Study On Mechanisms Of Reaction And SO₂&Alkali Metal Resistance Over Structure Optimized MnCoO_x Catalysts For Selective Catalytic Reduction Of NO_x With NH₃

The flue gas emitted from glass,ceramics industires with typical characteristics such as low gas temperature(180?250?),high nitrogen oxide(NOx)concentration(2000?3500mg/m3),certain amount of sulfur dioxide(SO2)and alkali/alkaline metals.The selective catalytic reduction(NH3-SCR)with NH3 is one of the main purification techniques.Mn based catalysts have been widely investigated in the field of low temperature denitrification due to their more suitable low temperature active windows and mild and non-toxic active components,but the resistance to SO2 and alkali/alkaline metals at low temperature still needs to be further improved.Hence,the structure of the Mn based catalyst was optimized by combining the action mechanism of SO2 and alkali/alkaline metals in order to develop functional materials with excellent low temperature activity and high SO2 resistance and alkali/alkaline metal toxicity,which broaden the application of catalysts.In this paper,on the basis of traditional MnCoOx granular catalysts,the synthesis strategy of functional materials with active site protection was proposed by summarizing the common laws of SO2 and alkali/alkaline metals acting on the catalysts.The multi-stage layered rod-like tetragonal phase t type(Co2+)tet(Mn3+Co3+)octO4 spinel structure catalyst(Mn(1.5)Co(1.5)Ox-ROD)with Mn-enriched surface was designed.The structure was further optimized based on the common laws and differences of their better catalytic and resistance properties,then the Co-enriched surface hollow flower-like microsphere cubic phase c type(Co3+)tet(Mn4+Co2+)octO4 spinel structure catalyst(Mn(1.5)Co(1.5)Ox-HFM)with uniform morphology and large specific surface area was synthesized.This catalyst has excellent low temperature catalytic performance,and its ability to resist SO2 and alkali/alkaline metals toxicity is greatly improved.The low temperature acvitity of the catalyst were enhanced by 16.0%and 88.5%compared to that of the traditional granular MnCoOx catalyst under the conditions of 10 vol%H2O&200 ppm SO2 and 4%supported alkali metal at 150?,respectively.To further clarify the physicochemical properties of the optimized catalyst and the intrinsic reasons for low temperature catalytic activity and resistance enhancement,the structure-activity relationship and reaction mechanism,the action path and resistance mechanism of SO2 and alkali metals were clarified by characterization and DFT calculation.The results showed that Mn(1.5)Co(1.5)Ox-HFM had lower coordination number,the presence of(Co3+)tet(Mn4+Co2+)octO4 structure enables the Mn and Co to exert strong atomic-level interactions,enabling the catalyst to maintain excellent low-temperature catalytic performance.The Co-enriched surface cubic phase structure made the K to exist mainly in the form of Co-O-K binding and protected the octahedral infilled Mn as the main active sites from toxicity.The strong interaction between Mn and Co largely weakens the toxic sites of SO2 and alkali/alkaline metals.The dominant E-R pathway accompanied by the L-H mechanism are less affected by SO2 and alkali/alkaline metals.