Effects of mesopore introduction on the stability of zeolites for 4-iso-Propylphenol dealkylation

Low rank coal- and biomass-derived liquids generally contain a mixture of alkylphenols, which can be dealkylated over zeolites into phenol as a basic chemical. Zeolites with different pore structures were evaluated for the dealkylation of 4-iso-propylphenol as a model alkylphenol, among which HZSM-5 and HMCM-22 displayed the highest phenol selectivity above 96 %. However, HZSM-5 deactivated fastest among the catalysts due to coke deposition. Thus, mesopores were introduced by desilication into HZSM-5 catalysts to improve the catalytic stability. The mesopore incorporation enhanced the connectivity of the micropores with the crystal surface, and shortened the diffusion lengths. Coke location analysis revealed that micropore occlusion by the coke shell occurred on the parent HZSM-5, whereas the acid sites in the desilicated catalysts were more accessible for fully utilization, even though the coke mainly deposited in the micropores. Furthermore, the coke on the desilicated HZSM-5 displayed a lower graphitization degree.

Automated summary

The study demonstrated that HZSM-5 and HMCM-22 are effective catalysts for dealkylation reactions, with HZSM-5 showing the fastest deactivation rate due to coke deposition. Introducing mesopores to improve the catalytic stability of HZSM-5 could potentially enhance its application in the dealkylation of alkylphenols.