WO2012137051A1 - Catalyst and catalytic apparatus for nox reduction - Google Patents

Catalyst and catalytic apparatus for nox reduction Download PDF

Info

Publication number
WO2012137051A1
WO2012137051A1 PCT/IB2012/000630 IB2012000630W WO2012137051A1 WO 2012137051 A1 WO2012137051 A1 WO 2012137051A1 IB 2012000630 W IB2012000630 W IB 2012000630W WO 2012137051 A1 WO2012137051 A1 WO 2012137051A1
Authority
WO
WIPO (PCT)
Prior art keywords
particle
catalyst
νοχ
reduction
exhaust gas
Prior art date
Application number
PCT/IB2012/000630
Other languages
French (fr)
Inventor
Mayuko OSAKA
Yoshiaki Inagaki
Atsushi Tanaka
Masao Watanabe
Original Assignee
Toyota Jidosha Kabushiki Kaisha
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Toyota Jidosha Kabushiki Kaisha filed Critical Toyota Jidosha Kabushiki Kaisha
Publication of WO2012137051A1 publication Critical patent/WO2012137051A1/en

Links

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
    • B01J23/72—Copper
    • 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
    • B01D53/9418—Processes characterised by a specific catalyst for removing nitrogen oxides by selective catalytic reduction [SCR] using a reducing agent in a lean exhaust gas
    • 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
    • B01J23/74—Iron group metals
    • B01J23/755—Nickel
    • 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
    • B01J23/76—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
    • B01J23/83—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36 with rare earths or actinides
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J35/00—Catalysts, in general, characterised by their form or physical properties
    • B01J35/30—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
    • 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
    • B01J37/0018—Addition of a binding agent or of material, later completely removed among others as result of heat treatment, leaching or washing,(e.g. forming of pores; protective layer, desintegrating by heat)
    • 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
    • B01D2255/20—Metals or compounds thereof
    • B01D2255/206—Rare earth metals
    • B01D2255/2065—Cerium
    • 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
    • B01D2255/20707—Titanium
    • 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
    • B01D2255/20715—Zirconium
    • 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
    • B01D2255/00—Catalysts
    • B01D2255/20—Metals or compounds thereof
    • B01D2255/207—Transition metals
    • B01D2255/20761—Copper
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2255/00—Catalysts
    • B01D2255/20—Metals or compounds thereof
    • B01D2255/209—Other metals
    • B01D2255/2092—Aluminium
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2255/00—Catalysts
    • B01D2255/90—Physical characteristics of catalysts
    • B01D2255/92—Dimensions
    • B01D2255/9202—Linear dimensions
    • 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
    • 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
    • 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
    • B01J35/20—Catalysts, in general, characterised by their form or physical properties characterised by their non-solid state
    • B01J35/23—Catalysts, in general, characterised by their form or physical properties characterised by their non-solid state in a colloidal state
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
    • F01N3/18—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control
    • F01N3/20—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control specially adapted for catalytic conversion ; Methods of operation or control of catalytic converters
    • F01N3/2066—Selective catalytic reduction [SCR]
    • 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 invention relates to a catalyst and a catalytic apparatus for nitroxide (hereinafter sometimes abbreviated as ⁇ ) reduction. More specifically, it relates to a catalyst for ⁇ reduction that can demonstrate a high ⁇ reduction activity by using a specific base metal, and to a catalytic apparatus that can reduce ⁇ equally or more compared to a noble metal catalyst by using the catalyst.
  • ⁇ nitroxide
  • JP-2001-3733 A an exhaust gas control apparatus is described, which, in a diesel engine that processes the exhaust gas with an active-metal-containing ⁇ catalyst, causes the ⁇ contained in the exhaust gas to react with the active metal in the catalyst to be decomposed into nitrogen and oxygen when the exhaust gas is in the lean state, and forms a rich atmosphere of exhaust gas when the catalyst activity has decreased, and thus may process exhaust gas over long term with high efficiency.
  • a copper-containing purification catalyst is shown as a concrete example of ⁇ catalyst, produced by an impregnation method, where a zirconia carrier powder is added to an aqueous solution of copper salt and mixed, then, solid residue is dried, heat-treated in a hydrogen-containing nitrogen gas stream, causing zirconia to carry copper. Results are shown, that the ⁇ reduction rate of this copper-containing purification catalyst is 77 to 84% in comparison to noble metal-carrying catalysts.
  • a base metal-carrying catalyst for ⁇ reduction has a low ⁇ reduction activity compared to a noble metal-carrying catalyst for ⁇ reduction.
  • the ⁇ reduction activity of the catalyst for ⁇ reduction is low. Consequently, an object of the invention is to provide a base metal-carrying catalyst for ⁇ reduction that may have a ⁇ reduction activity, which, in comparison to a noble metal-carrying catalyst for ⁇ reduction, is equal or greater.
  • an object of the invention is to provide a catalytic apparatus including a base metal-carrying catalyst for ⁇ reduction that may have a ⁇ reduction activity, which, in comparison to a catalytic apparatus including a noble metal-carrying catalyst for ⁇ reduction, is equal or greater.
  • a first aspect of the invention is a catalyst for ⁇ reduction containing copper (hereinafter may also be noted as Cu) or nickel (hereinafter may also be noted as Ni) as an active species.
  • the catalyst for ⁇ reduction contains a carrier particle and a nano-particle containing copper or nickel or an oxide of either copper or nickel carried by the carrier particle.
  • a particle size of the nano-particle is 1.2 nm or greater, and the ratio (carrying amount/particle size) between a carrying amount (% by mass), which indicates a proportion by mass of copper or nickel with respect to the carrier particle, and the particle size of the nano-particle (nm), is 0.125 or greater.
  • a second aspect of the invention is a catalytic apparatus.
  • the catalytic apparatus includes an exhaust gas flow path through which exhaust gas from an internal combustion engine flows, the catalyst provided in the exhaust gas flow path, and a control device that controls an air-fuel ratio (A/F).
  • the control device i) controls the exhaust gas to be in contact with the catalyst so as to reach an atmosphere with an air- fuel ratio satisfying A/F ⁇ 14.4 when copper is the active species, and ii) controls the exhaust gas so as to reach an atmosphere with an air-fuel ratio satisfying A/F ⁇ 14.2 when nickel is the active species.
  • the particle size of the nano-particle is the size of the particle measured by the methods described in the section of exemplary embodiments below.
  • a ⁇ reduction activity which, in comparison to a noble metal-carrying catalyst for ⁇ reduction, is equal or greater, herein means that the ⁇ reduction activity is 90% or greater at rich atmosphere in an optimal exhaust gas with respect to the catalyst for ⁇ reduction of the invention, compared to the ⁇ reduction activity demonstrated at stoichiometric atmosphere by an exhaust gas purification catalyst carrying a noble metal such as Pt, Au or Rh on an oxide carrier conventionally in general use.
  • a base metal-carrying catalyst for ⁇ reductipn can be obtained, which may have an equal or greater ⁇ reduction activity compared to a noble metal-carrying catalyst for ⁇ reduction.
