JP2001185195A - Producing method of hydrogen for fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a producing method of hydrogen for a fuel cell, in which the temperature of a catalyst in made uniform is a methanol reforming reactor vessel of self heat supply type a long and stable use of a catalyst is possible, and a reformed gas mainly composed of hydrogen is produced efficiently. SOLUTION: In production of the reformed gas mainly composed of hydrogen by letting water vapor and air react with methanol under the existence of the catalyst, the catalyst having copper-zinc as the main components is carried on a metal or alloy carrier whose heat conductivity at 300 K is 20 W/m.K or more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an improvement in a method for producing hydrogen for a fuel cell. More specifically, the present invention provides
The present invention relates to a method for producing hydrogen for a fuel cell, in which a catalyst temperature is made uniform by a self-heating supply type methanol reforming reactor and a reformed gas mainly composed of hydrogen is efficiently generated.

[0002]

2. Description of the Related Art In recent years, attention has been paid to hydrogen as an energy source replacing fossil fuels. Hydrogen can only produce water when burned, and does not emit carbon dioxide or harmful nitrogen oxides that cause global warming. Therefore, hydrogen is expected as clean energy in the future. It is well known that methanol is relatively easily reformed into a gas mainly composed of hydrogen in the presence of a catalyst. In particular, by reacting methanol with water vapor, the gas is reformed into a gas containing almost no carbon monoxide, which is difficult to separate, and thus attracts attention as a simple supply source of hydrogen which is expected to increase in the future.

On the other hand, as a power generation system that suppresses emission of carbon dioxide, which is a main cause of global warming, and does not emit nitrogen oxides that cause air pollution, research and development of fuel cells is currently being actively conducted. This fuel cell converts chemical energy into electric energy by electrochemically reacting hydrogen and oxygen. It has high energy utilization efficiency, and has a phosphoric acid type and a molten type depending on the type of electrolyte. There are types such as carbonate type, solid oxide type and solid polymer type. As a fuel, it is common to use a hydrocarbon-based substance such as natural gas or methanol and reform it in an apparatus to produce hydrogen.

[0004] Such a fuel cell is attracting attention as an environmentally friendly technology. For example, it can be used as a power source for vehicles such as automobiles and ships, as well as for private power generation in factories, buildings, apartment houses, etc., and uninterruptible power supplies in hospitals handling medical equipment. It is expected to be used as a power source. In particular, in the automotive field, the development of methanol reformed fuel cell vehicles has been actively pursued. Since a fuel cell mounted on an automobile is required to have a small and simple structure, air is introduced into the reactor to supply reaction heat necessary for steam reforming of methanol by combustion heat. Development of a self-heating supply reactor is underway.

[0005] In this self-heat supply type reactor, the steam reforming reaction of methanol and the combustion reaction of methanol occur simultaneously, and the heat of reaction in the steam reforming reaction is promptly replenished by the combustion reaction of methanol. Is required. In order to satisfy such demands, for example, JP-A-6-31165 discloses that a catalyst component is contained on the surface of a core made of metal or ceramic in order to fix a catalyst in a package type reactor and enhance heat transfer. There is disclosed a thin film catalyst for steam reforming having a layer formed thereon. However, in a self-heat supply type reactor in which a steam reforming reaction and a combustion reaction of methanol occur simultaneously, the reaction rate of the combustion reaction is faster than that of the steam reforming reaction. Therefore, the inlet of the reactor particularly at a high SV (space velocity). It is difficult to obtain a uniform temperature distribution because the internal temperature rises sharply in the part. For the methanol reforming reaction, a copper-zinc catalyst or the like is often used, but when the temperature rises, the activity is apt to sharply decrease, making it difficult to use the catalyst for a long period of time.

[0006]

SUMMARY OF THE INVENTION In the present invention, when producing hydrogen for a fuel cell under such circumstances, the catalyst temperature is made uniform in a self-heating supply type methanol reforming reactor.
It is an object of the present invention to provide a method for producing hydrogen for a fuel cell, in which a catalyst can be used stably for a long period of time, and a reformed gas mainly composed of hydrogen is efficiently generated.

