JP6315194B2 - Exhaust gas purification catalyst, method for producing the same, and exhaust gas purification method using the same - Google Patents

Description

  The present invention relates to an exhaust gas purification catalyst, a method for producing the same, and an exhaust gas purification method using the same.

  The gas discharged from the internal combustion engine contains harmful substances such as particulate matter (PM) generated by combustion, ash composed of additives in oil, and the like. Among such harmful substances, particulate substances are known as air pollutants that adversely affect animals and plants. Therefore, a purification filter (DPF: Diesel Particulate Filter) is used to collect particulate matter contained in the exhaust gas discharged from the internal combustion engine.

  As such a purification filter, Japanese Patent Application Laid-Open No. 2002-188435 (Patent Document 1) is an exhaust gas purification filter that captures and burns particulates contained in exhaust gas of a diesel engine and stores and reduces NOx, A monolith support having a plurality of cells formed by partition walls, the one end side and the other end side of the cells being alternately sealed, and a catalyst component and NOx occlusion material supported on the monolith support, An exhaust gas purification filter is disclosed which has a high oxidation capacity on the exhaust gas inflow side and a large NOx purification capacity on the outflow side. However, in recent years, the required characteristics of exhaust gas purification catalysts have been increasing, and there has been a demand for exhaust gas purification catalysts having sufficiently high particulate matter purification performance and sufficiently high NOx purification performance. It was.

JP 2002-188435 A

  The present invention has been made in view of the above-mentioned problems of the prior art, and has a sufficiently high particulate matter purification performance and a sufficiently high NOx purification performance, a method for producing the exhaust gas purification catalyst, and An object of the present invention is to provide an exhaust gas purification method using the same.

  As a result of intensive studies to achieve the above object, the present inventors have sealed the gas inflow passage of a filter base such as DPF used in an exhaust gas passage containing NOx and particulate matter. Particulate material oxidation catalyst on the surface of the partition wall on the end side (second partition wall surface), NO oxidation catalyst and / or NOx purification catalyst on the surface of the partition wall on the opening end side of the gas inflow passage (first partition wall surface), gas The NOx purification catalyst is supported on the surface of the partition wall (third partition wall surface) on the sealing end side of the outflow passage, and the NOx purification catalyst is supported on the surface of the partition wall (fourth partition surface) on the opening end side of the gas outflow passage. As a result, it was surprisingly found that an exhaust gas purification catalyst having sufficiently high particulate matter purification performance and sufficiently high NOx purification performance can be obtained by using the exhaust gas purification catalyst. It came to do.

That is, the exhaust gas purifying catalyst of the present invention is disposed in the exhaust gas flow path containing NOx and particulate matter, and has an inflow surface on the exhaust gas inflow side and an exhaust surface on the exhaust gas exhaust side. An exhaust gas purifying catalyst comprising:
A gas inflow passage having one end opened on the inflow surface and the other end sealed on the discharge surface side, and a gas having one end opened on the discharge surface and the other end sealed on the inflow surface side An outflow passage is defined by a porous partition wall, and a wall-through filter base body in which the exhaust gas flowing into the gas inflow passage passes through the partition wall and is discharged from the gas outflow passage;
Exhaust gas is present on the surface in contact with the gas inflow passage of the partition wall (first partition wall) on the opening end side of the gas inflow passage and on the surface in the pores (first partition wall surface) inside the first partition wall . A first catalyst layer supported so as to pass through one partition wall and comprising a NO oxidation catalyst and / or a NOx purification catalyst;
Exhaust gas is present on the surface of the partition wall (second partition wall) on the sealing end side of the gas inflow passage in contact with the gas inflow passage and on the surface in the pores inside the second partition wall (second partition surface). A second catalyst layer which is supported so as to pass through the second partition and is made of a particulate matter oxidation catalyst;
Exhaust gas is present on the surface of the partition wall (third partition wall) on the sealing end side of the gas outflow passage in contact with the gas outflow passage and on the surface in the pores (third partition wall surface) inside the third partition wall. A third catalyst layer which is supported so as to pass through the third partition wall and which consists of a NOx purification catalyst;
Exhaust gas is produced on the surface of the partition wall (fourth partition wall) on the opening end side of the gas outflow passage in contact with the gas outflow passage and on the surface in the pores in the fourth partition wall (surface of the fourth partition wall) . A fourth catalyst layer which is supported so as to pass through the four partition walls and is made of a NOx purification catalyst;
It is characterized by having.

  In the exhaust gas purification catalyst of the present invention, the particulate matter oxidation ability of the particulate matter oxidation catalyst is higher than the particulate matter oxidation ability of the NOx purification catalyst, and the NOx purification ability of the NOx purification catalyst is: It is preferable that it is higher than the NOx purification capacity of the particulate matter oxidation catalyst.

  Further, in the exhaust gas purifying catalyst of the present invention, the particulate matter oxidation catalyst is a particulate matter oxidation catalyst in which silver is supported on or complexed with cerium oxide, and the NO oxidation catalyst is platinum is aluminum oxide. And the NOx purification catalyst is preferably a NOx occlusion reduction catalyst and / or a NOx selective reduction catalyst.

The method for producing an exhaust gas purifying catalyst of the present invention is arranged in a flow path of exhaust gas containing NOx and particulate matter, and includes an inflow surface on the exhaust gas inflow side and an exhaust surface on the exhaust gas exhaust side. A method for producing an exhaust gas purifying catalyst having
A gas inflow passage having one end opened on the inflow surface and the other end sealed on the discharge surface side, and a gas having one end opened on the discharge surface and the other end sealed on the inflow surface side An outflow passage is defined by a porous partition wall and arranged side by side, and a wall-through type filter substrate is prepared in which exhaust gas flowing into the gas inflow passage passes through the partition wall and is discharged from the gas outflow passage. And a process of
NO oxidation catalyst is formed on the surface of the partition wall (first partition wall) on the opening end side of the gas inflow passage in contact with the gas inflow passage and on the surface in the pores (first partition wall surface) inside the first partition wall. And / or supporting the first catalyst slurry, which is a precursor of the NOx purification catalyst, so that the exhaust gas passes through the first partition wall ;
The surface of the partition wall (second partition wall) on the sealing end side of the gas inflow passage in contact with the gas inflow passage and the surface inside the pores (second partition wall surface) inside the second partition wall are in the form of particles. Supporting a second catalyst slurry, which is a precursor of the material oxidation catalyst, so that the exhaust gas passes through the second partition wall ;
NOx purification is performed on the surface in contact with the gas outflow passage of the partition wall (third partition wall) on the sealing end side of the gas outflow passage and on the surface in the pores (third partition wall surface) inside the third partition wall. Supporting a third catalyst slurry, which is a catalyst precursor, so that exhaust gas passes through the third partition ;
A NOx purification catalyst is formed on the surface of the partition wall (fourth partition wall) on the opening end side of the gas outflow passage in contact with the gas outflow passage and on the surface in the pores (fourth partition wall surface) inside the fourth partition wall. Supporting a fourth catalyst slurry that is a precursor of the exhaust gas so that the exhaust gas passes through the fourth partition wall ;
A step of obtaining the exhaust gas purifying catalyst of the present invention by performing a heat treatment on the filter substrate carrying the catalyst slurry; and
The manufacturing method characterized by including.

  The exhaust gas purifying method of the present invention uses the exhaust gas purifying catalyst of the present invention, and flows exhaust gas containing NOx and particulate matter from the gas inflow passage of the exhaust gas purifying catalyst and from the gas outflow passage. It is an exhaust gas purification method characterized by exhausting.

The reason why the exhaust gas purification catalyst of the present invention makes it possible to obtain an exhaust gas purification catalyst having sufficiently high particulate matter purification performance and sufficiently high NOx purification performance is not necessarily clear. The present inventors infer as follows. That is, first, in the present invention, the first catalyst layer is formed on the surface of the partition wall (first partition wall surface) on the opening end side of the gas inflow passage of the wall-through filter base. Since the first catalyst layer is composed of a NO oxidation catalyst and / or a NOx purification catalyst, the exhaust gas flowing into the opening end side of the gas inflow passage of the filter base, the surface of the first partition wall, and the surface thereof oxidation removal in the vicinity of the particulate matter (PM), the reaction for oxidizing NO into NO _2, or, it is possible to purify the nitrogen oxides (NOx).

  In the present invention, the second catalyst layer is formed on the surface of the partition wall (second partition wall surface) on the sealing end side of the gas inflow passage of the filter base. Since such a 2nd catalyst layer consists of a particulate matter oxidation catalyst, sufficiently high particulate matter purification performance can be exhibited. That is, when a filter such as DPF is used for purification of exhaust gas containing NOx and particulate matter, the particulate matter (PM) contained in the exhaust gas is separated from the surface of the partition wall on the gas inflow passage side (particularly, the second The particulate matter oxidation catalyst is supported on the surface of the second partition wall, so that the active species of the particulate matter oxidation catalyst can be arranged at the contact interface with PM. Therefore, the contact property with PM is improved, and higher PM oxidation removal performance can be exhibited.

  Further, in the present invention, a third catalyst layer on the surface of the partition wall (third partition wall surface) on the sealing end side of the gas outflow passage of the filter base, and the open end side of the gas outflow passage of the filter base. A fourth catalyst layer is formed on the surface of the partition wall (the surface of the fourth partition wall). Since the third catalyst layer and the fourth catalyst layer are made of NOx purification catalyst, it is possible to purify NOx.

  As described above, in the present invention, due to the interaction between the first catalyst layer, the second catalyst layer, the third catalyst layer, and the fourth catalyst layer, which are separately arranged at specific locations of the partition wall of the filter base. The present inventors speculate that it becomes possible to provide a catalyst having sufficiently high particulate matter purification performance and sufficiently high NOx purification performance.

  According to the present invention, it is possible to provide an exhaust gas purification catalyst having sufficiently high particulate matter purification performance and sufficiently high NOx purification performance, a method for producing the same, and an exhaust gas purification method using the same. It becomes possible.

