US3928241A - Catalysts for purifying exhaust gas - Google Patents

Catalysts for purifying exhaust gas Download PDF

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US3928241A
US3928241A US331888A US33188873A US3928241A US 3928241 A US3928241 A US 3928241A US 331888 A US331888 A US 331888A US 33188873 A US33188873 A US 33188873A US 3928241 A US3928241 A US 3928241A
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alloy
hours
oxidized
exhaust gas
catalyst
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Itaru Niimi
Yasuhisa Kaneko
Akiyoshi Morita
Yasuo Nemoto
Mitsuyoshi Sato
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Toyota Motor Corp
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Toyota Motor Corp
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with 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
    • 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
    • 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
    • B01J23/84—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 arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
    • B01J23/85—Chromium, molybdenum or tungsten
    • B01J23/86—Chromium
    • B01J23/868—Chromium copper and chromium
    • 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
    • B01J37/16—Reducing
    • B01J37/18—Reducing with gases containing free hydrogen
    • 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
    • B01D2255/20738—Iron
    • 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
    • B01D2255/20746—Cobalt
    • 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
    • B01D2255/207—Transition metals
    • B01D2255/20784—Chromium

Definitions

  • ABSTRACT Exhaust gas purifying catalysts characterized in that alloys comprising 01-40% of Cu and the balance of Ni and/or Fe by weight as fundamental components are shaped as desired and are activated, at least partially, by providing their surfaces with oxidized enriched Cu layers thicker than 10 1 in the oxidization atmosphere or by partially reducing the oxidized layers with hydrogen gas at high temperature.
  • Oxidized at 900C. for 24 hours) X 1000 Surface of alloy without oxidized layer X 1000 X 3000 Fe-52.0ZNi-26. 4ZCu Fe52.0ZNi-26. rZCu (Oxidized layer thickness 0.6mm (Oxidized layer thickness 0.6mm
  • the present invention relates to a catalyst for purifying exhaust gas.
  • catalysts suitable for purifying exhaust gas are agents which are generally made by allowing carriers such as alumina to carry noble metals such as Pt or Pd or carry or mix with oxides of Ni, Cu or Cr. But these are significantly disadvantageous in that catalytic agents comprising noble metals such as Pt or Pd are expensive, their resources are insufficiently available, inferiority in heat resistance and durability, and unsuitability for quantity production due to difficult manufacturing methods.
  • Various other alloy system catalysts are known in addition to catalysts as mentioned above, but these do not demonstrate their effects if temperature is not high.
  • the present invention relates to exhaust gas purifying catalysts having characteristics for removing harmful nitrogen oxide (NOx) components contained in exhaust gases, particularly those from internal combustion engines, by reduction, and is characterized in that alloys comprising 01 40% of Cu and the balance of Ni and/or Fe by weightare provided with enriched Cu layers on their surface portions, or further, the oxidized layers are partially activated.
  • NOx harmful nitrogen oxide
  • FIG. 1 is a diagram of alloy composition ranges of the I catalysts according to the present invention.
  • FIG. 2 is a graph diagram showing therelationship between NO and CO purification rates and catalyst bed temperatures
  • FIG. 3 through 8 are microscopic photographs of typical alloys and catalysts obtained in embodying Examples I through 6 according to the present invention.
  • FIG. 9 is a photograph made by a scanning-type electronic microscope illustrating the state of an alloy surface in the case where an oxidized layer is absent from the surface.
  • FIG. 10 comprises photographs made by a scanningtype electronic microscope illustrating the state of an alloy surface in the case where an oxidized layer thicker than 10g. is present.
  • the present invention is intended to provide catalysts for reducingand removingNOx contained'in exhaust gas discharged from internal combustion engines.
  • catalysts of this invention comprise a binary Fe-Cu or Ni-Cu or a ternary Fe-Ni-Cu system alloy (hereinafter referred to as this systems alloy) always containing less than 99.9% of Fe and Ni and the balance of Cu.
  • FIG. 1 A composition range of this systems alloy for the catalysts according to the present invention is given in FIG. 1.
  • a portion rectangularly surrounded by ABCD is a standard composition range. Even in case other additive elements are contained, if the composition rate is within a diagonallylined range, that composition is acceptable.
