WO2010131369A1 - Catalyseur de purification de gaz d'échappement et son procédé de fabrication - Google Patents

Catalyseur de purification de gaz d'échappement et son procédé de fabrication Download PDF

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Publication number
WO2010131369A1
WO2010131369A1 PCT/JP2009/059096 JP2009059096W WO2010131369A1 WO 2010131369 A1 WO2010131369 A1 WO 2010131369A1 JP 2009059096 W JP2009059096 W JP 2009059096W WO 2010131369 A1 WO2010131369 A1 WO 2010131369A1
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Prior art keywords
catalyst
exhaust gas
layer thickness
layer
catalyst layer
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PCT/JP2009/059096
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English (en)
Japanese (ja)
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智章 砂田
秀章 植野
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トヨタ自動車株式会社
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Priority to PCT/JP2009/059096 priority Critical patent/WO2010131369A1/fr
Publication of WO2010131369A1 publication Critical patent/WO2010131369A1/fr

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J35/00—Catalysts, in general, characterised by their form or physical properties
    • B01J35/50—Catalysts, in general, characterised by their form or physical properties characterised by their shape or configuration
    • B01J35/56—Foraminous structures having flow-through passages or channels, e.g. grids or three-dimensional monoliths
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
    • B01J23/54—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
    • B01J23/56—Platinum group metals
    • B01J23/63—Platinum group metals with rare earths or actinides
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J35/00—Catalysts, in general, characterised by their form or physical properties
    • B01J35/19—Catalysts containing parts with different compositions
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J35/00—Catalysts, in general, characterised by their form or physical properties
    • B01J35/30—Catalysts, in general, characterised by their form or physical properties characterised by their physical properties
    • B01J35/396—Distribution of the active metal ingredient
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/02—Impregnation, coating or precipitation
    • B01J37/0215—Coating
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B38/00—Porous mortars, concrete, artificial stone or ceramic ware; Preparation thereof
    • C04B38/0006—Honeycomb structures
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
    • F01N3/24—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by constructional aspects of converting apparatus
    • F01N3/28—Construction of catalytic reactors
    • F01N3/2803—Construction of catalytic reactors characterised by structure, by material or by manufacturing of catalyst support
    • F01N3/2825—Ceramics
    • F01N3/2828—Ceramic multi-channel monoliths, e.g. honeycombs
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2510/00—Surface coverings
    • F01N2510/06—Surface coverings for exhaust purification, e.g. catalytic reaction
    • F01N2510/068—Surface coverings for exhaust purification, e.g. catalytic reaction characterised by the distribution of the catalytic coatings
    • F01N2510/0682—Surface coverings for exhaust purification, e.g. catalytic reaction characterised by the distribution of the catalytic coatings having a discontinuous, uneven or partially overlapping coating of catalytic material, e.g. higher amount of material upstream than downstream or vice versa

Definitions

  • the present invention relates to an exhaust gas purification catalyst suitable for purifying gas such as NO x contained in exhaust gas, and a method for producing the same.
  • a purification catalyst having a two-layer structure for example, in addition to a single layer structure in which a metal component is present in a single layer has been proposed.
  • a catalyst provided with two upper and lower catalyst layers in which Pt and Rh are included in different layers is known in consideration of the influence on catalytic activity due to solid solution of metals.
  • the exhaust gas-purifying catalyst In the exhaust gas-purifying catalyst, heat on the upstream side is easily dissipated to the downstream side, and heat degradation on the upstream side can be suppressed, and a certain degree of improvement is expected in terms of warm-up characteristics.
  • the temperature of the exhaust gas When the temperature of the exhaust gas is low, or when the gas temperature temporarily drops due to exhaust stop due to intermittent operation, etc., the heat retention performance that can maintain the purification activity may not be stably maintained.
  • the catalyst temperature is low immediately after the engine is started, and unpurified exhaust gas tends to flow out until the catalyst is activated.
  • the present invention has been made in view of the above situation. Under these circumstances, it is necessary to provide an exhaust gas purification catalyst that is hardly affected by the exhaust gas emission conditions, can maintain the catalytic activity stably, and maintain the purification performance, and a method for producing the same. ing.
  • the present invention provides the thinnest region (layer thickness Y) in the middle of the catalyst layer in the exhaust gas flow direction, and provides regions that are twice or more thicker than the layer thickness Y on the upstream side and downstream side thereof.
  • the present inventors have obtained knowledge that the balance between heat transfer ability and heat capacity that can enhance early activation and heat retention of the catalyst from a low temperature can be optimized, and is based on such knowledge.
  • the exhaust gas purifying catalyst according to the first aspect of the present invention includes a region having a layer thickness X that is twice or more the thinnest layer thickness Y at the intermediate position between the upstream end surface and the downstream end surface in the exhaust gas flow direction.
