Abstract: A method of purifying an exhaust gas, includes: disposing a NOx trapping catalyst in an exhaust pipe of an internal combustion engine, the NOx trapping catalyst including: a metal substrate including cells, a corner portion of each of cells having an acute angle; and a catalyst layer supported in the metal substrate and including a noble metal, a heat-resistant inorganic oxide and a NOx trapping material, the catalyst layer having pores formed by addition of a pore formation promoting material, and the NOx trapping catalyst: adsorbing NOx in the exhaust gas when an exhaust air-fuel ratio is in a lean state; and desorbing and reducing the adsorbed NOx when the exhaust air-fuel ratio is in a stoichiometric state or a rich state; and removing the NOx by the exhaust air-fuel ratio being shifted between the lean state and the rich state.

Abstract: An exhaust gas purifying catalyst which is disposed in an exhaust pipe of an internal combustion engine, includes: a substrate; and a catalyst layer, supported in the substrate and including: noble metals including platinum (Pt) and palladium (Pd); a heat-resistant inorganic oxide; and a NOx trapping material. The exhaust gas purifying catalyst adsorbs NOx in an exhaust gas when an exhaust air-fuel ratio is in a lean state and desorbs and reduces the adsorbed NOx when the exhaust air-fuel ratio is in a stoichiometric state or a rich state. (Pt/Pd) which is a ratio of amount of the platinum (Pt) to amount of the palladium (Pd) is 0.7 or more and less than 1.0.

Abstract: A method of purifying an exhaust gas, includes: disposing a NOx trapping catalyst in an exhaust pipe of an internal combustion engine, the NOx trapping catalyst including: a metal substrate including cells, a corner portion of each of cells having an acute angle; and a catalyst layer supported in the metal substrate and including a noble metal, a heat-resistant inorganic oxide and a NOx trapping material, the catalyst layer having pores formed by addition of a pore formation promoting material, and the NOx trapping catalyst: adsorbing NOx in the exhaust gas when an exhaust air-fuel ratio is in a lean state; and desorbing and reducing the adsorbed NOx when the exhaust air-fuel ratio is in a stoichiometric state or a rich state; and removing the NOx by the exhaust air-fuel ratio being shifted between the lean state and the rich state.

Abstract: An exhaust gas purifying catalyst which is disposed in an exhaust pipe of an internal combustion engine, includes: a substrate; and a catalyst layer, supported in the substrate and including: noble metals including platinum (Pt) and palladium (Pd); a heat-resistant inorganic oxide; and a NOx trapping material. The exhaust gas purifying catalyst adsorbs NOx in an exhaust gase when an exhaust air-fuel ratio is in a lean state and desorbs and reduces the adsorbed NOx when the exhaust air-fuel ratio is in a stoichiometric state or a rich state. (Pt/Pd) which is a ratio of amount of the platinum (Pt) to amount of the palladium (Pd) is 0.7 or more and less than 1.0.

Abstract: As forcible modulation parameters, a cycle and an amplitude are set so that O2 and CO concentrations in emissions at a catalyst inlet can be increased, and based upon the preset parameters, forcible modulation that forcibly fluctuates an exhaust air-fuel ratio is carried out to facilitate catalysis for early activation, and the forcible modulation is then switched to O2-F/B control.

Abstract: By performing main fuel injection and sub fuel injection to perform rich operation of an engine, NOx purging of a NOx catalyst is carried out, and in the NOx purging, the ratio between the main fuel injection quantity and the sub fuel injection quantity is variably determined, within the range of 5:1 to 2:1 where the ratio of the sub fuel injection quantity is relatively great, such that the ratio of the sub fuel injection quantity is greater as the temperature of a three-way catalyst becomes higher.

Abstract: There is provided an exhaust emission purifying catalyst device which is comprised of a carrier disposed in an exhaust passage and including through holes passed through the carrier in an axial direction (flowing direction), and supporting layers made of fire-resistance inorganic oxide formed on inner surfaces of the through holes. The supporting layers support noble metal and NOx trapping agents which occlude NOx in exhaust gas when the exhaust air-fuel ratio is lean, and emits and reduces the occluded NOx when the exhaust air-fuel ratio is stoichiometric or rich. The amount of the supported noble metal is set to be smaller in an exhaust passage upstream area of the carrier than in an exhaust passage downstream area of the carrier.

Abstract: By performing main fuel injection and sub fuel injection to perform rich operation of an engine, NOx purging of a NOx catalyst is carried out, and in the NOx purging, the ratio between the main fuel injection quantity and the sub fuel injection quantity is variably determined, within the range of 5:1 to 2:1 where the ratio of the sub fuel injection quantity is relatively great, such that the ratio of the sub fuel injection quantity is greater as the temperature of a three-way catalyst becomes higher.

Abstract: There is provided an exhaust emission purifying catalyst device which is comprised of a carrier disposed in an exhaust passage and including through holes passed through the carrier in an axial direction (flowing direction), and supporting layers made of fire-resistance inorganic oxide formed on inner surfaces of the through holes. The supporting layers support noble metal and NOx trapping agents which occlude NOx in exhaust gas when the exhaust air-fuel ratio is lean, and emits and reduces the occluded NOx when the exhaust air-fuel ratio is stoichiometric or rich. The amount of the supported noble metal is set to be smaller in an exhaust passage upstream area of the carrier than in an exhaust passage downstream area of the carrier.