The Preparation Of The Denitration Catalysts Used In CO-SCR Process And Their Proformance Evaluation

NO_x is a kind of major pollutants for air.NO_x emission from refineries accounts for about 10% of total emission of NO_x into air.Although the amount of NO_x emission from refineries is not enough large,it causes great harm to the environment and health of human body since the most of refineries are located closely to the human living area.Fluid catalytic cracking?FCC?unit is the major source of NO_x emission in refinery.Until now,there is not an effective denitration technology for the effluent of partial regenerator in refinery.According to the composition of flue gas from partial regenerator,a new selective catalytic reduction?SCR?technology is developed in which CO is used as reductant.The paper aims at developing a proper catalyst used in this new process.A series of catalysts were prepared with Al₂O₃ as carrier via Sol-gel method,and were modified with multiple kinds of metal oxides,respectively.The catalytic performance of developed catalysts was evaluated by a fixed bed microreactor.And the proper conditions,such as the loading amount of active component,calcination temperature,volumetric ratio of CO and NO,space velocity and reaction temperature were determined.The effects of SO2 and pretreatment under reducing atmosphere on the catalytic activity were investigated.The relationship between the structure of catalyst and its performance were explored by means of BET,XRD,TG and N2 isothermal adsorption-desorption curve.Moreover,the reaction kinetics of NO and CO was determined.The main contents of this paper are of as followings:Adopt sol-gel method,a series of catalysts with Al₂O₃ as carrier were prepared in which copper oxide,iron oxide,nickel oxide,silver oxide and chromium oxide were used as the active components.The catalystic activity evaluation results demomstrated that the C uO/Al₂O₃ catalyst possed the best catalytic activity,and the proper loading amount of C uO was 8wt.%.Modified with CeO2,Cr₂O₃,Co2O3,ZnO and La2O3,respectively,it was found that C uO-Cr₂O₃/Al₂O₃ catalyst had the highest catalytic activity under lower temperature.The proper loading amount of Cr₂O₃ was 1wt.%.XRD pattern of CuO/Al₂O₃ catalyst illustrated that the dispersion of CuO at Al₂O₃ surface was better when the loading amount of C uO was less than 10 wt.%,and the XRD pattern of CuO-Cr₂O₃/Al₂O₃ catalyst only appeared characteristic diffraction peaks of ?-Al₂O₃ crystalline,it meant that copper and chromium elements on the carrier surface were well dispersed.Besides,CuO and Cr₂O₃ had a better synergy.The effects of preparations and application conditions of catalysts on the removal efficiency of NO were investigated.When the loading amount of C uO was less than 5wt.%,the catalytic activity of catalyst prepared by sol-gel was better.The suitable calcination temperature was 750?.The characteristic results by XRD,BET and N2 isothermal adsorption-desorption curves indicated that catalysts calcined at 750? possessed higher crystallinity and moderate pore structure.The pretreatment in reducing atmosphere would improve activity of catalysts.XRD patterns of catalyst dispayed that the activity of catalyst enhanced since the Cu2+ on surface of catalyst was reduced in C u0 and Cu1+,and the catalyst pretreated under H2 atmosphere had higher activity than that under CO atmosphere.The pretreatment temperature had little effect on the removal efficiency of NO.The proper volumetric ratio of CO to NO and space velocity were 1.2 and 13000 h-1,respectively.Moreover,the impact of SO2 on removal efficiency of NO was investigated,and it was found that the removal efficiency of NO could keep at above 80% before the catalyst was saturated by sulfur element.Based on the composition characteristics of flue gas from partial regenerator,it could be dierctly used to regenerate the deactivated catalysts.By means of the periodic operation of multiple reactors,the target o f stable operation could be achieved.By a fixed bed microreactor,the kinetics of CO and NO on CuO-Cr₂O₃/Al₂O₃ catalyst was determined.The results demonstrated that the CuO-Cr₂O₃/Al₂O₃ catalyst could effectively reduce the activation energy of CO and NO,and the activation energy of reaction was 34.5kJ/mol.