It is a schematic longitudinal cross-sectional view which shows typically the one part longitudinal cross-section of suitable one Embodiment of the catalyst for exhaust gas purification of this invention. It is a schematic longitudinal cross-sectional view which shows typically the longitudinal cross-section of a part of filter base material in suitable one Embodiment of the catalyst for exhaust gas purification of this invention. 2 is a schematic longitudinal sectional view schematically showing a catalyst slurry press-fitting means in the manufacture of the exhaust gas purifying catalyst of Example 1. FIG. It is a graph which shows the NOx purification rate and complete oxidation rate of the catalyst for exhaust gas purification obtained in Example 1 and Comparative Examples 1-2 . It is a graph which shows the NOx purification rate and complete oxidation rate of the exhaust gas purification catalyst obtained in Example 2 and Comparative Examples 4-5. It is a graph which shows the NOx purification rate and complete oxidation rate of the catalyst for exhaust gas purification obtained in Example 3 and Comparative Examples 6-7. It is a graph which shows the NOx purification rate and complete oxidation rate of the exhaust gas purification catalyst obtained in Example 4 and Comparative Examples 8-9.

  Hereinafter, the present invention will be described in detail with reference to preferred embodiments thereof.

The exhaust gas purifying catalyst of the present invention is disposed in a flow path of exhaust gas containing NOx and particulate matter, and has an inflow surface on the exhaust gas inflow side and an exhaust surface on the exhaust gas exhaust side. A gas inflow passage having one end opened on the inflow surface and the other end sealed on the discharge surface side; and one end opened on the discharge surface and the other end on the inflow surface side. And a gas outlet passage sealed with a wall formed by a porous partition wall, and exhaust gas flowing into the gas inlet passage passes through the partition wall and is discharged from the gas outlet passage. A through-type filter base,
A first catalyst layer supported on the surface of the partition wall (first partition wall surface) on the opening end side of the gas inflow passage and made of a NO oxidation catalyst and / or a NOx purification catalyst;
A second catalyst layer supported on the surface of the partition wall (second partition wall surface) on the sealing end side of the gas inflow passage and made of a particulate matter oxidation catalyst;
A third catalyst layer supported on the surface of the partition wall (third partition wall surface) on the sealing end side of the gas outflow passage and made of a NOx purification catalyst;
And a fourth catalyst layer that is supported on the surface of the partition wall (the fourth partition wall surface) on the opening end side of the gas outflow passage and is made of a NOx purification catalyst. By setting it as such an exhaust gas purification catalyst, it is possible to provide an exhaust gas purification catalyst having sufficiently high particulate matter purification performance and sufficiently high NOx purification performance.

(Filter base)
The filter base in the exhaust gas purifying catalyst of the present invention is disposed in a flow path of exhaust gas containing NOx and particulate matter, and has an inflow surface on the exhaust gas inflow side and an exhaust surface on the exhaust gas exhaust side. And a gas inflow passage having one end opened on the inflow surface and the other end sealed on the discharge surface side, and one end opened on the discharge surface. And a gas outflow passage whose other end is sealed on the inflow surface side is formed by a porous partition wall, and the exhaust gas flowing into the gas inflow passage passes through the partition wall and passes through the partition wall. This is a wall-through type filter base that is discharged from a gas outflow passage.

  Such a filter substrate is not particularly limited, but has a wall-through type (wall-through structure) honeycomb shape (a cross-sectional shape perpendicular to the axial direction of the gas passage is a polygonal shape such as a square or a hexagon, a circular shape, an oval shape) (Including those having various cross-sectional shapes such as shapes). For example, the gas inflow passage and the gas outflow passage are defined by a porous partition wall and are formed in a honeycomb shape. A monolith ceramic filter made of a monolith carrier substrate such as a honeycomb-shaped ceramic filter or a high-density honeycomb can be suitably used. The “honeycomb shape” means that in the filter base, gas inflow passages and gas outflow passages are alternately defined and arranged in parallel by porous partition walls. It is a structure formed by porous partition walls so as to be substantially parallel to each other. The cross-sectional shape of the gas inflow passage and the gas outflow passage in the direction orthogonal to the axial direction of the gas passage includes various cross-sectional shapes such as a polygonal shape such as a square and a hexagon, a circular shape, and an elliptical shape. It is preferably a polygonal shape such as hexagon. In addition, such a filter base is alternately sealed in a checkered pattern in cross-section in the direction perpendicular to the axial direction of the gas passage at the opening end on the gas inflow passage side and the opening end on the gas outflow passage side. More preferably, the structure is the same.

  Further, the material of the filter base of such a filter is not particularly limited, but for example, a porous ceramic filter material such as cordierite, silicon carbide, mullite, alumina, aluminum titanate, silicon carbide, silicon nitride is preferably used. Can be used. Among these, cordierite and silicon carbide are more preferable from the viewpoint of strength and cost.

  Further, the thickness of the partition wall of such a filter base is not particularly limited, but for example, the thickness of the partition wall is preferably 100 to 400 μm, and more preferably 200 to 300 μm. When the thickness of the partition wall is less than the lower limit, the strength of the filter tends to decrease. On the other hand, when the thickness of the partition wall exceeds the upper limit, pressure loss when exhaust gas or the like passes increases. There is a tendency. Further, the pore diameter (pore diameter) and the porosity (porosity) of the filter base are appropriately set within a range where the partition functions as a filtering material for filtering particulate matter (PM) in the exhaust gas. . For example, the average pore diameter (pore diameter) of the partition walls is preferably 5 to 60 μm, and more preferably 15 to 40 μm. When the average pore diameter (pore diameter) is less than the lower limit, the pressure loss due to the partition walls tends to increase. On the other hand, when the upper limit is exceeded, the strength of the partition walls tends to be insufficient. The collection efficiency tends to decrease. Further, the porosity (porosity) of the filter substrate is preferably 40 to 80%, and more preferably 50 to 75%. If such a porosity (porosity) is less than the lower limit, the pore (pore) surface area is insufficient, and the exhaust gas purification performance and PM supplementation performance tend to decrease. The strength tends to decrease and become insufficient.

  FIG. 1 is a schematic longitudinal sectional view schematically showing a part of a longitudinal section of a preferred embodiment of the exhaust gas purifying catalyst of the present invention. FIG. 2 is a schematic longitudinal sectional view schematically showing a longitudinal section of a part of the filter base material in a preferred embodiment of the exhaust gas purifying catalyst of the present invention.

  As shown in FIGS. 1 and 2, the exhaust gas-purifying catalyst 1 is disposed in an exhaust gas flow path containing NOx and particulate matter, and an inflow surface 11 on the side into which the exhaust gas flows and a purified gas are discharged. The exhaust gas purifying catalyst 1 has a discharge surface 12 on the side, and includes a filter base 2, a first catalyst layer 3, a second catalyst layer 4, a third catalyst layer 5, and a fourth catalyst. Layer 6. The filter base 2 has a gas inflow passage 13 having one end opened on the inflow surface 11 and the other end sealed on the discharge surface side, and one end opened on the discharge surface 12 and the other end on the inflow surface. The gas outflow passage 14 sealed by the sealing portion 22 on the side is defined by the porous partition wall 21 and arranged side by side, and the exhaust gas flowing into the gas inflow passage 13 passes through the partition wall 21. This is a wall-through filter that is discharged from the gas outflow passage 14. The gas inflow passage 13 and the gas outflow passage 14 have a honeycomb structure formed so as to be substantially parallel to each other (the cross-sectional shape in a direction perpendicular to the axial direction of the gas passage is a polygonal shape such as a square or a hexagon). Yes. Further, as shown in FIG. 1, the exhaust gas containing particulate matter (PM) flowing in from the inflow surface 11 side (upstream side) of the filter base 2 passes through the gas inflow passage 13 from the inflow surface 11 side to the discharge surface side ( Passes through the porous partition wall 21 of the filter base 2 in the process of flowing toward the sealing end side and the downstream side. At this time, the particulate matter (PM) contained in the exhaust gas cannot pass through the porous partition wall 21, The particulate matter (PM) was removed by adhering to or collecting on the exposed surface of the porous partition wall 21 in contact with the gas inflow passage 13 and / or the surface in the pores inside the porous partition wall 21. The exhaust gas flows in the gas outflow passage 14 from the inflow surface side (sealing end side) to the discharge surface 12 and is discharged out of the filter base 2.

  Further, as shown in FIG. 2, the surface of the porous partition wall 21 of the gas inflow passage 13 and the gas outflow passage 14 (the surface in contact with the gas inflow passage or the gas outflow passage) has a partition wall on the opening end side of the gas inflow passage. Surface (first partition wall surface) A, surface of the partition wall on the sealing end side of the gas inflow passage (second partition wall surface) B, surface of the partition wall on the sealing end side of the gas outflow passage (third partition wall surface) C and a partition wall surface (fourth partition wall surface) D on the opening end side of the gas outflow passage are formed.

  The length of the first partition wall surface A and the second partition wall surface B (the length in the exhaust gas flow direction, that is, the length in the direction parallel to the gas inflow passage) and the depth (the exhaust gas flow direction). The length in the vertical direction (that is, the length in the direction perpendicular to the gas inflow passage) is not particularly limited, but the length of the surface of the partition wall of the gas inflow passage is L1, and the length of the first partition wall surface A is LA may be any of LA> LB, LA = LB, LA <LB when the length of the surface of the second partition wall B is LB, and the first partition wall surface A and the second partition wall Even if the surface B is continuous, there may be a gap between them, or they may overlap slightly. Further, the length LA of the first partition wall surface A is preferably at least 15% of the region that can be LA: LB, and is preferably in the range of 20 to 80%. If the length LA of the first partition wall surface A is less than the lower limit, the NOx purification ability tends to be lowered, and if it exceeds the upper limit, the PM oxidation removal performance tends to be lowered.

  Further, the length (the length in the exhaust gas flow direction, that is, the length in the direction parallel to the gas outflow passage) and the depth (perpendicular to the exhaust gas flow direction) of the third partition wall surface C and the fourth partition wall surface D. The length of the first partition wall, that is, the length in the direction perpendicular to the gas outlet passage is not particularly limited, but the length of the partition wall surface of the gas outlet passage is L2, and the length of the third partition wall surface C is LC. When the length of the fourth partition wall surface D is LD, any of LC> LD, LC = LD, and LC <LD may be used. The third partition wall surface C and the fourth partition wall surface D may be continuous, there may be a gap between them, or they may overlap slightly. The length LC of the third partition wall surface C is preferably at least 5% of the region that can be LC: LD, and is preferably in the range of 10 to 90%. When the length LC of the third partition wall surface C is less than the lower limit, the effect of the third catalyst tends to be reduced. On the other hand, when the length LC exceeds the upper limit, the effect of the fourth catalyst tends to be reduced. is there.

