Study On Reduction Of NO With Mn-Fe-Ce/TiO₂ As Catalyst At Low Temperature And Molding Of Catalyst

Nitric oxide(NO) is one of the major air pollutants. Selective Catalytic Reduction (SCR) has been generally recognized as the most effective removal technology of NO_x emitted from the stationary sources. And the widely commercial used catalyst of SCR must be operated at high temperature over 350℃. To cut down cost and match domestic boiler conveniently, Efficient Catalyst at low temperature was greatly needed. The key to the research of the low temperature SCR catalysts is their resistance to the deactivation of SO2 and H2O. In recent research, Mn-based catalysts have good low temperature activity and good resistance to the deactivation. Result of Mn-Ce /TiO₂ catalyst which was studied previous in our workgroup conformed to this point. Therefore, this research focused on development of new style Mn-based catalyst which has excellent low temperature activity and good resistance to the deactivation.The Mn-Fe-Ce/TiO₂ catalyst was prepared by impregnation method. The influence of component ratio, calcination temperature, feed composition, gas hourly space velocity(GHSV),oxygen content and NH₃/NO on NO conversion were examined.The effect of steam and SO₂ was discussed.The results showed that when Mn:Fe:Ce was 5:2:4, calcination temperature was 500℃, Mn-Fe-Ce/TiO₂ catalyst indicated good SCR activity at low temperature.When in the absence of steam and SO₂, NO conversion was about 98% at 130℃. Addition of Fe improved the resistance to the deactivation of H2O and to the deactivation of both SO2 and H2O. In presence of steam with 10%(v/v), the conversion was more than 96% at 130℃. The NO conversion decreased only from 99.9% to 97% within 400 min after SO₂ and H2O were added into the reaction gas. When only SO₂ was added, the activity would be seriously affected and couldn't recover after SO₂ off. Transient response experiments results of NO and NH3 showed that the SCR reaction mechanism on Mn-Fe-Ce/TiO₂ catalyst were consistent with Eley-Ridea's theory.The catalyst that TiO₂ honeycomb ceramics support prepared by sol-gel method, active components supported onto honeycomb ceramics by simultaneously impregnation and with"TiO₂-active components-TiO₂-active components"supporting modes had the best effect. When in the absence of steam and SO₂, about 90% NO was converted at 160℃. And the resistance to the deactivation of H₂O was good. Properties of the catalyst were characterized by means of X-ray Diffraction(XRD), Brunauer Emmett Teller(BET) and Infrared-Ray Test Techniques(IR). A further discussion was made in related mechanism of the deactivation. The results showed that the reason of the deactivation was that the metal oxides were sulfated.With its excellent low temperature activity and good resistance to the deactivation of H₂O, this catalyst is going to be applied in de-NO_x of exhaust gas without SO₂ at low temperature.