EP3191696A1

EP3191696A1 - Particle filter and method for producing a particle filter

Info

Publication number: EP3191696A1
Application number: EP15760439.8A
Authority: EP
Inventors: Rolf BRÜCK; Peter Hirth; Thomas HÄRIG
Original assignee: Continental Automotive GmbH
Current assignee: Continental Automotive GmbH
Priority date: 2014-09-08
Filing date: 2015-09-07
Publication date: 2017-07-19
Also published as: DE102014112862A1; CN106795794A; RU2017111878A; WO2016037981A1; KR20170053698A; US20170284248A1

Abstract

The invention relates to a particle filter (1) for an exhaust gas system (2), and to a method for producing a particle filter. The particle filter (1) comprises a plurality of flow channels (5), which extend from a first end face (6) towards a second end face (7) and which are separated from one another by porous channel walls (8). On the end faces (6, 7), the flow channels (5) each have mutual closing means (9) such that an exhaust gas (10) enters a flow channel (5) that is open on the first end face (6), flows through the channel wall (8), and escapes from the particle filter (1) by way of an adjacent flow channel (5) that is open on the second end face (7). In a direction of flow (11), the channel wall (8) has, in succession, the following layers: a particle filter layer (13); an intermediate layer (14) comprising a first SCR coating (15) having a first catalytic activity (16); a second SCR coating (18) having a second catalytic activity (19), wherein the second catalytic activity (19) is different from the first catalytic activity (16).

Description

description

Particle filter and method for producing a particle ^¬ filter

The invention relates to a particulate filter and a method for producing a particulate filter. The particulate filter is used in particular as an exhaust gas treatment unit in an exhaust system, preferably in an exhaust system of a diesel internal combustion engine of a motor vehicle.

The particle filter named here is formed, in particular, from a porous, optionally extruded, structure, for example in the manner of a honeycomb structure. The shape of this honeycomb structure is not particularly limited. As the outer cross-sectional shape of the honeycomb structure, however, can be used in ^¬ play, a circle, an ellipse or an oval. The cross-sectional shape of the flow channels is also not limited, however, a rectangular cross-sectional shape is regularly preferred, for example in the manner of a triangle, a quadrangle, a hexagon or the like. The cell density for the flow channels can also be varied within wide limits, for example, the shape with a flow channel density in the range of 50 to 400 cells per square inch (7.8 to 62 cells per square centimeter) is preferred. The porous channel walls can be formed, for example, with ceramic. Here, for example, silicon carbide or metal silicon and silicon carbide has been found suitable. When the ceramic as a main crystal phase, a metal silicon and silicon carbide formed by Si (Si + SiC) de ^¬ finierte Si content is preferably 5 to 50% by mass, preferably 10 to 40% by mass.

Such particulate filters are regularly referred to as "wall-flow filters" because they force at least a large part of the exhaust gas flow through the porous channel walls, for which purpose it is known to arrange the adjacent flow channels of the channel To close the particle filter alternately at the two end faces. A "lock" can be embodied by ^¬ opening with a ge ^¬ genüber the channel cross-section (significantly) smaller, particularly when selected or all the channels which is provided at the second (abgasausströmseitigen) end face, so that a bypass (and thus a Blocking of the particulate filter, if the duct wall can not be flowed through correctly due to the particle loading.) Thus, a partial exhaust gas stream flows into a first flow channel, which is open at the exhaust gas inlet side, and by the Ver ^¬ closing means at the end of this flow channel (during normal operation of the particulate filter At least for the most part), forced through the porous channel wall to flow into a be ^¬ adjacent flow channel and through the open end at the exhaust gas outlet side flow When flowing through the porous channel walls also entrained in the exhaust gas particles can be stored and optionally reduced or in gaseous ge components are implemented. Such particle filters with porous walls regularly have a particularly large inner surface, so that a very large catalytically active surface can be provided here on a relatively small structural volume with a corresponding coating. Therefore, the use of such particulate filter is preferably also proposed in combination with an SCR system. In the case of selective catalytic reduction (SCR), the nitrogen oxides (NO, NO ₂ ) are preferably reduced, while undesired ^secondary reactions (such as, for example, the oxidation of sulfur oxide to sulfur trioxide) are largely suppressed. At the end of this reaction ammonia (NH ₃ ) is regularly used as Redukti ^¬ onsmittel, which is added to the exhaust gas. The products of the reaction are water (H ₂ O) and nitrogen (N ₂ ). Suitable catalysts which are used here are, for example, titanium dioxide, vanadium pentoxide and / or tungsten oxide. The use of zeolites is possible. The SCR process is used especially in diesel vehicles, especially in commercial vehicles, used to reduce the pollutant emissions in terms of nitrogen oxide pollution.

