Efficient heterogeneous catalyst for biodiesel production from soybean oil over modified CaO

Biodiesel production by transesterification of soybean oil with methanol was carried out efficiently over modified CaO by using octadecyltrichlorosilane as surface modifier. It was found that the fatty acid methyl esters (FAME) yield was significantly enhanced from 35.4% to 93.5% over modified CaO with a methanol/oil ratio of 15 : 1 at 65°C after 3 h. Furthermore, good catalytic activity, i.e. 82.8% yield of FAME, remains even with a 2% water-content condition over modified CaO. The higher catalytic activity and good stability of modified CaO should be mainly attributed to the organic layer formed by the modifier over the CaO surface, which promotes the absorption of grease to CaO surface and protects CaO from water at the same time.