Suchergebnisse

[EN] Non-oxidative methane aromatization is an attractive direct route for producing higher hydrocarbons. It is highly selective to benzene despite the low conversion due to thermodynamic limitations, and Mo/H-ZSM-5, the first catalyst proposed for this reaction, is still considered as one of the most adequate. The major problem of this process is the severe catalyst deactivation due to the rapid build-up of carbonaceous deposits on the catalysts. Here we present an effective regeneration procedure that extends the life of Mo/zeolite based catalysts by combining reaction periods of 1.5 h with 0.5 h regeneration steps in a continuous cyclic mode and methane activation after each regeneration stage. Benzene productivity obtained with Mo/ZSM-5 is shown to be almost constant for increasing TOS ranges when applying this new cyclic protocol, and threefold values are achieved for an 18 h on stream period by limiting the reaction steps to the first 1.5 h of maximum benzene selectivity (97 vs. 33 g benzene per kg cat h) compared to a conventional single run. ; Funding from the European Community's 7th Framework Program through the Collaborative Project Next-GTL (agreement n° 229183) and financial support by the Spanish GovernmentMINECO through "Severo Ochoa" (SEV 2012-0267), Consolider Ingenio 2010-Multicat, MAT2012-37160 and MAT2012-31657 are acknowledged. The authors thank B. Esparcia for technical assistance and the Electron Microscopy Service of the UPV for their help in sample characterization. ; Portilla Ovejero, MT.; Llopis Alonso, F.; Martínez, C. (2015). Non-oxidative dehydroaromatization of methane:an effective reaction regeneration cyclic operation for catalyst life extension. Catalysis Science and Technology. 5(7):3806-3821. https://doi.org/10.1039/C5CY00356C ; S ; 3806 ; 3821 ; 5 ; 7

3806 3821 5 7 ; S ; [EN] Non-oxidative methane aromatization is an attractive direct route for producing higher hydrocarbons. It is highly selective to benzene despite the low conversion due to thermodynamic limitations, and Mo/H-ZSM-5, the first catalyst proposed for this reaction, is still considered as one of the most adequate. The major problem of this process is the severe catalyst deactivation due to the rapid build-up of carbonaceous deposits on the catalysts. Here we present an effective regeneration procedure that extends the life of Mo/zeolite based catalysts by combining reaction periods of 1.5 h with 0.5 h regeneration steps in a continuous cyclic mode and methane activation after each regeneration stage. Benzene productivity obtained with Mo/ZSM-5 is shown to be almost constant for increasing TOS ranges when applying this new cyclic protocol, and threefold values are achieved for an 18 h on stream period by limiting the reaction steps to the first 1.5 h of maximum benzene selectivity (97 vs. 33 g benzene per kg cat h) compared to a conventional single run. Funding from the European Community's 7th Framework Program through the Collaborative Project Next-GTL (agreement n° 229183) and financial support by the Spanish GovernmentMINECO through "Severo Ochoa" (SEV 2012-0267), Consolider Ingenio 2010-Multicat, MAT2012-37160 and MAT2012-31657 are acknowledged. The authors thank B. Esparcia for technical assistance and the Electron Microscopy Service of the UPV for their help in sample characterization. Portilla Ovejero, MT.; Llopis Alonso, F.; Martínez, C. (2015). Non-oxidative dehydroaromatization of methane:an effective reaction regeneration cyclic operation for catalyst life extension. Catalysis Science and Technology. 5(7):3806-3821. https://doi.org/10.1039/C5CY00356C

[EN] Upgrading of the heavy reformate fraction (HR), containing mainly C9+ aromatics, is usually performed by dealkylation or by transalkylation with added benzene and/or toluene to obtain the more valuable xylenes. However, when the costs related to the use of benzene and toluene are considered, the one-step dealkylation/transalkylation of the C9+ alkylaromatics to xylenes becomes economically attractive. Thus, in a first step, ethylmethylbenzenes (EMB) will have to be dealkylated to toluene, which will then react with the trimethylbenzenes (TMB) present in the HR feed to produce xylenes by transalkylation. Medium pore zeolites will favor dealkylation, whereas large pore zeolites will be more adequate for carrying out the transalkylation reaction. In this work, we present the one-pot synthesis of beta-pentasil aggregates with tunable ratios of the large pore beta to the medium pore component. We show that the close proximity of the beta and pentasil nanocrystals obtained by one-pot co-crystallization synthesis, results in a highly efficient catalyst for the consecutive dealkylation/transalkylation process. The bifunctional catalyst based on the co-crystallized aggregate is more active and selective to xylenes than a catalyst based on a physical mixture of equivalent beta and pentasil nanozeolites synthesized following an analogous procedure. The small crystallite sizes of the co-crystallized zeolites provide the additional advantage of a lower deactivation rate as compared to a reference benchmark catalyst. Results are shown on both, model molecules and industrial HR feed. ; This work has been supported by Saudi Aramco, by the Spanish Government-MICINN through "Severo Ochoa" (SEV 2012-0267) and RTI2018-101033-B-I00, by the European Union through ERC-AdG-2014-671093 (SynCatMatch) and by the Ftmdacion Ramon Areces through a research contract of the "Life and Materials Science" program. We thank Belen Esparcia for technical assistance, and the Electron Microscopy Service of the UPV for their help in sample ...

