JP2011078899A - Catalyst-supporting filter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a catalyst-supporting filter that can satisfactorily catch particulate matters in exhaust, can satisfactorily remove NO<SB>x</SB>in exhaust, can effectively prevent an excessive increase of a pressure drop, and can be made to have a compact structure. <P>SOLUTION: The catalyst-supporting filter 1A includes a honeycomb 2 comprising a separation wall 4 made from porous ceramic, and a plurality of plugging members 13 disposed to plug the openings of a plurality of cells 3 alternately on the end part 7 of the inflowing side of the honeycomb 2 and on the end part 8 of the outflowing side thereof. A catalyst 5 that decomposes NO<SB>x</SB>is supported on a part of the surface of a separation wall 4a, extending from the end face 7a of the end part 7 of the inflowing side of the honeycomb 2 in a range of at least one eighth to not greater than one half of the longitudinal length of the honeycomb 2 (i.e., the length in the direction of penetrating the cells), which separation wall 4a forms cells 3a each opening at the end part 7 of the inflowing side of the honeycomb 2, among the plurality of cells 3. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

The present invention relates to a catalyst-carrying filter. More particularly, an internal combustion engine such as a diesel engine, or the collection of particulate matter contained in exhaust gas discharged from a combustion device, a catalyst-carrying filter capable of satisfactorily for purifying NO _x.

  Particulate matter mainly composed of soot (graphite) (hereinafter referred to as “particulate matter” as appropriate) is used as exhaust gas discharged from internal combustion engines such as diesel engines or various combustion devices (hereinafter referred to as “internal combustion engines”). , “Particulate” or “PM”). When this particulate is released into the atmosphere as it is, environmental pollution is caused. Therefore, a filter for collecting particulates is generally mounted in an exhaust gas flow path from an internal combustion engine or the like.

  As a filter used for such a purpose, for example, it has a honeycomb structure substrate in which a plurality of cells serving as exhaust gas flow paths are partitioned by partition walls made of porous ceramics having a large number of pores, A honeycomb filter in which one open end portion and the other end portion of the plurality of cells are alternately plugged by plugging portions can be given.

For example, the honeycomb filter 110 shown in FIG. 8 has a honeycomb structure base material (for example, the honeycomb structure 100) in which a plurality of cells 101 are defined by partition walls 105 made of porous ceramics having a large number of pores. In addition, one open end X and the other end Y of the plurality of cells 101 are alternately plugged by plugging portions 107. Such honeycomb filter 110, passes through the gas G ₁ from one cell 101a which opening end portions X is open flows, the partition wall 105 from the surface of the partition wall 105 which defines a cell 101a, the other end Y There the gas G ₂ is arranged to flow out from the cell 101b which is open. That is, the gas G ₁ flowing into the cell 101 a flows out to the cell 101 b via the pores formed in the partition wall 105 and is discharged from the other end Y of the honeycomb filter 110. Then, when the exhaust gas as described above (gas G ₁₎ passes through the partition walls, particulates in the exhaust gas is trapped by the partition walls, purified gas is purified.

In recent years, regulations on harmful substances in exhaust gas from automobiles have been strengthened worldwide. Against this background, the above honeycomb filter (for example, diesel particulate filter ( Hereinafter, in addition to “DPF”)), a diesel oxidation catalyst (DOC), a NO _x selective reduction catalyst (SCR), a NO _x storage reduction catalyst (LNT), a three-way catalyst, and the like have also been developed. For example, as an exhaust gas purification device for a diesel engine vehicle in recent times, a device provided with a DPF and an SCR can be cited (for example, see Patent Documents 1 and 2).

For example, in Patent Document 1, a catalyst for reducing and purifying NO _x is disposed in an exhaust passage of a diesel engine, and an oxidation catalyst and exhaust gas from a diesel engine are sequentially arranged upstream from the upstream side of the NO _x purification catalyst. A diesel engine exhaust gas purification apparatus in which a filter capable of collecting the PM to be collected and an oxidation catalyst for the purpose of oxidizing a part of NO into NO ₂ are arranged in series is disclosed.

  Reference 2 discloses a first active component having a catalytic action that causes a nitrogen oxide to react with ammonia and decompose against partition walls that form cells into which exhaust gas flows in a honeycomb structure carrier. For example, a selective reduction type catalyst is disclosed in which a second active component having a catalytic action to oxidize ammonia is supported on a partition wall that defines a cell on which an exhaust gas flows out. .

Japanese Patent Laid-Open No. 2004-138022 Japanese Patent Laid-Open No. 2007-21422

  However, in the exhaust gas purifying apparatus described in Patent Document 1, a carrier that supports a catalyst (that is, two honeycomb structures for DOC) and a carrier that constitutes a filter (that is, a single exhaust gas purifying apparatus) DPF honeycomb structure), the exhaust gas purification device becomes too large (that is, long in the flow direction of the exhaust gas), and the type of vehicle on which such an exhaust gas purification device can be mounted is limited. There was a problem. For example, it is extremely difficult for the exhaust gas purification apparatus described in Patent Document 1 to secure a mounting space for a passenger car of a general size. Further, if the number of carriers increases, the exhaust resistance (pressure loss) increases accordingly, which causes a problem of deterioration of fuel consumption.

  In addition, the selective reduction catalyst described in Patent Document 2 can reduce the carrier on which the catalyst for oxidizing ammonia is supported, and the exhaust gas purification apparatus can be made somewhat compact. Since the carrier on which the catalyst for oxidizing ammonia is supported is a small carrier, it does not sufficiently contribute to the improvement of mountability. On the other hand, even when the selective catalytic reduction catalyst described in Patent Document 2 is used, it is necessary to include a carrier that supports the catalyst and a carrier that constitutes a filter. There is a problem that the exhaust gas purifying apparatus described in the above item is increased and fuel consumption is further deteriorated.

The present invention has been made in view of the above-described problems of the prior art, and performs good collection of particulate matter in exhaust gas and purification of harmful components (particularly NO _x ) in exhaust gas. In addition, it is possible to provide a catalyst-carrying filter that can effectively suppress an excessive increase in pressure loss and can have a compact configuration.

  The present invention provides the following catalyst-carrying filter.

[1] A honeycomb structure having partition walls made of a porous ceramic having a large number of pores, in which a plurality of cells serving as exhaust gas flow paths are defined by the partition walls, and openings of the plurality of cells A plugging portion disposed so as to alternately plug at an inflow side end portion and an outflow side end portion of the honeycomb structure, and the honeycomb structure includes the plurality of cells. A range of 1/8 or more and 1/2 or less of the length in the longitudinal direction of the honeycomb structure from the end surface at the inflow side end of the partition wall surface defining the inflow side open cell in which the inflow side end is open the catalyst-carrying filter _the NO _x purification catalyst is one that is supported for purifying NO _x.

[2] The catalyst-carrying filter according to [1], wherein the honeycomb structure has the NO _x purification catalyst carried inside the pores of the partition walls.

[3] The above [1] or [2], wherein the NO _x purification catalyst is also carried on the inflow side end face of the plugging portion that seals the inflow side end of the honeycomb structure. Catalyst-carrying filter.

[4] The NO _x purification catalyst is supported so that the supported amount per unit length in the longitudinal direction of the honeycomb structure gradually increases from the end surface at the inflow end to the end surface at the outflow end. The catalyst-carrying filter according to any one of [1] to [3].

[5] The NO _x purification catalyst is supported so that the supported amount per unit length in the longitudinal direction of the honeycomb structure gradually decreases from the end surface at the inflow side end toward the end surface at the outflow side end. The catalyst-carrying filter according to any one of [1] to [3].

