锡催化二羟基丙酮制备乳酸甲酯及其反应过程

Tin-Catalyzed Conversion of Dihydroxyacetone to Methyl Lactate and Its Reaction Process

采用间歇式反应器考察了甲醇溶剂中不同金属盐催化1,3-二羟基丙酮(DHA)制备乳酸甲酯的性能及其反应过程。结果表明:具有强Lewis酸性的金属阳离子能够有效催化DHA向乳酸甲酯的转化,其中Sn离子性能最佳;Sn离子催化DHA制备乳酸甲酯的性能与其配位阴离子密切相关,Cl-和Br-有利于获得高的反应活性和选择性。此外,提高温度有利于SnCl 2催化DHA向乳酸甲酯的转化,在反应温度为100℃时,DHA的转化率和乳酸甲酯的选择性分别高达98.2%和96.0%。反应过程分析表明,SnCl 2催化DHA向乳酸甲酯的转化主要采用序列-平行反应路径,丙酮醛及其与甲醇的半缩醛为反应中间产物,乳酸甲酯为热力学稳定产物。

The catalytic behaviors of various tin compounds for the conversion of 1,3-dihydroxyacetone(DHA)to methyl lactate(ML)in methanol,as well as the reaction process,were briefly investigated in a batch reactor.The results indicated that metal cations with strong Lewis acidity,in particular Sn 2+and Sn 4+,catalyzed efficiently the conversion of DHA to ML.The performance of tin cation was closely related to its counterpart anions,with the halide anions(Cl-and Br-)acting as promoters.Besides,high temperature favored the yield of methyl lactate when SnCl2 served as a catalyst,yielding the DHA conversion and ML selectivity of 98.2%and of 96.0%respectively at 100℃.Moreover,the evolution of reaction products against time suggested that the conversion of DHA to ML proceeded through a combination of consecutive and parallel reaction steps.Pyruvic aldehyde hemiacetal was the detectable reaction intermediate,whereas ML proved to be final products.