EXHAUST PURIFICATION DEVICE

Abstract

comprising exhaust gas purification device (1): a honeycomb substrate (10); and a catalyst layer on the inflow cell side (20), wherein the honeycomb substrate (10) includes a porous partition (14) defining a plurality of cells (12) extending from an inflow-side end surface (10Sa) to an outflow-side end surface (10Sb), wherein the majority of cells (12) include an inlet cell (12A) and an outlet cell (12B) which are adjacent to each other and between which the partition (14) is arranged, wherein the inlet cell (12A) has an open, inlet-side end (12Aa) and a closed, outlet-side end (12Ab), wherein the outflow cell (12B) has a closed, inflow-side end (12Ba) and an open, outflow-side end (12Bb), wherein the inlet cell-side catalyst layer (20) is arranged on a surface on the inlet cell side in an inlet-side region from the inlet-side end (12Aa) to a predetermined position (14m) on an outlet side of the partition, and where, if a gas permeability coefficient of an inlet-side partition section (14a) comprising the inlet-side area of ​​the partition (14Ra) and the inlet-cell-side catalyst layer (20) is Ka, and if a gas permeability coefficient of an outlet-side partition section (14Rb) comprising at least an outlet-side area from the predetermined position (14m) to the outlet-side end of the partition (14b) is Kb, then a Ka / Kb ratio of the gas permeability coefficients lies in a range of 0.4 or more and 0.8 or less, wherein the gas permeability coefficient Kb lies in a range of 2.0E-16 m 2 or more and 2.0E-13 m2 or less.

Description

BACKGROUND Technical area

[0001] The present invention relates to an exhaust gas purification device comprising a catalyst in a filter with a wall flow structure. Description of the state of the art

[0002] Exhaust gas emitted from a combustion engine, such as in a car, contains fine particulate matter (PM), which consists mainly of carbon, a cause of air pollution, ash as a non-combustible component, and similar materials. Filters with a wall-flow structure are widely used to capture and remove PM from the exhaust gas.

[0003] The wall-flow filter typically incorporates a honeycomb substrate. This substrate includes a porous partition that defines multiple cells extending from an inlet end face to an outlet end face. These multiple cells comprise inlet and outlet cells that are adjacent to each other, with the partition positioned between them. The inlet cell has an open inlet end and a closed outlet end, and the outlet cell has a closed inlet end and an open outlet end. The exhaust gas flowing into the inlet cells from the inlet ends passes through the partition and flows into the outlet cells, exiting from the outlet ends of the outlet cells. As the exhaust gas passes through the partition, the PMs (permanent particles) are trapped within its pores.Examples of filters with a wall flow structure include a diesel particulate filter (DPF) for diesel engines and a gasoline particulate filter (GPF, abbreviated as "GPF" in some cases below) for gasoline engines.

[0004] However, in addition to PM, the exhaust gas also contains harmful components such as carbon monoxide (CO), hydrocarbons (HC), and nitrogen oxides (NOx). These harmful components can be removed from the exhaust gas by a filter fitted with a catalyst, such as a precious metal catalyst. Therefore, to remove both PM and the harmful components from the exhaust gas, an exhaust gas purification device has recently been used that incorporates a catalyst within a filter featuring a wall-flow structure.

[0005] For example, an exhaust gas purification device containing a catalyst in a filter with a wall flow structure is known, comprising a first catalyst layer arranged on a surface of an inlet cell side of a partition wall in a length shorter than the total length of the partition wall along the extension direction of the partition wall from an inlet-side end of an exhaust gas, and a second catalyst layer arranged in at least a part of an area within the partition wall and opposite the outlet cells along the extension direction of the partition wall from an outlet-side end of the exhaust gas (Japanese Patent JP 6 386 697 B1).

[0006] Furthermore, the published patent applications US 2008 / 0241013A1 and WO 2019 / 188620A1 disclose exhaust gas purification devices from the prior art. SUMMARY

[0007] However, if, in the exhaust gas purification device described in Japanese patent JP 6 386 697 B1, the density of the first catalyst layer, which is arranged on the surface of the inlet cell side of the partition, is increased to improve purification performance, the exhaust gas flowing into the inlet cell from the inlet end will have an excessively reduced velocity to traverse an inlet-side partition section, including the partition and the first catalyst layer, and an excessively increased velocity to flow along the first catalyst layer of the partition. This makes it difficult to bring the exhaust gas into contact with the first catalyst layer in such a way as to clean the exhaust gas efficiently, and a pressure drop may be increased.On the other hand, if the density of the second catalyst layer, which is located at least in part of the area inside the partition and opposite the exhaust cell, is increased, the velocity at which the exhaust gas flows through the inlet-side partition section, including the partition and the first catalyst layer, is excessively increased, and the exhaust gas has an excessively reduced velocity for flowing along the first catalyst layer of the partition. Therefore, it can become difficult to bring the exhaust gas into contact with the first catalyst layer in such a way as to clean the exhaust gas efficiently.

[0008] The present invention was made with such points in mind, and the present invention provides an exhaust gas purification device that ensures improved cleaning performance and suppressed pressure loss.

[0009] To solve the aforementioned problem, an exhaust gas purification device according to the present invention comprises a honeycomb substrate and a catalyst layer on the inlet cell side. The honeycomb substrate includes a porous partition that defines a plurality of cells extending from an inlet-side end face to an outlet-side end face. The plurality of cells includes an inlet cell and an outlet cell arranged adjacent to one another, with the partition between them. The inlet cell has an open inlet-side end and a closed outlet-side end. The outlet cell has a closed inlet-side end and an open outlet-side end. The catalyst layer on the inlet cell side is arranged on a surface on the inlet cell side in an inlet-side region from the inlet-side end to a predetermined position on an outlet side of the partition.If a gas permeability coefficient of an inlet-side partition section including the inlet-side area of ​​the partition and the inlet-cell-side catalyst layer is Ka, and a gas permeability coefficient of an outlet-side partition section including at least an outlet-side area from the predetermined position to the outlet-side end of the partition is Kb, then a ratio Ka / Kb of the gas permeability coefficients lies in a range of 0.4 or more and 0.8 or less, wherein the gas permeability coefficient Kb lies in a range of 2.0E-16 m. 2 or more and 2.0E-13 m 2 or less. EFFECT

[0010] The present invention ensures improved cleaning performance and suppressed pressure loss. BRIEF DESCRIPTION OF THE DRAWING Fig.Figure 1 is a perspective view that schematically illustrates an exhaust gas purification device of a first example according to an embodiment; Fig. Figure 2 is a cross-sectional view that schematically illustrates a main component or main part of a cross-sectional area that runs parallel to the extension direction of a cell in the exhaust gas purification device of the first example according to the embodiment; Fig. Figure 3 is a cross-sectional view that schematically illustrates a main component of a cross-sectional area parallel to the extension direction of a cell in an exhaust gas purification device of a second example according to the embodiment; Fig.Figures 4A to 4C are cross-sectional views that schematically illustrate the respective main components of cross-sectional areas parallel to the extension directions of cells in exhaust gas purification devices manufactured in Example, Comparative Example 1 and Comparative Example 2; Fig. Figure 5 is a graph illustrating changes in the 20% NOx conversion temperature in relation to pressure losses in the exhaust gas purification devices of the example, comparison example 1 and comparison example 2; Fig. Figure 6 is a graph illustrating a change in a calculated pressure loss result relative to a Ka / Kb ratio of gas permeability coefficients; Fig. 7 are drawings accordingly Fig.2 of a reference document (R. Horn et al. / Journal of Catalysis 249 (2007) 380-393) and are graphs whose upper sections illustrate changes in the O2 conversion rate, the CH4 conversion rate and the discharge gas temperatures of the respective catalysts relative to a C / O ratio of a feed gas or supply gas, and whose lower section illustrates changes in the H2 selectivities, the CO selectivities, the CO2 selectivities and the H2O selectivities of the respective catalysts relative to the C / O ratio of the feed gas; and Fig. 8 is a drawing that Fig.This corresponds to section 3 of the reference document and includes graphs, the upper section on the left being a graph illustrating the flow velocities of CH4 and O2 and the bed temperatures at their respective positions in the flow direction of a feed gas from a reactor containing a rhizome-containing catalyst. The middle section on the left is a graph illustrating the flow velocities of H2 and CO at their respective positions in the flow direction of the feed gas from the reactor containing the rhizome-containing catalyst. The lower section on the left is a graph illustrating the flow velocities of H2O and CO2 at their respective positions in the flow direction of the feed gas from the reactor containing the rhizome-containing catalyst. Fig.Figure 8 contains further graphs. The upper section to the right shows a graph illustrating the flow velocities of CH4 and O2 and the bed temperatures at their respective positions in the feed gas flow direction of the reactor containing a Pt-containing catalyst. The middle section to the right shows a graph illustrating the flow velocities of H2 and CO at their respective positions in the feed gas flow direction of the reactor containing the Pt-containing catalyst. The lower section to the right shows a graph illustrating the flow velocities of H2O and CO2 at their respective positions in the feed gas flow direction of the reactor containing the Pt-containing catalyst. DETAILED DESCRIPTION OF THE EXECUTION FORMS

[0011] According to one embodiment of the present invention, an exhaust gas purification device is an exhaust gas purification device comprising a honeycomb substrate and an inlet-cell-side catalyst layer. The honeycomb substrate includes a porous partition that defines a plurality of cells extending from an inlet-side end face to an outlet-side end face. The plurality of cells comprises an inlet cell and an outlet cell that are adjacent to one another, and between which the partition is arranged. The inlet cell has an open inlet-side end and a closed outlet-side end. The outlet cell has a closed inlet-side end and an open outlet-side end.The inlet-side catalyst layer is arranged on a surface on the inlet-side of the partition in an inlet-side region extending from the inlet end to a predetermined position on an outlet side of the partition. If the gas permeability coefficient of an inlet-side partition section, including the inlet-side region of the partition and the inlet-side catalyst layer, is Ka, and if the gas permeability coefficient of an outlet-side partition section, including at least one outlet-side region from the predetermined position to the outlet-side end of the partition, is Kb, then the Ka / Kb ratio of the gas permeability coefficients lies in the range of 0.4 or more and 0.8 or less. Here, the "inlet side" means a side from which exhaust gas flows into the exhaust gas purification device, and the "outlet side" means a side from which the exhaust gas flows out of the exhaust gas purification device.