[6] The [1] to [5], wherein the honeycomb structure is made of a material including at least one selected from the group consisting of cordierite, silicon carbide, aluminum titanate, silicon nitride, mullite, alumina, and silica. The catalyst-carrying filter according to any one of the above.

[7] The catalyst-carrying filter according to any one of [1] to [6], wherein the NO _x purification catalyst includes at least a urea selective reduction type NO _x catalyst.

[8] the _the NO _x purification catalyst is copper, vanadium, zeolite, titania, tungsten oxide, silver, and said containing at least one selected from the group consisting of alumina [1] to according to any one of [7] Catalyst-carrying filter.

[9] The catalyst-carrying filter according to any one of [1] to [8], wherein a region including at least a part of a lower layer portion of the region where the NO _x purification catalyst is carried is coated with an oxidation catalyst.

[10] Any of the above [1] to [8], wherein the partition wall of the honeycomb structure has an oxidation catalyst supported on at least a part of a region other than the region where the NO _x purification catalyst is supported. The catalyst-carrying filter according to 1.

[11] The catalyst-carrying filter according to [9] or [10], wherein the oxidation catalyst includes at least one selected from the group consisting of platinum, ceria, and palladium.

[12] After the oxidation catalyst is carried on the partition walls of the honeycomb structure, the catalyst-carrying filter according to any one of the above said _the NO _x purification catalyst is supported [9] to [11].

The catalyst-carrying filter of the present invention can effectively collect particulate matter in exhaust gas and purify harmful components (especially NO _x ) in exhaust gas, and effectively suppress an excessive increase in pressure loss. And a compact configuration.

That is, the catalyst-carrying filter of the present invention is one of the filter, and collecting the particulate matter, both the purification of the NO _x can be performed well, the number of carriers required for the purification of exhaust gas, Since it decreases compared with the conventional exhaust gas purification apparatus, an excessive increase in pressure loss can be effectively suppressed. In addition, since the structure can be made extremely compact, it can be mounted on a general passenger car or the like, where securing the mounting space has been an important issue.

It is a perspective view showing typically one embodiment of a catalyst carrying filter of the present invention. It is a top view which shows one end surface of the catalyst carrying filter shown in FIG. It is sectional drawing which shows typically the cross section of the catalyst carrying filter shown in FIG. It is sectional drawing which shows typically other embodiment of the catalyst carrying filter of this invention. It is sectional drawing which shows typically other embodiment of the catalyst carrying filter of this invention. It is sectional drawing which shows typically other embodiment of the catalyst carrying filter of this invention. It is explanatory drawing which shows typically the exhaust gas purification system using the catalyst carrying filter of this invention, and shows the cross section which cut | disconnected the exhaust gas purification system in the flow path direction of exhaust gas. It is sectional drawing which shows the structure of the conventional honeycomb filter typically.

  Hereinafter, the form for implementing the catalyst carrying filter of this invention is demonstrated concretely. However, the present invention broadly includes a catalyst-carrying filter having the invention-specific matters, and is not limited to the following embodiments.

[1] The catalyst-carrying filter of the present invention:
Here, FIG. 1 is a perspective view schematically showing one embodiment of the catalyst-carrying filter of the present invention, and FIG. 2 is a plan view showing one end face of the catalyst-carrying filter shown in FIG. FIG. 3 is a cross-sectional view schematically showing a cross section of the catalyst-carrying filter shown in FIG.

  As shown in FIGS. 1 to 3, the catalyst-carrying filter 1 </ b> A of the present embodiment has a partition wall 4 made of porous ceramic having a large number of pores, and the partition wall 4 serves as a plurality of exhaust gas flow paths. Arranged so that the honeycomb structure 2 in which the cells 3 are defined and the openings of the plurality of cells 3 are alternately plugged at the inflow side end 7 and the outflow side end 8 of the honeycomb structure 2. The catalyst-carrying filter 1 </ b> A includes the plugged portion 13.

The honeycomb structure 2 of the catalyst-carrying filter 1A of the present embodiment has an inflow side on the surface of the partition wall 4a that defines the inflow side opening cell 3a in which the inflow side end 7 of the plurality of cells 3 is opened. NO _x purification catalyst that purifies NO _x within a range from 1/8 to 1/2 of the length in the longitudinal direction of the honeycomb structure 2 (that is, the length in the cell penetration direction) from the end surface 7a of the end portion 7. 5 is carried.

With this configuration, the catalyst-carrying filter of the present embodiment can collect particulate matter in exhaust gas and purify harmful components in exhaust gas, particularly NO _x , and can reduce pressure loss. Excessive increase in the amount can be effectively suppressed, and a compact configuration can be achieved. That is, the catalyst-carrying filter of the present embodiment, a single filter, the collection of the particulate matter, both the purification of the NO _x can be performed well, if the number of carriers required for purification of exhaust gas Since it becomes less than that of a conventional exhaust gas purification apparatus, an excessive increase in pressure loss can be effectively suppressed. In addition, since the structure can be made extremely compact, it can be mounted on a general passenger car or the like, where securing the mounting space has been an important issue. Further, if the number of carriers increases, the exhaust resistance (pressure loss) increases accordingly, and further fuel consumption deteriorates. In the present embodiment, it is possible to expect an effect of suppressing an increase in pressure loss and further improving fuel consumption. In particular, with regard to the effect of improving the fuel efficiency, a greater effect can be expected when mounted on a commercial vehicle.

As a specific exhaust gas purification process, when the catalyst-carrying filter 1A of the present embodiment as shown in FIGS. 1 to 3 is installed and used in an exhaust system of an internal combustion engine such as a diesel engine, the present embodiment is implemented. First, the exhaust gas flowing in from the inflow side opening cell 3a of the catalyst-carrying filter 1A of the embodiment is 1/8 or more and 1/2 or less of the length in the longitudinal direction of the honeycomb structure 2 (length in the cell penetration direction). The NO _x component is purified by the NO _x purification catalyst 5 supported in the range. Further, the exhaust gas passes through the partition wall 3 that defines the inflow side opening cell 3a, flows into the inflow side opening cell 3b in which the outflow side end portion 8 is opened, and has been purified from the end face side of the outflow side end portion 8. It is discharged as gas. At this time, the partition walls defining the cells 3 serve as filtration layers, and particulate matter (particulates) in the exhaust gas is collected by the partition walls.

In the catalyst-carrying filter of the present embodiment, as _the NO _x purification catalyst described above, the catalyst can be suitably used comprising at least urea selective reduction the NO _x catalyst. Such urea selective reduction the NO _x catalyst, at further upstream side of the exhaust system is installed of catalyst, and aqueous ammonia solution, supplying a urea aqueous solution to produce ammonia by hydrolysis, of the exhaust gas and ammonia as a reducing agent Purify. In the catalyst-carrying filter of the present embodiment, the NO _x purification catalyst is carried on the upstream side in the longitudinal direction of the honeycomb structure (that is, in the range of 1/8 or more and 1/2 or less from the end surface at the inflow side end). The above-described purification of exhaust gas using ammonia as a reducing agent can be performed more satisfactorily.

For example, if another oxidation catalyst (for example, an oxidation catalyst for oxidizing particulates) or the like is supported upstream of the region where the NO _x purification catalyst is supported in the same filter, consisting of ammonia is oxidized by the oxidation catalyst, the function of the urea selective reduction the NO _x catalyst as described above is significantly reduced.

