JP2002136874A - Catalyst and apparatus for reducing co concentration in fuel-reformed gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a catalyst for reducing CO concentration, by which the heat generated at oxidation reaction can be removed efficiently without the necessity of a large-sized or complicated CO oxidizing/removing apparatus and to provide an apparatus for reducing CO concentration by using the catalyst. SOLUTION: This catalyst contains catalytic metal and a highly thermally conductive material having 30 W.m-1.K-1 or higher thermal conductivity for oxidizing/removing CO in a fuel-reformed gas. This apparatus for reducing CO concentration by using the catalyst is provided with a cooling means for removing the heat generated at the oxidation reaction of CO.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a CO concentration reducing catalyst for selectively oxidizing and removing CO in a gas containing hydrogen as a main component and containing CO, and a CO concentration reducing device using the same. More specifically, the present invention relates to a catalyst for reducing a CO concentration in a fuel reformed gas supplied to a fuel electrode side of a fuel cell in a fuel cell power generation device, and a CO concentration reduction device using the same.

[0002]

2. Description of the Related Art Hydrogen-oxygen fuel cells are classified into various types according to the type of electrolyte, the type of electrode, and the like. Representative types are an alkaline type, a phosphoric acid type, a molten carbonate type, a solid electrolyte type, and the like. There is a solid polymer type. Among these, polymer electrolyte fuel cells that can operate at low temperatures (usually 100 ° C or lower) have attracted attention, and have recently been developed as low-pollution power sources for automobiles.
Practical use is progressing.

[0003] The structure of a polymer electrolyte fuel cell has a structure in which a catalyst and an electrode are adhered to an ion-exchange polymer membrane as an electrolyte. As the ion-exchangeable polymer membrane material, a membrane formed of a solid polymer material such as a fluororesin can be used. The electrodes (anode and cathode) generally have a sandwich structure in which an ion-exchange polymer membrane is sandwiched on the surface coated with a catalyst of platinum or an alloy of platinum and another metal. Then, a separator that forms a flow path for the fuel gas and the oxidizing gas while sandwiching the sandwich structure from both sides, and a current collector plate that is disposed outside the separator and serves as an anode and a cathode current collector are provided. The basic structure is as described above, but when actually used, a plurality of sets of a separator, an anode, an ion-exchange polymer membrane, a cathode, and a separator are stacked in this order, and a current collector is disposed outside the set. A structure is used.

[0004] The polymer electrolyte fuel cell having such a configuration has a low operating temperature of 60 to 100 ° C and a maximum efficiency of close to 60%, which is recognized as a performance suitable for a motor for an automobile. .

[0005] As a catalyst for a polymer electrolyte fuel cell, a platinum-based electrode catalyst similar to the phosphoric acid fuel cell is used. However, the platinum-based catalyst used for the electrode is susceptible to poisoning by CO, and if the concentration of CO in the fuel exceeds a certain level, the power generation performance may be reduced, or depending on the concentration, power generation may not be possible at all. . Poisoning by CO is remarkable at lower temperatures, and poisoning by CO is a particularly serious problem in polymer electrolyte fuel cells that can operate at low temperatures.

Accordingly, pure hydrogen is preferably used as the fuel for the fuel cell. However, from the practical point of view, various types of fuel (for example, methane) which are inexpensive, have excellent storage properties, and are easy to set up in a public supply system. , Natural gas (LNG), petroleum gas (LPG) such as propane, butane, naphtha, kerosene,
Hydrogen-rich reformed gas by mixing hydrocarbon fuel such as light oil, alcohol-based fuel such as methanol, city gas, and other fuels for hydrogen production) with steam and performing steam reforming and other reactions in a reformer. What is said is common.

However, since CO is generated as a side reaction during the reforming reaction, the reformed gas contains a considerable concentration of CO in addition to hydrogen. Therefore, this C
There is a strong demand for the development of a technique for converting O into CO ₂ that is harmless to the platinum electrode catalyst and reducing the CO concentration of the hydrogen-containing gas. At that time, it is considered desirable to reduce the CO concentration to a low concentration of usually 100 ppm or less, preferably 40 ppm or less. Note that CO in the reformed gas
The concentration is determined by the type of the catalyst filled in the reforming reaction section, the operating temperature of the reforming reaction section, the raw material supply temperature per unit catalyst volume to the reforming reaction section, and the like.