  • a base metal-carrying ⁇ reduction catalytic apparatus can be obtained, which may demonstrate an equal or greater ⁇ reduction activity compared to a noble metal-carrying catalyst apparatus for ⁇ reduction.
  • FIG. 1 is a graph showing the ranges of particle sizes and carrying amounts of Cu and Ni in a catalyst for ⁇ reduction of an embodiment of the invention
  • FIG. 2 is a graph comparatively. showing ⁇ reduction activities by catalysts for ⁇ reduction within the ranges and outside the ranges of the invention when the hydrogen concentration in the exhaust gas is changed;
  • FIG. 3 is a graph comparatively showing ⁇ reduction activities by a Cu- or Ni-carrying catalyst for ⁇ reduction when the hydrogen concentration in the exhaust gas is changed;
  • FIG. 4A is a schematic diagram related to, the structure of an apparatus for ⁇ reduction according to an embodiment of the invention.
  • FIG. 4B is a schematic diagram showing an example of control by an apparatus for ⁇ reduction aceording-to an embodiment of the invention.
  • FIG. 5 is a graph comparatively showing ⁇ reduction activities by various metal-carrying catalysts for ⁇ reduction under stoichiometric exhaust gas conditions
  • FIG. 6A and FIG. 6B are graphs showing A/F purification characteristics for Pt-carrying catalyst and Pd-carrying catalyst quoted from "Environment Handbook” (issued by Japan Environmental Management Association for Industry; 2002);
  • FIG. 7 is a graph showing results from measurements by X-ray photoelectron spectroscopy (XPS) of binding energies for nano-particles in the catalyst for ⁇ reduction having as active species Ni within the ranges and outside the ranges of thei invention;
  • XPS X-ray photoelectron spectroscopy
  • FIG. 8 is a copy of a photograph showing a scanning transmission electron microscopy (STEM) image of nano-particles with an Ni particle size of 7 nm in an Ni/A1 2 Q 3 type catalyst for ⁇ reduction obtained in an example;
  • STEM scanning transmission electron microscopy
  • FIG. 9 is a copy of a photograph showing a transmission electron microscopy (TEM) image of nano-particles with a Cu particle size of 8.0 nm in a Cu/Al 2 0 3 type catalyst for ⁇ reduction obtained in an example;
  • TEM transmission electron microscopy
  • FIG. 10 is a copy of a photograph showing a TEM image of nano-particles with a Cu particle size of 1 nm in a Cu/Al 2 0 3 type catalyst for ⁇ reduction obtained in another example;
  • FIG. 11 is a graph showing results from measurements for determining particle sizes by X-ray diffraction (XRD) of an Ni/Si0 2 type catalyst for ⁇ reduction obtained in an example;
  • FIG. 12 is a graph showing transmission electron microscope-energy dispersive X-ray (TEM-EDX) analysis results for a Cu/Si0 2 type catalyst for NO x reduction obtained in an example.
  • TEM-EDX transmission electron microscope-energy dispersive X-ray
  • FIG. 13 is a graph showing TEM-EDX analysis results for a Ni/Si0 2 type catalyst for ⁇ reduction obtained in an example.
  • the -catalyst— for-NOx-reduction according-to ⁇ an embodiment of the invention includes a Cu- or Ni-active species.
  • the catalyst for ⁇ reduction contains a carrier particle and a nano-particle containing Cu or Ni or an oxide of either Cu or Ni carried by the carrier particle.
  • the particle size of the nano-particle is 1.2 nm or greater, and, the ratio (carrying amount/particle size) between the carrying amount (% by mass), which indicates the proportion by mass of copper or nickel with respect to the carrier particle, and the particle size of the nano-particle (nm), is 0.125 or greater..
  • the nano-particle may consist of Cu or Ni or an oxide of either Cu or Ni.
  • the catalyst for ⁇ reduction is provided in an exhaust gas flow path from an internal combustion engine, controlling the exhaust gas to be in contact with the catalyst to a rich atmosphere where the air-fuel ratio (A/F) satisfies ⁇ 14.4 when copper is the active species and to a rich atmosphere where A/F ⁇ 14.2 is satisfied when nickel is the active species.
  • A/F air-fuel ratio
  • the catalyst in which the carrier particle is an A1 2 0 3 particle, an Si0 2 particle, a Ce0 2 particle, a Zr0 2 particle, a Ti0 2 particle, a Ce0 2 -Zr0 2 complex oxide particle, a Ce0 2 -Al 2 0 3 complex oxide particle, a Ce0 2 -Ti0 2 complex oxide particle, a Ce0 2 -Si0 2 complex oxide particle, a Ce0 2 -Zr0 2 -Al 2 0 3 complex oxide particle or a carbon particle.
  • catalysts for ⁇ reduction having Fe, Co, Mn, Ag or Au as an active species which are metals other than Cu and Ni, compared to the catalyst for ⁇ reduction having Pd as active species, have low NO reduction capabilities under conditions where A/F satisfies A/F ⁇ 14.6, that is to say, even at stoichiometric and rich atmospheres.
  • the particle size of the nano-particle is preferably in a range of 1.2 to 10 nm.
  • the ratio (carrying amount/particle size) is preferably in a range of 0.125 to 8,
  • the ⁇ catalytic apparatus of the embodiment of the invention includes an exhaust gas flow path 2 through which exhaust gas from an internal combustion engine 1 flows, a catalyst 3 for ⁇ reduction provided in the exhaust gas flow path 2, an electronic control unit 4 (ECU) serving as a control device that controls the air-fuel ratio (A/F value), and a detection device 5 that detects the air-fuel ratio of the exhaust gas prior to being introduced in the catalyst 3 for ⁇ reduction. Then, based on the air-fuel ratio detected by the detection device 5, the electronic control unit 4 controls the air- fuel ratio (A/F) of the exhaust gas to be in contact with the catalyst 3. Specifically, the electronic control unit 4 performs control to an atmosphere where A/F ⁇ 14.4 is satisfied when the catalyst has copper as active species, and to an atmosphere where A/F ⁇ 14.2 is satisfied when the catalyst has nickel as active species.
  • conventional techniques in the relevant field may be used, such as means for maintaining the state as-is if the A/F detection value from the detection device that detects the A/F value prior to being introduced in the catalyst for ⁇ reduction of the embodiment of the invention is in the above range, and means for injecting fuel in a smaller amount than the main injection with a reducing agent such as hydrogen or hydrocarbon before or after the main fuel injection if the detection value is outside the range.
  • a reducing agent such as hydrogen or hydrocarbon
  • the catalyst for ⁇ reduction of the embodiment of the invention containing Cu or Ni as an active species, the particle size of the nano-particle containing Cu or Ni or an oxide of either Cu or Ni carried by a carrier particle being 1.2 nm or greater, and the ratio (carrying amount/particle size) between the Cu- or Ni-carrying amount and the particle size of the nano-particle (nm) being 0.125 or greater, there is still insufficient theoretical consideration for requiring that these conditions be satisfied.
  • one reason is thought to be that, from the XPS Ni2P3 spectra of Ni/A1 2 Q 3 after 3 ⁇ 4 reduction as shown in FIG.
  • the particle size of the nano-particle is 1 nm and outside the range of the embodiment of the invention, there is no reduction even with H 2 gas treatment, and the oxide carrier affects significantly from the XPS. In addition, it is thought that if the carrying amount/particle size is less than 0.125, there are fewer active points for the base metal, which decreases the NO reduction activity.
  • the catalyst for ⁇ reduction of the embodiment of the invention can be obtained, for instance, in the following manner.
  • a Cu salt or an Ni salt is added into a solution of organic protectant, which is a high molecular compound.
  • the pH of the obtained mixed solution is adjusted to on the order of 7 to 9 with alkali, for instance, NaOH at 1 M, then, the mixed solution is heated, for instance, heated to on the order of, for example, 150 to 200°C (preferably 190 to 200°C) and mixed, then, the mixed solution is cooled at a temperature of on the order of room temperature, and then left to stand still to generate a nano-particle.
