Preparation Of Catalyst And Mechanism In Hydrogenation Of Polyaromatics

With the stringent requirements of clean oil quality,the reduction of demand in the diesel marketing and the growth of the light aromatics marketing,the effective conversion of FCC diesel that rich in polyaromatics has become a good way for refining and chemical enterprises to tap potential.At present,industrially applied technologies include hydrocracking technology and hydrotreating-catalytic cracking combined processes.Selective hydrogenation of polyaromatics to monocyclic aromatics is the key to the technology.In this paper,we used anthracene as the model compound,made systematic research of the selective hydrogenation mechanism of polyaromatics,optimized the selective hydrogenation performance of Ni Mo/Al₂O₃ catalysts by regulating the P content and calcination temperature.And provided technical support for the utilization of FCC diesel.We studied the reaction pathways of anthracene hydrogenation and its influencing factors.Results demonstrated that anthracene is first hydrogenated to form 9,10-dihydroanthracene,and further hydrogenated to form 1,4-tetrahydroanthracene,1,8-octahydroanthracene and1,10-octaanthracene are simultaneously produced,and finally hydrogenated to form perhydrohydroquinone.By reducing the severity of the raction,the hydrogenation depth of anthracene can be controlled to achieve highly selective hydrogenation.What's more,the presence of sulfur-nitrogen compounds inhibits the hydrogenation of anthracene because of the competitive adsorption,and the inhibition effect of quinoline is stronger than dibenzothiophene.As the temperature increases,the inhibition effect gets smaller.The effect of P promoter content on the hydrogenation activity was investigated.The results showed that the suitable P content allows the catalysts to have more stacking number and shorter length of Mo S₂ slabs,which leads to more exposed active sites.The catalyst with1.0wt%P content exhibits the highest anthracene hydrogenation activity and OHA selectivity.The conversion of anthracene can reach 99.5%and the selectivity of OHA can reach 88.75%at the reaction temperature of 300?.The effect of calcination temperature on the performance of the catalyst was also investigated.It was found that the increasement of calcination temperature could strengthen the interaction between active metals and interaction between active metals and the support,which leads to the active metals were difficult to reduced,thereby reducing the sulfidation degree of the catalysts.The catalyst calcinated at 350? has the best selectivie hydrogenation performance,and its selectivity towards OHA can reach 91.20%at the reaction temperature of300?.Finally,the optimized catalyst was evaluated for Qingdao refinery FCC diesel hydrogenation.When the reaction pressure is 6.0 MPa,the reaction temperature is 340?,the H₂/oil ratio is 500,and the LHSV is 1.0 h^-1,the desulfurization rate can reach 89.0%,the denitrification rate can reach 87.6%,the conversion of polyaromatics can reach 65.4%,the selectivity of monocyclic aromatics can reach 83.0%,and the monocyclic aromatics content can reach 56.4%.In addition,a kinetic model for the hydrogenation of aromatics with corrections was established.