Exhaust gas purification catalyst device

Abstract

Disclosed is an exhaust gas purification catalyst device which comprises a base material and a catalyst coating layer that is disposed on the base material, wherein: the catalyst coating layer has four regions, specifically a first region to a fourth region, in this order from the upstream side of exhaust gas flow; each region of the catalyst coating layer contains a catalytic noble metal; and the amount of a specific catalytic noble metal, which is defined as a value obtained by dividing the mass of the catalytic noble metal contained in each region by the volume of the base material corresponding to the region, satisfies the relationship of the first region > the third region > the fourth region ≥ the second region.

Description

Exhaust gas purification catalyst device

[0001] The present invention relates to an exhaust gas purification catalyst device.

[0002] Exhaust gas discharged from a diesel engine contains particulate matter (PM) such as soot, in addition to NOx (nitrogen oxides), CO (carbon monoxide), and HC (hydrocarbons). As a system for effectively purifying these, it is known to use a combination of a DOC (diesel oxidation catalyst device) and a DPF (diesel particulate filter).

[0003] In the combination of a DOC and a DPF, when PM accumulates in the DPF, control called "DPF regeneration" is performed to apply heat to the PM and burn it off. During DPF regeneration, light oil is supplied to the DOC and burned, and the heat of this combustion flows into the DPF, causing the PM to burn. Therefore, if the temperature-rising property of the DOC during DPF regeneration is insufficient, the combustion efficiency of the PM will decrease.

[0004] In this regard, in a DOC, attempts have been made to improve the catalyst performance including the temperature-rising performance by dividing the catalyst coat layer on the substrate into a plurality of regions and adjusting the concentration of the catalytic noble metal contained in each region.

[0005] For example, in Patent Document 1, the catalyst coat layer on the substrate is divided into three regions, namely a first region, a second region, and a third region, in order from the upstream side of the exhaust gas flow, and it is proposed that the catalytic noble metal concentration in each region be in the order of second region > first region > third region. Also, in Patent Document 2, the catalyst coat layer on the substrate is divided into three regions similar to those in Patent Document 1, and it is proposed that the catalytic noble metal concentration in the second region among these be lower than that in the first region and the third region.

[0006] Japanese Unexamined Patent Application Publication No. 2019 - 162622, Japanese Patent Application Publication No. 2009 - 522094

[0007] Including those described in Patent Documents 1 and 2, the DOC in the prior art has insufficient temperature-rising property of the DOC during DPF regeneration.

[0008] The present invention aims to improve this situation, and its objective is to provide an exhaust gas purification catalyst with high temperature rise, in particular an exhaust gas purification catalyst with high temperature rise during DPF regeneration when used as a DOC.

[0009] The present invention is as follows:

[0010] <Aspect 1> An exhaust gas purification catalyst apparatus having a substrate and a catalyst coating layer on the substrate, wherein the catalyst coating layer has four regions in the order of a first region to a fourth region from the upstream side of the exhaust gas flow, each region of the catalyst coating layer contains a catalyst precious metal, and the specific amount of catalyst precious metal, defined as the value obtained by dividing the mass of catalyst precious metal contained in each region by the volume of the substrate corresponding to that region, has the relationship first region > third region > fourth region ≥ second region. <Aspect 2> The exhaust gas purification catalyst apparatus according to aspect 1, wherein the specific amount of coating, defined as the value obtained by dividing the coating amount of each region by the volume of the substrate corresponding to that region, has the relationship first region > third region > fourth region ≥ second region. <Aspect 3> The exhaust gas purification catalyst apparatus according to aspect 1, wherein the specific amount of catalyst precious metal in the third region is 15% or more and 50% or less of the specific amount of catalyst precious metal in the first region. <Aspect 4> The exhaust gas purification catalyst apparatus according to Aspect 1, wherein the amount of specific catalyst noble metal in the fourth region and the second region is 25% or more and 75% or less of the amount of specific catalyst noble metal in the third region, respectively. <Aspect 5> The exhaust gas purification catalyst apparatus according to Aspect 1, wherein the length of the first region is 15% or more and 60% or less of the total length of the substrate. <Aspect 6> The exhaust gas purification catalyst apparatus according to Aspect 1, wherein the length of the third region is 3% or more and 30% or less of the total length of the substrate. <Aspect 7> The exhaust gas purification catalyst device according to Aspect 1, wherein the amount of specific catalyst precious metal in the third region is 15% or more and 50% or less of the amount of specific catalyst precious metal in the first region, the specific coat amount, defined as the value obtained by dividing the coat amount of each region by the volume of the substrate that corresponds to that region, has the relationship first region > third region > fourth region ≥ second region, the amount of specific catalyst precious metal in the fourth region and the second region is 25% or more and 75% or less of the amount of specific catalyst precious metal in the third region, the length of the first region is 10% or more and 60% or less of the total length of the substrate, and the length of the third region is 5% or more and 30% or less of the total length of the substrate. <Aspect 8> The exhaust gas purification catalyst device according to any one of Aspects 1 to 7, wherein the catalyst precious metal is one or two selected from platinum and palladium. <Aspect 9> The exhaust gas purification catalyst device according to Aspect 8, which is a diesel oxidation catalyst device.<Aspect 10> An exhaust gas purification catalyst system comprising an exhaust gas purification catalyst device according to any one of aspects 1 to 7 and a diesel particulate filter. <Aspect 11> The exhaust gas purification catalyst system according to aspect 10, wherein the catalytic precious metal in the exhaust gas purification catalyst device is one or two selected from platinum and palladium. <Aspect 12> The exhaust gas purification catalyst system according to aspect 11, wherein the exhaust gas purification catalyst device is a diesel oxidation catalyst device. 《Aspect 13》A method for manufacturing an exhaust gas purification catalyst according to any one of aspects 1 to 7, comprising: forming a first catalyst coating layer in a range corresponding to the total length of the third and fourth regions from the downstream end of the exhaust gas flow of the substrate; forming a second catalyst coating layer in a range corresponding to the total length of the first to third regions from the upstream end of the exhaust gas flow of the substrate after the formation of the first catalyst coating layer; and forming a third catalyst coating layer in a range corresponding to the length of the first region from the upstream end of the exhaust gas flow of the substrate after the formation of the first and second catalyst coating layers, wherein the formation order of the first to third catalyst coating layers is either the first catalyst coating layer, the second catalyst coating layer, and the third catalyst coating layer; or the second catalyst coating layer, the first catalyst coating layer, and the third catalyst coating layer; and the first region is formed by laminating the second catalyst coating layer and the third catalyst coating layer. A method for manufacturing an exhaust gas purification catalyst, comprising forming a second region composed of the second catalyst coating layer, a third region composed of the first catalyst coating layer and the second catalyst coating layer stacked on top of each other, wherein each of the first to third catalyst coating layers contains a catalytic precious metal. <Aspect 14> The manufacturing method according to aspect 13, wherein the catalytic precious metal is one or two selected from platinum and palladium.