[0012] In this embodiment, while the extension direction of the partition is not particularly restricted, it is normally approximately the same as the axial direction of the honeycomb substrate, and while the extension direction of the cell is not particularly restricted, it is normally approximately the same as the extension direction of the partition. In the following description, "extension direction" means the extension directions of the partition and the cell, i.e., the direction in which the inlet and outlet sides face each other, and signifies the direction that is approximately equal to the axial direction of the honeycomb substrate. A first embodiment and a second embodiment are described below as embodiments. I. First embodiment

[0013] An exhaust gas purification device of a first embodiment includes an outflow cell-side catalyst layer in an inner region of the outflow cell side in the outflow-side region of the partition, and the outflow-side partition section includes the outflow-side region of the partition and the outflow cell-side catalyst layer.

[0014] The exhaust gas purification device according to the first embodiment is first outlined below using examples. Fig. 1 a perspective view which schematically illustrates the exhaust gas purification device of a first embodiment according to the embodiment. Fig. Figure 2 is a cross-sectional view that schematically illustrates a main component on a cross-sectional area parallel to the extension direction of the cell in the exhaust gas purification device of the first embodiment according to the embodiment.

[0015] As in Fig.1 and Fig.As illustrated in Figure 2, an exhaust gas purification device 1 of the first example comprises a honeycomb substrate 10, closure sections or sealing sections 16, inlet-cell-side catalyst layers 20, and outlet-cell-side catalyst layers 30. The honeycomb substrate 10 is a substrate in which a cylindrical frame section 11 and partitions 14, which divide a space within the frame section 11 into a honeycomb shape, are formed in one piece or integrated. The partitions 14 are porous bodies that define a plurality of cells 12 extending from an inlet-side end face 10Sa to an outlet-side end face 10Sb of the honeycomb substrate 10.The partition 14 comprises a plurality of wall sections 14L, which are separated from one another and arranged parallel to one another, such that cross-sectional areas perpendicular to the direction of extension of the plurality of cells 12 have square shapes, and a plurality of wall sections 14S, which are orthogonal to the plurality of wall sections 14L and separated from one another and arranged parallel to one another. A cross-sectional area of ​​the partition 14 perpendicular to the direction of extension has a grid shape.

[0016] The majority of cells 12 comprise inlet cells 12A and outlet cells 12B, which are adjacent to one another and between which the partition 14 is arranged. The inlet cell 12A has an open inlet-side end 12Aa and an outlet-side end 12Ab, which is closed by the closure section 16. The outlet cell 12B has an inlet-side end 12Ba, which is closed by the closure section 16, and an open outlet-side end 12Bb.

[0017] The inlet-cell-side catalyst layer 20 is arranged on a surface 14SA on the inlet-cell side in an inlet-side region 14Ra from an inlet-side end 14a to a predetermined position 14m on the outlet-side side of the partition 14. The inlet-cell-side catalyst layer 20 comprises catalyst metal particles (not illustrated) containing platinum (Pt) and a support (not illustrated) that carries them. The inlet-cell-side catalyst layer 20 has a content of a catalytic metal, etc., adjusted to achieve a required purification performance, and also has properties, etc., such as its density, thickness, mean particle diameter of the support and any cocatalyst, and porosity, adjusted such that the Ka / Kb ratio of the gas permeability coefficients described later falls within a range of 0.4 or more and 0.8 or less.

[0018] The outflow cell-side catalyst layer 30 is arranged in an inner region 14NB on the outflow cell side, in an outflow-side region 14Rb from the predetermined position 14m to an outflow-side end 14b of the partition 14, and in an overlapping region 14Rr that extends from the predetermined position 14m to the inflow side and overlaps the inflow-side region 14Ra. The outflow cell-side catalyst layer 30 comprises catalyst metal particles (not illustrated) containing rhodium (Rh) and a support (not illustrated) that carries them.The outflow cell-side catalyst layer 30 has a content of catalytic metal and the like, adjusted to achieve a required purification performance, and also has properties and the like, such as its density, thickness, mean grain diameter of the support and a cocatalyst, and porosity, adjusted such that the Ka / Kb ratio of the gas permeability coefficients described later is within a range of 0.4 or more and 0.8 or less.

[0019] If the gas permeability coefficient of the inlet-side partition section including the inlet-side area 14Ra of the partition 14 and the inlet-cell-side catalyst layer is 20 Ka and the gas permeability coefficient of the outlet-side partition section including the outlet-side area 14Rb of the partition 14 and the outlet-cell-side catalyst layer is 30 Kb, the Ka / Kb ratio of the gas permeability coefficients is in the range of 0.4 or more and 0.8 or less.

[0020] If, in order to improve the cleaning performance, the gas permeability coefficient Ka is reduced by increasing the density of the inlet-cell-side catalyst layer 20 to decrease the Ka / Kb ratio of the gas permeability coefficients to less than 0.4, the velocity of the exhaust gas flowing from the inlet-side end 14a to the inlet cell 12A as it passes through the inlet-side partition section is excessively reduced, while the velocity of the exhaust gas flowing along the inlet-cell-side catalyst layer 20 is excessively increased. This makes it difficult to bring the exhaust gas into contact with the inlet-cell-side catalyst layer 20 sufficiently for efficient cleaning, and the pressure drop is increased.Furthermore, the excessively increased velocity of the exhaust gas passing through the outflow-side partition section can make it difficult to bring the exhaust gas into contact with the outflow-cell-side catalyst layer 30 in such a way as to clean the exhaust gas efficiently. However, if the gas permeability coefficient Kb is reduced by increasing the density of the outflow-cell-side catalyst layer 30 to increase the Ka / Kb ratio of the gas permeability coefficients to more than 0.8, the velocity of the exhaust gas flowing from the inflow-side end 14a to the inflow cell 12A and passing through the inflow-side partition section will be excessively increased, even in a region where the gas permeability coefficient Ka does not exceed the gas permeability coefficient Kb, and the velocity of the exhaust gas flowing along the inflow-cell-side catalyst layer 20 will be excessively reduced.This leads to a difficulty in bringing the exhaust gas into contact with the inlet-cell-side catalyst layer 20 in such a way that the exhaust gas is efficiently cleaned. Furthermore, the excessively reduced velocity of the exhaust gas passing through the outlet-side partition section can increase the pressure drop and cause a difficulty in bringing the exhaust gas into contact with the outlet-cell-side catalyst layer 30 in such a way that the exhaust gas is efficiently cleaned.

[0021] In contrast, in the exhaust gas purification device 1 of the first example, the velocity of the exhaust gas flowing from the inlet-side end 14a into the inlet cell 12A and passing through the inlet-side partition section, the velocity of the exhaust gas flowing along the inlet-side catalyst layer 20, and the velocity of the exhaust gas passing through the outlet-side partition section are adjusted to be within a desired range by causing the Ka / Kb ratio of the gas permeability coefficients to fall within the range of 0.4 or more and 0.8 or less, thereby ensuring that the exhaust gas is brought into contact with the inlet-side catalyst layer 20 and the outlet-side catalyst layer 30 in such a way that the exhaust gas is efficiently purified and a suppressed pressure drop is ensured.

[0022] Therefore, in the exhaust gas purification device of the first embodiment, similar to the first example, improved cleaning performance and suppressed pressure loss are ensured by adjusting the flow of the exhaust gas in the exhaust gas purification device by causing the Ka / Kb ratio of the gas permeability coefficients to fall into the range of 0.4 or more and 0.8 or less.

[0023] Each configuration of the exhaust gas purification device of the first embodiment is described in detail below. 1. Ratio Ka / Kb of gas permeability coefficients

[0024] If the gas permeability coefficient of the inlet-side partition section including the inlet-side area of ​​the partition and the inlet-cell-side catalyst layer is Ka, and the gas permeability coefficient of the outlet-side partition section including the outlet-side area of ​​the partition and the outlet-cell-side catalyst layer is Kb, the ratio Ka / Kb of the gas permeability coefficients is in the range of 0.4 or more and 0.8 or less.

[0025] The “gas permeability coefficient” here means a Darcy permeability coefficient and refers to a coefficient that is calculated according to the following formula. K=QVT / AM (where K = gas permeability coefficient (m 2 ), Q = flow velocity of the gas (unit: m²) 3 / s), V = viscosity of the gas (unit: Pa·s), T = thickness of the partition section (unit: m), A = cross-sectional area perpendicular to the gas flow direction of the part through which the gas flows in the partition section (unit: m²) 2 ), M = differential pressure between the inlet side and the outlet side of the partition section when the gas passes through the partition section with the flow velocity Q (unit: Pa)).

[0026] While a method for measuring the gas permeability coefficient is not particularly restricted, examples of the method include, for instance, a method that measures the flow velocity of an air when a differential pressure between the inlet and outlet sides of the partition section becomes 10 kPa and calculates the coefficient from the formula using the measured flow velocity of the air when 25 °C air is passed at a flow velocity of 1 L / min to 200 L / min through a 10 mm square section (a part in the partition section that the gas passes through) of the partition section while the gas pressure is changed, for example, using a commercially available permeometer (for example, a permeometer manufactured by Porous Materials Inc. (PMI)).

[0027] The gas permeability coefficient Ka is a coefficient obtained from the flow velocity of the gas as it passes through the inlet-side partition section and the pressure differential between the gas inlet and outlet sides of the inlet-side partition section. The gas permeability coefficient Kb is a coefficient obtained from the flow velocity of the gas as it passes through the outlet-side partition section and the pressure differential between the gas inlet and outlet sides of the outlet-side partition section.

[0028] The Ka / Kb ratio of the gas permeability coefficients is not particularly restricted, as long as it lies within a range of 0.4 or more and 0.8 or less. In some embodiments, the Ka / Kb ratio lies within a range of 0.5 or more and 0.7 or less. The reason for this is that if the Ka / Kb ratio of the gas permeability coefficients is equal to or greater than the lower limit of these ranges, the excessively reduced velocity of the exhaust gas passing through the inlet-side partition section and the excessively increased velocity of the exhaust gas passing through the outlet-side partition section are suppressed, and the exhaust gas flow in the exhaust gas purification device can be effectively controlled.The reason for this is that if the Ka / Kb ratio of the gas permeability coefficients is equal to or less than the upper limit of these ranges, the excessively increased velocity of the exhaust gas passing through the inlet-side partition section and the excessively decreased velocity of the exhaust gas passing through the outlet-side partition section can be suppressed, and the flow of the exhaust gas in the exhaust gas cleaning device can be effectively controlled.

