PREPARATION OF MONOLITHIC CATALYST FOR PURIFYING EXHAUST GAS

PURPOSE:To reduce the support quantity of a catalyst in the outer peripheral part of a monolithic carrier, by a method wherein the cell end parts of the outer peripheral part of the carrier are sealed and a catalyst support layer is formed to the carrier and, after the outer peripheral sealed part is impregnated with an acid, a catalytic component is supported by the catalyst support layer. CONSTITUTION:For example, only one end part of a monolithic carrier 1 is immersed in an acid solution 13 for 10min. The immersion width of the carrier is set to 30-50mm from the end surface thereof where the poisoning deterioration of Pb or P is severest on the upstream side of the carrier 1. After immersion, the carrier 1 is taken out from the acid solution 13 and dried. Thereafter, the carrier 1 is immersed in an aqueous solution of platinum diamine and an aqueous rhodium chloride solution in such a state that the outer peripheral surface thereof is masked, and Pt and Rh are supported by the carrier 1 to obtain a monolithic catalyst A wherein the support quantity of Pt is 1.0g/catalyst and that of Rh is 0.1g/catalyst. In this catalyst, the quantity of the catalytic components supported by the outer peripheral part impregnated with the acid is reduced and the exhaust gas purifying characteristic of the monolithic catalyst when the same amount of the catalytic components are supported by the monolithic carrier is enhanced.