Silicalite-1 Derivational Desilication-Recrystallization to Prepare Hollow Nano-ZSM-5 and Highly Mesoporous Micro-ZSM-5 Catalyst for Methanol to Hydrocarbons

Mesoporous ZSM-S zeolites were directly synthesized by desilication-recrystallization of silicalite-1 with NaAlO2 as Al source and TPAOH as template. The fabrication mechanism of mesopores was studied based on the different crystal size of silicalite-1 and liquid-to-solid ratio. This revealed that TPA(+) played a protective role in the controllable desilication while Na+ induced the production of mesopores during the recrystallization. When silicalite-1 with a crystal size of 200 nm was treated in a liquid-to-solid ratio of 10 mL/g, hollow structured nano-ZSM-5 with many mesopores (similar to 23 nm) in the shell was produced and its external surface area reached 121 m(2) g(-1). In comparison, homogeneous mesopores (similar to 15 nm) were introduced into the bulk of micro-ZSM-5 under a higher liquid-to-solid ratio of 30 mL/g, providing a maximal external surface area of 171 m(2) g(-1). The catalytic lifetime reached 192 h in methanol to hydrocarbons reaction at a weight hourly space velocity of 4.7 h(-1), four times greater than that of the micro-ZSM-5 synthesized via the traditional hydrothermal synthesis.