Further, when the NO _x purification catalyst is supported on the partition walls of the honeycomb structure, the pressure loss of the honeycomb structure (in other words, the pressure loss of the catalyst support filter) tends to increase, but the catalyst support filter of the present embodiment in, for _the NO _x purification catalyst from an end face at the inlet side end portions in the longitudinal length of 1/8 to 1/2 of the range of the honeycomb structured body is supported, suppresses an excessive increase in pressure loss be able to. For example, if _the NO _x purification catalyst to a range of more than 1/2 of the longitudinal length of the honeycomb structure is supported, the pressure loss of the catalyst-carrying filter is large, fuel efficiency deteriorates. If the honeycomb structure is less than 1/8 of the length in the longitudinal direction, the range in which the NO _x purification catalyst is supported is too narrow, and the NO _x purification efficiency cannot be sufficiently obtained.

Note that, in the catalyst-carrying filter of the present embodiment, the NO _x purification catalyst is carried in a range corresponding to 1/6 to 1/2 of the length in the longitudinal direction of the honeycomb structure from the end face at the inflow side end. It is more preferable that the NO _x purification catalyst is supported in a range corresponding to a length of 1/3 to 1/2. With this configuration, it is possible to satisfactorily purify NO _x while suppressing an excessive increase in pressure loss. That is, considering the balance between the increase in pressure loss and the NO _x purification efficiency, it is effective to set the range supported by the NO _x purification catalyst within the above range.

In the catalyst-carrying filter of the present embodiment, as shown in FIGS. 1 to 3, the partition wall 3 of the honeycomb structure 2 is provided at least in a part other than the region where the NO _x purification catalyst 5 is carried. The oxidation catalyst 6 may be supported. By configuring in this way, particulate matter such as soot contained in the exhaust gas collected on the partition wall surface can be oxidized by the oxidation catalyst 6 to regenerate the purification performance (collection performance) of the filter. . For example, when the ammonia the urea selective reduction the NO _x catalyst of the reducing agent, excessively in the catalyst-carrying filter 1A with the exhaust gas and (i.e., an amount more than needed for purification of NO _x) inflow, the oxidation Ammonia can be oxidized into harmless components by the catalyst 6 and discharged from the end face at the outflow side end of the catalyst-carrying filter 1A. Therefore, in the case of using the urea selective reduction the NO _x catalyst, it was separately provided on the downstream side, since it does not require a catalyst carrier for ammonia oxidation can be made more compact configuration.

The oxidation catalyst is at least in a range from the end face at the inflow side end portion to 1/2 or more of the length in the longitudinal direction of the honeycomb structure (that is, a partition wall downstream of the region where the NO _x purification catalyst is supported). It is preferably supported. With such a configuration, particulate matter such as soot collected by the partition walls can be combusted and removed satisfactorily by the oxidation catalyst.

If such an oxidation catalyst is supported in a portion other than the region where the NO _x purification catalyst is supported, for example, the honeycomb structure can be formed from the end face of the inflow side end of the partition wall defining the inflow side opening cell. It may be carried in the range of 1/2 or more of the length in the longitudinal direction, or may be carried in the pores of the partition walls in the range of 1/2 or more. Moreover, you may carry | support on the surface of the partition which forms the inflow side opening cell which the outflow side edge part opened. In FIG. 3, the range from the end surface 7 a at the inflow side end portion 7 to 1/2 or more of the length in the longitudinal direction of the honeycomb structure 2, the inside of the pores of the partition walls, and the outflow side end portion 8 are opened. An example in which the oxidation catalyst 6 is supported on the surface of the partition wall 3 that forms the inflow side opening cell 33b and the inside of the pore is shown.

Further, in the catalyst-carrying filter of the present embodiment, an oxidation catalyst may be coated (carrying) on a region including at least a part of a lower layer portion of a region carrying the NO _x purification catalyst. That is, in the catalyst-carrying filter as described above, divides the region carrying the _the NO _x purification catalyst and oxidation catalyst at the inlet side and the outlet side has been described for the case where the expression of each of the catalytic function, the present embodiment The catalyst-carrying filter may be carried in a region where the NO _x purification catalyst and the oxidation catalyst partially overlap. However, when the respective catalysts (NO _x purification catalyst and oxidation catalyst) are supported on the partially overlapping areas as described above, the area includes at least a part of the lower layer portion of the area where the NO _x purification catalyst is supported. Further, an oxidation catalyst is coated (supported). That is, in the overlapping region, the NO _x purification catalyst is supported on the upper layer of the oxidation catalyst, and the end surface at the inflow side end is within the range of 1/8 to 1/2 of the longitudinal length of the honeycomb structure. The uppermost layer needs to carry a NO _x purification catalyst.

For example, when the oxidation catalyst on NO _x purification catalyst is supported is, NO _x ammonia as a reducing agent purification catalyst is oxidized by the oxidation catalyst, the function of _the NO _x purification catalyst is significantly reduced Sometimes.

In the case where the NO _x purification catalyst and the oxidation catalyst are carried separately in the carrying region, the partition wall permeability in the region carrying the oxidation catalyst is determined by the partition wall permeation in the region carrying the NO _x purification catalyst. It is preferable to be configured to be lower than the ability. With this configuration, the exhaust gas that has flowed into the inflow side opening cell passes through (permeates) more partition walls in the region where the oxidation catalyst is supported, and particles are positively formed on the partition walls where the oxidation catalyst is supported. The particulate matter is collected, and the efficiency of combustion and removal of the particulate matter can be improved. In addition, when the NO _x purification catalyst and the oxidation catalyst are supported so as to overlap each other, inevitably the permeability of the overlapping region (that is, the region where the NO _x purification catalyst is exposed in the upper layer) is increased, and the Particulate matter is collected on the partition wall on which the oxidation catalyst is supported.

In addition, “permeability” in this specification refers to a physical property value calculated by the following formula (1), and is a value serving as an index representing a passage resistance when a predetermined gas passes through the material (partition). It is. In the following formula (1), C is permeability (m ² ), F is a gas flow rate (cm ³ / sec), T is a sample thickness (cm), and V is a gas viscosity (dynes · sec / cm ² ). , D represents the sample diameter (cm), and P represents the gas pressure (PSI). Moreover, the numerical value in following formula (1) is 13.839 (PSI) = 1 (atm), and 68947.6 (dynes * sec / cm < ² >) = 1 (PSI).

  As a procedure for measuring the permeability, the height of the remaining part (rib remaining) of the partition wall arranged so that one partition wall continuous in one direction in the honeycomb structure is perpendicular to the partition wall is 0.2 mm or less. A square plate or a disk-shaped test piece cut out as described above is prepared, room temperature air is passed through this test piece (that is, a part of the partition wall), the passage resistance at that time is measured, and the above equation (1) is used. Ask. At this time, it is desirable to use a fluid seal such as grease together so that air does not leak from a gap with the seal formed by the remaining ribs. Moreover, as an air flow rate range, the measurement result in the range from which the calculated partition wall passage flow velocity is 0.1 cm / sec or more and 1 cm / sec or less is used.

Region in the catalyst-carrying filter of the present embodiment, after the oxidation catalyst is carried on the partition walls of the honeycomb structure, if _the NO _x purification catalyst is configured to be supported, i.e., containing at least a part of the upper portion of the oxidation catalyst if _the NO _x purification catalyst is supported, the inevitably permeability of the portion _the NO _x purification catalyst is coated is increased, the exhaust gas, the more passes (transmits bulkhead area carrying only oxidation catalyst Therefore, the particulate matter is positively collected on the partition wall on which the oxidation catalyst is supported, and the efficiency of combustion and removal of the particulate matter can be improved. Further, by _the NO _x purification catalyst is coated on the upper layer of the oxidation catalyst, it is possible to prevent the front in the oxidation of ammonia produced from injected urea of the honeycomb structure.

