Dealkylation properties of alkylphenols over hierarchical ZSM-5 synthesized by desilication with TPAOH

In order to improve the catalytic performance of zeolite catalysts in alkylphenol dealkylation, TPAOH was used to introduce mesoporous structure to ZSM-5 zeolite in weak base NH4OH, and the content and dimension of mesoporous were changed by TPAOH concentration. The catalytic activity and lifetime of hierarchical zeolite were studied. The results showed that the phenol selectivity of hierarchical zeolite was slightly reduced, but the phenol yield was relatively stable. Higher TPAOH concentration expanded the introduced mesoporous structure, resulting in increased complexity of the catalytic products, including a certain amount of cresol, xylene, etc. Due to the mesoporous structure, the catalytic stability of hierarchical zeolite ZSM-5-0.3 was most significantly improved. Compared to commercial ZSM-5, the mixed phenol conversion rate of the first recycle reaction increased from 30.7% to 78.2%. By N2 adsorption-desorption tests, it was clear that coke deposition was located in the micropores of zeolite. The formation of mesoporous shortens the diffusion path of reactants in zeolite and thus reduced the formation of coke deposition. ZSM-5 zeolite still had good dealkylation performance in coal tar, and hierarchical zeolite had more significant catalytic stability.