Tailoring β-Zeolite Polymorphs by In Situ Crystallization on Layered Double Hydroxides for Enhanced Benzene Alkylation with Propene

Cumene, produced via the alkylation of benzene with propene, is a crucial intermediate for phenol and acetone. The catalytic performance depends on framework architecture, crystal size, and the acid properties of zeolites. Co-Al-LDO-β was synthesized by anchoring nanosized β zeolite onto cobalt-aluminum layered double hydroxide (Co-Al-LDH) via an in situ strategy, where Co-Al-LDH served as both an aluminum source and support. The uniform dispersion of β zeolites on the LDH allowed for tuning of the polymorph A/B ratio. The influence of polymorph distribution on pore architecture and acid site distribution was investigated by XRD, HRTEM, NMR, and pyridine-FTIR. The results show that polymorph B enriches framework aluminum at T2 sites, forming accessible Brønsted acid sites. Polymorph A induces aluminum migration to constrained T7 and T5+T6 sites and extraframework aluminum, increasing Lewis acidity. The B-type dominant β zeolite has a favorable pore structure and acid site distribution, leading to superior catalytic performance in benzene–propene alkylation.