| Abstract: | A widely used method to determine base oil aromaticity was introduced by G. Brandes in 1956 and is based on a correlation between the infrared aromatic absorption band at 1610 cm−1 and the aromaticity determined by the n-d-M method. Accurate and absolute aromaticities can be measured by carbon-13 NMR but, infortunately, this technique is not suitable for routine analysis. The aromaticities measured by NMR are almost invariably significantly lower than those obtained by Brandes' method. In this study, the areas of the infrared aromatic bands at 1610 and 815 cm−1 of over 70 base oils with aromaticities ranging from 1–16% were correlated by multilinear regression with their carbon-13 NMR aromaticities. An equation to calculate the aromaticity from infrared absorptions was derived. These aromaticities show an excellent match with carbon-13 NMR data. This new infrared method can be applied as a fast and convenient base-oil quality control tool. |
