This NOx reduction control method is for an exhaust gas aftertreatment device having an oxidation catalyst and an LNT catalyst which are disposed in an exhaust pipe and repeating an adsorption or occlusion of NOx which is executed when an air-fuel ratio is in a lean state and a reduction of NOx which is executed when the air-fuel ratio is in a rich state, the method including executing a post-injection or an exhaust pipe injection and causing HC to be adsorbed in the oxidation catalyst when an exhaust gas temperature is low, and causing the HC which is adsorbed in the oxidation catalyst to be desorbed and reducing an adsorbed NOx in the LNT catalyst by raising the exhaust gas temperature during the rich state.

An exhaust purification system includes a NOx reduction catalyst which is provided on an exhaust passage of an internal combustion engine, a SOx purging control module for executing a SOx purging control for restoring the NOx reduction catalyst from sulfur poisoning by increasing a temperature of the exhaust gas to a first target temperature at which SOx are desorbed through an injection system control to increase a fuel injection amount, a prohibition module for prohibiting an execution of the SOx purging control according to an operating state of the internal combustion engine, and a temperature retention mode control module for executing a temperature retention mode control for maintaining the temperature of the exhaust gas at a second target temperature which is lower than the first target temperature by controlling the fuel injection amount during a period of time during which the SOx purging control is prohibited.

A method for monitoring a nitrogen oxide storage catalyst in an exhaust system of an internal combustion engine, in which a reduction of nitrogen oxides is carried out by means of a reducing agent is disclosed. During a regeneration of the nitrogen oxide storage catalyst, the following steps are carried out: A measurement is carried out, from which a slip rate of the reducing agent not absorbed in the nitrogen oxide storage catalyst is ascertained. In addition, at least one expected value for the slip rate of the reducing agent is ascertained from at least one model. Subsequently, a computation of a monitoring variable is carried out by means of the slip rate of the reducing agent ascertained from the measurement and the at least one expected value for the slip rate of the reducing agent. Finally, a diagnosis of the storage capacity of the nitrogen oxide storage catalyst is carried out on the basis of the monitoring variable.

An apparatus for diagnosing deterioration of an NOx storage-reduction catalyst for purifying an exhaust gas discharged from an internal engine, including an intake air amount detection unit for detecting an intake air amount to the internal combustion engine, an exhaust gas temperature detection unit for detecting the temperature of an exhaust gas passing through the NOx storage-reduction catalyst, an NOx purification rate detection unit for detecting NOx in an exhaust gas flowing into the NOx storage-reduction catalyst and in an exhaust gas flowing out of the NOx storage-reduction catalyst, thereby detecting an NOx purification rate, and a diagnostic unit for, when the temperature of the exhaust gas passing through the NOx storage-reduction catalyst increases following an increase in the intake air flow rate to the internal combustion engine and in turn, the temperature of the NOx storage-reduction catalyst greatly increases over a first predetermined threshold value, calculating a difference in the NOx purification rate between before and after the rise of temperature of the NOx storage-reduction catalyst, and diagnosing the NOx storage-reduction catalyst as being deteriorated when the NOx purification rate difference is larger than a second predetermined threshold value.

A system includes a catalyst for receiving and treating exhaust gas generated by an engine, a passive NOx adsorber (PNA) positioned upstream of the catalyst, a bypass valve positioned upstream of the catalyst and the PNA, and a controller. The controller is configured to: while controlling the bypass valve to direct exhaust gas to the PNA, detect a torque demand that is greater than a threshold value; responsive to detecting that the torque demand is greater than the threshold value, engage a motor, coupled with a battery system, with a drive shaft of the system to meet at least a portion of the torque demand; in response to the engagement of the motor with the drive shaft not meeting all of the torque demand, engage the engine with the drive shaft to meet a remainder of the torque demand.

Various embodiments include a catalyst measuring system for determining the aging state of a catalytic converter comprising: an SCR catalytic converter; and a high-frequency measuring arrangement including a processor, a first antenna, and a second antenna. The first antenna is located upstream of the SCR catalytic converter in the exhaust tract and the second antenna is located downstream of the catalytic converter. The processor instructs the antennas to selectively emit and receive electromagnetic signals and evaluates the transmitted and the received electromagnetic signals to compare them with predefined threshold values. The processor determines an aging state of the SCR catalytic converter based on the comparison.

The present subject matter relates to a method and a treatment system monitor for monitoring an engine exhaust after-treatment system containing more than one Lean NO.sub.x Traps (LNT). The method includes receiving an exhaust gas of a desired air-fuel ratio upstream of a respective LNT. The LNT is further regenerated using a richer than stoichiometric exhaust air-fuel ratio and subsequently an air-fuel ratio received downstream of the LNT is evaluated. Further, a working state of a respective LNT is determined based on the monitoring of the air-fuel ratio and oxygen level upstream and downstream of the LNT.

An exhaust gas control apparatus for an internal combustion engine includes: an SCR catalyst including transition metal ions for reducing NO.sub.X in exhaust gas with NH.sub.3 as a reducing agent; detection means for detecting temperature of the SCR catalyst; and a heater configured to heat the SCR catalyst. When NO.sub.X does not flow into the SCR catalyst, and the temperature detected by the detection means is below a first temperature that is a temperature causing exhibition of valence recovery of transition metal ions, the heater is controlled such that the SCR catalyst is heated up to a first temperature or above and that the SCR catalyst is maintained at or above the first temperature for a prescribed period so as to achieve valence recovery of the transition metal ions put in a deteriorated state.

A method for monitoring and diagnosing an engine exhaust treatment of an internal combustion engine in a motor vehicle includes monitoring a nitrogen oxides (NOx) storage catalyst disposed in an engine exhaust stream downstream of the engine, determining a first diagnostic condition of the NOx storage catalyst based on data from a first EGT sensor and a second EGT sensor; determining a second diagnostic condition of the NOx storage catalyst based on a comparison of temperatures reported by a first NOx sensor and a second NOx sensor, selectively pausing the first diagnostic condition and the second diagnostic condition during a predetermined NOx storage catalyst regeneration period, and selectively generating a notification for an operator of the motor vehicle.

There is provided an exhaust gas purification system including: a NOx storage-reduction catalyst that is provided in an exhaust system of an internal combustion engine to reduce and purify NOx in exhaust gas; a degree of deterioration estimation module 120 for estimating a degree of deterioration of the NOx storage-reduction catalyst; a regeneration control unit 100 for executing a regeneration process in which exhaust gas is enriched so as to restore a NOx storage capacity of the NOx storage-reduction catalyst; an interval setting module for setting a target interval from an end of the regeneration process to a start of the subsequent regeneration process by the regeneration control unit; and an interval target value correction module for correcting the target interval based on the degree of deterioration that is estimated by the degree of deterioration estimation module.