Regular solution based approach to modeling asphaltene precipitation from native and reacted oils: Part 2, molecular weight, density, and solubility parameter of saturates, aromatics, and resins

The molecular weight, density, and solubility parameter of the crude oil medium are inputs to regular solution based models for asphaltene precipitation. For native oils, these properties can be determined from a SARA (saturate, aromatic, resin, asphaltene) assay and existing correlations for each SARA component. However, thermo- and hydrocracking alter these properties and these changes must be accounted for when modeling the solubility of reacted oils. The effect of cracking on asphaltene properties was considered in a previous study. In the current study, the molecular weight and density for saturate, aromatic, and resin fractions from 15 native and reacted fluid samples are measured. The solubility parameters of saturates and aromatics are determined by fitting asphaltene precipitation yield data in these solvents with a modified regular solution model. The solubility parameter of resins is calculated using correlations previously developed for the asphaltenes. An elemental analysis of each fraction is also performed. The effect of thermo- and hydrocracking on the SAR fraction properties is discussed. Average properties and correlations are developed to predict the SAR fraction properties in the absence of direct measurements. These properties and correlations are a key step in extending regular solution models for asphaltene precipitation to refinery streams.