WO2020163123A1

WO2020163123A1 - Zone-coated ceramic particulate partial filter

Info

Publication number: WO2020163123A1
Application number: PCT/US2020/015523
Authority: WO
Inventors: Suhao He; Rohit Kataria; Nilesh Ashok LENDE; Senthil Kumaran Sridharan RAMEYA; Sunil Kumar Singh
Original assignee: Corning Incorporated
Priority date: 2019-02-08
Filing date: 2020-01-29
Publication date: 2020-08-13

Abstract

A catalyzed partial wall-flow filter comprises: a ceramic honeycomb body comprising an inlet end, an outlet end, and a plurality of porous walls having wall surfaces defining a plurality of inner channels including unplugged, flow-through channels and plugged channels; a first portion of the plugged channels being plugged adjacent to the inlet end and a second portion of the plugged channels being plugged adjacent to the outlet end; a first zone extending from the inlet end to a length that is less than the axial length of the porous walls comprising an oxidation catalyst residing in the porous walls; and a second zone extending from the outlet end to the first zone that is uncoated by the oxidation catalyst; wherein the partial wall-flow filter has a particulate matter filtration efficiency of greater than or equal to 50% at soot loadings of less than or equal to 3 g/L.

Description

ZONE-COATED CERAMIC PARTICULATE PARTIAL FILTER

[0001] This application claims the benefit of priority under 35 U.S.C. § 119 of U.S. Provisional Application No. 62/802,835 filed on February 8, 2019, the content of which is incorporated herein by reference in its entirety.

BACKGROUND

Field

[0002] The present specification relates generally to wall-flow filters used to filter exhaust gases, and exhaust systems and methods incorporating such filters, and more particularly to wall-flow filters having some plugged and some unplugged channels and which comprise catalyst material, such as for systems for single-cylinder diesel engine powered vehicles that comprise such filters.

Technical Background

[0003] Ceramic wall flow filters are employed to remove particulates from fluid exhaust streams, such as from combustion engine exhaust. Examples include ceramic soot filters used to remove particulates from diesel engine exhaust gases; and gasoline particulate filters (GPF) used to remove particulates from gasoline engine exhaust gases. For wall flow filters, exhaust gas to be filtered enters inlet cells and passes through the cell walls to exit the filter via outlet channels, with the particulates being trapped on or within the inlet cell walls as the gas traverses and then exits the filter.

[0004] Single-cylinder diesel engine powered vehicles have become popular for public and goods transport because of low cost and easy maneuverability. Such diesel engines include the following types: mechanical unit pump and electronic injection unit pump. Single cylinder diesel engine powered vehicles include three-wheeled vehicles and two-wheeled vehicles.

[0005] There is a need for emission controls for single-cylinder diesel engine powered vehicles that accommodate performance needs of the vehicle.

SUMMARY

[0006] Aspects of the disclosure pertain to a catalyzed partial wall-flow filter comprising: a ceramic honeycomb body comprising an inlet end, an outlet end, and a plurality of porous walls having wall surfaces defining a plurality of inner channels comprising unplugged, flow- through channels and plugged channels; a first zone extending from the inlet end to a length that is less than the axial length of the porous walls comprising an oxidation catalyst residing in the porous walls; and a second zone extending from the outlet end to the first zone that is uncoated by the oxidation catalyst; wherein the partial wall-flow filter has a particulate matter filtration efficiency of greater than or equal to 50% at soot loadings of less than or equal to 3 g/L.

[0007] Another aspect is a catalyzed partial wall-flow filter comprising: a ceramic honeycomb body comprising an inlet end, an outlet end, and a plurality of porous walls having wall surfaces defining a plurality of inner channels comprising unplugged, flow through channels and plugged channels, a hydraulic diameter of the unplugged, flow-through channels being smaller than a hydraulic diameter of the plugged channels; the plugged channels being plugged adjacent to the outlet end and no channels being plugged adjacent to the inlet end; the unplugged, flow-through channels being evenly distributed among the plugged channels; a first zone extending from the inlet end to a length that is less than the axial length of the porous walls comprising a diesel oxidation catalyst (DOC) residing in the porous walls, the DOC being effective to oxidize carbon monoxide (CO), hydrocarbons (HC), and/or particulate matter; and a second zone extending from the outlet end to the first zone that is uncoated by the diesel oxidation catalyst; wherein the first zone extends a length that is less than or equal to 40% of the axial length of the porous walls and the second zone extends a length that is greater than or equal to 60% of the axial length of the porous walls; and the partial wall-flow filter has a particulate matter filtration efficiency of greater than or equal to 70% at soot loadings of less than or equal to 3 g/L.