  • a catalyst layer having upstream and downstream of the position of the layer thickness Y in the exhaust gas flow direction is provided on the support base material.
  • the thickness Y of the layer is preferably in the range of 10 to 80 ⁇ m.
  • the position of the layer thickness Y is based on the center position at an equal distance L from both ends of the exhaust gas flow direction of the catalyst layer, the position up to L ⁇ 3/10 on the upstream side in the exhaust gas flow direction and L ⁇ 3 on the downstream side. The case where it has between the position to / 10 is preferable.
  • the intermediate position between the upstream end face and the downstream end face includes not only a position equidistant from the upstream end face and the downstream end face, but also an arbitrary position between the upstream end face and the downstream end face.
  • the exhaust gas purification catalyst In the exhaust gas purification catalyst according to the first aspect of the present invention, it is twice the thinnest layer thickness Y provided between the upstream end surface and the downstream end surface of the catalyst layer in the exhaust gas flow direction in which the exhaust gas flows.
  • the regions having the above layer thickness X are provided on the upstream side and the downstream side in the exhaust gas flow direction as viewed from the position of the layer thickness Y, and the thickness of the catalyst layer once decreases from the exhaust gas inflow side and then increases.
  • the catalyst in a low temperature state is activated in a short time, and for example, the engine of a hybrid vehicle in which gas emission stops and the catalyst temperature decreases
  • the heat of the catalyst can be maintained during intermittent stops or during low speed operation in which the catalyst temperature decreases as the exhaust gas temperature decreases.
  • the exhaust gas purifying catalyst of the first invention by providing a region where the layer thickness of the catalyst layer is increased to increase the pressure loss, heat transfer from the exhaust gas to the catalyst layer is accelerated, Since the heat capacity is reduced by providing the thin region having the layer thickness Y, the rate of temperature increase of the catalyst layer can be increased. Further, since the heat capacity is increased by increasing the upstream layer thickness and the downstream layer thickness of the region of the layer thickness Y, the heat is retained even when a relatively low temperature exhaust gas flows, Since the region of thickness Y is the thinnest, heat transfer to the downstream side in the exhaust gas flow direction is reduced, so that a temperature decrease on the downstream side of the region of layer thickness Y can be prevented.
  • the purification catalyst is activated in a short time, and when there is a possibility that the catalyst temperature is lowered, the heat is maintained and the catalyst activity is kept high, and the exhaust gas can be stably purified.
  • the ratio of the layer thickness X to the layer thickness Y is preferably 3.0 or more.
  • X / Y is 3.0 or more, it is possible to expand the catalyst temperature range in which the exhaust gas purification performance can be maintained to the low temperature side. As a result, the influence of the catalyst temperature on the catalyst performance is suppressed, the catalyst activity is kept high, and the exhaust gas can be stably purified.
  • the catalyst layer is provided on the upstream side from an intermediate position between the upstream end surface and the downstream end surface in the exhaust gas flow direction, and the first catalyst layer region in which the layer thickness gradually increases from the layer thickness Y toward the upstream side.
  • a second catalyst layer region which is provided downstream from the intermediate position and whose layer thickness gradually increases from the layer thickness Y toward the downstream side. That is, the volume of the in-cell gas flow passage increases from the upstream end surface in the exhaust gas flow direction toward the region of the layer thickness Y, and the volume decreases from the position of the layer thickness Y toward the downstream end surface.
  • the catalyst layer can be configured in a two-layer structure, and when configured in a two-layer structure, the catalyst layer includes a region having a total thickness of two layers and a layer thickness X that is twice or more the layer thickness Y. be able to.
  • the upper layer or the lower layer, or both the upper layer and the lower layer have a region having a layer thickness X that is twice or more the layer thickness Y, upstream of the position of the layer thickness Y in the exhaust gas flow direction It can be configured in a concave structure provided on the downstream side.
  • the method for producing an exhaust gas purification catalyst according to the second invention comprises a catalyst metal and a thickener, and the ratio of the viscosity b at a solid content of 80% by mass to the viscosity a at a solid content of 20% by mass (b / a ) Is provided at one end of the supporting base material, and the slurry is sucked from the other end, and the layer thickness is from one end of the supporting base material to the one end side from the middle position of the other end.
  • a first step of forming a catalyst layer having a region including a layer thickness X that is twice or more the thinnest layer thickness Y at the intermediate position; and the other end of the support substrate on which the catalyst layer is formed Providing the slurry, sucking the slurry from the one end, and a catalyst layer having a region including a layer thickness X that is twice or more as large as the layer thickness Y from the intermediate position to the other end side; And a second step to be formed.
  • the viscosity a at a solid content of 20% by mass is preferably in the range of 200 to 1000 mPa ⁇ s.
