Levulinic Acid Esterification with n-Butanol over a Preyssler Catalyst in a Microwave-Assisted Batch Reactor: A Kinetic Study

A Preyssler-type heteropolyacid supported on silica, synthesized and characterized by FTIR, was tested for levulinic acid (LA) esterification with n-butanol under microwave-assisted batch reaction conditions. The optimal conditions were found to be 40 mg of catalyst, a 5:1 n-butanol/LA molar ratio at 160 °C and 3 h, resulting in 77% conversion with 100% selectivity. The catalytic effect was observed at low temperatures (100 °C), and the microwave effect was observed at high temperatures (160 °C). Yield to levulinate was improved (82%) with CuSO4 as a dehydrating agent. A kinetic study using a pseudohomogeneous reversible model (PH, EForward = 31.60 kJ mol–1 and EReverse = 11.53 kJ mol–1) and a Eley–Rideal model (ER, E = 31.06 kJ mol–1) provided the best fitting to the experimental data. The Preyssler-based catalyst has potential for sustainable synthesis of n-butyl levulinate, a promising fuel additive and can be used at least five times without a loss of activity.