JP2002233756A - Fuel reforming catalyst manufacturing method and fuel reforming catalyst by the manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel reforming catalyst manufacturing method by which a fuel reforming catalyst can be manufactured so that active metal components for exhibiting a catalytic activity are uniformly distributed therein. SOLUTION: A mixed solution of at least two kinds of metallic compounds is prepared, and an amorphous composite oxide or hydroxide containing at least two kinds of catalytically active components is formed from the mixed solution.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a fuel reforming catalyst. The present invention particularly relates to a method for producing a fuel reforming catalyst for a polymer electrolyte fuel cell, and more particularly to a method for producing a fuel reforming catalyst excellent for use in vehicles.

[0002]

2. Description of the Related Art In a fuel cell, an electromotive force is obtained by a cell reaction of obtaining water from hydrogen and oxygen. The raw material hydrogen is obtained by reacting methanol and water in the presence of a reforming catalyst.
Here, such a fuel reforming catalyst is manufactured by, for example, a method called a coprecipitation method.

In this coprecipitation method, first, an aqueous solution of a precipitant is kept warm, and while stirring, an aqueous solution of a metal salt such as Cu or Zn is dropped to precipitate a precipitate. This operation is a neutralization reaction in which an aqueous solution of a precipitant as an alkaline solution is added to an aqueous solution of a metal as an acid solution. Precipitate, if Cu, are usually in the form of Zn (OH) ₂ hydroxide if Cu (OH) _2, Zn. In the case of a Cu—ZnO catalyst, a catalyst powder is obtained by drying and calcining such a coprecipitate.

[0004] In the neutralization reaction, however, the pH point at which hydroxide is generated differs depending on the ionic species. Therefore, Cu
The hydroxides of (OH) ₂ and Zn (OH) ₂ do not always have a uniform component composition and tend to have a non-uniform composition. For this reason, it is difficult to secure a catalytically active point formed between the Cu particles and the ZnO particles of the Cu—ZnO catalyst obtained after drying and calcining, and there is a disadvantage that the catalytic activity cannot be obtained.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to produce a fuel reforming catalyst so that an active metal component for exhibiting catalytic activity is uniformly present. It is an object of the present invention to provide a method for manufacturing a fuel reforming catalyst that has been made possible.

[0006]

To achieve the above object, the present invention provides a method for producing a fuel reforming catalyst, comprising preparing at least two or more metal compounds in the form of a mixed solution of the metal compounds. And forming an amorphous composite oxide or hydroxide containing at least two or more catalytically active components from the mixed solution. The present invention, in a preferred embodiment thereof, is a method for producing a fuel reforming catalyst,
At least two or more organometallic compounds are prepared in the form of a mixed solution of the organometallic compounds, an organic component is removed from the mixed solution, and an amorphous composite oxide or water containing at least two or more catalytically active components is prepared. Forming an oxide. In the method for producing a fuel reforming catalyst according to the present invention, the method is in the form of a mixed solution of a metal compound. In this mixed solution,
An active metal component for exhibiting catalytic activity is homogenized.
In the case of an inorganic metal compound, nitrate ions and oxychloride ions are removed from the homogenized mixed solution, and in the case of an organic metal compound, organic components are removed to obtain a gel-like substance. This gel-like substance is still an amorphous composite oxide or hydroxide containing the active metal component uniformly. The fuel reforming catalyst obtained by drying and calcining this is
Active metal components are uniformly dispersed, catalyst active sites are secured,
Shows good catalytic activity. As another aspect, the present invention is a fuel reforming catalyst manufactured by the method for manufacturing a fuel reforming catalyst according to the present invention.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a method for producing a fuel reforming catalyst according to the present invention will be described in more detail. In the present invention, first,
At least two or more metal compounds are prepared in the form of a mixed solution of the metal compounds. In the case of an inorganic metal compound, "preparing in the form of a mixed solution of a metal compound" means that, when water is a solvent, a solution of an inorganic metal compound containing each metal which is a catalytically active component is prepared. This means that individual solutions are mixed to prepare a uniform mixed aqueous solution.
In the case of an alcohol solvent, an alcohol complex mixed solution is obtained. In the case of an organometallic compound, "preparing in the form of a mixed solution of a metal compound" means that a solution of an organometallic compound containing each metal which is a catalytically active component is prepared, and such individual solutions are mixed. To be prepared as a mixed solution. Further, in addition to such a case, a mixture of compounds containing respective catalytically active components is prepared, and an organic compound is added to the mixture to prepare a solution of an organometallic compound. That is, in addition to preparing two or more kinds of solutions prepared as organometallic compounds from the beginning to prepare a mixed solution, an organic compound containing two or more kinds of catalytically active components by reacting an organic compound with a mixture of metal compounds. It also includes the case where the compound is prepared in the form of a solution of the compound.

