Exhaust gas purification catalyst system

Abstract

To provide an exhaust gas purification catalyst system that is excellent in all of pressure loss properties, warm-up properties, and exhaust gas purification efficiency while using a metal substrate.SOLUTION: An exhaust gas purification catalyst system includes an upstream side exhaust gas purification catalyst device and a downstream side exhaust gas purification catalyst device, wherein the upstream side exhaust gas purification catalyst device has an upstream side substrate and an upstream side catalyst coat layer on the upstream side substrate. The upstream side substrate is constituted by a wound body of a laminate of a planar metal foil and a corrugated metal foil, and the planar metal foil and / or the corrugated metal foil of the upstream side substrate has holes. The downstream side exhaust gas purification catalyst device has a downstream side substrate and a downstream side catalyst coat layer on the downstream side substrate. The downstream side substrate is constituted by a wound body of a laminate of the planar metal foil and the corrugated metal foil, and the planar metal foil and / or the corrugated metal foil of the downstream side substrate has holes. A gap is provided between the upstream side exhaust gas purification catalyst device and the downstream side exhaust gas purification catalyst device.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an exhaust gas purification catalyst system using a metal substrate. [Background technology]

[0002] Exhaust gas emitted from an internal combustion engine such as an automobile engine is purified by an exhaust gas purification catalytic device before being released into the atmosphere. The exhaust gas purification catalytic device is composed of, for example, a honeycomb-shaped substrate and a catalyst coating layer formed on this substrate.

[0003] In exhaust gas purification catalyst devices for internal combustion engines for motorcycles, generators, agricultural machinery, etc., exhaust gas purification catalyst devices using a metal substrate as the honeycomb substrate are widely used.

[0004] For example, Patent Document 1 discloses a metal carrier in which multiple metal honeycomb bodies are bonded via a brazing material within a metal casing, and it is described that such a metal carrier has excellent long-term durability.

[0005] Patent Document 2 discloses a catalyst substrate having a plurality of exhaust gas flow paths, including a first flow path with a closed inlet end and an open outlet end, and a second flow path adjacent to the first flow path and with both the inlet and outlet ends open, with communication holes formed in the wall separating the first and second flow paths. Patent Document 2 explains that an exhaust gas purification catalyst using such a substrate turbulently produces an exhaust gas flow, improving the efficiency of exhaust gas purification. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 8-131845 [Patent Document 2] Japanese Patent Application Laid-Open No. 2015-120134 Summary of the Invention [Problem to be solved by the invention]

[0007] Exhaust gas purification catalyst devices manufactured using conventionally known metal substrates, including the substrates disclosed in Patent Documents 1 and 2, are insufficient in at least one of pressure loss characteristics, warm-up characteristics, and exhaust gas purification efficiency.

[0008] An object of the present invention is to provide an exhaust gas purification catalyst system that uses a metal substrate and is excellent in all of pressure loss characteristics, warm-up characteristics, and exhaust gas purification efficiency. [Means for solving the problem]

[0009] The present invention is as follows.

[0010] Aspect 1: An exhaust gas purification catalyst system including an upstream-side exhaust gas purification catalyst device and a downstream-side exhaust gas purification catalyst device, The upstream exhaust gas purification catalyst device, an upstream substrate; and an upstream catalyst coating layer on the upstream substrate; the upstream substrate is formed of a wound laminate of a flat metal foil and a corrugated metal foil, At least one of the flat metal foil and the corrugated metal foil constituting the upstream base material has holes, the downstream exhaust gas purification catalyst device, a downstream substrate and a downstream catalyst coating layer on the downstream substrate; the downstream-side substrate is composed of a wound laminate of a flat metal foil and a corrugated metal foil, At least one of the flat metal foil and the corrugated metal foil constituting the downstream-side base material has holes, and a gap is provided between the upstream catalytic converter and the downstream catalytic converter; Exhaust gas purification catalyst system. Aspect 2: The exhaust gas purification catalyst system according to aspect 1, wherein the porosity of the upstream substrate is equal to or greater than the porosity of the downstream substrate. Aspect 3: The exhaust gas purification catalyst system according to aspect 1, wherein the gap between the upstream-side exhaust gas purification catalyst device and the downstream-side exhaust gas purification catalyst device is 5 mm or more. Aspect 4: The exhaust gas purification catalyst system according to aspect 3, wherein the gap between the upstream-side exhaust gas purification catalyst device and the downstream-side exhaust gas purification catalyst device is 150 mm or less. Aspect 5: The exhaust gas purification catalyst system according to aspect 2, wherein the gap between the upstream-side exhaust gas purification catalyst device and the downstream-side exhaust gas purification catalyst device is 5 mm or more. Aspect 6: The exhaust gas purification catalyst system according to aspect 5, wherein the gap between the upstream-side exhaust gas purification catalyst device and the downstream-side exhaust gas purification catalyst device is 150 mm or less. Aspect 7: The catalyst system for purifying exhaust gas according to any one of Aspects 1 to 6, wherein the upstream-side catalyst device for purifying exhaust gas and the downstream-side catalyst device for purifying exhaust gas are mounted in an outer cylinder. Aspect 8: A substrate set for use in the exhaust gas purification catalyst system according to any one of Aspects 1 to 6, comprising: the substrate set includes an upstream substrate and a downstream substrate; The upstream substrate is It is composed of a rolled laminate of flat metal foil and corrugated metal foil, At least one of the flat metal foil and the corrugated metal foil has holes, The downstream substrate is It is composed of a rolled laminate of flat metal foil and corrugated metal foil, At least one of the flat metal foil and the corrugated metal foil has holes. Base material set. Aspect 9: The catalyst system for exhaust gas purification according to any one of Aspects 1 to 6 is disposed in an exhaust system of an internal combustion engine so that the upstream catalyst device for exhaust gas purification is located upstream of the exhaust gas flow; and contacting the exhaust gas emitted from the internal combustion engine; A method for purifying exhaust gas, comprising: Aspect 10: The exhaust gas purification method according to Aspect 9, wherein the internal combustion engine is an engine of an automobile or a motorcycle. [Effects of the Invention]

