Abstract: In methanol to propylene (MTP) reaction, due to the strong acidity of ZSM-5 molecular sieve, the secondary reactions such as hydrogen transfer and aromatization between methanol and ZSM-5 are easy to block the pores, making its microporous structure more unfavorable to the diffusion of molecules, accelerating the carbon deposition and deactivation of the catalyst, resulting in the decrease of propylene selectivity and propylene/ethylene (P/E) ratio. Therefore, in this paper, ZSM-5 molecular sieve was modified by CeO₂ with high catalytic activity to effectively reduce its acidity and increase mesoporous, so as to improve propylene selectivity and P/E ratio. The effects of different n(SiO₂)/n(Al₂O₃) and mass ratio of two phases (m(CeO₂)/m(ZSM-5)) on the physicochemical properties of CeO₂/ZSM-5 catalysts were investigated by XRD, XRF, NH₃-TPD and N₂ adsorption and desorption. When the reaction temperature was 480 ℃, the weight hourly space velocity was 2.6 h^-1, the nitrogen flow rate was 100 mL·min^-1, the pressure was atmospheric and pure methanol was fed, and the MTP catalytic performance of the prepared composite catalyst was investigated. The results indicate that the composite catalyst with n(SiO₂)/n(Al₂O₃) of 250 and m(CeO₂)/m(ZSM-5) of 1∶4 exhibits better MTP catalytic performance than the previous research results, with conversion of methanol of 99.9%, selectivity of propylene of 42.78%, and P/E ratio of 6.3.

Key words: compound modification, methanol to propylene, acid, mesoporous structure, selectivity of propylene, propylene/ethylene ratio