Investigation of solvent-free esterification of levulinic acid in the presence of tin(IV) complexes

Abstract

In this study, for the first time, the use of dibutyltin dichloride (Bu2SnCl2), dimethyltin dichloride (Me2SnCl2), butyltin trichloride (BuSnCl3) and butyl stannoic acid (BuSnO(OH)) as catalysts in the esterification of levulinic acid (LA) was investigated through a comparison with reactions performed without the use of a catalyst. The most active system (BuSnCl3) led to 93% conversion of LA in 360 min at 110 °C with an LA:EtOH:CAT molar ratio of 1:5:0.01. The apparent rate constants (kap) for LA conversion confirm these results, and values of 6.2 × 10−3, 12.5 × 10−3 and 19.4 × 10−3 min−1 were obtained at 70, 90 and 110 °C, respectively. The activation energy for LA conversion was determined employing BuSnCl3 and the value was 31.2 kJ mol−1.