency of oil refining is largely based on the use of zeolites as catalysts. The use of zeolites as catalysts in refining and petrochemistry has been considered as one of the major accomplishments in the chemistry of the XXth century. In this tutorial review, the introductory part describes the main features of zeolites in connection with their use as solid acids. The main body of the review describes important refining processes in which zeolites are used including light naphtha isomerization, olefin alkylation, reforming, cracking and hydrocracking. The final section contains our view on future developments in the field such as the increase in the quality of the transportation fuels and the coprocessing of increasing percentage of biofuels together with oil streams. This review is intended to provide the rudiments of zeolite science applied to refining catalysis.

  10. Modified zeolite-based catalyst for effective extinction hydrocracking

    SciTech Connect

    Yan, T.Y. )

    1989-10-01

    The shape selectivity of zeolites makes them generally ineffective for extinction hydrocracking of polycyclic aromatic feeds. To overcome this problem, the zeolite can be modified with an amorphous cracking component to form a composite catalyst. This composite catalyst will be effective for extinction hydrocracking and retain the superior performance characteristics of a zeolite catalyst at the same time because the zeolite and the amorphous components of the catalyst operate complementarily. To illustrate this principle, NiW/REX-NiW/SiO/sub 2/Al/sub 2/O/sub 3/ composite catalyst was tested in the pilot plant. It was active, low in aging rate, resistant to nitrogen poisoning and high in selectivities for naphthas. The aged catalyst could be oxidatively regenerated to fully recover the activity and the product selectivities. This composite catalyst was superior to both individual (zeolite and amorphous) components for extinction hydrocracking. Catalysts similar to this have been used commercially for many years.

  11. Chemical interactions in multimetal/zeolite catalysts

    SciTech Connect

    Sachtler, W.M.H.

    1992-12-21

    Research is proposed on two groups of zeolite based catalysts that contain two transition elements. In one group both metals are fully reduced, in the other group one element is left as a positive ion; it can act as a chemical anchor'', or as a catalyst promoter for the reduced metal. The objective is to explore the potential of such materials for designing superior catalysts for synthesis and conversion of hydrocarbons and other energy carriers. ENDOR, EXAFS, CO-FTIR and TPD will be used to identify the interaction of Mn[sup 2+] ions with Rh[sub n] particles in the same zeolite cage. EXAFS at the Kedge of Fe and Pd, FTIR and Moessbauer spectroscopy will be used to characterize Fe ions and alloyed Fe atoms in PdFe/NaHY. The catalysts will be probed with CO hydrogenation and conversion of hydrocarbons. Methods Which proved successful in our study of Y supported bimetal systems will be applied to identify the state of Pt and Cu in ZSM-5, a catalyst system holding large promise for NO abatement, even in the presence of oxygen.

  12. Microstructure, elastic, and inelastic properties of biomorphic carbons carbonized using a Fe-containing catalyst

    NASA Astrophysics Data System (ADS)

    Orlova, T. S.; Kardashev, B. K.; Smirnov, B. I.; Gutierrez-Pardo, A.; Ramirez-Rico, J.

    2016-12-01

    The microstructure and amplitude dependences of the Young's modulus E and internal friction (logarithmic decrement δ), and microplastic properties of biocarbon matrices BE-C(Fe) obtained by beech tree carbonization at temperatures T carb = 850-1600°C in the presence of an iron-containing catalyst are studied. By X-ray diffraction analysis and transmission electron microscopy, it is shown that the use of Fe-catalyst during carbonization with T carb ≥ 1000°C leads to the appearance of a bulk graphite phase in the form of nanoscale bulk graphite inclusions in a quasi-amorphous matrix, whose volume fraction and size increase with T carb. The correlation of the obtained dependences E( T carb) and δ( T carb) with microstructure evolution with increasing T carb is revealed. It is found that E is mainly defined by a crystalline phase fraction in the amorphous matrix, i.e., a nanocrystalline phase at T carb < 1150°C and a bulk graphite phase at T carb > 1300°C. Maximum values E = 10-12 GPa are achieved for samples with T carb ≈ 1150 and 1600°C. It is shown that the microplasticity manifest itself only in biocarbons with T carb ≥ 1300°C (upon reaching a significant volume of the graphite phase); in this case, the conditional microyield stress decreases with increasing total volume of introduced mesoporosity (free surface area).

  13. The role of zeolite in the Fischer-Tropsch synthesis over cobalt-zeolite catalysts

    NASA Astrophysics Data System (ADS)

    Sineva, L. V.; Asalieva, E. Yu; Mordkovich, V. Z.

    2015-11-01

    The review deals with the specifics of the Fischer-Tropsch synthesis for the one-stage syncrude production from CO and H2 in the presence of cobalt-zeolite catalytic systems. Different types of bifunctional catalysts (hybrid, composite) combining a Fischer-Tropsch catalyst and zeolite are reviewed. Special attention focuses on the mechanisms of transformations of hydrocarbons produced in the Fischer-Tropsch process on zeolite acid sites under the synthesis conditions. The bibliography includes 142 references.

  14. An analysis of commerical zeolite catalysts by multinuclear NMR

    SciTech Connect

    Flanagan, L.

    1990-09-21

    This work involves studying two commercial hydrocracking catalysts by solid state multinuclear NMR silicon 29 and aluminum 27 with the goal of developing a method of determining the fraction zeolite in the catalysts. The zeolite fraction is known to be one of the faujasite zeolites type X or Y. The clay matrix of the catalyst is assumed to be kaolinite. Fresh, air-exposed commercial hydrocracking catalysts were provided by Phillips Petroleum. Sample 33351-86 was known to be a physical mixture of a Y zeolite and a clay matrix. The other catalyst, 33351-20, was composed of a faujasite zeolite grown within a clay matrix. Both were suspected of being about 20 wt % zeolite. Nothing is known about the state of pretreatment or cation exchange. A portion of each catalyst was calcined in a porcelain crucible in air at 500{degree}C for two hours with a hour heating ramp preceding and a two hour cooling ramp following calcination. 64 refs., 21 figs., 8 tabs.

  15. Synthesis of novel perfluoroalkylglucosides on zeolite and non-zeolite catalysts.

    PubMed

    Nowicki, Janusz; Mokrzycki, Łukasz; Sulikowski, Bogdan

    2015-04-08

    Perfluoroalkylglucosides comprise a very important class of fluorine-containing surfactants. These compounds can be synthesized by using the Fisher reaction, starting directly from glucose and the required perfluoroalcohols. We wish to report on the use of zeolite catalysts of different structure and composition for the synthesis of perfluoroalkylglucosides when using glucose and 1-octafluoropentanol as substrates. Zeolites of different pore architecture have been chosen (ZSM-5, ZSM-12, MCM-22 and Beta). Zeolites were characterized by XRD, nitrogen sorption, scanning electron microscopy (SEM) and solid-state 27Al MAS NMR spectroscopy. The activity of the zeolite catalysts in the glycosidation reaction was studied in a batch reactor at 100 °C below atmospheric pressure. The performance of zeolites was compared to other catalysts, an ion-exchange resin (Purolite) and a montmorillonite-type layered aluminosilicate. The catalytic performance of zeolite Beta was the highest among the zeolites studied and the results were comparable to those obtained over Purolite and montmorillonite type catalysts.

  16. Catalytic Fast Pyrolysis of Cellulose Using Nano Zeolite and Zeolite/Matrix Catalysts in a GC/Micro-Pyrolyzer.

    PubMed

    Lee, Kyong-Hwan

    2016-05-01

    Cellulose, as a model compound of biomass, was catalyzed over zeolite (HY,.HZSM-5) and zeolite/matrix (HY/Clay, HM/Clay) in a GC/micro-pyrolyzer at 500 degrees C, to produce the valuable products. The catalysts used were pure zeolite and zeolite/matrix including 20 wt% matrix content, which were prepared into different particle sizes (average size; 0.1 mm, 1.6 mm) to study the effect of the particle size of the catalyst for the distribution of product yields. Catalytic pyrolysis had much more volatile products as light components and less content of sugars than pyrolysis only. This phenomenon was strongly influenced by the particle size of the catalyst in catalytic fast pyrolysis. Also, in zeolite and zeolite/matrix catalysts the zeolite type gave the dominant impact on the distribution of product yields.

  17. Nanocrystalline zeolite beta and zeolite Y as catalysts in used palm oil cracking for the production of biofuel

    NASA Astrophysics Data System (ADS)

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

    2011-08-01

    Nanocrystalline zeolites with crystal size smaller than 100 nm are potential replacement for conventional zeolite catalysts due to their unique characteristics and advantages. In this study, the synthesis of nanocrystalline zeolite Y (FAU) and nanocrystalline zeolite beta (BEA) under hydrothermal conditions is reported. The effect of crystal size on the physico-chemical characteristics of the zeolite, Y (FAU), and beta (BEA) is reported. The properties of nanocrystalline zeolites Y and Beta with crystal size around 50 nm are compared with the microcrystalline zeolite Y and microcrystalline zeolite beta, respectively. The performance of the nanocrystalline zeolite as a catalyst was investigated in the cracking of used palm oil for the production of biofuel. The nanocrystalline zeolite catalytic activity was compared with the activity of microcrystalline zeolite in order to study the effect of crystal size on the catalytic activity. Both nanocrystalline zeolites gave better performance in terms of conversion of used palm oil as well as selectivity for the formation of gasoline fraction. The increase in surface area and improved accessibility of the reactant in nanocrystalline zeolites enhanced the cracking activity as well as the desired product selectivity.

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

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

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

  19. XPS and EDX study on an RuKL zeolite hydrogenation catalyst

    NASA Astrophysics Data System (ADS)

    Liu, You Ying; Zhao, Weijun; Zhang, Shuji; Fang, Yanquan

    Among several zeolite catalysts, synthesized in our laboratories, for hydrogenation reactions, an RuKL zeolite catalyst appeared to be the best. The activity of this RuKL catalyst remained nearly constant after several hydrogenation cycles. To understand the nature of the catalyst XPS and EDX have been applied. According to the analytical results the active components in the catalyst are Ru 3+ and Ru 0.

  20. Mesopore quality determines the lifetime of hierarchically structured zeolite catalysts

    NASA Astrophysics Data System (ADS)

    Milina, Maria; Mitchell, Sharon; Crivelli, Paolo; Cooke, David; Pérez-Ramírez, Javier

    2014-05-01

    Deactivation due to coking limits the lifetime of zeolite catalysts in the production of chemicals and fuels. Superior performance can be achieved through hierarchically structuring the zeolite porosity, yet no relation has been established between the mesopore architecture and the catalyst lifetime. Here we introduce a top-down demetallation strategy to locate mesopores in different regions of MFI-type crystals with identical bulk porous and acidic properties. In contrast, well-established bottom-up strategies as carbon templating and seed silanization fail to yield materials with matching characteristics. Advanced characterization tools capable of accurately discriminating the mesopore size, distribution and connectivity are applied to corroborate the concept of mesopore quality. Positron annihilation lifetime spectroscopy proves powerful to quantify the global connectivity of the intracrystalline pore network, which, as demonstrated in the conversions of methanol or of propanal to hydrocarbons, is closely linked to the lifetime of zeolite catalysts. The findings emphasize the need to aptly tailor hierarchical materials for maximal catalytic advantage.

  1. Supercritical fluid removal of hydrocarbons adsorbed on wide pore zeolite catalysts

    SciTech Connect

    Lucia M. Petkovic; Daniel M. Ginosar; Kyle C. Burch

    2005-06-01

    The effect of zeolite pore structure on coke removal by supercritical fluid regeneration (SFR) was studied on a series of wide pore zeolite catalysts, which included acidic Y, beta, L, and mordenite zeolites. Catalyst samples were deactivated under liquid phase isobutane/butene alkylation reaction conditions and treated under flowing supercritical isobutane for 60 min. The chemical nature of the species remaining on the catalyst surface before and after SFR was analyzed by temperature-programmed oxidation (TPO), diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), and ultraviolet-visible (UV-Vis) spectroscopy. Zeolite pore structure played an important role not only in hydrocarbon deposition during alkylation but also in hydrocarbon transformation and removal during SFR. During SFR, the formation of unsaturated cyclic or polycyclic compounds, which likely affects catalyst long-term activity after cyclic alkylation/SFR treatments, was hindered on beta zeolites and favored on catalysts containing periodic expansions or cages, such as Y and L zeolites.

  2. Heterogeneities of the nanostructure of platinum/zeolite y catalysts revealed by electron tomography.

    PubMed

    Zečević, Jovana; van der Eerden, Ad M J; Friedrich, Heiner; de Jongh, Petra E; de Jong, Krijn P

    2013-04-23

    To develop structure-performance relationships for important catalysts, a detailed characterization of their morphology is essential. Using electron tomography, we determined in three dimensions the structure of Pt/zeolite Y bifunctional catalysts. Optimum experimental conditions enabled for the first time high-resolution 3D imaging of Pt particles as small as 1 nm located inside zeolite micropores. Semiautomated image analysis of 3D reconstructions provided an efficient study of numbers, size distributions, and interparticle distances of thousands of Pt particles within individual zeolite crystals. Upon extending this approach to a number of zeolite crystals of one batch of Pt/zeolite Y catalyst, heterogeneities were revealed. The Pt loading, an important parameter for catalyst performance, varied between zeolite crystals up to a factor of 35. This discovery calls for re-evaluation of catalyst preparation methods and suggests potential for lowering the nominal loading with noble metals.

  3. 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.

  4. Catalyst Activity Comparison of Alcohols over Zeolites

    SciTech Connect

    Ramasamy, Karthikeyan K.; Wang, Yong

    2013-01-01

    Alcohol transformation to transportation fuel range hydrocarbon on HZSM-5 (SiO2 / Al2O3 = 30) catalyst was studied at 360oC and 300psig. Product distributions and catalyst life were compared using methanol, ethanol, 1-propanol or 1-butanol as a feed. The catalyst life for 1-propanol and 1-butanol was more than double compared to that for methanol and ethanol. For all the alcohols studied, the product distributions (classified to paraffin, olefin, napthene, aromatic and naphthalene compounds) varied with time on stream (TOS). At 24 hours TOS, liquid product from 1-propanol and 1-butanol transformation primarily contains higher olefin compounds. The alcohol transformation process to higher hydrocarbon involves a complex set of reaction pathways such as dehydration, oligomerization, dehydrocyclization, and hydrogenation. Compared to ethylene generated from methanol and ethanol, oligomerization of propylene and butylene has a lower activation energy and can readily take place on weaker acidic sites. On the other hand, dehydrocyclization of propylene and butylene to form the cyclic compounds requires the sits with stronger acid strength. Combination of the above mentioned reasons are the primary reasons for olefin rich product generated in the later stage of the time on stream and for the extended catalyst life time for 1 propanol and 1 butanol compared to methanol and ethanol conversion over HZSM-5.

  5. In Situ Observation of Active Oxygen Species in Fe-Containing Ni-Based Oxygen Evolution Catalysts: The Effect of pH on Electrochemical Activity.

    PubMed

    Trześniewski, Bartek J; Diaz-Morales, Oscar; Vermaas, David A; Longo, Alessandro; Bras, Wim; Koper, Marc T M; Smith, Wilson A

    2015-12-09

    Ni-based oxygen evolution catalysts (OECs) are cost-effective and very active materials that can be potentially used for efficient solar-to-fuel conversion process toward sustainable energy generation. We present a systematic spectroelectrochemical characterization of two Fe-containing Ni-based OECs, namely nickel borate (Ni(Fe)-B(i)) and nickel oxyhydroxide (Ni(Fe)OOH). Our Raman and X-ray absorption spectroscopy results show that both OECs are chemically similar, and that the borate anions do not play an apparent role in the catalytic process at pH 13. Furthermore, we show spectroscopic evidence for the generation of negatively charged sites in both OECs (NiOO(-)), which can be described as adsorbed "active oxygen". Our data conclusively links the OER activity of the Ni-based OECs with the generation of those sites on the surface of the OECs. The OER activity of both OECs is strongly pH dependent, which can be attributed to a deprotonation process of the Ni-based OECs, leading to the formation of the negatively charged surface sites that act as OER precursors. This work emphasizes the relevance of the electrolyte effect to obtain catalytically active phases in Ni-based OECs, in addition to the key role of the Fe impurities. This effect should be carefully considered in the development of Ni-based compounds meant to catalyze the OER at moderate pHs. Complementarily, UV-vis spectroscopy measurements show strong darkening of those catalysts in the catalytically active state. This coloration effect is directly related to the oxidation of nickel and can be an important factor limiting the efficiency of solar-driven devices utilizing Ni-based OECs.

  6. Improved Catalysts for Heavy Oil Upgrading Based on Zeolite Y Nanoparticles Encapsulated Stable Nanoporous Host

    SciTech Connect

    Conrad Ingram; Mark Mitchell

    2007-09-30

    The objective of this project is to synthesize nanocrystals of highly acidic zeolite Y nanoclusters, encapsulate them within the channels of mesoporous (nanoporous) silicates or nanoporous organosilicates, and evaluate the 'zeolite Y/Nanoporous host' composites as catalysts for the upgrading of heavy petroleum feedstocks. In comparison to conventionally-used zeolite Y catalysts of micron size particles, the nanocrystals (< 100 nm particle size) which contain shorter path lengths, are expected to allow faster diffusion of large hydrocarbon substrates and the catalysis products within and out of the zeolite's channels and cages (<1 nm size). This is expected to significantly reduce deactivation of the catalyst and to prolong their period of reactivity. Encapsulating zeolite Y nanocrystals within the nanoporous materials is expected to protect its external surfaces and pore entrances from being blocked by large hydrocarbon substrates, since these substrates will initially be converted to small molecules by the nanoporous host (a catalyst in its own right). The project consisted of four major tasks as follows: (1) synthesis of the nanoparticles of zeolite Y (of various chemical compositions) using various techniques such as the addition of organic additives to conventional zeolite Y synthesis mixtures to suppress zeolite Y crystal growth; (2) synthesis of nanoporous silicate host materials of up to 30 nm pore diameter, using poly (alkylene oxide) copolymers which when removed will yield a mesoporous material; (3) synthesis of zeolite Y/Nanoporous Host composite materials as potential catalysts; and (4) evaluation of the catalyst for the upgrading of heavy petroleum feedstocks.

  7. Sc(III)-doped zeolites as new heterogeneous catalysts: mukaiyama aldol reaction.

    PubMed

    Olmos, Andrea; Alix, Aurélien; Sommer, Jean; Pale, Patrick

    2009-10-26

    Sc(III)-doped solids based on zeolite materials have been investigated for the first time as catalysts in organic synthesis. Sc(III)-USY zeolite proved to be a novel and very efficient heterogeneous catalyst for the Mukaiyama aldol reaction. This easy-to-prepare catalyst exhibited wide scope and compatibility with functional groups and is very simple to use, easy to remove (by simple filtration), and is recyclable (up to three times without loss of activity).

  8. Molecular Chemistry in a Zeolite: Genesis of a Zeolite Y-Supported Ruthenium Complex Catalyst

    SciTech Connect

    Ogino, I.; Gates, B.C.

    2009-05-22

    Dealuminated zeolite Y was used as a crystalline support for a mononuclear ruthenium complex synthesized from cis-Ru(acac){sub 2}(C{sub 2}H{sub 4}){sub 2}. Infrared (IR) and extended X-ray absorption fine structure spectra indicated that the surface species were mononuclear ruthenium complexes, Ru(acac)(C{sub 2}H{sub 4}){sub 2}{sup 2+}, tightly bonded to the surface by two Ru-O bonds at Al{sup 3+} sites of the zeolite. The maximum loading of the anchored ruthenium complexes was one complex per two Al{sup 3+} sites; at higher loadings, some of the cis-Ru(acac){sub 2}(C{sub 2}H{sub 4}){sub 2} was physisorbed. In the presence of ethylene and H{sub 2}, the surface-bound species entered into a catalytic cycle for ethylene dimerization and operated stably. IR data showed that at the start of the catalytic reaction, the acac ligand of the Ru(acac)(C{sub 2}H{sub 4}){sub 2}{sup 2+} species was dissociated and captured by an Al{sup 3+} site. Ethylene dimerization proceeded 600 times faster with a cofeed of ethylene and H{sub 2} than without H{sub 2}. These results provide evidence of the importance of the cooperation of the Al{sup 3+} sites in the zeolite and the H{sub 2} in the feed for the genesis of the catalytically active species. The results presented here demonstrate the usefulness of dealuminated zeolite Y as a nearly uniform support that allows precise synthesis of supported catalysts and detailed elucidation of their structures.

  9. Selective Ring Opening of 1-Methylnaphthalene Over NiW-Supported Catalyst Using Dealuminated Beta Zeolite.

    PubMed

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

    2016-02-01

    Nanoporous Beta zeolite was dealuminated by weak acid treatment for reducing the acidity. Bi-functional catalysts were prepared using commercial Beta zeolites and the dealuminated zeolites for acidic function, NiW for metallic function. 1-Methylnaphthalene was selected as a model compound for multi-ring aromatics in heavy oil, and its selective ring opening reaction has been investigated using the prepared bi-functional catalysts with different acidity in fixed bed reaction system. The dealuminated Beta zeolites, which crystal structure and nanoporosity were maintained, showed the higher SiO2/Al2O3 ratio and smaller acidity than their original zeolite. NiW-supported catalyst using the dealuminated Beta zeolite with SiO2/Al203 mole ratio of 55 showed the highest performance for the selective ring opening. The acidity of catalyst seemed to play an important role as active sites for the selective ring opening of 1-methylnaphthalene but there should be some optimum catalyst acidity for the reaction. The acidity of Beta zeolite could be controlled by the acid treatment and the catalyst with the optimum acidity for the selective ring opening could be prepared.

  10. Effect of zeolite catalyst on sugar dehydration for 5-Hydroxymethylfurfural synthesis

    NASA Astrophysics Data System (ADS)

    Mostapha, Marhaini; Jahar, Noorhasmiera Abu; Chin, Siew Xian; Jaafar, Sharifah Nabihah Syed; Zakaria, Sarani; Aizat, Wan M.; Azizan, Kamalrul Azlan

    2016-11-01

    The effectiveness in the dehydration of sugars into 5-Hydroxymethylfurfural is related to the catalyst existence. A comprehensive synthesis of 5-Hydroxymethylfurfural from fructose, glucose and sucrose (3.73 mmol) with and without addition zeolite catalyst was performed in this study. The reactions were carried out in water-methanol solvent system for 3 hours reaction time at 180°C temperature. The catalytic results from HPLC showed that the reaction with zeolite increases the yield of 5-Hydroxymethylfurfural with 51.72 %, 34.01% and 50.10% for fructose, glucose and sucrose respectively. The study suggests that zeolites promote the isomerization of glucose into fructose to occur and simultaneously catalyze the dehydration of fructose into 5-Hydroxymethylfurfural. Only slight changes on FT-IR spectra of use zeolite after the reaction was observed. Thus suggest that zeolite was a potential catalyst for catalytic reaction for the conversion of sugar into 5-Hydroxymethylfurfural.

  11. Nanocrystalline SSZ-39 zeolite as an efficient catalyst for the methanol-to-olefin (MTO) process.

    PubMed

    Martín, Nuria; Li, Zhibin; Martínez-Triguero, Joaquín; Yu, Jihong; Moliner, Manuel; Corma, Avelino

    2016-04-26

    The synthesis of nanosized SSZ-39 zeolite has been achieved using a high silica FAU zeolite as the Si and Al source and tetraethylphosphonium (TEP) cations as OSDAs. The obtained SSZ-39 material shows a remarkably high catalyst lifetime compared to conventional SSZ-13 and SSZ-39 materials.

  12. Stable Fe/ZSM-5 Nanosheet Zeolite Catalysts for the Oxidation of Benzene to Phenol

    PubMed Central

    2017-01-01

    Fe/ZSM-5 nanosheet zeolites of varying thickness were synthesized with di- and tetraquaternary ammonium structure directing agents and extensively characterized for their textural, structural, and catalytic properties. Introduction of Fe3+ ions in the framework of nanosheet zeolites was slightly less effective than in bulk ZSM-5 zeolite. Steaming was necessary to activate all catalysts for N2O decomposition and benzene oxidation. The higher the Fe content, the higher the degree of Fe aggregation was after catalyst activation. The degree of Fe aggregation was lower when the crystal domain size of the zeolite or the Fe content was decreased. These two parameters had a substantial influence on the catalytic performance. Decreasing the number of Fe sites along the b-direction strongly suppressed secondary reactions of phenol and, accordingly, catalyst deactivation. This together with the absence of diffusional limitations in nanosheet zeolites explains the much higher phenol productivity obtainable with nanostructured Fe/ZSM-5. Steamed Fe/ZSM-5 zeolite nanosheet synthesized using C22-6-3·Br2 (domain size in b-direction ∼3 nm) and containing 0.24 wt % Fe exhibited the highest catalytic performance. During the first 24 h on stream, this catalyst produced 185 mmolphenol g–1. Calcination to remove the coke deposits completely restored the initial activity.

  13. Palladium Catalyst Supported on Zeolite for Cross-coupling Reactions: An Overview of Recent Advances.

    PubMed

    Kumbhar, Arjun

    2017-02-01

    Over the last 30-40 years, Pd-catalyzed C-C bond-forming reactions have gained immense importance for their use in synthesis of biologically and pharmaceutically important organic fragments. Heterogeneous Pd catalysts supported on porous materials, especially zeolites, have many advantages as they have high surface area with tunable acidity and basicity, hydrophobic and hydrophilic character, shape and size selectivity, as well as chemical and thermal stability. They also offer very easy recovery and reusability. This review covers the literature published on the synthesis and characterization of Pd catalysts supported on zeolites and their applications in various organic transformations.

  14. Transition metals incorporated zeolites as environmental catalysts for indoor air ozone decomposition.

    PubMed

    Mohamed, E F; Awad, G; Zaitan, H; Andriantsiferana, C; Manero, M-H

    2017-04-03

    The present study aimed to prepare catalysts of Fe and Cu loaded zeolite via ion exchange technique using dilute solutions of metal nitrate precursors followed by calcination at 600 °C in the air for 4 hours. Commercial zeolite ZSM-5 with specific surface area of 400 m(2)/g and diameter particle of 1.2-2 mm was used as a parent support. The prepared catalysts were characterized by Fourier transform infrared spectroscopy (FT-IR) analysis. The IR absorbed bands of Cu-ZSM-5 and Fe-ZSM-5 revealed a shift in the frequency and a reduction in the intensity framework. This indicates that both catalysts have a significant change in the number of the zeolite structure bonds. The catalytic activity of the prepared materials compared to the parent zeolite was evaluated for the catalytic ozone decomposition. Ozone stream of initial concentration (13g/m(3)) with air flows rate (Q) of 0.18 m(3)/h was passed through a glass jacket column reactor filled with a fixed bed of 40 g zeolites. It was showed that the ozone removal efficiency by Cu-ZSM-5 and Fe-ZSM-5 was obviously higher than that found with the parent ZSM-5. In terms of O3 removal efficiency, zeolite samples could be ranked as follows: Fe-ZSM-5>Cu-ZSM-5> parent ZSM-5. The results revealed about 90% O3 removal efficiency for Fe-ZSM-5 and 70% for Cu-ZSM-5 as compared to nearly 40% for the parent zeolite. Consequently, the incorporation of Fe and Cu metals onto zeolite surface plays a key role for enhancing the gaseous ozone elimination.

  15. "Click chemistry" in zeolites: copper(I) zeolites as new heterogeneous and ligand-free catalysts for the Huisgen [3+2] cycloaddition.

    PubMed

    Chassaing, Stefan; Sani Souna Sido, Abdelkarim; Alix, Aurélien; Kumarraja, Mayilvasagam; Pale, Patrick; Sommer, Jean

    2008-01-01

    For the first time, copper(I)-exchanged zeolites were developed as catalysts in organic synthesis. These solid materials proved to be versatile and efficient heterogeneous, ligand-free catalytic systems for the Huisgen [3+2] cycloaddition. These cheap and easy-to-prepare catalysts exhibited a wide scope and compatibility with functional groups. They are very simple to use, easy to remove (by filtration), and are recyclable (up to three times without loss of activity). Investigations with deuterated alkynes and deuterated zeolites proved that this Cu(I)-zeolite-catalyzed "click" reaction exhibited a mechanism different from that reported for the Meldal-Sharpless version.

  16. A large-cavity zeolite with wide pore windows and potential as an oil refining catalyst.

    PubMed

    Corma, Avelino; Díaz-Cabañas, María J; Martínez-Triguero, Joaquín; Rey, Fernando; Rius, Jordi

    2002-08-01

    Crude oil is an important feedstock for the petrochemical industry and the dominant energy source driving the world economy, but known oil reserves will cover demand for no more than 50 years at the current rate of consumption. This situation calls for more efficient strategies for converting crude oil into fuel and petrochemical products. At present, more than 40% of oil conversion is achieved using catalysts based on faujasite; this zeolite requires extensive post-synthesis treatment to produce an ultrastable form, and has a large cavity accessible through four 0.74-nm-wide windows and thus limits the access of oil molecules to the catalytically active sites. The use of zeolites with better accessibility to their active sites should result in improved catalyst efficiency. To date, two zeolites with effective pore diameters exceeding that of faujasite have been reported, but their one-dimensional pore topology excludes use in oil refining. Similarly, zeolites with large pores and a three-dimensional pore topology have been reported, but in all these materials the pore openings are smaller than in faujasite. Here we report the synthesis of ITQ-21, a zeolite with a three-dimensional pore network containing 1.18-nm-wide cavities, each of which is accessible through six circular and 0.74-nm-wide windows. As expected for a zeolite with this structure, ITQ-21 exhibits high catalytic activity and selectivity for valuable products in preliminary oil refining tests.

  17. Zeolite-based SCR catalysts and their use in diesel engine emission treatment

    DOEpatents

    Narula, Chaitanya K.; Yang, Xiaofan

    2016-08-02

    A catalyst comprising a zeolite loaded with copper ions and at least one trivalent metal ion other than Al.sup.+3, wherein the catalyst decreases NO.sub.x emissions in diesel exhaust. The trivalent metal ions are selected from, for example, trivalent transition metal ions, trivalent main group metal ions, and/or trivalent lanthanide metal ions. In particular embodiments, the catalysts are selected from Cu--Fe-ZSM5, Cu--La-ZSM-5, Fe--Cu--La-ZSM5, Cu--Sc-ZSM-5, and Cu--In-ZSM5. The catalysts are placed on refractory support materials and incorporated into catalytic converters.

  18. Zeolite-based SCR catalysts and their use in diesel engine emission treatment

    DOEpatents

    Narula, Chaitanya K; Yang, Xiaofan

    2015-03-24

    A catalyst comprising a zeolite loaded with copper ions and at least one trivalent metal ion other than Al.sup.+3, wherein the catalyst decreases NO.sub.x emissions in diesel exhaust. The trivalent metal ions are selected from, for example, trivalent transition metal ions, trivalent main group metal ions, and/or trivalent lanthanide metal ions. In particular embodiments, the catalysts are selected from Cu--Fe-ZSM5, Cu--La-ZSM-5, Fe--Cu--La-ZSM5, Cu--Sc-ZSM-5, and Cu--In-ZSM5. The catalysts are placed on refractory support materials and incorporated into catalytic converters.

  19. Studying Zeolite Catalysts with a 2D Model System

    SciTech Connect

    Boscoboinik, Anibal

    2016-12-07

    Anibal Boscoboinik, a materials scientist at Brookhaven’s Center for Functional Nanomaterials, discusses the surface-science tools and 2D model system he uses to study catalysis in nanoporous zeolites, which catalyze reactions in many industrial processes.

  20. Evaluation of photocatalytic activities of supported catalysts on NaX zeolite or activated charcoal.

    PubMed

    de Brites-Nóbrega, Fernanda F; Polo, Aldino N B; Benedetti, Angélica M; Leão, Mônica M D; Slusarski-Santana, Veronice; Fernandes-Machado, Nádia R C

    2013-12-15

    This study aimed to evaluate the photocatalytic activity of ZnO and Nb2O5 catalysts, both supported on NaX zeolite and activated charcoal (AC). The synergistic effect between oxide and support and the influence of solution pH (3, 7 and 9) on photocatalytic degradation of reactive blue 5G (C.I. 222) were analyzed. The catalysts Nb2O5/NaX, Nb2O5/AC and ZnO/NaX, ZnO/AC with 5 and 10% (wt%) were prepared by wet impregnation. The results showed that the catalysts exhibit quite different structural and textural properties. The synergic effect between ZnO and NaX support was higher than that with the activated charcoal, showing that these catalysts were more efficient. The most photoactive catalyst was 10% ZnO/NaX which showed 100% discoloration of the dye solution at pH 3, 7 and 9 after 0.5, 5 and 2h of irradiation, respectively. The hydrolytic nature of zeolite favored the formation of surface hydroxyl radicals, which increased the activity of the photocatalyst. Thus, catalysts supported on NaX zeolite are promising for use in photocatalysis.

  1. CoMOR zeolite catalyst prepared by buffered ion exchange for effective decomposition of nitrous oxide.

    PubMed

    Zhang, Xinyan; Shen, Qun; He, Chi; Wang, Yufei; Cheng, Jie; Hao, Zhengping

    2011-09-15

    Co contained MOR zeolite catalysts with high Co loadings were successfully synthesized by buffered ion exchange at pH 8, and were tested for N(2)O catalytic decomposition. The high exchange level of synthesized CoMOR(x)-BIE catalysts probably benefits from the maximizing hydroxycomplexes Co(OH)(+) ion in the buffered solution, which is more preferred for the ion exchange with the zeolites. It has been found that the novel CoMOR(x)-BIE catalysts exhibit excellent catalytic activities, which is attributed to the large population of isolated Co(2+) ions on ion exchange positions. The most active CoMOR(130)-BIE catalyst shows high resistance to the inhibition of oxygen, NO and water vapor. Furthermore, stability tests indicate that the CoMOR(130)-BIE catalyst has no obvious deactivation under simulated emission conditions after reaction for more than 100 h. This extraordinary durability could be related to its high Co(2+) content and low Brönsted acidity sites in the catalyst, which facilitate the stability of active isolated Co(2+) on ion exchange positions. Thus, the CoMOR(130)-BIE catalyst shows a great potential as a cost-effective catalyst for N(2)O elimination in future applications.

  2. Studying Zeolite Catalysts with a 2D Model System

    ScienceCinema

    Boscoboinik, Anibal

    2016-12-14

    Anibal Boscoboinik, a materials scientist at Brookhaven’s Center for Functional Nanomaterials, discusses the surface-science tools and 2D model system he uses to study catalysis in nanoporous zeolites, which catalyze reactions in many industrial processes.

  3. Advanced NMR characterization of zeolite catalysts. Third quarterly report, March 1-May 31, 1984

    SciTech Connect

    Welsh, L.B.

    1984-06-01

    The program discussed in this report is a two-year two-phase joint UOP-University of Illinois study of the application of improved high resolution solid state nuclear magnetic resonance (NMR) techniques to the characterization of zeolite catalysts. During the first phase of this program very pure, and in some cases isotopically enriched faujasites will be prepared and studied by majic angle sample spinning NMR (MASS NMR) and variable angle sample spinning NMR (VASS NMR) on 500 and 360 MHz (Proton frequency) NMR spectrometers. During the second phase of this program these NMR techniques will be used to study the effects of impurity concentration, dealumination treatments and cation exchange on the NMR properties of faujasites. The initial emphasis of this program during Phase I is on the preparation and measurement of the NMR properties of /sup 17/O enriched Na-Y faujasites. The effort in each phase is broken into four tasks: (1) zeolite preparation. (2) standard zeolite characterization; (3) measurement of zeolite NMR properties; and (4) analysis of NMR data. The main efforts during the third three month period of the program have been the characterization of the /sup 17/O enriched zeolites, particularly X and Y zeolites, by high resolution sample spinning /sup 17/O NMR, and the preparation of additional /sup 17/O enriched zeolites. X and Y zeolites with Si/Al framework ratios from 1.22 to 7.6 have been prepared in either the Na, NH/sub 4/ or Ba form. MASS NMR and VASS NMR as well as static NMR measurements have been made on these materials for /sup 17/O NMR frequencies from 20.4 to 67.8 MHz. Computer simulations of the experimental NMR lineshapes are in progress. Results to date indicate that the observed spectra arise from two different types of oxygen sites, possibly O in Al-O-Si links and chemically bound OH groups. 2 references, 1 figure, 1 table.

  4. Improved Catalysts for Heavy Oil Upgrading Based on Zeolite Y Nanoparticles Encapsulated Stable Nanoporous Host

    SciTech Connect

    Conrad Ingram; Mark Mitchell

    2006-09-30

    The addition of hydrothermally-aged zeolite Y precursor to an SBA-15 synthesis mixture under a mildly acidic condition resulted in the formation of mesoporous aluminosilicate catalyst, Al-SBA-15, containing strong Broensted acid sites and aluminum (Al) stabilized in a totally tetrahedral coordination. The physicochemical characteristics of the catalyst varied as a function of the synthesis conditions. The catalyst possessed surface areas ranging between 690 and 850 m{sup 2}/g, pore sizes ranging from 5.6 to 7.5 nm, and pore volumes up 1.03 cm{sup 3}, which were comparable to the parent SBA-15 synthesized under similar conditions. Two wt% Al was present in the catalyst that was obtained from the reaction mixture that contained the highest Al content. The Al remained stable in totally tetrahedral coordination after calcination at 550 C. The Al-SBA-15 mesoporous catalyst showed significant catalytic activity for cumene dealkylation, and the activity increased as the amount of zeolite precursor added to the SBA-15 mixture was increased. In preparation for the final phase of the project, the catalyst was embedded into psuedoboemite alumina (catapal B) matrix and then formed into pellets. In the final phase of the project, the pelletized catalyst will be evaluated for the conversion of heavy petroleum feedstocks to naphtha and middle distillates.

  5. Spectroscopic and XRD characterisation of zeolite catalysts active for the oxidative methylation of benzene with methane.

    PubMed

    Adebajo, Moses O; Long, Mervyn A; Frost, Ray L

    2004-03-01

    The benzene methylation with methane over zeolite catalysts was previously shown in our laboratory to require the presence of oxygen. Thus, a two-step mechanism involving the intermediate formation of methanol by partial oxidation of methane followed by the methylation of benzene with methanol in the second step, was postulated. This paper now reports the results of the characterisation of the zeolite catalysts used for the oxidative benzene methylation reaction in order to provide some information about their composition, structure, properties and their behaviour before and after the reaction. The catalysts were characterised by X-ray diffraction (XRD), inductively coupled plasma atomic emission spectroscopy (ICP-AES), X-ray fluorescence (XRF), FT-IR and solid state NMR. XRD results indicate that the crystalline structures of all the ZSM-5 and H-beta catalysts remained unchanged after batch reaction of benzene with methane over the catalysts in agreement with the observation that the catalysts recovered from the reactor could be reused without loss of activity. Elemental analyses and FT-IR data show that as the level of metal ion exchange increases, the Brönsted acid concentration decreases but this metal ion exchange does not totally remove Brönsted acidity. FT-IR results further show that only a small amount of acid sites is actually necessary for a catalyst to be active since used catalysts containing highly reduced Brönsted acidity are found to be reusable without any loss of their activity. 29Si and 27Al magic angle spinning (MAS) NMR together with FT-IR spectra also show that all the active zeolites catalysts contain some extra-framework octahedral aluminium in addition to the normal tetrahedral framework aluminium. The presence of this extra-lattice aluminium does not, however, have any adverse effect on the crystallinity of the catalysts both before and after oxidative benzene methylation reaction. There appears also to be no significant dealumination

  6. Spectroscopic and XRD characterisation of zeolite catalysts active for the oxidative methylation of benzene with methane

    NASA Astrophysics Data System (ADS)

    Adebajo, Moses O.; Long, Mervyn A.; Frost, Ray L.

    2004-03-01

    The benzene methylation with methane over zeolite catalysts was previously shown in our laboratory to require the presence of oxygen. Thus, a two-step mechanism involving the intermediate formation of methanol by partial oxidation of methane followed by the methylation of benzene with methanol in the second step, was postulated. This paper now reports the results of the characterisation of the zeolite catalysts used for the oxidative benzene methylation reaction in order to provide some information about their composition, structure, properties and their behaviour before and after the reaction. The catalysts were characterised by X-ray diffraction (XRD), inductively coupled plasma atomic emission spectroscopy (ICP-AES), X-ray fluorescence (XRF), FT-IR and solid state NMR. XRD results indicate that the crystalline structures of all the ZSM-5 and H-beta catalysts remained unchanged after batch reaction of benzene with methane over the catalysts in agreement with the observation that the catalysts recovered from the reactor could be reused without loss of activity. Elemental analyses and FT-IR data show that as the level of metal ion exchange increases, the Brönsted acid concentration decreases but this metal ion exchange does not totally remove Brönsted acidity. FT-IR results further show that only a small amount of acid sites is actually necessary for a catalyst to be active since used catalysts containing highly reduced Brönsted acidity are found to be reusable without any loss of their activity. 29Si and 27Al magic angle spinning (MAS) NMR together with FT-IR spectra also show that all the active zeolites catalysts contain some extra-framework octahedral aluminium in addition to the normal tetrahedral framework aluminium. The presence of this extra-lattice aluminium does not, however, have any adverse effect on the crystallinity of the catalysts both before and after oxidative benzene methylation reaction. There appears also to be no significant dealumination

  7. IMPROVED CATALYSTS FOR HEAVY OIL UPGRADING BASED ON ZEOLITE Y NANOPARTICLES ENCAPSULATED STABLE NANOPOROUS HOST

    SciTech Connect

    Conrad Ingram; Mark Mitchell

    2006-06-20

    Al-SBA-15 mesoporous catalysts with strong Broensted acid sites and Al stabilized in a totally tetrahedral coordination was synthesized from the addition of hydrothermally aged zeolite Y precursor to SBA-15 synthesis mixture under mildly acidic condition of pH 5.5. The materials possessed surface areas between 690 and 850 m{sup 2}/g, pore sizes ranging from 5.6 to 7.5 nm and pore volumes up 1.03 cm{sup 3}, which were comparable to parent SBA-15 synthesized under similar conditions. Up to 2 wt. % Al was present in the most aluminated sample that was investigated, and the Al remained stable in totally tetrahedral coordination, even after calcination at 550 C. The Al-SBA-15 mesoporous catalyst showed significant catalytic activity for cumene dealkylation, and activity increased as the amount of zeolite precursor added to the SBA-15 mixture was increased. The catalyst's activity was not affected by the aging time of the precursor for up to the 24 hr aging time investigated. This method of introducing Al and maintaining it in a total tetrahedral coordination is very effective, in comparison to other direct and post synthesis alumination methods reported. The catalytic performance of the zeolite Y/SBA-15 composite materials will be compared with that of pure SBA-15. The catalysts will then be evaluated for the conversion of heavy petroleum feedstocks.

  8. 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%.

  9. Characterization of Na+- beta-Zeolite Supported Pd and Pd Ag Bimetallic Catalysts using EXAFS, TEM and Flow Reactor

    SciTech Connect

    Huang,W.; Lobo, R.; Chen, J.

    2008-01-01

    Flow reactor studies of the selective hydrogenation of acetylene in the presence of ethylene have been performed on Na+ exchanged {beta}-zeolite supported Pd, Ag and PdAg catalysts, as an extension of our previous batch reactor studies [W. Huang, J.R. McCormick, R.F. Lobo, J.G. Chen, J. Catal. 246 (2007) 40-51]. Results from flow reactor studies show that the PdAg/Na+-{beta}-zeolite bimetallic catalyst has lower activity than Pd/Na+-{beta}-zeolite monometallic catalyst, while Ag/Na+-{beta}-zeolite does not show any activity for acetylene hydrogenation. However, the selectivity for the PdAg bimetallic catalyst is much higher than that for either the Pd catalyst or Ag catalyst. The selectivity to byproduct (ethane) is greatly inhibited on the PdAg bimetallic catalyst as well. The results from the current flow reactor studies confirmed the pervious results from batch reactor studies [W. Huang, J.R. McCormick, R.F. Lobo, J.G. Chen, J. Catal. 246 (2007) 40-51]. In addition, we used transmission electron microscope (TEM), extended X-ray absorption fine structure (EXAFS), and FTIR of CO adsorption to confirm the formation of Pd-Ag bimetallic alloy in the PdAg/Na+-{beta}-zeolite catalyst.

  10. IMPROVED CATALYSTS FOR HEAVY OIL UPGRADING BASED ON ZEOLITE Y NANOPARTICLES ENCAPSULATED IN STABLE NANOPOROUS HOST

    SciTech Connect

    Conrad Ingram; Mark Mitchell

    2005-03-31

    The objectives of this project are to synthesis nanocrystals of highly acidic zeolite Y, encapsulate them within the channels of mesoporous (nanoporous) silicates or nanoporous organosilicates and evaluate the ''zeolite Y/Nanoporous host'' composites as catalysts for the upgrading of heavy petroleum feedstocks. Our results to date are summarized as follows. The synthesis of high surface ordered nanoporous silica of expanded pore diameter of 25 nm (larger than the standard size of 8.4 nm) using trimethylbenzene as a pore size expander was accomplished. The synthesis of zeolite Y nanoparticles with median pore size of approximately 50 nm (smaller than the 80 nm typically obtained with TMAOH) using combined TMABr/TMAOH as organic additives was also accomplished. The successful synthesis of zeoliteY/Nanoporous host composite materials by sequential combination of zeolite precursors and nanoporous material precursor mixtures was implied based on results from various characterization techniques such as X-Ray diffraction, infrared spectra, thermal analysis, porosimetry data. The resulting materials showed pore sizes up to 11 nm, and infrared band at 570 cm{sup -1} suggesting the presence of both phases. New results indicated that good quality highly ordered nanoporous silica host can be synthesized in the presence of zeolite Y seed precursor depending on the amount of precursor added. Preliminary research on the catalytic performance of the materials is underway. Probe acid catalyzed reactions, such as the cracking of cumene is currently being conducted. Work in the immediate future will be focused on the following three areas: (1) Further characterization of all-silica and aluminosilicate mesoporous materials with expanded pore sizes up to 30 nm will continue; (2) Research efforts to reduce the average particle size of zeolite nanoparticles down to 35-30 nm will continue; (3) Further synthesis of ZeoliteY/Nanoporous host composite catalysts of improved structural and

  11. Catalytic wet peroxide oxidation of azo dye (Congo red) using modified Y zeolite as catalyst.

    PubMed

    Kondru, Arun Kumar; Kumar, Pradeep; Chand, Shri

    2009-07-15

    The present study explores the degradation of azo dye (Congo red) by catalytic wet peroxide oxidation using Fe exchanged commercial Y zeolite as a catalyst. The effects of various operating parameters like temperature, initial pH, hydrogen peroxide concentration and catalyst loading on the removal of dye, color and COD from an aqueous solution were studied at atmospheric pressure. The percent removals of dye, color and COD at optimum pH(0) 7, 90 degrees C using 0.6 ml H(2)O(2)/350 ml solution and 1g/l catalyst was 97% (in 4h), 100% (in 45 min) and 58% (in 4h), respectively. The % dye removal has been found to be less in comparison to % color removal at all conditions, e.g. dye removal in 45 min and at above conditions was 82%, whereas the color removal was 100%. The results indicate that the Fe exchanged Y zeolite is a promising catalyst for dye removal. Fe exchanged catalyst is characterized using XRD, SEM/EDAX, surface area analyzer and FTIR. Though the dye, color and COD removals were maximum at pH(0) 2 but as the leaching of Fe from the catalyst was more in acidic pH range, pH(0) 7 was taken as operating pH due to almost comparable removals as of pH(0) 2 and no leaching of Fe ions.

  12. DIRECT DECOMPOSITION OF METHANE TO HYDROGEN ON METAL LOADED ZEOLITE CATALYST

    SciTech Connect

    Lucia M. Petkovic; Daniel M. Ginosar; Kyle C. Burch; Harry W. Rollins

    2005-08-01

    The manufacture of hydrogen from natural gas is essential for the production of ultra clean transportation fuels. Not only is hydrogen necessary to upgrade low quality crude oils to high-quality, low sulfur ultra clean transportation fuels, hydrogen could eventually replace gasoline and diesel as the ultra clean transportation fuel of the future. Currently, refinery hydrogen is produced through the steam reforming of natural gas. Although efficient, the process is responsible for a significant portion of refinery CO2 emissions. This project is examining the direct catalytic decomposition of methane as an alternative to steam reforming. The energy required to produce one mole of hydrogen is slightly lower and the process does not require water-gas-shift or pressure-swing adsorption units. The decomposition process does not produce CO2 emissions and the product is not contaminated with CO -- a poison for PEM fuel cells. In this work we examined the direct catalytic decomposition of methane over a metal modified zeolite catalyst and the recovery of catalyst activity by calcination. A favorable production of hydrogen was obtained, when compared with previously reported nickel-zeolite supported catalysts. Reaction temperature had a strong influence on catalyst activity and on the type of carbon deposits. The catalyst utilized at 873 and 973 K could be regenerated without any significant loss of activity, however the catalyst utilized at 1073 K showed some loss of activity after regeneration.

  13. IMPROVED CATALYSTS FOR HEAVY OIL UPGRADING BASED ON ZEOLITE Y NANOPARTICLES ENCAPSULATED STABLE NANOPOROUS HOST

    SciTech Connect

    Conrad Ingram; Mark Mitchell

    2005-03-21

    The objectives of this project are to synthesis nanocrystals of highly acidic zeolite Y, encapsulate them within the channels of mesoporous (nanoporous) silicates or nanoporous organosilicates and evaluate the ''zeolite Y/Nanoporous host'' composites as catalysts for the upgrading of heavy petroleum feedstocks. Our results to date are summarized as follows. The synthesis of high surface ordered nanoporous silica of expanded pore diameter of 25 nm (larger than the standard size of 8.4 nm) using trimethylbenzene as a pore size expander was accomplished. The synthesis of zeolite Y nanoparticles with median pore size of approximately 50 nm (smaller than the 80 nm typically obtained with TMAOH) using combined TMABr/TMAOH as organic additives was also accomplished. The successful synthesis of zeoliteY/Nanoporous host composite materials by sequential combination of zeolite precursors and nanoporous material precursor mixtures was implied based on results from various characterization techniques such as X-Ray diffraction, infrared spectra, thermal analysis, porosimetry data. The resulting materials showed pore sizes up to 11 nm, and infrared band at 570 cm{sup -1} suggesting the presence of both phases. Work in the immediate future will be focused on the following three areas: (1) Further characterization of all-silica and aluminosilicate mesoporous materials with expanded pore sizes up to 30 nm will continue; (2) Research efforts to reduce the average particle size of zeolite nanoparticles down to 35-30 nm will continue; (3) Further synthesis of polymer-SBA15 nanocomposites will be conducted by changing the amount and chemistry of the zeolitic precursors added; and (4) Investigation on the catalytic properties of the materials using probe catalytic reactions (such as cumene cracking), followed by catalytic testing for heavy oil conversion.

  14. Zealous zeolites

    SciTech Connect

    Hairston, D.W.

    1996-07-01

    Zeolites have made significant inroads in fluid cracking catalysts for gasoline and have pushed phosphates out of laundry detergents. But these crystalline aluminosilicate structures are just beginning to make their mark in chemical processes and environmental applications. Ideally suited for work as molecular sieves and catalysts, zeolites sport uniform surface pores and channels that are receptive only to molecules of a specific size and shape. This high selectivity makes zeolites a good alterative to some of the conventional products used for chemical reaction and filtration. One of the most potentially lucrative markets for zeolites is chemical catalyst replacements for liquid acids, such as hydrofluoric acid and sulfuric acid, and aluminum chloride in a number of alkylation and acrylation reactions. Zeolites are also being considered for oligomerization,isomerization, amination and condensation processes for the manufacture of chemical intermediates. The paper discusses the market and manufacturers of zeolites, justifying the cost of converting to zeolite catalysts, and natural zeolites.

  15. Iron/zeolite catalysts for synthesis of hydrocarbons from CO and H/sub 2/

    SciTech Connect

    Lapidus, A.L.; Savel'ev, M.M.; Muranova, L.M.; Borisovich, I.G.; Vasserberg, V.E.; Minachev, Kh.M.

    1986-07-10

    Catalysts obtained by deposition of Fe(CO)/sub 5/ on Y zeolites containing bivalent cations are active in the synthesis of C/sub 1/-C/sub 4/ hydrocarbons from CO and H/sub 2/ at 300-400/sup 0/C and atmospheric pressure. The activity of the iron-containing catalysts increases in the same order as the increase in basicity of the cation: BeY < MgY < CaY < SrY < BaY. The content of C/sub 2/-C/sub 3/ olefins in the products from synthesis at 350-373/sup 0/C on the iron-containing zeolites increases in the series BeY < MgY < CaY < SrY < BaY.

  16. Improved Catalysts for Heavy Oil Upgrading Based on Zeolite Y Nanoparticles Encapsulated Stable Nanoporous Host

    SciTech Connect

    Conrad Ingram; Mark Mitchell

    2007-03-31

    The addition of hydrothermally-aged zeolite Y precursor to an SBA-15 synthesis mixture under a mildly acidic condition resulted in the formation of a mesoporous aluminosilicate catalyst, AlSBA-15. The Al-SBA-15 mesoporous catalyst contains strong Br{umlt o}nsted acid sites and aluminum (Al) stabilized in a totally tetrahedral coordination. The physicochemical characteristics of the catalyst varied as a function of the synthesis conditions. The catalyst possessed surface areas ranging between 690 and 850 m{sup 2}/g, pore sizes ranging from 5.6 to 7.5 nm, and pore volumes up 1.03 cm{sup 3}, which were comparable to the parent SBA-15 synthesized under similar conditions. Two wt % Al was present in the catalyst that was obtained from the reaction mixture that contained the highest Al content. The Al remained stable in totally tetrahedral coordination after calcination at a temperature of 550 C. The Al-SBA-15 mesoporous catalyst showed significant catalytic activity for cumene dealkylation, and the activity increased as the amount of zeolite precursor added to the SBA-15 mixture was increased. In preparation for the final phase of the project, the catalyst was embedded into a psuedoboemite alumina (catapal B) matrix and then formed into pellets. In the final phase of the project, the pelletized catalyst is being evaluated for the conversion of a heavy petroleum feedstock to naphtha and middle distillates. This phase was significantly delayed during the past six months due to a serious malfunction of the fume hoods in the Clark Atlanta University's Research Center for Science and Technology, where the project is being conducted. The fume hood system was repaired and the catalyst evaluation is now underway.

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

    PubMed Central

    Devaraj, Arun; Vijayakumar, Murugesan; Bao, Jie; Guo, Mond F.; Derewinski, Miroslaw A.; Xu, Zhijie; Gray, Michel J.; Prodinger, Sebastian; Ramasamy, Karthikeyan K.

    2016-01-01

    The formation of carbonaceous deposits (coke) in zeolite pores during catalysis leads to temporary deactivation of catalyst, necessitating regeneration steps, affecting throughput, and resulting in partial permanent loss of catalytic efficiency. Yet, even to date, the coke molecule distribution is quite challenging to study with high spatial resolution from surface to bulk of the catalyst particles at a single particle level. To address this challenge we investigated the coke molecules in HZSM-5 catalyst after ethanol conversion treatment by a combination of C K-edge X-ray absorption spectroscopy (XAS), 13C Cross polarization-magic angle spinning nuclear magnetic resonance (CP-MAS NMR) spectroscopy, and atom probe tomography (APT). XAS and NMR highlighted the aromatic character of coke molecules. APT permitted the imaging of the spatial distribution of hydrocarbon molecules located within the pores of spent HZSM-5 catalyst from surface to bulk at a single particle level. 27Al NMR results and APT results indicated association of coke molecules with Al enriched regions within the spent HZSM-5 catalyst particles. The experimental results were additionally validated by a level-set–based APT field evaporation model. These results provide a new approach to investigate catalytic deactivation due to hydrocarbon coking or poisoning of zeolites at an unprecedented spatial resolution. PMID:27876869

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

    NASA Astrophysics Data System (ADS)

    Devaraj, Arun; Vijayakumar, Murugesan; Bao, Jie; Guo, Mond F.; Derewinski, Miroslaw A.; Xu, Zhijie; Gray, Michel J.; Prodinger, Sebastian; Ramasamy, Karthikeyan K.

    2016-11-01

    The formation of carbonaceous deposits (coke) in zeolite pores during catalysis leads to temporary deactivation of catalyst, necessitating regeneration steps, affecting throughput, and resulting in partial permanent loss of catalytic efficiency. Yet, even to date, the coke molecule distribution is quite challenging to study with high spatial resolution from surface to bulk of the catalyst particles at a single particle level. To address this challenge we investigated the coke molecules in HZSM-5 catalyst after ethanol conversion treatment by a combination of C K-edge X-ray absorption spectroscopy (XAS), 13C Cross polarization-magic angle spinning nuclear magnetic resonance (CP-MAS NMR) spectroscopy, and atom probe tomography (APT). XAS and NMR highlighted the aromatic character of coke molecules. APT permitted the imaging of the spatial distribution of hydrocarbon molecules located within the pores of spent HZSM-5 catalyst from surface to bulk at a single particle level. 27Al NMR results and APT results indicated association of coke molecules with Al enriched regions within the spent HZSM-5 catalyst particles. The experimental results were additionally validated by a level-set–based APT field evaporation model. These results provide a new approach to investigate catalytic deactivation due to hydrocarbon coking or poisoning of zeolites at an unprecedented spatial resolution.

  19. The curious case of zeolite-clay/binder interactions and their consequences for catalyst preparation.

    PubMed

    Whiting, Gareth T; Chowdhury, Abhishek Dutta; Oord, Ramon; Paalanen, Pasi; Weckhuysen, Bert M

    2016-07-04

    Zeolite-based catalyst bodies are commonly employed in a range of important industrial processes. Depending on the binder and shaping method chosen, vast differences in the reactivity, selectivity and stability are obtained. Here, three highly complementary micro-spectroscopic techniques were employed to study zeolite ZSM-5-binder interactions in SiO2-, Al2O3-, SiO2 : Al2O3- (2 : 1 mix) and kaolinite-bound catalyst pellets. We establish how their preparation influences the zeolite-clay/binder interactions. Using thiophene as an acid-catalyzed staining reaction, light absorbing oligomers produced in each sample were followed. To our surprise, kaolinite decreased the overall reactivity of the sample due to the phase change of the binder, creating a hard impenetrable outer layer. Aluminum migration to the zeolite was observed when Al2O3 was selected as a binder, creating additional Brønsted acid sites, which favored the formation of ring-opened thiophene oligomers compared to the larger oligomer species produced when SiO2 was used as a binder. In the latter case, the interaction of the Si-OH groups in the binder with thiophene was revealed to have a large impact in creating such large oligomer species. Furthermore, the combination of a SiO2 : Al2O3 mix as a binder enhanced the reactivity, possibly due to the creation of additional Brønsted acid sites between the two binder components during pellet preparation. It is evident that, independent of the shaping method, the intimate contact between the zeolite and binder heavily impacts the reactivity and product selectivity, with the type of binder playing a vital role.

  20. Effect of Unburned Methyl Esters on the NOx Conversion of Fe-Zeolite SCR Catalyst

    SciTech Connect

    Williams, A.; Ratcliff, M.; Pedersen, D.; McCormick, R.; Cavataio, G.; Ura, J.

    2010-03-01

    Engine and flow reactor experiments were conducted to determine the impact of biodiesel relative to ultra-low-sulfur diesel (ULSD) on inhibition of the selective catalytic reduction (SCR) reaction over an Fe-zeolite catalyst. Fe-zeolite SCR catalysts have the ability to adsorb and store unburned hydrocarbons (HC) at temperatures below 300 C. These stored HCs inhibit or block NO{sub x}-ammonia reaction sites at low temperatures. Although biodiesel is not a hydrocarbon, similar effects are anticipated for unburned biodiesel and its organic combustion products. Flow reactor experiments indicate that in the absence of exposure to HC or B100, NO{sub x} conversion begins at between 100 and 200 C. When exposure to unburned fuel occurs at higher temperatures (250-400 C), the catalyst is able to adsorb a greater mass of biodiesel than of ULSD. Experiments show that when the catalyst is masked with ULSD, NO{sub x} conversion is inhibited until it is heated to 400 C. However, when masked with biodiesel, NO{sub x} conversion is observed to begin at temperatures as low as 200 C. Engine test results also show low-temperature recovery from HC storage. Engine tests indicate that, overall, the SCR system has a faster recovery from HC masking with biodiesel. This is at least partially due to a reduction in exhaust HCs, and thus total HC exposure with biodiesel.

  1. Selective synthesis and chain growth of linear hydrocarbons in the Fischer-Tropsch synthesis over zeolite-entrapped cobalt catalysts

    SciTech Connect

    Koh, D.J.; Chung, J.S.; Kim, Y.G.

    1995-06-01

    The impregnation of NaOH solution into the pores of cobalt-exchanged zeolite promoted the conventional reduction of cobalt ions with hydrogen gas. The method yielded catalysts that had high degrees of reduction and small cobalt clusters located inside zeolite pores. In the Fischer-Tropsch synthesis these catalysts showed a chain-extension effect, producing hydrocarbons higher than C{sub 10} in appreciable amounts, and an enhanced production of linear hydrocarbons such as 1-olefins and n-paraffins. The formation of long-chain hydrocarbons is attributed to an increased chance of the chain growth owing to a hold-up effect of reaction intermediates, especially 1-olefins, which are accumulated inside zeolite pores during the reaction. Hydrocarbon isomers are produced over acidic sites of zeolite by secondary reactions (isomerization and cracking), which result in a chain shortening of the long-chain hydrocarbons.

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

    SciTech Connect

    Devaraj, Arun; Vijayakumar, Murugesan; Bao, Jie; Guo, Mond F.; Derewinski, Miroslaw A.; Xu, Zhijie; Gray, Michel J.; Prodinger, Sebastian; Ramasamy, Karthikeyan K.

    2016-11-23

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

  3. Local ammonia storage and ammonia inhibition in a monolithic copper-beta zeolite SCR catalyst

    SciTech Connect

    Auvray, Xavier P; Partridge Jr, William P; Choi, Jae-Soon; Pihl, Josh A; Yezerets, Alex; Kamasamudram, Krishna; Currier, Neal; Olsson, Louise

    2012-01-01

    Selective catalytic reduction of NO with NH{sub 3} was studied on a Cu-beta zeolite catalyst, with specific focus on the distributed NH{sub 3} capacity utilization and inhibition. In addition, several other relevant catalyst parameter distributions were quantified including the SCR zone, or catalyst region where SCR occurs, and NO and NH{sub 3} oxidation. We show that the full NH{sub 3} capacity (100% coverage) is used within the SCR zone for a range of temperatures. By corollary, unused NH{sub 3} capacity exists downstream of the SCR zone. Consequently, the unused capacity relative to the total capacity is indicative of the portion of the catalyst unused for SCR. Dynamic NH{sub 3} inhibition distributions, which create local transient conversion inflections, are measured. Dynamic inhibition is observed where the gas phase NH{sub 3} and NO concentrations are high, driving rapid NH{sub 3} coverage buildup and SCR. Accordingly, we observe dynamic inhibition at low temperatures and in hydrothermally aged states, but predict its existence very near the catalyst front in higher conversion conditions where we did not specifically monitor its impact. While this paper addresses some general distributed SCR performance parameters including Oxidation and SCR zone, our major new contributions are associated with the NH{sub 3} capacity saturation within the SCR zone and dynamic inhibition distributions and the associated observations. These new insights are relevant to developing accurate models, designs and control strategies for automotive SCR catalyst applications.

  4. 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.

  5. Zeolites

    NASA Technical Reports Server (NTRS)

    1992-01-01

    Zeolites are crystalline aluminosilicates that have complex framework structures. However, there are several features of zeolite crystals that make unequivocal structure determinations difficult. The acquisition of reliable structural information on zeolites is greatly facilitated by the availability of high-quality specimens. For structure determinations by conventional diffraction techniques, large single-crystal specimens are essential. Alternatively, structural determinations by powder profile refinement methods relax the constraints on crystal size, but still require materials with a high degree of crystalline perfection. Studies conducted at CAMMP (Center for Advanced Microgravity Materials Processing) have demonstrated that microgravity processing can produce larger crystal sizes and fewer structural defects relative to terrestrial crystal growth. Principal Investigator: Dr. Albert Sacco

  6. Syngas to olefins via dimethyl ether over zeolite catalysts

    SciTech Connect

    Lee, B.G.; Sardesai, A.; Lee, S.

    1998-12-31

    Coal or natural gas-based syngas can be converted to dimethyl ether (DME) in a dual catalytic, single-stage liquid phase process. The process described here converts dimethyl ether to lower olefins, such as ethylene, propylene, and butenes. Thus, a novel process of producing olefins from syngas via dimethyl ether has been introduced. The process feasibility of dimethyl ether conversion has been evaluated and the range of products of this process has also been identified. The effect of operating parameters and catalyst characteristics on product selectivity has been studied. The superior process advantages as well as its competitive economics quite clearly identify this process to be quite promising when conducted on an industrial scale.

  7. Dynamic Structural Changes in a Molecular Zeolite-Supported Iridium Catalyst for Ethene Hydrogenation

    SciTech Connect

    Uzun, Alper; Gates, Bruce C.

    2009-11-16

    The structure of a catalyst often changes as a result of changes in the reactive environment during operation. Examples include changes in bulk phases, extended surface structures, and nanoparticle morphologies; now we report real-time characterization of changes in the structure of a working supported catalyst at the molecular level. Time-resolved extended X-ray absorption fine structure (EXAFS) data demonstrate the reversible interconversion of mononuclear iridium complexes and tetrairidium clusters inside zeolite Y cages, with the structure controlled by the C{sub 2}H{sub 4}/H{sub 2} ratio during ethene hydrogenation at 353 K. The data demonstrate break-up of tetrairidium clusters into mononuclear complexes indicated by a decrease in the Ir-Ir coordination number in ethene-rich feed. When the feed composition was switched to first equimolar and then to a H{sub 2}-rich (C{sub 2}H{sub 4}/H{sub 2} = 0.3) feed, the EXAFS spectra show the reformation of tetrairidium clusters as the Ir-Ir coordination number increased again. When the feed composition was cycled from ethene-rich to H{sub 2}-rich, the predominant species in the catalyst cycled accordingly. Evidence confirming the structural change is provided by IR spectra of iridium carbonyls formed by probing of the catalyst with CO. The data are the first showing how to tune the structure of a solid catalyst at the molecular scale by choice of the reactant composition.

  8. Highly-basic large-pore zeolite catalysts for NOx reduction at low temperatures

    DOEpatents

    Penetrante, Bernardino M.; Brusasco, Raymond M.; Merritt, Bernard T.; Vogtlin, George E.

    2004-02-03

    A high-surface-area (greater than 600 m2/g), large-pore (pore size diameter greater than 6.5 angstroms), basic zeolite having a structure such as an alkali metal cation-exchanged Y-zeolite is employed to convert NO.sub.x contained in an oxygen-rich engine exhaust to N.sub.2 and O.sub.2. Preferably, the invention relates to a two-stage method and apparatus for NO.sub.x reduction in an oxygen-rich engine exhaust such as diesel engine exhaust that includes a plasma oxidative stage and a selective reduction stage. The first stage employs a non-thermal plasma treatment of NO.sub.x gases in an oxygen-rich exhaust and is intended to convert NO to NO.sub.2 in the presence of O.sub.2 and added hydrocarbons. The second stage employs a lean-NO.sub.x catalyst including the basic zeolite at relatively low temperatures to convert such NO.sub.2 to environmentally benign gases that include N.sub.2, CO.sub.2, and H.sub.2 O.

  9. Hollow zeolitic imidazolate framework nanospheres as highly efficient cooperative catalysts for [3+3] cycloaddition reactions.

    PubMed

    Zhang, Fang; Wei, Yongyi; Wu, Xiaotao; Jiang, Huangyong; Wang, Wei; Li, Hexing

    2014-10-08

    Herein we describe a novel, hollow-structured zeolitic imidazolate framework (ZIF-8-H) nanosphere as a highly efficient catalyst for [3+3] cycloaddition reactions. The programmed installation of acidic Zn(2+) species and basic imidazolate moieties creates a synergistic catalytic system. Appropriate positioning of these functionalities in the catalytic system makes it possible to bring two substrates into close proximity and activate them cooperatively. Moreover, the flexible shell and the surface mesopores of ZIF-8-H provide the capacity for favorable binding of various sized substrates, stabilizing intermediates via their multiple force networks and the increased accessibility of the active sites. These features render ZIF-8-H a more highly active promoter than its homogeneous precursors, bulk ZIF-8 and ZIF-8-N nanoparticles. Finally, the robust catalyst can be easily recovered and reused 10 times without loss of catalytic activity.

  10. Production of aromatic hydrocarbons by catalytic pyrolysis of microalgae with zeolites: catalyst screening in a pyroprobe.

