Investigation of Sn(IV) catalysts in glycerol acetylation

Abstract

The catalysts dibutyltin dichloride (Bu2SnCl2), dimethyltin dichloride (Me2SnCl2), butyltin trichloride (BuSnCl3), dibutyltin dilaurate (Bu2SnLau2), butyl stannoic acid [BuSnO(OH)], and di-n-butyl-oxo-stannane (Bu2SnO) were investigated in the acetylation of glycerol (GLY). To the best of our knowledge, this is the first time that this family of catalysts is employed for this reaction and the catalysts bearing chlorine substituents provided the best results. The most active system (BuSnCl3) leads to the total conversion of GLY and shows very good selectivity (25.7, 43.5 and 30.8 % for MA, DA and TA, respectively) under mild reaction conditions (80 °C, AA:GLY molar ration of 4:1 with 3 h of reaction). The apparent rate constants (kap) for the GLY conversion confirm these results, since values of 29.1 × 10−3, 67.9 × 10−3 and 87.2 × 10−3 h−1 were obtained at 40, 80 and 120 °C, respectively. The activation energy for GLY conversion was determined and for the reaction performed without catalyst the estimated value was 23.9 kJ mol−1 while using BuSnCl3 it was 14.3 kJ mol−1, representing a decrease of around 50 %.