Preparation Conditions And Performance Of Mn-containing Molecular Sieve Catalysts For Low-temperature NH₃-SCR

Nitrogen oxide (NOx) as one of the major air pollutants does great harm tohuaman health and environmental. At present, Selective Catalytic Reduction (SCR) isthe most favored technologies to remove the NOx in flue gas emissions from stationarysource. And low-temperature SCR technology has attracted more and moreresearchers’ attention due to its features of energy conservation and consumptionreduction and low operation cost. In order to increase the catalytic activity oflow-temperature SCR, the denitration performance of Mn-containing molecular sievecatalysts for low-temperature NH3-SCR were studied in this paper.In this paper, experiments were made through orthogonal design to findappropriate preparation conditions. Impregnation method and citric acid method areapplied to prepare SCR molecular sieve catalysts, respectively. Meanwhile,denitrification performance of catalysts at low temperature and specific surface areawere tested. The preparation conditions of impregnation method and citric acid methodwere respectively optimized by using extreme difference analysis and comprehensivebalance method. The optimal catalyst was decided by their denitrification performanceand specific surface area.Transition metal Fe and Cu are doped into the optimalcatalyst as a promoter to improve the denitration activity. And the paper also hasinvestigated the influence of transition metal on the catalyst structure and surfacecharacteristics with various characterization methods.The results are as follows: the SCR molecular sieve based catalyst prepared byimpregnation method shows better low-temperature catalytic activity when itscarrier isbeta molecular sieve, the capacity for active ingredients of the catalyst8%,thecalcination time6hours,and calcination temperature550℃. The SCR molecular sieve based catalyst prepared by critic acid method shows better low-temperature catalyticactivity when its carrier is beta molecular sieve, the capacity for active ingredients3%,the calcination time5hours, and the calcination temperature550℃. From denitrationefficiency tests and physical and chemical performance results, it was found thatMn3%-beta prepared by critic acid method has good catalytic activity and waterresistance. But the sulfur-resistant behavior of the Mn3%-beta needs to bestrengthened.Doping transition metal Fe and Cu into catalyst Mn3%-beta can increase itsdenitration efficiency and the sulfur-resistant behavior. At90℃, the denitrationefficiency of catalyst Fe1%Cu4%Mn3%-beta is63%. This catalyst could maintain75%of denitration efficiency in the presence of858mg/m3SO2at210℃,it`s better thanMn3%-beta.