  • a water-soluble polymer can be suitably used.
  • a catalyst layer having a thickness that changes. Thereby, it has the area
  • a catalyst layer can be formed.
  • the slurry provided at one end of the support substrate is sucked from the other end, and the layer thickness is the thinnest layer thickness at the intermediate position from the intermediate position toward the one end.
  • the slurry is provided on the other end of the support substrate on which the catalyst layer is formed, and the slurry is sucked from the one end, A second catalyst layer region in which the layer thickness gradually increases from the layer thickness Y toward the other end from the intermediate position can be formed.
  • the present invention maintains catalytic activity that is easily impaired by the influence of operating conditions such as cold engine start, intermittent engine stop in a hybrid vehicle, and low speed operation, and exhibits stable and excellent exhaust gas purification performance.
  • a purifying system that can do this can be constructed.
  • an exhaust gas purification catalyst that is hardly affected by exhaust gas emission conditions (particularly gas temperature) and that can stably maintain catalytic activity and maintain purification performance, and a method for producing the same. Can do.
  • FIG. 1 is a perspective view showing a schematic structure of an exhaust gas purification catalyst according to a first embodiment of the present invention. It is a perspective view which expands and shows schematic structure of the cell which comprises the exhaust gas purification catalyst of FIG.
  • FIG. 3 is a cross-sectional view taken along line A-A ′ of FIG. 2. It is process drawing for demonstrating the process order which forms the catalyst layer of the exhaust gas purification catalyst of this invention. It is a schematic sectional drawing which shows the internal structure of the cell in the exhaust gas purification catalyst of 2nd Embodiment of this invention. It is a schematic sectional drawing which shows the internal structure of the cell in the exhaust gas purification catalyst of 3rd Embodiment of this invention.
  • the exhaust gas purification catalyst of the present embodiment is a catalyst layer having a single layer structure in which the layer thickness gradually increases from the center position of the catalyst layer that is equidistant from the inflow side end surface and the outflow side end surface of the exhaust gas toward each end surface. Is provided.
  • the exhaust gas purification catalyst 100 of the present embodiment has a plurality of through-holes (cells; hereinafter referred to as “cells”) 11 that divide the interior with walls and penetrate from one end to the other end. And a cylindrical monolith substrate having a porous structure formed thereon. Exhaust gas (gas) flowing in the direction of the arrow flows from one end surface of the cylindrical shape, is purified when flowing through the inside, and the purified gas is discharged from the other end.
  • cells through-holes
  • each cell constituting the exhaust gas purification catalyst 100 is in the half of the inflow side between the exhaust gas inflow end surface 12 and the outflow side end surface 13 with different thickness gradients of the catalyst layer in the cylindrical axial direction.
  • the region 15 and the half 16 on the outflow side are configured.
  • An example of a perspective configuration of each cell of the exhaust gas purification catalyst 100 is shown in FIG.
  • the cell 11 is formed in a cylindrical shape having a quadrangular cross section surrounded by walls on all sides, and exhaust gas can flow through a hollow portion inside the cylinder.
  • the interior of the cell 11 is centered on a position P that is equidistant (distance L) from each of the inflow side end surface 12 and the outflow side end surface 13, toward the inflow side end surface 12 and the outflow side end surface 13.
  • the catalyst layer 17 is formed so that the thickness gradually increases. That is, at the position P, the layer thickness is the thinnest.
  • the catalyst layer 17 is provided on the inner wall surface of the wall 14 forming each cell 11 as shown in FIG.
  • FIG. 3 is a view showing a cross section taken along the line A-A ′ of FIG. 2.
  • the catalyst layer 17 gradually starts from the layer thickness Y at the position P where the thickness is the smallest from the center position P that is equidistant from both end faces of the cell 11 (the inflow end face 12 and the outflow end face 13).
  • the layer thickness is increased. That is, the catalyst layer 17 includes a first catalyst layer region 15a in which the layer thickness gradually increases from the layer thickness Y toward the upstream side from the position P on the upstream side of the position P in the flow direction of the exhaust gas (gas).
  • a second catalyst layer region 16a On the downstream side of P, a second catalyst layer region 16a whose layer thickness gradually increases from the layer thickness Y from the position P toward the downstream side is provided.
  • the layer thickness X of the catalyst layer 17 on both end faces of the cell 11 is formed to be twice or more (X / Y ⁇ 2.0) with respect to the layer thickness Y at the position P.
  • the first catalyst layer region 15a and the second catalyst layer region 16a have the same catalyst configuration.
  • the layer thickness increases from the position P where the layer thickness is the thinnest, and the pressure loss increases.
  • the heat capacity can be reduced, so that the heating rate of the catalyst layer can be increased.
