Study On Hydrothermal Visbreaking Of Inferior Heavy Oil Of Venezuela

With the continuous exploitation of crude oil,the current growth in lighter liquid oils demand is outpacing the supply of conventional crude oil sources.This gap is being filled through the production of unconventional oil sources,such as inferior heavy oil and bitumen.This kind of oil resource is characterized by high viscosity,high density,high heteroatom content and high metal content,which brought great challenges to its exploitation,transportation and processing.How to upgrade this kind of inferior heavy oil efficiently has become the hotspot in research.Study on visbreaking and hydrothermal visbreaking of Venezualan heavy oil was carried out in this paper in order to find ways of upgrading heavy oil efficiently.The influence of reaction conditions on visbroken oil quality was analyzed,based on which the kinetic model was built.Gas composition and structure of asphaltenes in visbroken oil before and after thermal reaction was examined to reveal how the steam and transition metal catalysts affect the visbreaking process of Venezuelan vacumm residue.The coke formation was suppressed and the stability of visbroken oil was improved in the hydrothermal visbreaking process.With the presence of transition metal catalysts,more active hydrogen was transferred from water to heavy oil through steam reforming reaction.As a consequence,the heavy oil was upgraded.The sort order of ideal conversion ratio of VR was CHVB>HVB>VB on the condition of the same coking rate(0.1w%).The result of kinetic research shows that the reaction rate of VR to all the products in HVB process was lower and the corresponding activation energy was higher comparing to the rate in VB process,which revealed that the steam can mitigated the thermal conversion of VR by releasing active hydrogen radical.Transition metal catalysts can effectively improve the reaction rate by changing the reaction route and reducing the activation energy.The blending experiment was carried out to screen the optimum technology condition and the result was 410?,20 min,steam to oil ratio 6w%,nickel naphthenate addition 0.1w%,at which it can make its upgraded oil suitable for transportation.The analysis of gas composition shows that steam did participate in the thermal reaction rather than chemically inert.Hydrogen was produced by steam reforming reaction between steam and VR compounds in the presence of catalyst and then consumed in hydrodesulfurization and the inhibition of hydrogen abstraction from macrohydrocarbon molecules.The reaction of chain cleavage,hydrogenation,ring opening and hydrodesulfurization happens between steam and heteroatom compound is the important part of hydrothermal visbreaking reaction of VR.