The Acidity of Zeolites: Concepts, Measurements and Relation to Catalysis: A Review on Experimental and Theoretical Methods for the Study of Zeolite Acidity

Derouane, Éric G.; Védrine, J.C.; Pinto, R. Ramos; Borges, P.; Costa, Luís; Lemos, M.A.N.D.A.; Lemos, F.; Ribeiro, F. Ramôa

doi:10.1080/01614940.2013.822266

Cited by 269 publications

(183 citation statements)

References 326 publications

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“…Disproportionation needs higher concentrations of acid sites [9] and the strength of these sites follows the trend: isomerization < dealkylation < disproportionation [10,11]. The acidity of zeolites is determined by their Si/Al ratio, with the total number of acid sites decreasing with increasing Si/Al ratio due to the lower amount of Al [2,5,12,13]. The strength of each site is enhanced by their separation among them, up to a maximum given by the specific topology of the zeolite [5,14].…”

Section: Introductionmentioning

confidence: 99%

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Xylene Isomerization in the Liquid Phase Using Large‐Pore Zeolites

Gonçalves

Rodrigues

2015

Chem Eng & Technol

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Three large-pore zeolites, Beta with Si/Al ratios of 25 and 35 and Mordenite with an Si/Al ratio of 30, were studied in the conversion of o-xylene at 493 K. Maximum conversion was achieved by the catalyst with the highest Si/Al ratio due to faster diffusion of the isomer inside the zeolite channels because of the lower acidity of the solid even with larger crystal size. A kinetic study was then carried out over this catalyst between 473 and 513 K in a batch reactor in the liquid phase. The activation energies obtained do not indicate the presence of diffusional constraints towards any isomer. Finally, the kinetic model obtained was simulated in a fixed-bed reactor and compared to ZSM-5 in the temperature range from 493 to 533 K. An increment in p-xylene production of 20 % on average was obtained.

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Section: Introductionmentioning

confidence: 99%

“…The proton donors in zeolites are the Brønsted acid sites provided by the bridging OH linking Si to Al within the framework; Lewis sites are electron donors constituted by extra-framework Al [5]. Xylene isomerization, disproportionation, and dealkylation are catalyzed by Brønsted acid sites [6][7][8].…”

Section: Introductionmentioning

confidence: 99%

Xylene Isomerization in the Liquid Phase Using Large‐Pore Zeolites

Gonçalves

Rodrigues

2015

Chem Eng & Technol

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“…IR spectra and adsorption enthalpies. 116,117 Acid strength also seems to influence the relative reactivity of propene and benzene in the two isostructural AFI materials.…”

Section: Reactivity Indices From MDmentioning

confidence: 99%

Towards molecular control of elementary reactions in zeolite catalysis by advanced molecular simulations mimicking operating conditions

Wispelaere

Bailleul

Speybroeck

2016

Catal. Sci. Technol.

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Title: Towards molecular control of elementary reactions in zeolite catalysis by advanced molecular simulations mimicking operating conditions Advanced ab initio molecular dynamics techniques enable study of the infl uence of catalyst topology and acidity, reaction temperature and the presence of additional guest molecules on methylation reactions of benzene and propene, which are crucial reaction steps in the conversion of methanol into hydrocarbons. Our advanced simulations provide detailed insight into how operating conditions impact the competition of the concerted and stepwise methylation mechanism and thus the reaction kinetics. As featured in:See and mechanism of individual reaction steps at operating conditions. Herein we use state-of-the-art advanced ab initio molecular dynamics techniques to study the influence of catalyst topology and acidity, reaction temperature and the presence of additional guest molecules on elementary reactions. Such advanced modeling techniques provide complementary insight to experimental knowledge as the impact of individual factors on the reaction mechanism and kinetics of zeolite-catalyzed reactions may be unraveled. We study key reaction steps in the conversion of methanol to hydrocarbons, namely benzene and propene methylation. These reactions may occur either in a concerted or stepwise fashion, i.e. methanol directly transfers its methyl group to a hydrocarbon or the reaction goes through a framework-bound methoxide intermediate. The DFT-based dynamical approach enables mimicking reaction conditions as close as possible and studying the competition between two methylation mechanisms in an integrated fashion. The reactions are studied in the unidirectional AFI-structured H-SSZ-24, H-SAPO-5 and TON-structured H-ZSM-22 materials. We show that varying the temperature, topology, acidity and number of protic molecules surrounding the active site may tune the reaction mechanism at the molecular level. Obtaining molecular control is crucial in optimizing current zeolite processes and designing emerging new technologies bearing alternative feedstocks.

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“…The acidic properties of solid acids such as silica-aluminas, zeolites, heteropolyacids or sulfated oxides have always been the subject of numerous studies [1][2][3]. However, their acid strength values, which determine their catalytic activity, are either difficult to find in the literature, or presented as rough estimates.…”

Section: Introductionmentioning

confidence: 99%

Styrene and styrene dimer derivatives, cyclohexene, tert-butylbenzene and cumene as test reactions for acid strength measurements of crystalline and amorphous silica-aluminas, sulfated oxides and Amberlyst

Marczewski

Marczewska

Popielarska

et al. 2015

Reac Kinet Mech Cat

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The minimal H O values required for cyclohexene, a-methylstyrene, styrene, 2,4-diphenyl-4-methyl-1-pentene, 4-phenyl-1-butene, tert-butylbenzene and cumene to undergo the chosen test reactions over solid acids at 303 K have been established. The chosen reactions and the respective H O min values obtained are as follows: a-methylstyrene and styrene oligomerization (-3.3 and -5.3), 2,4-diphenyl-4-methyl-1-pentene and 4-phenyl-1-butene oligomerization and isomerization (-6.9 and -7.9), cyclohexene oligomerization (-7.8), tert-butylbenzene disproportionation (-10.8) and cumene disproportionation (-11.5). The above mentioned test reactions were used to study the acid strength of different solid acids.

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The Acidity of Zeolites: Concepts, Measurements and Relation to Catalysis: A Review on Experimental and Theoretical Methods for the Study of Zeolite Acidity

Cited by 269 publications

References 326 publications

Xylene Isomerization in the Liquid Phase Using Large‐Pore Zeolites

Xylene Isomerization in the Liquid Phase Using Large‐Pore Zeolites

Towards molecular control of elementary reactions in zeolite catalysis by advanced molecular simulations mimicking operating conditions

Styrene and styrene dimer derivatives, cyclohexene, tert-butylbenzene and cumene as test reactions for acid strength measurements of crystalline and amorphous silica-aluminas, sulfated oxides and Amberlyst

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