  • the heat capacity is increased by increasing the layer thickness from the layer thickness Y to twice or more in the first catalyst layer region 15a and the second catalyst layer region 16a, so that a relatively low temperature exhaust gas is generated. Even if it flows in, heat is retained.
  • the catalyst temperature tends to be low, but it is possible to activate the catalyst in a low temperature state in a short time.
  • the catalyst temperature is likely to drop when the gas emission is stopped, and during low speed operation, the exhaust gas temperature itself is low and the catalyst temperature is likely to drop. It is possible to maintain heat so that the catalytic activity can be purified.
  • the ratio (X / Y) of the layer thickness X on the upstream side and downstream side of the position P of the thinnest layer thickness Y to the layer thickness Y in the exhaust gas flow direction is 2.0 or more.
  • the ratio X / Y is preferably 3.0 or more.
  • the ratio X / Y is 3.0 or more, particularly when the temperature of the catalyst is raised, it is possible to maintain good purification performance even when the catalyst temperature is relatively low. Therefore, the temperature range in which the purification performance can be maintained is widened under both conditions of temperature rise and temperature fall, and a reduction in the purification performance due to the temperature fluctuation of the catalyst can be suppressed.
  • the ratio X / Y is preferably 3.0 or more, 6.0 or less, more preferably 4.0 or more, and 6.0 or less, and still more preferably 5. It is 0 or more and 6.0 or less.
  • the thinnest layer thickness Y is preferably in the range of 10 to 80 ⁇ m, more preferably in the range of 20 to 60 ⁇ m. If the thickness of the layer thickness Y is 10 ⁇ m or more, more preferably 20 ⁇ m or more, the desired performance can be maintained without impairing the purification efficiency of the exhaust gas flowing in, and if it is 80 ⁇ m or less, further 60 ⁇ m or less, the heat capacity This is advantageous in that becomes smaller.
  • the position of the thinnest layer thickness Y of the catalyst layer may be provided so as to be deviated from the center position equidistant from both end faces toward one end face side, and the same effect as when the layer thickness Y is at the position P is obtained. It is done.
  • the position of the thinnest layer thickness Y is the direction of the exhaust gas flow in the catalyst layer from the viewpoint of rapidly activating the catalyst at low temperatures and enhancing the heat retention when conditions such as the temperature and discharge amount of the exhaust gas fluctuate.
  • the center position P that is equidistant (distance L) from both ends is preferably between the position up to L ⁇ 3/10 on the upstream side and the position up to L ⁇ 3/10 on the downstream side.
  • the case where the layer thickness X in the first catalyst layer region 15a of the catalyst layer 17 and the layer thickness X in the second catalyst layer region 16a are the same has been described as an example.
  • the catalyst layer region 15a and the second catalyst layer region 16a may be configured to have different thicknesses and ratios of increasing thickness.
  • the catalyst layer 17 has a shape in which the thickness gradually increases from the position P toward both end faces as in the present embodiment, and the thickness is a stepped stepwise with a predetermined thickness from the position P toward both end faces.
  • the thickness may be increased, or the thickness may be gradually or stepwise increased from the position P to a predetermined position that does not reach the end face, and after reaching that thickness, the end face may have the same thickness, or a catalyst layer may be provided. No shape is acceptable.
  • the catalyst layer 17 may be configured to be provided on the wall 14 by coating a noble metal having catalytic ability as a catalyst metal.
  • the catalyst layer 17 stores, for example, NO x in an oxygen-excess lean atmosphere, and releases the occluded NO x by changing the exhaust gas atmosphere to a rich atmosphere with excess reducing components such as stoichiometric hydrogen.
  • it can be a NO x storage-and-reduction type of purification catalyst for reducing component is reacted with reduced purification such as HC and CO by the action of the noble metal.
  • noble metals include platinum (Pt), palladium (Rh), rhodium (Rh), and the like.
  • the catalyst layer can contain a NO x storage material such as an alkali metal such as Li, K, Na, Mg, Ca, St, or Ba, or an alkaline earth metal.
  • Pt is excellent in NO oxidation activity.
  • concentration of Pt in the catalyst layer is preferably in the range of 0.1 to 5 g / L from the viewpoint of NO oxidation efficiency. Further, Pd is higher the NO x reduction activity has oxidation activity of NO. Moreover, since Pd is highly stable in a lean atmosphere, the presence of Pd together with Pt can suppress the growth of Pt grains and keep the NO oxidation activity of Pt high.
  • Pt and Pd can be supported on a desired carrier and contained in the catalyst layer.
  • a desired carrier zirconium dioxide (ZrO 2 ), aluminum oxide (Al 2 O 3 ), silica, silica-alumina, ceria (CeO 2 ), oxide particles such as zeolite, and mixed particles thereof can be used.