  • this system's alloy within the above composition range is obtained by the conventional method and is shaped in workable plasticity types such as a sheet, bar, pipe, line or alloy powder, casting materials, etc., according to alloy compositions and applications for use as catalysts.
  • the catalysts according to the present invention can function satisfactory with an oxidized layer only, but those are further improved by reducing the oxidized layers formed on alloys. Descriptions as to examples embodying the present invention are given below. In each of these examples only one-half of the specimen is reduced after oxidation to thereby provide a comparison between oxidation alone and reduction after oxidation.
  • EXAMPLE 1 After melting Fe-Ni-Cu ternary alloys with various compositions as given in Table 1 at l600C. by using a Tammann furnace, a casting was made in a stainless steel (SUS 27) mold coated with a sufficient thickness of graphite. After casting, casted cylindrical bars'obtained were machined tomake cuttings and were subjected to oxidization treatment in a high temperature atmosphere at 1000C. for six hours to obtain catalyst cuttings.
  • SUS 27 stainless steel
  • the dimensions of the cuttings vary with the material, but those within the range of 0.1 0.5mm in thickness, 2mm-20mm in length and lmm-3mm in width are desirable.
  • the term Cuttings in this Example and hereinafter, represents granularity almost within the above range.
  • Table 1 Compositions and purification rates of Fe-Ni-Cu system allo
  • the catalysts apparent surface area of 10ml is desped- Chemical component Npyurjficmion mite pendent on the catalyst components, but is almost 1 p i g i y ft within 100 l000cm Unless otherwise specified,- the Cu Ni Fe :f; surface area 15 identical to that in Example 1.
  • the binary alloy with a COmPOSIUOIIOOf Fe and Cu as 5 26 m bal 195 64.3 given in Table 2 was casted at 1650 C. in the same 6 4,4 50,8 bal 51.3 86.2 metal mold as in Example 1 after being melted in a high 3-; 2:: 2-3 23-? frequency f q 9 6:4 17:5 bal 313 800
  • Casted cylindrical bars obtained were machined to 1? g-g 2% make cuttings and the cuttings were subjected to oxldi- 12 5 4 zation treatment in an atmosphere at 1100 C. for three 13 10.9 42.1 bal 0 72.1 hours to obtain catalysts.
  • half of the cuttings were 14 223 bal 0 0 15 26.4 52.0 bal 0 78.5 reduced m hydrogen gas at 800 C. for two hours to obtain catalysts.
  • a sheet-type catalyst was obtained by subjecting Compositions and purification rates of 0.5mm thickness of an Ni-Cu alloy to atmospheric System alloys N0 oxldlzatlon 800C l and 1 for Speci- Chemical Oxidation/Reduction purification 24, 12, 6 and 3 hours, respectively. men component rate This sheet-type catalyst had been shaped cylindri- Fe cally at 0.5mm in thickness, 2.5mm in width and 15mm 16 2 5 b l 0 6 8 an n in length. A half: of the catalyst was Sub ected to hydroa f f 2 gen gas reduction at 800C. for 2 hours. Apparent oxidization 70.0 surface area of a 10ml catalyst obtained by the above 17 bal process was approximately 100cm.
  • EXAMPLE 4 Fe-Ni-Cu alloy comprising other additive elements as Table 3 givenin Table 4 was made into cuttings and subjected Treatment conditions and purification to high temperature atmospheric oxidization at S Ch I I 6 9 7 yg C0 ecl- 8111108 Xl 1Z3 1011 1000C. for 6 hours, and a half was Subjec to y glen component Reduction purification purification gen gas reduction at 800C. for 2 hours. No. c N rate rate EXAMPLE 5 40 80.0%.
  • Fe-Cu binary alloy comprising other additive eleg 'g'fi g: ments as given in Table 5 was made into cuttings and after subjected to high temperature atmospheric oxidization 6323 at 1 100C. for three hours, and a half was subjected to oxidizatjon 763 hydrogen gas reduction at 800C. for 2 hours. Redactlon a er 18 24 66 oxidization 54.3 46.0 EXAMPLE 6 1990,?
  • Ni-Cu alloy comprising other additive elements as 0 0 eductlon given 111 Table 6 was formed into a 1.0mm thick sheet after and subjected to high temperature atmospheric oxidigggg 531 zation at 900C. for twelve hours to obtain a sheet-type oxidimion 0 1 catalyst, and a half was sub ected to hydrogen gas re- Redpction 0 8 181' duction at 800 C. for 2 hours.
  • Cu when this system s alloy has been oxidized and subsequently reduced to impart a catalyst effect, CuO* is formed on the alloy surface, and CuO* being diffused into FeO* and NiO* is presumed to play a significant role for catalytic effect.
  • CuO* herein represents oxidized Cu, but since the state of achieving the optimum catalytic effect is unknown and content of oxygen can not be determined, representation is made by 0*.
  • Catalytic activity is deemed to become present when 0* in oxides is almost nil.
  • FeO* and NiO* denote the same as in CuO*.
  • compositions were proven as follows.
  • the reason for restricting the Cu content is that when Cu exceeds 40% or becomes less than 0.1% by weight, diffusion of CuO* into NiO* and FeO* becomes dense and coarse respectively, and either case adversely affects the catalytic effect. In case Cu is excessive, it separates and deposits in the alloy provided that it does not form a solid solution or intermetallic compound.
