SnO_x-CeO₂-MnOx-loaded spherical activated carbons for the selective catalytic reduction of NO

A series of SnO_x-CeO₂-MnO_x-loaded spherical activated carbons (SACs) with different Sn/Mn molar ratios were preparedas catalysts for the selective reduction of NO and the influence of the SnO_x contenton their catalytic activities was investigated. The physicochemical properties of the catalysts were characterized by nitrogen adsorption, X-ray diffraction, X-ray photoelectron spectroscopy and temperature-programmed NH₃ desorption. Results indicate that the addition of an appropriate amount of SnO_x to the CeO₂-MnO_x-loaded SACs significantly reduces NO reduction activity in the low temperature range 80-120 ℃. However, the NO conversion is higher than 95.8% in the temperature range 200-280 ℃ when the Sn/Mn ratio of the catalyst is 0.25. The SnO_x addition increasesthe acidity of the catalyst surface, especially the number of the medium-strong acid sites, which favors the adsorption anddehydrogenation of NH₃. An appropriate amount of SnO₂ increasesthe dispersion of CeO₂ on the support with out sacrificing the high dispersion of MnO_x. These factors jointly contribute to the increaseof NO reduction activity over the SnO_x-CeO₂-MnOx-loaded SACs at temperatures from 200 to 280 ℃.