(173b) Investigation of Asphaltene Precipitation from Bitumen As a Function of Diluent Type and Concentration

Asphaltene precipitation from diluted bitumen has been extensively studied previously; however, previous work has not considered the slow kinetic precipitation of asphaltenes. Consequently, it is important to revisit asphaltene stability in diluted bitumen and monitor asphaltene kinetic precipitation for more accurate estimates of the asphaltene phase envelope and solubility. The amount of asphaltenes precipitated as a function of diluent type and concentration using various bitumen samples was obtained after monitoring the kinetic aggregation process. Bitumen samples with and without the presence of inorganic solids were evaluated, and naphtha and heptol were used as diluents. The results revealed that the mass of precipitated asphaltenes at equilibrium increases with higher diluent concentrations, in agreement with previous work. At low diluent concentrations, the mass of precipitated asphaltenes was similar regardless of the diluent type. At high diluent concentrations, a large difference was observed in the asphaltene solubility between naphtha and heptol diluents. The results showed that the presence of inorganic solids in the bitumen greatly enhanced the rate of asphaltene precipitation. These results suggest a heterogeneous precipitation mechanism for asphaltenes when inorganic solids are present in bitumen or petroleum samples.