COMPOSITE OXIDE AND CATALYST FOR PURIFYING EXHAUST GAS

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PROBLEM TO BE SOLVED : To provide a catalyst for purifying an exhaust gas where the stability and the easy reducibility of a rhodium oxide coexist by controlling solid basicity in a suitable range. SOLUTION : A composite oxide comprises at least one kind (a) of metal elements selected from an alkali metal, an alkaline earth metal, a rare earth element, a group 3 element and a group 4 element except Zr, and ZrO2. The CO2 adsorbing amount per unit weight of the composite oxide after heat-treated in 3 hours or more at 1, 000°C is 8.2-29 μmol/g and the CO2 adsorbing amount per unit specific surface area of the complex oxide is 0.2-2.3 μmol/m2. As the stability and the easy reducibility of the rhodium oxide coexist by controlling the solid basicity in the suitable range, the purifying activity of the catalyst is high from a low temperature region and is kept high after exposed in a high temperature atmosphere and its durability is excellent. COPYRIGHT : (C)2006, JPO&NCIPI