Pilot Study Of High Acid Value Of Vegetable Oil Biodiesel Production

Biodiesel, as the perfect substitutite of fossil diesel, is one kind of typical "green Energy sources". As for its good combustibility, renewable resource, environmental friendly, biodiesel has become the focus for enterprises and researchers.There are physical, chemical, biological and supercritical methods for preparation of biodiesel. Supercritical method is a new technology, which is characterized by free-catalyst and short reaction time, but it requires a rigorous reaction conditions and higher requirement for equipment. Therefore, the two-step supercritical method was proposed, which consists of hydrolysis of triglycerides to fatty acids in subcritical water and subsequent methyl esterication of fatty acids to their methylesters in supercritical methanol. It has lower reaction condition than that of the one-step supercritical methanol method.Biodiesel was prepared from rubber seed oil, with two-step supercritical methanol method. The properties of rubber seed oil and biodiesel, hydrolysis of rubber seed oil in sub-critical water, esterification of its fatty acids were researched. The composition of rubber seed oil and Biodiesel were analyzed by UPLC.Physical and chemical characteristics and fatty acid composition of subber seed oil were analyzed. The result showed that viscosity and acid value of rubber seed oil were high.The main components of fatty acids of subber seed oil were oleic acid38.4%, linoleic acid24.4%, linolenic acidl9.3%, stearic acid8.7%and palmitic acid7.6%by UPLC analysis. Molecular structure of biodiesel product was similar to that of diesel, fitting to conditions of alternative fuel.The influence of reaction temperature, reaction time, reaction pressure and mole ratio of raw material were discussed by single factor experimentation on hydrolysis and methyl esterication.The uniform design method was applied to optimize hydrolysis conditions.The results show that the highest yield of fatty acids is 97.9% at 290℃and 50 min reaction time with a ratio of water to fatty acid 4:1(V:V). The orthogonal experiments design was applied to optimize esterification conditions. The results show that the highest yield of biodiesel is 99.2%at 290℃and 30 min reaction time with a ratio of methanol to fatty acid 4:1(V:V).The kinetics calculation indicates that the reaction order and activation energy of rubber seed oil hydrolysis in sub-critical water is 1.4 and 43.5kJ/mol, respectively; the reaction order and activation energy of esterification in supercritical methanol is 1.4 and 20.3 kJ/mol, respectively. Dynamic transformation model was established.Biodiesel prepared by rubber seed oil was analyzed for its physical and chemical characteristics. Its characteristics meet standards of biodiesel in china, such as flash point, acid value, sulfur contents,distillation range,solidifying point and impurity content,etc. The biodiesel made from rubber seed is mainly made up of 18-c and 16-c fatty acid methyl esters, suitable for substituting of diesel, except for higher mositure content and copper corrosion.