JP2002028490A - Water vapor reforming catalyst and producing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water vapor reforming catalyst which is miniaturized, light in weight, enables obtaining effective catalytic area of a large surface area, moreover, does not cause pressure loss, enable to obtain high performance catalytic activity and is suitable for an on-vehicle fuel cell and a producing method thereof. SOLUTION: This water vapor reforming catalyst is constituted in such a manner that a catalytic substance 2 consisting of ruthenium or ruthenium alloy is deposited on a planar catalyst carrier 1 comprising a metallic foam. Therein, the catalytic substance 2 is deposited on the catalyst carrier 1 by subjecting the catalytic substance 2 to the ion displacement from an acid solution.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steam reforming catalyst for obtaining a hydrogen-containing gas by reacting methanol or methane with steam, and more particularly to a fuel reformer (reactor) for a fuel cell for a vehicle. The present invention relates to a steam reforming catalyst which is effective for a hydrogen production process incorporated in the above) and a production method thereof.

[0002]

2. Description of the Related Art Pure hydrogen is used as a fuel for a low-temperature fuel cell, particularly a solid polymer electrolyte fuel cell, which has recently attracted the most attention. At present, attempts have been made to operate a fuel cell by receiving hydrogen gas from a hydrogen cylinder or hydrogen gas from a hydrogen storage metal that has stored hydrogen as fuel for a vehicle-mounted fuel cell. By the way, it is necessary to periodically replenish (supply) such a hydrogen cylinder or hydrogen storage metal with hydrogen gas, and therefore, it is necessary to install a hydrogen supply base (hydrogen stand). Therefore, it is considered that a considerable amount of time will be required in order to put these into practical use.

Another alternative is to mount a fuel reformer for a fuel cell on an automobile, load methanol as fuel, react the methanol with water vapor, extract hydrogen, and supply it to the fuel cell. Attempts have been made. By the way, a non-precious metal such as chromium has been conventionally used as a reforming catalyst used in a fuel reformer.
This non-precious metal has a high reforming temperature of 700 ° C or higher,
It has been pointed out that the reforming apparatus becomes large and the energy efficiency in the reforming becomes poor. It is said that it is necessary to control the concentration of carbon monoxide in hydrogen gas, which is the most problematic for reformed hydrogen, to about 1 ppm or less, especially for hydrogen used in fuel cells, and is attached to a reformer (also called a reactor). However, there is a problem that the reforming apparatus becomes large, and that extra energy is required for the salt.

[0004] In order to solve such problems, ruthenium metal, which is one of platinum group metals, has recently been used as a reforming catalyst. This makes it possible to lower the reforming temperature to 400 ° C. or less when the hydrogen source is methanol. It is also stated that the concentration of carbon monoxide can be lowered from the Budoar equilibrium reaction.

[0005]

Therefore, the use of ruthenium catalysts has recently attracted attention. However, in order to manufacture a compact and efficient reformer for a vehicle fuel cell, the use of a catalyst is inevitable. A small and highly active one is required.

[0006] As the ruthenium catalyst which has been attracting attention as described above, a pellet-shaped catalyst in which ruthenium metal is supported on the surface of alumina pellets is mainly used in the past. Become. In addition, there is a problem that the weight becomes large. Therefore, as a method of increasing the effective catalyst area by reducing the size and weight, there is a method of reducing the particle size of the above-mentioned alumina pellets and increasing the catalyst area per volume using a hollow alumina carrier such as foamed alumina. In this case, the pressure loss increases, the size of the pumping device such as a blower that feeds a mixed gas of methanol and water vapor increases, the stable operation becomes difficult, and the gas flow increases due to the large pressure loss. And the problem of removal of unreacted substances occurs. Therefore, usually the average particle size of the pellets 2
The limit is about 5 mm, which not only makes it impossible to use fine particles, but also increases the apparent volume of the catalyst.

In order to solve such a problem, it is conceivable to use a metal escaping mesh and carry ruthenium metal on its surface. However, this expanding mesh has a relatively small surface area. In terms of weight, since the carrier itself is pure, there is a problem in terms of weight that the weight per area is inevitably increased.

