Process for preparing catalytic materials for purifying exhaust gas and catalytic materials prepared thereby

Claim 1

A process for preparing a catalyst for purifying exhaust gas comprising the steps of: impregnating a heat-resistant ceramic material as the carrier for the catalyst with an impregnating liquid consisting essentially of an aqueous solution containing (A) 0.1-60 g/l calculated as the metal ion of at least one Platinum Group metal compound selected from the group consisting of platinous chloride, platinic chloride, chloroplatinous acid, chloroplatinic acid, platinous potassium chloride, platinic potassium chloride, palladium chloride, palladium nitrate, palladium acetate and palladium sulfate and (B) at least one organic compound selected from the group consisting of (1) organic nitrogen compounds which are azodicarbonamide, cyanuric acid, azobisisobutyronitrile, guanidine and melamine and (2) organic phosphorus compounds which are trimethyl phosphite, triethyl phosphite and diethyl phosphite, said at least one organic compound (B) being in an amount of 0.5-6 mols per mol of the Platinum Group metal, drying the thus-impregnated carrier, keeping the thus-dried impregnated carrier in a reducing gas stream at an elevated temperature to reduce the Platinum Group metal compound (A) impregnated in the carrier, and calcining the thus-reduced impregnated carrier at a temperature not lower than the temperature at which said at least one organic compound (B) is thermally decomposed, for a time enough to burn off the organic compound (B) impregnated in the carrier thereby obtaining the desired catalyst.