Center for Molecular Modeling - T. V. Janssens

Hydrogen transfer versus methylation: on the genesis of aromatics formation in the Methanol-To-Hydrocarbons over H-ZSM-5

kristof — Fri, 19 May 2017 22:58:55 +0000

J. S. Martínez-Espín, K. De Wispelaere, T. V. Janssens, S. Svelle, K. P. Lillerud, P. Beato, V. Van Speybroeck, U. Olsbye

ACS Catalysis

7, 5773–5780

2017

Abstract

The catalytic conversion of methanol (MeOH) and dimethyl ether (DME) into fuels and chemicals over zeolites (MTH process) is industrially emerging as an alternative route to conventional oil-derived processes. After 40 years of research, a detailed mechanistic understanding of the intricate reaction network is still not fully accomplished. The overall reaction is described as two competitive catalytic cycles, dominated by alkenes and arenes, which are methylated and cracked or dealkylated to form effluent products. Herein, we present the reaction of isobutene with methanol and DME as an efficient tool for measuring the relative formation rates of alkenes and arenes, and we provide detailed mechanistic insight into the hydrogen-transfer reaction. We provide experimental and theoretical evidence that manifest a strong competition of methylation and hydrogen transfer of isobutene by methanol, while methylation is substantially favored by DME. Experiments performed at higher conversion facilitate projection of the results to the product distribution obtained when using MeOH or DME as feedstock during the MTH reaction.

DOI

http://dx.doi.org/10.1021/acscatal.7b01643

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acscatal.7b01643.pdf

Benzene co-reaction with methanol and dimethyl ether over zeolite and zeotype catalysts: Evidence of parallel reaction paths to toluene and diphenylmethane

kristof — Sun, 18 Sep 2016 19:16:42 +0000

J. S. Martínez-Espín, K. De Wispelaere, M. Westgård Erichsen, S. Svelle, T. V. Janssens, V. Van Speybroeck, P. Beato, U. Olsbye

Journal of Catalysis

349, 136-148

2017

Abstract

The reactivity of methanol (MeOH) and dimethyl ether (DME) toward benzene was studied over zeolitic materials with different topology and acid strength (H-ZSM-5, H-SSZ-24, and H-SAPO-5) at 250–350 °C. Higher rates of methylation, and subsequent de-alkylation reactions, were observed with DME compared to MeOH. In addition, significant differences in product distribution based on the choice of methylating agent were observed. For reactions between MeOH and benzene a fraction of diphenylmethanes (DPMs) was formed, while this product group was nearly absent during reactions between DME and benzene. A range of co-feed and isotopic labeling experiments was performed, mainly over H-ZSM-5, in order to elucidate mechanistic information on the pathway from methanol and benzene to DPMs. Overall, these studies revealed that DPM formation involves the dehydrogenation of methanol to formaldehyde on the Brønsted acid site, followed by subsequent reaction with two benzene molecules. Theoretical calculations confirmed the higher reactivity of DME compared to MeOH toward benzene methylation and suggested a plausible route from formaldehyde and benzene to DPM.

Open Access version available at UGent repository

Green Open Access

DOI

http://dx.doi.org/10.1016/j.jcat.2017.03.007

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1-s2.0-S0021951717300842-main.pdf

Benzene co-reaction with methanol and dimethyl ether over zeolitic catalysts

kristof — Tue, 16 May 2017 21:04:21 +0000

J. S. Martínez-Espín, K. De Wispelaere, M. Westgård Erichsen, S. Svelle, T. V. Janssens, V. Van Speybroeck, P. Beato, U. Olsbye

ISBN/ISSN:

Talk

Conference / event / venue

25th North American Meeting of the Catalysis Society (NAM25)

Denver, CO, USA

Sunday, 4 June, 2017 to Friday, 9 June, 2017