Further, in the catalyst-carrying filter 1A shown in FIG. 3, an example in which the NO _x purification catalyst 5 is carried in a predetermined range on the surface of the partition wall 3 is shown. For example, the catalyst-carrying filter 1B shown in FIG. As described above, the above-mentioned NO _x purification catalyst 5 may be further carried inside the pores of the partition walls 3 constituting the honeycomb structure 2 (inside the pores in the predetermined range). . With this configuration, NO _x can be purified well. In the case where _the NO _x purification catalyst is supported in the interior of the pores of the partition walls, the partition wall surface, the outlet side near the surface (i.e., the surface on the opposite side of the partition wall) _the NO _x purification catalyst until be supported Also good. Here, FIG. 4 is a cross-sectional view schematically showing another embodiment of the catalyst-carrying filter of the present invention. In the catalyst-carrying filter shown in FIG. 4, the same components as those in the catalyst-carrying filter shown in FIG.

Further, in the catalyst-carrying filter 1B shown in FIG. 4, the carrying amount of the NO _x purification catalyst 5 carried on the surface of the partition wall 3 and inside the pores is changed from the end surface 7a at the inflow side end 7 to the outflow side end 8. Although toward the end face 8a shows an example of a case of a constant in, for example, as a catalyst-carrying filter 1C shown in FIG. 5, NO _x purifying catalyst 5, the longitudinal direction of the per unit length of the honeycomb structure 2 May be carried so as to gradually decrease from the end surface 7 a at the inflow side end 7 toward the end surface 8 a at the outflow side end 8. With this configuration, the vicinity of the region where the plugging portion is disposed at the end portion on the inflow side has a small role as a filter (that is, a filtration membrane), and the NO _x purification catalyst is placed in such a region. By carrying a large amount, NO _x purification efficiency can be increased. Also, toward the outlet side of the role of the filter is increased, by gradually reducing the loading amount of the NO _x purification catalyst, it is possible to ensure the effective filter area.

Incidentally, in the case where the thus gradually decrease the loading amount of the NO _x purification catalyst, with respect to the loading amount of the NO _x purifying catalyst in the inflow side end faces of, the loading amount of the NO _x purification catalyst at the end toward the outflow side It is preferable to be configured to be 3/4 or less. For example, the thickness of the catalyst layer formed by the NO _x purification catalyst is preferably configured so that the end toward the outflow side is 3/4 or less with respect to the end surface on the inflow side. When the amount of the NO _x purification catalyst supported is gradually decreased, it may be decreased approximately linearly at a constant rate, or may be decreased curvilinearly, for example, exponentially. However, it is preferable that it is decreased substantially linearly.

Further, for example, as in the catalyst-carrying filter 1D shown in FIG. 6, the NO _x purification catalyst 5 has a carrying amount per unit length in the longitudinal direction of the honeycomb structure 2 flowing out from the end surface 7a at the inflow side end portion 7. It may be supported so as to gradually increase toward the end surface 8a of the side end portion 8. With this configuration, it is possible to suppress a decrease in hydraulic diameter due to the NO _x purification catalyst on the end surface on the inflow side. For example, for vehicles with low exhaust gas temperature characteristics, when the hydraulic diameter is reduced, the cell opening may be blocked by the collected particulate matter, but the reduction of the hydraulic diameter by the NO _x purification catalyst is suppressed. Therefore, blockage of the cell opening can be effectively prevented.

Incidentally, in the case where the thus escalating the loading amount of the NO _x purification catalyst, with respect to the loading amount of the NO _x purifying catalyst in the inflow side end faces of, the loading amount of the NO _x purification catalyst at the end toward the outflow side It is preferable to be configured to be 4/3 or more. For example, the thickness of the catalyst layer formed by the NO _x purification catalyst is preferably configured such that the end toward the outflow side is 4/3 or more with respect to the end surface on the inflow side. In addition, when gradually increasing the loading amount of the NO _x purification catalyst, it may be increased approximately linearly at a constant rate, or may be increased linearly, for example, exponentially. Is preferably increased substantially linearly.

  Here, FIG.5 and FIG.6 is sectional drawing which shows typically other embodiment of the catalyst carrying filter of this invention, respectively. In the catalyst-carrying filter shown in FIGS. 5 and 6, the same components as those of the catalyst-carrying filter shown in FIG. 3 are denoted by the same reference numerals and description thereof is omitted.

Note that there is no particular limitation on the loading amount of the NO _x purifying catalyst, for example, is preferably 30 to 200 g / L, more preferably from 50 to 150 g / L, is 60 to 100 / L Is particularly preferred. With this configuration, NO _x can be purified well. For example, the loading amount of the NO _x purification catalyst, in the case of less than 30 g / L is too small, _the NO _x purification catalyst, it may not be sufficiently performed purification of the NO _x. On the other hand, even _if the loading amount of the NO _x purification catalyst exceeds 200 g / L, no significant improvement in the NO _x purification performance can be expected, and conversely, the NO _x purification catalyst is excessive on the surface of the partition walls and inside the pores. The pressure loss of the catalyst-carrying filter may increase. In this specification, the supported amount of catalyst (g / L) indicates the amount (g) of the catalyst supported per unit volume (L) of the honeycomb structure.

As shown in FIGS. 1 to 3, in the catalyst-carrying filter 1 _{</ b} > A of the present embodiment, the NO _x purification catalyst 5 has a plugging portion 13 that seals the inflow side end portion 7 of the honeycomb structure 2. Also, it is preferably carried on the inflow side end face. By configuring in this way, it is also possible to purify NO _x with respect to the exhaust gas contacting the end surface 7a at the inflow side end 7 of the catalyst-carrying filter 1A, and to further improve the NO _x purification efficiency. .

  Hereinafter, each component of the catalyst-carrying filter of the present embodiment will be described more specifically.

[1-1] Honeycomb structure and plugging portion:
As shown in FIGS. 1 to 3, the honeycomb structure constituting the catalyst-carrying filter of the present embodiment has partition walls 4 made of a porous ceramic having a large number of pores 5. A plurality of cells 5 serving as flow paths are partitioned. In the honeycomb structure 2, the openings of the plurality of cells 3 are alternately plugged by the plugging portions 13 at the inflow side end portion 7 and the outflow side end portion 8 of the honeycomb structure 2. The inflow side open cells 3a having the side end portions 7 opened, the outflow side open cells 3b having the outflow side end portions 8 opened, and the partition walls 4 are alternately arranged.

  There is no restriction | limiting in particular about the whole shape of a honeycomb structure, For example, shapes, such as quadratic prism shape and triangular prism shape other than the cylindrical shape as shown in FIG.1 and FIG.2, can be mentioned.

  Further, as the shape of the cells formed in the honeycomb structure (cell shape in a cross section perpendicular to the cell formation direction), for example, a square cell, a hexagonal cell, a triangular cell, etc. as shown in FIG. The shape can be mentioned. However, it is not limited to such a shape, and can widely include known cell shapes. More preferable cell shapes include a circular cell or a polygonal cell having a quadrangle or more. Such a circular cell or a polygonal cell having a quadrangle or more is more preferable because the thickness of the catalyst at the corner portion partitioning the cell is reduced and the thickness when the catalyst is supported on the partition wall is uniform in the cell cross section. Because it can.

The cell density of the honeycomb structure is not particularly limited, but when used as a catalyst-carrying filter as in the present embodiment, it is in the range of 15.5 to 62 cells / cm ² (100 to 400 cells / square inch). The range is preferably 31 to 46.5 cells / cm ² (200 to 300 cells / in ² ). The partition wall thickness is preferably in the range of 0.254 to 0.4318 mm, and more preferably in the range of 0.305 to 0.381 mm.

