Synthesis and application of functional Brφnsted acid binuclear ionic liquid

A functional Brφnsted acid binuclear imidazole ionic liquid catalyst was synthesized by a two-step proceeding and its structure was characterized by ¹H-NMR and FT-IR, respectively. The catalytic performance of the prepared ionic liquid catalyst used in the synthesizing butyl acetate by esterification of acetic acid and butyrate with high selectivity was systematically investigated. The results show that the prepared functional Brφnsted acid binuclear imidazole ionic liquid has perfect catalytic activity which is closely related to the kinds of active anions in it. It was found that the bis-(3-methyl-1-imidazole)butylidene double bisulfate (MTEIMHS) has the best catalytic activity, and under the optimal operation conditions found (catalyst used dosage 1.6% (wt), reaction temperature 90°C and time 4 h), the conversion ratio of acetic acid can reach 82% and the selectivity is near up to 99.9%. It was confirmed that the MTEIMHS binuclear ionic liquid is expected to be a kind of potential catalyst for esterification.