Study On Catalytic Ozonation Of NO By Metal Oxides Catalysts Using ?-Al₂O₃ As Supporter At Low Temperature

Recently,air pollution is becoming more and more serious.As one of the major pollutants,the removal of NO_x has become many researchers'focus.Currently,the denitrification process of flue gas that has been studied has many disadvantages,including high cost,large energy consumption,low catalytic efficiency in low-temperature range,secondary pollution and so on.In order to solve these problems,the catalytic oxidation of NO was investigated by using O₃ as oxidant and?-Al₂O₃ doped with transition metal oxides as catalysts to obtain a high removal efficiency of NO in low temperature.The reaction product was absorbed by ammonia and made into nitrogen fertilizer for resource utilization.The specific research work was as follows:?1?A series of metal oxides catalysts were prepared by incipient wetness impregnation method using?-Al₂O₃ as supporter.Effects of types and doping amounts of main active component and mixed component as well as calcination temperature on removal of NO was investigated in this article.Bisides,some characterization methods,includig SEM,NH₃-TPD,BET,XRD and XPS,were used to identify surface pore structure,surface acid amounts,crystallinity and valence state of the elements of catalysts.Finally 3%MnO_x-CeO_x?0.4?/?-Al₂O₃?500??was chosen as the best catalyst owing to good catalytic activity of MnO_x at low temperature,more activated oxygen species stored and better dispersed MnO_x on surpporter with the addition of Ce.?2?O₃ was selected as oxidant and 3%MnO_x-CeO_x?0.4?/?-Al₂O₃?500??as catalyst in experiment.Different process conditions?NO initial concentration,reaction temperature,GHSV,O₃/NO mole ratio?were studied in ozonation and catalytic ozonation of NO.O₃/NO mole ratio was the most important factor in ozonation system.When O₃/NO mole ratio came to1.0,the conversion rate of NO achived above 90%.Different process conditions influenced efficiency of catalytic ozonation system greatly.When NO initial concentration was 500 ppm,the reaction temperature was 100?,the GHSV was 2100 h^-1 and O₃/NO molar ratio was 0.2,the conversion rate of NO got to above 70%.?3?Resistance of catalyst to H₂O and SO₂ was tested,which showed that catalyst had good resistance to SO₂ but poor resistance to H₂O.Catalyst activity could be improved apparently after water was cut off.When SO₂ and H₂O were added into the flue gas simultaneously,catalyst activity droped sharply.