Synergistic effects between copper and tungsten on the structural and acidic properties of CuOx/WOx-ZrO2 catalyst

Different amounts of tungsten oxide were introduced to zirconia to form WOx-ZrO2 solid solutions by a coprecipitation method, followed by impregnation with copper nitrate. The received catalysts were characterized by X-ray diffraction, Brunauer-Emmett-Teller surface area, X-ray photoelectron spectroscopy, Raman spectroscopy, diffuse reflectance UV-vis spectroscopy, H-2 temperature-programmed reduction and in situ FTIR of NH3/NO + O-2 adsorption. Higher dispersions of CuOx are obtained on the tungsten-containing catalysts due to the increased surface area of the support. Highly dispersed WOx clusters in tetrahedral coordination are generated when tungsten exceeds its solubility in the solid solutions, and polymerized WOx clusters are formed for further increasing the loading amount of tungsten. The formation of Cun+ -O2--Wn+ bonds at the interface between CuOx and WOx clusters leads to an improved capacity to form nitrite and an enhanced Bronsted acidity, which enhance the activity of the catalyst for NH3-SCR reaction.