The Study On Heterogeneous Catalyst And Reaction Process In Biodiesel Production

Biodiesel will be extensively used in the near future. There are many advantages using solid base as a catalyst for the transesterification of vegetable oils to biodiesel, such as environmentally benign, easy recycle. However, the reported supported solid base catalysts have many disadvantages for industrial application, such as active ingredients are dissolvable in polar solvent, the catalyst lifetime is short, etc. Thinking of presenting problems, this research mainly studied some solid base catalysts which own higher catalysis ability and longer lifetime. Then, the phase diagram and equilibrium data of oil-alcohol-biodiesel-glycerol multiphase system were measured because the biodiesel producing process lacks of thermodynamic data.Based on a double-membranes theory and the thermodynamic data, a kinetic model was proposed. In addition, a mult-step extraction process was proposed to dispose the jatropha curcas l oil with high acid value in order to decrease the acid value. Then, a new technology of biodiesel producing using solid base as a catalyst was developed. The study objects and results are as follows. Firstly, some alkaline earth oxides and methoxides solid base catalysts were produced such as CaO, SrO, Ca(OCH3)2, Ca(OCH2CH3)2. The physical and chemical characterizations were measured, such as BET area, heat behavior, particles size distribution. Then biodiesel was produced by transesterification of soybean oil with methanol using the above catalysts. The results indicated that the optimum conditions is a 12:1 molar ratio of methanol to oil, 65℃, 3 h of reaction time. The biodiesel yield reached 95%. The biodiesel yield has little decrease after reused for 10-20 times. By comparison, calcium methoxide has higher stability and better catalysis ability.The phase equilibrium data of SBO-FAME-Methanol, SBO-FAEE-Ethanol and Glycerol-FAEE-Ethanol systems were measured. The results indicated that it involved two different stages: liquid-liquid-solid reaction stage and liquid-solid reaction stage. When the molar ratio of methanol to oil is 12:1 at 65℃, the turning point is at a 55% biodiesel yield. The liquid-liquid-solid reaction model was proposed based on the double-membranes theory. It indicated that the process is reaction and mass transfer controlled together at the first stage, and the second stage is reaction controlled. The predictions of the model are matched with the experimental results.In the end, the acid was extracted using methanol and ethanol from jatropha curcas l oil. The acid value decreased to 0.31 mgKOH/g from 9.4 mgKOH/g after extracted for 4 times with a 2:1 volume ratio of ethanol to oil at 25℃. The residual oil was catalyzed to produce biodiesel using calcium methoxide as a solid base catalyst. The biodiesel yield reached 95%. However, it was only 89.7% if the jatropha curcas oil wasn't extracted. A new technology of biodiesel production using jatropha curcas l oil as a feedstock was developed.The stirring reactor was simulated using the CFD technology. The fluid flow behavior and mass transfer behavior were obtained in the reactor. The results can provide useful information for the reactor scale up and operation optimization.