JP2013111525A - Exhaust gas purifying catalyst - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust gas purifying catalyst capable of efficiently purifying carbon monoxide (CO), hydrocarbon (HC) and nitrogen oxide (NO), especially hydrocarbon (HC).SOLUTION: An alloy of nickel and copper and a composite oxide supporting the alloy are contained in the exhaust gas purifying catalyst. In this exhaust gas purifying catalyst, since the support amount of the alloy to composite oxide is 6-35 pts.mass based on 100 pts.mass of the total amount of the alloy and the composite oxide, hydrocarbon (HC) can be efficiently purified.

Description

The present invention relates to an exhaust gas purifying catalyst, and more particularly, to carbon monoxide (CO), hydrocarbon (HC) and nitrogen oxide (NO _x ), particularly hydrocarbon ( The present invention relates to an exhaust gas purifying catalyst for efficiently purifying HC).

An exhaust gas purifying catalyst comprising a three-way catalyst capable of simultaneously purifying carbon monoxide (CO), hydrocarbon (HC) and nitrogen oxide (NO _x ) contained in exhaust gas is a precious metal such as Pt, Rh and Pd. Active substance.

  Since such noble metals are expensive and the price fluctuates severely, various catalyst compositions that can be produced at low cost without using noble metals have been studied.

  As such an exhaust gas purification catalyst, for example, a nitrogen oxide purification catalyst obtained by supporting copper and at least one selected from nickel, cobalt and iron as an oxide on a support made of alumina, more specifically, Specifically, a nitrogen oxide purification catalyst obtained by supporting copper oxide and nickel oxide on a support made of alumina has been proposed (see, for example, Patent Document 1).

JP-A-8-108071

However, such a catalyst is excellent in the purification rate of nitrogen oxides (NO _x ), but may be inferior in the purification rate of hydrocarbons (HC).

An object of the present invention is to provide an exhaust gas purifying catalyst capable of efficiently purifying carbon monoxide (CO), hydrocarbons (HC) and nitrogen oxides (NO _x ), especially hydrocarbons (HC). It is in.

  In order to achieve the above object, an exhaust gas purifying catalyst of the present invention includes an alloy made of nickel and copper and a composite oxide supporting the alloy, and the amount of the alloy supported on the composite oxide The total amount of the alloy and the composite oxide is 6 to 35 parts by mass with respect to 100 parts by mass.

  In the exhaust gas purifying catalyst of the present invention, an alloy composed of nickel and copper is supported on a composite oxide, and the supported amount of the alloy is 6 to 35 parts by mass with respect to 100 parts by mass of the total amount of the alloy and the composite oxide. Therefore, in particular, hydrocarbon (HC) can be efficiently purified.

The HC purification rate of the exhaust gas purification catalyst obtained in Examples 1-3 and Comparative Examples 1-2 is shown.

  The exhaust gas purifying catalyst of the present invention contains an alloy composed of nickel and copper.

  The method for obtaining an alloy composed of nickel and copper is not particularly limited, and a known method can be employed. Specifically, for example, a method of firing nickel and copper in a reducing atmosphere can be mentioned.

  The reducing atmosphere is not particularly limited, and examples thereof include a nitrogen atmosphere containing 5 to 10% by volume of hydrogen.

  Moreover, as baking conditions, heating temperature is 600-1000 degreeC, for example, Preferably, it is 700-850 degreeC, and heating time is 1 to 8 hours, for example, Preferably, it is 3 to 5 hours.

  In the alloy, the content ratio of nickel and copper is, for example, 1 to 99 parts by mass, preferably 58 to 78 parts by mass of nickel with respect to 100 parts by mass of the total amount of nickel and copper. 1 to 99 parts by mass, preferably 22 to 42 parts by mass.

  The molar ratio of nickel and copper is, for example, 1 to 99 mol, preferably 60 to 80 mol, and 1 to 99 mol of copper, for example, with respect to the total amount of nickel and copper of 100 mol. , Preferably, it is 20-40 mol.

  The average particle size of the alloy (measurement method: X-ray diffraction analysis and Scherrer's formula) is, for example, 8 to 17 nm, preferably 8 to 13 nm.