[0011] According to the present invention, there is provided an exhaust gas purification catalyst system that uses a metal substrate and yet is excellent in all of pressure loss characteristics, warm-up characteristics, and exhaust gas purification efficiency. DETAILED DESCRIPTION OF THE INVENTION

[0012] <Exhaust gas purification catalyst system> The exhaust gas purification catalyst system of the present invention comprises: An exhaust gas purification catalyst system including an upstream-side exhaust gas purification catalyst device and a downstream-side exhaust gas purification catalyst device, The upstream exhaust gas purification catalyst device an upstream substrate and an upstream catalyst coating layer on the upstream substrate; the upstream substrate is composed of a wound laminate of a flat metal foil and a corrugated metal foil; At least one of the flat metal foil and the corrugated metal foil constituting the upstream base material has holes, The downstream exhaust gas purification catalyst device a downstream substrate and a downstream catalyst coating layer on the downstream substrate; the downstream-side substrate is composed of a wound laminate of a flat metal foil and a corrugated metal foil; At least one of the flat metal foil and the corrugated metal foil constituting the downstream-side base material has holes, and A gap is provided between the upstream exhaust gas purification catalyst device and the downstream exhaust gas purification catalyst device. It is an exhaust gas purification catalyst system.

[0013] In the exhaust gas purification system of the present invention, both the upstream substrate and the downstream substrate have holes, and there is a gap between the upstream catalytic device for exhaust gas purification and the downstream catalytic device for exhaust gas purification. Due to these features, the exhaust gas purification system of the present invention has at least the following advantages. (1) Because it has holes, it has a small heat capacity and is easy to warm up. (2) Because there is a gap between the upstream-side exhaust gas purification catalyst device and the downstream-side exhaust gas purification catalyst device, the upstream-side exhaust gas purification catalyst device is warmed up intensively without the heat from the exhaust gas being lost to the downstream-side exhaust gas purification catalyst device when the engine is cold. (3) The presence of holes makes the exhaust gas flow turbulent, improving the contact efficiency between the exhaust gas and the purification active species in the catalyst coating layer, thereby demonstrating excellent exhaust gas purification performance with a small amount of catalyst.

[0014] <Upstream exhaust gas purification catalyst device> In the exhaust gas purification catalyst system of the present invention, the upstream exhaust gas purification catalyst device is an upstream substrate and an upstream catalyst coating layer on the upstream substrate; the upstream substrate is composed of a wound laminate of a flat metal foil and a corrugated metal foil; At least one of the flat metal foil and the corrugated metal foil that constitute the upstream base material has holes.

[0015] (Upstream substrate) The upstream substrate is formed of a wound laminate of flat metal foil and corrugated metal foil, and at least one of the flat metal foil and the corrugated metal foil has holes. Both the flat metal foil and the corrugated metal foil constituting the upstream substrate may have holes.

[0016] -Flat metal foil- When the flat metal foil has holes, the shape of the holes may be, for example, circular, elliptical, polygonal, irregular, or a combination of these. The holes present in the flat metal foil may all have the same shape, or may have holes of different shapes. The holes may be present uniformly over the entire surface of the flat metal foil, or may be present with an uneven distribution.

[0017] The holes may or may not be present at the ends of the flat metal foil. For example, the holes may not be present within a range of 1 mm or more, 3 mm or more, 5 mm or more, or 10 mm or more from the outer edges of the two sides that will become the end faces when the rectangular metal foil is rolled up, and 30 mm or less, 25 mm or less, 20 mm or less, 15 mm or less, or 10 mm or less from the outer edges of the two sides that will become the end faces when the rectangular metal foil is rolled up. For example, the holes may be present up to the ends of the two sides that will be parallel to the axis when the rectangular metal foil is rolled up.

[0018] The flat metal foil may be an expanded metal.

