Separation and Tribological Evaluation of Paraffinic Base Stocks

• Published in: Tribology transactions 1990-01, Vol.33 (1), p.85-95
• Main Authors: Benchaita, M. T., Schwartz, R. D., Lockwood, F. E.
• Format: Article
• Language: English
• Subjects: Applied sciences; Crude oil, natural gas and petroleum products; Energy; Exact sciences and technology; Fuels; Petroleum products, gas and fuels. Motor fuels, lubricants and asphalts
• ISSN: 1040-2004; 1547-397X
• DOI: 10.1080/10402009008981934

A new liquid-solid chromatography method, using a two-stage silica gel, was applied to the separation of nine paraffinic base stocks into hydrocarbon saturates and aromatics, and polar fractions. The base stocks of various crude origin and refining process were tested for their tribological performance in the elasto-hydrodynamic regime and in the boundary regime. Two existing methods of calculation of viscosity-pressure coefficients, one based on chemical composition and the other on physical properties, indicate that the former compares better with experimental data. In wear testing, unformulated base stocks behaved like their aromatic fraction or saturate fraction depending upon crude origin, processing, separation method, and test conditions. Solvent-extracted base stocks of high polar content showed stable friction, whereas hydrotreated base stocks with low polar content showed transition to high friction within a typical temperature range. Most saturate fractions showed average wear rates and stable friction, whereas the aromatic fractions separated from mild hydrotreated base stocks showed higher wear rates and unstable friction.