US20010021358A1 - Exhaust gas purifying catalyst and method of producing same - Google Patents

Exhaust gas purifying catalyst and method of producing same Download PDF

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Publication number
US20010021358A1
US20010021358A1 US09/794,010 US79401001A US2001021358A1 US 20010021358 A1 US20010021358 A1 US 20010021358A1 US 79401001 A US79401001 A US 79401001A US 2001021358 A1 US2001021358 A1 US 2001021358A1
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coat layer
slurry
catalytic
substrate
catalyst
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Hiroto Kikuchi
Tsuguhiro Ohnuma
Motohisa Kamijo
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Nissan Motor Co Ltd
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Nissan Motor Co Ltd
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Assigned to NISSAN MOTOR CO., LTD. reassignment NISSAN MOTOR CO., LTD. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: KAMIJO, MOTOHISA, KIKUCHI, HIROTO, OHNUMA, TSUGUHIRO
Publication of US20010021358A1 publication Critical patent/US20010021358A1/en
Priority to US11/090,248 priority Critical patent/US7208444B2/en
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases
    • B01D53/94—Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
    • B01D53/9445—Simultaneously removing carbon monoxide, hydrocarbons or nitrogen oxides making use of three-way catalysts [TWC] or four-way-catalysts [FWC]
    • B01D53/945—Simultaneously removing carbon monoxide, hydrocarbons or nitrogen oxides making use of three-way catalysts [TWC] or four-way-catalysts [FWC] characterised by a specific catalyst
    • 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
    • B01J33/00—Protection of catalysts, e.g. by coating
    • 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
    • B01J37/024—Multiple impregnation or coating
    • B01J37/0244—Coatings comprising several layers
    • 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
    • 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
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A50/00—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE in human health protection, e.g. against extreme weather
    • Y02A50/20—Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/10—Internal combustion engine [ICE] based vehicles
    • Y02T10/12—Improving ICE efficiencies
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T29/00—Metal working
    • Y10T29/49—Method of mechanical manufacture
    • Y10T29/49345—Catalytic device making

Definitions

  • This invention relates to improvements in an exhaust gas purifying catalyst for purifying exhaust gas discharged from an internal combustion engine of an automotive vehicle or the like so as to remove HC (hydrocarbons), CO (carbon monoxide) and NOx (nitrogen oxides) from exhaust gas and to a method of producing the exhaust gas purifying catalyst, and more particularly to the exhaust gas purifying catalyst arranged to prevent a catalytic coat layer from being cracked thereby protecting the catalytic coat layer from being peeled off from a substrate such as a ceramic monolithic substrate or a metallic honeycomb-type substrate and to the producing method of such exhaust gas purifying catalyst.
  • a variety of methods of producing exhaust gas purifying catalysts have been proposed and put into practical use, in which a catalytic coat layer is formed on a monolithic substrate such as a ceramic monolithic substrate or a metallic honeycomb-type substrate.
  • a monolithic substrate such as a ceramic monolithic substrate or a metallic honeycomb-type substrate.
  • a compound including alumina and ceria carrying noble metals is mixed with an acetic acid aqueous solution and pulverized to form a catalytic slurry.
  • the catalytic slurry was coated on the ceramic monolithic substrate, followed by drying and firing.
  • Another one is disclosed in Japanese Patent Provisional Publication No.
  • the catalytic slurry largely contracts owing to evaporation of water content at drying and firing steps for fixing the coated catalytic slurry, and therefore a catalytic coat layer formed of the catalytic slurry cannot be endurable to tension generated in the catalytic coat layer.
  • cracks or crazes are produced in the catalytic coat layer formed on the monolithic substrate after firing (at a stage where the coated monolithic substrate is formed, in the producing method of Japanese Patent Provisional Publication No. 58-122044).
  • the cracks in the catalytic coat layer may cause the catalytic coat layer to be peeled off from the monolithic substrate, thereby degrading the durability of the catalyst.
  • Another object of the present invention is to provide an improved exhaust gas purifying catalyst and a method of producing the same catalyst, which can largely improve durability of exhaust gas purifying catalysts.
