Synthesis of biodiesel in subcritical water and methanol

A novel method for biodiesel production without the need of conventional catalyst such as potassium hydroxide and sulfuric acid was proposed in this study. In the presence of water, biodiesel can be produced by reacting methanol with feedstock oil under subcritical condition. When refined soybean oil was used, high biodiesel conversion (96.4%) can be achieved in a reasonable short time (4 h). The conversion was 92.6% when soybean oil with a water content of 9 wt.% was used. The possibility of using oils with high acid and water contents as feedstock was also investigated. Since no catalyst was employed, the process is simpler and more environmental friendly than traditional methods.