  The alloy thus obtained is preferably supported on a composite oxide.

  Examples of the complex oxide include perovskite complex oxide, spinel complex oxide, zirconia complex oxide, ceria complex oxide, and alumina.

  The perovskite complex oxide is represented by the following general formula (1).

ABO ₃ (1)
(In the formula, A represents at least one element selected from rare earth elements and alkaline earth metals, and B represents at least one element selected from transition elements excluding noble metals and Al.)
In the general formula (1), examples of the rare earth element represented by A include Sc (scandium), Y (yttrium), La (lanthanum), Ce (cerium), Pr (praseodymium), Nd (neodymium), Pm ( Promethium), Sm (samarium), Eu (europium), Gd (gadolinium), Tb (terbium), Dy (dysprosium), Ho (holmium), Er (erbium), Tm (thulium), Yb (ytterbium), Lu ( Lutetium).

  Examples of the alkaline earth metal represented by A include Be (beryllium), Mg (magnesium), Ca (calcium), Sr (strontium), Ba (barium), and Ra (radium). These may be used alone or in combination of two or more.

  In the general formula (1), the transition element excluding the noble metal represented by B and Al are, for example, according to the periodic table (IUPAC Periodic Table of the Elements (version date 19 February 2010). 21 (Sc) to atomic number 30 (Zn), atomic number 39 (Y) to atomic number 48 (Cd), and atomic number 57 (La) to atomic number 80 (Hg) (provided that noble metal (atom No. 44-47 and 76-78)), and Al, preferably Ti (titanium), Cr (chromium), Mn (manganese), Fe (iron), Co (cobalt), Ni (nickel) Cu (copper), Zn (zinc) and Al (aluminum). These may be used alone or in combination of two or more.

  Such a perovskite complex oxide is not particularly limited, and for example, for preparing a complex oxide in accordance with the description of paragraph numbers [0039] to [0059] of JP-A-2004-243305. It can be produced by an appropriate method, for example, a production method such as a coprecipitation method, a citric acid complex method, or an alkoxide method.

  The spinel complex oxide is represented by the following general formula (2).

MO.nAl ₂ O ₃ (2)
(Wherein M represents at least one element selected from Mg, Fe, Co and Ni, and n represents 0.08 to 5)
In the general formula (2), M represents at least one element selected from Mg (magnesium), Fe (iron), Co (cobalt), and Ni (nickel). These elements may be used alone or in combination of two or more.

  Moreover, in General formula (2), n shows 0.08-5, Preferably, 0.16-5 is shown.

  Note that when n is 1, the composite oxide described in the above formula (2) is a composite oxide having a spinel crystal phase of stoichiometry (stoichiometric composition, stoichiometry) (hereinafter referred to as a constant ratio). This is referred to as a spinel type complex oxide).

  On the other hand, when n is less than 1 or exceeds 1, the composite oxide described in the above formula (2) has a spinel crystal phase as a main crystal phase and other crystal phases. For example, a composite oxide having a non-stoichiometric (non-stoichiometric composition, non-stoichiometric) spinel crystal phase (hereinafter referred to as indefinite) having a magnetoplumbite crystal phase, an alumina crystal phase, etc. Called a specific spinel type complex oxide).

  Such a spinel type complex oxide is not particularly limited, and for example, for preparing a complex oxide in accordance with the description of paragraph numbers [0014] to [0021] of JP2011-45840A. It can be produced by an appropriate method, for example, a coprecipitation method, a citric acid complex method, an alkoxide method, or the like.

  The zirconia composite oxide is represented by the following general formula (3).

Zr _{1- (a + b)} Ce _a L _b O _2-c (3)
(In the formula, L represents an alkaline earth metal and / or rare earth element (excluding Ce), a represents the atomic ratio of Ce, b represents the atomic ratio of L, and 1- ( a + b) indicates the atomic ratio of Zr, and c indicates the amount of oxygen defects.)
In the general formula (3), the alkaline earth metal represented by L includes the alkaline earth metal represented by the general formula (1). The rare earth element represented by L includes the rare earth metal represented by the general formula (1) (excluding Ce). These alkaline earth metals and rare earth elements may be used alone or in combination of two or more.

