Selective Asphaltene Precipitation from Hydroconverted Bottoms

A novel method is described that selectively precipitates the least soluble asphaltenic material from hydroconverted bottoms (HCB) using a dual immiscible solvent approach. This approach separates asphaltenes from the deasphalted (DAO)/precipitant layer by adding acetonitrile (CH3CN) as a second immiscible phase. The three phase system precipitates asphaltenes to the bottom which becomes separated from the top DAO/precipitant layer by a middle CH3CN layer. Due to some CH3CN dissolving in the DAO/precipitant layer, the solvent parameter (and possibly other chromatographic or specific interactions) of the precipitating medium is increased causing less overall asphaltenes to be precipitated, but more of the least soluble precoke-like asphaltenes are selectively precipitated. This treatment produces DAO that is more thermally stable with regard to coke formation compared to DAO generated using only the aliphatic precipitant which precipitates out more asphaltenes. The immiscible CH3CN layer reaches a steady state saturation level of HCB components and can be reused multiple times without additional treatment. HCB components that become dissolved into the CH3CN are primarily smaller molecular weight aromatics with very little contamination from Ni and V complexes.