Abstract
A series of Mn-Ce-V-WOx/TiO2 composite oxide catalysts with different molar ratios (active components/TiO2 = 0.1, 0.2, 0.3, 0.6) have been prepared by wet impregnation method and tested in selective catalytic reduction (SCR) of NO by NH3 in a wide temperature range. These catalysts were also characterized by X-ray diffraction (XRD), Transmission Electron Microscope (TEM), in situ Fourier Transform infrared spectroscopy (in situ FTIR), H2-Temperature programmed reduction (H2-TPR) and X-ray photoelectron spectroscopy (XPS). The results show the catalyst with a molar ratio of active components/TiO2 = 0.2 exhibits highest NO conversion value between 150 °C to 400 °C and good resistance to H2O and SO2 at 250 °C with a gas hourly space velocity (GHSV) value of 40,000 h−1. Different oxides are well dispersed and interact with each other. NH3 and NO are strongly adsorbed on the catalyst surface and the adsorption of the reactant gas leads to a redox cycle with the valence state change among the surface oxides. The adsorption of SO2 on Mn4+ and Ce4+ results in good H2O and SO2 resistance of the catalyst, but the effect of Mn and Ce are more than superior water and sulfur resistance. The diversity of valence states of the four active components and their high oxidation-reduction performance are the main reasons for the high NO conversion in this system.
Highlights
The selective catalytic reduction (SCR) of NOx with NH3 in the presence of O2 has been widely used to control the emissions of NOx from mobile and stationary sources, such as coal-fired power plants and automobiles [1,2,3,4]
It can be inferred that the effect of Mn and Ce are more than superior water and sulfur resistance in the catalytic system
The results of H2 temperature-programmed reduction (H2 -TPR) suggest that active components of the composite catalyst reveal characteristic redox properties, which is different from that of being alone, and the results indicate that the existence of a strong interaction among the active components on the surface of support is conducive to the promotion of reduction performance
Summary
The selective catalytic reduction (SCR) of NOx with NH3 in the presence of O2 has been widely used to control the emissions of NOx from mobile and stationary sources, such as coal-fired power plants and automobiles [1,2,3,4]. V2 O5 -WO3 /TiO2 is the most used commercial catalyst for SCR of NOx at a relatively high temperature platform of 300 ◦ C to 400 ◦ C [5,6,7]. The catalytic performance can be seriously deactivated by H2 O and SO2 in the emission [8,9,10]. A low temperature catalyst with good resistance to SO2 and H2 O is urgently needed for the SCR system to improve the situation
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