In the past decades, gas chromatography-mass spectrometry (GC-MS) with filed ionization (FI) or nitric oxide chemical ionization (NOISE) have been used for the molecular characterization of the lubricant base oils, as well as other petroleum distillation fractions. However, both FI and NOISE have discrimination on saturated hydrocarbons with low degrees of condensation, resulting in relatively lower abundance of paraffins. In addition, GC based techniques were not suitable for analyzing heavy petroleum fractions. In this study, we introduced a novel approach for the molecular characterization of lubricant base oils. The base oils were subjected to ruthenium ion catalyzed oxidation (RICO) derivatization, saturate hydrocarbons in the base oils were oxidized into corresponding alcohols and ketones. The ketones were then reduced into alcohols by lithium aluminum hydride (LiAlH<sub>4</sub>). All the mono-alcohol derivatives were differentiated from other by-products using negative-ion electrospray ionization (ESI) Fourier transform ion cyclotron mass spectrometry (FT-ICR MS). The composition of alcohols can be used to represent the composition of the original hydrocarbons in the base oils. The results were generally agree with the results from FI analysis and more close to the elemental analysis results and the group compositions obtained by ASTM D2786. In addition, the method has no boiling point limit for the heavy fractions. The method is potential to be used for the routine molecular compositional analysis of petroleum lubricant base oils.

Molecular composition analysis of lubricant base oils by using RICO redox derivatization followed by ESI FT-ICR MS

255th National Meeting (2018)

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