Optimization Of Catalytic Performance And Anti-K Toxicity Of Cerium-based Denitration Catalyst

Nitrogen oxide（NO_x,including NO and NO₂）is one of the main pollutants in the prevention and control of atmospheric environmental pollution.According to the statistics of NO_x emissions in 2019,industrial sources of nitrogen oxide emissions accounted for 44.4%of the national nitrogen oxide emissions,there is an urgent need to research and develop green,energy saving,safe treatment measures to reduce NO_xemissions from industrial sources,and then solve the resulting environmental pollution problems.Ammonia selective catalytic reduction（NH₃-SCR）is one of the most effective application technologies for NO_x removal from fixed source fossil fuel combustion devices.Catalyst is the core part of the SCR system.V₂O₅-WO₃（Mo O₃）/Ti O₂ catalysts have been used commercially due to their high denitration activity,but their poor selectivity of N₂ at high temperatures,and the biological toxicity of vanadium species to the environment limit their wide application in flue gas denitration.Cerium dioxide（CeO₂）is one of the most chemically active rare earth oxides,with abundant sources of no pollution to the environment and good oxygen storage/release capacity.Cerium-tin oxide（CeO₂-SnO₂）catalyst has attracted extensive attention due to their excellent catalytic activity at medium and high temperature and N₂ selectivity.However,toxic inactivation caused by alkali metals in flue gas has also been found.Therefore,this paper attempt to solve these problems by studying environment-friendly cerium-based denitration catalysts.In order to improve the anti-alkali metal poisoning performance of CeO₂-SnO₂catalyst,this paper optimized CeO₂-SnO₂ catalyst from two aspects of preparation method and sulfuric acid pretreatment,and analyzed the reasons for the improvement of catalyst performance through various characterization.The main research results are as follows:Firstly,the CeO₂-SnO₂ denitration catalyst was prepared by hydrothermal method and co-precipitation method,and then potassium species were introduced to simulate the alkali metal poisoning of CeO₂-SnO₂ catalyst.The results showed that the denitration activity of CeO₂-SnO₂ prepared by hydrothermal method was higher than that prepared by co-precipitation method,and its anti-K poisoning performance was increased by 15%.The enhancement of denitration activity and anti-K poisoning were related to the good distribution of Sn⁴⁺and the excellent redox performance and surface acidity.Moreover,the Sn-O in the CeO₂-SnO₂ catalyst prepared by hydrothermal method is more likely to bind with the introduced potassium species,thus protecting the Ce-O active sites.Secondly,the CeO₂-SnO₂/Ti O₂ nanotube（CS/TNTs）catalyst was obtained by loading the CeO₂-SnO₂ component on the titanium dioxide nanotube carrier made of commercial P25.S-CS/TNTs catalyst was obtained by pretreating CS/TNTs with H₂SO₄.Then potassium species was introduced into the fresh catalyst and sulfurated catalyst respectively.The effect of H₂SO₄ pretreatment on the anti-K poisoning of CS/TNTs catalyst was studied.The results showed that H₂SO₄ pretreatment effectively enhanced the anti-K poisoning performance of CS/TNTs.This is mainly because acidification greatly enriches the Br（?）nsted acid sites on CS/TNTs catalyst surface,and also enhances the acidity and surface chemisorbed oxygen content of the catalyst,effectively promoting the catalytic reduction reaction.The introduced potassium species is easy to interact with the sulfate radical on the surface of S-CS/TNTs,thus reducing the toxic inactivation of the potassium species to the Ce-O active site on the catalyst,which makes the acidification catalyst show good resistance to K poisoning.