[0029] The gas permeability coefficient Ka is not particularly limited. For example, in some embodiments, the gas permeability coefficient Ka lies in the range of 1.0 x 10⁻¹⁶ m. 2 or more and 1.0E-13 m 2 or less, and the gas permeability coefficient Ka can in some embodiments be in a range of 1.0E-15 m 2 or more and 5.0E-14 m 2or less. The reason for this is that if the gas permeability coefficient Ka is equal to or greater than the lower limit of these ranges, the excessively reduced velocity of the exhaust gas passing through the inlet-side partition section can be suppressed. The reason for this is that if the gas permeability coefficient Ka is equal to or less than the upper limit of these ranges, the excessively increased velocity of the exhaust gas passing through the inlet-side partition section can be suppressed.

[0030] While a method for adjusting the gas permeability coefficient Ka is not particularly restricted and a common procedure can be used, examples of the method include, for example, a method that adjusts the gas permeability coefficient of the inflow-cell-side catalyst layer by producing properties and the like, such as density, thickness, mean grain diameters of the support and cocatalyst, and porosity of the inflow-cell-side catalyst layer; a method that arranges a layer that blocks the pores of the partition on a surface on the inflow-cell side in the inflow-side region of the partition; and a method that adjusts the gas permeability coefficient in the inflow-side region of the partition by preparing properties and the like, such as the porosity of the partition.

[0031] The gas permeability coefficient Kb lies in the range of 2.0E-16 m2 or more and 2.0E-13 m 2 or less, and the gas permeability coefficient Kb can in some embodiments be in a range of 2.0E-15 m 2 or more and 1.0E-13 m 2 or less. If the gas permeability coefficient Kb is equal to or greater than the lower limit of these ranges, the excessively reduced velocity of the exhaust gas passing through the outflow-side partition section can be suppressed. If the gas permeability coefficient Kb is equal to or less than the upper limit of these ranges, the excessively increased velocity of the exhaust gas passing through the outflow-side partition section can be suppressed.

[0032] While a method for adjusting the gas permeability coefficient Kb is not particularly restricted and a conventional method can be used, examples of the method include, for instance, a method that adjusts the gas permeability coefficient of the outflow cell-side catalyst layer by producing properties and the like, such as density, thickness, mean grain diameters of the support and cocatalyst, and porosity of the outflow cell-side catalyst layer, and a method that adjusts the gas permeability coefficient in the outflow-side region of the partition by producing properties and the like, such as porosity of the partition.

[0033] A length in the extension direction of the inlet-side partition section corresponds to a length in the extension direction of the inlet-side region of the partition, i.e., a length in the extension direction from the inlet-side end to the predetermined position on the outlet side of the partition, and a length in the extension direction of the inlet-cell-side catalyst layer. A length in the extension direction of the outlet-side partition section is a length obtained by subtracting the length in the extension direction of the inlet-side partition section from the total length in the extension direction of the partition. Note that the length in the extension direction of the outlet-side partition section corresponds to a length in the extension direction of the outlet-side region of the partition.

[0034] The length in the extension direction of the inlet-side partition section is not particularly limited. For example, in some embodiments, the length is in the range of 1 / 100 or more and 90 / 100 or less of the total length in the extension direction of the partition, and in some embodiments, the length may be in the range of 1 / 100 or more and 20 / 100 or less of the total length in the extension direction of the partition. The reason for this is that a length equal to or greater than the lower limit of these ranges ensures improved cleaning performance by providing a sufficiently long period of time for the exhaust gas to be in contact with the inlet-cell-side catalyst layer, even in situations where the exhaust gas flow velocity is high under a high-load operating condition.The reason for this is that a length equal to or less than the upper limit of these areas ensures that the pressure drop is effectively suppressed, and ensures a length exceeding an expected ash deposition thickness, rather than a length in the extension direction of an area where the inflow cell-side catalyst layer is not located in the partition. 2. catalyst layer on the inflow cell side

[0035] The inlet-cell-side catalyst layer is positioned on the surface of the inlet-cell side in the inlet-side region, extending from the inlet-side end to a predetermined position on the outlet side of the partition. This causes the inlet-cell-side catalyst layer to block the pores of the inlet-side region of the partition facing the inlet cell, resulting in a lower gas permeability coefficient for the inlet-side partition section, including the inlet-side region of the partition and the inlet-cell-side catalyst layer, than for the outlet-side partition section, including the outlet-side region of the partition and the outlet-cell-side catalyst layer.

[0036] Here, "the predetermined position on the outflow side of the partition" indicates a position that is closer to the outflow end than to the inflow end of the partition. Furthermore, "arranged on the surface on the inflow cell side in the inflow-side region from the inflow-side end to the predetermined position on the outflow side of the partition" indicates that it is arranged so that it is in contact with the surface on the inflow cell side in the inflow-side region of the partition outside the partition.

[0037] The length in the extension direction of the inflow-side area of ​​the partition, i.e., the length in the extension direction from the inflow-side end to the predetermined position of the partition, and the length in the extension direction of the inflow-cell-side catalyst layer correspond to the length in the extension direction of the inflow-side partition section.

[0038] The density of the catalyst layer on the inlet cell side is not particularly restricted, and a common density can be used. For example, in some embodiments the density is in the range of 30 g / L or more and 350 g / L or less, the density can be in the range of 50 g / L or more and 300 g / L or less, and in some embodiments it can also be in the range of 50 g / L or more and 250 g / L or less. This is because a density equal to or greater than the lower limit of this range facilitates the improvement of purification performance. Conversely, a density equal to or less than the upper limit of this range facilitates the suppression of pressure drop.It should be noted that “the density of the inflow-cell-side catalyst layer” indicates a value obtained by dividing a mass of the inflow-cell-side catalyst layer by a volume of a part in the axial direction of the honeycomb substrate that has the same length in the axial direction as the length in the extension direction of the inflow-cell-side catalyst layer.

[0039] The thickness of the inlet-side catalyst layer is not particularly restricted, and a conventional thickness can be used. For example, in some embodiments, the thickness is in a range of 5% or more and 100% or less of the partition thickness, and in some embodiments, the thickness can be in a range of 10% or more and 40% or less. This is because a thickness equal to or greater than the lower limit of this range makes it easier to suppress excessively increased exhaust gas velocity passing through the inlet-side partition section. Conversely, a thickness equal to or less than the upper limit of this range makes it easier to suppress excessively reduced exhaust gas velocity passing through the inlet-side partition section.

[0040] While the catalyst layer on the inflow cell side is not particularly restricted as long as it contains a catalytic metal, it typically comprises catalyst metal particles and a support that carries the catalyst metal particles. For example, the catalyst layer on the inflow cell side is a porous sintered body of a support containing the catalyst, which carries the catalyst metal particles.

[0041] While the material of the catalytic metal is not particularly restricted and a common material can be used, examples include a precious metal such as rhodium (Rh), palladium (Pd), and platinum (Pt). The catalytic metal material can be one metal, two or more metals, or an alloy containing two or more metals. In some embodiments, the catalytic metal material is at least one of Pt, Pd, and the like, and in some embodiments, the material can be Pt.

[0042] The mean grain diameter of the catalyst metal particles is not particularly restricted, and a common mean grain diameter can be used. For example, in some embodiments, the mean grain diameter lies in the range of 0.1 nm or more and 20 nm or less. This is because a mean grain diameter equal to or less than the upper limit of this range ensures that the contact area with the exhaust gas is increased. It should be noted that the mean grain diameter of the catalyst metal particle, for example, represents an average value obtained from a grain diameter measured using a transmission electron microscope (TEM).

[0043] The concentration of the catalytic metal per 1 L of substrate is not particularly limited, and a typical concentration can be used. The concentration varies depending on the specific catalytic metal. For example, if it is Pd, Pt, or Rh, the concentration in some embodiments ranges from 0.05 g or more to 5 g or less. A concentration equal to or greater than the lower limit of this range ensures sufficient catalytic activity, while a concentration equal to or less than the upper limit of this range suppresses grain growth of the catalytic metal, which also offers a cost advantage.Here, “the content of the catalytic metal per 1 L volume of the substrate” refers to a value obtained by dividing a mass of the catalytic metal containing the inflow-cell-side catalyst layer by a volume of a part in the axial direction of the honeycomb substrate that has the same length in the axial direction as the length in the extension direction of the inflow-cell-side catalyst layer.

[0044] The material of the support is not particularly restricted, and a conventional material can be used. Examples of the material include, for instance, a metallic oxide such as aluminum oxide (Al₂O₃), zirconium dioxide (ZrO₂), cerium oxide (CeO₂), silicon dioxide (SiO₂), magnesium oxide (MgO), and titanium dioxide (TiO₂), or, for instance, a solid solution thereof, such as a cerium oxide-zirconium dioxide (CeO₂-ZrO₂) compound oxide. The support material can be one, two, or more of these. In some embodiments, the support material is at least one of, for example, aluminum oxide, a cerium oxide-zirconium dioxide compound oxide, and the like. While the shape of the support is not particularly restricted, and a conventional shape can be used, in some embodiments it is in powder form. This is because a larger, specific surface area can be ensured.

[0045] The mean particle diameter of the powdered support is not particularly restricted. For example, the mean particle diameter may be in a range of 0.1 µm or more and 20 µm or less, and in some embodiments, the mean particle diameter may be in a range of 1 µm or more and 10 µm or less. A mean particle diameter equal to or greater than the lower limit of this range not only ensures sufficient heat resistance and suppresses the penetration of a slurry into the inner region of the partition when the slurry containing the powdered support is applied to the partition surface to form the inlet-side catalyst layer, but also facilitates the suppression of excessively reduced velocity of the exhaust gas flowing through the inlet-side partition section.The mean particle diameter, being equal to or less than the upper limit of this range, not only ensures improved cleaning performance by guaranteeing sufficient dispersibility of the catalyst metal particles, but also facilitates the suppression of excessively increased exhaust gas velocity as it passes through the inlet-side partition section. It should be noted that "the mean particle diameter of the powdered support" refers, for example, to the mean particle diameter obtained through a laser diffraction and scattering process.

[0046] The mass ratio of catalyst metal particles to the total mass of catalyst metal particles and support is not particularly restricted, and a conventional mass ratio can be used. For example, in some embodiments, the mass ratio lies in a range of 0.01 wt% or more and 10 wt% or less. This is because a mass ratio equal to or greater than the lower limit of this range ensures sufficient catalytic activity, while a mass ratio equal to or less than the upper limit of this range suppresses grain growth of the catalyst metal particles, while simultaneously offering cost advantages.

[0047] While a process that causes the support to carry the catalyst metal particles is not particularly restricted, and a conventional method can be used, examples of the process include, for instance, a process that dries and burns the support after immersion of the support in an aqueous solution containing a catalytic metal salt (such as nitrate) or a catalytic metal complex (such as tetraammine complex).

