Efficient synthesis of alkyl levulinates fuel additives using sulfonic acid functionalized polystyrene coated coal fly ash catalyst

Abstract

In this study, sulfonic acid functionalized polystyrene coated coal fly ash catalyst (CFA@PS-SO₃H) was designed and prepared by the post-synthesis method, which exhibited excellent catalytic performance for esterification of levulinic acid (LA) to afford alkyl levulinates. Four significant factors, including reaction time, catalyst dosage, alcohol-to-acid molar ratio and reaction temperature were evaluated systematically. Response surface methodology based on Box-Behnken design (BBD) was carried out to determine the optimal parameters. The maximum yield could reach 99.6% under the mild conditions. Furthermore, kinetics of the esterification reaction between levulinic acid and n-butanol were analyzed and the activation energies of the first and second step of esterification reaction were found to 52.18 and 59.81 kJ/mol, respectively. The CFA@PS-SO₃H also showed high catalytic activity for the esterification of levulinic acid with other linear alcohols, which made it a low cost, environmentally friendly and promising solid catalyst for the synthesis of alkyl levulinates.