Patent Description:
It is a known problem that close coupled selective catalytic reduction (SCR) catalysts based on copper containing zeolitic material having a framework structure of the type CHA, may be sulfated with time even though there is no upstream oxidation catalyst due to the sulfur trioxide exiting from engine and internally generated by SCR catalysts. Here, the term "close coupled" catalyst is used herein to define a catalyst which is the first catalyst receiving the exhaust gas stream exiting from an engine. Accordingly, it results that close coupled SCR catalysts are not able to provide sufficient DeNOx to meet the Ultra-low nitrogen oxides (NOx) and nitrous oxide (N<NUM>O) emissions, such as CARB after sulfation.

<CIT> discloses different exhaust gas treatment systems in order to meet the Ultra-low nitrogen oxides (NOx) and nitrous oxide (N<NUM>O) emissions, such as CARB after sulfation regeneration. However, there is still a need for further reducing nitrous oxides emissions while maintaining or increasing DeNOx.

Therefore, it was an object of the present invention to provide an exhaust gas treatment system for treating an exhaust gas stream exiting a diesel engine which prevents sulfating in order to maintain sufficient DeNOx, to meet the environmental requirements, and greatly reduce nitrous oxide emissions.

Surprisingly, it was found that the exhaust gas treatment system for treating an exhaust gas stream leaving a diesel engine according to the present invention and described in the following permits the regeneration after sulfating in order to maintain sufficient DeNOx or even increasing DeNOx, to meet the environmental requirements, as well as to greatly reduce the nitrous oxide emissions.

Therefore, the present invention relates to an exhaust gas treatment system for treating an exhaust gas stream exiting a diesel engine, said exhaust gas treatment system having an upstream end for introducing said exhaust gas stream into said exhaust gas treatment system, wherein said exhaust gas treatment system comprises.

wherein in the exhaust gas treatment system, the second catalyst according to (ii) is located downstream of the first catalyst according to (i) and wherein the inlet end of the second catalyst is arranged upstream of the outlet end of the second catalyst.

It is preferred that the outlet end of the first catalyst according to (i) is in fluid communication with the inlet end of the second catalyst according to (ii) and that between the outlet end of the first catalyst according to (i) and the inlet end of the second catalyst according to (ii), no catalyst for treating the exhaust gas stream exiting the first catalyst is located in the exhaust gas treatment system.

Preferably from <NUM> to <NUM> weight-%, more preferably from <NUM> to <NUM> weight-%, more preferably from <NUM> to <NUM> weight-% of the oxidic material comprised in the coating of the first catalyst according to (i) consist of zirconium and oxygen, preferably of zirconia.

Preferably the oxidic material comprised in the coating of the first catalyst according to (i) further comprises one or more of lanthanum, hafnium, aluminum, silicon and titanium, more preferably one or more of lanthanum and hafnium, more preferably lanthanum and hafnium.

Preferably from <NUM> to <NUM> weight-%, more preferably from <NUM> to <NUM> weight-%, more preferably from <NUM> to <NUM> weight-% of the oxidic material comprised in the coating of the first catalyst according to (i) consist of oxygen, zirconium, lanthanum and hafnium. More preferably from <NUM> to <NUM> weight-%, more preferably from <NUM> to <NUM> weight-%, of the oxidic material consist of lanthanum, calculated as La<NUM>O<NUM>, and more preferably from <NUM> to <NUM> weight-%, more preferably from <NUM> to <NUM> weight-%, of the oxidic material consist of hafnium, calculated as HfO<NUM>.

Preferably from <NUM> to <NUM> weight-%, more preferably from <NUM> to <NUM> weight-%, more preferably from <NUM> to <NUM> weight-%, of the coating of the first catalyst according to (i) consist of the oxidic material.

As to the coating of the first catalyst, it is preferred that it comprises palladium at a loading, calculated as elemental Pd, in the range of from <NUM> to <NUM>/ft3, more preferably in the range of from <NUM> to <NUM>/ft<NUM>, more preferably in the range of from <NUM> to <NUM>/ft<NUM>, more preferably in the range of from <NUM> to <NUM>/ft3 (<NUM>/ft3 <=> <NUM>/l).

It is preferred that the coating of the first catalyst according to (i) comprises the zeolitic material comprising one or more of copper and iron, wherein from <NUM> to <NUM> weight-%, more preferably from <NUM> to <NUM> weight-%, more preferably from <NUM> to <NUM> weight-%, of the coating of the first catalyst according to (i) consist of the zeolitic material comprising one or more of copper and iron.

As to the zeolitic material comprised in the coating of the first catalyst, it is preferred that said zeolitic material has a framework structure of the type AEI, GME, CHA, MFI, BEA, FAU, MOR or mixtures of two or more thereof, preferably a framework structure of the type AEI, CHA, BEA or mixtures of two or more thereof, more preferably a framework structure of the type CHA or AEI, more preferably a framework structure of the type CHA.

Preferably the zeolitic material comprised in the coating of the first catalyst, more preferably having a framework structure type CHA, has a mean crystallite size of at least <NUM> micrometer, more preferably in the range of from <NUM> to <NUM> micrometers, more preferably in the range of from <NUM> to <NUM> micrometer, more preferably in the range of from <NUM> to <NUM> micrometer determined via scanning electron microscopy.

It is preferred that the zeolitic material comprised in the coating of the first catalyst comprises copper, wherein the amount of copper comprised in the zeolitic material, calculated as CuO, is more preferably in the range of from <NUM> to <NUM> weight-%, more preferably in the range of from <NUM> to <NUM> weight-%, more preferably in the range of from <NUM> to <NUM> weight-%, more preferably in the range of from <NUM> to <NUM> weight-%, based on the weight of the zeolitic material. It is more preferred that the amount of iron comprised in the zeolitic material, calculated as Fe<NUM>O<NUM>, is in the range of from <NUM> to <NUM> weight-%, more preferably in the range of from <NUM> to <NUM> weight-%, more preferably in the range of from <NUM> to <NUM> weight-%, based on the weight of the zeolitic material.

It is preferred that the zeolitic material has a framework structure of the type CHA and comprises copper, more preferably in the amount disclosed above.

Preferably from <NUM> to <NUM> weight-%, more preferably from <NUM> to <NUM> weight-%, more preferably from <NUM> to <NUM> weight-%, of the framework structure of the zeolitic material of the coating of the first catalyst consist of Si, Al, O, and optionally one or more of H and P, wherein in the framework structure, the molar ratio of Si to Al, calculated as molar SiO<NUM> : Al<NUM>O<NUM>, is more preferably in the range of from <NUM>:<NUM> to <NUM>:<NUM>, more preferably in the range of from <NUM>:<NUM> to <NUM>:<NUM>, more preferably in the range of from <NUM>:<NUM> to <NUM>:<NUM>, more preferably in the range of from <NUM>:<NUM> to <NUM>:<NUM>.

It can also be preferred that the zeolitic material comprised in the coating of the first catalyst comprises iron, wherein the amount of iron comprised in the zeolitic material, calculated as Fe<NUM>O<NUM>, is more preferably in the range of from <NUM> to <NUM> weight-%, more preferably in the range of from <NUM> to <NUM> weight-%, more preferably in the range of from <NUM> to <NUM> weight-% based on the weight of the zeolitic material. More preferably from <NUM> to <NUM> weight-%, more preferably from <NUM> to <NUM> weight-%, more preferably from <NUM> to <NUM> weight-%, of the framework structure of said zeolitic material consist of Si, Al, O, and optionally one or more of H and P, wherein in the framework structure, the molar ratio of Si to Al, calculated as molar SiO<NUM> : Al<NUM>O<NUM>, is more preferably in the range of from <NUM>:<NUM> to <NUM>:<NUM>, more preferably in the range of from <NUM>:<NUM> to <NUM>:<NUM>, more preferably in the range of from <NUM>:<NUM> to <NUM>: <NUM>, more preferably in the range of from <NUM>: <NUM> to <NUM>: <NUM>.