[0048] The catalyst layer on the inflow cell side can include, in addition to the catalyst metal particles and the support, a cocatalyst that does not support the catalyst metal particles. While the material of the cocatalyst is not particularly restricted and a conventional material may be used, examples include aluminum oxide, silicon dioxide, and cerium oxide-zirconium oxide composite oxide. While the shape of the cocatalyst is not particularly restricted and a conventional shape may be used, in some embodiments it is in powder form. The mass ratio of the cocatalyst to a total mass of the catalyst metal particles, the support, and the cocatalyst is not particularly restricted, and a conventional mass ratio may be used. For example, in some embodiments the mass ratio is in the range of 30 wt% or more and 80 wt% or less.The mean particle diameter of the cocatalyst in powder form is similar to the mean particle diameter of the support in powder form, therefore a description is omitted here.

[0049] While a method for forming the inflow-cell-side catalyst layer is not particularly restricted and a conventional method can be used, examples of the method include, for instance, a process that dries and burns a slurry after applying the slurry to the surface on the inflow-cell side in the inflow-side area of ​​the partition.

[0050] While the slurry is not particularly restricted as long as it contains a catalytic metal in addition to a solvent, it typically includes the catalyst metal particles and the support. While the solvent is not particularly restricted and a common solvent can be used, examples include water, such as ion-exchanged water, a water-soluble organic solvent, and a mixture of water and a water-soluble organic solvent. The slurry may further contain any necessary components, such as a cocatalyst, an oxygen absorption / emission material, a binder, and an additive.

[0051] The mean particle diameters and the like of the support and the cocatalyst in powder form contained in the slurry, and the properties and the like, such as the solids concentration and the viscosity, of the slurry can be adjusted in a suitable manner so that the slurry does not penetrate into the inner region of the partition and the gas permeability coefficient Ka of the inflow-side partition section falls into the desired range.

[0052] While the method of applying the slurry to the surface on the inlet cell side of the partition is not particularly restricted and a conventional method can be used, examples of the method include, for instance, a process that immerses the honeycomb substrate into the slurry from the inlet end face and removes it from the slurry after a predetermined period. In this method, the outflow cell can be pressurized from the outflow end face to create a pressure difference between the outflow cell and the inlet cell side, thus preventing the slurry from penetrating the inner area of ​​the partition.

[0053] In the process, which dries and fires the slurry after its application to the surface on the inlet cell side in the inlet-side region of the partition, the drying condition is not particularly restricted. The drying condition is influenced by the shape and dimensions of the honeycomb substrate or the support; for example, the drying condition is one in which drying is carried out at a temperature in the range of 80 °C or more and 300 °C or less for a period of one hour or more and ten hours or less in some embodiments. The firing condition is not particularly restricted.For example, the firing condition is a condition in which firing is carried out at a temperature in a range of 400 °C or more and 1000 °C or less for a period of time in a range of one hour or more and four hours or less in some embodiments.

[0054] It should be noted that the properties and the like, such as density, thickness and porosity of the inflow cell-side catalyst layer, can be produced by the amount of slurry applied, shape, mean particle diameter and content of each component, such as catalyst metal particles, support and cocatalyst, contained in the slurry, the properties of the slurry, the drying conditions, the firing conditions and the like. 3. catalyst layer on the outflow cell side

[0055] The catalyst layer on the outflow cell side is located in the inner area on the outflow cell side in the outflow-side area of ​​the partition.

[0056] Here, “arranged in the inner area on the outflow cell side in the outflow-side area of ​​the partition” means that it is arranged in an area opposite the outflow cells within the outflow-side area of ​​the partition.

[0057] While the outflow cell-side catalyst layer is not particularly restricted, as long as it is located, for example, in the inner region on the outflow cell side in the outflow-side region of the partition, it is normally located in the inner region on the outflow cell side in the outflow-side region of the partition and the overlapping region that extends from the predetermined position of the partition to the inflow side and overlaps the inflow-side region, as in the Fig.Figure 2 illustrated the catalyst layer on the outflow cell side. It can suppress the exhaust gas from passing through a part without a catalyst layer and thus being released.

[0058] The length in the extension direction of the outflow-side region of the partition, i.e., a length in the extension direction from the predetermined position to the outflow-side end of the partition, corresponds to the length in the extension direction of the outflow-side partition section. A length in the extension direction of the outflow-cell-side catalyst layer corresponds to the length in the extension direction of the outflow-side region if the outflow-cell-side catalyst layer is located only in the outflow-side region of the partition. However, if the outflow-cell-side catalyst layer is located in the outflow-side region of the partition and the overlapping region, the length in the extension direction of the outflow-cell-side catalyst layer corresponds to a total length in the extension direction of the outflow-side region of the partition and the overlapping region.

[0059] The length in the direction of extension of the overlapping portion of the partition is not particularly limited in this case. For example, in some embodiments, the length is in a range of 2 / 100 or more and 60 / 100 or less of the total length in the direction of extension of the partition; in some embodiments, the length may be in a range of 5 / 100 or more and 50 / 100 or less of the total length in the direction of extension of the partition; and in some embodiments, the length may also be in a range of 5 / 100 or more and 20 / 100 or less of the total length in the direction of extension of the partition. This is because lengths equal to or greater than the lower limit of these ranges ensure that the passage of exhaust gas through the portion without a catalyst layer is effectively suppressed.This is because lengths equal to or less than the upper limit of these areas reduce the effect of the reduced velocity of the exhaust gas passing through the overlapping area of ​​the partition, thus ensuring that the cleaning performance is reduced and the pressure drop is increased.

[0060] The density of the outflow cell-side catalyst layer is not particularly restricted, and a common density can be used. For example, in some embodiments, the density is in the range of 20 g / L or more and 300 g / L or less; the density can be in the range of 40 g / L or more and 250 g / L or less; and in some embodiments, the density can also be in the range of 60 g / L or more and 200 g / L or less. This is because a density equal to or greater than the lower limit of these ranges facilitates improved purification performance. Conversely, a density equal to or less than the upper limit of these ranges facilitates pressure drop suppression.It should be noted that "the density of the outflow cell-side catalyst layer" is a value obtained by dividing the mass of the outflow cell-side catalyst layer by the volume of a portion in the axial direction of the honeycomb substrate that has the same axial length as the length in the extension direction of the outflow cell-side catalyst layer. In some embodiments, the density of the outflow cell-side catalyst layer is lower than the density of the inflow cell-side catalyst layer. This is because the exhaust gas flows uniformly from the inflow cells to the outflow cells, which can facilitate improved cleaning performance and suppression of pressure drop.

[0061] The thickness of the exhaust-side catalyst layer is not particularly restricted, and a conventional thickness can be used. For example, in some embodiments, the thickness is in the range of 1% or more and 100% or less of the partition thickness, and in others, the thickness can be in the range of 1% or more and 20% or less. The reason for this is that a thickness equal to or greater than the lower limit of these ranges makes it easier to suppress excessively increased exhaust gas velocity as it passes through the exhaust-side partition section, in addition to ensuring a contact frequency between the exhaust gas and the catalyst as the exhaust gas passes through the exhaust-side partition section.Because the thickness, which is equal to or less than the upper limit of this area, makes it easier to suppress the excessively reduced velocity of the exhaust gas passing through the outflow-side partition section.

[0062] While the outflow cell-side catalyst layer is not particularly restricted as long as it contains the catalytic metal, it typically includes the catalyst metal particles and the support that carries the catalyst metal particles. For example, the outflow cell-side catalyst layer is configured such that the support carrying the catalyst metal particles is located within the pore in the inner region of the partition.

[0063] The catalytic metal material is similar to that of the catalytic metal included in the inlet-cell-side catalyst layer, except that in some embodiments rhodium (Rh) and the like are used, and therefore its description is omitted here. The mean grain diameter of the catalyst metal particles is similar to that of the catalytic metal particles included in the inlet-cell-side catalyst layer, and therefore its description is omitted here as well.

[0064] The concentration of the catalytic metal per liter of substrate is not particularly limited, and a typical concentration can be used. The concentration varies depending on the material of the catalytic metal and, in some embodiments, ranges from 0.01 g or more to 2 g or less if the material is Rh, Pd, or Pt. This is because a concentration equal to or greater than the lower limit of this range ensures sufficient catalytic activity, while a concentration equal to or less than the upper limit offers a cost advantage while simultaneously ensuring suppressed grain growth of the catalytic metal.Here, the content of the catalytic metal per 1 l volume of the substrate means a value obtained by dividing the mass of the catalytic metal contained in the outflow cell-side catalyst layer by a volume of a part in the axial direction of the honeycomb substrate that has the same length in the axial direction as the length in the extension direction of the outflow cell-side catalyst layer.

[0065] The material and shape of the support are similar to those of the support contained in the catalyst layer on the inflow cell side, and therefore the description is omitted here.

[0066] The mean particle diameter of the powdered carrier is not particularly restricted. For example, the mean particle diameter may be in the range of 0.01 µm or more and 5 µm or less, and in some embodiments, it may be in the range of 0.1 µm or more and 1 µm or less. A mean particle diameter equal to or greater than the lower limit of these ranges facilitates suppressing excessively reduced exhaust gas velocity as it passes through the outflow-side partition section and also ensures adequate heat resistance.The mean grain diameter, which is equal to or less than the upper limit of this range, makes it easier to suppress the excessively increased velocity of the exhaust gas passing through the outflow-side partition section, and also ensures that the slurry penetrates the inner area of ​​the partition when the slurry containing the carrier in powder form is fed to the inner area of ​​the partition to form the outflow-cell-side catalyst layer.

[0067] The mass ratio of the catalyst metal particles to the total mass of the catalyst metal particles and the support is similar to the mass ratio of the catalyst metal particles in the inflow-cell-side catalyst layer, and therefore its description is omitted here. A method for causing the support to carry the catalyst metal particles is similar to the method for causing the support to carry the catalyst metal particles in the inflow-cell-side catalyst layer, and therefore its description is omitted here. The outflow-cell-side catalyst layer may contain, in addition to the catalyst metal particles and the support, the cocatalyst, which does not carry the catalyst metal particles. The material, shape, and mass ratio of the cocatalyst are similar to those of the cocatalyst contained in the inflow-cell-side catalyst layer, and therefore its description is omitted here.The mean particle diameter of the cocatalyst in powder form is similar to the mean particle diameter of the support in powder form, and therefore the description is omitted here.

[0068] While a shaping process for the outflow cell-side catalyst layer is not particularly restricted and a conventional method can be used, examples of the process include, for instance, a process that dries and burns a slurry after the slurry has been introduced to the inner area on the outflow cell side in the outflow-side area of ​​the partition.

