Highly shape‐selective Zn‐P/HZSM‐5 zeolite catalyst for methanol conversion to light aromatics
Yanming Jia, Junwen Wang, Kan Zhang, Chuanmin Ding
Abstract
A highly shape‐selective and relatively long‐lifetime HZSM‐5‐based catalyst (Zn‐2P/HZSM‐5) was prepared by chemical modification with both ZnSiF 6 ·6H 2 O and H 3 PO 4 solution. The phosphoric acid modification could effectively modulate the Brønsted acid strength of the HZSM‐5 catalyst, which promotes the oligomerization, alkylation, cyclization, and hydrogen transfer reactions. The introduction of Zn‐Lewis acid sites significantly improved the dehydroaromatization of higher olefins. All of these were very beneficial for the generation of BTX (i.e. b enzene, t oluene, and x ylene) hydrocarbons in aromatization of methanol. The coke amount and the average rate of coke formation decreased over the Zn‐2P/HZSM‐5 catalysts, which may largely be ascribed to its lower strong acid sites and lower outer surface acidity. The catalytic performance of methanol aromatization showed that the Zn‐2P/HZSM‐5 catalyst exhibited the highest BTX selectivity of about 46.76% and the longest catalytic lifetime of about 498 h at T = 400 °C, P = 0.1 MPa, and weight hourly space velocity = 0.7 h −1 .