Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
  • B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
  • B01J23/89—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with noble metals
  • B01J23/892—Nickel and noble metals
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
  • B01D53/34—Chemical or biological purification of waste gases
  • B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases
  • B01D53/94—Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
  • B01D53/9404—Removing only nitrogen compounds
  • B01D53/9409—Nitrogen oxides
  • B01D53/9413—Processes characterised by a specific catalyst
  • B01D53/9422—Processes characterised by a specific catalyst for removing nitrogen oxides by NOx storage or reduction by cyclic switching between lean and rich exhaust gases (LNT, NSC, NSR)
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J2235/00—Indexing scheme associated with group B01J35/00, related to the analysis techniques used to determine the catalysts form or properties
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J2235/00—Indexing scheme associated with group B01J35/00, related to the analysis techniques used to determine the catalysts form or properties
  • B01J2235/15—X-ray diffraction
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J2235/00—Indexing scheme associated with group B01J35/00, related to the analysis techniques used to determine the catalysts form or properties
  • B01J2235/30—Scanning electron microscopy; Transmission electron microscopy
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J35/00—Catalysts, in general, characterised by their form or physical properties
  • B01J35/30—Catalysts, in general, characterised by their form or physical properties characterised by their physical properties
  • B01J35/391—Physical properties of the active metal ingredient
  • B01J35/393—Metal or metal oxide crystallite size
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J35/00—Catalysts, in general, characterised by their form or physical properties
  • B01J35/40—Catalysts, in general, characterised by their form or physical properties characterised by dimensions, e.g. grain size
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J35/00—Catalysts, in general, characterised by their form or physical properties
  • B01J35/40—Catalysts, in general, characterised by their form or physical properties characterised by dimensions, e.g. grain size
  • B01J35/45—Nanoparticles
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
  • B01J37/02—Impregnation, coating or precipitation
  • B01J37/0201—Impregnation
  • B01J37/0203—Impregnation the impregnation liquid containing organic compounds
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
  • B01J37/02—Impregnation, coating or precipitation
  • B01J37/0201—Impregnation
  • B01J37/0211—Impregnation using a colloidal suspension
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2255/00—Catalysts
  • B01D2255/10—Noble metals or compounds thereof
  • B01D2255/104—Silver
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2255/00—Catalysts
  • B01D2255/20—Metals or compounds thereof
  • B01D2255/207—Transition metals
  • B01D2255/20753—Nickel
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2258/00—Sources of waste gases
  • B01D2258/01—Engine exhaust gases
  • B01D2258/012—Diesel engines and lean burn gasoline engines

Definitions

• the present invention relates to a nitrogen oxide (hereinafter, may be also abbreviated as NO x ) purification catalyst and a method of producing the same. More particularly, the present invention relates to a novel NO x purification catalyst in which particulates consisting of specifically of two kinds of metals are supported on a metal oxide carrier and to a method of producing the same .
• NO x nitrogen oxide
• exhaust gas purification catalysts are used in internal-combustion engines.
• noble metals such as Pt, Pd and Rh are used as a catalyst component.
• exhaust gas purification catalyst in which a metal other than the aforementioned noble metals, for example, a base metal, is supported on a metal oxide carrier commonly used as a carrier in exhaust gas purification catalysts have hitherto exhibited low purification performance for the aforementioned three components in exhaust gases, particularly NO x .
• an exhaust gas purification catalyst in which the effect of the gas composition of the exhaust gas on the catalytic activity is small is demanded.
• JP H11-342339A discloses an exhaust gas purification catalyst comprising a first catalyst for oxidizing NO to NO2 and a second catalyst which cracks HC having a large number of carbon atoms to HC having a small number of carbon atoms and reduces N0 2 by allowing the thus cracked HC to react with NO2, the first of these catalyst contains Ag and Ni as catalytic metals, the first catalyst being supported on a carrier and the amount of the supported Ag and Ni being 20 to 60 g and 20 to 50 g, respectively, with respect to 1 L of the
• WO 2008-088027 discloses an exhaust gas purification device which comprises an oxidation catalyst and oxidizes particulate matters (PM) present in exhaust gas using metal oxide particulates, in which oxidation catalyst metal oxide particulates having an average primary particle diameter of 1 to 400 nm are dispersed on a catalytic metal support made of a first metal of at least one selected from the group consisting of Ag, Pt, Rh, Pd, Ru, Ir, Os, Au and Cu, the metal oxide
• particulates being selected from the group consisting of: oxides in which the metal has a variable valance and is one of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y, Zr, Fe, Ti, Al, Mg, Co, Ni, Mn, Cr, Mo, W, V, Zn and Sn; solid solutions thereof; and composite oxides thereof.