[0069] While the slurry is not particularly restricted as long as it contains the catalytic metal in addition to the solvent, it typically includes the catalyst metal particles and the support. A solvent similar to that used in the slurry for forming the inflow-cell-side catalyst layer is omitted here. The slurry may also contain any necessary components, such as a cocatalyst, an oxygen absorption / emission material, a binder, and an additive.

[0070] The properties and the like, such as the mean particle diameters of the support and the cocatalyst in powder form contained in the slurry, and a solids concentration, viscosity and the like of the slurry, can be adjusted in a suitable manner so that the slurry penetrates the inner region of the partition and the gas permeability coefficient Kb of the outflow-side partition section falls into the desired range.

[0071] While a method for supplying the slurry to the inner area of ​​the outflow cell side in the outflow-side area of ​​the partition is not particularly restricted and a conventional method can be used, examples of the method include, for example, a method in which a honeycomb substrate is immersed in the slurry from the outflow-side end surface and, after a predetermined period of time, the honeycomb substrate is removed from the slurry.

[0072] A drying condition and a firing condition in the process which dries and fires the slurry after the slurry has been fed to the inner area on the outflow cell side in the outflow side area of ​​the partition, are similar to the drying condition and the firing condition in the shaping process for the inflow cell side catalyst layer, and therefore the description is omitted here.

[0073] It should be noted that the properties and the like, such as density, thickness and porosity, of the outflow cell-side catalyst layer can be produced by a feed quantity of the slurry, a shape, a mean particle diameter and a content of each component, such as the catalyst metal particles, the support and the cocatalyst contained in the slurry, properties of the slurry, a drying condition, a firing condition and the like. 4. Honeycomb substrate

[0074] The honeycomb substrate features porous partitions that define a plurality of cells extending from the inlet end face to the outlet end face. The plurality of cells includes the inlet cells and the outlet cells, which are adjacent to one another and between which the partition is located. The inlet cell has an open inlet end and a closed outlet end, and the outlet cell has a closed inlet end and an open outlet end. The honeycomb substrate is a so-called wall-flow honeycomb substrate.

[0075] The honeycomb substrate is a substrate in which a frame-like section or a framing section and the partitions that divide the space within the frame-like section in a honeycomb shape are formed in one piece.

[0076] The axial length of the honeycomb substrate is not particularly limited, and a standard length can be used. For example, the length ranges from 10 mm or more to 500 mm or less in some embodiments, and from 50 mm or more to 300 mm or less in others. The capacity of the honeycomb substrate, i.e., the total volume of the cells, is not particularly limited, and a standard capacity can be used. For example, the capacity ranges from 0.1 l or more to 5 l or less in some embodiments.

[0077] While the material of the honeycomb substrate is not particularly restricted and a common material can be used, examples of the material include ceramics such as cordierite, silicon carbide (SiC) and aluminum titanate, alloys such as stainless steel, and the like.

[0078] While one shape of the frame-like section is not particularly restricted and a common shape can be used, examples of the shape include not only a cylindrical shape but also a tubular shape, such as an elliptical tube shape and a polygonal tube shape. Other configurations of the frame-like section are not particularly restricted, and common configurations can be used.

[0079] The shape of the partition is not particularly restricted, and a conventional shape can be used. The overall length of the partition in the extensional direction is not particularly restricted, but it generally corresponds approximately to the length of the honeycomb substrate in the axial direction. The thickness of the partition is not particularly restricted, and a conventional thickness can be used. For example, in some embodiments, the thickness ranges from 50 µm or more to 2000 µm or less, and in some embodiments, the thickness can range from 100 µm or more to 1000 µm or less. The thickness of the partition in these ranges ensures that sufficient PM trapping performance is maintained and that pressure drop is adequately suppressed, while ensuring the strength of the substrate.

[0080] The partition wall has a porous structure that allows exhaust gas to pass through. The porosity of the partition wall is not particularly restricted, and a typical porosity can be used. For example, in some embodiments, the porosity is in the range of 40% or more and 70% or less, and in others, it can be in the range of 50% or more and 70% or less. This is because a porosity equal to or greater than the lower limit of these ranges ensures effective pressure loss, and a porosity equal to or less than the upper limit of these ranges ensures sufficient mechanical strength. The mean pore diameter of the partition wall pores is not particularly restricted, and a typical mean pore diameter can be used.For example, in some embodiments the mean pore diameter is in the range of 1 µm or more and 60 µm or less, and in others the mean pore diameter can be in the range of 5 µm or more and 30 µm or less. The mean pore diameter of the pores in these ranges ensures that sufficient PM trap performance is maintained and pressure drop is adequately suppressed. It should be noted that "the mean pore diameter of the partition pores" refers, for example, to a measurement using the bubble point method with a permeability porometer.

[0081] The inlet and outlet cells are formed by the partitions that separate the space within the framing section or frame section, and are adjacent to one another, with the partitions positioned between them. The inlet and outlet cells typically have a direction perpendicular to the direction of extension enclosed by the partitions.

[0082] In the inlet cell, the outlet end is typically closed by a sealing section. Similarly, in the outlet cell, the inlet end is typically closed by a sealing section. The length of the sealing section is not particularly limited and can be a standard length. In some embodiments, for example, the length ranges from 2 mm or more to 20 mm or less. The material of the sealing section is not particularly limited and can be a standard material.

[0083] The cross-sectional shape perpendicular to the direction of extension of the inlet and outlet cells is not particularly restricted, and any conventional shape may be used, which can be suitably adjusted taking into account the flow velocity, elements, and the like of the exhaust gas flowing through the exhaust gas purification device. Examples of cross-sectional shapes include, for instance, a rectangular shape, such as a square shape, a polygonal shape, including a hexagonal shape, and a circular shape. The cross-sectional area perpendicular to the direction of extension of the inlet and outlet cells is not particularly restricted, and any conventional cross-sectional area may be used. For example, the cross-sectional area may be in the range of 1 mm². 2 or more and 7 mm 2or less. The length in the extension direction of the inlet and outlet cells is not particularly limited. The length is usually approximately the same as the length obtained by subtracting the length in the extension direction of the closure section from the length in the axial direction of the honeycomb substrate. Examples of an arrangement aspect of the inlet and outlet cells include, for example, an aspect such as a checkerboard pattern, in which the inlet and outlet cells are arranged alternately, as in the arrangement aspects in the first and second examples. 5. Exhaust gas purification device

[0084] The exhaust gas purification device of the first embodiment includes the honeycomb substrate, the catalyst layer on the inlet cell side, and the catalyst layer on the outlet cell side. The exhaust gas purification device typically also includes the sealing sections that close or seal the outlet end of the inlet cell and the inlet end of the outlet cell. The exhaust gas purification device of the embodiment can further improve the purification performance by also including the catalyst layer on the outlet cell side, compared to the second embodiment.

[0085] The exhaust gas purification device is not particularly restricted as long as it includes the honeycomb substrate, the inlet-cell-side catalyst layer, and the outlet-cell-side catalyst layer. The inlet-cell-side catalyst layer contains the catalytic metal, which includes at least one of platinum (Pt) and palladium (Pd), and the outlet-cell-side catalyst layer contains the catalytic metal, which in some embodiments includes rhodium (Rh). Since at least one of the Pt and Pd contained in the inlet-cell-side catalyst layer can efficiently oxidize hydrocarbons (HC) in the rich-atmosphere exhaust gas, the poisoning of the outlet-cell-side catalyst layer by HC can be suppressed, with Ce as a starting point.In addition to the fact that the oxidation of hydrocarbons (HC) by at least one of the elements Pt and Pd results in greater heat generation and a greater amount of H₂O production than in the case of oxidation with rhizome (Rh), since Rh exhibits a higher steam reforming activity than Pt and Pd, HC can be efficiently reformed with the exhaust gas-side catalyst layer. In some embodiments, the exhaust gas cleaning device can also be the inlet-side catalyst layer, which contains the catalytic metal containing Pt. This is because the cleaning performance can be further and effectively improved. II. Second embodiment

[0086] An exhaust gas purification device of the second embodiment does not include the catalyst layer in the inner area on the outflow cell side in the outflow-side area of ​​the partition, but rather the outflow-side partition section includes the outflow-side area of ​​the partition.

[0087] First, an example sketch of the exhaust gas purification device of the second embodiment is described.

[0088] This is Fig. 3 A cross-sectional view schematically illustrates a main component of a cross-sectional area parallel to the extension direction of the cells in the exhaust gas purification device of the second example according to the embodiment. It should be noted that the exhaust gas purification device in the second example is shown in perspective view in Fig. 1 is illustrated schematically, similar to the first example.

[0089] As in Fig. 1 and Fig.As illustrated in Figure 3, the exhaust gas purification device 1 of the second example includes the honeycomb substrate 10, the closure sections 16, and the inlet cell-side catalyst layers 20. The configurations of the honeycomb substrate 10 and the closure section 16 are similar to those of the first example.

[0090] The inlet-cell-side catalyst layer 20 is arranged on the surface 14SA on the inlet-cell side in the inlet-side region 14Ra from the inlet-side end 14a to the predetermined position 14m on the outlet side of the partition 14. The inlet-cell-side catalyst layer 20 comprises catalyst metal particles (not illustrated) with platinum (Pt) and a support (not illustrated) that carries them. The content of the inlet-cell-side catalyst layer 20 of catalytic metal and the like is adjusted to achieve the required purification performance, and its properties and the like, such as density, thickness, mean particle diameter of the support and the cocatalyst, and porosity, are adjusted such that the Ka / Kb ratio of the gas permeability coefficients described later falls within the range of 0.4 or more and 0.8 or less.The catalyst layer is missing in the inner area 14NB on the outflow cell side in the outflow-side area 14Rb from the predetermined position 14m to the outflow-side end 14b of the partition 14.

[0091] If the gas permeability coefficient of the inlet-side partition section including the inlet-side area 14Ra of the partition 14 and the inlet-cell-side catalyst layer 20 Ka is and the gas permeability coefficient of the outlet-side partition section including only the outlet-side area 14Rb of the partition 14 Kb is Kb, the Ka / Kb ratio of the gas permeability coefficients is in the range of 0.4 or more and 0.8 or less.