  • the generated nano-particle is treated and purified with an organic solvent, for instance, acetone, and the supernatant is subjected to a decantation method or is centrifuged to acquire a colloid of nano-particle.
  • the obtained purified colloid is dispersed in alcohol, for instance, ethanol, to obtain an alcohol suspension of - colloid.
  • A-predetermined amount-of carrier is introduced into a -container, air i s removed, the alcohol suspension of colloid is added, stirred and mixed, the solvent is removed under vacuum, the obtained solid is fired under vacuum or in air at 200 to 700°C for on the order of 1 to 30 hours to remove the colloid, obtaining a catalyst powder.
  • the particle size of the nano-particle may be controlled by the amount of the high molecular compound protectant. Generally, then the amount of high molecular compound is large with respect to Cu salt or Ni salt, the particle size of the nano-particle becomes small, and if the amount of high molecular compound is large, the particle size of the nano-particle becomes large. While the amount of high molecular compound used differs according to the species of the high molecular compound used, it is in general 0.1 to 50 times by mole, and in particular on the order of 0.2 to 30' times by mole, with respect to the amount of Cu salt or Ni salt. In addition, the carrying amount can be determined according to the amount of metal salt used with respect to the carrier.
  • the catalyst for ⁇ reduction of the embodiment of the invention is obtained, for instance by evaporation of a metal ion solution, in the following manner.
  • a Cu salt or an Ni salt is dissolved in water.
  • the aqueous solution of metal salt is added to an aqueous solution of colloid suspension into which a predetermined amount of carrier has been introduced, and left for on the order of 1 to 3 hours.
  • high molecular compounds having H, OH, COOH or NH 2 within a molecule that may coordinate with Cu or Ni, for instance, poly-n-vinylpyrrolidone (PVP), polyvinyl alcohol, polyamine, and the like, may be used.
  • PVP poly-n-vinylpyrrolidone
  • polyvinyl alcohol polyvinyl alcohol
  • polyamine polyamine
  • nitrate, sulfate, acetate, sulfonate, phosphate, and preferably, nitrate, sulfate, acetate and the like, of the Cu or Ni may be used.
  • the copper oxide or nickel oxide generated by firing as described above become active species of Cu or Ni by streaming a reductive gas such as hydrogen, CO or C 3 H 6 , and —preferably hydrogen.
  • a reductive gas such as hydrogen, CO or C 3 H 6 , and —preferably hydrogen.
  • A1 2 0 3 particle, Si0 2 particle, Ce0 2 particle, Zr0 2 particle, Ti0 2 particle, Ce0 2 -Zr0 2 complex oxide particle, Ce0 2 -Al 2 0 3 complex oxide particle, Ce0 2 -Ti0 2 complex oxide particle, Ce0 2 -Si0 2 complex oxide particle, Ce0 2 -Zr0 2 -Al 2 0 3 complex oxide particle or carbon particle, and preferably A1 2 0 3 particle or Si0 2 particle may be used.
  • the catalyst for ⁇ reduction of the embodiment of the invention may be used suitably as a purification catalyst for internal combustion engines such as an automobile engine.
  • the catalyst for ⁇ reduction of the embodiment of the invention is in general used by being layered over a substrate such as a honeycomb.
  • a honeycomb that may be used as the substrate is formed by a ceramics material such as cordierite, stainless steel or the like.
  • the catalyst for purifying exhaust gases of the embodiment of the invention may be formed into any shape.
  • A1 2 0 3 manufactured by C. I. Kasei CO., LTD. (product name: NanoTek; average particle size: 31)
  • Si0 2 manufactured by C. I. Kasei CO., LTD. (product name: NanoTek; average particle size: 25)
  • the carrier is an Si0 2 carrier
  • changing the carrier from A1 2 0 3 to Si0 2 in the preparation is not believed to vary the Ni- or Cu-carrying particle size
  • the catalyst was prepared using SiC"2 to carry out the measurements.
  • Verification of metal particle was carried out for Cu/Si0 2 catalyst and Ni/Si0 2 catalyst with an energy dispersive fluorescence X ray spectrometer (EDX, apparatus: HITACHI HD2000).
  • EDX energy dispersive fluorescence X ray spectrometer
  • the PVP indicated in Table 1 was added to 120 mL of an anhydrous ethylene glycol.
  • the nickel sulfate-7-hydrate or the copper acetate- 1 -hydrate indicated in Table 1 was added to this mixture, and stirred at 80°C for three hours. Thereafter, the solution was cooled to 0°C in a cooling bath, 50 mL of 1,4-dioxane was added and stirred uniformly.
  • the pH of the mixed solution was adjusted to as to reach 7 to 9 with NaOH at 1 M (few mL). Next, the mixed solution was heated to 198°C, kept for three hours while stirring, and cooled to room temperature to obtain a light brown solution.
  • the obtained catalyst powder was measured for the carrying amount of the carried nano-particle, the particle size, and TEM-EDX spot analysis.
  • the obtained results are shown in Table 1 , FIG. 1 and FIGS. 7 to 13 along with other results.
  • Catalyst powders and catalyst pellets were obtained in a similar manner to Example 1 except that the amounts of PVP, nickel sulfate-7-hydrate or copper acetate- 1 -hydrate were changed to the amounts indicated in Table 2.
  • the obtained catalyst powder was measured for the carrying amount of the carried nano-particle and the particle size. In addition, NO reduction activity was measured using the pellets. The obtained results are shown in Table 2, FIGS. 1 to 3 and FIG. 5 along with the comparative examples. [0032] . [Table 1]
  • Pd-carrying catalyst powder and pellets were obtained in a similar manner to Example 1 except that palladium chloride was used instead of nickel sulfate-7-hydrate. NO reduction activity was measured using the pellets. The obtained results are shown in FIGS. 2 to 3 and FIG. 5 along with the other results.
  • Fe-carrying catalyst powder, Co-carrying catalyst powder, Mn-carrying catalyst powder, Ag-carrying catalyst powder, Au-carrying catalyst powder and respective pellets were obtained in a similar manner to Example 1 except that instead of nickel sulfate-7-hydrate, iron nitrate-9-hydrate, cobalt acetate-4-hydrate, manganese acetate-4-hydrate, silver nitrate or chlorauric acid-4-hydrate was used. NO reduction activity was measured using the pellets. The obtained results are shown in FIG. 2 along with the other results.
  • the Cu-carrying catalyst and the Ni-carrying catalyst of the invention have the ⁇ reduction activity of noble metals or greater at an atmosphere where A/F ⁇ 14.4 is satisfied when copper is the active species, and at an atmosphere where A/F ⁇ 14.2 is satisfied when nickel is the active species.
  • the Cu-carrying catalyst and the Ni-carrying catalyst were shown to accomplish high ⁇ reduction activities, when the particle size of the nano-particle constituted from metal or metal oxide is 1.2 nm or greater, and the ratio (metal constituent-carrying amount/particle size) between the carrying amount (% by mass), which indicates the proportion of copper or nickel with respect to the carrier particle, and the particle size of the nano-particle (nm) is 0.125 or greater.
  • the Cu-carrying catalyst and the Ni-carrying catalyst obtained in the examples were shown to have Cu nano-particle or Ni nano-particle carried by a carrier.
  • the catalyst for ⁇ reduction of the invention can increase ⁇ reduction activity to be equal or greater in comparison to a noble metal-carrying catalyst, for ⁇ reduction, even by using a base metal.
  • the ⁇ reduction catalytic apparatus of the invention allows exhaust gas purification of automobile engines and other internal combustion engines to be realized.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Materials Engineering (AREA)
  • Organic Chemistry (AREA)
  • Environmental & Geological Engineering (AREA)
  • Health & Medical Sciences (AREA)
  • Biomedical Technology (AREA)
  • Combustion & Propulsion (AREA)
  • Analytical Chemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Catalysts (AREA)
  • Exhaust Gas After Treatment (AREA)
  • Electrical Control Of Air Or Fuel Supplied To Internal-Combustion Engine (AREA)
  • Exhaust Gas Treatment By Means Of Catalyst (AREA)

