DETERMINATION OF PHYSICOCHEMICAL PROPERTIES AND CARBON-TYPE ANALYSIS OF BASE OILS USING MID-IR SPECTROSCOPY AND PARTIAL LEAST-SQUARES REGRESSION-ANALYSIS

It has been well recognized that the chemical composition of the base oil is primarily responsible for its physicochemical properties such a s viscosity, viscosity index (VI) and pour point etc., which in turn i nfluence the performance of the finished formulation. Hence, it is ver y essential to determine the chemical composition of the base oil to u nderstand the physicochemical properties. The paper highlights an expe rimental and computational protocol for the simultaneous determination of physicochemical properties (viscosity index and pour point) and ca rbon type analysis (C-A, C-P, C-N, and isoparaffin carbon content, I-P ) of base oils from their IR spectral features. IR spectra of 60 base oils of different origin and processing schemes are recorded using the horizontal attenuated total reflectance accessory with ZnSe windows. Partial least-squares (PLS) technique has been applied to construct th e mathematical models which correlate the IR spectral features with th e experimentally determined values (using NMR and standard ASTM tests) . The regression coefficients are found to be in the range 0.80-0.95.