H2O and SO2 deactivation mechanism of MnOx/MWCNTs for low-temperature SCR of NOx with NH3

The effect of H2O and SO2 on the catalytic activity of manganese oxides supported on multi-walled carbon nanotubes (MnOx/MWCNTs) for low-temperature selective catalytic reduction (SCR) of NOx with NH3 was studied. Also, N-2 adsorption, transient response experiments, X-ray powder diffraction (XRD), Raman spectroscopy, Fourier transform infrared (FT-IR) spectroscopy and in situ FT-IR spectroscopy were performed to investigate the deactivation mechanism of MnOx/MWCNTs catalyst in the presence of H2O or SO2. Experimental results showed that H2O had a reversible negative effect on the catalytic activity of the catalyst. When the temperature was higher than 270 degrees C, the effect of H2O could be negligible. The competitive adsorption of H2O and NH3 on the Lewis acid sites contributed to the deactivation of the catalyst. The integrity increase of MWCNTs in the presence of H2O might be another reason for the deactivation of the catalyst. However, SO2 led to the irreversible deactivation of the catalyst. The higher the reaction temperature, the more dramatically the catalystic activity decreased. The sulfation of the active center atoms was the main poisoning route. Also, formation of ammonium sulfates on the catalyst surface and the competitive adsorption between SO2 and NO were responsible for the partial deactivation of the catalyst to some extent. (c) 2013 Elsevier B.V. All rights reserved.