Spectroscopic analysis of structural transformation in biodiesel degradation

• Main Authors: Saifuddin, N., Refal, H.
• Format: Article
• Language: en_US
• Published: 2017

The vegetable oil, fats and their biodiesel suffer with the drawback of deterioration of its quality during long term storage unlike petroleum diesel. The oxidation and thermal stability of two biodiesels of different origins, viz. palm oil derived biodiesel and used cooking oil based biodiesel were analyzed. The structural transformation of Fatty Acid Methyl Ester (FAME) of the biodiesels was analyzed by an infrared spectrometer and an ultraviolet absorption spectrometer. The infrared spectra of the samples were recorded by FTIR spectroscopy. The absorbance values of the spectrum bands were observed and it was determined that some of the chemical groups of oxidized oils caused changes in absorbance. The spectroscopic data of degraded biodiesel suggested oxidative polymerization. The results demonstrated that the oxidation behavior of biodiesels of different origins was closely related to the composition and distribution of FAMEs. Higher concentration of unsaturated FAME with multi-double bonds exhibited poorer oxidation resistance. In this study, in order to increase the stability of biodiesel, against oxidation process during the storage and distribution, different percentages (0.02, 0.05, 0.1 and 0.2% (w/v), respectively) of caffeic acid, were added as natural antioxidants. The antioxidant effect increased with concentration up to an optimal level. Above the optimal level, the increase in antioxidant effect with its concentration was relatively small. © Maxwell Scientific Organization, 2014.