    PubMed

    Du, Zhenyi; Ma, Xiaochen; Li, Yun; Chen, Paul; Liu, Yuhuan; Lin, Xiangyang; Lei, Hanwu; Ruan, Roger

    2013-07-01

    Catalytic pyrolysis of microalgae and egg whites was investigated to evaluate the performance of different zeolites for the production of aromatic hydrocarbons. Three zeolites with different structures (H-Y, H-Beta and H-ZSM5) were used to study the effect of catalyst type on the aromatic yield. All three catalysts significantly increased the aromatic yields from pyrolysis of microalgae and egg whites compared with non-catalytic runs, and H-ZSM5 was most effective with a yield of 18.13%. Three H-ZSM5 with silica-to-alumina ratios of 30, 80 and 280 were used to study the effect of Si/Al ratio on the aromatic yield. The maximum yield was achieved at the Si/Al ratio of 80, which provides moderate acidity to achieve high aromatic production and reduce coke formation simultaneously. Aromatic production increased with the incorporation of copper or gallium to HZSM-5. However, other studied metals either had no significant influence or led to a lower aromatic yield.

  11. Copper(I) zeolites as heterogeneous and ligand-free catalysts: [3+2] cycloaddition of azomethine imines.

    PubMed

    Keller, Murielle; Sido, Abdelkarim Sani Souna; Pale, Patrick; Sommer, Jean

    2009-01-01

    Copper(I)-exchanged zeolites were used as heterogeneous ligand-free catalysts for [3+2] cycloaddition of azomethine ylides, which allows versatile, efficient, and highly regioselective synthesis of pyrazolone derivatives. These cheap and easy-to-prepare catalysts exhibit wide scope and compatibility with functional groups. They are very simple to use, easy to remove (by simple filtration), and recyclable (up to six times without loss of activity).

  12. IMPROVED CATALYSTS FOR HEAVY OIL UPGRADING BASED ON ZEOLITE Y NANOPARTICLES ENCAPSULATED IN STABLE NANOPOROUS HOST

    SciTech Connect

    Conrad Ingram; Mark Mitchell

    2005-11-15

    Composite materials of SBA-15/zeolite Y were synthesized from zeolite Y precursor and a synthesis mixture of mesoporous silicate SBA-15 via a hydrothermal process in the presence of a slightly acidic media of pH 4-6 with 2M H{sub 2}SO{sub 4}. The SBA-15/ZY composites showed Type IV adsorption isotherms, narrow BJH average pore size distribution of 4.9 nm, surface areas up to 800 m{sup 2}2/g and pore volumes 1.03 cm{sup 3}, all comparable to pure SBA-15 synthesized under similar conditions. Chemical analysis revealed Si/Al ratio down to 8.5 in the most aluminated sample, and {sup 27}AlSS MAS NMR confirmed aluminum was in tetrahedral coordination. This method of introduction of Al in pure T{sub d} coordination is effective in comparison to other direct and post synthesis alumination methods. Bronsted acid sites were evident from a pyridinium peak at 1544 cm-1 in the FTIR spectrum after pyridine adsorption, and from NH{sub 3} -TPD experiments. SBA-15/ZY composites showed significant catalytic activities for the dealkylation of isopropylbenzene to benzene and propene, similar to those of commercial zeolite Y. It was observed that higher conversion for catalysts synthesized with high amount of ZY precursor mixture added to the SBA-15. Over all the composites has shown good catalytic activity. Further studies will be focused on gaining a better understand the nature of the precursor, and to characterize and to locate the acid sites in the composite material. The composite will also be evaluated for heavy oil conversion to naphtha and middle distillates.

  13. Structure, dynamics, and reactivity of an alkoxy intermediate formed from acetylene on zeolite catalysts: An in situ solid-state NMR study

    SciTech Connect

    Lazo, N.D.; White, J.L.; Munson, E.J.; Lambregts, M.; Haw, J.F. )

    1990-05-09

    Recently, there has been much interest in reactive intermediates formed by the adsorption of organic compounds on zeolites and alumina. In this communication, they present evidence for a vinyl alkoxy species, analogous to IV, which is formed at high temperatures from acetylene on zeolites HY and HZSM-5. Upon exposure of the catalyst to water, the intermediate was converted quantitatively to acetaldehyde.

  14. Design and modification of zeolite capsule catalyst, a confined reaction field, and its application in one-step isoparaffin synthesis from syngas

    SciTech Connect

    Guohui Yang; Jingjiang He; Yi Zhang; Yoshiharu Yoneyama; Yisheng Tan; Yizhuo Han; Tharapong Vitidsant; Noritatsu Tsubaki

    2008-05-15

    Four kinds of zeolite capsule catalyst with different crystallization conditions were prepared and utilized for the middle isoparaffin direct synthesis via Fischer-Tropsch synthesis (FTS) reaction. Characterization results exhibited that these capsule catalysts had a compact, integral H-ZSM-5 shell. In FTS reactions on these zeolite capsule catalysts, hydrocarbons of C11+ were totally suppressed, accompanied by a sharp anti-Anderson-Schultz-Flory (ASF) law product distribution. The selectivity of light isoparaffin was improved obviously, but with the increase of the olefin's selectivity. Two-stage isoparaffin synthesis reaction, using the combination of zeolite capsule catalyst with hydrogenation catalyst of Pd/SiO{sub 2} in a single reactor as dual-bed catalyst, was also conducted for converting the residual olefins produced by the single zeolite capsule catalyst. Dependent on the palladium role of hydrogenation and hydrogen spillover, almost all the olefins effused from the first stage of zeolite capsule catalyst were hydrogenated, mostly converted to isoparaffin. The selectivity of isoparaffin in the final products was increased markedly as expected. 10 refs., 7 figs., 2 tabs.

  15. Effect of Reaction Temperature on Biodiesel Production from Chlorella vulgaris using CuO/Zeolite as Heterogeneous Catalyst

    NASA Astrophysics Data System (ADS)

    Dianursanti; Delaamira, M.; Bismo, S.; Muharam, Y.

    2017-02-01

    Human needs for fossil energy increase every year. Biodiesel is the main way to resolve this world problem. Biodiesel produces from vegetable oil. But then, the alternative way came from the uses of microalgae in Chlorella vulgaris type causes by its simplicity of growing. In the other hand, this microalgae known for its high lipid content by considering several parameter such as light intensity, medium nutrition, pH and also salinity. Lipid content will be extracted by using Bligh-Dryer method which will be reacted with methanol along transesterification. Beside, there come another matter which is the utilization of homogeny catalyst. The difficulty of separation is the main matter so then biodiesel need to be washed in case normalizing the pH and this process will decrease the quality of biodiesel. To resolve this problem, we’ll be using a heterogeneous catalyst, zeolite, with ability to catalyst the process. Zeolite is easier to separate from the biodiesel so there will not be needed washing process. Heterogeneous catalyst work as well as homogeneous. Variation implemented on transesterification included reaction temperature of 40°C, 60°C, and 80°C. Reaction time, catalyst percentage and the solvent amount remain steady on 4 hours, 3% and 1:400. Complete best result obtained at 60°C with the yield of 36,78%. Through this, heterogeneous catalyst CuO/Zeolite proved to have a capability for replacing homogeneous catalyst and simplify the production of biodiesel particularly in separation step.

  16. Influence of n Si/ n Al ratio of HY zeolite catalysts on alkylation of toluene with tert-butanol

    NASA Astrophysics Data System (ADS)

    Wang, Yuanyuan; Song, Hua; Sun, Xinglong; Song, HuaLin

    2016-12-01

    The highly selective synthesis of 4- tert-butyltoluene from toluene and tert-butanol over HY zeolites was performed in liquid phase. The effect of Si/Al ratio (6.3, 7.5, 11, 12) of HY zeolites on the alkylation performance was studied. The catalysts were characterized by SEM, XRD, FT-IR, and NH3-TPD methods. With increase of Si/Al ratio, the conversion of toluene and the selectivity towards 4- tert-butyltoluene increased gradually. HY-12 was found to be more suitable for the tert-butylation of toluene. When the alkylation reaction was conducted at 180°C for 4 h using HY-12 catalyst, the conversion and the selectivity of 4- tertbutyltoluene reached 40.74 and 70.91%, respectively.

  17. Heteropoly acid encapsulated into zeolite imidazolate framework (ZIF-67) cage as an efficient heterogeneous catalyst for Friedel–Crafts acylation

    SciTech Connect

    Ammar, Muhammad; Jiang, Sai; Ji, Shengfu

    2016-01-15

    A new strategy has been developed for the encapsulation of the phosphotungstic heteropoly acid (H{sub 3}PW{sub 12}O{sub 40} denoted as PTA) into zeolite imidazolate framework (ZIF-67) cage and the PTA@ZIF-67(ec) catalysts with different PTA content were prepared. The structure of the catalysts was characterized by XRD, BET, SEM, FT-IR, ICP-AES and TG. The catalytic activity and recovery properties of the catalysts for the Friedel-Crafts acylation of anisole with benzoyl chloride were evaluated. The results showed that 14.6–31.7 wt% PTA were encapsulated in the ZIF-67 cage. The PTA@ZIF-67(ec) catalysts had good catalytic activity for Friedel-Crafts acylation. The conversion of anisole can reach ~100% and the selectivity of the production can reach ~94% over 26.5 wt% PTA@ZIF-67(ec) catalyst under the reaction condition of 120 °C and 6 h. After reaction, the catalyst can be easily separated from the reaction mixture by the centrifugation. The recovered catalyst can be reused five times and the selectivity can be kept over 90%. - Graphical abstract: The PTA@ZIF-67 catalysts with different PTA content were prepared by encapsulating the PTA into ZIF-67 cage and the as-synthesized catalysts exhibited good catalytic activity for the Friedel–Craft acylation of anisole with benzoyl chloride.

  18. Non-Precious Metal Catalysts Prepared By Zeolitic Imidazolate Frameworks: The Ligand Influence to Morphology and Performance

    SciTech Connect

    Barkholtz, H. M.; Chong, L.; Kaiser, Z. B.; Liu, D. -J

    2016-08-01

    A new, “one-pot” synthesis to produce highly active non-PGM electrocatalysts for PEM fuel cells was previously developed by pyrolyzing Fe doped zeolitic imidazolate framework (ZIF) materials prepared by solid-state interaction. Excellent catalytic oxygen reduction reaction (ORR) activities were found through rotating ring-disk electrode (RRDE) and single fuel cell tests. In this study, we compared the ORR activities and structural properties of two catalysts derived from ZIFs containing imidazole and methyl imidazole ligands, respectively. Our results indicate that alkyl group substitution in the imidazolate ligand has a profound effect on the final catalyst performance.

  19. Elucidation of Diels-Alder Reaction Network of 2,5-Dimethylfuran and Ethylene on HY Zeolite Catalyst

    SciTech Connect

    Do, Phuong T. M.; McAtee, Jesse R.; Watson, Donald A.; Lobo, Raul F.

    2012-12-12

    The reaction of 2,5-dimethylfuran and ethylene to produce p-xylene represents a potentially important route for the conversion of biomass to high-value organic chemicals. Current preparation methods suffer from low selectivity and produce a number of byproducts. Using modern separation and analytical techniques, the structures of many of the byproducts produced in this reaction when HY zeolite is employed as a catalyst have been identified. From these data, a detailed reaction network is proposed, demonstrating that hydrolysis and electrophilic alkylation reactions compete with the desired Diels–Alder/dehydration sequence. This information will allow the rational identification of more selective catalysts and more selective reaction conditions.

  20. Degradation of a textile dye, Rhodamine 6G (Rh6G), by heterogeneous sonophotoFenton process in the presence of Fe-containing TiO2 catalysts.

    PubMed

    Demir, Nazlı; Gündüz, Gönül; Dükkancı, Meral

    2015-03-01

    In this study, degradation of Rhodamine 6G (Rh6G) was investigated with ultrasound-assisted heterogeneous photoFenton process by iron-containing TiO2 catalysts. The catalysts were prepared by incipient wetness impregnation method and characterized by XRD, SEM, FT-IR, nitrogen adsorption, and ICP-AES measurements. Almost complete color removal (99.9 %) was achieved after a reaction time of 90 min while chemical oxygen demand (COD) could be removed by 24 % only with the 1 wt% iron-containing TiO2 catalyst. Initial color removal after 15 min of reaction and total COD abatement after 90 min of reaction decreased with increasing calcination temperature of the catalyst from 573 to 973 K. This indicated that the catalytic activity of the catalyst depend on the percentage of anatase phase in the TiO2, which was decreased with increasing calcination temperature.

  1. Systems including catalysts in porous zeolite materials within a reactor for use in synthesizing hydrocarbons

    DOEpatents

    Rolllins, Harry W [Idaho Falls, ID; Petkovic, Lucia M [Idaho Falls, ID; Ginosar, Daniel M [Idaho Falls, ID

    2012-07-24

    Catalytic structures include a catalytic material disposed within a zeolite material. The catalytic material may be capable of catalyzing a formation of methanol from carbon monoxide and/or carbon dioxide, and the zeolite material may be capable of catalyzing a formation of hydrocarbon molecules from methanol. The catalytic material may include copper and zinc oxide. The zeolite material may include a first plurality of pores substantially defined by a crystal structure of the zeolite material and a second plurality of pores dispersed throughout the zeolite material. Systems for synthesizing hydrocarbon molecules also include catalytic structures. Methods for synthesizing hydrocarbon molecules include contacting hydrogen and at least one of carbon monoxide and carbon dioxide with such catalytic structures. Catalytic structures are fabricated by forming a zeolite material at least partially around a template structure, removing the template structure, and introducing a catalytic material into the zeolite material.

  2. Magnetic and Mössbauer study of metal-zeolite interaction in catalysts

    NASA Astrophysics Data System (ADS)

    Pannaparayil, Thomas; Oskooie-Tabrizi, M.; Lo, C.; Mulay, L. N.; Melson, G. A.; Rao, V. U. S.

    1984-03-01

    Molecular sieve aluminosilicates, such as ZSM-5 and mordenite, when impregnated with highly dispersed Fe, yield catalysts for the selective conversion of coal-derived syngas (CO+H2) to liquid hydrocarbon fuels. Fe performs the primary Fischer-Tropsch (FT) syngas to yield light olefins which are converted by the acidic (H+) and shape-selective function of the zeolite to high octane gasoline components. The physical aspects of the Fe-mordenite interaction studied by magnetic measurements, Mössbauer, and IR spectroscopy are reported and correlations with the catalytic properties are drawn. Mordenite samples with [SiO2/Al2O3] ratio in the range 12 - 60 were impregnated with 15 wt. % Fe using Fe3(CO)12; decarbonylation yielded superparamagmetic dispersions of γ-Fe2O3, in the range 1.4-5.0 nm; the smallest particles were obtained for a ratio=17. Hydrogen chemisorption also revealed a similar trend in Fe dispersions. No samples, other than the one with a ratio=60 and containing the largest particles could be carbided under usual conditions. The acidity of the mordenite and the aromatics fraction in liquid hydrocarbons from syngas conversion also showed maxima at a ratio=17. The presence of a strong metal-support interaction between Fe and mordenite was thus influenced by the varying ratios in the mordenite in a manner that paralleled the acidity and catalytic activity.

  3. Heteropoly acid encapsulated into zeolite imidazolate framework (ZIF-67) cage as an efficient heterogeneous catalyst for Friedel-Crafts acylation

    NASA Astrophysics Data System (ADS)

    Ammar, Muhammad; Jiang, Sai; Ji, Shengfu

    2016-01-01

    A new strategy has been developed for the encapsulation of the phosphotungstic heteropoly acid (H3PW12O40 denoted as PTA) into zeolite imidazolate framework (ZIF-67) cage and the PTA@ZIF-67(ec) catalysts with different PTA content were prepared. The structure of the catalysts was characterized by XRD, BET, SEM, FT-IR, ICP-AES and TG. The catalytic activity and recovery properties of the catalysts for the Friedel-Crafts acylation of anisole with benzoyl chloride were evaluated. The results showed that 14.6-31.7 wt% PTA were encapsulated in the ZIF-67 cage. The PTA@ZIF-67(ec) catalysts had good catalytic activity for Friedel-Crafts acylation. The conversion of anisole can reach ~100% and the selectivity of the production can reach ~94% over 26.5 wt% PTA@ZIF-67(ec) catalyst under the reaction condition of 120 °C and 6 h. After reaction, the catalyst can be easily separated from the reaction mixture by the centrifugation. The recovered catalyst can be reused five times and the selectivity can be kept over 90%.

  4. Natrolite zeolite supported copper nanoparticles as an efficient heterogeneous catalyst for the 1,3-diploar cycloaddition and cyanation of aryl iodides under ligand-free conditions.

    PubMed

    Nasrollahzadeh, Mahmoud; Sajadi, S Mohammad; Rostami-Vartooni, Akbar; Khalaj, Mehdi

    2015-09-01

    In this paper, we report the preparation of Natrolite zeolite supported copper nanoparticles as a heterogeneous catalyst for 1,3-diploar cycloaddition and synthesis aryl nitriles from aryl iodides under ligand-free conditions. The catalyst was characterized using XRD, SEM, TEM, EDS and TG-DTA. The experimental procedure is simple, the products are formed in high yields and the catalyst can be recycled and reused several times without any significant loss of catalytic activity.

  5. Kinetics and Mechanism of Deoxygenation Reactions over Proton-Form and Molybdenum-Modified Zeolite Catalysts

    NASA Astrophysics Data System (ADS)

    Bedard, Jeremy William

    .04-0.10, HCOOH/CH 4 = 0.01-0.03, CO2/CH4 = 0.01-0.03) on Mo/H-ZSM-5 formulations at 950 K and atmospheric pressure in an effort to couple deoxygenation and dehydrogenation reaction sequences results instead in a two-zone, stratified bed reactor configuration consisting of upstream oxygenate/CH4 reforming and downstream CH4 dehydroaromatization. X-ray absorption spectroscopy and chemical transient experiments show that molybdenum carbide is formed inside zeolite micropores during CH4 reactions. The addition of an oxygenate co-feed causes oxidation of the active molybdenum carbide catalyst while producing CO and H2 until completely converted. Forward rates of C6H6 synthesis are unperturbed by the introduction of an oxygenate co-feed after rigorously accounting for the thermodynamic reversibility caused by the H2 produced in oxygenate reforming reactions and the fraction of the active catalyst deemed unavailable for CH 4 dehydroaromatization. All effects of co-processing C1-2 oxygenates and molecular H2 with CH4 can be interpreted in terms of an approach to equilibrium. Co-processing H2O, CO2, or light (C1-2, C/Heff < 0.25) oxygenates with CH4 at 950 K over Mo/H-ZSM-5 catalysts results in complete fragmentation of the oxygenate and CO as the sole oxygen-containing product. The C/Heff accounts for removal of O as CO and describes the net C6H6 and total hydrocarbon synthesis rates at varying (0.0-0.10) C1-2 oxygenate and H2 to CH4 co-feed ratios. Co-processing larger (C 3-5, C/Heff ≥ 0.25) oxygenates with CH4 results in incomplete fragmentation of the co-fed oxygenate and preferential pathways of C6H6 synthesis that exclude CH4 incorporation. This results in greater net C6H6 synthesis rates than would be predicted from observations made when co-processing C1-2 oxygenates. Catalytic technologies have served a crucial role in processing petroleum feedstocks and are faced with new challenges as the feedstock shifts to chemically diverse but renewable biomass sources. This research

  6. Fe-containing phases in hydrated cements

    SciTech Connect

    Dilnesa, B.Z.; Wieland, E.; Lothenbach, B.; Dähn, R.; Scrivener, K.L.

    2014-04-01

    In this study synchrotron X-ray absorption spectroscopy (XAS) has been applied, an element specific technique which allows Fe-containing phases to be identified in the complex mineral mixture of hydrated cements. Several Fe species contributed to the overall Fe K-edge spectra recorded on the cement samples. In the early stage of cement hydration ferrite was the dominant Fe-containing mineral. Ferrihydrite was detected during the first hours of the hydration process. After 1 day the formation of Al- and Fe-siliceous hydrogarnet was observed, while the amount of ferrihydrite decreased. The latter finding agrees with thermodynamic modeling, which predicts the formation of Fe-siliceous hydrogarnet in Portland cement systems. The presence of Al- and Fe-containing siliceous hydrogarnet was further substantiated in the residue of hydrated cement by performing a selective dissolution procedure. - Highlights: • Fe bound to ferrihydrite at early age hydration • Fe found to be stable in siliceous hydrogarnet at longer term age hydration • Fe-containing AFt and AFm phases are less stable than siliceous hydrogarnet. • The study demonstrates EXAFS used to identify amorphous or poorly crystalline phases.

  7. Fully Copper-Exchanged High-Silica LTA Zeolites as Unrivaled Hydrothermally Stable NH3 -SCR Catalysts.

    PubMed

    Ryu, Taekyung; Ahn, Nak Ho; Seo, Seungwan; Cho, Jung; Kim, Hyojun; Jo, Donghui; Park, Gi Tae; Kim, Pyung Soon; Kim, Chang Hwan; Bruce, Elliott L; Wright, Paul A; Nam, In-Sik; Hong, Suk Bong

    2017-03-13

    Diesel engine technology is still the most effective solution to meet tighter CO2 regulations in the mobility and transport sector. In implementation of fuel-efficient diesel engines, the poor thermal durability of lean nitrogen oxides (NOx ) aftertreatment systems remains as one major technical hurdle. Divalent copper ions when fully exchanged into high-silica LTA zeolites are demonstrated to exhibit excellent activity maintenance for NOx reduction with NH3 under vehicle simulated conditions even after hydrothermal aging at 900 °C, a critical temperature that the current commercial Cu-SSZ-13 catalyst cannot overcome owing to thermal deactivation. Detailed structural characterizations confirm the presence of Cu(2+) ions only at the center of single 6-rings that act not only as a catalytically active center, but also as a dealumination suppressor. The overall results render the copper-exchanged LTA zeolite attractive as a viable substitute for Cu-SSZ-13.

  8. Electrode-Modified Zeolites - Electrode Microstructures Contained in and on a Heterogeneous Catalyst

    DTIC Science & Technology

    1988-07-15

    CH3CN of ferrocene and a bulky ferrocene derivative too large to enter the zeolite [42]. No difference was observed after normalizing the current...of electrode-modified zeolites and dispersi, electrolysis now permits an investigation of the confluence and possible syn. 0 19 of electrocatalysis and

  9. Features of non-oxidative conversion of methane into aromatic hydrocarbons over Mo-containing zeolite catalysts

    NASA Astrophysics Data System (ADS)

    Stepanov, A. A.; Korobitsyna, L. L.; Vosmerikov, A. V.

    2016-09-01

    The results of study of methane conversion under non-oxidative conditions over molybdenum containing zeolite catalysts prepared by solid-phase synthesis using nanosized molybdenum powder are presented. The kinetic mechanisms of the process behavior under different conditions of methane dehydroaromatization are determined. It is shown that nonoxidative conversion of methane can occur both in the external diffusion and kinetic regions, depending on the methane flow rate. It is found out, that the optimum temperature of the methane conversion is 750 °C. It is shown that increased methane conversion is observed at the feed space velocity of methane decreasing from 1500 to 500 h-1.

  10. Acidic and basic properties of zeolite-containing cracking catalyst in the process of butene-1 isomerization

    NASA Astrophysics Data System (ADS)

    Mursalova, L. A.; Guseinova, E. A.; Adzhamov, K. Yu.

    2016-08-01

    The process of butene-1 isomerization in the presence of two groups of samples of zeolite-containing catalyst (ZCC) that earlier participated in the traditional and oxidative catalytic cracking of vacuum gasoil is investigated. It is established that the nature of the reaction mixture and conditions of the cracking process are key factors in forming the acidic and basic properties of the catalyst. It is shown that the highest activity in the butene-1 isomerization into cis-/ trans-butene-2 is demonstrated by ZCC samples that participated in the oxidative catalytic cracking (oxycracking). It is suggested that the enhanced catalytic activity of this group of ZCC samples was related to the availability of acid-base centers in the form of radical-like oxygen along with protic- and aprotic-type acidic centers in the structure of the oxidative compaction products.

  11. ZEOLITES: EFFECTIVE WATER PURIFIERS

    EPA Science Inventory

    Zeolites are known for their adsorption, ion exchange and catalytic properties. Various natural zeolites are used as odor and moisture adsorbents and water softeners. Due to their acidic nature, synthetic zeolites are commonly employed as solid acid catalysts in petrochemical ind...

  12. Capture and isotopic exchange method for water and hydrogen isotopes on zeolite catalysts up to technical scale for pre-study of processing highly tritiated water

    SciTech Connect

    Michling, R.; Braun, A.; Cristescu, I.; Dittrich, H.; Gramlich, N.; Lohr, N.; Glugla, M.; Shu, W.; Willms, S.

    2015-03-15

    Highly tritiated water (HTW) may be generated at ITER by various processes and, due to the excessive radio toxicity, the self-radiolysis and the exceedingly corrosive property of HTW, a potential hazard is associated with its storage and process. Therefore, the capture and exchange method for HTW utilizing Molecular Sieve Beds (MSB) was investigated in view of adsorption capacity, isotopic exchange performance and process parameters. For the MSB, different types of zeolite were selected. All zeolite materials were additionally coated with platinum. The following work comprised the selection of the most efficient zeolite candidate based on detailed parametric studies during the H{sub 2}/D{sub 2}O laboratory scale exchange experiments (about 25 g zeolite per bed) at the Tritium Laboratory Karlsruhe (TLK). For the zeolite, characterization analytical techniques such as Infrared Spectroscopy, Thermogravimetry and online mass spectrometry were implemented. Followed by further investigation of the selected zeolite catalyst under full technical operation, a MSB (about 22 kg zeolite) was processed with hydrogen flow rates up to 60 mol*h{sup -1} and deuterated water loads up to 1.6 kg in view of later ITER processing of arising HTW. (authors)

  13. Structural Descriptors of Zeolitic-Imidazolate Frameworks Are Keys to the Activity of Fe-N-C Catalysts.

    PubMed

    Armel, Vanessa; Hindocha, Sheena; Salles, Fabrice; Bennett, Stephen; Jones, Deborah; Jaouen, Frédéric

    2017-01-11

    Active and inexpensive catalysts for oxygen reduction are crucially needed for the widespread development of polymer electrolyte fuel cells and metal-air batteries. While iron-nitrogen-carbon materials pyrolytically prepared from ZIF-8, a specific zeolitic imidazolate framework (ZIF) with sodalite topology, have shown enhanced activities toward oxygen reduction in acidic electrolyte, the rational design of sacrificial metal-organic frameworks toward this application has hitherto remained elusive. Here, we report for the first time that the oxygen reduction activity of Fe-N-C catalysts positively correlates with the cavity size and mass-specific pore volume in pristine ZIFs. The high activity of Fe-N-C materials prepared from ZIF-8 could be rationalized, and another ZIF structure leading to even higher activity was identified. In contrast, the ORR activity is mostly unaffected by the ligand chemistry in pristine ZIFs. These structure-property relationships will help identifying novel sacrificial ZIF or porous metal-organic frameworks leading to even more active Fe-N-C catalysts. The findings are of great interest for a broader application of the class of inexpensive metal-nitrogen-carbon catalysts that have shown promising activity also for the hydrogen evolution (Co-N-C) and carbon dioxide reduction (Fe-N-C and Mn-N-C).

  14. CHARACTERIZATION OF H-Y AND CR-Y ZEOLITE CATALYSTS DURING THE OXIDATIVE DESTRUCTION OF CFC11 AND CFC12

    EPA Science Inventory

    The long term stability-deactivation characteristics of two Y zeolite catalysts, namely H-Y and cation exchanged Cr-Y, were studied during the oxidative destruction of CFC11 and CFC12 feeds. Experiments were carried out at 300 degrees C and 500 h-1 space velocity. Properties of...

  15. Chemical imaging of catalyst deactivation during the conversion of renewables at the single particle level: etherification of biomass-based polyols with alkenes over H-Beta zeolites.

    PubMed

    Parvulescu, Andrei N; Mores, Davide; Stavitski, Eli; Teodorescu, Cristian M; Bruijnincx, Pieter C A; Gebbink, Robertus J M Klein; Weckhuysen, Bert M

    2010-08-04

    The etherification of biomass-based alcohols with various linear alpha-olefins under solvent-free conditions was followed in a space- and time-resolved manner on 9 microm large H-Beta zeolite crystals by confocal fluorescence microscopy. This allowed us to visualize the interaction with the substrate and distribution of the coke products into the catalyst at the level of an individual zeolite crystal during the etherification process. The spectroscopic information obtained on the micrometer-scale zeolite was in line with the results obtained with bulk characterization techniques and further confirmed by the catalytic results obtained both for micrometer-scale and nanoscale zeolites. This allowed us to explain the influence of the substrate type (glycerol, glycols, and alkenes) and zeolite properties (Si/Al ratio and particle size) on the etherification activity. The etherification of the biomass-based alcohols takes place mainly on the external surface of the zeolite particles. The gradual blockage of the external surface of the zeolite results in a partial or total loss of etherification activity. The deactivation could be attributed to olefin oligomerization. The high conversions obtained in the etherification of 1,2-propylene glycol with long linear alkenes (up to 80%) and the pronounced deactivation of the zeolite observed in the etherification of glycerol with long linear alkenes (max. 20% conversion) were explained by the spectroscopic measurements and is due to differences in the adsorption, i.e., in the center of the zeolite particle for glycerol and on the external surface in the case of glycols.

  16. IMPROVED CATALYSTS FOR HEAVY OIL UPGRADING BASED ON ZEOLITE Y NANOPARTICLES ENCAPSULATED IN STABLE NANOPOROUS HOSTS

    SciTech Connect

    Conrad Ingram; Mark Mitchell

    2004-06-30

    The focus of this project is to improve the catalytic performance of zeolite Y for heavy petroleum hydrocracking by synthesizing nanoparticles of the zeolite ({approx}20-30 nm) inside nanoporous silicate or aluminosilicate hosts of similar pore diameters. The encapsulated zeolite nanoparticles are expected to possess pores of reduced diffusional path lengths, hence hydrocarbon substrates will diffuse in, are converted and the products quickly diffused out. This is expected to prevent over-reaction, hence minimizing pore blockage and active sites deactivation. In this phase of the project, research activities were focused on refining procedures to: (a) improve the synthesis of ordered, high surface area nanoporous silica, such as SBA-15, with expanded pore size using trimethylbenzene as additive to the parent SBA-15 synthesis mixture; and (b) reduce the particle size of zeolite Y such that they can be effectively incorporated into the nanoporous silicas. The synthesis of high surface ordered nanoporous silica containing enlarged pores of diameter of 25 nm (larger than the standard size of 8.4 nm) using trimethylbenzene as a pore size expander was accomplished. The synthesis of zeolite Y nanoparticles with median pore size of approximately 50 nm (smaller than the 80 nm typically obtained with TMAOH) using combined TMABr/TMAOH as organic additives was also accomplished.

  17. IMPROVED CATALYSTS FOR HEAVY OIL UPGRADING BASED ON ZEOLITE Y NANOPARTICLES ENCAPSULATED IN STABLE NANOPOROUS HOSTS

    SciTech Connect

    Conrad Ingram

    2003-09-03

    The focus of this project is to improve the catalytic performance of zeolite Y for petroleum hydrocracking by synthesizing nanoparticles of the zeolite ({approx}20-25 nm) inside nanoporous silicate or aluminosilicate hosts. The encapsulated zeolite nanoparticles are expected to possess reduced diffusional path lengths, hence hydrocarbon substrates will diffuse in, are converted and the products quickly diffused out. This is expected to prevent over-reaction and the blocking of the zeolite pores and active sites will be minimized. In this phase of the project, procedures for the synthesis of ordered nanoporous silica, such as SBA-15, using block copolymers and nonionic surfactant were successful reproduced. Expansion of the pores sizes of the nanoporous silica using trimethylbenzene is suggested based on shift in the major X-Ray Diffraction peak in the products to lower 2 angles compared with the parent SBA-15 material. The synthesis of ordered nanoporous materials with aluminum incorporated in the predominantly silicate framework was attempted but is not yet successful, and the procedures needs will be repeated and modified as necessary. Nanoparticles of zeolite Y of particle sizes in the range 40 nm to 120 nm were synthesized in the presence of TMAOH as the particle size controlling additive.

  18. The Effect of Time dealumination and Solvent Concentration in Synthesis of Zeolite Catalyst and Catalytic Test for DiEthyl Ether Production Process

    SciTech Connect

    Widayat; Roesyadi, A.; Rachimoellah, M.

    2009-09-14

    Ethanol is an alternative energy, but its has three distinct disadvantages as a transportation fuel. Its availability is currently limited, and it has a lower volumetric heating value and a lower Reid vapour pressure (RVP) than gasoline. This paper focuses for this disadvantages and to solve this problem can do with converts ethanol to DiEthyl Ether product. This research produced DiEthyl Ether by ethanol dehydration process with zeolite as catalyst. The catalyst synthesis from natural material from District Gunung Kidul, Indonesia. The catalyst produced with dealumination, neutralization, drying and calcination processes. The zeolite catalyst was analysed of Si/Al, X-ray Diffraction and specific surface area. The catalyst product then used for ethanol dehydration to produce DiEthyl Ether. The results shown the biggest surface area is 184,52 m{sup 2}/gram at catalyst production at 10 hours for time dealumination. The crystallite of catalyst product is similar like shown at diffractogram of XRD analysis. The ratio Si/Al biggest is 313.7 that obtaining at catalyst production with 7 hours for time dealumination. The catalytic test use fixed bed reactor with 1 inci diameter and ethanol fermentation both as feed. The operation condition is 150 deg. C at temperature and atmosphere pressure. The compounds product in liquid phase are diethyl ether, methanol and water.

  19. The Effect of Time dealumination and Solvent Concentration in Synthesis of Zeolite Catalyst and Catalytic Test for DiEthyl Ether Production Process

    NASA Astrophysics Data System (ADS)

    Widayat, Widayat; Roesyadi, A.; Rachimoellah, M.

    2009-09-01

    Ethanol is an alternative energy, but its has three distinct disadvantages as a transportation fuel. Its availability is currently limited, and it has a lower volumetric heating value and a lower Reid vapour pressure (RVP) than gasoline. This paper focuses for this disadvantages and to solve this problem can do with converts ethanol to DiEthyl Ether product. This research produced DiEthyl Ether by ethanol dehydration process with zeolite as catalyst. The catalyst synthesis from natural material from District Gunung Kidul, Indonesia. The catalyst produced with dealumination, neutralization, drying and calcination processes. The zeolite catalyst was analysed of Si/Al, X-ray Diffraction and specific surface area. The catalyst product then used for ethanol dehydration to produce DiEthyl Ether. The results shown the biggest surface area is 184,52 m 2 / gram at catalyst production at 10 hours for time dealumination. The crystallite of catalyst product is similar like shown at diffractogram of XRD analysis. The ratio Si/Al biggest is 313.7 that obtaining at catalyst production with 7 hours for time dealumination. The catalytic test use fixed bed reactor with 1 inci diameter and ethanol fermentation borth as feed. The operation condition is 150° C at temperature and atmosphere pressure. The compounds product in liquid phase are diethyl ether, methanol and water.

  20. Conversion of waste cooking oil to jet biofuel with nickel-based mesoporous zeolite Y catalyst.

    PubMed

    Li, Tao; Cheng, Jun; Huang, Rui; Zhou, Junhu; Cen, Kefa

    2015-12-01

    Three types of zeolites (Meso-Y, SAPO-34, and HY) loaded with nickel were used to convert waste cooking oil to jet biofuel. Mesoporous zeolite Y exhibited a high jet range alkane selectivity of 53% and a proper jet range aromatic hydrocarbon selectivity of 13.4% in liquid fuel products. Reaction temperature was optimized to produce quality jet biofuel. Zeolite Meso-Y exhibited a high jet range alkane yield of 40.5% and a low jet range aromatic hydrocarbon yield of 11.3% from waste cooking oil at 400°C. The reaction pathway for converting waste cooking oil to jet biofuel was proposed. Experimental results showed that waste cooking oil mainly deoxygenated to heptadecane (C17H36) and pentadecane (C15H30) through the decarbonylation pathway for the first 3h. Long chain alkanes cracked into jet range alkanes (C8-C16). Cycloalkanes and aromatic hydrocarbons were produced through cyclization and dehydrogenation pathways.

  1. Noble-metal-based catalysts supported on zeolites and macro-mesoporous metal oxide supports for the total oxidation of volatile organic compounds.

    PubMed

    Barakat, Tarek; Rooke, Joanna C; Tidahy, Haingomalala Lucette; Hosseini, Mahsa; Cousin, Renaud; Lamonier, Jean-François; Giraudon, Jean-Marc; De Weireld, Guy; Su, Bao-Lian; Siffert, Stéphane

    2011-10-17

    The use of porous materials to eliminate volatile organic compounds (VOCs) has proven very effective towards achieving sustainability and environmental protection goals. The activity of zeolites and macro-mesoporous metal-oxide supports in the total oxidation of VOCs has been investigated, with and without noble-metal deposition, to develop highly active catalyst systems where the formation of by-products was minimal. The first catalysts employed were zeolites, which offered a good activity in the oxidation of VOCs, but were rapidly deactivated by coke deposition. The effects of the acido-basicity and ionic exchange of these zeolites showed that a higher basicity was related to exchanged ions with lower electronegativities, resulting in better catalytic performances in the elimination of VOCs. Following on from this work, noble metals were deposited onto macro-mesoporous metal-oxide supports to form mono and bimetallic catalysts. These were then tested in the oxidation of toluene to study their catalytic performance and their deactivation process. PdAu/TiO(2) and PdAu/TiO(2) -ZrO(2) 80/20 catalysts demonstrated the best activity and life span in the oxidation of toluene and propene and offered the lowest temperatures for a 50 % conversion of VOCs and the lowest coke content after catalytic testing. Different characterization techniques were employed to explain the changes occurring in catalyst structure during the oxidation of toluene and propene.

  2. Investigation of PCDD/F emissions from mobile source diesel engines: impact of copper zeolite SCR catalysts and exhaust aftertreatment configurations.

    PubMed

    Liu, Z Gerald; Wall, John C; Barge, Patrick; Dettmann, Melissa E; Ottinger, Nathan A

    2011-04-01

    This study investigated the impact of copper zeolite selective catalytic reduction (SCR) catalysts and exhaust aftertreatment configurations on the emissions of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) from mobile source diesel engines. Emissions of PCDD/Fs, reported as the weighted sum of 17 congeners called the toxic equivalency quotient (TEQ), were measured using a modified EPA Method 0023A in the absence and presence of exhaust aftertreatment. Engine-out emissions were measured as a reference, while aftertreatment configurations included various combinations of diesel oxidation catalyst (DOC), diesel particulate filter (DPF), Cu-zeolite SCR, Fe-zeolite SCR, ammonia oxidation catalyst (AMOX), and aqueous urea dosing. In addition, different chlorine concentrations were evaluated. Results showed that all aftertreatment configurations reduced PCDD/F emissions in comparison to the engine-out reference, consistent with reduction mechanisms such as thermal decomposition or combined trapping and hydrogenolysis reported in the literature. Similarly low PCDD/F emissions from the DOC-DPF and the DOC-DPF-SCR configurations indicated that PCDD/F reduction primarily occurred in the DOC-DPF with no noticeable contribution from either the Cu- or Fe-zeolite SCR systems. Furthermore, experiments performed with high chlorine concentration provided no evidence that chlorine content has an impact on the catalytic synthesis of PCDD/Fs for the chlorine levels investigated in this study.

  3. A Single-Site Platinum CO Oxidation Catalyst in Zeolite KLTL: Microscopic and Spectroscopic Determination of the Locations of the Platinum Atoms

    SciTech Connect

    Kistler, Joseph D.; Chotigkrai, Nutchapon; Xu, Pinghong; Enderle, Bryan; Praserthdam, Piyasan; Chen, Cong-Yan; Browning, Nigel D.; Gates, Bruce C.

    2014-07-01

    A stable site-isolated mononuclear platinum catalyst with a well-defined structure is presented. Platinum complexes supported in zeolite KLTL were synthesized from [Pt(NH3)4](NO3)2, oxidized at 633 K, and used to catalyze CO oxidation. Finally, IR and X-ray absorption spectra and electron micrographs determine the structures and locations of the platinum complexes in the zeolite pores, demonstrate the platinum-support bonding, and show that the platinum remained site isolated after oxidation and catalysis.

  4. Control of carbon monoxide (CO) from automobile exhaust by a dealuminated zeolite supported regenerative MnCo2O4 catalyst.

    PubMed

    Arun, P S; Ranjith, B P; Shibli, S M A

    2013-03-19

    We synthesized MnCo(2)O(4) catalyst with very high porosity on the surface of dealuminated zeolite molecular sieves (DAZMS) for CO oxidation under actual automobile conditions. The MnCo(2)O(4) catalyst was selected on the basis of preliminary DFT study using the software ADF BAND. The MnCo(2)O(4) catalyst had comparatively higher CO adsorption energy and very low oxygen vacancy formation energy. The synthesized MnCo(2)O(4)/DAZMS catalyst was characterized by XRD, XRF, BET, SEM, and Confocal Microscopy. The Confocal microscopic analysis revealed that porosity of the dealuminated zeolite surface was significantly enhanced after the catalyst loading process. The completely precious metal free and DAZMS-supported catalyst exhibited excellent CO oxidation ability with renewed activity for seven months under actual automobile conditions with reference to normal and cold start conditions. The synthesized MnCo(2)O(4)/DAZMS not only exhibited surprisingly high catalytic activity for CO oxidation at a temperature resembling a cold start period but was also sufficiently stable/active under actual automobile conditions and ambient conditions containing large amounts of CO,H(2)O,CO(2), and NO(x) at 155-715 °C. These significant results revealed the flexible use of the present catalyst system for a wide variety of automobiles from a small gasoline-fuelled vehicle to a large diesel-fuelled vehicle that may produce high CO-content exhaust.

  5. HERFD-XANES and XES as complementary operando tools for monitoring the structure of Cu-based zeolite catalysts during NOx-removal by ammonia SCR

    NASA Astrophysics Data System (ADS)

    Günter, T.; Doronkin, D. E.; Carvalho, H. W. P.; Casapu, M.; Grunwaldt, J.-D.

    2016-05-01

    In this article, we demonstrate the potential of hard X-ray techniques to characterize catalysts under working conditions. Operando high energy resolution fluorescence detected (HERFD) XANES and valence to core (vtc) X-ray emission spectroscopy (XES) have been used in a spatially-resolved manner to study Cu-zeolite catalysts during the standard-SCR reaction and related model conditions. The results show a gradient in Cu oxidation state and coordination along the catalyst bed as the reactants are consumed. Vtc-XES gives complementary information on the direct adsorption of ammonia at the Cu sites. The structural information on the catalyst shows the suitability of X-ray techniques to understand catalytic reactions and to facilitate catalyst optimization.

  6. Zeolite catalysis: technology

    SciTech Connect

    Heinemann, H.

    1980-07-01

    Zeolites have been used as catalysts in industry since the early nineteen sixties. The great majority of commercial applications employ one of three zeolite types: zeolite Y; Mordenite; ZSM-5. By far the largest use of zeolites is in catalytic cracking, and to a lesser extent in hydrocracking. This paper reviews the rapid development of zeolite catalysis and its application in industries such as: the production of gasoline by catalytic cracking of petroleum; isomerization of C/sub 5/ and C/sub 6/ paraffin hydrocarbons; alkylation of aromatics with olefins; xylene isomerization; and conversion of methanol to gasoline.

  7. One-Pot Process for Hydrodeoxygenation of Lignin to Alkanes Using Ru-Based Bimetallic and Bifunctional Catalysts Supported on Zeolite Y.

    PubMed

    Wang, Hongliang; Ruan, Hao; Feng, Maoqi; Qin, Yuling; Job, Heather; Luo, Langli; Wang, Chongmin; Engelhard, Mark H; Kuhn, Erik; Chen, Xiaowen; Tucker, Melvin P; Yang, Bin

    2017-02-22

    The synthesis of high-efficiency and low-cost catalysts for hydrodeoxygenation (HDO) of waste lignin to advanced biofuels is crucial for enhancing current biorefinery processes. Inexpensive transition metals, including Fe, Ni, Cu, and Zn, were severally co-loaded with Ru on HY zeolite to form bimetallic and bifunctional catalysts. These catalysts were subsequently tested for HDO conversion of softwood lignin and several lignin model compounds. Results indicated that the inexpensive earth-abundant metals could modulate the hydrogenolysis activity of Ru and decrease the yield of low-molecular-weight gaseous products. Among these catalysts, Ru-Cu/HY showed the best HDO performance, affording the highest selectivity to hydrocarbon products. The improved catalytic performance of Ru-Cu/HY was probably a result of the following three factors: (1) high total and strong acid sites, (2) good dispersion of metal species and limited segregation, and (3) high adsorption capacity for polar fractions, including hydroxyl groups and ether bonds. Moreover, all bifunctional catalysts proved to be superior over the combination catalysts of Ru/Al2 O3 and HY zeolite.

  8. Superior performance of metal-organic frameworks over zeolites as solid acid catalysts in the Prins reaction: green synthesis of nopol.

    PubMed

    Opanasenko, Maksym; Dhakshinamoorthy, Amarajothi; Hwang, Young Kyu; Chang, Jong-San; Garcia, Hermenegildo; Čejka, Jiří

    2013-05-01

    The catalytic performance of a set of metal-organic frameworks [CuBTC, FeBTC, MIL-100(Fe), MIL-100(Cr), ZIF-8, MIL-53(Al)] was investigated in the Prins condensation of β-pinene with formaldehyde and compared with the catalytic behavior of conventional aluminosilicate zeolites BEA and FAU and titanosilicate zeolite MFI (TS-1). The activity of the investigated metal-organic frameworks (MOFs) increased with the increasing concentration of accessible Lewis acid sites in the order ZIF-8zeolites BEA and FAU, which showed significantly lower selectivity to the target nopol than the MOFs. Its high activity, the preservation of its structure and active sites, and the possibility to use it in at least three catalytic cycles without loss of activity make MIL-100 (Fe) the best performing catalyst of the series for the Prins condensation of β-pinene and paraformaldehyde. Our report exemplifies the advantages of MOFs over zeolites as solid catalysts in liquid-phase reactions for the production of fine chemicals.

  9. Chromium removal by zeolite-rich materials obtained from an exhausted FCC catalyst: Influence of chromium incorporation on the sorbent structure.

    PubMed

    Gonzalez, Maximiliano R; Pereyra, Andrea M; Torres Sánchez, Rosa M; Basaldella, Elena I

    2013-10-15

    A spent FCC catalyst was converted into a zeolitic mixture, and the product obtained was afterward used as trapping material for Cr(III) species frequently found in aqueous solutions. Eventual changes in the sorbent structure produced by Cr incorporation were studied by different characterization techniques such as point of zero charge determinations (PZC), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), and infrared absorption (FTIR). The XRD and FTIR analyses indicated that chromium incorporation produces an amorphization of the material, and PZC measurements show no surface adsorption of charged chromium species. SEM and EDX analyses clearly show that after chromium sorption, the initial microspheroidal catalyst morphology was maintained, and the presence of chromium species was mainly detected in the outer microsphere surface, where the zeolite crystals were hydrothermally grown.

  10. Production of High Density Aviation Fuels via Novel Zeolite Catalyst Routes

    DTIC Science & Technology

    1989-10-23

    of hydrogen was such that the hydrocarbon feed to the ricictor was in the vapor phase . The catalytic reactor was operated to crack kerosene and diesel... Phase Hydrogenation of Benzene Using Phosphate- Supported Nickel Catalysts ,’ J. Catal., 98, 64-69, 1986 PAPER NUMBER: 233 Wilson, G.R., and Hall, W.K...followed by hydrogenation of the aromatic species. This report summarizes a research program aimed at developing catalyst and processing concepts for

  11. Decomposition of phenol by hybrid gas/liquid electrical discharge reactors with zeolite catalysts.

    PubMed

    Kusić, Hrvoje; Koprivanac, Natalija; Locke, Bruce R

    2005-10-17

    Application of hybrid gas/liquid electrical discharge reactors and a liquid phase direct electrical discharge reactor for degradation of phenol in the presence and absence of zeolites have been investigated. Hybrid gas/liquid electrical discharges involve simultaneous high voltage electrical discharges in water and in the gas phase above the water surface leading to the additional OH radicals in the liquid phase and ozone formation in the gas phase with subsequent dissolution into the liquid. The role of applied zeolites, namely NH4ZSM5, FeZSM5 and HY, were also studied. Phenol degradation and production of primary phenol by-products, catechol and hydroquinone, during the treatment were monitored by HPLC measurements. The highest phenol removal results, 89.4-93.6%, were achieved by electrical discharge in combination with FeZSM5 in all three configurations of corona reactors. These results indicate that the Fenton reaction has significant influence on overall phenol removal efficiency in the electrical discharge/FeZSM5 system due to the additional OH radical formation from hydrogen peroxide generated by the water phase discharge.

  12. Evidence for an initiation of the methanol-to-olefin process by reactive surface methoxy groups on acidic zeolite catalysts.

    PubMed

    Wang, Wei; Buchholz, Andreas; Seiler, Michael; Hunger, Michael

    2003-12-10

    Recent progress reveals that, in the methanol-to-olefin (MTO) process on acidic zeolites, the conversion of an equilibrium mixture of methanol and DME is dominated by a "hydrocarbon pool" mechanism. However, the initial C-C bond formation, that is, the chemistry during the kinetic "induction period" leading to the reactive hydrocarbon pool, still remains unclear. With the application of a stopped-flow protocol, in the present work, pure surface methoxy groups [SiO(CH(3))Al] were prepared on various acidic zeolite catalysts (H-Y, H-ZSM-5, H-SAPO-34) at temperatures lower than 473 K, and the further reaction of these methoxy species was investigated by in situ (13)C MAS NMR spectroscopy. By using toluene and cyclohexane as probe molecules which are possibly involved in the MTO process, we show the high reactivity of surface methoxy species. Most importantly, the formation of hydrocarbons from pure methoxy species alone is demonstrated for the first time. It was found that (i) surface methoxy species react at room temperature with water to methanol, indicating the occurrence of a chemical equilibrium between these species at low temperatures. In the presence of aromatics and alkanes, (ii) the reactivity of surface methoxy groups allows a methylation of these organic compounds at reaction temperatures of ca. 433 and 493 K, respectively. In the absence of water and other organic species, that is, under flow conditions and on partially methylated catalysts, (iii) a conversion of pure methoxy groups alone to hydrocarbons was observed at temperatures of T >/= 523 K. This finding indicates a possible formation of the first hydrocarbons during the kinetic induction period of the MTO process via the conversion of pure surface methoxy species (case iii). After the first hydrocarbons are formed, or in the presence of a small amount of organic impurities, surface methoxy groups contribute to a further methylation of these organic compounds (case ii), leading to the formation of

  13. Rapid synthesis of beta zeolites

    DOEpatents

    Fan, Wei; Chang, Chun -Chih; Dornath, Paul; Wang, Zhuopeng

    2015-08-18

    The invention provides methods for rapidly synthesizing heteroatom containing zeolites including Sn-Beta, Si-Beta, Ti-Beta, Zr-Beta and Fe-Beta. The methods for synthesizing heteroatom zeolites include using well-crystalline zeolite crystals as seeds and using a fluoride-free, caustic medium in a seeded dry-gel conversion method. The Beta zeolite catalysts made by the methods of the invention catalyze both isomerization and dehydration reactions.

  14. A Comparative Study of N2O Formation during the Selective Catalytic Reduction of NOx with NH3 on Zeolite Supported Cu Catalysts

    SciTech Connect

    Chen, Hai-Ying; Wei, Zhehao; Kollar, Marton; Gao, Feng; Wang, Yilin; Szanyi, Janos; Peden, Charles HF

    2015-09-01

    A comparative study was carried out on a small-pore CHA.Cu and a large-pore BEA.Cu zeolite catalyst to understand the lower N2O formation on small-pore zeolite supported Cu catalysts in the selective catalytic reduction (SCR) of NOx with NH3. On both catalysts, the N2O yield increases with an increase in the NO2/NOx ratios of the feed gas, suggesting N2O formation via the decomposition of NH4NO3. Temperature-programmed desorption experiments reveal that NH4NO3 is more stable on CHA.Cu than on BEA.Cu. In situ FTIR spectra following stepwise (NO2 + O2) and (15NO + NH3 + O2) adsorption and reaction, and product distribution analysis using isotope-labelled reactants, unambiguously prove that surface nitrate groups are essential for the formation of NH4NO3. Furthermore, CHA.Cu is shown to be considerably less active than BEA.Cu in catalyzing NO oxidation and the subsequent formation of surface nitrate groups. Both factors, i.e., (1) the higher thermal stability of NH4NO3 on CHA.Cu, and (2) the lower activity for this catalyst to catalyze NO oxidation and the subsequent formation of surface nitrates, likely contribute to the higher SCR selectivity with less N2O formation on this catalyst as compared to BEA.Cu. The latter is determined as the primary reason since surface nitrates are the source that leads to the formation of NH4NO3 on the catalysts.

  15. NO oxidation on Zeolite Supported Cu Catalysts: Formation and Reactivity of Surface Nitrates

    SciTech Connect

    Chen, Hai-Ying; Wei, Zhehao; Kollar, Marton; Gao, Feng; Wang, Yilin; Szanyi, Janos; Peden, Charles HF

    2016-04-18

    The comparative activities of a small-pore Cu-CHA and a large-pore Cu-BEA catalyst for the selective catalytic reduction (SCR) of NOx with NH3, and for the oxidation of NO to NO2 and the subsequent formation of surface nitrates were investigated. Although both catalysts are highly active in SCR reactions, they exhibit very low NO oxidation activity. Furthermore, Cu-CHA is even less active than Cu-BEA in catalyzing NO oxidation but is clearly more active for SCR reactions. Temperature-programed desorption (TPD) experiments following the adsorption of (NO2 + NO + O2) with different NO2:NO ratios reveal that the poor NO oxidation activity of the two catalysts is not due to the formation of stable surface nitrates. On the contrary, NO is found to reduce and decompose the surface nitrates on both catalysts. To monitor the reaction pathways, isotope exchange experiments were conducted by using 15NO to react with 14N-nitrate covered catalyst surfaces. The evolution of FTIR spectra during the isotope exchange process demonstrates that 14N-nitrates are simply displaced with no formation of 15N-nitrates on the Cu-CHA sample, which is clearly different from that observed on the Cu-BEA sample where formation of 15N-nitrates is apparent. The results suggest that the formal oxidation state of N during the NO oxidation on Cu-CHA mainly proceeds from its original +2 to a +3 oxidation state, whereas reaching a higher oxidation state for N, such as +4 or +5, is possible on Cu-BEA. The authors at PNNL gratefully acknowledge the US Department of Energy (DOE), Energy Efficiency and Renewable Energy, Vehicle Technologies Office for the support of this work. The research described in this paper was performed at the Environmental Molecular Sciences Laboratory (EMSL), a national scientific user facility sponsored by the DOE’s Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory (PNNL). PNNL is operated for the US DOE by Battelle.

  16. Transient Spectroscopic Characterization of the Genesis of a Ruthenium Complex Catalyst Supported on Zeolite Y

    SciTech Connect

    Ogino, Isao; Gates, Bruce C.

    2010-01-12

    A mononuclear ruthenium complex anchored to dealuminated zeolite HY, Ru(acac)(C{sub 2}H{sub 4}){sup 2+} (acac = acetylacetonate, C{sub 5}H{sub 7}O{sup 2}{sup -}), was characterized in flow reactors by transient infrared (IR) spectroscopy and Ru K edge X-ray absorption spectroscopy. The combined results show how the supported complex was converted into a form that catalyzes ethene conversion to butene. The formation of these species resulted from the removal of acac ligands from the ruthenium (as shown by IR and extended X-ray absorption fine structure (EXAFS) spectra) and the simultaneous decrease in the symmetry of the ruthenium complex, with the ruthenium remaining mononuclear and its oxidation state remaining essentially unchanged (as shown by EXAFS and X-ray absorption near-edge structure spectra). The removal of anionic acac ligands from the ruthenium was evidently compensated by the bonding of other anionic ligands, such as hydride from H2 in the feed stream, to form species suggested to be Ru(H)(C{sub 2}H{sub 4}){sub 2}{sup +}, which is coordinatively unsaturated and inferred to react with ethene, leading to the observed formation of butene in a catalytic process.

  17. Zeolites: Exploring Molecular Channels

    SciTech Connect

    Arslan, Ilke; Derewinski, Mirek

    2015-05-22

    Synthetic zeolites contain microscopic channels, sort of like a sponge. They have many uses, such as helping laundry detergent lather, absorbing liquid in kitty litter, and as catalysts to produce fuel. Of the hundreds of types of zeolites, only about 15 are used for catalysis. PNNL catalysis scientists Ilke Arslan and Mirek Derewinksi are studying these zeolites to understand what make them special. By exploring the mystery of these microscopic channels, their fundamental findings will help design better catalysts for applications such as biofuel production.

  18. Zeolites: Exploring Molecular Channels

    ScienceCinema

    Arslan, Ilke; Derewinski, Mirek

    2016-07-12

    Synthetic zeolites contain microscopic channels, sort of like a sponge. They have many uses, such as helping laundry detergent lather, absorbing liquid in kitty litter, and as catalysts to produce fuel. Of the hundreds of types of zeolites, only about 15 are used for catalysis. PNNL catalysis scientists Ilke Arslan and Mirek Derewinksi are studying these zeolites to understand what make them special. By exploring the mystery of these microscopic channels, their fundamental findings will help design better catalysts for applications such as biofuel production.

  19. 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.

  20. 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

  1. I. Synthesis, characterization, and base catalysis of novel zeolite supported super-basic materials II. Oxidative dehydrogenation of ethane over reduced heteropolyanion catalysts

    NASA Astrophysics Data System (ADS)

    Galownia, Jonathan M.

    reliable precursor for the formation of zeolite supported super-basic materials. The second part of this thesis describes the oxidative dehydrogenation of ethane over partially reduced heteropolyanions. Niobium and pyridine exchanged salts of phosphomolybdic (NbPMo12Pyr) and phosphovanadomolybdic (NbPMo11VPyr) acids are investigated as catalyst precursors to prepare materials for catalyzing the oxidative dehydrogenation of ethane to ethylene and acetic acid at atmospheric pressure. The effects of feed composition, steam flow, temperature, and precursor composition on catalytic activity and selectivity are presented for both ethane and ethylene oxidation. Production of ethylene and acetic acid from ethane using the catalytic materials exceeds that reported in the literature for Mo-V-Nb-Ox systems under atmospheric or elevated pressure. Production of acetic acid from ethylene is also greater than that observed for Mo-V-Nb-Ox systems. Addition of vanadium reduces catalytic activity and selectivity to both ethylene and acetic acid while niobium is essential for the formation of acetic acid from ethane. Other metals such as antimony, iron, and gallium do not provide the same beneficial effect as niobium. Molybdenum in close proximity to niobium is the active site for ethane activation while niobium is directly involved in the transformation of ethylene to acetic acid. A balance of niobium and protonated pyridine is required to produce an active catalyst. Water is found to aid in desorption of acetic acid, thereby limiting deep oxidation to carbon oxides. A reaction scheme is proposed for the production of acetic acid from ethane over the catalytic materials.

  2. Conversions of lower olefins in the presence of a superhigh-silica zeolite catalyst with added V/sub 2/O/sub 5/

    SciTech Connect

    Minachev, Kh.M.; Kondrat'ev, D.A.; Degachev, A.A.; Borvinskaya, T.B.; Bondarenko, T.N.; Nefedov, B.K.; Alekseeva, T.V.

    1982-02-20

    The addition of V/sub 2/O/sub 5/ is known to increase the selectivity of formation of p-xylene (PX) from 1-octene in the presence of the Na form of superhigh-silica zeolite (SHSZ). The preferential formation of PX from ethylene, propene, and 1-hexene in the presence of SHSZ of the ZSM type with added Sb/sub 2/O/sub 3/, MgO, and B/sub 2/O/sub 3/ has been reported in patents. Continuing our study of the catalytic properties of SHSZ, we have examined the effects of adding V/sub 2/O/sub 5/ on the conversions of C/sub 3/-C/sub 4/ olefins. For purposes of comparison, experiments using ethylene with the original and modified catalysts were carried out, since the reactions of ethylene over catalysts of this type have been thoroughly studied.

  3. Catalytic performance of Metal-Organic-Frameworks vs. extra-large pore zeolite UTL in condensation reactions

    PubMed Central

    Shamzhy, Mariya; Opanasenko, Maksym; Shvets, Oleksiy; Čejka, Jiří

    2013-01-01

    Catalytic behavior of isomorphously substituted B-, Al-, Ga-, and Fe-containing extra-large pore UTL zeolites was investigated in Knoevenagel condensation involving aldehydes, Pechmann condensation of 1-naphthol with ethylacetoacetate, and Prins reaction of β-pinene with formaldehyde and compared with large-pore aluminosilicate zeolite beta and representative Metal-Organic-Frameworks Cu3(BTC)2 and Fe(BTC). The yield of the target product over the investigated catalysts in Knoevenagel condensation increases in the following sequence: (Al)beta < (Al)UTL < (Ga)UTL < (Fe)UTL < Fe(BTC) < (B)UTL < Cu3(BTC)2 being mainly related to the improving selectivity with decreasing strength of active sites of the individual catalysts. The catalytic performance of Fe(BTC), containing the highest concentration of Lewis acid sites of the appropriate strength is superior over large-pore zeolite (Al)beta and B-, Al-, Ga-, Fe-substituted extra-large pore zeolites UTL in Prins reaction of β-pinene with formaldehyde and Pechmann condensation of 1-naphthol with ethylacetoacetate. PMID:24790940

  4. Catalytic performance of Metal-Organic-Frameworks vs. extra-large pore zeolite UTL in condensation reactions.

    PubMed

    Shamzhy, Mariya; Opanasenko, Maksym; Shvets, Oleksiy; Cejka, Jiří

    2013-01-01

    Catalytic behavior of isomorphously substituted B-, Al-, Ga-, and Fe-containing extra-large pore UTL zeolites was investigated in Knoevenagel condensation involving aldehydes, Pechmann condensation of 1-naphthol with ethylacetoacetate, and Prins reaction of β-pinene with formaldehyde and compared with large-pore aluminosilicate zeolite beta and representative Metal-Organic-Frameworks Cu3(BTC)2 and Fe(BTC). The yield of the target product over the investigated catalysts in Knoevenagel condensation increases in the following sequence: (Al)beta < (Al)UTL < (Ga)UTL < (Fe)UTL < Fe(BTC) < (B)UTL < Cu3(BTC)2 being mainly related to the improving selectivity with decreasing strength of active sites of the individual catalysts. The catalytic performance of Fe(BTC), containing the highest concentration of Lewis acid sites of the appropriate strength is superior over large-pore zeolite (Al)beta and B-, Al-, Ga-, Fe-substituted extra-large pore zeolites UTL in Prins reaction of β-pinene with formaldehyde and Pechmann condensation of 1-naphthol with ethylacetoacetate.

  5. SSZ-52, a zeolite with an 18-layer aluminosilicate framework structure related to that of the DeNOx catalyst Cu-SSZ-13.

    PubMed

    Xie, Dan; McCusker, Lynne B; Baerlocher, Christian; Zones, Stacey I; Wan, Wei; Zou, Xiaodong

    2013-07-17

    A new zeolite (SSZ-52, |(C14H28N)6Na6(H2O)18|[Al12Si96O216]), related to the DeNOx catalyst Cu-SSZ-13 (CHA framework type), has been synthesized using an unusual polycyclic quaternary ammonium cation as the structure-directing agent. By combining X-ray powder diffraction (XPD), high-resolution transmission electron microscopy (HRTEM) and molecular modeling techniques, its porous aluminosilicate framework structure (R3m, a = 13.6373(1) Å, c = 44.7311(4) Å), which can be viewed as an 18-layer stacking sequence of hexagonally arranged (Si,Al)6O6 rings (6-rings), has been elucidated. The structure has a three-dimensional 8-ring channel system and is a member of the ABC-6 family of zeolites (those that can be described in terms of 6-ring stacking sequences) like SSZ-13, but it has cavities that are twice as large. The code SFW has been assigned to this new framework type. The large cavities contain pairs of the bulky organic cations. HRTEM and XPD simulations show that stacking faults do occur, but only at the 5-10% level. SSZ-52 has considerable potential as a catalyst in the areas of gas conversion and sequestration.

  6. Structure and nuclearity of active sites in Fe-zeolites: comparison with iron sites in enzymes and homogeneous catalysts.

    PubMed

    Zecchina, Adriano; Rivallan, Mickaël; Berlier, Gloria; Lamberti, Carlo; Ricchiardi, Gabriele

    2007-07-21

    Fe-ZSM-5 and Fe-silicalite zeolites efficiently catalyse several oxidation reactions which find close analogues in the oxidation reactions catalyzed by homogeneous and enzymatic compounds. The iron centres are highly dispersed in the crystalline matrix and on highly diluted samples, mononuclear and dinuclear structures are expected to become predominant. The crystalline and robust character of the MFI framework has allowed to hypothesize that the catalytic sites are located in well defined crystallographic positions. For this reason these catalysts have been considered as the closest and best defined heterogeneous counterparts of heme and non heme iron complexes and of Fenton type Fe(2+) homogeneous counterparts. On this basis, an analogy with the methane monooxygenase has been advanced several times. In this review we have examined the abundant literature on the subject and summarized the most widely accepted views on the structure, nuclearity and catalytic activity of the iron species. By comparing the results obtained with the various characterization techniques, we conclude that Fe-ZSM-5 and Fe-silicalite are not the ideal samples conceived before and that many types of species are present, some active and some other silent from adsorptive and catalytic point of view. The relative concentration of these species changes with thermal treatments, preparation procedures and loading. Only at lowest loadings the catalytically active species become the dominant fraction of the iron species. On the basis of the spectroscopic titration of the active sites by using NO as a probe, we conclude that the active species on very diluted samples are isolated and highly coordinatively unsaturated Fe(2+) grafted to the crystalline matrix. Indication of the constant presence of a smaller fraction of Fe(2+) presumably located on small clusters is also obtained. The nitrosyl species formed upon dosing NO from the gas phase on activated Fe-ZSM-5 and Fe-silicalite, have been analyzed

  7. Zeolite membrane application in hydrocarbon processing

    SciTech Connect

    Suzuki, H.

    1988-06-01

    Zeolites are of great importance in hydrocarbon processing either as adsorbents or catalysts. This paper presents a research since 1973 about the transformation of zeolite into membrane zeolite, that dramatically contributes to the free world of peace and prosperity. Commercial and organic membranes are of two categories: anisotropic membrane, e.g. cellulose acetate, and composite membrane, e.g. plasma {und in}-{und situ} polymerization on polysulfone support. Zeolite membrane belongs to the latter category, zeolite {und in}-{und situ} hydrothermalization on porous glass. Basically zeolite membrane is consisted of three groups: (1) eight-oxygen ring window, zeolite A, (2) ten-oxygen ring window, Pentasil, and (3) twelve-oxygen ring window, Faujasite. The technology of zeolite membrane synthesis and subsequent treatment is almost transferred from the one applied to powder zeolites. Zeolite membrane is expected to play a major role in the field of hydrocarbon processing, that is, PSA, Distillation/Extraction, and Catalytic Reactions.

  8. Zeolite framework stabilized copper complex inspired by the 2-His-1-carboxylate facial triad motif yielding oxidation catalysts.

    PubMed

    Kervinen, Kaisa; Bruijnincx, Pieter C A; Beale, Andrew M; Mesu, J Gerbrand; van Koten, Gerard; Klein Gebbink, Robertus J M; Weckhuysen, Bert M

    2006-03-15

    The stabilization of a mononuclear copper(II) complex with one MIm2Pr ligand [MIm2Pr = 3,3-bis(1-methylimidazol-2-yl)propionate] in the supercages of zeolite Y was attempted, and the resulting materials were tested for their activity in oxidation catalysis. The preparation procedure yielded initially two species (labeled 1 and 2) within the pore system of the zeolite material, which differ in molecular structure and chemical composition as determined by UV/vis, ESR, IR, and XAFS spectroscopy. In species 1, the copper was found to be five-coordinated, with one MIm2Pr ligand in a facial-type NNO coordination toward copper, the other two coordination sites being occupied by oxygen atoms from either the zeolite framework and/or a water molecule. The total charge of this complex is 1+. In species 2, the copper is surrounded by two MIm2Pr ligands, both in a facial-type coordination mode, identical to the homogeneous Cu(MIm2Pr)2 complex. This neutral species 2 is easily washed out of the zeolite, whereas the mononuclear species 1 remains inside the zeolite material upon washing. The spectroscopic characteristics and activity for 3,5-di-tert-butylcatechol and benzyl alcohol oxidation of species 1 compared closely with that of the zeolite-immobilized Cu(histidine) complexes but differed from that of the homogeneous Cu(MIm2Pr)2 complex. It was therefore found that encapsulation in zeolite offers a route to stabilize a 5-fold-coordinated copper complex with novel catalytic properties. This 1:1 Cu(MIm2Pr) complex is not formed in solution.