  • a further object of the present invention is to provide an improved exhaust gas purifying catalyst and a method of producing the same catalyst, which can effectively prevent cracks from being produced in a catalytic coat layer when the catalytic coat layer is formed on a substrate such as a ceramic monolithic substrate or a metallic honeycomb-type substrate, thereby protecting the catalytic coat layer from peeling off from the substrate.
  • An aspect of the present invention resides in an exhaust gas purifying catalyst comprising a substrate.
  • a catalytic coat layer containing a catalyst component is formed on the substrate.
  • the catalytic coat layer is formed by coating a slurry containing the catalyst component on a surface of the substrate.
  • a crack-preventing coat layer is formed on an upper-most surface of the catalytic coat layer.
  • the crack-preventing coat layer has a thickness of not larger than 50 ⁇ m.
  • Another aspect of the present invention resides in a method of producing an exhaust gas purifying catalyst.
  • the method comprising (a) coating a substrate with a first slurry containing a catalytic component; (b) drying and firing the first slurry on the substrate to form a first catalytic coat layer on the substrate; (c) coating a second slurry containing a catalytic component, on an upper-most surface of the catalytic coat layer, the second slurry containing particle materials having an average particle size ranging from 3 to 7 ⁇ m; and (d) drying and firing the second slurry on the first catalytic coat layer to form a second catalytic coat layer having a thickness of not larger than 50 ⁇ m.
  • a further aspect of the present invention resides in a method of producing an exhaust gas purifying catalyst.
  • the method comprising (a) preparing a slurry including a catalyst component and water which containing anion other than OH ⁇ in a content of not larger than 50 ppm and cation other than H + in a content of not larger than 50 ppm; (b) coating a substrate with the slurry; and (c) drying and firing the slurry on the substrate to form a catalytic coat layer on the substrate.
  • FIG. 1A is an electronmicrograph obtained by a scanning electron microscope (SEM), of a section of an example (Example 1) of an exhaust gas purifying catalyst according to the present invention
  • FIG. 1B is an enlarged electronmicrograph depicting a part of the section of FIG. 1A;
  • FIG. 2 is an electronmicrograph obtained by a SEM, of a section of another example (Example 2) of the exhaust gas purifying catalyst according to the present invention
  • FIG. 3A is an electronmicrograph obtained by a SEM, of a section of a reference example (Comparative Example 1) of an exhaust gas purifying catalyst outside the scope of the present invention
  • FIG. 3B is an enlarged electronmicrograph depicting a part of the section of FIG. 3A;
  • FIG. 4 is an electronmicrograph obtained by a SEM, of a section of a further example (Example 3) of the exhaust gas purifying catalyst according to the present invention.
  • FIG. 5 is an electronmicrograph obtained by a SEM, of a section of a further example (Example 4) of the exhaust gas purifying catalyst according to the present invention.
  • FIG. 6 is an electronmicrograph obtained by a SEM, of a section of a further example (Example 5) of the exhaust gas purifying catalyst according to the present invention.
  • FIG. 7 is an electronmicrograph obtained by a SEM, of a section of another reference example (Comparative Example 2) of the exhaust gas purifying catalyst outside the scope of the present invention.
  • FIG. 8 is an electronmicrograph obtained by a SEM, of a section of a further reference example (Comparative Example 3) of the exhaust gas purifying catalyst outside the scope of the present invention.
  • FIG. 9 is an electronmicrograph obtained by a SEM, of a section of a further reference example (Comparative Example 4) of the exhaust gas purifying catalyst outside the scope of the present invention.
  • an exhaust gas purifying catalyst comprises a substrate on which a catalytic coat layer containing a catalyst component is formed.
  • the catalytic coat layer is formed by coating a slurry containing the catalyst component on a surface of the substrate.
  • a crack-preventing coat layer is formed on an upper-most surface of the catalytic coat layer.
  • the crack-preventing coat layer has a thickness of not larger than 50 ⁇ m.
