Catalytic Activity and Surface Characteristics of WO3-doped MnOx-TiO2 Catalysts for Low-temperature Selective Catalytic Reduction of NOx with NH3

The effect of added WO3 on the catalytic activity and surface characteristics of the MnOx-TiO2 system was investigated for the low-temperature selective catalytic reduction of NOx with NH3. Based on physio-chemical characterizations, the specific surface areas of the WO3-MnOx-TiO2 catalysts increased from 76.12 m(2)/g to 90.29 m(2)/g as the WO3 content increased, and the crystallinity of the anatase TiO2 phase decreased. The NOx conversion efficiency of the WO3-MnOx-TiO2 catalysts with WO3 content was over 70% at 200 degrees C, and their efficiency was over 90% at 300 degrees C. The results of Fourier transform infrared spectroscopy indicated that the 1438 and 1632 cm(-1) values, which were assigned to Lewis and Bronsted acid sites, increased with the increase in WO3 content. The enhanced catalytic acidity originated from changes to the physical and chemical structures on the surface. MnOx formed on the TiO2 surface of the 15 wt% WO3-doped MnOx-TiO2, and amorphous state Mn2O3 (Mn3+) and WO3 (W6+) existed on the surface, which led to the improved Lewis and Bronsted acid sites, respectively.