  9. Chemical Imaging of Catalyst Deactivation during the Conversion of Renewables at the Single Particle Level: The Etherification of Biomass-based Polyols with Alkenes over H-Beta Zeolites

    SciTech Connect

    A Parvulescu; D Mores; E Stavitski; C Teodorescu; P Bruijnicx; R Klein Gebbing; B Weckhuysen

    2011-12-31

    The etherification of biomass-based alcohols with various linear {alpha}-olefins under solvent-free conditions was followed in a space- and time-resolved manner on 9 {micro}m large H-Beta zeolite crystals by confocal fluorescence microscopy. This allowed us to visualize the interaction with the substrate and distribution of the coke products into the catalyst at the level of an individual zeolite crystal during the etherification process. The spectroscopic information obtained on the micrometer-scale zeolite was in line with the results obtained with bulk characterization techniques and further confirmed by the catalytic results obtained both for micrometer-scale and nanoscale zeolites. This allowed us to explain the influence of the substrate type (glycerol, glycols, and alkenes) and zeolite properties (Si/Al ratio and particle size) on the etherification activity. The etherification of the biomass-based alcohols takes place mainly on the external surface of the zeolite particles. The gradual blockage of the external surface of the zeolite results in a partial or total loss of etherification activity. The deactivation could be attributed to olefin oligomerization. The high conversions obtained in the etherification of 1,2-propylene glycol with long linear alkenes (up to 80%) and the pronounced deactivation of the zeolite observed in the etherification of glycerol with long linear alkenes (max. 20% conversion) were explained by the spectroscopic measurements and is due to differences in the adsorption, i.e., in the center of the zeolite particle for glycerol and on the external surface in the case of glycols.

  10. Transition metal sulfide loaded catalyst

    DOEpatents

    Maroni, V.A.; Iton, L.E.; Pasterczyk, J.W.; Winterer, M.; Krause, T.R.

    1994-04-26

    A zeolite-based catalyst is described for activation and conversion of methane. A zeolite support includes a transition metal (Mo, Cr or W) sulfide disposed within the micropores of the zeolite. The catalyst allows activation and conversion of methane to C[sub 2]+ hydrocarbons in a reducing atmosphere, thereby avoiding formation of oxides of carbon.

  11. Transition metal sulfide loaded catalyst

    DOEpatents

    Maroni, Victor A.; Iton, Lennox E.; Pasterczyk, James W.; Winterer, Markus; Krause, Theodore R.

    1994-01-01

    A zeolite based catalyst for activation and conversion of methane. A zeolite support includes a transition metal (Mo, Cr or W) sulfide disposed within the micropores of the zeolite. The catalyst allows activation and conversion of methane to C.sub.2 + hydrocarbons in a reducing atmosphere, thereby avoiding formation of oxides of carbon.

  12. Zeolites US market to reach $1 billion by 2000

    SciTech Connect

    Morris, G.D.L.

    1997-02-05

    This article describes the growth of the U.S. market for zeolites, specifically sodium aluminosilicate. The largest application for zeolites is for petrochemical and petroleum catalysts; however, detergents are also a specific application addressed in the article.

  13. Selective synthesis and characterization of single-site HY zeolite-supported rhodium complexes and their use as catalysts for ethylene hydrogenation and dimerization

    NASA Astrophysics Data System (ADS)

    Khivantsev, Konstantin

    Single-site Rh(CO)2, Rh(C2H4)2 and Rh(NO)2 complexes anchored on various dealuminated HY zeolites can be used as precursors for the selective surface mediated synthesis of well-defined site-isolated Rh(CO)(H)x complexes. DFT calculations and D 2 isotope exchange experiments provide strong evidence for the formation of a family of site isolated mononuclear rhodium carbonyl hydride complexes (including the first examples of RhH complexes with undissociated H2 ligands): Rh(CO)(H2), Rh(CO)(H)2, and Rh(CO)(H). The fraction of each individual complex formed varies significantly with the Si/Al ratio of the zeolite and the nature of the precursor used. HY zeolite-supported mononuclear Rh(CO)2 complexes are very active in ethylene hydrogenation and ethylene dimerization under ambient conditions. There is strong evidence for the cooperation mechanism between mononuclear rhodium complexes and Bronsted acid sites of the zeolite support in C-C bond formation process, as well as ethane formation. Finally, it is shown that the dimerization pathway selectivity can be progressively tuned (and completely switched off) by modifying the number of Bronsted acid sites on the zeolite surface. HY zeolite-supported mononuclear Rh(NO)2 complexes can be selectively formed upon exposure of Rh(CO)2/HY to the gas phase NO/He. They are structurally similar to Rh(CO)2/HY with Rh(I) retaining square planar geometry and nitrosyl ligands adopting a linear configuration. Rh(NO)2/HY30 is active in ethylene hydrogenation and ethylene dimerization under ambient conditions. This is the first unprecedented example of a supported transition-metal nitrosyl complex capable of performing a catalytic reaction. Moreover, this is the first example of a site-isolated Rh complex with ligands other than ethylene or carbonyl, which can catalyze both ethylene hydrogenation and dimerization. Unlike its dicarbonyl counterpart, dinitrosyl rhodium complex has a uniquely different reactivity towards ethylene and hydrogen

  14. Flexibility of zeolite frameworks

    NASA Astrophysics Data System (ADS)

    Kapko, Vitaliy; Treacy, Michael; Thorpe, Michael

    2009-03-01

    Zeolites are an important class of industrial catalysts because of their large internal surfaces and molecular-sieving properties. Recent geometric simulations (1) show that almost all of the known zeolites can exist without distortion of their tetrahedra within some range of densities, which we call the flexibility window. Within this window, the framework accommodates density changes by rotations about the shared tetrahedral corners. We argue that the presence of a flexibility window can be used as a topological criterion to select potential candidates for synthesis from millions of hypothetical structures. We also investigate the exceptions to the rule, as well as the shape of the flexibility window and the symmetric properties of zeolites inside it. (1) A. Sartbaeva, S.A. Wells, M.M.J. Treacy and M.F. Thorpe The flexibility window in zeolites, Nature Materials 5, 962-965 (2006); I. Rivin, commentary 931-932.

  15. The effect of supercritical isobutane regeneration on the nature of hydrocarbons deposited on a USY zeolite catalyst utilized for isobutane/butene alkylation

    SciTech Connect

    Daniel M. Ginosar; Lucia M. Petkovic

    2004-11-01

    The chemical nature of hydrocarbons remaining on an ultrastable Y-zeolite (USY) utilized for liquid phase isobutane/butene alkylation reaction at 333 K and 1.1x107 Pa before and after supercritical isobutane regeneration (SFR) at 453 K and 1.1x107 Pa are presented. Catalyst samples were deactivated to different levels by running the alkylation reaction for different times on stream (TOS) and regenerated under flowing supercritical isobutane for 60 min. Nitrogen physisorption, temperature-programmed oxidation (TPO), diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), and ultraviolet-visible (UV-Vis) spectroscopy measurements suggested that the SFR process was effective in recovering catalyst surface area and micropore volume and that most coke precursors were removed from samples regenerated after short TOS, when the level of activity for trimethylpentanes (TMP) production was high. Samples that were allowed to react for longer TOS contained unsaturated hydrocarbons that, instead of being extracted by the supercritical fluid, dehydrogenated during the SFR process to produce more condensed species.

  16. Nanocrystalline Zeolite Y: Synthesis and Characterization

    NASA Astrophysics Data System (ADS)

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

    2011-02-01

    Nanocrystalline zeolite has received significant attention in the catalysis community. Zeolites with a crystal size smaller than 100 nm are the potential replacement for existing zeolite catalysts due to its unique features with added advantages. Zeolite FAU type Y is one of the most studied framework of all zeolites, and has been used as catalysts for number of reactions in the refinery and petrochemical industry. The present paper covers the synthesis of nanocrystalline zeolite Y under hydrothermal conditions from clear synthesis mixtures. The crystal size of zeolite Y is influenced by temperature, aging time, alkalinity, and water content. The synthesized Y is characterized by X-ray diffraction (XRD), Fourier Transmission Infrared Sprectroscopy (FTIR), Transmission Electron Microscope (TEM), Scanning Electron Microscope (SEM) and Nitrogen Adsorption.

  17. Molecular models of site-isolated cobalt, rhodium, and iridium catalysts supported on zeolites: Ligand bond dissociation energies

    DOE PAGES

    Chen, Mingyang; Serna, Pedro; Lu, Jing; ...

    2015-09-28

    The chemistry of zeolite-supported site-isolated cobalt, rhodium, and iridium complexes that are essentially molecular was investigated with density functional theory (DFT) and the results compared with experimentally determined spectra characterizing rhodium and iridium species formed by the reactions of Rh(C2H4)2(acac) and Ir(C2H4)2(acac) (acac = acetylacetonate) with acidic zeolites such as dealuminated HY zeolite. The experimental results characterize ligand exchange reactions and catalytic reactions of adsorbed ligands, including olefin hydrogenation and dimerization. Two molecular models were used to characterize various binding sites of the metal complexes in the zeolites, and the agreement between experimental and calculated infrared frequencies and metal-ligand distancesmore » determined by extended X-ray absorption fine structure spectroscopy was generally very good. The calculated structures and energies indicate a metal-support-oxygen (M(I)-O) coordination number of two for most of the supported complexes and a value of three when the ligands include the radicals C2H5 or H. The results characterizing various isomers of the supported metal complexes incorporating hydrocarbon ligands indicate that some carbene and carbyne ligands could form. Ligand bond dissociation energies (LDEs) are reported to explain the observed reactivity trends. The experimental observations of a stronger M-CO bond than M-(C2H4) bond for both Ir and Rh match the calculated LDEs, which show that the single-ligand LDEs of the mono and dual-ligand complexes for CO are similar to 12 and similar to 15 kcal/mol higher in energy (when the metal is Rh) and similar to 17 and similar to 20 kcal/mol higher (when the metal is Ir) than the single-ligand LDEs of the mono and dual ligand complexes for C2H4, respectively. The results provide a foundation for the prediction of the catalytic properties of numerous supported metal complexes, as summarized in detail here.« less

  18. Molecular models of site-isolated cobalt, rhodium, and iridium catalysts supported on zeolites: Ligand bond dissociation energies

    SciTech Connect

    Chen, Mingyang; Serna, Pedro; Lu, Jing; Gates, Bruce C.; Dixon, David A.

    2015-09-28

    The chemistry of zeolite-supported site-isolated cobalt, rhodium, and iridium complexes that are essentially molecular was investigated with density functional theory (DFT) and the results compared with experimentally determined spectra characterizing rhodium and iridium species formed by the reactions of Rh(C2H4)2(acac) and Ir(C2H4)2(acac) (acac = acetylacetonate) with acidic zeolites such as dealuminated HY zeolite. The experimental results characterize ligand exchange reactions and catalytic reactions of adsorbed ligands, including olefin hydrogenation and dimerization. Two molecular models were used to characterize various binding sites of the metal complexes in the zeolites, and the agreement between experimental and calculated infrared frequencies and metal-ligand distances determined by extended X-ray absorption fine structure spectroscopy was generally very good. The calculated structures and energies indicate a metal-support-oxygen (M(I)-O) coordination number of two for most of the supported complexes and a value of three when the ligands include the radicals C2H5 or H. The results characterizing various isomers of the supported metal complexes incorporating hydrocarbon ligands indicate that some carbene and carbyne ligands could form. Ligand bond dissociation energies (LDEs) are reported to explain the observed reactivity trends. The experimental observations of a stronger M-CO bond than M-(C2H4) bond for both Ir and Rh match the calculated LDEs, which show that the single-ligand LDEs of the mono and dual-ligand complexes for CO are similar to 12 and similar to 15 kcal/mol higher in energy (when the metal is Rh) and similar to 17 and similar to 20 kcal/mol higher (when the metal is Ir) than the single-ligand LDEs of the mono and dual ligand complexes for C2H4, respectively. The results provide a foundation for the prediction

  19. The effect of soot on ammonium nitrate species and NO2 selective catalytic reduction over Cu-zeolite catalyst-coated particulate filter.

    PubMed

    Mihai, Oana; Tamm, Stefanie; Stenfeldt, Marie; Olsson, Louise

    2016-02-28

    interacting with the ammonium nitrate species on the CuxOy or other copper species on the surface of the zeolite particles, which reduces the ammonium nitrate blocking of the catalyst and thereby results in higher NO2 SCR activity.

  20. Preparation of USY zeolite VOx supported catalysts from V(AcAc)3 and NH4VO3. Catalytic properties for the dehydrogenation of n-butane in oxygen-free atmosphere.

    PubMed

    Garcia, Elba M; Sanchez, Miguel D; Tonetto, Gabriela; Volpe, María A

    2005-12-01

    The preparation of different samples of vanadia supported on ultrastable zeolite (VO(x)/USY) is discussed. The samples were prepared in order to obtain highly dispersed V-species, avoiding the formation of crystalline vanadia and the destruction of the zeolite framework. Two methods were employed for preparing VO(x)/USY samples: an organic route using V(AcAc)3 and an inorganic route using NH4VO3. The characterization of the samples was performed with XRD, TPR, NH3-TPD, and N2 isotherms. From these results it is concluded that when VO(x) is supported on the surface of USY from acidic aqueous solution of ammonium metavanadate, the destruction of the zeolite framework is accomplished. For higher pH values in the impregnating solution, undesired V2O5 is formed on the USY surface. On the other hand, VO(x)/USY prepared from the organic precursor shows no destruction of the USY structure. In addition, highly dispersed VO(x) are formed, though for relatively high V loadings (6%) an obstruction of the zeolite windows takes place. The samples are tested as catalysts for gas phase dehydrogenation of n-butane to olefins. The catalysts prepared from NH4VO3 are almost inactive for the reaction. On the other hand, both samples prepared from V(AcAc)3 present initial conversion levels in the 8-12% range. However, the selectivity depends on the V loading, the catalysts with 6% loading being the most selective (75%). The catalytic patterns of the samples (activity and selectivity) are in agreement with the physicochemical features of the VO(x)/USY surface.

  1. Synthesis and testing of nanosized zeolite Y

    NASA Astrophysics Data System (ADS)

    Karami, Davood

    This work focuses on the synthesis and testing of nanosized zeolite Y. The synthesis formulations of faujasite-type structure of zeolite Y prepared in nanosized form are described. The synthetic zeolite Y is the most widely employed for the preparation of fluid catalytic cracking (FCC) catalysts. The synthesis of zeolite Y is very complicated process. The mean particle size of zeolite Y is 1800 nm. The major challenge of this work involved reducing this average particle size to less than 500 nm. The preliminary experiments were conducted to obtain the pure zeolite Y using the soluble silicates as a silica source. This was achieved by applying the experimental design approach to study the effects of many parameters. The ageing time turned out to be the most significant variable affecting product purity. Based on the preliminary results, a detailed investigation was carried out to determine the effects of silica-alumina precursor preparations on zeolite Y synthesis. Aluminosilicate precursors were prepared by gelling and precipitation of soluble silicate. The as-prepared precursors were used for the hydrothermal synthesis of zeolite Y. The procedure of the precipitation of soluble silicate yielded pure zeolite Y at the conventional synthesis conditions. The extent of purity of zeolite Y depends on the surface areas of aluminosilicate precursors. A novel approach to zeolite Y synthesis was employed for the preparation of the pure nanosized zeolite Y. This was achieved by applying the method of impregnation of precipitated silica. This novel method of impregnation for zeolite Y preparation allows eliminating the vigorous agitation step required for the preparation of a homogeneous silica solution, thereby simplifying the synthesis of zeolite Y in one single vessel. In case of the synthesis of nanosized zeolite Y, the effect of varying the organic templates on the formation of nanosized particles of zeolite Y was investigated, while all other reaction parameters were

  2. NO{sub X} REDUCTION BEHAVIOR OF ALUMINA AND ZEOLITE CATALYSTS IN COMBINATION WITH NON-THERMAL PLASMA

    SciTech Connect

    Panov, A.G.

    2000-08-20

    Lean burn gasoline and diesel engines provide improved fuel economy when compared to engines operating under stoichiometric fuel/air conditions. At the same time, lean burn and diesel engines present a problem for emission control. Because they operate under oxidizing conditions, the conventional three-way catalyst is not effective in NOx reduction [1,2]. In addition, the wide temperature range of automobile exhaust gases present a challenge for catalyst design. The temperature of exhaust gases from a light duty diesel engine can vary from 150 to 500 C, depending on the operating conditions. To date, a catalyst that operates with high NOx conversion efficiency over the entire operating range has not been found. Non-thermal plasma assisted catalysis has been shown to be a promising technology for NOx reduction in lean burn and diesel exhaust gases [3,4]. The approach exploited in this paper is to use a plasma in combination with several catalysts, each of which are active over unique temperature ranges. It was reported in the literature, that the one of the essential roles of plasma treatment is to oxidize NO to easier reducible NO2 [7]. In this contribution, the other important function of plasma treatment, namely partial oxidation of propylene, will be demonstrated.

  3. Reforming catalysts

    SciTech Connect

    Givens, E.N.; Plank, C.J.; Rosinski, E.J.

    1980-03-04

    Crystalline aluminosilicate zeolites are mixed with conventional reforming catalysts to produce new catalytic compositions with high catalytic activity and selectivity and excellent aging characteristics. These new catalytic compositions may be utilized alone or in conjunction with conventional reforming catalysts. The acidic activity of the total catalyst system is controlled within defined limits. When so controlled the utility of these catalyst systems in reforming hydrocarbon mixtures is to reduce the C1 and C2 concentrations in reformer gas product, while increasing the C3 and C4 concentrations and maintaining high liquid yield at high octane numbers.

  4. Cracking vegetable oil from Callophylluminnophyllum L. seeds to bio-gasoline by Ni-Mo/Al2O3 and Ni-Mo/Zeolite as micro-porous catalysts

    NASA Astrophysics Data System (ADS)

    Savitri, Effendi, R.; Tursiloadi, S.

    2016-02-01

    Natural minerals such as zeolite are local natural resources in the various regions in Indonesia. Studies on the application of natural mineral currently carried out by national research institutions, among others, as a filler, bleaching agent, or dehydration agent. However, not many studies that utilize these natural minerals as green catalysts material which has high performance for biomass conversion processes and ready to be applied directly by the bio-fuel industry. The trend movement of green and sustainable chemistry research that designing environmentally friendly chemical processes from renewable raw materials to produce innovative products derived biomass for bio-fuel. Callophylluminnophyllum L. seeds can be used as raw material for bio-energy because of its high oil content. Fatty acid and triglyceride compounds from this oil can be cracked into bio-gasoline, which does not contain oxygen in the hydrocarbon structure. Bio-gasoline commonly is referred to as drop-in biofuel because it can be directly used as a substitute fuel. This paper focused on the preparation and formulation of the catalyst NiMo/H-Zeolite and Ni-Mo/Al2O3 which were used in hydro-cracking process of oil from Callophylluminnophyllum L. seeds to produce bio-gasoline. The catalysts were analyzed using XRD, BET and IR-adsorbed pyridine method. The results of hydro-cracking products mostly were paraffin (C10-C19) straight chain, with 59.5 % peak area based on GC-MS analysis.

  5. Zeolitic catalytic conversion of alochols to hydrocarbons

    DOEpatents

    Narula, Chaitanya K.; Davison, Brian H.; Keller, Martin

    2017-01-03

    A method for converting an alcohol to a hydrocarbon, the method comprising contacting said alcohol with a metal-loaded zeolite catalyst at a temperature of at least 100.degree. C. and up to 550.degree. C., wherein said alcohol can be produced by a fermentation process, said metal is a positively-charged metal ion, and said metal-loaded zeolite catalyst is catalytically active for converting said alcohol to said hydrocarbon.

  6. Fluoride-assisted synthesis of bimodal microporous SSZ-13 zeolite.

    PubMed

    Zhu, Xiaochun; Kosinov, Nikolay; Hofmann, Jan P; Mezari, Brahim; Qian, Qingyun; Rohling, Roderigh; Weckhuysen, Bert M; Ruiz-Martínez, Javier; Hensen, Emiel J M

    2016-02-21

    The presence of small amount of fluoride in alkaline hydrothermal synthesis of SSZ-13 zeolite yields bimodal microporous particles with substantially improved performance in the methanol-to-olefins (MTO) reaction. Hydrocarbon uptake measurements and fluorescence microspectroscopy of spent catalysts demonstrate enhanced diffusion through micropores at the grain boundaries of nanocrystals running through the zeolite particles. Fluoride-assisted SSZ-13 synthesis is a cheap and scalable approach to optimize the performance of MTO zeolite catalysts.

  7. Towards a full understanding of the nature of Ni(II) species and hydroxyl groups over highly siliceous HZSM-5 zeolite supported nickel catalysts prepared by a deposition-precipitation method.

    PubMed

    Chen, Bao-Hui; Chao, Zi-Sheng; He, Hao; Huang, Chen; Liu, Ya-Juan; Yi, Wen-Jun; Wei, Xue-Ling; An, Jun-Fang

    2016-02-14

    Highly siliceous HZSM-5 zeolite supported nickel catalysts prepared by a deposition-precipitation (D-P) method were characterized by Fourier transform infrared (FT-IR), hydrogen temperature programmed reduction (H2-TPR), X-ray diffraction (XRD), N2-absorption/desorption, field emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS), and (27)Al magic-angle nuclear magnetic resonance (MAS NMR) techniques. The results showed that the D-P of nickel species occurred predominantly on the internal surface of highly siliceous HZSM-5 zeolite, in which the internal silanol groups located on the hydroxylated mesopores or nanocavities played a key role. During the D-P process, nickel hydroxide was first deposited-precipitated via olation/polymerization of neutral hydroxoaqua nickel species over the HZSM-5 zeolite. With the progress of the D-P process, 1 : 1 nickel phyllosilicate was formed over the HZSM-5 via the hetero-condensation/polymerization between charged hydroxoaqua nickel species and monomer silicic species generated due to the partial dissolution of the HZSM-5 framework. The 1 : 1 nickel phyllosilicate could also be generated via the hydrolytic adsorption of hydroxoaqua nickel species and their subsequent olation condensation. After calcination, the deposited-precipitated nickel hydroxide was decomposed into nickel oxide, while the 1 : 1 nickel phyllosilicate was transformed into 2 : 1 nickel phyllosilicate. According to the above mechanism, Ni(ii) species were present both in the form of nickel oxide and 2 : 1 nickel phyllosilicate, which were mutually separated from each other, being highly dispersed over HZSM-5 zeolite.

  8. Nanostructured Basic Catalysts: Opportunities for Renewable Fuels

    SciTech Connect

    Conner, William C; Huber, George; Auerbach, Scott

    2009-06-30

    This research studied and developed novel basic catalysts for production of renewable chemicals and fuels from biomass. We focused on the development of unique porous structural-base catalysts zeolites. These catalysts were compared to conventional solid base materials for aldol condensation, that were being commercialized for production of fuels from biomass and would be pivotal in future biomass conversion to fuels and chemicals. Specifically, we had studied the aldolpyrolysis over zeolites and the trans-esterification of vegetable oil with methanol over mixed oxide catalysts. Our research has indicated that the base strength of framework nitrogen in nitrogen substituted zeolites (NH-zeolites) is nearly twice as strong as in standard zeolites. Nitrogen substituted catalysts have been synthesized from several zeolites (including FAU, MFI, BEA, and LTL) using NH3 treatment.

  9. Functionalization of zeolitic cavities: grafting NH2 groups in framework T sites of B-SSZ-13--a way to obtain basic solids catalysts?

    PubMed

    Regli, Laura; Bordiga, Silvia; Busco, Claudia; Prestipino, Carmelo; Ugliengo, Piero; Zecchina, Adriano; Lamberti, Carlo

    2007-10-10

    Insertion of B atoms into an Al-free zeolitic framework with CHA topology results in the formation of B-SSZ-13 zeotype with Si/B = 11. B K-edge NEXAFS testifies that B forms [B(OSi)4] units in a Td-like geometry (sp3-hybridized B atoms). According to B K-edge NEXAFS and IR, template burning results in the formation of [B(OSi)3] units in a D3h-like geometry (sp2-hybridized B atoms) with a break of a B-O-Si bond and the formation of a Si-OH group. The activated material contains B(III) Lewis acid centers able to specifically coordinate bases like NH3. Such [B(OSi)3] units are reactive toward ammonia, resulting in the formation of B-NH2 surface functionality inside the pores of B-SSZ-13 already under mild conditions, i.e., 35 mbar of NH3 at 373 K for 30 min and without crystallinity degradation. A minor fraction of Si-NH2 cannot be excluded owing to the presence of two IR doublets at 3500 and 3430 cm-1 and at 1600 and 1550 cm-1. Ab initio B3LYP/6-31+G(d,p) calculations on a cluster model, supported by a single-point MP2 on B3LYP/6-31+G(D,P) optimized structures, found the break by NH3 of a B-O-Si bond of the [B(OSi)3] unit with formation of [SiOH] and [H2N-B(OSi)2] species to be energetically favored. Comparison between experimental and computed frequency shifts shows them to be in semiquantitative agreement. The high stability of the B-NH2 surface functionality is probed by N K-edge NEXAFS spectra collected under UHV conditions. These findings can open a new route in the preparation of shape selective solid basic catalysts.

  10. The catalytic and photocatalytic oxidation of organic substances using heterogeneous Fenton-type catalysts.

    PubMed

    Kuznetsova, E V; Savinov, E N; Vostrikova, L A; Echevskii, G V

    2004-01-01

    This paper deals with catalytic and photocatalytic oxidation of organic substances using H202 over heterogeneous Fenton-type catalysts. In the study a series of Fe-containing catalysts was experienced. A zeolite named as FeZSM-5 was selected as the most active heterogeneous Fenton-type catalyst. The FeZSM-5 reported was prepared by hydrothermal crystallization in the presence of iron salt. In contrast to the homogeneous Fenton system the catalyst prepared had minimal, if any, leaching of iron ions, was stable during 30 catalytic runs and didn't lose its activity in the presence of complexing agents, e.g. P2O7(4-). The catalyst was active in oxidation of organic substances at pH from 1.5 to 8, maximum activity was observed at pH = 3. The FeZSM-5 effectively oxidized a simulant of the warfare agent, diethylnitrophenil phosphate, which is hardly detoxified by other methods. It appeared that the rate of oxidation of formic acid, ethanol and benzene over FeZSM-5 increased under the action of visible light (lambda > 436 nm), quantum efficiency being 0.06-0.14.

  11. Experiments with Zeolites at the Secondary School Level: Experience from The Netherlands

    NASA Astrophysics Data System (ADS)

    Coker, Eric N.; Davis, Pamela J.; Kerkstra, Aonne; van Bekkum, Herman

    1999-10-01

    This article describes a number of experiments that involve zeolites and are suitable for secondary-school chemistry laboratories. The experiments have been introduced successfully into secondary schools in The Netherlands. Zeolites are used in enormous quantities as builders (water softeners) in laundry detergents; they account for 15-30 wt % of most laundry detergents currently on the European market. In a series of experiments, students test the hardness of tap water before and after treatment with some zeolite and perform tests with a range of commercial laundry detergents containing zeolites. Zeolites are also used as catalysts in numerous industrial processes; another experiment described here highlights the use of zeolites as recyclable catalysts in an esterification reaction. A duplicate reaction is carried out in parallel, but using the conventional sulfuric acid catalyst instead of the zeolite. This experiment provides a good example of the benefit of a recyclable, heterogeneous catalyst over the conventional homogeneous one that is discarded as waste material.

  12. Conversion of Ethanol to Hydrocarbons on Hierarchical HZSM-5 Zeolites

    SciTech Connect

    Ramasamy, Karthikeyan K.; Zhang, He; Sun, Junming; Wang, Yong

    2014-02-22

    This study reports synthesis, characterization, and catalytic activity of the nano-size hierarchical HZSM-5 zeolite with high mesoporosity produced via a solvent evaporation procedure. Further, this study compares hierarchical zeolites with conventional HZSM-5 zeolite with similar Si/Al ratios for the ethanol-to-hydrocarbon conversion process. The catalytic performance of the hierarchical and conventional zeolites was evaluated using a fixed-bed reactor at 360 °C, 300 psig, and a weight hourly space velocity of 7.9 h-1. For the low Si/Al ratio zeolite (~40), the catalytic life-time for the hierarchical HZSM-5 was approximately 2 times greater than the conventional HZSM-5 despite its coking amount deposited 1.6 times higher than conventional HZSM-5. For the high Si/Al ratio zeolite (~140), the catalytic life-time for the hierarchical zeolite was approximately 5 times greater than the conventional zeolite and the amount of coking deposited was 2.1 times higher. Correlation was observed between catalyst life time, porosity, and the crystal size of the zeolite. The nano-size hierarchical HZSM-5 zeolites containing mesoporosity demonstrated improved catalyst life-time compared to the conventional catalyst due to faster removal of products, shorter diffusion path length, and the migration of the coke deposits to the external surface from the pore structure.

  13. Zeolite-Based Organic Synthesis (ZeoBOS) of Acortatarin A: First Total Synthesis Based on Native and Metal-Doped Zeolite-Catalyzed Steps.

    PubMed

    Wimmer, Eric; Borghèse, Sophie; Blanc, Aurélien; Bénéteau, Valérie; Pale, Patrick

    2017-01-31

    Similarly to polymer-supported assisted synthesis (PSAS), organic synthesis could be envisaged being performed by using zeolites, native or metal-doped, as heterogeneous catalysts. To illustrate this unprecedented Zeolite-Based Organic Synthesis (ZeoBOS), the total synthesis of acortatarin A was achieved through a novel strategy and using five out of eleven synthetic steps catalyzed by H- or metal-doped zeolites as catalysts. Notably, the formation of an yne-pyrrole intermediate with a copper-doped zeolite and the spiroketalization of an alkyne diol with a silver-doped zeolite have been developed as key steps of the synthesis.

  14. [What a physician should know about zeolites].

    PubMed

    Boranić, M

    2000-01-01

    Zeolites are natural and synthetic hydrated crystalline aluminosilicates endowed with absorptive and ion exchange properties. They have found numerous and multifarous applications--in industry as catalysts and absorbents, in water sanitation for the removal of ammonia and heavy metals, in agriculture as fertilizers, and in animal husbandry as the absorbents of excreted material and as food additives. Medical applications have included the use in filtration systems for anesthesia or dialysis and as the contrast materials in NMR imaging. Recently, zeolite powders for external use have found application as deodorants, antimycotic agents and wound dressings. Peroral use of encapsulated zeolite powders enriched with vitamins, oligoelements or other ingredients has been claimed to exert beneficial medical effects. Ingestion of zeolites may be considered analogous to the clay eating (geophagia), considered in traditional medicine as a remedy for various illnesses. Being amphoteric, zeolites are partly soluble in acid or alkaline media, but within the physiological pH range the solubility is generally low. Minimal amounts of free aluminium or silicium from the ingested zeolites are resorbed from the gut. The bulk of ingested zeolite probably remains undissolved in the gut. In view of the ion exchange properties, zeolites may be expected to change the ionic content, pH and buffering capacity of the gastrointestinal secretions and to affect the transport through the intestinal epithelium. In addition, zeolites could affect the bacterial flora and the resorption of bacterial products, vitamins and oligoelements. The contact of zeolite particles with gastrointestinal mucosa may elicit the secretion of cytokines with local and systemic actions. Reactive silicium ions might react with biomolecules of the intestinal epithelium, and if resorbed, do so in other cells. Mutagenic and carcinogenic effects of zeolite particles have been described, resembling such effects of asbestos

  15. Cracking catalyst

    SciTech Connect

    Otterstedt, J. E. A.; Jaras, S. G.; Pudas, R.; Upson, L. L.

    1985-05-07

    A cracking catalyst having good resistance to metal poisoning has at least two particle fractions of different particle sizes, the cracking catalyzing zeolite material being concentrated to the coarser particle size fractions, and the finer particle size fractions being formed from material having relatively lower or no or insignificant cracking catalyzing activity. The particles of the finer particle size fractions have a matrix of kaolin and amorphous alumina--silica and may contain for example, an SO /SUB x/ eliminating additive such as Al/sub 2/O/sub 3/, CaO and/or MgO. The coarser particle size fractions having cracking catalyzing effect have a mean particle size of from 80 to 125 ..mu..m and the finer particle size fractions a mean particle size of from 30 to 75 ..mu..m. The coarser particle size fractions have a zeolite content of at least 20 weight % and may have a zeolite content of up to 100 weight %, the remainder consisting essentially of material which has relatively lower or no or insignificant cracking-catalyzing activity and which consists of kaolin and amorphous alumina-silica. The catalyst mass as a whole may have a zeolite content of up to 50 weight %.

  16. Zeolitic materials with hierarchical porous structures.

    PubMed

    Lopez-Orozco, Sofia; Inayat, Amer; Schwab, Andreas; Selvam, Thangaraj; Schwieger, Wilhelm

    2011-06-17

    During the past several years, different kinds of hierarchical structured zeolitic materials have been synthesized due to their highly attractive properties, such as superior mass/heat transfer characteristics, lower restriction of the diffusion of reactants in the mesopores, and low pressure drop. Our contribution provides general information regarding types and preparation methods of hierarchical zeolitic materials and their relative advantages and disadvantages. Thereafter, recent advances in the preparation and characterization of hierarchical zeolitic structures within the crystallites by post-synthetic treatment methods, such as dealumination or desilication; and structured devices by in situ and ex situ zeolite coatings on open-cellular ceramic foams as (non-reactive as well as reactive) supports are highlighted. Specific advantages of using hierarchical zeolitic catalysts/structures in selected catalytic reactions, such as benzene to phenol (BTOP) and methanol to olefins (MTO) are presented.

  17. Catalytic Oxidation by Transition Metal Ions in Zeolites.

    DTIC Science & Technology

    1984-09-28

    nmber) Zeolite, Oxidation Catalysis, Molybdenum Zeolite, Cobalt Zeolite, Oxygen Adduct, Cobalt-Oxygen Complexes, Epoxidation _j-J AVIATRACr .1kisa...and substrate ligands. Molybdenum-Y seolites were effective catalysts for the epoxidation of propylene using tert-butyl hydroperoxide as the source...of oxygen. They exhibited high selectivity to the epoxide , and initially were quite active. The activity, *I 0 OF, , , , , ,, , , UNCLASSIFIED -4 1 0 1

  18. Properties of Zeolite A Obtained from Powdered Laundry Detergent: An Undergraduate Experiment.

    ERIC Educational Resources Information Center

    Smoot, Alison L.; Lindquist, David A.

    1997-01-01

    Presents experiments that introduce students to the myriad properties of zeolites using the sodium form of zeolite A (Na-A) from laundry detergent. Experiments include extracting Na-A from detergent, water softening properties, desiccant properties, ion-exchange properties, and Zeolite HA as a dehydration catalyst. (JRH)

  19. Removal of ethylene from air stream by adsorption and plasma-catalytic oxidation using silver-based bimetallic catalysts supported on zeolite.

    PubMed

    Trinh, Quang Hung; Lee, Sang Baek; Mok, Young Sun

    2015-03-21

    Dynamic adsorption of ethylene on 13X zeolite-supported Ag and Ag-M(x)O(y) (M: Co, Cu, Mn, and Fe), and plasma-catalytic oxidation of the adsorbed ethylene were investigated. The experimental results showed that the incorporation of Ag into zeolite afforded a marked enhancement in the adsorptivity for ethylene. The addition of transition metal oxides was found to have a positive influence on the ethylene adsorption, except Fe(x)O(y). The presence of the additional metal oxides, however, appeared to somewhat interrupt the diffusion of ozone into the zeolite micro-pores, leading to a decrease in the plasma-catalytic oxidation efficiency of the ethylene adsorbed there. Among the second additional metal oxides, Fe(x)O(y) was able to reduce the emission of ozone during the plasma-catalytic oxidation stage while keeping a high effectiveness for the oxidative removal of the adsorbed ethylene. The periodical treatment consisting of adsorption followed by plasma-catalytic oxidation may be a promising energy-efficient ethylene abatement method.

  20. Zeolites Remove Sulfur From Fuels

    NASA Technical Reports Server (NTRS)

    Voecks, Gerald E.; Sharma, Pramod K.

    1991-01-01

    Zeolites remove substantial amounts of sulfur compounds from diesel fuel under relatively mild conditions - atmospheric pressure below 300 degrees C. Extracts up to 60 percent of sulfur content of high-sulfur fuel. Applicable to petroleum refineries, natural-gas processors, electric powerplants, and chemical-processing plants. Method simpler and uses considerably lower pressure than current industrial method, hydro-desulfurization. Yields cleaner emissions from combustion of petroleum fuels, and protects catalysts from poisoning by sulfur.

  1. Enhanced Activity of Nanocrystalline Beta Zeolite for Acylation of Veratrole with Acetic Anhydride.

    PubMed

    Aisha Mahmood Abdulkareem, Al-Turkustani; Selvin, Rosilda

    2016-04-01

    Friedel-Craft acylation of veratrole using homogeneous acid catalysts such as AlCl3, FeCl3, ZnCl2, and HF etc. produces acetoveratrone, (3',4'-dimethoxyacetophenone), which is the intermediate for synthesis of papavarine alkaloids. The problems associated with these homogeneous catalysts can be overcome by using heterogeneous solid catalysts. Since acetoveratrone is a larger molecule, large pore Beta zeolites with smaller particle sizes are beneficial for the liquid-phase acylation of veratrole, for easy diffusion of reactants and products. The present study aims in the acylation of veratrole with acetic anhydride using nanocrystalline Beta Zeolite catalyst. A systematic investigation of the effects of various reaction parameters was done. The catalysts were characterized for their structural features by using XRD, TEM and DLS analyses. The catalytic activity of nanocrystalline Beta zeolite was compared with commercial Beta zeolite for the acylation and was found that nanocrystalline Beta zeolite possessed superior activity.

  2. Synthesis and characterization of Sn/zeolite and catalytic activity test in the esterification reaction of sludge oil

    NASA Astrophysics Data System (ADS)

    Alimuddin, Andi Hairil; Usman, Thamrin; Wahyuni, Nelly; Rudiyansyah, Prawatya, Yopa Eka; Astar, Ismail; Yustira, Yudi

    2017-03-01

    Synthesis of Sn-Zeolite has been made to use for esterification reaction of free fatty acids in sludge oil. Catalyst characterization was accomplished using X-Ray Diffraction (XRD), X-Ray Flourecence (XRF), and Fourier Transform Infra Red (FTIR). Catalyst Sn/zeolite was synthesized by impregnated Sn of SnCl2 into the zeolite. The amount of Sn impregnated base on the value of cation exchange capacity (CEC) of zeolites. Esterification reaction of fatty acids from sludge oil using Sn/Zeolite catalyst was did by variated the reaction time. XRD analysis results showed that the catalyst Sn/zeolite was dominated by modernit and quartz. XRF analysis results was increasing amount of Sn metal and the Si/Al ratio on Sn/zeolite catalyst along with addition of Sn metal. FTIR analysis results showed that the catalyst synthesized had Bronsted acid side (the spectrum 1639.4; 1656.7; 1654.8 cm-1) and the Lewis acid (spectrum 1400.2 and 1402.2 cm-1). The results showed that the optimum conditions of esterification reaction in 4 hours reaction time, 5% concentration of the catalyst, and molar ratio was about 1:10 with a conversion percentage of products reached 96.00%, which can be achieved with a ratio was about 4:1 between Sn and zeolite on Sn/zeolite catalyst.

  3. Zeolite catalysis in conversion of cellulosics. Annual report

    SciTech Connect

    Tsao, G.T.

    1994-02-01

    The authors have studied the kinetics of oxylose/xylulose isomerization in significant detail over a variety of zeolites and obtained the pseudo-first order reaction rate constants. The authors have found that HY zeolite is still the best material and zeolites are more selective than homogeneous acid catalysts where decomposition of the sugar compounds is much faster. They have completed, as described in the Year 2 Work Plan, the study of cellobiose hydrolysis with an ion exchange resin. The kinetics of the solid-catalyzed reaction is qualitatively similar to that for catalysis by homogeneous acids. The planned program of NMR studies has revealed the dynamics of sugar molecules within the zeolite cavities. Two chemisorbed and a physisorbed state have been identified in HY zeolite. A new state, accounting for as much as a half of the sugar, has been found in ZSM-5 zeolite.

  4. Atomic sites and stability of Cs+ captured within zeolitic nanocavities

    NASA Astrophysics Data System (ADS)

    Yoshida, Kaname; Toyoura, Kazuaki; Matsunaga, Katsuyuki; Nakahira, Atsushi; Kurata, Hiroki; Ikuhara, Yumi H.; Sasaki, Yukichi

    2013-08-01

    Zeolites have potential application as ion-exchangers, catalysts and molecular sieves. Zeolites are once again drawing attention in Japan as stable adsorbents and solidification materials of fission products, such as 137Cs+ from damaged nuclear-power plants. Although there is a long history of scientific studies on the crystal structures and ion-exchange properties of zeolites for practical application, there are still open questions, at the atomic-level, on the physical and chemical origins of selective ion-exchange abilities of different cations and detailed atomic structures of exchanged cations inside the nanoscale cavities of zeolites. Here, the precise locations of Cs+ ions captured within A-type zeolite were analyzed using high-resolution electron microscopy. Together with theoretical calculations, the stable positions of absorbed Cs+ ions in the nanocavities are identified, and the bonding environment within the zeolitic framework is revealed to be a key factor that influences the locations of absorbed cations.

  5. "Ab initio" synthesis of zeolites for preestablished catalytic reactions.

    PubMed

    Gallego, Eva María; Portilla, M Teresa; Paris, Cecilia; León-Escamilla, Alejandro; Boronat, Mercedes; Moliner, Manuel; Corma, Avelino

    2017-03-10

    Unlike homogeneous catalysts that are often designed for particular reactions, zeolites are heterogeneous catalysts that are explored and optimized in a heuristic fashion. We present a methodology for synthesizing active and selective zeolites by using organic structure-directing agents that mimic the transition state (TS) of preestablished reactions to be catalyzed. In these zeolites, the pores and cavities could be generated approaching a molecular-recognition pattern. For disproportionation of toluene and isomerization of ethylbenzene into xylenes, the TSs are larger than the reaction products. Zeolite ITQ-27 showed high disproportionation activity, and ITQ-64 showed high selectivity for the desired para and ortho isomers. For the case of a product and TS of similar size, we synthesized a catalyst, MIT-1, for the isomerization of endo-dicyclopentane into adamantane.

  6. [Zeolite catalysis in conversion of cellulosics

    SciTech Connect

    Tsao, G.T.

    1992-12-31

    To transform biomass into fermentable substrate for yeast, we are using zeolites instead of enzymes to catalyze the two bottleneck reactions in biomass conversion, xylose isomerization and ceuobiose hydrolysis. The experimental results on these reactions carried out over various zeolites and other catalysts are presented herein. The advantages and disadvantages of using these catalysts over enzymes are also discussed. Heterogeneous solid catalysts other than zeolites has been employed for cellobiose-to-glucose hydrolysis. The size and shape selectivity that makes zeoutes unique for some reactions can add diffusional hindrance. We have spent some time screening various known solid acidic catalysts. We report that a class of cationic ion exchange resins in the acidified form (e.g. Amberlite) has worked well as an acidic catalyst in hydrolyzing cellobiose to glucose. Our experimental results, together with those obtained from a homogeneous acid catalyst (e.g. sulfuric acid) for comparison are provided. Having succeeded in finding an alternative solid acid catalyst for hydrolysis, we explored other solid resin or other homogeneous but non-enzyme catalyst to carry out the xylose-to-xylulose isomerization. A fairly extensive search has been made. We explored the use of sodium aluminates in the homogeneous phase isomerization of glucose to fructose and obtained a very high conversion of glucose to fructose with the final mixture containing 85% of fructose instead of the common 45%. Fructose apparently complexes with aluminates, and its equilibrium concentration is shifted to considerably higher values than permitted by simple glucose/fructose equilibrium. We have recently found a number of catalysts capable of promoting isomerization between aldoses and ketoses. One solid resin, known as polyvinyl pyridine (PVP), is able to convert xylose to xylulose at a pH below 7. Our usage of alternative isomerization catalysts, including PVP, are described.

  7. [Zeolite catalysis in conversion of cellulosics

    SciTech Connect

    Tsao, G.T.

    1992-01-01

    To transform biomass into fermentable substrate for yeast, we are using zeolites instead of enzymes to catalyze the two bottleneck reactions in biomass conversion, xylose isomerization and ceuobiose hydrolysis. The experimental results on these reactions carried out over various zeolites and other catalysts are presented herein. The advantages and disadvantages of using these catalysts over enzymes are also discussed. Heterogeneous solid catalysts other than zeolites has been employed for cellobiose-to-glucose hydrolysis. The size and shape selectivity that makes zeoutes unique for some reactions can add diffusional hindrance. We have spent some time screening various known solid acidic catalysts. We report that a class of cationic ion exchange resins in the acidified form (e.g. Amberlite) has worked well as an acidic catalyst in hydrolyzing cellobiose to glucose. Our experimental results, together with those obtained from a homogeneous acid catalyst (e.g. sulfuric acid) for comparison are provided. Having succeeded in finding an alternative solid acid catalyst for hydrolysis, we explored other solid resin or other homogeneous but non-enzyme catalyst to carry out the xylose-to-xylulose isomerization. A fairly extensive search has been made. We explored the use of sodium aluminates in the homogeneous phase isomerization of glucose to fructose and obtained a very high conversion of glucose to fructose with the final mixture containing 85% of fructose instead of the common 45%. Fructose apparently complexes with aluminates, and its equilibrium concentration is shifted to considerably higher values than permitted by simple glucose/fructose equilibrium. We have recently found a number of catalysts capable of promoting isomerization between aldoses and ketoses. One solid resin, known as polyvinyl pyridine (PVP), is able to convert xylose to xylulose at a pH below 7. Our usage of alternative isomerization catalysts, including PVP, are described.

  8. Analysis of the adsorption state and desorption kinetics of NO(2) over Fe-zeolite catalyst by FT-IR and temperature-programmed desorption.

    PubMed

    Iwasaki, Masaoki; Shinjoh, Hirofumi

    2010-03-14

    States of NO(2) adsorption and kinetics of NO(2) desorption over a Fe-loaded ZSM-5 type zeolite were investigated using Fourier transform infrared (FT-IR) spectroscopy and temperature-programmed desorption (TPD). The FT-IR spectra in NO(2)/N(2) flows showed that several adsorption species (NO(2), nitrite, nitrate, and NO(+)) existed; except for NO(2), these were considered to be formed via NO(2) dimerization and disproportionation reactions. The TPD spectra showed two distinct peaks, a low-temperature (LT) peak that can be assigned to weakly adsorbed NO(x) in the zeolite channel and a high-temperature (HT) peak that can be assigned to chemisorbed NO(x) bonded to ion-exchanged Fe sites. By varying flow rates and heating rates in TPD measurements, the peak maximum temperatures in the both peaks were found to be constant with the former, but shifted to higher temperatures with the latter; this suggests that desorption is not controlled by an adsorption/desorption equilibrium, i.e., in the no-readsorption limit. Furthermore, it was found that desorption at both LT and HT peaks proceeds at second order; this implies that the reverse reaction of NO(2) dimerization and disproportionation and/or some sort of lateral interaction between NO(2) molecules might be occurring. The desorption energies and the pre-exponential factors were estimated to be 67 +/- 1 kJ mol(-1) and 10(5.5+/-0.2) s(-1) for the LT peak and 138 +/- 4 kJ mol(-1) and 10(9.8+/-0.3) s(-1) for the HT peak. These values show that interaction strengths between adsorbed NO(x) and Fe sites are relatively large.

  9. Experimental research of pulsed discharge plasma and TiO2/Zeolite coupling technology for formaldehyde removal

    NASA Astrophysics Data System (ADS)

    Dong, Bingyan; Lan, Shuirong

    2013-03-01

    The pulsed discharge plasma combining with catalyst to remove formaldehyde is a novel type of advanced oxidation technology. In the present work, taking wire-tube pulsed discharge plasma and TiO2/Zeolite coupling technology for formaldehyde removal. The studies have investigated the wire-tube reactor with zeolite, TiO2, TiO2/Zeolite for formaldehyde removal respectively. Results show that in the optimal experimental conditions and the baking time is 120 min, the baking temperature is 450 °C, that TiO2/Zeolite catalyst which made by sol-gel shows higher photocatalytic activity and efficiency. The pulsed discharge with TiO2/Zeolite catalyst for formaldehyde removal has higher removal efficiency than pulsed discharge with zeolite or TiO2. Therefore, pulsed discharge plasma with TiO2/Zeolite for the removal of formaldehyde can greatly increase the removal efficiency.

  10. Olefins from methanol by modified zeolites

    SciTech Connect

    Inui, T.; Takegami, Y.

    1982-11-01

    Compares the effects of modified catalysts (ZSM-34 and ZSM-5 class zeolites) on methanol conversion to olefins (MTO) with regard to olefin selectivity and cost. Presents tables with prices of olefins in the US and Japan; comparison of methanol-cracking with naphtha cracking; methanol conversion data for Type-1, Type-II and reference catalysts; hydrocarbon distribution from MTO processes; and speculative economics for MTO processes of Concept-1 and 2. Diagrams the proposed MTO process scheme. Scanning electron micrographs of the zeolite catalysts are shown. Graphs indicate the change of ethylene prices in the US since 1978 and forecast ethylene prices in several countries. Concludes that the prices of ethylene for both MTO processes examined compare favorably with products of conventional processes.

  11. Hydrophobic Fe-zeolites for removal of MTBE from water by combination of adsorption and oxidation.

    PubMed

    Gonzalez-Olmos, Rafael; Kopinke, Frank-Dieter; Mackenzie, Katrin; Georgi, Anett

    2013-03-05

    Several zeolites were evaluated as adsorbents for the removal of MTBE from water in a screening process. It was observed that the SiO2/Al2O3 molar ratio is a decisive factor for the adsorption properties, at least in the case of ZSM5 zeolites. ZSM5 zeolites with SiO2/Al2O3 ratios >200 were found to provide the best sorption properties for MTBE. To design a combined sorption/reaction method, regeneration of the loaded zeolites by selected advanced oxidation processes (AOP) was studied: (1) Fenton treatment using H2O2 with dissolved iron salts and (2) heterogeneous Fenton-like oxidation with Fe immobilized on the zeolites. The first was ineffective in regenerating loaded zeolites. However, heterogeneous catalysis using Fe species immobilized on the zeolite by liquid ion exchange was markedly more effective. Although these hydrophobic zeolites have a low ion exchange capacity, resulting in iron loadings of ≤ 0.09 wt %, it was possible to obtain sufficiently active catalysts. Hydrophobic Fe-zeolites can therefore be regarded as promising materials for the removal of MTBE from water, since they allow the combination of efficient adsorption and oxidative degradation of MTBE by H2O2. In contrast to the homogeneous catalysis by dissolved iron ions, these heterogeneous catalysts work at near-neutral pH and can be easily reused. Fe-zeolites as adsorbents/catalysts showed a good stability in both batch and column experiments.

  12. Development of GREET Catalyst Module

    SciTech Connect

    Wang, Zhichao; Benavides, Pahola T.; Dunn, Jennifer B.; Cronauer, Donald C.

    2015-09-01

    In this report, we develop energy and material flows for the production of five different catalysts (tar reforming, alcohol synthesis, Zeolite Socony Mobil-5 [ZSM-5], Mo/Co/ γ-Al2O3, and Pt/ γ-Al2O3) and two chemicals (olivine, dimethyl ether of polyethylene glycol [DEPG]). These compounds and catalysts are now included in the Greenhouse Gases, Regulated Emissions and Energy Use in Transportation (GREET™) catalyst module.

  13. Catalysts and process for liquid hydrocarbon fuel production

    DOEpatents

    White, Mark G; Liu, Shetian

    2014-12-09

    The present invention provides a novel process and system in which a mixture of carbon monoxide and hydrogen synthesis gas, or syngas, is converted into hydrocarbon mixtures composed of high quality gasoline components, aromatic compounds, and lower molecular weight gaseous olefins in one reactor or step. The invention utilizes a novel molybdenum-zeolite catalyst in high pressure hydrogen for conversion, as well as a novel rhenium-zeolite catalyst in place of the molybdenum-zeolite catalyst, and provides for use of the novel catalysts in the process and system of the invention.

  14. Synthesis and catalytic applications of combined zeolitic/mesoporous materials

    PubMed Central

    Vernimmen, Jarian; Cool, Pegie

    2011-01-01

    Summary In the last decade, research concerning nanoporous siliceous materials has been focused on mesoporous materials with intrinsic zeolitic features. These materials are thought to be superior, because they are able to combine (i) the enhanced diffusion and accessibility for larger molecules and viscous fluids typical of mesoporous materials with (ii) the remarkable stability, catalytic activity and selectivity of zeolites. This review gives an overview of the state of the art concerning combined zeolitic/mesoporous materials. Focus is put on the synthesis and the applications of the combined zeolitic/mesoporous materials. The different synthesis approaches and formation mechanisms leading to these materials are comprehensively discussed and compared. Moreover, Ti-containing nanoporous materials as redox catalysts are discussed to illustrate a potential implementation of combined zeolitic/mesoporous materials. PMID:22259762

  15. Synthesis strategies in the search for hierarchical zeolites.

    PubMed

    Serrano, D P; Escola, J M; Pizarro, P

    2013-05-07

    formation of organic-inorganic composites that, upon calcination, are transformed into hierarchical zeolites. However, in spite of this impressive progress in novel strategies for the preparation of hierarchical zeolites, significant challenges are still ahead. The overall one is the development of methods that are versatile in terms of zeolite structures and compositions, capable of tuning the secondary porosity properties, and being scaled up in a cost-effective way. Recent works have demonstrated that it is possible to scale-up easily the synthesis of hierarchical zeolites by desilication. Economic aspects may become a significant bottleneck for the commercial application of hierarchical zeolites since most of the synthesis strategies so far developed imply the use of more expensive procedures and reagents compared to conventional zeolites. Nevertheless, the use of hierarchical zeolites as efficient catalysts for the production of high value-added compounds could greatly compensate these increased manufacturing costs.

  16. Synthesis and characterization of nitrogen substituted zeolites

    NASA Astrophysics Data System (ADS)

    Dogan, Fulya

    The interest in basic solid materials, particularly for basic zeolites has considerably increased in the last two decades because of their potential use in catalysis and separation. Basic zeolites have most often been obtained by ion-exchange or impregnation with alkali metal cations or grafting of organic bases onto zeolite pore walls. Such materials often suffer from instability and/or pore blockage, because none of these approaches places basic sites directly into the zeolite framework. Recently zeolitic materials have been made with some of the bridging oxygen atoms in Si--O--Si and/or Si--O--Al linkages replaced by NH groups, i.e. by substitution of framework oxygen by nitrogen. As a result, the basic strength of the framework increases due to the lower electronegativity of nitrogen with respect to oxygen. In this study, solid base catalysts are obtained by nitrogen substitution of the faujasite type of zeolites under ammonia flow at high temperatures. The efficiency of the reaction is tested by using zeolites with different aluminum contents and extraframework cations and varying the reaction conditions such as ammonia flow rate, reaction temperature and duration. The characterization studies show that high levels of nitrogen substitution can be achieved while maintaining porosity, particularly for NaY and low-aluminum HY zeolites, without a significant loss in the crystallinity. 27Al and 29 Si MAS NMR experiments performed on the nitrogen substituted zeolites show dealumination of the framework and preferential substitution for Si--OH--Al sites at the early stages of the reaction (temperatures at 750--800 °C). No preference is seen for reactions performed at higher temperatures and longer reaction times (e.g., 850 °C and 48 h). X-ray PDF analysis performed on the modified zeolites show that the Si-N distance in the 1st shell is longer than Si-O bond distance and Si-Si/Al bond distance of the Si-O/N-Si/Al linkage decreases, as an indication of a decrease in

  17. Towards a sustainable manufacture of hierarchical zeolites.

    PubMed

    Verboekend, Danny; Pérez-Ramírez, Javier

    2014-03-01

    Hierarchical zeolites have been established as a superior type of aluminosilicate catalysts compared to their conventional (purely microporous) counterparts. An impressive array of bottom-up and top-down approaches has been developed during the last decade to design and subsequently exploit these exciting materials catalytically. However, the sustainability of the developed synthetic methods has rarely been addressed. This paper highlights important criteria to ensure the ecological and economic viability of the manufacture of hierarchical zeolites. Moreover, by using base leaching as a promising case study, we verify a variety of approaches to increase reactor productivity, recycle waste streams, prevent the combustion of organic compounds, and minimize separation efforts. By reducing their synthetic footprint, hierarchical zeolites are positioned as an integral part of sustainable chemistry.

  18. Distribution of metal and adsorbed guest species in zeolites

    SciTech Connect

    Chmelka, B.F.

    1989-12-01

    Because of their high internal surface areas and molecular-size cavity dimensions, zeolites are used widely as catalysts, shape- selective supports, or adsorbents in a variety of important chemical processes. For metal-catalyzed reactions, active metal species must be dispersed to sites within the zeolite pores that are accessible to diffusing reactant molecules. The distribution of the metal, together with transport and adsorption of reactant molecules in zeolite powders, are crucial to ultimate catalyst performance. The nature of the metal or adsorbed guest distribution is known, however, to be dramatically dependent upon preparatory conditions. Our objective is to understand, at the molecular level, how preparatory treatments influence the distribution of guest species in zeolites, in order that macroscopic adsorption and reaction properties of these materials may be better understood. The sensitivity of xenon to its adsorption environment makes {sup 129}Xe NMR spectroscopy an important diagnostic probe of metal clustering and adsorbate distribution processes in zeolites. The utility of {sup 129}Xe NMR depends on the mobility of the xenon atoms within the zeolite-guest system, together with the length scale of the sample heterogeneity being studied. In large pore zeolites containing dispersed guest species, such as Pt--NaY, {sup 129}Xe NMR is insensitive to fine structural details at room temperature.

  19. Lithium modified zeolite synthesis for conversion of biodiesel-derived glycerol to polyglycerol

    SciTech Connect

    Ayoub, Muhammad; Abdullah, Ahmad Zuhairi; Inayat, Abrar

    2014-10-24

    Basic zeolite has received significant attention in the catalysis community. These zeolites modified with alkaline are the potential replacement for existing zeolite catalysts due to its unique features with added advantages. The present paper covers the preparation of lithium modified zeolite Y (Li-ZeY) and its activity for solvent free conversion of biodiesel-derived glycerol to polyglycerol via etherification process. The modified zeolite was well characterized by X-ray diffraction (XRD), Scanning Electron Microscope (SEM) and Nitrogen Adsorption. The SEM images showed that there was no change in morphology of modified zeolite structure after lithium modification. XRD patterns showed that the structure of zeolite was sustained after lithium modification. The surface properties of parent and modified zeolite was also observed N{sub 2} adsortion-desorption technique and found some changes in surface area and pore size. In addition, the basic strength of prepared materials was measured by Hammet indicators and found that basic strength of Li-ZeY was highly improved. This modified zeolite was found highly thermal stable and active heterogamous basic catalyst for conversion of solvent free glycerol to polyglycerol. This reaction was conducted at different temperatures and 260 °C was found most active temperature for this process for reaction time from 6 to 12 h over this basic catalyst in the absence of solvent.

  20. Production of hydroxyl radicals from Fe-containing fine particles in Guangzhou, China

    NASA Astrophysics Data System (ADS)

    Ma, Shexia; Ren, Ke; Liu, Xiaowen; Chen, Laiguo; Li, Mei; Li, Xiaoying; Yang, Jian; Huang, Bo; Zheng, Mei; Xu, Zhencheng

    2015-12-01

    Reactive oxygen species (ROS) production from ambient fine particles has been correlated with the soluble transition metal content of PM2.5, which also has clear association with particle-mediated cardiopulmonary toxicity. Hydroxyl radical (rad OH) is the most harmful ROS species through chemical reactions of redox-active particle components. Atmospheric Fe, as the dominant species of the transition metals in the atmosphere, is associated with rad OH generation in ambient particle extracts. Our results revealed that Fe-containing particles (18,730 in total number) contributed approximately 3.7% on average to all detected particles throughout the summer and winter sampling period in Guangzhou, which was clustered into four distinct particle classes, including Fe-rich, Metal-rich, NaK-rich and Dust-rich. Fe-rich class was the dominant one with a fraction of 61%, followed by Dust-rich (14%), Metal-rich (13%). and NaK-rich (12%). The iron oxide was enriched in the Fe-rich class. rad OH generation induced by Fe-containing fine particles collected in Guangzhou (GZ) was quantified in a surrogate lung fluid (SLF), and it was found that Fe-containing fine particles were generally much reactive in generating rad OH in the presence of four antioxidants (200 μM ascorbate, 300 μM citrate, 100 μM reduced L-glutathione, and 100 μM uric acid). The annual average rad OH amount produced in our samples was 132.98 ± 27.43 nmol rad OH mg-1 PM2.5. rad OH production had a clear seasonal pattern with higher amount in summer and lower in winter. By measuring the amount of total and SLF-soluble metal in our PM2.5 samples using ICP-MS, we found that ROS activities were associated with the ionizable Fe through Fenton type reactions in the Guangzhou PM2.5. Expected burdens of PM2.5 derived rad OH in human lung lining fluid suggests that typical daily particulate matter exposure in Guangzhou is already a concern, and it could produce much higher levels of rad OH, leading to higher

  1. Controlling chemistry with cations: photochemistry within zeolites.

    PubMed

    Ramamurthy, V; Shailaja, J; Kaanumalle, Lakshmi S; Sunoj, R B; Chandrasekhar, J

    2003-08-21

    The alkali ions present in the supercages of zeolites X and Y interact with included guest molecules through quadrupolar (cation-pi), and dipolar (cation-carbonyl) interactions. The presence of such interactions can be inferred through solid-state NMR spectra of the guest molecules. Alkali ions, as illustrated in this article, can be exploited to control the photochemical and photophysical behaviors of the guest molecules. For example, molecules that rarely phosphoresce can be induced to do so within heavy cation-exchanged zeolites. The nature (electronic configuration) of the lowest triplet state of carbonyl compounds can be altered with the help of light alkali metal ions. This state switch (n pi*-pi pi*) helps to bring out reactivity that normally remains dormant. Selectivity obtained during the singlet oxygen oxidation of olefins within zeolites illustrates the remarkable control that can be exerted on photoreactions with the help of a confined medium that also has active sites. The reaction cavities of zeolites, like enzymes, are not only well-defined and confined, but also have active sites that closely guide the reactant molecule from start to finish. The examples provided here illustrate that zeolites are far more useful than simple shape-selective catalysts.

  2. Hierarchical zeolites from class F coal fly ash

    NASA Astrophysics Data System (ADS)

    Chitta, Pallavi

    Fly ash, a coal combustion byproduct is classified as types class C and class F. Class C fly ash is traditionally recycled for concrete applications and Class F fly ash often disposed in landfills. Class F poses an environmental hazard due to disposal and leaching of heavy metals into ground water and is important to be recycled in order to mitigate the environmental challenges. A major recycling option is to reuse the fly ash as a low-cost raw material for the production of crystalline zeolites, which serve as catalysts, detergents and adsorbents in the chemical industry. Most of the prior literature of fly ash conversion to zeolites does not focus on creating high zeolite surface area zeolites specifically with hierarchical pore structure, which are very important properties in developing a heterogeneous catalyst for catalysis applications. This research work aids in the development of an economical process for the synthesis of high surface area hierarchical zeolites from class F coal fly ash. In this work, synthesis of zeolites from fly ash using classic hydrothermal treatment approach and fusion pretreatment approach were examined. The fusion pretreatment method led to higher extent of dissolution of silica from quartz and mullite phases, which in turn led to higher surface area and pore size of the zeolite. A qualitative kinetic model developed here attributes the difference in silica content to Si/Al ratio of the beginning fraction of fly ash. At near ambient crystallization temperatures and longer crystallization times, the zeolite formed is a hierarchical faujasite with high surface area of at least 360 m2/g. This work enables the large scale recycling of class F coal fly ash to produce zeolites and mitigate environmental concerns. Design of experiments was used to predict surface area and pore sizes of zeolites - thus obviating the need for intense experimentation. The hierarchical zeolite catalyst supports tested for CO2 conversion, yielded hydrocarbons

  3. Click chemistry in CuI-zeolites: the Huisgen [3 + 2]-cycloaddition.

    PubMed

    Chassaing, Stefan; Kumarraja, Mayilvasagam; Souna Sido, Abdelkarim Sani; Pale, Patrick; Sommer, Jean

    2007-03-01

    [reaction: see text] CuI-exchanged solids based on zeolite materials were investigated for the first time as catalysts in organic synthesis. The catalytic potential of these materials was evaluated in the Huisgen [3 + 2]-cycloaddition. Five CuI-exchanged zeolites were examined and CuI-USY proved to be a novel and efficient heterogeneous ligand-free catalyst for this "click chemistry"-type transformation.

  4. Zeolite membranes from kaolin

    SciTech Connect

    Karle, B.G.; Brinker, C.J. |; Phillips, M.L.F.

    1996-07-01

    Zeolite films are sought as components of molecular sieve membranes. Different routes used to prepare zeolite composite membranes include growing zeolite layers from gels on porous supports, depositing oriented zeolites on supports, and dispersing zeolites in polymeric membranes. In most cases, it is very difficult to control and avoid the formation of cracks and/or pinholes. The approach to membrane synthesis is based on hydrothermally converting films of layered aluminosilicates into zeolite films. The authors have demonstrated this concept by preparing zeolite A membranes on alumina supports from kaolin films. The authors have optimized the process parameters not only for desired bulk properties, but also for preparing thin (ca. 5 {micro}m), continuous zeolite A films. Scanning electron microscopy shows highly intergrown zeolite A crystals over most of the surface area of the membrane, but gas permeation experiments indicate existence of mesoporous defects and/or intercrystalline gaps. It has been demonstrated that the thickness of the final zeolite A membrane can be controlled by limiting the amount of precursor kaolin present in the membrane.

  5. The Influence of Zeolites on Radical Formation During Lignin Pyrolysis.

    PubMed

    Bährle, Christian; Custodis, Victoria; Jeschke, Gunnar; van Bokhoven, Jeroen A; Vogel, Frédéric

    2016-09-08

    Lignin from lignocellulosic biomass is a promising source of energy, fuels, and chemicals. The conversion of the polymeric lignin to fuels and chemicals can be achieved by catalytic and noncatalytic pyrolysis. The influence of nonporous silica and zeolite catalysts, such as silicalite, HZSM5, and HUSY, on the radical and volatile product formation during lignin pyrolysis was studied by in situ high-temperature electron paramagnetic resonance spectroscopy (HTEPR) as well as GC-MS. Higher radical concentrations were observed in the samples containing zeolite compared to the sample containing only lignin, which suggests that there is a stabilizing effect by the inorganic surfaces on the formed radical fragments. This effect was observed for nonporous silica as well as for HUSY, HZSM5, and silicalite zeolite catalysts. However, the effect is far larger for the zeolites owing to their higher specific surface area. The zeolites also showed an effect on the volatile product yield and the product distribution within the volatile phase. Although silicalite showed no effect on the product selectivity, the acidic zeolites such as HZSM5 or HUSY increased the formation of deoxygenated products such as benzene, toluene, xylene (BTX), and naphthalene.

  6. Catalytic test reactions for the evaluation of hierarchical zeolites.

    PubMed

    Hartmann, Martin; Machoke, Albert Gonche; Schwieger, Wilhelm

    2016-06-13

    Hierarchical zeolites have received increasing attention in the last decade due to their outstanding catalytic performance. Several types of hierarchical zeolites can be prepared by a large number of different techniques. Hierarchical zeolites combine the intrinsic catalytic properties of conventional zeolites and the facilitated access and transport in the additional meso- or macropore system. In this tutorial review, we discuss several test reactions that have been explored to show the benefit of the hierarchical pore system with respect to their suitability to prove the positive effects of hierarchical porous zeolites. It is important to note that positive effects on activity, stability and less frequently selectivity observed for hierarchically structured catalysts not necessarily are only a consequence of the additional meso- or macropores but also the number, strength and location of active sites as well as defects and impurities. With regard to these aspects, the test reaction has to be chosen carefully and potential changes in the chemistry of the catalyst have to be considered as well. In addition to the determination of conversion, yield and selectivity, we will show that the calculation of the activation energy and the determination of the Thiele modulus and the effectiveness factor are good indicators of the presence or absence of diffusion limitations in hierarchical zeolites compared to their parent materials.

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

    PubMed Central

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

    2010-01-01

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

  8. Molecular simulations and experimental studies of zeolites

    NASA Astrophysics Data System (ADS)

    Moloy, Eric C.

