DE202017007046U1 - Catalytically active particle filter - Google Patents

Abstract

A particulate filter comprising a length L wall flow filter and two equal composition coatings Y and Z, the wall flow filter comprising channels E and A extending in parallel between first and second ends of the wall flow filter and separated by porous walls Form surfaces O _E and O _A respectively and wherein the channels E at the second end and the channels A are closed at the first end, and wherein the coatings Y and Z comprise the same oxygen storage components and the same support materials for noble metals, characterized in that
Coating Y is located in the channels E on the surfaces O _E and extends over 57 to 80% of the length L starting from the first end of the wall-flow filter,
Coating Z is located in the channels A on the surfaces O _A and extending from the second end of the wall-flow filter over 57 to 80% of the length L,
and the coatings Y and Z alumina in an amount of 20 to 70 wt .-%, based on the total weight of the coating Y or Z, rhodium, palladium or palladium and rhodium and one or more oxygen storage components in an amount of 30 to 80 wt .-%, based on the total weight of the coating Y or Z contains.

Description

The present invention relates to a catalytically active particulate filter, which is particularly suitable for the removal of particles, carbon monoxide, hydrocarbons and nitrogen oxides from the exhaust gas of combustion engines operated with stoichiometric air / fuel mixture.

Exhaust gases from stoichiometric air / fuel mixture operated internal combustion engines, so gasoline engines are cleaned in conventional methods using three-way catalysts. These are able to simultaneously convert the three major gaseous pollutants of the engine, namely hydrocarbons, carbon monoxide and nitrogen oxides to harmless components.
In addition to these gaseous pollutants, the exhaust gas from gasoline engines also contains very fine particles (PM), which result from the incomplete combustion of the fuel and consist essentially of soot. In contrast to the particle emission of diesel engines, the particles in the exhaust gas of stoichiometrically operated internal combustion engines are very small and have an average particle size of less than 1 μm. Typical particle sizes range from 10 to 200 nm. Furthermore, the amount of particles emitted is very small and ranges from 2 to 4 mg / km.
With the European emission standard EU- 6c is a changeover of the limit value for such particles from the particle mass limit value to a more critical particle number limit value of 6 × 10 ¹¹ / km (in the Worldwide Harmonized Light Vehicles Test Cycle - WLTP). This creates a need for exhaust gas purification concepts for stoichiometrically powered internal combustion engines that include effective particle removal equipment.

In the field of purification of exhaust gas from lean-burn engines, ie in particular diesel engines, wall flow filters made of ceramic materials such as silicon carbide, aluminum titanate and cordierite have proven successful. These are composed of a plurality of parallel channels formed by porous walls. The channels are mutually closed at one of the two ends of the filter to form channels A which are open on the first side of the filter and closed on the second side of the filter, and channels B which are closed on the first side of the filter and are open on the second side of the filter. The exhaust gas flowing, for example, into the channels A can leave the filter only via the channels B, and must flow through the porous walls between the channels A and B for this purpose. As the exhaust gas passes through the wall, the particles are retained and the exhaust gas purified.
The particles thus retained must subsequently be burned or oxidized to prevent clogging of the filter or an unacceptable increase in the back pressure of the exhaust system. For this purpose, for example, the wall-flow filter is provided with catalytically active coatings which reduce the ignition temperature of soot.
It is already known to apply such coatings to the porous walls between the channels (so-called on-wall coating) or to introduce them into the porous walls (so-called in-wall coating). The EP 1 657 410 A2 also already describes a combination of both types of coatings, ie one part of the catalytically active material is present in the porous walls and another part on the porous walls.

The concept of removing particles from the exhaust gas by means of wall flow filtering has already been applied to the purification of exhaust gas from stoichiometric air / fuel mixture internal combustion engines, see for example US Pat EP 2042226 A2 , According to their teachings, a wall flow filter carries two superposed layers, one in the porous wall and the other on the porous wall.
A similar concept pursues the DE 102011050788 A1 , There, the porous filter walls contain a catalyst material of a three-way catalyst, while in addition a catalyst material of a three-way catalyst is applied to portions of the filter walls.