(First catalyst layer)
In the exhaust gas purifying catalyst of the present invention, the first catalyst layer supported on the surface of the partition wall (first partition wall surface) on the opening end side of the gas inflow passage and made of a NO oxidation catalyst and / or a NOx purification catalyst is provided. I have. Such a first catalyst layer is not particularly limited except that it is a catalyst layer comprising a NO oxidation catalyst and / or a NOx purification catalyst, but such a first catalyst layer is formed on the surface of the first partition wall. It is preferable to form the exposed surface (the surface in contact with the gas inflow passage) and the surface in the pores inside the porous partition wall of the first partition wall surface. Further, the formation range of the first catalyst layer is preferably formed in the range of 70 to 100% of the first partition wall surface A, and more preferably in the range of 80 to 100%. . When the formation range of such a catalyst layer is less than the lower limit, the effect due to the addition of the first catalyst layer tends not to be obtained. In addition, it is preferable that the formation range of such a 1st catalyst layer is formed in the range of 20 to 80% of the porous partition wall surface of a gas inflow passage. Further, the depth of the first catalyst layer is not particularly limited, but is preferably within a range of 1/4 to 3/4 of the partition wall thickness, and more preferably 1/3 to 2/3. preferable. If the depth of the first catalyst layer is less than the lower limit, the effect due to the addition of the first catalyst layer tends not to be obtained. On the other hand, if the depth exceeds the upper limit, the third catalyst layer overlaps with the third catalyst layer. It tends to rise.

The NO oxidation catalyst in the first catalyst layer is not particularly limited as long as it is a NO oxidation catalyst capable of oxidizing NO (carbon monoxide) in the exhaust gas. For example, the porous oxide carrier, A NO oxidation catalyst that includes a noble metal supported on a carrier and can efficiently oxidize NO in exhaust gas to NO ₂ is preferably used. The metal oxide constituting such a porous oxide carrier is not particularly limited. For example, alumina, silica, titania, zirconia, ceria, ceria-alumina solid solution, ceria-titania solid solution, ceria-zirconia solid solution, zirconia -A titania solid solution, a silica-alumina solid solution, a zeolite, etc. can be mentioned. In addition, the porous oxide carrier can be used as a single oxide of a single metal oxide, a combination of two or more metal oxides, or a composite oxide. The amount of the porous oxide carrier is not particularly limited, but is preferably in the range of 10 to 100 g per liter (L) of the filter substrate. Examples of the noble metal include platinum (Pt), palladium (Pd), rhodium (Rh), iridium (Ir), and ruthenium (Ru). Among these, Pt is particularly preferable from the viewpoint of high NO oxidation activity. The amount of such noble metal supported is not particularly limited, but is preferably in the range of 0.5 to 5 g per liter (L) of the filter substrate. Furthermore, you may carry | support metals, such as V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Mo, Ag, In, on a porous oxide support | carrier.

  The NOx purification catalyst in the first catalyst layer is not particularly limited as long as it is a NOx purification catalyst capable of purifying NOx in the exhaust gas. For example, the NOx purification catalyst described later in the third catalyst layer is used. Can be used.

(Second catalyst layer)
In the exhaust gas purifying catalyst of the present invention, the second catalyst is supported on the surface of the partition wall (second partition wall surface) on the sealing end side of the gas inflow passage and is made of a particulate matter oxidation catalyst (PM oxidation catalyst). With layers. Such a second catalyst layer is not particularly limited except that it is a catalyst layer made of a particulate matter oxidation catalyst. However, such a second catalyst layer is an exposed surface (gas gas) of the second partition wall surface. It is preferable to form it on the surface in the pores inside the porous partition wall on the surface of the second partition wall and the surface in contact with the inflow passage. In addition, the formation range of the second catalyst layer is preferably formed in the range of 70 to 100% of the second partition wall surface B, and more preferably in the range of 80 to 100%. . If the formation range of such a catalyst layer is less than the lower limit, the effect of adding the second catalyst layer tends not to be obtained. In addition, it is preferable that the formation range of such a 2nd catalyst layer is formed in the range of 20 to 80% of the porous partition wall surface of a gas inflow passage. Further, the depth of the second catalyst layer is not particularly limited, but is preferably in the range of 1/4 to 3/4 of the partition wall thickness, more preferably 1/3 to 2/3. preferable. If the depth of the second catalyst layer is less than the lower limit, the effect of adding the second catalyst layer tends not to be obtained. On the other hand, if the depth exceeds the upper limit, the fourth catalyst layer overlaps with the fourth catalyst layer. It tends to rise. In addition, the second catalyst layer may be provided separately from the first catalyst layer (with a portion not supporting the catalyst layer), but continuously provided following the first catalyst layer. It is preferable. By doing so, more catalyst can be coated and the performance tends to be improved.

  The particulate matter oxidation catalyst (PM oxidation catalyst) in the second catalyst layer is not particularly limited as long as it is a catalyst that can oxidize particulate matter (PM), and for example, A PM oxidation catalyst capable of oxidizing (burning) and removing particulate matter collected by the filter from a relatively low temperature is preferable.

As such a PM oxidation catalyst, cerium oxide (CeO ₂ , ceria), zirconium oxide (ZrO ₂ , zirconia), aluminum oxide (Al ₂ O ₃ , alumina), or a composite oxidation composed of two or three of these. It is preferable to carry a noble metal such as platinum (Pt), palladium (Pd), rhodium (Rh) or silver (Ag) on the product. Furthermore, for example, alkali metals such as potassium (K), sodium (Na), lithium (Li), and cesium (Cs), alkaline earth metals such as barium (Ba), calcium (Ca), and strontium (Sr), lanthanum One or more of rare earth elements such as (La), yttrium (Y), and cerium (Ce), and transition metals such as iron (Fe) may be added.

As such a PM oxidation catalyst, an oxide or composite oxide containing cerium oxide (ceria) is supported with silver (Ag) as an active species, or a composite of Ag and CeO _2. More preferably. By supporting silver (Ag) as an active species, particulate matter (PM) tends to be combusted at a relatively low temperature, and by using an oxide or a composite oxide containing cerium oxide (ceria), By releasing active oxygen, the oxidation removal of PM is promoted, and the aggregation and volatilization of silver (Ag) can be suppressed, and the heat resistance of the PM oxidation catalyst tends to be improved. Also, by supporting silver (Ag) on an oxide or composite oxide containing cerium oxide (ceria), the burning rate of PM at the initial stage of regeneration can be increased, and the time required for filter regeneration can be shortened. is there. When a filter such as DPF is used for purification of exhaust gas containing NOx and particulate matter, the particulate matter (PM) contained in the exhaust gas is separated from the surface of the partition wall on the gas inflow passage side (particularly, the second Since it is easy to deposit on the partition wall surface, by supporting such a PM oxidation catalyst on the second partition surface, silver (Ag) as an active species can be arranged at the contact interface with PM. The contact property with PM can be improved, PM oxidation removal performance can be improved, and oxidation removal can be performed from a lower temperature. Further, such a PM oxidation catalyst can efficiently burn PM with a smaller amount of the PM oxidation catalyst, so that the amount of the PM oxidation catalyst can be reduced. Therefore, since the coating amount of the PM oxidation catalyst can be suppressed to the necessary minimum, the coating amount of the NOx purification catalyst and the like can be ensured, and high NOx purification performance can be obtained. Furthermore, PM accumulates in the vicinity of such a PM oxidation catalyst, and since the distance between the PM and the PM oxidation catalyst is close to each other, PM combustion efficiency is improved and complete oxidation proceeds. For example, it is known that when a regeneration process of PM deposited on DPF or the like not coated with a PM oxidation catalyst is performed, a large amount of CO is generated. By forming the catalyst layer, it is possible to oxidize CO generated by self-combustion of PM into CO ₂ and to lower the combustion temperature of PM. Further, in such a PM oxidation catalyst, rare earth elements other than cerium (Ce) such as lanthanum (La) and neodymium (Nd), zirconium (Zr), yttrium (Y), aluminum (Al), and silicon (Si) It is particularly preferred that the composition further contains at least one additive component selected from the group consisting of: By including such an additive component, the mobility of oxygen active species in the ceria fine particles of the PM oxidation catalyst can be increased and coarsening of the ceria particles can be more effectively prevented, and the oxidation removal of PM can be further promoted. The heat resistance of the PM oxidation catalyst tends to be further improved. Furthermore, the PM oxidation catalyst is more preferably a PM oxidation catalyst in which Ag and Pd are supported on ceria and zirconia.

  The amount of the PM oxidation catalyst supported in the second catalyst layer is not particularly limited, but is appropriately set according to the exhaust characteristics of the internal combustion engine or the like, the desired purification performance, and the like. L) is preferably in the range of 10 to 100 g.

(Third catalyst layer)
The exhaust gas purifying catalyst of the present invention includes a third catalyst layer which is supported on the surface of the partition wall (third partition wall surface) on the sealing end side of the gas outflow passage and is made of a NOx purification catalyst. Such a third catalyst layer is not particularly limited except that it is a catalyst layer made of a NOx purification catalyst, but such a third catalyst layer is an exposed surface (gas outflow passage) on the surface of the third partition wall. And a surface in the pores inside the porous partition wall on the surface of the third partition wall. In addition, the formation range of the third catalyst layer is preferably formed in the range of 70 to 100% of the third partition wall surface C, and more preferably in the range of 80 to 100%. . If the formation range of such a catalyst layer is less than the lower limit, the effect of adding the third catalyst layer tends not to be obtained. In addition, it is preferable that the formation range of such a 3rd catalyst layer is formed in the range of 20 to 80% of the porous partition wall surface of a gas outflow passage. Furthermore, the depth of the third catalyst layer is not particularly limited, but is preferably in the range of 1/4 to 3/4 of the partition wall thickness, more preferably 1/3 to 2/3. preferable. If the depth of the third catalyst layer is less than the lower limit, the effect due to the addition of the third catalyst layer tends not to be obtained. On the other hand, if the depth exceeds the upper limit, the first catalyst layer overlaps with the first catalyst layer. It tends to rise.

  The NOx purification catalyst in the third catalyst layer is not particularly limited as long as it is a catalyst capable of purifying NOx in the exhaust gas, and examples thereof include a NOx storage reduction catalyst and a NOx selective reduction catalyst. .