In the context of the present invention, it is preferred that the coating of the first catalyst further comprises a metal oxide, wherein the metal oxide more preferably comprises one or more of zirconia, alumina, titania, silica, and a mixed oxide comprising two or more of Zr, Al, Ti, and Si, more preferably comprises one or more of alumina and zirconia, more preferably comprises, more preferably is, zirconia.

It is preferred that the coating of the first catalyst comprises said metal oxide, more preferably zirconia, in an amount in the range of from <NUM> to <NUM> weight-%, more preferably from <NUM> to <NUM> weight-%, more preferably from <NUM> to <NUM> weight-%, based on the weight of the zeolitic material comprising one or more of copper and iron.

Preferably, as an alternative, the coating of the first catalyst according to (i) comprises a vanadium oxide and not the zeolitic material comprising one or more of copper and iron. It is more preferred that the vanadium oxide is one or more of a vanadium (V) oxide and a vanadium (IV) oxide, wherein the vanadium oxide optionally contains one or more of tungsten, iron and antimony. It is preferred that the vanadium oxide is supported on an oxidic material comprising one or more of titanium, silicon and zirconium, more preferably an oxidic material comprising one or more of titanium and silicon, more preferably an oxidic material comprising one or more of titania and silica, more preferably on titania, wherein titania optionally contains one or more of tungsten and silicon.

In the context of the present invention, it is preferred that, from <NUM> to <NUM> weight-%, more preferably from <NUM> to <NUM> weight-%, more preferably from <NUM> to <NUM> weight-%, more preferably from <NUM> to <NUM> weight-%, of the coating of the first catalyst consist of palladium supported on an oxidic material, a zeolitic material having a framework structure of the type CHA comprising copper, and more preferably a metal oxide as defined in the foregoing.

It is preferred that the substrate of the first catalyst comprises a ceramic or metallic substance.

Preferably the substrate of the first catalyst comprises, more preferably consists of, a ceramic substance, wherein the ceramic substance more preferably comprises, more preferably consists of, one or more of an alumina, a silica, a silicate, an aluminosilicate, preferably a cordierite or a mullite, an aluminotitanate, a silicon carbide, a zirconia, a magnesia, preferably a spinel, and a titania, more preferably one or more of a silicon carbide and a cordierite, more preferably a cordierite. It is preferred that the substrate of the first catalyst is a cordierite. Alternatively, the substrate of the first catalyst preferably comprises, more preferably consists of, a metallic substance, wherein the metallic substance preferably comprises, more preferably consists of, oxygen and one or more of iron, chromium, and aluminum.

It is preferred that the substrate of the first catalyst is a monolith, more preferably a honeycomb monolith, more preferably a flow-through honeycomb monolith.

Preferably the substrate of the first catalyst has a substrate length and the coating of the first catalyst is disposed on the substrate over from <NUM> to <NUM> %, more preferably from <NUM> to <NUM> %, of the substrate length.

It is preferred that the first catalyst comprises the coating at a loading in the range of from <NUM> to <NUM>/in<NUM>, more preferably in the range of from <NUM> to <NUM>/in<NUM>, more preferably in the range of from <NUM> to <NUM>/in<NUM> (<NUM>/in<NUM> <_> <NUM>/l).

It is preferred that the coating of the first catalyst is the sole coating of the first catalyst.

Preferably at most <NUM> weight-%, more preferably from <NUM> to <NUM> weight-%, more preferably from <NUM> to <NUM> weight-%, of the coating of the first catalyst consists of platinum, iridium, osmium and rhodium. In other words, it is preferred that the coating of the first catalyst is substantially free of, more preferably free of, platinum, iridium, osmium and rhodium.

Preferably at most <NUM> weight-%, more preferably from <NUM> to <NUM> weight-%, more preferably from <NUM> to <NUM> weight-%, more preferably from <NUM> to <NUM> weight-%, of the coating of the first catalyst consists of ceria. In other words, it is preferred that the coating of the first catalyst is substantially free of, more preferably free of, ceria.

It is preferred that the second catalyst according to (ii) is a selective catalytic reduction catalyst.

Indeed, it is more preferably a selective catalytic reduction catalyst for the selective catalytic reduction of NOx.

As to the coating of the second catalyst according to (ii), it is preferred that it comprises a zeolitic material comprising one or more of copper and iron; wherein from <NUM> to <NUM> weight-%, more preferably from <NUM> to <NUM> weight-%, more preferably from <NUM> to <NUM> weight-%, of the coating of the second catalyst according to (ii) consist of the zeolitic material comprising one or more of copper and iron.

Preferably the zeolitic material comprised in the coating of the second catalyst has a framework structure of the type AEI, GME, CHA, MFI, BEA, FAU, MOR or mixtures of two or more thereof, more preferably a framework structure of the type AEI, CHA, BEA or mixtures of two or more thereof, more preferably a framework structure of the type CHA or AEI, more preferably a framework structure of the type CHA.

Preferably the zeolitic material comprised in the coating of the second catalyst, preferably having a framework structure type CHA, has a mean crystallite size of at least <NUM> micrometer, more preferably in the range of from <NUM> to <NUM> micrometers, more preferably in the range of from <NUM> to <NUM> micrometer, more preferably in the range of from <NUM> to <NUM> micrometer determined via scanning electron microscopy.

It is preferred that the zeolitic material comprised in the coating of the second catalyst comprises copper, wherein the amount of copper comprised in the zeolitic material, calculated as CuO, is more preferably in the range of from <NUM> to <NUM> weight-%, more preferably in the range of from <NUM> to <NUM> weight-%, more preferably in the range of from <NUM> to <NUM> weight-%, more preferably in the range of from <NUM> to <NUM> weight-%, based on the weight of the zeolitic material.

It is more preferred that the amount of iron comprised in the zeolitic material, calculated as Fe<NUM>O<NUM>, is in the range of from <NUM> to <NUM> weight-%, more preferably in the range of from <NUM> to <NUM> weight-%, more preferably in the range of from <NUM> to <NUM> weight-%, based on the weight of the zeolitic material.

It is preferred that the zeolitic material comprised in the coating of the second catalyst has a framework structure of the type CHA and comprises copper, more preferably in the amount disclosed above.

Preferably from <NUM> to <NUM> weight-%, more preferably from <NUM> to <NUM> weight-%, more preferably from <NUM> to <NUM> weight-%, of the framework structure of the zeolitic material comprised in the coating of the second catalyst consist of Si, Al, O, and optionally one or more of H and P, wherein in the framework structure, the molar ratio of Si to Al, calculated as molar SiO<NUM> : Al<NUM>O<NUM>, is more preferably in the range of from <NUM>:<NUM> to <NUM>:<NUM>, more preferably in the range of from <NUM>:<NUM> to <NUM>:<NUM>, more preferably in the range of from <NUM>:<NUM> to <NUM>: <NUM>, more preferably in the range of from <NUM>: <NUM> to <NUM>: <NUM>.

It can also be preferred that the zeolitic material comprised in the coating of the second catalyst comprises iron, wherein the amount of iron comprised in the zeolitic material, calculated as Fe<NUM>O<NUM>, is more preferably in the range of from <NUM> to <NUM> weight-%, more preferably in the range of from <NUM> to <NUM> weight-%, more preferably in the range of from <NUM> to <NUM> weight-%, based on the weight of the zeolitic material. More preferably from <NUM> to <NUM> weight-%, more preferably from <NUM> to <NUM> weight-%, more preferably from <NUM> to <NUM> weight-% of the framework structure of the zeolitic material consist to Si, Al, O, and optionally one or more of H and P, wherein in the framework structure, the molar ratio of Si to Al, calculated as molar SiO<NUM> : Al<NUM>O<NUM>, is more preferably in the range of from <NUM>:<NUM> to <NUM>:<NUM>, more preferably in the range of from <NUM>:<NUM> to <NUM>:<NUM>, more preferably in the range of from <NUM>:<NUM> to <NUM>: <NUM>, more preferably in the range of from <NUM>: <NUM> to <NUM>: <NUM>.