Other documents describing filter substrates provided with catalytically active coatings are EP 3205388 A1 . EP 3207977 A1 . EP 3207978 A1 . EP 3207987 A1 . EP 3207989 A1 . EP 3207990 A1 and EP 3162428 A1 ,

There is still a need for catalytically active particulate filters that combine the functionalities of a particulate filter and a three-way catalytic converter, while allowing for compliance with future limits.

The present invention relates to a particulate filter for removing particulates, carbon monoxide, hydrocarbons and nitrogen oxides from exhaust gas of stoichiometric air / fuel mixture internal combustion engines comprising a wall-flow filter of length L and two coatings Y and Z, the wall-flow filter comprising channels E and A. which extend in parallel between a first and a second end of the wall-flow filter and which are separated by porous walls, the surfaces O _E or. O _A and wherein the channels E are closed at the second end and the channels A at the first end, and wherein the coatings Y and Z comprise the same oxygen storage components and the same support materials for noble metals, characterized in that coating Y in the channels E on the surfaces O _E extends and extending from the first end of the wall flow filter to a length of 51 to 90% of the length L and coating Z in the channels A on the surfaces O _A and extending from the second end of the wall flow filter to a length of 51 to 90% of the length L.

The coatings Y and Z are three-way catalytically active, especially at operating temperatures of 250 to 1100 ° C. They usually contain one or more noble metals fixed on one or more support materials and one or more oxygen storage components.
The coatings X and Y comprise the same oxygen storage components and the same support materials for noble metals in different, but preferably in equal amounts. The coatings X and Y also contain the same or different precious metals in equal or different amounts.

Particularly suitable noble metals are platinum, palladium and rhodium, preference being given to palladium, rhodium or palladium and rhodium, and palladium and rhodium being particularly preferred.
Based on the particle filter according to the invention, the proportion of rhodium in the total noble metal content is in particular greater than or equal to 10 wt .-%.

The porous walls of the particulate filter according to the invention are preferably free of noble metals.

The noble metals are usually used in amounts of 0.15 to 5 g / l, based on the volume of the wall-flow filter.

Suitable carrier materials for the noble metals are all those skilled in the art for this purpose materials. Such materials are in particular metal oxides having a BET surface area of from 30 to 250 m ² / g, preferably from 100 to 200 m ² / g (determined by DIN 66132 ).
Particularly suitable support materials for the noble metals are selected from the series consisting of alumina, doped alumina, silica, titania and mixed oxides of one or more thereof. Doped aluminas are, for example, lanthanum oxide, zirconium oxide and / or titanium oxide doped aluminas. Lanthanum-stabilized aluminum oxide is advantageously used, with lanthanum being used in amounts of 1 to 10% by weight, preferably 3 to 6% by weight, calculated in each case as La ₂ O ₃ and based on the weight of the stabilized aluminum oxide.

Another suitable carrier material is lanthanum-stabilized alumina, the surface of which is coated with lanthanum oxide, with barium oxide or with strontium oxide.

Particularly suitable oxygen storage components are cerium / zirconium / rare earth metal mixed oxides. The term "cerium / zirconium / rare earth mixed oxide" in the context of the present invention excludes physical mixtures of ceria, zirconia and rare earth oxide. Rather, "cerium / zirconium / rare earth mixed oxides" are characterized by a substantially homogeneous, three-dimensional crystal structure which is ideally free of phases of pure ceria, zirconia or rare earth oxide. Depending on the manufacturing process, however, it is also possible for products which are not completely homogeneous to form, which as a rule can be used without disadvantage.
Incidentally, in the context of the present invention, the term rare earth metal or rare earth metal oxide does not include cerium or cerium oxide.

