Reactions of CO and NO over La(2-x)A(x)' Cu1-yBy ' O-4 center dot A K2NiF4-Type Mixed Oxide

Seven La(2-x)A(x)'Cu1-yBy'O-4 +/-delta (A' = Sr, Ce; B' = Al, Zr; x or y = 0-0.5) catalysts were prepared. It was demonstrated that the oxidation number of copper in the bulk and on the surface could be well controlled by the substitution of the constituent elements without change of the K2NiF4-type structure. For example, the average oxidation number of copper in the bulk, determined by iodometry, increased to 2.30 with Sr2+ substitution for La3+, while it decreased to 1.65 with Zr4+ substitution for Cu2+. The surface composition and the oxidation number of copper, which was estimated by the ratio of the satellite peak to main peak of Cu 2p(3/2) and the Auger parameter, were close to those of the bulk. The reaction of NO and CO to give N-2 and CO2 was carried out over these catalysts at 673 K in a recirculation system. It was found that the catalysts having an average oxidation number of copper close to 2 were most active for the reaction.