Thermodynamic Equilibrium and Reaction Kinetics for the Esterification of Lactic Acid with Ethanol Catalyzed by Acid Ion-Exchange Resin

Abstract

The heterogeneous catalysis of lactic acid (88 wt %) esterification with ethanol in the presence of Amberlyst 15-wet was studied for catalyst loading of 1.2−3.9 wt %, initial molar ratio of reactants of 1.1−2.8, and temperature from 50 to 90 °C. In this work a methodology based on the UNIQUAC model was developed to determine the thermodynamic equilibrium constant since in the literature there is inconsistency concerning the temperature dependence of the thermodynamic equilibrium constant. A simplified Langmuir−Hinshelwood kinetic model was used to predict the experimental data. The proposed rate law is r = k c ( a Eth a La − a EL a W / K )/(1 + K Eth a Eth + K W a W ) 2; the kinetic parameters are the preexponential factor, k c,0 = 2.70 × 10 7 mol·g -1 ·min -1, and the activation energy, E a = 49.98 kJ/mol. The equilibrium reaction constant is K = 19.35 exp(−515.13/ T (K)) with reaction enthalpy 4.28 kJ/mol. The model reasonably predicts the kinetic experimental data, and it will be very useful to apply to the design and optimization of industrial hybrid reactive separation processes.