Enhancing the NH3-SCR denitration activity at low temperature and H2O and SO2 resistance over Nb-modified FeVO4 catalysts

Abstract

Novel Nb-modified FeVO₄ (Nb_aFeVO₄) samples were fabricated via utilizing the citric method for employing in selective catalytic reduction NO_x with NH₃ (NH₃-SCR). The Nb_aFeVO₄ catalysts exhibit good NH₃-SCR activity compared with FeVO₄. In addition, a range of characterization methods was applied to explore the impact of Nb introduction on catalytic activity and tolerance to SO₂ and H₂O, comprising N₂ physical adsorption, XRF, XRD, NH₃-TPD, Raman spectroscopy, H₂-TPR, XPS, SEM, HR-TEM and DRIFTS. The findings demonstrate that the addition of Nb to FeVO₄ can inhibit the crystallization of FeVO₄ and lead to improvement in the specific surface area, thereby exposing a greater number of active sites. The introduction of Nb leads to the increase of acid content on Nb_aFeVO₄, and the increase of specific surface area can effectively improve the NH₃-SCR activity of the catalyst. Among all Nb_aFeVO₄ catalysts, Nb_0.3FeVO₄ exhibits the best catalytic activity, and the NO conversion can reach more than 90 % at 210–360 °C, and it also exhibits better resistance to H₂O and SO₂ than FeVO₄. This can be explained the fact that the addition of Nb can increase the ratio of V⁴⁺/V on the surface of FeVO₄, which can inhibit the ability of the Nb_0.3FeVO₄ catalyst to absorb SO₂ and improve the SO₂ resistance of Nb_0.3FeVO₄. The good water and sulfur resistance of Nb_0.3FeVO₄ makes it in the face of complex flue gas composition in practical applications. Furthermore, the in-situ DRIFTS was utilized to explore the NH₃-SCR reaction mechanism.