Thermodynamic analysis, experimental and kinetic modeling of levulinic acid esterification with ethanol at supercritical conditions

Abstract

Ethyl levulinate is an environmentally friendly biomass-derived ester that is an alternative to the classic petroleum-derived fuel additives. Several studies have been addressed to its chemical production pathways. The supercritical esterification of levulinic acid to ethyl levulinate, however, remains understudied. This work reports the effect of process variables and a kinetic study for the esterification of levulinic acid with ethanol under sub and supercritical conditions. Experimental data were obtained in a continuous tubular reactor at a fixed pressure of 100 bar. The reaction temperature varied from 220 to 280 °C, and the ethanol to levulinic acid molar ratios from (2:1) to (9:1). Ethyl levulinate was synthesized with high selectivity under all evaluated reaction conditions, achieving conversions up to 80% and 93% when ethanol to levulinic acid molar ratios of (2:1) and (9:1) were used, respectively. A PFR model approach was considered with an elementary reversible self-catalyzed rate law, and the effect of considering the mixture density behavior through the reactor using the PC-SAFT equation of state was discussed. The proposed kinetic approach was able to correlate the kinetic experimental data for all experimental conditions used in this study. Furthermore, a thermodynamic analysis was performed to elucidate trends in reaction performance.