  The material of the honeycomb structure is not particularly limited, but is made of a material containing at least one selected from the group consisting of cordierite, silicon carbide, aluminum titanate, silicon nitride, mullite, alumina, and silica. Is preferred. In particular, from the viewpoint of strength, heat resistance, corrosion resistance, etc., a material made of a material containing at least one selected from the group consisting of cordierite, silicon carbide, and aluminum titanate can be suitably used.

  The average pore diameter of the partition walls is preferably 10 to 50 μm, more preferably 10 to 30 μm, and particularly preferably 15 to 25 μm.

  Moreover, it is preferable that the porosity of a partition wall is 40 to 70%, More preferably, the porosity of a gas purification catalyst layer is 45 to 65%. If it is less than 40%, there may be a problem that the pressure loss increases. On the other hand, if the porosity exceeds 70%, the strength of the partition walls may be insufficient and damage may occur.

  Further, in this specification, “average pore diameter” and “porosity” mean the average pore diameter and porosity measured by the mercury intrusion method. However, as will be described later, it is performed by appropriately adding and binarizing an image photographed by an SEM (scanning electron microscope) and measuring and evaluating it.

  Further, the honeycomb structure is not limited to an integrated honeycomb structure in which partition walls are integrally formed. For example, although not shown, the honeycomb structure has porous partition walls, and fluid flows through the partition walls. A honeycomb structure having a structure in which a plurality of columnar honeycomb segments in which a plurality of cells serving as roads are partitioned are combined via a bonding material layer (hereinafter, sometimes referred to as a “bonded honeycomb structure”) There may be.

  As the plugging portions arranged so as to plug the opening portions of the cells, those configured in the same manner as the plugging portions used in known honeycomb filters can be used.

  In addition, such a honeycomb structure in which the opening of the cell is plugged with the plugging member can be manufactured according to a conventionally known method for manufacturing a honeycomb filter.

  For example, first, talc, kaolin, alumina, silica, etc. are prepared at a predetermined blending ratio so as to become cordierite after firing, a binder, a surfactant, water are added, and coke is used as a pore former. To obtain a clay. Regarding the cordierite-forming raw material, the particle size, components, etc. ultimately affect the porosity and thermal expansion rate, but can be selected by those skilled in the art as appropriate, and the binder and surfactant are also selected. It is possible to set appropriately.

  The obtained clay is extruded using an extrusion molding machine with a die, and after drying, plugged alternately at each end face so that each end face of the obtained honeycomb formed body has a checkered pattern. Part was formed.

  As described above, a honeycomb structure in which the opening of the cell is plugged with the plugging portion can be manufactured. In addition, the formation method of such a plugging part can be performed according to the preparation method of the plugging part in a well-known honeycomb filter, for example.

  Note that it is preferable to use the same material as that of the honeycomb main body for the plugged portion because the expansion coefficient at the time of firing with the honeycomb formed body can be made the same, leading to improvement of durability.

  Further, in the production method described above, a method for producing an integral honeycomb structure is described.For example, in the case of producing the above-described joined honeycomb structure, a plurality of honeycomb segment molded bodies are obtained. A plurality of honeycomb segments may be formed by bonding a plurality of obtained honeycomb segments through a bonding agent after preparing a plurality of the above raw materials.

[1-2] NO _x purification catalyst:
In the catalyst-carrying filter of the present embodiment, 1/8 or more of the length in the longitudinal direction of the honeycomb structure from the end surface at the inflow side end of the partition wall surface defining the inflow side opening cell of the honeycomb structure. / 2 the following range of _the NO _x purification catalyst.

The NO _x purification catalyst is not particularly limited as long as it has a NO _x purification action, and a known NO _x purification catalyst such as a selective reduction type NO _x catalyst or a NO _x storage catalyst is preferably used. Can be used.

Here, _"the NO _x storage-reduction catalyst" (when the exhaust gas was the fuel rich) air-fuel ratio occludes NO _x when the lean state, when a rich spike at given intervals, occluded NO _x Refers to a catalyst that reduces N ₂ to N ₂ . For example, a metal oxide coating material such as alumina, zirconia, or titania carries a noble metal such as platinum, palladium, or rhodium and at least one metal selected from the group consisting of alkali metals and alkaline earth metals. Can be obtained.

Further, the “selective reduction type NO _x catalyst” refers to a catalyst that purifies by selectively reacting NO _x with a reducing component in a lean atmosphere. For example, at least one noble metal selected from the group consisting of copper, cobalt, nickel, iron, gallium, lanthanum, cerium, zinc, titanium, calcium, barium and silver is supported on a coating material containing zeolite or alumina. Obtainable.

As the NO _x purification catalyst used in the catalyst-carrying filter of the present embodiment, for example, a catalyst containing at least one selected from the group consisting of copper, vanadium, zeolite, titania, tungsten oxide, silver, and alumina is suitable. In particular, zeolite can be used more suitably in terms of catalyst coatability and heat resistance.

As a method for supporting such a NO _x purification catalyst in a predetermined region of the honeycomb structure, for example, a honeycomb structure in which a plugging portion is provided in a container in which a slurry of the NO _x purification catalyst is stored. and from the inlet-side end, a range of supporting the catalyst (e.g., longitudinal extent of 1/2) is immersed, can be loaded _the NO _x purification catalyst by sucking the slurry from the outflow side end face.

Incidentally, and the viscosity of the slurry of the NO _x purifying catalyst as described above, the particle diameter of _the NO _x purification catalyst contained, also, by adjusting the suction force for sucking the slurry, not only on the surface of the partition walls, the pores of the partition walls The catalyst can be supported up to the inside of the catalyst, and the amount of the supported catalyst can be adjusted. Further, the amount of the catalyst to be supported can be adjusted by performing the suction of the slurry a plurality of times.

In the case where the loading amount of the NO _x purification catalyst is gradually increased or decreased from the end surface at the inflow side end portion toward the end surface at the outflow side end portion, the viscosity, particle size, absorption capacity, and number of loadings of the slurry described above. Thus, the amount of the catalyst supported on each region can be adjusted.

[1-3] Oxidation catalyst:
In the catalyst-carrying filter of this embodiment, as described above, the oxidation catalyst may be carried on at least a part of the partition of the honeycomb structure other than the region where the NO _x purification catalyst is carried.

As such an oxidation catalyst, an oxidation catalyst capable of promoting the oxidation of the particulate matter contained in the exhaust gas can be suitably used. Further, by carrying such an oxidation catalyst, it can be carried out the oxidation of ammonia to be used as a reducing agent for selective reduction the NO _x catalyst.

  As such an oxidation catalyst, platinum, ceria, palladium or the like can be suitably used.

  Although there is no restriction | limiting in particular about the carrying amount in carrying | supporting such an oxidation catalyst, For example, it is preferable that it is 3-100 g / L, it is more preferable that it is 5-80 g / L, and 5-50 g / L. It is particularly preferred that By comprising in this way, the particulate matter collected with the partition of the catalyst carrying filter can be burned and removed satisfactorily.

As a method for supporting such an oxidation catalyst in a predetermined region of the honeycomb structure, for example, a honeycomb structure in which a plugging portion is disposed in a container in which a slurry of the oxidation catalyst is stored is discharged from the honeycomb structure. It can be carried out by immersing the catalyst supporting range (for example, a range other than ½ of the longitudinal direction supporting the NO _x purification catalyst) from the side end surface and sucking the slurry from the inflow side end surface.

  By adjusting the viscosity of the oxidation catalyst slurry, the particle diameter of the contained oxidation catalyst, and the suction force for sucking the slurry, not only the surface of the partition wall but also the inside of the pores of the partition wall. The catalyst can be supported, and the amount of the supported catalyst can be adjusted. Further, the amount of the catalyst to be supported can be adjusted by performing the suction of the slurry a plurality of times.