As such a NOx storage reduction catalyst (NSR catalyst: NOx Storage Reduction catalyst) in the third catalyst layer, NOx is occluded at a low temperature or when the air-fuel ratio is in a lean state, etc., and a rich spike at a high temperature or at regular intervals. when performing long catalyst which can purify NOx in the exhaust gas by reducing the NOx that is occluded in (exhaust gas when the fuel-rich) or the like N _2, is not particularly limited, for example, alumina (Al ₂ O ₃ ), zirconia (ZrO ₂ ), titania (TiO ₂ ) and other metal oxides, platinum (Pt), palladium (Pd), rhodium (Rh) and other precious metals as catalyst components, potassium (K), Sodium (Na), lithium (Li), alkali metals such as cesium (Cs), barium (Ba), calcium A NOx occlusion reduction catalyst on which an NOx occlusion component composed of at least one selected from the group consisting of alkaline earth metals such as (Ca) and rare earth elements such as lanthanum (La) and yttrium (Y) is supported. It is preferable. Further, the amount of the NOx storage reduction catalyst supported in the third catalyst layer is not particularly limited, but is appropriately set according to the exhaust characteristics of the engine, desired purification specifications, etc., for example, 1 liter (L ) Is preferably in the range of 10 to 100 g.

Further, the NOx selective reduction catalyst (SCR catalyst: Selective Catalytic Reduction catalysts) in the third catalyst layer is not particularly limited as long as it is a catalyst that can be purified by selectively reacting NOx with a reducing component. For example, (a) zeolite or alumina (Al ₂ O ₃ ), etc., at least one selected from the group consisting of copper, cobalt, nickel, iron, gallium, lanthanum, cerium, zinc, titanium, calcium, barium and silver And, if necessary, a NOx selective reduction catalyst in which at least one noble metal selected from the group consisting of platinum, iridium, palladium and rhodium is supported, (b) ceria (CeO ₂ ), titania (TiO ₂ ) the metal oxide ₂₎ an element selected from tungsten ( ), Molybdenum (Mo) and iron (Fe), at least one metal selected from the group consisting of oxides thereof, and, if necessary, copper (Cu), chromium (Cr), cobalt (Co) and manganese ( And a NOx selective reduction catalyst in which at least one metal selected from the group consisting of Mn) is supported.

The NOx selective reduction catalyst of the above (a) is preferably a NOx selective reduction catalyst in which copper (Cu) or iron (Fe) is supported on the zeolite, and a zeolite such as silica aluminophosphate zeolite. More preferred is a NOx selective reduction catalyst in which copper (Cu) is supported. Such a NOx selective reduction catalyst has high NOx purification activity and tends to exhibit sufficient NOx purification activity even in a high temperature range. Furthermore, it is preferable to contain at least one additive metal selected from the group consisting of nickel (Ni), cobalt (Co), tin (Sn), and titanium (Ti). The NOx selective reduction catalyst (b) is preferably a NOx selective reduction catalyst in which tungsten (W) or molybdenum (Mo) is supported on ceria (CeO ₂ ), and tungsten (W) or tungsten (W) is supported on ceria (CeO ₂ ). More preferred is a NOx selective reduction catalyst on which W) is supported. Such a NOx selective reduction catalyst has high NOx purification activity and high heat resistance, and tends to exhibit sufficient NOx purification activity even in a low temperature range.

  Further, the amount of the NOx selective reduction catalyst supported in the third catalyst layer is not particularly limited, but is appropriately set according to the exhaust characteristics of the internal combustion engine or the like, the desired purification performance, and the like. It is preferable that it is the range of 10-100g per (L).

(Fourth catalyst layer)
The exhaust gas purifying catalyst of the present invention includes a fourth catalyst layer which is supported on the surface of the partition wall (the fourth partition wall surface) on the opening end side of the gas outflow passage and is made of a NOx purification catalyst. Such a fourth catalyst layer is not particularly limited except that it is a catalyst layer made of a NOx purification catalyst, but such a fourth catalyst layer is an exposed surface (gas outflow passage) on the surface of the fourth partition wall. And a surface in the pores inside the porous partition wall on the surface of the fourth partition wall. In addition, the formation range of the fourth catalyst layer is preferably formed in a range of 70 to 100% of the fourth partition wall surface D, and more preferably in a range of 80 to 100%. . If the formation range of such a catalyst layer is less than the lower limit, the effect due to the addition of the fourth catalyst layer tends not to be obtained. In addition, it is preferable that the formation range of such a 4th catalyst layer is formed in the range of 20 to 80% of the porous partition wall surface of a gas outflow passage. When the same NOx purification catalyst as the third catalyst layer is used as the fourth catalyst layer, the formation range of the fourth catalyst layer and the third catalyst layer is 80 of the porous partition wall surface of the gas outflow passage. It is preferable to be formed in a range of ˜100%. Further, the depth of the fourth catalyst layer is not particularly limited, but is preferably within a range of 1/4 to 3/4 of the partition wall thickness, and more preferably 1/3 to 2/3. preferable. If the depth of the fourth catalyst layer is less than the lower limit, the effect due to the addition of the fourth catalyst layer tends not to be obtained. On the other hand, if the depth exceeds the upper limit, the second catalyst layer overlaps with the second catalyst layer. It tends to rise.
In addition, the fourth catalyst layer may be provided separately from the third catalyst layer (with a portion not supporting the catalyst layer), but provided continuously after the third catalyst layer. It is preferable. By doing so, more catalyst can be coated and the performance tends to be improved. Furthermore, the same NOx purification catalyst as the third catalyst layer may be used as the fourth catalyst layer, or a different one may be used.

  The NOx purification catalyst in the fourth catalyst layer is not particularly limited as long as it is a catalyst capable of purifying NOx in the exhaust gas, and examples thereof include a NOx storage reduction catalyst and a NOx selective reduction catalyst. . The NOx occlusion reduction catalyst and the NOx selective reduction catalyst in the fourth catalyst layer are not particularly limited. For example, the NOx purification catalyst described in the third catalyst layer can be used.

  Further, the amount of the NOx selective reduction catalyst supported in the fourth catalyst layer is not particularly limited, but is appropriately set according to the exhaust characteristics of the internal combustion engine or the like, the desired purification performance, and the like. It is preferable that it is the range of 10-100g per (L).

(Exhaust gas purification catalyst)
In the exhaust gas purification catalyst of the present invention, the particulate matter oxidation ability of the particulate matter oxidation catalyst is higher than the particulate matter oxidation ability of the NOx purification catalyst, and the NOx purification ability of the NOx purification catalyst is: It is preferable that it is higher than the NOx purification capacity of the particulate matter oxidation catalyst. As a result, it is possible to provide an exhaust gas purification catalyst that has a sufficiently high level of particulate matter purification performance and also has a sufficiently high level of NOx purification performance. In addition, when the particulate matter oxidation ability of the particulate matter oxidation catalyst in such an exhaust gas purification catalyst is lower than the particulate matter oxidation ability of the NOx purification catalyst, the combustion of PM is not promoted and deposited. The pressure loss tends to increase due to the PM. Further, when the NOx purification capacity of the NOx purification catalyst is lower than the NOx purification capacity of the particulate matter oxidation catalyst, NOx reduction does not proceed, and sufficient NOx purification capacity tends not to be obtained.

  Further, in the exhaust gas purifying catalyst of the present invention, the particulate matter oxidation catalyst is a particulate matter oxidation catalyst in which silver is supported on or complexed with cerium oxide, and the NO oxidation catalyst is platinum is aluminum oxide. It is preferable that the NO oxidation catalyst supported on the catalyst and the NOx purification catalyst be a NOx storage reduction catalyst and / or a NOx selective reduction catalyst. As a result, it is possible to provide an exhaust gas purification catalyst that has a sufficiently high level of particulate matter purification performance and also has a sufficiently high level of NOx purification performance.

  Furthermore, in the exhaust gas purifying catalyst of the present invention, the filter substrate preferably has a porosity (porosity) of 40 to 80%, preferably 50 to 75% in a state where the catalyst is supported. More preferred. If such a porosity (porosity) is less than the lower limit, the pore (pore) surface area is insufficient, and the exhaust gas purification performance and PM supplementation performance tend to decrease. The strength tends to decrease and become insufficient. Moreover, the average pore diameter (pore diameter) of the porous partition walls of the filter base is preferably 5 to 60 μm, more preferably 15 to 40 μm in a state where the catalyst is supported. When the average pore diameter (pore diameter) is less than the lower limit, the porous partition wall pressure loss tends to increase. On the other hand, when the upper limit is exceeded, the strength of the porous partition wall tends to be insufficient. , PM collection efficiency tends to decrease.

[Method for producing exhaust gas-purifying catalyst]
Next, a method for producing the gas purification catalyst of the present invention will be described. The method for producing an exhaust gas purifying catalyst of the present invention is arranged in a flow path of exhaust gas containing NOx and particulate matter, and includes an inflow surface on the exhaust gas inflow side and an exhaust surface on the exhaust gas exhaust side. A method for producing an exhaust gas purifying catalyst having
A gas inflow passage having one end opened on the inflow surface and the other end sealed on the discharge surface side, and a gas having one end opened on the discharge surface and the other end sealed on the inflow surface side An outflow passage is defined by a porous partition wall and arranged side by side, and a wall-through type filter substrate is prepared in which exhaust gas flowing into the gas inflow passage passes through the partition wall and is discharged from the gas outflow passage. A process (filter substrate preparation process),
A step of supporting a first catalyst slurry that is a precursor of a NO oxidation catalyst and / or a NOx purification catalyst on the surface of the partition wall (first partition wall surface) on the opening end side of the gas inflow passage (first catalyst slurry) Loading process),
A step of supporting the second catalyst slurry, which is a precursor of the particulate matter oxidation catalyst, on the surface of the partition wall (second partition wall surface) on the sealing end side of the gas inflow passage (second catalyst slurry support step). When,
A step of supporting a third catalyst slurry, which is a precursor of the NOx purification catalyst, on the surface of the partition wall (third partition wall surface) on the sealing end side of the gas outflow passage (third catalyst slurry support step);
A step (fourth catalyst slurry supporting step) of supporting a fourth catalyst slurry, which is a precursor of the NOx purification catalyst, on the surface of the partition wall (fourth partition surface) on the opening end side of the gas outflow passage;
And a step of obtaining the exhaust gas-purifying catalyst of the present invention by performing a heat treatment on the filter base on which the catalyst slurry is supported (a calcination step). By such a method, the exhaust gas purifying catalyst of the present invention having a sufficiently high particulate matter purification performance and a sufficiently high NOx purification performance can be produced.

