Research On Mechanism Of Tin Doped Cobalt Metal Oxides As A Catalyst For NO And Hg~0 Oxidation

Nitrogen oxide as the main air pollutants has become an increasingly serious problem.Flue gas is the main stationary sources of nitrogen oxides.NO_x control technology is difficult to meet ultra-low emission standards,using catalyst oxidizes residue NO of SCR to NO₂,and then combined with a wet absorber to further removal of NO_x is a feasible technical approach.The method can also oxidizes Hg⁰ to Hg²⁺to achieve cooperative control of mercury.This paper examines the different metal oxides as NO oxidation catalyst and screened cobalt oxide for the study.Then tin-doped to cobalt oxide for further improving its NO and Hg⁰ oxidation,while improving the water resistance of cobalt-based catalyst.The main conclusions are as follows:At first,a series of metal oxide catalysts were investigated as NO oxidation catalyst and have the following NO oxidation activity order:Mn>Co>Cu>Ni>Ce>Fe>Zn..The NO conversions over Co and Mn oxides catalysts were more than 80%at a certain temperature range.Then SnO₂-CoO_x catalyst were synthesized by co-precipitation method and NO oxidation activity were evaluated by activity evaluation system XRD,XPS,BET,Hg-TPD,H₂-TPR were used to analyze the catalysts.Sn?0.75?-Co-O has good performance under high space velocity conditions as NO oxidation catalyst,doped tin significantly improve the water resistance of cobalt-based catalyst.The main reason may be:tin added to improve the cobalt-based catalyst specific surface area and the ratio of oxygen chemisorption significantly increased which is further improved redox of catalyst and surface active sites distribution.At the same time,the doped tin oxide improved NO adsorption properties of cobalt oxide,in particular to provide more NO adsorption sites in the presence of water.At last,SnO₂-CoO_x catalyst were tested for mercury oxidation,discuss the mercury oxidation mechanism and the impact of NO composition on mercury oxidation properties.The results showed that,Sn?0.75?-Co-O catalyst also has a good mercury oxidation activity which is more than 90%.The reasons may be that catalyst has a strong performance of Hg⁰ adsorption,a large number of surface oxygen vacancies exist to promote the oxygen adsorption and activation.At the same time,the strength of the catalyst surface basic sites may be appropriate to promote the adsorption and activation of HCl.This paper also found that NO has a role in promoting Hg⁰ oxidation and made the foundation for the development of co-oxidation catalyst of NO and Hg⁰.