  • the slurry contains particle materials whose average particle size affects the density of a solid content in the slurry obtained after drying the slurry, in which the density of the coat layer decreases to increase the coefficient of contraction of the coat layer as the average particle size decreases. Accordingly, when the particle size of the particle materials of the slurry for the coat layer having the upper-most surface is large, the density of the solid content obtained after drying the slurry is low thereby decreasing the amount of shrinkage of the coat layer so that crack or craze is difficult to be formed in the catalytic coat layer.
  • the average particle size of the particle materials of the slurry is not smaller than 3 ⁇ m, taking account of the shape of a ceramic honeycomb-type monolithic substrate and a metallic monolithic substrate and various conditions of a drying step, for a practical exhaust gas purifying catalyst.
  • the average particle size of the particle materials of the slurry exceeds 7 ⁇ m, there are tendencies that cells of the monolithic substrate are clogged with the particle materials of the slurry during coating of the slurry, and the catalytic coat layer itself becomes brittle. Accordingly, it is preferable that the average particle size of particle materials of the slurry is within a range of from 3 to 7 ⁇ m. In this case, the average particle size was measured by a laser diffraction scattering method using a light source of semiconductor laser having a wavelength of 680 nm and an output power of 3 mW.
  • the crack-preventing coat layer is formed as a finish or upper-most coat layer and has the thickness of not larger than 50 ⁇ m. Consequently, crack or craze cannot be produced in the crack-preventing coat layer. Even in case that crack is formed in the catalytic coat layer below the crack-preventing coat layer, the materials of the crack-preventing coat layer will cover or is filled in the crack thereby ensuring the strength of the catalytic coat layer, thus preventing the materials of the monolithic substrate from being separated from the monolithic substrate.
  • the crack-preventing coat layer may be so thin as not to be able to be recognized as a layer with naked eye, after firing thereof, however, the materials of the slurry is filled into the crack in the catalytic coat layer thereby ensuring the strength of the catalytic coat layer.
  • any kind of catalyst components or metals may be contained in the materials of the slurry used for the crack-preventing coat layer. Accordingly, for example, even in case that a particular catalytic coat layer is required as the upper-most coat layer from the viewpoint of catalytic performance design, the upper-most coat layer can be formed as a crack-resistant structure layer containing necessary catalyst components, thereby ensuring freedom in catalyst design and sufficient strength of the particular catalytic coat layer.
  • a (catalytic) slurry containing particle materials having an average particle size ranging from 3 to 7 ⁇ m is coated at the upper-most surface of the catalytic coat layer in a condition in which the catalytic slurry is formed into a coat layer having a thickness of not larger than 50 ⁇ m upon firing. Accordingly, even if there is crack in the lower or catalytic coat layer, the catalytic slurry will cover or is filled into the crack in the lower coat layer, so that a high quality catalytic layer without crack or craze is formed upon drying and firing. This can provide the catalytic coat layer which is improved in strength and excellent in separation or peeling-resistance of the coat layer from the substrate.
  • the slurry for forming the crack-preventing coat layer preferably contains porous substance such as alumina and/or zeolite, or may contain ⁇ -alumina and/or titania which have relatively small surface area.
  • each of anions other than hydroxide ion (OH ⁇ ) and cations other than hydrogen ion (H + ) in the slurry for forming the catalytic coat layer on the surface of the substrate is suppressed to a value of not larger than 50 ppm.
  • the anions other than hydrogen ion (OH ⁇ ) are nitrate ions (NO 3 ⁇ ), chlorine ion (Cl ⁇ ), sulfate ion (SO 4 ⁇ 2 ), acetate ion (CH 3 COO ⁇ ) and the like.
  • H + hydrogen ion
  • Al +3 aluminum ion
  • Na + sodium ion
  • Mg +2 magnesium ion
  • Ca +2 calcium ion
  • nitrate ion is used in a catalyst production method as disclosed in Japanese Patent Provisional Publication No. 58-122044, in which complex ion layer containing acetate ion or nitrate ion is formed around alumina particle and/or the like.
  • complex ion layer containing acetate ion or nitrate ion is formed around alumina particle and/or the like.
