Spectroscopic studies of oxidative degradation of base oils

NMR and FTIR spectroscopies have been used for obtaining component-level information on the thermo-oxidation of some base oils. Base oils were first separated by column chromatography into their saturates, aromatics, and polars. These fractions as well as the neat base oil were oxidized by a modified IP 306 benchtop (simulated) method. A H-1 and C-13 NMR-derived structural model was utilized to monitor the structural changes and rearrangements occurring in the carbon skeleton of the hydrocarbons during oxidation of base oils/fractions. FTIR was used to measure variations in the concentration profiles in the carbonyl absorption region (1649-1815 cm(-1)). Difference FTIR spectra and deconvolution techniques were employed to detect new compounds formed as well as minor concentration changes in oil components. NMR and FTIR results were utilized to study the role of different hydrocarbon types in the oxidation of base oil and to establish the reaction mechanism responsible for the degradation of base oils.