  • Intermetallic compounds are difficult to oxidize, and even if oxidized, those compounds do not form oxidized layers having catalytic effect. Therefore, although Cu is contained therein, it adversely affects the catalytic effect. The more this systems alloy contains solid solution Fe-Ni-Cu or Fe-Cu, the greater the catalytic effect becomes. Now, as for Ni and Fe, it is felt that Ni and Fe act to promote the catalytic effect rather than to provide the direct reduction effect to NOx, that is, a dispersed state of CuO* is thereby made effective and the effect of adsorbing molecules such as CO and H useful for reduction of NO is excellent.
  • Ni is effective for expanding a solid solution limit of Cu into Fe, which can be presumed from the binary state diagram of Ni-Cu and Fe-Ni given in FIG. 1. Coexistence and independent existence of Ni and Fe are acceptable.
  • 1f additive elements satisfy the following conditions when added to this systems alloys of Fe-Ni-Cu, Fe-Cu or Ni-Cu, the catalytic effect will not be reduced much, that is;
  • FIGS. 3 through 8 microscopic photographs of casted and annealed structures of component elements given in Examples 1 through 6 are presented in FIGS. 3 through 8 in order to clarify the effect of each component.
  • Annealed structures are those which are annealed by furnace cooling after heating at l000C. for 6 hours.
  • Oxidized layers are formed by oxidizing in atmospheric conditions. Since thicknesses of oxidized layers vary with alloy compositions, surface condition, oxidizing temperature, and period of oxidizing time, treatment conditions can not be formulated, but desired thickness is obtainable by selecting conditions within temperatures ranging from 700 to 1 100C. and time periods ranging from 1/2 hour to 24 hours or temperatures ranging from 800 to 1300C and time periods ranging from 3 to 24 hours.
  • the thickness of oxidized layers are required to be at least 10p. and a thickness above 10p. is unlimitedly permissible, to the extreme of up to the center portion of the alloys.
  • the oxidized layer with a thickness of at least 10p. is necessary to provide oxidized layers with corrugation and to increase the surface area as will be described later.
  • An enriched Ni layer is also formed at the portion near the surface, but slightly lower than the enriched Fe and Cu layers, and after subsequent reduction treatment, in the same position as that of the enriched Fe layer or slightly close to the surface.
  • the enriched Cu layer formed near the top surface exists independent from other additive elements.
  • Co displays an enriched state similar to that of Cu.
  • the oxidized layer is thinner than 10 1.
  • the enriched oxidized layer as described above, can not be formed.
  • the above tendency becomes considerably more, that is, Cu enriches in the surface and diffuses into Ni and Fe. This is an advantageous condition for catalytic effect.
  • the thickness of all oxidized layers were made in 0.5 1.0mm,
  • FIG. 9 shows the surface when the oxidized layer is insufficiently formed and corrugation and porosity are not seen therein, but are apparent in FIG. 8 which shows the state of a sufficiently oxidized layer.
  • the reduction treatment of an oxidized layer is the processing in hydrogen gas and the treatment condition is determined within the treatment period of time ranging from 24 hours in accordance with the state of the subject oxidized layer, and at least, partial treatment is acceptable.
  • TEST EXAMPLE 1 The purification rate as to NO was measured under the following conditions in order to certify the effect of each catalyst obtained in the embodying Examples l6.
  • Catalyst bed temperature Catalyst surface area:
  • the catalysts according to the present invention also act effectively as an oxidization catalyst for hydrocarbon (HC) and carbon monoxide (CO) if an oxidization atmosphere is available.
  • HC hydrocarbon
  • CO carbon monoxide
  • the catalyst was made by machining this 'systems (1) Test alloy with various components, as given in Table 7, to
  • Test gas CQ produce cuttings by forming an oxidized layer, by reg gggg PP"! ducing, and then stuffing into the catalyst converter for N: the rest ,I purifying internal combustion engine exhaust gas.
  • the alloy is a highly strong and zatlon denotes that it was subsequently subjected to excellent in plasticity, workability and castability as hydrogen gas reduction at 800C. for 2 hours. well as heat resistance and corrosion resistance. Therefore, it can advantageously be formed into cuttings, sheets, pipes, etc. according to application.
  • An exhaust gas purifying catalyst comprising an alloy consisting essentially of 01-40% Cu and the balance of at least one of the group consisting of Ni, Fe, and a combination of Ni and Fe by weight as fundamental components, and including a surface formed by first oxidizing the alloy by heating at 700C. 1100C. in an oxidizing atmosphere for k to 24 hours to provide an oxidized layer at least p. in thickness, and thereafter reducing the oxidized layer in a reducing atmosphere at approximately 800C. for about 2 hours.

