Catalytic Oxidation Denitrification And Anti-Sulfur Stability Study Based On Zr And Cu Modified Fe/TiO₂ Catalyst With Vaporized H₂O₂

Using vaporized H₂O₂ steam as the oxidant,catalytic oxidation denitrification technology catalyzed the oxidation of NO into high-valence nitrogen oxides which would be adsorbed in the absorbent to achieve the removal of NO_x.This method not only had higher efficiency in the low-temperature reaction windows,but also had the advantages of low investment cost,small floor space and simple system transformation.Therefore,this technology could be applied to the start-stop and low-load stage of large-scale power station boilers,as well as to various industrial furnaces.In the field of catalytic oxidation denitrification,Fe/TiO₂ catalyst had become a very promising catalyst due to its low cost,easy acquisition and high efficiency.However,due to the poor resistance of Fe/TiO₂ catalyst to SO₂,its industrial application value was limited.Therefore,we first prepared a series of Fe/TiO₂ catalysts with different Fe loading ratios by co-precipitation method,and tested their denitrification reaction activity in the low temperature reaction windows（120℃-240℃）in the presence of SO₂.In the 24h stability test,the sulfur poisoning phenomenon of2%Fe/TiO₂catalyst was found.Subsequently,a series of characterizations such as XRD,BET,XPS,EPR,FTIR and SO₂-TPD explained the mechanism of sulfur poisoning from the perspectives of the catalyst crystal structure,surface oxygen vacancies and surface sulfate.The research results showed that SO₂ was oxidized to form adsorbed SO₃ and a series of sulfates were attached to the surface of the catalyst,resulting in the loss of active sites.At the same time,the chemically adsorbed oxygen Oαwas also consumed by SO₂,thereby reducing the surface oxygen vacancy concentration.Strongly adsorbed sulfate was also formed inside the cell of the 2%Fe/TiO₂ catalyst,destroying the unit cell structure.these factors commonly led to the phenomenon of sulfur poisoning in the catalyst.On the basis of this research,the Fe/TiO₂ catalyst was modified with active metals Zr and Cu,aiming to improve the stability of the catalyst against SO₂.Through experiments,the optimal doping ratio of Zr and Cu and the optimal reaction conditions were screened out in the low-temperature reaction windows（120℃-240℃）,and then the 24h stability test were carried out respectively.It was found that the anti-sulfur stability of Zr-Fe/TiO₂ catalyst and Cu-Fe/TiO₂ catalyst were both improved,but the doping of Zr would decrease the oxygen vacancies of the catalyst.The doping of Cu could not only improve the sulfur resistance but also increase the oxygen vacancies of the catalyst,thus improving the removal efficiency.Subsequently,a series of characterizations such as XRD,XPS,EPR,FTIR and SO₂-TPD were carried out to clarify the importance of Zr and Cu doping on the improvement of stability from the perspectives of the catalyst crystal structure,surface oxygen vacancies and surface sulfate.The research results illustrated that the doping of active metals could effectively reduce the consumption of chemically adsorbed oxygen by SO₂ and decrease the steady-state sulfate content,thereby ensuring a certain surface oxygen vacancy concentration and protecting the active sites from being covered by sulfate.