[0019] The equivalent circular diameter of the hole may be, for example, 5.0 mm or more, 7.5 mm or more, 10.0 mm or more, or 12.5 mm or more, and may be, for example, 20.0 mm or less, 17.5 mm or less, 15.0 mm or less, or 12.5 mm or less. By setting the equivalent circular diameter of the hole in the flat metal foil within this range, the exhaust gas passing through the upstream substrate can be moderately turbulent, the contact probability between the exhaust gas and the upstream catalyst coating layer can be increased, and the strength of the upstream substrate is not impaired. In this specification, the equivalent circular diameter of the hole means the diameter of a circle having the same area as the area of ​​the hole.

[0020] The porosity of the flat metal foil may be, for example, 10.0% or more, 15.0% or more, 20.0% or more, or 25.0% or more, or 50.0% or less, 45.0% or less, 40.0% or less, 35.0% or less, or 30.0% or less. By setting the porosity within this range, the exhaust gas passing through the upstream substrate can be moderately turbulent, an area other than the holes for forming the upstream catalyst coating layer can be secured, and the strength of the upstream substrate is not impaired. In this specification, the porosity of the metal foil refers to the ratio of the total area of ​​the holes to the total area of ​​the metal foil (the area of ​​the metal foil assuming that the metal foil has no holes). Furthermore, if there is a region at the end of the metal foil where no holes exist, the area of ​​this region is also included in the calculation of the porosity.

[0021] -Corrugated metal foil- The corrugated metal foil is a metal foil that has been corrugated. The wave pitch may be, for example, 2.0 mm or more and 5.0 mm or less, and the wave depth may be, for example, 0.5 mm or more and 3.0 mm or less. In this specification, the wave pitch refers to the distance between two adjacent wave crests, and the wave depth refers to the distance from the wave crest to the wave trough.

[0022] When the corrugated metal foil has holes, the same description as for the flat foil having holes may be applied to the shape and distribution of the holes. As in the case of the flat foil, the holes in the corrugated metal foil do not have to be present at the edges of the foil.

[0023] The corrugated metal foil may be, for example, an expanded metal that has been processed into a corrugated shape.

[0024] The equivalent circle diameter of the holes in the corrugated metal foil may be 1.0 mm or more, 2.0 mm or more, 3.0 mm or more, or 4.0 mm or more, and may be, for example, 8.0 mm or less, 6.0 mm or less, 5.5 mm or less, or 5.0 mm or less. By setting the equivalent circle diameter of the holes in the corrugated metal foil within this range, the exhaust gas passing through the upstream substrate can be appropriately turbulent, the probability of contact between the exhaust gas and the upstream catalyst coating layer can be increased, and the strength of the upstream substrate can be maintained.

[0025] The equivalent circular diameter of the holes in the corrugated metal foil may be smaller than the equivalent circular diameter of the holes in the flat metal foil. The smaller equivalent circular diameter of the holes in the corrugated metal foil than the equivalent circular diameter of the holes in the flat metal foil achieves both low pressure loss and high exhaust gas purification performance. This is thought to be because, when the holes in the corrugated metal foil are enlarged, the pressure loss decreases and the exhaust gas purification performance also decreases, whereas when the holes in the flat metal foil are enlarged, the pressure loss decreases without significantly decreasing the exhaust gas purification performance. Therefore, by adjusting the equivalent circular diameters of the holes in both metal foils to the above-mentioned size relationship, it is thought that an exhaust gas purification catalyst device with an excellent balance between pressure loss and exhaust gas purification performance can be obtained. The equivalent circle diameter of the holes in the corrugated metal foil may be, for example, 80% or less, 60% or less, 50% or less, 45% or less, 40% or less, or 35% or less of the equivalent circle diameter of the holes in the flat metal foil, and may be, for example, 10% or more, 15% or more, 20% or more, 25% or more, or 30% or more.

[0026] The corrugated metal foil may have an aperture ratio of, for example, 15.0% or more, 20.0% or more, 25.0% or more, or 30.0% or more, or 60.0% or less, 50.0% or less, 40.0% or less, or 35.0% or less. By setting the aperture ratio within this range, exhaust gas passing through the upstream substrate can be appropriately turbulent, an area other than the holes for forming the upstream catalyst coating layer can be secured, and the strength of the upstream substrate is not impaired.

[0027] The porosity of the corrugated metal foil may be greater than that of the flat metal foil, and may be, for example, 105% or more, 110% or more, or 115% or more, or 150% or less, 140% or less, 130% or less, or 120% or less, based on the porosity of the flat metal foil.

[0028] -Metal foil material and thickness- The exhaust gas purification catalyst system of the present invention is intended to be placed in the exhaust system of an internal combustion engine and to be in direct contact with the exhaust gas emitted from the internal combustion engine. Therefore, the flat metal foil and corrugated metal foil constituting the upstream substrate of the exhaust gas purification catalyst system are desired to have heat resistance capable of withstanding the temperature of the exhaust gas emitted from the internal combustion engine. Furthermore, the flat metal foil and corrugated metal foil are desired to have processability capable of forming predetermined holes. Furthermore, they are desired to be stable against various chemical species contained in the exhaust gas.

