Manganese oxide nanorod catalysts for low-temperature selective catalytic reduction of NO with NH3.

Abstract

MnOx nanorod catalysts were successfully synthesized by two different preparation methods using porous SiO2 nanorods as the template and investigated for the low-temperature selective catalytic reduction (SCR) of NO with NH3. The catalysts were characterized by scanning electron microscopy, transmission electron microscopy, nitrogen adsorption, X-ray diffraction, X-ray photoelectron spectroscopy, and NH3 temperature-programmed desorption. The results show that the obtained MnOx-P nanorod catalyst prepared by redox precipitation method exhibits higher NO removal activity than that prepared by the solvent evaporation method in the low temperature range of 100–180 °C, where about 98% NO conversion is achieved over MnOx(0.36)-P nanorods. The reason is mainly attributed to MnOx(0.36)-P nanorods possessing unique flower-like morphology and mesoporous structures with high pore volume, which facilitates the exposure of more active sites of MnOx and the adsorption of reactant gas molecules. Furthermore, there is a lower crystallinity of MnOx, higher percentage of Mn4+ species and a large amount of strong acid sites on the surface. These factors contribute to the excellent low-temperature SCR activity of MnOx(0.36)-P nanorods.