Evaluation thermal and oxidative degradation of lubricant oil using spectroscopy and chemometrics

The purpose of this study, was to evaluation of the chemical changes in lubricant oil during the thermal and oxidative agent by spectroscopic – chemometrics method. In order to evaluate the reaction, nuclear magnetic resonance spectroscopy was employed to obtain data from lubricant oil used in different kilometres and spectral data were processed by multivariate curve resolution alternating least squares (MCR-ALS) chemometrics techniques to monitoring the reaction .Engine oils consist of a variety of additives dispersed in a hydrocarbon oil [1]. motor oil may contain minute quantities of gasoline, additives (detergents, dispersants, oxidation inhibitors, rust inhibitors ,viscosity improvers) , nitrogen and sulfur compounds, a broad range of aromatic and aliphatic hydrocarbons with chain lengths ranging from C 15 to C50 , and metals such as lead ,(Pb), zinc (Zn), calcium (Ca), barium (Ba) and magnesium (Mg).The prediction of the oil aging processes and the role of additives is complicated. In Figure 1 shows the oxidation reaction in lubricant oils. In general, the oil aging process is an irreversible modification of the physicochemical properties of the oil. [2,3] , MCR-ALS method resolves NMR data into pure spectra of species produced during the reaction and their associated concentration profiles(figure2), in concentration profile (green line), these contaminants arise from heating and oxidation of lubricating oil during engine operation, Used oil contain higher percentages of polycyclic aromatic hydrocarbons (PAHs) compared to fresh oil.. As a result of the oxidation reaction, Alkyl and aryl oxidized forms are produced. Therefor NMR spectra combined with multivariate curve resolution alternative least square have been used widely for monitoring of various chemical reaction.