Selective Hydrogenation Of Polycyclic Aromatic Hydrocarbons Over Ni Catalysts

Polycyclic aromatic hydrocarbons(PAHs)are semivolatile organic compounds containing two or more fused benzene rings.Most of these compounds are suspected mutagens and carcinogens and are widely distributed in terrestrial and aquatic environments.They are most formed during the incomplete combustion of fossil fuels.As a consequence of the stringent environmental regulations directed to lower hazard emissions from vehicle exhausts,together with the growing demand for high quality fuels.Catalytic hydrogenation was be regarded as an effective way in the modern refinery strategies.So develop highly active hydrogenation catalysts has a great significance.A highly active nickel catalysts were prepared successfully with co-precipitation method and evaluated in the deep hydrogenation of polyaromatic hydrocarbons(PAHs),including naphthalene and anthracene.The features of the NiAl catalysts were fully investigated via TG,FTIR,XRD,SEM-EDX,HRTEM,BET,H2-TPR,XPS.The nitrogen adsorption-desorption curves showed that NiAl catalyst was characteristic of disordered porous materials,it is worthnoting that NiAl samples possesse higher BET surface area and small particle size about 10 nm.H2 temperature programmed reduction and X-ray photoelectron spectroscopy experiments showed that the moderate metal-support interaction(MSI)could hinder the aggregation of Ni0 in the reduction process and improves the dispersion of the catalyst.From what has been discussed above,the NiAl catalyst calcinated and reduced at 500 ? exhibited high activity and selectivity for the hydrogenation of polyaromatic compounds.The influence of the various reaction parameters(reaction solvents,time,temperature,pressure,etc.)on the hydrogenation of naphthalene with NiAl catalyst were studied in this paper.It was found that hydrogenation of naphthalene is acontinuous reaction,naphthalene is first converted into tetralin,and this is followedby the formation of decalin.Under the mild condition(200?,3 Mpa),NiAl catalyst exhibited excellent performance in the saturated selective hydrogenation of naphthalene to decalin with full conversion and 98.02%selectivity.It was concludedthat hydrogenation of naphthalene fits to pseudo-first-order kinetic well and the activation energy was34.36 KJ/mol,which is lower than the previous studies,it suggesting that the catalyst has excellent hydrogenation performance.In the case of anthracene,the products were mainly consisted of 9,10-dihydroanthracene(DHA),tetrahydroanthracene(THA),sym-1,2,3,4,5,6,7,8-octahydroant hracene(sym-OHA),(cis+trans)-1,2,3,4,4a,9,9a,10-octahydroanthracenes(cis+trans-OHA)and perhydroanhtracene(PHA).The effect of reaction time,temperature and pressure on anthracene hydrogenation conversion and product distribution were studied.We could control the distribution of productsthrough adjustig reaction conditions,at 200 ? and 1Mpa,90.67%of selectivity towards sym-OHA was achieved,and the selectivity of perhydroanthracene(PHA)can reached 96.65%at 200? and 3 MPa.