An investigation on the effect of cross-linking state of silicon species on the distribution of framework Al atoms in ZSM-5 zeolite and its catalytic performance for MTO reaction

Abstract

Controllable regulation of Al atoms distribution in ZSM-5 zeolite framework can effectively modulate product selectivity for MTO reaction. Here, the Al atoms distribution of ZSM-5 zeolite can be adjusted by controlling the cross-linking state of silicon species. Detailed explorations show that, the surface of ZSM-5 zeolite is rich in silicon when low cross-linking state silicon species is silicon source, while the surface of ZSM-5 zeolite is rich in aluminum when high cross-linking state silicon species is silicon source. When the cross-linking state of silicon species presents a “gripper-like” states, Al atoms of ZSM-5 zeolites are homogeneously distributed, and thus, Al atoms tends to be distributed in straight or sinusoidal channels, resulting in high olefin selectivity and low double cycle index in the catalytic MTO reaction process. This work would be beneficial to the design of ZSM-5 zeolite catalyst with desirable acid site distribution for specific reactions.