(Filter substrate preparation process)
In the method for producing an exhaust gas purifying catalyst of the present invention, first, a gas inflow passage having one end opened on the inflow surface and the other end sealed on the discharge surface side, and one end opened on the discharge surface. And a gas outflow passage whose other end is sealed on the inflow surface side is formed by a porous partition wall, and the exhaust gas flowing into the gas inflow passage passes through the partition wall and passes through the partition wall. A wall-through type filter substrate discharged from the gas outflow passage is prepared (filter substrate preparation step).

  The filter base used in the filter base preparation step according to the manufacturing method of the present invention is not particularly limited. For example, a commercially available wall-through honeycomb-shaped ceramic filter can be used, and a known ceramic filter manufacturing method can be used. Can also be obtained as appropriate. In addition, the thing similar to what was demonstrated in the catalyst for exhaust gas purification | cleaning of the said invention can be used for such a filter base | substrate.

(First catalyst slurry supporting step, second catalyst slurry supporting step, third catalyst slurry supporting step, and fourth catalyst slurry supporting step)
Next, a first catalyst slurry which is a precursor of a NO oxidation catalyst and / or a NOx purification catalyst is applied to the surface of the partition wall (first partition wall surface) on the opening end side of the gas inflow passage on the prepared filter base. The second catalyst slurry, which is a precursor of the particulate matter oxidation catalyst, is supported on the surface of the partition wall (second partition wall surface) on the sealing end side of the gas inflow passage. Caging (second catalyst slurry supporting step), supporting a third catalyst slurry, which is a precursor of the NOx purification catalyst, on the surface of the partition wall (third partition wall surface) on the sealing end side of the gas outflow passage (first catalyst slurry supporting step). 3 catalyst slurry supporting step), a fourth catalyst slurry that is a precursor of the NOx purification catalyst is supported on the surface of the partition wall (the surface of the fourth partition wall) on the opening end side of the gas outflow passage (fourth catalyst slurry). Loading step). The order in which the catalyst slurry is supported is not particularly limited, but the types of the first catalyst layer, the second catalyst layer, the third catalyst layer, and the fourth catalyst layer to be formed, and the supporting method (means) ) And loading amount, etc., the loading order of the catalyst slurry is appropriately determined. In addition, after the first catalyst slurry supporting step, the second catalyst slurry supporting step, the third catalyst slurry supporting step, and the fourth catalyst slurry supporting step, the filter substrate coated with the catalyst slurry is dried. It is preferable. Moreover, it is preferable to repeat the above-described catalyst slurry carrying and drying operations until the amount of the coated catalyst slurry reaches a predetermined amount of catalyst. Furthermore, it does not specifically limit as a catalyst slurry used in such a catalyst slurry carrying | support process, For example, it can obtain by employ | adopting a well-known manufacturing method suitably.

  Further, the method for supporting the catalyst slurry on the partition walls of the filter base is not particularly limited. For example, a method in which the catalyst slurry is press-fitted by a press-fitting means, a method in which the catalyst slurry is dipped in the catalyst slurry and coated by suction (dipping method) And a wash coat method.

  As a method of supporting such a catalyst slurry, a method of press-fitting the catalyst slurry by press-fitting means is preferable. In particular, in the second catalyst slurry supporting step, as a method of supporting the catalyst slurry, which is a precursor of the particulate matter oxidation catalyst, on the surface of the partition wall (second partition surface) on the sealing end side of the gas inflow passage. It is particularly preferable to use a method in which such a catalyst slurry is press-fitted by press-fitting means.

  The method for press-fitting such a catalyst slurry by the press-fitting means is not particularly limited, and for example, a method for press-fitting the catalyst slurry using a catalyst component-containing liquid (catalyst slurry) press-fitting device using a syringe (press-fitting means). And a method of press-fitting the catalyst slurry using press-fitting means such as a liquid pump and a tube pump. Among these, it is particularly preferable that the catalyst slurry is press-fitted using a catalyst slurry press-fitting device using a syringe. By such a method, a desired amount of the catalyst slurry for forming the catalyst layer can be reliably coated on a desired portion (part) of the partition wall of the filter base. For example, a desired catalyst slurry for forming a second catalyst layer made of a particulate matter oxidation catalyst at a predetermined portion of the partition wall which becomes the surface of the partition wall (second partition wall surface) on the sealing end side of the gas inflow passage is desired. Can be reliably coated by the amount of.

  In addition, the method of dipping in the catalyst slurry and inhaling and coating is not particularly limited. For example, the filter substrate is immersed in the catalyst slurry (catalyst component-containing liquid) up to a predetermined position, and the surface of the partition wall by capillary action. In addition, a desired amount of catalyst slurry is applied (coated) at a predetermined location so that the catalyst slurry is sucked into the pores (pores). Specifically, first, one open end (outflow surface or inflow surface) of the filter base is covered with a resin film or the like so that air does not escape from the other open end (inflow surface or outflow surface). . Next, only a desired portion of the filter base in the catalyst slurry prepared in advance (for example, only the surface of the partition wall (first partition wall surface) on the opening end side of the gas inflow passage of the filter base, or the opening of the gas outflow passage) The surface of the partition wall on the end side (only the surface of the fourth partition wall) is immersed. At this time, the filter base is immersed in the slurry so that the axial direction of the filter base is parallel to the vertical direction. If necessary, the immersion treatment is performed while applying ultrasonic waves. After a predetermined time has elapsed, the filter substrate is pulled up to remove excess slurry and dried. Such an operation is repeated until a predetermined amount of catalyst slurry is supported. As a result, a dried catalyst slurry layer in which a predetermined amount of the catalyst slurry (dried material) is supported on a desired portion of the filter base is formed.

(Baking process)
Next, the filter base on which the catalyst slurry is supported is subjected to heat treatment to obtain the exhaust gas purifying catalyst of the present invention (firing step).

  In such a firing step, it is preferable to fire the filter substrate carrying the catalyst slurry for forming the catalyst layer at a temperature in the range of 200 to 700 ° C. If the calcination temperature is less than the lower limit, the catalyst component tends not to adhere strongly to the base material. On the other hand, if it exceeds the upper limit, the catalyst component tends to undergo alteration such as grain growth. In addition, it is more preferable that such a calcination temperature is a temperature within a range of 200 to 600 ° C. from the viewpoint of ensuring adhesion and working efficiency. Further, the firing (heating) time cannot be generally described because it varies depending on the firing temperature, but it is preferably 0.5 to 10 hours, and more preferably 1 to 5 hours. Furthermore, the atmosphere in such a firing step is not particularly limited, but is preferably in the air or in an inert atmosphere.

  As mentioned above, although suitable embodiment of the manufacturing method of the catalyst for exhaust gas purification of this invention was described, it is not limited to the said embodiment.

[Exhaust gas purification method]
Next, the exhaust gas purification method of the present invention will be described. The exhaust gas purifying method of the present invention uses the exhaust gas purifying catalyst of the present invention, and flows exhaust gas containing NOx and particulate matter from the gas inflow passage of the exhaust gas purifying catalyst and from the gas outflow passage. It is the method characterized by discharging | emitting.

  In such an exhaust gas purification method of the present invention, the method for causing the exhaust gas to flow into the exhaust gas purification catalyst is not particularly limited, and a known method can be adopted as appropriate, for example, gas discharged from an internal combustion engine. By disposing the exhaust gas purifying catalyst according to the present invention in the exhaust gas pipe through which the exhaust gas flows, the exhaust gas containing NOx and particulate matter discharged from the internal combustion engine flows into the gas inflow passage with respect to the exhaust gas purifying catalyst. A method of squeezing may be adopted.

  The exhaust gas purification catalyst of the present invention has a sufficiently high particulate matter purification performance and has a sufficiently high NOx purification performance. Therefore, in the exhaust gas purification catalyst of the present invention, For example, by contacting exhaust gas discharged from an internal combustion engine such as a diesel engine, sufficiently high particulate matter purification performance and sufficiently high NOx purification performance can be exhibited. From such a viewpoint, the exhaust gas purification method using the exhaust gas purification catalyst of the present invention is, for example, particulate matter in exhaust gas containing NOx and particulate matter that are discharged from an internal combustion engine such as a diesel engine. In addition, it can be suitably employed as a method for purifying NOx.

  EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to a following example.

(Preparation Example 1)
<Preparation of catalyst slurry as precursor of PM oxidation catalyst>
First, a nitrate solution in which 50.46 g of Ce (NO ₃ ) ₃ .6H ₂ O, 5.59 g of La (NO ₃ ) ₃ and 29.62 g of AgNO ₃ were dissolved in 120 mL of water ([charged Amount ratio (molar ratio)] Ce: Ag: La = 90: 135: 10) was prepared. Next, ammonia water was prepared by diluting 38.21 g of 25 mass% ammonia water in 100 g of water. Next, the nitrate solution was added to the ammonia water while stirring (reverse precipitation), and stirring was continued for 10 minutes. Then, the mixture was heated to 120 ° C. in the presence of water in a closed system at 2 atm. Then, an aggregation treatment for 2 hours was performed to prepare an aggregate precursor (La-added CeO ₂ -Ag precursor).

  Next, the precipitate (aggregate precursor) after the reverse precipitation and the aggregation treatment described above is recovered by centrifugation, and then water is added to the recovered aggregate to thereby prepare a precursor of the PM oxidation catalyst having a concentration of 15% by mass. The catalyst slurry which is a body was prepared. When the particle size distribution of such a slurry was measured, aggregates having an average particle size of 0.1 μm were stably dispersed.

(Preparation Example 2)
<Preparation of catalyst slurry as precursor of NOx purification catalyst (1)>
First, the zeolite powder (manufactured by Tosoh Corporation, “ZSM-5 powder”, Si / Al ratio 23, specific surface area 300 m ² / g) is put into an aqueous solution (containing 6% by mass of copper) in which copper acetate is dissolved. The mixture was stirred at 30 ° C. for 24 hours, and ion exchange with copper ions was performed. Thereafter, filtration, washing, and evaporation to dryness were performed, followed by firing for 1 hour at a temperature of 500 ° C. to prepare copper ion exchanged ZSM-5 (Cu / ZSM-5 catalyst powder).