  • ZrO 2 zirconium dioxide
  • Al 2 O 3 aluminum oxide
  • silica silica-alumina
  • oxide particles such as zeolite, and mixed particles thereof can be used. .
  • Pt-supported oxide particles supporting Pt may be mixed with Pd-supported oxide particles supporting Pd, or both Pt and Pd are supported.
  • Oxide particles may be used.
  • the Pt-supported oxide is, for example, a mixture of an oxide powder or granular material such as ZrO 2 powder and a diammineplatinum dinitrate solution, a platinum chloride solution, an ammineplatinum solution, and the like, followed by drying and firing (for example, 400 to For example, about 800 ° C.).
  • the oxide particles supporting both Pt and Pd are, for example, oxide powder such as ZrO 2 powder and granular materials, diammine platinum nitrate solution, platinum chloride solution, ammine platinum solution, and palladium nitrate. It can be obtained by mixing a solution, a palladium chloride solution and the like, drying, firing (for example, about 400 to 800 ° C.), and the like.
  • Rh is excellent in reducing activity of NO x.
  • the Rh to another layer from the layer containing Pt (preferably supported on a support) by the presence, is suppressed solid solution with Pt, favorably reducing NO x in a rich atmosphere, to purify NO x.
  • Rh can be supported on a desired carrier and contained in the layer, and the same carrier as described above can be used.
  • an Rh-supported oxide carrying Rh is prepared by mixing oxide powder such as ZrO 2 powder or granular material with a rhodium nitrate solution, a rhodium chloride solution, an ammine rhodium solution, and drying and firing (for example, For example, about 400 to 800 ° C.).
  • the first catalyst layer region 15a and the second catalyst layer region 16a of the catalyst layer 17 may have the same or different catalyst composition such as the type and ratio of the catalyst metal contained.
  • the supporting base material supports the catalyst layer, and a known material made of ceramics or metal can be selected depending on the purpose or circumstances. Specific examples include cordierite honeycomb substrates, SiC honeycomb substrates, metal honeycomb substrates, and the like.
  • the exhaust gas purification catalyst 100 includes a catalyst metal and a thickener, and the ratio (b / a) of the viscosity b at a solid content of 80% by mass to the viscosity a at a solid content of 20% by mass is 2.4 or more.
  • this slurry is provided on the exhaust gas inflow end surface 12 of the support base material, and the slurry is sucked from the outflow side end surface 13 which is the other end, whereby the inflow side end surface 12 and the outflow side end surface 13 of the support base material.
  • first catalyst layer region 15a in which the layer thickness gradually increases from the thinnest layer thickness Y at the position P from the center position P that is equidistant to the inflow side end surface 12, respectively.
  • the slurry is provided on the outflow side end surface 13 which is the other end of the support base in which the region 15a is formed, and the slurry is sucked from the inflow side end surface 12 of the exhaust gas, so that the center position P toward the outflow side end surface 13 Layer thickness It can be prepared by providing a step of forming a second catalyst layer region 16a which gradually increases from the thickness Y.
  • slurry is sequentially provided to one end (exhaust gas inflow end surface 12) and the other end (exhaust gas outflow end surface 13) of the support base material. It can be produced by performing an operation of sucking from the side where the slurry is not provided.
  • a holding member 53 that holds a predetermined amount of slurry is provided at one end (an inflow side end surface 12 in FIG. 1) of a support base material 51 such as a monolith base material. After supplying the slurry 52 (I slurry installation; coat (1)), the slurry is sucked from the other end (outflow side end face 13 in FIG. 1) to be absorbed into the supporting substrate (II slurry suction).
  • the holding member 53 covers the end of the support base 51 and holds the slurry supplied from a slurry supply member (not shown) on the end.
  • a slurry supply member (not shown)
  • suction may be performed simultaneously when slurry is supplied to the end face, or suction may be started after a predetermined amount of slurry is supplied to the end face.
  • the catalyst layer can be formed with a distribution in the coat thickness by utilizing the abrupt viscosity change caused by the increase in the solid content.
  • regions having a layer thickness X that is twice or more the layer thickness Y can be formed on the upstream side and the downstream side in the exhaust gas flow direction at the position of the layer thickness Y, respectively.
  • the outflow side end surface 13 that has been sucked is coated with slurry (III slurry installation; Coat (2)) and then sucking from the opposite outflow side end face 12 to absorb the slurry (IV slurry suction).
  • a thickener is used, and a slurry in which the ratio of the viscosity b to the viscosity a (b / a) satisfies b / a ⁇ 2.4 when the solid content changes is used.