The term “solution” generally refers to a solution in which a solute is dissolved in a solvent. In the present specification, for example, in the case of “form of a solution of a metal compound”, for example, in the case of an organometallic compound, When it exists in a liquid state, it is referred to as a “solution” for convenience.

The metal compounds such as the above-mentioned inorganic metal compounds and organic metal compounds are prepared in the form of a mixed solution, either when preparing individual solutions or when preparing a mixed solution without passing through individual solutions. It must be in a liquid state for handling. By handling in a liquid state,
This is because a uniform mixed state can be obtained. The temperature condition for maintaining the liquid state is not particularly limited. It is enough to adjust the handling temperature. However, it is preferably 50 to 130 ° C, more preferably 70 to 100 ° C.
Metal compounds prepared as liquids at ° C are preferred. Specifically, an alkoxide or complex of a metal having catalytic activity is preferable as the organometallic compound.

Examples of the inorganic metal compound that can be used in the present invention include nitrates such as Ni (NO ₃ ) ₂ (nickel nitrate), Cr (NO ₃ ) ₃ (chromium nitrate), CsNO ₃ (cesium nitrate), and the like. ZrOCl ₂ (zirconium oxychloride), AlOCl (aluminum oxychloride)
And the like. As the organometallic compound, Al (OC ₃ H ₇ ) ₃ (aluminum isopropoxide), Zn (OC ₂ H ₅ ) ₂ (zinc ethoxide), Cu (OCH ₃ ) ₂ (copper methoxide), Ga (O
C ₂ H ₅ ) ₃ (gallium ethoxide), Ge (OC ₂ H ₅ ) ₄
Metal alkoxides such as (germanium ethoxide), L
a [Al (OC ₃ H ₇ ) ₄ ] ₃ , Mg [Al (OC
_{3 H 7) 4] 2,} Ni [Al (OC 3 H 7) 4] bimetallic alkoxides _{2 such, Zn (COCH 2 COCH 3)} ( zinc acetylacetonate) metal acetylacetonates, such as, Cu
(CH ₃ COO) ₂ (copper acetate), Mg (CH ₃ COO)
₂ (magnesium acetate), CH ₃ COOCs (cesium acetate), CuC ₂ O ₄ (copper oxalate), MnC ₂ O ₄ (manganese oxalate), ZnC ₂ O ₄ (zinc oxalate), CaC ₂
Metal carboxylate such as O ₄ (calcium oxalate) can be mentioned.

For example, ethoxy copper and ethoxy zinc are liquids at room temperature. If these are mixed well, a mixed solution of an organometallic compound containing two kinds of metals that can be sufficiently dissolved and become a catalytically active component can be prepared. Also, when copper nitrate and zinc nitrate are mixed and ethylene glycol (dihydric alcohol) is added to these, these metal components are complexed,
It is possible to prepare a mixed solution of an organometallic compound containing two metals that can be a catalytically active component.

In the method for producing a fuel reforming catalyst according to the present invention, an amorphous composite oxide or hydroxide containing at least two or more catalytically active components is formed from the mixed solution. In the case of an inorganic metal compound, the metal complex present in the mixed solution is precipitated and then washed with water to remove the coordinated nitrate ions and oxychlorine, thereby forming a hydroxide, and further via such a hydroxide. The resulting mixture is polycondensed to prepare a hydroxide or an amorphous composite oxide. In the case of an organic compound, an alkoxyl group, an acetic acid group or the like becomes a hydroxyl group by hydrolysis, and undergoes polycondensation, so that an organic component is removed and a hydroxide or an amorphous composite oxide is prepared. Here, the amorphous composite oxide is one in which two or more types of metal elements form one oxide network, and Al-O-Si-
It forms a bond like O-Al-. However, 1
There is also Al-O-Al-O-Si-O- even if it is not one-to-one. A hydroxide is strictly a single molecule like Al (OH) ₃ . However, in this specification, it extends the concept, 2 (OH) as Al-O-Al (OH) 2, but two or more molecules are attached represent those relatively hydroxyl many ( Oxides have hydroxyl groups on the surface, but have a large amount of bonds via oxygen). As described above, the amorphous composite oxide gel is understood as one macromolecule, and the hydroxide gel is regarded as an aggregate of small molecules. To remove organic components,
For example, in the case of a mixed solution of ethoxy copper and ethoxy zinc, a predetermined amount of water (such as distilled water) is added and hydrolysis is performed. As a result, it is separated into a portion of ethyl alcohol and a portion of a gel-like substance. This portion of the gel-like substance forms an amorphous composite oxide or hydroxide in which copper atoms and zinc atoms are uniformly present.