The previously proposed systems for particle reduction on the one hand and the nitrogen oxide reduction on the other hand are sometimes very complex and require a lot of space. It is also necessary for some systems is that a complex conditioning of the reducing agent (example ^¬, urea or the like) external exhaust gas and / or must be carried out in the exhaust system itself, wherein a complete conversion can not be ensured in part. Therefore, the provision of a so-called barrier catalyst is often proposed, which is intended to prevent a breakthrough of nitrogen oxides in insufficient conversion of the reducing agent.

On this basis, it is an object of the present invention, at least partially solve the problems described with reference to the prior art. In particular, a particle filter is to be specified which, especially in SCR systems, offers advantages with regard to the complete conversion of the SCR reactions or the hydrolysis of added reducing agent. In addition, a method for the production of such particulate filters is to be proposed so that process-reliable and cost-effective production is made possible.

These objects are achieved with a particle filter according to the features of patent claim 1 and by a method for producing a particulate filter according to the features of claim 3. In particular, the method is for Her ^¬ position of the particulate filter according to the invention. Further part exemplary embodiments ^¬ before the particle filter and the method are specified in the dependent claims. The features listed individually in the patent claims are mutually definable in existing combinatorial ^¬ liebiger technologically meaningful manner and can explanatory issues from the Description are supplemented, with further embodiments of the invention are shown.

Accordingly, a particulate filter for an exhaust system is pre ^¬ suggested, in particular for a motor vehicle with a sel ^¬ sel internal combustion engine, wherein the particulate filter comprises a plurality of flow channels extending from a first end side to a second end side and separated by porous channel walls are. The flow channels have mutually on the end faces on each closure means, so that an exhaust gas enters a open at the first end flow channel, flows through the channel wall and flows out of the particulate filter via an open at the second end, adjacent Strö ^¬ mungskanal. The channel wall has in a flow direction of the exhaust gas behind one another at least the following layers:

• at the exhaust gas inlet side, a particulate filter layer having a porosity of 60 to 90%, preferably from 80 to 90%, and an average pore size of 2 to 10 pm [microns], preferably from 3 to 5 pm;

An intermediate layer having a porosity of from 40 to 60%, preferably from 50 to 60% and an average pore size of from 10 to 20 μm [micrometers], preferably from 14 to 16 μm, the intermediate layer comprising a first SCR coating with a first catalytic layer Activity includes;

• on the exhaust gas outlet side, a second coating with a second SCR catalytic activity, wherein the second catalytic activity of the first catalytic Ak ^¬ tivity is different.

The particulate filter layer is used in particular for filtering solid particles (soot or the like) from the exhaust gas flow. These particles are retained through the small pores in the Partikelfil ^¬ terschicht, so that a large part of the particles (preferably at least 80% by mass) can not penetrate into the interim ^¬ rule layer. The particulate filter layer may be in can be regenerated at freely definable time intervals or continuously (CRT), so that particles are converted by O ₂ contained in the exhaust gas or by thermal oxidation. In particular, the particulate layer in addition so that an upstream of added from the particulate reducing agent precursor comprises a hydrolysis coating, (eg. As urea-water solution) flows through the Partikelfil ^¬ terschicht at least partially to a reducing agent (eg., Ammonia) is reacted.

The particulate filter layer is applied in particular in the form of a coating on the exhaust gas inlet side of the porous channel walls, so that there is a sharp separation between the particulate filter layer and the intermediate layer. The particle filter layer consists in particular of at least one

Washcoat (A1 ₂ 0 ₃ ),

Optionally additionally comprising a hydrolysis coating, the hydrolysis coating in particular

o titanium dioxide or

o titania-supported Wolframdioxid- and Vanadi ^¬ comprises micron tungsten oxide catalysts.

The thickness of the particulate filter layer is in particular 30 to 150 pm. preferably 50 to 100 pm.

The intermediate layer disposed downstream of the particulate filter layer has a first SCR coating with a first activity. The first activity of the first SCR coating in the intermediate layer may also be indicated by a density of the catalytically active material or by the average distance of catalytically active centers. Specifically, the particulate filter has a porous channel wall which at least in the region of the intermediate layer (prior to coating with the first Be ^¬ SCR coating) (only), a ceramic base material (see Introduction). Only in a separately carried out coating step, the first SCR coating is applied, so that then present the above-described properties of the intermediate layer in terms of porosity and pore size.

