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The oxidation behavior of three biodiesels of different origins,viz.rapeseed oil derived biodiesel,soybean oil derived biodiesel and waste oil based biodiesel,were tested on an oxidation tester.The chemical compositions of the biodiesels were characterized by gas chromatography.Thereafter,the structural transformation of fatty acid methyl ester(FAME)of the biodiesels was analyzed by an infrared spectrometer and an ultraviolet absorption spectrometer.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.Furthermore,cis-trans isomerization transformation occurred in the unsaturated FAME molecules and conjugated double-bond produced during the oxidation process of biodiesel.Greater cis-trans variations corresponded to deeper oxidation degree.The higher the content of unsaturated FAME with multi-double bonds in a biodiesel,the more the conjugated double bonds was formed.
The oxidation behavior of three biodiesels of different origins, viz. Rapeseed oil derived biodiesel, soybean oil derived biodiesel and waste oil based biodiesel, were tested on an oxidation tester. The chemical compositions of the biodiesels were characterized by gas chromatography. Afterafter, the structural transformation of fatty acid methyl ester (FAME) of the biodiesels was analyzed by an infrared spectrometer and an ultraviolet absorption spectrometer. 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. Still further, cis-trans isomerization transformation occurred in the unsaturated FAME molecules and conjugated double-bond produced during the oxidation process of biodiesel. Greater cis-trans variation corresponded to deeper oxidation degree. higher the content of unsaturated FAME with m ulti-double bonds in a biodiesel, the more the conjugated double bonds was formed.