  Moreover, the atomic ratio of Ce shown by a is in the range of 0.1 to 0.65, and preferably in the range of 0.1 to 0.5.

  In addition, the atomic ratio of L represented by b is in the range of 0 to 0.55 (that is, R is an optional component that is arbitrarily included rather than an essential component, and if included, 0.55 or less. Atomic ratio). If it exceeds 0.55, phase separation or other complex oxide phases may be generated.

  In addition, the atomic ratio of Zr represented by 1- (a + b) is in the range of 0.35 to 0.9, and preferably in the range of 0.5 to 0.9.

  Further, c represents the amount of oxygen defects, which means the ratio of vacancies formed in the crystal lattice in the fluorite-type crystal lattice usually formed by the oxides of Zr, Ce and L.

  Such a zirconia-based composite oxide is not particularly limited, and for example, for preparing a composite oxide according to the description of paragraph numbers [0090] to [0102] of JP-A-2004-243305. It can be produced by an appropriate method, for example, a production method such as a coprecipitation method, a citric acid complex method, or an alkoxide method.

  The ceria-based composite oxide is represented by the following general formula (4).

Ce _{1- (d + e)} Zr _d L _e O _2-f (4)
(In the formula, L represents an alkaline earth metal and / or rare earth element (excluding Ce), d represents the atomic ratio of Zr, e represents the atomic ratio of L, and 1- ( d + e) indicates the atomic ratio of Ce, and f indicates the amount of oxygen defects.)
In the general formula (4), the alkaline earth metal represented by L includes the alkaline earth metal represented by the general formula (1). The rare earth element represented by L includes the rare earth metal represented by the general formula (1) (excluding Ce). These alkaline earth metals and rare earth elements may be used alone or in combination of two or more.

  Further, the atomic ratio of Zr represented by d is less than the atomic ratio of Zr in the zirconia-based composite oxide, and is in the range of 0.2 to 0.7, preferably in the range of 0.2 to 0.5. It is.

  In addition, the atomic ratio of L represented by e is in the range of 0 to 0.2 (that is, L is an optional component that is optionally included rather than an essential component, and if included, 0.2 or less) Atomic ratio). If it exceeds 0.2, phase separation or other complex oxide phases may be generated.

  Further, the atomic ratio of Ce represented by 1- (d + e) is larger than the atomic ratio of Ce of the zirconia-based composite oxide, and is in the range of 0.3 to 0.8, preferably 0.4 to 0. .6 range.

  Further, f represents the amount of oxygen defects, which means the ratio of vacancies formed in the crystal lattice in the fluorite-type crystal lattice usually formed by Ce, Zr and L oxides.

  Such a ceria-based composite oxide can be manufactured by a manufacturing method similar to the above-described manufacturing method of the zirconia-based composite oxide.

  Examples of alumina include α alumina, θ alumina, and γ alumina.

  α-alumina has an α-phase as a crystal phase, and examples thereof include AKP-53 (trade name, high-purity alumina, manufactured by Sumitomo Chemical Co., Ltd.). Such α-alumina can be obtained by a method such as an alkoxide method, a sol-gel method, or a coprecipitation method.

  θ-alumina is a kind of intermediate (transition) alumina that has a θ-phase as a crystal phase and transitions to α-alumina, and includes, for example, SPHERALITE 531P (trade name, γ-alumina, manufactured by Procatalyze). . Such θ-alumina can be obtained, for example, by subjecting commercially available activated alumina (γ-alumina) to heat treatment at 900 to 1100 ° C. for 1 to 10 hours in the air.

  γ-alumina has a γ-phase as a crystal phase and is not particularly limited, and examples thereof include known ones used for exhaust gas purification catalysts.

  Moreover, the said alumina containing La and / or Ba can also be used as an alumina. Alumina containing La and / or Ba can be produced according to the description in paragraph [0073] of JP-A No. 2004-243305.

  Furthermore, as a complex oxide, other complex oxides (for example, magnesium oxide) etc. can be contained in an appropriate ratio according to the purpose and application.

