Study On Carrier Of Heavy-oil Hydrocracking Multi-yield Monocyclic Aromatic Hydrocarbon Catalysts

Heavy oil contains a large number of polycyclic aromatic hydrocarbons,and the polycyclic aromatic hydrocarbons in heavy oil can be efficiently cracked into high-value light aromatic hydrocarbons by hydrocracking technology.The cost of industrial hydrogen sources is relatively high,and in recent years,research on the use of relatively low-cost methane to replace part of hydrogen to achieve heavy oil lightness has gradually emerged,and methane is activated in the hydrocracking reaction to participate in the reaction,which can reduce hydrogen consumption and improve the selectivity of light aromatic hydrocarbon products.The catalyst with β zeolite as the carrier and metal Zn has good hydrocracking activity under methane-containing atmosphere,but the catalyst is easily inactivated in the long-term reaction due to the limitation of the microporous properties of the β zeolite sieve.Therefore,naphthalene was mainly used as a model compound,and the pore structure and acid properties of the β zeolite were improved by acid-base or composite treatment,and the hydrocracking reaction activity and stability of the catalyst under methane-containing atmosphere were improved.Firstly,different catalysts were prepared after treating β molecular sieve with various acid-base solutions and loading the same proportion of metal Zn,and the effects of molecular sieve treatment liquid type and treatment solution concentration on the hydrocracking performance of catalyst under methane-containing atmosphere were investigated by reaction.The results showed that treating the molecular sieve with 0.1 M sodium hydroxide solution for30 min at room temperature β improve the activity stability of the catalyst in the reaction,and treating the molecular sieve with 0.1 M citric acid solution for 30 min at room temperature could improve the reactivity of the corresponding catalyst β.Then,on the basis of knowing that citric acid treatment β molecular sieve can improve the reactivity of the corresponding catalyst,the influence of citric acid treatment solution concentration on the reactivity and stability of the catalyst was studied,and the optimal concentration of citric acid treatment solution was selected.The results show that the treatment of β molecular sieve with 0.08 M citric acid solution can significantly improve the activity and stability of hydrocracking of the corresponding catalyst under methane-containing atmosphere.The conversion rate of naphthalene,BTX selectivity,liquid product yield and carbon deposition were 99.82%,61.84%,90.5% and 2.4%,respectively,and the selectivity of benzene,toluene and xylene was 21.61%,21.48% and 18.75%,respectively.Finally,by treating citric acid β retreating the molecular sieve with different concentrations of sodium hydroxide solution,the reactivity and activity stability of the catalyst can continue to be improved.The results show that the hydrocracking activity and stability of the corresponding catalyst under methane-containing atmosphere can be improved after the βmolecular sieve is treated with 0.08 M citric acid solution and 0.075 M sodium hydroxide solution.The conversion rate of naphthalene,BTX selectivity,liquid product yield and carbon deposition were 99.88%,65.64%,91.43% and 1.97%,respectively,and the selectivity of benzene,toluene and xylene was 22.77%,21.84% and 21.03%,respectively.