Effect of Ni addition on the catalytic performance of Cu/γ-Al₂O₃ in the combustion of lean methane containing SO₂

The Cu/γ-Al₂O₃ catalyst promoted with Ni was prepared by incipient wetness impregnation and used in the catalytic combustion of lean methane (3%) containing SO₂ (0.01%) in a fixed bed reactor; the effect of Ni addition on the catalytic activity of Cu/γ-Al₂O₃ and stability against sulfur poisoning in lean methane combustion was investigated. The results showed that Cu/γ-Al₂O₃ catalyst is facilely poisoned by SO₂ in the feed gas and its resistance against sulfur poisoning can be effectively improved through the addition of Ni as a promoter. The stability of Cu/γ-Al₂O₃ catalyst is increased with the increase of Ni content; over the Cu/γ-Al₂O₃ catalyst promoted by 10% Ni, the conversion of CH₄ remains above 96% after reaction at 650 ℃ for 10 h. The catalysts were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and NH₃ temperature-programmed desorption (NH₃-TPD); the results illustrated that NiAl₂O₄ spinel is formed on the Ni-promoted Cu/γ-Al₂O₃ catalyst. Upon the formation of NiAl₂O₄ spinel, the surface Lewis acidity is reduced, and meanwhile, the adsorption of SO₂ is weakened and the retention time of CO₂ on the surface is reduced, all these may contribute to the high activity and stability against sulfur poisoning of the Ni-promoted Cu/γ-Al₂O₃ catalyst in lean methane combustion.