Promotional effects of Nb on selective catalytic reduction of NO with NH3 over Fe -Nb0.5--Ce0.5 (x = 0.45, 0.4, 0.35) oxides catalysts

Citric acid method was employed to prepare a series of Nb-promoted Fex-Nb0.5-x-Ce0.5 (x = 0.45, 0.4, 0.35) oxides for selective catalytic reduction with NH3 (NH3-SCR) of NO process. The structure, redox ability and reactivity of NH3 and absorbed NO species on the catalysts were explored by using various characterization techniques such as X-ray diffraction (XRD), temperature program reduction with H2 (H2-TPR), temperature program desorption of NH3 (NH3-TPD), temperature program desorption of NO (NO-TPD), X-ray photoelectron spectroscopy (XPS) and in situ diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS). It was found that the Nb promoted Fex-Nb0.5-x-Ce0.5 (x = 0.45, 0.4, 0.35) oxides catalysts showed outstanding NH3-SCR of NO activity, excellent N2 selectivity and remarkable SO2/H2O resistance, meanwhile, Fe0.4-Nb0.1-Ce0.5 exhibited above 90% NO conversion in the range of 180–400 °C, together with near 100% N2 selectivity. The characterization results point out that the excellent catalytic performance of Fe0.4-Nb0.1-Ce0.5 can be ascribed to the strong interaction among Nb, Fe and Ce oxides. The strong interaction not only increases the BET surface area and redox ability of the catalyst, but also significantly improves the acid amount leading to the enhancement of the adsorption and activation of NH3, which is advantage of the reactivity of adsorbed nitrate together with the adsorbed NH3 species.