Non-pyrolytic heat induced deposition from heavy oils

Deposition below pyrolysis temperatures (<340°C) is due to the heat-induced removal of the intermediate polarity solvating layer around polar asphaltene cores. Predictability is needed to control undesired deposition. Five residua were evaluated for non-pyrolytic heat-induced deposition tendencies. A new hot deposition testing apparatus was devised. Residua were heated in aluminum pans to 100, 175, 250 and 300°C. The heated material was decanted under an argon gas atmosphere and deposition was quantified by microscope as spots per unit area on the lower surface of the pouring pan. Deposition at 250°C was also observed on stainless steel, but not on a Teflon® surface. Using a suspended particle solution model incorporating relative viscosities, Heithaus titration parameters, and asphaltene content, the interaction energy for the solvation of asphaltene cores was estimated for five residua to range from 400–1600 cal/mol. Heat induced deposition tendencies were related to residua system free solvent volumes.