Preparation And Denitration Performance Of Sulfate-modified CeO₂-based Catalysts

As one of the components of air pollutants,nitrogen oxides not only caused acid rain,photochemical smog,ozone and other environmental pollution,but also caused pneumonia,bronchitis,cancer and other diseases.NH₃selective catalytic reduction of NO_xwas the most effective nitrogen oxide removal technology.Although the commercial catalyst showed high activity at 300-400℃,its further application in industry was limited due to its narrow temperature window,high toxicity and poor N₂selectivity.Therefore,it was necessary to study environmentally friendly CeO₂-based catalysts.However,pure CeO₂catalyst had some disadvantages,such as low activity and poor nitrogen selectivity.In order to solve this problem,the CeO₂catalyst modified by sulfates was prepared.By promoting the surface acidity of the catalyst,we found that the SCR activity and N₂selectivity of the catalyst were improved.In this paper,by changing the content of sulfuric acid and the preparation method,a series of studies on the catalyst were carried out:（1）By preparing xH₂SO₄/CeO₂catalysts with different sulfuric acid content,the denitration performance of each catalyst was compared when the sulfuric acid content xwas 1%,3%,5%and 10%,respectively.The results showed that the catalyst with x=3%showed the excellent activity and wide activity temperature window.The larger specific surface area,pore volume and average pore diameter were helpful to improve the adsorption capacity of NH₃or NO_x.Moreover,the wider pore size could improve the pore diffusion of reactant gas and promote the conversion of NO_x.The stronger H₂-TPR reduction peak intensity indicated that there were more active species on the surface of the catalyst,which was beneficial to enhance the activity of the catalyst.All of these might be the reason for promoting the SCR activity of 3%H₂SO₄/CeO₂.（2）The 3%H₂SO₄/CeO₂was prepared by different methods.Among them,OP（one pot method）3%H₂SO₄/CeO₂showed the best activity,which could be attributed to its larger surface area,excellent pore volume,favored average pore size and moreO_α/（O_α+O_β）.In addition,the desorption peak of NH₃-TPD overOP3%H₂SO₄/CeO₂possessed weak acid sites and strong acid sites,and the peak intensity was stronger than that of other samples.In conclusion,the above factors might be the main factors for the excellent activity of the catalyst.