[0011] According to the present invention, an exhaust gas purification catalyst device with high temperature rise capability is provided, in particular an exhaust gas purification catalyst device with high temperature rise capability during DPF regeneration when used as a DOC. Therefore, when the exhaust gas purification catalyst device of the present invention is used in combination with a DPF, the combustion efficiency of PM during DPF regeneration is excellent.

[0012] Figure 1 is a schematic cross-sectional view showing an example of the configuration of the catalyst coating layer in the exhaust gas purification catalyst device of the present invention. Figure 2 is a schematic cross-sectional view showing another example of the configuration of the catalyst coating layer in the exhaust gas purification catalyst device of the present invention. Figure 3 is a graph showing the temperature at each measurement point of the exhaust gas purification catalyst device 300 seconds after the start of fuel addition for DPF regeneration during manual DPF regeneration in the examples and comparative examples.

[0013] The exhaust gas purification catalyst device of the present invention is an exhaust gas purification catalyst device having a substrate and a catalyst coating layer on the substrate, wherein the catalyst coating layer has four regions in the order of first region to fourth region from the upstream side of the exhaust gas flow, each region of the catalyst coating layer contains a catalyst precious metal, and the specific amount of catalyst precious metal, defined as the value obtained by dividing the mass of the catalyst precious metal contained in each region by the volume of the substrate that corresponds to that region, has the relationship first region > third region > fourth region ≥ second region.

[0014] The exhaust gas purification catalyst device of the present invention may have a specific coating amount, defined as the value obtained by dividing the coating amount of each region by the volume of the substrate that corresponds to that region, such that the relationship is first region > third region > fourth region ≥ second region.

[0015] As described above, the conventional DOC, including those proposed in Patent Documents 1 and 2, suffers from insufficient temperature rise during DPF regeneration. The inventors have considered the following reasons for this.

[0016] In the DOC described in Patent Document 1, the amount of noble metal catalyst (catalyst metal concentration) in each region is lowest in the third region, which is the third region from the upstream side of the exhaust gas flow. Therefore, it is presumed that the heating performance was insufficient because, during DPF regeneration, the HC that could not be completely purified in the first and second regions could not be sufficiently burned in the downstream third region.

[0017] Furthermore, in the DOC described in Patent Document 2, the amount of specific catalyst noble metal in each region is relatively high in the third region, which is the downstreammost region of the exhaust gas flow. In this DOC, it is thought that the specific coating amount in the third region is large in order to increase the amount of specific catalyst noble metal in the third region. Therefore, it is presumed that the heating performance was insufficient due to insufficient gas diffusion in the third region, which is the downstreammost region.

[0018] In contrast to these, the exhaust gas purification catalyst device of the present invention increases the amount of specific catalyst noble metal in the third region, making it possible to maintain a highly active state of the catalytic reaction, and improves the temperature rise by ensuring the complete combustion of HC that could not be purified in the first and second regions.

[0019] Furthermore, a fourth region with a smaller amount of catalytic noble metal (and therefore a smaller amount of specific coating) was established further downstream of this third region, thereby improving the heating performance by ensuring gas diffusivity in the furthest downstream region.

[0020] The exhaust gas purification catalyst device of the present invention is expected to exhibit high temperature rise during DPF regeneration when used as a DOC due to the above-described mechanism of action. However, the present invention is not bound by any particular theory.

[0021] The exhaust gas purification catalyst device of the present invention comprises a substrate and a catalyst coating layer on the substrate.

[0022] The elements constituting the exhaust gas purification catalyst device of the present invention will be described in order below.