Suitable rare earth metal oxides in the cerium / zirconium / rare earth metal mixed oxides are, for example, lanthanum oxide, yttrium oxide, praseodymium oxide, neodymium oxide and / or samarium oxide.
Lanthanum oxide, yttrium oxide and / or praseodymium oxide are preferred. Lanthanum oxide and / or yttrium oxide are particularly preferred and very particular preference is given to lanthanum oxide and yttrium oxide, yttrium oxide and praseodymium oxide, and also lanthanum oxide and praseodymium oxide.
In embodiments of the present invention, the oxygen storage components are free of neodymium oxide.

According to the invention, the mass ratio of ceria to zirconia in the cerium / zirconium / rare earth mixed oxides can vary widely. It is for example 0.1 to 1.5, preferably 0.2 to 1 or 0.3 to 0.5.

If the cerium / zirconium / rare earth metal mixed oxides contain yttrium oxide as the rare earth metal, its proportion is in particular 5 to 15% by weight.

If the cerium / zirconium / rare earth metal mixed oxides contain rare earth metal praseodymium oxide, the proportion thereof is in particular 2 to 10% by weight.

If the cerium / zirconium / rare earth metal mixed oxides contain lanthanum oxide and yttrium oxide as the rare earth metal, the mass ratio thereof is in particular from 0.1 to 1.

If the cerium / zirconium / rare earth metal mixed oxides contain lanthanum oxide and praseodymium oxide as the rare earth metal, the mass ratio thereof is in particular from 0.1 to 1.

Typically, coatings Y and Z contain oxygen storage components in amounts of from 15 to 120 g / L, based on the volume of the wallflow filter.

The mass ratio of carrier materials and oxygen storage components in the coatings Y and Z is usually 0.3 to 1.5, for example 0.4 to 1.3.

In embodiments of the present invention, one or both of the coatings Y and Z contain an alkaline earth compound such as e.g. Strontium oxide, barium oxide or barium sulfate. The amount of barium sulfate per coating is in particular 2 to 20 g / l volume of the wall-flow filter.

In further embodiments of the present invention, one or both of the coatings Y and Z contain additives such as rare earth compounds such as e.g. Lanthanum oxide and / or binders, such as e.g. Aluminum compounds. These additives are used in amounts which can vary within wide limits and which the skilled person can determine in a concrete case by simple means.

In embodiments of the present invention, coatings X and Y include lanthanum stabilized alumina, rhodium, palladium or palladium, and rhodium, and an oxygen storage component comprising zirconia, ceria, yttria, and lanthana.

In other embodiments of the present invention, coatings X and Y include lanthanum stabilized alumina, rhodium, palladium or palladium and rhodium and an oxygen storage component comprising zirconia, ceria, praseodymia and lanthana.

In other embodiments of the present invention, coatings X and Y include lanthanum stabilized alumina, rhodium, palladium or palladium and rhodium, an oxygen storage component comprising zirconia, ceria, yttria, and lanthana, as well as oxygen storage comprising zirconia, ceria, yttria, and praseodymium oxide. component.

The coatings Y and Z comprise in embodiments each lanthanum-stabilized alumina in amounts of 20 to 70 wt .-%, particularly preferably 30 to 60 wt .-%, and the oxygen storage component in amounts of 30 to 80 wt .-%, particularly preferably 40 to 70 wt .-%, each based on the total weight of the coating Y or Z.

In embodiments of the present invention, the coating Y extends from the first end of the wall-flow filter over 55 to 80%, in particular over 57 to 65% of the length L of the wall-flow filter. The loading of the wall-flow filter with coating Y is preferably 33 to 125 g / l, based on the volume of the wall-flow filter.

In embodiments of the present invention, the coating Z extends from the second end of the wall-flow filter over 55 to 80%, in particular over 57 to 65% of the length L of the wall-flow filter. The loading of the wall-flow filter with coating Z is preferably 33 to 125 g / l, based on the volume of the wall-flow filter.

