Study On Catalyst For Hydrogenation And Debenzolization Of Light Naphtha

With the continuous growth of the people's demand for material living standards and the continuous progress of industrial technology,the solvent oil products are developing in the direction of more harmless and green.As one of the raw materials for the production of solvent oil,light naphtha has been widely concerned because of its high content of alkanes and naphthenic hydrocarbons and less benzene content.Now,in order to make solvent oil more environmentally friendly,on the basis of producing solvent oil with light naphtha as raw material,a small amount of benzene is also needed to be removed.Catalytic hydrogenation is the most important technology for the hydrogenation and removal of benzene from light naphtha.This technology focuses on how to remove benzene from light naphtha to the greatest extent under mild technological conditions,and it has become a research hotspot in the field of benzene removal.In this paper,the preparation methods of Ni/Al₂O₃,Ni-B/Al₂O₃ and Raney Ni/Al₂O₃ are discussed in detail.The main factors that affect the catalytic activity of the three catalysts are systematically investigated,and the influence principles of these factors are explored from the microscopic perspective by means of XRD,BET and other characterization methods.In this paper,orthogonal experiments were conducted to evaluate the effects of three catalysts on the final conversion rate of light naphtha hydrogenation and debenzene reaction,and the best experimental conditions were given.?1?Ni/Al₂O₃ catalystThe Ni/Al₂O₃ catalyst was prepared by equal volume impregnation method with Al₂O₃ as the carrier.Four preparation conditions were studied by orthogonal test.They were Ni load,impregnation time,calcination time and calcination temperature.It can be seen from the orthogonal experimental results that the Ni loading and calcination temperature have great influence on the catalytic activity in the preparation conditions,and the influence of impregnation time and roasting time on the experimental results is relatively small.Four influencing factors were further explored by means of XRD,TPR and hydrogenation activity evaluation.The results show that the proper increase of the load is beneficial to the improvement of the activity of the catalyst.The high temperature of roasting reduces the activity of the catalyst.The effect of calcination time and impregnation time on the experimental results is not significant.But the shorter calcination time and impregnation time will increase the activity of the catalyst slightly.Therefore,it is concluded that the preparation of benzene can reach more than 98wt%when the loading amount is 25?,the calcination temperature is 550?,the roasting time is 3 h,and the impregnation time is 3h^-1.?2?Ni-B/Al₂O₃ catalystIn this paper,Ni-B/Al₂O₃ catalyst was prepared by liquid phase deposition.The influence of activation time,activation temperature,nickel boron ratio and nickel content on the activity of Ni-B/Al₂O₃ catalyst was investigated by orthogonal test.It can be seen from the results that the activation temperature and the content of nickel have great influence on the activity of the catalyst.By means of single factor test and XRD BET characterization,the optimum activation conditions were obtained as follows:nickel loading is 5wt%,Ni-B ratio is 1:3,activation temperature is 220?.The activation time is 30min.Under the optimum operating conditions,the Ni-B/Al₂O₃ catalyst prepared on this condition can make the conversion of benzene in the light naphtha reach 60wt%.?3?Raney Ni/Al₂O₃ catalystIn this paper,Raney Ni/Al₂O₃ catalyst was prepared by kneading method.The results of hydrogenation and debenzene reaction of light naphtha under different reaction conditions were evaluated by orthogonal test.It can be seen from the results that the reaction pressure has the greatest influence,followed by the reaction temperature and the volume ratio of hydrogen and oil,while the effect of air velocity is less.Through the single factor experiment,the optimum reaction conditions are as follows:the temperature is 140?,the reaction pressure is 0.2MPa,the volume ratio of hydrogen and oil is 120,the airspeed is 2h^-1.Under this condition,the conversion rate of benzene is close to 100wt%.To sum up,under the action of Raney Ni/Al₂O₃ catalyst,the conversion rate of naphtha hydrogenation and debenzene reaction is close to 100wt%.,and the conversion rate is about 98wt%under the action of Ni/Al₂O₃ catalyst,while the conversion rate is only about 60wt%under the action of Ni-B/Al₂O₃ catalyst.Therefore,the Raney Ni/Al₂O₃ catalyst prepared from nickel aluminum alloy powder and pseudo-boehmite has high hydrogenation activity and can be widely used in the field of light naphtha hydrogenation and benzene removal.