Copper oxycarbonates

We had observed prewously [7] by XPS and IR study of CO adsorption that the La2Cuo.9Pdo.i04+s catalyst was deeply modified after light-oflF tests in the presence of CO, NO and C3H6, even though the reactant gas mix is stoichiometric, it is transformed into highly dispersed copper and palladium species in various oxidation states (Cu, Cu Pd and Pd"), in a lanthanum oxycarbonate matrix. This instability is shown here to be connected with the reaction of the solid with CO. 

In the case of La2Cuo.9Pdo.i04+8, the structure is not stable in the presence of CO, leading to well dispersed Cu and Pd species in a lanthanum oxycarbonate matrix. This is supposed to be due to the different crystal structure of this latter solid, where layers of La-0 are present, and to the easy reduction of Cu and Pd ions by CO into the metallic state. However the copper and palladium are easily reduced and reoxidised under mild conditions (400°C), these reactions being fast enough to supply and retain oxygen when the composition oscillates between rich and lean. 

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