Low level noble metal-supporting three-way catalyst

A two-layer catalyst for catalytically removing three components, which are carbon monoxide, hydrocarbons, and nitrogen oxides from combustion exhaust gas generated by combusting fuel at around a stoichiometric air to fuel ratio by bringing the combustion exhaust gas into contact therewith, the catalyst consisting essentially of:

• a surface catalyst layer;
• and
• an inner catalyst layer,
• wherein the surface catalyst layer consists essentially of:
• (A) a first catalyst component comprising at least one member selected from the group consisting of rhodium, platinum, and palladium in a content from 0.01 to 0.5% by weight;
• and
• (B) a second catalyst component, which is a remainder of the surface catalyst layer, consisting of a composite oxide or a mixed oxide that consists of:
• (a) at least one oxide selected from the group consisting of zirconium oxide and titanium oxide;
• and
• (b) an oxide of at least one element selected from the group consisting of praseodymium, yttrium, neodymium, tungsten, niobium, silicon, and aluminum,
• wherein a content of the oxide (a) in the composite oxide or the mixed oxide is in a range from 70 to 95% by weight, and
• wherein the first catalyst component is supported by the second catalyst component;
• and
• wherein the inner catalyst layer comprises:
• (A) a first catalyst component comprising at least one member selected from the group consisting of rhodium, platinum, and palladium in a content from 0.01 to 0.5 % by weight;
• and
• (B) a second catalyst component, which is a remainder of the inner catalyst layer, comprising
• (a) ceria, or
• (b) a composite oxide or a mixed oxide comprising:
• (i) ceria;
• and
• (ii) an oxide of at least one element selected from the group consisting of zirconium, lanthanum, praseodymium, neodymium, and yttrium,
• wherein a content of the oxide (i) in the composite oxide or mixed oxide is in a range from 50 to 95% by weight.