[0008] Another aspect is an emission treatment system for treatment of an exhaust of a single-cylinder diesel engine comprising: the catalyzed partial wall-flow filter of any embodiment herein downstream of the single-cylinder diesel engine.

[0009] A further aspect is a method of treating diesel emissions comprising: directing an exhaust stream of a single cylinder diesel engine through the emission treatment system of any embodiment herein.

[0010] Additional features and advantages will be set forth in the detailed description, which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the embodiments described herein, comprising the detailed description, which follows, the claims, as well as the appended drawings.

[0011] It is to be understood that both the foregoing general description and the following detailed description describe various embodiments and are intended to provide an overview or framework for understanding the nature and character of the claimed subject matter. The accompanying drawings are included to provide a further understanding of the various embodiments, and are incorporated into and constitute a part of this specification. The drawings illustrate the various embodiments described herein, and together with the description serve to explain the principles and operations of the claimed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] FIG. 1 schematically depicts a honeycomb structure for a partial wall-flow filter such as for use in the exhaust system of FIG. 2 according to embodiments disclosed and described herein;

[0013] FIGS. 2A and 2B are a schematic example of a honeycomb structure that may be employed for the partial wall-flow filter according to an exemplary embodiment, with plugs visible in FIG. 2B; and

[0014] FIG. 3 is a schematic diagram of an exhaust system according to an embodiment disclosed and described herein.

DETAILED DESCRIPTION

[0015] Reference will now be made in detail to embodiments of catalyzed partial wall-flow filters comprising a catalyst-coated first zone and an uncoated second zone, embodiments of which are illustrated in the accompanying drawings. Whenever possible, the same reference numerals will be used throughout the drawings to refer to the same or like parts. In embodiments, a ceramic honeycomb body comprising an inlet end, an outlet end, and a plurality of porous walls having wall surfaces defining a plurality of inner channels comprising unplugged, flow-through channels and plugged channels. A first zone comprising an oxidation catalyst residing in the porous walls extends from the inlet end to a length that is less than the axial length of the porous walls. A second zone that is uncoated by the oxidation catalyst extends from the outlet end to the first zone. The partial wall-flow filter has a particulate matter filtration efficiency of greater than or equal to 50% at soot loadings of less than or equal to 3 g/L. The filtration efficiency may be greater than or equal to 55%, greater than or equal to 60%, greater than or equal to 65%, greater than or equal to 70%, greater than or equal to 75%, greater than or equal to 80%, greater than or equal to 85%, or more, and all values and subranges therein. Various embodiments of catalyzed partial wall- flow filters and methods for forming such catalyzed partial wall-flow filters will be described herein with specific reference to the appended drawings.

[0016] In an embodiment, the plugged channels are plugged adjacent to the outlet end only. In one or more embodiments, there are not any channels plugged adjacent to the inlet end. In an embodiment, the unplugged, flow-through channels are evenly distributed among the plugged channels. Hydraulic diameters of the unplugged, flow-through channels and the plugged channels may be different. For example, the hydraulic diameter of the plugged channels may be larger than the hydraulic diameter of the unplugged, flow-through channels. In one or more embodiments, an area ratio of plugged face area relative to unplugged face area may be greater than or equal to 1.1, greater than or equal to 1.2, greater than or equal to 1.3, greater than or equal to 1.5, or greater than or equal to 3, and all values and subranges therebetween.

[0017] As used in this specification and the appended claims, the singular forms "a", "an", and "the" encompass embodiments having plural referents, unless the content clearly dictates otherwise. As used in this specification and the appended claims, the term "or" is generally employed in its sense including "and/or" unless the content clearly dictates otherwise.

[0018] As used herein, "have", "having", "include", "including", "comprise", "comprising" or the like are used in their open ended sense, and generally mean“including, but not limited to”.