  • the ion layer is diminished during drying and firing of the catalytic coat layer so that particles are combined with each other. This reduces the volume of the catalytic coat layer thereby producing crack in the catalytic coat layer and/or a coat layer formed of alumina compound.
  • the content of ions other than hydroxide ion (OH ⁇ ) and hydrogen ion (H + ) in the catalytic slurry is suppressed as little as possible, so that thin ion layer is formed around alumina particle or the like. Consequently, ion layer is hardly formed among particles when the catalytic slurry is coated on the substrate, and therefore shrinkage of the catalytic coat layer cannot be produced during drying and during firing thereby preventing production of crack and craze in the catalytic coat layer.
  • the crack-preventing coat layer having the thickness of not larger than 50 ⁇ m is formed at the upper-most surface of the catalytic coat layer. Accordingly, no crack or craze can be produced in the crack-preventing coat layer thereby maintaining a sufficient strength of the catalytic coat layer so that the catalytic coat layer can be prevented from being separated or peeled off from the substrate, which is highly advantageous.
  • the catalytic slurry containing particle materials having the average particle size ranging from 3 to 7 ⁇ m is coated at the upper-most surface of the catalytic coat layer in the condition in which the catalytic slurry is formed into a finish coat layer having a thickness of not larger than 50 ⁇ m upon firing. Accordingly, the high quality catalytic layer without crack or craze is formed upon drying and firing, which is also highly advantageous.
  • the content of each of anions other than hydroxide ion (OH ⁇ ) and cations other than hydrogen ion (H + ) in the slurry for forming the catalytic coat layer on the surface of the substrate is suppressed as small as possible.
  • the catalytic slurry containing each of anions other than hydroxide ion (OH ⁇ ) and cations other than hydrogen ion (H + ) in an amount of not larger than 50 ppm is used.
  • ion layer is hardly formed among particles when the catalytic slurry is coated on the substrate, and therefore shrinkage of the catalytic coat layer cannot be produced during drying and during firing thereby preventing production of crack and craze in the catalytic coat layer.
  • This makes it possible to largely improve durability of the exhaust gas purifying catalyst, which is also highly advantageous.
  • a porcelain ball mill was charged with 500 g of MFI (zeolite), 100 g of silica sol and 1000 g of pure water, followed by mixing and pulverizing, thereby obtaining a slurry containing particle materials whose average particle size was 2.1 ⁇ m.
  • This slurry was coated on a cordierite ceramic honeycomb-type monolithic substrate having a volume of 1.3 liters, 400 (axially extending) cells per square inch, an elliptic cross-section, a cross-sectional area of 113 cm 2 and a length of 115 mm, so that thin walls of cells were coated with the slurry.
  • the coated monolithic substrate was blown with air stream to remove excessive slurry in the cells, and then dried and fired at 400° C. for 1 hour.
  • a catalyst was prepared in which a catalytic or inner coat layer was formed on the wall of the cells of the monolithic substrate.
  • the weight of the catalytic coat layer was 150 g per one liter of the monolithic substrate.
  • an alumina powder was impregnated with an aqueous solution of palladium compound, followed by drying at 150° C. for 12 hours and then by firing at 400° C. for 1 hour, thereby preparing a Pd-carried alumina powder.
  • a porcelain ball mill was charged with 1000 g of the Pd-carried alumina powder, 11 g of activated alumina and 1500 g of an aqueous solution of nitric acid, followed by mixing and pulverizing, thereby obtaining a slurry which contains particle materials whose average particle size was 4.6 ⁇ m.
  • This slurry was coated on the above catalyst provided with the catalytic coat layer, so that the walls of the cells were coated with the slurry. Thereafter, the coated catalyst was blown with air stream to remove excessive slurry in the cells, and then dried and fired at 400° C. for 1 hour.
  • a catalyst of Example 1 was prepared in which an outer coat layer was formed on the inner coat layer of the catalyst, in which the weight of the outer coat layer was 75 g per one liter of the monolithic substrate. The weight of total coat layers was 225 g per one liter of the monolithic substrate.
