Influence of Diffusion and Acid Properties on Methane and Propane Selectivity in Methanol-to-Olefins Reaction

ZSM-5 zeolites with different particle sizes and mesoporous structures were evaluated in a methanol-to-olefins (MTO) reaction. The results show that the efficient diffusion leads to a low methane selectivity in the initial stage of reaction and a slight increase in methane selectivity throughout the reaction. ZSM-5 zeolites with different acid amounts were also evaluated, and the results indicate that ZSM-5 with a few acid sites exhibits a low initial methane selectivity and a slight increase with prolonged reaction time. In addition, a low initial propane selectivity was observed. [Fe]-[Al]-ZSM-5 zeolites with different Fe/Al ratios were also evaluated in MTO reaction, and a low propane selectivity was observed over ZSM-5 with a weak acid strength (high Fe/Al ratio). Those results are very useful for the understanding of methane and propane formation mechanism. Furthermore, it contributes to a further study of methanol conversion mechanism and deactivation mechanism.