Copper nitrate and zinc nitrate are mixed, ethylene glycol (dihydric alcohol) is added thereto, and a complexed mixed solution is subjected to hydrolysis by adding a predetermined amount of water (such as distilled water). As a result, the ethylene glycol part and the gel substance part are separated. This portion of the gel-like substance forms an amorphous composite oxide or hydroxide in which copper atoms and zinc atoms are uniformly present.

In the method for producing a fuel reforming catalyst according to the present invention, it is preferable that at least one of the catalytically active components of the metal contained in the prepared catalyst is Cu, and the other metal component is Zn ( Zinc), Al, Mg, G
a, Fe, Cr, Ni, Co, V, Mn, Cs, Ce,
Zr and La can be included. At least one of these metal components is contained in addition to Cu. These metal components are contained in the prepared catalyst in the form of a simple metal or a compound such as an oxide.

In preparing the catalyst, as described above, in the case of an organometallic compound, an alkoxide of such a metal element or the like is used as a raw material. Alternatively, nitrates, acetates, sulfates, or chlorides of these metal elements are mixed, and an organic compound such as ethylene glycol is allowed to act thereon to form a complex, thereby obtaining a mixed solution of the organic metal compound. In this case, nitrates are most preferred. When the alkoxide and the complex are well mixed, one of the metal elements is prepared as an alkoxide, the other one of the metal elements is prepared as a complex, and these are combined and mixed to form a mixed solution. it can.

In the method for producing a fuel reforming catalyst according to the present invention, when an inorganic metal compound is used as a raw material as described above, coordinated nitrate ions and oxychlorine are removed. Is prepared by removing an organic component, drying and calcining the obtained gel-like substance to obtain a copper-based fuel reforming catalyst. The obtained copper-based fuel reforming catalyst can be further supported on an appropriate carrier, or formed into a predetermined shape by adding a binder. The fuel reforming catalyst produced according to the present invention is suitable for reforming lower alcohol. Examples of the lower alcohol include methanol, ethanol, propanol and the like.

Next, an embodiment of a PEFC device using a fuel reforming catalyst according to the present invention will be described. FIG. 1 is a block diagram illustrating an outline of an embodiment of a PEFC device to which a fuel reforming catalyst manufactured according to the present invention is suitably applied. This PEFC device 1
It includes a methanol reformer 2, a CO selective oxidizer 3, a fuel cell 4, an evaporator 5, and an exhaust gas combustor 6. These devices function according to the steady state gas flow shown by the bold solid line. The function will be described together with the outline of each device.

Methanol reformer [LTS (low t
is a device for performing methanol reforming by the fuel reforming catalyst according to the present invention, and receives methanol and water, and obtains hydrogen from methanol by the following reaction. I have. CH ₃ OH + H ₂ O → CO ₂ + 3H ₂ (1) CH ₃ OH + ／ O ₂ → CO + H ₂ + H ₂ O (2) CO + H ₂ O → CO ₂ + H ₂ (3) The reaction (1) reforms methanol. This is a reaction for obtaining hydrogen. This reaction (1) is an endothermic reaction. Therefore, heat for maintaining the reforming reaction is obtained by the reaction (2) which is an exothermic reaction. However, in this reaction (2), CO is generated. CO hinders the operation of the fuel cell 4. Therefore, CO is removed by the reaction (3).

The gas from the methanol reformer 2 is added to air and sent to the CO selective oxidizer 3. The CO selective oxidizing device 3 is a device for selectively removing CO by a CO selective oxidizing catalyst.
Is removed. CO + 1 / 2O ₂ → CO ₂ (4) CO generated in the methanol reformer 2 is removed by the reaction (3). However, in the methanol reformer 2, the amount is reduced to 0.3 to 0.4%. In this CO selective oxidation device 3, CO is further removed to 20 ppm or less.

The gas containing hydrogen from the CO selective oxidizer 3 is sent to the fuel cell 4. The fuel cell 4 causes the following reaction at the anode electrode 7 by the anode electrode catalyst. H ₂ → 2H ⁺ + 2e ⁻ (5) H ⁺ generated by this reaction (5) diffuses. on the other hand,
The following reaction is caused in the cathode electrode 8 by the cathode electrode catalyst. 2H ⁺ + 2e ⁻ + ／ O ₂ → H ₂ O (6) These reactions (5) and (6) constitute a battery reaction, and an electromotive force can be obtained.

