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 H4SiW12O40 (HSiW), H3PW12O40 (HPW) and H3PMo12O40 (HPMo) as active compounds. The as-prepared catalysts were characterized by N2-physisorption, XRD, Raman spectroscopy, NH3-TPD, FTIR of pyridine adsorption and H2O-TPD. Among the catalysts tested, HSiW/ZrO2 achieved the best catalytic performance owing to the better combination of surface Brّnsted 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 4 h of reaction time in the presence of HSiW/ZrO2. This catalyst also presented consistent activity for four consecutive reaction cycles, while HPW/ZrO2 and HPMo/ZrO2 exhibited distinct deactivation after reusability tests. In addition, HSiW/ZrO2 can be resistant to the impurities present in bulk glycerol.