  Next, 100 parts by weight of this Cu / ZSM-5 catalyst powder is put into 40 parts by weight of silica sol (silica 20% by weight) and 140 parts by weight of ion-exchanged water, and mixed and ground using an attritor (wet grinding). Thus, a catalyst slurry which is a precursor of the NOx purification catalyst (1) of Cu / ZSM-5 (9% by mass) and silica sol (1% by mass) was prepared. When the particle size distribution of such a slurry was measured, aggregates having an average particle size of 1.5 μm were stably dispersed.

(Preparation Example 3)
<Preparation of catalyst slurry as precursor of NO oxidation catalyst>
First, alumina powder (γ-Al ₂ O ₃ , manufactured by Grace, average particle size: 7.3 μm) is impregnated with a predetermined amount of dinitrodiammineplatinum nitric acid aqueous solution, evaporated and dried to a temperature condition of 500 ° C. Was then calcined for 3 hours to prepare a Pt-supported alumina powder. The amount of Pt supported was 1 g with respect to 100 g of the carrier powder. Next, 100 parts by weight of the obtained Pt-supported alumina powder, 400 parts by weight of 18% aluminum nitrate, and 50 parts by weight of ion-exchanged water were mixed to prepare a catalyst slurry that is a precursor of the NO oxidation catalyst. Incidentally, Pt / _Al 2 _{O 3} of the slurry was 20 wt%. Further, when the particle size distribution of such a slurry was measured, aggregates having an average particle size of 4.0 μm were stably dispersed.

(Preparation Example 4)
<Preparation of catalyst slurry as precursor of NOx purification catalyst (2)>
First, 15 g of CeO ₂ powder (specific surface area of 138 m ² / g) is suspended in 100 ml of ion-exchanged water, and a predetermined amount of ammonium metatungstate [(NH] is added so that the WO ₃ content is 12.6% by mass. ₄ ) ₆ (H ₂ W ₁₂ O ₄₀ )] was added, and the mixture was heated and stirred at a temperature of 90 ° C. to evaporate the water to obtain a solidified substance of tungsten-ceria (W / CeO ₂ ). The tungsten-carrying ceria was prepared by firing at 500 ° C. for 3 hours.

Next, 100 parts by weight of this tungsten-supported ceria is added to 383 parts by weight of ion-exchanged water and 67 parts by weight of ceria sol (ceria 15% by mass), and mixed and pulverized using an attritor (wet pulverization). A catalyst slurry, which is a precursor of the ceria (W / CeO ₂ , 20 mass%) NOx purification catalyst (2), was prepared. When the particle size distribution of such a slurry was measured, aggregates having an average particle size of 1.3 μm were stably dispersed.

(Preparation Example 5)
<Preparation of catalyst slurry as precursor of NOx purification catalyst (3)>
First, alumina powder (average secondary particle size: 8 μm, specific surface area: 200 m ² / g) in an aqueous solution (Pd concentration: 0.0175% by mass) in which 0.038 g of Pd (NO ₃ ) ₂ was dissolved in 100 g of water. After stirring for 1 hour, the powder was taken out and dried in the atmosphere at a temperature of 110 ° C. for 24 hours to obtain alumina powder (Pd / Al ₂ O ₃ powder) carrying palladium particles. It was. Next, the obtained Pd / Al ₂ O ₃ powder is placed in an atmosphere having a hydrogen concentration of 5% by volume (balance gas is nitrogen) and subjected to a hydrogenation treatment at 400 ° C. for 3 hours. An alumina powder in which hydrogen was dissolved in palladium particles was obtained. Subsequently, 0.070 g of Pt (NO ₂ ) ₂ (NH ₃ ) ₂ was directly added to 100 g of the obtained powder from the container maintained in an atmosphere having a hydrogen concentration of 5% by volume without being exposed to the atmosphere. The solution was poured into an aqueous solution (Pt concentration: 0.0425% by mass) dissolved in water and stirred for 1 hour, and then the powder was taken out and dried in air at a temperature of 110 ° C. for 24 hours. By performing a heat treatment for 3 hours at a temperature of 300 ° C., a powder (metal particle-supported powder) on which metal particles made of a solid solution of palladium and platinum were supported was obtained. Next, the obtained metal particle-supported powder was dissolved in an aqueous solution containing (CH ₃ COO) ₂ Ba, CH ₃ COOK, and CH ₃ COOLi (Ba concentration: 0.1 mol / L, K concentration: 0.1 mol / L, Li After soaking in a concentration of 0.2 mol / L), the powder is taken out and dried in the air at a temperature of 110 ° C. for 24 hours to evaporate to dryness. Further, in the air at a temperature of 300 ° C. for 3 hours The NOx purification catalyst powder was obtained by performing the heat treatment. The supported amount of metal particles composed of a solid solution of palladium and platinum in the obtained catalyst was 0.60 parts by mass with respect to 100 parts by mass of the alumina powder, and the composition ratio of palladium and platinum was (Pd) 3 atoms. %: (Pt) 4 atomic%. The supported amounts of Ba, K, and Li in the obtained catalyst were 0.1 mol / 100 g, 0.1 mol / 100 g, and 0.2 mol / 100 g, respectively, with respect to 100 parts by mass of the alumina powder.

Next, 100 parts by weight of this [(Ba, K, Li) / (Pt, Pd) / Al ₂ O ₃ ] NOx purification catalyst powder is added to 400 parts by weight of ion-exchanged water and 50 parts by weight of alumina sol (alumina 20% by mass). And mixed and pulverized using an attritor (wet pulverization), and a [(Ba, K, Li) / (Pt, Pd) / Al ₂ O ₃ ] (20 mass%) NOx purification catalyst (3 The catalyst slurry which is a precursor of) was prepared. When the particle size distribution of such a slurry was measured, aggregates having an average particle diameter of 3.5 μm were stably dispersed.

Example 1
First, DPF (made by cordierite, porosity 65%, average pore diameter 30 μm, diameter 30 mm × length 50 mm, partition wall thickness 0.2 mm) of test piece size (35 ml) is prepared as a filter substrate (base material). did.

  Next, a catalyst slurry that is a precursor of the NOx purification catalyst (1) prepared in Preparation Example 2 is used on the surface (A) of the partition wall on the opening end side of the gas inflow passage of the filter base material. 1 is a catalyst that is a precursor of the PM oxidation catalyst prepared in Preparation Example 1 on the surface of the partition wall (second partition wall surface) (B) on the sealing end side of the gas inflow passage of the filter substrate. A second catalyst layer made of a PM oxidation catalyst is formed using slurry, and the surface of the partition wall (third partition wall surface) (C) on the sealing end side of the gas outflow passage of the filter base and the opening of the gas outflow passage Using the catalyst slurry that is the precursor of the NOx purification catalyst (1) prepared in Preparation Example 2 on the surface (D) of the partition wall on the end side, the third catalyst layer and the fourth catalyst layer made of the NOx purification catalyst are formed. Thus, a catalyst sample for exhaust gas purification was obtained.

  That is, first, the filter substrate (base material) is immersed in ion-exchanged water, and the water absorption amount of the filter base material is measured by measuring the weight when excess water is blown off with an air gun and the weight when dried. Then, the water absorption amount of the substrate wall surface was calculated.

Next, the surface of the partition wall (second partition wall surface) on the sealing end side of the gas inflow passage 13 of the filter base material 2 from the syringe tip 72 by the slurry (catalyst component-containing liquid material) press-fitting device 70 using the syringe 71. A catalyst slurry ( La-added CeO ₂ -Ag-containing liquid material ) that is a precursor of the PM oxidation catalyst is press-fitted into (B), and the partition wall surface on the open end side of the gas inflow passage 13 (first partition wall surface) (A), the surface of the partition wall on the sealing end side of the gas outflow passage 14 (third partition wall surface) (C) and the surface of the partition wall on the opening end side of the gas outflow passage 14 (fourth partition surface) (D) A catalyst slurry ( Cu / ZSM-5-containing liquid material ) which is a precursor of the NOx purification catalyst (1) was sequentially injected into the catalyst, and a predetermined catalyst slurry was coated by controlling the coating amount by the method shown in FIG. FIG. 3 is a longitudinal sectional view schematically showing a catalyst slurry press-fitting means in the production of the exhaust gas purifying catalyst.

  Next, the filter base material 2 ′ coated with the catalyst slurry was dried in air at a temperature of 250 ° C. for 30 minutes.

  Next, by repeating the coating of the catalyst slurry and the drying of the filter base material 2 ′ coated with the catalyst slurry, the surface of the partition wall on the sealing end side of the gas inflow passage (second partition wall surface) (B) The coating amount of the catalyst slurry 4 ′ is 50 g / L of the supported catalyst amount (g) per volume (L) of the catalyst formation site, and the partition wall surface (first partition wall surface) (A ) Catalyst slurry 3 ', the surface of the partition wall on the sealing end side of the gas outflow passage (third partition wall surface) (C) the catalyst slurry 5' and the surface of the partition wall on the opening end side of the gas outflow passage (fourth) A filter base material 2 ′ in which the coating amount of the catalyst slurry 6 ′ on the partition wall surface (D) was 50 g / L in terms of the amount (g) of supported catalyst per volume (L) of the catalyst formation site was obtained.

  Subsequently, the filter base material 2 ′ coated with the catalyst slurry was fired in the atmosphere at a temperature condition of 500 ° C. for 1 hour to obtain an exhaust gas purification catalyst.

(Comparative Example 1)
PM oxidation catalyst using catalyst slurry, which is a precursor of the PM oxidation catalyst prepared in Preparation Example 1, on the surface of the partition wall (first partition wall surface) (A) on the opening end side of the gas inlet passage of the partition wall of the filter base material A catalyst for comparison was obtained by calcining after coating the catalyst slurry in the same manner as in Example 1 except that the catalyst layer was formed. The coating amount of the catalyst slurry on the first partition wall surface (A) was 50 g / L.

