Alkylation of isobutane with butene catalyzed by deep eutectic ionic liquids

Abstract

The alkylation process of isobutane with butene is important in the petroleum industry. Ionic liquids (ILs) are considered as attractive alternative catalysts for isobutane alkylation besides strong liquid acids (H2SO4 or HF) and solid superacids. In this study, ILs based on amides-aluminum chloride (AlCl3) were synthesized and characterized, which exhibited both Lewis and Brønsted acidities. These deep eutectic ILs were found to be efficient catalysts for isobutane alkylation. The influences of the amide substrate, AlCl3/amide molar ratio, and metal additive on Lewis and Brønsted acidities were observed together with the synergetic effect of Lewis and Brønsted acid sites in the catalytic process. CuCl modified Urea-1.6AlCl3 showed the best catalytic performance. The butene conversion was about 99.9% and C8 selectivity reached 57.6% under optimized reaction conditions (temperature of 15 °C, stirring rate of 1500 rpm, hydrocarbon feeding rate of 300 mL/h, isobutane/olefin molar ratio of 15:1, and reaction time of 15 min). In addition, Urea-1.6AlCl3-0.13CuCl could be recycled and reused for at least 20 times without obvious loss in catalytic activity.