Kinetic study of the levulinic acid esterification with ethanol promoted by Amberlyst-15

Levulinic acid (LA) was recognized by the U.S. Department of Energy as one of the top biomass-derived platform molecules, due to its high reactivity and for its low-cost production from lignocellulose wastes. Levulinic acid esters may find applications as alternative green solvents, polymer plasticizers and fragrances [1]. LA esterification with alcohols is an acid catalyzed reaction, promoted by homogeneous catalysts (i.e. sulfuric acid [2]); since recent times a variety of heterogeneous acid catalysts have been used (i.e. zeolites, sulfated metal oxides, silica, sulfonated resins) [2,3]. Amberlyst-15 showed a remarkable high yield to ethyl levulinate, due to the acidity provided by sulfonic groups. In the present work, the kinetics of the levulinic acid esterification with ethanol in the presence of Amberlyst-15 was investigated. Experiments were conducted by evaluating the effect of different operating conditions on the reaction rate (i.e. stirring rate, temperature, catalyst loading and reactants ratio). Through this study it was possible to evaluate the activation energy value (49.39 kJ/mol). The collected experimental data were interpreted with a reliable model taking into account also for the mass transfer phenomena involved in the reaction network, such as eventual fluid-solid and intraparticle mass-transfer limitations. The mixed PDE/ODE system (Eq.1) given by the mass balance equations, was solved with advanced numerical techniques. (1) The results can be considered as good starting point for continuous reactors optimization.