In embodiments of the present invention, the sum of the lengths of coating Y and coating Z is from 110 to 160% of the length L.

In embodiments of the present invention, the coatings Y and Z contain no zeolite and no molecular sieve.

The total loading of the particle filter according to the invention with the coatings Y and Z is in particular 40 to 150 g / l, based on the volume of the wall-flow filter.
In one embodiment of the present invention, it relates to a particulate filter comprising a wall-flow filter of length L and two coatings Y and Z, the wall-flow filter comprising channels E and A extending in parallel between a first and a second end of the wall-flow filter and passing through porous walls are separated, the surfaces O _E or. O _A and wherein the channels E are closed at the second end and the channels A at the first end, and wherein the coatings Y and Z comprise the same oxygen storage components and the same support materials for noble metals, characterized in that
Coating Y in the channels E on the surfaces O _E and extending from the first end of the wall flow filter over 57 to 65% of the length L,
Coating Z itself in the channels A on the surfaces O _A and extending from the second end of the wall flow filter over 57 to 65% of the length L,
and the coatings Y and Z alumina in an amount of 20 to 70 wt .-%, based on the total weight of the coating Y or Z, rhodium, palladium or palladium and rhodium and an oxygen storage component in an amount of 30 to 80 wt. %, based on the total weight of coating Y or Z, wherein the oxygen storage component comprises zirconia, ceria, lanthana and yttria or zirconia, ceria, lanthana and praseodymia or a mixture of two oxygen storage components, wherein an oxygen storage component is zirconia, ceria, lanthana and yttria and the other contains zirconia, ceria, lanthana and praseodymium oxide.

Wall-flow filters which can be used in accordance with the present invention are known and available on the market. They consist for example of silicon carbide, aluminum titanate or cordierite, for example, have a cell density of 200 to 400 cells per inch and usually a wall thickness between 6 and 12 mil, or 0.1524 and 0.305 millimeters They have uncoated, for example, porosities from 50 to 80, especially 55 to 75%. Their average pore size when uncoated, for example, 10 to 25 microns. As a rule, the pores of the wall-flow filter are so-called open pores, that is to say they have a connection to the channels. Furthermore, the pores are usually interconnected. This allows, on the one hand, the slight coating of the inner pore surfaces and, on the other hand, an easy passage of the exhaust gas through the porous walls of the wall-flow filter.

The production of the particulate filter according to the invention can be carried out by methods familiar to the person skilled in the art, for example by applying a coating suspension, which is usually called washcoat, to the wall-flow filter by means of one of the customary dip-coating methods or pump and suction coating methods. Thermal aftertreatment or calcination usually follow.
The coatings Y and Z are obtained in separate and sequential coating steps.

It is known to those skilled in the art that the average pore size of the wallflow filter and the average particle size of the catalytically active materials must be matched to achieve an on-wall or in-wall coating. In the case of in-wall coating, the average particle size of the catalytically active materials must be small enough to penetrate into the pores of the wall flow filter. In contrast, in the case of on-wall coating, the average particle size of the catalytically active materials must be large enough not to penetrate into the pores of the wall-flow filter.

In embodiments of the present invention, the coating suspensions for preparing the coatings Y and Z are milled to a particle size distribution of d ₅₀ = 4 to 8 μm and d ₉₉ = 22 to 16 μm.

The particle filter according to the invention is outstandingly suitable for removing particles, carbon monoxide, hydrocarbons and nitrogen oxides from the exhaust gas of combustion engines operated with a stoichiometric air / fuel mixture.

The present invention thus also relates to a process for the removal of particulates, carbon monoxide, hydrocarbons and nitrogen oxides from the exhaust gas of stoichiometric air / fuel mixture operated internal combustion engines, which is characterized in that the exhaust gas is passed through a particulate filter according to the invention.

In this case, the exhaust gas can be passed through a particulate filter according to the invention so that it enters the particulate filter through the channels E and exits through channels A again.
But it is also possible that the exhaust gas through the channels A enters the particulate filter and it through channels e leaves again.

