Synthesis and Consequence of Aggregated Nanosized ZSM-5 Zeolite Crystals for Methanol to Propylene Reaction

Aggregated nanosized ZSM-5 crystals with a different size from 30–50 nm to 1000–2000 nm were prepared by a hydrothermal synthesis method using a two-step crystallization procedure for methanol to propylene (MTP) reaction. The decrease of crystal size leads to the growth of the ratio of weak acid sites to strong acid sites, and the number of Brønsted acid sites (BAS) at the external surface, but also to the decrease of Bronsted acid sites to Lewis acid sites (B/L) ratio and the number of BAS within zeolite. The study on the effect of crystal size and BAS location on the product distribution and lifetime of zeolite shows that internal BAS within the micropore is key to activation of the methanol to hydrocarbon, and the reduction of crystal size and the generation of mesopores of zeolite promote the selectivity of propylene as well as the lifetime of zeolite.