Mechanism of olefin synthesis from methanol and dimethyl ether over zeolite catalysts: A review

Abstract

This review presents various first C-C bond and lower olefins formation mechanisms during the conversion of methanol or dimethyl ether (DME) over zeolite catalysts. The reaction is commonly described using both consecutive and parallel mechanisms. In terms of the first one concept, the oxonium ylide, carbene, carbocationic, methane-formaldehyde, and free radical mechanisms are analyzed. The parallel formation of the C-C bond is represented as the “hydrocarbon pool” mechanism which assumes the reaction occurs through alkene and arene cycles. It is shown that in the case of the arene cycle, olefins can be formed owing to the side chain growth of polymethylbenzenes (the so-called side-chain mechanism) or owing to the number of carbon atoms decrease in the aromatic ring (paring mechanism). Along with the isomerization and synchronous mechanisms wich assume that the route of the process substantially determined by the temperature range and the catalysts properties are discussed.