In the context of the present invention, it is preferred that the coating of the second catalyst further comprises a metal oxide, wherein the metal oxide more preferably comprises one or more of zirconia, alumina, titania, silica, and a mixed oxide comprising two or more of Zr, Al, Ti, and Si, more preferably comprises one or more of alumina and zirconia, more preferably comprises, more preferably is, zirconia.

Preferably the coating of the second catalyst comprises the metal oxide, more preferably zirconia, in an amount in the range of from <NUM> to <NUM> weight-%, more preferably from <NUM> to <NUM> weight-%, more preferably from <NUM> to <NUM> weight-%, based on the weight of the zeolitic material comprising one or more of copper and iron.

Preferably from <NUM> to <NUM> weight-%, more preferably from <NUM> to <NUM> weight-%, more preferably from <NUM> to <NUM> weight-%, more preferably from <NUM> to <NUM> weight-%, of the coating of the second catalyst comprise a zeolitic material comprising one or more of copper and iron, more preferably having a framework structure of the type CHA, and preferably a metal oxide as defined in the foregoing.

It is preferred that the coating of the second catalyst comprises a vanadium oxide, wherein the vanadium oxide is more preferably one or more of a vanadium (V) oxide and a vanadium (IV) oxide, wherein the vanadium oxide optionally contains one or more of tungsten, iron and antimony. Preferably the vanadium oxide is supported on an oxidic material comprising one or more of titanium, silicon and zirconium, more preferably an oxidic material comprising one or more of titanium and silicon, more preferably an oxidic material comprising one or more of titania and silica, more preferably on titania, wherein titania optionally contains one or more of tungsten and silicon.

Preferably from <NUM> to <NUM> weight-%, more preferably from <NUM> to <NUM> weight-%, more preferably from <NUM> to <NUM> weight-%, more preferably from <NUM> to <NUM> weight-% of the coating of the second catalyst consist of a vanadium oxide, preferably supported on an oxidic material as defined in the foregoing.

Preferably from <NUM> to <NUM> weight-%, more preferably from <NUM> to <NUM> weight-%, more preferably from <NUM> to <NUM> weight-%, of the coating of the second catalyst consists of platinum group metal. In other words, it is preferred that the coating of the second catalyst is substantially free, more preferably free, of platinum group metal.

It is preferred that the substrate of the second catalyst comprises a ceramic or metallic substance.

It is preferred that the substrate of the second catalyst comprises, more preferably consists of, a ceramic substance, wherein the ceramic substance more preferably comprises, more preferably consists of, one or more of an alumina, a silica, a silicate, an aluminosilicate, preferably a cordierite or a mullite, an aluminotitanate, a silicon carbide, a zirconia, a magnesia, preferably a spinel, and a titania, more preferably one or more of a silicon carbide and a cordierite, more preferably a cordierite. It is more preferred that the substrate of the second catalyst is a cordierite. Alternatively, it is preferred that the substrate of the second catalyst comprises, more preferably consists of, a metallic substance, wherein the metallic substance more preferably comprises, more preferably consists of, oxygen and one or more of iron, chromium, and aluminum.

Preferably the substrate of the second catalyst is a monolith, more preferably a honeycomb monolith, more preferably a flow-through honeycomb monolith.

Preferably the substrate of the second catalyst has a substrate length and the coating of the second catalyst is disposed on the substrate over from <NUM> to <NUM> %, more preferably from <NUM> to <NUM> % of the substrate length.

As to the second catalyst, it is preferred that said second catalyst comprises the coating at a loading in the range of from <NUM> to <NUM>/in<NUM>, more preferably in the range of from <NUM> to <NUM>/in<NUM>, more preferably in the range of from <NUM> to <NUM>/in<NUM> (<NUM>/in<NUM> <=> <NUM>/l).

As to the coating of the second catalyst, it is preferred that said coating is the sole coating of the second catalyst.

It is preferred that the coating of the first catalyst comprises, more preferably consists of, palladium supported on an oxidic material comprising zirconium, and a zeolitic material having a framework structure of the type CHA and comprising copper, and more preferably a metal oxide as defined in the foregoing, and that the coating of the second catalyst comprises, more preferably consists of, a zeolitic material having a framework structure of the type CHA and comprising copper, and more preferably a metal oxide as defined in the foregoing, wherein at most <NUM> weight-% of the coating of the second catalyst consists of platinum group metal.

It is preferred that the substrate of the first catalyst comprises, more preferably consists of, a cordierite and the substrate of the second catalyst comprises, more preferably consists of, a cordierite.

Preferably the substrate of the first catalyst on which substrate the coating of the first catalyst is disposed, is a first substrate and the substrate of the second catalyst on which substrate the coating of the second catalyst is disposed, is a second substrate, wherein the first substrate and the second substrate are different from each other. Alternatively, it is preferred that the substrate of the first catalyst, on which substrate the coating of the first catalyst is disposed, and the substrate of the second catalyst, on which substrate the coating of the second catalyst is disposed, together form a single substrate, wherein said single substrate comprises an inlet end and an outlet end, wherein the inlet end is arranged upstream of the outlet end, and wherein the coating of the first catalyst is disposed on said single substrate from the inlet end towards the outlet end of said single substrate and the coating of the second catalyst is disposed on said single substrate from the outlet end towards the inlet end of said single substrate, wherein the coating of the first catalyst covers from <NUM> to <NUM> % of the substrate length and the coating of the second catalyst covers from <NUM> to <NUM> % of the substrate length.

It is more preferred that the coating of the first catalyst covers from <NUM> to <NUM> %, more preferably from <NUM> to <NUM> %, more preferably from <NUM> to <NUM> %, of the substrate length and the coating of the second catalyst covers from <NUM> to <NUM> %, more preferably from <NUM> to <NUM> %, more preferably from <NUM> to <NUM> % of the substrate length. Alternatively, it is more preferred that the coating of the first catalyst covers from <NUM> to <NUM> %, more preferably from <NUM> to <NUM> % of the substrate length and the coating of the second catalyst covers from <NUM> to <NUM> %, more preferably from <NUM> to <NUM> % of the substrate length.

It is preferred that the coating of the first catalyst and the coating of the second catalyst overlap. Or, it is preferred that there is a gap between the coating of the first catalyst and the coating of the second catalyst.

In the context of the present invention, it is preferred that the substrate of the first catalyst has a substrate length in the range of from <NUM> to <NUM> inches, more preferably in the range of from <NUM> to <NUM> inches, more preferably in the range of from <NUM> to <NUM> inches, more preferably in the range of from <NUM> to <NUM> inches (<NUM> inch <=> <NUM>).

Preferably the substrate of the second catalyst has a substrate length in the range of from <NUM> to <NUM> inches, more preferably in the range of from <NUM> to <NUM> inches, more preferably in the range of from <NUM> to <NUM> inches, more preferably in the range of from <NUM> to <NUM> inches (<NUM> inch <=> <NUM>).

Preferably the length of the first substrate is greater than the length of the second substrate, wherein the ratio of the length of the first substrate relative to the length of the second substrate is more preferably in the range of from <NUM>:<NUM> to <NUM>:<NUM>, more preferably in the range of from <NUM>:<NUM> to <NUM>:<NUM>, more preferably in the range of from <NUM>:<NUM> to <NUM>:<NUM>.

Preferably the substrate of the first catalyst has a substrate width in the range of from <NUM> to <NUM> inches, more preferably in the range of from <NUM> to <NUM> inches, more preferably in the range of from <NUM> to <NUM> inches, more preferably in the range of from <NUM> to <NUM> inches, more preferably in the range of from <NUM> to <NUM> inches (<NUM> inch <=> <NUM>).