(Comparative Example 2)
It consists of PM oxidation catalyst using the catalyst slurry which is the precursor of PM oxidation catalyst prepared in Preparation Example 1 on the surface of the partition wall (fourth partition wall surface) (D) on the opening end side of the gas outflow passage of the filter base material A catalyst for comparison was obtained by calcining after coating the catalyst slurry in the same manner as in Example 1 except that the catalyst layer was formed. The coating amount of the catalyst slurry on the fourth partition wall surface (D) was 50 g / L.

[Evaluation of characteristics of catalysts obtained in Example 1 and Comparative Examples 1 and 2 ]
<Catalyst performance evaluation test>
Using the catalyst samples obtained in Example 1 and Comparative Examples 1 and 2 , activity evaluation by NOx selective reduction reaction using ammonia as a reducing agent was performed. That is, each catalyst sample was installed in an atmospheric pressure fixed bed flow type reactor (manufactured by Best Sokki Co., Ltd.). Next, 20 L of a model gas composed of NO (440 ppm), NH ₃ (550 ppm), O ₂ (10% by volume), CO ₂ (10% by volume), H ₂ O (10% by volume) and N ₂ (remainder) is added. The gas flow rate was adjusted to 400 ° C. with a gas flow rate of (liter) / min. Next, the catalyst-containing gas temperature is maintained at 400 ° C. for 10 minutes, and after pretreatment, the temperature is lowered, and the NOx concentration in the catalyst-containing gas and the catalyst exit gas at the input gas temperature of 250 ° C. to 400 ° C. is measured. The NOx purification rate (%) was calculated from the value. The obtained results are shown in FIG.

<Simulated PM adhesion treatment>
Next, using the catalyst samples obtained in Example 1 and Comparative Examples 1 and 2, simulated PM adhesion treatment was performed. That is, first, 0.03 g of carbon powder (trade name “Printex-U” manufactured by Degussa), which is a model particulate matter (PM), is mixed with 50 ml of special grade ethanol, and sufficiently dispersed using an ultrasonic cleaner. A PM dispersion was obtained. Next, with the upstream side of each catalyst sample coated with the catalyst facing upward, the PM dispersion liquid is poured into each catalyst sample, and then the PM dispersion liquid that has passed through is collected, and the PM dispersion liquid that has passed through is again poured from above Was repeated until the PM dispersion became almost transparent, and then dried to adhere the carbon powder to the catalyst sample (PM adhesion treatment). By the PM adhesion treatment, almost the entire amount of carbon powder in the PM dispersion was filtered to the catalyst sample (DPF), and the carbon adhesion amount in each catalyst sample was 0.8 g / L.

<PM regeneration test>
Next, a PM regeneration test for burning and removing PM was performed on each catalyst sample after the PM adhesion treatment. That is, first, each catalyst sample after the PM adhesion treatment was placed in an atmospheric pressure fixed bed flow type reactor (manufactured by Best Instrument Co., Ltd.). N ₂ (entered gas) is supplied to each catalyst sample after the PM adhesion treatment at 500 ° C. (entered gas temperature) for 15 minutes at a gas flow rate of 15 L / min, heated, and pretreated. While supplying _two gases, the inside of the exhaust pipe was naturally cooled to 200 ° C. Next, for each catalyst sample, the gas composition was changed to an oxidizing atmosphere gas composition (mixed gas, entering gas) composed of O ₂ (10% by volume), H ₂ O (10% by volume), and N ₂ (remainder), and gas temperature. Was supplied at a gas flow rate of 15 L / min while increasing the temperature from 200 ° C. to 720 ° C. at a rate of temperature increase of 20 ° C./min, and the CO desorption amount and CO ₂ desorption amount at 720 ° C. were measured. Then, from the CO desorption amount and the CO ₂ desorption amount thus measured, the ratio of the CO ₂ desorption amount to the sum of the CO desorption amount and the CO ₂ desorption amount [(CO ₂ desorption amount / (CO desorption amount + CO ₂ desorption amount)) × 100] (%) was determined, and this ratio was defined as the complete oxidation rate in the present invention. The obtained results are shown in FIG.

FIG. 4 is a graph showing the NOx purification rate and complete oxidation rate of the exhaust gas purification catalysts obtained in Example 1 and Comparative Examples 1-2 .

As is clear from the comparison between the results of Example 1 shown in FIG. 4 and the results of Comparative Examples 1 and 2 , the exhaust gas purifying catalyst of Example 1 is compatible with both high NOx purification rate and complete oxidation rate. Thus, it was confirmed that the catalyst for exhaust gas purification has sufficiently high particulate matter purification performance and sufficiently high NOx purification performance.

(Example 2)
Using the catalyst slurry which is the precursor of the NO oxidation catalyst prepared in Preparation Example 3 on the surface of the partition wall (first partition wall surface) (A) on the opening end side of the gas inflow passage of the filter base material, Pt / Al ₂ O Except that the NO oxidation catalyst layer (first catalyst layer) consisting of ₃ was formed, the catalyst slurry was coated and fired in the same manner as in Example 1 to obtain an exhaust gas purification catalyst. The coating amount of the catalyst slurry on the first partition wall surface (A) was an amount that would be 50 g / L in terms of the amount of supported catalyst (g) per volume (L) of the catalyst formation site.

(Comparative Example 4)
From the NO oxidation catalyst using the catalyst slurry that is the precursor of the NO oxidation catalyst prepared in Preparation Example 3 on the surface of the partition wall (second partition wall surface) (B) on the sealing end side of the gas inflow passage of the filter base material A catalyst for comparison was obtained by calcining after coating the catalyst slurry in the same manner as in Example 2 except that the catalyst layer was formed. The coating amount of the catalyst slurry on the second partition wall surface (B) was 50 g / L.

(Comparative Example 5)
Using the catalyst slurry which is the precursor of the NO oxidation catalyst prepared in Preparation Example 3 on the surface of the partition wall (first partition wall surface) (A) on the opening end side of the gas inflow passage of the filter base material, Pt / Al ₂ O _A NO oxidation catalyst layer (first catalyst layer) consisting of ₃ is formed and prepared in Preparation Example 1 on the surface of the partition wall (second partition wall surface) (B) on the sealing end side of the gas inflow passage of the filter base material. A second catalyst layer made of the PM oxidation catalyst is formed using the catalyst slurry that is the precursor of the PM oxidation catalyst, and the surface of the partition wall on the sealing end side of the gas outflow passage of the filter base (the surface of the third partition wall) ) Using (C) the catalyst slurry that is the precursor of the NO oxidation catalyst prepared in Preparation Example 3 to form a NO oxidation catalyst layer (third catalyst layer) made of Pt / Al ₂ O ₃ , and further filter Prepared in Preparation Example 1 on the surface (D) of the partition wall on the open end side of the gas outflow passage of the base material The catalyst slurry, which is a precursor of the PM oxidation catalyst, was used as the fourth catalyst layer made of the PM oxidation catalyst, except that the catalyst slurry was coated and calcined in the same manner as in Example 1 for comparison. A catalyst was obtained. The coating amount of the catalyst slurry on the first partition wall surface (A) is 50 g / L, the coating amount of the catalyst slurry on the second partition wall surface (B) is 50 g / L, and the catalyst on the third partition wall surface (C). The coating amount of the slurry was 50 g / L, and the coating amount of the catalyst slurry on the fourth partition wall surface (D) was 50 g / L.

[Evaluation of characteristics of catalysts obtained in Example 2 and Comparative Examples 4 to 5]
Using the catalyst samples obtained in Example 2 and Comparative Examples 4 to 5, a catalyst performance evaluation test, a simulated PM adhesion treatment, and a PM regeneration test were performed in the same manner as in Example 1. The obtained results are shown in FIG. FIG. 5 is a graph showing the NOx purification rate and complete oxidation rate of the exhaust gas purification catalysts obtained in Example 2 and Comparative Examples 4 to 5.

  As is clear from the comparison between the result of Example 2 shown in FIG. 5 and the results of Comparative Examples 4 to 5 and the result of Comparative Example 1 shown in FIG. 4, the exhaust gas-purifying catalyst of Example 2 is NOx. It was confirmed that the catalyst is an exhaust gas purification catalyst having both a high purification rate and a complete oxidation rate, a sufficiently high particulate matter purification performance, and a sufficiently high NOx purification performance.

(Example 3)
Using the catalyst slurry, which is the precursor of the NOx purification catalyst (2) prepared in Preparation Example 4, on the surface of the partition wall (first partition wall surface) (A) on the opening end side of the gas inflow passage of the filter base material, tungsten is supported. Except that the high heat-resistant NOx purification catalyst layer (first catalyst layer) made of ceria (W / CeO ₂ ) is formed, the catalyst slurry is coated and fired in the same manner as in Example 1 to obtain exhaust gas. A purification catalyst was obtained. The coating amount of the catalyst slurry on the first partition wall surface (A) was an amount that would be 50 g / L in terms of the amount of supported catalyst (g) per volume (L) of the catalyst formation site.

(Comparative Example 6)
NOx using the catalyst slurry which is the precursor of the NOx purification catalyst (1) prepared in Preparation Example 2 on the surface of the partition wall (second partition wall surface) (B) on the sealing end side of the gas inflow passage of the filter base material. A catalyst layer made of a purification catalyst is formed, and is a precursor of the NOx purification catalyst (2) prepared in Preparation Example 4 on the surface of the partition wall (third partition wall surface) (C) on the sealing end side of the gas outflow passage. A catalyst for comparison was obtained by coating the catalyst slurry and calcining in the same manner as in Example 3 except that a catalyst layer composed of a highly heat-resistant NOx purification catalyst was formed using the catalyst slurry. The coating amount of the catalyst slurry on the second partition wall surface (B) was 50 g / L, and the coating amount of the catalyst slurry on the third partition wall surface (C) was 50 g / L.

(Comparative Example 7)
Using the catalyst slurry which is the precursor of the NOx purification catalyst (2) prepared in Preparation Example 4 on the surface of the partition wall (second partition wall surface) (B) on the sealing end side of the gas inflow passage of the filter base material, A comparative catalyst was obtained by coating the catalyst slurry and calcining in the same manner as in Example 3 except that a catalyst layer composed of a heat-resistant NOx purification catalyst was formed. The coating amount of the catalyst slurry on the second partition wall surface (B) was 50 g / L.