In particular, the thickness of the intermediate layer is 200 to 500 μm, preferably 200 to 400 μm. The particulate filter has, in addition, on the side opposite the Partikelfil ^¬ terschicht side of the intermediate layer, a second SCR coating, wherein the second catalytic activity (of the first catalytic activity therefore each present density or type of catalytically active material or are each present average distance catalytically active centers) is different.

In particular, the catalytic activity of the first and second SCR coating by the proportion of catalytically active materials on the coating, so z. As titanium dioxide, tungsten dioxide, vanadium pentoxide or zeolite adjusted.

In particular, the thickness of the second SCR coating is 10 to 200 μm, preferably 10 to 50 μm.

The arrangement of the particulate filter layer upstream of the intermediate layer and upstream of the second SCR coating ensures that soot particles can be reacted by O ₂ contained in the exhaust gas. The O ₂ in the exhaust gas is thus especially at low temperatures exclusively for the order ^¬ reduction of soot particles available. Only after flowing through the particulate filter layer is O ₂ (and other NO _x compounds) reacted in the SCR-coated intermediate layer and in the second SCR coating according to the following reactions:

4 NH ₃ + 4 NO + 0 ₂ -> ■ 4 N ₂ + 6 H ₂ 0 ("Standard SCR")

2 NH ₃ + NO + N0 ₂ -> ■ 2 N ₂ + 3 H ₂ 0 ("Fast SCR")

4 NH ₃ + 3 N0 ₂ -> ■ 3.5 N ₂ + 6 H ₂ 0 ("N0 ₂ SCR") In particular, the first SCR coating in the ^intermediate layer has a lower first catalytic activity than the second catalytic activity of the second SCR coating.

In particular, the porous intermediate layer makes it possible for nitrogen oxides to be intermediately stored and to be discharged successively back to the exhaust gas flow. The second SCR coating arranged downstream of the intermediate layer ensures (in particular with higher catalytic activity) that (almost) complete conversion of the nitrogen oxides takes place. The multi-stage coating of the particulate filter makes it possible to ensure separation of particle separation and conversion on the one hand and nitrogen oxide reduction on the other hand. Thus, the O ₂ contained in the exhaust gas can be effectively used for the continuous regeneration of the particulate filter, wherein immediately downstream of the particulate filter ^¬ layer, in the same channel wall of the particulate filter, the further conversion of the then existing nitrogen oxides takes place. Furthermore, a space-saving arrangement of particle filter and SCR catalyst (possibly additionally also hydrolysis catalyst) can be created, wherein at the same time large surfaces for particle deposition and catalytic conversion are provided. In addition, the (ceramic) may have porous channel wall of a (conventional) particulate filter now simultaneously / conversion be used for (Hyd ^¬ rolyse,) particulate filtering and nitric oxide caching. The required SCR activity and buffer capacity can be accurately set by the different first and second SCR coatings, so that effective utilization of the catalytically active Ma ^¬ terialien is possible.

Furthermore, a method for producing a particle ^¬ filter is proposed, in particular for the production of a particulate filter ^according to the invention. The method comprises to ^¬ least the following steps: a) providing a particulate filter having a plurality of flow channels, which extend from a first end face to a second end face and are separated by porous Ka ^¬ cal walls;

b) alternating arrangement of closure means in the flow channels at the end faces;

c) coating the porous channel wall with a first SCR coating comprising a first catalytic activity;

d) coating the walls of the channel open towards the second end face flow channels with a second coating with a second SCR catalytic activity, wherein the second catalytic activity of the first catalytic Ak ^¬ tivity is different;

e) arranging a particle filter layer on channel walls of the flow channels open to the first end face, the particle filter layer having a porosity of 5 to 50% and an average pore size of 5 to 15 μm [micrometers], preferably of 5 to 10 μm.

It is expressly pointed out that the comments on the particulate filter can also be applied to the method and vice versa. This applies in particular to designs for the particulate filter layer, the first and second SCR coating and the intermediate layer.

According to a preferred embodiment, at least the channel walls according to step a) and the particle filter layer according to step e) are produced by a printing process. In particular, a 3-dimensional printing method can be used, by which a particle filter and in particular the channel walls can be produced in layers. Can be traversed by a pressure ^¬ the different properties of the individual layers (particle filter layer, intermediate layer) are sharply separated. According to an advantageous development, the particle ^¬ filter layer according to step e) is applied by a coating process. In particular, the circuit Ver ^¬ medium according to step b) are arranged so that the coating can be made via the exhaust gas inlet side of the particulate filter before the step e) (via the open to the exhaust gas inlet side of the particulate filter channels).