Preferably the substrate of the second catalyst has a substrate width in the range of from <NUM> to <NUM> inches, more preferably in the range of from <NUM> to <NUM> inches, more preferably in the range of from <NUM> to <NUM> inches, more preferably in the range of from <NUM> to <NUM> inches, more preferably in the range of from <NUM> to <NUM> inches (<NUM> inch <=> <NUM>).

It is preferred that the exhaust gas treatment system of the present invention further comprises a first injector for injecting a fluid into the exhaust gas stream exiting the diesel engine, said first injector being located upstream of the first catalyst and downstream of the upstream end of the exhaust gas treatment system. Preferably the fluid is an aqueous urea solution.

It is preferred that the exhaust gas treatment system of the present invention further comprises a second injector for injecting a fluid into the exhaust gas stream exiting the diesel engine, said injector being located upstream of the first catalyst and downstream of the upstream end of the exhaust gas treatment system, wherein the fluid more preferably comprises hydrocarbons.

It is preferred that the exhaust gas treatment system of the present invention further comprises
(iii) a third catalyst having an inlet end and an outlet end and comprising a first coating disposed on a substrate and a second coating disposed on the first coating,.

wherein in the exhaust gas treatment system, the third catalyst according to (iii) is located downstream of the second catalyst according to (ii) and wherein the inlet end of the third catalyst is arranged upstream of the outlet end of the third catalyst.

It is preferred that the outlet end of the second catalyst according to (ii) is in fluid communication with the inlet end of the third catalyst according to (iii) and that between the outlet end of the second catalyst according to (ii) and the inlet end of the third catalyst according to (iii), no catalyst for treating the exhaust gas stream exiting the second catalyst is located in the exhaust gas treatment system.

As to the third catalyst according to (iii), it is preferred that said catalyst is an ammonia oxidation catalyst.

Preferably the platinum group metal comprised in the first coating of the third catalyst according to (iii) is one or more of platinum, palladium, rhodium, iridium and osmium, more preferably one or more of platinum, palladium and rhodium, more preferably one or more of platinum and palladium, more preferably platinum.

As to the first coating of the third catalyst, it is preferred that said first coating comprises the platinum group metal, more preferably platinum, at a loading, calculated as elemental metal, more preferably as elemental Pt, in the range of from <NUM> to <NUM>/ft3, more preferably in the range of from <NUM> to <NUM>/ft3, more preferably in the range of from <NUM> to <NUM>/ft3 (<NUM>/ft3 <=> <NUM>/l).

Preferably the oxidic material comprised in the first coating of the third catalyst according to (iii) comprises one or more of titania, zirconia, and alumina, more preferably one or more of titania and zirconia, more preferably titania. It is more preferred that from <NUM> to <NUM> weight-%, more preferably from <NUM> to <NUM> weight-%, of the oxidic material consist of titania, calculated as TiO<NUM>.

Preferably the oxidic material comprised in the coating of the third catalyst according to (iii) further comprises one or more of silicon, aluminum, titanium and zirconium, more preferably one or more of silicon and aluminum, more preferably silicon.

Preferably from <NUM> to <NUM> weight-%, more preferably from <NUM> to <NUM> weight-%, more preferably from <NUM> to <NUM> weight-%, of the oxidic material comprised in the coating of the third catalyst according to (iii) consist of oxygen, titanium and silicon. More preferably from <NUM> to <NUM> weight- %, more preferably from <NUM> to <NUM> weight-%, of the oxidic material consist of silicon, calculated as SiO<NUM>.

It is preferred that from <NUM> to <NUM> weight-%, more preferably from <NUM> to <NUM> weight-%, more preferably from <NUM> to <NUM> weight-%, more preferably from <NUM> to <NUM> weight-%, more preferably from <NUM> to <NUM> weight-%, of the first coating of the third catalyst according to (iii) consist of the oxidic material.

As an alternative, it is preferred that from <NUM> to <NUM> weight-%, more preferably from <NUM> to <NUM> weight- %, more preferably from <NUM> to <NUM> weight-%, of the first coating of the third catalyst according to (iii) consist of the oxidic material.

Preferably the first coating of the third catalyst according to (iii) comprises the zeolitic material comprising one or more of copper and iron, wherein from <NUM> to <NUM> weight-%, more preferably from <NUM> to <NUM> weight-%, more preferably from <NUM> to <NUM> weight-%, of the first coating of the third catalyst according to (iii) consist of the zeolitic material comprising one or more of copper and iron.

As to the zeolitic material comprised in the first coating of the third catalyst, it is preferred that said zeolitic material has a framework structure of the type AEI, GME, CHA, MFI, BEA, FAU, MOR or mixtures of two or more thereof, more preferably a framework structure of the type AEI, CHA, BEA or mixtures of two or more thereof, more preferably a framework structure of the type CHA or AEI, more preferably a framework structure of the type CHA.

Preferably the zeolitic material comprised in the first coating of the third catalyst, more preferably having a framework structure type CHA, has a mean crystallite size of at least <NUM> micrometer, more preferably in the range of from <NUM> to <NUM> micrometers, more preferably in the range of from <NUM> to <NUM> micrometer, more preferably in the range of from <NUM> to <NUM> micrometer determined via scanning electron microscopy.

Preferably the zeolitic material comprised in the first coating of the third catalyst comprises copper, wherein the amount of copper comprised in the zeolitic material, calculated as CuO, is more preferably in the range of from <NUM> to <NUM> weight-%, more preferably in the range of from <NUM> to <NUM> weight-%, more preferably in the range of from <NUM> to <NUM> weight-%, more preferably in the range of from <NUM> to <NUM> weight-%, based on the weight of the zeolitic material. Preferably the amount of iron comprised in the zeolitic material, calculated as Fe<NUM>O<NUM>, is in the range of from <NUM> to <NUM> weight-%, more preferably in the range of from <NUM> to <NUM> weight-%, more preferably in the range of from <NUM> to <NUM> weight-%, based on the weight of the zeolitic material.

It is preferred that the zeolitic material comprised in the first coating of the third catalyst has a framework structure of the type CHA and comprises copper, more preferably in the amount disclosed above.

Preferably from <NUM> to <NUM> weight-%, more preferably from <NUM> to <NUM> weight-%, more preferably from <NUM> to <NUM> weight-%, of the framework structure of the zeolitic material comprised in the first coating of the third catalyst consist of Si, Al, O, and optionally one or more of H and P, wherein in the framework structure, the molar ratio of Si to Al, calculated as molar SiO<NUM> : Al<NUM>O<NUM>, is more preferably in the range of from <NUM>:<NUM> to <NUM>:<NUM>, more preferably in the range of from <NUM>:<NUM> to <NUM>:<NUM>, more preferably in the range of from <NUM>:<NUM> to <NUM>: <NUM>, more preferably in the range of from <NUM>: <NUM> to <NUM>: <NUM>.

It is preferred that the zeolitic material comprised in the first coating of the third catalyst comprises iron, wherein the amount of iron comprised in the zeolitic material, calculated as Fe<NUM>O<NUM>, is more preferably in the range of from <NUM> to <NUM> weight-%, more preferably in the range of from <NUM> to <NUM> weight-%, more preferably in the range of from <NUM> to <NUM> weight-% based on the weight of the zeolitic material. More preferably from <NUM> to <NUM> weight-%, more preferably from <NUM> to <NUM> weight-%, more preferably from <NUM> to <NUM> weight-%, of the framework structure of the zeolitic material consist of Si, Al, O, and optionally one or more of H and P, wherein in the framework structure, the molar ratio of Si to Al, calculated as molar SiO<NUM> : Al<NUM>O<NUM>, is more preferably in the range of from <NUM>:<NUM> to <NUM>:<NUM>, more preferably in the range of from <NUM>:<NUM> to <NUM>:<NUM>, more preferably in the range of from <NUM>:<NUM> to <NUM>: <NUM>, more preferably in the range of from <NUM>: <NUM> to <NUM>: <NUM>.

