JP4551538B2 - Method for producing steam reforming catalyst - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention is incorporated into relates methanol or methanes method of manufacturing a steam reforming catalyst to obtain a gas containing hydrogen is reacted with steam, in particular the fuel reformer of the in-vehicle fuel cell (reactor) the method for producing a valid steam reforming catalysts in hydrogen production processes.
[0002]
[Prior art]
Pure hydrogen is used as a fuel for a low-temperature fuel cell, particularly a polymer solid electrolyte fuel cell that has attracted the most attention in recent years.
At present, attempts have been made to operate a fuel cell by receiving hydrogen gas from a hydrogen cylinder as a fuel for an on-vehicle fuel cell or hydrogen gas from a hydrogen storage metal that has stored hydrogen.
By the way, since such hydrogen cylinders and hydrogen storage metals need to be replenished (supplied) with hydrogen gas periodically, it is necessary to install a hydrogen supply base (hydrogen stand). For this reason, it is considered that it will take a considerable time in the future to put these into practical use.
[0003]
As an alternative to this, there is a new attempt to install a fuel cell fuel reformer on an automobile, load methanol as fuel, react this methanol with water vapor, extract hydrogen, and supply it to the fuel cell. Has been done.
By the way, non-noble metals such as chromium have been conventionally used for reforming catalysts used in fuel reformers. The non-noble metal is that the reforming temperature is as high as 700 ° C. or higher, with such that the reformer is large problem, problems energy efficiency Tsu had become worse in the reforming have been pointed out. Particularly hydrogen for use in fuel cells We have a possible need to keep the carbon monoxide concentration in the hydrogen gas to be most problematic in reformed hydrogen to 1ppm about or less, the reformer (I had reactor both) incidental with reformer increases to, there is a problem that will have as requiring further extra energy.
[0004]
In order to solve such problems, recently, ruthenium metal which is one of platinum group metals has been used as a reforming catalyst. Thereby, when the hydrogen source is methanol, the reforming temperature can be lowered to 400 ° C. or lower. In addition, it is said that the carbon monoxide concentration can also be lowered from the Butard equilibrium reaction.
[0005]
[Problems to be solved by the invention]
Recently, however, the use of ruthenium catalysts has attracted attention. However, in order to produce a small and efficient reformer for in-vehicle fuel cells, the catalyst must be small and highly active. Become.
[0006]
As a ruthenium catalyst that has been attracting attention in this way, conventionally, a pellet-like catalyst in which ruthenium metal is supported on the surface of an alumina pellet has been the mainstream, and therefore the apparent volume of the catalyst is extremely large compared to the effective catalyst area. Further, there is a problem that will have the even greater weight basis.
Therefore, as a method of increasing the effective catalyst area by reducing the size and weight, there is an idea of reducing the particle size of the above-mentioned alumina pellets and increasing the catalyst area per volume by using a hollow alumina carrier such as foamed alumina, In this case, since the pressure loss increases, the pressure feeding device such as a blower for sending the mixed gas of methanol and water vapor becomes large, stable operation becomes difficult, and the pressure loss is large, so the gas circulation Worsens and causes problems in removing unreacted materials.
Therefore, usually an average particle size of about 2~5mm limitations of pellets, or whereby only is is impossible to use a fine particle, a problem that will have the apparent volume of the catalyst is increased.
[0007]
In order to solve such a problem, it is conceivable to use a metal escapand mesh and to support ruthenium metal on the surface, but this expanded mesh has a relatively small surface area and is heavy in weight. from that the carrier itself is a solid, there is a problem in the weight is large becomes to cause the have the Hare weight of view per absolutely area.
[0008]
In view of such conventional circumstances, the present invention has been achieved by accumulating numerous experiments over many years, and the object of the present invention is to achieve an effective catalyst area with a small surface area and a large surface area. , moreover, is to provide a method of manufacturing a suitable steam reforming catalysts for automotive fuel cell pressure loss performance of catalytic activity can be obtained without.
[0009]
[Means for achieving the object]
To accomplish the object, by ion substitution of acid solution, the plate-shaped metal porous body serving as a catalyst carrier, is responsible lifting a catalyst material consisting of an alloy containing ruthenium or ruthenium steam it is a manufacturing method of the reforming catalyst.
[0011]
In the present invention, the metal porous body is a metal foam or a short metal fiber sintered body. Here, when the metal porous body is made of a metal foam, the catalytic substance is connected to the pore surface of the continuous pore group, which is dotted (existing) in a continuous manner in the thickness direction of the foam, or a branch part that three-dimensionally connects the pore group. It is uniformly supported on the entire foam.
In the present invention, the material of the metal porous body is iron, nickel, or an alloy thereof.
In the present invention, the catalyst material which is an alloy containing ruthenium is Ru: Pt = 90: 10 (mol).
