Preparation of highly active manganese oxides supported on functionalized MWNTs for low temperature NOx reduction with NH3

Manganese oxide catalysts (MnOx) supported on functionalized multi-walled carbon nanotubes (FMWNTs) for low temperature selective catalytic reduction (LTSCR) of nitrogen oxides (NOx) with NH3 in the presence of excess O-2 were prepared by the incipient wetness impregnation method. These catalysts were characterized by N-2 adsorption, Fourier transform infrared spectroscopy (FTIR), transmission electron microscope (TEM), X-ray diffraction (XRD), thermal gravimetric analysis (TGA) and H-2-temperature programmed reduction (H-2-TPR) methods. The effects of reaction temperature, MnOx loading, calcination temperature and calcination time were investigated. The presence of surface nitrate species under moderate calcination conditions may play a favorable role in the LTSCR of NOx with NH3. Under the reaction conditions of 200 degrees C, 1 bar, NO = NH3 = 900 ppm, O-2 = 5 vol%, GHSV = 30,000 h(-1) and 12 wt% MnOx, NOx conversion and N-2 selectivity were 97% and 99.5%, respectively. The SCR activity was reduced in the presence of 100 ppm SO2 and 2.5 vol% H2O from 97% to 92% within 6 h at 200 degrees C, however such an effect was shown to be reversible by exposing the catalyst to a helium flow for 2 h at 350 degrees C due to thermal decomposition of ammonium sulphate salts. (C) 2013 Elsevier B.V. All rights reserved.