Abstract

A catalyst for ΝΟχ reduction containing Cu or Ni as active species contains a carrier particle and a nano-particle containing Cu or Ni or an oxide of either Cu or Ni carried by the carrier particle. The particle size of the nano-particle is 1.2 nm or greater, and the ratio between the carrying amount (% by mass) and the particle size of the nano-particle (nm) is 0.125 or greater. A catalytic apparatus includes the catalyst provided in an exhaust gas flow path from an internal combustion engine, and controls exhaust gas steadily to an atmosphere where A/F ≤ 14.4 is satisfied when Cu is the active species, and to an atmosphere where A/F ≤ 14.2 is satisfied when Ni is the active species.

Description

CATALYST AND CATALYTIC APPARATUS FOR NOx REDUCTION
BACKGROUND OF THE INVENTION
1. Field of the Invention
[0001] The invention relates to a catalyst and a catalytic apparatus for nitroxide (hereinafter sometimes abbreviated as ΝΟχ) reduction. More specifically, it relates to a catalyst for ΝΟχ reduction that can demonstrate a high ΝΟχ reduction activity by using a specific base metal,, and to a catalytic apparatus that can reduce ΝΟχ equally or more compared to a noble metal catalyst by using the catalyst.
2. Description of Related Art
[0002] In recent years, from the point of view of global environment protection, exhaust gas regulations are being intensified internationally year after year. As a compliance measure thereto, a catalyst for purifying exhaust gases are being used in internal combustion engines. In this exhaust gas purification catalyst, a noble metal such as Pt, Au or Rh is used as a catalyst constituent, in order to remove HC, CO and ΝΟχ inside exhaust gases efficiently. However, all these noble metals are produced in production countries that are limited to specific countries, and moreover, bear the problem of resource depletion. Although the use of a base metal other than a noble metal has been examined as a metal for this catalyst for purifying exhaust gases, the exhaust gas purification activity, and in particular, the ΝΟχ reduction activity of base metal-carrying catalysts for purification being lower compared to noble metal-carrying catalysts for purification using noble metals, they have not reached practical application yet.
[0003] Meanwhile, in automobiles that use this catalyst for purification, for instance gasoline cars or diesel cars, a variety of systems are used with the intent of improving fuel consumption at the same time as the purification activity of the catalyst. For instance, in the case of a gasoline car, combustion during steady-state run is under conditions where the air-fuel ratio (A/F) is stoichiometric (stoichiometric air-fuel ratio A/F = 14.6), and in the case of a diesel car, combustion during steady-state run is under conditions where the air-fuel ratio (A/F) is lean (excess oxygen), the combustion being temporarily under stoichiometric (stoichiometric air-fuel ratio A/F = 14.6) to rich (excess fuel) conditions in order to increase the catalyst activity. Thusly, appropriate exhaust gas conditions with regard to the exhaust gas to be processed exist for catalysts for ΝΟχ reduction that use noble metals and catalytic apparatuses using such catalysts.
[0004] For instance, in Japanese Patent Application Publication No. 2001-3733 (JP-2001-3733 A), an exhaust gas control apparatus is described, which, in a diesel engine that processes the exhaust gas with an active-metal-containing ΝΟχ catalyst, causes the ΝΟχ contained in the exhaust gas to react with the active metal in the catalyst to be decomposed into nitrogen and oxygen when the exhaust gas is in the lean state, and forms a rich atmosphere of exhaust gas when the catalyst activity has decreased, and thus may process exhaust gas over long term with high efficiency. Then, in the publication, a copper-containing purification catalyst is shown as a concrete example of ΝΟχ catalyst, produced by an impregnation method, where a zirconia carrier powder is added to an aqueous solution of copper salt and mixed, then, solid residue is dried, heat-treated in a hydrogen-containing nitrogen gas stream, causing zirconia to carry copper. Results are shown, that the ΝΟχ reduction rate of this copper-containing purification catalyst is 77 to 84% in comparison to noble metal-carrying catalysts.
SUMMARY OF THE INVENTION
[0005] As discussed above, a base metal-carrying catalyst for ΝΟχ reduction has a low ΝΟχ reduction activity compared to a noble metal-carrying catalyst for ΝΟχ reduction. In addition, in a catalytic apparatus provided with a base metal-carrying catalyst in the exhaust gas flow path, the ΝΟχ reduction activity of the catalyst for ΝΟχ reduction is low. Consequently, an object of the invention is to provide a base metal-carrying catalyst for ΝΟχ reduction that may have a ΝΟχ reduction activity, which, in comparison to a noble metal-carrying catalyst for ΝΟχ reduction, is equal or greater. In addition, an object of the invention is to provide a catalytic apparatus including a base metal-carrying catalyst for ΝΟχ reduction that may have a ΝΟχ reduction activity, which, in comparison to a catalytic apparatus including a noble metal-carrying catalyst for ΝΟχ reduction, is equal or greater.
[0006] A first aspect of the invention is a catalyst for ΝΟχ reduction containing copper (hereinafter may also be noted as Cu) or nickel (hereinafter may also be noted as Ni) as an active species. The catalyst for ΝΟχ reduction contains a carrier particle and a nano-particle containing copper or nickel or an oxide of either copper or nickel carried by the carrier particle. A particle size of the nano-particle is 1.2 nm or greater, and the ratio (carrying amount/particle size) between a carrying amount (% by mass), which indicates a proportion by mass of copper or nickel with respect to the carrier particle, and the particle size of the nano-particle (nm), is 0.125 or greater.
[0007] In addition, a second aspect of the invention is a catalytic apparatus. The catalytic apparatus includes an exhaust gas flow path through which exhaust gas from an internal combustion engine flows, the catalyst provided in the exhaust gas flow path, and a control device that controls an air-fuel ratio (A/F). The control device i) controls the exhaust gas to be in contact with the catalyst so as to reach an atmosphere with an air- fuel ratio satisfying A/F < 14.4 when copper is the active species, and ii) controls the exhaust gas so as to reach an atmosphere with an air-fuel ratio satisfying A/F < 14.2 when nickel is the active species. The particle size of the nano-particle is the size of the particle measured by the methods described in the section of exemplary embodiments below. In addition, a ΝΟχ reduction activity, which, in comparison to a noble metal-carrying catalyst for ΝΟχ reduction, is equal or greater, herein means that the ΝΟχ reduction activity is 90% or greater at rich atmosphere in an optimal exhaust gas with respect to the catalyst for ΝΟχ reduction of the invention, compared to the ΝΟχ reduction activity demonstrated at stoichiometric atmosphere by an exhaust gas purification catalyst carrying a noble metal such as Pt, Au or Rh on an oxide carrier conventionally in general use.
[0008] According to the first aspect of the invention, a base metal-carrying catalyst for ΝΟχ reductipn can be obtained, which may have an equal or greater ΝΟχ reduction activity compared to a noble metal-carrying catalyst for ΝΟχ reduction. In addition, according to the second aspect of the invention, a base metal-carrying ΝΟχ reduction catalytic apparatus can be obtained, which may demonstrate an equal or greater ΝΟχ reduction activity compared to a noble metal-carrying catalyst apparatus for ΝΟχ reduction.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] Features, advantages, and technical and industrial significance of exemplary embodiments of the invention will be described below with reference to the accompanying drawings, in which like numerals denote like elements, and wherein:
