Promoter for purifying internal engine exhaust and method for preparing the same

Abstract

The promoter includes (A) particulate aluminum oxide and (B) a double oxide of (i) cerium and (ii) at least one member selected from the group consisting of zirconium, yttrium, strontium, barium and rare earth elements, supported on the particulate aluminum oxide. A solution of (i) a water-soluble salt of cerium and (ii) a water-soluble salt of at least one member selected from the group consisting of zirconium, yttrium, strontium, barium and rare earth elements is formed. Particulate aluminum oxide is added to the solution to form a dispersion. An aqueous solution of ammonium hydrogen carbonate is added to the dispersion to obtain particulate aluminum oxide coated with a reaction product. The particulate aluminum oxide coated with the reaction product is fired. Alternatively, an aqueous solution containing (i) the water-soluble salt of cerium and (ii) the water-soluble salt of the at least one member dissolved therein is adhered onto particulate aluminum oxide. The particulate aluminum oxide provided thereon with the aqueous solution adhered thereto is brought into contact with an aqueous solution of ammonium hydrogen carbonate to cause a reaction between these solutions and to thus deposit a reaction product on the particulate aluminum oxide. The particulate aluminum oxide with the reaction product deposit is fired.

Dependencies are inferred from the claim text.