Engineering Binary CrmNb1-mOx (m = 0.1, 0.3, 0.5) Oxides Catalysts to Enhance Its NH3-SCR Denitration Activity and SO2 Resistance: Study on the Influence of Redox Property and Acidity

It is still a challenge to create novel simply environmentally friendly NH 3 -SCR denitration catalysts in presence of SO 2 and H 2 O, and to further understand the role of redox property and acidity of catalyst. In this work, a series of binary Cr m Nb 1-m O x (m = 0.1, 0.3 and 0.5) oxides with different Cr/Nb ratio were engineered for NH 3 -SCR denitration by using the citric acid complex method. Among these catalysts, Cr 0.3 Nb 0.7 O x revealed best catalytic performance with over 90 % NO conversion in the range of 210 -390 degrees C and great SO 2 and H 2 O resistance. The effects of different Cr/Nb ratio on catalytic activity was investigated though following characterization such as Raman spectroscopy, Transmission electron microscopy (TEM), X-ray powder diffraction (XRD), N 2 physical adsorption, NO -Temperature programmed desorption (NO-TPD), H 2 -Temperature program reduction (H 2 -TPR), X-ray photoelectron spectra (XPS), NH 3 -Temperature programmed desorption (NH 3 -TPD) and In situ Diffuse reflectance infrared Fourier transform spectroscopy ( In situ DRIFTS). The impact of surface redox property and acidity on catalytic performance was further investigated by changing the Cr/Nb ratio. The results suggest that different Cr/Nb ratio result in catalysts having different Brunauer-Emmett-Teller (BET) surface area, and variation of crystal structure, generating the improvement of the surface acid amount and the enhancement of the oxidizing ability due to existence of more surface active oxygen species. Besides, the results of in situ DRIFTS verify that more acid sites are exposed on the Cr 0.3 Nb 0.7 O x surface and react with absorbed NO x even in the existence of SO 2 , which followed Langmuir-Hinshelwood (L -H) mechanism.