Sm-Mn De-NO_x Catalyst And Its Low Temperature Sulfur Resistance Study

In recent years,low temperature SCR technology has become a research hotspot of nitrogen oxide emission reduction technology due to its low energy consumption and operating cost.Among them,MnO_x catalyst has attracted much attention because of its excellent low-temperature denitrification activity,but it is easily deactivated in sulfur-containing atmosphere,which has become the main obstacle for the industrial application of MnO_x catalyst.In this study,Sm-Mn system catalyst was taken as the research object,and its sulfur resistance property and mechanism were studied,which is of great significance for industrial application of MnO_x catalyst.In this study,Sm-Mn catalyst was firstly prepared by coprecipitation method,and the optimal preparation condition of Sm-Mn catalyst was investigated.The relationship between phase composition,structure and performance of Sm-Mn catalyst was studied by XRD,SEM-EDS,and TEM-EDS analyses,and the influence mechanism of preparation condition was revealed by kinetics study.The results showed that there were electron transfer between Sm and Mn element,which can promote the redox cycle of catalytic reaction.When the mole ratio of Sm/Mn was 0.1and the solution adding velocity was 60 d/min and using Na₂CO₃ solution as precipitant,Sm³⁺and Mn²⁺could be uniformly coprecipitated to obtain spherical structure with Sm/Mn atomic ratio close to 0.1 and Sm and Mn elements uniformly distributed.This spherical structure exhibited excellent denitrification activity,maintaining above 80%of the NO conversion at 80²40?.In addition,the anti-SO₂ poisoning mechanism of Sm-Mn catalyst was also studied.The results showed that SO₂ had strong poisoning effects on MnO_x catalyst,mainly because SO₂ reacted with NH₃ to form ammonium sulfate deposited on the catalyst surface and manganese oxides were sulfated by SO₂.In addition,SO₂ would cause the loss of Lewis acid site and Bronsted acid site on the surface of MnO_x catalyst,which would affect the adsorption and activation of NH₃.And at the same time,the adsorption of NO on the surface of the MnO_x catalyst was inhibited,which hindered the SCR reaction.The addition of Sm could significantly improved the SO₂resistance of manganese-based catalysts,and the NO conversion of Sm-Mn catalyst could still be maintained at 75%after 8 hours of 100 ppm SO₂ treatment.Sm incorporation could not only effectively inhibit the sulfation of active components,but also increase the SCR reaction pathway of the catalyst,which was beneficial to enhance the anti-SO₂ poisoning ability.Under the effect of SO₂,More Bronsted acid sites were formed on the surface of Sm-Mn catalyst.These Bronsted acid sites could adsorb NH₃ to produce more NH₄⁺reacting with gaseous or weakly adsorbed NO.Therefore,Sm-Mn catalyst still maintained a certain SCR activity,and its SO₂tolerance was enhanced.