Study of the Cu-Ce synergism for NO reduction with CO in the presence of O₂, H₂O and SO₂ in FCC operation

Three catalysts, CuMgAIO (Cu-cat), CeMgAIO (Ce-cat), and CuCeMgAIO (CuCe-cat), were prepared by coprecipitation and characterized by XRD, XPS and N₂ adsorption-desorption. The NO reduction activity with CO in the presence of O₂, H₂O and SO₂ was investigated under conditions similar to those found in the dense phase bed of fluid catalytic cracking (FCC) regenerator. Under NO + CO + O₂ reaction system and low temperature, NO conversion was much higher over CuCe-cat than that over Ce-cat or Cu-cat. The addition of H₂O to the feed significantly hindered the NO reduction over Cu-cat while it markedly promoted the activity of CuCe-cat at low temperature. The presence of SO₂ in the feed deactivated Cu-cat and Ce-cat drastically while no deactivation of CuCe-cat was observed. These results indicate that for NO reduction with CO, CuCe-cat has high activity and excellent resistance to H₂O and SO₂ poisoning. The enhanced performance of CuCe-cat can be explained by the synergistic effect between copper and cerium ions, which results in the formation of large amounts of Cu⁺ ions and oxygen vacancies in the samplE.