Experimental Study On The Characteristics And Preparation Of SCR Denitration Catalyst Mn-Fe-Ce/TiO₂

NOxis one of the major air pollutants. The selective catalytic reduction (SCR) is usedwidely to reduce NOxfrom stationary sources in industry. The SCR DeNOxcatalyst withsulfur resistance at low temperature was prepared to overcome the application problems, suchas high reaction temperature, poor sulfur resistance and so on.First, the Mn-Fe-Ce/TiO2catalyst was prepared by sol-gel method, dipping method,coprecipitation method to study the effect of preparation methods on the performance. Resultsshowed that the sample prepared by sol-gel method with load capacity30%, the catalyst ofmolar ratio of Mn/Fe/Ce4:1:0.1, calcination temperature500℃performed high NOxconversion of over96%at standard reaction condition; MnOx and CeOxwere amorphous onthe carrier surface.The effect of operating conditions including NO input concentrations, O2concentrations,space velocity, NH3/NO molar ratio and reaction temperature on activity of catalystMn-Fe-Ce/TiO2for selective catalytic reduction of nitric oxides by NH3at low temperaturewere investigated. Results showed that the catalyst performed high NOxconversion of over95%when NO input concentration was0.8%(vol), NH3/NO molar ratio was1, O2concentration was3%(vol), space velocity was30000h-1, and reaction temperature was140℃, the continuous experiment showed good stability. Kinetics analysis of Mn-Fe-Ce/TiO2had been carried out. On the premise of removing influence of internal and external diffusion,the activation energy of the reaction and the index factor were calculated according toArrhenius formula, reaction order of NO and reaction order of O2had been attained bycomputing, thus the reaction rate equations of Mn-Fe-Ce/TiO2catalyst were attained.Finally, the effect of SO2on the SCR activity as well as its mechanism were investigateddetailedly. Results showed that a serious deactivation by SO2was detected on Mn-Fe/TiO2and Mn-Fe-Ce/TiO2catalysts. The deposition of ammonium sulfate species on catalyst surface and the sulfation of catalyst active phase were proved to be the main reasons for thecatalyst deactivation in the presence of SO2. Ce doping could effectively inhibit the sulfationof catalyst active phase. The activity decreased more rapidly as SO2concentration increased.The deactivation behavior was irreversible when the concentration of SO2in flue was higherthan70mg/m3. The poisoned catalyst could be regenerated after washed by water. Besides,the catalyst showed good low-temperature activity and stability after modification and itssulfur resistance increased with the addition of SO2.