[0023] <Substrate> The substrate in the exhaust gas purification catalyst device of the present invention may be a substrate having a plurality of cell channels separated by partitions, and may be a honeycomb substrate used in conventional exhaust gas purification catalyst devices. The partitions of the substrate may have pores that fluidly communicate between adjacent exhaust gas channels, or they may not have such pores.

[0024] The constituent material of the substrate may be, for example, a refractory inorganic oxide such as cordierite or silicon carbide (SiC), or it may be a metal. The substrate may be of the straight flow type or the wall flow type.

[0025] The substrate in the method for manufacturing the exhaust gas purification catalyst of the present invention may typically be, for example, a straight-flow type monolithic honeycomb substrate made of cordierite or SiC, a metal honeycomb substrate, or the like.

[0026] The shape of the base material may be cylindrical, elliptical, polygonal, or the like.

[0027] The capacity of the base material may be, as an apparent capacity expressed by base area × length, for example, 500 mL or more, 800 mL or more, 1.0 L or more, or 1.2 L or more, for example, 8.0 L or less, 5.0 L or less, 3.0 L or less, 2.0 L or less, 1.5 L or less, or 1.2 L or less.

[0028] 《Catalyst Coating Layer》 The catalyst coating layer is placed on the substrate. Typically, the catalyst coating layer is positioned as a coating layer formed from the surface of the substrate's partition wall toward the cell flow channel side. Here, if the substrate has pores, a portion of the catalyst coating layer may penetrate into the pores.

[0029] The catalyst coating layer has four regions, from the upstream side of the exhaust gas flow, in the order of the first region to the fourth region.

[0030] Each region of the catalyst coating layer contains a catalytic precious metal. This catalytic precious metal may be a platinum group metal, and is typically one or two selected from platinum and palladium. Here, the exhaust gas purification catalyst device of the present invention is intended to be applied as a DOC (Discharge Oxide). Therefore, each region of the catalyst coating layer does not need to contain rhodium.

[0031] The catalytic precious metal may be in particulate form. The average particle size of the particulate catalytic precious metal may be between 1 nm and 50 nm. The average particle size of the catalytic precious metal may be, for example, a value calculated from the results of gas adsorption measurements, a value calculated using the Scherrer formula from the results of XRD analysis, etc.

[0032] Each region of the catalyst coating layer may contain optional components other than the catalyst precious metal. These optional components may be, for example, inorganic oxides, binders, etc.

[0033] The inorganic oxide may be an oxide of one or more elements selected from, for example, Al, Si, Ti, Zr, Ce, and rare earth elements other than Ce. The inorganic oxide may further contain, as an additive, elements selected from, for example, alkali metals, alkaline earth metals, and other transition metals. Specific examples of inorganic oxides include, for example, alumina, zirconia, ceria, cerium-zirconium composite oxides, and zeolites.

[0034] The inorganic oxide may be in particulate form. The average particle size of the particulate inorganic oxide may be between 0.5 μm and 20.0 μm. The average particle size of the inorganic oxide may be measured as the particle size (median diameter, D50) at which the cumulative volume frequency is 50% in the particle size distribution obtained by dynamic light scattering.

[0035] The catalytic precious metal may be supported on part or all of the inorganic oxide. The support rate of the catalytic precious metal in the inorganic oxide may be 0.1% by mass or more and 10.0% by mass or less, as the mass ratio of the catalytic precious metal to the total mass of the catalytic precious metal and the inorganic oxide.

[0036] Each region of the catalyst coating layer in the exhaust gas purification catalyst device of the present invention may contain, for example, an inorganic oxide supporting a catalyst metal and an inorganic oxide not supporting a catalyst metal.

[0037] The binder may be selected from, for example, alumina-based binders, silica-based binders, zirconia-based binders, etc.

[0038] <Amount of catalytic precious metals in each region> In the exhaust gas purification catalyst device of the present invention, the relative amount of catalytic precious metals, defined as the value obtained by dividing the mass of catalytic precious metals contained in each region of the catalyst coating layer by the volume corresponding to that region of the base material's volume, has the relationship: Region 1 > Region 3 > Region 4 ≥ Region 2. The relative amount of catalytic precious metals in Region 4 and Region 2 may be the same, or the relative amount of catalytic precious metals in Region 4 may be greater than the relative amount of catalytic precious metals in Region 2.

[0039] From the perspective of maintaining the highly active state of the catalytic reaction in the third region, the specific catalytic noble metal amount in the third region of the catalyst coat layer may be 15% or more, 17% or more, 20% or more, 22% or more, or 25% or more of the specific catalytic noble metal amount in the first region. On the other hand, from the perspective of ensuring the catalytic noble metal amount in the first region, the specific catalytic noble metal amount in the third region of the catalyst coat layer may be 50% or less, 45% or less, 40% or less, 35% or less, or 30% or less of the specific catalytic noble metal amount in the first region.

[0040] From the perspective of expressing the combustibility of HC over the entire region of the catalyst coat layer, the specific catalytic noble metal amounts in the fourth region and the second region may each be 25% or more, 30% or more, 35% or more, or 40% or more of the specific catalytic noble metal amount in the third region. On the other hand, from the perspective of ensuring the gas diffusibility in the fourth region and the second region and enhancing the temperature rise property, the specific catalytic noble metal amounts in the fourth region and the second region may each be 75% or less, 70% or less, 65% or less, 60% or less, or 55% or less of the specific catalytic noble metal amount in the third region.

