Kinetic regimes in the tandem reactions of H-BEA catalyzed formation of p-xylene from dimethylfuran

C. Luke Williams, Katherine P. Vinter, Chun Chih Chang, Ruichang Xiong, Sara K. Green, Stanley I. Sandler, Dionisios G. Vlachos, Wei Fan, Paul J. Dauenhauer

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26 Scopus citations

Abstract

Reaction kinetics and pathways of p-xylene formation from 2,5-dimethylfuran (DMF) and ethylene via cascade reactions of Diels-Alder cycloaddition and subsequent dehydration over H-BEA zeolite (Si/Al = 12.5) were characterized. Two distinct kinetic regimes were discovered corresponding to the rate limiting reaction, namely Diels-Alder cycloaddition and cycloadduct dehydration, as the concentration of Brønsted acid sites decreases. At catalyst loadings with effective acid site concentrations exceeding a critical value (~2.0 mM), the rate of formation of Diels-Alder products becomes constant. Under these conditions, the measured activation energy of 17.7 ± 1.4 kcal mol -1 and reaction orders correspond to the [4 + 2] Diels-Alder cycloaddition reaction of DMF and ethylene. Conversely, at catalyst loadings below the critical value, the formation rate of p-xylene becomes first order in catalyst loading, and the measured activation energy of 11.3 ± 3.5 kcal mol -1 is consistent with dehydration of the Diels-Alder cycloadduct to p-xylene. Experimental comparison between H-BEA and H-Y zeolite catalysts at identical conditions indicates that the micropore structure controls side reactions such as furan dimerization and hydrolysis; the latter is supported via molecular simulation revealing a substantially higher loading of DMF within H-Y than within H-BEA zeolites at reaction conditions.

Original languageEnglish (US)
Pages (from-to)178-187
Number of pages10
JournalCatalysis Science and Technology
Volume6
Issue number1
DOIs
StatePublished - Jan 7 2016

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Publisher Copyright:
© The Royal Society of Chemistry 2016.

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