Abstract:  Based on density functional theory calculation with periodic boundary conditions, the possibility of the direct coupling of methanol into ethene by oxonium ylide mechanism was investigated. The calculated results indicate that the energy barriers for the formation of dimethyl ether and trimethyl oxonium ion inside HSAPO-34 zeolite are 1.68 and 0.93 eV, respectively. The suggested intermediate oxonium ylide is very unstable and the energy barriers for the formation of C–C bond are over 3.0 eV by concerted pathway. It is thus concluded that the methanol to olefin reaction cannot follow the oxonium ylide mechanism.

Key words: HSAPO-34 zeolite, methanol to olefin process, oxonium ylide mechanism, density functional theory, trimethyl oxonium ion