Autocatalyzed and heterogeneously catalyzed esterification kinetics of glycolic acid with ethanol

The chemical equilibrium and reaction kinetics in homogeneously and heterogeneously catalyzed systems were investigated for the reversible esterification reaction of glycolic acid with ethanol. In a first approach, the thermodynamic equilibrium of the reaction was established for temperatures between 50 °C and 75 °C. To differentiate catalytic from homogeneous contribution, the esterification was first studied without a catalyst and the data obtained were then used to model the autocatalyzed homogeneous reaction kinetics. The impact of different commercial solid catalysts such as zeolites, oxides and ion exchange resins on the esterification reaction was also investigated. For the latter, the amount of total acid sites was quantified in order to correlate this parameter to the reaction rate and glycolic acid conversion. Finally, the effects of catalyst loading, temperature, presence of water and recyclability were examined for the most efficient catalyst, Amberlyst 70. Moreover, a kinetic adjustment of the experimental results was carried out by fitting the data to a pseudo-homogeneous model and comparing to adsorption-based models.