  These composite oxides may be used alone or in combination of two or more.

  As the composite oxide, a composite oxide containing magnesium is preferable.

  Specific examples of the composite oxide containing magnesium include, for example, a perovskite-type composite oxide containing Mg as an alkaline earth metal represented by A in the above formula (1), and represented by M in the above formula (2). A stoichiometric spinel composite oxide containing Mg as an element and n is 1, and an indefinite ratio containing Mg as an element represented by M in the above formula (2) and n being less than 1 or exceeding 1. Spinel-type composite oxide, zirconia-based composite oxide containing Mg as an alkaline earth metal represented by L in the above formula (3), and Mg as an alkaline earth metal represented by L in the above formula (4) And ceria-based composite oxide.

If a composite oxide containing magnesium is used as the composite oxide, carbon monoxide (CO), hydrocarbon (HC), and nitrogen oxide (NO _x ), particularly nitrogen oxide (NO _x ), have excellent efficiency. Can be purified.

  In such a complex oxide, the magnesium content is, for example, 32 parts by mass or less, preferably 11 parts by mass or less, more preferably 8 parts by mass with respect to 100 parts by mass of the total amount of the complex oxide. Hereinafter, it is usually 2 parts by mass or more.

  More preferably, the composite oxide further includes a composite oxide containing aluminum.

  Specifically, as the composite oxide containing aluminum and magnesium, for example, in the above formula (1), Mg is contained as the alkaline earth metal represented by A, and a transition element excluding the noble metal represented by B and Perovskite complex oxide containing Al as Al, a stoichiometric spinel complex oxide containing Mg as an element represented by M in the above formula (2) and n being 1, M in the above formula (2) Examples of the non-stoichiometric spinel-type composite oxide containing Mg as an element represented by and having n less than 1 or more than 1.

  In the case where the composite oxide contains magnesium and aluminum, the content ratio of magnesium in the composite oxide is, for example, 2.5 mol or less, preferably 1.5 mol or less, relative to 1 mol of aluminum. More preferably, it is 0.25 mol or less.

When the magnesium content is in the above range, carbon monoxide (CO), hydrocarbon (HC) and nitrogen oxide (NO _x ), particularly hydrocarbon (HC), can be purified with excellent efficiency.

  And in order to carry | support the alloy which consists of nickel and copper on said composite oxide, it does not restrict | limit in particular, A well-known method is employable. For example, there is a method in which a precursor of an alloy of nickel and copper and a composite oxide are mixed and then fired in a reducing atmosphere.

  Specifically, in this method, first, a precipitate of a precursor (hydroxide) of an alloy of nickel and copper is generated.

  For the precipitation of nickel and copper alloy precursor (hydroxide), for example, a mixed salt aqueous solution containing a copper and nickel salt in a predetermined stoichiometric ratio is prepared, and this mixed salt aqueous solution is added to the precipitant. Can be obtained by coprecipitation.

  Examples of the copper and nickel salts include inorganic salts such as sulfates, nitrates, chlorides and phosphates, and organic acid salts such as acetates and oxalates. The mixed salt aqueous solution can be prepared, for example, by adding copper and nickel salt to water at a ratio such that a predetermined stoichiometric ratio is obtained, and stirring and mixing.

  Examples of the precipitant include ammonia and tetramethylammonium hydroxide.

  Then, in this method, the obtained coprecipitate (precipitation of nickel and copper alloy precursor (hydroxide)) is optionally filtered and washed with water and mixed with the composite oxide.

  The mixing ratio of the precursor (hydroxide) of the nickel and copper alloy to the composite oxide is, for example, the precipitation of the precursor of the nickel and copper (hydroxide) and the total amount of the composite oxide of 100. Precipitation of nickel and copper alloy precursor (hydroxide) is, for example, 10 to 35 parts by mass, preferably 15 to 25 parts by mass, and the composite oxide is, for example, 65 parts by mass. -90 mass parts, Preferably, it is 75-85 mass parts.

  Next, in this method, the obtained mixture is dried as necessary, and then calcined in a reducing atmosphere.