In view of such circumstances, the present invention has been accomplished by conducting many experiments over many years, and the object of the present invention is to provide a small and light-weight, large surface area effective catalyst area. Another object of the present invention is to provide a steam reforming catalyst suitable for an in-vehicle fuel cell and a method for producing the same, which can obtain a high-performance catalytic activity without pressure loss.

[0009]

In order to achieve the object, the present invention provides a steam reforming method in which a plate-like porous metal body serving as a catalyst carrier carries a catalytic substance comprising ruthenium or an alloy containing ruthenium. It is a catalyst.

Further, in the present invention, a steam reforming catalyst is provided in which a plate-like porous metal serving as a catalyst carrier carries a catalyst material comprising ruthenium or a ruthenium-containing alloy by performing ion replacement from an acid solution. It is a manufacturing method.

In the present invention, the metal porous body is a metal foam or a sintered metal short fiber. Here, when the porous metal body is made of a metal foam, the catalyst material is formed of a continuous pore group that is scattered (exists) in the thickness direction of the foam in a continuous manner. It is uniformly supported on the entire foam. In the present invention, the material of the porous metal body is iron, nickel or an alloy thereof.
Further, in the present invention, the alloy containing ruthenium is R
u: Pt = 90: 10 (mol).

[0012]

Embodiments of the present invention will be described. FIG. 1 shows an example of an embodiment of the steam reforming catalyst A of the present invention, and a metal foam is desirable as the plate-shaped porous metal body serving as the catalyst carrier 1. The apparent surface area of this metal foam is 50 to 100 times that of the projection surface, and the expanded mesh is almost twice as large, which is extremely large. Moreover, the weight of the expanded mesh made from a plate having the same thickness is 1/2 that of the expanded mesh, whereas that of the metal foam is about 1/10, which indicates that the weight is extremely light. Incidentally, the metal foam is manufactured by using a urethane foam or the like as a core material, forming a metal layer on the foam surface by electroplating, and then removing the urethane foam as a core material by firing. Therefore, the metal foam used as the catalyst carrier 1 in the present invention is extremely lightweight, and the shape and thickness can be freely selected by arbitrarily adjusting the shape and thickness of the urethane foam as the core material. Has advantages. In addition, the cross-sectional structure has a plate-like structure having continuous pores scattered (existing) in the thickness direction thereof and branch portions connecting the pores three-dimensionally. can get. In addition, the resistance to gas permeation through a foam having such a large surface area is as low as that of an ordinary knitted mesh.

As the catalytic substance 2 supported on the catalyst carrier 1, platinum group metals are particularly excellent, and among them, ruthenium is stable and has excellent reducing ability. The catalyst substance 2 may be ruthenium alone or a ruthenium alloy obtained by adding other platinum group metals such as platinum and palladium to ruthenium.

When these ruthenium or ruthenium alloys are supported on a metal foam, the metal foam is three-dimensional, so that it can be easily and firmly supported by utilizing the ionization tendency. That is, when ruthenium has a very small ionization tendency and the metal foam is immersed in an acidic aqueous solution containing ruthenium metal, the metal is eluted and the ruthenium metal is easily attached to the surface of the metal foam by a substitution reaction. Here, when an acidic solution is used, the metal is eluted on the surface of the metal foam by the acidic solution, and a small amount of hydrogen is generated, which works effectively by the reduction of the ruthenium metal to deposit more firm ruthenium metal. Because it is.

For example, when a nickel foam is used as a catalyst carrier 1 and immersed in a 10% hydrochloric acid solution of ruthenic chloride, a part of nickel is eluted and black ruthenium metal is deposited on the surface by a substitution reaction. This substitution reaction continues until the ruthenium metal contained in the liquid is almost completely eliminated. At this time, the color of the hydrochloric acid solution changes from brown of ruthenic chloride to pale green of nickel. The substitution reaction ends when ruthenium in the liquid has almost completely disappeared.However, even if the reactants disappear, nickel elution may occur and hydrogen may be generated. good. Further, the substitution reaction time for supporting the ruthenium metal on the catalyst carrier 1 is not particularly limited, but may be about 10 minutes, depending on, for example, the amount (thickness) of the supported ruthenium metal. The temperature may be room temperature. At this time,
The reaction rate can be increased by heating.