FIG. 1 is a graph showing the ranges of particle sizes and carrying amounts of Cu and Ni in a catalyst for ΝΟχ reduction of an embodiment of the invention;
FIG. 2 is a graph comparatively. showing ΝΟχ reduction activities by catalysts for ΝΟχ reduction within the ranges and outside the ranges of the invention when the hydrogen concentration in the exhaust gas is changed;
FIG. 3 is a graph comparatively showing ΝΟχ reduction activities by a Cu- or Ni-carrying catalyst for ΝΟχ reduction when the hydrogen concentration in the exhaust gas is changed;
FIG. 4A is a schematic diagram related to, the structure of an apparatus for ΝΟχ reduction according to an embodiment of the invention;
FIG. 4B is a schematic diagram showing an example of control by an apparatus for ΝΟχ reduction aceording-to an embodiment of the invention; -
FIG. 5 is a graph comparatively showing ΝΟχ reduction activities by various metal-carrying catalysts for ΝΟχ reduction under stoichiometric exhaust gas conditions;
FIG. 6A and FIG. 6B are graphs showing A/F purification characteristics for Pt-carrying catalyst and Pd-carrying catalyst quoted from "Environment Handbook" (issued by Japan Environmental Management Association for Industry; 2002);
FIG. 7 is a graph showing results from measurements by X-ray photoelectron spectroscopy (XPS) of binding energies for nano-particles in the catalyst for ΝΟχ reduction having as active species Ni within the ranges and outside the ranges of thei invention;
FIG. 8 is a copy of a photograph showing a scanning transmission electron microscopy (STEM) image of nano-particles with an Ni particle size of 7 nm in an Ni/A12Q3 type catalyst for ΝΟχ reduction obtained in an example;
FIG. 9 is a copy of a photograph showing a transmission electron microscopy (TEM) image of nano-particles with a Cu particle size of 8.0 nm in a Cu/Al203 type catalyst for ΝΟχ reduction obtained in an example;
FIG. 10 is a copy of a photograph showing a TEM image of nano-particles with a Cu particle size of 1 nm in a Cu/Al203 type catalyst for ΝΟχ reduction obtained in another example;
FIG. 11 is a graph showing results from measurements for determining particle sizes by X-ray diffraction (XRD) of an Ni/Si02 type catalyst for ΝΟχ reduction obtained in an example;
FIG. 12 is a graph showing transmission electron microscope-energy dispersive X-ray (TEM-EDX) analysis results for a Cu/Si02 type catalyst for NOx reduction obtained in an example; and
FIG. 13 is a graph showing TEM-EDX analysis results for a Ni/Si02 type catalyst for ΝΟχ reduction obtained in an example.
DETAILED DESCRIPTION OF EMBODIMENTS
—[0010] The -catalyst— for-NOx-reduction according-to ^an embodiment of the invention includes a Cu- or Ni-active species. The catalyst for ΝΟχ reduction contains a carrier particle and a nano-particle containing Cu or Ni or an oxide of either Cu or Ni carried by the carrier particle. The particle size of the nano-particle is 1.2 nm or greater, and, the ratio (carrying amount/particle size) between the carrying amount (% by mass), which indicates the proportion by mass of copper or nickel with respect to the carrier particle, and the particle size of the nano-particle (nm), is 0.125 or greater.. This allows an ΝΟχ reduction activity to be obtained, which, compared to a noble metal-carrying catalyst for ΝΟχ reduction, is equal or greater. The nano-particle may consist of Cu or Ni or an oxide of either Cu or Ni.
[0011] In addition, in the catalytic apparatus of the embodiment of the invention, the catalyst for ΝΟχ reduction is provided in an exhaust gas flow path from an internal combustion engine, controlling the exhaust gas to be in contact with the catalyst to a rich atmosphere where the air-fuel ratio (A/F) satisfies < 14.4 when copper is the active species and to a rich atmosphere where A/F < 14.2 is satisfied when nickel is the active species. This allows an ΝΟχ reduction activity to be demonstrated, which, in comparison to a^noble metal-carrying catalyst apparatus for ΝΟχ reduction, is equal or greater.
[0012] In particular, the following embodiments can be described in the invention:
1) the catalyst in which the active species is copper,
2) the catalyst in which the active species is nickel,
3) the catalyst in which the particle size of the nano-particle is in a range of 1.2 to 10 nm,
4) the catalyst in which the ratio (carrying amount/particle size) is in a range of 0.125 to 8,
5) the catalyst in which the carrying amount is 0.15 to 10% by mass, and
6) the catalyst in which the carrier particle is an A1203 particle, an Si02 particle, a Ce02 particle, a Zr02 particle, a Ti02 particle, a Ce02-Zr02 complex oxide particle, a Ce02-Al203 complex oxide particle, a Ce02-Ti02 complex oxide particle, a Ce02-Si02 complex oxide particle, a Ce02-Zr02-Al203 complex oxide particle or a carbon particle.
[0013] Hereinafter, embodiments of the invention will be described in detail with references to figures. As shown in FIG. 1 , the catalyst for ΝΟχ reduction of an embodiment of the invention needs to be within the range enclosed by the curves x > 1.2 and y/x = 0.125, with the horizontal axis x in logarithmic representation being the particle size of the nano-particle containing Cu or Ni or an oxide of either Cu or Ni carried by a carrier particle, and the vertical axis y being the carrying amount (% by mass) indicating the proportion by mass of Cu or Ni being carried with respect to the carrier particle.
[0014] As shown in FIG. 2, if the catalyst for ΝΟχ reduction of the embodiment of the invention is a catalyst for ΝΟχ reduction containing Cu as an active species and satisfies the above conditions, then by establishing a rich atmosphere where A/F satisfies A/F < 14.4, preferably a rich atmosphere where A/F is 14.4 to 13.6, and in particular 14.4 to 14.0, the NO reduction capability of a catalyst for ΝΟχ reduction having Pd as an active species at stoichiometry (A/F = 14.6) may be equated or exceed. If the catalyst for ΝΟχ reduction of the embodiment of the invention is a catalyst for ΝΟχ reduction having Ni as an active species and satisfies the above conditions, then by establishing a rich atmosphere where A/F satisfies A/F < 14.2, preferably a rich atmosphere where A/F is 14.4 to 13.6, and in particular 14.2 to 14.0, the NO reduction capability of a catalyst for ΝΟχ reduction having Pd as an active species at stoichiometry (A/F = 14.6) may be equated or exceed.
In addition, from FIG. 2, it is clear that catalysts for ΝΟχ reduction having Fe, Co, Mn, Ag or Au as an active species, which are metals other than Cu and Ni, compared to the catalyst for ΝΟχ reduction having Pd as active species, have low NO reduction capabilities under conditions where A/F satisfies A/F < 14.6, that is to say, even at stoichiometric and rich atmospheres.
[0015] In addition, as shown in FIG. 3, even for those containing Cu or Ni as active species; if the conditions that the particle size of the nano-particle is 1.2 nm or greater and, that the ratio (carrying amount/particle size) between the carrying amount (% by mass) and the particle size of the nano-particle (nm) is 0.125 or greater are not satisfied, the NO reduction capability of the obtained catalyst for ΝΟχ reduction becomes low.
In particular, in the catalyst for ΝΟχ reduction of the embodiment of the invention, the particle size of the nano-particle is preferably in a range of 1.2 to 10 nm. In addition, the ratio (carrying amount/particle size) is preferably in a range of 0.125 to 8,