In the case of carrying such an oxidation catalyst is preferably performed before carrying _the NO _x purification catalyst described above. That is, when the NO _x purification catalyst and the oxidation catalyst are carried, it is preferable to carry the NO _x purification catalyst after carrying the oxidation catalyst.

[2] Application target of the present invention:
Next, an exhaust gas purification system using the catalyst-carrying filter of the present invention will be described. The exhaust gas purification system using the catalyst-carrying filter of the present invention (hereinafter referred to as “the present exhaust gas purification system”) is, as shown in FIG. 7, an exhaust gas purification system provided with the catalyst-carrying filter 1 of the present invention described so far. 50. That is, the catalyst-carrying filter 1 of the present invention disposed in the exhaust gas flow channel 51 through which the exhaust gas discharged from the diesel engine flows, and the exhaust gas flow channel 51 upstream of the catalyst-carrying filter 1 are disposed. Further, the exhaust gas purification system 50 includes a reducing agent supply unit 52 that injects and supplies urea aqueous solution or aqueous ammonia solution into the exhaust gas. Here, FIG. 7 is an explanatory view schematically showing an exhaust gas purification system (present exhaust gas purification system) using the catalyst-carrying filter of the present invention, and shows a cross section of the exhaust gas purification system cut in the direction of the exhaust gas flow path. .

This exhaust gas purification system is equipped with the catalyst-carrying filter of the present invention described so far, and can satisfactorily collect particulates in exhaust gas and purify NO _x in exhaust gas, An excessive increase in pressure loss can be effectively suppressed, and a compact configuration can be achieved.

  In the exhaust gas purification system 50 shown in FIG. 7, an example in which a diesel oxidation catalyst (DOC) 53 is further provided on the upstream side of the reducing agent supply unit 52 is shown. The catalyst-carrying filter 1 and the diesel oxidation catalyst (DOC) 53 are held by, for example, a ceramic non-thermally expandable mat 55 as a holding material, and canned by a metallic (for example, stainless steel) canning can body 54. Has been.

  The reducing agent supply unit is a supply unit that injects and supplies an aqueous ammonia solution into the exhaust gas, or generates ammonia by hydrolysis of urea by injecting an aqueous urea solution into the exhaust gas. (Selective Catalytic Reduction) What was comprised similarly to the reducing agent supply part used for a catalyst apparatus can be used suitably.

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. In Examples and Comparative Examples, diesel oxidation catalyst (DOC), a filter for collecting particulate matter, urea selective reduction the NO _x catalyst (urea SCR), and a cleaning member having a cleaning function of ammonia slip catalyst Evaluation was performed using an exhaust gas purification system provided. Various evaluations and measurements in the examples were carried out by the following methods.

[1] Evaluation of pressure loss:
Using a 7L diesel engine for the exhaust gas purification system, the pressure loss (pressure loss) when 250 ° C. exhaust gas was ventilated was measured. In addition, as evaluation of pressure loss, when pressure loss of more than 40% is reduced from the pressure loss value (2.7 kPa) measured with the catalyst-carrying filter of Comparative Example 1, “◎ (better)”, 20 to 20 The case where the pressure loss was reduced by 40% was evaluated as “◯ (good)”, and the case where the pressure loss was reduced or increased by less than 20% was determined as “× (impossible)”.

[2] Total length of exhaust gas purification system:
The total length of the exhaust gas purification system was measured. The total length of the exhaust gas purification system, a diesel oxidation catalyst (DOC), a filter for collecting particulate matter, urea selective reduction the NO _x catalyst (urea SCR), and the total length of the functional portion of the ammonia slip catalyst, the respective parts In the case of an exhaust gas purification system composed of separated devices, the total length of each length is taken as the total length, and in the case of a device in which at least a part of each function is integrated, the total length of the integrated portion is did. In addition, the total length does not include the length of piping connecting each device. In addition, as evaluation of the total length of the exhaust gas purification system, the case where the length of more than 40% was reduced with respect to the total length of the exhaust gas purification system of Comparative Example 1 (76.2 cm (30 inches)) was “◎ (Better) ”when 20 to 40% of the length was reduced,“ ◯ (good) ”, and when the length was reduced or increased by less than 20%,“ × (impossible) ”.

[3] Evaluation of collection efficiency:
Using a 7L diesel engine for the exhaust gas purification system, the exhaust gas at 250 ° C. is vented, and the mass of the particulate matter on the inlet side and the particulate matter on the outlet side of the exhaust gas purification system is measured. The collection efficiency (mass on the outlet side / mass on the inlet side × 100) was measured. In addition, as an evaluation of the collection efficiency, from the collection efficiency (98%) measured in Comparative Example 1, at least the collection efficiency was increased as “◎ (better)”. The case where the decrease was 10% or less was designated as “Δ (possible)”, and the case where the collection efficiency was reduced exceeding 10% was designated as “x (impossible)”.

[4] Evaluation of NO _x purification efficiency:
The exhaust gas purification system, 7L with diesel engines, aerated with 250 ° C. of the exhaust gas, and measures the concentration of NO _x and the concentration of NO _x outlet side of the inlet side of the exhaust gas purification system, NO _x purification of the exhaust gas purifying system It was measured efficiency (concentration of NO _x × 100 of the NO _x concentration / inlet side of the outlet side). At the time of exhaust gas purification by the exhaust gas purification system, urea water was added to the exhaust gas, and purification was performed with a NO _x purification catalyst. As the evaluation of the NO _x purification efficiency, from the measured _the NO _x purification efficiency in Comparative Example 1 (75%), the case where at least _the NO _x purification efficiency was increased "◎ (better)", NO The case where the decrease in _x purification efficiency was 10% or less was designated as “Δ (possible)”, and the case where the NO _x purification efficiency was reduced exceeding 10% was designated as “x (impossible)”.

Example 1
As the exhaust gas purification system of Example 1, an exhaust gas purification system including a diesel oxidation catalyst (DOC) and the catalyst-carrying filter of the present invention was produced.

  The honeycomb structure of the catalyst-carrying filter is prepared by blending talc, kaolin, alumina, and silica as raw materials at a predetermined blending ratio so as to become cordierite after firing, and adding a binder, a surfactant, a pore former, and water. And mixed to obtain a clay. Coke was used as the pore former. The obtained kneaded material is extruded using an extrusion molding machine with a die to obtain a honeycomb formed body, and after drying the obtained honeycomb formed body, each end face of the honeycomb formed body has a checkered pattern. In this way, plugged portions were alternately formed on each end face.

This honeycomb structure (honeycomb filter) has a cylindrical shape with a diameter of 266.7 mm and a length of 304.8 mm, a porosity of 59%, a partition wall thickness of 0.3 mm, and a cell density of 46.5 cells / cm ^2. It is.

In the honeycomb structure (honeycomb filter) obtained in this way, the partition wall surface defining the inflow side opening cell has a length equal to or less than ½ of the longitudinal length of the honeycomb structure from the end surface at the inflow side end. A catalyst-carrying filter was produced by carrying 100 g / L of a zeolite-based NO _x purification catalyst in the range.

As a specific supporting method, a range in which the catalyst is supported from the inflow side end face of the honeycomb structure in the container in which the slurry of the NO _x purification catalyst is stored (that is, a range of 1/2 in the longitudinal direction). ) was immersed, by sucking the slurry from the outflow side end face, it was supported _the NO _x purification catalyst to a predetermined region of the surface of the partition wall.