On the surface of the catalyst carrier 1 manufactured by the above-described method, a so-called ruthenium metal in a so-called ruthenium black state having a large surface area peculiar to the ruthenium metal and having high activity is deposited.
Typically, a metal foam as a catalyst carrier 1 is immersed in a 5 to 10% aqueous solution of ruthenic chloride in hydrochloric acid at room temperature.

In the case where the catalyst is an alloy, the ionization tendency of ruthenium metal (platinum group metal) is almost the same, and is significantly different from that of nickel or iron. Is obtained.
Thereby, an effective catalyst can be manufactured.

[0018] In addition, when the substance that obtains hydrogen by the steam reforming reaction is methanol, the reforming temperature is about 400 ° C, in the case of methane, it is about 700 ° C, and in the case of gasoline, the temperature is higher. The catalyst itself is stable. At this time, the catalyst support 1 made of a metal foam may become unstable, and it is important to change the specifications of the metal foam according to the operating temperature. That is, the finest in methanol,
In addition, a metal foam having a large surface area can be used. However, in the case of methane, in other cases, a foam structure considering heat resistance, for example, a wall thickness forming the foam (intermittently scattered in the thickness direction of the foam (internal ), It is necessary to increase the thickness (diameter) of the branch connecting the continuous pore group three-dimensionally.

Next, the present invention will be described in more detail with reference to Examples 1 to 3, but the present invention is not limited to these.

Example 1 A nickel foam having an apparent thickness of 5 mm is used as the catalyst carrier 1. As the nickel foam, commercially available product name: Celmet manufactured by Sumitomo Electric Industries, Ltd., or product name: Retec manufactured by Eltec Systems Co., Ltd. may be used. However, as necessary, urethane foam or the like may be used as described above. To manufacture. Ruthenium was supported as the catalyst substance 2 on this nickel foam. That is, ruthenic chloride (H ₂ Ru)
A 10% hydrochloric acid aqueous solution of Cl ₆ ) is prepared, and the nickel foam is cleaned and degreased with a neutral detergent. Then, the surface is activated by immersion in a 10% hydrochloric acid solution at 60 ° C. After this is further sufficiently washed by deionization, it is immersed in a ruthenic chloride solution at room temperature. As a result, no reaction was observed for the first 3 minutes, but the surface of the nickel foam was blackened and the color of the solution became lighter and changed to pale green. At this point, hydrogen generation occurred suddenly.
Then, it was confirmed that the entire foam, such as the pore surfaces of the continuous pore groups scattered (existing) in the thickness direction of the foam and the branches connecting the pore groups three-dimensionally, was covered with the black coating. (See the enlarged view of FIG. 1).

Then, the obtained steam reforming catalyst A of the present invention (hereinafter referred to as the present product) was dissolved and analyzed.
70 g / m ² of ruthenium was deposited on the projection surface.
It was also found that the ruthenium recovery at this time was 93 to 95%. Further, a reforming reaction test of methanol at a temperature of 400 ° C. as a catalyst was performed. At this time, 10 g of this product,
100 g of a conventional steam reforming catalyst in which ruthenium was supported on alumina particles (hereinafter referred to as a comparative product) was put into each reactor, and a reforming reaction test was performed through a mixed gas of steam and methanol, respectively. Pressure loss in the comparison product
Although the pressure was 0.5 atm, little pressure loss was observed with this product. This proved that the product could be easily modified. In addition, when the reforming reaction test was conducted continuously for 100 hours, no particular change was observed in both the product and the comparative product, and it was found that the product was effective as a catalyst similarly to the comparative product.

Example 2 A plate-shaped steam reforming was carried out by the same production method as in Example 1 using a nickel foam having an apparent thickness of 10 mm as the catalyst carrier 1 and an apparent thickness (wire diameter) of 2 mm for forming the foam. Catalyst A was made. At this time, Ru:
A ruthenium alloy having a composition of Pt = 90: 10 (mol) was used. More specifically, a treatment solution for treating nickel foam is 5% hydrochloric acid, and a mixed solution of ruthenium chloride and platinum chloride mixed with Ru: Pt at a ratio of 90:10 (mol) is used. It adhered to the surface of the nickel foam under exactly the same manufacturing conditions as in Example 1. Thereby, the surface of the nickel foam was covered with the black coating.