[0012]
DETAILED DESCRIPTION OF THE INVENTION
A specific example of the implementation 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-like metal porous body to be 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 about twice as large, so it is extremely large. Moreover, the expanded mesh made from a plate having the same thickness is 1/2 of the plate, whereas the metal foam is about 1/10, so that it can be seen that the weight is extremely light.
Incidentally, the metal foam is manufactured by using 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 the core material by firing.
Thus, metal foam with which the invention is used as a catalyst carrier 1, has the very lightweight, yet, by adjusting arbitrarily the shape and thickness of the urethane foam as a core material, you can select the shape and thickness freely Has the advantage. In addition, it has a plate-like cross-sectional structure having a continuous pore group or a branch part that three-dimensionally connects the pore groups in a continuous manner in the thickness direction of the plate, and therefore has an effective catalyst area with a large surface area. can get. In addition, the resistance to gas permeation through a foam having a large surface area is as low as that of a normal knitted mesh.
[0013]
As the catalyst substance 2 supported on the catalyst carrier 1, a platinum group metal is particularly excellent. Among them, ruthenium is stable and excellent in reducing ability.
The catalyst substance 2 may be ruthenium alone, or may be a ruthenium alloy obtained by adding other platinum group metals such as platinum and palladium to ruthenium.
[0014]
When these ruthenium or ruthenium alloy is supported on a metal foam, since the metal foam is three-dimensional, it can be easily and firmly supported by utilizing the ionization tendency. That is, ruthenium has a very low ionization tendency, and when the metal foam is immersed in an acidic aqueous solution containing a ruthenium metal, the metal is eluted and the ruthenium metal easily adheres to the surface of the metal foam by a substitution reaction.
Here, the acidic solution is used because the acidic solution elutes the metal on the surface of the metal foam, and a small amount of hydrogen is generated, which works more effectively by the reduction of the ruthenium metal and deposits a more solid ruthenium metal. Because to do.
[0015]
For example, when nickel foam is used as the catalyst carrier 1 and immersed in a 10% hydrochloric acid solution of ruthenium 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 ruthenium chloride to light green of nickel.
The substitution reaction is completed when the ruthenium in the liquid is almost completely removed, but even if the reaction product disappears, nickel elution may occur and hydrogen may be generated, so the reaction is stopped immediately before that. And good.
Further, the substitution reaction time for supporting the ruthenium metal on the catalyst carrier 1 is not particularly limited, but it may be about 10 minutes although it depends on the amount (thickness) of the ruthenium metal supported. The temperature may be room temperature. At this time, it is possible to increase the reaction rate by heating.
[0016]
Ruthenium metal in a so-called ruthenium black state having a large surface area specific to ruthenium metal and high activity is deposited on the surface of the catalyst carrier 1 manufactured by the above-described manufacturing method. Typically, the metal foam as the catalyst carrier 1 is immersed in a 5-10% hydrochloric acid aqueous solution of ruthenic acid chloride at room temperature.
[0017]
Even when the catalyst is an alloy, the ionization tendency of ruthenium metal (platinum group metal) is almost the same as that of nickel or iron. Is obtained. Thereby, an effective catalyst can be manufactured.
[0018]
The reforming temperature is about 400 ° C when methanol is a substance that obtains hydrogen by steam reforming reaction, about 700 ° C for methane, and even higher for gasoline, but the catalyst itself Is stable. At this time, the catalyst carrier 1 made of metal foam may become unstable, and it is important to change the specifications of the metal foam according to the use temperature. That is, metal foam with the finest surface area and the largest surface area can be used with methanol, but in methane and other cases, a foam structure that takes heat resistance into account, for example, the thickness of the foam (in the thickness direction of the foam) There is a need to increase the thickness (wire diameter) of the branch portion that three-dimensionally connects continuous pore groups interspersed in a continuous manner.
[0019]
EXAMPLES Next, although Example 1-3 is given and this invention is demonstrated further in detail, this invention is not limited to these.
[0020]
Example 1
A nickel foam having an apparent thickness of 5 mm is used as the catalyst carrier 1. Sumitomo Electric Industries Co., Ltd. under the trade name of the nickel form of the commercially available products: Serume Tsu door, or El-Tech Systems, Inc. under the trade name: may be used, such as Retekku but, as required by using a urethane foam or the like as described above Produced accordingly. Ruthenium was supported as catalyst material 2 on this nickel foam.
That is, a 10% hydrochloric acid aqueous solution of ruthenic acid chloride (H ₂ RuCl ₆ ) is prepared, and the nickel foam is washed and degreased with a neutral detergent. Then, the surface is activated by dipping in a 10% hydrochloric acid solution at 60 ° C. This is further sufficiently washed by deionization and then immersed in a ruthenium chloride solution at room temperature.