[0029] From these viewpoints, the flat metal foil and the corrugated metal foil may each be made of, for example, stainless steel, which may be, for example, ferritic stainless steel or austenitic stainless steel.

[0030] The thickness of the flat metal foil and the corrugated metal foil may be, for example, 20 μm or more, 40 μm or more, 80 μm or more, or 100 μm or more, and may be 500 μm or less, 300 μm or less, 200 μm or less, 100 μm or less, or 80 μm or less.

[0031] -Wound body- The upstream substrate in the present invention is composed of a wound laminate of a flat metal foil and a corrugated metal foil. The axis of this wound laminate may be parallel to the wave direction of the corrugated sheet (the direction of the ridges of the corrugated sheet where no curvature exists). The wound laminate, as observed from the axial direction of the wound laminate, may be wound in any manner, such as a spiral, S-shape, or Tomoe-shape.

[0032] In the upstream substrate, in the wound body, cell flow paths are formed in the gaps between the corrugations of the corrugated metal foil and the flat metal foil, allowing exhaust gas to flow in the corrugation direction of the corrugated metal foil. The number of cell flow paths in the upstream substrate may be, for example, 50 cells / square inch or more, 80 cells / square inch or more, 100 cells / square inch or more, 150 cells / square inch or more, 200 cells / square inch or more, or 300 cells / square inch or more, or may be, for example, 600 cells / square inch or less, 400 cells / square inch or less, 300 cells / square inch or less, 200 cells / square inch or less, or 150 cells / square inch or less.

[0033] -Upstream catalyst coating layer- The upstream catalyst coating layer is present on the upstream substrate. Specifically, the upstream catalyst coating layer is formed on each surface of the flat metal foil and the corrugated metal foil that constitute the upstream substrate so as to protrude toward the cell flow path side. The holes in the flat metal foil and the corrugated metal foil that constitute the upstream substrate do not need to have the upstream catalyst coating layer.

[0034] The upstream catalyst coating layer may have a structure known in the field of exhaust gas purification catalyst devices. The upstream catalyst coating layer may contain, for example, inorganic oxide particles and catalytic noble metal particles, and may contain other optional components as desired.

[0035] The inorganic oxide particles may be, for example, particles of alumina, zirconia, silica, titania, ceria, rare earth oxides other than ceria, etc., or composite oxides composed of a plurality of these, and one or more selected from these may be used. The catalytic noble metal may be, for example, a platinum group metal, specifically, for example, platinum, palladium, rhodium, etc., and one or more selected from these may be used. The catalytic noble metal may be in the form of fine particles and supported on one or more of the inorganic oxide particles described above.

[0036] The coating amount of the upstream catalyst coating layer and the amount of the catalytic precious metal may be appropriately determined by a person skilled in the art, taking into consideration the purpose of use of the exhaust gas purification catalyst system, the desired purification performance, etc. The coating amount of the upstream catalyst coating layer may be, for example, 50 g / L or more and 250 g / L or less in terms of the mass of the upstream catalyst coating layer per unit volume of the upstream substrate. The amount of the catalytic precious metal may be, for example, 0.1 g / L or more and 5.0 g / L or less in terms of the total metal-equivalent mass of the catalytic precious metal per unit volume of the upstream substrate.

[0037] -Length of upstream exhaust gas purification catalyst device- The length of the upstream catalytic device for exhaust gas purification (length in the direction of exhaust gas flow) may be appropriately determined by a person skilled in the art, taking into consideration the intended use of the catalytic system for exhaust gas purification of the present invention, etc.

[0038] The embodiment of the catalyst system for exhaust gas purification of the present invention, in which the upstream-side catalyst device for exhaust gas purification and the downstream-side catalyst device for exhaust gas purification are collectively loaded into a single outer casing, has the advantage that it can be handled in the same manner as a single catalyst device for exhaust gas purification. In this case, if the length of the catalyst system for exhaust gas purification is set to be approximately the same as that of an existing catalyst device for exhaust gas purification, it becomes possible to replace the existing catalyst device for exhaust gas purification with the catalyst system for exhaust gas purification of the present invention.

[0039] Taking such applications into consideration, the length of the upstream exhaust gas purification catalyst device may be, for example, 30 mm or more, 40 mm or more, 50 mm or more, 60 mm or more, 80 mm or more, or 100 mm or more, and may be, for example, 150 mm or less, 120 mm or less, 100 mm or less, 80 mm or less, 70 mm or less, or 60 mm or less.

[0040] <Downstream exhaust gas purification catalyst device> In the exhaust gas purification catalyst system of the present invention, the downstream exhaust gas purification catalyst device is a downstream substrate and a downstream catalyst coating layer on the downstream substrate; the downstream-side substrate is composed of a wound laminate of a flat metal foil and a corrugated metal foil; At least one of the flat metal foil and the corrugated metal foil that constitute the downstream-side base material has holes.