As one of means for reducing the CO concentration in the hydrogen-containing gas, a shift reaction (CO + H ₂ O → CO ₂ + H
It has been proposed to use ₂ ). However, in the CO converter, since the CO concentration can be reduced only to about 1% by volume due to restrictions on chemical equilibrium, it is necessary to further reduce the CO concentration by a CO concentration reduction device before the CO is supplied to the fuel cell.

Therefore, as a means for reducing the CO concentration to a lower concentration, there has been proposed a CO selective oxidation method in which oxygen or air is introduced into a hydrogen-containing gas to oxidize and remove CO to CO ₂ . Incidentally, O ₂ amount necessary to oxidize and remove CO is stoichiometrically relative CO1 molar contained in the fuel reforming gas is 0.5 mole (CO + 1 / 2O ₂
→ CO ₂ ).

As a catalyst for oxidizing CO to CO ₂ , an alumina catalyst supporting a noble metal has been used.
However, it is difficult for such an alumina catalyst supporting a noble metal to selectively oxidize a trace amount of CO in a gas containing hydrogen as a main component. Is introduced.

The oxygen added in excess usually reacts with hydrogen.
That is, the more oxygen is added, the more hydrogen that is used as fuel for the fuel cell is consumed, resulting in a decrease in fuel cell efficiency. Therefore, in order to remove CO by oxidation, it is desired to realize a high-performance CO removal method capable of selectively oxidizing a trace amount of CO in a gas containing hydrogen as a main component with as little oxygen as possible.

In the method of removing CO by oxidation, CO
It generates heat because it utilizes the oxidation reaction of. When the catalyst temperature rises due to this heat generation, the following undesired reaction proceeds, and conversely, the CO concentration increases.

[0013] Undesirable progress that proceeds with increasing catalyst temperature
One of the reactions is a reverse shift reaction (CO _Two+ H_Two→ CO + H_Two
O) and a shift reaction (CO_Two+ H_Two→
CO + H_TwoThe CO concentration is determined by the equilibrium constant with O)
You.

Another undesired reaction which proceeds with an increase in the catalyst temperature is a methanation reaction (CO + 3H ₂ → CH ₄ + H ₂ O) which proceeds at a higher temperature. In this reaction, CO concentration is H ₂ as a fuel for a fuel cell that reduces is consumed.

In order to prevent the progress of these undesired reactions such as the reverse shift reaction and the methanation reaction, C
When oxidizing and removing O, the heat of formation accompanying CO oxidation is removed,
It is necessary to maintain the catalyst temperature within a predetermined temperature range.

To solve the above problem, Japanese Patent Laid-Open Publication No.
In 000-95502, the heat exchanger is multi-staged, a plurality of oxygen introduction points are provided, and oxygen necessary for CO oxidation removal is divided and introduced, thereby suppressing heat generation due to oxidation.
A technique for oxidizing and removing CO with a smaller amount of oxygen is disclosed.

[0017]

However, in consideration of application to a low-pollution power source for automobiles, it is desirable that the CO oxidation removing device is small and simple. Therefore, increasing the number of reactors is not preferable because the size of the reforming system is increased. Further, it is not preferable that there are a plurality of oxygen inlets because the system configuration becomes complicated.

The present invention has been completed in view of the above-mentioned problems, and has been developed to achieve efficient removal of heat generated by an oxidation reaction without the need for a large or complicated CO oxidation removing device.
It is an object to provide an O concentration reduction catalyst and a CO concentration reduction device using the same.

[0019]

Means for Solving the Problems As a result of intensive studies, the present inventor has conducted a CO oxidation reaction by mixing a material having high thermal conductivity into the catalyst layer in order to quickly remove heat of reaction. The present inventors have found that cooling can be performed effectively from the vicinity of the catalyst and completed the present invention.

That is, the present invention is configured as follows for each claim.

