Synthesis of polymetallic oxides hollow spheres with superior activity, resistance to SO2, H2O and metal poisons for low-temperature NH3‑selective catalytic reduction of NOx

Abstract

NH3‑selective catalytic reduction as the fascinating technology for complete NOx removal, the key in practical applications is to explore advanced catalysts with high catalytic reactivity and stability at low temperature. Herein, a series of hollow spherical AMnOx (A = Ce, Cu, Ni) catalysts was fabricated by using carbon nanospheres as sacrificial template. Characterization analysis including XRD, ICP, BET, SEM, TEM, H2-TPR, NH3-TPD, XPS, in situ DRIFTS together with kinetic studies were applied to acquire knowledge of the morphological structure and surface features of the catalysts as-prepared. We also performed a comparative study on three samples with regard to their SCR activity at low temperatures. Notable, the catalytic activity of the NiMnOx catalyst (95.9 %) was vastly superior to that of the CeMnOx (85.4 %) and CuMnOx (30.5 %) at 100 °C. This enhanced low-temperature activity of NiMnOx are correlated against hollow structure with more active sites, wider pore distribution, higher surface Mn content and the enhancement in surface acidity and reducibility. Even with 5 vol% H2O in the reaction gas fraction, the catalytic performance of NiMnOx hollow spheres was superior to the other two catalysts. Besides, it can be used for six consecutive runs without suffering a substantial activity loss. Additionally, the impact of various crucial process variables, including space velocity, H2O, SO2, and metal poisons, on the denitrification efficiency of NH3-SCR was examined. The current researches have a positive guiding role in the development of high-efficiency low-temperature NH3-SCR denitrification catalysts to boost NOx degradation.