[0041] From the perspective of achieving complete combustion of HC, the specific catalytic noble metal amount in the fourth region may be greater than the specific catalytic noble metal amount in the second region. In this case, the specific catalytic noble metal amount in the fourth region may be 110% or more or 120% or more of the specific catalytic noble metal amount in the second region, and may be 150% or less, 140% or less, or 130% or less.

[0042] Each region of the catalyst coat layer preferably contains a predetermined amount of catalytic noble metal in order to exhibit the exhaust gas purification ability expected as a DOC.

[0043] The specific catalytic noble metal amount in each region of the catalyst coating layer may be, for example, as follows. First region: 1.00 g / L or more, 1.50 g / L or more, 2.00 g / L or more, or 2.50 g / L or more, and 5.00 g / L or less, 4.00 g / L or less, 3.50 g / L or less, or 3.00 g / L or less Second region: 0.1 g / L or more, 0.2 g / L or more, or 0.3 g / L or more, and 0.8 g / L or less, 0.6 g / L or less, or 0.4 g / L or less Third region: 0.3 g / L or more, 0.5 g / L or more, 0.6 g / L or more, or 0.7 g / L or more, and 1.50 g / L or less, 1.30 g / L or less, 1.00 g / L or less, 0.90 g / L or less, or 0.80 g / L or less Fourth region: 0.1 g / L or more, 0.2 g / L or more, or 0.3 g / L or more, and 1.0 g / L or less, 0.8 g / L or less, 0.6 g / L or less, or 0.5 g / L or less

[0044] 〈Coating amount of each region〉 In the exhaust gas purification catalyst device of the present invention, the specific coating amount defined as the value obtained by dividing the coating amount of each region of the catalyst coating layer by the capacity corresponding to the region in the capacity of the substrate may have the relationship of First region > Third region > Fourth region ≥ Second region. The main purpose of this requirement is to increase the temperature rising property by setting the specific coating amounts of the second region and the fourth region relatively low and increasing the gas diffusibility in these regions.

[0045] The specific coating amount in the third region of the catalyst coating layer may be 15% or more, 20% or more, 30% or more, 40% or more, or 50% or more of the specific coating amount in the first region, and 75% or less, 70% or less, 65% or less, 60% or less, or 55% or less.

[0046] The specific coating amounts in the fourth region and the second region may be 25% or more, 30% or more, 35% or more, 40% or more, or 45% or more of the specific coating amount in the third region, respectively, and 75% or less, 70% or less, 65% or less, 60% or less, 55% or less, or 50% or less.

[0047] The specific coating amount in the fourth region may be greater than the specific coating amount in the second region. In this case, the specific coating amount in the fourth region may be 110% or more, 120% or more, and 150% or less, 140% or less, or 130% or less of the specific coating amount in the second region.

[0048] The specific coating amounts for each region of the catalyst coating layer may be, for example, as follows: Region 1: 100 g / L or more, 120 g / L or more, 140 g / L or more, or 160 g / L or more, and 300 g / L or less, 250 g / L or less, 200 g / L or less, or 180 g / L or less Region 2: 10 g / L or more, 20 g / L or more, 30 g / L or more, or 40 g / L or more, and 100 g / L or less, 80 g / L or less, 60 g / L or less, or 50 g / L or less Region 3 Fourth region: 20 g / L or more, 40 g / L or more, 60 g / L or more, or 80 g / L or more, and 200 g / L or less, 180 g / L or less, 150 g / L or less, 120 g / L or less, or 100 g / L or less. Fourth region: 10 g / L or more, 20 g / L or more, 30 g / L or more, or 40 g / L or more, and 120 g / L or less, 100 g / L or less, 80 g / L or less, or 60 g / L or less.

[0049] <Length of each region> Each region of the catalyst coating layer may have a length sufficient to perform the function expected of that region. Specifically, the length of each region may be, for example, as a percentage of the total length of the substrate, as follows: Region 1: 15% or more, 20% or more, 25% or more, 30% or more, or 35% or more, and 60% or less, 55% or less, 50% or less, or 45% or less Region 2: 8% or more, 10% or more, 12% or more, or 15% or more, and 40% or less, 35% or less, 30% or less, or 25% or less Region 3: 3% or more, 5% or more, or 7% or more, and 30% or less, 25% or less, 20% or less, 15% or less, or 10% or less Region 4: 10% or more, 15% or more, 20% or more, or 25% or more, and 50% or less, 45% or less, 40% or less, or 35% or less

[0050] The lengths of each region in the catalyst coating layer may be, for example, in the following order: Region 1 > Region 4 > Region 2 > Region 3, Region 1 > Region 4 > Region 2 = Region 3, or Region 1 > Region 4 > Region 3 > Region 2. Region 3 has the function of maintaining a highly active state of the catalytic reaction during the combustion reaction in DPF regeneration, and its length does not need to be excessively long as long as it can perform this function.

[0051] <Application of the Exhaust Gas Purification Catalyst Device of the Present Invention> The exhaust gas purification catalyst device of the present invention contains one or two types of catalyst precious metals selected from, for example, platinum and palladium, and exhibits excellent combustion properties (oxidative purification properties) of HC and excellent temperature rise during DPF regeneration. Therefore, the exhaust gas purification catalyst device of the present invention can be suitably applied, for example, as a diesel oxidation catalyst device (DOC device).

