Homogeneous and Heterogeneous Catalytic Kinetics in the Production of Triethyl Citrate

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.