[0007]

Means for Solving the Problems The present inventors have conducted intensive studies to achieve the above object, and as a result, the temperature distribution of the catalyst layer has been reduced by supporting the catalyst component on a support having high thermal conductivity. It has been found that the catalyst has been improved and the catalyst can be used stably for a long period of time. The present invention has been completed based on such findings. That is, in the present invention, in producing a reformed gas mainly composed of hydrogen by reacting steam and air with methanol in the presence of a catalyst, a catalyst component containing copper-zinc as a main component at 300K is used as the above-mentioned catalyst. An object of the present invention is to provide a method for producing hydrogen for a fuel cell, comprising using a metal or an alloy having a thermal conductivity of 20 W / m · K or more supported on a support.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The method for producing hydrogen for a fuel cell according to the present invention is a method for producing a reformed gas mainly comprising hydrogen by reacting methanol with steam and air. A catalyst component having copper-zinc as a main component and having a thermal conductivity at 300 K of 20 W / m · K or more supported on a metal or alloy support is used. The metal is preferably at least one selected from Cu, Ag, Au and Al, and the alloy is preferably brass, aluminum bronze, phosphor bronze, white copper, gunmetal, or the like.

The method for producing the catalyst component containing copper-zinc as a main component is not particularly limited. In order to improve the catalytic activity and the strength, etc., a composition containing a compound such as aluminum, boron, and silicon can be used. Further, if necessary, Mg, Zr, La, Mn, Cr, Pd, Pt, A compound such as P may be added.

[0010] As a method of preparing these compositions, a slurry of copper and zinc is prepared from an aqueous solution containing copper and zinc.
For example, there are a method of precipitating with an alkali carbonate precipitating agent, a method of adding a zinc oxide slurry to a copper precipitation slurry, and converting the slurry to a carbonate with carbon dioxide gas. When an aluminum compound is added, it can be prepared from an aqueous solution containing aluminum with alkali hydroxide or alkali carbonate. The method of mixing the copper and zinc slurry and the alumina precursor is preferably carried out in a slurry state in order to uniformly mix both. Further, boron or a silicon compound can be added to a copper source, a zinc source, an aluminum source, or the like, and the silicon compound may be added in a kneading step described later, and can be appropriately selected.

The composition of the methanol reforming catalyst is copper:
The atomic ratio of zinc is 0.2 to 12: 1, preferably 0.3 to
7: 1. When the methanol reforming catalyst is made of copper, zinc and aluminum, the content of each atomic standard component is 35 to 80% by weight of copper, 15 to 50% by weight of zinc,
Preferably it is 20 to 40% by weight, aluminum is 1 to 20% by weight, preferably 4 to 16% by weight. When the methanol reforming catalyst is composed of copper, zinc, aluminum and boron, the content of each atomic standard component is copper 30 to 8
0% by weight, preferably 40-70% by weight, zinc 15-5%
0 wt%, preferably 20-40 wt%, aluminum 1-20 wt%, preferably 4-16 wt%, boron 0.3-5 wt%, preferably 0.5-3 wt%. When the methanol reforming catalyst is made of copper, zinc, aluminum, boron and silicon, the content of each atomic standard component is 35 to 80% by weight of copper, preferably 40 to 80% by weight.
70% by weight, 15 to 50% by weight of zinc, preferably 20 to
40% by weight, aluminum 1 to 20% by weight, preferably 4 to 16% by weight, boron 0.3 to 5% by weight, preferably 0.5 to 3% by weight, silicon 0.1 to 3.5% by weight, preferably Is 0.5 to 3% by weight.

As a copper source for the methanol reforming catalyst, water-soluble salts such as copper nitrate, copper sulfate, and copper acetate can be used. In particular, inexpensive copper sulfate is advantageous. As the zinc source, water-soluble salts such as zinc nitrate, zinc sulfate, and zinc acetate, and inexpensive zinc oxide can be used. As the aluminum source, water-soluble salts such as aluminum nitrate, aluminum sulfate, and aluminum acetate can be used. Boric acid, borax and the like can be used as the boron source. As the silicon source, an oxide or a silicon oxide precursor can be used, and particularly, a sodium silicate double-decomposed product or diatomaceous earth is advantageous. Further, if necessary, Mg, Zr, La, Mn, Cr, Pt, P
Precursors of oxides such as d and P, such as carbonates and oxyacid salts of phosphorus, can be added.

As a precipitant used for the aqueous metal salt solution of each of the above-mentioned components, an alkali metal or ammonium carbonate is used, and a combination of alkali hydroxide and carbon dioxide can also be used. The amount of these precipitants used is 1 to 2 times, preferably 1.1 to 1.6 times the equivalent amount to the metal salt. The temperature during preparation of the precipitate is 20 to 90 ° C, preferably 3 to 90 ° C.
5 to 80 ° C. At this time, the concentration of the water-soluble metal salt or the precipitant is 0.2 to 3 mol / L, preferably 0.5 to 3 mol / L.
A range of 2 mol / l is preferred. As a method of mixing the copper and zinc precipitation slurry with the alumina precursor, a method of precipitating copper and zinc in the presence of the alumina precursor, a method of simultaneously precipitating using a three-component aqueous solution of a copper, zinc, and aluminum source, and the like There is.

