Solvent fractionation is a very important process with in the refinery. It is a key process in readying some products of the refinery for commercial use. Solvent fractionation is a different from distillate in a variety of ways. Distillation achieves fractionation by using differences in boiling points to separate the components of the crude oil. Solvent fractionation uses the solubility or insolubility of molecular components in a solvent to separate the key components. This process is also called deasphalting and uses vacuum distillation residue as it’s feedstock. During the first step of deasphalting the vacuum distillation residue is completely dissolved in aromatic solvents. Examples of these aromatic solids are benzene and toluene. The highest molecular weight component of VDR is called asphaltene and can be separated by precipitation using a light paraffin solvent. This light solvent is mixed with the VDR previously solubilizied in a aromatic solvent. VDR is just a abbreviation for vacuum distillation residue. Maltenes are a portion of VDR that is soluble in the light solvent. This light solvent also defines the characteristics of the separated asphaltenes. Even a lighter solvent, propane, is used to separate n-pentane solubles. This process yields soft resins and oil products. The power of non-polar solvent is measured by the Hildebrand Solubility Parameters, also know as HSP. The 1st Hildebrand parameter is dependent on two variables, surface tension and molar volume of the solvent. The 2nd Hildebrand Parameter is dependent upon energy vaporization and molar volume. Both these parameters are accurate at expressing a dissolving power of a solvent. These parameters can be calculated using the equations given within the notes. Solubility parameters increase with increasing density with surface tension, or increasing latent heat of vaporization. It is for those properties that aromatic solids have higher solvent power then aliphatic hydrocarbons. In review the strength of nonpolar solvents is described by the two hildebrand solubility parameters.