WO3-TiO2 catalysts were prepared by an incipient wet-impregnation method for high-temperature selective catalytic reduction (SCR) of NOx. Structure, surface acidity, and catalytic performance of SCR catalyst according to WO3 content (4, 6, 8, and 10 wt.%) were characterized by morphological and spectroscopy analyses. The 10 wt.% WO3-TiO2 catalyst had high conversion efficiency due to the improvement of specific surface area, catalytic acidity, and monolayer capacity of TiO2 support. It was found that tungsten oxide species are dispersed in the interlayer between the grain and the grain boundary of TiO2 support in transmission electron microscopy. The WO3 affected the suppressed grain growth and the improved Bronsted acid sites that could provide much surface acidity by the grain boundary reinforcement. The structural interaction between the proper WO3 content and TiO2 support led to the existence of octahedrally and tetrahedrally coordinated WO3 structures on the surface in the Raman spectra. The enhanced catalytic activity of 10 wt.% WO3-TiO2 is attributed to the increase of the surface acidity (Bronsted acid sites) by the shell formation of WO3 species.

Keywords: WO3-TiO2 SCR catalysts; Surface acidity; Catalytic activity; Shell formation; Grain boundary reinforcement