Yield and component distribution of biodiesel by methanolysis of soybean oil with lipase-immobilized mesoporous silica

The activity and stability of mesoporous and macro-mesoporous silica immobilized with lipases PS and AK was investigated in methanolysis of soybean oil to biodiesel. Intermediate saturated heavy components of fatty acid methyl esters, linoceric and arachidic acid methyl esters were formed during the reaction. These were ultimately transformed to unsaturated (relatively fast) and saturated (slowly) acid methyl esters. Reaction time (similar to 72 h), reaction temperature (similar to 25 degrees C), pore size (similar to 80 nm), surface modification with OTES and an appropriate amount of water (1 mL per 0.33 g catalysts) resulted in high selectivity of unsaturated fatty acid methyl esters as well as high total yield. More than the critical mass of catalysts did not affect the total yield but raised the selectivity of the unsaturated components. Excessive increase in the number of methanol addition increased the total yield mainly by the formation of the heavy components. The addition of water as described also substantially increased the stability of the lipase-immobilized catalysts by the water residing inside pores, keeping the lipases to activate interfacially for their reuses. (C) 2010 Elsevier Inc. All rights reserved.