Mesoporous Beta zeolites with controlled distribution of Brønsted acid sites for alkylation of benzene with cyclohexene

Abstract

The distribution of Brønsted acid sites in three-dimensional 12-membered pore channels of Beta zeolite was a decisive factor in the alkylation of benzene with cyclohexene. Here, the Brønsted acid site distribution in Beta zeolitic channels was precisely regulated by tuning the content of Na+ in crystallization system combined with tetraethylammonium cation, the Beta-55 with Brønsted acid sites exclusively located in straight channels (along a- and b-axis directions) was successfully synthesized by utilizing tetraethylammonium as the structure-directing agents without Na+ species, and the fraction of Brønsted acid sites in sinusoidal/straight channels of Beta zeolites can be accurately controlled by tailoring the content of Na+ in synthesis gel. Catalytic properties in the liquid alkylation between benzene and cyclohexene exhibited that Beta-55 zeolites with the Brønsted acid sites solely located in a-axis and b-axis channels showed the highest cyclohexene conversion, cyclohexylbenzene selectivity and longest lifetime in this reaction. In addition, the resultant Beta zeolites also exhibited low coke generation rate and robust regeneration performance in the alkylation reaction.