Abstract: To strengthen the effect on vacuum distillation, 0.002% octadecanol was added into Venezuela atmospheric residue oil, resulting in 4.01% more waxy oil yield. The colloid diameter D and solvation factor K of asphaltene were calculated by Einstein law of viscosity and Pals-Rhodes equation based on the measured viscosities of residue oil（asphaltene）-toluene solutions. The results show that the colloid diameter of asphaltene measured by intrinsic viscosity method is the one of adsorption-solvation layer around colloidal nucleus of asphaltene, affected by solvation effect. It is confirmed that the colloidal diameter of asphaltene can be characterized by the viscosities of residue–toluene solution. The trends that the addition of octadecanol reduces the colloidal diameter of asphaltene and solvent effect have a good relationship with the increase of waxy oil yield. The active state of crude oil dispersion system can be predicted based on the colloidal diameter of asphaltene and solvent effect calculated by intrinsic viscosity method.

Key words: active state, intrinsic viscosity, colloid diameter, solvation effect