[0016] The ΝΟχ catalytic apparatus of the embodiment of the invention, as shown in FIG. 4A and FIG. 4B includes an exhaust gas flow path 2 through which exhaust gas from an internal combustion engine 1 flows, a catalyst 3 for ΝΟχ reduction provided in the exhaust gas flow path 2, an electronic control unit 4 (ECU) serving as a control device that controls the air-fuel ratio (A/F value), and a detection device 5 that detects the air-fuel ratio of the exhaust gas prior to being introduced in the catalyst 3 for ΝΟχ reduction. Then, based on the air-fuel ratio detected by the detection device 5, the electronic control unit 4 controls the air- fuel ratio (A/F) of the exhaust gas to be in contact with the catalyst 3. Specifically, the electronic control unit 4 performs control to an atmosphere where A/F < 14.4 is satisfied when the catalyst has copper as active species, and to an atmosphere where A/F < 14.2 is satisfied when the catalyst has nickel as active species.
As means for controlling the exhaust gas to a rich atmosphere of the above range, conventional techniques in the relevant field may be used, such as means for maintaining the state as-is if the A/F detection value from the detection device that detects the A/F value prior to being introduced in the catalyst for ΝΟχ reduction of the embodiment of the invention is in the above range, and means for injecting fuel in a smaller amount than the main injection with a reducing agent such as hydrogen or hydrocarbon before or after the main fuel injection if the detection value is outside the range.
[0017] The ΝΟχ catalyst having Pd as active species, which is a noble metal, demonstrates a high NO reduction capability in a stoichiometric atmosphere where A/F = 14.6 is satisfied and in a temperature range of 300°C or higher, as shown in FIG. 5.
ΝΟχ catalysts having Pt or Pd as active species, and in particular ΝΟχ catalyst having Pd as active species, have purification characteristics affected by the A/F value, demonstrating satisfactory NO reduction capability at a stoichiometric atmosphere where A/F = 14.6 is satisfied, as shown in FIG. 6A and FIG. 6B. In contrast, ΝΟχ catalysts having not only Cu and Ni but also Fe and Co as active species demonstrate low NO reduction capabilities in a stoichiometric atmosphere where A/F = 14.6 is satisfied and in a temperature range of 300 to 500°C, as shown in FIG. 5.
[0018] Regarding the catalyst for ΝΟχ reduction of the embodiment of the invention, containing Cu or Ni as an active species, the particle size of the nano-particle containing Cu or Ni or an oxide of either Cu or Ni carried by a carrier particle being 1.2 nm or greater, and the ratio (carrying amount/particle size) between the Cu- or Ni-carrying amount and the particle size of the nano-particle (nm) being 0.125 or greater, there is still insufficient theoretical consideration for requiring that these conditions be satisfied. However, one reason is thought to be that, from the XPS Ni2P3 spectra of Ni/A12Q3 after ¾ reduction as shown in FIG. 7, if the particle size of the nano-particle is 1 nm and outside the range of the embodiment of the invention, there is no reduction even with H2 gas treatment, and the oxide carrier affects significantly from the XPS. In addition, it is thought that if the carrying amount/particle size is less than 0.125, there are fewer active points for the base metal, which decreases the NO reduction activity.
[0019] The catalyst for ΝΟχ reduction of the embodiment of the invention can be obtained, for instance, in the following manner. First, a Cu salt or an Ni salt is added into a solution of organic protectant, which is a high molecular compound. The pH of the obtained mixed solution is adjusted to on the order of 7 to 9 with alkali, for instance, NaOH at 1 M, then, the mixed solution is heated, for instance, heated to on the order of, for example, 150 to 200°C (preferably 190 to 200°C) and mixed, then, the mixed solution is cooled at a temperature of on the order of room temperature, and then left to stand still to generate a nano-particle. The generated nano-particle is treated and purified with an organic solvent, for instance, acetone, and the supernatant is subjected to a decantation method or is centrifuged to acquire a colloid of nano-particle. The obtained purified colloid is dispersed in alcohol, for instance, ethanol, to obtain an alcohol suspension of - colloid. A-predetermined amount-of carrier is introduced into a -container, air i s removed, the alcohol suspension of colloid is added, stirred and mixed, the solvent is removed under vacuum, the obtained solid is fired under vacuum or in air at 200 to 700°C for on the order of 1 to 30 hours to remove the colloid, obtaining a catalyst powder.
[0020] When preparing the catalyst for ΝΟχ reduction of the embodiment of the invention, the particle size of the nano-particle may be controlled by the amount of the high molecular compound protectant. Generally, then the amount of high molecular compound is large with respect to Cu salt or Ni salt, the particle size of the nano-particle becomes small, and if the amount of high molecular compound is large, the particle size of the nano-particle becomes large. While the amount of high molecular compound used differs according to the species of the high molecular compound used, it is in general 0.1 to 50 times by mole, and in particular on the order of 0.2 to 30' times by mole, with respect to the amount of Cu salt or Ni salt. In addition, the carrying amount can be determined according to the amount of metal salt used with respect to the carrier.
[0021] Alternatively, the catalyst for ΝΟχ reduction of the embodiment of the invention is obtained, for instance by evaporation of a metal ion solution, in the following manner. First, a Cu salt or an Ni salt is dissolved in water. The aqueous solution of metal salt is added to an aqueous solution of colloid suspension into which a predetermined amount of carrier has been introduced, and left for on the order of 1 to 3 hours. Thereafter, by evaporating moisture, drying, firing the solid at 200 to 700°C for on the order of l.to 30 hours, a catalyst for ΝΟχ reduction is obtained.
[0022] As the high molecular compounds, high molecular compounds having H, OH, COOH or NH2 within a molecule that may coordinate with Cu or Ni, for instance, poly-n-vinylpyrrolidone (PVP), polyvinyl alcohol, polyamine, and the like, may be used.
As the Cu salts or the Ni salts, nitrate, sulfate, acetate, sulfonate, phosphate, and preferably, nitrate, sulfate, acetate and the like, of the Cu or Ni, may be used.
[0023] In the catalyst for ΝΟχ reduction of the embodiment of the invention, the copper oxide or nickel oxide generated by firing as described above become active species of Cu or Ni by streaming a reductive gas such as hydrogen, CO or C3H6, and —preferably hydrogen. '
[0024] As the carrier particle, A1203 particle, Si02 particle, Ce02 particle, Zr02 particle, Ti02 particle, Ce02-Zr02 complex oxide particle, Ce02-Al203 complex oxide particle, Ce02-Ti02 complex oxide particle, Ce02-Si02 complex oxide particle, Ce02-Zr02-Al203 complex oxide particle or carbon particle, and preferably A1203 particle or Si02 particle may be used.
[0025] The catalyst for ΝΟχ reduction of the embodiment of the invention may be used suitably as a purification catalyst for internal combustion engines such as an automobile engine.
In addition, the catalyst for ΝΟχ reduction of the embodiment of the invention is in general used by being layered over a substrate such as a honeycomb. A honeycomb that may be used as the substrate is formed by a ceramics material such as cordierite, stainless steel or the like. In addition, the catalyst for purifying exhaust gases of the embodiment of the invention may be formed into any shape.