[0019] A honeycomb body, as referred to herein, is a shaped ceramic honeycomb structure of intersecting walls to form cells the define channels. The ceramic honeycomb structure may be formed, extruded, or molded, and may be of any shape or size. For example, a ceramic honeycomb structure may be formed from cordierite or other suitable ceramic material.

[0020] A catalyzed partial wall-flow filter, as referred to herein, may be defined as a shaped ceramic honeycomb structure having a combination of plugged channels and unplugged flow-through channels and a catalyst in a zoned portion of the porous walls of the honeycomb structure. In the zoned portion, a catalyst such as a diesel oxidation catalyst treats carbon monoxide (CO), hydrocarbons (HC), and/or particulate matter. In an uncoated portion, the porous walls are configured to filter particulate matter from a gas stream.

[0021] An embodiment of a partial wall-flow filter 100 is shown and described with respect to FIG. 1. The partial wall-flow filter 100 is so-named because it has a combination of plugged channels and unplugged flow-through channels. In the unplugged flow-through channels, flow is generally straight through the channel, i.e., not through the wall. In the plugged channels some of the flow passes through the walls. Thus, the“partial” indicates that only a part of the flow is through the wall whereas part of the flow passes through the filter without flowing through a wall. The partial wall-flow filter 100 may, in embodiments, comprise a plurality of porous walls 115 defining a plurality of inner channels 110. The plurality of inner channels 110 and intersecting channel walls 115 extend between first (e.g., inlet) end 105 and second (e.g., outlet) end 135 of the partial wall-flow filter 100.

[0022] According to certain embodiments, the partial wall-flow filter 100 comprises a porous honeycomb body 102 having the plurality of porous walls 115 forming the channels 110. In this embodiment, there are not any plugged channels that are plugged adjacent to the inlet end 105 of the partial wall-flow filter 100. Some of the channels 110c are plugged adjacent to the outlet end 135 of the partial wall-flow filter 100, that is, at or near the outlet end. Plugs may be provided at, for example, an end face of some of the channels, while the remaining channels 110a remain open (unplugged). This differs from the conventional wall-flow filter where all the cell channels are end-plugged (at one end or the other). In some embodiments, the unplugged, flow-through channels 110a, which are open at both ends 105, 135 and are unplugged along their length, are evenly distributed among the plugged channels 110c at the outlet end 135. Optionally, the plugs may be provided at locations spaced in from the ends. In some embodiments, relatively more plugs are provided adjacent the outlet end 135 than near the inlet end.

[0023] According to further embodiments of the partial wall-flow filter catalyzed with a diesel oxidation catalyst, it has been discovered that combinations of good initial particulate matter filtration efficiency (@ 0 g/L) may be achieved. According to embodiments, the following features in partial wall-flow filter 100, when provided either singly, or in combination, have been found by the inventors to yield desirable filter properties. For example, it is possible to achieve excellent particulate matter filtration efficiency even when the total porosity (% P) is % P ³ 50%, or even % P ^³ 60% Transverse thickness, T wall, of the porous walls 115 may be greater than or equal to 305 micrometers, greater than or equal 254 micrometers, or even greater than or equal to 203 micrometers, while only marginally affecting back pressure. Also, increasing the mean pore diameter (MPD) increases filtration efficiency while only slightly decreasing back pressure. Thus, the porous walls 115 may incorporate pores having a mean pore diameter (MPD) wherein the MPD is greater than or equal to 20 micrometers, or greater than or equal to 15 micrometers; in some embodiments 12 micrometers = MPD = 30 micrometers. Additionally, filtration efficiency increases significantly with higher cell density (CD) with only a modest increase in back pressure. Accordingly, the partial flow filter 200 may have a cell density (CD) wherein the CD is greater than or equal to 250 channels per square inch (cpsi) (CD ^³ 37.5 cells/cm²), or even greater than or equal to 300 cpsi (CD ^³45 cells/cm²).