As a result, no reaction was observed for the first 3 minutes , but after that, the surface of the nickel foam was blackened and the color of the liquid became light and changed to light green. At this point, hydrogen generation suddenly occurred, so the liquid was raised and washed with water. Then, it was confirmed that the entire foam, such as the pore surfaces of the continuous pore groups scattered in the form of the foam in the thickness direction of the foam and the branches that three-dimensionally connect the pore groups, was covered with the black coating. (See the enlarged view of FIG. 1).
[0021]
The steam reforming catalyst A (hereinafter, have you this product) of the present invention thus obtained was analyzed by dissolving, 70 g / m ² of ruthenium deposition was observed with respect to the projection plane. 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. was performed as a catalyst. Kai At this time, the product 10 g, traditional steam reforming catalyst supported ruthenium alumina particles (hereinafter, will have a comparative product) was placed in a 100g each reactor, through a mixed gas of steam and methanol, respectively As a result of a quality reaction test, the pressure loss was 0.5 atm in the comparative product, but almost no pressure loss was observed in this product. As a result, it was found that the product can be easily modified.
Further, 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 as in the comparative product.
[0022]
Example 2
A plate-shaped steam reforming catalyst A was produced 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) forming foam of 2 mm. At this time, a ruthenium alloy having a composition of Ru: Pt = 90: 10 (mol) was used as the catalyst material 2 to be supported. Specifically, the treatment liquid for treating nickel foam is 5% hydrochloric acid, and this is carried out using a mixed liquid of ruthenium chloride and platinum chloride mixed in a ratio of Ru: Pt = 90: 10 (mol). It was made to adhere to the surface of nickel foam under the same manufacturing conditions as in Example 1. Thereby, the surface of the nickel foam was covered with the black coating.
[0023]
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. As a result, it was confirmed that the reforming was sufficiently performed with almost no pressure loss.
[0024]
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 with an apparent thickness of 3 mm was used as the catalyst carrier.
The obtained steam reforming catalyst was subjected to a steam reforming reaction test in which the same methane as in Example 2 was reacted with steam. Then, it was confirmed that hydrogen can be obtained with extremely good reforming efficiency.
Incidentally, in such a reforming test scoured hydrogen obtained by the reaction, CO _2, and a mixed gas of CO, energy efficiency because thereby the CO obtained was used for heating found to be 60% It was. However, the CO concentration in the produced hydrogen at this time was about 10 ppm, and it was confirmed that repurification was necessary.
[0025]
In addition, when incorporating the steam reforming catalyst A of the present invention obtained in Examples 1 to 3 into a reformer, one sheet of catalyst A manufactured to be thicker, and several sheets manufactured to be thinner than that, It is optional such as incorporating catalyst A in multiple layers. Also, empty Keru, and the like optionally a gap between the catalyst A in the case of incorporating several sheets in multiple layers.
[0026]
【The invention's effect】
Method for producing a steam reforming catalysts of the present invention exhibits the effect of the following from becoming configured as the ordination. According to the present invention, the catalyst carrier made of a plate-like metal porous body that supports a catalyst material made of ruthenium or a ruthenium alloy is a metal foam or a short metal fiber sintered body manufactured using iron, nickel, or an alloy thereof. is there. Therefore, a steam reforming catalyst that is small and light and has an effective catalyst area with a large surface area can be obtained. Therefore, by incorporating it in the reformer, it is possible to manufacture a small and light reformer that can obtain high-performance catalytic activity. That is, it is possible to provide a suitable steam reforming catalyst capable of reducing the size and weight of a fuel cell using methanol or methane as a fuel, particularly a vehicle fuel cell reformer.
[0027]
Further, according to the present invention, the resistance to gas permeation is similar to 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 feeding gas to the reforming catalyst can be small.
Therefore, as described above, since not only the reformer but also a small pressure feeding device is sufficient, the steam reforming catalyst is suitable as a reforming device for an on-vehicle fuel cell.
[0028]
Further, according to the present invention, since the ruthenium or ruthenium alloy is supported on the catalyst carrier by ion substitution from the acid solution, the above-described steam reforming catalyst capable of obtaining high-performance catalytic activity can be easily and inexpensively manufactured. can do.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an example of an embodiment of a steam reforming catalyst of the present invention.
A: Steam reforming catalyst 1: Catalyst carrier 2: Catalyst material

Claims (3)

A plate-shaped metal porous body, method for manufacturing a steam reforming catalyst, characterized in that is supported by a catalyst material consisting of an alloy containing ruthenium or ruthenium ions are substituted from the acid solution. The method for producing a steam reforming catalyst according to claim 1 , wherein the metal porous body is a metal foam or a metal short fiber sintered body. The method for producing a steam reforming catalyst according to claim 1 or 2 , wherein the porous metal body is made of iron, nickel, or an alloy thereof.

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