Dimethyl ether carbonylation over zeolites

Syngas to ethanol, consisting of dimethyl ether (DME) carbonylation to methyl acetate (MA) over zeolites and MA hydrogenation to ethanol on copper catalyst, has been developed in recent years. DME carbonylation over zeolites, a key step in this new process, has attracted increasing attention due to the high reaction efficiency and promising industrial application. In recent years, continuous efforts have been made on improving the activity and stability of the zeolites. From a mechanistic point of view, DME carbonylation to MA, involving the formation of C-C bond, is achieved via the Koch-type CO insertion into DME within the 8-member ring (8-MR) pores of zeolites, typically HMOR and HZSM-35. The unique geometric configuration of the 8-MR pore endowed the formation of the key intermediate (acetyl, CH3CO*), possibly by a spatial confinement of the transition state during CO insertion into the surface O-CH3 group. This review article summarizes the main progress on zeolite-catalyzed DME carbonylation, including reaction kinetics and mechanism, theoretical calculations, and experimental strategies developed for populating acid sites and engineering pore structure of the zeolites in order to enhance the overall performance. (C) 2019 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. and Science Press. All rights reserved.