Investigation of glycerol acetylation in the presence of Sb catalysts

Abstract

In this study, antimony complexes (SbCl5 and SbCl3) were investigated as catalysts in glycerol (GLY) esterification with acetic acid (AA), compared to Sb2O3 and Sb2O5. To the best of our knowledge, this is the first time that this class of catalysts is evaluated in GLY acetylation to produce monoacetin (MA), diacetin (DA), and triacetin (TA). The best result was obtained at 80 °C using 0.166 mmol of SbCl5, with total conversion attained after 15 min, and selectivity of 31, 47, and 22% for MA, DA, and TA, respectively, after 180 min. The apparent rate constants (kap) were determined and the values corroborate the catalytic efficiency of SbCl5, especially when compared to the reaction without catalyst. The activation energies (Ea) for GLY conversion were estimated to be 23.9 and 14.6 kJ mol−1, in the absence and presence of catalyst, respectively, indicating a reduction of around 40% in the Ea with the use of SbCl5. Studies using 13C NMR (in the case of complexes) and infrared spectroscopy (for Sb2O5) indicated the stability of the systems during the reaction process.