[0041] Downstream exhaust gas purification catalyst device A flat metal foil and a corrugated metal foil constituting a downstream-side substrate; The holes in these metal foils, A roll of a laminate of flat metal foil and corrugated metal foil constituting a downstream base material, and a downstream catalyst coating layer; and Length of downstream exhaust gas purification catalyst device The same explanation as given for the upstream exhaust gas purification catalytic device may be applied to each of the above.

[0042] The flat metal foil, corrugated metal foil, holes, laminate wound body configuration, and downstream catalyst coating layer of the downstream exhaust gas purification catalyst device may each be the same as or different from the corresponding parts of the upstream exhaust gas purification catalyst device.

[0043] <Opening ratio of upstream substrate and downstream substrate> In the exhaust gas purification catalyst system of the present invention, the porosity of the upstream substrate may be equal to or greater than the porosity of the downstream substrate, i.e., the porosity of the upstream substrate may be the same as or greater than the porosity of the downstream substrate.

[0044] In such an embodiment, the heat capacity of the upstream substrate can be effectively reduced while maintaining the effect of turbulence in the exhaust gas flow due to the formation of holes, thereby obtaining an exhaust gas purification catalyst system with excellent warm-up properties.

[0045] In this specification, the open area ratios of the upstream substrate and the downstream substrate refer to the ratio of the total area of ​​the holes in the flat metal foil and the corrugated metal foil to the total area of ​​the flat metal foil and the corrugated metal foil (the total area of ​​the metal foils when it is assumed that both metal foils have no holes). Furthermore, when there is a region at the end of each metal foil where no holes exist, the area of ​​this region is to be included in the calculation of the open area ratio.

[0046] The porosity of the downstream substrate may be, for example, 100% or less, less than 100%, 95% or less, 90% or less, 85% or less, 80% or less, or 75% or less of the porosity of the upstream substrate, or may be, for example, 40% or more, 50% or more, 60% or more, 70% or more, or 80% or more. By setting the porosity ratio of the two substrates within the above range, it is possible to ensure the area for forming the downstream catalyst coating layer while maintaining a balance between the turbulence of the exhaust gas flow and the warm-up ability of the exhaust gas purification catalyst system, thereby achieving a high level of exhaust gas purification performance.

[0047] <Gap between the upstream exhaust gas purification catalyst device and the downstream exhaust gas purification catalyst device> The exhaust gas purification catalyst system of the present invention has a gap between the upstream-side exhaust gas purification catalyst device and the downstream-side exhaust gas purification catalyst device. The existence of the gap between the upstream-side exhaust gas purification catalyst device and the downstream-side exhaust gas purification catalyst device allows the upstream-side exhaust gas purification catalyst device to be warmed up intensively during cold conditions, such as when starting the engine, without allowing heat from the exhaust gas to escape to the downstream-side exhaust gas purification catalyst device. Therefore, the exhaust gas purification catalyst system of the present invention has extremely high warm-up characteristics during cold conditions.

[0048] It is considered that the gap between the upstream catalytic device for exhaust gas purification and the downstream catalytic device for exhaust gas purification should be large from the viewpoint of suppressing heat dissipation when the device is cold, and should be small from the viewpoint of warming up the downstream catalytic device for exhaust gas purification. From this viewpoint, the gap between the upstream catalytic device for exhaust gas purification and the downstream catalytic device for exhaust gas purification may be, for example, 5 mm or more, 7 mm or more, 10 mm or more, 15 mm or more, 20 mm or more, 30 mm or more, 40 mm or more, or 50 mm or more, and may be, for example, 150 mm or less, 120 mm or less, 100 mm or less, 80 mm or less, 60 mm or less, 40 mm or less, 30 mm or less, 25 mm or less, 20 mm or less, or 15 mm or less.

[0049] <Outer barrel> In the exhaust gas purification catalyst system of the present invention, the upstream catalytic device for exhaust gas purification and the downstream catalytic device for exhaust gas purification may be loaded into an outer casing. The upstream catalytic device for exhaust gas purification and the downstream catalytic device for exhaust gas purification loaded into the outer casing may be fixed to the outer casing by an appropriate means such as fusion welding (arc welding, laser welding, etc.), pressure welding (resistance welding, diffusion bonding, etc.), or brazing (induction heating brazing, laser brazing, etc.).

[0050] The upstream catalytic converter and the downstream catalytic converter may be mounted in separate outer casings, or both may be mounted together in a single outer casing. Mounting the upstream catalytic converter and the downstream catalytic converter together in a single outer casing has the advantage that the entire system can be handled in the same way as a single catalytic converter.

[0051] The size of the outer cylinder may be appropriately set by a person skilled in the art within a range that allows the upstream exhaust gas purification catalytic device and the downstream exhaust gas purification catalytic device to be loaded and that substantially no gaps occur between each exhaust gas purification catalytic device and the inner surface of the outer cylinder.

