Esterification of lactic acid and ethanol with/without pervaporation

Reactors coupled with membrane separation, such as pervaporation, can help enhance the conversion of reactants for thermodynamically or kinetically limited reactions via selective removal of one or more product species from the reaction mixture. An example of these reactions is esterification of carboxylic acids and alcohols. Esterification of lactic acid (C3H6O3) and ethanol (C2H5OH) is studied in well-mixed reactors with/without a solid catalyst (Amberlyst XN-1010) in this paper. Rate expressions for homogeneous and heterogeneous esterification are obtained from the experimental data using differential and integral methods. Experiments with a closed-loop system of a "batch" catalytic reactor and a pervaporation unit reveal that fractional conversions of the two reactants and yield of ethyl lactate exceeding the corresponding maximum values in a reaction-only operation are obtained by stripping of the byproduct (water). The efficacy of pervaporation-aided esterification is illustrated by the substantial gains in fractional conversion of each reactant. A protocol for recovery of ethyl lactate from pervaporation retentate is proposed. Simulations based on empirical correlations for kinetics of esterification and pervaporation reveal the trends observed in experiments.