Using the obtained steam reforming catalyst A, a steam reforming test was conducted in which methane was reacted with steam. The reaction temperature at this time is 700 ° C. Then, it was confirmed that the reforming was sufficiently performed in a state where there was almost no pressure loss.

Example 3 A steam reforming catalyst was produced under exactly the same conditions as in Example 1 except that an iron short fiber sintered body having an apparent thickness of 3 mm was used as a catalyst carrier. The obtained steam reforming catalyst was subjected to the same steam reforming reaction test as in Example 2 in which methane was reacted with steam. Then, it was confirmed that hydrogen was obtained with extremely good reforming efficiency. In addition, in such a reforming test, a mixed gas of hydrogen, CO ₂ , and CO obtained by the reaction was scoured, and the obtained CO was used for heating, so that the energy efficiency was found to be 60% or more. Was. However, the CO concentration in the generated hydrogen at this time was about 10 ppm, and it was confirmed that repurification was necessary.

When the steam reforming catalyst A of the present invention obtained in Examples 1 to 3 was incorporated into a reformer, one thicker catalyst A was manufactured, and a thinner catalyst A was manufactured. Arbitrary, such as incorporating several catalysts A in multiple layers. Further, when several sheets are incorporated in a multilayer, it is optional such as opening a gap between the catalysts A.

[0026]

The steam reforming catalyst of the present invention and the method for producing the same have the following functions and effects because they are constituted as described above. According to the present invention, the catalyst support composed of a plate-shaped porous metal body supporting a catalyst material composed of ruthenium or a ruthenium alloy is iron, nickel or a metal foam or a metal short fiber sintered body manufactured using an alloy thereof. is there. Therefore, a small and lightweight steam reforming catalyst having an effective catalyst area with a large surface area can be obtained. Therefore, by incorporating the reformer into a reformer, it is possible to manufacture a compact and lightweight reformer capable of obtaining high-performance catalytic activity. That is, it is possible to provide a suitable steam reforming catalyst capable of extremely reducing the size and the size of a fuel cell using methanol or methane as a fuel, in particular, a reformer for an in-vehicle fuel cell.

Further, according to the present invention, the resistance to gas permeation is about the same as that of a normal knitted mesh. That is, since there is almost no gas pressure loss, the pumping capacity of a pumping device such as a blower for sending gas to the reforming catalyst can be small. Therefore,
As described above, not only the reformer but also a compact pumping device is required, so that the steam reforming catalyst is suitable as a reforming device for an on-vehicle fuel cell.

Further, according to the present invention, since the ruthenium or ruthenium alloy is supported on the catalyst carrier by ion replacement from an acid solution, the above-mentioned steam reforming catalyst capable of obtaining the high-performance catalytic activity can be easily and simply prepared. It can be manufactured at low cost.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an example of an embodiment of the steam reforming catalyst of the present invention.

[Explanation of symbols]

 A: Steam reforming catalyst 1: Catalyst carrier 2: Catalyst substance

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4G040 EA02 EA03 EA06 EC03 EC08 4G069 AA03 AA08 BA18 BB02A BB02B BC66A BC66B BC68A BC68B BC70A BC70B CC17 CC25 CC32 EB11 EB15Y FA02 FB16 FB26 5H027 AA02 BA01

Claims (6)

[Claims] 1. A steam reforming catalyst comprising a plate-shaped porous metal body, and a catalyst substance comprising ruthenium or an alloy containing ruthenium supported thereon. 2. The steam reforming catalyst according to claim 1, wherein the porous metal body is a metal foam or a sintered metal short fiber. 3. The porous metal body according to claim 1 or 2,
A steam reforming catalyst comprising iron, nickel or an alloy thereof. 4. A method for producing a steam reforming catalyst, comprising supporting a plate-shaped porous metal body with a catalyst substance made of ruthenium or an alloy containing ruthenium by ion-exchange from an acid solution. 5. A method for producing a steam reforming catalyst, wherein the porous metal body according to claim 4 is a metal foam or a sintered metal short fiber. 6. The metal porous body according to claim 4 or 5,
A method for producing a steam reforming catalyst comprising iron, nickel or an alloy thereof.