    Zeolites are microporous aluminosilicate tetrahedral framework materials that have symmetric cages and channels with open-diameters between 0.2 and 2.0 nm. Zeolites are used extensively in the petrochemical industries for both their microporosity and their catalytic properties. The role of water is paramount to the formation, structure, and stability of these materials. Zeolites frequently have extra-framework cations, and as a result, are important ion-exchange materials. Zeolites also play important roles as molecular sieves and catalysts. For all that is known about zeolites, much remains a mystery. How, for example, can the well established metastability of these structures be explained? What is the role of water with respect to the formation, stabilization, and dynamical properties? This dissertation addresses these questions mainly from a modeling perspective, but also with some experimental work as well. The first discussion addresses a special class of zeolites: pure-silica zeolites. Experimental enthalpy of formation data are combined with molecular modeling to address zeolitic metastability. Molecular modeling is used to calculate internal surface areas, and a linear relationship between formation enthalpy and internal surface areas is clearly established, producing an internal surface energy of approximately 93 mJ/m2. Nitrate bearing sodalite and cancrinite have formed under the caustic chemical conditions of some nuclear waste processing centers in the United States. These phases have fouled expensive process equipment, and are the primary constituents of the resilient heels in the bottom of storage tanks. Molecular modeling, including molecular mechanics, molecular dynamics, and density functional theory, is used to simulate these materials with respect to structure and dynamical properties. Some new, very interesting results are extracted from the simulation of anhydrous Na6[Si6Al 6O24] sodalite---most importantly, the identification of two distinct

  9. Enhanced catalyst for conversion of syngas to liquid motor fuels

    DOEpatents

    Coughlin, Peter K.; Rabo, Jule A.

    1985-01-01

    Synthesis gas comprising carbon monoxide and hydrogen is converted to C.sub.5.sup.+ hydrocarbons suitable for use as liquid motor fuels by contact with a dual catalyst system capable of enhancing the selectivity of said conversion to motor fuel range hydrocarbons and the quality of the resulting motor fuel product. The catalyst composition employs a Fischer-Tropsch catalyst, together with a co-catalyst/support component comprising SAPO silicoaluminophosphate, non-zeolitic molecular sieve catalyst.

  10. Enhanced catalyst for conversion of syngas to liquid motor fuels

    DOEpatents

    Coughlin, P.K.; Rabo, J.A.

    1985-12-03

    Synthesis gas comprising carbon monoxide and hydrogen is converted to C[sub 5][sup +] hydrocarbons suitable for use as liquid motor fuels by contact with a dual catalyst system capable of enhancing the selectivity of said conversion to motor fuel range hydrocarbons and the quality of the resulting motor fuel product. The catalyst composition employs a Fischer-Tropsch catalyst, together with a co-catalyst/support component comprising a SAPO silicoaluminophosphate, non-zeolitic molecular sieve catalyst.

  11. Effect of hierarchical porosity and phosphorus modification on the catalytic properties of zeolite Y

    NASA Astrophysics Data System (ADS)

    Li, Wenlin; Zheng, Jinyu; Luo, Yibin; Da, Zhijian

    2016-09-01

    The zeolite Y is considered as a leading catalyst for FCC industry. The acidity and porosity modification play important roles in determining the final catalytic properties of zeolite Y. The alkaline treatment of zeolite Y by dealumination and alkaline treatment with NaOH and NaOH&TBPH was investigated. The zeolites were characterized by X-ray diffraction, low-temperature adsorption of nitrogen, transmission electron microscope, NMR, NH3-TPD and IR study of acidity. Accordingly, the hierarchical porosity and acidity property were discussed systematically. Finally, the catalytic performance of the zeolites Y was evaluated in the cracking of 1,3,5-TIPB. It was found that desilication with NaOH&TBPH ensured the more uniform intracrystalline mesoporosity with higher microporosity, while preserving higher B/L ratio and moderate Brønsted acidities resulting in catalysts with the most appropriated acidity and then with better catalytic performance.

  12. Studying Two-Dimensional Zeolites with the Tools of Surface Science: MFI Nanosheets on Au(111)

    SciTech Connect

    J. D. Kestell; Zhong, J. Q.; Shete, M.; Waluyo, I.; Sadowski, J. T.; Stacchiola, D. J.; Tsapatsis, M.; Boscoboinik, J. A.

    2016-07-26

    While surface science has provided fundamental insights into a variety a materials, the most used catalysts in the industry, namely zeolites, still remain a challenge. The recent preparation of two-dimensional versions of MFI zeolite frameworks and the possibility of their deposition on electrically conductive supports provides for the first time a viable strategy to perform detailed studies on industrially relevant zeolites using the vast toolkit of surface science. In this work we demonstrate the use of infrared reflection absorption spectroscopy (IRRAS) and synchrotron-based x-ray photoelectron spectroscopy (XPS) to study these materials. Furthermore, polarization modulation IRRAS is used to study the adsorption of methanol and its effect in phonon vibrations of the zeolite framework. The possibility of using surface science methods, in particular under ambient pressure conditions, for the study of well-defined zeolites and other microporous structures opens new avenues to understand structural and mechanistic aspects of these materials as catalysts, adsorbents and molecular sieves.

  13. Hydrogen Adsorption in Zeolite Studied with Sievert and Thermogravimetric Methods

    NASA Astrophysics Data System (ADS)

    Lesnicenoks, P.; Sivars, A.; Grinberga, L.; Kleperis, J.

    2012-08-01

    Natural clinoptilolite (mixture from clinoptilolite, quartz and muscovite) is activated with palladium and tested for hydrogen adsorption capability at temperatures RT - 200°C. Thermogravimetric and volumetric methods showed that zeolite activated with palladium (1.25%wt) shows markedly high hydrogen adsorption capacity - up to 3 wt%. Lower amount of adsorbed hydrogen (~1.5 wt%) was found for raw zeolite and activated with higher amount of palladium sample. Hypothesis is proposed that the heating of zeolite in argon atmosphere forms and activates the pore structure in zeolite material, where hydrogen encapsulation (trapping) is believed to occur when cooling down to room temperature. An effect of catalyst (Pd) on hydrogen sorption capability is explained by spillover phenomena were less-porous fractions of natural clinoptilolite sample (quartz and muscovite) are involved.

  14. Reactivity of isobutane on zeolites: a first principles study.

    PubMed

    Zheng, Xiaobo; Blowers, Paul

    2006-02-23

    In this work, ab initio and density functional theory methods are used to study isobutane protolytic cracking, primary hydrogen exchange, tertiary hydrogen exchange, and dehydrogenation reactions catalyzed by zeolites. The reactants, products, and transition-state structures are optimized at the B3LYP/6-31G* level, and the final energies are calculated using the CBS-QB3 composite energy method. The computed activation barriers are 52.3 kcal/mol for cracking, 29.4 kcal/mol for primary hydrogen exchange, 29.9 kcal/mol for tertiary hydrogen exchange, and 59.4 kcal/mol for dehydrogenation. The zeolite acidity effects on the reaction barriers are also investigated by changing the cluster terminal Si-H bond lengths. The analytical expressions between activation barriers and zeolite deprotonation energies for each reaction are proposed so that accurate activation barriers can be obtained when using different zeolites as catalysts.

  15. The stability of copper oxo species in zeolite frameworks

    SciTech Connect

    Vilella, Laia; Studt, Felix

    2016-03-07

    Cu-exchanged zeolites are promising heterogeneous catalysts, as they provide a confined environment to carry out highly selective reactions. Furthermore, the knowledge of how the zeolite framework and the location of Al atoms therein affect the adsorption of copper species is still not well understood. In this work, DFT was used to investigate the adsorption of potential Cu oxo active species suggested in the literature [Cu(η2-O2), Cu(µ-O)Cu, and Cu2O2] into zeolites with different pore sizes and shapes (AFI, CHA, TON, MOR, and MFI). The calculations revealed that both monomeric and dimeric Cu oxo species bind strongly to the O atoms of the lattice. For the monometallic species similar adsorption energies are obtained with the different zeolite frameworks, whereas an optimum Al–Al distance is required for the dimeric species.

  16. The stability of copper oxo species in zeolite frameworks

    DOE PAGES

    Vilella, Laia; Studt, Felix

    2016-03-07

    Cu-exchanged zeolites are promising heterogeneous catalysts, as they provide a confined environment to carry out highly selective reactions. Furthermore, the knowledge of how the zeolite framework and the location of Al atoms therein affect the adsorption of copper species is still not well understood. In this work, DFT was used to investigate the adsorption of potential Cu oxo active species suggested in the literature [Cu(η2-O2), Cu(µ-O)Cu, and Cu2O2] into zeolites with different pore sizes and shapes (AFI, CHA, TON, MOR, and MFI). The calculations revealed that both monomeric and dimeric Cu oxo species bind strongly to the O atoms ofmore » the lattice. For the monometallic species similar adsorption energies are obtained with the different zeolite frameworks, whereas an optimum Al–Al distance is required for the dimeric species.« less

  17. Cluster formula of Fe-containing Monel alloys with high corrosion-resistance

    SciTech Connect

    Li Baozeng; Gu Junjie; Wang Qing; Ji Chunjun; Wang Yingmin; Qiang Jianbing; Dong Chuang

    2012-06-15

    The cluster-plus-glue-atom model is applied in the composition interpretation of Monel alloys. This model considers ideal atomic nearest neighbor configurations among the constituent elements and has been used in understanding compositions of complex alloys like quasicrystals, amorphous alloys, and cupronickels. According to this model, any structure can be expressed by cluster formula [cluster](glue atom){sub x}, x denoting the number of glue atoms matching one cluster. According to this model, two groups of experimental composition series [Fe{sub 1}Ni{sub 12}]Cu{sub x} and [Fe{sub y}Ni{sub 12}]Cu{sub 5} were designed which fell close to conventional Fe-containing Monel alloys. The designed alloys after solution treatment plus water quenching, are monolithic FCC Ni-based solid solutions. Among them, the [Fe{sub 1}Ni{sub 12}]Cu{sub 5} alloy has the highest corrosion resistance in simulated sea water, and its performance is superior to that of industrial Monel 400 alloy. - Highlights: Black-Right-Pointing-Pointer A stable solid solution model is proposed using our 'cluster-plus-glue-atom model'. Black-Right-Pointing-Pointer This model is used to develop Monel corrosion resistant alloys. Black-Right-Pointing-Pointer Single FCC structure is easily retained. Black-Right-Pointing-Pointer The alloys show good corrosion properties. Black-Right-Pointing-Pointer This work contributes to the general understanding of engineering alloys.

  18. Developing of a test procedure to evaluate FCC catalyst regenerability

    SciTech Connect

    Murthy, V.L.N.; Debnath, S.; Bao, M.R.

    1995-12-31

    FCC catalyst comprises various active ingredients e.g. Y Zeolites, ZSM-5 and other medium pore Zeolites, active, matrix etc. with wide variation in Zeolite/matrix ratio and pore size distribution. The effect of pore size distribution on the accessibility of the active sites is a subject for intensive research at present. The accessibility of these active sites has a major effect on the overall reaction and regeneration kinetics. Catalyst regenerability is a very important factor particularly for moderate and low temperature regenerators, since it directly effects the CRC (Coke on-Regenerated Catalyst) value. The regenerability of catalyst is critical to minimize the overall catalyst inventory. Unfortunately, till date, there is no suitable laboratory equipment available to test catalyst regenerability.

  19. Facile synthesis of hollow zeolite microspheres through dissolution–recrystallization procedure in the presence of organosilanes

    SciTech Connect

    Tao, Haixiang; Ren, Jiawen; Liu, Xiaohui; Wang, Yanqin; Lu, Guanzhong

    2013-04-15

    Hollow zeolite microspheres have been hydrothermally synthesized in the presence of organosilanes via a dissolution–recrystallization procedure. In the presence of organosilanes, zeolite particles with a core/shell structure formed at the first stage of hydrothermal treatment, then the core was consumed and recrystallized into zeolite framework to form the hollow structure during the second hydrothermal process. The influence of organosilanes was discussed, and a related dissolution–recrystallization mechanism was proposed. In addition, the hollow zeolite microspheres exhibited an obvious advantage in catalytic reactions compared to conventional ZSM-5 catalysts, such as in the alkylation of toluene with benzyl chloride. - Graphical abstract: Hollow zeolite spheres with aggregated zeolite nanocrystals were synthesized via a dissolution–recrystallization procedure in the presence of organosiline. Highlights: ► Hollow zeolite spheres with aggregated zeolite nanocrystals were synthesized via a dissolution–recrystallization procedure. ► Organosilane influences both the morphology and hollow structure of zeolite spheres. ► Hollow zeolite spheres showed an excellent catalytic performance in alkylation of toluene with benzyl chloride.

  20. Bifunctional Nanostructured Base Catalysts: Opportunities for BioFuels

    SciTech Connect

    Connor, William

    2010-12-30

    ABSTRACT This research studied and develop novel basic catalysts for production of renewable chemicals and fuels from biomass. We will focus on the development of unique porous structural-base catalysts formed by two techniques: from (mixed) metal-oxide bases and by nitrogen substitution for oxygen in zeolites. These catalysts will be compared to conventional solid base materials for aldol condensation, catalytic fast pyrolysis, and transesterification reactions. These reactions are important in processes that are currently being commercialized for production of fuels from biomass and will be pivotal in future biomass conversion to fuels and chemicals. Specifically, we have studied the aldol-condensation of acetone with furfural over oxides and zeolites, the conversion of sugars by rapid pyrolysis over zeolites and the trans-esterification of vegetable oil with methanol over mixed oxide catalysts. Our previous research has indicated that the base strength of framework nitrogen in nitrogen-substituted zeolites (NH-zeolites) is nearly twice as strong as in standard zeolites. Nitrogen substituted catalysts have been synthesized from several zeolites (including FAU, MFI, BEA, and LTL) using NH3 treatment.

  1. Catalytic pyrolysis of wheat bran for hydrocarbons production in the presence of zeolites and noble-metals by using TGA-FTIR method.

    PubMed

    Lazdovica, K; Liepina, L; Kampars, V

    2016-05-01

    Pyrolysis of wheat bran with or without catalysts was investigated using TGA-FTIR method in order to determine the influence of zeolite and noble metal catalysts on the evolution profile and relative yield of the volatile compounds. The addition of all catalysts decreased the volatile matter of wheat bran from 76.3% to 75.9%, 73.9%, 73.5%, 69.7% and increased the solid residue from 18.0% to 18.4%, 20.4%, 20.8%, 24.6% under the catalyst of ZSM-5, 5% Pd/C, MCM-41, and 5% Pt/C. Noble-metal catalysts had higher activity for deoxygenation of compounds containing carbonyl, carboxyl, and hydroxyl groups than zeolites. Degradation of nitrogen containing compounds atom proceeded better in presence of zeolites. Noble-metal catalysts promoted formation of aromatics and changed the profiles of evolved compounds whereas zeolites advanced formation of aliphatics and olefins.

  2. [Experimental and kinetic modeling of acid/base and redox reactions over oxide catalysts

    SciTech Connect

    Not Available

    1993-01-01

    The research has involved the characterization of catalyst acidity, [sup 2]D NMR studies of Bronsted acid sites, and kinetic, calorimetric, and spectroscopic studies of methylamine synthesis and related reactions over acid catalysts. Approach of this work was to explore quantitative correlations between factors that control the generation, type, strength, and catalytic properties of acid sites on zeolite catalysts. Microcalorimetry, thermogravimetric analysis, IR spectroscopy, and NMR spectroscopy have provided information about the nature and strength of acid sites in zeolites. This was vital in understanding the catalytic cycles involved in methylamine synthesis and related reactions over zeolite catalysts.

  3. Dual template synthesis of a highly mesoporous SSZ-13 zeolite with improved stability in the methanol-to-olefins reaction.

    PubMed

    Wu, Leilei; Degirmenci, Volkan; Magusin, Pieter C M M; Szyja, Bartłomiej M; Hensen, Emiel J M

    2012-10-04

    The dual template synthesis of zeolite SSZ-13 by use of trimethyl-adamantanammonium hydroxide and a diquaternary-ammonium mesoporogen induces considerable mesoporosity without impeding zeolite microporosity. The strongly improved accessibility of Brønsted sites in mesoporous SSZ-13 increases its stability during application as an acid catalyst in the methanol-to-olefins reaction.

  4. Evaporation Mechanism of Cu from Liquid Fe Containing C and S

    NASA Astrophysics Data System (ADS)

    Jung, Sung-Hoon; Kang, Youn-Bae

    2016-08-01

    A number of liquid-gas experiments were carried out in order to elucidate evaporation mechanism of Cu from liquid Fe containing C and S. Rate of Cu evaporation in liquid Fe droplets at 1873 K (1600 °C) was determined using electromagnetic levitation equipment. Evaporation rate of the Cu under various conditions (flow rate of gas mixtures, initial C, and S concentrations) was examined. It was found from a series of kinetic analyses of the experimental data that Cu evaporates in forms of Cu(g) and CuS(g). As was reported for the Sn evaporation from liquid iron (Jung et al. Met. Mater. Trans. 46B, 250-258, 2014), S plays two roles for the evaporation of Cu: accelerating the rate by forming CuS(g) and decelerating the rate by blocking evaporation sites. As a result of these combinatorial effects, the evaporation of Cu is decelerated at low S content, but is accelerated at high S content. Based on the elucidated mechanism, an evaporation model equation for Cu was developed in the present study, which takes into account (1) evaporation of Cu in the two forms (Cu(g) and CuS(g)), (2) surface blocking by S using ideal Langmuir adsorption, and (3) effect of C. The obtained rate constant of a reaction Cu i + S i = CuS i (g), k CuS R , is 1.37 × 10-9 m4 mol-1 s-1, and the residual rate constant, k CuS r , is 4.11 × 10-10 m4 mol-1 s-1 at 1873 K (1600 °C). Both of them were found to be one order lower than those for Sn evaporation.

  5. An investigation of resid cracking catalyst texture characteristics

    SciTech Connect

    Tu, S.Y.; Zhou, S.J.; Wang, S.Z.

    1995-12-31

    Various kinds of resid cracking catalysts have been developed by RIPP(SINOPEC) in recent years. Catalysts are mainly prepared with REUSY or REHY zeolites as the active components and kaolin clays combined with alumina sol or pseudo-boehmite as the matrices. The formation of the texture, namely the pore structure of the zeolites and the catalysts prepared thereof were greatly influenced by the process of preparation. The bottom crackability, the stability, the coke selectivity and metal tolerance of the catalysts were also investigated, and it is found that all these properties are to a certain extent relating to their texture characteristics.

  6. Lanthanum-catalysed synthesis of microporous 3D graphene-like carbons in a zeolite template

    NASA Astrophysics Data System (ADS)

    Kim, Kyoungsoo; Lee, Taekyoung; Kwon, Yonghyun; Seo, Yongbeom; Song, Jongchan; Park, Jung Ki; Lee, Hyunsoo; Park, Jeong Young; Ihee, Hyotcherl; Cho, Sung June; Ryoo, Ryong

    2016-07-01

    Three-dimensional graphene architectures with periodic nanopores—reminiscent of zeolite frameworks—are of topical interest because of the possibility of combining the characteristics of graphene with a three-dimensional porous structure. Lately, the synthesis of such carbons has been approached by using zeolites as templates and small hydrocarbon molecules that can enter the narrow pore apertures. However, pyrolytic carbonization of the hydrocarbons (a necessary step in generating pure carbon) requires high temperatures and results in non-selective carbon deposition outside the pores. Here, we demonstrate that lanthanum ions embedded in zeolite pores can lower the temperature required for the carbonization of ethylene or acetylene. In this way, a graphene-like carbon structure can be selectively formed inside the zeolite template, without carbon being deposited at the external surfaces. X-ray diffraction data from zeolite single crystals after carbonization indicate that electron densities corresponding to carbon atoms are generated along the walls of the zeolite pores. After the zeolite template is removed, the carbon framework exhibits an electrical conductivity that is two orders of magnitude higher than that of amorphous mesoporous carbon. Lanthanum catalysis allows a carbon framework to form in zeolite pores with diameters of less than 1 nanometre; as such, microporous carbon nanostructures can be reproduced with various topologies corresponding to different zeolite pore sizes and shapes. We demonstrate carbon synthesis for large-pore zeolites (FAU, EMT and beta), a one-dimensional medium-pore zeolite (LTL), and even small-pore zeolites (MFI and LTA). The catalytic effect is a common feature of lanthanum, yttrium and calcium, which are all carbide-forming metal elements. We also show that the synthesis can be readily scaled up, which will be important for practical applications such as the production of lithium-ion batteries and zeolite-like catalyst

  7. Zeolite Membrane Reactor for Water Gas Shift Reaction for Hydrogen Production

    SciTech Connect

    Lin, Jerry Y.S.

    2013-01-29

    Gasification of biomass or heavy feedstock to produce hydrogen fuel gas using current technology is costly and energy-intensive. The technology includes water gas shift reaction in two or more reactor stages with inter-cooling to maximize conversion for a given catalyst volume. This project is focused on developing a membrane reactor for efficient conversion of water gas shift reaction to produce a hydrogen stream as a fuel and a carbon dioxide stream suitable for sequestration. The project was focused on synthesizing stable, hydrogen perm-selective MFI zeolite membranes for high temperature hydrogen separation; fabricating tubular MFI zeolite membrane reactor and stable water gas shift catalyst for membrane reactor applications, and identifying experimental conditions for water gas shift reaction in the zeolite membrane reactor that will produce a high purity hydrogen stream. The project has improved understanding of zeolite membrane synthesis, high temperature gas diffusion and separation mechanisms for zeolite membranes, synthesis and properties of sulfur resistant catalysts, fabrication and structure optimization of membrane supports, and fundamentals of coupling reaction with separation in zeolite membrane reactor for water gas shift reaction. Through the fundamental study, the research teams have developed MFI zeolite membranes with good perm-selectivity for hydrogen over carbon dioxide, carbon monoxide and water vapor, and high stability for operation in syngas mixture containing 500 part per million hydrogen sulfide at high temperatures around 500°C. The research teams also developed a sulfur resistant catalyst for water gas shift reaction. Modeling and experimental studies on the zeolite membrane reactor for water gas shift reaction have demonstrated the effective use of the zeolite membrane reactor for production of high purity hydrogen stream.

  8. Cobalt and nickel supported on HY zeolite: Synthesis, characterization and catalytic properties

    SciTech Connect

    Garrido Pedrosa, Anne M. . E-mail: annemgp@yahoo.com; Souza, Marcelo J.B.; Melo, Dulce M.A.; Araujo, Antonio S.

    2006-06-15

    Bifunctional catalysts consisting of cobalt and nickel supported on HY zeolite were synthesized by solvent excess impregnation and characterized by X-ray diffraction, Fourier-transformed infrared spectroscopy, scanning electron microscopy, atomic absorption spectroscopy, thermogravimetric analysis and nitrogen adsorption. The profiles of metal reduction on zeolite were obtained by temperature-programmed reduction. The catalytic properties of the bifunctional catalysts were verified by n-hexane hydroconversion. X-ray diffraction and microstructural analyses showed the presence of crystalline phases in HY zeolite and in samples after impregnation. A decrease in the micropore surface area was observed by nitrogen adsorption experiments and attributed to a reduction in the accessibility to micropores. The catalysts showed catalytic activity in the hydroconversion of n-hexane with selectivity to branched hydrocarbons. Such catalytic activity was related to the acid and metallic properties of the bifunctional catalysts used.

  9. Visualizing Dealumination of a Single Zeolite Domain in a Real-Life Catalytic Cracking Particle.

    PubMed

    Kalirai, Sam; Paalanen, Pasi P; Wang, Jian; Meirer, Florian; Weckhuysen, Bert M

    2016-09-05

    Fluid catalytic cracking (FCC) catalysts play a central role in the chemical conversion of crude oil fractions. Using scanning transmission X-ray microscopy (STXM) we investigate the chemistry of one fresh and two industrially deactivated (ECAT) FCC catalysts at the single zeolite domain level. Spectro-microscopic data at the Fe L3 , La M5 , and Al K X-ray absorption edges reveal differing levels of deposited Fe on the ECAT catalysts corresponding with an overall loss in tetrahedral Al within the zeolite domains. Using La as a localization marker, we have developed a novel methodology to map the changing Al distribution of single zeolite domains within real-life FCC catalysts. It was found that significant changes in the zeolite domain size distributions as well as the loss of Al from the zeolite framework occur. Furthermore, inter- and intraparticle heterogeneities in the dealumination process were observed, revealing the complex interplay between metal-mediated pore accessibility loss and zeolite dealumination.

  10. Diagram of Zeolite Crystals

    NASA Technical Reports Server (NTRS)

    2003-01-01

    The Center for Advanced Microgravity Materials Processing (CAMMP) in Cambridge, MA, a NASA-sponsored Commercial Space Center, is working to improve zeolite materials for storing hydrogen fuel. CAMMP is also applying zeolites to detergents, optical cables, gas and vapor detection for environmental monitoring and control, and chemical production techniques that significantly reduce by-products that are hazardous to the environment. Depicted here is one of the many here complex geometric shapes which make them highly absorbent. Zeolite experiments have also been conducted aboard the International Space Station

  11. The growth of carbon nanotubes on montmorillonite and zeolite (clinoptilolite)

    NASA Astrophysics Data System (ADS)

    Kadlečíková, M.; Breza, J.; Jesenák, K.; Pastorková, K.; Luptáková, V.; Kolmačka, M.; Vojačková, A.; Michalka, M.; Vávra, I.; Križanová, Z.

    2008-06-01

    Synthesis of carbon nanotubes described in the present work is based on activation of methane in a hot filament CVD reactor and subsequent creation of nanostructures on a catalyst pre-treated polished surface of silicon. An essential step of the synthesis is the use of natural minerals as catalysts. We have studied the catalyst parameters, the way of its application and the amount of Fe 3+ cations on the surface of aluminosilicates on the quality of the grown nanotube layers. The growth of carbon nanotubes catalyzed by montmorillonite and zeolite (clinoptilolite) was confirmed by scanning electron microscopy and Raman spectroscopy.

  12. Characterization of Chemical Properties, Unit Cell Parameters and Particle Size Distribution of Three Zeolite Reference Materials: RM 8850 - Zeolite Y, RM 8851 - Zeolite A and RM 8852 - Ammonium ZSM-5 Zeolite

    SciTech Connect

    Turner,S.; Sieber, J.; Vetter, T.; Zeisler, R.; Marlow, A.; Moreno-Ramirez, M.; Davis, M.; Kennedy, G.; Borghard, W.; et al

    2008-01-01

    Zeolites have important industrial applications including use as catalysts, molecular sieves and ion exchange materials. In this study, three zeolite materials have been characterized by the National Institute of Standards and Technology (NIST) as reference materials (RMs): zeolite Y (RM 8850), zeolite A (RM 8851) and ZSM-5 zeolite (RM 8852). They have been characterized by a variety of chemical and physical measurement methods: X-ray fluorescence (XRF), gravimetry, instrumental neutron activation analysis (INAA), nuclear magnetic resonance (NMR), calorimetry, synchrotron X-ray diffraction, neutron diffraction, laser light extinction, laser light scattering, electric sensing zone, X-ray sedimentation, scanning transmission electron microscopy (STEM), scanning electron microscopy (SEM) and optical microscopy. The chemical homogeneity of the materials has been characterized. Reference values are given for the major components (major elements, loss on ignition [LOI] and loss on fusion [LOF]), trace elements and Si/Al and Na/Al ratios. Information values are given for enthalpies of formation, unit cell parameters, particle size distributions, refractive indices and variation of mass with variation in relative humidity (RH). Comparisons are made to literature unit cell parameters. The RMs are expected to provide a basis for intercomparison studies of these zeolite materials.

  13. Process for magnetic beneficiating petroleum cracking catalyst

    DOEpatents

    Doctor, R.D.

    1993-10-05

    A process is described for beneficiating a particulate zeolite petroleum cracking catalyst having metal values in excess of 1000 ppm nickel equivalents. The particulate catalyst is passed through a magnetic field in the range of from about 2 Tesla to about 5 Tesla generated by a superconducting quadrupole open-gradient magnetic system for a time sufficient to effect separation of said catalyst into a plurality of zones having different nickel equivalent concentrations. A first zone has nickel equivalents of about 6,000 ppm and greater, a second zone has nickel equivalents in the range of from about 2000 ppm to about 6000 ppm, and a third zone has nickel equivalents of about 2000 ppm and less. The zones of catalyst are separated and the second zone material is recycled to a fluidized bed of zeolite petroleum cracking catalyst. The low nickel equivalent zone is treated while the high nickel equivalent zone is discarded. 1 figures.

  14. Process for magnetic beneficiating petroleum cracking catalyst

    DOEpatents

    Doctor, Richard D.

    1993-01-01

    A process for beneficiating a particulate zeolite petroleum cracking catalyst having metal values in excess of 1000 ppm nickel equivalents. The particulate catalyst is passed through a magnetic field in the range of from about 2 Tesla to about 5 Tesla generated by a superconducting quadrupole open-gradient magnetic system for a time sufficient to effect separation of said catalyst into a plurality of zones having different nickel equivalent concentrations. A first zone has nickel equivalents of about 6,000 ppm and greater, a second zone has nickel equivalents in the range of from about 2000 ppm to about 6000 ppm, and a third zone has nickel equivalents of about 2000 ppm and less. The zones of catalyst are separated and the second zone material is recycled to a fluidized bed of zeolite petroleum cracking catalyst. The low nickel equivalent zone is treated while the high nickel equivalent zone is discarded.

  15. Gallium Zeolites for Light Paraffin Aromatization

    SciTech Connect

    Price, G.L.; Dooley, K.M.

    1999-02-10

    The primary original goal of this project was to investigate the active state of gallium-containing MFI catalysts for light paraffin aromatization, in particular the state of gallium in the active material. Our original hypothesis was that the most active and selective materials were those which contained gallium zeolitic cations, and that previously reported conditions for the activation of gallium-containing catalysts served to create these active centers. We believed that in high silica materials such as MFI, ion-exchange is most effectively accomplished with metals in their 1+ oxidation state, both because of the sparsity of the anionic ion-exchange sites associated with the zeolite, and because the large hydration shells associated with aqueous 3+ cations hinder transport. Metals such as Ga which commonly exist in higher oxidation states need to be reduced to promote ion-exchange and this is the reason that reduction of gallium-containing catalysts for light paraffin aromatization often yields a dramatic enhancement in catalytic activity. We have effectively combined reduction with ion-exchange and we term this combined process ''reductive solid-state ion-exchange''. Our hypothesis has largely been proven true, and a number of the papers we have published directly address this hypothesis.

  16. ZEOLITE CHARACTERIZATION TESTING

    SciTech Connect

    Jacobs, W; Herbert Nigg, H

    2007-09-13

    The Savannah River Site isolates tritium from its process streams for eventual recycling. This is done by catalyzing the formation of tritiated water (from process streams) and then sorbing that water on a 3A zeolite (molsieve) bed. The tritium is recovered by regenerating the saturated bed into a Mg-based water cracking unit. The process described has been in use for about 15 years. Recently chloride stress corrosion cracking (SCC) was noted in the system piping. This has resulted in the need to replace the corroded piping and associated molecular sieve beds. The source of chlorine has been debated and one possible source is the zeolite itself. Since new materials are being purchased for recently fabricated beds, a more comprehensive analysis protocol for characterizing zeolite has been developed. Tests on archived samples indicate the potential for mobile chloride species to be generated in the zeolite beds.

  17. Composite zeolite membranes

    DOEpatents

    Nenoff, Tina M.; Thoma, Steven G.; Ashley, Carol S.; Reed, Scott T.

    2002-01-01

    A new class of composite zeolite membranes and synthesis techniques therefor has been invented. These membranes are essentially defect-free, and exhibit large levels of transmembrane flux and of chemical and isotopic selectivity.

  18. Structural analysis of hierarchically organized zeolites

    PubMed Central

    Mitchell, Sharon; Pinar, Ana B.; Kenvin, Jeffrey; Crivelli, Paolo; Kärger, Jörg; Pérez-Ramírez, Javier

    2015-01-01

    Advances in materials synthesis bring about many opportunities for technological applications, but are often accompanied by unprecedented complexity. This is clearly illustrated by the case of hierarchically organized zeolite catalysts, a class of crystalline microporous solids that has been revolutionized by the engineering of multilevel pore architectures, which combine unique chemical functionality with efficient molecular transport. Three key attributes, the crystal, the pore and the active site structure, can be expected to dominate the design process. This review examines the adequacy of the palette of techniques applied to characterize these distinguishing features and their catalytic impact. PMID:26482337

  19. Zeolite A imidazolate frameworks

    NASA Astrophysics Data System (ADS)

    Hayashi, Hideki; Côté, Adrien P.; Furukawa, Hiroyasu; O'Keeffe, Michael; Yaghi, Omar M.

    2007-07-01

    Faujasite (FAU) and zeolite A (LTA) are technologically important porous zeolites (aluminosilicates) because of their extensive use in petroleum cracking and water softening. Introducing organic units and transition metals into the backbone of these types of zeolite allows us to expand their pore structures, enhance their functionality and access new applications. The invention of metal-organic frameworks and zeolitic imidazolate frameworks (ZIFs) has provided materials based on simple zeolite structures where only one type of cage is present. However, so far, no metal-organic analogues based on FAU or LTA topologies exist owing to the difficulty imposed by the presence of two types of large cage (super- and β-cages for FAU, α- and β-cages for LTA). Here, we have identified a strategy to produce an LTA imidazolate framework in which both the link geometry and link-link interactions play a decisive structure-directing role. We describe the synthesis and crystal structures of three porous ZIFs that are expanded analogues of zeolite A; their cage walls are functionalized, and their metal ions can be changed without changing the underlying LTA topology. Hydrogen, methane, carbon dioxide and argon gas adsorption isotherms are reported and the selectivity of this material for carbon dioxide over methane is demonstrated.

  20. Hydraulic conductivity of compacted zeolites.

    PubMed

    Oren, A Hakan; Ozdamar, Tuğçe

    2013-06-01

    Hydraulic conductivities of compacted zeolites were investigated as a function of compaction water content and zeolite particle size. Initially, the compaction characteristics of zeolites were determined. The compaction test results showed that maximum dry unit weight (γ(dmax)) of fine zeolite was greater than that of granular zeolites. The γ(dmax) of compacted zeolites was between 1.01 and 1.17 Mg m(-3) and optimum water content (w(opt)) was between 38% and 53%. Regardless of zeolite particle size, compacted zeolites had low γ(dmax) and high w(opt) when compared with compacted natural soils. Then, hydraulic conductivity tests were run on compacted zeolites. The hydraulic conductivity values were within the range of 2.0 × 10(-3) cm s(-1) to 1.1 × 10(-7) cm s(-1). Hydraulic conductivity of all compacted zeolites decreased almost 50 times as the water content increased. It is noteworthy that hydraulic conductivity of compacted zeolite was strongly dependent on the zeolite particle size. The hydraulic conductivity decreased almost three orders of magnitude up to 39% fine content; then, it remained almost unchanged beyond 39%. Only one report was found in the literature on the hydraulic conductivity of compacted zeolite, which is in agreement with the findings of this study.

  1. Discovery of optimal zeolites for challenging separations and chemical transformations using predictive materials modeling

    NASA Astrophysics Data System (ADS)

    Bai, Peng; Jeon, Mi Young; Ren, Limin; Knight, Chris; Deem, Michael W.; Tsapatsis, Michael; Siepmann, J. Ilja

    2015-01-01

    Zeolites play numerous important roles in modern petroleum refineries and have the potential to advance the production of fuels and chemical feedstocks from renewable resources. The performance of a zeolite as separation medium and catalyst depends on its framework structure. To date, 213 framework types have been synthesized and >330,000 thermodynamically accessible zeolite structures have been predicted. Hence, identification of optimal zeolites for a given application from the large pool of candidate structures is attractive for accelerating the pace of materials discovery. Here we identify, through a large-scale, multi-step computational screening process, promising zeolite structures for two energy-related applications: the purification of ethanol from fermentation broths and the hydroisomerization of alkanes with 18-30 carbon atoms encountered in petroleum refining. These results demonstrate that predictive modelling and data-driven science can now be applied to solve some of the most challenging separation problems involving highly non-ideal mixtures and highly articulated compounds.

  2. [Experimental and kinetic modeling of acid/base and redox reactions over oxide catalysts]. Technical progress report

    SciTech Connect

    Not Available

    1993-07-01

    The research has involved the characterization of catalyst acidity, {sup 2}D NMR studies of Bronsted acid sites, and kinetic, calorimetric, and spectroscopic studies of methylamine synthesis and related reactions over acid catalysts. Approach of this work was to explore quantitative correlations between factors that control the generation, type, strength, and catalytic properties of acid sites on zeolite catalysts. Microcalorimetry, thermogravimetric analysis, IR spectroscopy, and NMR spectroscopy have provided information about the nature and strength of acid sites in zeolites. This was vital in understanding the catalytic cycles involved in methylamine synthesis and related reactions over zeolite catalysts.

  3. Preparation of functionalized zeolitic frameworks

    DOEpatents

    Yaghi, Omar M; Furukawa, Hiroyasu; Wang, Bo

    2013-07-09

    The disclosure provides zeolitic frameworks for gas separation, gas storage, catalysis and sensors. More particularly the disclosure provides zeolitic frameworks (ZIFs). The ZIF of the disclosure comprises any number of transition metals or a homogenous transition metal composition.

  4. Preparation of functionalized zeolitic frameworks

    DOEpatents

    Yaghi, Omar M; Hayashi, Hideki; Banerjee, Rahul; Park, Kyo Sung; Wang, Bo; Cote, Adrien P

    2012-11-20

    The disclosure provides zeolitic frameworks for gas separation, gas storage, catalysis and sensors. More particularly the disclosure provides zeolitic frameworks (ZIFs). The ZIF of the disclosure comprises any number of transition metals or a homogenous transition metal composition.

  5. Preparation of functionalized zeolitic frameworks

    SciTech Connect

    Yaghi, Omar M.; Hayashi, Hideki; Banerjee, Rahul; Park, Kyo Sung; Wang, Bo; Cote, Adrien P.

    2014-08-19

    The disclosure provides zeolitic frameworks for gas separation, gas storage, catalysis and sensors. More particularly the disclosure provides zeolitic frameworks (ZIFs). The ZIF of the disclosure comprises any number of transition metals or a homogenous transition metal composition.

  6. Acid-Base Pairs in Lewis Acidic Zeolites Promote Direct Aldol Reactions by Soft Enolization.

    PubMed

    Lewis, Jennifer D; Van de Vyver, Stijn; Román-Leshkov, Yuriy

    2015-08-17

    Hf-, Sn-, and Zr-Beta zeolites catalyze the cross-aldol condensation of aromatic aldehydes with acetone under mild reaction conditions with near quantitative yields. NMR studies with isotopically labeled molecules confirm that acid-base pairs in the Si-O-M framework ensemble promote soft enolization through α-proton abstraction. The Lewis acidic zeolites maintain activity in the presence of water and, unlike traditional base catalysts, in acidic solutions.

  7. Determining the aluminium occupancy on the active T-sites in zeolites using X-ray standing waves

    NASA Astrophysics Data System (ADS)

    van Bokhoven, Jeroen A.; Lee, Tien-Lin; Drakopoulos, Michael; Lamberti, Carlo; Thieß, Sebastian; Zegenhagen, Jörg

    2008-07-01

    Zeolites are microporous crystalline materials that find wide application in industry, for example, as catalysts and gas separators, and in our daily life, for example, as adsorbents or as ion exchangers in laundry detergents. The tetrahedrally coordinated silicon and aluminium atoms in the zeolite unit cell occupy the so-called crystallographic T-sites. Besides their pore size, the occupation of specific T-sites by the aluminium atoms determines the performance of the zeolites. Despite its importance, the distribution of aluminium over the crystallographic T-sites remains one of the most challenging, unresolved issues in zeolite science. Here, we report how to determine unambiguously and directly the distribution of aluminium in zeolites by means of the X-ray standing wave technique using brilliant, focused X-rays from a third-generation synchrotron source. We report in detail the analysis of the aluminium distribution in scolecite, which demonstrates how the aluminium occupancy in zeolites can systematically be determined.

  8. Comparative Study of Catalysts containing Transition Metals in Production of Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

    Vesselényi, I.; Niesz, K.; Kónya, Z.; Nagy, J. B.; Kiricsi, I.

    2002-10-01

    For production of multiwall carbon nanotubes (MWNT) by catalytic chemical vapour deposition (CCVD) different transition metals supported on amorphous or crystalline oxides such as silica, alumina or zeolites were used. In several cases both the productivity of catalysts and the quality of MWNT are improved by using bimetallic catalysts such as Co-Fe, Co-V etc. In this publication we report the results in comparison of mono and bimetallic catalysts of Co, Fe, Ni and V supported on alumina, zeolite 13X-FAU and zeolite ZSM-5-MFI.

  9. Synthetic zeolites and other microporous oxide molecular sieves.

    PubMed

    Sherman, J D

    1999-03-30

    Use of synthetic zeolites and other microporous oxides since 1950 has improved insulated windows, automobile air-conditioning, refrigerators, air brakes on trucks, laundry detergents, etc. Their large internal pore volumes, molecular-size pores, regularity of crystal structures, and the diverse framework chemical compositions allow "tailoring" of structure and properties. Thus, highly active and selective catalysts as well as adsorbents and ion exchangers with high capacities and selectivities were developed. In the petroleum refining and petrochemical industries, zeolites have made possible cheaper and lead-free gasoline, higher performance and lower-cost synthetic fibers and plastics, and many improvements in process efficiency and quality and in performance. Zeolites also help protect the environment by improving energy efficiency, reducing automobile exhaust and other emissions, cleaning up hazardous wastes (including the Three Mile Island nuclear power plant and other radioactive wastes), and, as specially tailored desiccants, facilitating the substitution of new refrigerants for the ozone-depleting chlorofluorocarbons banned by the Montreal Protocol.

  10. The environmental applications of activated carbon/zeolite composite materials.

    PubMed

    Foo, K Y; Hameed, B H

    2011-02-17

    Over the past couple of years, the resurgence of placing an effective and sustainable amendment to combat against the auxiliary industrial entities, remains a highly contested agenda from a global point. With the renaissance of activated carbon, there has been a steadily growing interest in the research field. Recently, the adoption of zeolite composite, a prestigious advanced catalyst which formulates the enhancement of adsorption rate and hydrogen storage capability, has fore fronted to be a new growing branch in the scientific community. Confirming the assertion, this paper presents a state of art review of activated carbon/zeolite composite technology, its fundamental background studies, and environmental implications. Moreover, its major challenges together with the future expectation are summarized and discussed. Conclusively, the expanding of activated carbon/zeolite composite represents a potentially viable and powerful tool, leading to the plausible improvement of environmental preservation.

  11. Synthetic Zeolites and Other Microporous Oxide Molecular Sieves

    NASA Astrophysics Data System (ADS)

    Sherman, John D.

    1999-03-01

    Use of synthetic zeolites and other microporous oxides since 1950 has improved insulated windows, automobile air-conditioning, refrigerators, air brakes on trucks, laundry detergents, etc. Their large internal pore volumes, molecular-size pores, regularity of crystal structures, and the diverse framework chemical compositions allow "tailoring" of structure and properties. Thus, highly active and selective catalysts as well as adsorbents and ion exchangers with high capacities and selectivities were developed. In the petroleum refining and petrochemical industries, zeolites have made possible cheaper and lead-free gasoline, higher performance and lower-cost synthetic fibers and plastics, and many improvements in process efficiency and quality and in performance. Zeolites also help protect the environment by improving energy efficiency, reducing automobile exhaust and other emissions, cleaning up hazardous wastes (including the Three Mile Island nuclear power plant and other radioactive wastes), and, as specially tailored desiccants, facilitating the substitution of new refrigerants for the ozone-depleting chlorofluorocarbons banned by the Montreal Protocol.

  12. Potential of sustainable hierarchical zeolites in the valorization of α-pinene.

    PubMed

    Nuttens, Nicolas; Verboekend, Danny; Deneyer, Aron; Van Aelst, Joost; Sels, Bert F

    2015-04-13

    In the valorization of α-pinene, which is an important biomass intermediate derived from turpentine oil, hierarchical (mesoporous) zeolites represent a superior class of catalysts. Hierarchical USY, ZSM-5, and beta zeolites have been prepared, characterized, and catalytically evaluated, with the aim of combining the highest catalytic performance with the most sustainable synthetic protocol. These zeolites are prepared by alkaline treatment in aqueous solutions of NH4 OH, NaOH, diethylamine, and NaOH complemented with tetrapropylammonium bromide. The hierarchical USY zeolite is the most attractive catalyst of the tested series, and is able to combine an overall organic-free synthesis with an up to sixfold activity enhancement and comparable selectivity over the conventional USY zeolite. This superior performance relates to a threefold greater activity than that of the commercial standard, namely, H2 SO4 /TiO2 . Correlation of the obtained benefits to the amount of solid lost during the postsynthetic modifications highlights that the highest activity gains are obtained with minor leaching. Furthermore, a highly zeolitic character, as determined by bulk XRD, is beneficial, but not crucial, in the conversion of α-pinene. The alkaline treatments not only result in a higher overall activity, but also a more functional external surface area, attaining up to four times the pinene conversions per square nanometer. The efficiency of the hierarchical USY zeolite is concomitantly demonstrated in the conversion of limonene and turpentine oil, which emphasizes its industrial potential.

  13. Various conformations of carbon nanocoils prepared by supported Ni-Fe/molecular sieve catalyst.

    PubMed

    Yang, Shaoming; Chen, Xiuqin; Takeuchi, K; Motojima, Seiji

    2006-01-01

    The carbon nanocoils with various kinds of conformations were prepared by the catalytic pyrolysis of acetylene using the Ni metal catalyst supported on molecular Sieves which was prepared using Fe-containing kaolin as the raw material. There are four kinds of carbon nanocoils conformations produced by this catalyst. The influences of reaction temperature and gas conditions on the conformations of the nanocoils were investigated and the reasons of forming nano-size coils were discussed by comparison with pure Ni metal catalyst.

  14. Ru complexes of Hoveyda–Grubbs type immobilized on lamellar zeolites: activity in olefin metathesis reactions

    PubMed Central

    Žilková, Naděžda; Kubů, Martin; Mazur, Michal; Bastl, Zdeněk; Čejka, Jiří

    2015-01-01

    Summary Hoveyda–Grubbs type catalysts with cationic tags on NHC ligands were linker-free immobilized on the surface of lamellar zeolitic supports (MCM-22, MCM-56, MCM-36) and on mesoporous molecular sieves SBA-15. The activity of prepared hybrid catalysts was tested in olefin metathesis reactions: the activity in ring-closing metathesis of citronellene and N,N-diallyltrifluoroacetamide decreased in the order of support MCM-22 ≈ MCM-56 > SBA-15 > MCM-36; the hybrid catalyst based on SBA-15 was found the most active in self-metathesis of methyl oleate. All catalysts were reusable and exhibited low Ru leaching (<1% of Ru content). XPS analysis revealed that during immobilization ion exchange between Hoveyda–Grubbs type catalyst and zeolitic support occurred in the case of Cl− counter anion; in contrast, PF6 − counter anion underwent partial decomposition. PMID:26664629

  15. Fe-containing ionic liquids as effective and recoverable oxidants for dissolution of UO2 in the presence of imidazolium chlorides.

    PubMed

    Yao, Aining; Chu, Taiwei

    2013-06-21

    Imidazolium-based Fe-containing ionic liquids (ILs) can directly dissolve UO2 in the presence of their corresponding imidazolium chlorides without additional oxidants. The dissolution process follows pseudo first-order kinetics initially. Raman spectroscopic studies indicate that FeCl4(2-) is the predominant reduction product after UO2 dissolution, and attenuated total reflection-Fourier transform infrared spectroscopy indicates that the UO2(2+) complex is the principal product in the ILs. The dissolved uranyl species can be successfully separated from the Fe-containing ILs via a combination of centrifugation and solvent extraction, and also, the Fe-containing ILs can be recovered easily. In conclusion, imidazolium-based Fe-containing ionic liquids in the presence of imidazolium chlorides could be used as effective and recoverable oxidants for the dissolution of UO2.

  16. Effect of the Si/Al ratio and of the zeolite structure on the performance of dealuminated zeolites for the reforming of hydrocarbon mixtures

    SciTech Connect

    Smirniotis, P.G.; Zhang, W.

    1996-09-01

    Various 12-membered ring pore zeolites were employed for the reforming of synthetic hydrocarbon mixtures which simulate industrial naphthas. All the zeolites were dealuminated to various extents. It was found that, under the present conditions over the samples which are slightly dealuminated, bimolecular-condensation reactions followed by recracking are responsible for the relatively large selectivities of C{sub 4} paraffins. The monomolecular cracking (via pentacoordinated carbonium ions) of the latter hydrocarbons is responsible for the large generation of CH{sub 4} from the cracking of C{sub 4} paraffins. When the Si/Al ratio increases, the selectivity of methane passes through a steep minimum, while those of C{sub 3}, C{sub 4}, and C{sub 5} pass through a maximum. It was also found that the zeolite pore structure is a very important factor for the time on stream activity of zeolite-based catalysts. Zeolites with reduced aluminum content and pore structures, which do not favor the formation of coke precursors in their cavities, can lead to very promising catalysts for acid-catalyzed reactions. From this study a 12-membered ring pore zeolite, which demonstrates minimal coke deactivation, was identified.

  17. Synthesis of Zeolites Using the ADOR (Assembly-Disassembly-Organization-Reassembly) Route.

    PubMed

    Wheatley, Paul S; Čejka, Jiří; Morris, Russell E

    2016-04-03

    Zeolites are an important class of materials that have wide ranging applications such as heterogeneous catalysts and adsorbents which are dependent on their framework topology. For new applications or improvements to existing ones, new zeolites with novel pore systems are desirable. We demonstrate a method for the synthesis of novel zeolites using the ADOR route. ADOR is an acronym for Assembly, Disassembly, Organization and Reassembly. This synthetic route takes advantage of the assembly of a relatively poorly stable that which can be selectively disassembled into a layered material. The resulting layered intermediate can then be organized in different manners by careful chemical manipulation and then reassembled into zeolites with new topologies. By carefully controlling the organization step of the synthetic pathway, new zeolites with never before seen topologies are capable of being synthesized. The structures of these new zeolites are confirmed using powder X-ray diffraction and further characterized by nitrogen adsorption and scanning electron microscopy. This new synthetic pathway for zeolites demonstrates its capability to produce novel frameworks that have never been prepared by traditional zeolite synthesis techniques.

  18. Synthesis of Zeolites Using the ADOR (Assembly-Disassembly-Organization-Reassembly) Route

    PubMed Central

    Wheatley, Paul S.; Čejka, Jiří; Morris, Russell E.

    2016-01-01

    Zeolites are an important class of materials that have wide ranging applications such as heterogeneous catalysts and adsorbents which are dependent on their framework topology. For new applications or improvements to existing ones, new zeolites with novel pore systems are desirable. We demonstrate a method for the synthesis of novel zeolites using the ADOR route. ADOR is an acronym for Assembly, Disassembly, Organization and Reassembly. This synthetic route takes advantage of the assembly of a relatively poorly stable that which can be selectively disassembled into a layered material. The resulting layered intermediate can then be organized in different manners by careful chemical manipulation and then reassembled into zeolites with new topologies. By carefully controlling the organization step of the synthetic pathway, new zeolites with never before seen topologies are capable of being synthesized. The structures of these new zeolites are confirmed using powder X-ray diffraction and further characterized by nitrogen adsorption and scanning electron microscopy. This new synthetic pathway for zeolites demonstrates its capability to produce novel frameworks that have never been prepared by traditional zeolite synthesis techniques. PMID:27078165

  19. Catalytic activities of zeolite compounds for decomposing aqueous ozone.

    PubMed

    Kusuda, Ai; Kitayama, Mikito; Ohta, Yoshio

    2013-12-01

    The advanced oxidation process (AOP), chemical oxidation using aqueous ozone in the presence of appropriate catalysts to generate highly reactive oxygen species, offers an attractive option for removing poorly biodegradable pollutants. Using the commercial zeolite powders with various Si/Al ratios and crystal structures, their catalytic activities for decomposing aqueous ozone were evaluated by continuously flowing ozone to water containing the zeolite powders. The hydrophilic zeolites (low Si/Al ratio) with alkali cations in the crystal structures were found to possess high catalytic activity for decomposing aqueous ozone. The hydrophobic zeolite compounds (high Si/Al ratio) were found to absorb ozone very well, but to have no catalytic activity for decomposing aqueous ozone. Their catalytic activities were also evaluated by using the fixed bed column method. When alkali cations were removed by acid rinsing or substituted by alkali-earth cations, the catalytic activities was significantly deteriorated. These results suggest that the metal cations on the crystal surface of the hydrophilic zeolite would play a key role for catalytic activity for decomposing aqueous ozone.

  20. A high acid mesoporous USY zeolite prepared by alumination

    NASA Astrophysics Data System (ADS)

    Ma, Jinghong; Kang, Yuhong; Ma, Ning; Hao, Wenming; Wang, Yan; Li, Ruifeng

    2013-01-01

    A high-acidity HUSY zeolite with mesoporous structure was prepared by alumination with a dilute aqueous NaAlO2 solution and characterized by XRD, N2 adsorption, IR framework vibration and 29Si MAS NMR methods. The results indicated the extra-framework aluminum was reinserted into the tetrahedral framework through isomorphic substitution of framework Si (0Al) sites by Al ions, whereas the crystal and micropore structure were unaltered. FTIR spectra of hydroxyl vibrations and pyridine adsorbed on realuminated zeolites showed that the number of Brønsted acid sites and strong Lewis acid sites increased whereas weak Lewis acid sites decreased twice. The mesoporous structure composed of inter-and intra-crystalline pores in the aluminated HUSY increased the external surface area of the zeolite, improving accessibility of molecules to the active sites and enhancing its catalytic ability. The realuminated HUSY zeolite supported with Ru catalyst exhibited a higher catalytic activity for benzene hydrogenation than the parent HUSY zeolite; the reaction rate in comparison to the mesozeolite increased by 5.5 times.

  1. The growth of zeolites A, X and mordenite in space

    NASA Technical Reports Server (NTRS)

    Sacco, Albert, Jr.; Bac, N.; Coker, E. N.; Dixon, A. G.; Warzywoda, J.; Thompson, R. W.

    1994-01-01

    Zeolites are a class of crystalline aluminosilicate materials that form the backbone of the chemical process industry worldwide. They are used primarily as adsorbents and catalysts and support to a significant extent the positive balance of trade realized by the chemical industry in the United States (around $19 billion in 1991). The magnitude of their efforts can be appreciated when one realizes that since their introduction as 'cracking catalysts' in the early 1960's, they have saved the equivalent of 60 percent of the total oil production from Alaska's North Slope. Thus the performance of zeolite catalysts can have a profound effect on the U.S. economy. It is estimated that a 1 percent increase in yield of the gasoline fraction per barrel of oil would represent a savings of 22 million barrels of crude oil per year, representing a reduction of $400 million in the United States' balance of payments. Thus any activity that results in improvement in zeolite catalyst performance is of significant scientific and industrial interest. In addition, due to their 'stability,' uniformity, and, within limits, their 'engineerable' structures, zeolites are being tested as potential adsorbents to purify gases and liquids at the parts-per-billion levels needed in today's electronic, biomedical, and biotechnology industries and for the environment. Other exotic applications, such as host materials for quantum-confined semiconductor atomic arrays, are also being investigated. Because of the importance of this class of material, extensive efforts have been made to characterize their structures and to understand their nucleation and growth mechanisms, so as to be able to custom-make zeolites for a desired application. To date, both the nucleation mechanics and chemistry (such as what are the 'key' nutrients) are, as yet, still unknown for many, if not all, systems. The problem is compounded because there is usually a 'gel' phase present that is assumed to control the degree of

  2. Zeolites and Catalysis

    DTIC Science & Technology

    1999-12-15

    financial together as shown in the top line of Fig. 1, the market size (not in terms of tonnage) with an cubo-octahedron, also referred to as a sodalite ...various zeolite structures derive. If This review will cover the basic principles of sodalite units are connected via their hexagonal faces zeolite... Sodalite Unit 0.57 nm x’.1nm ZS - 0 .56 nm --- x 0.53 nm Si0 4 /2 - or -~ ~ IZSM-50.5n A10 dra - Silicalite-1 x 0.51 nm Tetrahedra X Pentasil Unit 0.45 nmx

  3. Rapid synthesis of an aluminum-rich MSE-type zeolite by the hydrothermal conversion of an FAU-type zeolite.

    PubMed

    Inagaki, Satoshi; Tsuboi, Yasuyuki; Nishita, Yuji; Syahylah, Tuan; Wakihara, Toru; Kubota, Yoshihiro

    2013-06-10

    An aluminum-rich MSE-type zeolite (Si/Al is as small as 7) has been successfully synthesized in a remarkably short crystallization period of only 3 days by the hydrothermal conversion of an FAU-type zeolite, presumably by the assembly of four-membered-ring (4-R) aluminosilicate oligomers supplied by the double 6-R (D6R) components of the FAU framework with the aid of the structure-directing agents and seed crystals. The dealuminated version of the aluminum-rich MSE-type zeolite showed a high level of coke durability in addition to a significant yield of propylene, which indicates that this novel zeolitic material is suitable for industrial applications as a highly selective and long-lived catalyst.

  4. Development of a stable cobalt-ruthenium Fisher-Tropsch catalyst. Final report

    SciTech Connect

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

    1995-02-01

    The reverse micelle catalyst preparation method has been used to prepare catalysts on four supports: magnesium oxide, carbon, alumina- titania and steamed Y zeolite. These catalysts were not as active as a reference catalyst prepared during previous contracts to Union Carbide Corp. This catalyst was supported on steamed Y zerolite support and was impregnated by a pore-filling method using a nonaqueous solvent. Additional catalysts were prepared via pore- filling impregnation of steamed Y zeolites. These catalysts had levels of cobalt two to three and a half times as high as the original Union Carbide catalyst. On a catalyst volume basis they were much more active than the previous catalyst; on an atom by atom basis the cobalt was about of the same activity, i.e., the high cobalt catalysts` cobalt atoms were not extensively covered over and deactivated by other cobalt atoms. The new, high activity, Y zerolite catalysts were not as stable as the earlier Union Carbide catalyst. However, stability enhancement of these catalysts should be possible, for instance, through adjustment of the quantity and/or type of trace metals present. A primary objective of this work was determination whether small amounts of ruthenium could enhance the activity of the cobalt F-T catalyst. The reverse micelle catalysts were not activated by ruthenium, indeed scanning transmission electronic microscopy (STEM) analysis provided some evidence that ruthenium was not present in the cobalt crystallites. Ruthenium did not seem to activate the high cobalt Y zeolite catalyst either, but additional experiments with Y zeolite-supported catalysts are required. Should ruthenium prove not to be an effective promoter under the simple catalyst activation procedure used in this work, more complex activation procedures have been reported which are claimed to enhance the cobalt/ruthenium interaction and result in activity promotion by ruthenium.

  5. Hydrogenation of artemisinin to dihydroartemisinin over heterogeneous metal catalysts

    NASA Astrophysics Data System (ADS)

    Kristiani, Anis; Pertiwi, Ralentri; Adilina, Indri Badria

    2017-01-01

    A series of heterogeneous metal catalysts of Ni, Pd, and Pt, both of synthesized and commercial catalysts were used for hydrogenation of artemisinin to dihydroartemisinin. Their catalytic properties were determsined by Surface Area Analyzer and Thermogravimetry Analyzer. The catalytic properties in various reaction conditions in terms of temperature, pressure, reaction time and reactant/catalyst ratio were also studied. The results catalytic activity tests showed that synthesized catalysts of Ni/zeolite, Ni-Sn/zeolite, Ni/bentonite and Ni-Sn/bentonite were not able to produced dihydroartemisinin and deoxyartemisinin was mainly formed. Meanwhile, commercial catalysts of Ni skeletal, Pd/activated charcoal and Pt/activated charcoal yielded the desired dihydroartemisinin product. Ni skeletal commercial catalyst gave the best performance of hydrogenation artemisinin to dihydroartemisinin in room temperature and low H2 pressure.

  6. Zeolite catalysis in the synthesis of isobutylene from hydrous ethanol

    NASA Astrophysics Data System (ADS)

    Phillips, Cory Bernard

    1999-11-01

    containing Pd are the most efficient catalysts for the dimerization reaction. Characterization results from x-ray diffraction (XRD), electron paramagnetic resonance (EPR) spectroscopy, and CTPAD suggest a stable, Pd species with a low oxidation state as part of the active site in Pd-exchanged zeolites. Isobutylene was present in the C4 fraction at reasonable quantities for most of the catalyst candidates, especially those containing an alkali metal co-cation.

  7. Zeolite crystal growth in space

    NASA Technical Reports Server (NTRS)

    Sacco, Albert, Jr.; Thompson, Robert W.; Dixon, Anthony G.

    1991-01-01

    The growth of large, uniform zeolite crystals in high yield in space can have a major impact on the chemical process industry. Large zeolite crystals will be used to improve basic understanding of adsorption and catalytic mechanisms, and to make zeolite membranes. To grow large zeolites in microgravity, it is necessary to control the nucleation event and fluid motion, and to enhance nutrient transfer. Data is presented that suggests nucleation can be controlled using chemical compounds (e.g., Triethanolamine, for zeolite A), while not adversely effecting growth rate. A three-zone furnace has been designed to perform multiple syntheses concurrently. The operating range of the furnace is 295 K to 473 K. Teflon-lined autoclaves (10 ml liquid volume) have been designed to minimize contamination, reduce wall nucleation, and control mixing of pre-gel solutions on orbit. Zeolite synthesis experiments will be performed on USML-1 in 1992.

  8. Catalysts for conversion of syngas to liquid motor fuels

    DOEpatents

    Rabo, Jule A.; Coughlin, Peter K.

    1987-01-01

    Synthesis gas comprising carbon monoxide and hydrogen is converted to C.sub.5.sup.+ hydrocarbons suitable for use as liquid motor fuels by contact with a dual catalyst composition capable of ensuring the production of only relatively minor amounts of heavy products boiling beyond the diesel oil range. The catalyst composition, having desirable stability during continuous production operation, employs a Fischer-Tropsch catalyst, together with a co-catalyst/support component. The latter component is a steam-stabilized zeolite Y catalyst of hydrophobic character, desirably in acid-extracted form.

  9. Synthesis and characterization of mesoporous hydrocracking catalysts

    NASA Astrophysics Data System (ADS)

    Munir, D.; Usman, M. R.

    2016-08-01

    Mesoporous catalysts have shown great prospective for catalytic reactions due to their high surface area that aids better distribution of impregnated metal. They have been found to contain more adsorption sites and controlled pore diameter. Hydrocracking, in the presence of mesoporous catalyst is considered more efficient and higher conversion of larger molecules is observed as compared to the cracking reactions in smaller microporous cavities of traditional zeolites. In the present study, a number of silica-alumina based mesoporous catalysts are synthesized in the laboratory. The concentration and type of surfactants and quantities of silica and alumina sources are the variables studied in the preparation of catalyst supports. The supports prepared are well characterized using SEM, EDX, and N2-BET techniques. Finally, the catalysts are tested in a high pressure autoclave reactor to study the activity and selectivity of the catalysts for the hydrocracking of a model mixture of plastics comprising of LDPE, HDPE, PP, and PS.

  10. Zeolites as nanoporous, gas-sensitive materials for in situ monitoring of DeNOx-SCR

    PubMed Central

    Simons, Thomas

    2012-01-01

    Summary In a proof-of-concept study we demonstrate in situ reaction monitoring of DeNOx-SCR on proton-conducting zeolites serving as catalyst and gas sensor at the same time. By means of temperature-dependent impedance spectroscopy we found that the thermally induced NH3 desorption in H-form and in Fe-loaded zeolite H-ZSM-5 follow the same process, while a remarkable difference under DeNOx-SCR reaction conditions was found. The Fe-loaded catalyst shows a significantly lower onset temperature, and time-dependent measurements suggest different SCR reaction mechanisms for the two catalysts tested. These results may help in the development of catalysts for the reduction of NOx emissions and ammonia consumption, and provide insight into the elementary catalytic process promoting a full description of the NH3-SCR reaction system. PMID:23213630

  11. Adsorption and photocatalytic degradation of pharmaceuticals and pesticides by carbon doped-TiO2 coated on zeolites under solar light irradiation.

    PubMed

    An, Ye; de Ridder, David Johannes; Zhao, Chun; Schoutteten, Klaas; Bussche, Julie Vanden; Zheng, Huaili; Chen, Gang; Vanhaecke, Lynn

    2016-01-01

    To evaluate the performance of zeolite-supported carbon-doped TiO(2) composite catalysts toward target pollutants under solar light irradiation, the adsorption and photocatalytic degradation of 18 pharmaceuticals and pesticides with distinguishing features (molecular size and volume, and photolysis) were investigated using mordenite zeolites with SiO(2)/Al(2)O(3) ratios of 18 and 240. Different quantities of carbon-doped TiO(2) were coated on the zeolites, and then the finished composite catalysts were tested in demineralized, surface, and hospital wastewater samples, respectively. The composite photocatalysts were characterized by X-ray diffraction, field emission scanning electron microscopy, and surface area and porosity analyses. Results showed that a dispersed layer of carbon-doped TiO(2) is formed on the zeolite surface; this layer blocks the micropores of zeolites and reduces their surface area. However, these reductions did not significantly affect adsorption onto the zeolites. Our results demonstrated that zeolite-supported carbon-doped TiO(2) systems can effectively degrade 18 pharmaceuticals and pesticides in demineralized water under natural and simulated solar light irradiation. In surface and hospital wastewaters, zeolite-supported carbon-doped TiO(2) systems present excellent anti-interference capability against radical scavengers and competitive organics for pollutants removal, and higher pollutants adsorption on zeolites evidently enhances the removal rate of target pollutants in surface and hospital wastewater samples with a complicated matrix.

  12. Squaraines inside Zeolites: Preparation, Stability, and Photophysical Properties.

    PubMed

    Cano, María Luz; Cozens, Frances L.; Esteves, María A.; Márquez, Francisco; García, Hermenegildo

    1997-10-17

    A series of four symmetrical squaraines (ditoylyl, di-m-xylyl, dianisyl, and diresorcinyl) incorporated inside zeolites Y, mordenite, and ZSM-5 have been obtained by treating squaric acid and the corresponding arene in the presence of acid zeolites. Acid sites and high reaction temperatures (150 degrees C) were found to be crucial for the success of the preparation procedure. Surprisingly, this method failed for the preparation of the squaraine derived from N,N-dimethylaniline, which is known to be readily formed from squaric acid in homogeneous phase without a catalyst. The solid samples containing squaraines were characterized by diffuse reflectance and Raman spectroscopies and by thermogravimetry-differential scanning calorimetry. Among the hosts, mordenite was found to be the most general and convenient zeolite for the preparation of the squaraines, while in the other solids either the organic content adsorbed was comparatively smaller (ZSM-5) or some squaraines were not very stable (Y zeolite for ditolyl and dixylyl squaraines). The absorption spectra of the samples correspond to the J-aggregation state of the squaraines, except for some ZSM-5 samples, where simultaneous observation of the bands due to both monomers and aggregates occurs. Aggregation also changes with the water content of the samples. Treatment of the zeolite-bound diresorcinyl squaraine with basic aqueous solutions leads to remarkable variations in the diffuse reflectance and Raman spectra. These changes in the Raman spectrum of the diresorcinyl squaraine were found to be reversible by basic or acid washings. Laser flash photolysis using the 355- or 532-nm output of a Nd-YAG laser (<10 ns pulses; zeolite host. On the basis of the similarity of the UV-vis absorption spectra obtained in solution, these transients have been identified as the radical cation (HY) and the triplet excited

  13. Novel modified zeolites for energy-efficient hydrocarbon separations.

    SciTech Connect

    Arruebo, Manuel; Dong, Junhang; Anderson, Thomas (Burns and McDonnell, Kansas City, MO); Gu, Xuehong; Gray, Gary (Goodyear Chemical Company, Akron, OH); Bennett, Ron (Goodyear Chemical Company, Akron, OH); Nenoff, Tina Maria; Kartin, Mutlu; Johnson, Kaylynn (Goodyear Chemical Company, Akron, OH); Falconer, John; Noble, Richard

    2006-11-01

    We present synthesis, characterization and testing results of our applied research project, which focuses on the effects of surface and skeletal modification of zeolites for significant enhancements in current hydrocarbon (HC) separations. Zeolites are commonly used by the chemical and petroleum industries as catalysts and ion-exchangers. They have high potential for separations owing to their unique pore structures and adsorption properties and their thermal, mechanical and chemical properties. Because of zeolites separation properties, low cost, and robustness in industrial process, they are natural choice for use as industrial adsorbents. This is a multidisciplinary effort to research, design, develop, engineer, and test new and improved materials for the separation of branched vs. linear organic molecules found in commercially important HC streams via adsorption based separations. The focus of this project was the surface and framework modification of the commercially available zeolites, while tuning the adsorption properties and the selectivities of the bulk and membrane separations. In particular, we are interested with our partners at Goodyear Chemical, on how to apply the modified zeolites to feedstock isoprene purification. For the characterization and the property measurements of the new and improved materials powder X-ray diffraction (PXRD), Residual Gas Analyzer-Mass Spectroscopy (RGA-MS), Electron Microscopy (SEM/EDAX), temperature programmed desorption (TPD) and surface area techniques were utilized. In-situ carbonization of MFI zeolite membranes allowed for the maximum separation of isoprene from n-pentane, with a 4.1% enrichment of the binary stream with n-pentane. In four component streams, a modified MFI membrane had high selectivities for n-pentane and 1-3-pentadiene over isoprene but virtually no separation for the 2-methyl-2-butene/isoprene pair.

