Modeling and Design of a Flow-Microreactor-Based Process for Synthesizing Ionic Liquids

• Yuichi Nakahara ^*†⊥
• Bert Metten ^‡
• Osamu Tonomura ^§⊥
• Aiichiro Nagaki ^∥⊥
• Shinji Hasebe ^§⊥
• Jun-ichi Yoshida ^⊥#
• Francesco Molinari ¹

• ^† New Frontiers Research Group, Frontier Research Laboratories, Institute For Innovation, Ajinomoto Co., Inc., 1-1 Suzuki-cho, Kawasaki-ku, Kawasaki, Kanagawa 210-8681, Japan
• ^‡ Ajinomoto Bio Pharma Services, Cooppallaan 91, B-9230 Wetteren, Belgium
• ^§ Department of Chemical Engineering, Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510, Japan
• ^∥ Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510, Japan
• ^⊥ Micro Chemical Production Study Consortium in Kyoto University, Kyoto University, Nishikyo-ku, Kyoto 615-8510, Japan
• ^# National Institute of Technology, Suzuka College, Shiroko-cho, Suzuka, Mie 510-0294, Japan

A synthesis process for the ionic liquid (IL) 1-butyl-3-methylimidazolium chloride (BMIM.Cl) was developed using a flow microreactor (FMR) in this study. After the reaction rate analysis, the FMR was efficiently designed using computational fluid dynamics simulation, which can shorten the process development time by reducing trial-and-error experimentation. The designed FMR is composed of a V-shaped mixer and a tubular reactor having a millimeter-scale inner diameter. From the viewpoint of process operation and control, reactors with larger inner diameter are basically preferable. The influence of three inner diameters, 0.75, 2.16, and 4.35 mm, that satisfy temperature constraints on product quality, product yield, and production volume was investigated. It was found that as the inner diameter becomes large, the product yield becomes low because the mass transfer approaches the rate-limiting step of the reaction process. To avoid this problem, it was proposed that static mixers should be built in the reactor having the inner diameter of 4.35 mm. As a result, its production volume, without lowering the product yield, could be improved about 39 times compared with the conventional one.

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