• the exhaust gas purification device which was obtained by adding an aqueous solution of Ce salt, La salt and Ag salt to ammonia water and coating aggregates prepared from the thus obtained solution by calcination onto DPF (made of cordierite) , exhibits favorable PM oxidation performance.
• JP 2010-88957A discloses an exhaust gas purification catalyst which comprises a porous metal having pores of 1 to 15 nm, the porous metal containing at least one metal selected from the group consisting of Ru, Os, Rh, Ir, Pd, Pt, Ag and Au and at least one metal selected from the group consisting of Fe, Cu, Co and Ni.
• the exhaust gas purification catalyst which was prepared by annealing and powdering an intermetallic compound obtained by melting and cooling Au and Al in an arc melting furnace device and by subsequently eluting Al with an alkali or acid, has superior CO oxidation performance .
• Patent Document 1 JP H11-342339A
• Patent Document 2 WO 2008-088027
• an object of the present invention is to provide a NO x purification catalyst which utilizes Ag as one of the catalyst components and which is capable of exhibiting NO x purification performance without adjusting conditions to a special exhaust gas composition.
• Another object of the present invention is to provide a method of producing a NO x purification catalyst which utilizes Ag as one of the catalyst
• the present invention relates to a nitrogen oxide purification catalyst (hereinafter, may be abbreviated as
• aforementioned particulates consist of Ag and Ni and the aforementioned Ag and Ni are at least partially alloyed.
• the present invention relates to a method of producing a nitrogen oxide purification
• the phrase "Ag and Ni are at least partially alloyed" means either that, when the X-ray diffraction peaks of the particulates supported on the carrier are measured for a catalyst sample in
• a suitable method is
• the former may be selected in the case of Al 2 0 3 , while the latter may be selected in the case of Si0 2 .
• the phrase "without adjustment to a special exhaust gas composition” means that the exhaust gas composition is, without any treatment by which to allow it to contain high-carbon- number HC, modified such as to revome a part of the aforementioned three components or the like, in a
• purification catalyst which utilizes Ag as a catalytic noble metal component and is capable of exhibiting NO x purification performance without adjustment to a special exhaust gas composition can be obtained.
• a NO x purification catalyst which utilizes Ag as a catalytic noble metal component and is capable of exhibiting NO x purification performance without adjustment to a special exhaust gas composition can be easily obtained.
• Fig. 1 is a graph comparing the NO reaction activity between the NO x purification catalyst obtained in an
• Example in which particulates containing Ag and Ni are supported on Al 2 0 3 carrier may be also simply referred to as Ag-Ni/Al 2 0 3 -based N0 X purification catalyst or Ag-Ni/Al 2 0 3 ) and an exhaust gas purification catalyst which is outside the scope of the present invention .
• Fig. 2 is a graph showing the relationship between the surface Ni concentrations of single-element metal and binary metal particles after adsorption of 1 Langmuir of NO at room temperature and the Nls peak intensity.
• Fig. 3 is a graph showing the results of measuring the NO thermal desorption temperature on thin films of alloys and single metals by in-situ XPS.
• Fig. 4 is a graph comparing the NO reaction activity between the Ag-Ni/Al 2 0 3 -based NO x purification catalyst obtained in an Example and an exhaust gas purification catalyst in which Ag and Ni were co-impregnated on AI2O3 carrier, which catalyst is outside the scope of the present invention (hereinafter, may be also simply abbreviated as Ag, Ni co-impregnation/Al 2 0 3 -based NO x purification catalyst or Ag, Ni co-impregnation/Al 2 0 3 ) .
• Fig. 5 is a graph showing the NO reaction activity of the Ag-Ni/Al 2 0 3 -based NO x purification catalyst
• Fig. 6 is a graph showing the NO reaction activity of a nitrogen oxide purification catalyst in which particulates of alloyed Au and Ni are supported on AI2O3 carrier, which catalyst is outside the scope of the present invention (hereinafter, may be also simply abbreviated as Au-Ni/Al 2 0 3 -based NO x purification
• Fig. 7 shows the Ols spectra on Ag-Ni alloy thin film at different temperatures obtained by XPS.
• Fig. 8 shows X-ray diffraction data for the metal particulates of a nitrogen oxide purification catalyst obtained in an Example in which particulates of alloyed
• Ag and Ni are supported on Si0 2 carrier (hereinafter, may be also simply abbreviated as Ag-Ni/Si0 2 -based N0 X
• Fig. 9A shows a TE image of the Ag-Ni/Al 2 0 3 -based NO x purification catalyst obtained in an Example.