  14. Trimethylamine as a probe molecule to differentiate acid sites in Y-FAU zeolite: FTIR study.

    PubMed

    Sarria, Francisca Romero; Blasin-Aubé, Vanessa; Saussey, Jacques; Marie, Olivier; Daturi, Marco

    2006-07-06

    In heterogeneous catalysis acidity has a very important influence on activity and selectivity: correct determination of acidic properties is a base to improve industrial processes. The aim of this work was to study trimethylamine (TMA) as a probe molecule able to distinguish between the different Brønsted acid sites in zeolitic frameworks. Our work mainly focused on faujasite-type zeolites because the HY zeolite is one of the most used acidic catalysts in industrial processes. In this paper, typical IR bands assigned to TMA-protonated species (formed in supercages) are detected in the HY zeolite. TMA interacting by hydrogen bonding with the acid sites located in the sodalite units is also observed. The wavenumbers of some typical IR bands assigned to TMA-protonated species appear to depend on the acidic strength, and a complementary study with ZSM-5 and X-FAU samples confirms this proposition.

  15. Hierarchical Macro-meso-microporous ZSM-5 Zeolite Hollow Fibers With Highly Efficient Catalytic Cracking Capability

    PubMed Central

    Liu, Jia; Jiang, Guiyuan; Liu, Ying; Di, Jiancheng; Wang, Yajun; Zhao, Zhen; Sun, Qianyao; Xu, Chunming; Gao, Jinsen; Duan, Aijun; Liu, Jian; Wei, Yuechang; Zhao, Yong; Jiang, Lei

    2014-01-01

    Zeolite fibers have attracted growing interest for a range of new applications because of their structural particularity while maintaining the intrinsic performances of the building blocks of zeolites. The fabrication of uniform zeolite fibers with tunable hierarchical porosity and further exploration of their catalytic potential are of great importance. Here, we present a versatile and facile method for the fabrication of hierarchical ZSM-5 zeolite fibers with macro-meso-microporosity by coaxial electrospinning. Due to the synergistic integration of the suitable acidity and the hierarchical porosity, high yield of propylene and excellent anti-coking stability were demonstrated on the as-prepared ZSM-5 hollow fibers in the catalytic cracking reaction of iso-butane. This work may also provide good model catalysts with uniform wall thickness and tunable porosity for studying a series of important catalytic reactions. PMID:25450726

  16. Efficient isomerization of glucose to fructose over zeolites in consecutive reactions in alcohol and aqueous media.

    PubMed

    Saravanamurugan, Shunmugavel; Paniagua, Marta; Melero, Juan A; Riisager, Anders

    2013-04-10

    Isomerization reactions of glucose were catalyzed by different types of commercial zeolites in methanol and water in two reaction steps. The most active catalyst was zeolite Y, which was found to be more active than the zeolites beta, ZSM-5, and mordenite. The novel reaction pathway involves glucose isomerization to fructose and subsequent reaction with methanol to form methyl fructoside (step 1), followed by hydrolysis to re-form fructose after water addition (step 2). NMR analysis with (13)C-labeled sugars confirmed this reaction pathway. Conversion of glucose for 1 h at 120 °C with H-USY (Si/Al = 6) gave a remarkable 55% yield of fructose after the second reaction step. A main advantage of applying alcohol media and a catalyst that combines Brønsted and Lewis acid sites is that glucose is isomerized to fructose at low temperatures, while direct conversion to industrially important chemicals like alkyl levulinates is viable at higher temperatures.

  17. Oxidation catalyst

    DOEpatents

    Ceyer, Sylvia T.; Lahr, David L.

    2010-11-09

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

  18. Zeolitic Boron Imidazolate Frameworks**

    PubMed Central

    Zhang, Jian; Wu, Tao; Zhou, Cong; Chen, Shumei; Feng, Pingyun; Bu, Xianhui

    2009-01-01

    From porous AlPO4 to porous BIFs Reported here are a family of crystalline materials based on boron imidazolate frameworks (BIFs). It is demonstrated that the synthetic method, which is based on the crosslinking of various pre-synthesized boron imidazolates by monovalent cations (Li+ and Cu+), is capable of generating a large variety of open frameworks ranging from the 4-connected zeolitic sodalite type to the 3-connected chiral (10,3)-a type. PMID:19241428

  19. Stability of a Bifunctional Cu-Based Core@Zeolite Shell Catalyst for Dimethyl Ether Synthesis Under Redox Conditions Studied by Environmental Transmission Electron Microscopy and In Situ X-Ray Ptychography.

    PubMed

    Baier, Sina; Damsgaard, Christian D; Klumpp, Michael; Reinhardt, Juliane; Sheppard, Thomas; Balogh, Zoltan; Kasama, Takeshi; Benzi, Federico; Wagner, Jakob B; Schwieger, Wilhelm; Schroer, Christian G; Grunwaldt, Jan-Dierk

    2017-04-05

    When using bifunctional core@shell catalysts, the stability of both the shell and core-shell interface is crucial for catalytic applications. In the present study, we elucidate the stability of a CuO/ZnO/Al2O3@ZSM-5 core@shell material, used for one-stage synthesis of dimethyl ether from synthesis gas. The catalyst stability was studied in a hierarchical manner by complementary environmental transmission electron microscopy (ETEM), scanning electron microscopy (SEM) and in situ hard X-ray ptychography with a specially designed in situ cell. Both reductive activation and reoxidation were applied. The core-shell interface was found to be stable during reducing and oxidizing treatment at 250°C as observed by ETEM and in situ X-ray ptychography, although strong changes occurred in the core on a 10 nm scale due to the reduction of copper oxide to metallic copper particles. At 350°C, in situ X-ray ptychography indicated the occurrence of structural changes also on the µm scale, i.e. the core material and parts of the shell undergo restructuring. Nevertheless, the crucial core-shell interface required for full bifunctionality appeared to remain stable. This study demonstrates the potential of these correlative in situ microscopy techniques for hierarchically designed catalysts.

  20. Method for the preparation of catalyst composition for use in cracking hydrocarbons

    SciTech Connect

    Nishimura, Y.; Ogata, M.; Ida, T.

    1987-01-13

    A method is described for preparing a catalyst composition for cracking hydrocarbons, which consists essentially of: spray drying an aqueous slurry containing (i) flash calcined alumina particles which have been prepared by contacting aluminum hydroxide which has been made by the Bayer process, with hot air having a temperature in the range of 350/sup 0/ to 700/sup 0/C., for 5 seconds or less, (ii) kaolin, (iii) a precursor of a siliceous inorganic oxide matrix, and (iv) a crystalline aluminosilicate zeolite, to obtain catalyst particles consisting essentially of from 10 to 30 wt. % of the flash-calcined alumina, from 30 to 55 wt. % of the kaolin, from 3 to 40 wt. % crystalline aluminosilicate zeolite and the balance is the siliceous inorganic oxide matrix. A method is also described in which the zeolite is rare earth exchange zeolite Y or hydrogen exchanged zeolite Y.

  1. Improved zeolite regeneration processes for preparing saturated branched-chain fatty acids

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Ferrierite zeolite solid is an excellent catalyst for the skeletal isomerization of unsaturated linear-chain fatty acids (i.e., oleic acid) to unsaturated branched-chain fatty acids (i.e., iso-oleic acid) follow by hydrogenation to give saturated branched-chain fatty acids (i.e., isostearic acid). ...

  2. Fixation of carbon dioxide into dimethyl carbonate over titanium-based zeolitic thiophene-benzimidazolate framework

    EPA Science Inventory

    A titanium-based zeolitic thiophene-benzimidazolate framework has been designed for the direct synthesis of dimethyl carbonate (DMC) from methanol and carbon dioxide. The developed catalyst activates carbon dioxide and delivers over 16% yield of DMC without the use of any dehydra...

  3. Zeolite vitrification demonstration program: characterization of radioactive vitrified zeolite materials

    SciTech Connect

    Barner, J O; Daniel, J L; Marshall, R K

    1984-01-01

    The leach behavior of radioactive vitrified zeolite material was studied as part of the Three Mile Island (TMI) Zeolite Vitrification Program conducted by Pacific Northwest Laboratory (PNL). Experimental procedures, test results, and discussions of the results are presented. The leach behavior of material from three canisters of vitrified zeolite is discussed in terms of the normalized weight loss of the glass-formers and the normalized activity loss of the fission products cesium and strontium. The leach behavior of the radioactive vitrified zeolite material is also compared to the leach behavior of MCC 76-68 reference glass. The effects of changes in the surface microstructure of the vitrified zeolite that occurred during leaching are also presented. 3 references, 23 figures, 10 tables.

  4. State of the art of Lewis acid-containing zeolites: lessons from fine chemistry to new biomass transformation processes.

    PubMed

    Moliner, Manuel

    2014-03-21

    The former synthesis of TS-1 opened new catalytic opportunities for zeolites, especially for their application as selective redox catalysts in several fine chemistry processes. Interestingly, isolated Ti species in the framework positions of hydrophobic zeolites, such as high silica zeolites, offer unique Lewis acid sites even in the presence of protic polar solvents (such as water). Following this discovery, other transition metals (such as Sn, Zr, V, Nb, among others) have been introduced in the framework positions of different hydrophobic zeolitic structures, allowing their application in new fine chemistry processes as very active and selective redox catalysts. Recently, these hydrophobic metallozeolites have been successfully applied as efficient catalysts for several biomass-transformation processes in bulk water. The acquired knowledge from the former catalytic descriptions in fine chemistry processes using hydrophobic Lewis acid-containing zeolites has been essential for their application in these novel biomass transformations. In the present review, I will describe the recent advances in the synthesis of new transition metal-containing zeolites presenting Lewis acid character, and their unique catalytic applications in both fine chemistry and novel biomass-transformations.

  5. New approach to the generation of metal-bearing, medium-pore, shape-selective zeolites for Fischer-Tropsch catalysis. Spectroscopic studies of zeolites

    SciTech Connect

    Iton, L.E.; Beal, R.B.; Hodul, D.T.

    1983-01-01

    Two recent developments in zeolite synthesis and modification were successfully combined to demonstrate a new approach to the generation of metal-bearing, medium-pore, shape-selective zeolites for use as catalysts in Fischer-Tropsch conversions. The steps are: (1) synthesis of an aluminoferrisilicate zeolite having the ZSM-5-type structure; (2) removal of the organic base template incorporated in the channel system during synthesis; (3) formation of a polycyano inclusion compound in the AFS zeolite; and (4) reduction of the inclusion compound by hydrogen at approx. 400/sup 0/C. PAS and EPR spectroscopy have been used to establish that the as-synthesized AFS zeolite contains Fe/sup 3 +/ ions in both framework and non-framework sites. FMR spectroscopy has been used to confirm the formation of the metallic (Fe) and bimetallic (Fe/Ru and Fe/Co) particles as products of the reduction of the inclusion compounds by hydrogen. The application of other spectroscopic techniques in recent studies of cations, complexes, and metal particles in zeolites is reviewed: high-resolution solid-state NMR, nuclear-spin-relaxation studies, FMR, EXAFS, and XANES.

  6. Conductivity in zeolite-polymer composite membranes for PEMFCs

    NASA Astrophysics Data System (ADS)

    Sancho, T.; Soler, J.; Pina, M. P.

    Structured materials, such as zeolites can be candidates to be used as electrolytes in proton exchange membrane fuel cells (PEMFC) to substitute polymeric membranes, taking advantage of their higher chemical and thermal stability and their specific adsorption properties. The possibility to work at temperatures of nearly 150 °C would make easy the selection of the fuel, decreasing the influence of CO in the catalyst poisoning, and it would also improve the kinetics of the electrochemical reactions involved. In this work, four zeolites and related materials have been studied: mordenite, NaA zeolite, umbite and ETS-10. In special, the influence of relative humidity and temperature have been carefully explored. A conductivity cell was designed and built to measure in cross direction, by using the electrochemical impedance spectroscopy. The experimental system was validated using Nafion ® as a reference material by comparing the results with bibliography data. Samples were prepared by pressing the zeolite powders, with size of 1 μm on average, using polymer PVDF (10 wt.%) as a binder. The results here obtained, in spite of not reaching the absolute values of the Nafion ® ones, show a lower effect of the dehydration phenomenon on the conduction performance in the temperature range studied (from room temperature to 150 °C). This increase of the operation temperature range would give important advantages to the PEMFC. ETS-10 sample shows the best behaviour with respect to conductivity exhibiting an activation energy value comparable with reported for Nafion ® membrane.

  7. Catalytic pyrolysis using UZM-44 aluminosilicate zeolite

    DOEpatents

    Nicholas, Christopher P; Boldingh, Edwin P

    2014-04-29

    A new family of aluminosilicate zeolites designated UZM-44 has been synthesized. These zeolites are represented by the empirical formula. Na.sub.nM.sub.m.sup.k+T.sub.tAl.sub.1-xE.sub.xSi.sub.yO.sub.z where "n" is the mole ratio of Na to (Al+E), M represents a metal or metals from zinc, Group 1, Group 2, Group 3 and or the lanthanide series of the periodic table, "m" is the mole ratio of M to (Al+E), "k" is the average charge of the metal or metals M, T is the organic structure directing agent or agents, and E is a framework element such as gallium. The process involves contacting a carbonaceous biomass feedstock with UZM-44 at pyrolysis conditions to produce pyrolysis gases comprising hydrocarbons. The catalyst catalyzes a deoxygenation reaction converting oxygenated hydrocarbons into hydrocarbons and removing the oxygen as carbon oxides and water. A portion of the pyrolysis gases is condensed to produce low oxygen biomass-derived pyrolysis oil.

  8. Catalytic pyrolysis using UZM-44 aluminosilicate zeolite

    DOEpatents

    Nicholas, Christopher P; Boldingh, Edwin P

    2013-12-17

    A new family of aluminosilicate zeolites designated UZM-44 has been synthesized. These zeolites are represented by the empirical formula Na.sub.nM.sub.m.sup.k+T.sub.tAl.sub.1-xE.sub.xSi.sub.yO.sub.z where "n" is the mole ratio of Na to (Al+E), M represents a metal or metals from zinc, Group 1, Group 2, Group 3 and or the lanthanide series of the periodic table, "m" is the mole ratio of M to (Al+E), "k" is the average charge of the metal or metals M, T is the organic structure directing agent or agents, and E is a framework element such as gallium. The process involves contacting a carbonaceous biomass feedstock with UZM-44 at pyrolysis conditions to produce pyrolysis gases comprising hydrocarbons. The catalyst catalyzes a deoxygenation reaction converting oxygenated hydrocarbons into hydrocarbons and removing the oxygen as carbon oxides and water. A portion of the pyrolysis gases is condensed to produce low oxygen biomass-derived pyrolysis oil.

  9. Understanding the dissolution of zeolites.

    PubMed

    Hartman, Ryan L; Fogler, H Scott

    2007-05-08

    Scientific knowledge of how zeolites, a unique classification of microporous aluminosilicates, undergo dissolution in aqueous hydrochloric acid solutions is limited. Understanding the dissolution of zeolites is fundamental to a number of processes occurring in nature and throughout industry. To better understand the dissolution process, experiments were carried out establishing that the Si-to-Al ratio controls zeolite framework dissolution, by which the selective removal of aluminum constrains the removal of silicon. Stoichiometric dissolution is observed for Type 4A zeolite in HCl where the Si-to-Al ratio is equal to 1.0. Framework silicon dissolves completely during Type 4A dissolution and is followed by silicate precipitation. However, for the zeolite analcime which has a Si-to-Al ratio of 2.0 dissolves non-stoichiometrically as the selective removal of aluminum results in partially dissolved silicate particles followed by silicate precipitation. In Type Y zeolite, exhibiting a Si-to-Al ratio of 3.0, there is insufficient aluminum to weaken the structure and cause silicon to dissolve in HCl. Thus, little or no precipitation is observed, and amorphous undissolvable silicate particles remain intact. The initial dissolution rates of Type Y and 4A zeolites demonstrate that dissolution is constrained by the number of available reaction sites, and a selective removal rate parameter is applied to delineate the mechanism of particle dissolution by demonstrating the kinetic influence of the Si-to-Al ratio. Zeolite framework models are constructed and used to undergird the basic dissolution mechanism. The framework models, scanning electron micrographs of partially dissolved crystals, and experimentally measured dissolution rates all demonstrate that a zeolite's Si-to-Al framework ratio plays a universal role in the dissolution mechanism, independent of framework type. Consequently, the unique mechanism of zeolite dissolution has general implications on how petroleum

  10. Comparative effect of organosulfur compounds on catalysts for the n-heptane isomerization reaction at medium pressure: Mo{sub 2}C-oxygen-modified, MoO{sub 3}-carbon-modified, Pt/{gamma}-Al{sub 2}O{sub 3}, and Pt/{beta}-zeolite catalysts

    SciTech Connect

    York, A.P.E.; Pham-Huu, C.; Del Gallo, P.; Ledoux, M.J.; Blekkan, E.A.

    1996-03-01

    Molybdenum oxycarbide formed from oxidized Mo{sub 2}C or reduced MoO{sub 3} is an active and very selective catalyst for the isomerization of n-heptane compared to supported Pt. Deactivation experiments performed on the catalysts with different concentrations of organosulfur compounds show that molybdenum oxycarbide exhibits a very high resistance to deactivation, whereas with platinum-based catalysts deactivation occurs even at low sulfur concentration in the feed. Deactivation can be slowed by increasing the hydrogen partial pressure from 6 to 20 bar. In these conditions, the molybdenum oxycarbide shows no deactivation with sulfur concentrations up to 120 ppm of S. In addition, the deactivated molybdenum catalysts can be easily regenerated by mild oxidative treatment under flowing air at atmospheric pressure and 723 K for 2 h followed by a reactivation period under the hydrogen and hydrocarbon mixture.

  11. Oxygen and hydrogen isotope geochemistry of zeolites

    NASA Technical Reports Server (NTRS)

    Karlsson, Haraldur R.; Clayton, Robert N.

    1990-01-01

    Oxygen and hydrogen isotope ratios for natural samples of the zeolites analcime, chabazite, clinoptilolite, laumontite, mordenite, and natrolite have been obtained. The zeolite samples were classified into sedimentary, hydrothermal, and igneous groups. The ratios for each species of zeolite are reported. The results are used to discuss the origin of channel water, the role of zeolites in water-rock interaction, and the possibility that a calibrated zeolite could be used as a low-temperature geothermometer.

  12. Hierarchical zeolites and their catalytic performance in selective oxidative processes.

    PubMed

    Ojeda, Manuel; Grau-Atienza, Aida; Campos, Rafael; Romero, Antonio A; Serrano, Elena; Maria Marinas, Jose; García Martínez, Javier; Luque, Rafael

    2015-04-24

    Hierarchical ZSM-5 zeolites prepared using a simple alkali treatment and subsequent HCl washing are found to exhibit unprecedented catalytic activities in selective oxidation of benzyl alcohol under microwave irradiation. The metal-free zeolites promote the microwave-assisted oxidation of benzyl alcohol with hydrogen peroxide in yields ranging from 45-35 % after 5 min of reaction under mild reaction conditions as well as the epoxidation of cyclohexene to valuable products (40-60 % conversion). The hierarchically porous systems also exhibited an interesting catalytic activity in the dehydration of N,N-dimethylformamide (25-30 % conversion), representing the first example of transition-metal free catalysts in this reaction.

  13. Shape-selective zeolite catalysis for bioplastics production

    NASA Astrophysics Data System (ADS)

    Dusselier, Michiel; Van Wouwe, Pieter; Dewaele, Annelies; Jacobs, Pierre A.; Sels, Bert F.

    2015-07-01

    Biodegradable and renewable polymers, such as polylactic acid, are benign alternatives for petrochemical-based plastics. Current production of polylactic acid via its key building block lactide, the cyclic dimer of lactic acid, is inefficient in terms of energy, time, and feedstock use. We present a direct zeolite-based catalytic process, which converts lactic acid into lactide. The shape-selective properties of zeolites are essential to attain record lactide yields, outperforming those of the current multistep process by avoiding both racemization and side-product formation. The highly productive process is strengthened by facile recovery and practical reactivation of the catalyst, which remains structurally fit during at least six consecutive reactions, and by the ease of solvent and side-product recycling.

  14. Template-free nanosized faujasite-type zeolites

    NASA Astrophysics Data System (ADS)

    Awala, Hussein; Gilson, Jean-Pierre; Retoux, Richard; Boullay, Philippe; Goupil, Jean-Michel; Valtchev, Valentin; Mintova, Svetlana

    2015-04-01

    Nanosized faujasite (FAU) crystals have great potential as catalysts or adsorbents to more efficiently process present and forthcoming synthetic and renewable feedstocks in oil refining, petrochemistry and fine chemistry. Here, we report the rational design of template-free nanosized FAU zeolites with exceptional properties, including extremely small crystallites (10-15 nm) with a narrow particle size distribution, high crystalline yields (above 80%), micropore volumes (0.30 cm3 g-1) comparable to their conventional counterparts (micrometre-sized crystals), Si/Al ratios adjustable between 1.1 and 2.1 (zeolites X or Y) and excellent thermal stability leading to superior catalytic performance in the dealkylation of a bulky molecule, 1,3,5-triisopropylbenzene, probing sites mostly located on the external surface of the nanosized crystals. Another important feature is their excellent colloidal stability, which facilitates a uniform dispersion on supports for applications in catalysis, sorption and thin-to-thick coatings.

  15. GREEN CHEMISTRY. Shape-selective zeolite catalysis for bioplastics production.

    PubMed

    Dusselier, Michiel; Van Wouwe, Pieter; Dewaele, Annelies; Jacobs, Pierre A; Sels, Bert F

    2015-07-03

    Biodegradable and renewable polymers, such as polylactic acid, are benign alternatives for petrochemical-based plastics. Current production of polylactic acid via its key building block lactide, the cyclic dimer of lactic acid, is inefficient in terms of energy, time, and feedstock use. We present a direct zeolite-based catalytic process, which converts lactic acid into lactide. The shape-selective properties of zeolites are essential to attain record lactide yields, outperforming those of the current multistep process by avoiding both racemization and side-product formation. The highly productive process is strengthened by facile recovery and practical reactivation of the catalyst, which remains structurally fit during at least six consecutive reactions, and by the ease of solvent and side-product recycling.

  16. Decoupling HZSM-5 catalyst activity from deactivation during upgrading of pyrolysis oil vapors.

    PubMed

    Wan, Shaolong; Waters, Christopher; Stevens, Adam; Gumidyala, Abhishek; Jentoft, Rolf; Lobban, Lance; Resasco, Daniel; Mallinson, Richard; Crossley, Steven

    2015-02-01

    The independent evaluation of catalyst activity and stability during the catalytic pyrolysis of biomass is challenging because of the nature of the reaction system and rapid catalyst deactivation that force the use of excess catalyst. In this contribution we use a modified pyroprobe system in which pulses of pyrolysis vapors are converted over a series of HZSM-5 catalysts in a separate fixed-bed reactor controlled independently. Both the reactor-bed temperature and the Si/Al ratio of the zeolite are varied to evaluate catalyst activity and deactivation rates independently both on a constant surface area and constant acid site basis. Results show that there is an optimum catalyst-bed temperature for the production of aromatics, above which the production of light gases increases and that of aromatics decrease. Zeolites with lower Si/Al ratios give comparable initial rates for aromatics production, but far more rapid catalyst deactivation rates than those with higher Si/Al ratios.

  17. Regeneration of Hydrotreating and FCC Catalysts

    SciTech Connect

    CM Wai; JG Frye; JL Fulton; LE Bowman; LJ Silva; MA Gerber

    1999-09-30

    Y zeolite in a silica-alumina matrix. X-ray fluorescence analyses showed that the rare earths used in preparing the catalysts were a mixture of lanthanum and cerium. Antimony found in the spent catalyst was added during operation of the FCC unit as a way to suppress the adverse effects of deposited nickel. The fresh HDS samples consisted of sulfided nickel and molybdenum on an alumina support. The spent catalyst showed nearly 10% vanadium on the catalyst and a modest increase in nickel and sulfur on the catalyst as a result of operations. Hydrocracking catalysts were not available for this study.

  18. Nano Catalysts for Diesel Engine Emission Remediation

    SciTech Connect

    Narula, Chaitanya Kumar; Yang, Xiaofan; Debusk, Melanie Moses; Mullins, David R; Mahurin, Shannon Mark; Wu, Zili

    2012-06-01

    The objective of this project was to develop durable zeolite nanocatalysts with broader operating temperature windows to treat diesel engine emissions to enable diesel engine based equipment and vehicles to meet future regulatory requirements. A second objective was to improve hydrothermal durability of zeolite catalysts to at least 675 C. The results presented in this report show that we have successfully achieved both objectives. Since it is accepted that the first step in NO{sub x} conversion under SCR (selective catalytic reduction) conditions involves NO oxidation to NO{sub 2}, we reasoned that catalyst modification that can enhance NO oxidation at low-temperatures should facilitate NO{sub x} reduction at low temperatures. Considering that Cu-ZSM-5 is a more efficient catalyst than Fe-ZSM-5 at low-temperature, we chose to modify Cu-ZSM-5. It is important to point out that the poor low-temperature efficiency of Fe-ZSM-5 has been shown to be due to selective absorption of NH{sub 3} at low-temperatures rather than poor NO oxidation activity. In view of this, we also reasoned that an increased electron density on copper in Cu-ZSM-5 would inhibit any bonding with NH{sub 3} at low-temperatures. In addition to modified Cu-ZSM-5, we synthesized a series of new heterobimetallic zeolites, by incorporating a secondary metal cation M (Sc{sup 3+}, Fe{sup 3+}, In{sup 3+}, and La{sup 3+}) in Cu exchanged ZSM-5, zeolite-beta, and SSZ-13 zeolites under carefully controlled experimental conditions. Characterization by diffuse-reflectance ultra-violet-visible spectroscopy (UV-Vis), X-ray powder diffraction (XRD), extended X-ray absorption fine structure spectroscopy (EXAFS) and electron paramagnetic resonance spectroscopy (EPR) does not permit conclusive structural determination but supports the proposal that M{sup 3+} has been incorporated in the vicinity of Cu(II). The protocols for degreening catalysts, testing under various operating conditions, and accelerated aging

  19. Studying Two-Dimensional Zeolites with the Tools of Surface Science: MFI Nanosheets on Au(111)

    DOE PAGES

    J. D. Kestell; Zhong, J. Q.; Shete, M.; ...

    2016-07-26

    While surface science has provided fundamental insights into a variety a materials, the most used catalysts in the industry, namely zeolites, still remain a challenge. The recent preparation of two-dimensional versions of MFI zeolite frameworks and the possibility of their deposition on electrically conductive supports provides for the first time a viable strategy to perform detailed studies on industrially relevant zeolites using the vast toolkit of surface science. In this work we demonstrate the use of infrared reflection absorption spectroscopy (IRRAS) and synchrotron-based x-ray photoelectron spectroscopy (XPS) to study these materials. Furthermore, polarization modulation IRRAS is used to study themore » adsorption of methanol and its effect in phonon vibrations of the zeolite framework. The possibility of using surface science methods, in particular under ambient pressure conditions, for the study of well-defined zeolites and other microporous structures opens new avenues to understand structural and mechanistic aspects of these materials as catalysts, adsorbents and molecular sieves.« less

  20. Properties and applications of zeolites.

    PubMed

    Rhodes, Christopher J

    2010-01-01

    Zeolites are aluminosilicate solids bearing a negatively charged honeycomb framework of micropores into which molecules may be adsorbed for environmental decontamination, and to catalyse chemical reactions. They are central to green-chemistry since the necessity for organic solvents is minimised. Proton-exchanged (H) zeolites are extensively employed in the petrochemical industry for cracking crude oil fractions into fuels and chemical feedstocks for other industrial processes. Due to their ability to perform cation-exchange, in which the cations that are originally present to counterbalance the framework negative charge may be exchanged out of the zeolite by cations present in aqueous solution, zeolites are useful as industrial water-softeners, in the removal of radioactive Cs+ and Sr2+ cations from liquid nuclear waste and in the removal of toxic heavy metal cations from groundwaters and run-off waters. Surfactant-modified zeolites (SMZ) find particular application in the co-removal of both toxic anions and organic pollutants. Toxic anions such as arsenite, arsenate, chromate, cyanide and radioactive iodide can also be removed by adsorption into zeolites that have been previously loaded with co-precipitating metal cations such as Ag+ and Pb2+ which form practically insoluble complexes that are contained within the zeolite matrix.

  1. 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.

  2. Highly efficient and recyclable basic mesoporous zeolite catalyzed condensation, hydroxylation, and cycloaddition reactions.

    PubMed

    Sarmah, Bhaskar; Satpati, Biswarup; Srivastava, Rajendra

    2017-05-01

    Crystalline mesoporous ZSM-5 zeolite was prepared in the presence of 1,4-diazabicyclo[2.2.2]octane derived multi-cationic structure directing agent. The calcined form of the mesoprous zeolite was treated with NH4OH to obtain basic mesoporous ZSM-5. Catalyst was characterized by the complementary combination of X-ray diffraction, N2-adsorption, electron microscopes, and temperature programme desorption techniques. Catalytic activity of the basic mesoporous ZSM-5 was systematically assessed using Knoevenagel condensation reaction for the synthesis a wide range of substituted styrene. Applications of the catalyst were investigated in the benzamide hydroxylation for the synthesis of carbinolamides and one-pot, multi-component condensation reaction for the synthesis of naphthopyrans. Finally, the catalyst was evaluated in the cycloaddition of CO2 to epoxide for the synthesis of cyclic carbonates. Recycling study shows that no significant decrease in the catalytic activity was observed after five recycles.

  3. Phosphorus promotion and poisoning in zeolite-based materials: synthesis, characterisation and catalysis

    PubMed Central

    van der Bij, Hendrik E.

    2015-01-01

    Phosphorus and microporous aluminosilicates, better known as zeolites, have a unique but poorly understood relationship. For example, phosphatation of the industrially important zeolite H-ZSM-5 is a well-known, relatively inexpensive and seemingly straightforward post-synthetic modification applied by the chemical industry not only to alter its hydrothermal stability and acidity, but also to increase its selectivity towards light olefins in hydrocarbon catalysis. On the other hand, phosphorus poisoning of zeolite-based catalysts, which are used for removing nitrogen oxides from exhaust fuels, poses a problem for their use in diesel engine catalysts. Despite the wide impact of phosphorus–zeolite chemistry, the exact physicochemical processes that take place require a more profound understanding. This review article provides the reader with a comprehensive and state-of-the-art overview of the academic literature, from the first reports in the late 1970s until the most recent studies. In the first part an in-depth analysis is undertaken, which will reveal universal physicochemical and structural effects of phosphorus–zeolite chemistry on the framework structure, accessibility, and strength of acid sites. The second part discusses the hydrothermal stability of zeolites and clarifies the promotional role that phosphorus plays. The third part of the review paper links the structural and physicochemical effects of phosphorus on zeolite materials with their catalytic performance in a variety of catalytic processes, including alkylation of aromatics, catalytic cracking, methanol-to-hydrocarbon processing, dehydration of bioalcohol, and ammonia selective catalytic reduction (SCR) of NOx. Based on these insights, we discuss potential applications and important directions for further research. PMID:26051875

  4. Enantioselective dehydration of butan-2-ol using zeolite Y modified with dithiane oxides

    SciTech Connect

    Feast, S.; Siddiqui, H.; Bethell, D.

    1997-04-15

    Modification of zeolite H-Y by dithiane oxides (2-R-1,3-dithiane 1-oxide; R = H, CH{sub 3}, C{sub 6}H{sub 5}) is shown to enhance significantly its activity for the acid catalyzed gas phase dehydration of butan-2-ol. The rate enhancement is observed for catalysts that are prepared by adding the dithiane oxide to the zeolite synthesis gel or by adsorption of the dithiane oxide onto commercial samples of zeolite H-Y. The origin of the rate enhancement is considered to result from a specific interaction between the dithiane oxide modifier with both the extra-framework and framework aluminum in the zeolite. Modification of zeolite H-Y with (R)-1,3-dithiane 1-oxide enhances the conversion of (S)-butan-2-ol compared to (R)-butan-2-ol in the temperature range 110-150{degrees}C when the two enantiomers are reacted separately. Modification with (S)-2-phenyl-1,3-dithiane 1-oxide gives a catalyst for which (R)-butan-2-ol is the most reactive of the two enantiomers. Reaction of racemic butan-2-ol over these chirally modified H-Y zeolites demonstrates that this modification procedure makes the zeolite enantiomerically discriminating and one enantiomer preferentially reacts, although both are present in the micropores under the reaction conditions. This effect is considered to be due to enantioselective rate enhancement, since, although the rate of dehydration of both enantiomers is enhanced in the chiral environment, the dehydration rate of one enantiomer is accelerated relative to the other. It is suggested that the effect is due to preferential adsorption at the chiral active site. 34 refs., 7 figs., 6 tabs.

  5. Phosphorus promotion and poisoning in zeolite-based materials: synthesis, characterisation and catalysis.

    PubMed

    van der Bij, Hendrik E; Weckhuysen, Bert M

    2015-10-21

    Phosphorus and microporous aluminosilicates, better known as zeolites, have a unique but poorly understood relationship. For example, phosphatation of the industrially important zeolite H-ZSM-5 is a well-known, relatively inexpensive and seemingly straightforward post-synthetic modification applied by the chemical industry not only to alter its hydrothermal stability and acidity, but also to increase its selectivity towards light olefins in hydrocarbon catalysis. On the other hand, phosphorus poisoning of zeolite-based catalysts, which are used for removing nitrogen oxides from exhaust fuels, poses a problem for their use in diesel engine catalysts. Despite the wide impact of phosphorus-zeolite chemistry, the exact physicochemical processes that take place require a more profound understanding. This review article provides the reader with a comprehensive and state-of-the-art overview of the academic literature, from the first reports in the late 1970s until the most recent studies. In the first part an in-depth analysis is undertaken, which will reveal universal physicochemical and structural effects of phosphorus-zeolite chemistry on the framework structure, accessibility, and strength of acid sites. The second part discusses the hydrothermal stability of zeolites and clarifies the promotional role that phosphorus plays. The third part of the review paper links the structural and physicochemical effects of phosphorus on zeolite materials with their catalytic performance in a variety of catalytic processes, including alkylation of aromatics, catalytic cracking, methanol-to-hydrocarbon processing, dehydration of bioalcohol, and ammonia selective catalytic reduction (SCR) of NOx. Based on these insights, we discuss potential applications and important directions for further research.

  6. Development of GREET Catalyst Module

    SciTech Connect

    Wang, Zhichao; Dunn, Jennifer B.; Cronauer, Donald C.

    2014-09-01

    Catalysts are critical inputs for many pathways that convert biomass into biofuels. Energy consumption and greenhouse gas (GHG) emissions during the production of catalysts and chemical inputs influence the life-cycle energy consumption, and GHG emissions of biofuels and need to be considered in biofuel life-cycle analysis (LCA). In this report, we develop energy and material flows for the production of three different catalysts (tar reforming, alcohol synthesis, Zeolite Socony Mobil-5 [ZSM-5]) and two chemicals (olivine, dimethyl ether of polyethylene glycol [DEPG]). These compounds and catalysts are now included in the Greenhouse Gases, Regulated Emissions and Energy Use in Transportation (GREET™) catalyst module. They were selected because they are consumed in existing U.S. Department of Energy (DOE) analyses of biofuel processes. For example, a thermochemical ethanol production pathway (indirect gasification and mixed alcohol synthesis) developed by the National Renewable Energy Laboratory (NREL) uses olivine, DEPG, and tar reforming and alcohol synthesis catalysts (Dutta et al., 2011). ZSM-5 can be used in biofuel production pathways such as catalytic upgrading of sugars into hydrocarbons (Biddy and Jones, 2013). Other uses for these compounds and catalysts are certainly possible. In this report, we document the data sources and methodology we used to develop material and energy flows for the catalysts and compounds in the GREET catalyst module. In Section 2 we focus on compounds used in the model Dutta et al. (2011) developed. In Section 3, we report material and energy flows associated with ZSM-5 production. Finally, in Section 4, we report results.

  7. Laser control of zeolite nucleation.

    PubMed

    Navarro, Marta; Mayoral, Alvaro; Mateo, Ester; Lahoz, Ruth; de la Fuente, Germán F; Coronas, Joaquín

    2012-02-01

    Precursor solutions for the synthesis of zeolites are irradiated by means of a Nd-YAG laser. These solutions are subsequently submitted to a hydrothermal treatment and the results analyzed by X-ray diffraction and electron microscopy. Laser irradiation promotes the formation of silica nanoparticles that nucleate into zeolite (silicalite-1), following a hydrothermal treatment. The average crystal size (in the 0.6-3.6 μm range) of the zeolite exponentially decreases as a function of laser irradiation time. In addition, a longer irradiation time results in a narrower crystal size distribution.

  8. Noble gas adsorption in two-dimensional zeolites: a combined experimental and density functional theory study

    NASA Astrophysics Data System (ADS)

    Wang, Mengen; Zhong, Jianqiang; Boscoboinik, Jorge Anibal; Lu, Deyu

    Zeolites are important industrial catalysts with porous three-dimensional structures. The catalytically active sites are located inside the pores, thus rendering them inaccessible for surface science measurements. We synthesized a two-dimensional (2D) zeolite model system, consisting of an (alumino)silicate bilayer weakly bound to a Ru (0001) surface. The 2D zeolite is suitable for surface science studies; it allows a detailed characterization of the atomic structure of the active site and interrogation of the model system during the catalytic reaction. As an initial step, we use Ar adsorption to obtain a better understanding of the atomic structure of the 2D zeolite. In addition, atomic level studies of rare gas adsorption and separation by zeolite are important for its potential application in nuclear waste sequestration. Experimental studies found that Ar atoms can be trapped inside the 2D-zeolite, raising an interesting question on whether Ar atoms are trapped inside the hexagonal prism nano-cages or at the interface between the (alumino)silicate bilayer and Ru(0001), or both. DFT calculations using van der Waals density functionals were carried out to determine the preferred Ar adsorption sites and the corresponding adsorption energies. This research used resources of the Center for Functional Nanomaterials, which is a U.S. DOE Office of Science Facility, at Brookhaven National Laboratory under Contract No. DE-SC0012704.

  9. Single Molecule Nanospectroscopy Visualizes Proton-Transfer Processes within a Zeolite Crystal

    PubMed Central

    2016-01-01

    Visualizing proton-transfer processes at the nanoscale is essential for understanding the reactivity of zeolite-based catalyst materials. In this work, the Brønsted-acid-catalyzed oligomerization of styrene derivatives was used for the first time as a single molecule probe reaction to study the reactivity of individual zeolite H-ZSM-5 crystals in different zeolite framework, reactant and solvent environments. This was accomplished via the formation of distinct dimeric and trimeric fluorescent carbocations, characterized by their different photostability, as detected by single molecule fluorescence microscopy. The oligomerization kinetics turned out to be very sensitive to the reaction conditions and the presence of the local structural defects in zeolite H-ZSM-5 crystals. The remarkably photostable trimeric carbocations were found to be formed predominantly near defect-rich crystalline regions. This spectroscopic marker offers clear prospects for nanoscale quality control of zeolite-based materials. Interestingly, replacing n-heptane with 1-butanol as a solvent led to a reactivity decrease of several orders and shorter survival times of fluorescent products due to the strong chemisorption of 1-butanol onto the Brønsted acid sites. A similar effect was achieved by changing the electrophilic character of the para-substituent of the styrene moiety. Based on the measured turnover rates we have established a quantitative, single turnover approach to evaluate substituent and solvent effects on the reactivity of individual zeolite H-ZSM-5 crystals. PMID:27709925

  10. Hydrothermally stable, low-temperature NO.sub.x reduction NH.sub.3-SCR catalyst

    DOEpatents

    Narula, Chaitanya K.; Yang, Xiaofan

    2016-10-25

    A catalyst composition includes a heterobimetallic zeolite characterized by a chabazite structure loaded with copper ions and at least one trivalent metal ion other than Al.sup.3+. The catalyst composition decreases NO.sub.x emissions in diesel exhaust and is suitable for operation in a catalytic converter.

  11. Hydrothermally stable, low-temperature NO.sub.x reduction NH.sub.3-SCR catalyst

    DOEpatents

    Narula, Chaitanya K; Yang, Xiaofan

    2015-03-24

    A catalyst composition includes a heterobimetallic zeolite characterized by a chabazite structure loaded with copper ions and at least one trivalent metal ion other than Al.sup.3+. The catalyst composition decreases NO.sub.x emissions in diesel exhaust and is suitable for operation in a catalytic converter.

  12. Highly selective Lewis acid sites in desilicated MFI zeolites for dihydroxyacetone isomerization to lactic acid.

    PubMed

    Dapsens, Pierre Y; Mondelli, Cecilia; Pérez-Ramírez, Javier

    2013-05-01

    Desilication of commercial MFI-type (ZSM-5) zeolites in solutions of alkali metal hydroxides is demonstrated to generate highly selective heterogeneous catalysts for the aqueous-phase isomerization of biobased dihydroxyacetone (DHA) to lactic acid (LA). The best hierarchical ZSM-5 sample attains a LA selectivity exceeding 90 %, which is comparable to that of the state-of-the-art catalyst (i.e., the Sn-beta zeolite); this optimized hierarchical catalyst is recyclable over three runs. The Lewis acid sites, which are created through desilication along with the introduction of mesoporosity, are shown to play a crucial role in the formation of the desired product; these cannot be achieved by using other post-synthetic methods, such as steaming or impregnation of aluminum species. Desilication of other metallosilicates, such as Ga-MFI, also leads to high LA selectivity. In the presence of a soluble aluminum source, such as aluminum nitrate, alkaline-assisted alumination can introduce these unique Lewis acid centers in all-silica MFI zeolites. These findings highlight the potential of zeolites in the field of biomass-to-chemical conversion, and expand the applicability of desilication for the generation of selective catalytic centers.

  13. Conversion of Methanol, Ethanol and Propanol over Zeolites

    SciTech Connect

    Ramasamy, Karthikeyan K.; Wang, Yong

    2013-06-04

    Renewable fuel from lignocellulosic biomass has recently attracted more attention due to its environmental and the potential economic benefits over the crude oil [1]. In particular the production of fuel range hydrocarbon (HC) from alcohol generated lots of interest since the alcohol can be produced from biomass via thermochemical [2] (mixed alcohol from gasification derived synthesis gas) as well as the biochemical routes [3] (alcohol fermentation). Along with the development of ZSM5 synthesis and the discovery of methanol-to-gasoline (MTG) process by Mobil in 1970’s triggered lots of interest in research and development arena to understand the reaction mechanisms of alcohols over zeolites in particular ZSM5 [4]. More detailed research on methanol conversion was extensively reported [5] and in recent times the research work can be found on ethanol [6] and other alcohols as well but comprehensive comparison of catalyst activity and the deactivation mechanism of the conversion of various alcohols over zeolites has not been reported. The experiments were conducted on smaller alcohols such as methanol, ethanol and 1-propanol over HZSM5. The experimental results on the catalyst activity and the catalyst deactivation mechanism will be discussed.

  14. Regeneration of a deactivated USY alkylation catalyst using supercritical isobutane

    SciTech Connect

    Daniel M. Ginosar; David N. Ghompson; Kyle C. Burch

    2005-01-01

    Off-line, in-situ alkylation activity recovery from a completely deactivated solid acid catalyst was examined in a continuous-flow reaction system employing supercritical isobutane. A USY zeolite catalyst was initially deactivated during the liquid phase alkylation of butene with isobutane in a single-pass reactor and then varying amounts of alkylation activity were recovered by passing supercritical isobutane over the catalyst bed at different reactivation conditions. Temperature, pressure and regeneration time were found to play important roles in the supercritical isobutane regeneration process when applied to a completely deactivated USY zeolite alkylation catalyst. Manipulation of the variables that influence solvent strength, diffusivity, surface desorption, hydride transfer rates, and coke aging, strongly influence regeneration effectiveness.

  15. Gallium zeolites for light paraffin aromatization. Progress report, August 15, 1992--February 15, 1994

    SciTech Connect

    Price, G.L.; Dooley, K.M.

    1994-03-01

    Focus of the research work is to relate the catalytic properties of Ga Zeolites to the preparation method and to unify the various theories about the active nature of Ga Zeolites for light paraffin aromatization. During this reporting period, thermal analysis of alkylamines has been studied extensively and applied with great success to the problem. New features of alkylamine thermal analysis have been discovered and described. Because of the success of this method for the characterization of cation-containing MFI, some spin-off work on Cu-MFI (which currently has broad interest as an NO decomposition catalyst) has been accomplished.

  16. Hydrodeoxygenation of fatty acid esters catalyzed by Ni on nano-sized MFI type zeolites

    SciTech Connect

    Schreiber, Moritz W.; Rodriguez-Niño, Daniella; Gutiérrez, Oliver Y.; Lercher, Johannes A.

    2016-01-01

    The impact of support morphology and composition on the intrinsic activity of Ni supported on MFI-type zeolite was explored in the hydrodeoxygenation of methyl stearate, tristearate, and algae oil (mixture of triglycerides). The nano-sized structure of the support (self-pillared nanosheets) is beneficial for the activity of the catalysts. Higher Ni dispersion and concomitant higher reaction rates were obtained on nano-structured supports than on zeolite with conventional morphology. Rates normalized to accessible Ni atoms (TOF), however, varied little with support morphology. Acidity of the support increases the rate of Ni-catalyzed C-O hydrogenolysis per surface metal site.

  17. Catalytic pyrolysis using UZM-39 aluminosilicate zeolite

    DOEpatents

    Nicholas, Christpher P; Boldingh, Edwin P

    2013-12-17

    A new family of coherently grown composites of TUN and IMF zeotypes has been synthesized and show to be effective catalysts for catalytic pyrolysis of biomass. These zeolites are represented by the empirical formula. Na.sub.nM.sub.m.sup.n+R.sub.rQ.sub.qAl.sub1-xE.sub.xSi.sub.yO.s- ub.z where M represents zinc or a metal or metals from Group 1, Group 2, Group 3 or the lanthanide series of the periodic table, R is an A,.OMEGA.-dihalosubstituted paraffin such as 1,4-dibromobutane, Q is a neutral amine containing 5 or fewer carbon atoms such as 1-methylpyrrolidine and E is a framework element such as gallium. The process involves contacting a carbonaceous biomass feedstock with UZM-39 at pyrolysis conditions to produce pyrolysis gases comprising hydrocarbons. The catalyst catalyzes a deoxygenation reaction converting oxygenated hyrdocarbons into hydrocarbons removing the oxygen as carbon oxides and water. A portion of the pyrolysis gases is condensed to produce low oxygen biomass-derived pyrolysis oil.

  18. Catalytic pyrolysis using UZM-39 aluminosilicate zeolite

    DOEpatents

    Nicholas, Christopher P; Boldingh, Edwin P

    2014-10-07

    A new family of coherently grown composites of TUN and IMF zeotypes has been synthesized and shown to be effective catalysts for catalytic pyrolysis of biomass. These zeolites are represented by the empirical formula. Na.sub.nM.sub.m.sup.n+R.sub.rQ.sub.qAl.sub.1-xE.sub.xSi.sub.yO.s- ub.z where M represents zinc or a metal or metals from Group 1, Group 2, Group 3 or the lanthanide series of the periodic table, R is an A,.OMEGA.-dihalosubstituted paraffin such as 1,4-dibromobutane, Q is a neutral amine containing 5 or fewer carbon atoms such as 1-methylpyrrolidine and E is a framework element such as gallium. The process involves contacting a carbonaceous biomass feedstock with UZM-39 at pyrolysis conditions to produce pyrolysis gases comprising hydrocarbons. The catalyst catalyzes a deoxygenation reaction converting oxygenated hydrocarbons into hydrocarbons and removing the oxygen as carbon oxides and water. A portion of the pyrolysis gases is condensed to produce low oxygen biomass-derived pyrolysis oil.

  19. Catalyst for reduction of nitrogen oxides

    DOEpatents

    Ott, Kevin C.

    2010-04-06

    A Selective Catalytic Reduction (SCR) catalyst was prepared by slurry coating ZSM-5 zeolite onto a cordierite monolith, then subliming an iron salt onto the zeolite, calcining the monolith, and then dipping the monolith either into an aqueous solution of manganese nitrate and cerium nitrate and then calcining, or by similar treatment with separate solutions of manganese nitrate and cerium nitrate. The supported catalyst containing iron, manganese, and cerium showed 80 percent conversion at 113 degrees Celsius of a feed gas containing nitrogen oxides having 4 parts NO to one part NO.sub.2, about one equivalent ammonia, and excess oxygen; conversion improved to 94 percent at 147 degrees Celsius. N.sub.2O was not detected (detection limit: 0.6 percent N.sub.2O).

  20. Zeolite micropattern for biological applications.

    PubMed

    Sun, Wenqing; Lam, Koon Fung; Wong, Ling Wai; Yeung, King Lun

    2005-10-21

    A facile method was established using composition-gradient pattern on zeolite surface to guide the deposition and formation of chemical and biomolecular patterns with features as small as five microns.

  1. In-situ imaging of reacting single-particle zeolites by non-linear optical microscopy

    NASA Astrophysics Data System (ADS)

    Wrzesinski, Paul J.; Slipchenko, Mikhail N.; Zaman, Taslima A.; Rioux, Robert M.; Gord, James R.; Roy, Sukesh

    2015-03-01

    Zeolite catalysis has been exploited by the petrochemical industry since the 1940's for catalytic cracking reactions of long chain hydrocarbons. The selectivity of zeolites strongly depends on a pore size, which is controlled by the chosen structure-directing agent (SDA) and by the SDA decomposition/removal process. Although zeolites are composed of micron-sized crystals, studies of zeolite materials typically focus on bulk (i.e., ensemble) measurements to elucidate structure-function information or to optimize catalysts and/or process parameters. To examine these phenomena on the microscale, non-linear optical microscopy is used to provide real-time imaging of chemical reactions in zeolites at temperatures exceeding 400°C. The template decomposition mechanism is studied, as elucidation of the mechanism is critical to understanding the relationship between the decomposition chemistry and the nanoscale features of the zeolite (topology, Si/Al ratio, added dopants). Forward stimulated Raman scattering (SRS), forward coherent anti-Stokes Raman scattering (CARS) and epi two-photon fluorescence (TPF) modalities are acquired simultaneously providing video-rate structural and chemical information. A high-temperature cell with gas inlet system is used for the study of reactions under various temperatures and gas environments. Examining the decomposition process with single-particle resolution enables access to ensemble-level and spatially-resolved behavior. Parallel experiments on bulk zeolite powders are conducted to enable comparison of ensemble and single-particle behavior during template decomposition. Our multi-technique approach has high potential for gaining insight into the link between nanoscale structure and catalytic activity and selectivity of zeolitic materials.

  2. New catalysts improves heavy feedstock hydro-cracking

    SciTech Connect

    Hoek, A.; Huizinga, T.; Esener, A.A.; Maxwell, I.E.; Stork, W. ); van de Meerakker, F.J. ); Sy, O. )

    1991-04-22

    A new zeolite-Y-based second-stage hydrocracking catalyst, designated S-703, has been developed by Shell. Laboratory testing and commercial use show it has significantly improved performance with respect to gas make and middle-distillate selectivity in processing heavy feedstocks when compared to a Shell catalyst, S-753, developed earlier. Further, the new catalyst exhibits enhanced stability. Extensive laboratory testing of the S-703 catalyst has been carried out under single-stage, stacked- bed, two-stage-flow, and series-flow conditions. Commercial experience with the new catalyst has now been obtained in several units. To date, the commercial results have confirmed the laboratory results in terms of the superior, heavy- feedstock processing performance of the new catalyst in all respects. Because the trend toward heavier feedstocks is expected to continue, it is likely that catalysts such as S- 703 will find increasing applications in hydrocrackers in the future.

  3. The Effect of Supercritical Fluids on Solid Acid Catalyst Alkylation

    SciTech Connect

    Ginosar, Daniel Michael; Thompson, David Neil; Burch, Kyle Coates; Zalewski, D. J.

    2002-05-01

    The alkylation of isobutane with trans-2-butene was explored over six solid acid catalysts in the liquid, near-critical liquid, and supercritical regions through the addition of an inert cosolvent to the reaction feed mixture. The addition of supercritical cosolvents did not result in sustained catalytic alkylation activity. A modest improvement in product yield was obtained with the addition of methane in the modified-liquid region; however, catalyst longevity and product selectivity were decreased compared to cosolvent-free liquid conditions. This paper describes the catalyst screening and selection process, an exploration of catalyst performance with varying concentrations of methane, and an examination of the effects of seven supercritical fluids on catalyst performance. The catalysts included two zeolites, two sulfated metal oxides, and two Nafion catalysts. Three hydrocarbons, two fluorocarbons, carbon dioxide, and sulfur hexafluoride were explored as inert cosolvents added to the reaction mixture.

  4. Development of catalyst production facilities at Ufa Oil Refinery

    SciTech Connect

    Propkopyuk, S.G.; Rozenbaum, B.L.; Putilin, N.Ye.; Amirkhanov, K.Sh.; Morozov, B.F.; Britenkova, T.G.

    1982-08-03

    The Ufa Order of Lenin Oil Refinery is one of the USSR's largest facilities for production of catalysts for oil refining and petrochemistry, as well as for the food industry. Nine types of catalysts are produced for cracking, selective hydrogenation and oligomerization. A plant for production of NaY zeolite catalysts by the ash method has been remodeled. The production of nickel catalysts on kieselgur is growing rapidly. The facility for producing copper-chromium type MKhB catalyst is to be remodeled during the 11th Five-Year Plan. Production of cracking catalysts will be basically redesigned, increasing the capacity by 50% and significantly improving the operating characteristics of microspherical catalysts.

  5. Time- and space-resolved high energy operando X-ray diffraction for monitoring the methanol to hydrocarbons reaction over H-ZSM-22 zeolite catalyst in different conditions

    NASA Astrophysics Data System (ADS)

    del Campo, Pablo; Slawinski, Wojciech Andrzej; Henry, Reynald; Erichsen, Marius Westgård; Svelle, Stian; Beato, Pablo; Wragg, David; Olsbye, Unni

    2016-06-01

    The conversion of methanol to hydrocarbons (MTH) over H-ZSM-22 was studied by operando time- and space-resolved X-ray diffraction (XRD) at 370-385 °C and WHSV = 2 g/g h at the Swiss-Norwegian Beamline at ESRF. The performance of a commercial H-ZSM-22 sample was compared before and after acid-base treatment, and with and without propanol co-feed, respectively. N2 adsorption, Scanning Electron Microscopy and propyl amine desorption experiments showed that acid-base treatment led to enhanced accessibility of acid sites, mainly due to the formation of mesopores between agglomerated H-ZSM-22 crystals. The catalytic set-up allowed us to simultaneously observe the catalyst activity and unit cell volume variations by time- and space-resolved HXRD in operando conditions. The expansion of the unit cell and final flattening at different positions in the catalytic bed matched very nicely with the catalytic activity gradients. Different scenarios provided different behaviors and gave insights in the effect of morphology and co-feed process on the activity in the MTH process. This technique is the only one which has so far been able to provide direct evidence of the behavior of the species inside the catalytic reactor.

  6. Zeolites as nanoporous, gas-sensitive materials for in situ monitoring of DeNO(x)-SCR.

    PubMed

    Simons, Thomas; Simon, Ulrich

    2012-01-01

    In a proof-of-concept study we demonstrate in situ reaction monitoring of DeNO(x)-SCR on proton-conducting zeolites serving as catalyst and gas sensor at the same time. By means of temperature-dependent impedance spectroscopy we found that the thermally induced NH(3) desorption in H-form and in Fe-loaded zeolite H-ZSM-5 follow the same process, while a remarkable difference under DeNO(x)-SCR reaction conditions was found. The Fe-loaded catalyst shows a significantly lower onset temperature, and time-dependent measurements suggest different SCR reaction mechanisms for the two catalysts tested. These results may help in the development of catalysts for the reduction of NO(x) emissions and ammonia consumption, and provide insight into the elementary catalytic process promoting a full description of the NH(3)-SCR reaction system.

  7. STRONTIUM AS AN EFFICIENT PROMOTER FOR SUPPORTED PALLADIUM HYDROGENATION CATALYSTS

    EPA Science Inventory

    The effect of strontium promotion is studied for a series of supported palladium catalysts such as Pd/zeolite-β, Pd/Al2O3, Pd/SiO2, Pd/hydrotalcite and Pd/MgO. Strontium is found to be an effective promoter for enhancing the metal area, perce...

  8. Exploring the reactivity of framework vanadium, niobium, and tantalum sites in zeolitic materials using DFT reactivity descriptors.

    PubMed

    Tielens, Frederik

    2009-09-01

    The acid-base properties of zeolites with group 5 transition metal framework sites are investigated, and a first step into the understanding of their acid/base and redox properties is undertaken using DFT reactivity descriptors. It is evidenced, using sodalite as model system, that zeolites with vanadium framework sites are more nucleophilic than zeolites with niobium and tantalum framework sites. It is predicted that the formation of carbonates would be favorable in zeolites with Ta framework sites compared with V framework sites, whereas the basicity of the bridging oxygens is predicted to interact preferentially with a soft nucleophile. In this context, the poisoning of the deNO(x) catalysts in the presence of SO2 is discussed.

  9. High-Resolution Single-Molecule Fluorescence Imaging of Zeolite Aggregates within Real-Life Fluid Catalytic Cracking Particles**

    PubMed Central

    Ristanović, Zoran; Kerssens, Marleen M; Kubarev, Alexey V; Hendriks, Frank C; Dedecker, Peter; Hofkens, Johan; Roeffaers, Maarten B J; Weckhuysen, Bert M

    2015-01-01

    Fluid catalytic cracking (FCC) is a major process in oil refineries to produce gasoline and base chemicals from crude oil fractions. The spatial distribution and acidity of zeolite aggregates embedded within the 50–150 μm-sized FCC spheres heavily influence their catalytic performance. Single-molecule fluorescence-based imaging methods, namely nanometer accuracy by stochastic chemical reactions (NASCA) and super-resolution optical fluctuation imaging (SOFI) were used to study the catalytic activity of sub-micrometer zeolite ZSM-5 domains within real-life FCC catalyst particles. The formation of fluorescent product molecules taking place at Brønsted acid sites was monitored with single turnover sensitivity and high spatiotemporal resolution, providing detailed insight in dispersion and catalytic activity of zeolite ZSM-5 aggregates. The results point towards substantial differences in turnover frequencies between the zeolite aggregates, revealing significant intraparticle heterogeneities in Brønsted reactivity. PMID:25504139

  10. Comparative IR spectroscopic study of Pt- and Pd-containing zeolites in the hydrodechlorination reaction of carbon tetrachloride

    NASA Astrophysics Data System (ADS)

    Imre, Béla; Hannus, István; Kiricsi, Imre

    2005-06-01

    Hydrodechlorination of CCl 4 was investigated on noble metal containing zeolite catalysts by IR spectroscopy. Both the surface species and the gas phase reaction products were simultaneously analysed. Results revealed that the reaction rate and the reaction products were different on Pt- and Pd-containing samples. The enhanced formation of ethane and the suppressed generation of methane over Pd/NaY-FAU zeolite and the formation of chloroform as intermediate product over Pt/NaY-FAU zeolite were explained by the different bond strength of reaction intermediates to the metal surface. The influence of acid sites on the product distribution was traced back to the local decomposition of zeolite framework. A combination of IR spectroscopic methods including simultaneous analysis of gas phase products and surface intermediates proved to be an excellent tool for investigating the reaction mechanism.

  11. MFI-type (ZSM-5) zeolite-filled TiO2 nanotubes for enhanced photocatalytic activity.

    PubMed

    Paramasivam, I; Avhale, A; Inayat, A; Bösmann, A; Schmuki, P; Schwieger, W

    2009-06-03

    The present work demonstrates enhanced photocatalytic activity for zeolite-filled TiO2 nanotubes. ZSM-5 zeolite nanocrystals were grown on and into a TiO2 nanotubular skeleton (TiNT/ZSM-5) by multi-step hydrothermal synthesis consisting of in situ seeding and multiple in situ crystallization (MISC). The resulting zeolite nanocrystals were in the range of a few nanometers and they adhere well to the nanotubular inner walls. After crystallization, the photocatalytic activity of this zeolite-filled nanotube catalyst system was compared with neat anatase TiO2 nanotube (TiNT) and with calcined ZSM-5 powder. The results show for TiNT/ZSM-5 a highly enhanced efficiency for the decomposition of acetophenone (used as an aromatic model organic pollutant).

  12. Synthetic zeolites and other microporous oxide molecular sieves

    PubMed Central

    Sherman, John D.

    1999-01-01

    Use of synthetic zeolites and other microporous oxides since 1950 has improved insulated windows, automobile air-conditioning, refrigerators, air brakes on trucks, laundry detergents, etc. Their large internal pore volumes, molecular-size pores, regularity of crystal structures, and the diverse framework chemical compositions allow “tailoring” of structure and properties. Thus, highly active and selective catalysts as well as adsorbents and ion exchangers with high capacities and selectivities were developed. In the petroleum refining and petrochemical industries, zeolites have made possible cheaper and lead-free gasoline, higher performance and lower-cost synthetic fibers and plastics, and many improvements in process efficiency and quality and in performance. Zeolites also help protect the environment by improving energy efficiency, reducing automobile exhaust and other emissions, cleaning up hazardous wastes (including the Three Mile Island nuclear power plant and other radioactive wastes), and, as specially tailored desiccants, facilitating the substitution of new refrigerants for the ozone-depleting chlorofluorocarbons banned by the Montreal Protocol. PMID:10097059

  13. Zeolites on Mars: Possible environmental indicators in soils and sediments

    NASA Technical Reports Server (NTRS)

    Ming, D. W.; Gooding, J. L.

    1988-01-01

    Weathering products should serve as indicators of weathering environments and may provide the best evidence of the nature of climate change on Mars. No direct mineralogical measurements of Martian regolith were performed by the Viking missions, but the biology and X-ray fluorescence experiments provided some information on the physiochemical properties of Martian regolith. Most post-Viking studies of candidate weathering products have emphasized phyllosilicates and Fe-oxides; zeolites are potentially important, but overlooked, candidate Martian minerals. Zeolites would be important on Mars for three different reasons. First, they are major sinks of atmospheric gases and, per unit mass, are stronger and more efficient sorbents than are phyllosilicates. Secondly, they can be virtually unique sorbents and shelters for organic compounds and possible catalysts for organic-based reactions. Finally, their exchangeable ions are good indicators of the chemical properties of solutions with which they have communicated. Accordingly, the search for information on past compositions of the Martian atmosphere and hydrosphere should find zeolites to be rich repositories.

  14. A new metal exchanged zeolite for a present environmental problem. An in-situ XAS study

    NASA Astrophysics Data System (ADS)

    Alonso-Escobar, C.; Franch-Martí, C.; Palomares, A. E.; Rey, F.; Guilera, G.

    2013-04-01

    The medium pore zeolite, TNU-9, is prepared and studied for the selective catalytic reduction (SCR) of NO using C3H8 as the reducing agent. The catalytic activity of TNU-9 zeolites for the SCR is comparable to other known highly active zeolites but with the advantage of TNU-9 of having almost the same catalytic performance in the presence of H2O during reaction. The nature and behaviour of Cu and Co active sites contained in the TNU-9 catalysts have been studied under operation conditions using X-ray Absorption Spectroscopy (XAS) to understand the key parameters controlling the performance of this reaction.1 It was found that the well dispersed Cu and Co centres need to be in a mixed valence state to obtain good catalytic results for the SCR and that the catalytic performance is related to the topology of the TNU-9 itself.

  15. Synthesis, characterisation, and catalytic evaluation of hierarchical faujasite zeolites: milestones, challenges, and future directions.

    PubMed

    Verboekend, D; Nuttens, N; Locus, R; Van Aelst, J; Verolme, P; Groen, J C; Pérez-Ramírez, J; Sels, B F

    2016-06-13

    Faujasite (X, Y, and USY) zeolites represent one of the most widely-applied and abundant catalysts and sorbents in the chemical industry. In the last 5 years substantial progress was made in the synthesis, characterisation, and catalytic exploitation of hierarchically-structured variants of these zeolites. Hererin, we provide an overview of these contributions, highlighting the main advancements regarding the evaluation of the nature and functionality of introduced secondary porosity. The novelty, efficiency, versatility, and sustainability of the reported bottom-up and (predominately) top-down strategies are discussed. The crucial role of the relative stability of faujasites in aqueous media is highlighted. The interplay between the physico-chemical properties of the hierarchical zeolites and their use in petrochemical and biomass-related catalytic processes is assessed.

  16. Influence of starting zeolite on synthesis of RUT type zeolite by interzeolite conversion method

    NASA Astrophysics Data System (ADS)

    Itakura, Masaya; Ota, Kai; Shibata, Shohei; Inoue, Takayuki; Ide, Yusuke; Sadakane, Masahiro; Sano, Tsuneji

    2011-01-01

    In this study, hydrothermal conversions of *BEA and FAU type zeolites using various structure-directing agents were carried out. Highly crystalline and pure RUT type zeolites were obtained from both zeolites in the presence of tetramethylammonium hydroxide. There were no major differences between the characteristics of the RUT type zeolites obtained from the two starting zeolites. However, the Si/Al ratio and the crystallization rate of the RUT type zeolites were strongly dependent on both the framework structure and the Si/Al ratio of the starting zeolite. That is, the crystallization rate of the RUT type zeolite from the *BEA type zeolite did not depend on the Si/Al ratio of the starting *BEA type zeolite, whereas the crystallization rate of the RUT type zeolite from the FAU type zeolite was dependent on the Si/Al ratio of the starting FAU type zeolite. This suggests that the chemical structure and the concentration of locally ordered aluminosilicate species produced by the decomposition/dissolution of the starting zeolite can be altered by changing the framework structure of the zeolite.

  17. Spectra of carbanions formed from allyl cyanide during isomerization in zeolite NaY-FAU with strong basic sites

    NASA Astrophysics Data System (ADS)

    Hannus, István; Förster, Horst; Tasi, Gyula; Kiricsi, Imre; Molnár, Árpád

    1995-03-01

    Double bond isomerization of allyl cyanide to crotononitrile over a basic zeolite catalyst was monitored by IR and UV-VIS spectroscopy in order to get information on the surface intermediates involved. Due to the spectral changes the occurence of a carbanionic intermediate seems to be highly probable characterized by an absorption at 400 nm.

  18. Ultrasound assisted, ruthenium-exchanged FAU-Y zeolite catalyzed alkylation of indoles with epoxides under solvent free conditions.

    PubMed

    Khorshidi, Alireza

    2012-05-01

    Ruthenium-exchanged FAU-Y zeolite (RuY) was used as a recyclable catalyst for regioselective ring-opening of epoxides with indoles under irradiation of sonic waves. It was found that a solvent free process, under the above mentioned conditions provides good yields of the desired 3-alkylated indole derivatives.

  19. Zeolite-supported rhodium complexes and clusters: switching catalytic selectivity by controlling structures of essentially molecular species.

    PubMed

    Serna, Pedro; Gates, B C

    2011-04-06

    Precise synthesis and characterization of site-isolated rhodium complexes and extremely small rhodium clusters supported on zeolite HY allow control of the catalyst selectivity in the conversion of ethene to n-butene or ethane, respectively, as a result of tuning the structure of the active sites at a molecular level.

  20. An efficient one-pot three-component synthesis of fused 1,4-dihydropyridines using HY-zeolite.

    PubMed

    Nikpassand, Mohammad; Mamaghani, Manouchehr; Tabatabaeian, Khalil

    2009-04-08

    A facile and convenient protocol was developed for the fast (2.5-3.5 h) and high yielding (70-90%) synthesis of fused 1,4-dihydropyridines from dimedone in the presence of HY-zeolite as an efficient recyclable heterogeneous catalyst.

  1. Nanoscale intimacy in bifunctional catalysts for selective conversion of hydrocarbons

    PubMed Central

    Zečević, Jovana; Vanbutsele, Gina; de Jong, Krijn P.; Martens, Johan A.