[0052] 《Method for Manufacturing an Exhaust Gas Purification Catalyst》According to another aspect of the present invention, a method for manufacturing an exhaust gas purification catalyst is provided.

[0053] The exhaust gas purification catalyst of the present invention may be manufactured by a method in which the order in which the first to third catalyst coat layers are formed is, for example, the first catalyst coat layer is formed in the order of the first catalyst coat layer, the second catalyst coat layer is formed in the order of the second catalyst coat layer, the first catalyst coat layer is formed in the order of the second catalyst coat layer and the third catalyst coat layer, and the third catalyst coat layer is formed in the order of the second catalyst coat layer, the second catalyst coat layer and the third catalyst coat layer, or the second catalyst coat layer, the third catalyst coat layer and the first catalyst coat layer.

[0054] The method for producing the exhaust gas purification catalyst of the present invention will be described in detail below with reference to the figures.

[0055] Figures 1 and 2 show schematic cross-sectional views illustrating an example of the configuration of the catalyst coating layer in the exhaust gas purification catalyst device of the present invention.

[0056] The exhaust gas purification catalyst device (100) shown in Figure 1 can be manufactured by a method that includes, for example, forming a first catalyst coating layer (121) in a range corresponding to the sum of the lengths of the third and fourth regions from the downstream end of the exhaust gas flow of the substrate (110), forming a second catalyst coating layer (122) in a range corresponding to the sum of the lengths of the first to third regions from the upstream end of the exhaust gas flow of the substrate (110) after the formation of the first catalyst coating layer (121), and forming a third catalyst coating layer (123) in a range corresponding to the length of the first region from the upstream end of the exhaust gas flow of the substrate (110) after the formation of the first catalyst coating layer (121) and the second catalyst coating layer (122).

[0057] Through this procedure, a first region (131) is formed by laminating a second catalyst coating layer (122) and a third catalyst coating layer (123); a second region (132) is formed from the second catalyst coating layer (122); a third region (133) is formed by laminating a first catalyst coating layer (121) and a second catalyst coating layer (122); and a fourth region (134) is formed from the first catalyst coating layer (121), thereby obtaining an exhaust gas purification catalyst device (100).

[0058] Here, the first catalyst coating layer (121) is divided into an upstream section and a downstream section, with the upstream section belonging to the third region (133) and the downstream section belonging to the fourth region (134).

[0059] The second catalyst coating layer (122) is divided into an upstream, a midstream, and a downstream section, with the upstream section belonging to the first region (131), the midstream section belonging to the second region (132), and the downstream section belonging to the third region (133).

[0060] The entirety of the third catalyst coating layer (123) belongs to the first region (131).

[0061] The exhaust gas purification catalyst device (200) shown in Figure 2 includes, for example, a method that includes, in this order, forming a second catalyst coating layer (222) in a range corresponding to the total length of the first to third regions from the upstream end of the exhaust gas flow of the substrate (210), forming a first catalyst coating layer (221) in a range corresponding to the total length of the third and fourth regions from the downstream end of the exhaust gas flow of the substrate (210) after the formation of the second catalyst coating layer (222), and forming a third catalyst coating layer (223) in a range corresponding to the length of the first region from the upstream end of the exhaust gas flow of the substrate (210) after the formation of the second catalyst coating layer (222) and the first catalyst coating layer (221), or forming a second catalyst coating layer (222) in a range corresponding to the total length of the first to third regions from the upstream end of the exhaust gas flow of the substrate (210), The product can be manufactured by a method that includes, in this order, forming a third catalyst coating layer (223) in a range corresponding to the length of the first region, starting from the upstream end of the exhaust gas flow of the substrate (210) after the formation of the second catalyst coating layer (222), and forming a first catalyst coating layer (221) in a range corresponding to the combined length of the third and fourth regions, starting from the downstream end of the exhaust gas flow of the substrate (210) after the formation of the second catalyst coating layer (222) and the third catalyst coating layer (223).

[0062] Through this procedure, a first region (231) is formed by laminating a second catalyst coating layer (222) and a third catalyst coating layer (223); a second region (232) is formed by the second catalyst coating layer (222); a third region (233) is formed by laminating a second catalyst coating layer (222) and a first catalyst coating layer (221); and a fourth region (234) is formed by the first catalyst coating layer (221), thereby obtaining an exhaust gas purification catalyst device (200).

[0063] Here, the first catalyst coating layer (221) is divided into an upstream section and a downstream section, with the upstream section belonging to the third region (233) and the downstream section belonging to the fourth region (234).

[0064] The second catalyst coating layer (222) is divided into an upstream, midstream, and downstream section, with the upstream section belonging to the first region (231), the midstream section belonging to the second region (232), and the downstream section belonging to the third region (233).

[0065] The entirety of the third catalyst coating layer (223) belongs to the first region (231).

[0066] In any of the above methods, the first catalyst coating layer (121, 221), the second catalyst coating layer (122, 222), and the third catalyst coating layer (123, 223) all contain a catalyst precious metal. The catalyst precious metal may be one or two selected from, for example, platinum and palladium.

[0067] The substrate may be appropriately selected and used according to the desired configuration of the exhaust gas purification catalyst. The substrate may be, for example, a straight-flow type monolithic honeycomb substrate made of cordierite or SiC, a metal honeycomb substrate, etc.