• Fig. 9B shows the results of TEM-EDX analyses performed on seven arbitrary particulates in the TEM image shown in Fig. 9A.
• Fig. 10A shows a TEM image of the Ag, Ni
• Fig. 10B shows the results of TEM-EDX analyses performed on seven arbitrary particulates in the TEM image shown in Fig. 10A.
• aforementioned at least partial alloying is one indicated by the fact that measured X-ray diffraction peaks of the particulates supported on the carrier are confirmed to have shifted to the side of higher angle relative to peaks for Ag, or one indicated by the fact that the existence of both Ag and Ni elements on the same carrier is confirmed by TEM-EDX analysis of TEM images of the particulates.
• aforementioned metal oxide carrier is A1 2 0 3 particles
• particulates consisting of Ag and Ni are supported on a metal oxide carrier and the
• the NO x purification catalyst can exhibit NO x purification performance without adjustment to a special exhaust gas composition.
• NO does not adsorb when the Ag concentration on the binary metal surface is greater than 90 at% and that, therefore, NO cannot be purified.
• the ratio of Ag with respect to the total amount of Ag and Ni in the particulates is not higher than 90 at%.
• the Ag-Ni bimetals imitating the catalyst according to an embodiment of the present invention have an oxygen desorption temperature of about 800°C or lower and, as described in the above, the decomposition reaction of N0 X proceeds as follows:
• the Ag-Ni bimetals can have low-temperature NO x purification performance equal to or greater than Rh, which exhibits oxygen desorption temperature of about
• the ratio of Ag with respect to the total amount of Ag and Ni in the particulates is should not be less than 10 at%, particularly and ideally not less than 20 at%.
• the Ag- N1/AI2O3 which is the NO x purification catalyst according to an embodiment of the present invention, exhibits high NO reaction activity in a wide temperature range of 200 to 500°C not only under the binary gas atmosphere as shown by the curve (1), but also under the quaternary gas atmosphere simulating an actual exhaust gas as shown by the curve (2) .
• the gas composition is NO-CO (stoichiometric) (shown by the curve (1)), NO-CO-O2-C3H6 (stoichiometric) (shown by the curve (2) ) and NO-C 3 H 6 (stoichiometric) (shown by the curve
• the Au-Ni/Al 2 0 3 which is a NO x purification catalyst not encompassed by the scope of the present invention, exhibits high NO reaction activity in a wide temperature range of 200 to 500°C in the case where the gas composition is NO-CO (stoichiometric) as shown by the curve (1), it exhibits relatively low NO reaction activity in a temperature range of 300 to 500°C in the case where the gas composition is NO-C 3 H 6 (stoichiometric)
• the Ag, Ni co-impregnation/Si0 2 which is outside the scope of the present invention, shows two peaks of Ag (111) and Ni (111) . From this, it is believed that, in the Ag, Ni co- impregnation/Si0 2 , Ag and Ni are not alloyed.
• particulates are shown to contain only a single element out of either Ag or Ni on the same carrier. From this as well, in the Ag, Ni co-impregnation/Al 2 C>3, it is believed that Ag and Ni are not alloyed.
• examples of the metal oxide carrier on which Ag and Ni are supported include A1 2 0 3 particles, Si0 2 particles, Ce0 2 particles, Zr0 2 particles, Ti0 2 particles, Ce0 2 -Zr0 2 composite oxide particles, Ce0 2 -Al 2 0 3 composite oxide particles, Ce0 2 -Ti02 composite oxide particles, Ce0 2 -Si0 2 composite oxide particles and Ce0 2 - Zr0 2 -Al 2 0 3 composite oxide particles.
• particulates which are binary alloy particles consisting of Ag and Ni are supported on the aforementioned metal oxide carrier and the Ag and Ni are at least partially alloyed when supported.
• the NO x purification catalyst according to the present invention can be obtained by, for example, a method comprising the steps of:
• Examples of the aforementioned silver salt include inorganic acid salts such as silver nitrate, silver sulfate, silver fluoride, silver chlorate, silver
• organic acid salts such as silver acetate and silver oxalate.
• the aforementioned silver salt can be used as an aqueous solution thereof or as an organic solvent
• solution thereof such as an alcohol solution or polyol solution of the silver salt.
• nickel salt examples include nickel sulfate, nickel nitrate, nickel chloride, nickel bromide, nickel acetate and nickel hydroxide.
