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Continuous flow synthesis of methyl acetoacetate in microchannel reactor
- Jianwu LIU Han JIANG Shenghu YAN Yue ZHANG Jiefa SHEN Daixiang CHEN
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Chin. J. Process Eng.. 2020, 20(9):
1082-1088.
DOI: 10.12034/j.issn.1009-606X.219308
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Synthesis using traditional batch reaction system has many problems. First of all, it is difficult to control temperature. Secondly, the production capacity is low, and lastly, the reaction time is more. In this work, using diketene and methanol as starting materials, a new method for synthesizing methyl acetoacetate in a microchannel reactor with variable diameter pulse structure, was explored. The method mainly studied the catalyst type, material ratio, residence time, reaction temperature, and catalyst dosage. The best combination of conditions included sodium methoxide as the catalyst, n(diketene):n(methanol):n(sodium methoxide)=1:1.1:0.02, reaction temperature of 90℃, and residence time of 90 s. Under these conditions, the conversion rate of diketene was 100% and the selectivity of methyl acetoacetate was 96.8%. Compared with the traditional batch process, the operating mode of the reaction was updated and the reaction was carried out in an entirely continuous manner. This could achieve continuous automatic control of the process, thus preventing process fluctuation, unstable product quality and safety concerns caused by intermittent manual operation. The challenge was to provide reliable guaranty of heat transfer, mass transfer, environmental protection, and safety. Through process enhancement, precise temperature control, and reduction of liquid holding capacity, the production of by-products was greatly reduced and the production capacity was significantly improved. The microchannel reactor showed strong mass transfer and heat transfer conditions, which strengthened the reaction conditions and completed the reaction in a short time. The safety parameters of the reactor were good, the liquid holding capacity in the reaction zone was small, no unstable intermediates remained, the system was closed, the amplification effect was weak, side reactions were lesser, yield was higher, reaction could be precisely controlled, product quantity increased, there was energy saving and emission reduction, and also quick response to unexpected situations.
