Application and analysis of rapid determination of oxidative degradation of biodiesel by surface tension and UV absorbance

In this paper, the accelerated degradation and oxidation of Jatropha biodiesel were carried out at 110 °C through the Rancimat method. The applicability of surface tension and UV absorbance in the fuel oxidation degree detection was studied through Gas Chromatography-Mass Spectrometer(GC-MS) and acid value titration. The analysis of experimental data demonstrated that the acid value, surface tension and density of Jatropha biodiesel increased by 551%, 3.8% and 0.91% following oxidation, respectively, while the UV absorption intensity at 230 nm increased nearly 2 times. Subsequently to oxidation, the correlations among surface tension, UV absorbance and acid value of Jatropha biodiesel were 0.9743 and 0.9702. Based on this fact, four prediction models for the degree prediction of fuel oxidation through surface tension and UV absorbance were proposed, while the cross-validation method was utilized. The test analysis finally determined that the two models were Logarithm model and Power model, while the RMESP and R values were 0.093, 0.9875, 0.0705 and 0.9928. Both the accuracy and correlation were high. The acid value prediction model based on surface tension was 7.8%, while the acid value prediction model based on UV absorbance was 3.8%. Both could accurately determine the oxidation degree of biodiesel.