Enhanced ethene to propene ratio over Zn-modified SAPO-34 zeolites in methanol-to-olefin reaction

A series of Zn-modified SAPO-34 zeolites were prepared by the impregnation method and the effect of Zn modification on the catalytic performance of SAPO-34 zeolite in the methanol-to-olefin (MTO) reaction was comprehensively investigated. The physicochemical properties of the parent and Zn-modified SAPO-34 zeolites were characterized by XRD, SEM, N-2 adsorption-desorption, NH3-TPD, H-2-TPR, FTIR, UV-vis DRS and TGA. The reaction results show that the ethene selectivity and ethene to propene ratio are significantly improved over Zn-modified SAPO-34 zeolites in the initial period of the MTO reaction, and the optimum catalytic performance is obtained over 2.0Zn/SAPO-34 zeolite with a methanol conversion of 99.1 wt%, an ethene selectivity of 54.6 C-%, a light olefin selectivity of 88.9 C-% and an ethene to propene ratio of 1.9. Based on the characterization and reaction results, the enhanced ethene selectivity and ethene to propene ratio over Zn-modified SAPO-34 zeolites are attributed to the increased diffusion hindrance originating from the incorporated Zn-related species enrichment and the facilitated formation of aromatics.