Study on the mean dipole moments of Dagang atmosphere residue fractions

The mean dipole moments of Dagang atmosphere residue (DG-AR) fractions were investigated. DG-AR can be partitioned into six fractions: saturates and light aromatics, heavy aromatics, light resins, middle resins, heavy resins, and asphaltenes. The mean dipole moments of these fractions are 1.19, 2.88, 3.79, 4.92, 6.36, and 11.70 Debye, respectively, which increase from saturates and light aromatics to asphaltenes. This result is consistent with the differences in solubility of solvents used in liquid chromatography separation. The contents of hydrogen, carbon, nitrogen, and sulfur in each fraction were also measured. Opposite to the polarity, the H/C ratio of the residue fractions decreases from saturates and light aromatics to asphaltene. The ratios of S/C and N/C of the residue fractions vary in the same sequence of the mean dipole moment, which indicates that the hetero-atom content is a factor that influences residue polarity.