[0026] Examples of the invention will be shown hereinafter. In each of the examples shown below, evaluation of the obtained catalyst was carried out by the measurement methods indicated below. The measurement methods in the following are exemplary methods, and measurements may be carried out by measurement methods that are deemed equivalent for a person of ordinary skill in the art.
In addition, in each of the following example, the carriers described below were used.
A1203: manufactured by C. I. Kasei CO., LTD. (product name: NanoTek; average particle size: 31)
Si02: manufactured by C. I. Kasei CO., LTD. (product name: NanoTek; average particle size: 25)
[0027] 1. Measurement of particle size
1) Regarding the Cu/Al203 catalyst, observations were made from TEM images by a scanning transmission electron microscope (STEM; apparatus: HITACHI S-4500) or a transmission electron microscope (TEM; apparatus: HITACHI HD20Q0), to calculate the average particle size from the mean value of 100 particle sizes.
2) Regarding the Ni/Si02 catalyst, from the width at half-height of the (111) diffraction peak near 44.5° due to Ni or the (012) peak near 43.3° due to NiO by X ray diffraction (apparatus: RIGAKU RINT 2000), the particle size was determined by the following formula (1) by Scherrer:
D = (Κλ)/(β cos Θ) (1)
o
(where λ: measurement X-ray wavelength (A); β: half-height width (rad); 0: incident X-ray angle; K: constant)
Regarding X-ray diffraction, as analysis is not possible unless the carrier is an Si02 carrier, and changing the carrier from A1203 to Si02 in the preparation (using colloid) is not believed to vary the Ni- or Cu-carrying particle size, the catalyst was prepared using SiC"2 to carry out the measurements.
2. Verification of metal particle
Verification of metal particle was carried out for Cu/Si02 catalyst and Ni/Si02 catalyst with an energy dispersive fluorescence X ray spectrometer (EDX, apparatus: HITACHI HD2000).
[0028] Examples 1 to 7
Inside a two-necked flask, the PVP indicated in Table 1 was added to 120 mL of an anhydrous ethylene glycol. The nickel sulfate-7-hydrate or the copper acetate- 1 -hydrate indicated in Table 1 was added to this mixture, and stirred at 80°C for three hours. Thereafter, the solution was cooled to 0°C in a cooling bath, 50 mL of 1,4-dioxane was added and stirred uniformly. The pH of the mixed solution was adjusted to as to reach 7 to 9 with NaOH at 1 M (few mL). Next, the mixed solution was heated to 198°C, kept for three hours while stirring, and cooled to room temperature to obtain a light brown solution.
[0029] This solution was left still to generate a nano-particle. A given amount containing this nano-particle was treated with a copious amount of acetone and purified. This extracted the protectant PVP into the acetone phase, aggregating the metal nano-particles. The supernatant was decanted to take the colloid out. The acetone phase was removed, then the purified colloid was"dispersed in pure ethanoTunder gentle stirring to obtain a suspension of colloid.
As a carrier, 10 g of A1203 or Si02 was introduced into a 100 mL Schlenk tube. The Schlenk tube was vacuumed, nitrogen was flown in to clean the tubing and completely eliminate air. The suspension of colloid synthesized earlier, was injected into the Schlenk tube through a rubber septum. The mixture was stirred at room temperature for. three hours, and the solvent was removed under vacuum. Thereafter, the colloid precipitate was fired under a 200 to 600°C vacuum or air atmosphere for 1 to 30 hours in order to eliminate the remaining protectant. Pressure was applied to the obtained catalyst powder to obtain approximately 2 mm pellets.
[0030] The obtained catalyst powder was measured for the carrying amount of the carried nano-particle, the particle size, and TEM-EDX spot analysis. The obtained results are shown in Table 1 , FIG. 1 and FIGS. 7 to 13 along with other results.
In addition, NO reduction activity was measured using the pellets, under the following conditions:
1) Measurement of NO-H2 reaction activity - H2 concentration dependency
Temperature: 500°C
NO: 500 ppm
H2: 0 to 5,000 ppm
N2: residual
2) Measurement of NO reduction rate and temperature dependency of NO-H2 reaction in stoichiometric atmosphere
Temperature: 100 to 500°C
NO: 1 ,000 ppm
H2: 1 ,000 ppm
N2: residual
The obtained results are shown in FIGS. 1 to 3 along with the comparative examples.
[0031] Comparative examples 1 to 5
Catalyst powders and catalyst pellets were obtained in a similar manner to Example 1 except that the amounts of PVP, nickel sulfate-7-hydrate or copper acetate- 1 -hydrate were changed to the amounts indicated in Table 2.
The obtained catalyst powder was measured for the carrying amount of the carried nano-particle and the particle size. In addition, NO reduction activity was measured using the pellets. The obtained results are shown in Table 2, FIGS. 1 to 3 and FIG. 5 along with the comparative examples. [0032] . [Table 1]
Example
1 2 3 4 5 6 7
Cu- or Ni-carrying .
Cu 3 Ni 3, Ni 9.5 Cu 9.5 Cu 5 Cu 3 Ni 3 amount/wt%
PVP amount/time by moles
10 10 5 5 30 1 . 2 (versus amount of metal)
Copper acetate amount/g 1 .020 - - 3.230 1.701 1.020 -
Nickel sulfate amount/g - ■ 1.435 4.544 - - 1.435
Cu or Ni particle size/nm 8 7 24 28 2 18 12.4
Carrying amount/particle size 0.38 0.43 0.40 0.34 2.5 0.17 0.16
Carrier species A1203 . A1203 A1203 A1203 AI2O3 A1203 A1203
[0033] [Table 2]
Figure imgf000016_0001
[0034] Reference example 1
Pd-carrying catalyst powder and pellets were obtained in a similar manner to Example 1 except that palladium chloride was used instead of nickel sulfate-7-hydrate. NO reduction activity was measured using the pellets. The obtained results are shown in FIGS. 2 to 3 and FIG. 5 along with the other results.
[0035] Comparative examples 6 to 9
Fe-carrying catalyst powder, Co-carrying catalyst powder, Mn-carrying catalyst powder, Ag-carrying catalyst powder, Au-carrying catalyst powder and respective pellets were obtained in a similar manner to Example 1 except that instead of nickel sulfate-7-hydrate, iron nitrate-9-hydrate, cobalt acetate-4-hydrate, manganese acetate-4-hydrate, silver nitrate or chlorauric acid-4-hydrate was used. NO reduction activity was measured using the pellets. The obtained results are shown in FIG. 2 along with the other results.
[0036] From the results of FIG. 2, the Cu-carrying catalyst and the Ni-carrying catalyst of the invention have the ΝΟχ reduction activity of noble metals or greater at an atmosphere where A/F < 14.4 is satisfied when copper is the active species, and at an atmosphere where A/F < 14.2 is satisfied when nickel is the active species.
From the results of FIG. 3, the Cu-carrying catalyst and the Ni-carrying catalyst were shown to accomplish high ΝΟχ reduction activities, when the particle size of the nano-particle constituted from metal or metal oxide is 1.2 nm or greater, and the ratio (metal constituent-carrying amount/particle size) between the carrying amount (% by mass), which indicates the proportion of copper or nickel with respect to the carrier particle, and the particle size of the nano-particle (nm) is 0.125 or greater.
From the results of FIG. 5, even when rich, the noble metal-carrying catalyst was shown to reach a limit without improvement of the ΝΟχ reduction activity.
From FIG. 12 and FIG. 13, the Cu-carrying catalyst and the Ni-carrying catalyst obtained in the examples were shown to have Cu nano-particle or Ni nano-particle carried by a carrier.
[0037] The catalyst for ΝΟχ reduction of the invention can increase ΝΟχ reduction activity to be equal or greater in comparison to a noble metal-carrying catalyst, for ΝΟχ reduction, even by using a base metal. In addition, the ΝΟχ reduction catalytic apparatus of the invention allows exhaust gas purification of automobile engines and other internal combustion engines to be realized.