  Examples of the reducing atmosphere include the same reducing atmosphere as described above, and specific examples include a nitrogen atmosphere containing 5 to 10% by volume of hydrogen.

  Moreover, as baking conditions, the baking conditions similar to the above are mentioned, Specifically, heating temperature is 600-1000 degreeC, for example, Preferably, it is 700-850 degreeC, and heating time is, for example, 1 -8 hours, preferably 3-5 hours.

  Thereby, an alloy of nickel and copper supported on the composite oxide can be obtained.

  Further, as a method of supporting an alloy composed of nickel and copper on a composite oxide, for example, a precipitate of a precursor (hydroxide) of an alloy of nickel and copper is generated by the above method, and the precipitate is generated. A method of mixing and mixing the composite oxide in the solvent (precipitating agent) in the above ratio, evaporating and drying, and then firing in the reducing atmosphere described above is also included.

  Further, for example, when a spinel type composite oxide is used as the composite oxide, a hydroxide containing nickel and copper and an element (for example, magnesium and aluminum) constituting the spinel type composite oxide, Preferably, a method of firing a hydrotalcite type hydroxide (an alloy of nickel and copper and a precursor of a composite oxide) in a reducing atmosphere is exemplified.

  Specifically, the hydrotalcite-type hydroxide is represented by the following general formula (5), for example.

(Ni _1-g Cu _g ) _0.5 Mg _2.5 Al (OH) ₈ 1 / 2CO ₃ ² · 2H ₂ O (5)
(In the formula, g represents 0.2 to 0.8.)
In General formula (5), the atomic ratio of Cu shown by g is the range of 0.2-0.8.

  In order to produce such a hydrotalcite type hydroxide, for example, first, a mixed salt containing a salt of each of the above elements (elements constituting the hydrotalcite type hydroxide) in a predetermined stoichiometric ratio. An aqueous solution is prepared, and this mixed salt aqueous solution is added to a precipitant to cause coprecipitation, and then the obtained coprecipitate is dried and then heat treated.

  Examples of the salt of each element include the inorganic salts described above and the organic acid salts described above. Further, the mixed salt aqueous solution can be prepared, for example, by adding the salt of each element to water at a ratio that gives a predetermined stoichiometric ratio and stirring and mixing.

  Thereafter, this mixed salt aqueous solution is coprecipitated with the above-mentioned precipitating agent, and the obtained coprecipitate is washed with water as necessary, for example, at 80 to 150 ° C., preferably at 100 to 120 ° C., for example, Dry for 8-24 hours, preferably 10-12 hours.

  And the hydrotalcite type hydroxide obtained by this is baked in the above-mentioned reducing atmosphere. Thereby, it is possible to obtain an exhaust gas purifying catalyst in which an alloy composed of nickel and copper is supported on a spinel type complex oxide.

  The method for producing the exhaust gas purifying catalyst is not limited to the above-described method, and various methods can be employed.

  In the exhaust gas purifying catalyst, the amount of nickel and copper alloy supported on the composite oxide (total amount of nickel and copper) is 6 to 35 parts by weight, preferably 100 parts by weight of the total amount of composite oxide and alloy, 10 to 30 parts by mass, and more preferably 10 to 20 parts by mass. Moreover, nickel is 3-12 mass parts with respect to 100 mass parts of total amounts of complex oxide and an alloy, Preferably, it is 6-9 mass parts, Copper is 3-12 mass parts, for example, Preferably, it is 6-9 mass parts.

If the amount of the alloy supported is less than the lower limit, exhaust gas (carbon oxide (CO), hydrocarbon (HC), nitrogen oxide (NO _x ), etc.) may not be sufficiently purified.

The average particle diameter (crystallite diameter) (measurement method: X-ray diffraction analysis and Scherrer formula) of the exhaust gas-purifying catalyst in which an alloy of nickel and copper is supported on the composite oxide is, for example, 8 to 17 nm, Preferably, it is 8-13 nm, and a specific surface area (BET specific surface area) is 100-160 m < ² > / g, for example, Preferably, it is 130-160 m < ² > / g.

