Fundamental Study On Preparation Of Black Rosin Biodiesel By Supercritical/Subcritical Methanol Method

Without catalyst and using heavy turpertine as solvent conditions, gas chromatography (GC) and the gas chromatography-mass spectroscopy (GC-MS) as analysis methods, the preparation of biodiesel through black rosin which were the residue formed from rosin production or rosin industrialized deep processes and supercritical/subcritical methanol were investigated with self-made high temperature and high pressure reaction equipment. The principal researches are as follows:Through single factor experiment, orthogonal experiment and the esterification rate of black rosin as evaluation index, the effects of different factors on reaction of black rosin and supercritical/subcritical methanol were discussed and the optimum conditions were confirmed, which are reaction temperature613K, reaction pressure10～12MPa, reaction time3h, the mass ratio of black rosin to methanol1:0.8, the mass ratio of black rosin to heavy turpertine1:1.2, rotational speed200r·min-1, the esterification rate for black rosin is94.54%.The composition and content of reaction system were determined by the GC and GC-MS, then the reaction process mechanisms were discussed and reaction networks were established. The results showed that the main reaction was the esterification of diterpenoid resin acids with supercritical methanol under optimum conditions, and the side reactions were disproportionation, isomerization and decomposition. Most of sesquiterpenes were not participated in reaction, and only a small number occurred disproportionation, rearrangement and decomposition reactions.With abietic acid as model compound, the esterification of abietic acid with methanol was selected as a probe reaction. The thermodynamics of reaction was analyzed by group-contribution method. The reaction enthalpy, entropy, Gibbs free energy and equilibrium constant were calculated in the temperature range of473-653K and the pressure range of0.1-20MPa. The effects of temperature and pressure on reaction were also discussed. The calculation results indicated that the reaction enthalpy is-46.31to-10.10kJ·mol-1and free energy is-53.26to25.49kJ·mol-1, showing a exothermic and spontaneous reaction. The equilibrium constant is136.32to748.89at standard pressure and1.1×104～3.2×104in the range of5-20MPa. By comparing with the esterification rate obtained from equipments in supercritical methanol conditions, the range of relative deviation is3.26%to4.02%, The experimental data are in agreement with thermodynamic calculation values by group-contribution method.Reaction kinetics analysis was studied by integration and Hooke-Jeeves pattern search method. In the range of temperature was573K to613K, the reaction orders of esterification reaction of black rosin in supercritical /subcritical methanol are1.42～1.62, the average order is1.51, the activation energy is81.36kJ·mol-1and the preexponential factor is5.65×105s-1. The experimental results are in good agreement with the kinetics model.The physicochemical properties of black rosin-based biodiesel were analyzed with national standard and its compounding performance was also studied. The results showed that the physicochemical properties of black rosin-based biodiesel blend fuel (B5) satisfied or exceeded the requirements of GB/T25199-2010biodiesel fuel blend (B5). The black rosin-based biodiesel can be a promising alternative to fossil diesel.