[0068] The formation of each catalyst coating layer on the substrate may be carried out by coating the substrate with a slurry for forming each catalyst coating layer from the upstream or downstream end over a predetermined length, and then firing it.

[0069] Each slurry for forming the catalyst coating layer may be appropriately determined according to the desired configuration of the catalyst coating layer. Each slurry for forming the catalyst coating layer may contain a catalyst noble metal or its precursor, may contain an inorganic oxide, and may further contain any component selected from binders, pH adjusters, viscosity adjusters, defoamers, etc.

[0070] If each catalyst coating layer forming slurry contains a catalyst precious metal, this catalyst precious metal may be supported on part or all of the inorganic oxide. If each catalyst coating layer forming slurry contains a precursor of the catalyst precious metal, this precursor will be converted into the catalyst precious metal during the coating and firing processes of the catalyst coating layer and supported on the inorganic oxide.

[0071] The catalyst precious metal precursor may be selected from chemical species soluble in the solvent, such as nitrates, sulfates, hydrochlorides, acetates, complex compounds, etc. of the desired catalyst precious metal. Here, if the catalyst precious metal ion has multiple stable values, the valency of the precious metal ion in the catalyst precious metal precursor may be any of the multiple stable values. For example, when using platinum nitrate as the catalyst precious metal precursor, either platinum(II) nitrate or platinum(IV) nitrate may be used. When using palladium nitrate, palladium(II) nitrate may be used.

[0072] The solvent for each catalyst coating layer forming slurry may be water, or a mixed solvent of water and a water-soluble organic solvent, and is typically water.

[0073] In the exhaust gas purification catalyst device of the present invention, the constituent components of the first to fourth regions are specified, rather than the constituent components of the first to third catalyst coating layers. The composition of the catalyst coating layer forming slurry to be applied to each region of the catalyst coating layer containing the desired constituent components can be easily calculated by a person skilled in the art, without trial and error.

[0074] The first to third catalyst coating layers (121, 122, 123 (Figure 1), or 221, 222, 223 (Figure 2)) may be fired individually after the formation of each catalyst coating layer, or they may be fired together after the formation of all catalyst coating layers.

[0075] The firing may be carried out by known methods, for example, at a temperature of 400°C to 1,000°C for a period of time of 10 minutes to 24 hours. The firing atmosphere may be a reducing atmosphere, an inert atmosphere, or an oxidizing atmosphere, or it may be in air.

[0076] 《Exhaust Gas Purification Catalyst System》 According to yet another aspect of the present invention, an exhaust gas purification catalyst system is provided.

[0077] The exhaust gas purification catalyst system of the present invention is an exhaust gas purification catalyst system that includes the exhaust gas purification catalyst device of the present invention as described above and a diesel particulate filter (DPF). In the exhaust gas purification catalyst system of the present invention, the exhaust gas purification catalyst device and the DPF may be arranged in this order from the upstream side to the downstream side of the exhaust gas flow.

[0078] In the exhaust gas purification catalyst system of the present invention, the above description may be applied directly to the exhaust gas purification catalyst device of the present invention. Therefore, this exhaust gas purification catalyst device includes one or two types selected from, for example, platinum and palladium as the catalyst precious metal, and may be, for example, a DOC device.

[0079] 1. Preparation of PtPd-supported powder a: To 200 parts by mass of pure water, platinum(II) nitrate equivalent to 1.875 parts by mass in terms of metallic Pt, palladium(II) nitrate equivalent to 0.625 parts by mass in terms of metallic Pd, and 96.5 parts by mass of alumina were added and mixed at room temperature for 30 minutes. Then, the resulting mixture was heated at 120°C for 8 hours to dry it, and then calcined in air at 500°C for 2 hours to obtain PtPd-supported powder a.

[0080] 2. Preparation of PtPd Slurry A The obtained PtPd-supported powder a, BEA-type zeolite, boehmite binder, and pH adjuster were mixed dry for 5 minutes. Pure water was added to the resulting mixture to form a slurry, which was then pulverized wet to adjust the average particle size of the solid content to 4.0 μm. Cellulose resin was added as a thickening agent to the slurry after particle size adjustment to prepare PtPd slurry A.

[0081] 3. Preparation of PtPd-supported powder b PtPd-supported powder b was obtained in the same manner as the preparation of PtPd-supported powder a, except that the amounts of platinum(IV) nitrate, palladium(II) nitrate, and alumina used were changed to 0.375 parts by mass equivalent to metallic Pt, 0.125 parts by mass equivalent to metallic Pd, and 49.0 parts by mass, respectively.

[0082] 4. Preparation of PtPd Slurry B PtPd slurry B was obtained in the same manner as the preparation of PtPd slurry A, except that PtPd-supported powder b obtained above was used instead of PtPd-supported powder a.

[0083] Example 1 (1) Exhaust gas purification catalyst device: Diameter 143.8 mm, length 90.0 mm, partition wall thickness 0.4 mil (0.1016 mm), and cell count 400 sell / inch ２ (0.620cell / mm ２ A straight-flow honeycomb substrate made of cordierite (apparent capacity 1.5 L) was coated with 30.21 g of PtPd slurry B (containing 0.181 g of Pt and 0.060 g of Pd) over a range of 38% of the substrate length from the outlet end face on the cell channel partition wall, and dried at 100°C (first coating layer (C1)). Next, a range of 44.79 g of PtPd slurry B (containing 0.269 g of Pt and 0.090 g of Pd) was coated over a range of 70% of the substrate length from the inlet end face of the honeycomb substrate, and dried at 100°C (second coating layer (C2)).

