Reaction mechanism of co-coupling conversion of propane and methanol over H-ZSM-5 zeolite

Co-coupling conversion of propane and methanol is an effective method to promote the activation of pro-pane; however, the reaction mechanism has not been fully understood due to the complex reaction net-work. In this study, the reaction kinetics and thermodynamics of various elementary steps for propane activation under the assistance of methanol over H-ZSM-5 zeolite were systemically investigated by den-sity functional theory (DFT) calculations combining with model experiments. The results show that direct dehydrogenation of propane on the acid sites of zeolite is very difficult, while introduction of methanol considerably decreases the free energy barrier for propane activation. This is because large amounts of active intermediates, such as surface methoxy and alkene-based species, are generated in methanol con -version that promote the propane dehydrogenation through hydrogen transfer reactions. Among these active intermediates, alkene-based species (including adsorbed alkene and tertiary carbocations) show higher activity towards C-H bond activation of propane.& COPY; 2023 Elsevier Inc. All rights reserved.