[0052] When the upstream catalytic converter and the downstream catalytic converter are mounted in separate outer casings, the lengths of the upstream catalytic converter and the downstream catalytic converter may be substantially the same as the lengths of the corresponding catalytic converters. In this case, the lengths of the upstream and downstream catalytic converters may be, for example, 30 mm or more, 40 mm or more, 50 mm or more, 60 mm or more, 80 mm or more, or 100 mm or more, and may be, for example, 150 mm or less, 120 mm or less, 100 mm or less, 80 mm or less, 70 mm or less, or 60 mm or less.

[0053] On the other hand, when the upstream catalytic converter and the downstream catalytic converter are mounted together in a single outer casing, the length of the outer casing may be substantially equal to the total length of the upstream catalytic converter and the downstream catalytic converter plus the length of the gap between the two catalytic converters. In this case, the length of the outer casing may be appropriately set within the range of, for example, 65 mm to 450 mm.

[0054] Furthermore, as described above, if the upstream exhaust gas purification catalyst device and the downstream exhaust gas purification catalyst device are loaded together into one outer cylinder, and the length of the exhaust gas purification catalyst system (i.e., the length of the outer cylinder) is set to be approximately the same as that of an existing exhaust gas purification catalyst device, it will be possible to replace the existing exhaust gas purification catalyst device with the exhaust gas purification catalyst system of the present invention.

[0055] Taking such applications into consideration, the length of the outer cylinder may be determined appropriately within the range of, for example, 65 mm or more and 200 mm or less.

[0056] The outer casing, like the upstream and downstream exhaust gas purification catalyst devices, is required to have heat resistance capable of withstanding the temperature of the exhaust gas, suitable workability, stability against chemical species in the exhaust gas, and the like.

[0057] From these viewpoints, the outer cylinder may be made of, for example, stainless steel. This stainless steel may be, for example, ferritic stainless steel, austenitic stainless steel, etc. The outer cylinder may be made of the same material as the metal foils that constitute the upstream-side catalytic device for purifying exhaust gas and the downstream-side catalytic device for purifying exhaust gas, or may be made of a different material.

[0058] The thickness of the outer cylinder may be, for example, 0.5 mm or more, 1.0 mm or more, or 1.2 mm or more, and may be 5.0 mm or less, 3.0 mm or less, 2.0 mm or less, or 1.5 mm or less.

[0059] <<Substrate set>> According to another aspect of the present invention, there is provided a substrate set for use in the above-mentioned catalyst system for purifying exhaust gases of the present invention.

[0060] The substrate set of the present invention includes an upstream substrate and a downstream substrate, The upstream substrate is It is composed of a rolled laminate of flat metal foil and corrugated metal foil, At least one of the flat metal foil and the corrugated metal foil has holes, The downstream substrate is It is composed of a rolled laminate of flat metal foil and corrugated metal foil, At least one of the flat metal foil and the corrugated metal foil has holes. This is a substrate set.

[0061] The substrate set of the present invention may be loaded into an outer cylinder.

[0062] The descriptions of the upstream and downstream substrates and the outer casing in the substrate set of the present invention for the corresponding parts in the exhaust gas purification catalyst system of the present invention may be applied as they are.

[0063] <Exhaust gas purification method> According to yet another aspect of the present invention, there is provided a method for purifying exhaust gases using the above-mentioned catalyst system for purifying exhaust gases of the present invention.

[0064] The method for purifying exhaust gas of the present invention comprises disposing the exhaust gas purification catalyst system of the present invention in the exhaust system of an internal combustion engine so that the upstream exhaust gas purification catalyst device is located upstream of the exhaust gas flow; Contact with exhaust gases emitted from an internal combustion engine The exhaust gas purification method includes the steps of:

[0065] The internal combustion engine may be, for example, an automobile engine, a motorcycle engine, a utility engine, etc., and in particular may be an automobile or motorcycle engine. [Example]

[0066] Example 1 (1) Manufacturing of upstream exhaust gas purification catalyst devices A flat plate with holes and a corrugated plate with holes are laminated together, and the diameter is 73.3 mm (cross-sectional area is 4,220 mm 2 ), wound into a size of 60 mm in length and 253 mL in apparent volume, inserted into a stainless steel outer cylinder with an outer diameter of 76.3 mm and a wall thickness of 1.5 mm, and fixed by brazing to form a cell count of 400 cells / inch. 2 The upstream substrate was prepared. Both the flat plate and corrugated plate used here were made of SUS with a thickness of 50 μm. The diameter of the holes in the flat plate was 13.0 mm, and the diameter of the holes in the corrugated plate was 4.5 mm. The aperture ratio of the flat plate was 26.0%, and the aperture ratio of the corrugated plate was 34.2%, with the average aperture ratio of the flat plate and the corrugated plate being 30.9%.

[0067] An upstream catalyst coating layer-forming coating liquid containing alumina particles, ceria-zirconia composite oxide particles (ceria content 40% by mass), and a Pt precursor compound and a Rh precursor compound was applied to the obtained upstream substrate and fired to form an upstream catalyst coating layer, thereby obtaining an upstream exhaust gas purification catalyst device.