[0092] If the Ka / Kb ratio of the gas permeability coefficients is reduced to less than 0.4 by decreasing the gas permeability coefficient Ka through increasing the density of the inlet-cell-side catalyst layer 20 to improve cleaning performance, the velocity of the exhaust gas flowing from the inlet-side end 14a to the inlet cell 12A is excessively reduced as it passes through the inlet-side partition section, and the velocity of the exhaust gas flowing along the inlet-cell-side catalyst layer 20 is excessively increased. This makes it difficult to bring the exhaust gas into contact with the inlet-cell-side catalyst layer 20 in such a way as to clean the exhaust gas efficiently, and the pressure drop is increased.However, if the Ka / Kb ratio of the gas permeability coefficients is increased to more than 0.8 by increasing the gas permeability coefficient Ka through a decrease in the density of the inlet-cell-side catalyst layer 20, the velocity of the exhaust gas flowing from the inlet-side end 14a to the inlet cell 12A is excessively increased as it passes through the inlet-side partition section, and the velocity of the exhaust gas flowing along the inlet-cell-side catalyst layer 20 is excessively decreased. This, in turn, makes it difficult to bring the exhaust gas into contact with the inlet-cell-side catalyst layer 20 in such a way as to clean the exhaust gas efficiently.

[0093] In contrast, in the exhaust gas purification device 1 of the second example, the velocity of the exhaust gas flowing from the inlet-side end 14a to the inlet cell 12A as it passes through the inlet-side partition section and the velocity of the exhaust gas flowing along the inlet-cell-side catalyst layer 20 are set within desired ranges by adjusting the Ka / Kb ratio of the gas permeability coefficients to the range of 0.4 or more and 0.8 or less, thus ensuring that the exhaust gas is brought into contact with the inlet-cell-side catalyst layer 20 in such a way that the exhaust gas is efficiently purified and the pressure drop is suppressed.

[0094] Therefore, in the second embodiment of the exhaust gas purification device, the flow of the exhaust gas in the exhaust gas purification device is adjusted by ensuring that the Ka / Kb ratio of the gas permeability coefficients falls into the range of 0.4 or more and 0.8 or less, as in the second example, thereby ensuring improved purification performance and suppressed pressure loss.

[0095] Each configuration of the exhaust gas purification device of the second embodiment is described in detail below. 1. Ratio Ka / Kb of gas permeability coefficients

[0096] If the gas permeability coefficient of the inlet-side partition section including the inlet-side area of ​​the partition and the inlet-cell-side catalyst layer is Ka, and the gas permeability coefficient of the outlet-side partition section including the outlet-side area of ​​the partition is Kb, the ratio Ka / Kb of the gas permeability coefficients is in the range of 0.4 or more and 0.8 or less.

[0097] The definition of the term "gas permeability coefficient" and the method for measuring the gas permeability coefficient are similar to those in the first embodiment; therefore, the description is omitted here.

[0098] The gas permeability coefficient Ka is similar to that in the first embodiment. The gas permeability coefficient Kb is that obtained from the flow velocity of the gas and the differential pressure between the inlet and outlet sides of the outlet-side partition section when the gas passes through the outlet-side area of ​​the partition contained within the outlet-side partition section.

[0099] The Ka / Kb ratio of the gas permeability coefficients is similar to that of the first embodiment, therefore the description is omitted here.

[0100] The gas permeability coefficient Ka is not particularly limited. For example, in some embodiments, the gas permeability coefficient Ka has a similar range to the gas permeability coefficient Ka in the first embodiment. This is due to the similarity with the first embodiment. A method for adjusting the gas permeability coefficient Ka is similar to that of the first embodiment; therefore, its description is omitted here.

[0101] The gas permeability coefficient Kb is not particularly limited. For example, in some embodiments, the gas permeability coefficient Kb has a similar range to the gas permeability coefficient Kb in the first embodiment. This is due to the similarity with the first embodiment.

[0102] The length in the direction of extension of the inlet-side partition section is similar to that of the first embodiment; its description is omitted here. The length in the direction of extension of the outflow-side partition section is similar to that of the first embodiment; its description is omitted here. 2. Catalyst layer on the inflow cell side

[0103] The inlet-cell-side catalyst layer is positioned on the surface on the inlet-cell side in the inlet-side region, extending from the inlet-side end of the partition to the predetermined position on the outlet side of the partition. This causes the inlet-cell-side catalyst layer to block the pores opposite the inlet cells in the inlet-side region of the partition, and to reduce the gas permeability coefficient of the inlet-side partition section, which includes the inlet-side region of the partition and the inlet-cell-side catalyst layer, to a lower value than that of the outlet-side partition section, including the outlet-side region of the partition.

[0104] Here, the definitions of "the predetermined position on the outflow side of the partition" and "arranged on the surface on the inflow cell side in the inflow-side area from the inflow-side end to the predetermined position on the outflow side of the partition" are similar to those in the first embodiment, and therefore the descriptions are omitted here.

[0105] The density of the catalyst layer on the inlet cell side is not particularly restricted, and a conventional density can be used. For example, in some embodiments, the density has a similar range to the density of the catalyst layer on the inlet cell side in the first embodiment. This is due to the similar rationale as in the first embodiment.

[0106] The thickness of the catalyst layer on the inlet cell side is not particularly limited, and a conventional thickness can be used. In some embodiments, for example, the thickness is in a similar range to that of the catalyst layer on the inlet cell side in the first embodiment. This is due to the similar rationale as in the first embodiment.

[0107] While the catalyst layer on the inflow cell side is not particularly restricted as long as it contains the catalytic metal, it typically includes the catalyst metal particles and the support that carries the catalyst metal particles. The catalyst layer on the inflow cell side is, for example, a porous sintered body of the support containing the catalyst and carrying the catalyst metal particles.

[0108] The material of the catalytic metal and the average grain diameter of the catalyst metal particles are similar to those of the first embodiment; therefore, a description is omitted here. The content of the catalytic metal per 1 liter of the support volume is also similar to that of the first embodiment; therefore, a description is omitted here.

[0109] The material and shape of the carrier are similar to those of the first embodiment; therefore, their description is omitted here. The mean grain diameter of the carrier in powder form is also similar to that of the first embodiment; therefore, its description is omitted here as well.

[0110] A mass ratio of the catalyst metal particles to the total mass of the catalyst metal particles and the support, and a method to cause the support to carry the catalyst metal particles, are similar to those of the first embodiment, and therefore the description is omitted here.

[0111] The catalyst layer on the inflow cell side can contain, in addition to the catalyst metal particles and the support, a cocatalyst that does not support the catalyst metal particles. The cocatalyst is similar to that in the first embodiment; therefore, its description is omitted here.

[0112] A shaping method for the inlet-cell-side catalyst layer and a slurry application are similar to those in the first embodiment, and therefore their description is omitted here. It should be noted that a method for adjusting properties such as density, thickness, and porosity of the inlet-cell-side catalyst layer is similar to that of the first embodiment, which is why its description is omitted here. 3. Others

[0113] The exhaust gas purification device of the second embodiment includes the honeycomb substrate and the catalyst layer on the inlet cell side. The honeycomb substrate is similar to that of the first embodiment; therefore, a description of it is omitted here. The exhaust gas purification device typically also includes the closing sections that close or seal the outlet-side ends of the inlet cells and the inlet-side ends of the outlet cells. EXAMPLES

[0114] The exhaust gas purification device of the embodiment is described in more detail below with an example, a comparative example and a reference example. 1. Change in the 20% NOx conversion temperature as a function of pressure loss

[0115] For example 1, comparison example 1, and comparison example 2, corresponding exhaust gas purification devices were manufactured, and the changes in the 20% NOx conversion temperature as a function of pressure drop were evaluated for these exhaust gas purification devices. Here are Fig. 4A to Fig. 4C Cross-sectional views that schematically illustrate the respective main components of the cross-sectional areas parallel to the extension direction of the cells in the exhaust gas purification devices produced in the example, comparative example 1 and comparative example 2. [Example]

[0116] The in Fig.The exhaust gas purification device 1 illustrated in Figure 4A was manufactured. In the exhaust gas purification device 1, the inlet-side catalyst layer 20 is arranged on the inlet-side surface 14SA in the inlet-side region 14Ra from the inlet-side end 14a to the predetermined position 14m on the outlet side of the partition 14. The outlet-side catalyst layer 30 is arranged in the inner region 14NB on the outlet side in the outlet-side region 14Rb from the predetermined position 14m to the outlet-side end 14b of the partition 14 and the overlapping region 14Rr, which extends from the predetermined position 14m to the inlet side and overlaps the inlet-side region 14Ra.

[0117] The length in the extension direction of the inlet-side region 14Ra of the partition 14 is 40% of the length in the extension direction of the partition 14. The length in the extension direction of the outflow-side region 14Rb in the partition 14 is 60% of the length in the extension direction of the partition 14. The length in the extension direction of the overlapping region 14Rr of the partition 14 is 20% of the length in the extension direction of the partition 14.

[0118] The inlet-cell-side catalyst layer 20 comprises catalyst metal particles containing Pd and a powdered aluminum oxide support, which carries the catalyst metal particles and an OSC material. The density of the inlet-cell-side catalyst layer 20 is 49 g / L, the thickness of the inlet-cell-side catalyst layer 20 is 10% of the partition, and the Pd content is 0.6 g / L. The outlet-cell-side catalyst layer 30 comprises catalyst metal particles containing Rh and a powdered aluminum oxide support, which carries the catalyst metal particles and an OSC material. The density of the outlet-cell-side catalyst layer 30 is 100 g / L, and the Rh content is 0.3 g / L.

[0119] In the manufacture of the exhaust gas purification device 1, a GPF without a catalyst coating was initially produced. The GPF comprised the cordierite honeycomb substrate 10 and the closure section 16. The honeycomb substrate 10 is formed in one piece from a cylindrical, frame-like section (not illustrated) and the partitions 14, which divide the space within the frame-like section into a honeycomb pattern. The partitions 14 are porous bodies that define the plurality of cells 12, which extend from the inlet-side end face 10Sa of the honeycomb substrate 10 to the outlet-side end face 10Sb. The plurality of cells 12 comprise the inlet cells 12A and the outlet cells 12B, which are adjacent to one another, with the partitions 14 positioned between them.The inlet cell 12A has the open inlet-side end 12Aa and the outlet-side end 12Ab, which is closed by the closure section 16, and the outlet cell 12B has the inlet-side end 12Ba, which is closed by the closure section 16, and the open outlet-side end 12Bb. The size and structure of the honeycomb substrate 10 of the GPF and its length in the extension direction of the closure section 16 are as follows. (Configuration of the honeycomb substrate and the closure section of the GPF) Size of the honeycomb substrate: Outer diameter × Length in the axial direction = 117 mm × 122 mm Partition wall thickness: 200 µm Cell density: 300 per square inch Length in the extension direction of the locking section: 4 mm

[0120] Next, a slurry for the inlet-cell-side catalyst layer was prepared by mixing the support with the catalyst, the support carrying powdered catalyst metal particles with Pd and a solvent. The slurry for the inlet-cell-side catalyst layer was then dried and fired after being applied to surface 14SA on the inlet-cell side in the inlet-side region 14Ra of the partition 14. This formed the inlet-cell-side catalyst layer 20.