  • Table 1 shows results of measurement and observation of the catalyst of Example 1, including the thickness of the inner and outer coat layers and the presence or absence of crack in the catalyst. Additionally, FIGS. 1A and 1B show observation results (electronmicrographs at 50 and 300 magnifications) of the cross-sectional surface of the coat layers of the catalyst of Example 1.
  • FIG. 1 is an electronmicrograph indicating mainly a section around a gas passage (in the catalyst) through which exhaust gas to be purified is to flow. The gas passage was formed inside each cell of the monolithic substrate.
  • FIG. 1B is an enlarged electronmicrograph indicating a part of the section of FIG. 1.
  • the inner coat layer was formed of the particle materials which were so fine as to have the average particle size of 2.1 ⁇ m and was so thick as to have the thickness of 133 ⁇ m. Consequently, production of many cracks due to shrinkage during drying and firing had been observed.
  • the outer coat layer was formed of the particle materials having the average particle size of 4.6 ⁇ m and had the thickness of 43 ⁇ m, serving as a crack-preventing coat layer which had no crack. It had been confirmed that the materials of the outer layer were filled in the cracks of the inner coat layer thereby reinforcing the inner or catalytic coat layer.
  • Example 2 A catalyst of Example 2 was obtained in a similar manner to that of Example 1 with the exception that the inner and outer coat layers were formed respectively thinner than those in Example 1.
  • Results of measurement and observation of the catalyst of Example 2 including the thickness of the inner and outer coat layers and the presence or absence of crack in the catalyst are shown in Table 1. Additionally, FIG. 2 shows observation results (an electronmicrograph at 1000 magnifications) of the cross-sectional surface of the catalyst of Example 1. FIG. 2 is an electronmicrograph indicating mainly a section between adjacent two gas passages in the catalyst.
  • the inner coat layer was so thin as to have a thickness of 25 ⁇ m; however, it was formed of the particle materials which were so fine as to have the average particle size of 2.1 ⁇ m. Consequently, production of cracks due to shrinkage had been observed.
  • the outer coat layer was formed of the particle materials having the average particle size of 4.6 ⁇ m and had the thickness of 18 ⁇ m, serving as a crack-preventing coat layer which had no crack. It had been confirmed that the materials of the outer layer reinforced the inner or catalytic coat layer.
  • a catalyst of Comparative Example 1 was obtained in a similar manner to that of Example 1 with the exception that the amount of water contained in the slurries was decreased by about 20% by weight while the inner and outer coat layers were formed respectively thicker than those in Example 1 so that the weights of the inner and outer coat layers were respectively 250 g and 120 g per liter of the monolithic substrate.
  • FIGS. 3A and 3B show observation results (electronmicrographs at 50 and 200 magnifications) of the coat layers of the catalyst of Comparative Example 1.
  • FIG. 3A is an electronmicrograph indicating mainly a section around a gas passage through which exhaust gas is to flow.
  • FIG. 3B is an enlarged electronmicrograph indicating a part of the section of FIG. 3A.
  • the inner coat layer was formed of the particle materials which were so fine as to have the average particle size of 2.1 ⁇ m and was so thick as to have the thickness of 150 ⁇ m. Consequently, production of many cracks due to shrinkage during drying and firing had been observed as in Example 1. While the outer coat layer was formed of the particle materials having the average particle size of 4.6 ⁇ m, it was so thick as to have the thickness of 75 ⁇ m. Consequently, shrinkage during drying and firing became remarkable, and therefore product ion of cracks was observed.
  • This catalytic powder in an amount of 500 g was mixed with 1250 g of water to form a slurry.
  • This slurry was pulverized by a ball mill so that the particle materials in the slurry had particle sizes of not larger than 9 ⁇ m.
  • the slurry was coated or impressed on a cordierite ceramic honeycomb-type monolithic substrate having a volume of 1.3 liters, about 62 (axially extending) cells per cm 2 , an elliptic cross-section, a cross-sectional area of 113 cm 2 and a length of 115 mm, so that thin walls of cells were coated with the slurry. Thereafter, the coated monolithic substrate was blown with air stream to remove excessive slurry in the cells, and then dried 120° C. and fired at 400° C. for 1 hour. As a result, a catalyst of Example 3 was prepared in which a catalytic coat layer was formed on the wall of the cells of the monolithic substrate. The weight of the catalytic coat layer was 100 g per one liter of the monolithic substrate.
