Direct observation of olefin homologations on zeolite ZSM-22 and its implications to methanol to olefin conversion

In this paper, we studied olefin homologation reactions on zeolite ZSM-22, whose one dimensional pore structure inhibited the hydrocarbon pool mechanism and secondary reactions of the methanol to olefin (MTO) conversion. Homologation of ethylene, propylene and styrene were directly observed between 13C labeled methanol and olefins. Isotopic tracking shows high selectivity for homologation reaction, e.g. from ethylene, propene has one 13C atom, butene has two 13C atoms, and pentene has three 13C atoms. Homologation of styrene's side chain also showed very specific isotopic pattern. The role of olefin homologation is speculated as a key reaction during the induction time of MTO process.