Effect of Co occurrence state on catalytic and coke resistance performance of SAPO-34 in MTO reaction

Abstract

This paper prepared two different occurrence state of cobalt-modified SAPO-34 by impregnation and in situ synthesis, investigating effects on methanol-to-olefin reaction performance. The results showed that the Co modification improved the pore structure, increased the weak acid concentration, and extended the catalytic lifetime of SAPO-34. Among them, the framework-substituted Co-based zeolite has higher olefin selectivity and longer life than SAPO-34 with metal Co on the surface. Besides, the key coke precursors like methyl-substituted benzenes were preferentially deposited in micropores and strong acid sites, and significantly promote the generation of condensed ring aromatic hydrocarbons. While the relatively large mesopore volume and slightly lower strong acid concentration of the framework-substituted Co-based zeolite can synergize reduce the formation rate of coke and inhibit the formation of polycyclic aromatic hydrocarbons, thus improving SAPO-34's anti-coking performance. This revelation sparked a novel concept aimed at enhancing the anti-coking capabilities of metal-based zeolites.