METHOD FOR CARRYING NOx OCCLUSION MATERIAL

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PROBLEM TO BE SOLVED : To provide a catalyst capable of sufficiently uniformly carrying a Ba-Ti composite oxide or the like so as to be able to prevent a deterioration due to sulfur poisoning. SOLUTION : A porous oxide is impregnated with a composite oxide precursor aqueous solution that is prepared by dissolving a first compound containing at least one type of element selected from among alkaline earth metals and rare earth elements, a second compound containing at least one type of element selected from among 3rd group elements, 4th group elements, and transition metals, a third compound having polydentate ligands, and hydrogen peroxide in water and is adjusted to have a pH of 4 to 7. The porous oxide is dried and then fired. The concentration of the composite oxide precursor can be increased while delaying the gelation, so that a sufficient amount of the composite oxide precursor can be carried in a single step of water absorption and impregnation. Thus, the structure of the composite oxide will never be destroyed. COPYRIGHT : (C)2008, JPO&INPIT