[0024] The partial wall-flow filter 100 comprises the porous honeycomb body 102 having, for example, a generally cylindrical shape. The transverse cross-section of the honeycomb body 102 may be circular, oval, elliptical, square, or may have other desirable shape. The honeycomb body 102 has inlet end 105, outlet end 135, and interior porous walls 115 extending between the ends. The channels may have a square cross-section or other type of cross-section, e.g., triangle, circle, oval, octagon, rectangle, hexagon, tessellated, or combinations thereof, and may be arranged in any suitable geometric configuration. The honeycomb substrate 102 is preferably made of a porous ceramic material. In one or more embodiments, the honeycomb body may be formed from cordierite, aluminum titanate, enstatite, mullite, forsterite, corundum (SiC), spinel, sapphirine, and periclase. In general, cordierite is a solid solution having a composition according to the formula (Mg,Fe)2Ah(Si5A10i8). In some embodiments, the pore size of the ceramic material may be controlled, the porosity of the ceramic material may be controlled, and the pore size distribution of the ceramic material may be controlled, for example by varying the particle sizes of the ceramic raw materials. In addition, pore formers may be included in ceramic batches used to form the honeycomb body.

[0025] In the partial wall-flow filters described herein, in the uncoated portion, soot accumulates on the porous walls as exhaust passes through the filter. This accumulation of soot decreases the permeability of the walls and reduces exhaust flow to channels adjacent to the unplugged, flow-through channels 110a. Thus, the ability of the partial wall-flow filter to capture soot decreases as soot is accumulated in the filter. One advantage of a filter which decreases in filtration efficiency is that a maximum soot load can be established for the filter and overloading of soot in the filter is less likely to occur in a partial wall-flow filter. In conventional wall-flow filters, filtration efficiency generally increases as soot load accumulation on the porous walls increases, making the filter more susceptible to soot overload. Soot overload is undesirable because maximum temperatures encountered in the filter during regeneration are generally directly proportional to soot load. The partial wall- flow filter of the embodiments has a built-in protection against high temperature excursions resulting from soot overload.

[0026] Partial plugging patterns may be used to achieve acceptable pressure drop and conversion/particle retention. FIGS. 2 A and 2B are a schematic example of a honeycomb structure that may be employed for a partial wall-flow filter according to an exemplary embodiment. FIG. 2A shows an inlet end 205 and FIG. 2B shows the corresponding an outlet end 235 for channels having different hydraulic diameters: channels 210a have a diameter of di, and channels 210c have a diameter of d2, where d2 is greater than di. At the inlet end 205 of FIG. 2 A, no plugs are present. At the outlet end 235 of FIG. 2B, plugs are present in an even distribution among the unplugged, flow-through channels. Channels 210a are unplugged, flow-through channels and channels 210c are plugged channels. In this embodiment, plugs of the plugged channels 210c are located adjacent to the outlet end 235. An area ratio of the plugged area to open area of the filter may be greater than or equal to 1.1, greater than or equal to 1.2, greater than or equal to 1.3, greater than or equal to 1.5, or greater than or equal to 3, and all values and subranges therebetween. In an embodiment, the area ratio of the plugged area to open area of the filter is greater than or equal to 1.1 and less than or equal to 10. In an embodiment, the area ratio is 1.3² to 1.7. In an embodiment, the area ratio is 1.5² to 2.3.

[0027] In various embodiments the honeycomb body is configured to filter particulate matter from a gas stream. Accordingly, the mean pore size, porosity, geometry and other design aspects of both the bulk and the surface of the honeycomb body are selected taking into account these filtration requirements of the honeycomb body.

[0028] In various embodiments the honeycomb body comprises an oxidation catalyst to convert carbon monoxide (CO) and hydrocarbons (HC) of a gas stream. In an embodiment, the oxidation catalyst is a diesel oxidation catalyst. [0029] Turning to FIG. 3, an exhaust system 500 comprises a catalyzed partial wall-flow filter 506 disposed adjacent to an inlet end 501 of an exhaust line 502 downstream of a single cylinder engine 507 (for example a diesel engine) and its exhaust manifold 505. Exhaust systems 500 downstream of single cylinder engines can be compact due to space limitations. Configurations, shapes, and sizes of the exhaust manifold 505 and exhaust line 502 depend on availability of space for each type of vehicle.

[0030] The inlet end 501 of the exhaust line 502 is coupled to the engine 507 through the exhaust manifold 505. The inlet end 501 may comprise a connection device 504, which may take on any suitable form. For example, the connection device 504 may be a flange that can be coupled to a similar flange on a connection portion 509 of the exhaust manifold 505.

[0031] Although the exhaust line 502 is shown as being generally straight, in practice it may take on other profiles and may comprise straight and curved sections and/or sections of differing diameter.

