A comparison of results of determining the hydrocarbon group-type composition of petroleum samples obtained using various test methods of open-column liquid chromatography

The hydrocarbon group-type composition (so-called SARA -composition) is one of the main characteristics of oil, providing an information about its chemical nature and determining the quality of the obtained petroleum products. In world laboratory practice, data on the hydrocarbon group-type composition of petroleum feedstock are widely used to assess its colloidal stability and compatibility with crude oil, reactivity in various conversion processes, predicting physical properties, etc. Traditionally, the hydrocarbon group-type composition is determined in accordance with standard and research chromatographic methods that differ significantly from each other, which often leads to obtaining incomparable analytical results. In this paper, a comparative analysis of the results of determining the hydrocarbon group-type composition obtained in accordance with two test methods within the open-column liquid chromatography method is carried out for various of petroleum samples of Russian origin (commercial oils of different classes and two petroleum products). Using the standard test method ASTM D4124 (method B) and the research test method developed by JSC VNII NP, the content of identical hydrocarbon groups in the maltene part of petroleum samples was determined: saturated hydrocarbons (SH) and paraffinic-naphthenic hydrocarbons (PNH), naphthenic aromatic (NAH) and aromatic hydrocarbons (AH), polar aromatic hydrocarbons (PAH) and resins (R), respectively. It is shown that with an increase the density and viscosity of petroleum samples, the content of less polar groups (SH and PNH) in their composition decreases and the content of more polar groups (PAH and R) obviously increases, and there is no pronounced distribution pattern of the NAH and AH groups. Statistical processing revealed insignificant differences in the results for «heavy and viscous» oils, despite the large error of those obtained according to the research test method. Obtaining comparable results justifies the use of both test methods not only for the analysis of high-boiling petroleum products, but also for the analysis «heavy and viscous» oil samples.