Preparation And Performance Of Mn-based Catalysts For Low-temperature NO Reduction With NH₃ And Their Application In Polyphenylene Sulfide Filter Material

NOx(x= 1,2)originated from the stationary sources can induce many environmental issues.Selective catalytic reduction of NO with NH3(SCR),as a mature technology,has been utilized in practice,of which the core is catalyst.However,commercialized V2O5 + WO3(MoO3)/TiO2 catalyst still has some drawbacks,including high working temperature window(300-400 ?),toxic V-based catalyst,and so on.Besides,to reduce the influences of flue ash and SO2,the catalyst should be installed at downstream of the dust removal and desulfurization devices,where the flue gas temperature(<200 ?)is lower than the working temperature window of existent catalysts.Therefore,development of SCR catalysts with excellent low-temperature(<200 ?)activity is important.Moreover,the high-temperature calcination treatment and high-pressure hydrothermal treatment are inconvenient for the preparation of SCR catalysts.Thus,this paper is dedicated to the simple preparation of SCR catalysts with outstanding low-temperature catalytic activities.And the active components were in-situ supported on the surface of inert polyphenylene sulfide(PPS)dust filter material according to the mechanism of relevant preparation methods,which endowed PPS dust filter material with denitration function.Unary MnOx/CNTs and MnO2/PDOPA@CNTs catalysts were fabricated via Na2CO3 in-situ precipitation method and poly(dopamine)(PDOPA)method,respectively.The NO conversion of optimal catalyst prepared by Na2CO3 in-situ precipitation method could achieve 57.4-89.2%at 80-180 ?,and 56.0%when 50 ppm SO2 was introduced(180 ?,5h).In order to reduce the contamination of acid treatment for carbon nanotubes(CNTs)and provide a functional platform on the surface of CNTs,PDOPA method was applied for the preparation of MnO2/PDOPA@CNTs catalysts.The NO conversion of optimum catalyst could reach 57.4-93.4%at 80-1 80 ?,and 68.5%when the 50 ppm SO2 was added(1 80 ?,5h).Furthermore,the catalyst presented a low Ea(19.2 kJ/mol),which was conducive to the SCR reaction.In order to improve the low-temperature SCR activity and SO2-resistance of unary Mn-based catalysts,one-step incipient wetness method(ethanol as solvent)and ambient-temperature redox methods were adopted to fabricate binary Mn-based catalysts,respectively.One-step incipient wetness method was in favor of the uniform dispersion of active components,and therefore,the Mn-FeOx/CNTs catalysts with superior comprehensive performances were obtained.To fulfill the simple preparation of binary Mn-based catalyst,the ambient-temperature redox methods(RM)were adopted to prepare the Mn-FeOx/CNTs-RM and Mn-CeOx/CNTs catalysts.The NO conversion of optimum catalysts could achieve 70.2-100%and 52.2-98.4%at 80-180 ?,as well as 78.9%and 84.2%after the introduction of 50 ppm SO2(1 80 ?.5h),exhibiting better relevant properties than the optimal unary Mn-based catalysts.The Ea(16.9 kJ/mol)over optimum binary Mn-CeOx/CNTs catalyst was lower than the Ea(19.2 kJ/mol)over optimal unary catalyst,further elucidating the outstanding SCR activity from the perspective of Ea.The mechanisms of room-temperature redox reactions were proposed,which provided a simple strategy for the fabrication of binary denitration filter material.To explore the low-temperature SCR activity and SO2-durability of ternary Mn-based catalysts,the Ce2O3-CeO2-CuO-MnO2/CNTs and MnO2-Fe2O3-CeO2-CeO2/CNTs catalysts were synthesized by room-temperature redox methods.The first-rate catalysts presented 66.0-85.1%and 52.8-99.4%NO conversion at 80-180 ?,as well as 74.1%and 80.0%NO conversion when 50 ppm SO2 was introduced(180 ?,5h).The formation mechanisms of ternary Mn-based SCR catalysts were proposed,which contributed to a mild technique for the preparation of ternary denitration filter material.In order to endow PPS dust filter material with denitration function,the active components were in-situ decorated on the surface of PPS via the mechanism of relevant redox reactions and the modification of modifier(MF).And the denitration filter materials over binary MnO2-CeO2-Ce2O3/PPS-MF and ternary Mn-Fe-CeOx/PPS-MF with excellent SCR activity were fabricated.The NO conversion of optimum denitration materials could reach 27.5-93.5%and 36.3-100%,whereas they reduced to 21.0%and 24.3%when 50 ppm SO2(180 ?,5h)was fed,indicating that they were possessed of salient low-temperature SCR activities,as well as general SO2-tolerance.