• the nickel salt may be a hydrate.
• the aforementioned nickel salt can be usually used as an aqueous solution thereof or as an organic solvent solution thereof, such as an alcohol solution or polyol solution of the nickel salt.
• Examples of the aforementioned polymer used as a protecting agent include functional group-containing polymers such as poly-N-vinylpyrrolidone, polyacrylamide, copolymer of N-vinylpyrrolidone and acrylic acid,
• polyvinyl methylketone poly ( 4-vinylphenol )
• oxazoline polymers polyalkylene imines and polyvinyl pyridine.
• the amount of the aforementioned polymer used as a protecting agent can be 1 to 20 times (mass ratio) , particularly 2 to 10 times (mass ratio) , with respect to the total amount of the silver salt and the nickel salt.
• the aforementioned polymer used as a protecting agent can be usually used as an organic solvent solution thereof, for example, as an alcohol solution such in methanol or ethanol.
• the mixture of a silver salt, a nickel salt and a polymer used as a protecting agent can be prepared usually by mixing a solution containing the silver salt, a solution containing the nickel salt and a solution containing the polymer used as a protecting agent. Further, the aforementioned mixture can be prepared by mixing the solutions in a container with stirring after, as required, heating or cooling each of the solutions. In the aforementioned method, the ratio of the aforementioned silver salt and the
• aforementioned nickel salt is one of which the ratio of Ag with respect to the total amount of Ag and Ni becomes
• the ratio of the silver salt and the nickel salt is outside the aforementioned range, the NO x purification performance of the resulting NO x purification catalyst can be impaired.
• a colloidal suspension is prepared by mixing the mixture obtained in the
• Examples of the aforementioned reducing agent include alcohols and polyols such as ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1, 2-propanediol, dipropylene glycol, 1,2- butanediol, 1, 3-butanediol, 1, 4-butanediol, 2,3- butanediol, 1 , 5-pentanediol and polyethylene glycol;
• alcohols and polyols such as ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1, 2-propanediol, dipropylene glycol, 1,2- butanediol, 1, 3-butanediol, 1, 4-butanediol, 2,3- butanediol, 1 , 5-pentanediol and polyethylene glycol;
• hydrazines such as dimethylamino boron, diethylamino boron, sodium borohydride, boron hydride and ammonia borane.
• the amount of the aforementioned reducing agent varies depending on the type thereof; however, in
• a NO x purification catalyst is obtained by the steps of:
• the ratio of the colloidal suspension and the metal oxide carrier can be a ratio at which, with respect to the amount of the metal oxide carrier, the total amount of the supported Ag and
• Ni becomes 0.05 to 10% by mass, particularly 0.5 to 5% by mass .
• examples of the method of removing solvent from the mixture of the colloidal suspension and the metal oxide carrier include a method in which solvent is removed under reduced pressure.
• the aforementioned activation can be performed in order to remove the polymer which is a protecting agent that may remain in the colloidal precipitate.
• heating including at reduced pressure
• centrifugation including at reduced pressure
• ultrasonic method ultrasonic method
• extraction methods or a combination of these may be used, with the heating methods being preferable.
• the mixture may be, as required, treated with an excessive amount (e.g. not less than 2-fold volumes, for example, 2 to 20-fold volumes, with respect to the aforementioned mixture) of an organic solvent such as a ketone (e.g. acetone, methylethyl ketone or methylbutyl ketone) or an ether (e.g. THF) , but preferably a ketone.
• an organic solvent such as a ketone (e.g. acetone, methylethyl ketone or methylbutyl ketone) or an ether (e.g. THF) , but preferably a ketone.
• Examples of the aforementioned heating method include a method in which heating is performed, for example, at a temperature of not less than 200°C, such as at a temperature of 200 to 300°C or 500°C at reduced pressure.
• the aforementioned heating can be performed usually for about 0.1 to 2 hours under vacuum.
• the NO x purification catalyst according to the present invention obtained by the aforementioned steps may be, as required, compression-molded into a pellet for use .
• the average particle diameter of the Ag-Ni particulates supported on a metal oxide carrier, which particulates consist of Ag and Ni that are at least partially alloyed may be about 0.2 to 100 nm.
• the NO x purification catalyst according to the present invention has superior NO x purification
• AI2O3 manufactured by C.I. Kasei Co., Ltd. ( ⁇ - ⁇ 1 2 0 3 ) Si0 2 : manufactured by C.I. Kasei Co., Ltd. (trade name: NanoTek) .
• the obtained samples were evaluated in accordance with the measurement method described below.
• the measurement method is not
• Measurement method measurement of XPS (X-ray photoelectron spectroscopy) spectra with changes in the heating temperature
• the NO dissociative adsorption temperature is defined as a temperature at which partially dissociated and adsorbed NO becomes completely dissociated when the temperature of Ag-Ni alloy thin film to which 1 Langmuir of NO was allowed to adsorb is increased at 4°C/min.
• the N 2 desorption temperature is defined as a temperature at which the peak of dissociated and adsorbed 0 disappears when the temperature of the film is further increased.
• Measuring device RIGAKU RINT 2000
• HRTEM measuring device HITACHI HD2000
• Measurement method measurement of composition ratio by TEM-EDS (EDS: energy dispersive X-ray spectroscopy)
• TEM-EDS measuring device HITACHI HD 2000
• a catalyst pellet is packed into a glass reaction tube and fixed with glass wool.
• the flow rate is
• the gas temperature is increased from 100°C to 500°C at a heating rate of 20°C/min.
• the NO concentration is measured by using an exhaust gas
• the partially dissociated and adsorbed NO becomes completely dissociated at about 180°C, and when the temperature exceeds 600°C, the peak for dissociated and adsorbed 0 disappears.
• An Ag-Ni thin film was prepared and evaluated in the same manner as in Reference Example 1 except that the ratio of Ag to Ni (Ag:Ni) was changed from 40:60 (at.
• a catalyst was prepared by the following steps:
• Solution 1 was heated to 50°C using an oil bath and mixed until the polymer was fully dissolved.
• Solution 1 was cooled to 0°C using an ice bath.
• Solution 2 was poured into Solution 1 whilst stirring to ensure homogenization .
• Solution 3 was poured into the combined Solutions 1 and 2 whilst stirring to ensure homogenization.
• the prepared nanoparticles were purified by treating an aliquot containing a desired amount of nanoparticles with a large excess of acetone (1:12 v/v) . This
• the purified colloids were redispersed in absolute ethanol by gentle stirring or by using an ultrasonic bath.
• a schlenk tube was charged with 5.1127g of support ( ⁇ - A1 2 0 3 ) .
• the system was evacuated and N 2 was used to flush the tube completely free of air. 17.
• the resulting colloidal precipitate was heated at 200°C under vacuum with the aim of removing any traces of the protecting agent.
• the catalyst powder was compressed in order to furnish pellets less than 2 mm in size.
• Fig. 9A shows the TE image of the thus obtained catalyst and Fig. 9B shows the results of TEM-EDX
• particulates (average particle diameter: 3.2 nm) consisting of Ag and Ni which were alloyed to each other were supported on the A1 2 0 3 particles.
• Example 2 The same silver salt as in Example 1 was dissolved in 100 mL of water. While stirring in another container, the silver salt solution or the nickel salt solution was poured to a suspension in which carrier (AI2O3) was placed in 200 mL of water, and the resulting mixture was left to stand for 2 hours. Thereafter, the water content was evaporated at 70 to 90°C. The thus obtained sample was dried at 120°C for 15 hours and then calcined at 500°C for 2 hours. The thus obtained catalyst powder was
• a catalyst pellet of about 2 mm in size was obtained in the same manner as in Comparative Example 1 except that the same nickel salt as in Example 1 was used in place of the silver salt of Comparative Example 1.
• Example 2 The same amounts of the same silver salt and nickel salt as in Example 1 were separately dissolved in 100 mL of water. While stirring in another container, the silver salt solution and the nickel salt solution were poured to a suspension of carrier (AI2O3) in 200 inL of water, and the resultant was left to stand for 2 hours. Thereafter, the water content was evaporated at 70 to 90°C. The thus obtained sample was dried at 120°C for 15 hours and then calcined at 500°C for 2 hours. The thus obtained catalyst powder was compressed to obtain a catalyst pellet of about 2 mm in size.
• carrier AI2O3
• a catalyst was obtained in the same manner as in Example 1 except that Si0 2 was used as the carrier in place of A1 2 0 3 .
• a co-impregnated catalyst was obtained in the same manner as in Comparative Example 3 except that Si0 2 was used as the carrier in place of A1 2 0 3 .
• a catalyst was obtained in the same manner as in Example 1 except that chloroauric acid was used in place of the silver salt.
• the NO x purification catalyst according to the present invention can utilize Ag and Ni existing in approximately the same amount as Cu in the earth and is capable of exhibiting favorable NO x purification performance without adjusting the exhaust gas emitted from an engine.

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• 2011
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