[0121] Next, a slurry for the exhaust-cell-side catalyst layer was prepared by mixing a support with a catalyst, the support containing powdered catalyst metal particles with rh and a solvent. The slurry for the exhaust-cell-side catalyst layer was then dried and fired after being fed to the inner region 14NB on the exhaust-cell side in the exhaust-side region 14Rb and the overlapping region 14Rr of the partition 14. This formed the exhaust-cell-side catalyst layer 30, thus completing the exhaust gas purification device 1. [Comparison example 1]

[0122] It was the in Fig.4B illustrated exhaust gas purification device 1 is manufactured. In the exhaust gas purification device 1, the inlet-cell-side catalyst layer 20 is arranged in an inner region 14NA on the inlet-cell side in the inlet-side region 14Ra of the partition 14. In this respect, the exhaust gas purification device 1 corresponds to the example except for a mean grain diameter of the powdered support contained in the inlet-cell-side catalyst layer 20 and a thickness of the inlet-cell-side catalyst layer 20.

[0123] A manufacturing process for the exhaust gas purification device 1 is the same as in the example, except that the inlet cell-side catalyst layer 20 is formed by drying and burning the slurry for the inlet cell-side catalyst layer after the slurry for the inlet cell-side catalyst layer has been supplied to the inner region 14NA on the inlet cell side in the inlet-side region 14Ra of the partition wall 14. [Comparative example 2]

[0124] The in Fig.The exhaust gas purification device 1 illustrated in Figure 4C was manufactured. In the exhaust gas purification device 1, a pretreatment layer 22 is arranged such that it blocks the pores of the partition on the surface 14SA on the inlet cell side 12A in the inlet-side region 14Ra of the partition 14. The inlet-cell-side catalyst layer 20 is arranged on a surface 22S of the pretreatment layer 22. Except for these points, the exhaust gas purification device 1 corresponds to the example.

[0125] In one manufacturing process of the exhaust gas purification device 1, the pretreatment layer 22 was formed by thinly applying a pretreatment slurry mixed with aluminum oxide (Al₂O₃) and a solvent, which did not contain any catalytic metal on the surface 14SA on the side of the inlet cell 12A in the inlet-side region 14Ra of the partition 14, before the inlet-side catalyst layer 20 was formed. Subsequently, the inlet-side catalyst layer 20 was formed by drying and burning the slurry for the outlet-side catalyst layer after the slurry for the outlet-side catalyst layer had been applied to the surface 22S of the pretreatment layer 22. The manufacturing process of the exhaust gas purification device 1 is the same as in the example, except for these points. [Evaluation]

[0126] After carrying out a durability test, the 20% NOx conversion temperatures and pressure losses were measured for the exhaust gas purification devices of the example, comparison example 1 and comparison example 2. <haltbarkeitstests>

[0127] The durability test was carried out by installing the exhaust gas purification devices into an exhaust system of a gasoline engine on the test bench and repeatedly passing exhaust gases with rich, stoichiometric and lean atmospheres alternately for specific periods over fifty hours at a catalyst bed temperature of 950 °C. <Messung der 20 % NOx-Umwandlungstemperatur>

[0128] While exhaust gas flowed at a velocity of 35 g / s in an atmosphere with an air-fuel ratio (A / F) of 14.4 to the exhaust aftertreatment devices installed in the exhaust system of the gasoline engine on the test bench, the inlet gas temperature was gradually increased from 200 °C to 600 °C using a heat exchanger installed in an upper stream of the exhaust aftertreatment device. The NOx concentrations of the inlet and outlet gases were measured at each inlet gas temperature to calculate the NOx conversion rates, and the inlet gas temperature at the time when 20% of the NOx had been converted was measured as the 20% NOx conversion temperature. <Messung des Druckverlustes>

[0129] A pressure difference between the inlet gas and the outlet gas, when the exhaust gas flowed at a flow velocity of 35 g / s to the exhaust gas cleaning device, which was installed in the exhaust system as described above, was measured as a pressure loss.

[0130] The measurement results for the 20% NOx conversion temperature and pressure loss are shown in Table 1 below. Fig. Figure 5 is a graph illustrating the changes in the 20% NOx conversion temperature relative to the pressure drop in the exhaust gas cleaning devices in Example 1, Comparative Example 1, and Comparative Example 2. As shown in Table 1 and Fig. As illustrated in Figure 5, the 20% NOx conversion temperature in Example 2 was reduced compared to Example 1. This is because the inlet-side catalyst layer 20 in Example 2 is located on surface 14SA on the inlet-side of the inlet-side area 14Ra of the partition 14, compared to the inlet-side catalyst layer 20 located in the inner area 14NA on the inlet-side of the partition 14 in Example 1. This reduces the velocity of the exhaust gas passing through the inlet-side partition section, ensuring that the exhaust gas comes into contact with the catalyst layer for efficient exhaust gas purification. In Example 2, compared to Example 1, the 20% NOx conversion temperature and pressure drop were increased.It is assumed that the fact that the pretreatment layer 22 is arranged in such a way that it blocks the pores of the partition on the surface 14SA on the inlet cell side in the inlet-side area 14Ra of the partition 14, in comparative example 2, excessively reduces the velocity of the exhaust gas passing through the inlet-side partition section, thus preventing the exhaust gas from coming into contact with the catalyst layer in such a way as to efficiently clean the exhaust gas, and preventing the pressure drop from being suppressed. [Table 1] Pressure loss (kPa) 20% NOx conversion temperature (°C) Example 3,72475 326 Comparative example 1 3,27095 333 Comparative example 2 4,6408 329 2. Change in pressure loss relative to the Ka / Kb ratio of the gas permeability coefficients

[0131] Using simulation software (axisuite (registered trademark), manufactured by Exothermia SA) for the analysis of exhaust gas cleaning devices, analytical models of the exhaust gas cleaning devices of Example, Comparison Example 1, and Comparison Example 2 were created, and changes in pressure drop relative to the Ka / Kb ratio of the gas permeability coefficients of the inlet-side partition section (gas permeability coefficient: Ka) and the outlet-side partition section (gas permeability coefficient: Kb) were obtained in the analytical models. Specifically, the analytical model of the exhaust gas cleaning device with the following configuration was first created using the simulation software. (Configuration of the analytical model) Shape of the honeycomb substrate: cylindrical shape Size of the honeycomb substrate: Outer diameter × Length in the axial direction = 117 mm × 122 mm Partition wall thickness: 200 µm Cell density: 300 per square inch Length in the extension direction of the locking section: 4 mm Length in the extension direction of the inflow-side partition section: 40% of the total length in the extension direction of the partition Length in the extension direction of the outflow-side partition section: 60% of the total length in the extension direction of the partition

[0132] Subsequently, after adjusting the gas permeability coefficient Ka of the inlet-side partition section and the gas permeability coefficient Kb of the outlet-side partition section using the simulation software to the corresponding values ​​for the respective conditions illustrated in Table 2 below, the pressure losses in the inlet and outlet sides of the exhaust gas cleaning device were calculated in a simulation condition in which air flowed in from the inlet-side end surface of the exhaust gas cleaning device and out from the outlet-side end surface at a flow velocity of 7 m / s. 3 The flow rate was / min at 25 °C. The calculated pressure loss results are illustrated in Table 2 below. Fig. Figure 6 is a graph illustrating the changes in the calculated results of the pressure loss depending on the Ka / Kb ratio of the gas permeability coefficients. [Table 2] Conditions Inlet-side partition section Gas permeability coefficient Ka(m) 2 ) Outflow-side partition section Gas permeability coefficient Kb(m²) 2 ) Gas permeability coefficients Ka / Kb ratio Pressure loss (kPa) 1 8,00E-14 8,00E-14 1 3,278 2 4,00E-14 8,00E-14 0,5 3,893 3 2,00E-14 8,00E-14 0,25 4,419 4 1,00E-14 8,00E-14 0,125 4,786 5 8,00E-15 8,00E-14 0,1 4,8695 6 8,00E-16 8,00E-14 0,01 5,2157 7 8,00E-17 8,00E-14 0,001 5,2544

[0133] It should be noted that the values ​​of the gas permeability coefficient Ka and the gas permeability coefficient Kb for the respective conditions illustrated in Table 2 are derived from an actual measured value (3.278 kPa) of the pressure loss in a GPF with the following configuration under real conditions (airflow velocity of 7 m). 3 / min at 25 °C) were identified as being the same as the simulation condition. In particular, it was assumed that the values ​​of the gas permeability coefficient Ka and the gas permeability coefficient Kb in condition 1, illustrated in Table 2, were identical. Additionally, the values ​​of the gas permeability coefficient Ka and the gas permeability coefficient Kb in condition 1 were set to values ​​corresponding to the actually measured value (3.278 kPa) of the pressure loss in the simulation state (airflow velocity 7 m / s). 3 / min at 25°C) was calculated in the analytical model using the simulation software. Additionally, the gas permeability coefficients Kb for conditions 2 to 7, illustrated in Table 2, were set to the same value as the gas permeability coefficient Kb in condition 1, and the gas permeability coefficients Ka for conditions 2 to 7 were set to the value obtained by decreasing the gas permeability coefficient Ka in condition 1. (GPF configuration)

[0134] Honeycomb substrate: Honeycomb substrate made of cordierite Shape of the honeycomb substrate: cylindrical shape Size of the honeycomb substrate: Outer diameter × Length in the axial direction = 117 mm × 122 mm Partition wall thickness: 200 µm Cell density: 300 per square inch Length in the extension direction of the locking section: 4 mm Length in the extension direction of the inflow-side partition section: 40% of the total length in the extension direction of the partition Length in the extension direction of the outflow-side partition section: 60% of the total length in the extension direction of the partition Catalyst layer 1: Catalyst layer arranged in the inner area on the inflow cell side in the inflow-side area of ​​the partition. Density of catalyst layer 1: 100 g / L Catalyst layer 2: Catalyst layer located in the inner area on the outflow cell side in the outflow-side area of ​​the partition. Density of catalyst layer 2: 100 g / L Here, the density of a catalyst layer 1 is given as a value obtained by dividing the mass of catalyst layer 1 by a volume of a part in the axial direction of the honeycomb substrate whose length in the axial direction is equal to the length in the extension direction of catalyst layer 1, and the density of a catalyst layer 2 is given as a value obtained by dividing the mass of catalyst layer 2 by a volume of a part in the axial direction of the honeycomb substrate whose length in the axial direction is equal to the length in the extension direction of catalyst layer 2.

