In this work, the production of tributyl citrate via catalytic and self-catalyzed esterification of citric acid with 1-butanol was studied. Both, methanesulfonic acid (MSA) and Amberlyst 70 ion-exchange resin were evaluated as catalysts in the reaction. The kinetic effects of the temperature (353–393 K), the feed molar ratio of alcohol to acid (8:1 to 16:1), and catalyst loadings (0.5–1.5 wt % of MSA, and the equivalent amount of Amberlyst 70) were evaluated. Experiments were carried out using stirred batch reactors under isothermal operation. A Box–Behnken design was used to optimize the number of experiments required to obtain a valid kinetic model. Chemical equilibrium conditions were evaluated independently from kinetic experiments, reducing the number of parameters to adjust during data regression. Self-catalytic rate of reaction was also evaluated, and it was included within the overall kinetic model. The obtained models show good agreement with experiments, and they can be used for process analysis and simulation.

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.