Fe-Mn/TiO₂ Catalysts For Catalytic Oxidation Of High Concentration NO And Resistance To Alkali Metal Poisoning

The ammonia selective catalytic reduction（NH₃-SCR）process is currently the most efficient denitrification method since the release of nitrogen oxides in smelting flue gas poses a major threat to the environment and to human health.There are few studies on manganese-based catalysts for high concentration NO removal,despite the fact that they have excellent low-temperature redox performance in NH₃-SCR and are ideal for low-temperature denitrification catalysts.Additionally,their limited operating temperature window and weak resistance to alkali metal neutrality remain the main barriers to their industrial application.In light of the aforementioned issues,this work investigates the denitrification activity and alkali metal toxicity resistance of the catalyst under conditions of high NO concentration using Fe-Mn/TiO₂as the research object.The main findings were as follows:（1）Investigated were the effects of the preparation circumstances on the efficiency of the Fe-Mn/TiO₂catalyst in denitrification.It was discovered that the catalyst had a97.7%denitration rate at 150℃when Fe/Ti=0.3 and was calcined at 450℃for 4 hours.According to the characterization analysis,adding the right amount of Fe to the catalyst increases its specific surface area,surface chemisorbed oxygen content,promotes high manganese oxide dispersion on the catalyst’s surface,lowers crystallinity,and speeds up the SCR reaction.In addition,the catalyst’s oxidative regeneration capacity was significantly improved after the Fe-modification,with a large number of Lewis and Br（?）nsted acid spots present on the catalytic surface,in response to the Langmuir-Hinshelwood mechanism and the Eley-Rideal mechanism.（2）Fe-Mn/TiO₂（0.3）catalyst was selected to simulate alkali metal poisoning.The results showed that the degree of alkali metal deactivation of the catalyst was:K>Ca>Na;With the increase of the content of alkaline metals,the decrease in catalyst dehydration activity increases.The characterization results showed that alkali metals blocked the surface pores of the catalyst,reduced the number of active sites,changed the crystal structure of the catalyst carrier,and affected the catalytic activity.At the same time,the alkali metal inhibited the formation of Mn⁴⁺and Fe³⁺on the catalyst surface,reduced the surface chemisorbed oxygen content,and weakened the catalytic performance of the catalyst,this leads to a decrease in catalyst activity.In situ DRIFTS results showed that alkali metal K inhibited the adsorption and activation of NH₃and NO on Fe-Mn/TiO₂catalyst to a certain extent,and reduced the rate of L-H and E-R mechanisms.（3）Based on the above research results,on the basis of Fe-Mn/TiO₂catalyst,Cu was further doped to improve the denitrification activity and alkali metal resistance of the catalyst.When the Cu/Ti molar ratio is 0.1 and the reaction temperature is 110℃,the denitration efficiency reaches 99.5%,increases the low-temperature activity of the catalyst.The addition of Cu increases the ratio of catalyst surfaceO_αand Mn⁴⁺,and the number of surface acid spots is greatly increased,The redox performance of the catalyst was significantly improved,and finally showed excellent low-temperature SCR activity.