[0032] During normal operation of the engine, an exhaust stream from the engine 507 and exhaust manifold 505 passes through the catalyzed partial wall-flow filter 506 as indicated by arrow 516 in FIG. 3. Particulates in the exhaust stream are trapped inside the catalyzed partial wall-flow filter 506 at least at the uncoated portion of the filter as the exhaust stream passes through it. Carbon monoxide (CO) and hydrocarbons (HC) of the exhaust stream are converted by the DOC. The engine operating conditions and location of the catalyzed partial wall-flow filter 506 relative to the engine 507 may be set to achieve a desired inlet temperature T1 of the exhaust stream at the catalyzed partial wall-flow filter 506.

[0033] Optionally, downstream of the catalyzed partial wall-flow filter 506, there may be additional exhaust treatment articles including but not limited to: other filters such as partial wall-flow filters and catalytic articles that a effective to reduce nitrogen oxides (NOx) such as deNOx articles (selective catalytic reduction (SCR) and/or lean NOx traps (LNT)).

[0034] In an embodiment, there are no additional exhaust treatment articles including but not limited to: other filters such as partial wall-flow filters and catalytic articles such as deNOx articles.

[0035] The catalyzed partial wall-flow filter 506 may comprise a partial wall-flow filter as a substrate for the DOC catalyst. In the unplugged flow-through channels of the partial wall- flow filter, flow is straight through the channel, i.e., not through the wall. Thus, the“partial” indicates that only a part of the flow is through the wall. Partial wall-flow filters may exhibit high porosity, greater than 45% and which have a combination of plugged and unplugged channels have been discovered to be most effective. Partial wall-flow filters having total porosities of 50% and more exhibit excellent filtration efficiency.

[0036] The diesel oxidation catalyst (DOC) of the catalyzed partial wall-flow filter may incorporate any known active catalytic species for purifying exhaust, such as catalytic species for oxidizing carbon monoxide, hydrocarbons, and soluble organic fraction of particulates, as is known in the art. The DOC is coated onto the partial wall-flow filter by washcoating technology. The exhaust system 500 may further comprise devices such as diffusion and expansion cones 510, 512 at the inlet and outlet ends of the catalyzed partial wall-flow filter 506 to aid in achieving desired exhaust flow distribution in the catalyzed partial wall-flow filter, and/or size and weight reductions in the exhaust line 502.

[0037] As described above with reference to FIG. 1, the porous honeycomb body can have an inlet end 105 and an outlet end 135. The inlet and outlet ends are separated by an axial length. The DOC is zoned on the partial wall-flow filter. In embodiments, the DOC in the walls of the honeycomb body extends less than the entire axial length of the honeycomb body {i.e., extends along less then or equal to 100% of the axial length). In an embodiment, the DOC in the walls of the honeycomb body extends along less than or equal to 50% of the axial length, such as extends along less than or equal to 45% of the axial length, extends along less than or equal to 40% of the axial length, extends along less than or equal to 35% of the axial length, extends along less than or equal to 30% of the axial length, or extends along less than or equal to 25% of the axial length.

[0038] In embodiments, the DOC in the walls of the honeycomb body extends from the first end of the honeycomb body to the second end of the honeycomb body. In embodiments, the DOC in the walls of the honeycomb body extends less than the entire distance from the first end of the honeycomb body to the second end of the honeycomb body {i.e., extends along less than 100% of a distance from the first end of the honeycomb body towards the second end of the honeycomb body). In an embodiment, the DOC in the walls of the honeycomb body extends along less than or equal to 50% of a distance from the first end of the honeycomb body towards the second end of the honeycomb body, such as extends along less than or equal to 45% of a distance from the first end of the honeycomb body to the second end of the honeycomb body, extends along less than or equal to 30% of a distance from the first end of the honeycomb body to the second end of the honeycomb body, or extends along less than or equal to 25% of a distance from the first end of the honeycomb body to the second end of the honeycomb body.

EXAMPLES

[0039] Embodiments will be further clarified by the following examples.