  • the above slurry coated on the monolithic substrate was subjected to a centrifugal separation to obtain a supernatant liquid. Then, the supernatant liquid was subjected to an analysis for ion concentration or content. As a result, the supernatant liquid had an ion concentration of 5 ppm of Na, 5 ppm of Ca and 10 ppm of Cl.
  • the catalyst was dipped in a liquid state epoxy resin. After the epoxy resin was solidified, the catalyst was cut to expose the cross-sectional or cut surface which was observed by a scanning electron microscope, providing an electronmicrograph (at 400 magnifications) shown in FIG. 4 which depicts a section around a gas passage of the catalyst. As a result of this observation, no production of crack was confirmed.
  • Activated alumina in an amount of 500 g and 120 g of lanthanum carbonate were cast into 645 g of a 6.5% aluminum nitrate aqueous solution, followed by stirring and mixing, so as to form a mixture.
  • the mixture was dried at 150° C. for 12 hours, and then fired at 700° C. for 2 hours, thereby obtaining mixture powder.
  • Water in an amount of 1250 g was added to this mixture powder, followed by pulverizing in a ball mill, thus obtaining a slurry to be coated.
  • the slurry was coated or impressed on a cordierite ceramic honeycomb-type monolithic substrate having a volume of 1.3 liters, about 62 (axially extending) cells per cm 2 , an elliptic cross-section, a cross-sectional area of 113 cm 2 and a length of 115 mm, so that thin walls of cells were coated with the slurry. Thereafter, the coated monolithic substrate was blown with air stream to remove excessive slurry in the cells, and then dried 120° C. and fired at 400° C. for 1 hour. As a result, a catalyst of Example 4 was prepared in which a catalytic coat layer was formed on the wall of the cells of the monolithic substrate. The weight of the catalytic coat layer was 100 g per one liter of the monolithic substrate.
  • the above slurry coated on the monolithic substrate was subjected to a centrifugal separation to obtain a supernatant liquid. Then, the supernatant liquid was subjected to an analysis for ion concentration or content. As a result, the supernatant liquid had an ion concentration or content of 45 ppm of NO 3 , 10 ppm of Cl, 5 ppm of Na, and 5 ppm of Ca.
  • the catalyst was dipped in a liquid state epoxy resin. After the epoxy resin was solidified, the catalyst was cut to expose the cross-sectional or cut surface which was observed by a scanning electron microscope, providing an electronmicrograph (at 400 magnifications) shown in FIG. 5 which depicts a section around a gas passage in the catalyst. As a result of this observation, no production of crack was confirmed.
  • This slurry was coated or impressed on a metallic honeycomb-type monolithic substrate having a volume of 1.3 liters, about 62 (axially extending) cells per cm 2 , an elliptic cross-section, a cross-sectional area of 113 cm 2 and a length of 115 mm, so that thin walls of cells were coated with the slurry. Thereafter, the coated monolithic substrate was blown with air stream to remove excessive slurry in the cells, and then dried 130° C. and fired at 400° C. for 1 hour. As a result, a catalyst of Example 5 was prepared in which a catalytic coat layer was formed on the wall of the cells of the monolithic substrate. The weight of the catalytic coat layer was 150 g per one liter of the monolithic substrate.
  • the above slurry coated on the monolithic substrate was subjected to a centrifugal separation to obtain a supernatant liquid. Then, the supernatant liquid was subjected to an analysis for ion concentration or content. As a result, the supernatant liquid had an ion concentration or content of 200 ppm of NO 3 , 7 ppm of Cl, 3 ppm of Na and 8 ppm of Ca.
  • the catalyst was dipped in a liquid state epoxy resin. After the epoxy resin was solidified, the catalyst was cut to expose the cross-sectional or cut surface which was observed by a scanning electron microscope, providing an electronmicrograph (at 200 magnifications) shown in FIG. 6 which depicts a section between two adjacent gas passages in the catalyst. As a result of this observation, no production of crack was confirmed.