1 shows a particle filter according to the invention, which is a wall flow filter of length L ( 1 ) with channels e ( 2 ) and channels A ( 3 ) extending in parallel between a first end ( 4 ) and a second end ( 5 ) of the wall flow filter and through porous walls ( 6 ) are separated, the surfaces O _E ( 7 ) or. O _A ( 8th ) and where the channels e ( 2 ) at the second end ( 5 ) and the channels A ( 3 ) at the first end ( 4 ) are closed. coating Y ( 9 ) is located in the channels e ( 2 ) on the surfaces O _E ( 7 ) and coating Z ( 10 ) in the channels A ( 3 ) on the surfaces O _A ( 8th ).

The invention is explained in more detail in the following examples.

Comparative Example 1

Lanthanum oxide stabilized alumina was suspended in water along with a first oxygen storage component comprising 40% by weight of ceria, zirconia, lanthana and praseodymia and a second oxygen storage component comprising 24% by weight of ceria, zirconia, lanthana and yttria. Both oxygen storage components were used in equal parts. The weight ratio of alumina and oxygen storage component was 30:70. The resulting suspension was then treated with continuous stirring with a palladium nitrate solution and a rhodium nitrate solution. The resulting coating suspension was used directly to coat a commercially available wall flow filter substrate, the coating being introduced into the porous filter wall over 100% of the substrate length. The total load of this filter was 75 g / l, the total noble metal loading was 1.27 g / l with a ratio of palladium to rhodium of 5: 1. The coated filter thus obtained was dried and then calcined. It will be referred to as VGPF1 below.

example 1

Coating of the input and output channels:

Alumina stabilized with lanthana was suspended in water along with an oxygen storage component comprising 24% by weight of ceria, zirconia, lanthana and yttria. The weight ratio of alumina and oxygen storage component was 56:44. The resulting suspension was then treated with continuous stirring with a palladium nitrate solution and a rhodium nitrate solution. The resulting coating suspension was used directly for coating a commercially available wall flow filter substrate. The coating suspension was applied to the Filter walls of the substrate coated first in the input channels to a length of 60% of the filter length. The loading of the inlet channel was 62.5 g / l, the noble metal loading 1.06 g / l with a ratio of palladium to rhodium of 5: 1. The coated filter thus obtained was dried and then calcined. Subsequently, the output channels of the filter were coated to a length of 60% of the filter length with the same coating suspension. The coated filter thus obtained was again dried and then calcined. The total loading of this filter was thus 75 g / l, the total precious metal loading 1.27 g / l with a ratio of palladium to rhodium of 5: 1. It is referred to below as GPF1.

Example 2

Lanthanum oxide stabilized alumina was suspended in water along with a first oxygen storage component comprising 40% by weight of ceria, zirconia, lanthana and praseodymia and a second oxygen storage component comprising 24% by weight of ceria, zirconia, lanthana and yttria. Both oxygen storage components were used in equal parts. The weight ratio of alumina and oxygen storage component was 30:70. The resulting suspension was then treated with continuous stirring with a palladium nitrate solution and a rhodium nitrate solution. The resulting coating suspension was used directly for coating a commercially available wall flow filter substrate. The coating suspension was coated on the filter walls of the substrate, first in the input channels to a length of 60% of the filter length. The loading of the inlet channel was 62.5 g / l, the noble metal loading 1.06 g / l with a ratio of palladium to rhodium of 5: 1. The coated filter thus obtained was dried and then calcined. Subsequently, the output channels of the filter were coated to a length of 60% of the filter length with the same coating suspension. The coated filter thus obtained was again dried and then calcined. The total loading of this filter was thus 75 g / l, the total precious metal loading 1.27 g / l with a ratio of palladium to rhodium of 5: 1. It is referred to below as GPF2.

