Investigating the Oxidation of Biodiesel From Used Vegetable Oil by FTIR Spectroscopy: Used Vegetable Oil Biodiesel Oxidation Study by FTIR

ABSTRACT The thermal oxidation of a biodiesel prepared from used vegetable oil was investigated using Fourier transform infrared (FTIR) spectroscopy. Spectral changes were observed in the hydroxyl, carbonyl, and cis/trans double bond regions for the control and Vitamin E–added samples. These spectral changes, increasing with increasing oxidation, were attributed to common oxidation products. IR results also suggested an oxidation-induced breakage of methyl ester linkages and agreed with those from selected physical property measurements. This preliminary study demonstrated the feasibility and potential of FTIR spectroscopy, a fast and reagent-free method, in assessing the oxidation state of biodiesel and providing understanding of its oxidative degradation.