Fuel Processing Technology, Vol.104, 310-318, 2012
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 (k(1), k(2), and k(3)) as well as its corresponding activation energy (E-1, E-2, and E-3) were found to be; k(1) = 2.07 x 10(6)beta(0.274) exp(-6890/T), E-1 = 57.26 kJ/mol k(2) = 18.66 beta(1.82) exp(-3830/T), E-2 = 31.87 kJ/mol k(3) = 1.16 beta(-0.474) exp(-1670/T), E-3 = 13.90 kJ/mol (C) 2012 Elsevier B.V. All rights reserved.