Ceria added Sb-V₂O₅/TiO₂ catalysts for low temperature NH₃ SCR: Physico-chemical properties and catalytic activity

A systematic investigation of the effect of ceria loading over Sb-V₂O₅/TiO₂ catalysts was carried out for the selective catalytic reduction (SCR) of NO_x by NH₃. The various ceria loaded Sb-V₂O₅/TiO₂ catalysts were prepared by deposition precipitation and impregnation methods. Addition of 10% ceria to Sb-V₂O₅/TiO₂ catalyst significantly enhanced the NO_x conversion at wide temperature range of 220-500°C. The 10% ceria loaded Sb-V₂O₅/TiO₂ catalyst showed superior N₂ selectivity (>95%) throughout the reaction temperatures. The physicochemical characteristics of the obtained catalysts were thoroughly characterized by BET surface area, X-ray diffractometry (XRD), temperature programmed desorption (TPD) of NO, SO₂ and NH₃, H₂- temperature programmed reduction (TPR), X-ray photoelectron spectroscopy (XPS) and in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The XRD results indicated the active components of antimony and vanadia were homogeneously dispersed over CeO₂/TiO₂. It was found that the addition of 10% ceria to Sb-V₂O₅/TiO₂ could enhance the total acidity and redox properties of the catalyst, which lead to show higher NO_x conversions at wide temperature window. In XPS studies, increase in intensity of the chemisorbed mobile oxygen peak was observed for ceria loaded catalysts. In particular, the DRIFT spectra of ceria loaded Sb-V₂O₅/TiO₂ catalysts showed abundant Brønsted acid sites at 1436 and 1673cm^-1 band, which are responsible for high NO_x conversion. Furthermore, the results of NO and SO₂ TPD of 10% ceria loaded Sb-V₂O₅/TiO₂ catalyst showed enhancement of NO adsorption and SO₂ inhibition properties, which is thought to play a significant role in long term stability of the catalyst during SO₂ on-off study for 38h at 240°C.