Preparation Of Mn-Based Composite Oxide Catalysts And The Investigation Of Their NO Elimination Performance

With the rapid development of Chinese economy,China's atmospheric environment is also facing more and more dangers.NOx is one of the most important air pollutants in the world,so it is very important to eliminate NOx.The elimination of nitrogen oxides from the source is of great significance to the maintenance of the atmospheric environment.NH3-SCR is considered to be the best way to eliminate NOx.CO-SCR has been paid more attention because of its ability to eliminate both CO and NO in the tail gas of the reaction at the same time.Mn-based catalyst is an excellent catalyst for denitrification at low temperature in NH3-SCR elimination.In CO-SCR reaction,Mn-based catalyst has a lot of active species because of its variable valence state.Therefore,Mn is the best choice as the research object of our project.The modified citric acid complexation method was used to prepare Mn-Ce-Ti-O catalysts with different content.The results showed that the activity of MCT-15/1 sample reached 100%at 125 "C.At the same time,we found that the doping of MnOx caused that crystal phase of the catalyst was transformed from anatase to rutile to form two-phase coexistence.When the doping content of MnOx was 15%,the integral area ratio of anatase and rutile has equal proportion.Then we tested the valence states of the catalyst elements by XPS,and found that there were electrons transfer of Mn3+ + Ti4+?Mn4+ + Ti3+and Mn3++Ce4+ ?Mn4+ + Ce3+.The H2-TPR results show that unique two-phase coexistence in catalysts was beneficial to the improvement of the reduction performance.A possible reaction mechanism was proposed by in situ DRIFTS analysis.Mn-TiSnOX catalysts with different grain sizes were prepared by changing the ratio of ethylene glycol and ethanol which was mixed solvothermal method.XRD results found that when the ratio of ethylene glycol to ethanol was 1:4,the particle size was the largest.SEM and TEM showed that the catalysts prepared by mixed solvothermal method have typical vesicle structure.Other physical and chemical characterizations investigated that the doping of SnOx improved the specific surface area and redox performance of the catalysts.The activity of the catalyst was greatly improved by the amount of acid sits on the surface of the catalyst.MnFeOx catalyst with flower structure was successfully prepared by ethylene glycol solvothermal method.SEM and BET tests showed that the unique morphology provided a very large frontal specific surface area and pore volume for FeOx.In situ DRIFTS analysis shows that the doping of FeOx improves the CO adsorption ability of the catalyst,which is beneficial to the selectivity of N2 and the activity of CO-SCR.