Reaction Kinetics and Chemical Equilibrium of Homogeneously and Heterogeneously Catalyzed Acetic Acid Esterification with Methanol and Methyl Acetate Hydrolysis

The reaction kinetics and chemical equilibrium of the reversible esterification of methanol with acetic acid were investigated. This system is of major importance as a model reaction for reactive distillation. The reaction has been catalyzed both homogeneously by acetic acid itself and heterogeneously by an acidic ion-exchange resin (Amberlyst 15). The chemical equilibrium composition was measured for various temperatures and starting compositions of the reactants and products. Kinetic information was obtained at temperatures between 303.15 and 343.15 K at various starting compositions covering concentration ranges from the stoichiometric regime to the dilute regions. Both the esterification and the hydrolysis reaction were investigated to yield a model which is applicable for any starting composition. The homogeneous reaction has been described with a simple power-law model. The use of activities in the kinetic model instead of mole fractions results in a much smaller residual error. To compare pseudohomogeneous and adsorption-based kinetic models for the heterogeneously catalyzed reaction, independent binary liquid adsorption experiments were used to fit the adsorption constants to keep the number of adjustable parameters the same for each model. The use of activities instead of mole fractions results in a slight improvement of the kinetic model only, while incorporating adsorption information into the kinetic model results in a much better fit. The chemical equilibrium composition calculated from the kinetic model is in agreement with the measured chemical equilibrium.