Catalytic characterization

The particulate filters VGPF1, GPF1 and GPF2 were aged together in an engine test bench aging. This consists of a fuel cut-off aging with 950 ° C exhaust gas temperature upstream of the catalyst inlet (maximum bed temperature 1030 ° C). The aging time was 19 hours (see Motortechnische Zeitschrift, 1994, 55, 214-218).
Subsequently, the catalytically active particulate filters were tested in the aged state on an engine test bench in the so-called "light-off test" and in the "lambda sweep test". In the light-off test, the light-off behavior is determined at a stoichiometric exhaust gas composition with a constant average air ratio A (λ = 0.999 with ± 3.4% amplitude).

Table 1 below contains the temperatures T ₅₀ at which in each case 50% of the components considered are reacted. Table 1 T ₅₀ HC stöch T ₅₀ CO stöch T ₅₀ NOx stöch VGPF1 376 384 398 GPF1 340 342 340 GPF2 376 384 390

The dynamic turnover behavior of the particle filters in the lambda sweep test was determined within a range of A = 0.99 - 1.01 at a constant temperature of 510 ° C. The amplitude of A was ± 3.4%. Table 2 shows the conversion at the intersection of the CO and NOx sales curves and the associated HC conversion of the aged particulate filters. Table 2 CO / NOx turnover at the crossing point HC conversion at the λ of the CO / NOx crossing point VGPF1 83% 96% GPF1 96% 97% GPF2 90% 97%

The particulate filters according to the invention GPF1 and GPF2 show a significant improvement in the light-off behavior and in the dynamic CO / NOx conversion compared to VGPF1 in the aged state.

Comparative Example 2:

Applying the in-wall coating:

Lanthanum oxide stabilized alumina was suspended in water along with a first oxygen storage component comprising 40% by weight of ceria, zirconia, lanthana and praseodymia, and a second oxygen storage component comprising 24% by weight of ceria, zirconia, lanthana and yttria. Both oxygen storage components were used in equal parts. The weight ratio of alumina and oxygen storage component was 30:70. The resulting suspension was then treated with continuous stirring with a palladium nitrate solution and a rhodium nitrate solution. The resulting coating suspension was used directly to coat a commercially used Wandflussfiltersubstrats, wherein the coating over 100% of the substrate length was introduced into the porous filter wall. The total loading of this filter was 100 g / l, the noble metal loading 2.60 g / l with a ratio of palladium to rhodium of 60: 13.75. The coated filter thus obtained was dried and then calcined.

Coating of the input channels

Alumina stabilized with lanthana was suspended in water along with an oxygen storage component comprising 40% by weight of ceria, zirconia, lanthana and praseodymia. The weight ratio of alumina and oxygen storage component was 50:50. The resulting suspension was then treated with continuous stirring with a palladium nitrate solution and a rhodium nitrate solution. The resulting coating suspension was used directly for coating the wall flow filter substrate obtained under a), wherein the filter walls of the substrate were coated in the input channels to a length of 25% of the filter length. The loading of the inlet channel was 58 g / l, the noble metal loading 2.30 g / l with a ratio of palladium to rhodium of 10: 3. The coated filter thus obtained was dried and then calcined.

Coating of the output channels

Alumina stabilized with lanthana was suspended in water along with an oxygen storage component comprising 24% by weight of ceria, zirconia, lanthana and yttria. The weight ratio of alumina and oxygen storage component was 56:44. The resulting suspension was then treated with continuous stirring with a palladium nitrate solution and a rhodium nitrate solution. The resulting coating suspension was used directly for coating the wall flow filter substrate obtained under b), wherein the filter walls of the substrate were coated in the output channels to a length of 25% of the filter length. The loading of the outlet channel was 59 g / l, the noble metal loading 1.06 g / l with a ratio of palladium to rhodium of 1: 2. The thus obtained coated filter was dried and then calcined. The total loading of this filter was thus 130 g / l, the total noble metal loading 3.44 g / l with a ratio of palladium to rhodium of 10: 3. It is referred to below as VGPF2.