In particular, the particle filter layer according to step e) is applied at least after step c). This ensures that catalytically active materials of the first SCR coating do not penetrate into the particle filter layer. A sharp separation of the first SCR coating and particle filter layer is thus possible.

In particular, the second catalytic activity of the second SCR coating is greater than the first catalytic activity of the first SCR coating. In particular, the first SCR coating used for step c) has a first viscosity and the second SCR coating used for step d) has a second viscosity, where: first viscosity <second viscosity. The low viscosity of the first SCR coating allows uniform (and continuous) coating of the ^intermediate layer, ie the porous channel wall, with catalytically active materials. The higher viscosity of the second SCR coating ensures that the second SCR coating does not mix with the first SCR coating or obscure it in the pores of the intermediate layer. In particular, this ensures that there is also a sharp spatial separation here between the first and second SCR coating. Specifically, the second SCR coating is thus applied only to the exhaust gas outlet side of the porous channel walls, wherein the second SCR coating layer especially not rule ^¬ in the interim, or penetrate into the porous channel wall. The invention is further directed to a motor vehicle having an internal combustion engine and an exhaust system, wherein the exhaust system comprises a particle filter according to the invention or a particle filter produced by the method according to the invention.

The invention and the technical environment will be explained in more detail with reference to FIGS. It should be noted that the figures and in particular the Darge in the figures presented ^¬ proportions are only schematically. Show it:

1 shows a motor vehicle with an exhaust system. 2 shows a section of a particle filter;

Fig. 3: a detail of Fig. 2;

Fig. 4: process step a);

Fig. 5: process step b);

Fig. 6: process step c); Fig. 7: process step d); and

Fig. 8: process step e).

1 shows a motor vehicle 3 with an internal combustion engine 4 and an exhaust system 2. The exhaust system 2 comprises an addition unit 22 for a reducing agent or a reducing agent precursor, which can be taken from a tank 23. Downstream of the metering unit 22 is arranged a particle filter ^¬ par. 1 An exhaust gas 10 flows through the exhaust gas system 2 starting from the internal combustion engine to the particle filter 1. The exhaust gas 10 passes through a first End face 6 in the particle filter 1 and on a second end face 7 again.

FIG. 2 shows a detail of the particle filter 1 from FIG. 1. The particle filter comprises a multiplicity of flow channels 5, which are mutually parallel and separated from one another by porous channel walls 8, extending from the first end face 6 to the second end face 7. Closure means 9 are mutually arranged in the flow channels 5 at the end faces 6 and 7. The exhaust gas 10 passes through the first end face 6 in the open flow channels 5 and is to flow through the channel walls 8 in the direction of flow 11 ge ^¬ forced by closure means. 9 Thus, the disclosed guided to the first end side 6 of ^¬ flow channels 5 form the exhaust gas inlet side 12 and the flow channels 5 open performed to the second end 7, the exhaust gas outlet side 17th

Fig. 3 shows a detail III of Fig. 2. A channel wall 8 extending from the first end face 6 toward the second end face 7. The porous channel wall 8 is traversed in perfusion ^¬ direction 11 from an exhaust 10th At the exit side 12 Abgasein ^¬ a particle filter layer 13 is arranged on the channel wall. 8 Downstream of the particulate filter layer 13, an intermediate layer 14 is formed in the porous channel wall 8, which comprises a first SCR coating 15 with a first catalytic activity 16. Downstream of the intermediate layer 14, on the exhaust gas outlet side 17 of the channel wall 8, a second SCR coating 18 with a second catalytic activity 19 is arranged.

It can be seen in FIG. 3 that the second SCR coating 18 was applied only after and that the particle filter layer 13 was applied before the closure means 9 were arranged. Particle filter layer 13, intermediate layer 14 and second SCR coating 18, each with (different thicknesses 24), form the channel wall 8 on the finished particle filter 1. Fig. 4 shows the method step a), so the (to be ^¬ coated) channel walls 8, forming the flow channels 5. FIG. 5 shows method step b), wherein mutually Ver ^¬ closing means 9 are arranged, so that now the flow ^¬ direction 11 is predetermined by the channel walls 8.