According to a first aspect of the present invention, CO in a fuel reformed gas containing a catalytic metal and a high thermal conductive material having a thermal conductivity of 30 (W · m ⁻¹ · K ⁻¹ ) or more is oxidized. CO to be removed
It is a concentration reduction catalyst.

According to a second aspect of the present invention, the catalyst metal is a noble metal.
O concentration reduction catalyst.

According to a third aspect of the present invention, there is provided the CO concentration reducing catalyst according to the first or second aspect, wherein the catalytic metal contains Pt and / or Ru.

According to a fourth aspect of the present invention, the catalyst metal has a particle size of 2 to 5 μm.
4. The catalyst for reducing CO concentration according to any one of 3.

According to a fifth aspect of the present invention, there is provided the CO concentration reducing catalyst according to any one of the first to fourth aspects, wherein the high thermal conductive material is silicon nitride or silicon carbide.

The invention according to claim 6 is the CO concentration reducing catalyst according to any one of claims 1 to 5, wherein the particle diameter of the high thermal conductive material is 5 to 10 μm. .

The invention according to claim 7 is the CO concentration reducing catalyst according to any one of claims 1 to 6, wherein the high thermal conductive material is contained in an amount of 30 to 80% by volume.

The invention according to claim 8 is the CO concentration reducing catalyst according to any one of claims 1 to 7, wherein the area ratio of the high thermal conductive material is 25 to 95%.

According to a ninth aspect of the present invention, there is provided a cooling means capable of removing heat generated by the CO oxidation reaction, and comprising a CO concentration-reducing catalyst according to any one of the first to eighth aspects.
This is an O concentration reduction device.

[0030]

According to the present invention configured as described above, the following effects can be obtained for each request.

In the first aspect of the present invention, not only the catalytic metal acting as a catalyst for reducing the CO concentration but also
By including a material having a high thermal conductivity in the CO concentration reducing catalyst and present in the vicinity of the catalytic metal, the cooling means can be effectively used, and the CO concentration in the fuel reformed gas can be effectively reduced.

According to the invention of claims 2 to 8, the touch
Medium metal and thermal conductivity 30 (W · m ^-1・ K^-1) More materials
By stipulating the fee, the effect of claim 1 can be improved.
It is possible to obtain a CO concentration reducing catalyst having a large amount.

According to the ninth aspect of the present invention, it is possible to obtain a CO concentration reducing device capable of efficiently removing the reaction heat of the CO oxidation reaction without requiring a large or complicated CO oxidation removing device. it can.

[0034]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the first invention of the present application, CO
The concentration reducing catalyst will be described. In the present invention, the particle size refers to an average particle size, which can be measured by a laser diffraction particle size distribution analyzer (SALD-2000) manufactured by Shimadzu Corporation.

The CO concentration reducing catalyst of the present invention oxidizes CO in a fuel reformed gas containing a catalytic metal and a high thermal conductive material having a thermal conductivity of 30 (W · m ⁻¹ · K ⁻¹ ) or more. It is a CO concentration reduction catalyst to be removed.

Not only a catalytic metal that acts as a catalyst for reducing the CO concentration, but also a material having high thermal conductivity (high thermal conductive material)
Is contained in the CO concentration reduction catalyst and is present in the vicinity of the catalyst metal, whereby the cooling means can be effectively used. That is,
The heat of reaction generated by the CO oxidation reaction can be quickly removed from the vicinity of the catalytically active site where heat is generated.
If the reaction heat can be quickly removed, it is possible to prevent the catalyst temperature from rising, and to suppress the regeneration of CO by the undesired reverse shift reaction and the consumption of hydrogen by the methanation reaction. Become. In addition, since a rise in the catalyst temperature can be prevented without using a special control device, simplification of the device can be achieved. Further, the CO concentration can be reduced to an allowable level of the fuel cell without providing a plurality of oxygen inlets, and the size of the apparatus can be reduced.

