Study On The Performance Of Low Temperature DeNO_x And Anti-H₂O/SO₂ Poisoning On Fe-based Catalysts

With rapid economic development,human production and life are inseparable from the combustion of coal and other energy sources.During the combustion of industrial coal,NO_x,SO_x and other fumes emitted have caused serious pollution to the atmosphere.Sulfur oxides control technology has basically been formed,but the technology to control nitrogen oxide emissions is still in the stage of continuous exploration.It has been confirmed that NH₃ selective catalytic reduction of NO?NH₃-SCR?technology is currently recognized as the most effective technology for controlling nitrogen oxide emissions.Because of its good catalytic activity and high N₂ selectivity,it is widely used in fixed source tail gas denitration processes.In the industrial tail gas treatment process,in order to prevent the catalytic efficiency from reducing or catalyst deactivating under high sulfur,the flue gas denitration system is generally applied to the wet desulfurization device,but a certain amount of H₂O and untreated clean SO₂ in flue gas will still exist after the wet desulfurization,which requires the catalyst to have good catalytic activity in the presence of H₂O and SO₂.This article designs and studies the SCR activity and H₂O/SO₂resistance of Sb-and Zr-doped Fe-based catalysts based on the above requirements,as follows:?1?A series of Fe_ySb_z O_x catalysts were prepared by co-precipitation method,and tested for NH₃-SCR activity,N₂ selectivity,and water/sulfur resistance.A variety of characterization methods such as XRD,XPS,H₂-TPR,NH₃-TPD,and in situ DRIFTs were used to explore the reasons for the excellent catalytic activity and selectivity of the catalyst.From the results of XPS and in situ DRIFTs,it can be seen that the addition of Sb causes a strong electronic interaction between Fe and Sb,and the electron transfer of Sb³⁺to Fe³⁺occurs,i.e.the 2Fe³⁺+Sb³⁺?2Fe²⁺+Sb⁵⁺redox cycle was existent.The introduction of Sb could significantly improve the adsorption of NO_x species and its conversion into N₂ and H₂O,and help to form surface adsorbed oxygen?O_??,which is conducive to promoting SCR reactions and increasing N₂ selectivity.In addition,the reaction mechanism of the catalyst was explored by in situ DRIFTs.The study found the NH₃-SCR reaction on pure Fe₂O₃ follows the E-R mechanism,while Fe_0.7Sb_0.3O_x has both E-R and L-H mechanism.?2?The reason why the Fe_0.7Sb_0.3O_x catalyst has good H₂O/SO₂ resistance was studied.By loading NH₄HSO₄ on the catalyst surface and pretreating the catalyst through sulfation,it was concluded that doping Sb can promote the decomposition of NH₄HSO₄ on the surface,thereby improving H₂O/SO₂ resistance of the catalyst.?3?A series of Fe_yZr_zO_x catalysts were prepared by the citric acid method,and NO_x conversion and N₂ selectivity were tested.It was found that the addition of a small amount of Zr can improve the catalytic performance of Fe₂O₃.XRD,H₂-TPR,in situ DRIFTs and other technologies were used to study the reason why the catalyst has good catalytic performance.From the XRD results,the citric acid method can incorporate Zr into the Fe₂O₃ lattice and the introduction of Zr can induce the crystal phase transition of Fe₂O₃.In order to study the effect of crystal phase transition on the activity,?-Fe₂O₃ and?-Fe₂O₃ were tested separately.As a result,it was found that the crystal phase change had no effect on the catalytic activity.In addition,it is known from H₂-TPR and in situ DRIFTs that the introduction of a small amount of Zr can increase redox property and surface acidity of the catalyst,and adjust two properties to reach equilibrium,which increases the NH₃-SCR activity of the Fe₂O₃.