[Evaluation of characteristics of catalysts obtained in Example 3 and Comparative Examples 6 to 7]
Using the catalyst samples obtained in Example 3 and Comparative Examples 6 to 7, a catalyst performance evaluation test, a simulated PM adhesion treatment, and a PM regeneration test were performed in the same manner as in Example 1. In the catalyst performance evaluation test, after performing an endurance test in which each catalyst sample was held at 750 ° C. for 5 hours in the atmosphere, a NOx concentration measurement test was performed in the same manner as in Example 1. The obtained result is shown in FIG. FIG. 6 is a graph showing the NOx purification rate and complete oxidation rate of the exhaust gas purification catalysts obtained in Example 3 and Comparative Examples 6-7.

  As is clear from the comparison between the results of Example 3 shown in FIG. 6 and the results of Comparative Examples 6-7, the exhaust gas purifying catalyst of Example 3 is compatible with both high NOx purification rate and complete oxidation rate. Thus, it was confirmed that the catalyst for exhaust gas purification has sufficiently high particulate matter purification performance and sufficiently high NOx purification performance.

Example 4
Surface of the partition wall on the opening end side of the gas inflow passage of the filter base material (first partition wall surface) (A), Surface of the partition wall on the sealing end side of the gas outflow passage of the partition wall of the filter base material (surface of the third partition wall) ) (C) and the catalyst slurry which is the precursor of the NOx purification catalyst (3) prepared in Preparation Example 5 on each of the partition wall surface (fourth partition wall surface) (D) on the opening end side of the gas outflow passage. [(Ba, K, Li) / (Pt, Pd) / Al ₂ O ₃ ] to form a first catalyst layer, a third catalyst layer, and a fourth catalyst layer made of NOx purification catalyst. Except for the above, a catalyst for exhaust gas purification was obtained in the same manner as in Example 1 by coating the catalyst slurry and then firing. The coating amount of the catalyst slurry on the first partition wall surface (A) of the filter base material, the third partition wall surface (C) and the fourth partition wall surface (D) of the filter base material is the volume of the catalyst formation site, respectively. The amount of the supported catalyst per (L) was 50 g / L.

(Comparative Example 8)
The surface of the partition wall (first partition wall surface) (A) on the opening end side of the gas inflow passage of the filter base material is composed of a PM oxidation catalyst using the catalyst slurry that is the precursor of the PM oxidation catalyst prepared in Preparation Example 1. A catalyst for comparison was obtained by calcining after coating the catalyst slurry in the same manner as in Example 4 except that the catalyst layer was formed. The coating amount of the catalyst slurry on the first partition wall surface (A) was 50 g / L.

(Comparative Example 9)
NOx using the catalyst slurry which is the precursor of the NOx purification catalyst (3) prepared in Preparation Example 5 on the surface of the partition wall (second partition wall surface) (B) on the sealing end side of the gas inflow passage of the filter base material A comparative catalyst was obtained by coating the catalyst slurry and calcining in the same manner as in Example 4 except that a catalyst layer composed of a purification catalyst was formed. The coating amount of the catalyst slurry on the second partition wall surface (B) was 50 g / L.

[Evaluation of characteristics of catalysts obtained in Example 4 and Comparative Examples 8 to 9]
Using the catalyst samples obtained in Example 4 and Comparative Examples 8 to 9, first, a catalyst performance evaluation test was performed by a NOx purification test. That is, 1.0 g of each catalyst sample is placed in a test container, and the rich gas and the lean gas having the composition shown in Table 1 are circulated under a temperature condition of 300 ° C. at intervals of lean / rich = 40 seconds / 5 seconds. The NOx purification rate in a steady state was measured. The NOx purification rate was determined on the basis of the value of the nitrogen oxide concentration obtained by measuring the concentration of nitrogen oxide (NOx) contained in the gas before and after contacting each catalyst sample in each catalyst sample. The obtained results are shown in FIG.

  Next, using the catalyst samples obtained in Example 4 and Comparative Examples 8 to 9, a simulated PM adhesion treatment and a PM regeneration test were performed in the same manner as in Example 1. The obtained results are shown in FIG. FIG. 7 is a graph showing the NOx purification rate and complete oxidation rate of the exhaust gas purification catalysts obtained in Example 4 and Comparative Examples 8-9.

  As is clear from the comparison between the results of Example 4 shown in FIG. 7 and the results of Comparative Examples 8 to 9, the exhaust gas purifying catalyst of Example 4 is compatible with both high NOx purification rate and complete oxidation rate. Thus, it was confirmed that the catalyst for exhaust gas purification has sufficiently high particulate matter purification performance and sufficiently high NOx purification performance.

  As described above, according to the present invention, it is possible to provide an exhaust gas purification catalyst having sufficiently high particulate matter purification performance and sufficiently high NOx purification performance.

  Therefore, the exhaust gas purifying catalyst of the present invention is particularly useful as an exhaust gas purifying catalyst for purifying particulate matter and NOx contained in exhaust gas from an internal combustion engine such as a diesel engine.

  1: exhaust gas purifying catalyst, 2: filter base, 3: first catalyst layer, 4: second catalyst layer, 5: third catalyst layer, 6: fourth catalyst layer, 11: inflow surface, 12 : Discharge surface, 13: gas inflow passage, 14: gas outflow passage, 21: porous partition wall, A: surface of the partition wall on the open end side of the gas inflow passage (first partition wall surface), B: sealing of the gas inflow passage Surface of the partition wall on the toe end side (second partition wall surface), C: Surface of the partition wall on the sealing end side of the gas outflow passage (third partition wall surface), D: Surface of the partition wall on the opening end side of the gas outflow passage (4th partition wall surface)

Claims (5)

An exhaust gas purifying catalyst which is disposed in a flow path of exhaust gas containing NOx and particulate matter, and has an inflow surface on the exhaust gas inflow side and an exhaust surface on the exhaust gas exhaust side,
A gas inflow passage having one end opened on the inflow surface and the other end sealed on the discharge surface side, and a gas having one end opened on the discharge surface and the other end sealed on the inflow surface side An outflow passage is defined by a porous partition wall, and a wall-through filter base body in which the exhaust gas flowing into the gas inflow passage passes through the partition wall and is discharged from the gas outflow passage;
Exhaust gas is present on the surface in contact with the gas inflow passage of the partition wall (first partition wall) on the opening end side of the gas inflow passage and on the surface in the pores (first partition wall surface) inside the first partition wall . A first catalyst layer supported so as to pass through one partition wall and comprising a NO oxidation catalyst and / or a NOx purification catalyst;
Exhaust gas is present on the surface of the partition wall (second partition wall) on the sealing end side of the gas inflow passage in contact with the gas inflow passage and on the surface in the pores inside the second partition wall (second partition surface). A second catalyst layer which is supported so as to pass through the second partition and is made of a particulate matter oxidation catalyst;
Exhaust gas is present on the surface of the partition wall (third partition wall) on the sealing end side of the gas outflow passage in contact with the gas outflow passage and on the surface in the pores (third partition wall surface) inside the third partition wall. A third catalyst layer which is supported so as to pass through the third partition wall and which consists of a NOx purification catalyst;
Exhaust gas is produced on the surface of the partition wall (fourth partition wall) on the opening end side of the gas outflow passage in contact with the gas outflow passage and on the surface in the pores in the fourth partition wall (surface of the fourth partition wall) . A fourth catalyst layer which is supported so as to pass through the four partition walls and is made of a NOx purification catalyst;
An exhaust gas purifying catalyst characterized by comprising: The particulate matter oxidation catalyst is a particulate matter oxidation catalyst in which silver is supported on or complexed with cerium oxide,
The NO oxidation catalyst is a NO oxidation catalyst in which platinum is supported on aluminum oxide, and
The NOx purification catalyst is a NOx storage reduction catalyst and / or a NOx selective reduction catalyst,
The exhaust gas-purifying catalyst according to claim 1 . A method for producing an exhaust gas purifying catalyst, which is disposed in a flow path of exhaust gas containing NOx and particulate matter, and has an inflow surface on the exhaust gas inflow side and an exhaust surface on the exhaust gas exhaust side. ,
A gas inflow passage having one end opened on the inflow surface and the other end sealed on the discharge surface side, and a gas having one end opened on the discharge surface and the other end sealed on the inflow surface side An outflow passage is defined by a porous partition wall and arranged side by side, and a wall-through type filter substrate is prepared in which exhaust gas flowing into the gas inflow passage passes through the partition wall and is discharged from the gas outflow passage. And a process of
NO oxidation catalyst is formed on the surface of the partition wall (first partition wall) on the opening end side of the gas inflow passage in contact with the gas inflow passage and on the surface in the pores (first partition wall surface) inside the first partition wall. And / or supporting the first catalyst slurry, which is a precursor of the NOx purification catalyst, so that the exhaust gas passes through the first partition wall ;
The surface of the partition wall (second partition wall) on the sealing end side of the gas inflow passage in contact with the gas inflow passage and the surface inside the pores (second partition wall surface) inside the second partition wall are in the form of particles. Supporting a second catalyst slurry, which is a precursor of the material oxidation catalyst, so that the exhaust gas passes through the second partition wall ;
NOx purification is performed on the surface in contact with the gas outflow passage of the partition wall (third partition wall) on the sealing end side of the gas outflow passage and on the surface in the pores (third partition wall surface) inside the third partition wall. Supporting a third catalyst slurry, which is a catalyst precursor, so that exhaust gas passes through the third partition ;
A NOx purification catalyst is formed on the surface of the partition wall (fourth partition wall) on the opening end side of the gas outflow passage in contact with the gas outflow passage and on the surface in the pores (fourth partition wall surface) inside the fourth partition wall. Supporting a fourth catalyst slurry that is a precursor of the exhaust gas so that the exhaust gas passes through the fourth partition wall ;
A step of obtaining a catalyst for exhaust gas purification according to claim 1 or 2 by subjecting the filter substrate carrying the catalyst slurry to a heat treatment,
A method for producing an exhaust gas purifying catalyst, comprising: 4. The exhaust gas purifying catalyst according to claim 3, wherein the first to fourth catalyst slurries are respectively supported on the first to fourth partition walls using a catalyst slurry press-fitting device using a syringe. 5. Manufacturing method. The exhaust gas purification catalyst according to claim 1 or 2 , wherein exhaust gas containing NOx and particulate matter flows in from the gas inflow passage of the exhaust gas purification catalyst and exhausts the purification gas from the gas outflow passage. An exhaust gas purification method characterized by the above.