V₂O₅-WO₃/TiO₂ Catalyst Denitration Performance And Optimization Of K Poisoning Performance

In recent years,air pollution has become the focus of public attention.And the nitrogen oxdie is a typical atmospheric pollutant.The selective catalytic reduction of NO by NH₃ has been considered as the most effective and widely used flue gas denitration technology,and the denitration catalyst is the key unit for this technology.At present,the commercial catalyst is V₂O₅-WO₃/TiO₂ which works under a high temperature and dust flue gas environment.However,the alkali metal in the flue gas will cause serious deactivation of the catalyst.Therefore,it is paramount to optimize the commercial V₂O₅-WO₃/TiO₂ catalyst to improve the denitration performance and alkali resistance of the catalyst.Firstly,the V₂O₅-WO₃/TiO₂ catalyst was used as the research object in the article,the TiO₂ with different exposed crystal faces was prepared by hydrothermal method,the V₂O₅-WO₃/TiO₂ catalysts with different exposed crystal planes of TiO₂ were studied.The activity,anti-K poisoning performance and water and sulfur resistance of these catalysts were tested,as well as TEM,XRD,Raman,N₂-physisorption,XPS,NH₃-TPD,and H₂-TPR characterization of the catalysts.And it is found that VWT-NRs catalyst with TiO₂ mainly exposed to the{100}face has the best denitrification performance and anti-K poisoning ability,which benefits from the more chemisorbed oxygen,and stronger interaction between active species and support,resulting in surface acidity,redox properties increased.The adsorption and activiation of the reaction species enhanced,so that the catalyst has the best activity and anti-K poisoning performance.Secondly,a new high-efficiency anti-K poisoning V₂O₅-WO₃/TiO₂-CeO₂-ZrO₂catalyst was prepared which the TiO₂ support modified by Ce⁴⁺and Zr⁴⁺.The denitrification and anti-K performance of the new catalyst were detected.And the physicochemical properties and mechanism of anti-K poisoning were characterizatied by XRD,BET,NH₃-TPD,H₂-TPR,and XPS.The results show that the co-doping of Ce⁴⁺and Zr⁴⁺can effectively improve the denitrification activity and anti-K poisoning ability of V₂O₅-WO₃/TiO₂ catalyst,and the reaction temperature window can be broadened.The NO_x conversion of fresh V₂O₅-WO₃/TiO₂-CeO₂-ZrO₂ catalyst can be achieved 97%during 300-400 ^oC.After the introduction of 1 wt%K₂O,the V₂O₅-WO₃/TiO₂ catalyst has been completely deactivated at this temperature,however,the modified catalyst still has a denitration activity of 75%.It can be seen that Ce⁴⁺and Zr⁴⁺co-doping can improve the surface acidity and redox performance of the catalyst,but also effectively reduce the impact of K poisoning.This is mainly because Ce⁴⁺can be combined with K to form Ce-O-K,which can protect the active species.And the addition of Zr⁴⁺can enhance the thermal stability of Ce⁴⁺,which making more Ce⁴⁺and K bonds,thereby maximizing the ability of the catalyst to resist K poisoning.The in-situ DRIFTS experiment showed that the NH₃-SCR reaction over V₂O₅-WO₃/TiO₂-CeO₂-ZrO₂ catayst followed an L-H mechanism,furthermore,K-poisoning did not change the reaction mechanism.In addition,the catalyst also exhibited good water and sulfur resistance.When H₂O and SO₂ were introduced at 350 ^oC,the activity was 15%higher than that of V₂O₅-WO₃/TiO₂ catalyst.Finally,the effects of introduction of Ce⁴⁺and Zr⁴⁺on denitrification permormance and anti-K poisoning performance of the catalysts were investigated,and the molar ration of Ce⁴⁺/Zr⁴⁺was optimized.The study found that the impregnation method can improve the activity of the catalyst,but it does not enhance the anti-K poisoning ability for 1wt%K₂O.However,the co-precipitation method can better improve the denitration performance of the catalyst,but also enhance the anti-K poisoning performance.It was found that the co-precipitation method can greatly improve the surface acidity and redox perfmance of the catalyst,and it can be effectively maintained after K poisoning.Furthermore,the Ce⁴⁺/Zr⁴⁺doping molar ratio was optimized,when the molar ratio of Ce⁴⁺/Zr⁴⁺was 2:1,the catalyst had the best anti-K poisoning performance.At 300-400°C,the catalyst still has an excellent denitrification activity up to 86%after K poisoning.