Preparation Of Cu-M(M=Mn,Fe And Co) Mixed Oxide Catalysts And Their Performances In Selective Catalytic Reduction Of NO_x

NO_x, as one of the main air pollutants, is harmful to both environment and human health. Up to now, selective catalytic reduction ?SCR? has been considered as one of the most promising technologies for elimination of NO_x. V-based catalysts have been widely used as commercial catalysts for SCR of NO_x. Nevertheless, some inevitable disadvantages still remain, such as poor activity at low temperature, narrow operating temperature window and the toxicity. Therefore, it is of great importance to develop environmentally friendly catalysts with high catalytic activity for SCR within low-temperature range.In this thesis, copper-based mixed oxide catalysts were prepared and employed in H₂-SCR. Their compositions, microstructures, surface elementary valence state and distribution were defined. The activities of the obtained catalysts were measured for SCR of NO_x with H₂. The relationships between such physicochemical properties and SCR activities were investigated by various kinds of techniques, such as XRD, N₂ physisorption, XPS, H₂-TPR and TEM. The key factors influencing SCR performance were clarified. The main research works are summarized as follows:1. The Cu-Mn, Cu-Fe and Cu-Co mixed oxides supported SBA-15 catalysts were prepared by impregnation method using their nitrates as precursors. Their structural and textural properties were well characterized by XRD, N₂ physisorption, H₂-TPR, XPS and TEM. The experimental results have demonstrated that the obtained ordered mesoporous Cu-Co/SBA-15 catalyst shows the best H₂-SCR performance, which may be ascribed to the fact that it possesses the largest surface areas, best redox properties and the highest surface oxygen species.2. H₂-SCR of NO_x in Cu-Co catalysts with different pore structures were investigated. A series of Cu-Co mixed oxide catalysts were prepared through co-precipitation ?NH₃·H₂O as precipitant? and template methods. Specifically, Cu-Co catalysts with 2D and 3D structures were obtained by using SBA-15 and KIT-6 as templates, respectively. Among them, CuCo-3D mixed oxide shows the best H₂-SCR performance at a low-temperature range of 150-250 ?. The superior SCR performance in CuCo-3D may be associated with its largest surface area and highest surface active oxygen species.3. The effect of Na on H₂-SCR performance in Cu-Mn catalysts was investigated. Cu-Mn mixed oxide catalysts with different amounts of Na were prepared by co-precipitation method with NaHCO3 as a precipitant. The properties of the obtained Cu-Mn mixed oxide catalysts were studied by XRD, ICP, N₂ physisorption, XPS and H₂-TPR. The results of H₂-SCR experiments clearly show that more Na in Cu-Mn mixed oxide catalyst result in lower catalytic activity, which can be ascribed to the decrement of surface area and pore volume as well as the concentration of surface Cu²⁺ and Mn³⁺.