Comparative Example 3

Applying the in-wall coating:

Lanthanum oxide stabilized alumina was suspended in water along with a first oxygen storage component comprising 40% by weight of ceria, zirconia, lanthana and praseodymia and a second oxygen storage component comprising 24% by weight of ceria, zirconia, lanthana and yttria. Both oxygen storage components were used in equal parts. The weight ratio of alumina and oxygen storage component was 30:70. The resulting suspension was then treated with continuous stirring with a palladium nitrate solution and a rhodium nitrate solution. The resulting coating suspension was used directly to coat a commercially available wall flow filter substrate, the coating being introduced into the porous filter wall over 100% of the substrate length. The loading of this filter was 100 g / l, the noble metal loading 2.07 g / l with a ratio of palladium to rhodium of 45: 13.5. The coated filter thus obtained was dried and then calcined.

Coating of the input channels

Alumina stabilized with lanthana was suspended in water along with an oxygen storage component comprising 40% by weight of ceria, zirconia, lanthana and praseodymia. The weight ratio of alumina and oxygen storage component was 50:50. The resulting suspension was then treated with continuous stirring with a palladium nitrate solution and a rhodium nitrate solution. The resulting coating suspension was used directly for coating the wall flow filter substrate obtained under a), wherein the filter walls of the substrate were coated in the input channels to a length of 60% of the filter length. The loading of the inlet channel was 90 g / l, the precious metal loading 2.30 g / l with a ratio of palladium to rhodium of 10: 3. The coated filter thus obtained was dried and then calcined. The total loading of this filter was thus 154 g / l, the total noble metal loading 3.44 g / l with a ratio of palladium to rhodium of 10: 3. It will be referred to as VGPF3 hereinafter.

Example 3

Coating of the input channels

a) Lanthanum oxide stabilized alumina was suspended in water along with an oxygen storage component comprising 24% by weight of ceria, zirconia, lanthana and yttria. The weight ratio of alumina and oxygen storage component was 56:44. The resulting suspension was then treated with continuous stirring with a palladium nitrate solution and a rhodium nitrate solution. The resulting coating suspension was used directly for coating a commercially available wall flow filter substrate. In this case, the coating suspension was coated on the filter walls of the substrate and in the input channels to a length of 60% of the filter length. The loading of the inlet channel was 83.33 g / l, the precious metal loading 2.87 g / l with a ratio of palladium to rhodium of 10: 3. The coated filter thus obtained was dried and then calcined. Subsequently, the output channels of the filter were coated to a length of 60% of the filter length with the same coating suspension. The coated filter thus obtained was again dried and then calcined. The total loading of this filter was thus 100 g / l, the total precious metal loading 3.44 g / l with a ratio of palladium to rhodium of 10: 3. It is referred to below as GPF3.

Catalytic characterization

The particulate filters VGPF2, VGF3 and GPF3 were aged together in an engine test bench aging. This consists of a fuel cut-off aging with 950 ° C exhaust gas temperature upstream of the catalyst inlet (maximum bed temperature 1030 ° C). The aging time was 76 hours (see Motortechnische Zeitschrift, 1994, 55, 214-218).
Subsequently, the catalytically active particulate filters were tested in the aged state on an engine test bench in the so-called "light-off test" and in the "lambda sweep test". In the light-off test, the light-off behavior is determined at a stoichiometric exhaust gas composition with a constant average air ratio A (λ = 0.999 with ± 3.4% amplitude).

