Biodiesel Production from Subcritical Methanol Transesterification of Soybean Oil with Sodium Silicate

Biodiesel from supercritical methanol reaction is a high-efficiency method of noncatalysis. Due to high temperature and pressure, this technology has been limited to practical applications. To improve the operation conditions, developing a mild method has become a new trend for biodiesel production. In this paper, the transesterification of soybean oil in subcritical methanol was studied with a small amount of catalyst of sodium silicate (Na2SiO3) to obtain biodiesel. Na2SiO3 as a catalyst can improve the transesterification reaction of soybean oil in supercritical methanol. The variables affecting the fatty acid methyl ester (FAME) yield during the transesterification reaction, such as the reaction temperature, catalyst content, reaction rate, and the molar ratio of soybean oil to methanol, were investigated and compared with those of noncatalyst experiments. The test results show that a FAME yield of 95.6% was achieved when the reaction was performed with a catalyst content of 0.5 wt % at 220 °C for 30 min.