Claims

CLAIMS:
1. A catalyst for ΝΟχ reduction containing copper or nickel as an active species, comprising:
a carrier particle; and
a nano-particle containing copper or nickel or an oxide of either copper or nickel carried by the carrier particle,
wherein a particle size of the nano-particle is 1.2 nm or greater, and the ratio between a carrying amount indicating a proportion by mass of copper or nickel with respect to the carrier particle, and the particle size of the nano-particle is 0.125 or greater, where the unit of the carryirig amount is % by mass and the unit of the particle size is nm.
2. The catalyst for ΝΟχ reduction according to claim 1, wherein
the active species is copper.
3. The catalyst for ΝΟχ reduction according to claim 1 , wherein
the active species is nickel.
4. The catalyst for NOx reduction according to any one of claims 1 to 3, wherein the particle size is in a range of 1.2 to 10 nm.
5. The catalyst for ΝΟχ reduction according to any one of claims 1 to 4, wherein the ratio is in a range of 0.125 to 8.
6. The catalyst for ΝΟχ reduction according to any one of claims 1 to 5, wherein the carrying amount is 0.15 to 10% by mass.
7. The cataly st for NOx reduction according to any one of claims 1 to 6, wherein the carrier particle is an A1203 particle, an Si02 particle, a Ge02 particle, a Zr02 particle, a Ti02 particle, a Ce02-Zr02 complex oxide particle, a ('ο02-Α1203 complex oxide particle, a Ce02-Ti02 complex oxide particle, a Ce02-Si02 complex oxide particle, a Ce02-Zr02-Al203 complex oxide particle or a carbon particle.
8. A catalytic apparatus comprising:
an exhaust gas flow path through which exhaust gas from an internal combustion engine flows;
the catalyst according to any one of claims 1 to 7 provided in the exhaust gas flow path; and
a control device that controls an air-fuel ratio, wherein the air-fuel ratio is indicated by A/F, .
wherein the control device i) controls the exhaust gas to be in contact with the catalyst so as to reach an atmosphere with an air-fuel ratio satisfying A/F < 14.4 when copper is the active species, and ii) controls the exhaust gas to be in contact with the catalyst so as to reach an atmosphere with an air-fuel ratio satisfying A/F < 14.2 when nickel is the active species.
PCT/IB2012/000630 2011-04-08 2012-03-29 Catalyst and catalytic apparatus for nox reduction WO2012137051A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP2011-086614 2011-04-08
JP2011086614A JP2012217936A (en) 2011-04-08 2011-04-08 CATALYST AND CATALYTIC APPARATUS FOR NOx PURIFICATION

Publications (1)

Publication Number Publication Date
WO2012137051A1 true WO2012137051A1 (en) 2012-10-11

Family

ID=46018008

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/IB2012/000630 WO2012137051A1 (en) 2011-04-08 2012-03-29 Catalyst and catalytic apparatus for nox reduction

Country Status (2)

Country Link
JP (1) JP2012217936A (en)
WO (1) WO2012137051A1 (en)

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4661468A (en) * 1982-07-13 1987-04-28 Cpus Corporation Catalyst for treatment and cleaning of exhaust fumes
JP2001003733A (en) 1999-06-17 2001-01-09 Hino Motors Ltd Exhaust emission control device
WO2010084930A1 (en) * 2009-01-22 2010-07-29 三菱化学株式会社 Catalyst for removing nitrogen oxides and method for producing same

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4661468A (en) * 1982-07-13 1987-04-28 Cpus Corporation Catalyst for treatment and cleaning of exhaust fumes
JP2001003733A (en) 1999-06-17 2001-01-09 Hino Motors Ltd Exhaust emission control device
WO2010084930A1 (en) * 2009-01-22 2010-07-29 三菱化学株式会社 Catalyst for removing nitrogen oxides and method for producing same
EP2380663A1 (en) * 2009-01-22 2011-10-26 Mitsubishi Plastics, Inc. Catalyst for removing nitrogen oxides and method for producing same

Non-Patent Citations (4)

* Cited by examiner, † Cited by third party
Title
KANG M ET AL: "Two-stage catalyst system for selective catalytic reduction of NOx by NH3 at low temperatures", APPLIED CATALYSIS B: ENVIRONMENTAL, ELSEVIER, AMSTERDAM, NL, vol. 68, no. 1-2, 26 October 2006 (2006-10-26), pages 21 - 27, XP028001140, ISSN: 0926-3373, [retrieved on 20061026], DOI: 10.1016/J.APCATB.2006.07.013 *
RICO M J O ET AL: "Study of nanoporous catalysts in the selective catalytic reduction of NOx", CATALYSIS TODAY, ELSEVIER, NL, vol. 158, no. 1-2, 5 December 2010 (2010-12-05), pages 78 - 88, XP027446443, ISSN: 0920-5861, [retrieved on 20100526], DOI: 10.1016/J.CATTOD.2010.04.016 *
ROY B ET AL: "Surface modification of solution combustion synthesized Ni/Al2O3 catalyst for aqueous-phase reforming of ethanol", INTERNATIONAL JOURNAL OF HYDROGEN ENERGY, ELSEVIER SCIENCE PUBLISHERS B.V., BARKING, GB, vol. 35, no. 21, 1 November 2010 (2010-11-01), pages 11700 - 11708, XP027383173, ISSN: 0360-3199, [retrieved on 20100909] *
TSENG H H ET AL: "Synthesis, characterization, and promoter effect of Cu-Zn/Al2O3 catalysts on NO reduction with CO", CHEMICAL ENGINEERING JOURNAL, ELSEVIER SEQUOIA, LAUSANNE, CH, vol. 160, no. 1, 15 May 2010 (2010-05-15), pages 13 - 19, XP027028177, ISSN: 1385-8947, [retrieved on 20100301] *

Also Published As

Publication number Publication date
JP2012217936A (en) 2012-11-12

Similar Documents

Publication Publication Date Title
EP3244995B1 (en) Nitrous oxide removal catalysts for exhaust systems
CA2648314C (en) Catalyst for purification of exhaust gas, regeneration method for the catalyst, and apparatus and method for purification of exhaust gas using the catalyst
EP1955765B1 (en) Process for producing a catalyst for exhaust-gas purification
JP4547935B2 (en) Exhaust gas purification catalyst, exhaust gas purification catalyst, and catalyst manufacturing method
JP6676394B2 (en) Core-shell carrier and method for producing the same, catalyst for purifying exhaust gas using the core-shell carrier, method for producing the same, and method for purifying exhaust gas using the catalyst for purifying exhaust gas
JP5583967B2 (en) Exhaust gas purification catalyst, exhaust gas purification apparatus and exhaust gas purification method using the same
JP2011045840A (en) Catalyst composition
CN105792930B (en) Hydrogen-storing material
KR20140011312A (en) Denitration catalyst composition and method of denitration using same
TW201031464A (en) Catalyst and process for purifying exhaust gas
EP2729248B1 (en) Nox purification catalyst and method of producing the same
EP2823887B1 (en) Oxidation catalyst and exhaust gas purification method using same
WO2012077510A1 (en) Production method for exhaust gas-purifying catalyst and motor vehicle
WO2013121636A1 (en) Catalyst system for exhaust gas purification utilizing base metals, and controlling method therefor
WO2012160437A1 (en) Exhaust gas control system, exhaust gas purification catalyst and method for the production of exhaust gas purification catalyst
EP2442893A1 (en) Exhaust gas purifying catalyst
EP2926900B1 (en) Method for supporting catalyst metal particles, and supported catalyst metal particles obtainable by said method
WO2012137051A1 (en) Catalyst and catalytic apparatus for nox reduction
WO2018088201A1 (en) Exhaust gas purifying three-way catalyst, method for manufacturing same, and exhaust gas purifying catalyst converter
JP2018075550A (en) Three-dimensional catalyst for exhaust gas purification and manufacturing method therefor, and catalyst converter for exhaust gas solidification
JP6096818B2 (en) Exhaust gas purification catalyst, method for producing the same, and exhaust gas purification method using the same
EP2177258B1 (en) Exhaust gas purification catalyst
JP6769862B2 (en) Three-way catalyst for exhaust gas purification, its manufacturing method, and catalyst converter for exhaust gas purification
JP5573799B2 (en) Exhaust gas purification catalyst and exhaust gas purification catalyst system including the same
JP2017094312A (en) Complex oxide carrier particle

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 12717471

Country of ref document: EP

Kind code of ref document: A1

NENP Non-entry into the national phase

Ref country code: DE

122 Ep: pct application non-entry in european phase

Ref document number: 12717471

Country of ref document: EP

Kind code of ref document: A1