  • This slurry was coated or impressed on a cordierite ceramic honeycomb-type monolithic substrate having a volume of 1.3 liters, about 62 (axially extending) cells per cm 2 , an elliptic cross-section, a cross-sectional area of 113 cm 2 and a length of 115 mm, so that thin walls of cells were coated with the slurry. Thereafter, the coated monolithic substrate was blown with air stream to remove excessive slurry in the cells, and then dried 120° C. and fired at 400° C. for 1 hour. As a result, a catalyst of this comparative example was prepared in which a catalytic coat layer was formed on the wall of the cells of the monolithic substrate. The weight of the catalytic coat layer was 100 g per one liter of the monolithic substrate.
  • the above slurry coated on the monolithic substrate was subjected to a centrifugal separation to obtain a supernatant liquid. Then, the supernatant liquid was subjected to an analysis for ion concentration or content. As a result, the supernatant liquid had an acetic acid ion concentration of 35000 ppm.
  • the catalyst was dipped in a liquid state epoxy resin. After the epoxy resin was solidified, the catalyst was cut to expose the cross-sectional or cut surface which was observed by a scanning electron microscope, providing an electronmicrograph (at 400 magnifications) shown in FIG. 7 which depicts a section around a gas passage in the catalyst. As a result of this observation, production of cracks in the catalytic coat layer was confirmed.
  • Activated alumina in an amount of 500 g and 120 g of lanthanum carbonate were cast into 645 g of a 6.5% aluminum nitrate aqueous solution, followed by stirring and mixing, so as to form a mixture.
  • the mixture was pulverized by a ball mill thereby obtaining a slurry to be coated.
  • This slurry was coated or impressed on a cordierite ceramic honeycomb-type monolithic substrate having a volume of 1.3 liters, about 62 (axially extending) cells per cm 2 , an elliptic cross-section, a cross-sectional area of 113 cm 2 and a length of 115 mm, so that thin walls of cells were coated with the slurry. Thereafter, the coated monolithic substrate was blown with air stream to remove excessive slurry in the cells, and then dried 120° C. and fired at 700° C. for 2 hour. As a result, a catalyst of this comparative example was prepared in which a catalytic coat layer was formed on the wall of the cells of the monolithic substrate. The weight of the catalytic coat layer was 100 g per one liter of the monolithic substrate.
  • the above slurry coated on the monolithic substrate was subjected to a centrifugal separation to obtain a supernatant liquid. Then, the supernatant liquid was subjected to an analysis for ion concentration. As a result, the supernatant liquid had a nitric acid ion concentration or content of 44000 ppm.
  • the catalyst was dipped in a liquid state epoxy resin. After the epoxy resin was solidified, the catalyst was cut to expose the cross-sectional or cut surface which was observed by a scanning electron microscope, providing an electronmicrograph (at 400 magnifications) shown in FIG. 8 which depicts a section around a gas passage in the catalyst. As a result of this observation, production of cracks in the catalytic coat layer was confirmed.
  • This slurry was coated or impressed on a metallic honeycomb-type monolithic substrate having a volume of 1.3 liters, about 62 (axially extending) cells per cm 2 , an elliptic cross-section, a cross-sectional area of 113 cm 2 and a length of 115 mm, so that thin walls of cells were coated with the slurry. Thereafter, the coated monolithic substrate was blown with air stream to remove excessive slurry in the cells, and then dried 130° C. and fired at 400° C. for 1 hour. As a result, a catalyst was prepared in which a catalytic coat layer was formed on the wall of the cells of the monolithic substrate. The weight of the catalytic coat layer was 150 g per one liter of the monolithic substrate.
  • the above slurry coated on the monolithic substrate was subjected to a centrifugal separation to obtain a supernatant liquid. Then, the supernatant liquid was subjected to an analysis for ion concentration or content. As a result, the supernatant liquid had a nitric acid ion concentration of 5800 ppm.
