Investigation of relations between properties of vacuum residual oils from different origin, and of their deasphalted and asphaltene fractions

Abstract

36 vacuum residual oils, obtained from all available groups of crude oils in the world along with their deasphalted oils and their asphaltene fractions have been investigated in this work. Correlations were derived which show that the vacuum residual oil bulk properties density, Conradson carbon content, and viscosity correlate with residual oil hydrogen content, H/C atomic ratio, the fraction of aromatic carbon, saturate, and asphaltene content. It was found that the VRO metal (Ni+V) content was almost evenly distributed between the maltene and the asphaltene fractions. The data in this work presented contradictory facts about the molecular weight of the VRO asphaltene fractions. The simulation distillation data (ASTM D-7169) and Goosens’ correlation support the statement of Mullins et al. that the asphaltene fractions may have molecular weight of about 750g/mole. The atmospheric residue physical distillation data (ASTM D-5236) and Riazi’s boiling point distribution model, however support the statement that the asphaltenes are concentrated in the higher boiling point, higher molecular weight VRO fractions. The higher the aromaticity of a heavy oil, the higher its viscosity is. Since the asphaltenes are the most aromatic compounds in a heavy oil their influence on the heavy oil viscosity is the biggest among all other heavy oil constituents. The converted vacuum residual oils (from visbreaking and residue ebullated bed H-Oil hydrocracking) demonstrated lower dependence of viscosity on the asphaltene content. This could be a result from decreasing of the dimensions of the macro-structure of the converted asphaltene molecule.