    2016-01-01

    The ability to precisely control nanoscale features is increasingly exploited to develop and improve monofunctional catalysts1–4. Striking effects might also be expected in the case of bifunctional catalysts, which play an important role in hydrocracking of fossil and renewable hydrocarbon sources to provide high-quality diesel fuel5–7. Such bifunctional hydrocracking catalysts contain metal sites and acid sites, and for more than 50 years the so-called ‘intimacy criterion’8 has dictated the maximum distance between the two site types beyond which catalytic activity decreases. The lack of synthesis and material characterization methods with nanometer precision has long prevented in-depth exploration of the criterion, which has often been interpreted simply as ‘the closer the better’ for positioning metal and acid sites8–11. Here we show for a bifunctional catalyst, comprised of an intimate mixture of zeolite Y and alumina binder and with platinum (Pt) metal controllably deposited20,21 on either the zeolite or the binder, that close proximity between metal and zeolite acid sites can be detrimental: the selectivity when cracking large hydrocarbon feedstock molecules for high-quality diesel production is optimized with the catalyst that contains Pt on the binder, i.e. with a larger distance between metal and acid sites. Cracking of the large and complex hydrocarbon molecules typically derived from alternative sources such as gas-to-liquid technology, vegetable oil or algal oil6–7 should thus benefit especially from bifunctional catalysts that avoid locating Pt on the zeolite as the traditionally assumed optimal location. More generally, we anticipate that the ability to spatially organize different active sites at the nanoscale demonstrated here will benefit the further development and optimization of the newly emerging generation of multifunctional catalysts12–15. PMID:26659185

  2. Photocatalysis of fenoxycarb over silver-modified zeolites.

    PubMed

    Ahern, John; Kanan, Sofian; Sara, Ziad; Job, Thomas; Alnaizy, Raafat; Abu Farha, Nedal; Patterson, Howard

    2015-03-01

    Two samples of silver doped into zeolite Y were prepared and characterized. ICP and SEM-EDS analysis indicate that the AgY1 sample contains twice the amount of silver compared to the AgY2 sample. Solid state luminescence spectroscopy shows variations in the emission modes of the site-selective luminescence where various luminophores might be excited upon selecting the proper excitation energy. The selected material effectively decomposed the pesticide fenoxycarb in aqueous solution. The photodecomposition of fenoxycarb reached 80 % upon irradiation for 60 min in the presence of the AgY1 catalyst. 2-(4-Phenoxy-phenoxy)ethyl] carbamic acid (1) and 1-amine-2-(phenoxy-4-ol) ethane (2) were identified as products for both uncatalyzed solution and the catalyzed fenoxycarb with AgY2 catalyst. Whereas, compound (2) was the only product identified in the catalyzed reaction with AgY1.

  3. Unstitching the nanoscopic mystery of zeolite crystal formation.

    PubMed

    Brent, Rhea; Cubillas, Pablo; Stevens, Sam M; Jelfs, Kim E; Umemura, Ayako; Gebbie, James T; Slater, Ben; Terasaki, Osamu; Holden, Mark A; Anderson, Michael W

    2010-10-06

    A molecular-scale understanding of crystal growth is critical to the development of important materials such as pharmaceuticals, semiconductors and catalysts. Only recently has this been possible with the advent of atomic force microscopy that permits observation of nanoscopic features on solid surfaces under a liquid or solution environment. This allows in situ measurement of important chemical transformations such as crystal growth and dissolution. Further, the microscope can access not only an accurate height measurement of surface topography, important to deduce structural elements, but also the forces involved during nanoscopic processes. We have discovered that it is possible to use these features to "illuminate" critical nanoscopic chemical events at crystal surfaces and at the same time extract the associated energies and unstitch the details of the stepwise mechanism of growth and dissolution. This approach has been developed using nanoporous crystals of the heterogeneous catalyst zeolite L; however, in principle the approach could be adapted to many crystal growth problems.

  4. Synthesis, characterization and catalytic activity of indium substituted nanocrystalline Mobil Five (MFI) zeolite

    SciTech Connect

    Shah, Kishor Kr.; Nandi, Mithun; Talukdar, Anup K.

    2015-06-15

    Highlights: • In situ modification of the MFI zeolite by incorporation of indium. • The samples were characterized by XRD, FTIR, TGA, UV–vis (DRS), SAA, EDX and SEM. • The incorporation of indium was confirmed by XRD, FT-IR, UV–vis (DRS), EDX and TGA. • Hydroxylation of phenol reaction was studied on the synthesized catalysts. - Abstract: A series of indium doped Mobil Five (MFI) zeolite were synthesized hydrothermally with silicon to aluminium and indium molar ratio of 100 and with aluminium to indium molar ratios of 1:1, 2:1 and 3:1. The MFI zeolite phase was identified by XRD and FT-IR analysis. In XRD analysis the prominent peaks were observed at 2θ values of around 6.5° and 23° with a few additional shoulder peaks in case of all the indium incorporated samples suggesting formation of pure phase of the MFI zeolite. All the samples under the present investigation were found to exhibit high crystallinity (∼92%). The crystallite sizes of the samples were found to vary from about 49 to 55 nm. IR results confirmed the formation of MFI zeolite in all cases showing distinct absorbance bands near 1080, 790, 540, 450 and 990 cm{sup −1}. TG analysis of In-MFI zeolites showed mass losses in three different steps which are attributed to the loss due to adsorbed water molecules and the two types TPA{sup +} cations. Further, the UV–vis (DRS) studies reflected the position of the indium metal in the zeolite framework. Surface area analysis of the synthesized samples was carried out to characterize the synthesized samples The analysis showed that the specific surface area ranged from ∼357 to ∼361 m{sup 2} g{sup −1} and the pore volume of the synthesized samples ranged from 0.177 to 0.182 cm{sup 3} g{sup −1}. The scanning electron microscopy studies showed the structure of the samples to be rectangular and twinned rectangular shaped. The EDX analysis was carried out for confirmation of Si, Al and In in zeolite frame work. The catalytic activities of

  5. Synthesis Strategies for Ultrastable Zeolite GIS Polymorphs as Sorbents for Selective Separations

    SciTech Connect

    Oleksiak, Matthew D.; Ghorbanpour, Arian; Conato, Marlon T.; McGrail, B. Peter; Grabow, Lars C.; Motkuri, Radha Kishan; Rimer, Jeffrey D.

    2016-10-05

    Designing nanoporous zeolites with tunable physicochemical properties can substantially impact their performance in commercial applications spanning diverse areas such as adsorption, separations, catalysis, and drug delivery. Zeolite synthesis typically requires the use of an organic structure-directing agent to facilitate the formation of crystals with specific pore size and topology. Attempts to remove organics from syntheses to achieve commercially-viable methods of preparing zeolites often lead to the formation of unwanted crystal polymorphs (i.e., impurities). Here, we present an organic-free synthesis of the small-pore zeolite P (GIS framework topology) that can be selectively tailored to produce two pure polymorphs: P1 and P2. To this end, we developed kinetic phase diagrams that identify synthesis compositions leading to the formation of GIS (P1 and P2), as well as their structural analogues MER and PHI. Using a combination of adsorption measurements and density functional theory (DFT) calculations, we also show that both GIS polymorphs are highly selective adsorbents for H2O relative to other light gases (e.g,, H2, N2, CO2). These studies highlight the potential application of GIS materials for dehydration processes, while our findings also refute prior theoretical studies postulating that GIS-type zeolites are excellent materials for CO2 separation/sequestration. Moreover, there is an impetus for discovering novel small-pore zeolites that are shape-selective catalysts for the production of value-added chemicals (e.g., light olefins); thus, our discovery of more thermally-stable P2 opens new avenues for exploring the potential role of this material as a high-performance catalyst.

  6. Reclaiming silver from silver zeolite

    SciTech Connect

    Reimann, G.A.

    1991-10-01

    Silver zeolite is used to capture radioiodines from air cleaning systems in some nuclear facilities at the Idaho National Engineering Laboratory. It may become radioactively contaminated and/or poisoned by hydrocarbon vapors, which diminishes its capacity for iodine. Silver zeolite contains up to 38 wt% silver. A pyrometallurgical process was developed to reclaim the silver before disposing of the unserviceable zeolite as a radioactive waste. A flux was formulated to convert the refractory aluminosilicate zeolite structure into a low-melting fluid slag, with Na{sub 2}O added as NAOH instead of Na{sub 2}CO{sub 3} to avoid severe foaming due to CO{sub 2} evolution. A propane-fired furnace was built to smelt 45 kg charges at 1300C in a carbon-bonded silicon carbide crucible. A total of 218 kg (7000 tr oz) of silver was reclaimed from 1050 kg of unserviceable zeolite. Silver recoveries of 97% were achieved, and the radioisotopes were fixed as stable silicates in a vitreous slag that was disposed of as a low level waste. Recovered silver was refined using oxygen and cast into 100 tr oz bars assaying 99.8+% silver and showing no radioactive contamination.

  7. Reclaiming silver from silver zeolite

    SciTech Connect

    Reimann, G.A.

    1991-10-01

    Silver zeolite is used to capture radioiodines from air cleaning systems in some nuclear facilities at the Idaho National Engineering Laboratory. It may become radioactively contaminated and/or poisoned by hydrocarbon vapors, which diminishes its capacity for iodine. Silver zeolite contains up to 38 wt% silver. A pyrometallurgical process was developed to reclaim the silver before disposing of the unserviceable zeolite as a radioactive waste. A flux was formulated to convert the refractory aluminosilicate zeolite structure into a low-melting fluid slag, with Na[sub 2]O added as NAOH instead of Na[sub 2]CO[sub 3] to avoid severe foaming due to CO[sub 2] evolution. A propane-fired furnace was built to smelt 45 kg charges at 1300C in a carbon-bonded silicon carbide crucible. A total of 218 kg (7000 tr oz) of silver was reclaimed from 1050 kg of unserviceable zeolite. Silver recoveries of 97% were achieved, and the radioisotopes were fixed as stable silicates in a vitreous slag that was disposed of as a low level waste. Recovered silver was refined using oxygen and cast into 100 tr oz bars assaying 99.8+% silver and showing no radioactive contamination.

  8. Zeolite membranes: microstructure characterization and permeation mechanisms.

    PubMed

    Yu, Miao; Noble, Richard D; Falconer, John L

    2011-11-15

    Since their first synthesis in the 1940s, zeolites have found wide applications in catalysis, ion-exchange, and adsorption. Although the uniform, molecular-size pores of zeolites and their excellent thermal and chemical stability suggest that zeolites could be an ideal membrane material, continuous polycrystalline zeolite layers for separations were first prepared in the 1990s. Initial attempts to grow continuous zeolite layers on porous supports by in situ hydrothermal synthesis have resulted in membranes with the potential to separate molecules based on differences in molecular size and adsorption strength. Since then, further synthesis efforts have led to the preparation of many types of zeolite membranes and better quality membranes. However, the microstructure features of these membranes, such as defect size, number, and distribution as well as structure flexibility were poorly understood, and the fundamental mechanisms of permeation (adsorption and diffusion), especially for mixtures, were not clear. These gaps in understanding have hindered the design and control of separation processes using zeolite membranes. In this Account, we describe our efforts to characterize microstructures of zeolite membranes and to understand the fundamental adsorption and diffusion behavior of permeating solutes. This Account will focus on the MFI membranes which have been the most widely used but will also present results on other types of zeolite membranes. Using permeation, x-ray diffraction, and optical measurements, we found that the zeolite membrane structures are flexible. The size of defects changed due to adsorption and with variations in temperature. These changes in defect sizes can significantly affect the permeation properties of the membranes. We designed methods to measure mixture adsorption in zeolite crystals from the liquid phase, pure component adsorption in zeolite membranes, and diffusion through zeolite membranes. We hope that better understanding can lead

  9. Confinement effect and synergistic function of H-ZSM-5/Cu-ZnO-Al2O3 capsule catalyst for one-step controlled synthesis.

    PubMed

    Yang, Guohui; Tsubaki, Noritatsu; Shamoto, Jun; Yoneyama, Yoshiharu; Zhang, Yi

    2010-06-16

    Dimethyl ether (DME) is an industrially important intermediate, as well as a promising clean fuel, but the effective production through traditionally consecutive steps from syngas to methanol and then to DME has been hindered by the poorly organized structure of the conventional physical mixture catalyst. Here, a novel zeolite capsule catalyst possessing a core-shell structure (millimeter-sized core catalyst and micrometer-sized acidic zeolite shell) was proposed initially through a well-designed aluminum migration method using the core catalyst as the aluminum resource and for the first time was applied to accomplish the DME direct synthesis from syngas. The selectivity of the expected DME on this zeolite capsule catalyst strikingly exceeded that of the hybrid catalyst prepared by the traditional mixing method, while maintaining the near-zero formation of the unexpected alkanes byproduct. The preliminary methanol synthesis reaction on the core catalyst and the following DME formation from methanol inside the zeolite shell cooperated concertedly and promoted mutually. This zeolite capsule catalyst with a synergetic confinement core-shell structure can be used to efficiently realize the combination of two and more sequential reactions with many synergistic effects.

  10. Parameters influencing zeolite incorporation in PDMS membranes

    SciTech Connect

    Vankelecom, I.F.J.; Scheppers, E.; Heus, R.; Uytterhoeven, J.B. )

    1994-11-24

    The incorporation of several types of zeolite in PDMS membranes is studied, by measuring the tensile strength, xylene sorption, and density of the membranes. The zeolite is shown to be involved in the cross-linking of the membrane. The interaction between the PDMS matrix and the zeolites results in reinforced membranes in the case of zeolite Y. The parameters influencing the dispersion of the zeolite in the membrane are investigated, as well as several aspects of the preparation method. Finally, the idea of cross-linking is applied to explain the results of water/ethanol pervaporation. 25 refs., 9 figs., 4 tabs.

  11. Method for regeneration and activity improvement of syngas conversion catalyst

    DOEpatents

    Lucki, Stanley J.; Brennan, James A.

    1980-01-01

    A method is disclosed for the treatment of single particle iron-containing syngas (synthes.s gas) conversion catalysts comprising iron, a crystalline acidic aluminosilicate zeolite having a silica to alumina ratio of at least 12, a pore size greater than about 5 Angstrom units and a constraint index of about 1-12 and a matrix. The catalyst does not contain promoters and the treatment is applicable to either the regeneration of said spent single particle iron-containing catalyst or for the initial activation of fresh catalyst. The treatment involves air oxidation, hydrogen reduction, followed by a second air oxidation and contact of the iron-containing single particle catalyst with syngas prior to its use for the catalytic conversion of said syngas. The single particle iron-containing catalysts are prepared from a water insoluble organic iron compound.

  12. Generation of basic centers in high-silica zeolites and their application in gas-phase upgrading of bio-oil.

    PubMed

    Keller, Tobias C; Rodrigues, Elodie G; Pérez-Ramírez, Javier

    2014-06-01

    High-silica zeolites have been reported recently as efficient catalysts for liquid- and gas-phase condensation reactions because of the presence of a complementary source of basicity compared to Al-rich basic zeolites. Herein, we describe the controlled generation of these active sites on silica-rich FAU, BEA, and MFI zeolites. Through the application of a mild base treatment in aqueous Na2CO3, alkali-metal-coordinating defects are generated within the zeolite whereas the porous properties are fully preserved. The resulting catalysts were applied in the gas-phase condensation of propanal at 673 K as a model reaction for the catalytic upgrading of pyrolysis oil, for which an up to 20-fold increased activity compared to the unmodified zeolites was attained. The moderate basicity of these new sites leads to a coke resistance superior to traditional base catalysts such as CsX and MgO, and comparable activity and excellent selectivity is achieved for the condensation pathways. Through strategic acid and base treatments and the use of magic-angle spinning NMR spectroscopy, the nature of the active sites was investigated, which supports the theory of siloxy sites as basic centers. This contribution represents a key step in the understanding and design of high-silica base catalysts for the intermediate deoxygenation of crude bio-oil prior to the hydrotreating step for the production of second-generation biofuels.

  13. Xylose isomerization with zeolites in a two-step alcohol-water process.

    PubMed

    Paniagua, Marta; Saravanamurugan, Shunmugavel; Melian-Rodriguez, Mayra; Melero, Juan A; Riisager, Anders

    2015-03-01

    Isomerization of xylose to xylulose was efficiently catalyzed by large-pore zeolites in a two-step methanol-water process that enhanced the product yield significantly. The reaction pathway involves xylose isomerization to xylulose, which, in part, subsequently reacts with methanol to form methyl xyluloside (step 1) followed by hydrolysis after water addition to form additional xylulose (step 2). NMR spectroscopy studies performed with (13) C-labeled xylose confirmed the proposed reaction pathway. The most active catalyst examined was zeolite Y, which proved more active than zeolite beta, ZSM-5, and mordenite. The yield of xylulose obtained over H-USY (Si/Al=6) after 1 h of reaction at 100 °C was 39%. After water hydrolysis in the second reaction step, the yield increased to 47%. Results obtained from pyridine adsorption studies confirm that H-USY (6) is a catalyst that combines Brønsted and Lewis acid sites, and isomerizes xylose in alcohol media to form xylulose at low temperature. The applied zeolites are commercially available; do not contain any auxiliary tetravalent metals, for example, tin, titanium, or zirconium; isomerize xylose efficiently; are easy to regenerate; and are prone to recycling.

  14. Adsorption of parent nitrosamine on the nanocrystaline H-zeolite: A theoretical study

    NASA Astrophysics Data System (ADS)

    Roohi, Hossein; Akbari, Fahemeah

    2010-10-01

    Adsorption of parent nitrosamine ( NA) on 5T and 10T cluster models of H-ZSM-5 catalyst has been theoretically investigated using quantum chemical B3LYP and MP2 methods. Three stable complexes ( A- C) were found on the potential energy surface of interaction between NA and cluster models of H-ZSM-5. NA can interact not only with acidic site of zeolite via the lone electron pair on nitrogen and oxygen atoms (O(N)⋯H ZO) but also with the oxygen atoms of the framework via the hydrogen atoms of NH 2 group (NH⋯O) as well. However, the Lewis acidity of zeolite framework is the dominating factor in the interaction between NA and zeolite. The calculated adsorption enthalpy of NA on 5T and 10T clusters of H-ZSM-5 catalyst at ONIOM(MP2/6-311++G(d,p):HF/6-31+G(d)) level ranges from -19.73 to -40.33 and -63.81 to -73.73 kJ/mol, respectively. Adsorption energy for A- C complexes increases in going from B3LYP method to MP2 one. The results of atoms in molecules (AIM) calculations showed that NH5⋯O interactions have electrostatic character, whereas O(N)⋯H Z interactions have partially covalent nature. The results of natural bond orbital (NBO) analysis showed that charge transfer occurs from NA to H-zeolite cluster.

  15. High-performance zeolite NaA membranes on polymer-zeolite composite hollow fiber supports.

    PubMed

    Ge, Qinqin; Wang, Zhengbao; Yan, Yushan

    2009-12-02

    We report a new strategy: use of polymer-zeolite composite hollow fibers as supports. Zeolite membranes with high performance (flux = 8.0-9.0 kg m(-2) h(-1), alpha >10 000) can be synthesized directly on polymer-zeolite composite hollow fiber supports by a single in situ hydrothermal crystallization. The zeolite crystals imbedded in the polymer hollow fiber serve as seeds for the zeolite membrane growth, and they also "anchor" the zeolite membrane to the support to increase the adhesion of the zeolite membrane. Therefore, a separate and often complex seeding process can be omitted. A very uniform crystal distribution can be obtained easily, so continuous zeolite membranes can be prepared with high reproducibility. These composite hollow fibers can be produced simply by blending zeolite crystals into the polymer feed before the hollow fiber extrusion and thus are expected to be inexpensive.

  16. Bubbling Reactor Technology for Rapid Synthesis of Uniform, Small MFI-Type Zeolite Crystals

    SciTech Connect

    Liu, Wei; Rao, Yuxiang; Wan, Haiying; Karkamkar, Abhijeet J.; Liu, Jun; Wang, Li Q.

    2011-06-27

    MFI-type zeolite is an important family of materials used in today’s industries as catalysts and adsorbents. Preparation of this type of zeolite material as uniform and pure crystals of sizes from tens of nanometer to hundreds of nanometer are not only desired by current catalytic and adsorption processes for enhanced reaction kinetics and/or selectivity, but also much needed by some new applications, such as CO2 capture adsorbents and composite materials. However, it has been a major challenge in the zeolite synthesis field to prepare small crystals of MFI-type zeolite over a range of Si/Al ratio with very high throughput. In this work, a gas-bubbling flow reactor is used to conduct hydrothermal growth of the zeolite crystals with controllable Si/Al ratio and crystal sizes. Distinctive, uniform ZSM-5 crystals are successfully synthesized within two hours of reaction time, exceptionally short compared to the conventional synthesis process. The crystals are small enough to form a stable milk-like suspension in water. The Si/Al ratio can be controlled by adjusting the growth solution composition and reaction conditions over a range from about 9 to infinity. Characterization by SEM/EDS, XRD, TEM, N2 adsorption/desorption, and NMR confirms ZSM-5 crystal structures and reveals presence of meso-porosity in the resulting crystals.

  17. Synthesis of mesoporous SAPO-34 zeolite from mesoporous silica materials for methanol to light olefins.

    PubMed

    Kang, Eun A; Kim, Tae-Wan; Chae, Ho-Jeong; Kim, Min; Jeong, Kwang-Eun; Kim, Joo-Wan; Kim, Chul-Ung; Jeong, Soon-Yong

    2013-11-01

    Mesoporous SAPO-34 zeolites were synthesized by using as-prepared mesoporous silica material as both silica source and mesopore tailor. The mesoporous SAPO-34 zeolite materials thus obtained are characterized by a series of different techniques, including poweder X-ray diffraction pattern, nitrogen physisorption analysis, scanning electron micrograph, temperature programmed desorption of ammonia, and inductively coupled plasma atomic emission spectrometry. The resultant mesoporous SAPO-34 crystals exhibit sphere-like particle with zeolite layer units. The mesopore size distribution and particle size can be changed by amounts of silica source and water. The methanol-to-olefins (MTO) reactions using these mesoporous SAPO-34 zeolites are carried out with a fixed-bed reactor. Catalytic tests exhibit that the mesoporous SAPO-34 zeolite materials show high catalytic activity compared with the conventional SAPO-34 for MTO reaction. The better catalytic activity and longer life time of the mesoporous SAPO-34 catalysts in MTO are mainly due to the existence of the mesoporosity of SAPO-34 with small particle size.

  18. The effect of alkali metal on the surface properties of potassium doped Au-Beta zeolites

    SciTech Connect

    Sobczak, Izabela; Rydz, Michal; Ziolek, Maria

    2013-02-15

    Graphical abstract: Display Omitted Highlights: ► Interaction of gold with K leads to the change of electronic state and redox properties of gold. ► The amount of potassium incorporated into Au-zeolites determines the size of gold particles. ► K(0.2 wt.%)/Au-Beta exhibits the best performance in decomposition of N{sub 2}O and removal of Bu{sub 2}S. -- Abstract: Beta zeolite was applied as support for gold introduced by gold-precipitation method and potassium added by impregnation or adsorption. The effect of zeolite composition and the amount of potassium introduced on the surface properties of the final materials was considered. Moreover, the interaction of gold and potassium species was found to be related to the adsorptive and catalytic behaviour of zeolites in NO reduction with propene and deodorization. K/Au-Beta(Impregnated) exhibits the best performance in the above mentioned processes because of the small gold particles (between 2 and 5 nm) and interaction of gold with potassium species leading to the change of electronic properties of the surface (the appearance of cationic gold species). Potassium added as a promoter improves the catalytic properties of Au-zeolite in N{sub 2}O decomposition and also in deodorization (increase of the ability to dibutyl sulphide oxidation). The catalysts prepared were characterized by XRD, XPS, UV–vis, TEM, pyridine adsorption combined with FTIR and test reaction (2-propanol transformation).

  19. Discovery of optimal zeolites for challenging separations and chemical conversions through predictive materials modeling

    NASA Astrophysics Data System (ADS)

    Siepmann, J. Ilja; Bai, Peng; Tsapatsis, Michael; Knight, Chris; Deem, Michael W.

    2015-03-01

    Zeolites play numerous important roles in modern petroleum refineries and have the potential to advance the production of fuels and chemical feedstocks from renewable resources. The performance of a zeolite as separation medium and catalyst depends on its framework structure and the type or location of active sites. To date, 213 framework types have been synthesized and >330000 thermodynamically accessible zeolite structures have been predicted. Hence, identification of optimal zeolites for a given application from the large pool of candidate structures is attractive for accelerating the pace of materials discovery. Here we identify, through a large-scale, multi-step computational screening process, promising zeolite structures for two energy-related applications: the purification of ethanol beyond the ethanol/water azeotropic concentration in a single separation step from fermentation broths and the hydroisomerization of alkanes with 18-30 carbon atoms encountered in petroleum refining. These results demonstrate that predictive modeling and data-driven science can now be applied to solve some of the most challenging separation problems involving highly non-ideal mixtures and highly articulated compounds. Financial support from the Department of Energy Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences and Biosciences under Award DE-FG02-12ER16362 is gratefully acknowledged.

  20. Simultaneous desulfurization and denitrification by microwave reactor with ammonium bicarbonate and zeolite.

    PubMed

    Wei, Zaishan; Lin, Zhehang; Niu, Hejingying; He, Haiming; Ji, Yongfeng

    2009-03-15

    Microwave reactor with ammonium bicarbonate (NH(4)HCO(3)) and zeolite was set up to study the simultaneous removal of sulfur dioxide (SO(2)) and nitrogen oxides (NO(x)) from flue gas. The results showed that the microwave reactor filled with NH(4)HCO(3) and zeolite could reduce SO(2) to sulfur with the best desulfurization efficiency of 99.1% and reduce NO(x) to nitrogen with the best NO(x) purifying efficiency of 86.5%. Microwave desulfurization and denitrification effect of the experiment using ammonium bicarbonate and zeolite together is much higher than that using ammonium bicarbonate or zeolite only. NO(x) concentration has little effect on denitrification but has no influence on desulfurization, SO(2) concentration has no effect on denitrification. The optimal microwave power and empty bed residence time (EBRT) on simultaneous desulfurization and dentrification are 211-280 W and 0.315 s, respectively. The mechanism for microwave reduced desulfurization and denitrification can be described as the microwave-induced catalytic reduction reaction between SO(2), NO(x) and ammonium bicarbonate with zeolite being the catalyst and microwave absorbent.

  1. Catalytic Oxidation of Methane into Methanol over Copper-Exchanged Zeolites with Oxygen at Low Temperature.

    PubMed

    Narsimhan, Karthik; Iyoki, Kenta; Dinh, Kimberly; Román-Leshkov, Yuriy

    2016-06-22

    The direct catalytic conversion of methane to liquid oxygenated compounds, such as methanol or dimethyl ether, at low temperature using molecular oxygen is a grand challenge in C-H activation that has never been met with synthetic, heterogeneous catalysts. We report the first demonstration of direct, catalytic oxidation of methane into methanol with molecular oxygen over copper-exchanged zeolites at low reaction temperatures (483-498 K). Reaction kinetics studies show sustained catalytic activity and high selectivity for a variety of commercially available zeolite topologies under mild conditions (e.g., 483 K and atmospheric pressure). Transient and steady state measurements with isotopically labeled molecules confirm catalytic turnover. The catalytic rates and apparent activation energies are affected by the zeolite topology, with caged-based zeolites (e.g., Cu-SSZ-13) showing the highest rates. Although the reaction rates are low, the discovery of catalytic sites in copper-exchanged zeolites will accelerate the development of strategies to directly oxidize methane into methanol under mild conditions.

  2. Reactivity of alkanes on zeolites: a computational study of propane conversion reactions.

    PubMed

    Zheng, Xiaobo; Blowers, Paul

    2005-12-01

    In this work, quantum chemical methods were used to study propane conversion reactions on zeolites; these reactions included protolytic cracking, primary hydrogen exchange, secondary hydrogen exchange, and dehydrogenation reactions. The reactants, products, and transition-state structures were optimized at the B3LYP/6-31G level and the energies were calculated with CBS-QB3, a complete basis set composite energy method. The computed activation barriers were 62.1 and 62.6 kcal/mol for protolytic cracking through two different transition states, 30.4 kcal/mol for primary hydrogen exchange, 29.8 kcal/mol for secondary hydrogen exchange, and 76.7 kcal/mol for dehydrogenation reactions. The effects of basis set for the geometry optimization and zeolite acidity on the reaction barriers were also investigated. Adding extra polarization and diffuse functions for the geometry optimization did not affect the activation barriers obtained with the composite energy method. The largest difference in calculated activation barriers is within 1 kcal/mol. Reaction activation barriers do change as zeolite acidity changes, however. Linear relationships were found between activation barriers and zeolite deprotonation energies. Analytical expressions for each reaction were proposed so that accurate activation barriers can be obtained when using different zeolites as catalysts, as long as the deprotonation energies are first acquired.

  3. Catalytic Oxidation of Methane into Methanol over Copper-Exchanged Zeolites with Oxygen at Low Temperature

    PubMed Central

    2016-01-01

    The direct catalytic conversion of methane to liquid oxygenated compounds, such as methanol or dimethyl ether, at low temperature using molecular oxygen is a grand challenge in C–H activation that has never been met with synthetic, heterogeneous catalysts. We report the first demonstration of direct, catalytic oxidation of methane into methanol with molecular oxygen over copper-exchanged zeolites at low reaction temperatures (483–498 K). Reaction kinetics studies show sustained catalytic activity and high selectivity for a variety of commercially available zeolite topologies under mild conditions (e.g., 483 K and atmospheric pressure). Transient and steady state measurements with isotopically labeled molecules confirm catalytic turnover. The catalytic rates and apparent activation energies are affected by the zeolite topology, with caged-based zeolites (e.g., Cu-SSZ-13) showing the highest rates. Although the reaction rates are low, the discovery of catalytic sites in copper-exchanged zeolites will accelerate the development of strategies to directly oxidize methane into methanol under mild conditions. PMID:27413787

  4. Sulfonated hierarchical H-USY zeolite for efficient hydrolysis of hemicellulose/cellulose.

    PubMed

    Zhou, Lipeng; Liu, Zhen; Shi, Meiting; Du, Shanshan; Su, Yunlai; Yang, Xiaomei; Xu, Jie

    2013-10-15

    Sulfonated hierarchical H-USY zeolite was prepared and characterized by X-ray diffraction, N2 physisorption, Fourier transform infrared spectroscopy, inductively coupled plasma atomic emission spectroscopy, temperature-programmed desorption of ammonia, and acid-base titration. It was proved that sulfonic group was successfully anchored onto the hierarchical H-USY zeolite. The acidity of the hierarchical H-USY was remarkably improved. Sulfonated hierarchical H-USY zeolite was efficient for the hydrolysis of hemicellulose and cellulose. The yield of TRS for hydrolysis of hemicellulose reached 78.0% at 140 °C for 9h. For hydrolysis of α-cellulose, 60.8% conversion with 22.4% yield of glucose was obtained. Even for microcrystalline cellulose, 43.7% conversion with 15.1% yield of glucose can be obtained. These results are much higher than those obtained over hierarchical H-USY zeolite, indicating that both the acidity and the pore structure determine the activity of zeolite as catalyst in the hydrolysis of biomass.

  5. Two-stage production of olefins utilizing a faujasite structure zeolite in hydrogenation stage

    SciTech Connect

    Kreuter, W.; Mansmann, M.; Watson, A.; Weber, H.; Wernicke, H.J.

    1980-02-12

    A process is disclosed for the production of olefins in two stages. In the first stage, heavy petroleum fractions are hydrogenated in the presence of hydrogen and a hydrogenation catalyst and, in the second stage, the thus-hydrogenated fractions are subjected to thermal cracking the presence of steam. The improvement comprises employing as the hydrogenation catalyst a zeolite of the faujasite structure combined with elements from groups VIB, VIIB and VIII of the periodic table of the elements, wherein the alkali component of the zeolite is exchanged at least partially for ammonium, hydronium, alkaline earth and/or rare earth ions, and the elements are present in a metallic, ionic, oxidic and/or sulfidic form.

  6. Enhanced selectivity of zeolites by controlled carbon deposition

    DOEpatents

    Nenoff, Tina M.; Thoma, Steven G.; Kartin, Mutlu

    2006-05-09

    A method for carbonizing a zeolite comprises depositing a carbon coating on the zeolite pores by flowing an inert carrier gas stream containing isoprene through a regenerated zeolite at elevated temperature. The carbonized zeolite is useful for the separation of light hydrocarbon mixtures due to size exclusion and the differential adsorption properties of the carbonized zeolite.

  7. Metal immobilization in soils using synthetic zeolites.

    PubMed

    Oste, Leonard A; Lexmond, Theo M; Van Riemsdijk, Willem H

    2002-01-01

    In situ immobilization of heavy metals in contaminated soils is a technique to improve soil quality. Synthetic zeolites are potentially useful additives to bind heavy metals. This study selected the most effective zeolite in cadmium and zinc binding out of six synthetic zeolites (mordenite-type, faujasite-type, zeolite X, zeolite P, and two zeolites A) and one natural zeolite (clinoptilolite). Zeolite A appeared to have the highest binding capacity between pH 5 and 6.5 and was stable above pH 5.5. The second objective of this study was to investigate the effects of zeolite addition on the dissolved organic matter (DOM) concentration. Since zeolites increase soil pH and bind Ca, their application might lead to dispersion of organic matter. In a batch experiment, the DOM concentration increased by a factor of 5 when the pH increased from 6 to 8 as a result of zeolite A addition. A strong increase in DOM was also found in the leachate of soil columns, particularly in the beginning of the experiment. This resulted in higher metal leaching caused by metal-DOM complexes. In contrast, the free ionic concentration of Cd and Zn strongly decreased after the addition of zeolites, which might explain the reduction in metal uptake observed in plant growth experiments. Pretreatment of zeolites with acid (to prevent a pH increase) or Ca (to coagulate organic matter) suppressed the dispersion of organic matter, but also decreased the metal binding capacity of the zeolites due to competition of protons or Ca.

  8. Catalytic activity in individual cracking catalyst particles imaged throughout different life stages by selective staining.

    PubMed

    Buurmans, Inge L C; Ruiz-Martínez, Javier; Knowles, William V; van der Beek, David; Bergwerff, Jaap A; Vogt, Eelco T C; Weckhuysen, Bert M

    2011-09-18

    Fluid catalytic cracking (FCC) is the major conversion process used in oil refineries to produce valuable hydrocarbons from crude oil fractions. Because the demand for oil-based products is ever increasing, research has been ongoing to improve the performance of FCC catalyst particles, which are complex mixtures of zeolite and binder materials. Unfortunately, there is limited insight into the distribution and activity of individual zeolitic domains at different life stages. Here we introduce a staining method to visualize the structure of zeolite particulates and other FCC components. Brønsted acidity maps have been constructed at the single particle level from fluorescence microscopy images. By applying a statistical methodology to a series of catalysts deactivated via industrial protocols, a correlation is established between Brønsted acidity and cracking activity. The generally applicable method has clear potential for catalyst diagnostics, as it determines intra- and interparticle Brønsted acidity distributions for industrial FCC materials.

  9. Catalytic activity in individual cracking catalyst particles imaged throughout different life stages by selective staining

    NASA Astrophysics Data System (ADS)

    Buurmans, Inge L. C.; Ruiz-Martínez, Javier; Knowles, William V.; van der Beek, David; Bergwerff, Jaap A.; Vogt, Eelco T. C.; Weckhuysen, Bert M.

    2011-11-01

    Fluid catalytic cracking (FCC) is the major conversion process used in oil refineries to produce valuable hydrocarbons from crude oil fractions. Because the demand for oil-based products is ever increasing, research has been ongoing to improve the performance of FCC catalyst particles, which are complex mixtures of zeolite and binder materials. Unfortunately, there is limited insight into the distribution and activity of individual zeolitic domains at different life stages. Here we introduce a staining method to visualize the structure of zeolite particulates and other FCC components. Brønsted acidity maps have been constructed at the single particle level from fluorescence microscopy images. By applying a statistical methodology to a series of catalysts deactivated via industrial protocols, a correlation is established between Brønsted acidity and cracking activity. The generally applicable method has clear potential for catalyst diagnostics, as it determines intra- and interparticle Brønsted acidity distributions for industrial FCC materials.

  10. NO.sub.x catalyst and method of suppressing sulfate formation in an exhaust purification system

    DOEpatents

    Balmer-Millar, Mari Lou; Park, Paul W.; Panov, Alexander G.

    2006-08-22

    The activity and durability of a zeolite lean-bum NOx catalyst can be increased by loading metal cations on the outer surface of the zeolite. However, the metal loadings can also oxidize sulfur dioxide to cause sulfate formation in the exhaust. The present invention is a method of suppressing sulfate formation in an exhaust purification system including a NO.sub.x catalyst. The NO.sub.x catalyst includes a zeolite loaded with at least one metal. The metal is selected from among an alkali metal, an alkaline earth metal, a lanthanide metal, a noble metal, and a transition metal. In order to suppress sulfate formation, at least a portion of the loaded metal is complexed with at least one of sulfate, phosphate, and carbonate.

  11. NO.sub.x catalyst and method of suppressing sulfate formation in an exhaust purification system

    DOEpatents

    Balmer-Millar, Mari Lou; Park, Paul W.; Panov, Alexander G.

    2007-06-26

    The activity and durability of a zeolite lean-burn NOx catalyst can be increased by loading metal cations on the outer surface of the zeolite. However, the metal loadings can also oxidize sulfur dioxide to cause sulfate formation in the exhaust. The present invention is a method of suppressing sulfate formation in an exhaust purification system including a NO.sub.x catalyst. The NO.sub.x catalyst includes a zeolite loaded with at least one metal. The metal is selected from among an alkali metal, an alkaline earth metal, a lanthanide metal, a noble metal, and a transition metal. In order to suppress sulfate formation, at least a portion of the loaded metal is complexed with at least one of sulfate, phosphate, and carbonate.

  12. Nanoscale intimacy in bifunctional catalysts for selective conversion of hydrocarbons

    NASA Astrophysics Data System (ADS)

    Zecevic, Jovana; Vanbutsele, Gina; de Jong, Krijn P.; Martens, Johan A.

    2015-12-01

    The ability to control nanoscale features precisely is increasingly being exploited to develop and improve monofunctional catalysts. Striking effects might also be expected in the case of bifunctional catalysts, which are important in the hydrocracking of fossil and renewable hydrocarbon sources to provide high-quality diesel fuel. Such bifunctional hydrocracking catalysts contain metal sites and acid sites, and for more than 50 years the so-called intimacy criterion has dictated the maximum distance between the two types of site, beyond which catalytic activity decreases. A lack of synthesis and material-characterization methods with nanometre precision has long prevented in-depth exploration of the intimacy criterion, which has often been interpreted simply as ‘the closer the better’ for positioning metal and acid sites. Here we show for a bifunctional catalyst—comprising an intimate mixture of zeolite Y and alumina binder, and with platinum metal controllably deposited on either the zeolite or the binder—that closest proximity between metal and zeolite acid sites can be detrimental. Specifically, the selectivity when cracking large hydrocarbon feedstock molecules for high-quality diesel production is optimized with the catalyst that contains platinum on the binder, that is, with a nanoscale rather than closest intimacy of the metal and acid sites. Thus, cracking of the large and complex hydrocarbon molecules that are typically derived from alternative sources, such as gas-to-liquid technology, vegetable oil or algal oil, should benefit especially from bifunctional catalysts that avoid locating platinum on the zeolite (the traditionally assumed optimal location). More generally, we anticipate that the ability demonstrated here to spatially organize different active sites at the nanoscale will benefit the further development and optimization of the emerging generation of multifunctional catalysts.

  13. Glycerol Dehydration to Acrolein Catalyzed by ZSM‐5 Zeolite in Supercritical Carbon Dioxide Medium

    PubMed Central

    Zou, Bin; Ren, Shoujie

    2016-01-01

    Abstract Supercritical carbon dioxide (SC‐CO2) has been used for the first time as a reaction medium for the dehydration of glycerol to acrolein catalyzed by a solid acid. Unprecedented catalyst stability over 528 hours of time‐on‐stream was achieved and the rate of coke deposition on the zeolite catalyst was the lowest among extensive previous studies, showing potential for industrial application. Coking pathways in SC‐CO2 were also elucidated for future development. The results have potential implications for other dehydration reactions catalyzed by solid acids. PMID:27796088

  14. Comparison of real waste (MSW and MPW) pyrolysis in batch reactor over different catalysts. Part II: contaminants, char and pyrolysis oil properties.

    PubMed

    Miskolczi, Norbert; Ateş, Funda; Borsodi, Nikolett

    2013-09-01

    Pyrolysis of real wastes (MPW and MSW) has been investigated at 500°C, 550°C and 600°C using Y-zeolite, β-zeolite, equilibrium FCC, MoO3, Ni-Mo-catalyst, HZSM-5 and Al(OH)3 as catalysts. The viscosity of pyrolysis oils could be decreased by the using of catalysts, especially by β-zeolite and MoO3. Both carbon frame and double bound isomerization was found in case of thermo-catalytic pyrolysis. Char morphology and texture analysis showed more coke deposits on the catalyst surface using MSW raw material. Pyrolysis oils had K, S, P Cl, Ca, Zn, Fe, Cr, Br and Sb as contaminants; and the concentrations of K, S, P, Cl and Br could be decreased by the using of catalysts.

  15. UTILITY OF ZEOLITES IN HAZARDOUS METAL REMOVAL FROM WATER

    EPA Science Inventory

    Zeolites are well known for their ion exchange, adsorption and acid catalysis properties. Different inorganic pollutants have been removed from water at room temperature by using synthetic zeolites. Zeolite Faujasite Y has been used to remove inorganic pollutants including arseni...

  16. Hydrogen Selective Exfoliated Zeolite Membranes

    SciTech Connect

    Tsapatsis, Michael; Daoutidis, Prodromos; Elyassi, Bahman; Lima, Fernando; Iyer, Aparna; Agrawal, Kumar; Sabnis, Sanket

    2015-04-06

    The objective of this project was to develop and evaluate an innovative membrane technology at process conditions that would be representative of Integrated Gasification Combined Cycle (IGCC) advanced power generation with pre-combustion capture of carbon dioxide (CO2). This research focused on hydrogen (H2)-selective zeolite membranes that could be utilized to separate conditioned syngas into H2-rich and CO2-rich components. Both experiments and process design and optimization calculations were performed to evaluate the concept of ultra-thin membranes made from zeolites nanosheets. In this work, efforts in the laboratory were made to tackle two fundamental challenges in application of zeolite membranes in harsh industrial environments, namely, membrane thickness and membrane stability. Conventional zeolite membranes have thicknesses in the micron range, limiting their performance. In this research, we developed a method for fabrication of ultimately thin zeolite membranes based on zeolite nanosheets. A range of layered zeolites (MWW, RWR, NSI structure types) suitable for hydrogen separation was successfully exfoliated to their constituent nanosheets. Further, membranes were made from one of these zeolites, MWW, to demonstrate the potential of this group of materials. Moreover, long-term steam stability of these zeolites (up to 6 months) was investigated in high concentrations of steam (35 mol% and 95 mole%), high pressure (10 barg), and high temperatures (350 °C and 600 °C) relevant to conditions of water-gas-shift and steam methane reforming reactions. It was found that certain nanosheets are stable, and that stability depends on the concentration of structural defects. Additionally, models that represent a water-gas-shift (WGS) membrane reactor equipped with the zeolite membrane were developed for systems studies. These studies had the aim of analyzing the effect of the membrane reactor integration into IGCC plants

  17. Intramolecular hydroalkoxylation of non-activated C=C bonds catalysed by zeolites: an experimental and theoretical study.

    PubMed

    Pérez-Mayoral, Elena; Matos, Ines; Nachtigall, Petr; Položij, Miroslav; Fonseca, Isabel; Vitvarová-Procházková, Dana; Čejka, Jiří

    2013-06-01

    The high activity and selectivity of zeolites in the cyclisation of unsaturated alcohols is reported for the first time; the details of a reaction mechanism based on quantum chemical calculations are also provided. The high efficiency of zeolites MFI, BEA and FAU in the cyclisation of unsaturated alcohols (cis-decen-1-ol, 6-methylhept-5-en-2-ol and 2-allylphenol) to afford oxygen-containing heterocyclic rings is demonstrated. The best catalytic performance is found for zeolites with the optimum concentration of Brønsted acid sites (ca. 0.2 mmol g(-1)) and the minimum number of Lewis acid sites. It is proposed that the efficiency of the catalysts is reduced by the existence of the so-called dual site, at which a molecule of unsaturated alcohol can simultaneously interact with two acid sites (an OH group with one and the double bond with the other Brønsted site), which increases the interaction strength. The formation of such adsorption complexes leads to a decrease in the catalyst activity because of (i) an increase in the reaction barrier, (ii) an unfavourable conformation and (iii) diffusion limitations. A new procedure for the preparation of tetrahydrofurans and pyrans over zeolite catalysts provides important oxygen-containing heterocycles with numerous applications.

  18. Tailored zeolites for the removal of metal oxyanions: overcoming intrinsic limitations of zeolites.

    PubMed

    Figueiredo, Hugo; Quintelas, Cristina

    2014-06-15

    This review aims to present a global view of the efforts conducted to convert zeolites into efficient supports for the removal of heavy metal oxyanions. Despite lacking affinity for these species, due to inherent charge repulsion between zeolite framework and anionic species, zeolites have still received considerable attention from the scientific community, since their versatility allowed tailoring them to answer specific requirements. Different processes for the removal and recovery of toxic metals based on zeolites have been presented. These processes resort to modification of the zeolite surface to allow direct adsorption of oxyanions, or by combination with reducing agents for oxyanions that allow ion-exchange with the converted species by the zeolite itself. In order to testify zeolite versatility, as well as covering the wide array of physicochemical constraints that oxyanions offer, chromium and arsenic oxyanions were selected as model compounds for a review of treatment/remediation strategies, based on zeolite modification.

  19. Ship-in-a-bottle catalysts

    DOEpatents

    Haw, James F.; Song, Weiguo

    2006-07-18

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

  20. Effects of catalyst support and chemical vapor deposition condition on synthesis of multi-walled carbon nanocoils

    NASA Astrophysics Data System (ADS)

    Suda, Yoshiyuki; Iida, Tetsuo; Takikawa, Hirofumi; Harigai, Toru; Ue, Hitoshi; Umeda, Yoshito

    2016-02-01

    Multi-walled carbon nanocoil (MWCNC) is a carbon nanotube (CNT) with helical shape. We have synthesized MWCNCs and MWCNTs hybrid by chemical vapor deposition (CVD). MWCNCs are considered to be a potential material in nanodevices, such as electromagnetic wave absorbers and field emitters. It is very important to take into account the purity of MWCNCs. In this study, we aimed to improve the composition ratio of MWCNCs to MWCNTs by changing catalyst preparation and CVD conditions. As a catalyst, Fe2O3/zeolite was prepared by dissolving Fe2O3 fine powder and Y-type zeolite (catalyst support material) in ethanol with an Fe density of 0.5wt.% and with a zeolite density of 3.5wt.%. The catalyst-coated Si substrate was transferred immediately onto a hotplate and was heated at 80°C for 5 min. Similarly, Fe2O3/Al2O3, Co/zeolite/Al2O3, Co/zeolite, and Co/Al2O3 were prepared. The effect of the difference of the composite catalysts on synthesis of MWCNCs was considered. The CVD reactor was heated in a tubular furnace to 660-790°C in a nitrogen atmosphere at a flow rate of 1000 ml/min. Subsequently, acetylene was mixed with nitrogen at a flow rate ratio of C2H2/N2 = 0.02-0.1. The reaction was kept under these conditions for 10 min. MWCNTs and MWCNCs were well grown by the catalysts of Co/zeolite and Co/Al2O3. The composition ratio of MWCNCs to MWCNTs was increased by using a combination of zeolite and Al2O3. The highest composition ratio of MWCNCs to MWCNTs was 12%.

  1. Propene poisoning on three typical Fe-zeolites for SCR of NOχ with NH₃: from mechanism study to coating modified architecture.

    PubMed

    Ma, Lei; Li, Junhua; Cheng, Yisun; Lambert, Christine K; Fu, Lixin

    2012-02-07

    Application of Fe-zeolites for urea-SCR of NO(x) in diesel engine is limited by catalyst deactivation with hydrocarbons (HCs). In this work, a series of Fe-zeolite catalysts (Fe-MOR, Fe-ZSM-5, and Fe-BEA) was prepared by ion exchange method, and their catalytic activity with or without propene for selective catalytic reduction of NO(x) with ammonia (NH(3)-SCR) was investigated. Results showed that these Fe-zeolites were relatively active without propene in the test temperature range (150-550 °C); however, all of the catalytic activity was suppressed in the presence of propene. Fe-MOR kept relatively higher activity with almost 80% NO(x) conversion even after propene coking at 350 °C, and 38% for Fe-BEA and 24% for Fe-ZSM-5 at 350 °C, respectively. It was found that the pore structures of Fe-zeolite catalysts were one of the main factors for coke formation. As compared to ZSM-5 and HBEA, MOR zeolite has a one-dimensional structure for propene diffusion, relatively lower acidity, and is not susceptible to deactivation. Nitrogenated organic compounds (e.g., isocyanate) were observed on the Fe-zeolite catalyst surface. The site blockage was mainly on Fe(3+) sites, on which NO was activated and oxidized. Furthermore, a novel fully formulated Fe-BEA monolith catalyst coating modified with MOR was designed and tested, the deactivation due to propene poisoning was clearly reduced, and the NO(x) conversion reached 90% after 700 ppm C(3)H(6) exposure at 500 °C.

  2. Bimetallic Catalysts.

    ERIC Educational Resources Information Center

    Sinfelt, John H.

    1985-01-01

    Chemical reaction rates can be controlled by varying composition of miniscule clusters of metal atoms. These bimetallic catalysts have had major impact on petroleum refining, where work has involved heterogeneous catalysis (reacting molecules in a phase separate from catalyst.) Experimentation involving hydrocarbon reactions, catalytic…

  3. Oxyhydrochlorination catalyst

    DOEpatents

    Taylor, Charles E.; Noceti, Richard P.

    1992-01-01

    An improved catalyst and method for the oxyhydrochlorination of methane is disclosed. The catalyst includes a pyrogenic porous support on which is layered as active material, cobalt chloride in major proportion, and minor proportions of an alkali metal chloride and of a rare earth chloride. On contact of the catalyst with a gas flow of methane, HCl and oxygen, more than 60% of the methane is converted and of that converted more than 40% occurs as monochloromethane. Advantageously, the monochloromethane can be used to produce gasoline boiling range hydrocarbons with the recycle of HCl for further reaction. This catalyst is also of value for the production of formic acid as are analogous catalysts with lead, silver or nickel chlorides substituted for the cobalt chloride.

  4. Characteristic of fly ash derived-zeolite and its catalytic performance for fast pyrolysis of Jatropha waste.

    PubMed

    Vichaphund, S; Aht-Ong, D; Sricharoenchaikul, V; Atong, D

    2014-01-01

    Fly ash from pulp and paper industries was used as a raw material for synthesizing zeolite catalyst. Main compositions of fly ash consisted of 41 wt%SiO2, 20 wt%Al2O3, 14 wt%CaO, and 8 wt% Fe2O3. High content of silica and alumina indicated that this fly ash has potential uses for zeolite synthesis. Fly ash was mixed with 1-3 M NaOH solution. Sodium silicate acting as silica source was added into the solution to obtain the initial SiO2/Al2O3 molar ratio of 23.9. The mixtures were then crystallized at 160 degrees C for 24 and 72 h. Zeolites synthesized after a long synthesis time of 72 h showed superior properties in terms of high crystallinity, less impurity, and small particle size. The catalytic activities of fly ash-derived zeolites were investigated via fast pyrolysis of Jatropha wastes using analytical pyrolysis-gas chromatograph/mass spectrometer (GC/MS). Pyrolysis temperature was set at 500 degrees C with Jatropha wastes to catalyst ratio of 1:1, 1:5, and 1:10. Results showed that higher amounts of catalyst have a positive effect on enhancing aromatic hydrocarbons as well as decreasing in the oxygenated and N-containing compounds. Zeolite Socony Mobil-5 (ZSM-5) treated with 3 M NaOH at 72 h showed the highest hydrocarbon yield of 97.4%. The formation of hydrocarbon led to the high heating value of bio-oils. In addition, the presence of ZSM-5 derived from fly ash contributed to reduce the undesirable oxygenated compounds such as aldehydes, acids, and ketones which cause poor quality of bio-oil to only 0.8% while suppressed N-compounds to 1.7%. Overall, the ZSM-5 synthesized from fly ash proved to be an effective catalyst for catalytic fast pyrolysis application.

  5. Fischer–Tropsch Synthesis: Effect of Reducing Agent for Aqueous-Phase Synthesis Over Ru Nanoparticle and Supported Ru Catalysts

    SciTech Connect

    Pendyala, Venkat Ramana Rao; Shafer, Wilson D.; Jacobs, Gary; Graham, Uschi M.; Khalid, Syed; Davis, Burtron H.

    2014-12-27

    The effect of the reducing agent on the performance of a ruthenium nanoparticle catalyst was investigated during aqueous-phase Fischer–Tropsch synthesis using a 1 L stirred tank reactor in the batch mode of operation. For the purpose of comparison, the activity and selectivity of NaY zeolite supported Ru catalyst were also studied. NaBH4 and hydrogen were used as reducing agents in our study, and hydrogen reduced catalysts exhibited higher activities than the NaBH4 reduced catalysts, because of higher extent of reduction and a relatively lower tendency toward agglomeration of Ru particles. The Ru nanoparticle catalyst displayed higher activities than the NaY zeolite supported Ru catalyst for both reducing agents. NaBH4 reduced catalysts are less active and the carbon dioxide selectivity is higher than the hydrogen reduced catalysts. The activity of the supported Ru catalyst (Ru/NaY) was 75 % of that of the Ru nanoparticle catalyst, and has the benefit of easy wax/catalyst slurry separation by filtration. Finally, the hydrogen reduced supported Ru catalyst exhibited superior selectivity towards hydrocarbons (higher C5+ selectivity and lower selectivity to methane) than all other catalysts tested.

  6. Mesoporosity--a new dimension for zeolites.

    PubMed

    Möller, Karin; Bein, Thomas

    2013-05-07

    Frameworks of precisely defined pores with diameters matching the size of small molecules endow crystalline zeolites with valuable size- and shape-selectivity. Being important selective adsorbers and separators, zeolites are also indispensable as solid acids in size-selective catalysis. However, despite being extremely beneficial, micropores impose restrictions on the mass transport of reactants, especially when bulky molecules are involved. The prospect to boost the catalytic power of zeolites and to extend their applications into new areas has prompted numerous efforts to synthesize mesoporous zeolitic materials that combine diffusional pathways on two different size scales. Our tutorial review will introduce the reader to this exciting recent development in zeolite science. We will give a general overview of the diverse strategies on how to implement a secondary pore system in zeolites. We will distinguish top-down from bottom-up and template-assisted from 'template-free' procedures. Advantages and limitations of the different methods will also be addressed.

  7. Pulsed Field Gradient Nuclear Magnetic Resonance and Applications in Yttrium Type Zeolites

    NASA Astrophysics Data System (ADS)

    Wu, Shaoxiong

    Molecular self-diffusion measurements by Pulsed Field Gradient Nuclear Magnetic Resonance (PFG NMR) spectroscopy can be applied to numerous fields. PFG NMR spectroscopy usually requires no special labeling for measuring hydrocarbon self-diffusion in a variety of samples. This is a significant advantage over using radioactive isotopes or photolabeled molecules since no special sample preparation or handling is required. A single set of experiments can yield diffusion coefficients and often can be performed in a few hours. The range of diffusion coefficients (10^{ -4} cm^2/s-10 ^{-10} cm^2/s) which can be determined by PFG NMR covers most ranges of molecular diffusion. This work describes the design of a PFG NMR spectrometer for measuring hydrocarbon self-diffusion in zeolites. The principles of PFG NMR spectroscopy are illustrated. A pulsed field gradient 60 MHz NMR spectrometer was constructed. Diffusion data were acquired by PFG NMR for standard samples of water, ammonia and glycerol and are in good agreement with those reported in the literature. Following verification of spectrometer performance, the self-diffusion coefficients of isobutane in cation exchanged Y type zeolites were determined. The results show that the mobility of molecules in zeolites depends on the nature of the cations. For small crystallite zeolites, intercrystalline and intracrystalline diffusion has been observed. The effective diffusion coefficients strongly depend on the concentration of adsorbate as well as the packing method. Large discrepancies between diffusion coefficients in zeolites measured by PFG NMR and by adsorption rate experiments have been reported. Surface area, crystallite size, percentage of water in the zeolite, percentage of cation exchanged into the zeolite and other physical chemical properties effect hydrocarbon diffusivity. Detailed methods for determining these properties are discussed. As an extended study of zeolite catalysts, the adsorption of ethylene on

  8. Improved synthesis of isostearic acid using zeolite catalysts

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Isostearic acids are unique and important biobased products with superior properties. Unfortunately, they are not widely utilized in industry because they are produced as byproducts from a process called clay-catalyzed oligomerization of tall oil fatty acids. Generally, this clay method results in...

  9. Synthesis of ‘unfeasible’ zeolites

    NASA Astrophysics Data System (ADS)

    Mazur, Michal; Wheatley, Paul S.; Navarro, Marta; Roth, Wieslaw J.; Položij, Miroslav; Mayoral, Alvaro; Eliášová, Pavla; Nachtigall, Petr; Čejka, Jiří; Morris, Russell E.

    2016-01-01

    Zeolites are porous aluminosilicate materials that have found applications in many different technologies. However, although simulations suggest that there are millions of possible zeolite topologies, only a little over 200 zeolite frameworks of all compositions are currently known, of which about 50 are pure silica materials. This is known as the zeolite conundrum—why have so few of all the possible structures been made? Several criteria have been formulated to explain why most zeolites are unfeasible synthesis targets. Here we demonstrate the synthesis of two such ‘unfeasible’ zeolites, IPC-9 and IPC-10, through the assembly-disassembly-organization-reassembly mechanism. These new high-silica zeolites have rare characteristics, such as windows that comprise odd-membered rings. Their synthesis opens up the possibility of preparing other zeolites that have not been accessible by traditional solvothermal synthetic methods. We envisage that these findings may lead to a step change in the number and types of zeolites available for future applications.

  10. Increased thermal conductivity monolithic zeolite structures

    DOEpatents

    Klett, James; Klett, Lynn; Kaufman, Jonathan

    2008-11-25

    A monolith comprises a zeolite, a thermally conductive carbon, and a binder. The zeolite is included in the form of beads, pellets, powders and mixtures thereof. The thermally conductive carbon can be carbon nano-fibers, diamond or graphite which provide thermal conductivities in excess of about 100 W/mK to more than 1,000 W/mK. A method of preparing a zeolite monolith includes the steps of mixing a zeolite dispersion in an aqueous colloidal silica binder with a dispersion of carbon nano-fibers in water followed by dehydration and curing of the binder is given.

  11. Computational study of the carbonyl-ene reaction of encapsulated formaldehyde in Na-FAU zeolite

    NASA Astrophysics Data System (ADS)

    Sangthong, Winyoo; Probst, Michael; Limtrakul, Jumras

    2005-06-01

    Density-functional theory (B3LYP/6-31G(d,p)) and the ONIOM (Our-own-N-layer Integrated molecular Orbital+molecular Mechanics) approach utilizing two-layer ONIOM schemes (B3LYP/6-31G(d,p):UFF) have been employed to investigate structures of Na-exchanged zeolite-encapsulated formaldehyde (HCHO@Na-zeolite) and their interactions with propylene. The carbonyl-ene reaction of propylene and formaldehyde was studied on three model systems: (1) formaldehyde in Na-exchanged zeolite: HCHO@Na-zeolite/CH 3CH dbnd6 CH 2; (2) naked Na(I) as catalyst: Na(I)/HCHO/CH 3CH dbnd6 CH 2; (3) a bare model where only the reactants are present: HCHO/CH 3CH dbnd6 CH 2. It is found that inclusion of the extended zeolite framework has an effect on the structure and energetics of the adsorption complexes and leads to a lower energy barrier (25.1 kcal/mol) of the reaction as compared to the bare model system (34.4 kcal/mol). If the naked Na(I) interacts with the HCHO/CH 3CH dbnd6 CH 2 complex the energy barrier of the system is even lower than HCHO@Na-zeolite/CH 3CH dbnd6 CH 2, due to the large electrostatic field generated by the naked Na(I) cation (17.5 kcal/mol). The carbonyl-ene reaction of propylene using HCHO@Na-faujasite takes place in a single concerted reaction step.

  12. Fiber-optic exhaust-gas sensor based on the fluorescence characteristics of Cu containing zeolites

    NASA Astrophysics Data System (ADS)

    Remillard, Jeffrey

    2000-03-01

    A single catalyst in the exhaust system can reduce the concentration of toxic gases emitted by automobiles if the engine is operated close to the stoichiometric air-fuel ratio. This is accomplished through the use of an electrochemical oxygen sensor in the exhaust stream. Near the stoichiometric point, this sensor produces a step-function response when the exhaust gas transitions from an oxygen-poor to an oxygen-rich condition. This talk describes a different kind of sensor based on the use of copper-containing zeolites that produces a proportional output. Zeolites are a class of aluminosilicate materials that have an open 3D structure containing channels and cavities. The Al sites are negatively charged and are generally compensated by cations present during formation of the zeolite. Our experiments use a zeolite designated Cu-ZSM-5, which has the protons originally present in the ZSM-5 material replaced with cupric (Cu^+2) ions. Exposure of this zeolite to a reducing gas results in the conversion of some cupric ions to cuprous (Cu^+1) ions. Subsequent exposure of the zeolite to an oxidizing gas reverses this reaction. The use of this material as a gas sensor is based on the observation that cuprous ions produce a green fluorescent emission when exposed to blue light, whereas no fluorescence is observed from cupric ions. Monitoring the fluorescence of Cu-ZSM-5 placed in a gas stream can thus provide information on the gas's reductant-to-oxidant ratio. We present the results of high temperature in-situ fluorescence spectra, intensity, and reponse-time measurements performed on samples of Cu-ZSM-5 exposed to various O_2-reductant combinations and also discuss data obtained from a single-fiber prototype sensor fabricated using a sol-gel processing technique.(J.T. Remillard et al.), Appl. Opt. 38 5306 (1999).

  13. Widening Synthesis Bottlenecks: Realization of Ultrafast and Continuous-Flow Synthesis of High-Silica Zeolite SSZ-13 for NOx Removal.

    PubMed

    Liu, Zhendong; Wakihara, Toru; Oshima, Kazunori; Nishioka, Daisuke; Hotta, Yuusuke; Elangovan, Shanmugam P; Yanaba, Yutaka; Yoshikawa, Takeshi; Chaikittisilp, Watcharop; Matsuo, Takeshi; Takewaki, Takahiko; Okubo, Tatsuya

    2015-05-04

    Characteristics of zeolite formation, such as being kinetically slow and thermodynamically metastable, are the main bottlenecks that obstruct a fast zeolite synthesis. We present an ultrafast route, the first of its kind, to synthesize high-silica zeolite SSZ-13 in 10 min, instead of the several days usually required. Fast heating in a tubular reactor helps avoid thermal lag, and the synergistic effect of addition of a SSZ-13 seed, choice of the proper aluminum source, and employment of high temperature prompted the crystallization. Thanks to the ultra-short period of synthesis, we established a continuous-flow preparation of SSZ-13. The fast-synthesized SSZ-13, after copper-ion exchange, exhibits outstanding performance in the ammonia selective catalytic reduction (NH3 -SCR) of nitrogen oxides (NOx ), showing it to be a superior catalyst for NOx removal. Our results indicate that the formation of high-silica zeolites can be extremely fast if bottlenecks are effectively widened.

  14. Method and apparatus for combination catalyst for reduction of NO.sub.x in combustion products

    DOEpatents

    Socha, Richard F.; Vartuli, James C.; El-Malki, El-Mekki; Kalyanaraman, Mohan; Park, Paul W.

    2010-09-28

    A method and apparatus for catalytically processing a gas stream passing therethrough to reduce the presence of NO.sub.x therein, wherein the apparatus includes a first catalyst composed of a silver containing alumina that is adapted for catalytically processing the gas stream at a first temperature range, and a second catalyst composed of a copper containing zeolite located downstream from the first catalyst, wherein the second catalyst is adapted for catalytically processing the gas stream at a lower second temperature range relative to the first temperature range.

  15. Selenium clusters in zeolites -- theory.

    NASA Astrophysics Data System (ADS)

    Demkov, Alex; Sankey, Otto

    1997-03-01

    We investigate theoretically atomic geometries, energetics and electronic properties of Se clusters in cages and channels of the zeolites Linde A and cancrinite, and compare them with the properties of the bulk Se phases. Such regular 3D arrays of nanosize clusters supported by a host crystalline matrix are known as supralattices (A.A. Demkov, and O.F. Sankey, Chem. Mater. 8), 1793 (1996). Host zeolite frameworks are transparent, and the presence of Se gives rise to electronic cluster-like states in the energy gap region of the host material. We find that the encapsulation causes structural changes in the cluster geometry which alter its electronic structure, we call this a ``pressure'' effect. In addition, the quantum confinement further changes these states upon the encapsulation. We discuss the relative importance of these two effects, and compare our calculations with the recent experimental work ( Y. Nozue, et al.), J. Phys.: Condens. Matter. 2, 5209 (1990).

  16. Zeolite-like liquid crystals

    PubMed Central

    Poppe, Silvio; Lehmann, Anne; Scholte, Alexander; Prehm, Marko; Zeng, Xiangbing; Ungar, Goran; Tschierske, Carsten

    2015-01-01

    Zeolites represent inorganic solid-state materials with porous structures of fascinating complexity. Recently, significant progress was made by reticular synthesis of related organic solid-state materials, such as metal-organic or covalent organic frameworks. Herein we go a step further and report the first example of a fluid honeycomb mimicking a zeolitic framework. In this unique self-assembled liquid crystalline structure, transverse-lying π-conjugated rod-like molecules form pentagonal channels, encircling larger octagonal channels, a structural motif also found in some zeolites. Additional bundles of coaxial molecules penetrate the centres of the larger channels, unreachable by chains attached to the honeycomb framework. This creates a unique fluid hybrid structure combining positive and negative anisotropies, providing the potential for tuning the directionality of anisotropic optical, electrical and magnetic properties. This work also demonstrates a new approach to complex soft-matter self-assembly, by using frustration between space filling and the entropic penalty of chain extension. PMID:26486751

  17. Zeolite-like liquid crystals

    NASA Astrophysics Data System (ADS)

    Poppe, Silvio; Lehmann, Anne; Scholte, Alexander; Prehm, Marko; Zeng, Xiangbing; Ungar, Goran; Tschierske, Carsten

    2015-10-01

    Zeolites represent inorganic solid-state materials with porous structures of fascinating complexity. Recently, significant progress was made by reticular synthesis of related organic solid-state materials, such as metal-organic or covalent organic frameworks. Herein we go a step further and report the first example of a fluid honeycomb mimicking a zeolitic framework. In this unique self-assembled liquid crystalline structure, transverse-lying π-conjugated rod-like molecules form pentagonal channels, encircling larger octagonal channels, a structural motif also found in some zeolites. Additional bundles of coaxial molecules penetrate the centres of the larger channels, unreachable by chains attached to the honeycomb framework. This creates a unique fluid hybrid structure combining positive and negative anisotropies, providing the potential for tuning the directionality of anisotropic optical, electrical and magnetic properties. This work also demonstrates a new approach to complex soft-matter self-assembly, by using frustration between space filling and the entropic penalty of chain extension.

  18. Catalytic Transformation of Bio-oil to Olefins with Molecular Sieve Catalysts

    NASA Astrophysics Data System (ADS)

    Huang, Wei-wei; Gong, Fei-yan; Zhai, Qi; Li, Quan-xin

    2012-08-01

    Catalytic conversion of bio-oil into light olefins was performed by a series of molecular sieve catalysts, including HZSM-5, MCM-41, SAPO-34 and Y-zeolite. Based on the light olefins yield and its carbon selectivity, the production of light olefins decreased in the following order: HZSM-5>SAPO-34>MCM-41> Y-zeolite. The highest olefins yield from bio-oil using HZSM-5 catalyst reached 0.22 kg/kgbio-oil with carbon selectivity of 50.7% and a nearly complete bio-oil conversion. The reaction conditions and catalyst characterization were investigated in detail to reveal the relationship between the catalyst structure and the production of olefins. The comparison between the pyrolysis and catalytic pyrolysis of bio-oil was also performed.

  19. Catalyst mixtures

    DOEpatents

    Masel, Richard I.; Rosen, Brian A.

    2017-02-14

    Catalysts that include at least one catalytically active element and one helper catalyst can be used to increase the rate or lower the overpotential of chemical reactions. The helper catalyst can simultaneously act as a director molecule, suppressing undesired reactions and thus increasing selectivity toward the desired reaction. These catalysts can be useful for a variety of chemical reactions including, in particular, the electrochemical conversion of CO.sub.2 or formic acid. The catalysts can also suppress H.sub.2 evolution, permitting electrochemical cell operation at potentials below RHE. Chemical processes and devices using the catalysts are also disclosed, including processes to produce CO, OH.sup.-, HCO.sup.-, H.sub.2CO, (HCO.sub.2).sup.-, H.sub.2CO.sub.2, CH.sub.3OH, CH.sub.4, C.sub.2H.sub.4, CH.sub.3CH.sub.2OH, CH.sub.3COO.sup.-, CH.sub.3COOH, C.sub.2H.sub.6, O.sub.2, H.sub.2, (COOH).sub.2, or (COO.sup.-).sub.2, and a specific device, namely, a CO.sub.2 sensor.

  20. Photo-oxidation catalysts

    DOEpatents

    Pitts, J. Roland; Liu, Ping; Smith, R. Davis

    2009-07-14

    Photo-oxidation catalysts and methods for cleaning a metal-based catalyst are disclosed. An exemplary catalyst system implementing a photo-oxidation catalyst may comprise a metal-based catalyst, and a photo-oxidation catalyst for cleaning the metal-based catalyst in the presence of light. The exposure to light enables the photo-oxidation catalyst to substantially oxidize absorbed contaminants and reduce accumulation of the contaminants on the metal-based catalyst. Applications are also disclosed.

