Preparation And Performance Of Sulfur And Water Resistant CH₄-SCR Denitration Catalyst For Flue Gas

Nitrogen oxides are the main air pollutants,which not only damage the environment,but also endanger human health.At present,the selective catalytic reduction method（NH₃-SCR）using ammonia as a reducing agent is a widely used denitration technology.In actual working conditions,NH₃-SCR still has problems such as secondary pollution and difficult transportation and storage,and using methane as a reducing agent can effectively avoid these problems.Therefore,methane selective catalytic reduction technology（CH₄-SCR）is a promising denitration technology.The previous research of the research group found that In/HBeta is a CH₄-SCR denitration catalyst with higher activity,but its sulfur and water resistance is poor.In actual working conditions,the problem of sulfur and water in the flue gas is inevitable.Therefore,in this paper,a denitrification catalyst that is resistant to sulfur and water is prepared.In,Al,Si,Ga,Ge,Sn,Sb,Bi were selected as the active center.and taking the NOx conversion rate under sulfur water conditions as the evaluation criteria,the catalyst with In as the active center is selected as the highest activity.On this basis,In was used as the active center,and Al₂O₃,ZrO₂,TiO₂,SiO₂,HBeta,HSSZ-13,ZSM-5,MCM-48,USY and composite metal oxide were selected as the carrier,and HSSZ-13 was selected as the carrier.At the same time,under the sulfur water condition,La₂O₃,Co₃O₄,Cr₂O₃,V₂O₅,CeO₂,CdO,Ga₂O₃,MoO₃,In₂O₃,WO₃,Nb₂O₅,NiO,CuO,Ta₂O₅,Sb₂O₃,SnO₂,GeO₂,Bi₂O₃,Fe₂O₃,MnO₂,ZnO were evaluated for activity.V₂O₅,La₂O₃,Cr₂O₃,Co₃O₄and Ce₂O₃were selected as co-catalysts.The preparation of the catalyst In/HSSZ-13 were further optimized,The experiment used the ion exchange method,HSSZ-13 silicon to aluminum ratio of 6,In ion concentration of 0.012M,ion exchange time of 8h,and calcination temperature of500℃.Under the conditions of 100ppmSO₂and 5vol.%water vapor,In/HSSZ-13 has a relatively high NO_xconversion rate reaching 39.8%at 550℃.In/HSSZ-13 was modified with metal ions and metal oxides of La,Co,Cr,V,and Ce,but the sulfur and water resistance of the modified catalyst was not effectively improved.under sulfur and water conditions,among In/HSSZ-13,In/HSSZ-13 doped and modified with Cr element has a relatively high NO_xconversion rate.Under the conditions of 100ppmSO₂and 5vol.%water vapor,the denitrification performance of the catalyst is significantly improved,and the In-Cr/HSSZ-13 has the best activity,and the NO_xconversion rate can reach 60.9%.Use characterization methods to clarify the influence of calcination atmosphere on catalyst activity.The results show that the morphology,molecular sieve crystal structure,and specific surface area of In/HSSZ-13 and In-Cr/HSSZ-13 under different calcination atmospheres are not significantly different,and both In and Cr are highly dispersed on the molecular sieve.The higher activity of catalyst for Ar+H₂+O₂atmosphere calcination may be due to more acidic sites and redox species,higher（InO）⁺amount,and higher Cr³⁺/Cr⁶⁺ratio.At the same time,In-Cr/HSSZ-13 catalyst was calcined in Ar+H₂+O₂atmosphere and reacted for 10h under sulfur-water conditions,and then the sulfur-water gas was stopped.The catalyst can gradually restore the NO_xconversion rate and remain stable.