Regeneration of the Waste Selective Catalytic Reduction Denitrification Catalyst by Nitric Acid Washing

In this study, the waste V₂O₅-WO₃/TiO₂ denitrification catalysts from the coal-fired power plant were washed with water or nitric acid, followed by impregnating different contents of V₂O₅. The effects of the HNO₃ concentration and the additional amount of vanadium on the low-temperature selective catalytic reduction denitrification activity were investigated under the condition of high concentration of SO₂ and H₂O. The catalysts were characterized by inductively coupled plasma optical emission spectrometry, X-ray powder diffraction , N₂ adsorption/desorption, H₂-temperature-programmed reduction, NH₃-temperature-programmed desorption , Fourier transform infrared spectroscopy , and Raman spectroscopy. The evaluation results revealed that optimum activity was achieved by using 0.8 mol/L HNO₃ solution and loading 1.60 wt % V₂O₅ to make the total V₂O₅ reach 2.3 wt %. The characterization results showed that nitric washing can remove most of the ammonium salts deposited on the surface of the waste catalyst and produce crystalline WO₃, which can effectively inhibit the agglomeration of vanadium species in the process of impregnation. Furthermore, it can also increase the amount of oligomeric VO , which can improve the denitration activity.