[0040] In the examples, an embodiment comprised: a partial wall-flow filter zone-coated with a diesel oxidation catalyst (DOC) to form a catalyzed partial wall-flow filter. The length of the partial wall-flow filter was 5 inches (12.7 centimeters), wherein a first zone containing the DOC extended from the inlet end towards the outlet end for 2 inches (5.08 centimeters) (40%), leaving 3 inches (7.62 centimeters) uncoated (60%). The honeycomb body of the partial wall-flow filter had 350 cells per square inch (CPSI), 12 mil thickness and was formed from an aluminum titanite material having high porosity and an asymmetric cell technology. In accordance with FIGS. 2A-2B, the plugged channels were plugged adjacent to the outlet end and there were not any channels plugged adjacent to the inlet end. The hydraulic diameter of the plugged channels was larger than the hydraulic diameter of the unplugged, flow-through channels. The unplugged, flow-through channels were evenly distributed among the plugged channels. The area ratio of the plugged area to open area of the filter was 1.3²-1.7. The DOC was present in an amount of 15 grams per cubic foot. The DOC was effective to convert carbon monoxide (CO), hydrocarbons (HC), and/or particulate matter.

[0041] Testing of the following examples of catalyzed partial wall-flow filters was conducted according to the Indian driving cycle (IDC) certification test for 3-wheeled vehicles. Data included emissions data and fuel economy measures. Emissions data was: carbon monoxide (CO) emissions (g/km), hydrocarbons (HC) emissions (g/km), nitrogen oxides (NOx) emissions (g/km), total HC+NOx (g/km), and particulate matter (PM) (g/km). For the emissions data,“margin” is provided, which is a percentage relative to the BS VI in 2020 regulation limit. A 100% margin means the emissions are right on the regulation limit. A 50% means the emissions are one-half of the regulation limit, providing a safety factor of 2. Fuel economy measures were: carbon dioxide (CO2) (g/km) and fuel consumption (FC) (Kmpl). [0042] For the purposes of particulate matter filtration efficiency, estimated engine-out particulate matter is 50-60 mg/kg in the absence of any aftertreatment. Soot loadings of less than or equal to 3 g/L are estimated.

EXAMPLE A - COMPARATIVE

[0043] For comparison, an exhaust system including a flow-through substrate including a DOC followed by a partial wall-flow filter (uncoated) was tested (IDC) in the exhaust system of two different 3 -wheeled vehicle designs, A and B, containing a single cylinder diesel engine. Table 1 contains the emissions results.

Table 1: COMPARATIVE: Flow-through substrate and uncoated partial filter

[0044] Estimated particulate matter filtration efficiency for Table 1 is in the range of 33% to 40%.

EXAMPLE 1

[0045] The catalyzed partial wall-flow filter embodiment described above was tested (IDC) in the exhaust system of three different 3 -wheeled vehicles, A, B, and C, containing a single cylinder diesel engine; and the results are provided in Table 2.

Table 2: same zone-coated partial filter tested with different vehicles

[0046] Estimated particulate matter filtration efficiency for Table 2 is in the range of 63% to 87%.

[0047] Table 1 showed that repeatability of the performance is good. System design has to meet not only PM emission, but also requirements on other emissions, CO/HC/NOx.

EXAMPLE 2

[0048] The catalyzed partial wall-flow filter embodiment described above was tested (IDC) in the exhaust system of five different 3-wheeled vehicles, 1, 2, 3, 4, and 5, containing a single cylinder diesel engine; and the results are provided in Table 3. Table 3: Multiple samples tested with different vehicles (n=2)

[0049] Estimated particulate matter filtration efficiency for Table 3 is in the range of 58% to 76%.

[0050] In Table 3, good repeatability was demonstrated.

EXAMPLE 3

[0051] The catalyzed partial wall-flow filter embodiment described above was tested according to the Indian driving cycle (IDC) certification test for 3 -wheeler fresh versus aged, and the results are provided in Table 4.

Table 4 Road aged samples

[0052] Estimated particulate matter filtration efficiency for Table 4 is in the range of 55% to 77%.

[0053] The road-aged samples of Table 3 met PM (BS IV) with IDC cycle. In-use performance is consistent, after 3 OK km durability test.

[0054] It will be apparent to those skilled in the art that various modifications and variations can be made to the embodiments described herein without departing from the spirit and scope of the claimed subject matter. Thus, it is intended that the specification cover the modifications and variations of the various embodiments described herein provided such modification and variations come within the scope of the appended claims and their equivalents.

