Selective catalytic reduction of NO with methane over Cu-alumina nanotubes

 A new type of tubular material, boehmite nanotube, was prepared by adjusting reaction condition with H₂O₂ in hydrothermal synthesis system. The nanotubes were characterized by XRD, nitrogen absorption and TEM etc. XRD results showed that the AlOOH nanotubes converted to γ-alumina nanotubes upon calcination at 520℃ for 2h. The nanotubes were about 300nm in length with outer diameter of 20nm, as recorded on TEM. BET surface area of the γ-Al₂O₃ nanotubes was higher than 230m²/g. γ-Al₂O₃ nanotubes were used as catalyst carriers by impregnating Cu(NO₃)₂ solution with different Cu content for the titled reaction. The influences of the amount of Cu, different carriers, O₂ concentration and SO₂ on the selective catalytic reduction of NO were studied. The results indicated that the γ-Al₂O₃ nanotubes loaded with 7% Cu possessed the highest activity which could reach 90% at 600℃; Further, the catalysts with nanotubes as carrier showed more active catalytic performance at low temperature (bellow 500℃) than those non-nano scale carrier fabricated based on alumina. Oxygen at low concentration (less than 0.25%(φ)) showed little effect on the conversion of NO while it improved the methane conversion when the concentration of O₂ was higher than 0.25%; the Cu-nanotubes catalyst also showed sulfur-resistant property.