The shape of the support for supporting the catalyst component is not particularly limited, and may be any of a honeycomb shape, a foil shape, a sheet shape, a fiber shape, a cloth shape and the like. The amount of the catalyst component to be carried is not particularly limited, but generally 1 to 30% by weight of the catalyst component,
It is a ratio of 0 to 99% by weight.

The following method can be used as a method for supporting the catalyst component. (1) Vacuum evaporation method: The catalyst component is heated to a high temperature and evaporated in a high vacuum, and the vapor is collided with a support, cooled and solidified. (2) Sputtering method: The surface of the solid catalyst component is irradiated with an ion beam having a kinetic energy of several tens eV or more to form a film. (3) Chemical method: a catalyst component is supplied to a support, and a desired catalyst component layer is formed by a chemical reaction. (4) dip coating method: dipping a support in a solution of a carrier component,
The process of blowing off the excess and drying is repeated to make the amount of the catalyst component carried after drying a predetermined amount.

In the present invention, a reformed gas containing hydrogen as a main component is produced by reacting methanol with steam and air in a self-heat supply type reactor using a catalyst supported on a support by the above method. The reaction conditions for reacting methanol with water vapor and air are as follows: the molar ratio of water vapor to methanol is usually 1 to 10 mol, preferably 1 to 5 mol, and the molar ratio of air to methanol is usually 0.3 to 10 mol.
5.0 mol, preferably 0.5 to 3.0 mol. The reaction temperature is usually 150 to 600 ° C, preferably 200 to 600 ° C.
At 500 ° C., the reaction pressure is from normal pressure to 0.5 MPa.
The liquid hourly space velocity (LHSV) per unit catalyst volume is 0.1 to 50 h ^-1 , preferably 0.5 to 0.5 in methanol LHSV.
４０40 h ⁻¹ .

[0017]

Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. In the following Examples and Comparative Examples, the catalyst performance was evaluated based on the methanol conversion from the gas composition at the outlet of the reactor according to the following equation. Methanol conversion (%) = ([CO] + [CO ₂ ]) / ([CO] + [CO ₂ ] +
[CH ₃ OH]) × 100

Production Example 1 177 g of sodium carbonate (anhydrous) was put into a 5 liter round bottom flask together with 1000 ml of ion-exchanged water and dissolved at 40 ° C. Here, copper sulfate (pentahydrate) 31
5 g and 19.7 g of boric acid were dissolved in 800 ml of ion-exchanged water, a solution adjusted to 40 ° C. was poured, and a slurry in which 77.0 g of zinc oxide was dispersed in 300 ml of ion-exchanged water was added. Carbon was blown in at a rate of 6 l / h. After 1 hour, the temperature was raised to 80 ° C. and maintained for 30 minutes. The blowing of carbon dioxide was stopped in 2 hours. Next, after cooling to 60 ° C., a solution of 51.4 g of aluminum sulfate dissolved in 150 ml of ion-exchanged water and 21.9 g of sodium hydroxide were added thereto.
g was dissolved in 160 ml of ion-exchanged water, and the resulting mixture was stirred for 20 minutes. The mixed slurry thus prepared was filtered, and 0.05 mol%
Was washed with 12 liters of aqueous sodium hydroxide solution and 3 liters of ion-exchanged water. Subsequently, it was dried at 80 ° C., and then calcined at 360 ° C. for 2 hours to obtain a Cu—Zn—Al catalyst. The method of supporting the obtained Cu-Zn-Al catalyst on the honeycomb is Cu-Zn
The n-Al catalyst is wet-pulverized, mixed with an alumina sol to form a slurry, and then immersed in a honeycomb of 400 cells / square inch, blown off an excessive amount, and dried to repeat the process. I made it.

Example 1 According to the method described in Production Example 1, the diameter was 1 inch and the height was 20 mm.
Cu-Z on Cu honeycomb (volume: 10.13 ml)
0.2 g of n-Al catalyst was supported. 180 before activity evaluation
Reduction treatment was performed at ℃. The thermal conductivity of Cu is 39
8 W / m · K. A methanol aqueous solution having a water / methanol ratio of 2.0 was introduced into the evaporator, and air was mixed at the outlet of the evaporator to form a mixed gas at 200 ° C., and the temperature of the introduction line was adjusted so as to enter the catalyst layer. In the methanol reforming reaction, the methanol LHSV was controlled at 10 h ^{-1 and} the amount of air was controlled so that the initial inlet temperature of the catalyst layer became a predetermined temperature, and the reaction was continued for 50 hours. The gas composition after the reaction was analyzed by gas chromatography and evaluated by the reaction rate of methanol. FIG. 1 shows the change in the methanol conversion rate with the reaction time.
FIG. 2 shows the change in the catalyst layer temperature difference.