  1. Monocopper active site for partial methane oxidation in Cu-exchanged 8MR zeolites

    SciTech Connect

    Kulkarni, Ambarish R.; Zhao, Zhi -Jian; Siahrostami, Samira; Nørskov, Jens K.; Studt, Felix

    2016-08-17

    Direct conversion of methane to methanol using oxygen is experiencing renewed interest owing to the availability of new natural gas resources. Copper-exchanged zeolites such as mordenite and ZSM-5 have shown encouraging results, and di- and tri-copper species have been suggested as active sites. Recently, small eight-membered ring (8MR) zeolites including SSZ-13, -16, and -39 have been shown to be active for methane oxidation, but the active sites and reaction mechanisms in these 8MR zeolites are not known. In this work, we use density functional theory (DFT) calculations to systematically evaluate monocopper species as active sites for the partial methane oxidation reaction in Cu-exchanged SSZ-13. On the basis of kinetic and thermodynamic arguments, we suggest that [CuIIOH]+ species in the 8MR are responsible for the experimentally observed activity. Furthermore, our results successfully explain the available spectroscopic data and experimental observations including (i) the necessity of water for methanol extraction and (ii) the effect of Si/Al ratio on the catalyst activity. Monocopper species have not yet been suggested as an active site for the partial methane oxidation reaction, and our results suggest that [CuIIOH]+ active site may provide complementary routes for methane activation in zeolites in addition to the known [Cu–O–Cu]2+ and Cu3O3 motifs.

  2. Monocopper active site for partial methane oxidation in Cu-exchanged 8MR zeolites

    DOE PAGES

    Kulkarni, Ambarish R.; Zhao, Zhi -Jian; Siahrostami, Samira; ...

    2016-08-17

    Direct conversion of methane to methanol using oxygen is experiencing renewed interest owing to the availability of new natural gas resources. Copper-exchanged zeolites such as mordenite and ZSM-5 have shown encouraging results, and di- and tri-copper species have been suggested as active sites. Recently, small eight-membered ring (8MR) zeolites including SSZ-13, -16, and -39 have been shown to be active for methane oxidation, but the active sites and reaction mechanisms in these 8MR zeolites are not known. In this work, we use density functional theory (DFT) calculations to systematically evaluate monocopper species as active sites for the partial methane oxidationmore » reaction in Cu-exchanged SSZ-13. On the basis of kinetic and thermodynamic arguments, we suggest that [CuIIOH]+ species in the 8MR are responsible for the experimentally observed activity. Furthermore, our results successfully explain the available spectroscopic data and experimental observations including (i) the necessity of water for methanol extraction and (ii) the effect of Si/Al ratio on the catalyst activity. Monocopper species have not yet been suggested as an active site for the partial methane oxidation reaction, and our results suggest that [CuIIOH]+ active site may provide complementary routes for methane activation in zeolites in addition to the known [Cu–O–Cu]2+ and Cu3O3 motifs.« less

  3. Selective catalytic conversion of bio-oil over high-silica zeolites.

    PubMed

    Widayatno, Wahyu Bambang; Guan, Guoqing; Rizkiana, Jenny; Du, Xiao; Hao, Xiaogang; Zhang, Zhonglin; Abudula, Abuliti

    2015-03-01

    Four high silica zeolites, i.e., HSZ-385, 890, 960, and 990 were utilized for the selective catalytic conversion of bio-oil from Fallopia japonica to certain chemicals in a fixed-bed reactor. The Beta-type HSZ-960 zeolite showed the highest selectivity to hydrocarbons, especially to aromatics as well as PAH compounds with the lowest unwanted chemicals while HSZ-890 showed high selectivity to aromatics. NH3-Temperature Programmed Desorption (TPD) analysis indicated that different amounts of acid sites in different zeolites determined the catalytic activity for the oxygen removal from bio-oil, in which the acid sites at low temperature (LT) region gave more contribution within the utilized temperature region. The reusability test of HSZ-960 showed the stability of hydrocarbons yield at higher temperature due to the significant contribution of coke gasification which assisted further deoxygenation of bio-oil. These results provide a guidance to select suitable zeolite catalysts for the upgrading of bio-oil in a practical process.

  4. Oxidation of H2 and CO over ion-exchanged X and Y zeolites.

    PubMed

    Lahr, Daniel G; Li, Junhui; Davis, Robert J

    2007-03-21

    Zeolites X and Y exchanged with Group IA cations were synthesized by aqueous ion exchange of NaX and NaY and used as catalysts in the oxidation of H2 and CO at temperatures ranging from 473 to 573 K. The CsX zeolite was the most active material of the series for both reactions whereas HX was the least active. Moreover, the oxidation of CO in H2 was very selective (approximately 80%) over the alkali-metal exchanged materials. Isotopic transient analysis of CO oxidation during steady-state reaction at 573 K was used to evaluate the coverage of reactive carbon-containing intermediates that lead to product as well as the pseudo-first-order rate constant of the reaction. A factor of 4 enhancement in activity achieved by exchanging Cs for Na was attributed to a higher coverage of reactive intermediates in CsX because the pseudo-first-order rate constant was nearly same for the two materials (approximately 0.7 s(-1)). The number of reactive intermediates on both materials was orders of magnitude below the number of alkali metal cations in the zeolites but was similar to the number of impurity Fe atoms in the samples. Because the trend in Fe impurity loading was the same as that for oxidation activity, a role of transition metal impurities in zeolite oxidation catalysis is suggested.

  5. Plasmonic nanostructures to enhance catalytic performance of zeolites under visible light

    NASA Astrophysics Data System (ADS)

    Zhang, Xingguang; Ke, Xuebin; Du, Aijun; Zhu, Huaiyong

    2014-01-01

    Light absorption efficiency of heterogeneous catalysts has restricted their photocatalytic capability for commercially important organic synthesis. Here, we report a way of harvesting visible light efficiently to boost zeolite catalysis by means of plasmonic gold nanoparticles (Au-NPs) supported on zeolites. Zeolites possess strong Brønsted acids and polarized electric fields created by extra-framework cations. The polarized electric fields can be further intensified by the electric near-field enhancement of Au-NPs, which results from the localized surface plasmon resonance (LSPR) upon visible light irradiation. The acetalization reaction was selected as a showcase performed on MZSM-5 and Au/MZSM-5 (M = H+, Na+, Ca2+, or La3+). The density functional theory (DFT) calculations confirmed that the intensified polarized electric fields played a critical role in stretching the C = O bond of the reactants of benzaldehyde to enlarge their molecular polarities, thus allowing reactants to be activated more efficiently by catalytic centers so as to boost the reaction rates. This discovery should evoke intensive research interest on plasmonic metals and diverse zeolites with an aim to take advantage of sunlight for plasmonic devices, molecular electronics, energy storage, and catalysis.

  6. Recent advances on Zeolite modification for direct alcohol fuel cells (DAFCs)

    NASA Astrophysics Data System (ADS)

    Makertihartha, I. G. B. N.; Zunita, M.; Rizki, Z.; Dharmawijaya, P. T.

    2017-03-01

    The increase of energy demand and global warming issues has driven studies of alternative energy sources. The polymer electrolyte membrane fuel cell (PEMFC) can be an alternative energy source by (partially) replacing the use of fossil fuel which is in line with the green technology concept. However, the usage of hydrogen as a fuel has several disadvantages mainly transportation and storage related to its safety aspects. Recently, alcohol has gained attention as an energy source for fuel cell application, namely direct alcohol fuel cell (DAFC). Among alcohols, high-mass energy density methanol and ethanol are widely used as direct methanol fuel cell (DMFC) and direct ethanol fuel cell (DEFC), respectively. Currently, the performance of DMFC is still rudimentary. Furthermore, the use of ethanol gives some additional privileges such as non-toxic property, renewable, ease of production in great quantity by the fermentation of sugar-containing raw materials. Direct alcohol fuel cell (DAFC) still has weakness in the low proton conductivity and high alcohol crossover. Therefore, to increase the performance of DAFC, modification using zeolite has been performed to improve proton conductivity and decrease alcohol crossover. Zeolite also has high thermal resistance properties, thereby increasing DAFC performance. This paper will discuss briefly about modification of catalyst and membrane for DAFC using zeolite. Zeolite modification effect on fuel cell performance especially proton conductivity and alcohol crossover will be presented in detail.

  7. Coke induced stabilization of catalytic activity of silylated ZSM-5 zeolite

    SciTech Connect

    Bhat, Y.S.; Das, J.; Halgeri, A.B.

    1995-08-01

    One of the ways to synthesize dialkylbenzenes is to alkylate monoalkylbenzene with an alkylating agent such as alcohol or olefin over a Friedel-Crafts or zeolite catalyst. The latter is gaining importance as it is an environmentally friendly system. Dialkylbenzenes like paraxylene, para-ethyltoluene, and para-diethylbenzene are sources for various monomers. Several techniques have been reported in the literature to modify the zeolite characteristics in such a way that the dialkylbenzenes formed during monoalkylbenzene alkylation contain more para isomer. Among these techniques, the chemical vapor deposition of silica (CVD) is drawing the attention of researchers. The silylation results in fine control of pore opening size with the silica deposited on the external surface. The internal structure remains unaffected; only the pore entrance is narrowed. It was observed that the silylated zeolite used for synthesizing para-dialkylbenzene by monoalkylbenzene alkylation deactivates with increased time on stream. This paper deals with the coke-induced stabilization of catalytic activity of ZSM-5 zeolite during alkylation of ethylbenzene with ethanol.

  8. Catalyst and method for reduction of nitrogen oxides

    DOEpatents

    Ott, Kevin C.

    2008-05-27

    A Selective Catalytic Reduction (SCR) catalyst was prepared by slurry coating ZSM-5 zeolite onto a cordierite monolith, then subliming an iron salt onto the zeolite, calcining the monolith, and then dipping the monolith either into an aqueous solution of manganese nitrate and cerium nitrate and then calcining, or by similar treatment with separate solutions of manganese nitrate and cerium nitrate. The supported catalyst containing iron, manganese, and cerium showed 80 percent conversion at 113 degrees Celsius of a feed gas containing nitrogen oxides having 4 parts NO to one part NO.sub.2, about one equivalent ammonia, and excess oxygen; conversion improved to 94 percent at 147 degrees Celsius. N.sub.2O was not detected (detection limit: 0.6 percent N.sub.2O).

  9. Catalyst and method for reduction of nitrogen oxides

    DOEpatents

    Ott, Kevin C.

    2008-08-19

    A Selective Catalytic Reduction (SCR) catalyst was prepared by slurry coating ZSM-5 zeolite onto a cordierite monolith, then subliming an iron salt onto the zeolite, calcining the monolith, and then dipping the monolith either into an aqueous solution of manganese nitrate and cerium nitrate and then calcining, or by similar treatment with separate solutions of manganese nitrate and cerium nitrate. The supported catalyst containing iron, manganese, and cerium showed 80 percent conversion at 113 degrees Celsius of a feed gas containing nitrogen oxides having 4 parts NO to one part NO.sub.2, about one equivalent ammonia, and excess oxygen; conversion improved to 94 percent at 147 degrees Celsius. N.sub.2O was not detected (detection limit: 0.6 percent N.sub.2O).

  10. UTILITY OF ZEOLITES IN ARSENIC REMOVAL FROM WATER

    EPA Science Inventory

    Zeolites are well known for their ion exchange and adsorption properties. So far the cation exchanger properties of zeolites have been extensively studied and utilized. The anion exchanger properties of zeolites are less studied. Zeolite Faujasite Y has been used to remove arseni...

  11. Theoretical evaluation of zeolite confinement effects on the reactivity of bulky intermediates.

    PubMed

    Lesthaeghe, David; Van Speybroeck, Veronique; Waroquier, Michel

    2009-07-14

    Zeolites provide a unique setting for heterogeneous Brønsted acid catalysis, because the effects of the surrounding framework on fundamental reaction kinetics go well beyond what would be expected for a mere reaction flask. This aspect becomes very pronounced when bulky molecules form key intermediates for the reaction under study, which is exactly when the interaction between the framework and the intermediate is maximal. We will use the example of methanol-to-olefin conversion (MTO), and, more specifically, the constant interplay between the inorganic host framework and the organic hydrocarbon pool co-catalyst, to illustrate how zeolite confinement directly influences catalytic reaction rates. Theoretical calculations are used to isolate and quantify these specific effects, with the main focus on methylbenzenes in ZSM-5, as the archetypical MTO catalyst. This review intends to give an overview of recent theoretical insights, which have proven to provide an ideal complementary tool to experimental investigations. In addition, we will also introduce the role of zeolite breathing in activating a catalytic cycle.

  12. Synthesis, structure, and carbon dioxide capture properties of zeolitic imidazolate frameworks.

    PubMed

    Phan, Anh; Doonan, Christian J; Uribe-Romo, Fernando J; Knobler, Carolyn B; O'Keeffe, Michael; Yaghi, Omar M

    2010-01-19

    Zeolites are one of humanity's most important synthetic products. These aluminosilicate-based materials represent a large segment of the global economy. Indeed, the value of zeolites used in petroleum refining as catalysts and in detergents as water softeners is estimated at $350 billion per year. A major current goal in zeolite chemistry is to create a structure in which metal ions and functionalizable organic units make up an integral part of the framework. Such a structure, by virtue of the flexibility with which metal ions and organic moieties can be varied, is viewed as a key to further improving zeolite properties and accessing new applications. Recently, it was recognized that the Si-O-Si preferred angle in zeolites (145 degrees ) is coincident with that of the bridging angle in the M-Im-M fragment (where M is Zn or Co and Im is imidazolate), and therefore it should be possible to make new zeolitic imidazolate frameworks (ZIFs) with topologies based on those of tetrahedral zeolites. This idea was successful and proved to be quite fruitful; within the last 5 years over 90 new ZIF structures have been reported. The recent application of high-throughput synthesis and characterization of ZIFs has expanded this structure space significantly: it is now possible to make ZIFs with topologies previously unknown in zeolites, in addition to mimicking known structures. In this Account, we describe the general preparation of crystalline ZIFs, discussing the methods that have been developed to create and analyze the variety of materials afforded. We include a comprehensive list of all known ZIFs, including structure, topology, and pore metrics. We also examine how complexity might be introduced into new structures, highlighting how link-link interactions might be exploited to effect particular cage sizes, create polarity variations between pores, or adjust framework robustness, for example. The chemical and thermal stability of ZIFs permit many applications, such as the

  13. The Zeolite Deposit of Hekimhan in the Malatya Basin

    NASA Astrophysics Data System (ADS)

    Önal, Mehmet; Depci, Tolga; Ceylan, Cigdem; Kizilkaya, Nilgun

    2016-10-01

    Zeolite deposits in the Malatya Basin which is formed of the Yüksekova Group were investigated in the present study. The zeolites were occurred in the two layers: the lower zeolite layer and the upper zeolite layer of the Sankiz Formation of Campanian-Maastrichtian age within the flysch like sediments at Hekimhan in the northern part of the Malatya Basin. Characterization studies of the zeolite samples were done by XRF, XRD and SEM images and the results showed that the main structures of the zeolites were clinoptilolite-(Cs), heulandite and calcite and the geological occurrences of zeolite is in marine environments.

  14. Anthemis xylopoda flowers aqueous extract assisted in situ green synthesis of Cu nanoparticles supported on natural Natrolite zeolite for N-formylation of amines at room temperature under environmentally benign reaction conditions.

    PubMed

    Nasrollahzadeh, Mahmoud; Sajadi, S Mohammad; Hatamifard, Arezo

    2015-12-15

    Zeolites, which are nontoxic, abundant, and cheap, are very promising supports for the design and preparation of new and environmentally benign catalysts. In this study, Cu nanoparticles (NPs) were immobilized on the surface of natural Natrolite zeolite by Anthemis xylopoda flowers aqueous extract as a reducing and stabilizing agent. Afterward, the catalytic performance of the prepared catalyst was investigated for N-formylation of amines at room temperature under environmentally benign reaction conditions. The catalyst could be reused at least 5 times without any decrease in activity. The advantages of the present protocol include the use of green catalyst, easy isolation of the products, reusability of catalyst, absence of nontoxic reagents, and excellent yield of the products.

  15. In –Situ Spectroscopic Investigation of Immobilized Organometallic Catalysts

    SciTech Connect

    Davis, Robert, J.

    2007-11-14

    Immobilized organometallic catalysts, in principle, can give high rates and selectivities like homogeneous catalysts with the ease of separation enjoyed by heterogeneous catalysts. However, the science of immobilized organometallics has not been developed because the field lies at the interface between the homogeneous and heterogeneous catalysis communities. By assembling an interdisciplinary research team that can probe all aspects of immobilized organometallic catalyst design, the entire reacting system can be considered, where the transition metal complex, the complex-support interface and the properties of the support can all be considered simultaneously from both experimental and theoretical points of view. Researchers at Georgia Tech and the University of Virginia are studying the fundamental principles that can be used to understand and design future classes of immobilized organometallic catalysts. In the framework of the overall collaborative project with Georgia Tech, our work focused on (a) the X-ray absorption spectroscopy of an immobilized Pd-SCS-O complex (b) the mode of metal leaching from supported Pd catalysts during Heck catalysis and (c) the mode of deactivation of Jacobsen’s Co-salen catalysts during the hydrolytic kinetic resolution of terminal epoxides. Catalysts containing supported Pd pincer complexes, functionalized supports containing mercapto and amine groups, and oligomeric Co-salen catalysts were synthesized at Georgia Tech and sent to the University of Virginia. Incorporation of Pd onto several different kinds of supports (silica, mercapto-functionalized silica, zeolite Y) was performed at the University of Virginia.

  16. Salt-thermal zeolitization of fly ash.

    PubMed

    Choi, C L; Park, M; Lee, D H; Kim, I E; Park, B Y; Choi, J

    2001-07-01

    The molten-salt method has been recently proposed as a new approach to zeolitization of fly ash. Unlike the hydrothermal method, this method employs salt mixtures as the reaction medium without any addition of water. In this study, systematic investigation has been conducted on zeolitization of fly ash in a NaOH-NaNO3 system in order to elucidate the mechanism of zeolite formation and to achieve its optimization. Zeolitization of fly ash was conducted by thermally treating a powder mixture of fly ash, NaOH, and NaNO3. Zeolitization of fly ash took place above 200 degrees C, a temperature lower than the melting points of salt and base in the NaOH-NaNO3 system. However, it was uncertain whether the reactions took place in a local molten state or in a solid state. Therefore, the proposed method is renamed the "salt-thermal" method rather than the "molten-salt" method. Mainly because of difficulty in mobility of components in salt mixtures, zeolitization seems to occur within a local reaction system. In situ rearrangement of activated components seems to lead to zeolite formation. Particle growth, rather than crystal growth through agglomeration, resulted in no distinct morphologies of zeolite phases. Following are the optimal zeolitization conditions of the salt-thermal method: temperature, 250-350 degrees C; time, 3-12 h; weight ratio of NaOH/NaNO3, 0.3-0.5; weight ratio of NaNO3/fly ash, 0.7-1.4. Therefore, it is clear from this work that the salt-thermal method could be applied to massive zeolitization of fly ash as a new alternative method for recycling this waste.

  17. 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...

  18. 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...

  19. Catalysts for converting syngas into liquid hydrocarbons and methods thereof

    DOEpatents

    Yu, Fei; Yan, Qiangu; Batchelor, William

    2016-03-15

    The presently-disclosed subject matter includes methods for producing liquid hydrocarbons from syngas. In some embodiments the syngas is obtained from biomass and/or comprises a relatively high amount of nitrogen and/or carbon dioxide. In some embodiments the present methods can convert syngas into liquid hydrocarbons through a one-stage process. Also provided are catalysts for producing liquid hydrocarbons from syngas, wherein the catalysts include a base material, a transition metal, and a promoter. In some embodiments the base material includes a zeolite-iron material or a cobalt-molybdenum carbide material. In still further embodiments the promoter can include an alkali metal.

  20. Highly dispersed metal catalyst

    DOEpatents

    Xiao, Xin; West, William L.; Rhodes, William D.

    2016-11-08

    A supported catalyst having an atomic level single atom structure is provided such that substantially all the catalyst is available for catalytic function. A process of forming a single atom catalyst unto a porous catalyst support is also provided.

  1. Reforming catalyst

    SciTech Connect

    Baird, W.C. Jr.; Swan, G.A.

    1991-11-19

    This patent describes a catalyst useful for reforming a naphtha feed at high severity reforming conditions. It comprises the metals, platinum, rhenium and iridium on a refractory porous inorganic oxide support, the support consisting essentially of alumina, wherein the concentration by weight of each of the metals platinum and rhenium is at least 0.1 percent and iridium at least 0.15 percent and at least one of the metals is present in a concentration of at least 0.3 percent, and the sum-total; concentration of the metals is greater than 0.9 percent, and wherein each catalyst particle contains all three of the metals platinum, rhenium and iridium. This patent also describes this composition wherein the catalyst contains from about 0.1 percent to about 3 percent of a halogen and from about 0.05 percent to about 0.02 percent sulfur.

  2. Catalytic conversion of Chlorella pyrenoidosa to biofuels in supercritical alcohols over zeolites.

    PubMed

    Yang, Le; Ma, Rui; Ma, Zewei; Li, Yongdan

    2016-06-01

    Microalgae have been considered as the feedstock for the third generation biofuels production, given its high lipid content and fast productivity. Herein, a catalytic approach for microalgae liquefaction to biocrude is examined in a temperature range of 250-300°C in methanol and ethanol over zeolites. Higher biocrude yield was achieved in ethanol and at lower temperatures, while better quality biocrude with higher light biocrude ratio and lower average molecular weight (Mw) was favored in methanol and at higher temperatures. Application of zeolites improves the biocrude quality significantly. Among the catalysts, HY shows the strongest acidity and performs the best to produce high quality biocrude. Solid residues have been extensively explored with thermal gravity analysis and elemental analysis. It is reported for the first time that up to 99wt.% of sulfur is deposited in the solid residue at 250°C for both solvents.

  3. Ion distribution in copper exchanged zeolites by using Si-29 spin lattice relaxation analysis

    NASA Astrophysics Data System (ADS)

    Palamara, Joseph; Seidel, Karsten; Moini, Ahmad; Prasad, Subramanian

    2016-06-01

    Transition metal-containing zeolites, particularly those with smaller pore size, have found extensive application in the selective catalytic reduction (SCR) of environmental pollutants containing nitrogen oxides. We report these zeolites have dramatically faster silicon-29 (Si-29) spin lattice relaxation times (T1) compared to their sodium-containing counterparts. Paramagnetic doping allows one to acquire Si-29 MAS spectra in the order of tens of seconds without significantly affecting the spectral resolution. Moreover, relaxation times depend on the method of preparation and the next-nearest neighbor silicon Qn(mAl) sites, where n = 4 and m = 0-4, respectively. A clear trend is noted between the effectiveness of Cu exchange and the Si-29 NMR relaxation times. It is anticipated that the availability of this tool, and the enhanced understanding of the nature of the active sites, will provide the means for designing improved SCR catalysts.

  4. Two new cracking catalysts are developed for TCC process

    SciTech Connect

    Anderson, C.D.; Breckenridge, L.L.; Bundens, R.G.; Dwyer, F.G.; Herbst, J.A.

    1987-06-01

    Two new catalysts, Durabead 12 and Durabead 14, have been developed during 1986 for Mobil's Thermofor Catalytic Cracking (TCC) units. Durabead 12 produces significantly more gasoline and distillate at the expense of coke and C/sub 4//sup -/ gas and shows good hydrothermal stability. Durabead 12 has the same low attrition and high density and diffusivity as previous Durabead catalysts (Table 1). As a result, unit retention, regenerability, and flow and pressure drop characteristics of Durabead 12 are excellent. Durabead 14 is a combination of Mobil's ZSM-5 shape-selective zeolite and Durabead 12. Durabead 14 has very favorable coke selectivity, octane, and potential alkylate enhancement with no gasoline yield loss compared to conventional rare earth Y (REY) cracking catalysts. Results of laboratory tests on both catalysts are presented in this article. Additional commercial evaluation of Durabead 12 were conducted. Those results are also presented.

  5. Correlating the Integral Sensing Properties of Zeolites with Molecular Processes by Combining Broadband Impedance and DRIFT Spectroscopy—A New Approach for Bridging the Scales

    PubMed Central

    Chen, Peirong; Schönebaum, Simon; Simons, Thomas; Rauch, Dieter; Dietrich, Markus; Moos, Ralf; Simon, Ulrich

    2015-01-01

    Zeolites have been found to be promising sensor materials for a variety of gas molecules such as NH3, NOx, hydrocarbons, etc. The sensing effect results from the interaction of the adsorbed gas molecules with mobile cations, which are non-covalently bound to the zeolite lattice. The mobility of the cations can be accessed by electrical low-frequency (LF; mHz to MHz) and high-frequency (HF; GHz) impedance measurements. Recent developments allow in situ monitoring of catalytic reactions on proton-conducting zeolites used as catalysts. The combination of such in situ impedance measurements with diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), which was applied to monitor the selective catalytic reduction of nitrogen oxides (DeNOx-SCR), not only improves our understanding of the sensing properties of zeolite catalysts from integral electric signal to molecular processes, but also bridges the length scales being studied, from centimeters to nanometers. In this work, recent developments of zeolite-based, impedimetric sensors for automotive exhaust gases, in particular NH3, are summarized. The electrical response to NH3 obtained from LF impedance measurements will be compared with that from HF impedance measurements, and correlated with the infrared spectroscopic characteristics obtained from the DRIFTS studies of molecules involved in the catalytic conversion. The future perspectives, which arise from the combination of these methods, will be discussed. PMID:26580627

  6. Zeolites on Mars: Prospects for Remote Sensing

    NASA Technical Reports Server (NTRS)

    Gaffney, E. S.; Singer, R. B.; Kunkle, T. D.

    1985-01-01

    The Martian surface composition measured by Viking can be represented by several combinations of minerals incorporating major fractions of zeolites known to occur in altered mafic rocks and polar soils on Earth. The abundant occurrence of zeolites on Mars is consistent with what is known about both the physical and chemical environment of that planet. The laboratory reflectance spectra (0.65 to 2.55 microns) of a number of relatively pure zeolite minerals and some naturally occurring zeolite-clay soils were measured. All of the spectra measured are dominated by strong absorption near 1.4 and 1.9 microns and a steep reflectance drop longward of about 2.2 microns, all of which are due to abundant H2O. Weaker water overtone bands are also apparent, and in most cases there is spectral evidence for minor Fe(3+). In these features the zeolite spectra are similar to spectra of smectite clays which have abundant interlayer water. The most diagnostic difference between clay and zeolite spectra is the total absence in the zeolites of the weak structural OH absorption.

  7. A comparative first principles study on trivalent ion incorporated SSZ-13 zeolites.

    PubMed

    Wen, Cui; Geng, Lu; Han, Lina; Wang, Jiancheng; Chang, Liping; Feng, Gang; Kong, Dejin; Liu, Jianwen

    2015-11-28

    The dispersion-corrected density functional theory has been used to study the trivalent ions B, Al, Ga, and Fe incorporated SSZ-13-type zeolites. The associated structure and Brønsted/Lewis acidity change caused by the incorporation ions were comparatively studied. It was found that the smaller the radius differences of the incorporation ions are, the smaller the changes in the structure will be and the less acidity will be enhanced for the Brønsted sites. The trivalent Al is found to be the most favorable trivalent incorporation ion and Na is found to be the most favorable charge balanced ion for the synthesis of SSZ-13-type zeolites due to size comparability, which are in line with the experimental observation. The substitution energies which show the relative synthesis difficulty level were also applied for B, Al, Ga, and Fe incorporated zeolites and found that the difficulty decreases with order of Fe > B > Ga ≫ Al, also in good agreement with the experimental observations. Adsorption studies for the NH3 and pyridine molecules indicate that adsorption on the Brønsted acid sites is more stable than on the Lewis acid sites. The Brønsted acidity was found to follow the order of HAl-SSZ-13 > HGa-SSZ-13 ≈ HFe-SSZ-13 > HB-SSZ-13 where the Lewis acidity was found to follow the order of HGa-SSZ-13 ≈ HFe-SSZ-13 > HAl-SSZ-13 > HB-SSZ-13. Our results provide new insights for the synthesis of the SSZ-13-type zeolites and fundamental information for the zeolitic catalyst designation to enhance the catalytic performance.

  8. On the interaction of 1-propanamine with cation-containing MFL zeolite

    SciTech Connect

    Kanazirev, V.I.; Price, G.L.; Dooley, K.M. )

    1994-07-01

    The interaction of 1-propanamine (1-PA) with H-MFI zeolite and its Ga, In, and Cu modifications, prepared by solid state ion exchange, has been studied by thermal analysis, high resolution gas chromatography, mass spectroscopy, and catalytic reactor experiments. Two completely different desorption features have been observed when the H-FMI sample is first equilibrated with 1-PA at 323 and 593 K and then heated to 823 K. These desorption features have been ascribed to the decomposition of propylammonium and dipropylammonium ions adsorbed at the proton sites of the zeolite. Catalytic experiments confirmed dipropylamine as the major product of 1-PA conversion at 593 K over an H-MFI catalyst. In contrast, a radical change in the interaction of 1-PA with the zeolite has been observed as a result of the replacement of the protons in FMI with Ga, In, or Cu cations. More than one 1-PA with cation containing MFI differ generally from those of pure H-FMI zeolite. NH[sub 3] product is desorbed at temperatures as much as 160 K below that of H-MFI. Nitriles, C[sub 2]-C[sub 6] hydrocarbons, and some aromatics appear in appreciable amounts in the decomposition products. Gas-phase hydrogen inhibits the dehydrogenation processes and prevents the formation of a residue. Catalytic experiments in a gradientless batch recirculating reactor have revealed that different dehydrogenation reactions predominate depending on the nature of the zeolite cation. While a C[sub 6]-imine appears as a major product of the reaction of 1-PA over In-MFI, more dehydrogenated N-containing compounds such as propionitrile and a C[sub 6]-nitrile predominate over Ga-MFI and Cu-MFI, respectively. These differences can be interpreted in terms of the differing Lewis acid strengths and reductibilities of the Ga, In, and Cu cations. 50 refs., 16 figs., 4 tabs.

  9. Synthesis, spectral investigation and catalytic aspects of entrapped VO(IV) and Cu(II) complexes into the supercages of zeolite-Y

    NASA Astrophysics Data System (ADS)

    Modi, Chetan K.; Gade, Bhagyashree G.; Chudasama, Jiten A.; Parmar, Digvijay K.; Nakum, Haresh D.; Patel, Arun L.

    2015-04-01

    VO(IV) and Cu(II) complexes with Schiff base ligand derived from 1-phenyl-3-methyl-4-formyl-2-pyrazolin-5-one (PMFP) and 2-amino phenol have been synthesized as their neat and entrapped complexes into the supercages of zeolite-Y. The compounds were characterized by chemical analysis (ICP-OES and elemental), electronic and/or UV reflectance spectra, FTIR spectroscopy, X-ray powder diffraction patterns, SEMs, BET and thermogravimetric (TG) analysis. All the prepared catalysts were tested on the liquid phase limonene oxidation reaction, using 30% H2O2 as an oxidant. Limonene glycol, carveol, carvone and limonene 1,2-epoxide were the main products obtained. It was observed that zeolite-Y entrapped complexes exhibited higher catalytic activity than neat complexes. The catalysts undergo no metal leaching and can be easily recovered and reused. The use of inexpensive catalyst and oxidant are significant practical advantages of this environmentally friendly process.

  10. Effect of internal noise on the oscillation of N{sub 2}O decomposition over Cu-ZSM-5 zeolites using a stochastic description

    SciTech Connect

    Liu, Fuliang; Li, Yaping Sun, Xiaoming

    2014-01-28

    When considering stochastic oscillations of heterogeneous catalyst systems, most researches have focused on the surface of a metal or its oxide catalysts, but there have been few studies on porous catalysts. In this work, the effects of internal noise on oscillations of N{sub 2}O decomposition over Cu-ZSM-5 zeolites are investigated, using the chemical Langevin equation and a mesoscopic stochastic model. Considering that Cu-ZSM-5 particles are finely divided particles, the number of Cu ions (N{sub s}) is proportional to the particle size at a certain Cu/Al, and the internal noise is inversely proportional to N{sub s}. Stochastic oscillations can be observed outside the deterministic oscillatory region. Furthermore, the performance of the oscillation characterized by the signal-to-noise ratio has a maximum within the optimal size range of 4–8 nm. This suggests that a nanometer-sized zeolite may be best for oscillations.

  11. Sustainable production of acrylic acid: alkali-ion exchanged beta zeolite for gas-phase dehydration of lactic acid.

    PubMed

    Yan, Bo; Tao, Li-Zhi; Liang, Yu; Xu, Bo-Qing

    2014-06-01

    Gas-phase dehydration of lactic acid (LA) to acrylic acid (AA) was investigated over alkali-exchanged β zeolite (M(x)Na(1-x)β, M=Li(+), K(+), Rb(+), or Cs(+)) of different exchange degrees (x). The reaction was conducted under varying conditions to understand the catalyst selectivity for AA production and trends of byproduct formation. The nature and exchange degree of M(+) were found to be critical for the acid-base properties and catalytic performance of the exchanged zeolite. K(x)Na(1-x)β of x=0.94 appeared to be the best performing catalyst whereas Li(x)Na(1-x)β and Naβ were the poorest in terms of AA selectivity and yield. The AA yield as high as 61 mol % (selectivity: 64 mol %) could be obtained under optimized reaction conditions for up to 8 h over the best performing K0.94Na0.06β. The acid and base properties of the catalysts were probed, respectively by temperature-programmed desorption (TPD) of adsorbed NH3 and CO2, and were related to the electrostatic potentials of the alkali ions in the zeolite, which provided a basis for the discussion of the acid-base catalysis for sustainable AA formation from LA.

  12. A unified single-event microkinetic model for alkane hydroconversion in different aggregation states on Pt/H-USY-zeolites.

    PubMed

    Laxmi Narasimhan, C S; Thybaut, Joris W; Martens, Johan A; Jacobs, Pierre A; Denayer, Joeri F; Marin, Guy B

    2006-04-06

    A single-event microkinetic model for the catalytic hydroconversion of hydrocarbons on Pt/H-US-Y bifunctional zeolite catalysts developed for low-pressure vapor phase conditions was extended to cover high-pressure vapor phase and liquid phase conditions. The effect of the density of the bulk hydrocarbon phase on the physisorption as well as on the protonation steps of the reaction network was accounted for explicitly and can be interpreted in terms of "compression" of the hydrocarbon sorbate inside the zeolite pores and "solvation" of the catalyst framework by the dense bulk hydrocarbon phase. The bulk phase density effect on the physisorbed state is described via a single excess free enthalpy of physisorption. A dense bulk hydrocarbon phase destabilizes the sorbate molecules inside the catalyst pores. An expression of the excess free enthalpy of physisorption involving the fugacity coefficient and a zeolite dependent factor allows description of physisorption data. Typical excess free enthalpy values are in the range 1.5-5.1 kJ mol(-1) increasing with carbon number in the series of C5-C16 alkanes. At high-pressure vapor phase and liquid phase conditions, the excess standard protonation enthalpy is estimated at -7.8 kJ mol(-1) leading to relatively more stable carbenium ions at dense bulk phase conditions. As a result of the excess physisorption and protonation properties, the lightest hydrocarbons in mixtures are more competitive at dense phase conditions and their conversion is enhanced compared to low-density conditions.

  13. Catalyst activator

    DOEpatents

    McAdon, Mark H.; Nickias, Peter N.; Marks, Tobin J.; Schwartz, David J.

    2001-01-01

    A catalyst activator particularly adapted for use in the activation of metal complexes of metals of Group 3-10 for polymerization of ethylenically unsaturated polymerizable monomers, especially olefins, comprising two Group 13 metal or metalloid atoms and a ligand structure including at least one bridging group connecting ligands on the two Group 13 metal or metalloid atoms.

  14. A Site-Isolated Iridium Diethylene Complex Supported on Highly Dealuminated Y Zeolite: Synthesis And Characterization

    SciTech Connect

    Uzun, A.; Bhirud, V.A.; Kletnieks, P.W.; Haw, J.F.; Gates, B.C.

    2009-06-04

    Highly dealuminated Y zeolite-supported mononuclear iridium complexes with reactive ethylene ligands were synthesized by chemisorption of Ir(C{sub 2}H{sub 4}){sub 2}(C{sub 5}H{sub 7}O{sub 2}). The resultant structure and its treatment in He, CO, ethylene, and H2 were investigated with infrared (IR) and extended X-ray absorption fine structure (EXAFS) spectroscopies. The IR spectra show that Ir(C{sub 2}H{sub 4}){sub 2}(C{sub 5}H{sub 7}O{sub 2}) reacted readily with surface OH groups of the zeolite, leading to the removal of C{sub 5}H{sub 7}O{sub 2} ligands and the formation of supported mononuclear iridium complexes, confirmed by the lack of Ir-Ir contributions in the EXAFS spectra. The EXAFS data show that each Ir atom was bonded to four carbon atoms at an average distance of 2.10 {angstrom}, consistent with the presence of two ethylene ligands per Ir atom and in agreement with the IR spectra indicating {pi}-bonded ethylene ligands. The EXAFS data also indicate that each Ir atom was bonded to two oxygen atoms of the zeolite at a distance of 2.15 {angstrom}. The supported iridium-ethylene complex reacted with H{sub 2} to give ethane, and it also catalyzed ethylene hydrogenation at atmospheric pressure and 294 K. Treatment of the sample in CO led to the formation of Ir(CO){sub 2} complexes bonded to the zeolite. The sharpness of the V{sub CO} bands indicates a high degree of uniformity of these complexes on the support. The iridium-ethylene complex on the crystalline zeolite support is inferred to be one of the most nearly uniform supported metal complex catalysts. The results indicate that it is isostructural with a previously reported rhodium complex on the same zeolite; thus, the results are a start to a family of analogous, structurally well-defined supported metal complex catalysts.

  15. Photocatalytic activity of undoped and Ag-doped TiO{sub 2}-supported zeolite for humic acid degradation and mineralization

    SciTech Connect

    Lazau, C.; Ratiu, C.; Orha, C.; Pode, R.; Manea, F.

    2011-11-15

    Highlights: {yields} Hybrid materials based on natural zeolite and TiO{sub 2} obtained by solid-state reaction. {yields} XRD proved the presence of anatase form of undoped and Ag-doped TiO{sub 2} onto zeolite. {yields} FT-IR spectra evidenced the presence on TiO{sub 2} bounded at the zeolite network. {yields} Ag-doped TiO{sub 2} onto zeolitic matrix exhibited an enhanced photocatalytic activity. -- Abstract: The hybrid materials based on natural zeolite and undoped and Ag-doped TiO{sub 2}, i.e., Z-Na-TiO{sub 2} and Z-Na-TiO{sub 2}-Ag, were successfully synthesized by solid-state reaction in microwave-assisted hydrothermal conditions. Undoped TiO{sub 2} and Ag-doped TiO{sub 2} nanocrystals were previously synthesized by sol-gel method. The surface characterization of undoped TiO{sub 2}/Ag-doped TiO{sub 2} and natural zeolite hybrid materials has been investigated by X-ray diffraction, DRUV-VIS spectroscopy, FT-IR spectroscopy, BET analysis, SEM microscopy and EDX analysis. The results indicated that anatase TiO{sub 2} is the dominant crystalline type as spherical form onto zeolitic matrix. The presence of Ag into Z-Na-TiO{sub 2}-Ag was confirmed by EDX analysis. The DRUV-VIS spectra showed that Z-Na-TiO{sub 2}-Ag exhibited absorption within the range of 400-500 nm in comparison with Z-Na-TiO{sub 2} catalyst. The enhanced photocatalytic activity of Z-Na-TiO{sub 2}-Ag catalyst is proved through the degradation and mineralization of humic acid under ultraviolet and visible irradiation.

  16. Quantitative 3D Fluorescence Imaging of Single Catalytic Turnovers Reveals Spatiotemporal Gradients in Reactivity of Zeolite H-ZSM-5 Crystals upon Steaming.

    PubMed

    Ristanović, Zoran; Hofmann, Jan P; De Cremer, Gert; Kubarev, Alexey V; Rohnke, Marcus; Meirer, Florian; Hofkens, Johan; Roeffaers, Maarten B J; Weckhuysen, Bert M

    2015-05-27

    Optimizing the number, distribution, and accessibility of Brønsted acid sites in zeolite-based catalysts is of a paramount importance to further improve their catalytic performance. However, it remains challenging to measure real-time changes in reactivity of single zeolite catalyst particles by ensemble-averaging characterization methods. In this work, a detailed 3D single molecule, single turnover sensitive fluorescence microscopy study is presented to quantify the reactivity of Brønsted acid sites in zeolite H-ZSM-5 crystals upon steaming. This approach, in combination with the oligomerization of furfuryl alcohol as a probe reaction, allowed the stochastic behavior of single catalytic turnovers and temporally resolved turnover frequencies of zeolite domains smaller than the diffraction limited resolution to be investigated with great precision. It was found that the single turnover kinetics of the parent zeolite crystal proceeds with significant spatial differences in turnover frequencies on the nanoscale and noncorrelated temporal fluctuations. Mild steaming of zeolite H-ZSM-5 crystals at 500 °C led to an enhanced surface reactivity, with up to 4 times higher local turnover rates than those of the parent H-ZSM-5 crystals, and revealed remarkable heterogeneities in surface reactivity. In strong contrast, severe steaming at 700 °C significantly dealuminated the zeolite H-ZSM-5 material, leading to a 460 times lower turnover rate. The differences in measured turnover activities are explained by changes in the 3D aluminum distribution due to migration of extraframework Al-species and their subsequent effect on pore accessibility, as corroborated by time-of-flight secondary ion mass spectrometry (TOF-SIMS) sputter depth profiling data.

  17. Quantitative 3D Fluorescence Imaging of Single Catalytic Turnovers Reveals Spatiotemporal Gradients in Reactivity of Zeolite H-ZSM-5 Crystals upon Steaming

    PubMed Central

    2015-01-01

    Optimizing the number, distribution, and accessibility of Brønsted acid sites in zeolite-based catalysts is of a paramount importance to further improve their catalytic performance. However, it remains challenging to measure real-time changes in reactivity of single zeolite catalyst particles by ensemble-averaging characterization methods. In this work, a detailed 3D single molecule, single turnover sensitive fluorescence microscopy study is presented to quantify the reactivity of Brønsted acid sites in zeolite H-ZSM-5 crystals upon steaming. This approach, in combination with the oligomerization of furfuryl alcohol as a probe reaction, allowed the stochastic behavior of single catalytic turnovers and temporally resolved turnover frequencies of zeolite domains smaller than the diffraction limited resolution to be investigated with great precision. It was found that the single turnover kinetics of the parent zeolite crystal proceeds with significant spatial differences in turnover frequencies on the nanoscale and noncorrelated temporal fluctuations. Mild steaming of zeolite H-ZSM-5 crystals at 500 °C led to an enhanced surface reactivity, with up to 4 times higher local turnover rates than those of the parent H-ZSM-5 crystals, and revealed remarkable heterogeneities in surface reactivity. In strong contrast, severe steaming at 700 °C significantly dealuminated the zeolite H-ZSM-5 material, leading to a 460 times lower turnover rate. The differences in measured turnover activities are explained by changes in the 3D aluminum distribution due to migration of extraframework Al-species and their subsequent effect on pore accessibility, as corroborated by time-of-flight secondary ion mass spectrometry (TOF-SIMS) sputter depth profiling data. PMID:25867455

  18. Ammonia removal from wastewaters using natural Australian zeolite. 1: Characterization of the zeolite

    SciTech Connect

    Cooney, E.L.; Booker, N.A.; Shallcross, D.C.; Stevens, G.W.

    1999-09-01

    This study considered the potential of a natural Australian zeolite, clinoptilolite, to remove ammonium from water. Ammonium-exchange capacity and rates of adsorption are critical to the assessment of the feasibility of the zeolite for application to continuous wastewater treatment. A laboratory study was undertaken, using pure solutions, to investigate the equilibria and kinetic characteristics of ammonium exchange in the zeolite. Binary equilibrium experiments provided information on the adsorption characteristics of the zeolite in terms of ammonia capacity at varying solution concentrations. These experiments also revealed that the highest ammonium removal efficiency was achieved when the zeolite`s exchange sites were converted to the sodium form. Multicomponent equilibrium experiments were carried out to determine the effects of competing cations on the ammonium-exchange capacity of the zeolite. The laboratory study indicated the zeolite`s selectivity for ammonium ions over other cations typically present in sewage (calcium, magnesium, and potassium), and provided information relevant to the design and operation of a continuous process.

  19. Copper-Exchanged Zeolite L Traps Oxygen

    NASA Technical Reports Server (NTRS)

    Sharma, Pramod K.; Seshan, Panchalam K.

    1991-01-01

    Brief series of simple chemical treatments found to enhance ability of zeolite to remove oxygen from mixture of gases. Thermally stable up to 700 degrees C and has high specific surface area which provides high capacity for adsorption of gases. To increase ability to adsorb oxygen selectively, copper added by ion exchange, and copper-exchanged zeolite reduced with hydrogen. As result, copper dispersed atomically on inner surfaces of zeolite, making it highly reactive to oxygen, even at room temperature. Reactivity to oxygen even greater at higher temperatures.

  20. Preparation and characterization of zeolitic membrane

    SciTech Connect

    Shuanshi Fan; Chunhua Li; Jinqu Wang

    1994-12-31

    Zeolites with less than 10 {angstrom} pores are desirable membrane materials, due to their crystallinity, resistance to high temperature, and chemical inertness. Although several works have been done on them, zeolitic membranes have not been developed so perfect at present. In this paper, the authors reported the preparation and some properties of an asymmetric zeolitic membrane synthesized by hydrothermal process on the intermediate layer which was made on a porous ceramic support, meanwhile the results of separation of ethanol-water mixture on pervaporation were discussed.

  1. Dual-mesoporous ZSM-5 zeolite with highly b-axis-oriented large mesopore channels for the production of benzoin ethyl ether.

    PubMed

    Zhou, Xiaoxia; Chen, Hangrong; Zhu, Yan; Song, Yudian; Chen, Yu; Wang, Yongxia; Gong, Yun; Zhang, Guobin; Shu, Zhu; Cui, Xiangzhi; Zhao, Jinjin; Shi, Jianlin

    2013-07-22

    Dual-mesoporous ZSM-5 zeolite with highly b axis oriented large mesopores was synthesized by using nonionic copolymer F127 and cationic surfactant CTAB as co-templates. The product contains two types of mesopores--smaller wormlike ones of 3.3 nm in size and highly oriented larger ones of 30-50 nm in diameter along the b axis--and both of them interpenetrate throughout the zeolite crystals and interconnect with zeolite microporosity. The dual-mesoporous zeolite exhibits excellent catalytic performance in the condensation of benzaldehyde with ethanol and greater than 99 % selectivity for benzoin ethyl ether at room temperature, which can be ascribed to the zeolite lattice structure offering catalytically active sites and the hierarchical and oriented mesoporous structure providing fast access of reactants to these sites in the catalytic reaction. The excellent recyclability and high catalytic stability of the catalyst suggest prospective applications of such unique mesoporous zeolites in the chemical industry.

  2. Seed-Assisted Synthesis of MWW-Type Zeolite with Organic Structure-Directing Agent-Free Na-Aluminosilicate Gel System.

    PubMed

    Kamimura, Yoshihiro; Itabashi, Keiji; Kon, Yoshihiro; Endo, Akira; Okubo, Tatsuya

    2017-03-02

    The seed-assisted synthesis of zeolites without using organic structure-directing agents (OSDAs) has enabled alternative routes to the simple, environmentally friendly and low-cost production of industrially important zeolites. In this study, the successful seed-assisted synthesis of MCM-22 (MWW-type) zeolite with an OSDA-free gel is reported for the first time. MWW-type zeolites are obtained by the addition of as-synthesized MCM-22 seeds prepared with hexamethyleneimine (HMI) into OSDA-free Na-aluminosilicate gels. Based on the results of XRD, ICP-AES, NMR, N2 physisorption and NH3 -TPD, the product exhibited different features compared to those of the seeds. The H-form product can serve as a catalyst in Friedel-Crafts alkylation reaction of anisole with 1-phenylethanol, and its catalytic activity is comparable to the seeds. Furthermore, XRD, FE-SEM, TG-DTA, CHN, FT-IR and NMR analyses of products and intermediates provide insights into the role of seeds and occluded HMI, the crystallization process, and key factors for achieving seed-assisted synthesis of MWW-type zeolites with an OSDA-free gel system. The present results provide a new perspective for the economical and environmentally friendly production of MWW-type zeolites.

  3. Tetraethylenepentamine embedded zeolite A for carbon dioxide adsorption.

    PubMed

    Kim, Young-Ki; Mo, Yong-Hwan; Lee, Jun; You, Hyo-Sang; Yi, Chang-Keun; Park, Young Cheol; Park, Sang-Eon

    2013-04-01

    Tetraethylenepentamine (TEPA) embedded zeolite A crystals were synthesized by using TEPA and the preformed zeolite A precursor under the microwave irradiation. The presence of TEPA in zeolite A crystal was confirmed by TG analysis and FTIR, Raman spectra. The CO2 adsorptive behavior of TEPA embedded zeolite A samples was investigated by CO2 isotherms measured at 25 degrees C comparing with zeolite A. The optimum CO2 sorption capacity was found in the case of 7.5% TEPA embedded zeolite A, which showed 3.75 mmol g(-1) where as the zeolite A showed less CO2 adsorption capacity of 2.88 mmol g(-1). The adsorption capacity of TEPA embedded Zeolite A was sustained up to 90% during 4 cycles of temperature swing adsorption (TSA) from 40 degrees C to 140 degrees C, indicating that the TEPA embedded Zeolite A was found to be useful as one of the application to solid amine adsorbent for CO2.

  4. Dye house wastewater treatment through advanced oxidation process using Cu-exchanged Y zeolite: a heterogeneous catalytic approach.

    PubMed

    Fathima, Nishtar Nishad; Aravindhan, Rathinam; Rao, Jonnalagadda Raghava; Nair, Balachandran Unni

    2008-01-01

    Catalytic wet hydrogen peroxide oxidation of an anionic dye has been explored in this study. Copper(II) complex of NN'-ethylene bis(salicylidene-aminato) (salenH2) has been encapsulated in super cages of zeolite-Y by flexible ligand method. The catalyst has been characterized by Fourier transforms infra red spectroscopy, X-ray powder diffractograms, Thermo-gravimetric and differential thermal analysis and nitrogen adsorption studies. The effects of various parameters such as pH, catalyst and hydrogen peroxide concentration on the oxidation of dye were studied. The results indicate that complete removal of color has been obtained after a period of less than 1h at 60 degrees C, 0.175M H2O2 and 0.3g l(-1) catalyst. More than 95% dye removal has been achieved using this catalyst for commercial effluent. These studies indicate that copper salen complex encapsulated in zeolite framework is a potential heterogeneous catalyst for removal of color from wastewaters.

  5. Catalysts as Sensors—A Promising Novel Approach in Automotive Exhaust Gas Aftertreatment

    PubMed Central

    Moos, Ralf

    2010-01-01

    Sensors that detect directly and in situ the status of automotive exhaust gas catalysts by monitoring the electrical properties of the catalyst coating itself are overviewed. Examples included in this review are the in-situ determination of the electrical impedance of three-way catalysts based on ceria-zirconia solutions and of lean NOx traps of earth-alkaline based coatings, as well as approaches to determine the ammonia loading in Fe-SCR-zeolites with electrical ac measurements. Even more sophisticated approaches based on interactions with electromagnetic waves are also reviewed. For that purpose, metallic stick-like antennas are inserted into the exhaust pipe. The catalyst properties are measured in a contactless manner, directly indicating the catalyst status. The radio frequency probes gauge the oxygen loading degree of three-way catalysts, the NOx-loading of lean NOx traps, and the soot loading of Diesel particulate filters. PMID:22163575

  6. Optimization of Rhodium-Based Catalysts for Mixed Alcohol Synthesis -- 2011 Progress Report

    SciTech Connect

    Gerber, Mark A.; Gray, Michel J.; Albrecht, Karl O.; Rummel, Becky L.

    2011-10-01

    Pacific Northwest National Laboratory has been conducting research to investigate the feasibility of producing mixed alcohols from biomass-derived synthesis gas (syngas). In recent years, this research has primarily involved the further development of catalysts containing rhodium and manganese based on the results of earlier catalyst screening tests. Research during FY 2011 continued to examine the performance of RhMn catalysts on alternative supports including selected zeolite, silica, and carbon supports. Catalyst optimization continued using both the Davisil 645 and Merck Grade 7734 silica supports. Research also was initiated in FY 2011, using the both Davisil 645 silica and Hyperion CS-02C-063 carbon supports, to evaluate the potential for further improving catalyst performance, through the addition of one or two additional metals as promoters to the catalysts containing Rh, Mn, and Ir.

  7. Diels–Alder reactions in confined spaces: the influence of catalyst structure and the nature of active sites for the retro-Diels–Alder reaction

    PubMed Central

    Cantín, Ángel

    2016-01-01

    Summary Diels–Alder cycloaddition between cyclopentadiene and p-benzoquinone has been studied in the confined space of a pure silica zeolite Beta and the impact on reaction rate due to the concentration effect within the pore and diffusion limitations are discussed. Introduction of Lewis or Brønsted acid sites on the walls of the zeolite strongly increases the reaction rate. However, contrary to what occurs with mesoporous molecular sieves (MCM-41), Beta zeolite does not catalyse the retro-Diels–Alder reaction, resulting in a highly selective catalyst for the cycloaddition reaction. PMID:27829925

  8. Factors affecting drug adsorption on beta zeolites.

    PubMed

    Pasti, Luisa; Sarti, Elena; Cavazzini, Alberto; Marchetti, Nicola; Dondi, Francesco; Martucci, Annalisa

    2013-05-01

    The adsorption behaviour of three commonly used drugs, namely ketoprofen, hydrochlorothiazide and atenolol, from diluted aqueous solutions on beta zeolites with different SiO2/Al2O3 ratio (i.e. 25, 38 and 360) was investigated by changing the ionic strength and the pH, before and after thermal treatment of the adsorbents. The selective adsorption of drugs was confirmed by thermogravimetry and X-ray diffraction. The adsorption capacity of beta zeolites was strongly dependent on both the solution pH and the alumina content of the adsorbent. Such a remarkable difference was interpreted as a function of the interactions between drug molecules and zeolite surface functional groups. Atenolol was readily adsorbed on the less hydrophobic zeolite, under pH conditions in which electrostatic interactions were predominant. On the other hand, ketoprofen adsorption was mainly driven by hydrophobic interactions. For undissociated molecules the adsorption capability increased with the increase of hydrophobicity.

  9. Ozone decomposition on Ag/SiO2 and Ag/clinoptilolite catalysts at ambient temperature.

    PubMed

    Nikolov, Penko; Genov, Krassimir; Konova, Petya; Milenova, Katya; Batakliev, Todor; Georgiev, Vladimir; Kumar, Narendra; Sarker, Dipak K; Pishev, Dimitar; Rakovsky, Slavcho

    2010-12-15

    Silver modified zeolite (Bulgarian natural clinoptilolite) and Ag/silica catalysts were synthesized by ion exchange and incipient wet impregnation method respectively and characterized by different techniques. DC arc-AES was used for Ag detection. XRD spectra show that Ag is loaded over the surface of the SiO(2) sample and that after the ion-exchange process the HEU type structure of clinoptilolite is retained. UV-VIS (specific reflection at 310 nm) and IR (band at 695 cm(-1)) spectroscopy analysis proved that silver is loaded as a T-atom into zeolite channels as Ag(+), instead of Na(+), Ca(2+), or K(+) ions, existing in the natural clinoptilolite form. The samples Ag/SiO(2) and Ag-clinoptilolite were tested as catalysts for decomposition of gas phase ozone. Very high catalytic activity (up to 99%) was observed and at the same time the catalysts remained active over time at room temperature.

  10. Catalyst suppliers consolidate further, offer more catalysts

    SciTech Connect

    Rhodes, A.K.

    1995-10-02

    The list of suppliers of catalysts to the petroleum refining industry has decreased by five since Oil and Gas Journal`s survey of refining catalysts and catalytic additives was last published. Despite the consolidation, the list of catalyst designations has grown to about 950 in this latest survey, compared to 820 listed in 1993. The table divides the catalysts by use and gives data on their primary differentiating characteristics, feedstock, products, form, bulk density,catalyst support, active agents, availability, and manufactures.

  11. Aromatization of Ethanol Over Desilicated ZSM-5 Zeolites: Effect of Pore Size in the Mesoporous Region.

    PubMed

    Jun, Jong Won; Hasan, Zubair; Kim, Chul-Ung; Jeong, Soon-Yong; Jhung, Sung Hwa

    2016-05-01

    Mesoporous ZSM-5 zeolites were obtained from microporous ZSM-5 by desilication using aqueous NaOH solutions, and their catalytic activity in the aromatization of ethanol was investigated in order to understand the effects of pore size, in the mesoporous region, on the product distribution and stability of the catalysts. Mesopores generally enhanced the selectivities towards aromatics and stability for aromatization. Mesopores with a maximum pore diameter of around 13 nm were the most effective in the aromatization process (especially for benzene and toluene), suggesting that pore-diameter optimization is necessary for efficient catalysis such as aromatization.

  12. Thermodynamic modeling of natural zeolite stability

    SciTech Connect

    Chipera, S.J.; Bish, D.L.

    1997-06-01

    Zeolites occur in a variety of geologic environments and are used in numerous agricultural, commercial, and environmental applications. It is desirable to understand their stability both to predict future stability and to evaluate the geochemical conditions resulting in their formation. The use of estimated thermodynamic data for measured zeolite compositions allows thermodynamic modeling of stability relationships among zeolites in different geologic environments (diagenetic, saline and alkaline lakes, acid rock hydrothermal, basic rock, deep sea sediments). This modeling shows that the relative cation abundances in both the aqueous and solid phases, the aqueous silica activity, and temperature are important factors in determining the stable zeolite species. Siliceous zeolites (e.g., clinoptilolite, mordenite, erionite) present in saline and alkaline lakes or diagenetic deposits formed at elevated silica activities. Aluminous zeolites (e.g., natrolite, mesolite/scolecite, thomsonite) formed in basic rocks in association with reduced silica activities. Likewise, phillipsite formation is favored by reduced aqueous silica activities. The presence of erionite, chabazite, and phillipsite are indicative of environments with elevated potassium concentrations. Elevated temperature, calcic water conditions, and reduced silica activity help to enhance the laumontite and wairakite stability fields. Analcime stability increases with increased temperature and aqueous Na concentration, and/or with decreased silica activity.

  13. Hydrocracking catalyst

    SciTech Connect

    Arias, B.; Galiasso, R.; Kum, H.

    1985-02-12

    The invention relates to a particular method for the preparation of a hydrocracking catalyst, using a high iron content bauxite as a basis. This bauxite is ground and screened to a specific size and mixed with three types of additives: a promoter additive of the P, Mo, Co, Ni, W type. A hardener additive of the phosphoric acid type, ammonium phosphate. And a lubricant and pore-generating additive of the polyvinyl alcohol, polyethylene-glycol, starch type. The particularity consists in that the three additives are added simultaneously during the extrusion of the sample. That way, a particular surface composition is obtained which allows for the activity of the catalyst. Extruded products are obtained in sizes of 1/8, 1/16, and 1/32'' and submitted to drying and calcination programs for their activation. The obtained catalyst offers a good mechanical strength, a high content in macropores and a high activity, specifically for the hydrocracking of heavy Venezuelan crudes or residues.

  14. HYBRID HETEROGENEOUS CATALYSTS FOR HYDROGENATION OF CARBON DIOXIDE

    SciTech Connect

    Licia M. Petkovic; Harry W. Rollins; Daniel M. Ginosar; Kyle C. Burch

    2006-09-01

    HYBRID HETEROGENEOUS CATALYSTS FOR HYDROGENATION OF CARBON DIOXIDE Lucia M. Petkovic, Harry W. Rollins, Daniel M. Ginosar, and Kyle C. Burch Idaho National Laboratory P.O. Box 1625 Idaho Falls, ID 83415-2208 Introduction Anthropogenic emissions of carbon dioxide, a gas often associated with global warming, have increased considerably since the beginning of the industrial age.1 In the U.S., stationary CO2 sources, such as electricity generation plants, produce about one-third of the anthropogenic CO2 generation. Reports2 indicate that the power required to recover 90% of the CO2 from an integrated coal-fired power-plant is about 10% of the power-plant capacity. This energy requirement can be reduced to less than 1% if the recovered CO2 is applied to the production of synthetic fuels. However, the lack of efficient catalysts along with the costs of energy and hydrogen has prevented the development of technologies for direct hydrogenation of CO2.3 Although the cost of hydrogen for hydrogenating CO2 is not economically attractive at present, the future production of hydrogen by nuclear power sources could completely change this scenario.2 Still, an efficient catalyst will be essential for commercial application of those processes. The objective of the work presented here was the development of hybrid catalysts for one-step carbon dioxide hydrogenation to liquid fuels. The hybrid catalysts, which were prepared by two novel techniques, included a copper/zinc oxide catalytic function distributed within an acidic zeolitic matrix. Results of catalyst activity and selectivity studies at atmospheric pressure are presented in this contribution. Experimental Catalysts were prepared by two novel techniques and under several different conditions to produce copper/zinc oxide/zeolite materials. Once synthesized, samples were pelletized and the fraction between 40-60 mesh was utilized for the experiments. Two hundred milligrams of catalyst were loaded in a U-tube stainless steel

  15. Effect of different glasses in glass bonded zeolite

    SciTech Connect

    Lewis, M.A.; Ackerman, J.P.; Verma, S.

    1995-05-01

    A mineral waste form has been developed for chloride waste salt generated during the pyrochemical treatment of spent nuclear fuel. The waste form consists of salt-occluded zeolite powders bound within a glass matrix. The zeolite contains the salt and immobilizes the fission products. The zeolite powders are hot pressed to form a mechanically stable, durable glass bonded zeolite. Further development of glass bonded zeolite as a waste form requires an understanding of the interaction between the glass and the zeolite. Properties of the glass that enhance binding and durability of the glass bonded zeolite need to be identified. Three types of glass, boroaluminosilicate, soda-lime silicate, and high silica glasses, have a range of properties and are now being investigated. Each glass was hot pressed by itself and with an equal amount of zeolite. MCC-1 leach tests were run on both. Soda-lime silicate and high silica glasses did not give a durable glass bonded zeolite. Boroaluminosilicate glasses rich in alkaline earths did bind the zeolite and gave a durable glass bonded zeolite. Scanning electron micrographs suggest that the boroaluminosilicate glasses wetted the zeolite powders better than the other glasses. Development of the glass bonded zeolite as a waste form for chloride waste salt is continuing.

  16. Supported Molecular Iridium Catalysts: Resolving Effects of Metal Nuclearity and Supports as Ligands

    SciTech Connect

    Lu, Jing; Serna, Pedro; Aydin, Cerem; Browning, Nigel D.; Gates, Bruce C.

    2012-02-07

    The performance of a supported catalyst is influenced by the size and structure of the metal species, the ligands bonded to the metal, and the support. Resolution of these effects has been lacking because of the lack of investigations of catalysts with uniform and systematically varied catalytic sites. We now demonstrate that the performance for ethene hydrogenation of isostructural iridium species on supports with contrasting properties as ligands (electron-donating MgO and electron-withdrawing HY zeolite) can be elucidated on the basis of molecular concepts. Spectra of the working catalysts show that the catalytic reaction rate is determined by the dissociation of H{sub 2} when the iridium, either as mono- or tetra-nuclear species, is supported on MgO and is not when the support is the zeolite. The neighboring iridium sites in clusters are crucial for activation of both H{sub 2} and C{sub 2}H{sub 4} when the support is MgO but not when it is the zeolite, because the electron-withdrawing properties of the zeolite support enable even single site-isolated Ir atoms to bond to both C{sub 2}H{sub 4} and H{sub 2} and facilitate the catalysis.

  17. Extended Catalyst Longevity Via Supercritical Isobutane Regeneration of a Partially Deactivated USY Alkylation Catalyst

    SciTech Connect

    Daniel M. Ginosar; David N. Thompson; Kyle C. Burch; David J. Zalewski

    2005-05-01

    Off-line, in situ activity recovery of a partially deactivated USY zeolite catalyst used for isobutane/butene alkylation was examined in a continuous-flow reaction system employing supercritical isobutane. Catalyst samples were deactivated in a controlled manner by running them to either to a fixed butene conversion level of 95% or a fixed time on stream of three hours, and then exposing the catalyst to supercritical isobutane to restore activity. Activity recovery was determined by comparing alkylation activity before and after the regeneration step. Both single and multiple regenerations were performed. Use of a 95% butene conversion level criterion to terminate the reaction step afforded 86% activity recovery for a single regeneration and provided nine sequential reaction steps for the multiple regeneration studies. Employing a fixed 3 h time on stream criterion resulted in nearly complete activity recovery for a single regeneration, and 24 reaction steps were demonstrated in sequence for the multiple regeneration process, producing only minor product yield declines per step. This resulted in a 12-fold increase in catalyst longevity versus unregenerated catalyst.

  18. The zeolite deposits of Greece

    USGS Publications Warehouse

    Stamatakis, M.G.; Hall, A.; Hein, J.R.

    1996-01-01

    Zeolites are present in altered pyroclastic rocks at many localities in Greece, and large deposits of potential economic interest are present in three areas: (1) the Evros region of the province of Thrace in the north-eastern part of the Greek mainland; (2) the islands of Kimolos and Poliegos in the western Aegean; and (3) the island of Samos in the eastern Aegean Sea. The deposits in Thrace are of Eocene-Oligocene age and are rich in heulandite and/or clinoptilolite. Those of Kimolos and Poliegos are mainly Quaternary and are rich in mordenite. Those of Samos are Miocene, and are rich in clinoptilolite and/or analcime. The deposits in Thrace are believed to have formed in an open hydrological system by the action of meteoric water, and those of the western Aegean islands in a similar way but under conditions of high heat flow, whereas the deposits in Samos were formed in a saline-alkaline lake.

  19. Congressionally Directed Project for Passive NOx Removal Catalysts Research

    SciTech Connect

    Schneider, William

    2014-12-29

    The Recipient proposes to produce new scientific and technical knowledge and tools to enable the discovery and deployment of highly effective materials for the selective catalytic reduction (SCR) of nitrogen oxides (NOx) from lean combustion exhaust. A second goal is to demonstrate a closely coupled experimental and computational approach to heterogeneous catalysis research. These goals will be met through the completion of four primary technical objectives: First, an in-depth kinetic analysis will be performed on two prominent classes of NOx SCR catalysts, Fe- and Cu-exchanged beta and ZSM-5 zeolites, over a wide range of catalyst formulation and under identical, high conversion conditions as a function of gas phase composition. Second, the nanoscale structure and adsorption chemistry of these high temperature (HT) and low temperature (LT) catalysts will be determined using in situ and operando spectroscopy under the same reaction conditions. Third, first-principles molecular simulations will be used to model the metal-zeolite active sites, their adsorption chemistry, and key steps in catalytic function. Fourth, this information will be integrated into chemically detailed mechanistic and kinetic descriptions and models of the operation of these well- defined NOx SCR catalysts under practically relevant reaction conditions. The new knowledge and models that derive from this work will be published in the scientific literature.

  20. Methylene blue removal from contaminated waters using O3, natural zeolite, and O3/zeolite.

    PubMed

    Valdés, H; Tardón, R F; Zaror, C A

    2009-01-01

    This paper compares experimental results on methylene blue (MB) removal systems based on ozone oxidation, zeolite adsorption, and simultaneous adsorption-oxidation using ozone in the presence of natural zeolite. The effect of pH (2-8), and the presence of radical scavengers (sodium acetate) on process rates and removal efficiencies are assessed at laboratory scale. The experimental system consisted of a 1 L differential circular flow reactor and an ozone generator rated at 5 g O3/h. Results show that ozone oxidation combined with zeolite adsorption increases the overall MB oxidation rate with respect to ozonation process and zeolite adsorption. In presence of free radical scavenger, only a 25% of reduction on MB removal rate are observed in the simultaneous treatment, as compared with 70% when ozonation treatment is used, suggesting that MB oxidation reactions take mainly place on the zeolite surface.

  1. Elastic and structural properties of zeolites: Sodalite and dehydrated zeolite A

    SciTech Connect

    Kim, S.; Keskar, N.R.; McCormick, A.V.; Chelikowsky, J.R.; Davis, H.T.