  In addition, as a diesel oxidation catalyst (DOC), talc, kaolin, alumina and silica are prepared at a predetermined mixing ratio so as to become cordierite after firing, and a binder, a surfactant and water are added, and a predetermined mixing ratio is obtained. To obtain a clay. The obtained clay is extruded using an extrusion molding machine with a die, dried and fired, and 20 g / L of platinum and ceria based oxidation catalyst are supported on the honeycomb structure obtained. Produced.

The honeycomb structure for diesel oxidation catalyst (DOC) has a cylindrical shape with a diameter of 266.7 mm and a length of 101.6 mm, a porosity of 35%, a partition wall thickness of 0.127 mm, and a cell density of 46.5 cells. / Cm ² .

The catalyst-carrying filter and diesel oxidation catalyst (DOC) obtained in this way were canned using a metallic canning can body to produce an exhaust gas purification system. Table 1 shows the results of the pressure loss evaluation, the total length of the exhaust gas purification system, the evaluation of the collection efficiency, and the evaluation of the NO _x purification efficiency described above.

Note that in the "construction of an exhaust gas purification system" of Table 1, "DOC" indicates a diesel oxidation catalyst, "SCRF" indicates _the NO _x purification catalyst-carrying filter "DPF" is carried in the honeycomb filter (catalyst None), “SCR” indicates a selective reduction type NO _x catalyst (urea selective reduction type NO _x catalyst), and “Slip” indicates an ammonia slip catalyst.

(Example 2)
The _the NO _x purification catalyst supported on the catalyst-carrying filter, except for changing as carried to the interior of the partition wall were produced exhaust gas purifying system using a catalyst-carrying filter constituted in the same manner as in Example 1. Note that the loading amount of the NO _x purification catalyst carried on the catalyst carrying filter is 100 g / L.

At the time of carrying _the NO _x purification catalyst, a slurry of the NO _x purification catalyst, by aspirating from the outlet end face, it was supported _the NO _x purification catalyst to a predetermined region of the surface of the partition wall. In Example 2, the catalyst was supported in the pores of the partition walls by adjusting the viscosity of the slurry to be used and the suction pressure.

(Example 3)
The amount of the NO _x purification catalyst supported on the catalyst-carrying filter is supported in a half of the longitudinal length of the honeycomb structure (that is, in the center in the longitudinal direction) with respect to the supported amount on the end face at the inflow side end. so it halved, i.e., except that _the NO _x purification catalyst is supported so as to gradually decrease in the longitudinal direction, to produce a exhaust gas purifying system using a catalyst-carrying filter constituted in the same manner as in example 1.

At the time of carrying _the NO _x purification catalyst, a slurry of the NO _x purification catalyst, it sucked from the outflow side end face, and this stepwise carrying _the NO _x purification catalyst by repeating a plurality of times.

Example 4
The amount of the NO _x purification catalyst supported on the catalyst-carrying filter is supported in a half of the longitudinal length of the honeycomb structure (that is, in the center in the longitudinal direction) with respect to the supported amount on the end face at the inflow side end. so it becomes twice, that is, except that _the NO _x purification catalyst is supported so as to incrementally longitudinally, to produce an exhaust gas purifying system using a catalyst-carrying filter constituted in the same manner as in example 1.

When carrying the NO _x purification catalyst, first, the slurry of the NO _x purification catalyst is sucked from the outflow side end face and carried to a range of 1/2, and then the partition wall surface is stepped from the inflow side end face side. by repeating supported catalyst was masked manner, was supported _the NO _x purification catalyst to a predetermined range.

(Example 5)
The NO _x purification catalyst supported on the catalyst support filter is the same as in Example 1 except that the NO _x purification catalyst is supported so as to be supported from the end face at the end portion on the inflow side to the range of ¼ of the longitudinal length of the honeycomb structure. An exhaust gas purification system was produced using the catalyst-carrying filter configured as described above.

(Example 6)
The NO _x purification catalyst carried on the catalyst carrying filter is the same as in Example 1 except that the NO _x purification catalyst is carried so as to be carried from the end face at the end portion on the inflow side to the range of 1/3 of the longitudinal length of the honeycomb structure. An exhaust gas purification system was produced using the catalyst-carrying filter configured as described above.

(Example 7)
After coated with the oxidation catalyst in the area of 3/4 from the outlet side end face of the catalyst-carrying filter, coated with _the NO _x purification catalyst from the inlet-side end to 1/2 of the area, the oxidation catalyst is overlapped with _the NO _x purification catalyst, the inflow In the range of 1/4 to 1/2 from the side end face, an exhaust gas purification system was produced using a catalyst-carrying filter in which a NO _x purification catalyst was coated on the upper layer of the oxidation catalyst.

(Comparative Example 1)
Not carrying _the NO _x purification catalyst on the honeycomb structure manufactured in Example 1 (honeycomb filter), was used as a mere filter, further urea selective reduction was supported _the NO _x purification catalyst the NO _x catalyst (urea SCR ) And an ammonia slip catalyst were separately used to produce an exhaust gas purification system. That is, the exhaust gas purifying system of Comparative Example 1, a diesel oxidation catalyst (DOC), a honeycomb filter, and a four purifier urea selective reduction the NO _x catalyst (urea SCR), and ammonia slip catalyst.

In Comparative Example 1 Urea selective reduction the NO _x catalyst (urea SCR) used is, 266.7Mm diameter, with a cylindrical carrier of 152.4mm length, porosity 35%, partition wall thickness 0. ^Two carriers having 127 mm and a cell density of 46.5 cells / cm ² were arranged in series, and the carrier was supported with 100 g / L of SCR catalyst.

The ammonia slip catalyst is a cylindrical support having a diameter of 266.7 mm and a length of 101.4 mm, having a porosity of 35%, a partition wall thickness of 0.127 mm, and a cell density of 46.5 cells / cm ² . A carrier on which an oxidation catalyst was supported at 20 g / L was used.

(Comparative Example 2)
The honeycomb structure (honeycomb filter) manufactured in Example 1 did not carry the NO _x purification catalyst, and was used as a simple filter to produce an exhaust gas purification system. That is, the exhaust gas purification system of Comparative Example 2 includes two purification members, a diesel oxidation catalyst (DOC) and a honeycomb filter.

(Comparative Example 3)
An exhaust gas purification system configured in the same manner as in Comparative Example 1 was produced except that the honeycomb filter used in Comparative Example 1 was not used. That is, the exhaust gas purifying system of Comparative Example 3, a diesel oxidation catalyst (DOC), and a three purifier urea selective reduction the NO _x catalyst (urea SCR), and ammonia slip catalyst.

(Comparative Example 4)
Without using ammonia slip catalyst used in Comparative Example 1, except that disposed upstream urea selective reduction the NO _x catalyst (urea SCR) of the honeycomb filter, the exhaust gas purification system is configured in the same manner as in Comparative Example 1 Was made. That is, the exhaust gas purifying system of Comparative Example 4, a diesel oxidation catalyst (DOC), and a three purifier urea selective reduction the NO _x catalyst (urea SCR), and the honeycomb filter.

(Comparative Example 5)
Without using ammonia slip catalyst used in Comparative Example 1, as a urea selective reduction the NO _x catalyst (urea SCR), exhaust gas cells carrying the urea selective reduction the NO _x catalyst on the partition wall for partitioning the flowing, the partition wall An exhaust gas purification system having the same configuration as that of Comparative Example 1 was prepared except that a partition wall partitioning a cell through which exhaust gas passed through was used. That is, the exhaust gas purifying system of Comparative Example 5, the diesel oxidation catalyst (DOC), and a three purifier of the honeycomb filter, and urea selective reduction the NO _x catalyst (urea SCR).

