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Abstract: In this study, transesterification of soybean oil to biodiesel using CaO as a solid base catalyst was studied. The reaction mechanism was proposed and the separate effects of the molar ratio of methanol to oil, reaction temperature, mass ratio of catalyst to oil and water content were investigated. The experimental results showed that a 12:1 molar ratio of methanol to oil, addition of 8% CaO catalyst, 65°C reaction temperature and 2.03% water content in methanol gave the best results, and the biodiesel yield exceeded 95% at 3h. The catalyst lifetime was longer than that of calcined K2CO3/γ-Al2O3 and KF/γ-Al2O3 catalysts. CaO maintained sustained activity even after being repeatedly used for 20 cycles and the biodiesel yield at 1.5h was not affected much in the repeated experiments. [Copyright &y& Elsevier]

Abstract: A system for continuous transesterification of vegetable oil using supercritical methanol was developed using a tube reactor. Increasing the proportion of methanol, reaction pressure and reaction temperature can enhance the production yield effectively. However, side reactions of unsaturated fatty acid methyl esters (FAME) occur when the reaction temperature is over 300°C, which lead to much loss of material. There is also a critical value of residence time at high reaction temperature, and the production yield will decrease if the residence time surpasses this value. The optimal reaction condition under constant reaction temperature process is: 40:1 of the molar ratio of alcohol to oil, 25min of residence time, 35MPa and 310°C. However, the maximum production yield can only be 77% in the optimal reaction condition of constant reaction temperature process because of the loss caused by the side reactions of unsaturated FAME at high reaction temperature. To solve this problem, we proposed a new technology: gradual heating that can effectively reduce the loss caused by the side reactions of unsaturated FAME at high reaction temperature. With the new reaction technology, the methyl esters yield can be more than 96%. [Copyright &y& Elsevier]

Abstract: In this study, physical and chemical characterizations of calcium methoxide were investigated to assess its performance as an excellent solid base catalyst using some instrumental methods, such as BET surface area measurement, scanning electron micrographs and particle size distribution. Then, it was used to catalyze transesterification of soybean oil to biodiesel with methanol. The effects of various factors such as mass ratio of catalyst to oil, reaction temperature and volume ratio of methanol to oil were studied to optimize the reaction conditions. The results showed that calcium methoxide has strong basicity and high catalytic activity as a heterogeneous solid base catalyst and it was obtained a 98% biodiesel yield within 2h in this reaction. Besides, the recycling experiment results showed it had a long catalyst lifetime and could maintain activity even after being reused for 20 cycles. [Copyright &y& Elsevier]