阳离子交换树脂催化合成乳酸甲酯动力学研究

Kinetic Study on the Synthesis of Methyl Lactate Catalyzed by Cation Exchange Resin

工业化生产乳酸甲酯需要特定催化剂的动力学数据进行模拟计算.本文研究了在大孔阳离子交换树脂DA330的催化作用下,乳酸和甲醇生成乳酸甲酯的反应动力学.乳酸甲酯是一种重要的化工生产基础原料,多用来作为合成香料和农药的原料.随着化石能源紧缺和环保要求提高,具有可降解和可再生特性的乳酸甲酯及其高聚物的需求也在与日俱增.乳酸甲酯的连续化生产是提高乳酸甲酯产量的关键,具有广阔的研究前景.采用固体大孔阳离子交换树脂代替传统浓硫酸作为催化剂,需要对动力学方程进行重新测定.本文针对乳酸甲酯反应体系外扩散影响、内扩散影响、酯化反应动力学、水解反应动力学分别进行了实验.采用气相色谱对反应体系中的乳酸甲酯含量进行测定.研究发现内、外扩散在实验条件范围内对反应速率无明显影响:以酯化反应为例,搅拌转速达400 r/min以上时体系内催化剂颗粒悬浮程度达到峰值,外扩散不影响酯化反应速率;在催化剂颗粒悬浮程度达到峰值之后,催化剂粒径大小不影响酯化反应速率.反应温度在实验范围内对反应速率呈现显著的正相关影响,酯化和水解实验数据拟合均符合Quasi-Homogeneous模型,最终得到DA330催化条件下的反应动力学.

The modeling of the commercial synthesis of methyl lactate requires kinetic data for particular catalysts.In this study,the reaction kinetics of the production of methyl lactate from lactic acid and methanol catalyzed by macroporous cation exchange resin DA330 was investigated.Methyl lactate is a key fundamental raw material for synthetic fragrances and pesticides.With the shortage of fossil energy and the increase in environmental protection requirements,the need for methyl lactate and its polymers with degradable and renewable properties is also increasing.The continuous production of methyl lactate is the key to improving the yield of methyl lactate and has broad research prospects.The use of solid macro-porous cation exchange resin as a catalyst rather than traditional concentrated sulfuric acid necessitates a redetermination of the kinetic equations.In this study,the reaction system’s external diffusion effect,internal diffusion effect,esterification reaction kinetics,and hydrolysis reaction kinetics were all tested.The methyl lactate content in the reaction system was determined by gas chromatography.It was found that in the experiment,the effect of internal and external diffusion on the reaction rate can be ignored.For example,in the esterification reaction,when the stirring speed exceeds more than 400 r/min,the suspension degree of catalyst particles in the system reaches a peak,and external diffusion has no effect on the esterification reaction rate.After the suspension degree of catalyst particles reaches the peak,the size of the catalyst particle size does not affect the esterification reaction rate.The reaction rate was significantly positively impacted by the reaction temperature.The fitting of esterification and hydrolysis experimental data was consistent with the Quasi-Homogeneous model.Finally,the reaction kinetics under DA330 catalytic conditions were obtained.