As to the first coating of the third catalyst, it is preferred that said coating further comprises a metal oxide, wherein the metal oxide more preferably comprises one or more of zirconia, alumina, titania, silica, and a mixed oxide comprising two or more of Zr, Al, Ti, and Si, more preferably comprises one or more of alumina and zirconia, more preferably comprises, more preferably is, zirconia.

Preferably the first coating of the third catalyst comprises the metal oxide, more preferably zirconia, in an amount in the range of from <NUM> to <NUM> weight-%, more preferably from <NUM> to <NUM> weight- %, more preferably from <NUM> to <NUM> weight-%, based on the weight of the zeolitic material comprising one or more of copper and iron.

Preferably from <NUM> to <NUM> weight-%, more preferably from <NUM> to <NUM> weight-%, more preferably from <NUM> to <NUM> weight-%, more preferably from <NUM> to <NUM> weight-%, of the first coating of the third catalyst consist of a platinum group metal, more preferably platinum, supported on an oxidic material, and a zeolitic material having a framework structure of the type CHA comprising copper, and preferably a metal oxide as defined in the foregoing.

It is preferred that the first coating of the third catalyst according to (iii) comprises a vanadium oxide and not the zeolitic material comprising one or more of copper and iron, wherein the vanadium oxide is more preferably one or more of a vanadium (V) oxide and a vanadium (IV) oxide, wherein the vanadium oxide optionally contains one or more of tungsten, iron and antimony.

Preferably the vanadium oxide is supported on an oxidic material comprising one or more of titanium, silicon and zirconium, more preferably an oxidic material comprising one or more of titanium and silicon, more preferably an oxidic material comprising one or more of titania and silica, more preferably on titania, wherein titania optionally contains one or more of tungsten and silicon.

Preferably from <NUM> to <NUM> weight-%, more preferably from <NUM> to <NUM> weight-%, more preferably from <NUM> to <NUM> weight-%, more preferably from <NUM> to <NUM> weight-% of the first coating of the third catalyst consist of a platinum group metal, more preferably platinum, supported on an oxidic material, and a vanadium oxide supported on an oxidic material as defined in the foregoing.

As to the second coating of the third catalyst according to (iii), it is preferred that said coating comprises a zeolitic material comprising one or more of copper and iron; wherein from <NUM> to <NUM> weight-%, more preferably from <NUM> to <NUM> weight-%, more preferably from <NUM> to <NUM> weight-%, of the second coating of the third catalyst according to (iii) consist of the zeolitic material comprising one or more of copper and iron.

It is preferred that the zeolitic material comprised in the second coating of the third catalyst has a framework structure of the type AEI, GME, CHA, MFI, BEA, FAU, MOR or mixtures of two or more thereof, more preferably a framework structure of the type AEI, CHA, BEA or mixtures of two or more thereof, more preferably a framework structure of the type CHA or AEI, more preferably a framework structure of the type CHA.

Preferably the zeolitic material comprised in the second coating of the third catalyst, preferably having a framework structure type CHA, has a mean crystallite size of at least <NUM> micrometer, more preferably in the range of from <NUM> to <NUM> micrometers, more preferably in the range of from <NUM> to <NUM> micrometer, more preferably in the range of from <NUM> to <NUM> micrometer determined via scanning electron microscopy.

It is preferred that the zeolitic material comprised in the second coating of the third catalyst comprises copper, wherein the amount of copper comprised in the zeolitic material, calculated as CuO, is preferably in the range of from <NUM> to <NUM> weight-%, more preferably in the range of from <NUM> to <NUM> weight-%, more preferably in the range of from <NUM> to <NUM> weight-%, more preferably in the range of from <NUM> to <NUM> weight-%, based on the weight of the zeolitic material. More preferably the amount of iron comprised in the zeolitic material, calculated as Fe<NUM>O<NUM>, is in the range of from <NUM> to <NUM> weight-%, more preferably in the range of from <NUM> to <NUM> weight-%, more preferably in the range of from <NUM> to <NUM> weight-%, based on the weight of the zeolitic material.

It is preferred that the zeolitic material comprised in the second coating of the third catalyst has a framework structure of the type CHA and comprises copper, more preferably in the amount disclosed above.

Preferably from <NUM> to <NUM> weight-%, more preferably from <NUM> to <NUM> weight-%, more preferably from <NUM> to <NUM> weight-%, of the framework structure of the zeolitic material comprised in the second coating of the third catalyst consist of Si, Al, O, and optionally one or more of H and P, wherein in the framework structure, the molar ratio of Si to Al, calculated as molar SiO<NUM> : Al<NUM>O<NUM>, is more preferably in the range of from <NUM>:<NUM> to <NUM>:<NUM>, more preferably in the range of from <NUM>:<NUM> to <NUM>:<NUM>, more preferably in the range of from <NUM>:<NUM> to <NUM>: <NUM>, more preferably in the range of from <NUM>: <NUM> to <NUM>: <NUM>.

It can also be preferred that the zeolitic material comprised in the second coating of the third catalyst comprises iron, wherein the amount of iron comprised in the zeolitic material, calculated as Fe<NUM>O<NUM>, is more preferably in the range of from <NUM> to <NUM> weight-%, more preferably in the range of from <NUM> to <NUM> weight-%, more preferably in the range of from <NUM> to <NUM> weight-%, based on the weight of the zeolitic material, and that more preferably from <NUM> to <NUM> weight-%, more preferably from <NUM> to <NUM> weight-%, more preferably from <NUM> to <NUM> weight-%, of the framework structure of the zeolitic material consist of Si, Al, O, and optionally one or more of H and P, wherein in the framework structure, the molar ratio of Si to Al, calculated as molar SiO<NUM> : Al<NUM>O<NUM>, is more preferably in the range of from <NUM>:<NUM> to <NUM>:<NUM>, more preferably in the range of from <NUM>:<NUM> to <NUM>:<NUM>, more preferably in the range of from <NUM>:<NUM> to <NUM>: <NUM>, more preferably in the range of from <NUM>: <NUM> to <NUM>: <NUM>.

As to the second coating of the third catalyst, it is preferred that said coating further comprises a metal oxide, wherein the metal oxide more preferably comprises one or more of zirconia, alumina, titania, silica, and a mixed oxide comprising two or more of Zr, Al, Ti, and Si, more preferably comprises one or more of alumina and zirconia, more preferably comprises, more preferably is, zirconia.

Preferably the second coating of the third catalyst comprises the metal oxide, more preferably zirconia, in an amount in the range of from <NUM> to <NUM> weight-%, more preferably from <NUM> to <NUM> weight-%, more preferably from <NUM> to <NUM> weight-%, based on the weight of the zeolitic material comprising one or more of copper and iron.

Preferably from <NUM> to <NUM> weight-%, more preferably from <NUM> to <NUM> weight-%, more preferably from <NUM> to <NUM> weight-%, more preferably from <NUM> to <NUM> weight-% of the second coating of the third catalyst consist of a zeolitic material comprising one or more of copper and iron, more preferably having a framework structure of the type CHA, and more preferably a metal oxide as defined in the foregoing.

It is preferred that the second coating of the third catalyst comprises a vanadium oxide, wherein the vanadium oxide is more preferably one or more of a vanadium (V) oxide and a vanadium (IV) oxide, wherein the vanadium oxide optionally contains one or more of tungsten, iron and antimony.

Preferably from <NUM> to <NUM> weight-%, more preferably from <NUM> to <NUM> weight-%, more preferably from <NUM> to <NUM> weight-%, more preferably from <NUM> to <NUM> weight-%, of the second coating of the third catalyst consist of a vanadium oxide, more preferably supported on an oxidic material as defined in the foregoing.

Preferably from <NUM> to <NUM> weight-%, more preferably from <NUM> to <NUM> weight-%, more preferably from <NUM> to <NUM> weight-%, of the second coating of the third catalyst consists of platinum group metal. In other words, it is preferred that the second coating of the third catalyst is substantially free, more preferably free, of platinum group metal.

