Performance of Cr-doped vanadia/titania catalysts for low-temperature selective catalytic reduction of NOx with NH3

Cr–V/TiO2 catalysts with different Cr/V molar ratios for low-temperature selective catalytic reduction (SCR) of NO with NH3 were prepared by impregnation. The samples were characterized using X-ray diffraction, NH3 temperature-programmed desorption, H2 temperature-programmed reduction, and X-ray photoelectron spectroscopy. The results show that doping with Cr ions increased the amounts of weak and medium acid sites on the catalyst surface, as well as the low-temperature reductive capacity for high-valence V ions, and promoted the chemical adsorption of oxygen on the catalyst surface, which enhanced the rate of the SCR reaction. The catalyst with a Cr/V molar ratio of 0.2:0.8 and 10 wt% loading gave the largest amount of weak acid sites and the best NOx-removing performance, with a NOx conversion greater than 90% at 160–300 °C. This catalyst had high stability in the presence of 0.01% SO2.

Graphical AbstractA large V4+/V5+ ratio could generate more free electrons, which were formed from the non-stoichiometric vanadium ions at different valence state conversion processes, and they were beneficial in improving the catalytic activity of the SCR reaction.Figure optionsDownload as PowerPoint slide