NH3-NO SCR Catalysts for Engine Exhaust Gases Abatement: Replacement of Toxic V2O5 with MnOx to Improve the Environmental Sustainability

Mn-WO/TiO catalysts were investigated for Selective Catalytic Reduction (SCR) of NO with NH. The catalysts were synthesized by wetness impregnation method with different Mn loadings (1.5-3-12 wt%) on 8wt%WO/TiO. All three catalysts were compared with 8wt%WO/TiO and bare MnO oxide, used as references. The 1.5wt%Mn-8wt%WO/TiO exhibited the highest performance in NO conversion and N selectivity. A commercial catalyst, based on titania supported vanadia and tungsta, (VO-WO/TiO), widely used for its high efficiency, was also investigated in the present work. The morphological, structural, redox and electronic properties of the catalysts and their thermal stability were studied by several techniques (N adsorption/desorption, X-ray diffraction, H temperature-programmed reduction, NH temperature programmed desorption, X-ray photoelectron spectroscopy). The aim of this paper is to study the effect of different Mn loadings on 8wt%WO/TiO with the ambition to obtain highly active and selective catalysts in a large window of temperature. The replacement of toxic vanadium used in the classic VO-WO/TiO catalyst with MnO in the best performing catalyst, 1.5wt%Mn-8wt%WO/TiO represents an important achievement to improve the environmental sustainability.