Anti-Oxidation Stability and its Mechanism of Soybean Biodiesel
The anti-oxidation stability of soybean biodiesel (SME) was evaluated on an oxidation simulator set up by the author. The results showed that oxidative stability of SME was worse than that of petrodiesel by exhibiting higher acid values and peroxide values, as well as greater viscosity increases after oxidation. Furthermore, a conjecture was taken about the configurational changes and the oxidation mechanisms of unsaturated fatty acid methyl ester molecules in the oxidation process, according to the principles of free radical reactions and the results of both infrared and ultraviolet spectroscopic analysis. An idea was put forward that, during oxidation, cis-trans isomerization might occur in unsaturated fatty acid methyl ester molecules and conjugated double-bond might produce due to transfer of double-bond.