Patent ID: 9429055
Filing Date: 2016-08-30
CPC Classification: B01D,B01J,F01N

Claim Text:
1. A method for purification of exhaust gas from an internal-combustion engine comprised by: providing a temperature-raising catalyst for exhaust gas from an internal-combustion engine in an exhaust gas passage of the internal-combustion engine, along flow of said exhaust gas, at an upstream side of a purification catalyst for said exhaust gas, a temperature of the exhaust gas increasing along the flow of the exhaust gas from an upstream side to a downstream side of the temperature-raising catalyst; and introducing hydrocarbon in an amount of 1,000 to 15,000 ppm, as converted to methane, at a temperature in the range of 200 to 350° C., from the upstream side of the temperature-raising catalyst, when a gas obtained from the temperature-raising catalyst is fed to the purification catalyst, catalytic activity of the temperature-raising catalyst not decreasing after introducing the hydrocarbon, wherein said temperature-raising catalyst has catalytically active components (A) supported onto refractory inorganic oxide powders (B) having a three-dimensional structure, wherein concentration of said components has a gradient such that said concentration gradually becomes lower from an inflow side toward an outflow side of said exhaust gas, wherein the catalytically active components (A) comprise at least one of a noble metal selected from the group consisting of platinum, palladium and rhodium, wherein a supporting amount of the catalytically active components (A) in said temperature-raising catalyst is 0.2 to 20 g/liter of the catalyst, and a supporting amount of said refractory inorganic oxide powders (B) is 10 to 300 g/liter of the catalyst, wherein a supporting amount of the catalytically active components (A) of the catalyst component, in said temperature-raising catalyst, in 10 to 66.7% of the total length from the inflow side of said exhausted gas on said refractory three-dimensional structure, is 20 to 80% of total catalytically active components (A), and a supporting amount of the catalytically active components (A) in 50% of the length of the inflow side is more than a supporting amount of the catalytically active components (A) in 50% of the outflow side, and wherein said gradient is formed stepwise.