  Further, the exhaust gas-purifying catalyst (nickel and copper alloy, composite oxide on which nickel and copper alloy are supported) thus obtained can be used as it is, for example, supported on a catalyst carrier. The catalyst compound can also be prepared by a known method.

  The catalyst carrier is not particularly limited, and examples thereof include known catalyst carriers such as a honeycomb monolith carrier made of cordierite.

  For carrying on the catalyst carrier, for example, first, water is added to the obtained exhaust gas-purifying catalyst to form a slurry, which is then coated on the catalyst carrier, dried, and then about 300 to 800 ° C., preferably Is heat-treated at about 300-600 ° C.

  In such a case, the exhaust gas purifying catalyst is used in combination with known heat-resistant oxides such as alumina and complex oxides (for example, perovskite complex oxide, fluorite complex oxide, etc.) if necessary. can do.

  The exhaust gas purifying catalyst thus obtained includes an alloy composed of nickel and copper and a composite oxide supporting the alloy, and the amount of the alloy supported on the composite oxide is the total amount of the alloy and the composite oxide. Since it is 6-35 mass parts with respect to 100 mass parts, especially hydrocarbon (HC) can be purified efficiently.

  Further, such an exhaust gas purifying catalyst is excellent in cost because it contains nickel and copper which are available at low cost as active components.

  Therefore, such an exhaust gas purifying catalyst is preferably used particularly as a three-way catalyst for an internal combustion engine in order to purify exhaust gas discharged from an internal combustion engine such as a gasoline engine or a diesel engine or a boiler. Can do.

  Next, although this invention is demonstrated based on an Example and a comparative example, this invention is not limited by the following Example.

Example 1
Copper (II) nitrate trihydrate 2.4558 g, Nickel nitrate (II) hexahydrate 4.4789 g, Magnesium nitrate hexahydrate 3.2579 g, Aluminum nitrate nonahydrate 19 2598 g was dissolved in about 30 mL of water, and the resulting solution was dropped into 400 mL of tetramethylammonium hydroxide at 5 mL / min, stirred for 2 hours, and aged overnight to precipitate (precursor). ) Was generated.

Subsequently, the obtained precipitate (precursor) is filtered by suction, dried in an oven at 110 ° C. for 12 hours, and pulverized in a mortar to obtain (Ni _0.6 Cu _0.4 ) _0.5 Mg _0.25. A powder of Al (OH) ₄ 1 / 2CO ₃ ² · 2H ₂ O was produced.

Next, 5 g of the obtained (Ni _0.6 Cu _0.4 ) _0.5 Mg _0.25 Al (OH) ₄ 1 / 2CO ₃ ² · 2H ₂ O was weighed and reduced on a quartz board ( 5 vol% H ₂ / N ₂ ) and calcined at 850 ° C. for 5 hours.

As a result, an exhaust gas purifying catalyst powder made of Mg _0.5 Al ₂ O ₄ carrying a Ni—Cu alloy was obtained.

  In the obtained powder, the supported concentration of Ni—Cu alloy was 30.5 mass%, the supported concentration of Ni was 17.7 mass%, the supported concentration of Cu was 12.8 mass%, and the molar ratio of Ni and Cu Was Ni: Cu = 60: 40.

Further, in the composite oxide (2MgO · (1/2) MgAl ₂ O ₄ ) supporting the Cu—Ni alloy, the Mg content is 2.5 times mol with respect to Al. Specifically, The amount was 6.1 parts by mass with respect to 100 parts by mass of the total amount of the composite oxide.

  Further, the crystallite diameter of the composite oxide supporting the obtained Cu—Ni alloy was found to be 13.1 nm by an X-ray diffractometer and Scherrer's equation.

Example 2
Copper (II) nitrate trihydrate 1.5211 g, Nickel nitrate (II) hexahydrate 2.7743 g, Magnesium nitrate hexahydrate 4.0366 g, Aluminum nitrate 9 hydrate 23 8600 g was dissolved in about 30 mL of water, and the obtained solution was dropped into 400 mL of tetramethylammonium hydroxide at 5 mL / min, stirred for 2 hours, and aged overnight to precipitate (precursor). ) Was generated.

