Biodiesel production from vegetable oil by using modified CaO as solid basic catalysts

A high efficient production of fatty acid methyl ester (FAME) from soybean oil and rapeseed oil was carried out using modified CaO as solid basic catalyst by connecting bromooctane to the surface of CaO chemically in a simple way. It was found that 99.5% yield of the FAME over modified CaO was obtained from soybean oil using 15:1 molar ratio of methanol to oil after 3 h at reaction temperature of 65 °C, which is much higher than the yield of 35.4% over commercial CaO at the same reaction conditions. For the transesterification between rapeseed oil and methanol, the reaction time to its highest yield, 99.8%, was shortened to 2.5 h. The physical and chemical properties of catalysts were characterized by using techniques of X-ray diffraction (XRD), scanning electron microscope (SEM), BET surface area measurement (BET), Fourier transform-infrared (FT-IR) spectroscopy and thermogravimeter (TG). The results indicated that well dispersed CaO with relatively small particle sizes and high surface areas were obtained after modification. Furthermore, the thermal stability of modified CaO is improved and the amount of Ca(OH)2 formed during the modifying process is very little. Influence of the amount of modifier and various reaction conditions, such as mass ratio of catalyst to oil, reaction temperature and molar ratio of methanol to oil, were investigated in detail. Furthermore, water-tolerance of the modified CaO was tested by adding water in the reaction system.