Table 3 below contains the temperatures T ₅₀ at which in each case 50% of the components considered are reacted. Table 3 T ₅₀ HC stöch T ₅₀ CO stöch T ₅₀ NOx stöch VGPF2 368 374 371 VGPF3 387 395 396 GPF3 323 325 319

The dynamic turnover behavior of the particle filters in the lambda sweep test was determined in a range of λ = 0.99 - 1.01 at a constant temperature of 510 ° C. The amplitude of λ was ± 3.4%. Table 4 shows the conversion at the intersection of the CO and NOx conversion curves and the associated HC conversion of the aged particulate filters. Table 4 CO / NOx turnover at the crossing point HC conversion at the λ of the CO / NOx crossing point VGPF2 92 97 VGPF3 93 97 GPF3 97 98

The particulate filter according to the invention GPF3 shows compared to VGPF2 and VGPF3 in the aged state, a significant improvement in the light-off and the dynamic CO / NOx conversion.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 1657410 A2 [0003]
• EP 2042226 A2 [0004]
• DE 102011050788 A1 [0004]
• EP 3205388 A1 [0005]
• EP 3207977 A1 [0005]
• EP 3207978 A1 [0005]
• EP 3207987 A1 [0005]
• EP 3207989 A1 [0005]
• EP 3207990 A1 [0005]
• EP 3162428 A1 [0005]

Cited non-patent literature

• DIN 66132 [0012]

Claims (11)

A particulate filter comprising a length L wall flow filter and two equal composition coatings Y and Z, the wall flow filter comprising channels E and A extending in parallel between first and second ends of the wall flow filter and separated by porous walls Forming surfaces O _E and O _A respectively and wherein the channels E are closed at the second end and the channels A are closed at the first end, and wherein the coatings Y and Z comprise the same oxygen storage components and the same support materials for noble metals, characterized in that coating Y is in the channels E is located on the surfaces O _E and extending over the first end of the wall flow filter over 57 to 80% of the length L, coating Z is located in the channels A on the surfaces O _A and 57, starting from the second end of the wall flow filter extends to 80% of the length L, and the coatings Y and Z alumina in from 20 to 70% by weight, based on the total weight of the coating, of Y or Z, rhodium, palladium or palladium and rhodium and one or more oxygen storage components in an amount of from 30 to 80% by weight, based on the total weight the coating Y or Z contains. Particulate filter according to Claim 1 , characterized in that the coating Y extends from the first end of the wall-flow filter to 57 to 65% of the length L of the wall-flow filter. Particulate filter according to Claim 1 and / or 2, characterized in that the coating Z extends from the second end of the wall-flow filter to 57 to 65% of the length L of the wall-flow filter. Particulate filter according to one or more of Claims 1 to 3 , characterized in that the coatings Y and Z each contain one or more noble metals, which are fixed on one or more support materials, and one or more oxygen storage components. Particulate filter according to claim, characterized in that the support materials for the noble metals are selected from the series consisting of alumina, doped alumina, silica, titania and mixed oxides of one or more thereof. Particle filter according to a Claims 4 or 5 , characterized in that the support materials for the noble metals metal oxides having a BET surface area of 30 to 250 m ² / g (determined according to DIN 66132). Particulate filter according to one or more of Claims 4 to 6 , characterized in that the coatings Y and Z contain as oxygen storage component, a cerium / zirconium / rare earth metal mixed oxides. Particulate filter according to Claim 7 , characterized in that the cerium / zirconium / rare earth metal mixed oxides contain as rare earth metal oxide lanthanum oxide, yttrium oxide, praseodymium oxide, neodymium oxide and / or samarium oxide Particulate filter according to Claim 7 and / or 8, characterized in that the cerium / zirconium / rare earth metal mixed oxides contain as rare earth metal oxide lanthanum oxide and yttrium oxide, yttrium oxide and praseodymium oxide or lanthanum oxide and praseodymium oxide. Particulate filter according to one or more of Claims 1 to 9 characterized in that the coatings Y and Z comprise both lanthanum stabilized alumina, rhodium, palladium or palladium and rhodium and an oxygen storage component comprising zirconia, ceria, yttria and lanthanum oxide. Particulate filter according to one or more of Claims 1 to 10 characterized in that the coatings Y and Z comprise both lanthanum stabilized alumina, rhodium, palladium or palladium and rhodium and an oxygen storage component comprising zirconia, ceria, praseodymia and lanthana.

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