Dual-site eutectic ionic liquids based microemulsion for boosting selective dimerization of isobutene

[Display omitted] •Interactions between IL Lewis anion and Brønsted cation enhance butene dimerization.•Eutectic systems enhance mass transfer and promote oriented conversion to dimer.•Microemulsion by IL emulsifier could significantly accelerate the oligomerization.•Dual-site eutectic IL based emulsion exhibits high conversion and dimer selectivity. Oligomerization is one of the efficient routes for making use of C4 olefins to produce high value-added chemicals. However, high reagent conversion is usually accompanied by low dimer product selectivity, and vice versa. Ionic liquids (ILs) with intense interaction between Lewis and Brønsted acidic sites were demonstrated to be excellent catalysts for butene oligomerization. Furthermore, it was found that eutectic IL could be formed by strong hydrogen bond when alcohol was added to the IL, which exhibited enhanced butene solubility and thus improved catalytic performance. Moreover, microemulsion could be constructed by adding an IL emulsifier into the IL catalyst, and the improved interfacial area further enhanced efficient contact between butene and catalyst. Combining the strategies of employing dual-site eutectic IL as the catalyst and microemulsion formation, butene conversion could reach 98%, while dimer selectivity was 91%, resolving the contradiction that high conversion and target product selectivity cannot be achieved simultaneously.