Research On The Preparation And Denitrification Performance Of Low Temperature SCR Catalyst

Nitrogen oxide is one of the pollutant, and the important factor that acid rain, photochemical fog form. Selective Catalytic Reduction (SCR) processes have been widely developed to convert the NOx to nitrogen and H₂O and thus limit the environment pollution. The low temperature (60℃-210℃) SCR unit upstream of the electrostatic precipitator,which decreased the operation cost and decreased the dust poison on the catalyst and prolonged catalyst(?)s life. Therefore there have been strong interests to develope highly active catalysts for low-temperature SCR .The catalysts were prepared by adding manganese nitrate and iron nitrate solution into TiO₂ sol. The preparation of MnO_x/TiO₂ and Fe₂O₃-MnO_x/TiO₂ needs the catalysts. Dried the older gelatin in 105℃, studied calcinations temperature of 450℃, 500℃, 550℃, 600℃to the catalyst active influence. As the gel was dried at 105℃, calcinatined at 500℃, the NO reduction can achieves best.The catalysts(?) denitrification activity was investigated on a fixed bed reactor.Studied the main factors include: reaction temperature, n(NH₃)/n(NO) ratio,O₂ content and flue gas inflow etal.The experimental temperature during 120℃-150℃, MnO_x/TiO₂ molar ratio of 0.4, the most appropriate n(NH₃)/n(NO) is 1.2, Fe loading of the 8% , the temperature of 120℃, the activity of the catalyst to achieve the best for the removal of NO up to 100%.The performances of catalysts were characterized by surface area (BET),thermogravimetry(TG-DTA) and X-ray Diffraction (XRD) methods. The results showed that carrier TiO₂ was of anatase crystal structure, most manganese oxide and ferric oxide were doped in the surface of the carrier as armorphous state while others were of Mn₂O₃, MnO and the Fe₂O₃ crystal structure. BET results showed that additive Fe helped increasement of specific surface area and deduction of hole volume. The XRD results showed Mn element existed in the form of Mn₂O₃ and the MnO structure, additive of the iron increased the dispersion degree of Mn on the carrier, while few assistant Fe exisited as the Fe₂O₃ crystal with others of indefinite states. TG/DTA The TG/DTA test result showed the catalyst structure didn't change with increasing temperature, which indicated that temperature has no significance on the structure.