Subsequently, the obtained precipitate (precursor) is suction filtered, dried in an oven at 110 ° C. for 12 hours, and pulverized in a mortar to obtain (Ni _0.6 Cu _0.4 ) _0.25 Mg _0.25. A powder of Al (OH) ₄ .2H ₂ O was produced.

Next, 5 g of the obtained (Ni _0.6 Cu _0.4 ) _0.25 Mg _0.25 Al (OH) ₄ .2H ₂ O was weighed and reduced on a quartz board (5% by volume H ₂ / N ₂ ) and calcined at 850 ° C. for 5 hours.

As a result, an exhaust gas purifying catalyst powder made of Mg _0.5 Al ₂ O ₄ carrying a Ni—Cu alloy was obtained.

  In the obtained powder, the supported concentration of Ni—Cu alloy was 18.9% by mass, the supported concentration of Ni was 11.0% by mass, the supported concentration of Cu was 7.9% by mass, and the molar ratio of Ni and Cu Was Ni: Cu = 60: 40.

Further, in the composite oxide (2MgO · (1/2) MgAl ₂ O ₄ ) supporting the Cu—Ni alloy, the Mg content is 2.5 times mol with respect to Al. Specifically, The amount of the composite oxide was 7.6 parts by mass with respect to 100 parts by mass.

  Further, the crystallite diameter of the obtained composite oxide carrying the Cu—Ni alloy was determined by an X-ray diffractometer and Scherrer's formula to be 10.4 nm.

Example 3
Copper (II) nitrate trihydrate 0.8637 g, Nickel nitrate (II) hexahydrate 1.5753 g, Magnesium nitrate hexahydrate 4.5834 g, Aluminum nitrate 9 hydrate 27 0.0960 g was dissolved in about 30 mL of water, and the resulting solution was dropped into 400 mL of tetramethylammonium hydroxide at 5 mL / min, stirred for 2 hours, and aged overnight to precipitate (precursor). ) Was generated.

Next, the obtained precipitate (precursor) is suction filtered, dried in an oven at 110 ° C. for 12 hours, and pulverized in a mortar, thereby (Ni _0.6 Cu _0.4 ) _0.125 Mg _0.25 was prepared _{al (OH) 3 · 3 /} 4CO 3 powder of 2-2H ₂ O.

Subsequently, the obtained _{(Ni 0.6} Cu _0.4) to _{0.125 Mg 0.25 Al (OH) 3} · 3 / 4CO 3 2- 2H 2 O and 5g weighed on a quartz board, a reducing atmosphere ( 5 vol% H ₂ / N ₂ ) and calcined at 850 ° C. for 5 hours.

As a result, an exhaust gas purifying catalyst powder made of Mg _0.5 Al ₂ O ₄ carrying a Ni—Cu alloy was obtained.

  In the obtained powder, the supported concentration of Ni—Cu alloy was 10.7 mass%, the supported concentration of Ni was 6.2 mass%, the supported concentration of Cu was 4.5 mass%, and the molar ratio of Ni and Cu Was Ni: Cu = 60: 40.

Further, in the composite oxide (2MgO · (1/2) MgAl ₂ O ₄ ) supporting the Cu—Ni alloy, the Mg content is 2.5 times mol with respect to Al. Specifically, The total amount of the composite oxide was 8.6 parts by mass.

  Further, the crystallite diameter of the composite oxide supporting the obtained Cu—Ni alloy was determined to be 9.8 nm by an X-ray diffractometer and Scherrer's equation.

Comparative Example 1
Copper (II) nitrate trihydrate 0.4630 g, Nickel nitrate (II) hexahydrate 0.8557 g, Magnesium nitrate hexahydrate 4.9140 g, Aluminum nitrate 9 hydrate 29 0.0506 g was dissolved in about 30 mL of water, and the resulting solution was added dropwise to 400 mL of tetramethylammonium hydroxide at 5 mL / min, stirred for 2 hours, and aged overnight to precipitate (precursor). ) Was generated.

Next, the obtained precipitate (precursor) is suction filtered, dried in an oven at 110 ° C. for 12 hours, and pulverized in a mortar to obtain (Ni _0.6 Cu _0.4 ) _0.0625 Mg _0.25. was prepared _{al (OH) 3 · 3 /} 5CO 3 powder of 2-2H ₂ O.

