Study On Biodiesel Synthesis By Transesterification With Vegetableseed Oil

Bio-diesel synthesized from vegetableseed oil and methanol by transesterification is an environmental friendly alternative fuel. Different types of catalyst applied to transesterification have been studied. With a traditional homogeneous base catalyst, the transesterification product is difficult to be purified and the waste catalyst may induce environmental problem. The water content in the system of transesterification with base catalyst has strong effect on the yield of biodiesel. Using heterogeneous acid catalyst, pure product can be obtained easily and the problem of catalyst separation can be avoided. A research on heterogeneous catalyst and catalytic transesterification reaction is meaningful for the improvement of biodiesel production and its application. The main work in this study is as follows:1,Bio-diesel was synthesized by homogeneous base catalyst. The suitable reaction conditions have been studied. The effect of the water content in the system on the yield of biodiesel with KOH catalyst has been investigated. The result showed when the KOH catalyst quantity is 1.0% of the vegetable seeds oil; the molar ratio of methanol and oil is 7:1; the reaction temperature is 50℃; the reaction time is 100 min, the yield ofbiodiesel is the highest. It has been proved by the study that the water content in the system has the linear relationship with the yield of biodiesel, when water content increased from 0.09% to 0.72%, the yield of biodiesel decreased from 95% to 86%. The result also showed reatction time is shorter with KOH catalyst than with NaOH catalyst, but with higher yield.2,Catalyst of SO₄^2-/Fe₂O₃ solid super acid was prepared by deposition dipping method. The deposition was carried in iced water bath and the calcination temperature of the catalyst was 500℃. The structure of catalyst has been characterized by FTIR and XRD. The effects of catalyst quantity, molar ratio of methanol and oil, reaction temperature and reaction time on the yield of biodiesel were discussed.3,On the basis of S₂O₈^2-/Fe₂O₃, the rare earth solid super acid S₂O₈^2-/Fe₂O₃-ZrO₂-La₂O₃ was prepared by chemical modifying of solid super acid with lanthanum. The effects of preparation conditions on catalytic activities in the transesterification of biodiesel were studied. The results showed that different dipping solution, n(Fe):n(Zr):n(La) atom ratio and calcination temperature had obviously effect on the activity of the catalyst. When n(Fe):n(Zr):n(La) is at 1:0.42:0.075, the activity of catalyst is much higher than that of single-component catalyst or double-component catalyst. Under the optimum preparation conditions of catalyst and transesterification reaction conditions, the biodiesel yield reached 90%. Aider the catalyst has been used for 50 hours, biodiesel yield was still above 83%. With the catalyst of S₂O₈^2-/Fe₂O₃-ZrO₂-La2O₃, the whole process of bio-diesel synthesis has no pollution, no erosion on equipment and in favor of continuous production of biodiesel.4,The biodiesel obtained by KOH catalyst and S₂O₈^2-/Fe₂O₃-ZrO₂-La₂O₃ catalyst has been characterized by GC/MS respectively. The result showed main components are fatty acid methyl esters of C₁₂～C₂₀, which indicated that the purity of biodiesel is higher.