Sulfur resistance of Ce-Mn/TiO(2) catalysts for low-temperature NH(3)–SCR

Ce-Mn/TiO(2) catalyst prepared using a simple impregnation method demonstrated a better low-temperature selective catalytic reduction of NO with NH(3) (NH(3)–SCR) activity in comparison with the sol-gel method. The Ce-Mn/TiO(2) catalyst loading with 20% Ce had the best low-temperature activity and achieved a NO conversion rate higher than 90% at 140–260°C with a 99.7% NO conversion rate at 180°C. The Ce-Mn/TiO(2) catalyst only had a 6% NO conversion rate decrease after 100 ppm of SO(2) was added to the stream. When SO(2) was removed from the stream, the catalyst was able to recover completely. The crystal structure, morphology, textural properties and valence state of the metals involving the novel catalysts were investigated using X-ray diffraction, N(2) adsorption and desorption analysis, X-ray photoelectron spectroscopy, scanning electron microscopy and energy dispersive spectroscopy, respectively. The decrease of NH(3)–SCR performance in the presence of 100 ppm SO(2) was due to the decrease of the surface area, change of the pore structure, the decrease of Ce(4+) and Mn(4+) concentration and the formation of the sulfur phase chemicals which blocked the active sites and changed the valence status of the elements.