[0084] Next, 75.00 g of PtPd slurry A (containing 1.125 g of Pt and 0.38 g of Pd) was coated onto the honeycomb substrate from the entrance end face to 40% of the substrate length, and dried at 100°C (third coating layer (C3)).

[0085] The exhaust gas purification catalyst device of Example 1 was manufactured by firing the coated and dried honeycomb substrate in air at 500°C for 2 hours.

[0086] The total dry mass of the first coating layer (C1) to the third coating layer (C3) applied here was 150.0 g (100 g / L), the total amount of Pt in metal equivalent was 1.58 g (1.05 g / L), the total amount of Pd in ​​metal equivalent was 0.53 g (0.35 g / L), and the total amount of Pt and Pd in ​​metal equivalent was 2.10 g (1.40 g / L).

[0087] The amount of coating (mass after drying) of the first coating layer (C1) to the third coating layer (C3) applied as described above, and the amount of precious metals contained therein in terms of metal, are shown in Table 1.

[0088]

[0089] In the exhaust gas purification catalyst device of Example 1, the first region of the catalyst coating layer is the area from the inlet end face of the honeycomb substrate to 40% of the substrate length (coat width is 40% of the substrate length), where the second coating layer (C2) and the third coating layer (C3) are laminated; the second region is the area from the inlet end face of the honeycomb substrate to 40% to 62% of the substrate length (coat width is 22% of the substrate length), consisting only of the second coating layer (C2); the third region is the area from the inlet end face of the honeycomb substrate to 62% to 70% of the substrate length (length is 8% of the substrate length), where the first coating layer (C1) and coating layer C2 are laminated; and the fourth region is the area from the inlet end face of the honeycomb substrate to 70% to 100% of the substrate length (coat width is 30% of the substrate length), consisting only of the first coating layer (C1).

[0090] (2) Evaluation of the exhaust gas purification catalyst The temperature rise behavior of the exhaust gas purification catalyst during manual DPF regeneration was investigated. Specifically, the following operations were performed.

[0091] A dry heat endurance test was conducted on the exhaust gas purification catalyst at 720°C for 33 hours. A 2.8L diesel engine, the exhaust gas purification catalyst after the endurance test, and a diesel particulate filter (DPF) were mounted on a test bench in that order. Manual DPF regeneration was then performed under the following conditions, and temperatures were measured at points 10mm, 30mm, 45mm, 60mm, and 80mm from the upstream end face of the exhaust gas purification catalyst. Temperature measurements were taken near the central axis of the exhaust gas purification catalyst at each measurement point. Furthermore, temperature measurements were taken 300 seconds after the start of fuel addition for DPF regeneration. Intake air mass flow rate Ga: 32 g / second; Exhaust gas purification catalyst entry gas temperature: 252°C; DPF regeneration fuel addition rate: 1.44 L / h

[0092] The results are shown in Table 3 and Figure 3.

[0093] <Examples 2 and Comparative Examples 1-3> Except for the fact that the coating widths of the first coating layer (C1) to the third coating layer (C3) were as shown in Table 2, an exhaust gas purification catalyst device was manufactured in the same manner as in Example 1. Here, the amount (dry mass) of PtPd slurry 2 used to form the first coating layer (C1) and the second coating layer (C2), respectively, and the amount (dry mass) of PtPd slurry 1 used to form the first coating layer (C1), were the same as in Example 1.

[0094] The coating width, coating amount, and specific coating amount of the first coating layer (C1) to the third coating layer (C3) in each exhaust gas purification catalyst device obtained above; and the composition, precious metal amount, and specific precious metal amount of the first to fourth regions are shown in Table 2.

[0095] The evaluation results are shown in Table 3 and Figure 3.

[0096]

[0097]

[0098] From the above results, it was confirmed that the exhaust gas purification catalyst devices of Examples 1 and 2, in which the specific precious metal content is in the order of Region 1 > Region 3 > Region 4 ≥ Region 2, exhibit excellent heating characteristics of the catalyst coating layer, particularly the heating characteristics downstream of the catalyst coating layer.

[0099] Examples 1-3 (1) Exhaust gas purification catalyst manufacturing diameter 143.8 mm, length 90.0 mm, partition wall thickness 0.4 mil (0.1016 mm), and cell count 400 sell / inch ２ (0.620cell / mm ２ A straight-flow honeycomb substrate made of cordierite (apparent capacity 1.5 L) was coated with 75.0 g of PtPd slurry B (containing 0.45 g of Pt and 0.15 g of Pd) over 100% of the substrate length on the cell channel partition wall, and dried at 100°C (first coating layer (C1)).

[0100] Next, 75.0 g of PtPd slurry A (containing 1.125 g of Pt and 0.375 g of Pd) was coated onto the honeycomb substrate from the entrance end face, varying the coating area, and dried at 100°C (third coating layer (C3)). Here, the coating area of ​​PtPd slurry A was 40% of the substrate length in Reference Example 1, 60% of the substrate length in Reference Example 2, and 80% of the substrate length in Reference Example 3.

