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The catalysts of cobalt and cerium doped Mn/TiO 2 were tested for low-temperature selective catalytic reduction of NO with NH 3 , and these samples were characterized by XRD, XPS, Raman, H 2 -TPR and NH 3 -TPD methods. The catalytic activity results showed that the NO x conversion was obviously improved by Co and Ce doping. Ternary metal oxide catalyst Mn-Co-Ce/TiO 2 exhibited the highest catalytic activity of 99 % at 423 K. The XRD and Raman analysis indicated formation of MnO 2 or CoMnO 3 phases on Mn/TiO 2 and Mn-Co/TiO 2 . The XPS results demonstrated that the metal cations existed mainly in the form of Mn 4? , Co 2? and Ce 4? , respectively. XPS and H 2 -TPR results supported the presence of Mn-Co mixed oxides. Doping of Ce could enhance dispersion of Mn-Co oxides on the surface. Addition of Co and Ce led to higher surface Mn 4? /Mn 3? ratio, chemisorbed oxygen, acidity and dispersity, which enhanced NH 3 adsorption and oxidation of NO to NO 2 , subsequently, the NO x reduction was accelerated through the Fast SCR reaction. Graphical Abstract

Abstract:A series of Mn-Co/TiO 2 catalysts were prepared by wet impregnation method and evaluated for the oxidation of NO to NO 2 . The effects of Co amounts and calcination temperature on NO oxidation were investigated in detail. The catalytic oxidation ability in the temperature range of 403-473 K was obviously improved by doping cobalt into Mn/TiO 2 . These samples were characterized by nitrogen adsorption-desorption, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscope (TEM) and hydrogen temperature programmed reduction (H 2 -TPR). The results indicated that the formation of dispersed Co 3 O 4¨C oMnO 3 mixed oxides through synergistic interaction between Mn-O and Co-O was directly responsible for the enhanced activities towards NO oxidation at low temperatures. Doping of Co enhanced Mn 4+ formation and increased chemical adsorbed oxygen amounts, which also accelerated NO oxidation.

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