On-Column Separation of Wax and Asphaltenes in Petroleum Fluids

• Published in: Energy & fuels 2008-11, Vol.22 (6), p.4019-4028
• Main Authors: Goual, Lamia, Schabron, John F, Turner, Thomas F, Towler, Brian F
• Format: Article
• Language: English
• Subjects: Applied sciences; Constitution and properties of crude oils, shale oils, natural gas and bitumens. Analysis and characteristics; Crude oil, natural gas and petroleum products; Energy; Exact sciences and technology; Fossil Fuels; Fuels
• ISSN: 0887-0624; 1520-5029
• DOI: 10.1021/ef800516j

The utility of a novel method based on the new on-column precipitation and redissolution technique is explored. This method, called waxphaltene determinator (WAD), is strictly solubility-based and allows for the detection of waxes and asphaltenes in minutes. The principle of the method is to first precipitate waxes and asphaltenes together on a ground polytetrafluoroethylene (PTFE)-packed column using methyl ethyl ketone at −20 °C and then redissolve the precipitate with solvents of increasing polarity at different temperatures. Waxes precipitated under these conditions are composed mainly of n-alkanes, with carbon numbers greater than C20, and heptane-soluble alkanes that are slightly to moderately branched. The method is first verified with model compounds, including n-alkanes and commercial waxes, and then applied to waxy crude oils and deposits. The method is compared to differential scanning calorimetry (DSC), and a linear correlation is found between the wax content by WAD and DSC. Asphaltene amounts by WAD also compare well to the gravimetric data.