Visbreaking Of Heavy Oil Under Supercritical Water Environment

Today,global oil reserves are continuously declining,coupled with serious deterioration of quality,high viscosity,high degree of cyclization,high levels of heteroatoms and heavy metals,making it difficult to transport and process heavy oils.It is of great significance to study the visbreaking law of heavy oil in SCW and lay a theoretical foundation for the visbreaking of heavy oil.The visbreaking of heavy oil under high-pressure N2 or supercritical water(SCW)environment was experimentally investigated.Despite the difference in the reaction media,the visbreaking follows the same mechanism,that is,dealkylation and condensation of aromatics.The presence of SCW makes it possible that the visbreaking of heavy oil is transferred to the SCW phase with superior diffusivity by which the visbreaking tends to be controlled by intrinsic reaction kinetics rather than by diffusion.Accordingly,dealkylation occurring in the SCW phase,which is vital to the viscosity reduction of heavy oil,responds sensitively to the increase in reaction temperature.Being the secondary reaction of dealkylation at moderate temperatures,condensation is effectively suppressed with reduced reaction time required for dealkylation.By the introduction of SCW and the adoption of an appropriate reaction temperature,the visbreaking efficiency could be drastically improved together with guaranteed stability of visbreaking products.