  • the slurry includes at least a catalytic metal and a thickener, and generally includes a solvent such as water. Moreover, a slurry can be comprised using another component as needed. Examples of the catalyst metal are as described above. Moreover, the said thickener is a compound which raises the viscosity of a slurry, For example, water-soluble polymers, such as hydroxyethyl cellulose (HEC), carboxymethylcellulose, methylcellulose, polyvinyl alcohol, etc. can be used. The solid content concentration of the slurry is generally adjusted to a range of 20 to 60% by mass.
  • HEC hydroxyethyl cellulose
  • carboxymethylcellulose methylcellulose
  • polyvinyl alcohol polyvinyl alcohol
  • the ratio of the viscosity b at a solid content of 80% by mass (b / a) to the viscosity a at a solid content of 20% by mass is 2.4 or more. If the ratio b / a is less than 2.4, the degree of thickening caused by the increase in the solid content when the slurry is sucked is too small, and 2 for the thinnest layer thickness Y of the catalyst layer. A catalyst layer having a region having a layer thickness more than twice cannot be formed.
  • the content of the thickener in the slurry is preferably 0.5 to 8.0% by mass in a range satisfying the b / a with respect to the total mass of the slurry.
  • the viscosity (25 ° C.) of the slurry used for forming the catalyst layer is preferably 200 to 1000 mPa ⁇ s, and preferably 400 to 800 mPa ⁇ s. More preferred.
  • the viscosity a on the low-viscosity side with a low solid content is 200 mPa ⁇ s or more, more preferably 400 mPa ⁇ s or more, because the amount of solvent (especially water) is not too much, so the viscosity increases rapidly due to moisture absorption. A viscosity change is obtained and the thickness of the catalyst layer is easily changed.
  • the viscosity a is 1000 mPa ⁇ s or less, and further 800 mPa ⁇ s or less, the amount of solvent (especially water) is not small, so that the viscosity change due to moisture absorption is kept large, and from the substrate end face side to the inside It is easy to form a catalyst layer that is inclined toward the surface.
  • the viscosity in the present invention means a viscosity at 25 ° C. when a shear rate of 1 sec ⁇ 1 is applied, and is measured by a TV33 viscometer (manufactured by Toki Sangyo Co., Ltd.).
  • the layer thickness is gradually increased from the center position of the catalyst layer toward the end surface as in the first embodiment.
  • a second catalyst layer is provided to form a two-layer structure.
  • the support substrate and the catalyst layer 17 can be configured in the same manner as in the first embodiment, and the same reference numerals are given to the same components as in the first embodiment, and the details thereof The detailed explanation is omitted.
  • a catalyst layer 22 carrying a noble metal (catalyst metal) having catalytic ability as a first catalyst layer.
  • a noble metal platinum (Pt), palladium (Rh), rhodium (Rh), and the like.
  • the catalyst layer can contain a NO x storage material such as an alkali metal such as Li, K, Na, Mg, Ca, St, or Ba, or an alkaline earth metal.
  • the thickness of the catalyst layer 22 is preferably in the range of 10 to 80 ⁇ m, more preferably in the range of 20 to 60 ⁇ m.
  • each cell constituting the exhaust gas purification catalyst 100 has a first catalyst layer region 15a in which the thickness of the catalyst layer gradually increases from the layer thickness Y toward the upstream side from the position P in the cylindrical axial direction. And a second catalyst layer region 16a in which the thickness of the catalyst layer gradually increases from the layer thickness Y toward the downstream side from the position P.
  • the thickness gradually increases from the inflow side end surface 12 and the outflow side end surface 13 toward the inflow side end surface 12 and the outflow side end surface 13 around the position P that is equidistant (distance L).
  • a third embodiment of the exhaust gas purification catalyst of the present invention will be described with reference to FIG.
  • a catalyst layer having a layer thickness that gradually increases from the center position of the catalyst layer toward the end surface as in the first embodiment Furthermore, a second catalyst layer having no inclination in the layer thickness is provided to form a two-layer structure.
  • the support base material and the catalyst layer 17 can be configured in the same manner as in the first embodiment, and the catalyst layer 22 can be configured in the same manner as in the second embodiment.
  • the same reference numerals are assigned and detailed description thereof is omitted.
  • both end surfaces of the cell 31 are formed on the inner wall surface of the wall 14 forming the cell 31 constituting the exhaust gas purification catalyst as a first catalyst layer.
  • a catalyst layer 17 is provided in which the layer thickness gradually increases from the layer thickness Y at the center position P to more than twice the layer thickness Y from the center position P that is equidistant from the center position toward each end face.
  • a catalyst layer 22 on which a noble metal (catalyst metal) having catalytic ability is supported is provided as a second catalyst layer. Examples of the noble metal and the NO x storage material are as described above.
  • each cell constituting the exhaust gas purification catalyst 100 has a first catalyst layer region 15a in which the thickness of the catalyst layer gradually increases from the layer thickness Y toward the upstream side from the position P in the cylindrical axial direction. And a second catalyst layer region 16a in which the thickness of the catalyst layer gradually increases from the layer thickness Y toward the downstream side from the position P.