Example 2 According to the method described in Production Example 1, the diameter was 1 inch and the height was 20 mm.
Al-honeycomb (volume 10.13 ml) with Cu-Z
The reaction was carried out under the same conditions as in Example 1 while supporting 200 g / l of the n-Al catalyst. FIG. 1 shows a change in the methanol reaction rate depending on the reaction time, and FIG. 2 shows a change in the catalyst layer temperature difference.
The thermal conductivity of Al is 237 W / m · K.

Comparative Example 1 According to the method described in Production Example 1, the diameter was 1 inch and the height was 20 mm.
A 200 g / L Cu-Zn-Al catalyst was supported on a cordierite honeycomb (volume: 10.13 ml), and the reaction was carried out under the same conditions as in Example 1. FIG. 1 shows a change in the methanol reaction rate depending on the reaction time, and FIG. 2 shows a change in the catalyst layer temperature difference. The thermal conductivity of cordierite is about 1 W /
m · K.

Comparative Example 2 According to the method described in Production Example 1, the diameter was 1 inch and the height was 20 mm.
The Cu-Zn-Al catalyst was supported at 200 g / liter on a stainless steel honeycomb (volume: 10.13 ml), and the reaction was carried out under the same conditions as in Example 1. FIG. 1 shows the change in the methanol reaction rate depending on the reaction time, and FIG. 2 shows the change in the catalyst layer temperature difference.
Shown in The thermal conductivity of stainless steel is 16 W / m · K
It is.

[0023]

According to the method of the present invention, the catalyst temperature is made uniform in the self-heating supply type methanol reforming reactor, the catalyst can be used stably for a long time, and the reformed gas mainly composed of hydrogen can be efficiently used. Hydrogen for a fuel cell can be produced industrially and advantageously. Further, as is apparent from the drawings of the examples, the thermal conductivity at 300K is 20 W according to the present invention.
In the case of using a catalyst supported on a support of not less than / m · K, the temperature difference of the catalyst layer is reduced, and the methanol conversion is significantly improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a change in a methanol reaction rate depending on a reaction time in Examples and Comparative Examples of the present invention.

FIG. 2 is a graph showing a change in a catalyst layer temperature difference depending on a reaction time in Examples and Comparative Examples of the present invention.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Mitsuyoshi Takamura 182 Niigata, Niigata City, Niigata Prefecture Niigata Research Laboratory Mitsubishi Gas Chemical Co., Ltd. (72) Inventor Masayuki Katagiri 182 Niigata, Niigata City, Niigata Address: Niigata Research Laboratory, Mitsubishi Gas Chemical Co., Ltd. (72) Mikio Yoneoka, 182, Niigata, Niigata City, Niigata Prefecture Niigata Research Laboratories: Niigata Research Laboratory, Mitsubishi Gas Chemical Co., Ltd. No. 1 Inside Honda R & D Co., Ltd. (72) Inventor Takahiro Naka 1-4-1 Chuo, Wako-shi, Saitama Pref. Inside Honda R & D Co., Ltd. (72) Hideaki Sumi 1-4-4 Chuo, Wako-City, Saitama Pref. No. 1 Inside Honda R & D Co., Ltd. (72) Inventor Masataka Koyama 1-4-1 Chuo, Wako-shi, Saitama The internal F-term (reference) 4G040 EA02 EA06 EA07 EC03 EC07 4G069 AA03 BB02A BC16A BC16B BC31A BC31B BC32A BC32B BC33A BC33B BC35A BC35B CC25 CC32 EC30 5H027 AA02 BA01

Claims (2)

[Claims] In producing a reformed gas mainly composed of hydrogen by reacting water vapor and air with methanol in the presence of a catalyst, a catalyst component mainly composed of copper-zinc is used as a catalyst at 300K. A method for producing hydrogen for a fuel cell, comprising using a metal or an alloy having a conductivity of 20 W / m · K or more supported on a support. 2. The method according to claim 1, wherein the support comprises Cu, Ag, Au and A.
2. The method for producing hydrogen for a fuel cell according to claim 1, wherein the method is at least one metal or alloy selected from the group consisting of: