WO2014156746A1 - Matière d'alumine contenant du sulfate de baryum et son procédé de production, et catalyseur destiné à être utilisé dans la purification de gaz d'échappement la comprenant - Google Patents

Matière d'alumine contenant du sulfate de baryum et son procédé de production, et catalyseur destiné à être utilisé dans la purification de gaz d'échappement la comprenant Download PDF

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WO2014156746A1
WO2014156746A1 PCT/JP2014/057060 JP2014057060W WO2014156746A1 WO 2014156746 A1 WO2014156746 A1 WO 2014156746A1 JP 2014057060 W JP2014057060 W JP 2014057060W WO 2014156746 A1 WO2014156746 A1 WO 2014156746A1
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alumina
barium sulfate
exhaust gas
oxide
catalyst
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PCT/JP2014/057060
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Japanese (ja)
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雄大 藤村
禎憲 高橋
豪人 高山
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エヌ・イーケムキャット株式会社
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Priority to JP2015508312A priority Critical patent/JP6272303B2/ja
Publication of WO2014156746A1 publication Critical patent/WO2014156746A1/fr

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    • C—CHEMISTRY; METALLURGY
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    • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F7/00—Compounds of aluminium
    • C01F7/02—Aluminium oxide; Aluminium hydroxide; Aluminates
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    • 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
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    • B01J21/00—Catalysts comprising the elements, oxides, or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium, or hafnium
    • B01J21/02—Boron or aluminium; Oxides or hydroxides thereof
    • B01J21/04—Alumina
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    • B01J35/64—Pore diameter
    • B01J35/647—2-50 nm
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    • B01J35/651—50-500 nm
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    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/0009—Use of binding agents; Moulding; Pressing; Powdering; Granulating; Addition of materials ameliorating the mechanical properties of the product catalyst
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    • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F11/00—Compounds of calcium, strontium, or barium
    • C01F11/46—Sulfates
    • C01F11/462—Sulfates of Sr or Ba
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    • B01D2255/908—O2-storage component incorporated in the catalyst
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    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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    • B01D2257/404—Nitrogen oxides other than dinitrogen oxide
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    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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    • B01D2258/00—Sources of waste gases
    • B01D2258/01—Engine exhaust gases
    • B01D2258/014—Stoichiometric gasoline engines
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    • C01P2006/12—Surface area
    • 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
    • F01N3/0807—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents
    • F01N3/0828—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents characterised by the absorbed or adsorbed substances
    • F01N3/0842—Nitrogen oxides
    • 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

Definitions

  • the present invention relates to an alumina material containing barium sulfate and a production method thereof, and an exhaust gas purifying catalyst using the same, and more specifically, an alumina material containing barium sulfate and a production method thereof, a catalyst and an adsorbent using the same,
  • the present invention relates to an exhaust gas purifying catalyst having excellent purifying performance of nitrogen oxide (NOx) in exhaust gas discharged from an internal combustion engine such as a gasoline vehicle.
  • NOx nitrogen oxide
  • Sulfuric acid a sulfuric acid compound of alkaline earth elements
  • a catalyst that decomposes high-boiling hydrocarbons such as heavy oil and light oil into lower-boiling hydrocarbons, or as an adsorbent that suppresses the release of sulfur oxides generated during petroleum refining
  • An alumina material containing calcium sulfate, barium sulfate, etc. in addition to magnesium is known (see Patent Document 1).
  • various catalysts have been used in catalyst devices for purifying exhaust gas discharged from an internal combustion engine such as a gasoline vehicle depending on the purpose.
  • This main catalyst component includes a platinum group metal, and is usually used in a highly dispersed state on a high surface area refractory inorganic oxide such as activated alumina (see Patent Document 2).
  • Platinum (Pt), palladium (Pd), and rhodium (Rh) are known as platinum group metals as catalyst components for purifying exhaust gas, and are widely used for purifying exhaust gas discharged from internal combustion engines such as gasoline cars. It has been used as a catalyst. Specifically, catalytically active species having excellent oxidation activity such as Pt and Pd are often used in combination with Rh having excellent NOx purification activity.
  • catalytically active species having excellent oxidation activity such as Pt and Pd are often used in combination with Rh having excellent NOx purification activity.
  • NOx NO and NO 2
  • Rh which is excellent in NOx purification activity.
  • the amount is small and expensive, and the market price has been rising in recent years. For this reason, attempts to utilize Pd as an alternative to Rh have been actively made in recent years.
  • Pd is known to exhibit NOx purification performance, although not as high as Rh, and if Pd is used to obtain Rh-like NOx purification activity, it will be very meaningful from the viewpoint of resource protection and
  • oxygen storage component Oxgen Storage Component: OSC
  • alkaline earth metal zirconium oxide, zeolite, and the like
  • Cerium oxide is known as an OSC that stores and releases oxygen in exhaust gas. Cerium oxide occludes oxygen as CeO 2 when the oxygen concentration in the exhaust gas is high, and releases oxygen as Ce 2 O 3 when the oxygen concentration is low.
  • the released oxygen is active oxygen and promotes the purification of HC and CO by being used for the oxidizing action by Pt and Pd.
  • the OSC also functions to buffer changes in oxygen concentration in the exhaust gas by storing and releasing oxygen. This action improves the exhaust gas purification performance of TWC.
  • TWC performs oxidation and reduction with a single catalyst, and has a range of exhaust gas components suitable for purification by design. This range often depends on the air-fuel ratio. Such a range is called a window, and in many cases, the exhaust gas burned in the vicinity of the stoichiometric air-fuel ratio called “Stoichio” is set as the window region. Since the change in the oxygen concentration in the exhaust gas is buffered, this window region is maintained for a long time, and the exhaust gas is effectively purified. This is said to have a great influence on the purification characteristics of NOx which are difficult to proceed particularly in the presence of O 2 .
  • cerium oxide pure cerium oxide can be used, but it is often used as a complex oxide with zirconium (see Patent Document 3).
  • Cerium-zirconium composite oxide has high heat resistance and is said to have a high oxygen storage / release rate. This is probably because the crystal structure of the cerium-zirconium composite oxide is stable and promotes the action of cerium oxide, which is the main OSC component, to function as an OSC up to the inside of the particle.
  • H 2 generated by the steam reforming reaction ⁇ reaction formula (2) ⁇ or the water gas shift reaction ⁇ reaction formula (5) ⁇ is also used in Pt and Pd. It is conceivable to promote the purification of NOx, and the use of alkaline earth metals made of water-soluble barium acetate as a promoter component has been studied (see Patent Document 5).
  • alkaline earth metals represented by the Ba component temporarily store NOx contained in the exhaust gas as a promoter component, and reduce the stored NOx to N 2 by a reducing component contained in the exhaust gas.
  • Purify see Patent Document 6.
  • the Ba component temporarily absorbs NOx generated in this way as Ba (NO 3 ) 2 .
  • the NOx absorbed in the Ba component is released from the Ba component when the concentration of NOx in the exhaust gas is low and the carbon dioxide (CO 2 ) concentration is high.
  • TWC (see Patent Document 7) using a Ba component (barium acetate or barium nitrate) and cerium oxide or the present applicant has proposed.
  • the purification performance may be lowered depending on the combination of the catalyst materials. For example, it has been reported that the purification performance of NOx is lowered when the Rh component and the Ba component are present in the same composition (Patent Document 9). reference).
  • the alkaline earth metal component has an action of occluding NOx, so that the NOx purification action in the Rh ingredient is hindered, or the inert oxidized Rh structure is stabilized by the electron donating action from Ba to Rh. It is thought to be due to this.
  • the NOx purification performance improves when the Pd component and the Ba component are close to each other (see Patent Document 10). This is because Pd is partially stabilized by electron donation from Ba to Pd, Pd sintering is suppressed, and the function of Pd with low NOx adsorption characteristics is compensated by the Ba component, and NOx in the vicinity of Pd is retained. It is thought that it is to make it.
  • the alkaline earth metal represented by barium is separated from OSC (cerium oxide, see Patent Document 11) and Ce.Zr-based composite oxide (see Patent Document 12) and is contained in different catalyst layers.
  • OSC ceramic oxide
  • Ce.Zr-based composite oxide see Patent Document 12
  • an exhaust gas purifying catalyst has been proposed.
  • the relationship between noble metals (Rh, Pd, etc.), OSC (cerium oxide, Ce / Zr composite oxide, etc.) and cocatalyst (Ba, etc.) has been studied, and combinations that have a positive effect on catalyst performance are gradually becoming apparent.
  • exhaust gas purification using a catalyst involves a complicated reaction path due to the mutual interaction of the catalyst components.
  • the arrangement (positional relationship) is still being explored and has not yet been established.
  • one exhaust gas purifying catalyst may be arranged in the exhaust gas flow path, but two or more exhaust gas purifying catalysts may be arranged.
  • This is a measure to make the best use of the characteristics of exhaust gas purifying catalysts in accordance with the tightening of exhaust gas regulations. ), To set the optimum position according to the catalyst characteristics (oxidation activity, reduction activity) and the like. Also, reducing the use of expensive noble metals and rare earths leads to the efficient use of limited resources, so the exhaust gas flow is optimally positioned according to the characteristics of each noble metal and rare earth It is required to install a gas purification catalyst.
  • exhaust gas regulations are becoming more and more strict, and it is desired to use a plurality of catalysts and to exhibit a catalyst that exhibits better exhaust gas purification performance.
  • the regulation value for NOx is particularly strict, and the need for an exhaust gas purification catalyst having excellent NOx purification performance is increasing.
  • Patent Document 10 an alumina material containing barium sulfate and Pd as a TWC material.
  • Pd is excellent in low-temperature purification of HC, but a phenomenon (sintering) in which particles are joined by heat to enlarge the particle size (sintering) is likely to occur. As a result, the low-temperature purification performance of HC is reduced.
  • Ba can suppress the sintering of Pd and maintain the activity of Pd by the electronic action of Ba.
  • Rh is excellent in NOx purification performance as a TWC material, Ba acts negatively on the NOx purification reaction by Rh and may reduce the activity of Rh. Therefore, while coexisting Pd and Ba on alumina, Ba is often used in order to prevent Ba from eluting in the slurry and contact with Rh to control the arrangement of the Ba component.
  • barium sulfate has a feature that it is decomposed in a reducing atmosphere at 700 ° C. or higher in exhaust gas and randomly dispersed in the catalyst layer.
  • a sparingly soluble barium sulfate on a porous inorganic oxide carrier such as alumina to limit the dispersion range of barium sulfate.
  • a porous inorganic oxide such as alumina in a highly dispersed state because the effective surface area of Ba increases and the function of the Ba component can be fully exhibited.
  • an aqueous solution containing a noble metal salt, alumina, OSC, barium sulfate having an average particle size of 0.05 to 0.7 ⁇ m and citric acid are mixed to form a slurry, which is then applied to a carrier (Patent Document) 13), and in order to further improve the purification performance, after preparing a slurry containing alumina powder, an organic solvent such as toluene, lauric acid trifluoroacetic acid and trifluoroacetic acid, an alkali such as barium oxide is prepared.
  • a slurry obtained by adding an earth metal oxide and adding an aqueous sodium sulfate solution and the like is stirred under specific conditions, and the filtered cake is dried and calcined, whereby sulfuric acid having an average particle size of 5 to 200 nm is obtained.
  • a material in which barium is selectively dispersed on an alumina surface has been proposed by the same applicant (see Patent Document 14).
  • barium sulfate particles are formed from a barium salt such as barium oxide by adding an aqueous sodium sulfate solution within the pores of alumina particles having a pore diameter of several nanometers to several tens of nanometers, the barium content is reduced.
  • trifluoroacetic acid is listed on the International Chemical Safety Card (ICSC) as “Avoid all contact” for human exposure.
  • ISC International Chemical Safety Card
  • organic solvents such as trifluoroacetic acid and toluene that are volatile at room temperature It is harmful to the human body and is not practical because it takes a huge amount of detoxification treatment after use.
  • JP-A 61-54234 JP 05-237390 A Japanese Patent Publication No. 06-75675 Republished Patent No. 2000/027508 Japanese Unexamined Patent Publication No. 07-255103 JP 2007-319768 A Japanese Patent Laid-Open No. 03-106446 JP 2010-22918 A JP 2002-326033 A JP 2010-274162 A Japanese Patent Application Laid-Open No. 08-57315 JP 2008-194605 A Republished Patent 2010/137658 Republished Patent 2010/147163
  • An object of the present invention is included in the exhaust material exhausted from an internal combustion engine such as an alumina material containing barium sulfate and a method for producing the same, a catalyst and an adsorbent using the alumina material, and in particular, a gasoline vehicle in view of the above-described problems of the prior art.
  • An object of the present invention is to provide an exhaust gas purification catalyst having excellent NOx purification performance suitable as a catalyst for purifying harmful substances.
  • the barium sulfate dispersion state in I) is a barium sulfate correlation coefficient of 0.3 or more in terms of the correlation coefficient between Ba and Al in the alumina material particles calculated based on the measured value of EPMA cross-sectional analysis.
  • An alumina material is provided.
  • the barium sulfate-containing alumina according to the first invention wherein the barium sulfate content is 5 to 100% by weight with respect to the alumina (I).
  • Material is provided.
  • the alumina (I) is one or more selected from the group consisting of ⁇ -alumina, ⁇ -alumina, ⁇ -alumina, and boehmite.
  • An alumina material comprising barium sulfate is provided.
  • the alumina (I) is further selected from the group of ceria, lanthanum oxide, neodymium oxide, praseodymium oxide, and yttrium oxide.
  • An alumina material comprising barium sulfate is provided that contains one or more rare earth oxides.
  • the content of the rare earth oxide contained in the alumina (I) is 30% by weight or less.
  • An alumina material comprising barium sulfate is provided.
  • an alumina material containing barium sulfate characterized in that, in any one of the first to fifth aspects, the average pore diameter after granulation is 5 to 100 nm. Is done.
  • alumina (I) and barium sulfate alone or a mixture of both are slurried with water and then averaged by a pulverizer. Crushing / dispersing treatment is performed until the particle diameter reaches 10 nm to 5 ⁇ m, and a mixed dispersion slurry containing alumina (I) particles having an average particle diameter of 300 nm to 5 ⁇ m and barium sulfate having an average particle diameter of 10 to 800 nm is prepared.
  • a method for producing an alumina material containing barium sulfate characterized in that it is granulated to 5 to 50 ⁇ m with a dryer and then calcined.
  • a method for producing an alumina material containing barium sulfate wherein a bead mill or a mixer and a bead mill are used in the pulverization / dispersion treatment step. Is done.
  • a method for producing an alumina material containing barium sulfate characterized by using a spray dryer or a fluidized bed granulation dryer in the granulation step.
  • the granulated product is heated at 300 to 700 ° C. for 20 to 120 minutes by the baking treatment, and the production of the alumina material containing barium sulfate A method is provided.
  • the alumina material containing barium sulfate according to any one of the first to sixth aspects, the noble metal, the inorganic oxide, and the oxygen storage / release component (OSC)
  • OSC oxygen storage / release component
  • the exhaust gas purifying catalyst is characterized in that the noble metal is one or more selected from the group consisting of palladium, rhodium and platinum. Is provided.
  • the inorganic oxide is one or more selected from the group consisting of alumina (II), zirconia, titania, silica, silica-alumina, and zeolite. There is provided an exhaust gas purifying catalyst.
  • the alumina (II) is at least one selected from the group consisting of ⁇ -alumina, ⁇ -alumina, ⁇ -alumina, and boehmite.
  • An exhaust gas purifying catalyst is provided.
  • the alumina (II) is further selected from the group consisting of ceria, lanthanum oxide, neodymium oxide, praseodymium oxide, and a rare earth oxide of yttrium oxide.
  • an exhaust gas purifying catalyst characterized by containing at least one selected from the above.
  • the content of the rare earth oxide contained in the alumina (II) is 30% by weight or less.
  • An exhaust gas purifying catalyst is provided.
  • the zirconia is further at least one selected from the group consisting of ceria, lanthanum oxide, neodymium oxide, praseodymium oxide, and a rare earth oxide of yttrium oxide.
  • an exhaust gas purifying catalyst characterized by containing.
  • the content of the rare earth oxide contained in zirconia is 40% by weight or less. Is provided.
  • an exhaust gas purification catalyst according to the eleventh aspect wherein the oxygen storage / release component (OSC) is ceria and / or ceria-zirconia.
  • the exhaust gas purifying catalyst according to the nineteenth aspect wherein the ceria-zirconia contains 10 to 70% by weight of zirconia.
  • the ceria-zirconia is further selected from the group consisting of lanthanum oxide, neodymium oxide, praseodymium oxide, and a rare earth oxide of yttrium oxide.
  • an exhaust gas purifying catalyst characterized by containing one or more kinds there is provided an exhaust gas purification catalyst according to any one of the nineteenth to twenty-first aspects, wherein the ceria-zirconia contains 20% by weight or less of rare earth oxide. Is done.
  • the exhaust gas purifying catalyst is further covered with an integral structure type carrier.
  • a purification catalyst is provided.
  • the exhaust gas purifying catalyst according to the twenty-third aspect wherein the catalyst layer is coated in an amount of 100 to 300 g / L.
  • the exhaust gas purification is characterized in that the total supported amount of the noble metal is 0.2 to 5.0 g / L in terms of metal.
  • a catalyst is provided.
  • the present invention relates to an alumina material having a specific average particle size containing barium sulfate, wherein the barium sulfate dispersed in the alumina material has an average particle size equal to or less than a specific value, and Ba— Since the correlation coefficient between Al meets specific requirements, it is excellent in nitrogen oxide removal activity and highly purified against nitrogen oxides emitted from various combustion devices when used as a material for exhaust gas purification catalysts. Demonstrate performance. Furthermore, the exhaust gas purifying catalyst of the present invention can be manufactured at low cost because the amount of expensive active metal used is small, and the exhaust gas purifying device can be stably produced and supplied.
  • FIG. 1 is a graph showing the average particle diameter of barium sulfate in barium sulfate-alumina particles calculated based on SEM measurement in Examples 1 to 5 and Comparative Example 1.
  • FIG. 2 is a graph showing the distribution of barium sulfate and alumina by measuring the cross section of one barium sulfate-alumina particle of Example 1 by EPMA.
  • FIG. 3 is a graph showing the distribution of barium sulfate and alumina by measuring the cross section of one barium sulfate-alumina particle of Example 2 by EPMA.
  • FIG. 4 is a graph showing the distribution of barium sulfate and alumina by measuring the cross section of one barium sulfate-alumina particle of Example 3 by EPMA.
  • FIG. 1 is a graph showing the average particle diameter of barium sulfate in barium sulfate-alumina particles calculated based on SEM measurement in Examples 1 to 5 and Comparative Example 1.
  • FIG. 2 is
  • FIG. 5 is a graph showing the distribution of barium sulfate and alumina by measuring the cross section of one barium sulfate-alumina particle of Example 4 by EPMA.
  • FIG. 6 is a graph showing the distribution of barium sulfate and alumina by measuring the cross section of one barium sulfate-alumina particle of Example 4 by EPMA.
  • FIG. 7 is a graph showing the distribution of barium sulfate and alumina obtained by EPMA measurement of the cross section of one barium sulfate-alumina particle of Comparative Example 1.
  • FIG. 8 is a graph showing the correlation coefficient between Ba—Al in barium sulfate-alumina particles calculated based on EPMA measurement in Examples 1 to 5 and Comparative Example 1.
  • FIG. 9 is a graph showing the relationship between the reduction rate of the BET specific surface area of barium sulfate-alumina after endurance treatment and the average particle diameter of barium sulfate in Examples 1 to 5 and Comparative Example 1.
  • FIG. 10 is a graph showing the relationship between the decomposition temperature of barium sulfate in barium sulfate-alumina and the average particle diameter in Examples 1 to 5 and Comparative Example 1.
  • FIG. 11 is a graph showing the relationship between the reduction rate of the BET specific surface area of barium sulfate-alumina after endurance treatment and the correlation coefficient between Ba—Al in the particles in Examples 1 to 5 and Comparative Example 1. It is.
  • FIG. 10 is a graph showing the relationship between the decomposition temperature of barium sulfate in barium sulfate-alumina and the average particle diameter in Examples 1 to 5 and Comparative Example 1.
  • FIG. 11 is a graph showing the relationship between the reduction rate of the BET specific surface area of barium sulf
  • FIG. 12 is a graph showing the relationship between the decomposition temperature of barium sulfate in barium sulfate-alumina and the correlation coefficient between Ba—Al in the particles in Examples 1 to 5 and Comparative Example 1.
  • FIG. 13 is a graph showing the amount of increase / decrease in OSC capacity with respect to those not including Ba in Example 6 and Comparative Examples 2 and 3.
  • FIG. 14 is a graph showing an average NOx purification rate when the direct-under catalyst and the under-floor catalyst are arranged in series at respective positions in Examples 7 to 10 and Comparative Example 4 and the vehicle engine runs in the LA-4 mode. is there.
  • FIG. 12 is a graph showing the relationship between the decomposition temperature of barium sulfate in barium sulfate-alumina and the correlation coefficient between Ba—Al in the particles in Examples 1 to 5 and Comparative Example 1.
  • FIG. 13 is a graph showing the amount of increase / decrease in OSC capacity with respect to those not including Ba in Example 6 and Comparative Examples 2 and 3.
  • FIG. 15 is a graph showing the relationship between the NOx average purification rate in Examples 7 to 10 and Comparative Example 4 and the average particle diameter of barium sulfate in barium sulfate-alumina used as an underfloor catalyst.
  • FIG. 16 is a graph showing the relationship between the NOx average purification rate in Examples 7 to 10 and Comparative Example 4 and the correlation coefficient between Ba—Al in barium sulfate-alumina used as an underfloor catalyst.
  • the alumina material containing barium sulfate of the present invention a method for producing the same, and an exhaust gas purifying catalyst using the same will be described in detail.
  • an embodiment of a gasoline engine will be mainly described, the present invention is not limited to automobile use, and can be widely applied to a denitration technique for nitrogen oxides in exhaust gas.
  • Alumina Material Containing Barium Sulfate produces a slurry in which alumina (I) particles having an average particle diameter of 300 nm to 5 ⁇ m and barium sulfate having an average particle diameter of 10 to 800 nm are uniformly dispersed.
  • the particles in the alumina material particles are particles having an average particle diameter of 5 to 50 ⁇ m, and the dispersion state of barium sulfate in alumina (I) is calculated based on the measured value of EPMA cross-sectional analysis.
  • the correlation coefficient between Ba and Al is 0.3 or more.
  • Barium sulfate Barium sulfate (BaSO 4 , hereinafter also referred to as Ba component) is extremely hardly soluble in water and acid. Therefore, even in the case of barium sulfate alone or inorganic oxide materials such as alumina and zirconia containing barium sulfate, barium does not dissolve in the slurry. It is possible to coexist in the slurry with an active ingredient such as Further, barium sulfate itself has a melting point of 1,345 ° C. and a boiling point of 1,600 ° C. (decomposes and volatilizes), and is a thermally stable material that hardly aggregates by heating. Furthermore, since barium sulfate is extremely insoluble in water and hardly soluble in acids and alkalis, it is the only barium salt that has been designated as a deleterious substance. There is no problem even above.
  • the temperature at which barium sulfate is changed to barium carbonate, barium aluminate (BaAl 2 O 4 ), barium oxide, etc. Is a very important factor.
  • barium sulfate alone has a BET specific surface area as small as 20 m 2 / g or less, and therefore has a low gas contact area even under a reducing atmosphere and is not easily decomposed (high decomposition temperature).
  • barium sulfate In order to improve the decomposability of barium sulfate, that is, to lower the decomposition temperature, increase the surface area of the reducing atmosphere, increase the surface area of the barium sulfate itself by reducing the particle size of the barium sulfate, or increase the surface area of the barium sulfate. It is effective to improve the contact probability of reducing gas by supporting barium sulfate on a base material having heat resistance. Also, in order to increase the amount of NOx adsorbed, the amount of barium sulfate itself is increased, or the effective surface area is increased by reducing the particle diameter of barium sulfate, or barium sulfate is added to a base material having a high surface area and high heat resistance. It is essential to increase the effective surface area of the barium component by supporting it, and both are common in many parts.
  • the average particle diameter of barium sulfate dispersed in the alumina material is 10 to 800 nm.
  • the average particle diameter is preferably 10 to 600 nm, more preferably 10 to 400 nm, and particularly preferably 20 to 300 nm. If the average particle diameter of barium sulfate exceeds 800 nm, the effective surface area of the barium component becomes small, and sufficient NOx adsorption characteristics cannot be obtained, which is not preferable.
  • barium sulfate exceed 800 nm exists on a base material having a high surface area
  • the barium sulfate is locally located on the base material, and noble metals such as palladium and platinum supported on the base material This is not preferable because the synergistic effect of NOx purification between barium and noble metal is reduced.
  • barium sulfate is preferable because the geometric surface area increases as the average particle size decreases.
  • the crushing time for crushing to a small size increases rapidly, which is not preferable in terms of work efficiency. Therefore, it is possible to select a raw material with a small primary particle size so that it can be easily crushed, or to finely pulverize the material when the primary particle size is large. It is important to choose.
  • alumina is used as an inorganic oxide base material for supporting Pd and Pt, which are noble metals, in addition to Ba (hereinafter referred to as alumina (I) when supporting barium sulfate, In the case where Pd and Pt are supported, they are referred to as alumina (II)).
  • the type of alumina is ⁇ -alumina, ⁇ -alumina, ⁇ -alumina, or boehmite.
  • alumina such as ⁇ -alumina having a large BET specific surface area is preferable.
  • ⁇ -alumina has a small BET specific surface area of 20 m 2 / g or less, so it is not preferable as a material for supporting barium sulfate having a low BET specific surface area, and has low gas retention and Pd dispersibility. Therefore, it is not preferable as a base material supporting Pd.
  • alumina having a BET specific surface area exceeding 400 m 2 / g is not preferable because the pore diameter of alumina is too small and gas diffusibility in the pores is lowered.
  • the BET specific surface area of alumina is preferably 60 to 400 m 2 / g. 80 to 300 m 2 / g is more preferable, and further 100 to 250 m 2 / g is particularly preferable.
  • the alumina preferably has a pore diameter (mode diameter, hereinafter the same) of 3 to 150 nm, more preferably 5 to 150 nm, and even more preferably 5 to 100 nm.
  • the pore diameter of alumina When the pore diameter of alumina is smaller than 3 nm, the diffusion of gas in the pores is slowed and the pores may be blocked by a coating substance or the like. On the other hand, if the pore diameter is larger than 150 nm, the BET specific surface area becomes relatively small, and the dispersibility of noble metals, promoters and the like is not preferable.
  • the average particle diameter of alumina (I) must be 300 nm to 5 ⁇ m, more preferably 400 nm to 4 ⁇ m, and particularly preferably 500 nm to 3 ⁇ m.
  • the average particle diameter of alumina exceeds 5 ⁇ m, the geometric surface area of alumina becomes small, and the dispersibility of barium sulfate existing on the alumina surface becomes low.
  • it is less than 300 nm, the gap between particles is too small, and gas diffusion between the gaps is slow, which is not preferable.
  • ceria, lanthanum oxide, neodymium oxide, praseodymium oxide, rare earth oxides such as yttrium oxide, alkaline earth metals such as magnesium, silica, zirconia, and the like may be added.
  • the addition amount of rare earth oxides and the like is preferably 30% by weight or less in order to avoid a significant reduction in the high BET specific surface area of alumina.
  • barium sulfate must be sufficiently dispersed with respect to alumina, and the correlation coefficient between Ba—Al in alumina particles containing barium sulfate must be a positive value.
  • the value of the correlation coefficient is 0.3 or more, preferably 0.4 or more, and more preferably 0.5 or more. Particularly preferred is 0.6 to 1.0.
  • the correlation coefficient was calculated according to the following equation by performing a cross-sectional analysis of alumina particles containing barium sulfate using EPMA.
  • the correlation coefficient R of the intra-particle distribution of Ba and Al is calculated by the following equation (6) from the intensity values of the characteristic X-rays of Ba and Al obtained by EPMA measurement.
  • the correlation coefficient between the intra-particle distributions of Ba and Al calculated by this method is an index of how much Ba particles are dispersed in the alumina particles, in other words, the degree of dispersion of Ba in the alumina particles.
  • the correlation coefficient is larger than +0.6, that is, when there is a strong positive correlation, the distribution of Al and Ba is well matched, and Ba is very highly dispersed in the alumina particles. I can say that.
  • a small correlation coefficient indicates that the correlation between the Al and Ba distribution is low, which means that the Ba dispersibility in the alumina particles is low.
  • the correlation coefficient between the distributions of Ba and Al is negative, the distribution of Al and the distribution of Ba are negatively correlated, that is, Al is present where there is a lot of Ba and Al is present where there is less Ba.
  • the degree of Ba dispersion in alumina particles containing barium sulfate can be estimated from the correlation coefficient.
  • the correlation coefficient between Ba—Al in the particles must be 0.3 or more, and when it is less than 0.3, the barium sulfate particles and the alumina particles are almost completely separated. Therefore, the effective surface area of the barium component is reduced, and sufficient NOx adsorption characteristics cannot be obtained. On the other hand, if it is less than 0.3, the distance between barium and noble metals such as palladium and platinum becomes long, and a synergistic effect on NOx purification between barium and noble metals cannot be expected.
  • alumina material containing barium sulfate for example, a slurry of barium sulfate and alumina is pulverized and / or dispersed (hereinafter, pulverized / dispersed), and then a predetermined particle size is obtained.
  • pulverized / dispersed examples of the method include the step of granulating to obtain a diameter.
  • the average particle size is measured when the particle size distribution of the powder sample is measured by a laser scattering method, and d50 (50% particle size: particles when the volume-based integrated value of the amount of particles under the sieve reaches 50% of the total particle size. (Diameter, median diameter).
  • d50 50% particle size: particles when the volume-based integrated value of the amount of particles under the sieve reaches 50% of the total particle size.
  • d50 50% particle size: particles when the volume-based integrated value of the amount of particles under the sieve reaches 50% of the total particle size. (Diameter, median diameter).
  • the mode diameter of each peak is calculated, and the large particle side is defined as the average particle diameter attributable to alumina.
  • the raw material of barium sulfate or alumina is not particularly limited, and an inexpensive one is selected in consideration of the raw material cost and the cost required for pulverization.
  • a commercially available product that has been finely pulverized in advance may be used as a raw material in order to save pulverization, and a raw material having a small primary particle diameter may be employed in order to reduce the cost required for pulverization.
  • barium sulfate having a small crystal diameter of 10 to 500 nm or boehmite, which is a precursor of ⁇ -alumina, is preferably used because it is easier to disperse.
  • the mixed slurry of barium sulfate and alumina obtained by the above pulverization / dispersion treatment is subjected to a granulation treatment using a spray dryer, a fluidized bed granulation dryer or the like.
  • the mixed slurry of barium sulfate and alumina must be sufficiently mixed in the slurry before granulation by sufficiently mixing with a stirrer or the like.
  • the average particle size after granulation is preferably 5 to 50 ⁇ m, more preferably 5 to 40 ⁇ m, and particularly preferably 10 to 30 ⁇ m.
  • the average particle diameter is 5 ⁇ m or less, it is preferable because the gap between the particles including the granulated particles in the catalyst layer is narrowed after coating on a structure such as a honeycomb, so that gas diffusion in the catalyst layer is delayed. Absent. On the other hand, if the average particle diameter of the granulated particles exceeds 50 ⁇ m, it is not preferable because it takes time for the gas to diffuse through the pores and reach the center of the granulated particles.
  • the firing temperature is preferably 300 to 700 ° C, more preferably 400 to 600 ° C. If the temperature is lower than 300 ° C., the bonding strength between alumina and barium sulfate becomes insufficient, and if it exceeds 700 ° C., the cost required for firing is increased and the durability of the apparatus is not preferable.
  • the firing time is preferably 20 to 120 minutes, more preferably 30 to 90 minutes.
  • the alumina material obtained by the above preparation method contains barium sulfate uniformly on the surface and inside of the alumina regardless of the amount of barium sulfate.
  • a pulverizer such as a bead mill
  • a spray dryer fluidized bed granulator, etc.
  • among the physical properties of the re-granulated particles, in particular, pore diameter, pore volume, etc. May differ from the pre-prepared alumina and barium sulfate.
  • the alumina material prepared by the above method has physical properties such as BET specific surface area, pore diameter, pore volume, and impurity level affected by the starting material containing barium before preparation, the amount used, and the properties of alumina.
  • the mixing ratio of barium sulfate to alumina is 5 to 100% by weight and the above preparation method (process) is used, the dispersion of barium sulfate is good and the gas easily diffuses to 20 to 250 m 2 / g BET specific surface area.
  • the amount of barium sulfate mixed with alumina is 5 to 100% by weight, the preferred amount is 10 to 90% by weight, and more preferably 12 to 80% by weight. If the amount of barium sulfate mixed is less than 5% by weight, a sufficient Ba addition effect cannot be obtained for the denitration performance of alumina alone, which is not preferable.
  • the mixing amount of barium sulfate exceeds 100% by weight, the content of alumina is relatively reduced, the effect of supporting barium sulfate on alumina having a high BET specific surface area is reduced, and the effective surface area of the Ba component is reduced. Therefore, only the effect of barium sulfate can be obtained, which is not preferable.
  • the BET specific surface area is 20 to 250 m 2 / g, preferably 30 to 200 m 2 / g, and more preferably 40 to 200 m 2 / g.
  • the pore diameter is 5 to 100 nm, preferably 5 to 80 nm, and more preferably 10 to 50 nm, with good dispersion of barium sulfate and easy gas diffusion.
  • the pore volume is similarly 0.4 to 2.5 cc / g, preferably 0.5 to 2.0 cc / g, with good dispersion of barium sulfate and easy gas diffusion. More preferably, it is 5 to 1.5 cc / g.
  • Patent Document 13 a slurry containing alumina powder, an organic solvent such as toluene, lauric acid trifluoroacetic acid and trifluoroacetic acid is prepared, and then an oxide of an alkaline earth metal such as barium oxide is added. Further, an aqueous sodium salt solution such as an aqueous sodium sulfate solution is added as necessary, and the resulting slurry is stirred at 65 ° C. for 24 hours, and then the filtered filter cake is dried and calcined (240 ° C., 12 Time), a material in which barium sulfate having an average particle diameter of 5 to 200 nm is selectively dispersed on the alumina surface is prepared.
  • an organic solvent such as toluene, lauric acid trifluoroacetic acid and trifluoroacetic acid is prepared
  • an oxide of an alkaline earth metal such as barium oxide
  • an aqueous sodium salt solution such as an aqueous sodium sulfate solution is
  • fine particles such as barium sulfate are dispersed in pores of several to several tens of nm in inorganic oxide particles having a high BET specific surface area such as alumina. Yes.
  • the particle size of the fine particles such as barium sulfate is small, so there is no adverse effect even within the pore size, but as the content increases, the pore size decreases within the pore size Or gas clogging, and the gas diffusion is also worsened. As a result, the exhaust gas purification reaction is suppressed.
  • Patent Document 13 describes a preparation method in which the ratio of alumina to barium sulfate is 90 g: 80 g, and the particles grow until the barium sulfate has an average particle diameter of 202 nm.
  • an aqueous sodium salt solution such as an aqueous sodium sulfate solution within the pores of alumina particles having a pore diameter of several to several tens of nanometers
  • barium sulfate particles are formed from a soluble barium salt such as barium oxide.
  • the pores are more likely to be clogged or narrowed, making it difficult for the exhaust gas to diffuse deep into the particles and reducing the contribution to the reaction.
  • barium sulfate fine particles and alumina particles are previously uniformly mixed in a slurry and then granulated by a spray dryer, a fluidized bed flow dryer or the like. Therefore, the fine particles of barium sulfate are present almost uniformly in the granulated alumina particles, and the pore size is reconfigured to the same pore size as the alumina particles before pulverization. Without blocking or narrowing the particles, particles such as barium sulfate can be highly dispersed into the alumina particles, and stable catalyst performance can be expected without reducing gas diffusion.
  • the present invention does not use highly harmful chemicals such as trifluoroacetic acid or volatile organic solvents such as toluene that are volatile at room temperature and absorbed by the skin, so it is only highly safe.
  • highly harmful chemicals such as trifluoroacetic acid or volatile organic solvents such as toluene that are volatile at room temperature and absorbed by the skin, so it is only highly safe.
  • the final chemical detoxification process is unnecessary and the mass production process is simple.
  • the exhaust gas purification catalyst of the present invention (hereinafter also referred to as catalyst composition) comprises at least a noble metal, the above-mentioned alumina material, and an inorganic oxide.
  • a noble metal for example, palladium and / or platinum may be supported on an alumina material containing barium sulfate.
  • Rh a part of Pd and / or Pt is close to Ba in the catalyst layer, and shows high NOx purification performance by a synergistic effect.
  • Rh when Rh is close to the Ba component, the catalyst performance deteriorates. Therefore, it is desirable that Rh be supported on an inorganic oxide carrier other than an alumina material containing barium sulfate.
  • the Ba component when the Ba component is present in the same layer as the Rh component, it exhibits high NOx purification performance due to its synergistic effect. Therefore, it is desirable to arrange the Rh-supported particles and the barium sulfate-supported alumina in the same layer.
  • inorganic oxide examples include alumina (II), zirconia, ceria, ceria-zirconia, titania, silica, silica-alumina, and zeolite. These may be used alone or in combination of two or more inorganic oxides.
  • Alumina (II) is an inorganic base material supporting a noble metal, and has been described in detail in the section of alumina (I).
  • the kind and physical properties of alumina (II) are the same as those of alumina (I) supporting Ba, and one or more selected from the group consisting of ⁇ -alumina, ⁇ -alumina, ⁇ -alumina, and boehmite can be used.
  • Alumina (II) can further contain one or more members selected from the group consisting of ceria, lanthanum oxide, neodymium oxide, praseodymium oxide, and rare earth oxides of yttrium oxide, and the rare earth contained in alumina (II)
  • the oxide content is preferably 30% by weight or less.
  • zirconia will be described below as an example of an inorganic oxide (inorganic base material) for supporting a noble metal or a promoter.
  • Zirconia is preferably a composite oxide of zirconium and rare earth elements. This is because zirconium oxide having a single component of zirconium has low heat resistance.
  • the rare earth oxide is preferably at least one selected from the group consisting of ceria, lanthanum oxide, neodymium oxide, praseodymium oxide, and yttrium oxide.
  • the ratio of the rare earth element in the zirconia material is 40% by weight or less on the oxide basis, preferably 2% by weight to 40% by weight, and more preferably 5% by weight to 30% by weight. When the ratio of the rare earth oxide is less than 2% by weight, the heat resistance of the zirconia material is lowered, and when it exceeds 40% by weight, the steam reforming function of the zirconia may be lowered.
  • a zirconia material containing a rare earth oxide is, for example, one or more inorganic or organic zirconium compounds calcined at 450 to 600 ° C. in the atmosphere, and the resulting oxide particles are pulverized as a raw material powder. It can be manufactured by mixing raw material powders. As described above, in the case of zirconia, the same applies to ceria, ceria-zirconia, titania, silica, silica-alumina, and zeolite.
  • Oxygen storage / release component examples include ceria and ceria-zirconia.
  • Ceria alone can be used under conditions where the temperature of the exhaust gas is low, but a composite oxide in which zirconia is combined with ceria is used under conditions where the temperature of the exhaust gas is high.
  • the content of zirconia contained in ceria-zirconia is not particularly limited, but is preferably 10 to 70% by weight, and 20 to 70% by weight for ceria to stably exhibit an oxygen storage / release function even at high temperatures. Is more preferable, and 30 to 60% by weight is particularly preferable.
  • the zirconia content in the ceria-zirconia is less than 10% by weight, the heat resistance of the ceria may be reduced. Release function may be reduced. Ceria-zirconia needs to be further improved in heat resistance because the exhaust gas temperature becomes remarkably high depending on the mounting position of the exhaust gas purifying catalyst. Therefore, further rare earth oxides such as lanthanum oxide, neodymium oxide, praseodymium oxide, yttrium oxide are added.
  • the content of the rare earth oxide contained in the ceria-zirconia is not particularly limited, but in order to stably exhibit the oxygen storage / release function even when the ceria-zirconia is exposed to a significantly high temperature, it is 20% by weight.
  • the amount of the rare earth oxide in the ceria-zirconia exceeds 20% by weight, the oxygen storage / release function of ceria may be reduced. As described above, excessive use of the rare earth oxide is desirable from the viewpoint of cost. Absent.
  • the noble metal element palladium can be used as the active metal.
  • Palladium is supported on the alumina material containing barium sulfate, and the starting salt used at that time is preferably palladium nitrate, palladium chloride, dinitrodiammine palladium or the like. In particular, it is preferable to use palladium nitrate or dinitrodiammine palladium which does not leave a residue such as chlorine or sulfide after firing.
  • the supported amount of palladium is preferably 0.2 to 5.0 g / L, more preferably 0.4 to 4.0 g / L. When the amount of palladium is less than 0.2 g / L, the denitration performance may be drastically lowered.
  • the noble metal element platinum can be used as the active metal. Platinum is supported on the alumina material containing barium sulfate, and the starting salts used at that time are platinum (IV) chloride, diammineplatinum (II) nitrite, amine hydroxide platinate, chloroplatinic acid, nitric acid. Platinum or the like is preferable. In particular, it is preferable to use diammine platinum (II) nitrite, amine amine platinate, or platinum nitrate that does not leave residues such as chlorine and sulfide after firing.
  • the supported amount of platinum is preferably 0.2 to 5.0 g / L, and more preferably 0.4 to 4.0 g / L. When the amount of platinum is less than 0.2 g / L, the denitration performance may be drastically lowered.
  • Rhodium (Rh) rhodium, a noble metal element that is excellent in NOx purification activity, can be used as the active metal.
  • Rhodium is supported on the porous inorganic oxide and is not supported on the alumina material containing barium sulfate. This is because when Rh is directly supported on an alumina material containing barium sulfate, Rh and Ba come close to each other and the catalyst performance deteriorates.
  • the starting salt used is preferably rhodium nitrate, rhodium chloride, rhodium acetate, rhodium sulfate or the like.
  • rhodium nitrate or rhodium acetate in which no residue such as chlorine and sulfide remains after firing.
  • the supported amount of rhodium on the porous inorganic oxide is preferably 0.05 to 2.0 g / L, more preferably 0.1 to 1.5 g / L. If the amount of rhodium is less than 0.05 g / L, the denitration performance is drastically lowered. If it is more than 2.0 g / L, there is no problem in the denitration performance, but it is not preferable in terms of price.
  • a binder component may be added as necessary.
  • various sols such as alumina sol, silica sol, zirconia sol, titania sol and the like can be used.
  • Soluble salts such as aluminum nitrate, aluminum acetate, zirconium nitrate, and zirconium acetate can also be used.
  • acids such as acetic acid, nitric acid, hydrochloric acid, and sulfuric acid can also be used as a solvent (pH adjuster).
  • the exhaust gas purifying catalyst of the present invention can be used as the catalyst composition alone, but it is preferably used as a structural type catalyst in which the catalyst component is coated on the surface of various carriers, particularly the monolithic structure type carrier.
  • the shape of the carrier is not particularly limited, and can be selected from a structural carrier such as a prismatic shape, a cylindrical shape, a spherical shape, a honeycomb shape, and a sheet shape.
  • the size of the structure-type carrier is not particularly limited, and a structural carrier having a diameter (length) of several millimeters to several centimeters can be used as long as it is any of a prismatic shape, a cylindrical shape, and a spherical shape. Among these, the use of a honeycomb-shaped honeycomb structure carrier is preferable.
  • a honeycomb structure carrier is made of a ceramic such as cordierite, silicon carbide, silicon nitride, or a metal such as stainless steel. It has a flow path. As a material, cordierite is preferable for reasons of durability and cost. Further, for such a honeycomb structure carrier, an appropriate number of holes is determined in consideration of the type of exhaust gas to be processed, gas flow rate, pressure loss, removal efficiency, etc. with respect to the number of holes in the opening.
  • the cell density is preferably 100 to 900 cells / inch 2 (15.5 to 139.5 cells / cm 2 ), more preferably 200 to 600 cells / inch 2 (31 to 93 cells / cm 2 ). .
  • the effective surface area of the catalyst decreases because the geometric surface area becomes small.
  • the cell density is the number of cells per unit area in a cross section when the honeycomb structure carrier is cut at right angles to the gas flow path.
  • the honeycomb structure carrier has a flow-through structure in which the gas flow path communicates with a part of the end face of the gas flow path, and gas can flow through the wall surface of the gas flow path.
  • a wall flow structure is widely known.
  • the flow-through structure has low air resistance and low exhaust gas pressure loss.
  • it is a wall flow type structure, it is possible to filter out the particulate component contained in exhaust gas.
  • the exhaust gas purifying catalyst of the present invention can be used for either structure.
  • the exhaust gas purifying catalyst of the present invention is obtained by coating one or more honeycomb structure carriers with the catalyst composition.
  • the layer structure may be one layer, but it is preferable to have two or more layers in order to improve the exhaust gas purification performance.
  • the coating amount of the catalyst composition serving as the catalyst layer is preferably 100 to 300 g / L, and more preferably 120 to 250 g / L.
  • the coating amount of the catalyst composition is less than 100 g / L, the activity decreases due to deterioration of the dispersibility of noble metals such as platinum carried, and when it exceeds 300 g / L, the inside of the cell becomes narrow. Since pressure loss increases, it is not preferable.
  • Catalyst preparation method In order to prepare the exhaust gas purifying catalyst of the present invention, the catalyst composition and, if necessary, a binder or the like are mixed with an aqueous medium to form a slurry mixture, and then applied to a monolithic support. Dry and fire. That is, first, the catalyst composition and the aqueous medium are mixed at a predetermined ratio to obtain a slurry mixture.
  • the aqueous medium may be used in such an amount that the catalyst composition can be uniformly dispersed in the slurry.
  • an acid or a base for adjusting the pH a surfactant for adjusting the viscosity or improving the slurry dispersibility, a dispersing resin or the like can be added.
  • a mixing method of the slurry pulverization and mixing by a ball mill or the like can be applied, but other pulverization or mixing methods may be applied.
  • the slurry-like mixture is applied to the monolithic structure type carrier.
  • a coating method is not particularly limited, but a wash coat method is preferable.
  • the exhaust gas purifying catalyst carrying the catalyst composition is obtained by drying and firing.
  • the drying temperature is preferably 70 to 150 ° C, more preferably 80 to 120 ° C.
  • the firing temperature is preferably 300 to 700 ° C, and preferably 400 to 600 ° C.
  • a heating means it can carry out by well-known heating means, such as an electric furnace and a gas furnace.
  • the catalyst device is configured by arranging the exhaust gas purification catalyst in an exhaust system from the engine.
  • the position and number of catalysts in the exhaust system from the engine can be appropriately designed according to the degree of exhaust gas regulation.
  • One vehicle can be used in a vehicle model that does not have strict exhaust gas regulations.
  • two catalysts can be used, and a catalyst directly below can be arranged upstream of the exhaust system, and a catalyst of the present invention that can exert an excellent effect on denitration performance can be arranged below the rear floor.
  • the catalyst of the present invention can also be used for the direct catalyst to improve the denitration performance. Is possible.
  • the layer structure of the catalyst of the present invention can be determined according to the NOx emission concentration and the operating system, and it can be a single layer catalyst composed of an alumina material containing barium sulfate and a single noble metal or a plurality of noble metals, or sulfuric acid.
  • a multi-layer catalyst composed of an alumina material containing barium and a single noble metal or a plurality of noble metals can be used.
  • the manufactured catalyst sample measured the physical property in the following way.
  • ⁇ SEM measurement> The powder samples of Examples and Comparative Examples were filled with resin and subjected to pretreatment for carbon deposition, and then SEM measurement was performed.
  • the catalyst structure was observed using a scanning electron microscope ULTRA55 manufactured by Carl Zeiss. Measurement was performed under the conditions of an acceleration voltage of 5 kV, an objective aperture of 60 ⁇ m, and a backscattered electron detector (RBSD). Further, the observed powder particles were qualitatively analyzed using an energy dispersive detector X-Fresh manufactured by Rontec.
  • the correlation coefficient R of the intra-particle distribution of Ba and Al was calculated by the following formula (6) from the intensity values of the characteristic X-rays of Ba and Al obtained by EPMA measurement.
  • the correlation coefficient between the intra-particle distributions of Ba and Al calculated by this method is an index of how much Ba particles are dispersed in the alumina particles, in other words, the degree of dispersion of Ba in the alumina particles.
  • the correlation coefficient is larger than +0.6, that is, when there is a strong positive correlation, the distribution of Al and Ba is well matched, and Ba is very highly dispersed in the alumina particles. I can say that.
  • a small correlation coefficient indicates that the correlation between the Al and Ba distribution is low, which means that the Ba dispersibility in the alumina particles is low.
  • the BET specific surface area of the powder sample before and after the following durability treatment was measured by the BET method.
  • the durability treatment of the powder sample was performed based on the following procedure. First, a ceramic container containing a powder sample was placed in a quartz tube for a tubular furnace, and reduction treatment was performed at 900 ° C. for 1 hour while flowing a gas having the composition shown in Table 1 at 2.0 L / min. Then, the container was moved to the electric furnace with the powder sample put therein, and baked in an air atmosphere at 1,100 ° C. for 12 hours.
  • the BET specific surface area reduction rate (%) was calculated by the following formula (7) from the BET specific surface area value at the time of preparation and the BET specific surface area value after durability.
  • ⁇ Particle size distribution measurement> The particle size distribution of the powder sample was measured by a laser scattering method using a nano particle size distribution analyzer SALD-7100 manufactured by SHIMADZU, and d50 (50% particle size: the volume-based integrated value of the amount of particles under the sieve is the whole.
  • d57.5 and d70 were also measured, and the median diameter (d50) was defined as the average particle diameter.
  • the mode diameter was also measured, and the average particle diameter attributable to alumina was determined (when two peaks appeared in the particle size distribution, the mode diameter of each peak was calculated, and the average particle diameter attributable to alumina was calculated on the large particle side. Diameter).
  • ⁇ XRD measurement> Components were identified by measuring diffraction patterns of various powder samples using an X-ray diffractometer X'Pert PRO MPD manufactured by PANalytical and collating with ICSD card data. Peak separation by a Gaussian function was performed from the obtained diffraction pattern, the half width was obtained, and the crystallite diameter (diameter) of the component was calculated using Scherrer's equation.
  • the decomposition temperature of barium sulfate in barium sulfate-alumina was measured with a thermogravimetric analyzer (TG) by grinding 10 mg of various powder samples with an agate mortar and placing them in an alumina sample holder. 1% H 2 / N 2 gas was used as the gas, and the flow rate was 100 mL / min. The temperature was raised to 1,100 ° C. at a rate of temperature increase of 10 ° C./min, and the temperature at which weight reduction after the desorption of moisture started was taken as the decomposition temperature of barium sulfate in each sample.
  • TG thermogravimetric analyzer
  • ⁇ OSC capacity measurement method 10 mg of the powder materials of the examples and comparative examples were sampled, and the OSC capacity was measured by TG-DTA.
  • TG-DTA TG-8120 manufactured by Rigaku was used.
  • pretreatment was performed at 650 ° C. for 10 minutes in air. After completion of the pretreatment, the temperature was lowered to 350 ° C. and kept at that temperature for 5 minutes. Thereafter, the atmosphere was switched to a 1.0% H 2 / N 2 atmosphere and held for 5 minutes, and the weight loss value ⁇ TG (350 ° C.) at that time was measured. It was returned to the air again and held for 5 minutes.
  • the weight loss value ⁇ TG (650 ° C.) at 650 ° C. was measured in the same manner.
  • the OSC capacity was calculated from ⁇ TG at each temperature and the change in molecular weight from CeO 2 to CeO 1.5 .
  • ⁇ Real machine durability treatment> Prepare two below-mentioned catalysts and six under-floor catalysts (Examples 1 to 5 and Comparative Example 1), which will be described later, and store the direct-under catalyst and under-floor catalyst one by one in the catalyst converter, and then the endurance bench Were installed at the position directly below the exhaust line of the engine for durability and the position below the floor. After that, the engine was operated, and under the A / F fluctuation, the catalyst for the directly underneath was set so that the catalyst bed temperature was set to 950 ° C. for 150 hours, and the catalyst for the under bed was set to 800 ° C. for 50 hours. Each endurance treatment was performed.
  • an acceleration region of 190 to 220 seconds in which the NOx purification reaction is difficult to proceed that is, a region where SV is high and NOx emission amount is large.
  • the average NOx purification rate was calculated from the NOx emission amount after passing through the underfloor catalyst with respect to the NOx emission amount.
  • Example 1 An alumina material carrying the barium sulfate of the present invention was prepared in the following manner, and its physical properties were measured. ⁇ BaSO 4 -Al 2 O 3 > Pure water is added to 848 g of ⁇ -alumina powder A having a BET specific surface area of 150 m 2 / g, an average pore size of 15 nm, and an average particle size of 35 ⁇ m, and pulverized by a wet milling apparatus, and an alumina having a median diameter (d50) of 1.5 ⁇ m. A dispersed slurry was obtained.
  • the particle size of the mixed slurry before granulation is shown in Table 2, the BET specific surface area of barium sulfate-alumina before and after endurance treatment, and the decomposition temperature of barium sulfate were measured. The results are shown in Table 3, and the average pore diameter is shown in Table 4.
  • the reduction rate of the BET specific surface area was determined from the BET specific surface area before and after the durability treatment, and the results are summarized in FIG.
  • the decomposition temperature of barium sulfate in barium sulfate-alumina was determined using a thermogravimetric analyzer (TG), and the results are summarized in FIG.
  • TG thermogravimetric analyzer
  • the relationship between the correlation coefficient between Ba-Al and the reduction rate of the BET specific surface area is summarized in FIG. 11, and the relationship with the decomposition temperature of barium sulfate is summarized in FIG.
  • Example 1 of the present invention when the barium sulfate in the obtained barium sulfate-alumina particles was measured by SEM, the average particle diameter was 300 nm (see FIG. 1 and Table 2).
  • the boundary between alumina particles generated on the cut surface is not clear in the measurement using SEM, it is difficult to specify the size, and the alumina particle cross section has the longest diameter accurately. Since it was not possible, it was impossible to specify the diameter. Therefore, an attempt was made to calculate the average particle size of alumina based on the particle size distribution of the mixed slurry of barium sulfate and alumina before granulation as surrogate characteristics.
  • the particle size distribution of the mixed slurry of barium sulfate and alumina if the average particle size of both is greatly different, the particle size distribution is separated into two peaks of barium sulfate and alumina, and the mode diameter of the peak on the large particle side was the average particle size attributable to alumina.
  • the mode diameter was 1.3 ⁇ m, and the average particle diameter of alumina before mixing was 1.5 ⁇ m.
  • the barium sulfate-alumina of Example 1 in such a situation is used as a catalyst material because the decrease in the BET specific surface area before and after the endurance treatment with the model gas is suppressed to 26.5% (see Table 3). It is expected to exhibit excellent durability even when Moreover, the decomposition temperature of barium sulfate under an oxidizing atmosphere is 1,600 ° C., but the decomposition temperature of barium sulfate under a reducing atmosphere is 832 ° C. as shown in Table 2, and is based on barium sulfate having poor reactivity. It is expected that the transition to a barium component that functions as an adsorbent for NOx will easily occur even under actual gasoline engine operation.
  • the average pore diameter (14 nm) of barium sulfate-alumina is almost the same as that of the starting material ⁇ -alumina A (15 nm) (see Table 4), and even when barium sulfate is added, the pores are not clogged. This suggests that the gas diffusion in the barium sulfate-alumina particles is at the same level as that of ⁇ -alumina.
  • Example 2 In Example 1, the alumina powder was pulverized after adding barium sulfate, but the slurry containing the alumina powder A and barium sulfate B was pulverized by a milling apparatus instead of a mixer, and the median diameter (d50) of both the mixtures was determined. A 600-nm alumina-barium sulfate dispersion slurry was obtained. This mixed slurry was granulated by the same method as in Example 1 until the average particle size became 15 ⁇ m, and 1,000 g of 15.2 wt% barium sulfate-alumina of Example 2 was obtained.
  • FIG. 3 shows a cross-sectional view of the barium sulfate-alumina EPMA particles of Example 2
  • Table 2 shows the particle size of the mixed slurry before granulation
  • Table 3 shows the BET specific surface area
  • the decomposition temperature of barium sulfate is summarized in Example 1.
  • Table 4 shows the correlation coefficient between Ba and Al
  • FIG. 8 shows the relationship between the average particle diameter of barium sulfate and the reduction rate of the BET specific surface area
  • FIG. 3 shows a cross-sectional view of the barium sulfate-alumina EPMA particles of Example 2
  • Table 2 shows the particle size of the mixed slurry before granulation
  • Table 3 shows the BET specific surface area
  • the decomposition temperature of barium sulfate shows the correlation coefficient between Ba and Al
  • FIG. 8 shows the relationship between the average particle diameter of barium sulfate and the reduction rate of the BET specific surface area
  • FIG. 10 shows the relationship between the decomposition temperature of barium sulfate and FIG. Summarized.
  • FIG. 11 shows the relationship between the correlation coefficient between Ba—Al and the reduction rate of the BET specific surface area
  • FIG. 12 shows the relationship between the decomposition temperature of barium sulfate.
  • the decomposition temperature of barium sulfate in a reducing atmosphere is 847 ° C (see Table 3), so it is easy to shift from poorly reactive barium sulfate to barium, which functions as an adsorbent for NOx, even under actual gasoline engine operation. Is expected to happen.
  • the average pore diameter (13 nm) of barium sulfate-alumina is almost the same as that of the starting material ⁇ -alumina A (15 nm) (see Table 4), and even when barium sulfate is added, the pores are not clogged. This suggests that the gas diffusion in the barium sulfate-alumina particles is at the same level as that of ⁇ -alumina.
  • Example 3 The same procedure as in Example 2 was used except that barium sulfate C having a crystallite diameter of 30 nm was used instead of barium sulfate B in Example 2, and 1,000 g of 15.2 wt% barium sulfate-alumina in Example 3 was used. Got. Next, the physical properties of barium sulfate in barium sulfate-alumina of Example 3 were measured in the same manner as in Example 1. The average particle diameters are summarized in FIG. 1 and Table 2, and the decomposition temperatures are summarized in FIG. In addition, FIG.
  • FIG. 4 is a cross-sectional view of the EPMA particles of barium sulfate-alumina of Example 3, Table 2 shows the particle size of the mixed slurry before granulation, Table 3 shows the BET specific surface area and barium sulfate decomposition temperature, and average pore diameter. Table 4 shows the correlation coefficient between Ba and Al, FIG. 8 shows the relationship between the average particle diameter of barium sulfate and the reduction rate of the BET specific surface area, and FIG. 10 shows the relationship between the decomposition temperature of barium sulfate and FIG. Summarized. FIG. 11 shows the relationship between the correlation coefficient between Ba—Al and the reduction rate of the BET specific surface area, and FIG. 12 shows the relationship between the decomposition temperature of barium sulfate.
  • the average particle diameter of barium sulfate in the particles was as very small as 65 nm (see FIG. 1 and Table 2), and the average particle diameter of alumina (mode) (Diameter) was 1.3 ⁇ m, which was almost the same as d57.6 (1.2 ⁇ m) (see Table 2), and was equivalent to Example 1. Furthermore, the correlation coefficient between Ba-Al in the same particle was 0.95, showing a very strong correlation (see FIG. 8). These results indicate that very fine particles of barium sulfate are dispersed almost uniformly in the barium sulfate-alumina particles.
  • the barium sulfate-alumina of Example 3 in such a situation has a decrease in BET specific surface area of 24.1% before and after the endurance treatment with model gas (see Table 3), and is used as a catalyst material. It is expected to exhibit excellent durability even when In addition, the decomposition temperature of barium sulfate in a reducing atmosphere is 752 ° C. (see Table 3), which is significantly lower than that of Example 1. It can be seen that barium sulfate in Example 3 is very easily decomposed.
  • the transition from barium sulfate, which is poor in reactivity, to barium, which functions as an adsorbent for NOx, is considered to occur very easily even under actual gasoline engine operation, and is expected to exhibit excellent denitration performance.
  • the average pore diameter (14 nm) of barium sulfate-alumina is almost the same as that of the starting material ⁇ -alumina A (15 nm) (see Table 4), and even when barium sulfate is added, the pores are not clogged. This suggests that the gas diffusion in the barium sulfate-alumina particles is at the same level as that of ⁇ -alumina.
  • Example 4 The same procedure as in Example 2 was used except that barium sulfate D having a crystallite diameter of 10 ⁇ m was used instead of barium sulfate B in Example 2, and 1,000 g of 15.2 wt% barium sulfate-alumina in Example 4 was used. Got. Next, in the same manner as in Example 1, the physical properties of barium sulfate in barium sulfate-alumina of Example 4 were measured. The average particle diameter was summarized in FIG. 1 and the decomposition temperature was summarized in FIG. Further, the EPMA particle cross section of barium sulfate-alumina of Example 4 is shown in FIG.
  • the particle size of the mixed slurry before granulation is shown in Table 2, the BET specific surface area, the decomposition temperature of barium sulfate in Table 3, and the average pore diameter Table 4 shows the correlation coefficient between Ba and Al
  • FIG. 8 shows the relationship between the average particle diameter of barium sulfate and the reduction rate of the BET specific surface area
  • FIG. 10 shows the relationship between the decomposition temperature of barium sulfate and FIG. It was.
  • FIG. 11 shows the relationship between the correlation coefficient between Ba—Al and the reduction rate of the BET specific surface area
  • FIG. 12 shows the relationship between the decomposition temperature of barium sulfate.
  • the average particle diameter of barium sulfate in the particles is 550 nm (see FIG. 1 and Table 2), and the average particle diameter (mode diameter) of alumina is 3.6 ⁇ m. It corresponds to d57.6 (3.6 ⁇ m) (see Table 2), is relatively large in the examples (see FIG. 1), and the correlation coefficient between Ba and Al in the particles is also 0. 34 and the correlation of the barium sulfate particles were slightly reduced (see FIG. 8). This result indicates that the dispersibility in the barium sulfate-alumina particles is slightly reduced when the barium sulfate particles are enlarged.
  • Example 4 In the barium sulfate-alumina of Example 4 in such a situation, the decrease in the BET specific surface area before and after the durability treatment with the model gas was 32.0%, which is slightly worse than that of Example 1 (see Table 3). It is believed that the dispersibility of barium sulfate can improve the thermal durability of the material. Moreover, the decomposition temperature of barium sulfate in a reducing atmosphere is 889 ° C. (see Table 3), which is slightly higher than that of Example 1, and it can be seen that barium sulfate is difficult to decompose.
  • barium sulfate which is poor in reactivity
  • barium which functions as an adsorbent for NOx
  • the average pore diameter (15 nm) of barium sulfate-alumina is the same as that of the starting material ⁇ -alumina A (15 nm) (see Table 4). Even if barium sulfate is added, the pores are blocked or narrowed. It does not occur, suggesting that gas diffusion within the barium sulfate-alumina particles is at the same level as ⁇ -alumina.
  • Example 5 A slurry containing 600 g of ⁇ -alumina powder A and 400 g of barium sulfate B was pulverized by a milling apparatus, and an alumina-barium sulfate dispersion slurry in which the median diameter (d50) of both the mixtures was 500 nm was obtained. This mixed slurry was granulated to 15 ⁇ m in the same manner as in Example 1 to obtain 1,000 g of 40 wt% barium sulfate-alumina of Example 5. Next, the physical properties of barium sulfate in barium sulfate-alumina of Example 5 were measured in the same manner as in Example 1. The average particle diameter is summarized in FIG.
  • FIG. 6 shows the EPMA particle cross-sectional view of barium sulfate-alumina of Example 5
  • the particle size of the mixed slurry before granulation is shown in Table 2
  • the average pore diameter Table 4 shows the correlation coefficient between Ba and Al
  • FIG. 8 shows the relationship between the average particle diameter of barium sulfate and the reduction rate of the BET specific surface area
  • FIG. 10 shows the relationship between the decomposition temperature of barium sulfate and FIG. Summarized.