Subsequently, the obtained _{(Ni 0.6} Cu _{0.4) 0.0625} a _{Mg 0.25 Al (OH) 3 ·} 3 / 5CO 3 2- 2H 2 O and 5g weighed on a quartz board, a reducing atmosphere ( 5 vol% H ₂ / N ₂ ) and calcined at 850 ° C. for 5 hours.

As a result, an exhaust gas purifying catalyst powder made of Mg _0.5 Al ₂ O ₄ carrying a Ni—Cu alloy was obtained.

  In the obtained powder, the supported concentration of Ni—Cu alloy was 5.7% by mass, the supported concentration of Ni was 3.3% by mass, the supported concentration of Cu was 2.4% by mass, and the molar ratio of Ni and Cu. Was Ni: Cu = 60: 40.

Further, in the composite oxide (2MgO · (1/2) MgAl ₂ O ₄ ) supporting the Cu—Ni alloy, the Mg content is 2.5 times mol with respect to Al. Specifically, The amount of the composite oxide was 9.2 parts by mass with respect to 100 parts by mass.

  Further, the crystallite diameter of the obtained composite oxide carrying the Cu—Ni alloy was determined by an X-ray diffractometer and Scherrer's formula to be 12.9 nm.

Comparative Example 2
θ Alumina 4.85 g, copper (II) nitrate trihydrate 0.2881 g, nickel nitrate (II) hexahydrate 0.3792 g was heated to 120 ° C. with a hot stirrer (rotation speed 250 to 300 rpm). Mixed.

  The resulting mixture was then fired. In firing, the mixture was heated to 300 ° C. over 1 hour, then heated to 650 ° C. over 1 hour, and then held at 650 ° C. for 1 hour.

As a result, an exhaust gas purifying catalyst powder made of Al ₂ O ₃ supporting Ni and Cu was obtained.

  In the obtained powder, the supported concentration of Ni was 1.5% by mass, and the supported concentration of Cu was 1.5% by mass.

  Table 1 shows the composition of the exhaust gas purifying catalyst in each Example and each Comparative Example.

評価
（ニッケルおよび銅からなる合金の効果）
実施例１〜３、比較例１および２において得られた排ガス浄化用触媒の粉末を、０．５〜１．０ｍｍのサイズのペレットに成型して試験片を調製した。

Evaluation (Effect of alloy consisting of nickel and copper)
Exhaust gas purifying catalyst powders obtained in Examples 1 to 3 and Comparative Examples 1 and 2 were molded into pellets having a size of 0.5 to 1.0 mm to prepare test pieces.

  Using a model gas having the composition shown in Table 2, each exhaust gas (temperature: 600 ° C., flow rate: 2.5 L / min) exhausted by combustion of this model gas (air-fuel ratio A / F = 14.5) It supplied to the test piece and measured the purification rate of HC (THC: total hydrocarbon) of each test piece.

  The result is shown in FIG.

図１より、実施例１〜３で得られた、複合酸化物に対する合金の担持量が、合金および複合酸化物の総量１００質量部に対して、６〜３５質量部である排ガス浄化用触媒は、比較例１および２で得られた、複合酸化物に対する合金の担持量が、上記の範囲に含まれない排ガス浄化用触媒に比べて、ＨＣ浄化率に優れることが確認された。

From FIG. 1, the exhaust gas purifying catalyst obtained in Examples 1 to 3 is 6 to 35 parts by mass with respect to 100 parts by mass of the total amount of the alloy and the complex oxide. It was confirmed that the amount of the alloy supported on the composite oxide obtained in Comparative Examples 1 and 2 was excellent in the HC purification rate compared to the exhaust gas purification catalyst not included in the above range.

Claims (1)

An alloy composed of nickel and copper, and a composite oxide supporting the alloy,
The exhaust gas purifying catalyst, wherein the amount of the alloy supported on the composite oxide is 6 to 35 parts by mass with respect to 100 parts by mass of the total amount of the alloy and the composite oxide.

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