Catalytic performance of nano zeolite ZSM-5 for the dealkylation reaction of alkylphenols

Abstract

To further enhance the dealkylation reactivity and catalytic stability of zeolites, nano zeolites with reduced thickness along the b-axis were successfully synthesized via a hydrothermal method using a soft template of tetrapropylammonium hydroxide (TPAOH, a structure-directing agent) and cetyltrimethylammonium bromide (CTAB, a morphology-directing agent), leveraging the pore structure characteristics of the ZSM-5 zeolite. Compared with those of commercial MFI zeolites, the crystal thickness of the ZSM-5 zeolite along the b-axis direction was reduced. The catalytic performance of the nano zeolite was systematically compared with those of hierarchical and commercial zeolites. Results demonstrated that the nano zeolite exhibited significantly improved phenol selectivity and the highest phenol yield. In terms of catalytic stability, the nano zeolite showed enhanced performance over three reaction cycles, with mixed phenol conversion rates increasing by 10%, 32%, and 17% (compared with those of the hierarchical zeolite) and 53%, 59%, and 37% (compared with those of the commercial zeolite). The analysis of coke deposition revealed that the hierarchical zeolite benefited from its abundant mesoporous structure, which enhanced carbon tolerance and delayed pore blockage. In contrast, the nano zeolite's shorter micropore channels improved molecular diffusion efficiency, preventing micropore clogging and fundamentally addressing zeolite deactivation. Additionally, the nano zeolite demonstrated enhanced catalytic performance and stability in the dealkylation of phenolic oil.