Detailed Characterization of Virgin Heavy Oil Resid and Its Thermally Cracked Resid

• Published in: Energy & fuels Vol. 28; no. 3; pp. 1664 - 1673
• Main Authors: Xu, Zhiming, van den Berg, Frans G. A, Sun, Xuewen, Xu, Chunming, Zhao, Suoqi
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Washington, DC American Chemical Society 20.03.2014
• Subjects: Applied sciences; Asphaltenes; Blends; Carbon; Conversion; Density; Energy; Energy. Thermal use of fuels; Exact sciences and technology; Fuels; Nuclear magnetic resonance; Pentanes; Solubility parameters; Characterization; Heavy oil
• ISSN: 0887-0624; 1520-5029
• DOI: 10.1021/ef4019383

The vacuum resid of a Canadian bitumen and the resid of its severely cracked product were separated into 16 and 11 fractions, respectively, by supercritical fluid extraction and fractionation with pentane, followed by a comprehensive analysis of the chemical and physical properties of the resulting fractions. Thus, the effect of thermal conversion could be analyzed in detail. Characterization of the fractions included elemental analysis, density and viscosity/temperature relationship, Conradson carbon residue (CCR), molecular weight and distribution by gel permeation chromatography (GPC), boiling point curves by simulated gas chromatography (GC) up to 750 °C, saturates, aromatics, resins, and C7 asphaltenes (SARA), C5 asphaltenes, and proton nuclear magnetic resonance (1H NMR). Moreover, the solubility parameters of selected fractions were determined from the phase equilibria of the oil fraction, propane or isobutane mixtures in a high-pressure PVT cell. The solubility parameter distribution of the C5 asphaltenes was obtained by mixing the asphaltenes with different pentane/toluene blends. The results provide new insights into the detailed mechanism of thermal conversion. Interestingly, the heaviest fractions exhibit a larger compositional change than the lighter fractions. The asphaltene fraction is most affected, which is tentatively ascribed to the presence of multi-core compounds in this end product. The decrease in asphaltene stability is mainly caused by the asphaltenes becoming more insoluble: the change in the solubility parameter distribution of the asphaltenes is larger than a concomitant increase in the solubility parameters of the lighter fractions. The combined analytical data were used to generate typical molecular models for each of the fractions. The observed trends clearly show that the so-called Boduszynski continuum, which has been postulated for virgin crude oils and residua, is also valid for thermally cracked streams.