Asphaltenes and resins of crude oil from the Usa oil field have been subjected to fractionation. The asphaltenes have been separated into fractions by fractional precipitation with chloroform/hexane solvent blends in the ratios of 30/70, 30/75, and 30/120. The resins have been fractionated by liquid adsorption chromatography on silica gel with hexane/benzene and hexane/ethanol mixed solvents taken in the ratios of 3/1, 1/1, and 10/1, 3/1, respectively. The obtained fractions have been analyzed by 1H and 13C nuclear magnetic resonance spectroscopy and infrared spectroscopy, their molecular masses have been measured, and the elemental composition has been investigated. On the basis of structuralgroup analysis data, the structures of the resin and asphaltene molecules have been hypothesized.