[EN] 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 methodol. for synthesizing active and selective zeolites by using org. 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 mol.-¿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. ; This work has been supported by the European Union through the European Research Council (grant ERC-AdG-2014-671093, SynCatMatch) and the Spanish government through the "Severo Ochoa Program" (grant SEV 2012-0267). The Electron Microscopy Service of the Universitat Politecnica de Valencia (UPV) is acknowledged for help with sample characterization. The Red Espanola de Supercomputacion (RES) and Centre de Calcul de la Universitat de Valencia are gratefully acknowledged for computational facilities and technical assistance. E.M.G. acknowledges "La Caixa-Severo Ochoa" International Ph.D. Fellowship (call 2015). We thank I. Millet for technical assistance and V. J. Margarit and A. Cantin for helpful discussions. ; Gallego-Sánchez, EM.; Portilla Ovejero, MT.; Paris-Carrizo, CG.; Leon Escamilla, EA.; Boronat Zaragoza, M.; Moliner Marin, M.; Corma Canós, A. (2017). "Ab initio" synthesis of zeolites for preestablished catalytic reactions. Science. 355(6329):1051-1054. https://doi.org/10.1126/science.aal0121 ; S ; 1051 ; 1054 ; 355 ; 6329 ; Vermeiren, W., & Gilson, J.-P. (2009). Impact of Zeolites on the Petroleum and Petrochemical Industry. Topics ...

1051 1054 355 6329 ; S Čejka, J., & Wichterlová, B. (2002). ACID-CATALYZED SYNTHESIS OF MONO- AND DIALKYL BENZENES OVER ZEOLITES: ACTIVE SITES, ZEOLITE TOPOLOGY, AND REACTION MECHANISMS. Catalysis Reviews, 44(3), 375-421. doi:10.1081/cr-120005741 J. R. Butler, X. Xiao, R. Hall, U.S. Patent 20,080,319,243 (2008). S. I. Zones, U.S. Patent 4,544,538 (1985). E. Mishani et al.,U.S. Patent 20,110,293,519 (2011). M. K. Rubin, P. Chu, U.S. Patent 4,954,325 (1990). A. S. Fung, S. L. Lawton, W. J. Roth, U.S. Patent 5,362,697 (1994). ; [EN] 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 methodol. for synthesizing active and selective zeolites by using org. 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 mol.-¿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. This work has been supported by the European Union through the European Research Council (grant ERC-AdG-2014-671093, SynCatMatch) and the Spanish government through the "Severo Ochoa Program" (grant SEV 2012-0267). The Electron Microscopy Service of the Universitat Politecnica de Valencia (UPV) is acknowledged for help with sample characterization. The Red Espanola de Supercomputacion (RES) and Centre de Calcul de la Universitat de Valencia are gratefully acknowledged for computational facilities and technical assistance. E.M.G. acknowledges "La Caixa-Severo Ochoa" International Ph.D. Fellowship (call 2015). We thank I. ...

[EN] Nano-crystalline MCM-22 zeolite was synthesized in a one-pot procedure by the use of an organosilane (dimethyl-octadecyl-(3-trimethoxysilylpropyl)-ammonium chloride, TPOAC) in the zeolite synthesis gel. This crystal growth inhibition procedure introduced mesopores in the MCM-22 crystallites. The lower mechanical stability of the nano-crystalline MCM-22 zeolite compared with bulk MCM-22 can be countered to some extent by pillaring. The increased external surface of the microporous zeolite domains resulted in increased accessibility of the Bronsted acid sites, as followed from the better performance in liquid-phase benzene alkylation with propylene as compared with bulk MCM-22. The increased accessibility of the internal acid sites in Mo-loaded hierarchical MCM-22 was also evident from the improved benzene selectivity during methane aromatization. Silylation of hierarchical Mo/MCM-22 was detrimental for the catalytic performance in MDA. The nano-crystalline MCM-22 has physico-chemical and catalytic properties intermediate between those of MCM-22 and ITQ-2 with the benefit over ITQ-2 that it can be synthesized in a single step. (C) 2015 Elsevier Inc. All rights reserved. ; Funding from the 7th Framework Program of the European Commission through the Collaborative Project Next-GTL (agreement no 229183) and financial support by the Spanish Government-MINECO through "Severo Ochoa" (SEV 2012-0267), Consolider Ingenio 2010-Multicat (CSD2009-00050) and MAT2012-31657 are acknowledged. Marta E. Martinez Armero thanks MINECO for economical support through pre-doctoral fellowship for doctors training (BES-2013-066800). The authors thank B. Esparcia for technical assistance. ; Tempelman, CHL.; Portilla Ovejero, MT.; Martínez Armero, ME.; Mezari, B.; De Caluwe, NGR.; Martínez, C.; Hensen, EJM. (2016). One-pot synthesis of nano-crystalline MCM-22. Microporous and Mesoporous Materials. 220:28-38. https://doi.org/10.1016/j.micromeso.2015.08.018 ; S ; 28 ; 38 ; 220