| Heavy oil is typically inferior in ultra-viscosity,high density and fluidity,compared with conventional crude oil,which has brought great challenges to exploitation,transportation and processing.Therefore,it is necessary to reduce the viscosity of heavy oil.Thermal upgrading can effectively reduce the viscosity of heavy oil and has obvious advantages such as mature technology and low investment cost.However,free radicals of heavy oil are prone to occur condensation,that will cause system coking and restrict the efficiency improvement of thermal upgrading.Partially hydrogenated aromatics can provide active hydrogen to improve hydrogen transfer.Active hydrogen can effectively block the free radicals of heavy oil,delay coking and improve the depth of upgrading.Polycyclic aromatic hydrocarbons of heavy oil can continuously convert to partially hydrogenated aromatics through hydrogenation with hydrogen in situ produced from Water-Gas Shift Reaction,that has great significance to improve the upgrading of heavy oil.Therefore,in this paper,using in situ hydrogen produced from Water-Gas Shift Reaction as hydrogen source to explore the laws of hydrogenation of polycyclic aromatic hydrocarbons over metal salts.Aiming at laying the basis for the development of thermal upgrading process with hydrogen in situ produced from Water-Gas Shift for heavy oil.In this paper,using anthracene as a model compound for polycyclic aromatic hydrocarbons of heavy oil,exploring the laws of hydrogenation of polycyclic aromatic hydrocarbons with Water-Gas Shift over oil-soluble metal salts and water-soluble metal salts.The impacts of the type and content of metal salts and reaction conditions to anthracene hydrogenation with in situ hydrogen were investigated.The effects of metal salts to the reaction of Water-Gas Shift and activate hydrogen were explicated.The interaction between Water-Gas Shift Reaction and anthracene hydrogenation reaction was analyzed.Finally,the mechanism of anthracene hydrogenation with in situ hydrogen produced from Water-Gas Shift over metal salts was explored.The research showed that,the efficiency of Water-Gas Shift Reaction was one of the controlling factors for anthracene hydrogenation;Metal salts could catalyze Water-Gas Shift,that increased the efficiency of anthracene hydrogenation with in situ hydrogen,thereby.When the metal content was 0.05 wt%,the effect of iron naphthenate on anthracene hydrogenation was better than nickel naphthenate.The best ratios of iron naphthenate and nickel naphthenate for anthracene hydrogenation were 0.05 wt%and 0.08 wt%,respectively,and there were synergistic effects in the combination of iron naphthenate and nickel naphthenate.For water-soluble metal salts,when the metal content was 0.05 wt%,Fe?NO3?3·9H2O had the best catalytic effect and better than iron naphthenate.Water-Gas Shift and anthracene hydrogenation reaction promoted each other and they had positive synergy effects.The thermal decomposition products of iron naphthenate and Fe?NO3?3·9H2O were Fe2O3,Fe2O3 could be partially reduced to Fe3O4under Water-Gas Shift,and Fe3O4 was the active component to the reaction of Water-Gas Shift.Therefore,it was possible to increase the efficiency of anthracene hydrogenation with in situ hydrogen.By molecular calculations,indicating that the energy barrier of the OH decomposition reaction in the oxidation-reduction mechanism was 91.67 kJ·mol-1 and the energy barrier for the adsorption of carboxyl groups by the interaction between adsorbed OH and adsorbed CO was 38.61 kJ·mol-1.The energy barrier of the redox mechanism was much higher than carboxylic acid decomposition mechanism,suggesting the intermediates of Water-Gas Shift Reaction prefer to undergo the carboxylic acid decomposition pathway.H-atoms recombination towards H2 was the rate determining step with an energy barrier of 124.47kJ·mol-1. |
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