Effects of MoOx on dispersion of vanadia and low-temperature NH3-SCR activity of titania supported catalysts: Liquid acidity and steric hindrance

Monometallic (V/TiO2 and Mo/TiO2) and bimetallic (V-Mo/TiO2) catalysts were prepared for selective catalytic reduction (SCR) of NOx with NH3 at low temperatures (100-300 degrees C). The effect of MoOx on the dispersion of vanadia with different V2O5 loadings was investigated on the basis of X-ray diffraction (XRD), inductively coupled plasma optical emission spectrometry (ICP-OES), N-2 adsorption-desorption, Raman spectroscopy, ultraviolet-visible (UV-Vis) spectroscopy, X-ray photoelectron spectroscopy (XPS), H-2 temperature-programmed reduction (H-2-TPR) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). As the molybdenum precursor, NH4Mo7O24 increased the solution acidity and promoted polymerization of VOx in liquid phase. At a low vanadia loading, polymerization of VOx, the adsorption rate of NH3 and transformation of active intermediate species -NH2 were enhanced by adding MoOx, while at a high vanadia loading, the steric hindrance became dominant leading to the formation of crystalline V2O5 and MoO3 and caused decline in SCR activity.

Automated summary

This study investigated the effect of MoOx on the dispersion of vanadia with different loadings using various analysis methods. The results showed that the addition of MoOx enhanced the polymerization of VOx and the activity of SCR reaction at low loadings, but led to a decline in activity at high loadings.