A method for operating an exhaust system, where the exhaust system has a first selective catalytic reduction (SCR) catalytic converter close to the engine and a second SCR catalytic converter arranged downstream of the first. A respective quantity of reducing agent to be introduced into the exhaust gas by a respective dosing element is set depending on a first temperature of the first SCR catalytic converter, where during a period of time during which the first temperature exceeds a predeterminable first threshold value and a second temperature of the second SCR catalytic converter exceeds a predeterminable second threshold value, which is lower than the first threshold value, the introduction of the reducing agent into the exhaust gas with regard to the dosing elements takes place exclusively via the second dosing element such that during the period of time, no introduction of the reducing agent into the exhaust gas takes place.

An exhaust gas purification apparatus for an internal combustion engine includes a filter supporting the catalyst with an oxygen storage capacity, an air fuel ratio sensor to detect an air fuel ratio of exhaust gas at the downstream side of the filter, and a controller configured to change an air fuel ratio of exhaust gas flowing into the filter, to estimate an amount of particulate matter deposited in an interior of a partition wall of the filter, estimate a maximum storable oxygen amount of the catalyst from a change of the air fuel ratio of exhaust gas obtained by the air fuel ratio sensor at the time when the air fuel ratio of exhaust gas is changed by the controller, and correct the maximum storable oxygen amount of the catalyst based on the amount of particulate matter deposited in the interior of the partition wall of the filter.

A decrease in purification performance of a system as a whole is suppressed in cases where catalysts are arranged in an upstream side portion and in a downstream side portion of an exhaust passage in an internal combustion engine. A first catalyst, a sensor and a second catalyst are sequentially arranged in the exhaust passage of the internal combustion engine, wherein a switch is made between lean control and rich control in such a manner that an amount of increase or decrease in a storage amount of oxygen falls within a predetermined range, and in cases where the rich control is carried out after performing a predetermined number of times of rich control, the rich control is continued until an air fuel ratio detected by the sensor becomes equal to or less than a rich determination threshold value which is smaller than a stoichiometric air fuel ratio.

A method for operating an exhaust system, where the exhaust system has a first selective catalytic reduction (SCR) catalytic converter close to the engine and a second SCR catalytic converter arranged downstream of the first. A respective quantity of reducing agent to be introduced into the exhaust gas by a respective dosing element is set depending on a first temperature of the first SCR catalytic converter, where during a period of time during which the first temperature exceeds a predeterminable first threshold value and a second temperature of the second SCR catalytic converter exceeds a predeterminable second threshold value, which is lower than the first threshold value, the introduction of the reducing agent into the exhaust gas with regard to the dosing elements takes place exclusively via the second dosing element such that during the period of time, no introduction of the reducing agent into the exhaust gas takes place.

An exhaust gas purification filter that suppresses an increase in pressure loss associated with the formation of a catalyst layer and is excellent in PM burning quality. The exhaust gas purification filter includes a base and a catalyst layer provided on the base. The catalyst layer contains a carrier and a metal catalyst. Large pores having a circle equivalent diameter greater than 5 m occupy, when an area of the catalyst layer is 100% in an electron microscope observation image of a cross section of the catalyst layer, 45% or more of the area.

The present disclosure describes, inter alia, binary catalyst compositions including a (metal) zeolite having a crystal lattice that incorporates a metal oxide, wherein the metal oxide is covalently bound to elements within the crystal lattice. The metal oxide forms an integral part of the (metal) zeolite crystal lattice, forming covalent bonds with at least the Si or Al atoms within the crystal lattice of the (metal) zeolite, and is dispersed throughout the (metal) zeolite crystal lattice. The metal oxide can substitute atoms within the crystal lattice of the (metal) zeolite.

A filter made of a sponge material having air permeability and elasticity is interposed between an exhaust port of an exhaust gas sampling unit and a sampling port to thereby close a gap between the exhaust port and the sampling port. In this state, when the exhaust gas sampling unit is suctioned at a constant flow rate, the exhaust gas and the outside air around the exhaust port are taken into the exhaust gas sampling unit from the sampling port. At this time, the flow rate of the outside air taken in through the filter is suppressed by the air-flow resistance of the filter, and therefore the total flow rate of the exhaust gas and the outside air taken into the exhaust gas sampling unit is caused to be less than the suction flow rate, thereby simply and reliably preventing the exhaust gas from leaking out.

A vehicle underbody structure includes a catalyst disposed in a front portion of an exhaust pipe; a cover member for covering the catalyst from above; and a heat insulator disposed inside a tunnel portion behind the catalyst and configured to cover the exhaust pipe from above. The heat insulator is disposed away from the tunnel portion by a predetermined gap in an up-down direction. A front portion of the heat insulator and a rear portion of the cover member are disposed in such a way as to overlap each other. A front end of the heat insulator is disposed on the upper side with respect to a rear end of the cover member.

A catalytic composite is formed of a catalytic layered assembly including a porous catalytic fluoropolymer film and one or more felt batts connected with the porous catalytic fluoropolymer film. At least one felt batt is positioned adjacent the upstream side of the porous catalytic fluoropolymer film to form the catalytic composite. The fluoropolymer film is perforated to allow for enhanced airflow therethrough while retaining the capability of catalyzing the reduction or removal of chemical species in fluid flowing through the catalytic composite.

A system for regulating pressure in a diesel exhaust fluid delivery system. The system includes a first dosing valve, a pump, a hydraulic line, and an electronic processor. The electronic processor is configured to determine a dosing demand, determine a time delay between the first dosing valve opening and the pump activating, and determine a first threshold time and a second threshold time based on the time delay. The electronic processor is also configured to activate a timer. When the timer reaches the first threshold time, the electronic processor is configured to freeze the dosing demand and activate the pump based on the dosing demand. When the timer reaches the second threshold time, the electronic processor is configured to open the first dosing valve and release the freeze on the dosing demand.