The off-gas from the fuel cell 4 is sent to an evaporator 5. The evaporator 5 has a function of gasifying water and methanol by using an attached combustor to burn about 20% of hydrogen contained in the off-gas with a combustion catalyst. The gasified water and methanol are sent to the methanol reformer 2 as described above. Further, the exhaust gas combustor 6 completely burns the remaining hydrogen by the combustion catalyst.

Heat exchangers 9, 10 and 11 are provided at the inlet of the fuel cell 4, the fuel cell 4 and the exhaust gas combustor 6, and cooling water is circulated from a cooling water source 12 by a circulation pump 13. The cooling water flows in the circulation line 14 (dotted line), and the temperature in the line 14 is detected by a temperature sensor (not shown). The temperature information from the temperature sensor is sent to the control system, and the temperature in the CO selective oxidizing device 3 and the fuel cell 4 is appropriately maintained by appropriately controlling the flow rate.

Further, the PEFC device 1 has an activation system. First, water and methanol are heated and evaporated by the electric heater 20 in advance, and are sent to the burner 21. Add air here to burn some of the methanol,
Raise the temperature to 250 ° C. Air is further added to the heated gas and sent to the methanol reformer 2. In the methanol reformer 2, the above-described reaction occurs. Then, the CO selective oxidation device 3 selectively oxidizes and removes CO as described above. The CO selective oxidizer 3 cannot sufficiently reduce the CO concentration unless the temperature becomes 100 ° C. or higher. The operation is performed on the starting route until the temperature in the CO selective oxidation device 3 becomes 100 ° C. or higher.
When the operation is switched to the steady operation, the use of the burner 21 and the like is stopped. The gas from the CO selective oxidizer 3 is sent to the fuel cell 4 to be in a state of obtaining electricity.

When the fuel reforming catalyst produced according to the present invention is used in the above-mentioned PEFC device, even if the PEFC device is mounted on a vehicle, good fuel reforming can be achieved even when the PEFC device is mounted on a vehicle because the metal as a catalytically active component is uniformly distributed. Characteristics can be exhibited, and stable running performance can be maintained especially when the vehicle is mounted on a vehicle.

[0025]

Examples Examples and comparative examples are given below to illustrate the present invention.
The method for producing the fuel reforming catalyst will be described in more detail.Example 1 [Cu-Zn catalyst] Copper nitrate (Cu (NO_Three)_Two・ 3H_TwoO) 36.3 g and nitrate
Zinc acid (Zn (NO_Three) _Two・ 6H_TwoO) Etch into 22.3g
Add 150 g of len glycol and stir at 120 ° C for 3 hours
did. Drop the liquid temperature to 80 ° C,^ThreeDistillation
When water is added, a gel-like substance in which Cu and Zn are mixed is produced.
Done. This was dried at 150 ° C. overnight, and then dried in an electric furnace for 3 hours.
It was calcined at 00 ° C. for 3 hours to obtain a Cu—ZnO catalyst. this
The atomic ratio between Cu and Zn at that time is 100: 50.

[0026]Example 2 [Cu-Zn-Al catalyst] Copper nitrate (Cu (NO_Three)_Two・ 3H_TwoO) 36.3 g and nitrate
Zinc acid (Zn (NO_Three) _Two・ 6H_TwoO) Etch into 22.3g
Add 150 g of len glycol and stir at 120 ° C for 3 hours
did. To this solution was added aluminum isopropoxide (Al
(OC_ThreeH₇)_Three) 1.5 g and then 120 ° C
For 2 hours to dissolve. Drop the liquid temperature to 90 ° C,
Distilled water 85cm^ThreeIs added with stirring to obtain Cu, Z
A gel-like substance in which n and Al were mixed was formed. At 150 ° C
After drying overnight, bake at 300 ° C for 3 hours in an electric furnace
CuO-ZnO-Al_TwoO_ThreeA catalyst was obtained. C at this time
The atomic ratio of u, Zn, and Al is 100: 50: 5.

[0027]Example 3 [Cu-Zn-Al-Mg catalyst] Copper nitrate (Cu (NO_Three)_Two・ 3H_TwoO) 36.3 g and nitrate
Zinc acid (Zn (NO_Three) _Two・ 6H_TwoO) Etch into 22.3g
Add 150 g of len glycol and stir at 120 ° C for 3 hours
did. To this solution was added aluminum isopropoxide (Al
(OC_ThreeH₇)_Three) 1.5 g, magnesium ethoxide
(Mg (OC_TwoH_Five)_Two) Add 0.085g and continue
The mixture was dissolved by stirring at 120 ° C. for 2 hours. Liquid temperature at 90 ° C
Drop, distilled water 85cm^ThreeWhile stirring, C
A gel-like substance in which u, Zn, Al and Mg are mixed
Was. After drying at 150 ° C overnight, in an electric furnace at 300 ° C
3 hours firing and CuO-ZnO-Al_TwoO_Three-MgO catalyst
I got At this time, the atomic ratio of Cu, Zn, Al, and Mg is
100: 50: 5: 5.

