Patent Number: 6,305,161

Title: Method of purifying exhaust gas of internal combustion engine and apparatus thereof

Abstract: A method of and apparatus for purifying an exhaust gas of an internal combustion engine comprising an NO.sub.x purifying catalyst arranged in an exhaust gas passage, wherein the NO.sub.x purifying catalyst is made of a composite material containing at least one kind of element selected from alkaline metals and alkaline earth metals, at least one kind of element selected from rare earth metals, at least one kind of element selected from platinoid metals, and titanium (Ti), the NO.sub.x purifying catalyst adsorbing NO.sub.x in the exhaust gas onto the surface when the exhaust gas is lean, and reducing the adsorbed NO.sub.x to N.sub.2 when the exhaust gas is stoichiometric or rich, and wherein the exhaust gas is purified by adsorbing NO.sub.x in the exhaust gas in the NO.sub.x purifying catalyst when the internal combustion engine is being operated under a lean condition, and by setting, after the adsorption, the exhaust gas to a stochiometric state or a rich state for 0.5 second to 4.5 seconds to reduce the NO.sub.x adsorbed in said NO.sub.x purifying catalyst to N.sub.2 through catalytic reaction with the reducing agent.

Inventors: Takanohashi; Toshikatsu (Takanezawa-machi, JP), Oono; Hiroshi (Utsunomiya, JP), Kuroda; Osamu (Hitachi, JP), Yamashita; Hisao (Hitachi, JP), Iizuka; Hidehiro (Hitachinaka, JP), Kitahara; Yuichi (Hitachinaka, JP)

Assignee: Hitachi, Ltd.

International Classification: B01D 53/94 (20060101); F01N 3/08 (20060101); F02D 41/02 (20060101); F01N 7/00 (20060101); F01N 7/02 (20060101); F01N 003/10 ()

Expiration Date: 10/23/2018