A converter containing a NOx absorbing and reducing catalyst is disposed in the exhaust passage of an internal combustion engine. The upstream half portion (portion of the inlet side) of the substrate of the NOx absorbing and reducing catalyst in the converter carries the oxygen storage component that absorbs oxygen in the exhaust gas when the air-fuel ratio of the exhaust gas is lean and releases the absorbed oxygen when the air-fuel ratio of the exhaust gas flowing in is rich in addition to carrying the NOx absorbing and reducing catalyst. After NOx is absorbed by the NOx absorbing and reducing catalyst as a result of operating the engine at a lean air-fuel ratio, the engine is operated at a rich air-fuel ratio, so that NOx is released from the NOx absorbing and reducing catalyst and is purified by reduction. Here, oxygen is released from the oxygen storage component carried by the upstream half portion of the substrate and is reacted with the H 2 and CO components in the exhaust gas, so that the temperature of the NOx absorbing and reducing catalyst is raised within short periods of time due to the heat of reaction. Therefore, the catalyst exhibits increased activity and the NOx absorbing and reducing catalyst exhibits improved NOx purification capability.

Exhaust gas purification device for an internal combustion engine

An exhaust gas purification device having a NOx absorbent includes a by-pass passage for by-passing the NOx absorbent, an exhaust gas flow rate control portion for regulating both a flow rate of exhaust gas flowing to the NOx absorbent and the flow rate of the exhaust gas bypassing the NOx absorbent, and a reductant addition portion for adding reductant into an exhaust passage upstream of the NOx absorbent In this device, when it is necessary to discharge sulfur components from the NOx absorbent, a temperature rise control is executed such that a temperature of the NOx absorbent becomes higher than a predetermined temperature Next, a rich condition control is executed such that an air-fuel ratio of the exhaust gas flowing to the NOx absorbent becomes one of a substantially stoichiometric condition and a rich condition The flow rate of the exhaust gas to the NOx absorbent during the temperature rise control is controlled so as to be higher than that during the rich condition control

exhaust gas purification device

A first cylinder and a second cylinder are provided. A first exhaust pipe is connected to the first cylinder and a second exhaust pipe is connected to the second cylinder. A communicating pipe connects together an intermediate portion of the first exhaust pipe with an intermediate portion of the second exhaust pipe. An exhaust gas control catalyst is arranged in the second exhaust pipe downstream of the portion to which the communicating pipe is connected. Exhaust gas amount reducing devices are provided which reduce the amount of exhaust gas that flows from the first exhaust pipe into the second exhaust pipe through the communicating pipe during execution of rich/lean burn control which performs combustion with an air-fuel ratio of an air-fuel mixture that is richer than the stoichiometric air-fuel ratio in one of the first cylinder and second cylinder and performs combustion with an air-fuel ratio of an air-fuel mixture that is leaner than the stoichiometric air-fuel ratio in the other cylinder.

Exhaust Gas Control Apparatus for Internal Combustion Engine

This catalyst system simultaneously removes ammonia and enhances net NOx conversion by placing an NH 3 -SCR catalyst formulation downstream of a lean NOx trap. By doing so, the NH 3 -SCR catalyst adsorbs the ammonia from the upstream lean NOx trap generated during the rich pulses. The stored ammonia then reacts with the NOx emitted from the upstream lean NOx trap—enhancing the net NOx conversion rate significantly, while depleting the stored ammonia. By combining the lean NOx trap with the NH 3 -SCR catalyst, the system allows for the reduction or elimination of NH 3 and NOx slip, reduction in NOx spikes and thus an improved net NOx conversion during lean and rich operation.

Catalyst system for the reduction of NOx and NH3 emissions

A method of selectively catalysing the reduction of NO x in an exhaust gas flowing in an exhaust system of an internal combustion engine comprising a filter ( 40 ) for particulate matter comprising a catalyst capable of selectively catalysing the reduction of NO x with a reducing agent, which method comprising introducing a reducing agent, or a precursor thereof, into the exhaust gas and contacting the resulting gas with the filter ( 40 ).

Selective catalytic reduction

An engine has a plurality of the cylinders. The cylinders are divided into a first cylinder group and a second cylinder group, and each cylinder group is connected, via a corresponding branch exhaust passage, to a common interconnecting exhaust passage. In the interconnecting exhaust passage, an exhaust gas purifying catalyst is arranged. The air-fuel ratio of the exhaust gas of the first cylinder group is made lean to feed oxygen to the exhaust gas purifying catalyst, and the air-fuel ratio of the second cylinder group is made rich to feed fuel for heating to the exhaust gas purifying catalyst, so that the oxygen and the fuel for heating react with each other to heat the exhaust gas purifying catalyst to reactivate the exhaust gas purifying catalyst when the reactivation of the exhaust gas purifying catalyst is must be performed. In each branch exhaust passage, a start catalyst is arranged.

Device for purifying exhaust gas of engine

An electrically heating catalytic apparatus that quickly heats catalyst to an activation temperature even when the engine is started at a low temperature below the catalyst activation temperature. The apparatus employs an electrically conductive catalyst carrier (15) that is electrically heated. The carrier (15) is provided with local hot spots (22) to be energized. Since the heat is locally generated, the heat capacity of the catalyst carrier (15) is small to shorten a temperature increasing time.

o Toyota Jidosha Kabushiki Kai. Yoshizaki

Papers

Device for purifying exhaust gas of engine

Electrically heating catalytic apparatus