  • FIG. 11 shows the relationship between the correlation coefficient between Ba—Al and the reduction rate of the BET specific surface area
  • FIG. 11 shows the relationship between the correlation coefficient between Ba—Al and the reduction rate of the BET specific surface area
  • the barium sulfate-alumina obtained in Example 5 of the present invention has an average particle diameter of 80 nm of barium sulfate in the particles, which is very small as in Example 3 (see FIG. 1 and Table 2).
  • the particle diameter (mode diameter) is also 0.7 ⁇ m ⁇ d70: when the mixing ratio of barium sulfate is 40% by weight and the mixing ratio of alumina is 60% by weight, a half value of 30% by weight and 70% by weight of barium sulfate are mixed. It almost coincided with the particle size (0.6 ⁇ m) of time (see Table 2), and was as small as Example 2.
  • Example 5 the mixing ratio of barium sulfate in the barium sulfate-alumina obtained in Example 5 is 40% by weight, which is 2.6 times that in Example 3 (15.2% by weight). This is thought to be due to the effect of the reduction in the BET specific surface area of barium itself.
  • the decomposition temperature of barium sulfate in a reducing atmosphere is 782 ° C. (see Table 3), which is slightly higher than that of Example 3 (752 ° C.), and barium sulfate in Example 5 is an example. As with No. 3, it can be seen that it is very easy to disassemble.
  • the transition from barium sulfate, which is poor in reactivity, to barium, which functions as an adsorbent for NOx, is considered to occur very easily even under actual gasoline engine operation, and excellent denitration performance is expected.
  • the average pore diameter (14 nm) of barium sulfate-alumina is almost the same as that of the starting material ⁇ -alumina A (15 nm) (see Table 4), and even when barium sulfate is added, the pores are not clogged. This suggests that the gas diffusion in the barium sulfate-alumina particles is at the same level as that of ⁇ -alumina.
  • FIG. 7 is a cross-sectional view of the EPMA particles of barium sulfate-alumina of Example 2
  • Table 2 shows the particle size of the mixed slurry before granulation
  • Table 3 shows the BET specific surface area and barium sulfate decomposition temperature
  • Ba—Al shows the correlation coefficient between them
  • FIG. 9 shows the relationship between the average particle diameter of barium sulfate and the reduction rate of the BET specific surface area
  • FIG. 10 shows the relationship between the decomposition temperature of barium sulfate.
  • FIG. 11 shows the relationship between the correlation coefficient between Ba—Al and the reduction rate of the BET specific surface area
  • FIG. 12 shows the relationship between the decomposition temperature of barium sulfate.
  • the barium sulfate-alumina obtained in Comparative Example 1 has an average dispersed particle diameter of barium sulfate in the particles of 1,000 nm (see FIG. 1 and Table 2), and the average particle diameter (mode diameter) of alumina is 34. It was 4 ⁇ m, almost coincident with d57.6 (34.6 ⁇ m) (see Table 2), and remained large. Further, the correlation coefficient between Ba—Al in the same particle was ⁇ 0.56, which was a relatively strong negative correlation (see FIG. 8). This result indicates that the barium sulfate particles remain large, and are present in the barium sulfate-alumina particles with little dispersion and exist individually.
  • the barium sulfate-alumina of Comparative Example 1 in such a situation has a reduction rate of the BET specific surface area of 41.2% before and after the endurance treatment with the model gas (see Table 3), and is used as a catalyst material. There is a risk of causing problems in durability performance.
  • the decomposition temperature of barium sulfate in a reducing atmosphere with model gas is as high as 932 ° C. (see Table 3), and it can be seen that barium sulfate is difficult to decompose.
  • Example 6 Pd-supported BaSO 4 —Al 2 O 3 , Pd-supported Al 2 O 3 , and Pd-supported CeO 2 —ZrO 2 -based composite oxides were prepared and combined with barium sulfate in various states. It was measured how the occlusion / release capacity (OSC capacity) changes.
  • OSC capacity occlusion / release capacity
  • ⁇ Pd-supported BaSO 4 -Al 2 O 3 > A palladium nitrate solution (1.2 g) was weighed out by weight of Pd, diluted with pure water, and impregnated and supported on 50 g of 40 wt% barium sulfate-alumina of Example 5. This water-containing powder was fired in air at 500 ° C.
  • ⁇ Pd-supported CeO 2 —ZrO 2 composite oxide> A palladium nitrate solution was weighed out by 0.8 g in terms of Pd weight, diluted with pure water, and 45.0 wt% ceria-5.0 wt% lanthanum oxide having a BET specific surface area of 70 m 2 / g and an average pore diameter of 16 nm-50. It was impregnated and supported on 80 g of 0 wt% zirconia composite oxide powder E. The hydrated powder was fired in air at 500 ° C. for 1 hour to prepare a 0.99 wt% Pd-supported ceria-zirconia composite oxide c.
  • the amount of OSC exceeds that containing no barium sulfate when the BaSO 4 content is 9% by weight or less. Further, when the BaSO 4 content exceeds 9% by weight, the amount of OSC is less than that containing no barium sulfate due to the effect of barium sulfate, but the decrease is within about 20 ⁇ mol / g, and the effect is slight. From this result, it is considered that the adverse effect of barium sulfate on OSC is slight if the barium sulfate-alumina of the present invention is physically mixed with OSC.
  • Example 2 The barium acetate crystals were weighed in two levels (0.5 g, 2.0 g) in terms of barium sulfate and then dissolved in pure water to prepare two types of barium acetate aqueous solutions.
  • Example 6 without using 2.36 wt% Pd-supported barium sulfate-alumina a, 0.99 wt% Pd-supported ceria-zirconia composite oxide c 8.08 g, 2.34 wt% Pd-supported alumina b 5.12 g was dispersed in pure water, and the two kinds of the aqueous barium acetate solution were added thereto, and stirred for about 30 minutes to adsorb barium onto alumina.
  • Example 7 Pd-supported Al 2 O 3 , Pd-supported CeO 2 —ZrO 2 -based composite oxide, Pd-supported BaSO 4 —Al 2 O 3 , and Pd-supported Nd 2 O 3 —ZrO 2 were prepared in the following manner.
  • ⁇ Pd-supported Al 2 O 3 > A palladium nitrate solution was weighed 1.84 g by weight of Pd, diluted with pure water, and impregnated on 400 g of ⁇ -alumina powder A. This water-containing powder was baked in air at 500 ° C. for 1 hour to prepare 0.458 wt% Pd-supported alumina d.
  • ⁇ Pd-supported CeO 2 —ZrO 2 composite oxide A palladium nitrate solution was weighed 1.35 g by weight of Pd, diluted with pure water, and impregnated and supported on 400 g of ceria-lanthanum oxide-zirconia composite oxide powder E. This hydrous powder was fired in air at 500 ° C. for 1 hour to prepare 0.336 wt% Pd-supported ceria-zirconia composite oxide e. ⁇ Pd-supported BaSO 4 -Al 2 O 3 > The palladium nitrate solution was weighed 1.76 g by Pd weight, diluted with pure water, and impregnated on 200 g of barium sulfate-alumina of Example 1.
  • the water-containing powder was fired in air at 500 ° C. for 1 hour to prepare 0.87 wt% Pd-supported barium sulfate-alumina f. Further, the same treatment was carried out using 3.6 g of palladium nitrate solution by weight of Pd and 450 g of barium sulfate-alumina of Example 1 to prepare 0.794 wt% Pd-supported barium sulfate-alumina g.
  • ⁇ Pd-supported Nd 2 O 3 —ZrO 2 > 3.6 g of palladium nitrate solution was weighed out by Pd weight, diluted with pure water, and 15 wt% neodymium oxide-5 wt% lanthanum oxide-80 wt% zirconia composite with a BET specific surface area of 65 m 2 / g and an average pore diameter of 25 nm.
  • the oxide powder F was impregnated and supported on 550 g.
  • the water-containing powder was fired in air at 500 ° C. for 1 hour to prepare 0.65 wt% Pd-supported neodymium oxide-zirconia composite oxide h.
  • a cordierite honeycomb carrier was applied in two layers in the following manner to obtain a catalyst of the present invention (underfloor catalyst).
  • Underfloor catalyst ⁇ Lower layer of underfloor catalyst> 0.458 wt% Pd-supported alumina d 400.23 g, 0.336 wt% Pd-supported ceria-zirconia composite oxide e 401.35 g, 0.87 wt% Pd-supported barium sulfate-alumina f 200.22 g pure water And mixed and ground in a pot mill to prepare a slurry.
  • a predetermined amount of this slurry is applied to a cordierite honeycomb carrier ⁇ (400 cells / inch 2 (620 k / m 2 ), 3.5 mil (0.089 mm) ⁇ ) having a volume of 1.0 L, and the slurry is applied at 80 ° C. for 20 minutes. After drying, calcination was performed at 450 ° C. for 1 hour to obtain a lower layer (catalyst weight: 100.18 g / L, Pd: 0.49 g / L) of the underfloor catalyst of Example 6.
  • ⁇ Upper layer of underfloor catalyst> Add pure water to 0.65 wt% Pd-supported neodymium oxide-zirconia composite oxide h (553.6 g), 0.794 wt% Pd-supported barium sulfate-alumina g (453.6 g), and alumina sol (5 g in terms of alumina).
  • a slurry was prepared by mixing and pulverizing. This slurry was applied to the honeycomb carrier coated with the lower layer of the underfloor catalyst to obtain an upper layer (catalyst weight: 101.22 g / L, Pd: 0.72 g / L) of the underfloor catalyst of Example 6.
  • the underfloor catalyst of Example 7 (total catalyst weight: 201.4 g / L, Pd: 1.21 g / L) was obtained by the above series of catalyst preparation methods.
  • each converter After storing each of the above underfloor catalysts in the catalytic converter together with the direct catalyst prepared in the following manner, each converter is installed at the position directly below the floor in the exhaust system of the durable gasoline engine.
  • the catalyst bed temperature was maintained at 950 ° C. for 150 hours, and the under-bed catalyst was maintained at a catalyst bed temperature of 800 ° C. for 50 hours.
  • each endurance-treated converter was installed immediately below the exhaust system of the evaluation vehicle and below the floor, and the evaluation was performed in the driving mode LA-4.
  • FIG. 14 shows the average NOx purification rate in the acceleration region during driving in the LA-4 mode.
  • the underfloor catalyst using the barium sulfate-alumina of the present invention exhibited a high denitration performance of 80.4%.
  • catalyst layer immediately below (catalyst weight: 162.0 g / L, Pd: 2.0 g / L).
  • the slurry was coated on a honeycomb carrier coated with the lower layer of the underfloor catalyst to obtain an upper layer (catalyst weight: 85.1 g / L, Pd: 1.6 g / L) immediately below the catalyst.
  • a catalyst directly underneath total catalyst weight: 247.1 g / L, Pd: 3.6 g / L was obtained.