  • the thickness gradually increases from the inflow side end surface 12 and the outflow side end surface 13 toward the inflow side end surface 12 and the outflow side end surface 13 around the position P that is equidistant (distance L).
  • a fourth embodiment of the exhaust gas purification catalyst of the present invention will be described with reference to FIG.
  • a catalyst layer having a non-inclined thickness is arranged in a partial region equidistant from the inflow side end surface and the outflow side end surface of the exhaust gas, and the layer thickness is directed to each end surface so as to sandwich the catalyst layer.
  • a catalyst layer that gradually increases in thickness is provided to form a single layer structure.
  • the support base and the catalyst layer 17 can be configured in the same manner as in the first embodiment, and the same reference numerals are given to the same components as in the first embodiment, and detailed description thereof is omitted.
  • the inner wall surface of the wall 14 forming the cell 41 constituting the exhaust gas purification catalyst has a center that is equidistant from both end surfaces (the inflow side end surface 12 and the outflow side end surface 13) of the cell 41.
  • a catalyst layer 17a on which a noble metal (catalytic metal) having catalytic ability is supported is provided in the region. Examples of the noble metal and the NO x storage material are as described above.
  • a catalyst layer 17 having a layer thickness that gradually increases from the end of the catalyst layer 17a is provided between the catalyst layer 17a, the inflow side end surface 12, and the outflow side end surface 13, a catalyst layer 17 having a layer thickness that gradually increases from the end of the catalyst layer 17a is provided.
  • the thickness of the catalyst layer 17a is the thinnest layer thickness Y in the cell, and the layer thickness gradually increases from the layer thickness Y toward both end surfaces of the cell.
  • the layer thickness of the catalyst layer at the outflow side end face 13 is more than twice the layer thickness Y.
  • the interior of each cell constituting the exhaust gas purification catalyst 100 has the first catalyst layer region 15a in which the thickness of the catalyst layer gradually increases from the layer thickness Y on the upstream side in the gas flow direction of the exhaust gas, and the downstream On the side, the second catalyst layer region 16a is formed such that the thickness of the catalyst layer gradually increases from the layer thickness Y.
  • the layer thickness Y can be in the same range as in the first embodiment.
  • the entire catalyst layer is formed so that the thickness gradually increases toward the inflow side end surface 12 and the outflow side end surface 13, so that the catalyst in the low temperature state can be quickly removed as in the first embodiment. It is possible to increase the temperature and activate the catalyst at the same time, improve the heat retaining property of the catalyst, and maintain the catalyst activity in a more stable range.
  • This Rh-supported oxide particle powder B was 60 g / L, a commercially available ⁇ -Al 2 O 3 powder 25 g / L, and hydroxyethyl cellulose in the amount shown in Table 1 below (ratio to the total mass of the slurry [mass%]). (Thickener) and 85 g / L of ion exchange water were mixed to form a slurry. As shown in Table 1 below, the content ratio of the thickener was changed to prepare six types of slurries having a solid content of 20% by mass.
  • each viscosity [mPa ⁇ s] at 25 ° C. when the solid content was adjusted from 20% by mass to 80% by mass every 20% by mass was given a shear rate of 1 sec ⁇ 1. It was measured using a viscometer (manufactured by Toki Sangyo Co., Ltd.). The measurement results are shown in Table 1 below and FIG.
  • the slurries 1 to 5 containing the thickener have a sharp increase in viscosity after the solid content exceeds 40% by mass, compared with the conventional slurry 6 containing no thickener. I understand.
  • a holding member 53 that holds a predetermined amount of slurry as shown in FIG. 4 is attached to one end of the monolith substrate on which the lower catalyst coat layer is formed, and the other end is opened in a substrate receiving portion that communicates with a decompression device (not shown).
  • the inside of the base material can be sucked by decompression.
  • the slurry obtained above was supplied to the attached holding member 53, and the inside of the cell was sucked at a linear velocity of 55 m / s by reducing the pressure.
  • the slurry spread from one end (inflow side end face 12 in FIG. 1) to the center position P by suction. Then, it was dried at 120 ° C.
  • the holding member 53 is attached to the other end of the monolith substrate that has been sucked, and the other end is inserted into the opening of the substrate receiving portion that communicates with the decompression device so that the inside of the substrate can be sucked from the one end.
  • the slurry was sequentially supplied to the holding member 53, and the inside of the cell was sucked at a linear velocity of 55 m / s by reducing the pressure. As shown in FIG. 5, the slurry spreads from the other end (outflow side end face 13 in FIG. 1) to the center position P. Then, it dried at 120 degreeC and further baked at 500 degreeC. In this way, an upper catalyst coat layer (second catalyst layer) having an X / Y gradient described in Table 1 below was formed. The amount of Rh supported was 0.15 g / L.
