Novel CH_4 Combustion Catalysts Derived from Cu-Co/X-Al (X = Fe, Mn, La, Ce) Hydrotalcite-like Compounds

摘要

Novel Cu_1Co_2/X_(0.2)Al_(0.8) well-mixed oxides (where X = Fe, Mn, Ce, La) were synthesized by calcinations of corresponding hydrotalcite-like compounds at 800 ℃ for 4 h. Their catalytic performance for the methane combustion was investigated. The oxides and their precursors were characterized by X-ray diffraction (XRD), thermogravimetry-differential scanning calorimetry (TG-DSC), temperature programmed reduction (TPR), X-ray photoelectron spectroscopy (XPS), and N_2 adsorption/desorption techniques. The derived oxides are mainly of spinel and tenorite phase, with surface area of 10-30 m~2/g, where new phase CeO_2 and LaCoO_3 are segregated in Ce- and La-containing oxides, respectively. The catalytic activities of the catalysts are related to the redox properties of the metal cations and the species in the surface. Incorporation of the Mn and Fe element is helpful to the reduction of the oxide catalysts, which may lead to the enhancement of the catalytic activity. Among the catalysts investigated, Cu_1Co_2/Mn_(0.2)Al_(0.8) gives the highest catalytic activity. Light-off and complete oxidation temperature was centered at about 374 and 496 ℃, respectively. The less active was Cu_1Co_2/ Fe_(0.2)Al_(0.8).The intensities of surface oxygen species over Mn- and Fe-containing oxides are much higher than other catalysts, implying the higher activity of surface oxygen for the methane combustion.