  • the catalyst was dipped in a liquid state epoxy resin. After the epoxy resin was solidified, the catalyst was cut to expose the cross-sectional or cut surface which was observed by a scanning electron microscope, providing an electronmicrograph (at 100 magnifications) shown in FIG. 9 which depicts a section between two gas passages in the catalyst. As a result of this observation, production of cracks in the catalytic coat layer was confirmed.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Ceramic Engineering (AREA)
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  • Combustion & Propulsion (AREA)
  • Health & Medical Sciences (AREA)
  • Materials Engineering (AREA)
  • General Chemical & Material Sciences (AREA)
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  • Environmental & Geological Engineering (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Biomedical Technology (AREA)
  • Toxicology (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Exhaust Gas Treatment By Means Of Catalyst (AREA)
  • Catalysts (AREA)
  • Exhaust Gas After Treatment (AREA)
US09/794,010 2000-02-28 2001-02-28 Exhaust gas purifying catalyst and method of producing same Abandoned US20010021358A1 (en)

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US20050215429A1 (en) * 2004-03-23 2005-09-29 Nissan Motor Co., Ltd Catalyst powder, exhaust gas purifying catalyst, and method of producing the catalyst powder
US20050221978A1 (en) * 2004-03-31 2005-10-06 Nissan Motor Co., Ltd. Catalyst powder, method of producing the catalyst powder, and exhaust gas purifying catalyst
US20070153390A1 (en) * 2003-12-25 2007-07-05 Masanori Nakamura Powdery catalyst, exhaust-gas purifying catalyzer, and powdery catalyst production method
US20070155626A1 (en) * 2004-02-17 2007-07-05 Nissan Motor Co., Ltd Catalyst powder, exhaust gas purifying catalyst, and method of producing the catalyst powder
US20070203021A1 (en) * 2004-02-24 2007-08-30 Nissan Motor Co., Ltd. Catalyst Powder, Exhaust Gas Purifying Catalyst, And Method Of Producing The Catalyst Powder
US20080187477A1 (en) * 2007-02-06 2008-08-07 Mitsubishi Heavy Industries, Ltd. Catalyst for treating exhaust gases, method for producing the same, and method for treating exhaust gases
US20090280978A1 (en) * 2004-12-22 2009-11-12 Nissan Motor Co., Ltd. Exhaust gas purifying catalyst and method of producing exhaust gas purifying catalyst

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BG64476B1 (bg) * 2002-03-04 2005-04-30 "Терем" Еад - Клон Търговище Оксиден катализатор за очистване на отработени и отпадъчни газове и метод за получаването му
US7316722B2 (en) * 2002-09-13 2008-01-08 Ibiden Co., Ltd. Honeycomb structure
JP2008023501A (ja) * 2006-07-25 2008-02-07 Toyota Motor Corp 排ガス浄化用触媒
US7741243B2 (en) * 2007-10-05 2010-06-22 Canon Kabushiki Kaisha Production method of catalyst layer
US20220016614A1 (en) * 2018-12-27 2022-01-20 Umicore Shokubai Japan Co., Ltd. Exhaust Gas Purification Catalyst and Exhaust Gas Purification Method

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US20040092395A1 (en) * 2002-08-05 2004-05-13 Denso Corporation Ceramic catalyst body
US7183236B2 (en) * 2002-08-05 2007-02-27 Denso Corporation Ceramic catalyst body
US7601669B2 (en) 2003-12-25 2009-10-13 Nissan Motor Co., Ltd. Powdery catalyst, exhaust-gas purifying catalyzer, and powdery catalyst production method
US20070153390A1 (en) * 2003-12-25 2007-07-05 Masanori Nakamura Powdery catalyst, exhaust-gas purifying catalyzer, and powdery catalyst production method
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JP2001232212A (ja) 2001-08-28
EP1127604A1 (en) 2001-08-29
DE60138582D1 (de) 2009-06-18
JP3777589B2 (ja) 2006-05-24
US20050170958A1 (en) 2005-08-04
EP1127604B1 (en) 2009-05-06
US7208444B2 (en) 2007-04-24

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