Enhancement of potassium resistance of Ce–Ti oxide catalyst for NH3-SCR reaction by modification with holmium

Alkali metal K in exhaust gas has a deactivation effect on NH3-SCR catalysts. In this work, it is discovered that the addition of Ho on CeTi catalyst can remarkably strengthen its K tolerance. The conclusions of Brunauer–Emmett–Teller (BET) , X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), NH3 temperature programmed desorption (NH3-TPD) and H2 temperature programmed reduction (H2-TPR) analyses demonstrate that the enhancement of K resistance mainly originates from its stronger surface acidity and redox capability, the higher concentration of Ce3+ species and surface chemisorbed oxygen. In situ DRIFT analysis reveals that the introduction of Ho on CeTi can remarkably improve the adsorption of NH3 and NOx species on catalyst surface, accompanied by the intensified reactivity of ad-NH3 species, which should also administer to improve the K resistance.