[0068] The coating amount of the upstream catalyst coating layer in the upstream exhaust gas purification catalyst device was 110 g / L, the amount of Pt was 0.5 g / L, and the amount of Rh was 0.3 g / L.

[0069] (2) Manufacturing of downstream exhaust gas purification catalyst devices The downstream exhaust gas purification catalyst device was manufactured in the same manner as the upstream exhaust gas purification catalyst device, except that the coating liquid for forming the upstream catalyst coat layer obtained above was used as the coating liquid for forming the downstream catalyst coat layer.

[0070] (3) Manufacturing of exhaust gas purification catalyst systems The upstream and downstream catalytic converters were then loaded into a stainless steel outer cylinder to produce a catalytic converter system for exhaust gas purification, with a gap of 10 mm between the upstream and downstream catalytic converters.

[0071] (4) Evaluation of exhaust gas purification catalyst systems i) Pressure loss evaluation Pressure gauges were installed on the upstream side (inlet gas side) and downstream side (outlet gas side) of the exhaust gas purification system, and the difference between the upstream pressure and the downstream pressure was measured when air was flowing from the upstream side at a space velocity SV = 100,000 (1 / h), and the obtained value was taken as the pressure loss.

[0072] ii) Warm-up characteristic test (bench evaluation) A switchable branch was installed in the exhaust system of a 2.4L gasoline engine. One branch was equipped with an exhaust gas purification catalyst system, and the other branch was an open system. The exhaust gas purification catalyst system was heated with a heater to a temperature of 50°C.

[0073] With the branch switched to the open system side, the engine was started and operated under stoichiometric conditions with an engine speed of 2,500 rpm and an air intake rate of 22.5 g / sec. When the exhaust gas temperature reached 530°C, the branch was switched to the engine side. The engine continued to operate under stoichiometric conditions, and the time from switching the branch to reaching a 50% purification rate for CO, total hydrocarbons (THC), and NOx in the exhaust gas was measured.

[0074] iii) Vehicle evaluation of THC emissions The resulting exhaust gas purification catalyst system was installed in the exhaust system of a motorcycle equipped with an 845cc gasoline engine, and the vehicle was run on a chassis dynamometer in WMTC mode, class 3-2, to examine total hydrocarbon (THC) emissions.

[0075] Comparative Example 1 (1) Manufacturing of upstream exhaust gas purification catalyst devices In the same manner as in Example 1, an upstream catalytic converter for purifying exhaust gas was manufactured.

[0076] (2) Manufacturing of downstream exhaust gas purification catalyst devices The downstream substrate was prepared in the same manner as the upstream catalytic converter for purifying exhaust gas, except that a flat plate and a corrugated plate made of SUS with a thickness of 50 μm and no holes were used.

[0077] A downstream-side catalyst coating layer-forming coating liquid having the same composition as the upstream-side catalyst coating layer-forming coating liquid, except for changing the amounts of the Pt precursor compound and the Rh precursor compound, was applied to the obtained downstream-side substrate and baked to form a downstream-side catalyst coating layer, thereby obtaining a downstream-side exhaust gas purification catalyst device.

[0078] The coating amount of the downstream catalyst coating layer in the downstream exhaust gas purification catalyst device was 160 g / L, the Pt amount was 0.5 g / L, and the Rh amount was 0.3 g / L. These Pt and Rh amounts are all expressed in terms of metal mass.

[0079] Comparative Example 2 An exhaust gas purification catalyst system was manufactured and evaluated in the same manner as in Example 1, except that the upstream substrate was a laminated wound body of a flat plate without holes and a corrugated plate with holes, similar to the downstream substrate, and the coating amount, Pt amount, and Rh amount of the upstream catalyst coating layer of the upstream exhaust gas purification catalyst device were changed to be the same as those of the downstream exhaust gas purification catalyst device.

[0080] The above results are summarized in Tables 1 and 2 below.

[0081] [Table 1]

[0082] [Table 2]

[0083] From Tables 1 and 2, it was verified that the exhaust gas purification catalyst system of Example 1, which used a laminated wound body of a flat plate with holes and a corrugated plate with holes as the upstream and downstream substrates, was comprehensively superior in pressure loss, warm-up characteristics, and THC emissions (assessed on an actual vehicle) compared to the exhaust gas purification catalyst system of Comparative Example 1, in which the downstream substrate had no holes, and the exhaust gas purification catalyst system of Comparative Example 2, in which neither the upstream nor downstream substrate had holes. It can be seen that the exhaust gas purification catalyst system of Example 1 is particularly excellent in THC emissions (assessed on an actual vehicle) and is suitable for practical use.

[0084] 《Reference examples 1 to 6》 In Reference Examples 1 to 6, the influence of the length of the gap between the upstream-side catalytic device for purifying exhaust gas and the downstream-side catalytic device for purifying exhaust gas on the exhaust gas purification performance was investigated.

