Performance And Kinetics Of NO_x Reduction With NH₃ Over Sulfated Sintered Ore Catalysts

Nitric oxide?NO_x?has great harm to environment and the human health.It has great importance of the denitrification of sintering flue gas.The sintered ore had good catalytic activity in the catalytic reduction of NO_x in sintering flue gas,and the denitrification efficiency was about 60%.So,the cost of using sintered ore as the catalyst for NH₃-SCR is very low.But with the increasingly stringent emission standards in China,the denitrification performance of sintered ore catalyst?SOC?is slightly insufficient,so it is necessary to further improve its denitrification performance.In this study,sulfuric acid solution was used to modified sintered ore.The sulfated sintered ore catalyst?SSOC?was prepared.The effects of preparation conditions on the performance of SSOC catalysts were studied.The results showed that SSOC-5?5 denotes sulfuric acid concentration?had the excellent denitrification performance when it was impregnated in 5mol/L sulfuric acid solution for 30 minutes and calcined at 400?for 3hours.The SSOC catalysts were characterized by XRF,XRD,BET and XPS.The results showed that the main active components of SSOC catalysts were iron oxides and iron sulfates.In-situ results represented that NH₃,NO and O₂ adsorbed on the catalyst surface to form NH₄⁺,amide?-NH₂?,weakly adsorbed NH₃,nitrate species and weakly adsorbed NO₂.DRIFTS results showed that sulfuric acid can enhance the number and intensity of acidic sites on the surface of the catalyst,and strengthen the adsorption and activation ability of SSOC catalyst for reaction gas,so the SCR reaction was promoted.On these bases,the effects of reaction temperature,NH₃/NO,GHSV,SO₂ and H₂O on the denitrification performance of SSOC-5 catalyst were systematically investigated.The experimental results show that the temperature window of SSOC-5 was 250-350?,NO_x conversion of SSOC-5 catalyst reaches 92.28%at 300?,NH₃/NO=1.0,GHSV=5000h^-1.The presence of SO₂ in flue gas has inhibitory effect on the denitrification activity of the catalyst.The NO_x conversion was 90%when SO₂was100ppm.The inhibitory effect is obvious when SO₂ and H₂O exist in flue gas.After300min,the NO_x conversion was reduced to 80%.The reaction kinetics of SOC and SSOC-5 catalysts were analyzed by using power function kinetic model.For SOC catalysts,the reaction order of NO,NH₃ and O₂ were1.0,0.3 and 0.15 respectively,and the apparent activation energy of NH₃-SCR reaction was 83.66 kJ/mol.For SSOC-5 catalysts,the reaction order of NO,NH₃ and O₂ were 0.8,0.06 and 0.1 respectively,and the apparent activation energy was 59.93 kJ/mol.After sulfuric acid modification,the apparent activation energy of sulfated sintered ore catalysts decreases significantly,which is more conductive to the reaction.