Roles of 8-ring and 12-ring channels in mordenite for carbonylation reaction: From the perspective of molecular adsorption and diffusion

Carbonylation of dimethyl ether with CO on zeolites is an industrially applied and environmentally friendly process for the production of methyl acetate. Compared with other 8-ring or 12-ring zeolite catalysts, mordenite (MOR) shows the most excellent performance for the carbonylation reaction. In this work, the diffusion behaviors of reactant and product molecules involved in carbonylation on MOR have been investigated by Monte Carlo associated with molecular dynamics simulation. Based on adsorption density map, diffusion trajectory and diffusion coefficient of reaction species, it is demonstrated that 8 ring and 12-ring pores of MOR play dramatically different roles. The 8-ring side pockets serve as the critical reactive centers not only due to the low activation barrier conferred by the constrained environment, but also owing to the aggregation of CO molecules around active sites, while 12-ring provide transport channels for both reactants and products. Therefore, the diffusion dynamics for reaction species, together with the reaction kinetics of the rate-determining step could significantly promote the activity of the carbonylation reaction inside MOR zeolite. Meanwhile, the diffusion dynamics and reaction kinetics for other zeolites with different pore frameworks (i.e., FER, GON, ATS, IRN, GME and OFF) has also been studied in detail, which further confirms our findings on carbonylation reaction inside MOR. (C) 2018 Elsevier Inc. All rights reserved.