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Graphene oxide (GO) has proved to be a highly active and reusable solid acid catalyst for glycerol esterification with acetic acid in the synthesis of bioadditives diacylglycerol (DAG) and triacylglycerol (TAG). The effects of reaction temperature, molar ratio of acetic acid to glycerol, catalyst amount and reaction time were investigated. A 90.2% combined selectivity of DAG and TAG with complete glycerol conversion was achieved at 120 °C for 6 h over GO. Final characterization shows that the active site of GO is the remaining SO 3 H group. [ABSTRACT FROM AUTHOR]

Highlights: [•] Ag1PW presented the best activity for glycerol esterification with acetic acid. [•] The TON of Ag1PW was up to 2189.9h−1. [•] Ag-exchanged HPW exhibited outstanding water-tolerant property. [•] A mechanistic scheme for glycerol esterification with acetic acid was proposed. [•] Ag1PW catalyst did not suffer from deactivation in five consecutive reaction tests. [ABSTRACT FROM AUTHOR]

Abstract: 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 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/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. [Copyright &y& Elsevier]