Production of bioadditives from glycerol esterification over zirconia supported heteropolyacids.

The synthesis of bioadditives for biofuels from glycerol esterification with acetic acid was performed over zirconia supported heteropolyacids catalysts using H(4)SiW(12)O(40) (HSiW), H(3)PW(12)O(40) (HPW) and H(3)PMo(12)O(40) (HPMo) as active compounds. The as-prepared catalysts were characterized by N(2)-physisorption, XRD, Raman spectroscopy, NH(3)-TPD, FTIR of pyridine adsorption and H(2)O-TPD. Among the catalysts tested, HSiW/ZrO(2) achieved the best catalytic performance owing to the better combination of surface Brønsted acid sites and hydrothermal stability. A 93.6% combined selectivity of glyceryl diacetate and glyceryl triacetate with complete glycerol conversion was obtained at 120°C and 4h of reaction time in the presence of HSiW/ZrO(2). This catalyst also presented consistent activity for four consecutive reaction cycles, while HPW/ZrO(2) and HPMo/ZrO(2) exhibited distinct deactivation after reusability tests. In addition, HSiW/ZrO(2) can be resistant to the impurities present in bulk glycerol.