FIG. 6 shows method step c), in which the porous channel wall 8 is provided with a first SCR coating 15, which has a first viscosity 20, so that an intermediate layer 14 is formed. This process step can also be carried out before process step b). Wherein said second SCR coating 18 having a second viscosity 21 is disposed on the exhaust gas outlet side 17 of the channel wall 8 on the intermediate layer 14 ^¬ Fig. 7 shows the method step d). The second viscosity 21 is greater than the first viscosity 20 of the first SCR coating 15, so that penetration of the second SCR coating 18 into the intermediate layer 14 is not possible.

Fig. 8 shows the method step e), wherein the Partikelfil ^¬ terschicht 13 is disposed at the exhaust gas inlet side 12 of the channel wall 8 on the intermediate layer 14.

As a precaution, it should be noted that the combinations of technical features shown in the figures are not generally mandatory. Thus, technical features of a figure can be combined with other technical features of another figure and / or the general description. Something else should only apply if the combination of features has been explicitly stated here and / or the person skilled in the art recognizes that otherwise the basic functions of the device / method can no longer be met. Reference sign list

1 particle filter

2 exhaust system

3 motor vehicle

4 internal combustion engine

5 flow channel

6 First face

7 Second end face

8 channel wall

9 closure means

10 exhaust

11 flow direction

12 exhaust inlet side

13 particle filter layer

14 intermediate layer

15 First SCR coating

16 First catalytic activity

17 exhaust outlet side

18 Second SCR coating

19 Second catalytic activity

20 First viscosity

21 Second viscosity

22 addition unit

23 tank

24 thickness

Claims

claims

1. Particle filter (1) for an exhaust system (2), wherein the particulate filter (1) comprises a plurality of flow channels (5) extending from a first end face (6) towards a second end face (7) and through porous channel walls (8) are separated from each other, wherein the flow channels (5) on the end faces (6, 7) each mutually closure means (9), so that an exhaust gas (10) in one at the first end face (6) open

Flow channel (5) enters, flows through the channel wall (8) and via an on the second end face (7) open, adjacent flow channel (5) flows out of the particle filter (1), wherein the channel wall (8) in a flow direction (11 ) in succession, at least the following

Layers comprising:

• at the exhaust gas inlet side (12) a particle filter ^¬ layer (13) with a porosity of 5 to 50% and an average pore size of 5 to 15 pm; An intermediate layer (14) with a porosity of 55 to

95% and an average pore size of 15 to 100 pm, the intermediate layer (14) comprising a first SCR coating (15) having a first catalytic activity (16);

· On the exhaust gas outlet side (17) a second

SCR coating (18) having a second catalytic activity (19), wherein the second catalytic activity (19) is different from the first catalytic activity (16).

2. Particle filter (1) according to claim 1, wherein the second catalytic activity (19) is greater than the first catalytic activity (16). 3. A method for producing a particulate filter (1), in particular for producing a particulate filter (1) according to one of the preceding claims, wherein the method comprises at least the following steps:

f) providing a particulate filter (1) having a plurality of flow channels (5) extending from a first end face (6) to a second end face (7) and separated by porous channel walls (8);

g) alternating arrangement of closure means (9) in the flow channels (5) at the end faces (6, 7); h) coating the porous channel wall (8) with a first SCR coating (15) comprising a first catalytic activity (16)

i) coating the channel walls (8) of (to the second end face 7) open towards the flow channels (5) having a second SCR coating (18) having a second ka- talytischen activity (19), wherein the second catalytically ^¬ diagram activity (19 ) is different from the first catalytic activity (16);

j) arranging a particle filter layer (13) to channel ^¬ walls (8) of (to the first end side 6) open towards the flow channels (5), wherein the particle filter layer (13) has a porosity of 5 to 50% and a-average through ^¬ pore size of 5 to 15 pm.

Method according to claim 3, wherein at least the channel walls (8) according to step a) and the particle filter ^¬ layer (13) according to step e) are produced by a printing process.

A method according to claim 3, wherein the Partikelfil ^¬ terschicht (13) according to step e) by a coating process is applied.

6. The method according to claim 5, wherein the Partikelfil ^¬ terschicht (13) according to step e) is applied at least after step c).

7. The method according to any one of claims 3 to 6, wherein the second catalytic activity (19) is greater than the first catalytic activity (16).

8. The method according to claim 3, wherein the first SCR coating (15) used for step c) has a first viscosity (20) and the second SCR coating (18) used for step d) has a second viscosity (21 ), where: first viscosity (20) <second viscosity (21).

9. Motor vehicle (3) with an internal combustion engine (4) and an exhaust system (2), wherein the exhaust system (2) comprises a particulate filter (1) according to claim 1 or 2 or a particle filter produced by a method according to one of the claims 3 to 8 (1) .