The acetylation of glycerol over amberlyst-15: Kinetic and product distribution

Glycerol is a byproduct of biodiesel synthesis and it can be converted into high value-added bioadditives. The heterogeneous acetylation of glycerol with acetic acid was conducted over Amberlyst 15 using a slurry reactor. The influence of reaction conditions such as the temperature and the molar ratio of acetic acid to glycerol (AA:G) on the product distribution was investigated. The results indicated that glycerol acetylation was a consecutive reaction. The equilibrium time for the product distribution shortened with decreasing AA:G molar ratio but with increasing temperature. It was also shown that the equilibrium conversion of glycerol as well as the combined yield of di- and triacetylated glycerols (DAG + TAG) increased with the AA:G molar ratio. Moreover, the AA:G molar ratio was the more influential factor on the yield of DAG + TAG than the temperature, although increasing the temperature might also have a positive influence on this yield. Reasonable yields of mono-, di- and triacetylated glycerols could be obtained by varying the reaction time, the AA:G molar ratio, and the temperature. The kinetic model based on homogeneous first-order consecutive reaction showed that the overall apparent rate constants (k1, k2, and k3) as well as its corresponding activation energy (E1, E2, and E3) were found to be; k 1 = 2 . 07 × 10 6 β 0.274 exp − 6890 T , E 1 = 57.26 kJ / mol k 2 = 18 . 66 β 1.82 exp − 3830 T , E 2 = 31.87 kJ / mol k 3 = 1 . 16 β − 0.474 exp − 1670 T , E 3 = 13.90 kJ / mol