Visbreaking Of Heavy Oil In Mixed Solvent Of Subcritical Water And Light Aromatics

In order to achieve high efficiency viscosity reducing of heavy oil and reduce the severity of the visbreaking process,the visbreaking of heavy oil in a mixed solvent of subcritical water(sub-CW)and light aromatics(LCO)was investigated,to explore the visbreaking effect of heavy oil in mixed solventsDue to the high activation energy of condensation reaction,a mild subcritical water environment was used as reaction medium.It was verified by asphaltene pyrolysis that by solubilizing sub-CW in heavy oil,the dealkylation involved in visbreaking follows not only free radical mechanism but also ionic mechanism.The solubility of sub-CW in oil phase accelerates the dealkylation reaction which determines the viscosity reduction efficiency,and also participates in the inhibition of condensation.To optimize the viscosity reduction effect,it is necessary to further enhance the solubility of sub-CW in the oil phase.LCO was used as the medium to enhance the solubility of sub-CW in the oil phase.The further introduction of light cycle oil(LCO)rich in light aromatics but containing olefin groups has a complicated influence on visbreaking.Due to the presence of olefin groups,the viscosity reduction efficiency is initially reduced.In addition,the condensation to asphaltenes is promoted in the late visbreaking stage.However,these adverse effects are offset by the promotion of the solubilization of sub-CW in heavy oil by light aromatics.With enhanced dealkylation in both free radical and ionic mechanisms,In this paper,the optimal viscosity reduction effect was obtained when the reaction temperature of 370?,water density of 0.2 g/mL,heavy oil/LCO ratio of 10:1,and reaction time of 20 min.A viscosity reduction rate of over 90%and reduced asphaltene formation can be obtained in the middle stage of visbreaking.