    1995-06-01

    A pairwise interatomic potential has been used to investigate elastic and structural properties of two cubic zeolites: sodalite and dehydrated zeolite A. Constant volume energy minimization has been used to determine the variation of lattice constants and atomic coordinates with pressure. The calculated structures of sodalite and dehydrated zeolite A obtained at zero pressure are in reasonably good agreement with the available experimental values. We find that the structures at zero pressure are largely determined by the Coulomb potential. The pressure dependence of bond lengths and bond angles show that both sodalite and dehydrated zeolite A are easily deformed by bending the Si--O--Al angles. As expected for a less dense crystal, the dehydrated zeolite A is softer than the sodalite. We have also obtained the equation of state of these materials.

  2. Comparision of real waste (MSW and MPW) pyrolysis in batch reactor over different catalysts. Part I: product yields, gas and pyrolysis oil properties.

    PubMed

    Ateş, Funda; Miskolczi, Norbert; Borsodi, Nikolett

    2013-04-01

    Pyrolysis of municipal solid waste (MSW) and municipal plastic waste (MPW) have been investigated in batch reactor at 500, 550 and 600°C both in absence and presence of catalysts (Y-zeolite, β-zeolite, equilibrium FCC, MoO3, Ni-Mo-catalyst, HZSM-5 and Al(OH)3). The effect of the parameters on the product properties was investigated. Products were characterized using gas-chromatography, GC/MS, (13)C NMR. Yields of volatile fractions increased, while reaction time necessity for the total cracking decreased in the presence of catalysts. Catalysts have productivity and selectivity in converting aliphatic hydrocarbons to aromatic and cyclic compounds in oil products. Gases from MSW consisted of hydrogen CO, CO2, while exclusively hydrogen and hydrocarbons were detected from MPW. Catalyst efficiency was higher using MPW than MSW. Pyrolysis oils contained aliphatic hydrocarbons, aromatics, cyclic compounds and less ketones, alcohols, acids or esters depending on the raw materials.

  3. Active Fe-containing superoxide dismutase and abundant sodF mRNA in Nostoc commune (Cyanobacteria) after years of desiccation.

    PubMed

    Shirkey, B; Kovarcik, D P; Wright, D J; Wilmoth, G; Prickett, T F; Helm, R F; Gregory, E M; Potts, M

    2000-01-01

    Active Fe-superoxide dismutase (SodF) was the third most abundant soluble protein in cells of Nostoc commune CHEN/1986 after prolonged (13 years) storage in the desiccated state. Upon rehydration, Fe-containing superoxide disumutase (Fe-SOD) was released and the activity was distributed between rehydrating cells and the extracellular fluid. The 21-kDa Fe-SOD polypeptide was purified, the N terminus was sequenced, and the data were used to isolate sodF from the clonal isolate N. commune DRH1. sodF encodes an open reading frame of 200 codons and is expressed as a monocistronic transcript (of approximately 750 bases) from a region of the genome which includes genes involved in nucleic acid synthesis and repair, including dipyrimidine photolyase (phr) and cytidylate monophosphate kinase (panC). sodF mRNA was abundant and stable in cells after long-term desiccation. Upon rehydration of desiccated cells, there was a turnover of sodF mRNA within 15 min and then a rise in the mRNA pool to control levels (quantity of sodF mRNA in cells in late logarithmic phase of growth) over approximately 24 h. The extensive extracellular polysaccharide (glycan) of N. commune DRH1 generated superoxide radicals upon exposure to UV-A or -B irradiation, and these were scavenged by SOD. Despite demonstrated roles for the glycan in the desiccation tolerance of N. commune, it may in fact be a significant source of damaging free radicals in vivo. It is proposed that the high levels of SodF in N. commune, and release of the enzyme from dried cells upon rehydration, counter the effects of oxidative stress imposed by multiple cycles of desiccation and rehydration during UV-A or -B irradiation in situ.

  4. 11. EASTERN END OF ZEOLITE BUILDING. NOTE DIAL TO LEFT ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    11. EASTERN END OF ZEOLITE BUILDING. NOTE DIAL TO LEFT OF CLOCK GAUGING TOTAL ZEOLITE INFLUENT IN MILLIONS OF GALLONS PER DAY. - F. E. Weymouth Filtration Plant, 700 North Moreno Avenue, La Verne, Los Angeles County, CA

  5. Temperature programmed oxidation of coked H-gallosilicate (MFI) propane aromatization catalyst: Influence of catalyst composition and pretreatment parameters

    SciTech Connect

    Choudhary, V.R.; Devadas, P.; Sansare, S.D.; Guisnet, M.

    1997-03-01

    Temperature programmed oxidation (TPO) of H-gallosilicate (MFI) coked in the propane aromatization at 550{degrees}C for a time-on-stream of 7-8 h has been investigated by measuring point to point the consumption of oxygen and also the formation of the both CO and CO{sub 2} (by GC analysis using a 16-loop gas sampling valve) during the TPO run from 50{degrees} to 900{degrees}C at a linear heating rate of 20{degrees}C min{sup -1} in a flow (50 cm{sup 3} min{sup -1}) of a O{sub 2}-He mixture (8.0 mol% O{sub 2}). The SiGa and Na/Ga ratios, calcination temperature, and hydrothermal pretreatments of the zeolite and also the presence of binder (silica or kaolin) in the catalyst have a strong influence on the TPO of coked zeolite. The influence is attributed to changes in the zeolite properties (viz., zeolitic acidity or framework Ga and non-GW Ga-oxide species), which affect the coke oxidation both directly and/or indirectly, by controlling the nature of coke formed during the coking process. 23 refs., 4 figs., 2 tabs.

  6. The impact of aqueous medium on zeolite framework integrity

    SciTech Connect

    Vjunov, Aleksei; Fulton, John L.; Camaioni, Donald M.; Hu, Jian Z.; Burton, Sarah D.; Arslan, Ilke; Lercher, Johannes A.

    2015-05-12

    Understanding the zeolite framework stability in aqueous phase is crucial to develop stable catalysts. Al K–edge, extended X–ray absorption fine structure and 27Al MAS NMR spectroscopies in combination with DFT calculations have been used to monitor both qualitative and quantitative structural changes of two well–characterized samples with BEA structure. The effects of various properties on stability were explored, including Al concentration, Al distribution, particle size and structural defects. As the samples were degraded by treatment in hot liquid water, the local structure about the Al T–site remained mostly intact, including the Al–O–Si angles and bond distances, while the nano–scale crystalline structure as measured by XRD and TEM was disrupted. The combined data suggest a three–step mechanism in which, initially, the HBEA framework crystallinity decreases via hydrolysis of T–O bonds along polymorph stacking faults and inter–grain boundaries in a mode similar to crack propagation in glass. With prolonged exposure, amorphization occurs via hydrolysis of surface Si–OH groups propagating inward through the zeolite lattice. In parallel, cracks propagate within the crystalline micro–domains along paths through specific T–O–T groups. Authors thank B. W. Arey (PNNL) for HIM measurements, T. Huthwelker for support during Al XAFS measurements at the Swiss Light Source (PSI, Switzerland) and M. Y. Hu (PNNL) for support during NMR experiments. This work was supported by the U. S. Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences & Biosciences. NMR experiments were performed at the Environmental Molecular Science Laboratory, a national scientific user facility sponsored by the DOE’s Office of Biological and Environmental Research, and Physical Science Laboratory both located at Pacific Northwest National Laboratory (PNNL). PNNL is a multi–program national laboratory

  7. Application of high silica zeolite ZSM-5 in a hybrid treatment process based on sequential adsorption and ozonation for VOCs elimination.

    PubMed

    Zaitan, Hicham; Manero, Marie Hélène; Valdés, Héctor

    2016-03-01

    In this study, a hydrophobic synthetic zeolite, namely ZSM-5 is chosen as an adsorbent/catalyst for toluene removal. Experimental results showed that toluene adsorption onto ZSM-5 was favourable, following a Langmuir adsorption isotherm model. ZSM-5 zeolite was regenerated using gaseous ozone at low temperature. Adsorbed toluene was oxidised, releasing mainly CO2 and H2O. Traces of oxidation by-products such as acetic acid and acetaldehyde were formed and remained adsorbed after the oxidativate regeneration with ozone. After four successive cycles of adsorption/ozonation, the adsorption efficiency was not affected (92%-99%). These results showed that volatile organic compound (VOC) removal by adsorption onto ZSM-5 zeolite followed by ozone regeneration could be used as a promising hybrid process for the control of VOC emissions in terms of efficiency.

  8. Hydrothermal conversion of FAU zeolite into LEV zeolite in the presence of non-calcined seed crystals

    NASA Astrophysics Data System (ADS)

    Yashiki, Ayako; Honda, Koutaro; Fujimoto, Ayumi; Shibata, Shohei; Ide, Yusuke; Sadakane, Masahiro; Sano, Tsuneji

    2011-06-01

    Hydrothermal conversion of Faujasite-type (FAU) zeolite into Levynite (LEV) zeolite without the use of an organic structure-directing agent (OSDA) was successfully achieved in the presence of non-calcined seed crystals. The interzeolite conversion depended strongly upon the alkalinity (OH -/SiO 2) of the starting gel, the Si/Al ratio of the starting FAU zeolite and the type of alkaline metal employed. Successful conversion of FAU zeolites into pure LEV zeolite was achieved only for FAU zeolites with Si/Al ratios in the range of 19-26, under highly alkaline conditions (OH -/SiO 2=0.6) by using NaOH as an alkali source. Although the yield of LEV zeolite prepared by this method was lower (18-26%) than that of the conventional hydrothermal synthesis with the use of SDA, the obtained LEV zeolite exhibited a unique core/shell structure.

  9. Suppressed N2O formation during NH3 selective catalytic reduction using vanadium on zeolitic microporous TiO2.

    PubMed

    Lee, Seung Gwan; Lee, Hyun Jeong; Song, Inhak; Youn, Seunghee; Kim, Do Heui; Cho, Sung June

    2015-08-03

    Emission of N2O from mobile and off-road engine is now being currently regulated because of its high impact compared to that of CO2, thereby implying that N2O formation from the exhaust gas after-treatment system should be suppressed. Selective catalytic reduction using vanadium supported TiO2 catalyst in mobile and off-road engine has been considered to be major source for N2O emission in the system. Here we have demonstrated that vanadium catalyst supported on zeolitic microporous TiO2 obtained from the hydrothermal reaction of bulk TiO2 at 400 K in the presence of LiOH suppresses significantly the N2O emission compared to conventional VOx/TiO2 catalyst, while maintaining the excellent NOx reduction, which was ascribed to the location of VOx domain in the micropore of TiO2, resulting in the strong metal support interaction. The use of zeolitic microporous TiO2 provides a new way of preparing SCR catalyst with a high thermal stability and superior catalytic performance. It can be also extended further to the other catalytic system employing TiO2-based substrate.

  10. Suppressed N2O formation during NH3 selective catalytic reduction using vanadium on zeolitic microporous TiO2

    PubMed Central

    Lee, Seung Gwan; Lee, Hyun Jeong; Song, Inhak; Youn, Seunghee; Kim, Do Heui; Cho, Sung June

    2015-01-01

    Emission of N2O from mobile and off-road engine is now being currently regulated because of its high impact compared to that of CO2, thereby implying that N2O formation from the exhaust gas after-treatment system should be suppressed. Selective catalytic reduction using vanadium supported TiO2 catalyst in mobile and off-road engine has been considered to be major source for N2O emission in the system. Here we have demonstrated that vanadium catalyst supported on zeolitic microporous TiO2 obtained from the hydrothermal reaction of bulk TiO2 at 400 K in the presence of LiOH suppresses significantly the N2O emission compared to conventional VOx/TiO2 catalyst, while maintaining the excellent NOx reduction, which was ascribed to the location of VOx domain in the micropore of TiO2, resulting in the strong metal support interaction. The use of zeolitic microporous TiO2 provides a new way of preparing SCR catalyst with a high thermal stability and superior catalytic performance. It can be also extended further to the other catalytic system employing TiO2-based substrate. PMID:26235671

  11. Heterogeneous catalytic degradation of phenolic substrates: catalysts activity.

    PubMed

    Liotta, L F; Gruttadauria, M; Di Carlo, G; Perrini, G; Librando, V

    2009-03-15

    This review article explored the catalytic degradation of phenol and some phenols derivates by means of advanced oxidation processes (AOPs). Among them, only the heterogeneous catalyzed processes based on catalytic wet peroxide oxidation, catalytic ozonation and catalytic wet oxidation were reviewed. Also selected recent examples about heterogeneous photocatalytic AOPs will be presented. In details, the present review contains: (i) data concerning catalytic wet peroxide oxidation of phenolic compounds over metal-exchanged zeolites, hydrotalcites, metal-exchanged clays and resins. (ii) Use of cobalt-based catalysts, hydrotalcite-like compounds, active carbons in the catalytic ozonation process. (iii) Activity of transition metal oxides, active carbons and supported noble metals catalysts in the catalytic wet oxidation of phenol and acetic acid. The most relevant results in terms of catalytic activity for each class of catalysts were reported.

  12. Transition Metal Ions in Zeolites: Coordination and activation of O2

    PubMed Central

    Smeets, Pieter J.; Woertink, Julia S.; Sels, Bert F.; Solomon, Edward I.; Schoonheydt, Robert A.

    2010-01-01

    Zeolites containing transition metal ions (TMI) often show promising activity as heterogeneous catalysts in pollution abatement and selective oxidation reactions. In this paper, two aspects of research on the TMI Cu, Co and Fe in zeolites are discussed: (i) coordination to the lattice and (ii) activated oxygen species. At low loading, TMI preferably occupy exchange sites in six-membered oxygen rings (6MR) where the TMI preferentially coordinate with the oxygen atoms of Al tetrahedra. High TMI loadings result in a variety of TMI species formed at the zeolite surface. Removal of the extra-lattice oxygens during high temperature pretreatments can result in auto-reduction. Oxidation of reduced TMI sites often results in the formation of highly reactive oxygen species. In Cu-ZSM-5, calcination with O2 results in the formation of a species, which was found to be a crucial intermediate in both the direct decomposition of NO and N2O and the selective oxidation of methane into methanol. An activated oxygen species, called α-oxygen, is formed in Fe-ZSM5 and reported to be the active site in the partial oxidation of methane and benzene into methanol and phenol, respectively. However, this reactive α-oxygen can only be formed with N2O, not with O2. O2 activated Co intermediates in Faujasite (FAU) zeolites can selectively oxidize α-pinene and epoxidize styrene. In Co-FAU, CoIII superoxo and peroxo complexes are suggested to be the active cores, whereas in Cu and Fe-ZSM-5 various monomeric and dimeric sites have been proposed, but no consensus has been obtained. Very recently, the active site in Cu-ZSM-5 was identified as a bent [Cu-O-Cu]2+ core (Proc. Natl. Acad. Sci. USA 2009, 106, 18908-18913). Overall, O2 activation depends on the interplay of structural factors such as type of zeolite, size of the channels and cages and chemical factors such as Si/Al ratio and the nature, charge and distribution of the charge balancing cations. The presence of several different TMI sites

  13. Photobioreactor cultivation and catalytic pyrolysis of the microalga Desmodesmus communis (Chlorophyceae) for hydrocarbons production by HZSM-5 zeolite cracking.

    PubMed

    Conti, Roberto; Pezzolesi, Laura; Pistocchi, Rossella; Torri, Cristian; Massoli, Patrizio; Fabbri, Daniele

    2016-12-01

    The study evaluated the growth of Desmodesmus communis on column photobioreactor and its thermochemical treatment by catalytic pyrolysis using HZSM-5 zeolite. D. communis showed good results in terms of growth (0.05gL(-1)d(-1)). Analytical pyrolysis of original algae and derived bio-oil mixed with zeolite was used as a screening method in order to gather information on the cracking process. Preparative pyrolysis on bench scale reactor was performed on algae biomass over a zeolite bed at 1:10 ratio (wt/wt). Py-GC-MS of biomass/catalyst mixture showed that the denitrogenation/deoxygenation increased with increasing zeolite load from 1:5 to 1:20 ratio and became significant at 1:10 ratio. The composition observed by analytical pyrolysis was featured by the predominance of alkylated monoaromatic hydrocarbons. The scaling-up to bench scale confirmed the results obtained with analytical pyrolysis in terms of monoaromatic hydrocarbons. However, low yield of catalytic oil (8% by weight) was observed.

  14. Enthalpy and entropy barriers explain the effects of topology on the kinetics of zeolite-catalyzed reactions.

    PubMed

    Van der Mynsbrugge, Jeroen; De Ridder, Jeroen; Hemelsoet, Karen; Waroquier, Michel; Van Speybroeck, Veronique

    2013-08-26

    The methylation of ethene, propene, and trans-2-butene on zeolites H-ZSM-58 (DDR), H-ZSM-22 (TON), and H-ZSM-5 (MFI) is studied to elucidate the particular influence of topology on the kinetics of zeolite-catalyzed reactions. H-ZSM-58 and H-ZSM-22 are found to display overall lower methylation rates compared to H-ZSM-5 and also different trends in methylation rates with increasing alkene size. These variations may be rationalized based on a decomposition of the free-energy barriers into enthalpic and entropic contributions, which reveals that the lower methylation rates on H-ZSM-58 and H-ZSM-22 have virtually opposite reasons. On H-ZSM-58, the lower methylation rates are caused by higher enthalpy barriers, owing to inefficient stabilization of the reaction intermediates in the large cage-like pores. On the other hand, on H-ZSM-22, the methylation rates mostly suffer from higher entropy barriers, because excessive entropy losses are incurred inside the narrow-channel structure. These results show that the kinetics of crucial elementary steps hinge on the balance between proper stabilization of the reaction intermediates inside the zeolite pores and the resulting entropy losses. These fundamental insights into their inner workings are indispensable for ultimately selecting or designing better zeolite catalysts.

  15. Pt-free carbon-based fuel cell catalyst prepared from spherical polyimide for enhanced oxygen diffusion.

    PubMed

    Nabae, Yuta; Nagata, Shinsuke; Hayakawa, Teruaki; Niwa, Hideharu; Harada, Yoshihisa; Oshima, Masaharu; Isoda, Ayano; Matsunaga, Atsushi; Tanaka, Kazuhisa; Aoki, Tsutomu

    2016-03-18

    The development of a non-precious metal (NPM) fuel cell catalyst is extremely important to achieve globalization of polymer electrolyte fuel cells due to the cost and scarcity of platinum. Here, we report on a NPM cathode catalyst prepared by the pyrolysis of spherical polyimide nanoparticles that contain small amounts of Fe additive. 60 nm diameter Fe-containing polyimide nanoparticles were successfully synthesized by the precipitation polymerization of pyromellitic acid dianhydride and 1,3,5-tris(4-aminophenyl)benzene with Fe(acac)3 (acac = acetylacetonate) as an additive. The particles were subsequently carbonized by multistep pyrolysis to obtain the NPM catalyst while retaining the small particle size. The catalyst has good performance and promising durability for fuel cell applications. The fuel cell performance under a 0.2 MPa air atmosphere at 80 °C of 1.0 A cm(-2) at 0.46 V is especially remarkable and better than that previously reported.

  16. Physico-chemical studies and CO adsorption on zeolite-encapsulated Mn II, Mn III-hydrazone complexes

    NASA Astrophysics Data System (ADS)

    Ahmed, Ayman H.

    2007-08-01

    Complexes of Mn(II) and Mn(III) with N 2O 3 hydrazone ligand derived from salicylaldehyde and benzenesulphonylhydrazide have been encapsulated in zeolite Y- supercages by a diffusion method. The synthesized new materials have been characterized by combination of elemental analysis, FT-IR, UV-vis., magnetic measurements, XRD, thermal analysis (TG, DTG and DTA), as well as surface area measurements and nitrogen adsorption studies. Investigation of the stereochemistry of these incorporated chelates pointed out that, Mn(II) complex is tetrahedral with involvement of zeolite oxygen in coordination meanwhile Mn(III) complex has octahedral configuration without contribution of the lattice oxygen. The intrazeolitic hydrazone complexes are thermally stable up to 1000 °C without decomposition. Catalytic activity towards CO adsorption for these zeolite encapsulated complexes has been investigated and compared with Mn II-Y using in situ FT-IR spectroscopy. The results revealed that, Mn II(SBSH)/Y and Mn III(SBSH)/Y give an elementary peak near 1728 cm -1 indicating a selectivity to form sbnd COOH species while Mn II-Y catalyst gives a broad band in the region of 1765-1560 cm -1 assigned to different ( sbnd COOH) and carbonates species. On the other hand, the in situ FT-IR data indicate that Mn II(SBSH)/Y and Mn III(SBSH)/Y can be used as reactive catalysts in water gas shift reaction (WGSR).

  17. Optimizing anti-coking abilities of zeolites by ethylene diamine tetraacetie acid modification on catalytic fast pyrolysis of corn stalk

    NASA Astrophysics Data System (ADS)

    Zhang, Bo; Zhong, Zhaoping; Song, Zuwei; Ding, Kuan; Chen, Paul; Ruan, Roger

    2015-12-01

    In order to minimize coke yield during biomass catalytic fast pyrolysis (CFP) process, ethylene diamine tetraacetie acid (EDTA) chemical modification method is carried out to selectively remove the external framework aluminum of HZSM-5 catalyst. X-ray diffraction (XRD), nitrogen (N2)-adsorption and ammonia-temperature programmed desorption (NH3-TPD) techniques are employed to investigate the porosity and acidity characteristics of original and modified HZSM-5 samples. Py-GC/MS and thermo-gravimetric analyzer (TGA) experiments are further conducted to explore the catalytic effect of modified HZSM-5 samples on biomass CFP and to verify the positive effect on coke reduction. Results show that EDTA treatment does not damage the crystal structure of HZSM-5 zeolites, but leads to a slight increase of pore volume and pore size. Meanwhile, the elimination of the strong acid peak indicates the dealumination of outer surface of HZSM-5 zeolites. Treatment time of 2 h (labeled EDTA-2H) is optimal for acid removal and hydrocarbon formation. Among all modified catalysts, EDTA-2H performs the best for deacidification and can obviously increase the yields of positive chemical compositions in pyrolysis products. Besides, EDTA modification can improve the anti-coking properties of HZSM-5 zeolites, and EDTA-2H gives rise to the lowest coke yield.

  18. Fluid catalytic cracking: recent developments on the grand old lady of zeolite catalysis.

    PubMed

    Vogt, E T C; Weckhuysen, B M

    2015-10-21

    Fluid catalytic cracking (FCC) is one of the major conversion technologies in the oil refinery industry. FCC currently produces the majority of the world's gasoline, as well as an important fraction of propylene for the polymer industry. In this critical review, we give an overview of the latest trends in this field of research. These trends include ways to make it possible to process either very heavy or very light crude oil fractions as well as to co-process biomass-based oxygenates with regular crude oil fractions, and convert these more complex feedstocks in an increasing amount of propylene and diesel-range fuels. After providing some general background of the FCC process, including a short history as well as details on the process, reactor design, chemical reactions involved and catalyst material, we will discuss several trends in FCC catalysis research by focusing on ways to improve the zeolite structure stability, propylene selectivity and the overall catalyst accessibility by (a) the addition of rare earth elements and phosphorus, (b) constructing hierarchical pores systems and (c) the introduction of new zeolite structures. In addition, we present an overview of the state-of-the-art micro-spectroscopy methods for characterizing FCC catalysts at the single particle level. These new characterization tools are able to explain the influence of the harsh FCC processing conditions (e.g. steam) and the presence of various metal poisons (e.g. V, Fe and Ni) in the crude oil feedstocks on the 3-D structure and accessibility of FCC catalyst materials.

  19. Fluid catalytic cracking: recent developments on the grand old lady of zeolite catalysis

    PubMed Central

    2015-01-01

    Fluid catalytic cracking (FCC) is one of the major conversion technologies in the oil refinery industry. FCC currently produces the majority of the world's gasoline, as well as an important fraction of propylene for the polymer industry. In this critical review, we give an overview of the latest trends in this field of research. These trends include ways to make it possible to process either very heavy or very light crude oil fractions as well as to co-process biomass-based oxygenates with regular crude oil fractions, and convert these more complex feedstocks in an increasing amount of propylene and diesel-range fuels. After providing some general background of the FCC process, including a short history as well as details on the process, reactor design, chemical reactions involved and catalyst material, we will discuss several trends in FCC catalysis research by focusing on ways to improve the zeolite structure stability, propylene selectivity and the overall catalyst accessibility by (a) the addition of rare earth elements and phosphorus, (b) constructing hierarchical pores systems and (c) the introduction of new zeolite structures. In addition, we present an overview of the state-of-the-art micro-spectroscopy methods for characterizing FCC catalysts at the single particle level. These new characterization tools are able to explain the influence of the harsh FCC processing conditions (e.g. steam) and the presence of various metal poisons (e.g. V, Fe and Ni) in the crude oil feedstocks on the 3-D structure and accessibility of FCC catalyst materials. PMID:26382875

  20. The catalytic conversion of methyl chloride to ethylene and propylene over phosphorus-modified Mg-ZSM-5 zeolites

    SciTech Connect

    Sun, Y.; Campbell, S.M.; Lunsford, J.H. ); Lewis, G.E.; Palke, D.; Tau, L.M. )

    1993-09-01

    A Mg-ZSM-5 zeolite modified with phosphorus is capable of catalyzing the reaction of CH[sub 3]Cl to C[sub 2]H[sub 4], C[sub 3]H[sub 6], C[sub 4]H[sub 8], and HCl at 500[degrees]C. At a WHSV of 20 h[sup [minus]1], an initial conversion level of 96% was achieved with combined C[sub 2]H[sub 4], C[sub 3]H[sub 6], and C[sub 4]H[sub 8] selectivities of about 80%. During the useful life of the catalyst the C[sub 3]H[sub 6] selectivity was 50-60%. The percent conversion decreased to 50% over a period of 20 h, but the catalyst could be regenerated by heating in flowing air. As the catalyst deactivated, the C[sub 3]H[sub 6] selectivity increased slightly and the C[sub 2]H[sub 4] selectivity decreased. Catalytic and spectroscopic results confirm that phosphorus, derived from trimethylphosphine, was responsible for a decrease in the strong Broensted acidity in the zeolite. For example, the phosphorus-modified zeolite was inactive for n-hexane cracking at 350[degrees]C, and the protonated amount of pyridine, added to the zeolite as a probe for acidity, decreased significantly. The catalyst, however, had sufficient acidity to crack hexene or octene at 500[degrees]C to propylene and ethylene in ratios that were very similar to those detected during the conversion of CH[sub 3]Cl. Without the strong Broensted acidity the PMg-ZSM-5 zeolite apparently is unable to convert the light olefins to paraffins and aromatics. A mechanism is proposed in which magnesium cations activate CH[sub 3]Cl to form HCl and a carbene intermediate. The latter is believed to be responsible for C-C bond formation via reaction with a surface methoxide species. Ethylene probably is the primary hydrocarbon, but it oligomerizes to a higher molecular weight olefin which cracks back to ethylene and propylene. 22 refs., 8 figs., 1 tab.

  1. 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.

  2. Growth of zeolite crystals in the microgravity environment of space

    NASA Technical Reports Server (NTRS)

    Sacco, A., Jr.; Sand, L. B.; Collette, D.; Dieselman, K.; Crowley, J.; Feitelberg, A.

    1986-01-01

    Zeolites are hydrated, crystalline aluminosilicates with alkali and alkaling earth metals substituted into cation vacancies. Typically zeolite crystals are 3 to 8 microns. Larger cyrstals are desirable. Large zeolite crystals were produced (100 to 200 microns); however, they have taken restrictively long times to grow. It was proposed if the rate of nucleation or in some other way the number of nuclei can be lowered, fewer, larger crystals will be formed. The microgravity environment of space may provide an ideal condition to achieve rapid growth of large zeolite crystals. The objective of the project is to establish if large zeolite crystals can be formed rapidly in space.

  3. Model reaction for the in situ characterization of the hydrogenating and acid properties of industrial hydrocracking catalysts

    SciTech Connect

    Guisnet, M.; Thomazeau, C.; Lemberton, J.L.; Mignard, S.

    1995-01-01

    A kinetic study of o-xylene transformation was carried out on a sulfided NiMo on Y zeolite catalyst during the hydrocracking of a model compound (n-heptane) under the following conditions of the process: high hydrogen pressure (5.7 MPa), presence of nitrogen and sulfur-containing compounds. o-Xylene inhibits n-heptane transformation, which can be explained by a competition for the adsorption on the acid sites between o-xylene and the olefinic intermediates of hydrocracking. The products of o-xylene transformation are the following: p- and m-xylenes (isomerization), toluene and trimethylbenzenes (disproportionation), and saturated C{sub 8} naphthenes (dimethylcyclohexane and trimethylcyclopentanes). It is shown that 1,3- and 1,4-dimethylcyclohexanes (and trimethylcyclopentanes) result from the isomerization of m- and p-xylenes. Therefore, the hydrogenating activity of hydrocracking catalysts can be characterized by the formation of dimethylyclohexanes and trimethylcyclopentanes. Furthermore, the isomerization of xylenes, which occurs through an acid mechanism, can be used for characterizing the acid activity of hydrocracking catalysts. This is not the case for disproportion whose rate depends on hydrogen pressure. The validity of o-xylene transformation for characterizing the acid and hydrogenating activities of bifunctional hydrocracking catalysts was confirmed by the use of a series of catalysts having either the same content of NiMo and different contents of zeolite or the same content of zeolite and different contents of NiMo. While the isomerization activity is strictly proportional to the zeolite content and independent of the NiMo content, and the hydrogenating activity is proportional to the NiMo content and independent of the zeolite content. 27 refs., 17 figs., 3 tabs.

  4. Effects of Hydrothermal Aging on NH3-SCR reaction over Cu/zeolites

    SciTech Connect

    Kwak, Ja Hun; Tran, Diana N.; Burton, Sarah D.; Szanyi, Janos; Lee, Jong H.; Peden, Charles HF

    2012-02-06

    The effects of hydrothermal treatment on model Cu/zeolite catalysts were investigated to better understand the nature of Cu species for the selective catalytic reduction of NO{sub x} by NH{sub 3}. After hydrothermal aging at 800 C for 16 h, the NO{sub x} reduction performance of Cu-ZSM-5 and Cu-beta were significantly reduced at low temperatures, while that of Cu-SSZ-13 was not affected. When the zeolite framework aluminum species were probed using solid state {sup 27}Al-NMR, significant reduction in the intensities of the tetrahedral aluminum peak was observed for Cu-ZSM-5 and Cu-beta, although no increase in the intensities of the octahedral aluminum peak was observed. When the redox behavior of Cu species was examined using H{sub 2}-TPR, it was found that Cu{sup 2+} could be reduced to Cu{sup +} and to Cu{sup 0} fir Cu-ZSM-5 and Cu-beta catalysts, while Cu{sup 2+} could be reduced to Cu{sup +} only for Cu-SSZ-13. After hydrothermal aging, CuO and Cu-aluminate species were found to form in Cu-ZSM-5 and Cu-beta, while little changes were observed for Cu-SSZ-13.

  5. Hydrogen Purification Using Natural Zeolite Membranes

    NASA Technical Reports Server (NTRS)

    DelValle, William

    2003-01-01

    The School of Science at Universidad del Turabo (UT) have a long-lasting investigation plan to study the hydrogen cleaning and purification technologies. We proposed a research project for the synthesis, phase analysis and porosity characterization of zeolite based ceramic perm-selective membranes for hydrogen cleaning to support NASA's commitment to achieving a broad-based research capability focusing on aerospace-related issues. The present study will focus on technology transfer by utilizing inorganic membranes for production of ultra-clean hydrogen for application in combustion. We tested three different natural zeolite membranes (different particle size at different temperatures and time of exposure). Our results show that the membranes exposured at 900 C for 1Hr has the most higher permeation capacity, indicated that our zeolite membranes has the capacity to permeate hydrogen.

  6. Synthesis of silver nanoclusters on zeolite substrates

    NASA Astrophysics Data System (ADS)

    Posada, Y.

    2009-06-01

    Silver nanoclusters were synthesized by reducing silver nitrate with ethylene glycol at 160 °C in the presence of zeolite. A one-pot procedure has rendered uniform size distributions of quasispherical silver clusters of average sizes of 100-200 nm synthesized on the surfaces of cubiclike zeolite substrates of ˜1 μm side. Bulk material microanalysis measurements showed samples with silver mass percentages of 20%-38%. Surface atomic composition analysis found silver concentrations of 3.1%-5.7%, zeolite compounds and nontraces of nitrogen were measured. The binding energy for the Ag 3d5/2 core electrons was shifted to higher energies at 368.6 eV compared to that of metallic silver. Herein, is presented a cost-effective technique for producing a narrow size distribution of silver nanocomposites with great potential for optoelectronics, catalysis, and nanobiotechnological applications.

  7. Structures and reaction mechanisms of cumene formation via benzene alkylation with propylene in a newly synthesized ITQ-24 zeolite: an embedded ONIOM study.

    PubMed

    Jansang, Bavornpon; Nanok, Tanin; Limtrakul, Jumras

    2006-06-29

    The cumene formation via benzene alkylation with propylene on the new three-dimensional nanoporous catalyst, ITQ-24 zeolite, has been investigated by using the ONIOM2(B3LYP/6-31G(d,p):UFF) method. Both consecutive and associative reaction pathways are examined. The contributions of the short-range van der Waals interactions, which are explicitly included in the ONIOM2 model, and an additional long-range electrostatic potential from the extended zeolite framework to the energy profile are taken into consideration. It is found that benzene alkylation with propylene in the ITQ-24 zeolite prefers to occur through the consecutive reaction mechanism. The benzene alkylation step is the reaction rate-determining step with an estimated activation energy of 35.70 kcal/mol, comparable with an experimental report in beta-zeolite of 34.9 kcal/mol. The electrostatic potential from the extended zeolite framework shows a much more significant contribution to the transition state selectivity than the van der Waals interactions.

  8. Theoretical insights into the mechanism of olefin elimination in the methanol-to-olefin process over HZSM-5, HMOR, HBEA, and HMCM-22 zeolites.

    PubMed

    Wang, Sen; Chen, Yanyan; Wei, Zhihong; Qin, Zhangfeng; Chen, Jialing; Ma, Hong; Dong, Mei; Li, Junfen; Fan, Weibin; Wang, Jianguo

    2014-10-02

    The mechanism of olefin elimination in the process of methanol-to-olefins (MTO) over a series of zeolites like HZSM-5, HMOR, HBEA, and HMCM-22 was investigated by DFT-D calculations, which is a crucial step that controls the MTO product distribution. The results demonstrate that the manners of olefin elimination are related to the pore structure of zeolite catalyst and the interaction between proton transfer reagent (water or methanol) and zeolite acidic framework. The indirect spiro mechanism is preferable to the direct mechanism over HMOR, HBEA, and HMCM-22 zeolites with large pores, as suggested by the energy barrier of rate-determining step and the potential energy surface (PES), but is unfavorable over HZSM-5 with medium-sized pores due to the steric hindrance of spiro intermediates. Over various zeolites, water and methanol perform differently in proton transfer to form the spiro intermediates; over HMOR and HBEA with strong acidity, water is superior to methanol in promoting propene elimination, whereas over HMCM-22 with relatively weaker acidity, methanol is more favorable as a proton transfer reagent.

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

    PubMed

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

    2014-11-07

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

  10. Adsorption of CO2 by alginate immobilized zeolite beads

    NASA Astrophysics Data System (ADS)

    Suratman, A.; Kunarti, E. S.; Aprilita, N. H.; Pamurtya, I. C.

    2017-03-01

    Immobilized zeolit in alginate beads for adsorption of CO2 was developed. Alginate immobilized zeolit beads was generated by dropping the mixture of Na-alginate and zeolite solution into Ca2+ solution. The adsorption efficacy such as the influence of contact time, mass of zeolite, flowrate of CO2, and mass of adsorbent was evaluated. The adsorption of CO2 onto alginate immobilized zeolit beads was investigated by performing both equilibrium and kinetic batch test. Bead was characterized by FTIR and SEM. Alginate immobilized zeolit beads demonstrated significantly higher sorption efficacy compared to plain alginate beads and zeolite with 0.25 mmol CO2 adsorbed /g adsorbent. Optimum condition was achieved with mass composition of alginate:zeolite (3:1), flowrate 50 mL/min for 20 minutes. The alginate immobilized zeolit beads showed that adsorption of CO2 followed Freundlich isotherm and pseudo second order kinetic model. Adsorption of CO2 onto alginate immobilized zeolite beads is a physisorption with adsorption energy of 6.37 kJ/mol. This results indicates that the alginate immobilized zeolit beads can be used as promising adsorbents for CO2.

  11. Natural zeolite reactivity towards ozone: the role of compensating cations.

    PubMed

    Valdés, Héctor; Alejandro, Serguei; Zaror, Claudio A

    2012-08-15

    Among indoor pollutants, ozone is recognised to pose a threat to human health. Recently, low cost natural zeolites have been applied as alternative materials for ozone abatement. In this work, the effect of compensating cation content of natural zeolite on ozone removal is studied. A Chilean natural zeolite is used here as starting material. The amount of compensating cations in the zeolite framework was modified by ion exchange using an ammonium sulphate solution (0.1 mol L(-1)). Characterisation of natural and modified zeolites were performed by X-ray powder diffraction (XRD), nitrogen adsorption at 77K, elemental analysis, X-ray fluorescence (XRF), thermogravimetric analysis coupled with mass spectroscopy (TGA-MS), and temperature-programmed desorption of ammonia (NH(3)-TPD). Ozone adsorption and/or decomposition on natural and modified zeolites were studied by diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). Results show that the zeolite compensating cation content affects ozone interaction with zeolite active sites. Ammonium ion-exchange treatments followed by thermal out-gassing at 823 K, reduces ozone diffusion resistance inside the zeolite framework, increasing ozone abatement on zeolite surface active sites. Weak and strong Lewis acid sites of zeolite surface are identified here as the main active sites responsible of ozone removal.

  12. Studies of anions sorption on natural zeolites.

    PubMed

    Barczyk, K; Mozgawa, W; Król, M

    2014-12-10

    This work presents results of FT-IR spectroscopic studies of anions-chromate, phosphate and arsenate - sorbed from aqueous solutions (different concentrations of anions) on zeolites. The sorption has been conducted on natural zeolites from different structural groups, i.e. chabazite, mordenite, ferrierite and clinoptilolite. The Na-forms of sorbents were exchanged with hexadecyltrimethylammonium cations (HDTMA(+)) and organo-zeolites were obtained. External cation exchange capacities (ECEC) of organo-zeolites were measured. Their values are 17mmol/100g for chabazite, 4mmol/100g for mordenite and ferrierite and 10mmol/100g for clinoptilolite. The used initial inputs of HDTMA correspond to 100% and 200% ECEC of the minerals. Organo-modificated sorbents were subsequently used for immobilization of mentioned anions. It was proven that aforementioned anions' sorption causes changes in IR spectra of the HDTMA-zeolites. These alterations are dependent on the kind of anions that were sorbed. In all cases, variations are due to bands corresponding to the characteristic Si-O(Si,Al) vibrations (occurring in alumino- and silicooxygen tetrahedra building spatial framework of zeolites). Alkylammonium surfactant vibrations have also been observed. Systematic changes in the spectra connected with the anion concentration in the initial solution have been revealed. The amounts of sorbed CrO4(2-), AsO4(3-) and PO4(3-) ions were calculated from the difference between their concentrations in solutions before (initial concentration) and after (equilibrium concentration) sorption experiments. Concentrations of anions were determined by spectrophotometric method.

  13. [Fe-ZSM-5 catalysts with different silica-alumina ratios for N2O, catalytic decomposition].

    PubMed

    Lu, Ren-Jie; Zhang, Xin-Yan; Hao, Zheng-Ping

    2014-01-01

    The Fe-ZSM-5 catalysts were prepared with H-ZSM-5 of different Si/Al ratios by wet ion exchange and chemical vapor deposition. Then the catalysts were investigated by XRD, BET, TEM, UV-vis and NH3-TPD technologies to analyze the iron states in Fe-ZSM-5 zeolites. The results showed that after H-ZSM-5 zeolites were prepared by chemical vapor deposition and heating wet ion exchange, the nano Fe2 O3 particles were uniformly dispersed with the sizes of 8 nm in the Fe-ZSM-5-25 (Si/A1-25). Moreover, there were more oligonuclear Fe3+ Oy clusters in the Fe-ZSM-5-25 catalysts than in Fe-ZSM-5-300 (Si/Al-300). The results of catalytic performance on N2O decomposition showed that Fe-ZSM-5-25 catalysts had higher catalytic activities than Fe-ZSM-5-300 catalysts. The Fe-ZSM-5 catalysts prepared by chemical vapor deposition achieved the best catalytic activity in N2O decomposition among the catalysts prepared by the three methods. Moreover, the presence of O2 only slightly reduced N2O conversion, while NO promoted the N2O decomposition. Finally, after reaction for more than 100 h, Fe-ZSM-5 catalyst showed no obvious deactivation under simulated emission conditions.

  14. Rationalizing Inter- and Intracrystal Heterogeneities in Dealuminated Acid Mordenite Zeolites by Stimulated Raman Scattering Microscopy Correlated with Super-resolution Fluorescence Microscopy

    PubMed Central

    2014-01-01

    Dealuminated zeolites are widely used acid catalysts in research and the chemical industry. Bulk-level studies have revealed that the improved catalytic performance results from an enhanced molecular transport as well as from changes in the active sites. However, fully exploiting this information in rational catalyst design still requires insight in the intricate interplay between both. Here we introduce fluorescence and stimulated Raman scattering microscopy to quantify subcrystal reactivity as well as acid site distribution and to probe site accessibility in the set of individual mordenite zeolites. Dealumination effectively introduces significant heterogeneities between different particles and even within individual crystals. Besides enabling direct rationalization of the nanoscale catalytic performance, these observations reveal valuable information on the industrial dealumination process itself. PMID:25402756

  15. Upgrading naphtha in a multiple riser fluid catalytic cracking operation employing a catalyst mixture

    SciTech Connect

    Herbst, J.A.; Owen, H.; Schipper, P.H.

    1989-05-16

    A process is described for producing gasoline comprising contacting a hydrocarbon feed having an initial boiling-point of at least 400/sup 0/F., a 50% boiling of at least 500/sup 0/F. and an end boiling point of at least 600/sup 0/F., in a first riser, with a two component catalyst under fluid catalytic cracking conditions. At least one component of the catalyst is stripped in a stripping unit to remove entrained hydrocarbons, and regenerated wherein the two component catalyst comprises a first catalyst component selected from the group consisting of an amorphous cracking catalyst and a large pore cracking catalyst, whereby a product comprising olefins and naphtha is produced. Ethylene introduced together with the two component catalyst to a second riser, for contacting ethylene with a second catalyst component which is a shape selective medium pore crystalline silicate zeolite to produce products heavier than ethylene and to increase the temperature of the catalyst to an optimum temperature for upgrading naphtha; and naphtha is introduced to the second riser, down stream of the point of ethylene introduction, for contact with the catalyst at the optimum temperature and the naphtha is upgraded to gasoline product.

  16. Supported Molecular Catalysts: Synthesis, in-situ Characterization and Performance

    SciTech Connect

    Haw, James F

    2010-12-14

    The technological advantages of solid catalysts (robustness for operation at high temperatures, lack of corrosion, and ease of separation of products) can be combined with the advantages of soluble catalysts (e.g., selectivity) by synthesis of structurally discrete, nearly uniform catalysts on supports. Our goal is to synthesize, characterize, test, and model such catalysts and their reactions, thereby opening a door to unprecedented fundamental understanding of the properties of such materials. We employ molecular chemistry in nano-scale cages of zeolites and on surfaces of tailored porous solids for the precise synthesis of catalysts with discrete, uniform, well-defined sites, primarily mononuclear metal complexes, characterizing them (sometimes in the functioning state) with a broad range of complementary experimental techniques and using computational chemistry to interpret the results, map out reaction paths, provide bases for the design of new catalysts, improve methods of data analysis, and identify key experiments. The effort is directly in support of DOE's energy, environmental, and national security missions as well as the support of DOE's basic science mission to develop the tools and understanding needed for the success of the applied mission areas. The research is demonstrating progress in understanding, modeling, and controlling chemical reactivity at interfaces to develop a fundamental understanding of how to control catalytic reactions for a broad range of applications.

  17. Separation of catalyst from Fischer-Tropsch slurry

    DOEpatents

    White, Curt M.; Quiring, Michael S.; Jensen, Karen L.; Hickey, Richard F.; Gillham, Larry D.

    1998-10-27

    In a catalytic process for converting synthesis gas including hydrogen and carbon monoxide to hydrocarbons and oxygenates by a slurry Fischer-Tropsch synthesis, the wax product along with dispersed catalyst is removed from the slurry and purified by removing substantially all of the catalyst prior to upgrading the wax and returning a portion to the Fischer-Tropsch reaction. Separation of the catalyst particles from the wax product is accomplished by dense gas and/or liquid extraction in which the organic compounds in the wax are dissolved and carried away from the insoluble inorganic catalyst particles that are primarily inorganic in nature. The purified catalyst free wax product can be subsequently upgraded by various methods such as hydrogenation, isomerization, hydrocracking, conversion to gasoline and other products over ZSM-5 aluminosilicate zeolite, etc. The catalyst particles are returned to the Fischer-Tropsch Reactor by slurring them with a wax fraction of appropriate molecular weight, boiling point and viscosity to avoid reactor gelation.

  18. Separation of catalyst from Fischer-Tropsch slurry

    DOEpatents

    White, C.M.; Quiring, M.S.; Jensen, K.L.; Hickey, R.F.; Gillham, L.D.

    1998-10-27

    In a catalytic process for converting synthesis gas including hydrogen and carbon monoxide to hydrocarbons and oxygenates by a slurry Fischer-Tropsch synthesis, the wax product along with dispersed catalyst is removed from the slurry and purified by removing substantially all of the catalyst prior to upgrading the wax and returning a portion to the Fischer-Tropsch reaction. Separation of the catalyst particles from the wax product is accomplished by dense gas and/or liquid extraction in which the organic compounds in the wax are dissolved and carried away from the insoluble inorganic catalyst particles that are primarily inorganic in nature. The purified catalyst-free wax product can be subsequently upgraded by various methods such as hydrogenation, isomerization, hydrocracking, conversion to gasoline and other products over ZSM-5 aluminosilicate zeolite, etc. The catalyst particles are returned to the Fischer-Tropsch Reactor by mixing them with a wax fraction of appropriate molecular weight, boiling point and viscosity to avoid reactor gelation. 2 figs.

  19. Evidences of the presence of different types of active sites for the oxygen reduction reaction with Fe/N/C based catalysts

    NASA Astrophysics Data System (ADS)

    Pérez-Alonso, Francisco J.; Domínguez, Carlota; Al-Thabaiti, Shaeel A.; Al-Youbi, Abdulrahman O.; Abdel Salam, Mohamed; Alshehri, Abdulmohsen A.; Retuerto, María; Peña, Miguel A.; Rojas, Sergio

    2016-09-01

    Fe/N/C catalysts are very active for the oxygen reduction reaction (ORR); however, the nature of the active site(s) is not fully understood. In this work, we study the performance of different types of N/C and Fe/N/C catalysts for the ORR, and the effect of the addition of NaCN. Phthalocyanine and graphene have been studied as model metal-free catalysts for the ORR. Fe-phthalocyanine (FePhcy), Fe-phthalocyanine dispersed in graphene (FePhcy/G) and Fe/N/G, have been used as model Fe-containing catalysts. FePhcy and FePhcy/G only contain Fe atoms coordinated to 4 nitrogen atoms. On the other hand, different species such as Fe-Nx and Fe3C coexist in Fe/N/G. In addition, Csbnd C ensembles are present in the graphene present in FePhcy/G and Fe/N/G. The ORR activity is characteristic of each catalyst, being the highest for the catalysts containing FeN4 ensembles. The addition of CN- results in the selective poisoning of the Fe-containing sites but it does not suppress the ORR activity of the Graphene containing samples. In-situ infrared spectroscopy studies during the ORR reveal that CN- poisoning of the Fe sites is reversible, desorbing at potentials less positive than ca. 600 mV. As a consequence, the ORR activity of the Fe-containing sites is recovered gradually.

  20. Effects of catalyst support and chemical vapor deposition condition on synthesis of multi-walled carbon nanocoils

    SciTech Connect

    Suda, Yoshiyuki Iida, Tetsuo; Takikawa, Hirofumi; Harigai, Toru; Ue, Hitoshi; Umeda, Yoshito

    2016-02-01

    Multi-walled carbon nanocoil (MWCNC) is a carbon nanotube (CNT) with helical shape. We have synthesized MWCNCs and MWCNTs hybrid by chemical vapor deposition (CVD). MWCNCs are considered to be a potential material in nanodevices, such as electromagnetic wave absorbers and field emitters. It is very important to take into account the purity of MWCNCs. In this study, we aimed to improve the composition ratio of MWCNCs to MWCNTs by changing catalyst preparation and CVD conditions. As a catalyst, Fe{sub 2}O{sub 3}/zeolite was prepared by dissolving Fe{sub 2}O{sub 3} fine powder and Y-type zeolite (catalyst support material) in ethanol with an Fe density of 0.5wt.% and with a zeolite density of 3.5wt.%. The catalyst-coated Si substrate was transferred immediately onto a hotplate and was heated at 80°C for 5 min. Similarly, Fe{sub 2}O{sub 3}/Al{sub 2}O{sub 3}, Co/zeolite/Al{sub 2}O{sub 3}, Co/zeolite, and Co/Al{sub 2}O{sub 3} were prepared. The effect of the difference of the composite catalysts on synthesis of MWCNCs was considered. The CVD reactor was heated in a tubular furnace to 660-790°C in a nitrogen atmosphere at a flow rate of 1000 ml/min. Subsequently, acetylene was mixed with nitrogen at a flow rate ratio of C{sub 2}H{sub 2}/N{sub 2} = 0.02-0.1. The reaction was kept under these conditions for 10 min. MWCNTs and MWCNCs were well grown by the catalysts of Co/zeolite and Co/Al{sub 2}O{sub 3}. The composition ratio of MWCNCs to MWCNTs was increased by using a combination of zeolite and Al{sub 2}O{sub 3}. The highest composition ratio of MWCNCs to MWCNTs was 12%.

  1. The Effects of Supercritical Propane on the Alkylation of Toluene with Ethylene over USY and Sulfated Zirconia Catalysts

    SciTech Connect

    Ginosar, Daniel Michael; Burch, Kyle Coates; Thompson, David Neal

    2002-11-01

    The alkylation of toluene with ethylene over microporous USY zeolite and mesoporous sulfated zirconia (S/ZrO2) catalysts was explored at liquid, near-critical liquid, and supercritical conditions using propane as the supercritical cosolvent. Liquid, near-critical liquid, and supercritical conditions were examined for their effects on product selectivity and catalyst activity maintenance. The S/ZrO2 catalyst demonstrated alkylation activity almost exclusively, whereas the USY catalyst demonstrated both alkylation and cracking/disproportionation activities. Near-critical and supercritical reaction conditions improved product selectivity with the USY catalyst through the suppression of disproportionation reactions and enhanced ortho- and para-ethyltoluene selectivity. However, the addition of the supercritical cosolvent resulted in increased deactivation for both the S/ZrO2 and USY catalysts, with deactivation increasing with propane mole fraction.

  2. Electrochemical catalyst recovery method

    DOEpatents

    Silva, Laura J.; Bray, Lane A.

    1995-01-01

    A method of recovering catalyst material from latent catalyst material solids includes: a) combining latent catalyst material solids with a liquid acid anolyte solution and a redox material which is soluble in the acid anolyte solution to form a mixture; b) electrochemically oxidizing the redox material within the mixture into a dissolved oxidant, the oxidant having a potential for oxidation which is effectively higher than that of the latent catalyst material; c) reacting the oxidant with the latent catalyst material to oxidize the latent catalyst material into at least one oxidized catalyst species which is soluble within the mixture and to reduce the oxidant back into dissolved redox material; and d) recovering catalyst material from the oxidized catalyst species of the mixture. The invention is expected to be particularly useful in recovering spent catalyst material from petroleum hydroprocessing reaction waste products having adhered sulfides, carbon, hydrocarbons, and undesired metals, and as well as in other industrial applications.

  3. Electrochemical catalyst recovery method

    DOEpatents

    Silva, L.J.; Bray, L.A.

    1995-05-30

    A method of recovering catalyst material from latent catalyst material solids includes: (a) combining latent catalyst material solids with a liquid acid anolyte solution and a redox material which is soluble in the acid anolyte solution to form a mixture; (b) electrochemically oxidizing the redox material within the mixture into a dissolved oxidant, the oxidant having a potential for oxidation which is effectively higher than that of the latent catalyst material; (c) reacting the oxidant with the latent catalyst material to oxidize the latent catalyst material into at least one oxidized catalyst species which is soluble within the mixture and to reduce the oxidant back into dissolved redox material; and (d) recovering catalyst material from the oxidized catalyst species of the mixture. The invention is expected to be particularly useful in recovering spent catalyst material from petroleum hydroprocessing reaction waste products having adhered sulfides, carbon, hydrocarbons, and undesired metals, and as well as in other industrial applications. 3 figs.

  4. Rigid zeolite containing polyurethane foams

    DOEpatents

    Frost, C.B.

    1984-05-18

    A closed cell rigid polyurethane foam has been prepared which contains up to about 60% by weight of molecular sieves capable of sorbing molecules with effective critical diameters of up to about 10 A. The molecular sieve component of the foam can be preloaded with catalysts or with reactive compounds that can be released upon activation of the foam to control and complete crosslinking after the foam is formed. The foam can also be loaded with water or other flame-retarding agents, after completion. Up to about 50% of the weight of the isocyanate component of the foam can be replaced by polyimide resin precursors for incorporation into the final polymeric network.

  5. Rigid zeolite containing polyurethane foams

    DOEpatents

    Frost, Charles B.

    1985-01-01

    A closed cell rigid polyurethane foam has been prepared which contains up to about 60% by weight of molecular sieves capable of sorbing molecules with effective critical diameters of up to about 10 .ANG.. The molecular sieve component of the foam can be preloaded with catalysts or with reactive compounds that can be released upon activation of the foam to control and complete crosslinking after the foam is formed. The foam can also be loaded with water or other flame-retarding agents, after completion. Up to about 50% of the weight of the isocyanate component of the foam can be replaced by polyimide resin precursors for incorporation into the final polymeric network.

  6. Design of Ru-zeolites for hydrogen-free production of conjugated linoleic acids.

    PubMed

    Philippaerts, An; Goossens, Steven; Vermandel, Walter; Tromp, Moniek; Turner, Stuart; Geboers, Jan; Van Tendeloo, Gustaaf; Jacobs, Pierre A; Sels, Bert F

    2011-06-20

    While conjugated vegetable oils are currently used as additives in the drying agents of oils and paints, they are also attractive molecules for making bio-plastics. Moreover, conjugated oils will soon be accepted as nutritional additives for "functional food" products. While current manufacture of conjugated vegetable oils or conjugated linoleic acids (CLAs) uses a homogeneous base as isomerisation catalyst, a heterogeneous alternative is not available today. This contribution presents the direct production of CLAs over Ru supported on different zeolites, varying in topology (ZSM-5, BETA, Y), Si/Al ratio and countercation (H(+), Na(+), Cs(+)). Ru/Cs-USY, with a Si/Al ratio of 40, was identified as the most active and selective catalyst for isomerisation of methyl linoleate (cis-9,cis-12 (C18:2)) to CLA at 165 °C. Interestingly, no hydrogen pre-treatment of the catalyst or addition of hydrogen donors is required to achieve industrially relevant isomerisation productivities, namely, 0.7 g of CLA per litre of solvent per minute. Moreover, the biologically most active CLA isomers, namely, cis-9,trans-11, trans-10,cis-12 and trans-9,trans-11, were the main products, especially at low catalyst concentrations. Ex situ physicochemical characterisation with CO chemisorption, extended X-ray absorption fine structure measurements, transmission electron microscopy analysis, and temperature-programmed oxidation reveals the presence of highly dispersed RuO(2) species in Ru/Cs-USY(40).

  7. Tuning interactions between zeolite and supported metal by physical-sputtering to achieve higher catalytic performances

    PubMed Central

    Li, Xin-Gang; Liu, Cheng; Sun, Jian; Xian, Hui; Tan, Yi-Sheng; Jiang, Zheng; Taguchi, Akira; Inoue, Mitsuhiro; Yoneyama, Yoshiharu; Abe, Takayuki; Tsubaki, Noritatsu

    2013-01-01

    To substitute for petroleum, Fischer-Tropsch synthesis (FTS) is an environmentally benign process to produce synthetic diesel (n-paraffin) from syngas. Industrially, the synthetic gasoline (iso-paraffin) can be produced with a FTS process followed by isomerization and hydrocracking processes over solid-acid catalysts. Herein, we demonstrate a cobalt nano-catalyst synthesized by physical-sputtering method that the metallic cobalt nano-particles homogeneously disperse on the H-ZSM5 zeolite support with weak Metal-Support Interactions (MSI). This catalyst performed the high gasoline-range iso-paraffin productivity through the combined FTS, isomerization and hydrocracking reactions. The weak MSI results in the easy reducibility of the cobalt nano-particles; the high cobalt dispersion accelerates n-paraffin diffusion to the neighboring acidic sites on the H-ZSM5 support for isomerization and hydrocracking. Both factors guarantee its high CO conversion and iso-paraffin selectivity. This physical-sputtering technique to synthesize the supported metallic nano-catalyst is a promising way to solve the critical problems caused by strong MSI for various processes. PMID:24085106

  8. Catalytic conversion of methane to methanol using Cu-zeolites.

    PubMed

    Alayon, Evalyn Mae C; Nachtegaal, Maarten; Ranocchiari, Marco; van Bokhoven, Jeroen A

    2012-01-01

    The conversion of methane to value-added liquid chemicals is a promising answer to the imminent demand for fuels and chemical synthesis materials in the advent of a dwindling petroleum supply. Current technology requires high energy input for the synthesis gas production, and is characterized by low overall selectivity, which calls for alternative reaction routes. The limitation to achieve high selectivity is the high C-H bond strength of methane. High-temperature reaction systems favor gas-phase radical reactions and total oxidation. This suggests that the catalysts for methane activation should be active at low temperatures. The enzymatic-inspired metal-exchanged zeolite systems apparently fulfill this need, however, methanol yield is low and a catalytic process cannot yet be established. Homogeneous and heterogeneous catalytic systems have been described which stabilize the intermediate formed after the first C-H activation. The understanding of the reaction mechanism and the determination of the active metal sites are important for formulating strategies for the upgrade of methane conversion catalytic technologies.

  9. Kinetics of the polymerization of alkenes on zeolites

    NASA Astrophysics Data System (ADS)

    Alberty, Robert A.

    1987-09-01

    The polymerization of alkenes at temperatures in the neighborhood of 600 K on a zeolite catalyst can be described in terms of a mechanism with bimolecular polymerization reactions and cracking reactions of isomer groups. The rate equations for the formation of isomer groups up to C13H26 have been integrated using the fourth-order Runge-Kutta method for polymerizations at constant temperature and pressure. In the absence of data on rate constants, calculations have been made on the basis of the assumption that all the bimolecular rate constants are equal or all the cracking constants are equal. In each case the rate constants for the reverse reactions have been calculated using the equilibrium constants for the steps in the mechanism. Under some circumstances the plots of weight fractions of isomer groups vs time have nearly the same shape for the two assumptions. However, it is possible to distinguish between the two assumptions by using experiments at sufficiently high pressures. The calculations show that it is of interest to examine the compositions arising from different starting materials, even though the equilibrium composition depends only upon temperature and pressure.

  10. Catalytic pyrolysis of oil fractions separated from food waste leachate over nanoporous acid catalysts.

    PubMed

    Kim, Seung-Soo; Heo, Hyeon Su; Kim, Sang Guk; Ryoo, Ryong; Kim, Jeongnam; Jeon, Jong-Ki; Park, Sung Hoon; Park, Young-Kwon

    2011-07-01

    Oil fractions, separated from food waste leachate, can be used as an energy source. Especially, high quality oil can be obtained by catalytic cracking. In this study, nanoporous catalysts such as Al-MCM-41 and mesoporous MFI type zeolite were applied to the catalytic cracking of oil fractions using the pyrolysis gas chromatography/mass spectrometry. Mesoporous MFI type zeolite showed better textural porosity than Al-MCM-41. In addition, mesoporous MFI type zeolite had strong Brönsted acidity while Al-MCM-41 had weak acidity. Significant amount of acid components in the food waste oil fractions were converted to mainly oxygenates and aromatics. As a result of its well-defined nanopores and strong acidity, the use of a mesoporous MFI type zeolite produced large amounts of gaseous and aromatic compounds. High yields of hydrocarbons within the gasoline range were also obtained in the case of mesoporous MFI type zeolite, whereas the use of Al-MCM-41, which exhibits relatively weak acidity, resulted in high yields of oxygenates and diesel range hydrocarbons.

  11. Zeolite 5A Catalyzed Etherification of Diphenylmethanol

    ERIC Educational Resources Information Center

    Cooke, Jason; Henderson, Eric J.; Lightbody, Owen C.

    2009-01-01

    An experiment for the synthetic undergraduate laboratory is described in which zeolite 5A catalyzes the room temperature dehydration of diphenylmethanol, (C[subscript 6]H[subscript 5])[subscript 2]CHOH, producing 1,1,1',1'-tetraphenyldimethyl ether, (C[subscript 6]H[subscript 5])[subscript 2]CHOCH(C[subscript 6]H[subscript 5])[subscript 2]. The…

  12. MERCURY SEPARATION FROM POLLUTANT WATER USING ZEOLITES

    EPA Science Inventory

    Arsenic is known to be a hazardous contaminant in drinking water that causes arsenical dermatitis and skin cancer. In the present work, the potential use of a variety of synthetic zeolites for removal of arsenic from water has been examined at room temperature. Experiments have...

  13. ARSENIC SEPARATION FROM WATER USING ZEOLITES

    EPA Science Inventory

    Arsenic is known to be a hazardous contaminant in drinking water. The presence of arsenic in water supplies has been linked to arsenical dermatosis and skin cancer . Zeolites are well known for their ion exchange capacities. In the present work, the potential use of a variety of ...

  14. Multicomponent liquid ion exchange with chabazite zeolites

    SciTech Connect

    Robinson, S.M.; Arnold, W.D. Jr.; Byers, C.W.

    1993-10-01

    In spite of the increasing commercial use of zeolites for binary and multicomponent sorption, the understanding of the basic mass-transfer processes associated with multicomponent zeolite ion-exchange systems is quite limited. This study was undertaken to evaluate Na-Ca-Mg-Cs-Sr ion exchange from an aqueous solution using a chabazite zeolite. Mass-transfer coefficients and equilibrium equations were determined from experimental batch-reactor data for single and multicomponent systems. The Langmuir isotherm was used to represent the equilibrium relationship for binary systems, and a modified Dubinin-Polyani model was used for the multicomponent systems. The experimental data indicate that diffusion through the microporous zeolite crystals is the primary diffusional resistance. Macropore diffusion also significantly contributes to the mass-transfer resistance. Various mass-transfer models were compared to the experimental data to determine mass-transfer coefficients. Effective diffusivities were obtained which accurately predicted experimental data using a variety of models. Only the model which accounts for micropore and macropore diffusion occurring in series accurately predicted multicomponent data using single-component diffusivities. Liquid and surface diffusion both contribute to macropore diffusion. Surface and micropore diffusivities were determined to be concentration dependent.

  15. Framework Al zoning in zeolite ECR-1.

    PubMed

    Shin, Jiho; Ahn, Nak Ho; Cho, Sung June; Ren, Limin; Xiao, Feng-Shou; Hong, Suk Bong

    2014-02-25

    Rietveld analyses of the synchrotron X-ray diffraction data for various cation forms of zeolite ECR-1 have demonstrated framework Al zoning, which parallels the alternation of Al-rich maz and Al-poor mor layers. This can be further supported by notable differences in the average bond valence of its 10 crystallographically distinct tetrahedral sites.

  16. The Determination of Zeolite Sorption Properties

    NASA Astrophysics Data System (ADS)

    Tishin, A. A.; Laguntsov, N. I.; Kurchatov, I. M.

    The installation and the measurement data procedure were established for the sorbent characteristics determination. Sorption isotherms of the three gases (nitrogen, oxygen and carbon dioxide) are obtained on the industrial zeolites NaX, NaX-BKO and NaA in a pressure range (0;7) bar.

  17. Silver clusters and chemistry in zeolites

    SciTech Connect

    Sun, T.; Seff, K. . Dept. of Chemistry)

    1994-06-01

    The spectroscopic work done on silver clusters trapped in solid noble gas matrices at low temperature has been extensively reviewed by Ozin, and Henglein has done the same for photochemical studies of colloidal silver particles in solution. This article will review the chemistry of silver in zeolite hosts, including the synthesis and structures of silver clusters. 127 refs.

  18. Enhanced chromium adsorption capacity via plasma modification of natural zeolites

    NASA Astrophysics Data System (ADS)

    Cagomoc, Charisse Marie D.; Vasquez, Magdaleno R., Jr.

    2017-01-01

    Natural zeolites such as mordenite are excellent adsorbents for heavy metals. To enhance the adsorption capacity of zeolite, sodium-exchanged samples were irradiated with 13.56 MHz capacitively coupled radio frequency (RF) argon gas discharge. Hexavalent chromium [Cr(VI)] was used as the test heavy metal. Pristine and plasma-treated zeolite samples were soaked in 50 mg/L Cr solution and the amount of adsorbed Cr(VI) on the zeolites was calculated at predetermined time intervals. Compared with untreated zeolite samples, initial Cr(VI) uptake was 70% higher for plasma-treated zeolite granules (50 W 30 min) after 1 h of soaking. After 24 h, all plasma-treated zeolites showed increased Cr(VI) uptake. For a 2- to 4-month period, Cr(VI) uptake increased about 130% compared with untreated zeolite granules. X-ray diffraction analyses between untreated and treated zeolite samples revealed no major difference in terms of its crystal structure. However, for plasma-treated samples, an increase in the number of surface defects was observed from scanning electron microscopy images. This increase in the number of surface defects induced by plasma exposure played a crucial role in increasing the number of active sorption sites on the zeolite surface.

  19. Energetics of sodium-calcium exchanged zeolite A.

    PubMed

    Sun, H; Wu, D; Guo, X; Shen, B; Navrotsky, A

    2015-05-07

    A series of calcium-exchanged zeolite A samples with different degrees of exchange were prepared. They were characterized by powder X-ray diffraction (XRD) and differential scanning calorimetry (DSC). High temperature oxide melt drop solution calorimetry measured the formation enthalpies of hydrated zeolites CaNa-A from constituent oxides. The water content is a linear function of the degree of exchange, ranging from 20.54% for Na-A to 23.77% for 97.9% CaNa-A. The enthalpies of formation (from oxides) at 25 °C are -74.50 ± 1.21 kJ mol(-1) TO2 for hydrated zeolite Na-A and -30.79 ± 1.64 kJ mol(-1) TO2 for hydrated zeolite 97.9% CaNa-A. Dehydration enthalpies obtained from differential scanning calorimetry are 32.0 kJ mol(-1) H2O for hydrated zeolite Na-A and 20.5 kJ mol(-1) H2O for hydrated zeolite 97.9% CaNa-A. Enthalpies of formation of Ca-exchanged zeolites A are less exothermic than for zeolite Na-A. A linear relationship between the formation enthalpy and the extent of calcium substitution was observed. The energetic effect of Ca-exchange on zeolite A is discussed with an emphasis on the complex interactions between the zeolite framework, cations, and water.

  20. Zeolite Nanoparticles for Selective Sorption of Plasma Proteins

    PubMed Central

    Rahimi, M.; Ng, E.-P.; Bakhtiari, K.; Vinciguerra, M.; Ahmad, H. Ali; Awala, H.; Mintova, S.; Daghighi, M.; Bakhshandeh Rostami, F.; de Vries, M.; Motazacker, M. M.; Peppelenbosch, M. P.; Mahmoudi, M.; Rezaee, F.

    2015-01-01

    The affinity of zeolite nanoparticles (diameter of 8–12 nm) possessing high surface area and high pore volume towards human plasma proteins has been investigated. The protein composition (corona) of zeolite nanoparticles has been shown to be more dependent on the plasma protein concentrations and the type of zeolites than zeolite nanoparticles concentration. The number of proteins present in the corona of zeolite nanoparticles at 100% plasma (in vivo state) is less than with 10% plasma exposure. This could be due to a competition between the proteins to occupy the corona of the zeolite nanoparticles. Moreover, a high selective adsorption for apolipoprotein C-III (APOC-III) and fibrinogen on the zeolite nanoparticles at high plasma concentration (100%) was observed. While the zeolite nanoparticles exposed to low plasma concentration (10%) exhibited a high selective adsorption for immunoglobulin gamma (i.e. IGHG1, IGHG2 and IGHG4) proteins. The zeolite nanoparticles can potentially be used for selectively capture of APOC-III in order to reduce the activation of lipoprotein lipase inhibition during hypertriglyceridemia treatment. The zeolite nanoparticles can be adapted to hemophilic patients (hemophilia A (F-VIII deficient) and hemophilia B (F-IX deficient)) with a risk of bleeding, and thus might be potentially used in combination with the existing therapy. PMID:26616161