(Comparative Example 6)
Implementation was carried out except that the NO _x purification catalyst carried on the catalyst carrying filter was carried on the partition wall surface and inside the partition wall from the end face at the inflow side end to 1/9 of the longitudinal length of the honeycomb structure. An exhaust gas purification system was produced using a catalyst-carrying filter configured in the same manner as in Example 1. Note that the NO _x purification catalyst carried on the catalyst carrying filter is not carried on the surface of the partition wall, and the carrying amount is 100 g / L.

(Comparative Example 7)
Example 1 except that the NO _x purification catalyst supported on the catalyst-carrying filter was supported only inside the partition walls, from the end face at the inflow side end to 3/4 of the longitudinal length of the honeycomb structure. An exhaust gas purification system was produced using a catalyst-carrying filter configured in the same manner as described above. Note that the NO _x purification catalyst carried on the catalyst carrying filter is not carried on the surface of the partition wall, and the carrying amount is 100 g / L.

(Comparative Example 8)
The honeycomb structure used in Example 1 with respect to (honeycomb filter), and uniformly supported an oxidation catalyst and _the NO _x purification catalyst to prepare a catalyst-carrying filter, the catalyst-carrying filter and diesel oxidation catalyst (DOC) And an exhaust gas purification system was produced. That is, the exhaust gas purification system of Comparative Example 8 is composed of two purification members, a diesel oxidation catalyst (DOC) and a catalyst-carrying filter.

(Comparative Example 9)
A catalyst configured in the same manner as in Example 1 except that the NO _x purification catalyst supported on the catalyst-carrying filter is supported in the range of ½ of the longitudinal length of the honeycomb structure from the end face at the outflow side end. An exhaust gas purification system was produced using a supported filter. Note that the NO _x purification catalyst carried on the catalyst carrying filter is not carried on the surface of the partition wall, and the carrying amount is 100 g / L.

(result)
The exhaust gas purification systems of Examples 1 to 7 use the catalyst-carrying filter of the present invention, and good results were obtained in all evaluations.

On the other hand, Comparative Example 2 was able to obtain good results for the evaluation of the pressure loss, the total length of the exhaust gas purification system, and the evaluation of the collection efficiency, but since the NO _x purification catalyst was not used, the NO _x It is something that cannot be purified. Further, in Comparative Example 3, since the honeycomb filter was not used, it was not possible to collect the particulate matter. Further, Comparative Example 4 and 5, the collection evaluation of efficiency, and NO _x could be obtained good results in the evaluation of purification efficiency, the number of cleaning members is increased, pressure loss is significantly increased, and The total length of the exhaust gas purification system has become longer.

Further, in Comparative Example 6, the NO _x purification catalyst was supported in a very short range inside the pores of the partition walls, and the NO _x purification efficiency was significantly reduced. Further, in Comparative Example 7, the range in which the NO _x purification catalyst was supported was too long, and the pressure loss significantly increased. Moreover, the collection efficiency and _the NO _x purification efficiency was reduced together. In Comparative Example 8, since the NO _x purification catalyst and the oxidation catalyst were uniformly supported, the NO _x purification efficiency was lowered. In addition, since the NO _x purification catalyst that causes an increase in pressure loss was supported over a wide range, an increase in pressure loss was also confirmed.

In Comparative Example 9, the NO _x purification catalyst was supported on the outflow side end of the catalyst-carrying filter, and thus the NO _x purification efficiency was significantly reduced. This ammonia reducing agent will be oxidized before reaching _the NO _x purification catalyst, the function of _the NO _x purification catalyst is expected to be due to not expressed.

  The catalyst-carrying filter of the present invention collects particulates contained in exhaust gas exhausted from diesel engines, ordinary automobile engines, internal combustion engines including engines for large vehicles such as trucks and buses, and various combustion devices. Alternatively, it can be suitably used for purification.

1, 1A, 1B, 1C, 1D: catalytic filter, 2: honeycomb structure, 3: cell, 3a: inflow side open cell, 3b: outflow side open cell, 4: partition wall, 4a: partition wall (inflow side open cell partition walls forming, by surrounding), 4b: partition wall (partition wall which partitions and forms the outflow side open cells), 5: NO _x purification catalyst, 6: oxidation catalyst 7: inlet side end portion, 7a: the end face of the end face (inlet side end portions ), 8: Outflow side end, 8a: End surface (end surface at the outflow side end), 13: Plugging unit, 50: Exhaust gas purification system, 51: Exhaust gas flow path, 52: Reductant supply unit, 53: Diesel Oxidation catalyst (DOC), 54: canning can body, 55: mat, 100: honeycomb structure, 101a, 101b: cells, 103: pores, 105: partition walls, 107: plugging portions, 109: openings, 110: (conventional) honeycomb filter, _{G 1,} G _2: gas.

Claims (12)

A honeycomb structure having a partition made of a porous ceramic having a large number of pores, wherein a plurality of cells serving as exhaust gas flow paths are partitioned by the partition;
A plugging portion disposed so as to alternately plug the openings of the plurality of cells at the inflow side end portion and the outflow side end portion of the honeycomb structure;
The honeycomb structure has a length in a longitudinal direction of the honeycomb structure from an end surface of the inflow side end portion of a partition wall surface defining an inflow side open cell in which the inflow side end portion of the plurality of cells is opened. is 1/8 to 1/2 in the following range, the catalyst-carrying filter _the NO _x purification catalyst is one that is supported for purifying NO _x. 2. The catalyst-carrying filter according to claim 1, wherein the honeycomb structure is one in which the NO _x purification catalyst is also carried inside pores of the partition walls. 3. The catalyst-carrying filter according to claim 1, wherein the NO _x purification catalyst is also carried on an inflow side end surface of the plugging portion that seals the inflow side end of the honeycomb structure. The NO _x purification catalyst is supported so that the supported amount per unit length in the longitudinal direction of the honeycomb structure gradually increases from the end surface at the inflow side end to the end surface at the outflow side end. The catalyst-carrying filter according to any one of claims 1 to 3. The NO _x purification catalyst is supported such that the supported amount per unit length in the longitudinal direction of the honeycomb structure gradually decreases from the end surface at the inflow side end portion toward the end surface at the outflow side end portion. The catalyst-carrying filter according to any one of claims 1 to 3.   The honeycomb structure according to any one of claims 1 to 5, wherein the honeycomb structure is made of a material containing at least one selected from the group consisting of cordierite, silicon carbide, aluminum titanate, silicon nitride, mullite, alumina, and silica. The catalyst-carrying filter as described. The catalyst-carrying filter according to any one of claims 1 to 6, wherein the NO _x purification catalyst includes at least a urea selective reduction type NO _x catalyst. The catalyst-carrying filter according to any one of claims 1 to 7, wherein the NO _x purification catalyst includes at least one selected from the group consisting of copper, vanadium, zeolite, titania, tungsten oxide, silver, and alumina. The catalyst-carrying filter according to any one of claims 1 to 8, wherein an oxidation catalyst is coated on a region including at least a part of a lower layer portion of a region on which the NO _x purification catalyst is carried. The partition walls of the honeycomb structure, the NO _x in at least part of the portion other than the purification catalyst is supported regions, the catalyst according to any one of claims 1 to 8, the oxidation catalyst is supported Carrier filter.   The catalyst-carrying filter according to claim 9 or 10, wherein the oxidation catalyst includes at least one selected from the group consisting of platinum, ceria, and palladium. Wherein after the oxidation catalyst to the partition walls of the honeycomb structure is supported, the catalyst-carrying filter according to any one of the _the NO _x purification catalyst according to claim is supported 9-11.

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