  • Example 8 The underfloor catalyst of Example 8 (total catalyst weight: 201.4 g / L) was used in the same manner as in Example 7, except that barium sulfate-alumina in Example 2 was used instead of barium sulfate-alumina in Example 1. , Pd: 1.21 g / L). (Catalyst performance) After storing the above-mentioned underfloor catalyst together with the direct catalyst in each catalytic converter, each converter is installed in the exhaust gas exhaust system of the durable gasoline engine at the position directly below and below the floor, and the catalyst directly below the catalyst bed temperature is 950 ° C. The underfloor catalyst was durable for 50 hours at a catalyst bed temperature of 800 ° C. for 150 hours.
  • FIG. 14 shows the average NOx purification rate in the acceleration region during driving in the LA-4 mode.
  • the underfloor catalyst using the barium sulfate-alumina of the present invention exhibited a high denitration performance of 85.6%.
  • Example 9 The underfloor catalyst of Example 9 (total catalyst weight: 201.4 g / L) was used in the same manner as in Example 7, except that barium sulfate-alumina in Example 3 was used instead of barium sulfate-alumina in Example 1. , Pd: 1.21 g / L). (Catalyst performance) After storing the above-mentioned underfloor catalyst together with the direct catalyst in each catalytic converter, each converter is installed in the exhaust gas exhaust system of the durable gasoline engine at the position directly below and below the floor, and the catalyst directly below the catalyst bed temperature is 950 ° C. The underfloor catalyst was durable for 50 hours at a catalyst bed temperature of 800 ° C. for 150 hours.
  • FIG. 14 shows the average NOx purification rate in the acceleration region during driving in the LA-4 mode.
  • the underfloor catalyst using barium sulfate-alumina of the present invention exhibited a high denitration performance of 89.2%.
  • Example 10 The underfloor catalyst of Example 10 (total catalyst weight: 201.4 g / L) was used in the same manner as in Example 7, except that barium sulfate-alumina in Example 4 was used instead of barium sulfate-alumina in Example 1. , Pd: 1.21 g / L). (Catalyst performance) After storing the above-mentioned underfloor catalyst together with the direct catalyst in each catalytic converter, each converter is installed in the exhaust gas exhaust system of the durable gasoline engine at the position directly below and below the floor, and the catalyst directly below the catalyst bed temperature is 950 ° C. The underfloor catalyst was durable for 50 hours at a catalyst bed temperature of 800 ° C. for 150 hours.
  • FIG. 14 shows the average NOx purification rate in the acceleration region during driving in the LA-4 mode.
  • the underfloor catalyst using barium sulfate-alumina of the present invention exhibited a relatively high denitration performance of 78.2%.
  • Comparative Example 4 The underfloor catalyst of Comparative Example 4 (total catalyst weight: 201.4 g / wt) was prepared in the same manner as in Example 6 except that the barium sulfate-alumina mixture of Comparative Example 1 was used instead of the barium sulfate-alumina of Example 1. L, Pd: 1.21 g / L). After storing each of the direct catalyst used in Example 6 and the underfloor catalyst of Comparative Example 1 in the catalytic converter, each was installed at the position directly below the exhaust line of the durable engine and the position below the floor. After that, the engine was operated, and the catalyst bed temperature of the catalyst directly below was adjusted to 950 ° C.
  • FIG. 15 summarizes the relationship between the average particle diameter of barium sulfate in the barium sulfate-alumina of Comparative Example 1 shown in FIG. 1 and the average NOx purification rate of FIG.
  • FIG. 14 shows the relationship between the correlation coefficient between Ba-Al of barium sulfate-alumina of Comparative Example 1 shown in FIG. 8 and the average NOx purification rate of FIG. 14.
  • each converter is installed in the exhaust gas exhaust system of the durable gasoline engine at the position directly below and below the floor, and the catalyst directly below the catalyst bed temperature is 950 ° C.
  • the underfloor catalyst was durable for 50 hours at a catalyst bed temperature of 800 ° C. for 150 hours.
  • each endurance-treated converter was installed immediately below the exhaust system of the evaluation vehicle and below the floor, and the evaluation was performed in the driving mode LA-4.
  • FIG. 14 shows the average NOx purification rate in the acceleration region during driving in the LA-4 mode.
  • the underfloor catalyst using barium sulfate-alumina for comparison had a low denitration performance of 71.8%.
  • the barium sulfate-alumina obtained in Examples 1 to 5 of the present invention all had an average dispersed particle diameter of barium sulfate in the particles of 600 nm or less.
  • the barium sulfate-alumina of Comparative Example 1 obtained by the same method had an average dispersed particle diameter of barium sulfate of 1,000 nm, which was larger than that of the present invention.
  • the barium sulfate-alumina of Examples 1 to 5 showed a positive correlation when the correlation coefficient between Ba—Al in the particles was 0.3 or more.
  • the barium sulfate-alumina of Comparative Example 1 obtained by the same method showed a negative correlation with a correlation coefficient between Ba—Al in the particles of ⁇ 0.6.
  • the decomposition temperature of barium sulfate was lower as the average particle size of barium sulfate was smaller.
  • the decrease rate of the BET specific surface area was deteriorated due to the decrease of the BET specific surface area of the barium sulfate itself.
  • a similar phenomenon is also observed in relation to the correlation coefficient between Ba-Al in barium sulfate-alumina. As is clear from FIGS. 11 and 12, the larger the average particle diameter, the more positive the Ba-Al relationship.
  • the decrease rate of the BET specific surface area decreased as the correlation coefficient decreased and the positive correlation coefficient between Ba and Al increased.
  • the mixing ratio of barium sulfate was extremely increased, the decrease rate of the BET specific surface area was deteriorated due to the decrease of the BET specific surface area of the barium sulfate itself.
  • the average particle diameter of barium sulfate in barium sulfate-alumina is 10 to 800 nm
  • the average particle diameter of alumina is 300 nm to 5 ⁇ m
  • the correlation coefficient between Ba and Al Is 0.3 or more, it indicates that the decrease in the BET specific surface area during durability is suppressed, and that the decomposition of barium sulfate also occurs from a low temperature. Barium is involved, and the catalyst is exposed to a high temperature. This suggests that it is effective in promoting a catalytic reaction that may occur.
  • the underfloor catalysts of Examples 7 to 10 manufactured using the barium sulfate-alumina of Examples 1 to 4 of the present invention have an average NOx purification rate of 75% or more in the acceleration region when running in the LA-4 mode. High performance was shown.
  • the underfloor catalyst of Comparative Example 4 produced using the barium sulfate-alumina of Comparative Example 1 had lower denitration performance than the underfloor catalysts of Examples 7 to 10.
  • the denitration performance improved as the average particle size of barium sulfate in barium sulfate-alumina decreased.
  • the relationship between barium sulfate-alumina and OSC of the present invention it can be seen from Example 6 in FIG. 13 that barium sulfate affects OSC as long as barium sulfate-alumina is physically mixed with OSC. The adverse effect is considered to be minor, and the denitration performance improved as the correlation coefficient between Ba-Al in barium sulfate-alumina increased with a positive value.
  • the particle diameter of barium sulfate and the correlation coefficient between Ba-Al in the alumina material containing barium sulfate added to the catalyst play an important role in improving the denitration performance.
  • the average particle diameter of barium sulfate dispersed in the alumina material is 10 to 800 nm
  • the average particle diameter of alumina is 300 nm to 5 ⁇ m
  • the correlation coefficient between Ba and Al is 0.3 or more.
  • the alumina material containing barium sulfate according to the present invention is used to purify NOx among carbon monoxide (CO), hydrocarbon (HC) and nitrogen oxide (NOx) in exhaust gas discharged from an internal combustion engine such as a gasoline engine. It can be used as a raw material for an exhaust gas purification catalyst having excellent performance, and can also be used as an adsorbent. Further, the exhaust gas purifying catalyst of the present invention is not limited to automotive applications, and can be widely applied to a denitration technique for nitrogen oxides in exhaust gas.

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  • General Chemical & Material Sciences (AREA)
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Abstract

L'invention concerne : une matière d'alumine contenant du sulfate de baryum et ayant un diamètre moyen de particule de 5 à 50 µm, dans laquelle le sulfate de baryum est dispersé dans des espaces formés parmi les particules d'alumine (I) finement et uniformément, ladite matière d'alumine étant caractérisée en ce qu'elle est produite par granulation d'une bouillie qui a été soumise à un traitement de broyage/dispersion de telle sorte que le diamètre moyen de particule de l'alumine (I) peut passer de 300 nm à 5 µm et le diamètre moyen de particule de sulfate de baryum peut passer de 10 à 800 nm, puis brûlure du produit de granulation, et étant également caractérisée en ce que le sulfate de baryum est dispersé dans l'alumine (I) dans un tel état qu'un coefficient de corrélation Ba-Al dans les particules de matière d'alumine est 0,3 ou plus, tel que calculé sur la base d'une valeur de mesure d'une analyse de section transversale EPMA ; un procédé de production de la matière d'alumine contenant du sulfate de baryum ; un catalyseur destiné à être utilisé dans la purification d'un gaz d'échappement, qui est produit à l'aide de la matière d'alumine contenant un sulfate de baryum ; et d'autres. On préfère que la matière d'alumine contenant du sulfate de baryum soit revêtue, comme couche de catalyseur, sur un support ayant une structure intégrée.
PCT/JP2014/057060 2013-03-28 2014-03-17 Matière d'alumine contenant du sulfate de baryum et son procédé de production, et catalyseur destiné à être utilisé dans la purification de gaz d'échappement la comprenant WO2014156746A1 (fr)

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WO2018190300A1 (fr) * 2017-04-11 2018-10-18 株式会社キャタラー Catalyseur pour la purification de gaz d'échappement
EP3854478A4 (fr) * 2018-10-04 2021-07-28 Cataler Corporation Catalyseur de purification de gaz d'échappement
WO2022030241A1 (fr) * 2020-08-07 2022-02-10 株式会社キャタラー Catalyseur de purification de gaz d'échappement
JP2022066935A (ja) * 2020-10-19 2022-05-02 トヨタ自動車株式会社 排ガス浄化装置
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WO2018190300A1 (fr) * 2017-04-11 2018-10-18 株式会社キャタラー Catalyseur pour la purification de gaz d'échappement
CN110494215A (zh) * 2017-04-11 2019-11-22 株式会社科特拉 排气净化用催化剂
JPWO2018190300A1 (ja) * 2017-04-11 2020-05-14 株式会社キャタラー 排ガス浄化用触媒
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JP2022030628A (ja) * 2020-08-07 2022-02-18 株式会社キャタラー 排ガス浄化用触媒
JP2022066935A (ja) * 2020-10-19 2022-05-02 トヨタ自動車株式会社 排ガス浄化装置
JP7317787B2 (ja) 2020-10-19 2023-07-31 トヨタ自動車株式会社 排ガス浄化装置
US11786885B2 (en) 2021-08-13 2023-10-17 Johnson Matthey Public Limited Company Sulfur-containing organic compound assisted metal nanoparticle synthesis for three-way catalysis application

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