Study On Catalytic Hydrodealkylation Of 2-methylnaphthalene To Naphthalene

Coal tar contains a large number of polycyclic aromatic hydrocarbon derivatives with side chains,and its components are small in content and dispersed in distribution,and monomer separation has poor economic efficiency.These polycyclic aromatic hydrocarbon derivatives are subjected to a dealkylation normalization pretreatment and then separated to obtain a relatively single component such as a bicyclic ring,a tricyclic ring or a tetracyclic aromatic compound.This can achieve efficient and refined utilization of polycyclic aromatic hydrocarbons in coal tar.In this paper,2-methylnaphthalene was used as the research object.Catalytic hydrodemethylation of 2-methylnaphthalene to naphthalene was carried out in a pressurized reactor.The law of removing the side chain of fused aromatic hydrocarbon derivatives and the selection of suitable catalysts were investigated,It provides theoretical and data support for the efficient and refined utilization of polycyclic aromatic hydrocarbons in coal tar.The SiO₂,Al₂O₃,ZSM-5,HY,Beta zeolite was used as a carrier for the catalytic hydrodealkylation of 2-methylnaphthalene at a reaction temperature of 480?,an initial pressure of 2Mpa,and a reaction time of 4h.It was found that HY zeolite as the carrier has the best catalytic effect.Therefore,an in-depth study of HY zeolite was conducted.A series of W/HY and Ni/HY with different active metal contents were prepared by using equal volume impregnation method with ammonium metatungstate and nickel hexahydrate as precursors,and HY zeolite as carrier for catalytic hydrodealkylation of 2-methylnaphthalene.The results show that the catalytic effect of W/HY catalyst is better than that of Ni/HY catalyst in HY zeolite catalyst with different metal components.For the W/HY catalyst,the selectivity of naphthalene was the highest when the loading was 6%,which was 64.22%.At this time,the conversion ratio of 2-methylnaphthalene was 81.23%.At the same time,6W/HY was used as catalyst to study the effect of reaction conditions on the performance of 2-methylnaphthalene catalytic hydrodealkylation.For Ni/HY catalysts,a suitable loading is between 3%and 6%.On this basis,the prepared catalyst was characterized by XRD,BET and NH₃-TPD,H₂-TPR,and the effects of specific surface area,acidity and reduction performance of the catalyst on the hydrodealkylation of 2-methylnaphthalene were investigated.In order to further improve the catalytic performance of W/HY catalyst for the hydrodealkylation of 2-methylnaphthalene,different amounts of La promoter were added to the 6W/HY catalyst for modification.The research shows that the introduction of La additive can not only improve the dispersibility of active metal W on HY zeolite,but also enhance the acidity of the catalyst.When the introduction amount of La is 0.8%,the catalyst has the best catalytic effect.The conversion of naphthalene was 87.48%,and the selectivity of naphthalene was 68.52%.