As to the substrate of the third catalyst, it is preferred that it comprises a ceramic or metallic substance.

Preferably the substrate of the third catalyst comprises, preferably consists of, a ceramic substance, wherein the ceramic substance preferably comprises, more preferably consists of, one or more of an alumina, a silica, a silicate, an aluminosilicate, preferably a cordierite or a mullite, an aluminotitanate, a silicon carbide, a zirconia, a magnesia, preferably a spinel, and a titania, more preferably one or more of a silicon carbide and a cordierite, more preferably a cordierite. It is more preferred that the substrate of the third catalyst comprises is a cordierite. Alternatively, it is preferred that the substrate of the third catalyst comprises, preferably consists of, a metallic substance, wherein the metallic substance preferably comprises, more preferably consists of, oxygen and one or more of iron, chromium, and aluminum.

Preferably the substrate of the third catalyst is a monolith, more preferably a honeycomb monolith, more preferably a flow-through honeycomb monolith.

Preferably the substrate of the third catalyst has a substrate length and the first coating of the third catalyst is disposed on the substrate over from <NUM> to <NUM> %, more preferably from <NUM> to <NUM> % of the substrate length and the second coating of the third catalyst is disposed over from <NUM> to <NUM> %, more preferably from <NUM> to <NUM> %, of the substrate length.

It is preferred that the third catalyst comprises the first coating at a loading in the range of from <NUM> to <NUM>/in<NUM>, more preferably in the range of from <NUM> to <NUM>/in<NUM>, more preferably in the range of from <NUM> to <NUM>/in<NUM> (<NUM>/in<NUM> <=> <NUM>/l).

Preferably the third catalyst comprises the second coating at a loading in the range of from <NUM> to <NUM>/in<NUM>, more preferably in the range of from <NUM> to <NUM>/in<NUM>, more preferably in the range of from <NUM> to <NUM>/in<NUM> (<NUM>/in<NUM> <=> <NUM>/l).

It is preferred that the third catalyst comprises a catalytic loading in the range of from <NUM> to <NUM>/in<NUM>, more preferably in the range of from <NUM> to <NUM>/in<NUM>, more preferably in the range of from <NUM> to <NUM>/in<NUM> (<NUM>/in<NUM> <=> <NUM>/l).

It is preferred that the third catalyst according to (iii) consists of the first coating and the second coating.

Therefore, the present invention preferably relates to the exhaust gas treatment system defined in the foregoing, wherein the coating of the first catalyst comprises, more preferably consists of, palladium supported on an oxidic material comprising zirconium, and a zeolitic material having a framework structure of the type CHA and comprising copper, and more preferably a metal oxide as defined in the foregoing,.

In the context of the present invention, it is preferred that the substrate of the first catalyst comprises, more preferably consists of, a cordierite, the substrate of the second catalyst comprises, more preferably consists of, a cordierite, and the substrate of the third catalyst comprises, more preferably consists of, a cordierite.

Preferably the substrate of the third catalyst has a substrate length in the range of from <NUM> to <NUM> inches, more preferably in the range of from <NUM> to <NUM> inches, more preferably in the range of from <NUM> to <NUM> inches, more preferably in the range of from <NUM> to <NUM> inches (<NUM> inch <_> <NUM>).

It is preferred that the substrate of the first catalyst has a substrate length, wherein the length of the first substrate is greater than the length of the third substrate, wherein the ratio of the length of the first substrate relative to the length of the third substrate is more preferably in the range of from <NUM>:<NUM> to <NUM>:<NUM>, more preferably in the range of from <NUM>:<NUM> to <NUM>:<NUM>, more preferably in the range of from <NUM>:<NUM> to <NUM>:<NUM>.

Preferably the substrate of the third catalyst has a substrate width in the range of from <NUM> to <NUM> inches, more preferably in the range of from <NUM> to <NUM> inches, more preferably in the range of from <NUM> to <NUM> inches, more preferably in the range of from <NUM> to <NUM> inches, more preferably in the range of from <NUM> to <NUM> inches (<NUM> inch <=> <NUM>).

It is preferred that the exhaust gas treatment system of the present invention further comprises one or more of a particulate filter, a diesel oxidation catalyst and an ammonia oxidation catalyst, wherein the one or more of a particulate filter, a diesel oxidation catalyst and an ammonia oxidation catalyst are located downstream of the second catalyst according to (ii). Alternatively, when the exhaust gas treatment system comprises a third catalyst according to (iii), it is preferred that said one or more of a particulate filter, a diesel oxidation catalyst and an ammonia oxidation catalyst are located downstream of the third catalyst according to (iii).

The present invention further relates to a method for the treatment of an exhaust gas stream exiting a diesel engine comprising.

The present invention is illustrated by the following set of embodiments and combinations of embodiments resulting from the dependencies and back-references as indicated. In particular, it is noted that in each instance where a range of embodiments is mentioned, for example in the context of a term such as "The system of any one of embodiments <NUM> to <NUM>", every embodiment in this range is meant to be explicitly disclosed for the skilled person, i.e. the wording of this term is to be understood by the skilled person as being synonymous to "The system of any one of embodiments <NUM>, <NUM>, <NUM> and <NUM>". Further, it is explicitly noted that the following set of embodiments is not the set of claims determining the extent of protection, but represents a suitably structured part of the description directed to general and preferred aspects of the present invention.

In the context of the present invention, the term "loading of a given component/coating" (in g/in<NUM> or g/ft<NUM>) refers to the mass of said component/coating per volume of the substrate, wherein the volume of the substrate is the volume which is defined by the cross-section of the substrate times the axial length of the substrate over which said component/coating is present. For example, if reference is made to the loading of a first coating extending over x % of the axial length of the substrate and having a loading of X g/in<NUM>, said loading would refer to X gram of the first coating per x% of the volume (in in<NUM>) of the entire substrate.

In the context of the present invention, it is noted that when the amount of copper and/or iron comprised in the zeolitic material is defined in weight-% based on the weight of the zeolitic material, this means that it is based on the weight of the zeolitic material, namely the zeolitic material comprising the respective copper and/or iron.

Further, in the context of the present invention, a term "X is one or more of A, B and C", wherein X is a given feature and each of A, B and C stands for specific realization of said feature, is to be understood as disclosing that X is either A, or B, or C, or A and B, or A and C, or B and C, or A and B and C. In this regard, it is noted that the skilled person is capable of transfer to above abstract term to a concrete example, e.g. where X is a chemical element and A, B and C are concrete elements such as Li, Na, and K, or X is a temperature and A, B and C are concrete temperatures such as <NUM>, <NUM>, and <NUM>. In this regard, it is further noted that the skilled person is capable of extending the above term to less specific realizations of said feature, e.g. "X is one or more of A and B" disclosing that X is either A, or B, or A and B, or to more specific realizations of said feature, e.g. "X is one or more of A, B, C and D", disclosing that X is either A, or B, or C, or D, or A and B, or A and C, or A and D, or B and C, or B and D, or C and D, or A and B and C, or A and B and D, or B and C and D, or A and B and C and D.

Furthermore, in the context of the present invention, the term "the surface of the internal walls" is to be understood as the "naked" or "bare" or "blank" surface of the walls, i.e. the surface of the walls in an untreated state which consists - apart from any unavoidable impurities with which the surface may be contaminated - of the material of the walls. For example, in the context of the present invention, it is preferred that the first coating of the third catalyst is disposed on the surface of the internal walls of a substrate, more preferably a flow-through substrate.

In the context of the present invention, the term "consists of' with regard to the weight-% of one or more components indicates the weight-% amount of said component(s) based on <NUM> weight-% of the entity in question. For example, the wording "wherein from <NUM> to <NUM> weight- % of the first coating consists of platinum group metal" indicates that among the <NUM> weight-% of the components of which said coating consists of, from <NUM> to <NUM> weight-% is platinum group metal(s).

The present invention is further illustrated by the following reference examples, comparative examples and examples.

