A passive NOx absorber for treating an exhaust gas from a diesel engine is described. The passive NOx absorber comprises a first washcoat region comprising a zeolite catalyst, the zeolite catalyst comprising a noble metal and a zeolite having a SAR of 2-15.

A lean NO.sub.x trap catalyst and its use in an emission treatment system for internal combustion engines is disclosed. The lean NO.sub.x trap catalyst comprises a first layer for storing nitrogen oxides (NOx) under lean exhaust gas conditions and releasing and/or reducing stored NOx during rich exhaust gas conditions, and a second layer, said second layer comprising a first zone for oxidizing carbon monoxide (CO) and/or hydrocarbons (HC), and a second zone for oxidizing nitric oxide (NO), and a substrate having an inlet end and an outlet end.

The invention discloses a visible light responsive tricobalt tetraoxide dodecahedron/carbon nitride nanosheet composite and an application thereof in exhaust gas treatment. The preparation method of the composite comprises the following steps: with urea as a precursor, carrying out twice calcination to obtain carbon nitride nanosheet; dispersing the carbon nitride nanosheet into methanol, sequentially adding cobalt nitrate hexahydrate and 2-methylimidazole, and carrying out a reaction to obtain a carbon nitride nanosheet composite; and calcining the carbon nitride nanosheet composite in an air atmosphere at a low temperature to obtain the tricobalt tetraoxide dodecahedron/carbon nitride nanosheet composite. The in-situ growth synthesis method can ensure that the tricobalt tetraoxide obtained by follow-up calcination is uniformly coated on the carbon nitride nanosheet to improve the catalytic performance; the low temperature calcination ensures that the carbon nitride can maintain its wrinkle state and chemical structure during the calcination process.

The present invention relates to a composite metal oxide which comprises 80 to 97 wt %, in relation to the weight of the composite metal oxide, of one or more oxides of cerium and 3 to 20 wt %, in relation to the composite metal oxide of a metal oxide comprising tin oxide (SnO.sub.2) and lanthanum oxide (La.sub.2O.sub.3) and/or aluminum oxide (AI.sub.2O.sub.3), a composite material for the storage of nitrogen oxides which comprises such composite metal oxide and palladium, as well as an exhaust gas system containing said composite material.

An oxidation catalyst for treating an exhaust gas from a diesel engine comprises: a first washcoat region for oxidising carbon monoxide (CO) and hydrocarbons (HCs), wherein the first washcoat region comprises a first platinum group metal (PGM) and a first support material, and wherein the first washcoat region does not comprise manganese or an oxide thereof; a second washcoat region for oxidising nitric oxide (NO), wherein the second washcoat region comprises platinum (Pt), manganese (Mn) and a second support material comprising a refractory metal oxide, which is silica-alumina or alumina doped with silica in a total amount of 0.5 to 45% by weight of the alumina, wherein the platinum (Pt) is disposed or supported on the second support material and the manganese (Mn) is disposed or supported on the second support material; and a substrate having an inlet end and an outlet end, and wherein the first washcoat region is a first washcoat layer and the second washcoat region is a second washcoat layer, and the second washcoat layer is disposed on the first washcoat layer; and wherein when the oxidation catalyst comprises a hydrocarbon adsorbent, which is a zeolite, then the first washcoat region further comprises the hydrocarbon adsorbent.

A method for operating an exhaust system of an internal combustion engine of a motor vehicle, in which exhaust gas from the internal combustion engine flows through a first SCR catalytic converter, which is followed by an ammonia barrier catalytic converter, and flows through a second SCR catalytic converter which is disposed downstream of the ammonia barrier catalyst, includes introducing a reducing agent introduced into the exhaust gas by a first metering device upstream of the first SCR catalytic converter and by a second metering device upstream of the second SCR catalytic converter. When a predetermined threshold value of a temperature of a region of the exhaust system is exceeded, a quantity of reducing agent introduced into the exhaust gas by the first metering device is increased.

A cold start catalyst is disclosed. The cold start catalyst is effective to adsorb NO.sub.x and hydrocarbons (HC) at or below a low temperature and to covert and release the adsorbed NO.sub.x and HC at temperatures above the low temperature. The cold start catalyst comprises a molecular sieve catalyst and a supported platinum group metal catalyst. The molecular sieve catalyst consists essentially of a noble metal and a molecular sieve. The supported platinum group metal catalyst comprises one or more platinum group metals and one or more inorganic oxide carriers. The invention also includes an exhaust system comprising the cold start catalyst, and a method for treating exhaust gas from an internal combustion engine utilizing the cold start catalyst.

The invention relates to the use of a catalyst as a passive nitrogen oxide adsorber, which has a carrier substrate, a zeolite, palladium, and platinum, wherein the palladium is provided in a quantity of 0.01 to 10 wt. %, based on the sum of the weights of zeolite, platinum, and palladium and calculated as a palladium metal, and platinum in a quantity of 0.1 to 10 wt. %, based on the weight of the palladium and calculated as a platinum metal. The invention also relates to the use of said catalyst in connection with a SCR catalyst in an exhaust gas system.

The present invention relates a system for the treatment of an exhaust gas of a diesel combustion engine, said system comprising a specific NOx adsorber component, a diesel oxidation catalyst (DOC) component, a selective catalytic reduction (SCR) component, a gas heating component, and a reductant injector, wherein in said system, the specific NOx adsorber component is arranged upstream of the gas heating component, the reductant injector is arranged up-stream of the SCR component, the gas heating component is arranged upstream of the reductant injector, the DOC component is arranged upstream of the reductant injector, and the DOC component and the gas heating component are directly consecutive components. Further, the present invention relates a process for preparing such a system and use thereof.

The present invention relates to the use of a material B containing palladium and platinum in a weight ratio of 2:3 to 10:1 for increasing the low-temperature storage of nitrogen oxides by means of a material A containing palladium and zeolite, wherein material A and material B are present on a carrier substrate of the length L, and wherein material A and material B are different from one another.