Promotional Mechanisms of Activity and SO2 Tolerance of NdVOx/TiO2 Catalysts for Selective Catalytic Reduction of NOx with NH3

A series of NdV/Ti- x % catalysts were prepared by a microwave-assisted deposition-precipitation method, and their catalytic performance for the selective catalytic reduction (SCR) of NO by NH 3 was investigated. Impressively, the SCR activity of the obtained catalyst was markedly influenced by the amount of vanadate added. The results show that the NdV/Ti- x % catalysts not only possess good low-temperature catalyst activities but also exhibit excellent SO 2 resistance performances in the presence of 300 ppm SO 2 and/or 10 vol % H 2 O. Furthermore, SO 2 promotes the activity of the NdV/Ti-10% catalyst. These catalysts were characterized using X-ray diffraction (XRD), H 2 temperature-programmed reduction (H 2 -TPR), NH 3 temperature-programmed desorption (NH 3 -TPD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), in situ diffuse reflectance Fourier transforms (DRIFTs), etc. The in situ DRIFT results indicate that the NH 3 -SCR reaction over the well-dispersed vanadate catalyst follows the Eley–Rideal (E–R) and Langmuir–Hinshelwood (L–H) mechanisms. In particular, the SCR reaction following the E–R mechanism is rapid and significantly improves SO 2 tolerance. In addition, the SO 2 adsorption could be restrained on the NdV/Ti-10% catalyst, which effectively restrained the deposition of sulfate species and endowed catalysts with strong SO 2 tolerance. Meanwhile, the effective suppression of SO 2 adsorption allowed the NdV/Ti-10% catalyst to maintain Eley–Rideal (E–R) pathways. This work paves the way for the development of high-performance SO 2 -tolerant SCR catalysts.