Defect-designed ZSM-12 zeolites for alkylation of phenol with tert‑butyl alcohol

Defect-engineered ZSM-12 zeolites are effective for the alkylation of phenol and tert‑butyl alcohol with the generation of deficiency in zeolite crystals through preliminary leaching by NaOH/piperidine system, leading to the selectivity of 4-TBP and conversion of phenol up to 80% and 95%, respectively. High stability with robust activity and selectivity for ZSM-12-AT-3P can be observed in the recycling test. Detailed investigations of this catalytic system uncover a complicated reaction network that high Brønsted acidity is beneficial for the formation of larger 2,4-DTBP with exposed Brønsted acid sites, low Brønsted acidity can generate the tertiary butyl phenyl ether (TBPE) regardless of accessibility of acid sites, while moderate Brønsted acidity with enhanced accessibility is favorable to producing the desired 4-TBP. The incorporation of extrinsic defects makes dissolution go beyond the limits set by the zeolite crystalline structure, which shorten the diffusion path lengths through interconnected micropore-to-mesopore networks as well as maintained sufficient acid sites, leading to an enhanced catalytic property as we observed.