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Mechanistic Insights into the Conversion of Dimethyl Ether over ZSM-5 Catalysts: A Combined Temperature Programmed Surface Reaction and Microkinetic Modelling Study

preprint
submitted on 08.03.2021, 19:17 and posted on 09.03.2021, 12:29 by Toyin Omojola, Andre van Veen
Rates of adsorption, desorption, and surface reaction of dimethyl ether (DME) to olefins over fresh and working ZSM-5 catalysts of different Si/Al ratios (36 and 135) have been decoupled using a combination of temperature programmed surface reaction experiments and microkinetic modelling. Transient reactor performance was simulated by solving coupled 1D non-linear partial differential equations accounting for elementary steps occurring during the induction period based on the methoxymethyl mechanism on the zeolite catalyst, and axial dispersion and convection in the reactor. Propylene is the major olefin formed and scaling relations between activation energies of DME desorption and barriers of formation of methoxymethyl and methyl propenyl ether are observed. Six ensembles of sites are observed with a maximum of three adsorption/desorption sites and three adsorption/desorption/reaction sites. Barriers are generally higher over working catalysts than fresh catalysts. Activation energies of propylene formation of ca. 200 kJ mol-1 are obtained corroborating direct mechanistic proposals.

Funding

Petroleum Technology Development Fund (PTDF/ED/PHD/OO/766/15)

7th Framework program BIOGO Project (604296)

History

Email Address of Submitting Author

toyin.omojola@bath.edu

Institution

University of Bath

Country

United Kingdom

ORCID For Submitting Author

0000-0001-9376-6977

Declaration of Conflict of Interest

no conflict of interest

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