  • the exhaust gas purification catalyst was placed in the start converter downstream of the engine, the engine was started, and the HC concentration [ppm] in the exhaust gas discharged was measured by MOTOR EXHAUST GAS ANALYZER [manufactured by Horiba, Ltd.].
  • the ratio of the HC gas concentration in the exhaust gas (outflow gas) after purification treatment (purification rate [%]) to the HC gas concentration in the introduced exhaust gas (inflow gas) is calculated from the following formula, and this is the gas purification capacity.
  • the following (1) was evaluated as an index for evaluating.
  • Purification rate [%] 100- ⁇ HC gas concentration in outflow gas / HC gas concentration in inflow gas x 100 ⁇
  • the evaluation was performed by adopting the temperature rise evaluation pattern shown in FIG. 9A and the temperature drop evaluation pattern shown in FIG. 9B. The former can evaluate the early activation of the catalyst, and the latter can evaluate the storage stability of the catalyst.
  • the “50% purification temperature” is the temperature of the inflowing gas when the purification rate becomes 50% in the temperature increase evaluation pattern and the temperature decrease evaluation pattern.
  • the temperature range in which the purification performance can be maintained is widened to the low temperature side as compared with the comparative (conventional) purification catalyst, and the purification performance is reduced due to the temperature drop. Suppressed. For this reason, it is possible to suppress the influence of operating conditions such as when the engine is cold started, when the engine is intermittently stopped in a hybrid vehicle, and during low-speed operation, and to stably exhibit excellent exhaust gas purification performance. Further, as shown in FIG.
  • the slurry prepared to a predetermined b / a value using a thickener has a large viscosity due to an increase in the solid content, and the formation of a catalyst layer having a desired X / Y can be achieved. I was able to do it.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Materials Engineering (AREA)
  • Organic Chemistry (AREA)
  • Ceramic Engineering (AREA)
  • Health & Medical Sciences (AREA)
  • Toxicology (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Structural Engineering (AREA)
  • Catalysts (AREA)
  • Exhaust Gas Treatment By Means Of Catalyst (AREA)

Abstract

L'invention porte sur un catalyseur de purification de gaz d'échappement (100) doté d'une couche de catalyseur (17) ayant une épaisseur de couche augmentant progressivement de la position centrale (P) d'une cellule (11), laquelle position centrale est équidistante d'une surface d'extrémité du côté entrée de gaz d'échappement (12) de la cellule et d'une surface d'extrémité du côté sortie de gaz d'échappement (13) de la cellule, vers les surfaces d'extrémité (12, 13), de sorte que l'épaisseur de la couche est Y, laquelle est la plus petite épaisseur de couche, au niveau de la position centrale (P) et est X, qui est plus grand d'un facteur d'au moins deux par rapport à l'épaisseur de couche Y, au niveau des surfaces d'extrémité (12, 13).
PCT/JP2009/059096 2009-05-15 2009-05-15 Catalyseur de purification de gaz d'échappement et son procédé de fabrication WO2010131369A1 (fr)

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WO2014080554A1 (fr) * 2012-11-20 2014-05-30 トヨタ自動車株式会社 Catalyseur pour le nettoyage de gaz d'échappement
JP2016193390A (ja) * 2015-03-31 2016-11-17 サンノプコ株式会社 増粘剤、排ガス浄化触媒用スラリー及びこの製造方法、並びに内燃機関
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Cited By (14)

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EP2875862B1 (fr) * 2012-11-20 2019-06-05 Toyota Jidosha Kabushiki Kaisha Catalyseur pour le nettoyage de gaz d'échappement
CN104582846A (zh) * 2012-11-20 2015-04-29 丰田自动车株式会社 废气净化用催化剂
US20150238951A1 (en) * 2012-11-20 2015-08-27 Toyota Jidosha Kabushiki Kaisha Exhaust gas catalyst
US9694354B2 (en) * 2012-11-20 2017-07-04 Toyota Jidosha Kabushiki Kaisha Exhaust gas catalyst
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KR20180059895A (ko) * 2015-09-30 2018-06-05 존슨 맛쎄이 퍼블릭 리미티드 컴파니 가솔린 미립자 필터
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JPWO2022209533A1 (fr) * 2021-03-30 2022-10-06
WO2022209533A1 (fr) * 2021-03-30 2022-10-06 三井金属鉱業株式会社 Composition de catalyseur pour purification de gaz d'échappement et catalyseur de purification de gaz d'échappement
JP7278518B2 (ja) 2021-03-30 2023-05-19 三井金属鉱業株式会社 排ガス浄化用触媒組成物及び排ガス浄化用触媒

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