As a method for producing a catalyst for reducing the concentration of CO, a method in which a catalyst metal is supported on a carrier, a slurry in which the carrier supporting the catalyst metal is mixed with a high heat conductive material, and a slurry is applied to a desired portion is used. It is possible to use, but not limited to, various known methods of mixing a catalyst metal and a high heat conductive material. As a method of adjusting the particle size of the catalyst powder and the high thermal conductive material, a method of mixing and pulverizing both is preferable from the viewpoint of workability. There is no problem even if it is crushed into pieces and then mixed.

As the catalytic metal, noble metals (Au, Ag,
Ru, Rh, Pd, Os, Ir, and Pt). Ni or Fe can be used as a catalyst metal other than the noble metal that can be contained in the CO concentration reducing catalyst, but is preferably a noble metal from the viewpoint of the CO concentration reducing effect. It is more preferable that the catalytic metal contains Pt and / or Ru from the viewpoint of the effect of reducing the CO concentration. In this,
Ru is more preferable, and particularly when Ru and Pt are contained, the effect of reducing the CO concentration becomes remarkable.

The particle size of the catalyst metal is preferably 2 to 5 μm. The catalyst metal particles are preferably smaller in order to increase the number of contact points with the reaction gas. However, if the particle size is too small, the catalyst surface becomes unstable, which is not preferable. Further, in order to reduce the particle size, it takes a long time for the pulverization, which is not efficient. Therefore, the particle size of the catalyst metal is preferably larger than 2 μm. On the other hand, when the particle diameter of the catalytic metal particles exceeds 5 μm, the effect of the present invention of effectively cooling through the high heat conductive material is undesirably reduced.

As the carrier, any carrier may be used as long as it is a refractory inorganic oxide carrier, but alumina, titania,
It is preferable to use at least one selected from the group consisting of silica and zirconia. These are widely used as catalyst carrier components, and raw materials can be easily obtained, and a method for producing and handling a carrier is easy. Titania exhibits suitable activity as a carrier component, but may cause problems in molding. In this case, titania can be used together with a carrier component having good moldability such as alumina.

For example, as a method for producing a carrier composed of titania and alumina, a method of mixing titania and alumina and a method of adhering titania to an alumina molded body can be used. As a method of mixing titania and alumina, there is a method of mixing titania powder and alumina powder or pseudo-boehmite alumina with water, followed by molding, drying and firing. Extrusion molding can be used for molding, and in that case, an organic binder can be added to improve moldability. As a method for adhering titania to the alumina molded body, titania powder (titania supporting a catalyst metal may be used) in an organic solvent, and if necessary, an organic binder and pseudo-boehmite alumina powder are added. There is a method in which the alumina molded body is sufficiently immersed in the liquid, the titania powder is adhered to the alumina molded body, dried and fired.

The alumina source used for producing the carrier is not particularly limited as long as it contains an aluminum atom. Specific examples include aluminum nitrate, aluminum hydroxide, aluminum alkoxide, pseudoboehmite alumina, α-alumina, and γ-alumina. Aluminum nitrate, aluminum hydroxide, and aluminum alkoxide can be converted into pseudo-boehmite alumina, α-alumina, and γ-alumina using known techniques. These alumina sources may be appropriately selected according to the production method and the like.

The titania source is not particularly limited as long as it contains a titanium atom. Specific examples include titanium alkoxide, titanium tetrachloride, amorphous titania powder, anatase titania powder, rutile titania powder, and the like. These raw materials may be appropriately selected according to the production method and the like.

The zirconia source is not particularly limited as long as it contains a zirconium atom. In particular,
Examples include zirconium hydroxide, zirconium oxychloride, zirconium oxynitrate, zirconium tetrachloride, and zirconia powder. These raw materials may be appropriately selected according to the production method and the like.

The silica source is not particularly limited as long as it contains a silicon atom. Specific examples include silicon tetrachloride, sodium silicate, ethyl silicate, silica gel, silica sol and the like.

