Intrinsic Mechanism Of Inferior Coker Gas Oil With Low Sulfur Content And High Nitrogen Content Which Is Difficult To Hydrotreat

Lightweight and cleaner production of inferior heavy oil is the focus of current refining technology development.Hydrotreating is the main means to achieve efficient conversion of inferior heavy oil.However,the difficulty of hydrotreating low-sulfur and high-nitrogen inferior coker gas oil becomes an urgent problem to be solved.To this end,the paper aims to reveal the interaction mechanism of hydrodesulfurization of sulfur and nitrides under different N/S mass ratios and provide a theoretical guide for the performance improvement of inferior coker gas oil hydrotreating catalysts,which is based on the hydrogenation of model compounds(such as dibenzothiophene,acridine and carbazole)and coker gas oil.The experimental results show that the H₂S produced by the dibenzothiophene hydrogenation reaction increases the amount of Bronsted acid and-SH groups on the catalyst,promotes the cleavage of the C(sp³)-N bond HDN reactivity.However,the presence of H₂S inhibits the hydrogenation of the aromatic ring substituted by the nitride and the cleavage of the C(sp²)-N bond.Therefore,the hydrogenation activity and hydrogenolysis activity of the catalyst must be balanced,and the sulfide content of the reaction system is one of the influencing factors.The low content of nitride has a significant inhibitory effect on the HDS reaction of DBT.The HYD path is more affected than DDS path;For the DBT hydrodesulfurization,acridine inhibits more strongly than carbazole.The inhibitory effect mainly comes from the acridine hydrogenation intermediate(OHA1),while the inhibitory effect of carbazole is because of itself.The apparent adsorption equilibrium constants of acridine and carbazole on NiW/Al₂O₃ catalyst are 3.62×10^-2 g/?g and 2.45×10^-3 g/?g at 340?,respectively.The reaction order is 1.49 and 1.18,respectively,indicating that the adsorption capacity of acridine is greater than that of carbazole,occupying more active centers,and inhibiting the adsorption and reaction of sulfides.The apparent adsorption equilibrium constant of hydrodesulfurization of Liaohe coker gas oil is 1.59×10^-3(?g S·g^-0.9h)^-1which is at 340?over NiW/Al₂O₃ catalyst.Meanwhile,the reaction order is about 1.9.When the N/S mass ratio is lower than 0.79,the sulfide promotes the removal of nitrides from Liaohe coker gas oil.Among them,the promotion effect of basic nitrogen is the most obvious,and the removal rate is increased by 20 percentage points.The total nitrogen removal rate is similar to the non-basic nitrogen removal rate,and the change trend is basically the same,indicating that improving the hydrodenitrogenation rate of Liaohe coker gas oil still needs to start with increasing the non-basic nitride removal rate.The inhibitory factor of sulfide HDS by nitrides in Liaohe coker gas oil is much smaller than that of the model system.There is no linear relationship between the inhibitory factorand the N/S mass ratio.When the nitride concentration in the system reaches a certain level,the inhibitory effect becomes stable.