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

Abstract

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 NH3 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 SO2 resistance performances in the presence of 300 ppm SO2 and/or 10 vol % H2O. Furthermore, SO2 promotes the activity of the NdV/Ti-10% catalyst. These catalysts were characterized using X-ray diffraction (XRD), H2 temperature-programmed reduction (H2-TPR), NH3 temperature-programmed desorption (NH3-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 NH3-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 SO2 tolerance. In addition, the SO2 adsorption could be restrained on the NdV/Ti-10% catalyst, which effectively restrained the deposition of sulfate species and endowed catalysts with strong SO2 tolerance. Meanwhile, the effective suppression of SO2 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 SO2-tolerant SCR catalysts.