This work deals with the determination of kinetic models for the esterification of citric acid with ethanol for the synthesis of triethyl citrate. Methanesulfonic acid (MSA) and an ion-exchange resin Amberlyst 70 (A70) were used as catalysts. Experiments were carried out under batch operation at temperatures between 345 and 393 K and at different initial reactant concentrations and catalyst loadings. The evolution of concentrations along the reaction was tracked by liquid chromatography. The proposed model corresponds to an activity-based kinetic expression, and the activity coefficients were calculated with UNIQUAC equation. The adjustment of the corresponding kinetic parameters for each catalyst was done with a genetic algorithm by minimization of the squared differences between experiments and model predictions. The obtained models exhibited good agreement with experiments and can be used for further process development. MSA exhibited around 10 times the activity of A70 under similar conditions. In the case of A70, this catalyst has not only higher temperature stability but also showed higher activity than previously reported Amberlyst 15. Both studied catalysts seem feasible alternatives for the implementation of homogenously or heterogeneously catalyzed reactive distillation processes for triethyl citrate production.

中文翻译：

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柠檬酸三乙酯生产中的均相和非均相催化动力学

这项工作涉及确定柠檬酸与乙醇酯化合成柠檬酸三乙酯的动力学模型。甲磺酸（MSA）和离子交换树脂Amberlyst 70（A70）用作催化剂。实验是在345至393 K之间的温度下，以不同的初始反应物浓度和催化剂载量分批操作进行的。通过液相色谱追踪反应中浓度的变化。提出的模型与基于活动的动力学表达式相对应，并使用UNIQUAC方程计算活动系数。通过最小化实验和模型预测之间的平方差，使用遗传算法对每种催化剂的相应动力学参数进行调整。所获得的模型与实验具有良好的一致性，可用于进一步的工艺开发。在相似条件下，MSA的活性约为A70的10倍。在A70的情况下，该催化剂不仅具有更高的温度稳定性，而且还比以前报道的Amberlyst 15具有更高的活性。两种研究的催化剂似乎都是可行的替代方法，可用于实施柠檬酸三乙酯生产均相或异相催化的反应性蒸馏工艺。