Claims

What is claimed is:

1. A catalyzed partial wall-flow filter comprising:

a ceramic honeycomb body comprising an inlet end, an outlet end, and a plurality of porous walls having wall surfaces defining a plurality of inner channels comprising unplugged, flow-through channels and plugged channels;

a first zone extending from the inlet end to a length that is less than the axial length of the porous walls comprising an oxidation catalyst residing in the porous walls; and a second zone extending from the outlet end to the first zone that is uncoated by the oxidation catalyst;

wherein the partial wall-flow filter has a particulate matter filtration efficiency of greater than or equal to 50% at soot loadings of less than or equal to 3 g/L.

2. The catalyzed partial wall-flow filter of claim 1, wherein the particulate matter filtration efficiency is greater than or equal to 70%.

3. The catalyzed partial wall-flow filter of claim 1, wherein the plugged channels are plugged adjacent to the outlet end.

4. The catalyzed partial wall-flow filter of claim 1, wherein there are not any channels plugged adjacent to the inlet end.

5. The catalyzed partial wall-flow filter of claim 1, wherein the unplugged, flow-through channels are evenly distributed among the plugged channels.

6. The catalyzed partial wall-flow filter of claim 1, wherein hydraulic diameters of the unplugged, flow-through channels and the plugged channels are different.

7. The catalyzed partial wall-flow filter of claim 6, wherein the hydraulic diameter of the plugged channels are larger than the hydraulic diameter of the unplugged, flow-through channels.

8. The catalyzed partial wall-flow filter of claim 1, wherein an area ratio of plugged face area relative to unplugged face area is greater than or equal to 1.1.

9. The catalyzed partial wall-flow filter of claim 1, wherein the first zone extends a length that is less than or equal to 50% of the axial length of the porous walls and the second zone extends a length that is greater than or equal to 50% of the axial length of the porous walls.

10. The catalyzed partial wall-flow filter of claim 9, wherein the first zone extends a length that is less than or equal to 40% of the axial length of the porous walls and the second zone extends a length that is greater than or equal to 60% of the axial length of the porous walls.

11. The catalyzed partial wall-flow filter of claim 1, wherein the oxidation catalyst is a diesel oxidation catalyst effective to oxidize carbon monoxide (CO), hydrocarbons (HC), and/or particulate matter.

12. The catalyzed partial wall-flow filter of claim 1 in the absence of a catalyst effective to reduce nitrogen oxides (NOx).

13. A catalyzed partial wall-flow filter comprising:

a ceramic honeycomb body comprising an inlet end, an outlet end, and a plurality of porous walls having wall surfaces defining a plurality of inner channels comprising unplugged, flow-through channels and plugged channels, a hydraulic diameter of the unplugged, flow-through channels being smaller than a hydraulic diameter of the plugged channels;

the plugged channels being plugged adjacent to the outlet end and no channels being plugged adjacent to the inlet end;

the unplugged, flow-through channels being evenly distributed among the plugged channels;

a first zone extending from the inlet end to a length that is less than the axial length of the porous walls comprising a diesel oxidation catalyst (DOC) residing in the porous walls, the DOC being effective to oxidize carbon monoxide (CO), hydrocarbons (HC), and/or particulate matter; and

a second zone extending from the outlet end to the first zone that is uncoated by the diesel oxidation catalyst;

wherein the first zone extends a length that is less than or equal to 40% of the axial length of the porous walls and the second zone extends a length that is greater than or equal to 60% of the axial length of the porous walls; and the partial wall-flow filter has a particulate matter filtration efficiency of greater than or equal to 70% at soot loadings of less than or equal to 3 g/L.

14. An emission treatment system for treatment of an exhaust of a single-cylinder diesel engine comprising:

the catalyzed partial wall-flow filter of any preceding claim downstream of the single cylinder diesel engine.

15. The emission treatment system of claim 14 that is effective to treat carbon monoxide (CO), hydrocarbons (HC), and/or particulate matter.

16. The emission treatment system of claim 14, wherein no other filters and/or catalytic articles are present downstream of the catalyzed partial wall-flow filter.

17. A method of treating diesel emissions comprising: directing an exhaust stream of a single cylinder diesel engine through the emission treatment system of claim 14.