Application And Performance Of Bimetallic Pd-based Catalyst In Anthracene Hydrogenation

Polycyclic aromatic hydrocarbons widely exist in heavy fossil resources.The presence of polycyclic aromatic hydrocarbons in oils will reduce the cetane number of oil products and degrade their quality.Incomplete combustion and emission of polycyclic aromatic hydrocarbons will cause serious environmental pollution and pose a great threat to human health.The catalytic hydrogenation of polycyclic aromatic hydrocarbons is a key topic in the utilization of heavy fossil resources.The development of highly active catalysts is the key technology of polycyclic aromatic hydrocarbons hydrogenation.Supported noble metal catalysts are important catalysts for oil hydrofining in industrial production,and show excellent catalytic hydrogenation activity.In this paper,a series of Pd based catalysts were prepared withγ-Al₂O₃ as carrier and precious metal Pd for the hydrogenation of model compound anthracene.The structure and morphology of the catalyst were analyzed by different characterization methods.The research contents of this paper are as follows:Pd based catalysts with different supports were prepared,and the application of Pd based catalysts with different supports in anthracene hydrogenation was studied.The results showed thatγ-Al₂O₃ carrier showed good activity in anthracene hydrogenation.The carrierγ-Al₂O₃was modified with boric acid and diamine hydrogen phosphate to improve the acid strength of the carrierγ-Al₂O₃,and its effect on the hydrogenation of anthracene was studied.The effect of 5 wt%B₂O₃ modified carrierγ-Al₂O₃ is the best,and the conversion rate of anthracene can reach 97.48%.The effect of 1 wt%P₃O₄ modified carrierγ-Al₂O₃ is the best,and the conversion rate of anthracene can reach 96.95%.The supportγ-Al₂O₃ was prepared by hydrothermal synthesis.The effects of different morphology of supportγ-Al₂O₃ on the hydrogenation of reactive anthracene were studied.It is found that the reaction effect of small sphericalγ-Al₂O₃ is the best when the amount of citric acid is 1.5 g.The activity of catalysts supported onγ-Al₂O₃ with individual metals（La,Zr,Au）was compared.It was considered that Pd metal was the active component in the hydrogenation of anthracene.The application of bimetallic Pd based catalyst in anthracene hydrogenation was investigated.It is considered that Pd metal is the active component of anthracene hydrogenation.PdLa/γ-Al₂O₃ catalyst showed the highest activity,the hydrogenation conversion of anthracene was 100%,and the selectivity of total hydrogenated anthracene was89%.The structure,active metal dispersion and electronic state of the catalyst were analyzed by XRD,TEM and XPS.It is considered that the active metal Pd adsorbs anthracene molecules and catalyzes the transfer of diatomic hydrogen,whileγ-Al₂O₃ promotes the transfer of monatomic hydrogen.The Pd0 species in the catalyst are more electron deficient under the action of La,which inhibits the shedding of intermediate products on the active metal,thus improving the selectivity of total hydrogen anthracene.After the introduction of Zr and Au,the Pd0 species in the catalyst are more electron rich.Although the adsorption binding is weak,it promotes the rate of H₂ molecule to H atom and hydrogen overflow.After the introduction of these three metals,the amount of acid has also been increased in varying degrees,which is considered to promote the hydrogen overflow and improve the selectivity of total hydrogen anthracene.The effect of different La loading on the activity of PdLa/γ-Al₂O₃ catalyst was studied.The results show that when the loading amount of La metal is 1 wt%,the hydrogenation effect is the best,the conversion rate of anthracene is 100%,and almost all of them produce total hydrogen anthracene.Through XRD,BET,XPS and other characterization analysis,the introduction of appropriate La promotes the dispersion of Pd metal.When the load of La is too large,it may cover the active site of Pd metal.It is considered that the binding energy of Pd decreases with the increase of the binding energy of La in a certain range of metal loading,and the binding energy of La increases with the increase of Pd loading.It makes Pd metal form an electron deficient state,which is conducive to the adsorption of anthracene molecules and intermediate products,and promotes the complete hydrogenation of anthracene.The process conditions of anthracene hydrogenation on PdLa/γ-Al₂O₃ catalyst were explored.When the temperature was 275℃,the pressure was 4 MPa and the reaction time was 4 h,the hydrogenation effect of anthracene was the best,anthracene could be fully hydrogenated and the selectivity of total hydrogenated anthracene was 98.49%.