Alkylation of benzene with Cl6~Cl8 olefins catalyzed by [Bmim]Cl/AlCl₃ ionic liquid

The alkylation of benzene with α-Cl6~C18 olefins catalyzed by l-butyl-3-methylimidazolium-aluminum chloride ([Bmim]Cl/AlCl₃) ionic liquid with different aluminum chloride molar fractions was studied under different reaction conditions. At room temperature, a high conversion rate of 98% of olefins and a high selectivity of 46% of 2-alkylbenzene were obtained within 30 min when the aluminum chloride molar fraction x was 0.67 and molar ratio of AlCl₃ in the catalyst to olefins was 0.04. The Lewis acidity strength of the ionic liquids with different molar fractions of aluminum chloride, which was characterized by infrared spectroscopy using acetonitrile molecule as probe, was correlated with the performance of catalyst in alkylation reaction. The ionic liquid showing a strong Lewis acidity strength had good performance in alkylation reaction. Strong polarizabilities of the ionic liquid characterized by FT-IR spectra using benzene as molecule probe could stabilize the carbenium ion intermediate. In addition, the effect of different olefins on alkylation reaction was also investigated.