Using a Microchannel Reactor to Optimize the Production of 1-Alkyl-3-Methylimidazolium Chlorides

The possibility of using microchannel flow reactors to obtain the kinetic and technological parameters of the synthesis of 1-butyl-3-methylimidazolium chloride (BMIMCl) ionic liquid is demonstrated for the reaction of 1-methylimidazole (MIm) with 1-chlorobutane with no solvents. BMIMCl is produced with high selectivity and specific output in a microchannel flow reactor at temperatures of 120–180°C a contact time of 2–45 min, and a pressure of 20 bar. A positive result is obtained, due to the laminar profile of the flow and a uniform distribution of the reagents concentration over the microchannel cross section. Studying the kinetics of the process in a microchannel flow reactor reveals a shift of the reaction to the mode of diffusive inhibition at temperatures above 150°C. The kinetic data obtained for BMIMCl synthesis are used to develop ways of producing 1-ethyl-3-methylimidazolium and 1-hexyl-3-methylimidazolium chlorides (EMIMCl and HMIMCl, respectively) under the conditions of a microchannel flow reactor. The approach proposed in this work is of interest in developing flow and periodic facilities for the low-tonnage production of dialkylimidazolium, ammonium, and pyridinium salts via quaternization of the corresponding alkyl chlorides and nitrogen-containing bases.