PROCESS TO PRODUCE BIODIESEL FUEL USING SOLID CATALYST TO DECREASE THE EMISSION

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Fatty acid alkyl esters produced by the transesterification from vegetable oils or animal fats with alcohol is called as biodiesel fuel(BDF) and used as a substitute for diesel fuel. Usually methanol has been used as alcohol and then produced BDF is methyl ester form. Sodium hydroxide or potassium hydroxide dissolved in methanol is industrially used as homogeneous catalysts. However, homogeneous catalysts cause some problems. Since these basic catalysts are dissolved in the by-product ; glycerol, it is difficult to treat this by-product after the separation. The process using heterogeneous catalysts would be simple and the catalysts are easily separated from the products. Therefore, the purification process of yielded glycerol will be simplified. In addition, the solid catalysts would be used for the reaction repeatedly or successively. In this study, since calcium oxide is not expensive, we investigated the catalytic activity of calcium oxide. Even when the powdery calcium oxide was used, the activity of this catalyst was much lower than that of the homogeneous catalysts such as potassium hydroxide. We also tested the calcium oxide catalysts supported on porous alumina. The conversion reached 90 % after 2 h, when 30 g of vegetable oil and 10 g of methanol were reacted with 0.8 g of the highest active calcium oxide at 60 ℃. The activity of the catalyst decreased with the repetition of the reaction. The deactivation could not be prevented by the calcinations and methanol washing after the use. In the present study, we have not identified the main cause of this deactivation. However, it is important to improve the performance of calcium oxide catalyst for industrial use.