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  • Organic Chemistry (AREA)
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  • Chemical Kinetics & Catalysis (AREA)
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  • Combustion & Propulsion (AREA)
  • Health & Medical Sciences (AREA)
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US331888A 1972-02-12 1973-02-12 Catalysts for purifying exhaust gas Expired - Lifetime US3928241A (en)

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JP (1) JPS5230957B2 (enrdf_load_stackoverflow)
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CA (1) CA1002030A (enrdf_load_stackoverflow)
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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4642303A (en) * 1985-12-27 1987-02-10 Texaco Inc. Catalyst composition
US5482629A (en) * 1994-12-07 1996-01-09 Universal Environmental Technologies, Inc. Method and apparatus for separating particles from liquids
US5843394A (en) * 1995-03-02 1998-12-01 Wabco Gmbh Catalyst for the oxidation of gaseous sulphur compounds
US20070166220A1 (en) * 2006-01-19 2007-07-19 Massachusetts Institute Of Technology Oxidation catalyst
CN106232208A (zh) * 2014-04-18 2016-12-14 株式会社渥美精机 废气净化系统、催化剂及废气净化方法

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2564844A (en) * 1948-05-06 1951-08-21 Battelle Development Corp Copper-iron-chromium alloy
US3206414A (en) * 1962-07-10 1965-09-14 Gunther Arnold Method of preparing a catalyst composition comprising nickel, iron and copper and the product thereof
US3565574A (en) * 1968-04-23 1971-02-23 Exxon Research Engineering Co Catalytic conversion of exhaust gas impurities
US3699683A (en) * 1971-04-05 1972-10-24 Chemical Construction Corp Engine exhaust emission control system
US3718733A (en) * 1970-02-20 1973-02-27 North American Rockwell Catalytic treatment of exhaust gases
US3773894A (en) * 1971-07-22 1973-11-20 Exxon Nitrogen oxide conversion using reinforced nickel-copper catalysts

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2564844A (en) * 1948-05-06 1951-08-21 Battelle Development Corp Copper-iron-chromium alloy
US3206414A (en) * 1962-07-10 1965-09-14 Gunther Arnold Method of preparing a catalyst composition comprising nickel, iron and copper and the product thereof
US3565574A (en) * 1968-04-23 1971-02-23 Exxon Research Engineering Co Catalytic conversion of exhaust gas impurities
US3718733A (en) * 1970-02-20 1973-02-27 North American Rockwell Catalytic treatment of exhaust gases
US3699683A (en) * 1971-04-05 1972-10-24 Chemical Construction Corp Engine exhaust emission control system
US3773894A (en) * 1971-07-22 1973-11-20 Exxon Nitrogen oxide conversion using reinforced nickel-copper catalysts

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4642303A (en) * 1985-12-27 1987-02-10 Texaco Inc. Catalyst composition
US5482629A (en) * 1994-12-07 1996-01-09 Universal Environmental Technologies, Inc. Method and apparatus for separating particles from liquids
US5843394A (en) * 1995-03-02 1998-12-01 Wabco Gmbh Catalyst for the oxidation of gaseous sulphur compounds
US20070166220A1 (en) * 2006-01-19 2007-07-19 Massachusetts Institute Of Technology Oxidation catalyst
US7829035B2 (en) 2006-01-19 2010-11-09 Massachusetts Institute Of Technology Oxidation catalyst
CN106232208A (zh) * 2014-04-18 2016-12-14 株式会社渥美精机 废气净化系统、催化剂及废气净化方法
US20170113186A1 (en) * 2014-04-18 2017-04-27 Atsumitec Co., Ltd. Exhaust gas purification system, catalyst, and exhaust gas purification method

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CA1002030A (en) 1976-12-21
AU474848B2 (en) 1976-08-05
JPS5230957B2 (enrdf_load_stackoverflow) 1977-08-11
JPS4896476A (enrdf_load_stackoverflow) 1973-12-10
GB1423422A (en) 1976-02-04
AU5208373A (en) 1974-08-15
DE2306785A1 (de) 1973-08-23
DE2306785B2 (de) 1976-09-02

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