The particle size distributions were determined by a static light scattering method using Sympatec HELOS equipment, wherein the optical concentration of the sample was in the range of from <NUM> to <NUM> %.

The BET specific surface area was determined according to DIN <NUM> or DIN ISO <NUM> using liquid nitrogen.

In order to coat a flow-through substrate with one or more coats, the flow-through substrate was immersed vertically in a given mixture for a specific length of the substrate, to fill the substrate with a charge of the mixture. In this manner, the mixture contacted the walls of the substrate. The substrate was left in the mixture for a specific period of time, usually for <NUM>-<NUM> seconds. Vacuum was applied to draw the mixture into the substrate. The substrate was then removed from the mixture. The substrate was rotated about its axis such that the immersed side now points up and a high pressure of air forces the charged mixture through the substrate.

An incipient wetness impregnation of Pd onto a zirconium based oxidic support (<NUM> weight-% of ZrO<NUM> with <NUM> weight-% La<NUM>O<NUM> and <NUM> weight-% HfO<NUM>, having a BET specific surface area of <NUM><NUM>/g, a Dv50 of <NUM> micrometers and a Dv90 of <NUM> micrometers). Firstly, the available pore volume of the oxidic support was determined and, based on this value, a diluted palladium salt solution with a volume equal to the available pore volume was made. The diluted solution was then added dropwise to the Zr-based oxidic support over <NUM> minutes under constant stirring resulting in a moist material. The resulting material was then calcined in an oven at <NUM> and allowed to cool. After calcination, the resulting powder was mixed with distilled water to form an aqueous mixture with <NUM>% solids and the pH was adjusted to <NUM> using an organic acid. At this point, the slurry was milled until the particles of the mixture had a Dv90 of <NUM> micrometers.

Separately, a Cu-CHA zeolitic material (Cu: <NUM> weight-%, calculated as CuO, based on the weight of the Cu-CHA, CHA having a Dv90 of <NUM> micrometers, a SiO<NUM>: Al<NUM>O<NUM> of <NUM>, and a BET specific surface area of about <NUM><NUM>/g) was added to deionized water, forming a mixture. Further, a soluble zirconium solution (<NUM> weight-% ZrO<NUM>) was added as a binder to the mixture comprising water and Cu-CHA. The pH was adjusted to <NUM>. The final mixture solid content was <NUM> weight-%.

At this point, the Pd-impregnated ZrO<NUM> mixture was mixed into the Cu-CHA mixture and the pH was again adjusted to <NUM>. The final mixture was ready for disposal on a honeycomb flow-through monolith cordierite substrate (diameter: <NUM> (<NUM> inches) x length: <NUM> (<NUM> inches) cylindrically shaped substrate with <NUM>/(<NUM>)<NUM> cells per square centimeter and <NUM> millimeter (<NUM> mil) wall thickness). The substrate was coated with the final mixture according to the coating method defined in Reference Example <NUM> herein. To achieve the targeted washcoat loading of <NUM>/in<NUM>, the substrate was coated twice along its entire length, once from the inlet end of the substrate to the outlet end and once from the outlet end of the substrate to the inlet end, with a drying and calcination steps after each coating step. To dry a coated substrate, the substrate was placed in an oven at <NUM> for about <NUM> minutes. After drying, the coated substrate was calcined for <NUM> minutes at <NUM>. The final loading of the coating in the catalyst after calcination was of <NUM>/in<NUM>, including <NUM>/in<NUM> Cu-CHA, <NUM>/in<NUM> of zirconia/HfO<NUM>/La<NUM>O<NUM>, <NUM>/in<NUM> of zirconia (binder) and a Pd loading of <NUM>/ft<NUM>. <NUM>/ft<NUM> <=> <NUM>/l; <NUM>/in<NUM> <=> <NUM>/l; <NUM> inch <=> <NUM>.

An aqueous zirconyl-acetate solution was diluted in water. The amount of zirconyl-acetate was calculated such that the loading of zirconia in the catalyst after calcination, calculated as ZrO<NUM>, was <NUM>/in<NUM>. To this, a Cu-CHA zeolite, prepared according to inventive example <NUM> of <CIT>, column <NUM>, lines <NUM> to <NUM> except that the zeolite was spray-dried, were added. The amount of Cu-CHA was calculated such that the loading of Cu-CHA in the catalyst after calcination was <NUM>/in<NUM>. The resulting slurry was then milled until the resulting Dv90 determined as described in Reference Example <NUM> herein was <NUM> micrometers.

The final slurry was then disposed over the full length of an uncoated honeycomb flow-through cordierite monolith substrate (diameter: <NUM> (<NUM> inches) × length: <NUM> (<NUM> inches) cylindrically shaped substrate with <NUM>/(<NUM>)<NUM> cells per square centimeter and <NUM> millimeter (<NUM> mil) wall thickness). Afterwards, the coated substrate was dried at <NUM> for <NUM> minutes and at <NUM> for <NUM> minutes and was then calcined at <NUM> for <NUM> minutes. The washcoat loading after calcination was <NUM>/in<NUM>. <NUM>/in<NUM> <=> <NUM>/l.

To a Si-doped titania powder (<NUM> wt% SiO<NUM>, BET specific surface area of <NUM><NUM>/g, a Dv90 of <NUM> micrometers) was added a platinum ammine solution. After calcination at <NUM> the final Pt/Si-titania had a Pt content of <NUM> weight-% based on the weight of Si-titania. This material was added to water and the slurry was milled until the resulting Dv90 was <NUM> micrometers, as described in Reference Example <NUM>. To an aqueous slurry of Cu-CHA zeolitic material (<NUM> weight- % CuO and a SiO<NUM>:Al<NUM>O<NUM> molar ratio of <NUM>) was added a zirconyl-acetate solution to achieve <NUM> weight-% ZrO<NUM> after calcination based on the weight of the zeolitic material. To this Cu-CHA slurry, the Pt-containing slurry was added and stirred, creating the final slurry. The final slurry was then disposed over the full length of an uncoated honeycomb flow-through cordierite monolith substrate (diameter: <NUM> (<NUM> inches) x length: <NUM> (<NUM> inches) cylindrically shaped substrate with <NUM>/(<NUM>)<NUM> cells per square centimeter and <NUM> millimeter (<NUM> mil) wall thickness), from the inlet side of the substrate towards the outlet side, using the coating method described in Reference Example <NUM>, forming the first (bottom) coating. Afterwards, the coated substrate was dried and calcined. The loading of the first coating, after calcination was about <NUM>/in<NUM> with a Cu-CHA loading of <NUM>/in<NUM>, a ZrO<NUM> loading of <NUM>/in<NUM>, a Si-titania loading of <NUM>/in<NUM> and a PGM loading of <NUM>/ft<NUM>. <NUM>/ft3 <=> <NUM>/l and <NUM>/in<NUM> <=> <NUM>/l.

To an aqueous slurry of Cu-CHA zeolitic material (<NUM> weight-% CuO and a SiO<NUM>:Al<NUM>O<NUM> molar ratio of <NUM>) was added a zirconyl-acetate solution to achieve <NUM> weight-% ZrO<NUM> after calcination based on the weight of the zeolitic material. The slurry was then disposed over the full length of the honeycomb cordierite monolith substrate, coated with the first coating, from the inlet side of the substrate towards the outlet side and covering the first coating using the coating method described in Reference Example <NUM>. Afterwards, the coated substrate was dried and calcined. The loading of this second coating after calcination was <NUM>/in<NUM>. <NUM>/in<NUM> <=> <NUM>/l.

The final catalytic loading (bottom + top coatings) in the catalyst after calcination was about <NUM>/in3.

The final slurry was then disposed over the full length of an uncoated honeycomb cordierite monolith substrate (diameter: <NUM> (<NUM> inches) x length: <NUM> (<NUM> inches) cylindrically shaped substrate with <NUM>/(<NUM>)<NUM> cells per square centimeter and <NUM> millimeter (<NUM> mil) wall thickness). Afterwards, the coated substrate was dried at <NUM> for <NUM> minutes and at <NUM> for <NUM> minutes and was then calcined at <NUM> for <NUM> minutes. The washcoat loading after calcination was <NUM>/in<NUM>. <NUM>/in<NUM> <=> <NUM>/l.

