微通道反应器中乙酰乙酸甲酯的连续流合成工艺

Continuous flow synthesis of methyl acetoacetate in microchannel reactor

传统的间歇反应合成存在温度不易控制、生产能力低、时间长等一系列问题,而微通道反应器可大幅度提高反应过程中的资源和能量的利用效率,减小过程系统的体积或提高单位体积的生产能力,实现化工过程强化、微型化和绿色化。本工作以双乙烯酮与甲醇为原料,探究在变径脉冲结构的微通道反应器中合成乙酰乙酸甲酯新方法。对催化剂类型、物料配比、停留时间、反应温度及催化剂用量进行了考察分析,最佳条件组合结果显示,当催化剂选择甲醇钠,且双乙烯酮:甲醇:甲醇钠=1:1.1:0.02(摩尔比),反应温度为90℃,停留时间为90 s时,双乙烯酮的转化率达100%,乙酰乙酸甲酯的选择性达96.8%,用此方法可以直接体现微通道反应器连续流合成的优势。

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 of90 ℃, 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.