Dual-Acid-Site Engineering in Ti-β Zeolites for Enhanced Benzene Alkylation with Cyclohexene

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The alkylation of benzene with cyclohexene provides a direct and atom-efficient route to cyclohexylbenzene (CHB), a key intermediate for advanced chemical manufacturing. The role of Lewis acid sites (LAS) in homogeneous alkylation is well established; however, their function and synergy with Brønsted acid sites (BAS) in solid acid catalysts remain elusive. Herein, we proposed a dual-acid-site engineering strategy to construct titanium-incorporated β zeolites (Hβ-at- x ) via sequential dealumination and titanation. Structural and spectroscopic characterizations confirmed that Ti was anchored in silanol nests, generating electron-deficient Ti-LAS while tuning the Al-BAS to establish synergetic dual-acid-site. It was demonstrated that Ti-modified Al-BAS facilitated the protonation of cyclohexene, and benzene was adsorbed and enriched on Ti-LAS via π-complexation adjacent to BAS. The optimized Hβ-at-50 catalyst achieved complete cyclohexene conversion, even under the currently lowest benzene-to-cyclohexene volume ratio of 7:1. Furthermore, it demonstrated a significantly enhanced CHB formation rate of 18.6 mmol CHB ·g cat –1 ·h –1, surpassing that of the parent Hβ catalyst (2.98 mmol CHB ·g cat –1 ·h –1 ) and the Hβ-at catalyst (2.29 mmol CHB ·g cat –1 ·h –1 ). The superior activity was corroborated by a reduced apparent activation energy ( E a = 35.1 kJ·mol –1 ) compared to the parent Hβ catalyst ( E a = 57.3 kJ·mol –1 ). The catalytic stability decreased during cycling due to the light olefin polymerization, and its activity could be fully restored via thermal treatment. This work provides mechanistic insight into dual-site catalysis and a design framework for high-performance zeolite catalysts for hydrocarbon upgrading.