An incipient wetness impregnation of Pd onto a zirconium based oxidic support (<NUM> weight-% of ZrO<NUM> with <NUM> weight-% La<NUM>O<NUM> and <NUM> weight-% HfO<NUM>, having a BET specific surface area of <NUM><NUM>/g, a Dv50 of <NUM> micrometers and a Dv90 of <NUM> micrometers). Firstly, the available pore volume of the given oxidic support was determined and, based on this value, a diluted palladium salt solution with a volume equal to the available pore volume was made. A palladium nitrate solution (palladium content, calculated as elemental Pd, of <NUM> weight-%) was mixed with distilled water until the solid content was reduced to <NUM>%. The diluted solution was then added dropwise to the Zr-based oxidic support over <NUM> minutes under constant stirring resulting in a solid material with about <NUM> weight-% of water. The resulting material was then calcined in an oven at <NUM> and allowed to cool. After calcination, the resulting powder was mixed together with distilled water to form a mixture in which the final solid content was <NUM> weight-%, based on the weight of the mixture, and the pH of the aqueous phase of the mixture was set to <NUM> using an organic acid. At this point, the slurry was milled until the particles of the mixture had a Dv90 of <NUM> micrometers.

After milling, a zirconium hydroxide solution (a zirconia content, calculated as ZrO<NUM>, of <NUM> weight-%) and a zirconium acetate solution (a zirconia content, calculated as ZrO<NUM>, of <NUM> weight-%) were added to the mixture. The amount of ZrOH was calculated such that it represented <NUM>/ <NUM> of the amount of the Al-based oxidic support. The amount of ZrOAc was calculated such that it represented <NUM>/<NUM> of the amount of the Al-based oxidic support. The obtained final mixture had a solid content decreased to <NUM> weight-% based on the weight of said final mixture. At this point, the mixture was ready for disposal over the substrate already coated with the bottom coating. The substrate coated with the bottom coating was coated once with said final mixture over the entire length of the substrate, according to the coating method as defined in Reference Example <NUM> herein. Drying conditions were the same as for the bottom coating and the coated substrate was calcined in band-calciner oven with varying temperature stages, including about <NUM> minutes at <NUM>. The final loading of the top coating in the catalyst after calcination was <NUM>/in<NUM>, including <NUM>/in<NUM> of Zr-based oxidic support, <NUM>/in<NUM> of zirconia (from ZrOH and ZrOAc) and a Pd loading of <NUM>/ft<NUM>. <NUM>/ft3 <=> <NUM>/l and <NUM>/in<NUM> <=> <NUM>/l.

The system of Comparative Example <NUM> was prepared by combining three catalysts, namely a multifunctional layered catalyst according to Reference Example <NUM> (catalyst A), a selective catalytic reduction catalyst according to Reference Example <NUM> (catalyst B) and an ammonia oxidation catalyst according to Reference Example <NUM> (catalyst C). The catalyst A is the first catalyst of the system and located upstream of catalyst B, the catalyst B is located downstream of the catalyst A and upstream of the catalyst C and the catalyst C is located downstream of the catalyst B.

The system of Example <NUM> was prepared by combining three catalysts, namely a multifunctional mixed catalyst according to Reference Example <NUM> (catalyst A), a selective catalytic reduction catalyst according to Reference Example <NUM> (catalyst B) and an ammonia oxidation catalyst according to Reference Example <NUM> (catalyst C). The catalyst A is the first catalyst of the system and located upstream of catalyst B, the catalyst B is located downstream of the catalyst A and upstream of the catalyst C and the catalyst C is located downstream of the catalyst B.

The system of Comparative Example <NUM> was prepared by combining three catalysts, namely a multifunctional mixed catalyst according to Reference Example <NUM> (catalyst A), an ammonia oxidation catalyst according to Reference Example <NUM> (catalyst B) and an ammonia oxidation catalyst according to Reference Example <NUM> (catalyst C). The catalyst A is the first catalyst of the system and located upstream of catalyst B, the catalyst B is located downstream of the catalyst A and upstream of the catalyst C and the catalyst C is located downstream of the catalyst B.

The system of Comparative Example <NUM> was prepared by combining three catalysts, namely a multifunctional layered catalyst according to Reference Example <NUM> (catalyst A), a multifunctional layered catalyst according to Reference Example <NUM> (catalyst B) and an ammonia oxidation catalyst according to Reference Example <NUM> (catalyst C). The catalyst A is the first catalyst of the system and located upstream of catalyst B, the catalyst B is located downstream of the catalyst A and upstream of the catalyst C and the catalyst C is located downstream of the catalyst B.

The NOx conversion and the N<NUM>O emissions were measured at high temperature at the entrance of the systems, namely at <NUM>. The tests have been made on a EU VI <NUM> engine under steady state conditions.

As may be taken from <FIG>, the exhaust gas treatment system of Example <NUM> permits to obtain a NOx conversion of <NUM> % at the outlet end of the catalyst A, of <NUM> % at the outlet end of the catalyst B and of <NUM> % at the outlet end of the catalyst C of the two systems. In contrast, the exhaust gas treatment system of Comparative Examples <NUM> to <NUM> exhibits lower or similar NOx conversion at the outlet end of the catalyst A, namely of about <NUM> % or <NUM> %, and lower NOx conversion at the outlet end of the catalyst B, namely of about less than <NUM> % and less than <NUM> %. Further, as may be taken from <FIG>, the lowest nitrous oxide emissions are obtained with the system of Example <NUM> according to the present invention which comprises a multifunctional mixed catalyst as the first catalyst (A) and a downstream SCR catalyst free of platinum group metal (B). Therefore, this example demonstrates that the systems according to the present invention permits to improve NOx conversions while decreasing the nitrous oxide emissions compared to other systems which uses a layered multifunctional catalyst as the first catalyst of the system and/or a second catalyst comprising platinum group metal. The comparative examples illustrates the prior art, such as <CIT>.

The NOx conversion and the N<NUM>O emissions were measured over a transient HDD US FTP legal cycle with temperatures at the entrance of the systems ranging from <NUM> to <NUM> over the cycle. The tests have been made on a EU VI <NUM> with engine out NOx emissions of <NUM> over the FTP and urea dosing was performed using a NOx follow dosing strategy with an ANR of <NUM>. Three FTPs were run in sequence with a cold soak in between the cycles. The results of the third FTP are reported to ensure stable readings and eliminate ammonia storage influences over the Cu-zeolite.

Claim 1:
An exhaust gas treatment system for treating an exhaust gas stream exiting a diesel engine, said exhaust gas treatment system having an upstream end for introducing said exhaust gas stream into said exhaust gas treatment system, wherein said exhaust gas treatment system comprises
(i) a first catalyst having an inlet end and an outlet end and comprising a coating disposed on a substrate, wherein the coating comprises palladium supported on an oxidic material comprising zirconium and further comprises one or more of a vanadium oxide and a zeolitic material comprising one or more of copper and iron;
(ii) a second catalyst having an inlet end and an outlet end and comprising a coating disposed on a substrate, wherein the coating comprises one or more of a vanadium oxide and a zeolitic material comprising one or more of copper and iron, wherein at most <NUM> weight-% of the coating of the second catalyst consists of platinum group metal;
wherein the first catalyst according to (i) is the first catalyst of the exhaust gas treatment system downstream of the upstream end of the exhaust gas treatment system and wherein the inlet end of the first catalyst is arranged upstream of the outlet end of the first catalyst;
wherein in the exhaust gas treatment system, the second catalyst according to (ii) is located downstream of the first catalyst according to (i) and wherein the inlet end of the second catalyst is arranged upstream of the outlet end of the second catalyst.