Synthesis Of Surface Modified Cerium Based Catalyst And Its Low Temperature Selective Catalytic Reduction Of NO

Nitrogen oxide（NO_x）is one of the common air pollutants,so it is particularly important to take effective measures to reduce NO_x emissions.At present,selective catalytic reduction technology with NH₃ as reducing agent is considered to be the most effective technology to reduce NO_x emissions.At present,V₂O₅-WO₃-TiO₂ catalyst has been used in commercial production,and some problems have been exposed in actual production,such as low operating temperature window（300-400℃）alyst has been used in commeivity,toxicity of V₂O₅ itself,harmful to human health,etc.Therefore,the development of new environmentally friendly and efficient non-v-based catalysts is the current research hotspot.Ce based catalysts are widely used in NH₃-SCR reaction because of their good oxygen storage capacity.However,the low-temperature denitration activity of single Ce based catalyst as active component is not high.Therefore,in order to solve this problem,this paper designed and synthesized new efficient Ce based catalyst to improve the low-temperature activity of Ce based catalyst.In this paper,Ce based catalysts were selected as active components for NH₃-SCR reaction,and the effects of adding different promoters,adjusting plasma parameters,auxiliary treatment and improving preparation methods on catalyst denitration were explored.XRD,BET,TG and SEM were used to characterize the structure of the catalyst.The main research contents are as follows1.In this paper,the impregnation method is used to optimize the content of active components and the first auxiliary agent,and to synthesize three kinds of catalysts:10%Ce-10%Mn-TiO₂,10%Ce-0.5%Mo-TiO₂,10%Ce-0.5%W-TiO₂,The NH₃-SCR denitration activity of the above three catalysts was tested and characterized.The research results show that the 10%Ce-10%Mn-TiO₂ catalyst has the best low-temperature denitrification activity.At 200℃,the NO_x conversion rate is as high as75%;the 10%Ce-0.5%Mo-TiO₂ catalyst,at 250℃,The NO_x conversion rate is as high as 91%,the operating temperature window is T₈₀=225-375℃;10%Ce-0.5%W-TiO₂catalyst,at 250℃,the NO_x conversion rate is as high as 93%,and the operating temperature window is T₈₀=190-440℃.XRD,BET and TG characterization results show that the addition of additives Mn,Mo,W improves the dispersion of active components on the carrier and increases the specific surface area of the catalyst,which may be the reason for the enhanced denitration activity of the catalyst.2.Based on the three catalysts synthesized above（10%Ce-10%Mn-TiO₂,10%Ce-0.5%Mo-TiO₂,10%Ce-0.5%W-TiO₂）,the plasma treatment technology is introduced to assist treatment catalyst.Three methods of roasting,roasting first and then plasma and plasma followed by roasting are used to treat the three catalysts of 10%Ce-10%Mn-TiO₂,10%Ce-0.5%Mo-TiO₂,10%Ce-0.5%W-TiO₂ After treatment,the NH₃-SCR denitration activity was studied,combined with characterization technology to analyze,and finally it was determined that the catalyst was prepared by the method of plasma first and then calcination.The plasma parameters of the catalyst（treatment atmosphere,discharge power and treatment time）were explored,and the respective optimal plasma conditions were finally screened out.10%Ce-10%Mn-TiO₂-PC has the best denitrification activity under the conditions of H₂ atmosphere,150W discharge power and 10min treatment time.The NO_x conversion rate is 85%at 200℃;10%Ce-0.5%Mo-TiO₂ has the best denitrification activity under the condition of H₂ atmosphere,discharge power 100W,treatment time 10min,NO_x conversion rate 94%at 200℃;10%Ce-0.5%W-TiO₂ under H₂ atmosphere,discharge power It has the best denitrification activity under the conditions of 50W and 20min treatment time,and its NO_x conversion rate can reach 100%at 250℃;XRD,BET,TG and SEM characterization results show that the plasma-assisted treatment catalyst can increase The degree of dispersion of the catalyst enhances the denitration activity of the catalyst.3.The three catalysts were prepared by impregnation method,citric acid complexation method and coprecipitation method respectively,and the effects of different preparation methods on NO_x conversion were studied.The results show that the 10%Ce-10%Mn-TiO₂-CA catalyst prepared by citric acid complexing method has the best denitration effect,its NO_x removal rate is significantly improved（T≤200℃）rate is significantly improved(T₆₀=130-280℃,T₆₀=110-330℃)is signif TG results show that some amorphous materials are formed between Ce and Mn,which needs to be verified by other characterization methods;for 10%Ce-0.5%Mo-TiO₂ catalyst,the relationship between preparation method and catalytic performance is as follows:coprecipitation method>citric acid complexation method>traditional impregnation method.The conversion of 10%Ce-0.5%Mo-TiO₂-CO catalyst prepared by coprecipitation method is about 97%at 250℃,which is much higher than that of10%Ce-0.5%Mo-TiO₂-IM（88%）prepared by traditional impregnation method;XRD,BET and TG characterization results show that the catalyst prepared by coprecipitation method increases the specific surface area of the catalyst,improves the dispersion of the catalyst,and finally improves the SCR activity of the catalyst.For 10%Ce-0.5%W-TiO₂ catalyst,the catalyst prepared by coprecipitation method has the highest denitration performance.The maximum NO_x removal rate of 10%Ce-0.5%W-TiO₂-IM prepared by traditional impregnation method is 94%at 250℃,while the NO_x removal rate of 10%Ce-0.5%W-TiO₂-CO prepared by coprecipitation method is more than 98%at 200℃,while the NO_x removal rate of 10%Ce.The maximum NO cipitation method increases the specific surface area of the cataex and coprecipitation increase,which may be the reason for the enhanced denitration activity of the catalyst.