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;k1=2.07×106β0.274exp−6890T,E1=57.26kJ/molk2=18.66β1.82exp−3830T,E2=31.87kJ/molk3=1.16β−0.474exp−1670T,E3=13.90kJ/mol

► The consecutive mechanism was confirmed and a number of features were disclosed.
► The AA:G molar ratio was more influential on product distribution than the temperature.
► The kinetic parameters were calculated using the first-order consecutive reaction model.
► The k values were found to be dependent on both AA:G molar ratio and temperature.