Comparative Example [Powder mixing method: Cu-Zn catalyst] Basic copper carbonate (CuCO ₃ .Cu (OH) .H ₂ O) 7.
17 g and basic zinc carbonate (2ZnCO ₃ .3Zn (O
H) takes ₂ · H ₂ O) 3.4g, dried small amount of cyclohexane and accompanied to the powder were mixed in a mortar, an electric furnace 300
Calcination was performed at 3 ° C. for 3 hours to obtain a CuO—ZnO catalyst. At this time, the atomic ratio of Cu and Zn is 100: 50.

Each of the catalysts obtained in Examples 1 to 3 and Comparative Example 1 was compression-molded, and then crushed to a size of 2 to 4 mm using 2.2 cc of nitrogen gas containing 1% of hydrogen. After reducing the catalyst at a temperature of 150 ° C., S /
A / C (molar ratio of air / methanol) = 0.0 together with a raw material having C (water / methanol molar ratio) = 2.2.
GHSV = 5000
Under a condition of h ^-1 and a reaction pressure of 2 kg / cm ² G, the mixture was passed through the catalyst layer to cause a steam reforming reaction of methanol and a partial oxidation reaction to occur simultaneously. Table 1 shows the catalytic activity at 240 ° C. of each of the obtained catalysts. At this time, the catalytic activity was the conversion rate of methanol, 1- [CH ₃ OH] / ([CO ₂ ] + [CO] +
[CH ₃ OH]).

[0030]

[Table 1] Thus, it was found that the methanol conversion rate was higher than that of the comparative catalyst.

[0031]

As is apparent from the above description, according to the method for producing a fuel reforming catalyst according to the present invention, a fuel in which an active metal component (catalytic active component) for exhibiting catalytic activity is uniformly present. A reforming catalyst can be obtained, and such a fuel reforming catalyst satisfactorily reforms methanol and the like.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an embodiment of a PEFC device using a fuel reforming catalyst obtained by a fuel reforming catalyst according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 PEFC apparatus 2 Methanol reformer 3 CO selective oxidation apparatus 4 Fuel cell 5 Evaporator 6 Exhaust gas combustor 7 Anode electrode 8 Cathode electrode 9, 10, 11 Heat exchanger 12 Cooling water source 13 Circulation pump 14 Circulation line 20 Electric heater 21 Burner

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Toshinobu Yasutake 4-2-2 Kannon Shinmachi, Nishi-ku, Hiroshima City, Hiroshima Prefecture Mitsubishi Heavy Industries, Ltd. Hiroshima Research Laboratory F-term (reference) 4G040 EA02 EA06 EC01 EC02 EC04 EC05 4G069 AA02 AA08 BB06A BB06B BC06A BC10A BC10B BC16A BC16B BC17A BC31A BC35A BC35B BC42A BC43A BC51A BC54A BC58A BC62A BC66A BC67A BC68A CC17 CC25 CC32 FA01 FB09 4G140 EA02 EA06 EC01 EC02 EC04 EC05 5H027 AA06 BA01

Claims (4)

[Claims] At least two or more metal compounds are prepared in the form of a mixed solution of the metal compounds, and an amorphous composite oxide or hydroxide containing at least two or more catalytically active components is prepared from the mixed solution. A method for producing a fuel reforming catalyst comprising forming. 2. An at least two or more organometallic compounds are prepared in the form of a mixed solution of the organometallic compounds, an organic component is removed from the mixed solution, and an amorphous material containing at least two or more catalytically active components is prepared. A method for producing a fuel reforming catalyst, comprising forming a composite oxide or hydroxide. 3. The method for producing a fuel reforming catalyst according to claim 1, wherein at least one of the catalytically active components of the metal contained in the prepared catalyst is Cu, and the other catalytically active component is Z.
n, Al, Mg, Ga, Fe, Cr, Ni, Co, V,
A method for producing a fuel reforming catalyst, comprising at least one catalytically active component selected from the group consisting of Mn, Cs, Ce, Zr, and La. 4. A fuel reforming catalyst produced by the method for producing a fuel reforming catalyst according to claim 1.