[0085] (1) Manufacturing of upstream and downstream exhaust gas purification catalyst devices For both the upstream-side catalytic device for exhaust gas purification and the downstream-side catalytic device for exhaust gas purification, a laminated wound body of a flat plate and a corrugated plate without holes was used as a substrate. On these substrates, a catalyst coating layer having the same configuration as the downstream-side catalytic coating layer of the downstream-side catalytic device for exhaust gas purification in Example 1 was provided, except that the coating amount, Pt amount, and Rh amount were changed as follows, to manufacture the upstream-side catalytic device for exhaust gas purification and the downstream-side catalytic device for exhaust gas purification. Coating amount: 110g / L Pt amount: 1.0g / L Rh amount: 0.3g / L

[0086] (2) Manufacturing of exhaust gas purification catalyst systems The obtained upstream catalytic device and downstream catalytic device for exhaust gas purification were loaded into an outer cylinder made of SUS to manufacture an exhaust gas purification catalyst system. At this time, a gap shown in Table 3 was provided between the upstream catalytic device and the downstream catalytic device for exhaust gas purification. In Reference Example 1, no gap was provided between the upstream catalytic device and the downstream catalytic device for exhaust gas purification, and the two were loaded into the outer cylinder in a state of contact with each other.

[0087] (3) Evaluation of exhaust gas purification catalyst systems The obtained exhaust gas purification catalyst system was installed in the exhaust system of a motorcycle (scooter) equipped with a 125cc four-stroke gasoline engine, and the vehicle was run on a chassis dynamometer in ECE-40 mode to examine the purification rates of CO, HC, and NOx.

[0088] The results are shown in Table 3.

[0089] [Table 3]

[0090] According to Table 3, it was confirmed that the exhaust gas purification catalyst systems of Reference Examples 2 to 6, in which a gap is provided between the two, exhibit overall superior exhaust gas purification performance compared to the exhaust gas purification catalyst system of Reference Example 1, in which no gap is provided between the upstream exhaust gas purification catalyst device and the downstream exhaust gas purification catalyst device.

Claims

1. An exhaust gas purification catalyst system including an upstream-side exhaust gas purification catalyst device and a downstream-side exhaust gas purification catalyst device, The upstream exhaust gas purification catalyst device, an upstream substrate; and an upstream catalyst coating layer on the upstream substrate; the upstream substrate is formed of a wound laminate of a flat metal foil and a corrugated metal foil, At least one of the flat metal foil and the corrugated metal foil constituting the upstream base material has holes, the downstream exhaust gas purification catalyst device, a downstream substrate and a downstream catalyst coating layer on the downstream substrate; the downstream-side substrate is composed of a wound laminate of a flat metal foil and a corrugated metal foil, At least one of the flat metal foil and the corrugated metal foil constituting the downstream-side base material has holes, and a gap is provided between the upstream catalytic converter and the downstream catalytic converter; Exhaust gas purification catalyst system.

2. 2. The exhaust gas purification catalyst system according to claim 1, wherein the porosity of the upstream substrate is equal to or greater than the porosity of the downstream substrate.

3. 2. The catalyst system for purifying exhaust gas according to claim 1, wherein a gap between the upstream side catalyst device for purifying exhaust gas and the downstream side catalyst device for purifying exhaust gas is 5 mm or more.

4. 4. The catalyst system for purifying exhaust gas according to claim 3, wherein a gap between the upstream side catalyst device for purifying exhaust gas and the downstream side catalyst device for purifying exhaust gas is 150 mm or less.

5. 3. The catalyst system for purifying exhaust gas according to claim 2, wherein a gap between the upstream side catalyst device for purifying exhaust gas and the downstream side catalyst device for purifying exhaust gas is 5 mm or more.

6. 6. The catalyst system for purifying exhaust gas according to claim 5, wherein a gap between the upstream side catalyst device for purifying exhaust gas and the downstream side catalyst device for purifying exhaust gas is 150 mm or less.

7. 7. The exhaust gas purification catalyst system according to claim 1, wherein the upstream side exhaust gas purification catalyst device and the downstream side exhaust gas purification catalyst device are mounted in an outer casing.

8. A substrate set for use in the exhaust gas purification catalyst system according to any one of claims 1 to 6, the substrate set includes an upstream substrate and a downstream substrate; The upstream substrate is It is composed of a rolled laminate of flat metal foil and corrugated metal foil, At least one of the flat metal foil and the corrugated metal foil has holes, The downstream substrate is It is composed of a rolled laminate of flat metal foil and corrugated metal foil, At least one of the flat metal foil and the corrugated metal foil has holes. Base material set.

9. The exhaust gas purification catalyst system according to any one of claims 1 to 6 is disposed in an exhaust system of an internal combustion engine so that the upstream side exhaust gas purification catalyst device is located upstream of the exhaust gas flow; and contacting the exhaust gas emitted from the internal combustion engine; A method for purifying exhaust gas, comprising:

10. The exhaust gas purification method according to claim 9, wherein the internal combustion engine is an engine of an automobile or a motorcycle.

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