[0101] The exhaust gas purification catalyst devices for each reference example were manufactured by firing the coated and dried honeycomb substrate in air at 500°C for 2 hours.

[0102] (2) Evaluation of the exhaust gas purification catalyst device Using the obtained exhaust gas purification catalyst device, the temperature rise behavior of the exhaust gas purification catalyst device during manual DPF regeneration was investigated in the same manner as in Example 1, except that the intake air mass flow rate, the gas temperature entering the exhaust gas purification catalyst device, and the amount of fuel added for DPF regeneration were changed as follows: Intake air mass flow rate Ga: 41 g / sec Exhaust gas purification catalyst device temperature: 300°C Amount of fuel added for DPF regeneration: 2.10 L / h

[0103] Table 4 shows the temperature at a point 80 mm from the upstream end face of the exhaust gas purification catalyst at this time.

[0104]

[0105] From the results of the above reference examples, it was found that the first region on the uppermost side of the catalyst coating layer exhibits superior heating characteristics when the amount of noble metal is high, even if the coating area is short.

[0106] 100, 200 Exhaust gas purification catalyst device 110, 210 Substrate 121, 221 First catalyst coating layer 122, 222 Second catalyst coating layer 123, 223 Third catalyst coating layer 131, 231 First region 132, 232 Second region 133, 233 Third region 134, 234 Fourth region

Claims

1. An exhaust gas purification catalyst apparatus having a substrate and a catalyst coating layer on the substrate, wherein the catalyst coating layer has four regions in the order of a first region to a fourth region, starting from the upstream side of the exhaust gas flow, each region of the catalyst coating layer contains a catalyst precious metal, and the specific amount of catalyst precious metal, defined as the value obtained by dividing the mass of the catalyst precious metal contained in each region by the volume of the substrate corresponding to that region, has the relationship first region > third region > fourth region ≥ second region.

2. The exhaust gas purification catalyst device according to claim 1, wherein the specific coating amount, defined as the value obtained by dividing the coating amount of each region by the volume of the substrate that corresponds to that region, has the relationship: first region > third region > fourth region ≥ second region.

3. The exhaust gas purification catalyst device according to claim 1, wherein the amount of specific catalyst noble metal in the third region is 15% or more and 50% or less of the amount of specific catalyst noble metal in the first region.

4. The exhaust gas purification catalyst device according to claim 1, wherein the amount of specific catalyst precious metal in the fourth region and the second region is 25% or more and 75% or less of the amount of specific catalyst precious metal in the third region, respectively.

5. The exhaust gas purification catalyst device according to claim 1, wherein the length of the first region is 15% or more and 60% or less of the total length of the base material.

6. The exhaust gas purification catalyst device according to claim 1, wherein the length of the third region is 3% or more and 30% or less of the total length of the substrate.

7. The exhaust gas purification catalyst device according to claim 1, wherein the amount of specific catalyst precious metal in the third region is 15% or more and 50% or less of the amount of specific catalyst precious metal in the first region, the specific coat amount, defined as the value obtained by dividing the coat amount of each region by the volume of the substrate that corresponds to that region, has the relationship first region > third region > fourth region ≥ second region, the amount of specific catalyst precious metal in the fourth region and the second region is 25% or more and 75% or less of the amount of specific catalyst precious metal in the third region, the length of the first region is 10% or more and 60% or less of the total length of the substrate, and the length of the third region is 5% or more and 30% or less of the total length of the substrate.

8. The exhaust gas purification catalyst device according to any one of claims 1 to 7, wherein the catalyst precious metal is one or two selected from platinum and palladium.

9. The exhaust gas purification catalyst device according to claim 8, which is a diesel oxidation catalyst device.

10. An exhaust gas purification catalyst system comprising an exhaust gas purification catalyst device according to any one of claims 1 to 7 and a diesel particulate filter.

11. The exhaust gas purification catalyst system according to claim 10, wherein the catalytic precious metal in the exhaust gas purification catalyst device is one or two selected from platinum and palladium.

12. The exhaust gas purification catalyst system according to claim 11, wherein the exhaust gas purification catalyst device is a diesel oxidation catalyst device.

13. A method for manufacturing an exhaust gas purification catalyst according to any one of claims 1 to 7, comprising: forming a first catalyst coating layer in a range corresponding to the total length of the third and fourth regions from the downstream end of the exhaust gas flow of the substrate; forming a second catalyst coating layer in a range corresponding to the total length of the first to third regions from the upstream end of the exhaust gas flow of the substrate after the formation of the first catalyst coating layer; and forming a third catalyst coating layer in a range corresponding to the length of the first region from the upstream end of the exhaust gas flow of the substrate after the formation of the first and second catalyst coating layers, wherein the formation order of the first to third catalyst coating layers is either the first catalyst coating layer, the second catalyst coating layer, and the third catalyst coating layer; or the second catalyst coating layer, the first catalyst coating layer, and the third catalyst coating layer; and the first region is formed by laminating the second catalyst coating layer and the third catalyst coating layer. A method for manufacturing an exhaust gas purification catalyst, comprising forming a second region composed of the second catalyst coating layer, a third region composed of the first catalyst coating layer and the second catalyst coating layer stacked on top of each other, wherein each of the first to third catalyst coating layers contains a catalytic precious metal.

14. The manufacturing method according to claim 13, wherein the catalyst precious metal is one or two selected from platinum and palladium.

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