[0135] As shown in Table 2 and Fig. As illustrated in Figure 6 above, the pressure loss increased when the Ka / Kb ratio of the gas permeability coefficients was reduced by decreasing the gas permeability coefficient Ka of the inlet-side partition section while keeping the gas permeability coefficient Kb of the outlet-side partition section constant, while decreasing the Ka / Kb ratio of the gas permeability coefficients. [Overall evaluation]

[0136] From the results of the evaluations of the changes in the 20% NOx conversion temperature with respect to the pressure drop and the changes in the pressure drop with respect to the Ka / Kb ratio of the gas permeability coefficients described above, it is assumed that the pressure drop at which the 20% NOx conversion temperature in the exhaust gas cleaning device is minimized is approximately 3.7 kPa, and a range of the Ka / Kb ratio of the gas permeability coefficients in which the pressure drop at which the 20% NOx conversion temperature is reduced can be obtained is the range of 0.4 or more and 0.8 or less.Furthermore, it is assumed that if the Ka / Kb ratio of the gas permeability coefficients is increased to more than the upper limit of this range while the pressure drop is reduced, the 20% NOx conversion temperature increases, and if the Ka / Kb ratio of the gas permeability coefficients is reduced to less than the lower limit of this range, the pressure drop increases and the 20% NOx conversion temperature increases.

[0137] Accordingly, the exhaust gas purification device assumes that adjusting the Ka / Kb ratio of the gas permeability coefficients within the range of 0.4 or more and 0.8 or less ensures that the exhaust gas is brought into contact with the inlet cell-side catalyst layer 20 and the outlet cell-side catalyst layer 30, so that the exhaust gas is efficiently cleaned and the pressure loss is suppressed. 3. Reference: Arrangement of the catalytic metal

[0138] In the exhaust gas purification device of the embodiment, the inlet-cell-side catalyst layer contains a catalytic metal comprising at least one of palladium (Pd) and platinum (Pt), while the outlet-cell-side catalyst layer comprises a catalytic metal that, in some embodiments, contains rhodium (Rh). The reason can be explained with reference to a reference example disclosed in the reference document (R. Horn et al. / Journal of Catalysis 249 (2007) 380-393). The reason is described below with reference to the reference example disclosed in the reference document. [Reference example 1]

[0139] The reference document describes the following measurements when a mixed gas of methane (CH4) and oxygen (O2) is fed into the respective reactors, which contain a Pt-containing catalyst and an Rh-containing catalyst. Changes in the O2 conversion rates, CH4 conversion rates, and discharge gas temperatures, as well as the H2, CO, CO2, and H2O selectivities of the respective catalysts, are measured relative to the C / O ratio (ratio of carbon atoms to oxygen atoms) of the feed gas. It should be noted that the design of the Pt-containing catalyst, the Rh-containing catalyst, and the feed gas in this case are as follows. (Pt-containing catalyst) - Support made of α-Al2O3 support 5±1 mass-% Pt. - It is produced by impregnating the α-Al2O3 support with 5 mass-% Pt and then firing the support in a mixed gas of hydrogen (H2) and nitrogen (N2) containing 10 volume-% H2 at 500 °C for five hours. (Rh-containing catalyst) - Support made of α-Al2O3 with 5±1 mass-% Rh. - It is produced by impregnating the α-Al2O3 support with 5 mass-% Rh and then firing the support in an atmosphere at 600°C for six hours. (Gas gas)

[0140] Composition: Mixed gas of CH4 and O2 (C / O ratio = 0.6 to 2.6) Flow rate: 4.7 L / min Pressure: 1 atm Temperature: 400 °C

[0141] Fig. 7 is a drawing that Fig. 2 of the reference document, and the upper part is a graph illustrating changes in the O2 conversion rates, the CH4 conversion rates and the discharge gas temperatures of the respective catalysts relative to the C / O ratio of the feed gas, and the lower part is a graph illustrating changes in the H2 selectivities, the CO selectivities, the CO2 selectivities and the H2O selectivities of the respective catalysts relative to the C / O ratio of the feed gas. [Reference example 2]

[0142] The reference document describes the following: when a mixed gas of methane (CH4) and oxygen (O2) is fed to the respective reactors containing the Pt-containing catalyst and the Rh-containing catalyst, the flow velocities of the respective elements and the bed temperatures are measured at each position in the direction of flow of the reactor feed gas. It should be noted that in this case, the Pt-containing catalyst and the Rh-containing catalyst are arranged as described above, and the feed gas design is as follows. (Gas gas)

[0143] Composition: Mixed gas of CH4 and O2 (C / O ratio = 1.0 (stoichiometric)) Flow rate: 4.7 L / min Pressure: 1 atm Temperature: 400 °C

[0144] Fig. 8 is a drawing that Fig. 3 of the reference document, and the upper part on the left is a graph illustrating the flow velocities of CH4 and O2 and the bed temperatures at each position in the feed gas flow direction in the reactor where the rh-containing catalyst is located; the middle part on the left is a graph illustrating the flow velocities of H2 and CO at each position in the feed gas flow direction in the reactor where the rh-containing catalyst is located; and the lower part on the left is a graph illustrating the flow velocities of H2O and CO2 at each position in the feed gas flow direction in the reactor where the rh-containing catalyst is located. Furthermore, in Fig. 8 The upper part on the right is a graph illustrating the flow velocities of CH4 and O2 and the bed temperatures at each position in the feed gas flow direction in the reactor where the Pt-containing catalyst is located; the middle part on the right is a graph illustrating the flow velocities of H2 and CO at each position in the feed gas flow direction in the reactor where the Pt-containing catalyst is located; and the lower part on the right is a graph illustrating the flow velocities of H2O and CO2 at each position in the feed gas flow direction in the reactor where the Pt-containing catalyst is located. [Evaluation]

[0145] From the in Fig. 7 of reference example 1 and Fig. The measurement results illustrated in Figure 8 of Reference Example 2 show that the Pt-containing catalyst exhibits high heat generation through partial oxidation and high H2O selectivity, and likely readily oxidizes CH4 to CO2 in conjunction with further heat generation, since the Pt-containing catalyst has a high catalyst bed temperature across the entire C / O ratio range compared to the Rh-containing catalyst. In contrast, the Rh-containing catalyst shows low heat generation through partial oxidation, but high steam reforming activity and high H2 selectivity.

[0146] Accordingly, in the exhaust gas purification device, where the inlet-side catalyst layer contains Pt and the outlet-side catalyst layer contains Rh, the Pt contained in the inlet-side catalyst layer can efficiently oxidize hydrocarbons (HC) in the rich-atmosphere exhaust gas. Therefore, it is considered possible to prevent HC poisoning of the outlet-side catalyst layer, starting with Ce. When Pt oxidizes the HC, the heat generation and the amount of H₂O produced are greater than when Rh oxidizes the HC. Furthermore, the steam reforming activity of Rh is higher than that of Pt, and therefore, it is assumed that the HC can be efficiently reformed by the outlet-side catalyst layer.

[0147] While embodiments of the exhaust gas purification device of the present invention have been described in detail, the present invention is not limited to the aforementioned embodiments. DESCRIPTION OF REFERENCE MARKS 1 Exhaust gas purification device 10 honeycomb substrate 10Sa Inflow-side end surface of the honeycomb substrate 10Sb Outflow-side end surface of the honeycomb substrate 12 cells 12A inlet cell 12Aa Inlet-side end of the inlet cell 12Ab Outflow-side end of the inflow cell 12B Outflow cell 12Ba Inlet-side end of the outlet cell 12Bb Outflow-side end of the outflow cell 14 Partition wall 14a Inlet-side end of the partition 14m Predetermined position of the partition wall 14b Outflow-side end of the partition 14Ra Inflow-side area of ​​the partition 14Rb Outflow-side area of ​​the partition 14Rr Overlapping area of ​​the partition 14SA Surface of the inlet cell side of the partition 14NA Inner area of ​​the inlet cell side of the partition 14NB Inner area of ​​the outflow cell side of the partition 16 Closure section 20 inflow cell-side catalyst layer 30 outflow cell side catalyst layer< / haltbarkeitstests>

Claims

[1] comprising an exhaust gas purification device (1): a honeycomb substrate (10); and a catalyst layer on the inflow cell side (20), wherein the honeycomb substrate (10) includes a porous partition (14) defining a plurality of cells (12) extending from an inflow-side end surface (10Sa) to an outflow-side end surface (10Sb), wherein the majority of cells (12) include an inlet cell (12A) and an outlet cell (12B) which are adjacent to each other and between which the partition (14) is arranged, wherein the inlet cell (12A) has an open, inlet-side end (12Aa) and a closed, outlet-side end (12Ab), wherein the outflow cell (12B) has a closed, inflow-side end (12Ba) and an open, outflow-side end (12Bb), wherein the inlet cell-side catalyst layer (20) is arranged on a surface on the inlet cell side in an inlet-side region from the inlet-side end (12Aa) to a predetermined position (14m) on an outlet side of the partition, and where, if a gas permeability coefficient of an inlet-side partition section (14a) comprising the inlet-side area of ​​the partition (14Ra) and the inlet-cell-side catalyst layer (20) is Ka, and if a gas permeability coefficient of an outlet-side partition section (14Rb) comprising at least an outlet-side area from the predetermined position (14m) to the outlet-side end of the partition (14b) is Kb, then a Ka / Kb ratio of the gas permeability coefficients lies in a range of 0.4 or more and 0.8 or less, wherein the gas permeability coefficient Kb lies in a range of 2.0E-16 m 2 or more and 2.0E-13 m 2or less. [2] Exhaust gas purification device (1) according to claim 1, wherein an outflow cell-side catalyst layer (30) is arranged in an inner region on the outflow cell side (14NB) in the outflow-side region of the partition (14Rb), and wherein the outflow-side partition section includes the outflow-side region of the partition (14Rb) and the outflow cell-side catalyst layer (30). [3] Exhaust gas purification device (1) according to claim 2, wherein the inlet cell side catalyst layer (20) includes a catalytic metal containing at least one of platinum (Pt) and palladium (Pd), and wherein the outlet cell side catalyst layer (30) includes a catalytic metal containing rhodium (Rh). [4] Exhaust gas purification device (1) according to claim 1, wherein any catalyst layer is missing in an inner area on the outflow cell side (14NB) in the outflow side area of ​​the partition (14Rb), and wherein the outflow side partition section includes the outflow side area of ​​the partition (14Rb).

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