Enhanced benzene alkylation via cyclohexene activation regulated by grafted sulfonic groups

The Friedel-Crafts alkylation of benzene with cyclohexene is crucial for producing high value cyclohexylbenzene industrially. Zeolites are effective solid acid catalysts, but enhancing strong acid site density can further improve cyclohexene activation, especially under low benzene-to-cyclohexene ratios. This study presents an innovative strategy of grafting sulfonic acid groups onto the pore openings of HY zeolite (HY-SO 3 H), which boosts strong acid sites and offers enhanced Brønsted acid sites for alkylation. Remarkably, under a 7:1 benzene-cyclohexene volume ratio, the HY-SO 3 H-2.5 catalyst achieves a cyclohexene conversion of 93.9 % and a cyclohexylbenzene selectivity of 99.3 %, outperforming the conventional HY catalyst (44.5 % conversion, 98.2 % selectivity). Additionally, HY-SO 3 H-2.5 maintaining stable catalytic performance over five consecutive cycles without significant sulfonic acid group loss. This indicates the zeolite matrix effectively stabilizes the sulfonic acid groups. This work provides insights for addressing the activation of key reactive species by tuning the strength and density of strong acidity in zeolite-based catalysts, offering guidance for designing more efficient catalytic systems.