Next, a method for supporting the catalyst metal on the carrier will be described. The loading of the catalyst metal on the carrier can be carried out using a catalyst preparation liquid and using various known techniques such as an impregnation method, a coprecipitation method and a competitive adsorption method. The treatment conditions may be appropriately selected according to various methods.
The carrier may be brought into contact with the catalyst preparation solution for 10 minutes to 10 hours. After the catalyst metal is supported on the carrier, drying is performed. As the drying method, for example, natural drying, evaporation to dryness, rotary evaporator, or air drying can be used. After applying these measures, usually 350
Baking at ５550 ° C. for about 2 to 6 hours. As the catalyst preparation liquid, a salt containing a desired catalyst metal (for example, a platinum salt such as platinum chloride when supporting platinum, or a ruthenium salt such as ruthenium chloride when supporting ruthenium) is dissolved in water, ethanol, or the like. A solution obtained by dissolution can be used.

The catalyst for reducing CO concentration of the present invention is characterized by containing a high thermal conductive material in addition to the catalytic metal, and the high thermal conductive material has a thermal conductivity of 30 (W · m ⁻¹ · K ⁻¹ ). It is preferably at least 50 (W · m ⁻¹ · K ⁻¹ ) or more. For example, alumina generally used as a catalyst carrier has a thermal conductivity of about 25 (W · m
⁻¹ · K ⁻¹ ) or more and less than 30 (W · m ⁻¹ · K ⁻¹ ),
By mixing a material having a higher thermal conductivity than such a catalyst carrier, the temperature of the CO concentration reduction catalyst can be effectively cooled.

As the high thermal conductive material, copper, aluminum,
Many materials are known, including activated carbon, silicon nitride, and silicon carbide.However, in a fuel reforming gas, any material can be stably present without a decrease in thermal conductivity due to corrosion, oxidation, or the like. Anything can be used. Among the high thermal conductive materials, silicon nitride (such as Si ₃ N ₄ ) or silicon carbide (Si
C) is preferred.

The particle size of the high thermal conductive material is preferably 5 to 10 μm. When it is less than 5 μm or more than 10 μm,
This is not preferable because the reaction heat of the CO oxidation reaction cannot be effectively removed and the CO concentration cannot be effectively reduced.

The high thermal conductive material is preferably contained in the CO concentration reducing catalyst in an amount of 30 to 80% by volume. 30% by volume
If it is less than 80 vol%, it is not preferable because the effective cooling by the high thermal conductive material is hindered.
The volume ratio of the high thermal conductive material in the CO concentration reduction catalyst is:
It can be adjusted by the charged volume ratio of the CO concentration reduction catalyst.

The area ratio of the high thermal conductive material is 25 to 9
Preferably, it is 5%. The area ratio is calculated by the following equation (1):

[0052]

(Equation 1)

(Where D _cat is the particle size of the catalyst powder supporting the metal catalyst, and D _min is the thermal conductivity of 30 (W · m ⁻¹ ·
K ⁻¹ ) or more, and a is a numerical value obtained by dividing the volume fraction of the material having a thermal conductivity of 30 (W · m ⁻¹ · K ⁻¹ ) or more in the CO concentration reduction catalyst by 100. . ), And the particle size is 30 (W · m ⁻¹ · K ⁻¹ ) with the catalytic metal.
It can be measured when the above materials are mixed to form a slurry. When the area ratio is less than 25%, the contact portion between the catalyst metal and the high thermal conductive material is small, and it is not preferable because the reaction heat cannot be efficiently removed. When the area ratio exceeds 95%, the amount of the catalyst decreases, which is not preferable. In addition,
The measurement in a slurry state is for ease of measurement, and the particle diameter in the slurry state and the particle diameter in the case where the slurry is dried to produce a CO concentration reduction catalyst are substantially the same.

The second invention of the present application is a CO concentration reducing apparatus comprising a cooling means capable of removing heat generated by a CO oxidation reaction, and using the above-mentioned CO concentration reducing catalyst.

The structure of the apparatus is a CO apparatus in which CO mixed with reformed hydrogen generated by reforming a hydrocarbon-based raw material is brought into contact with oxygen in the presence of a catalyst to denature the reformed hydrogen. There is no particular limitation as long as an introduction path and an oxygen supply means are provided and the inside thereof can accommodate the CO concentration reduction catalyst of the present invention.

Various known techniques can be applied to the control of the CO concentration reducing device of the present invention. For example, a CO sensor is provided to detect the CO concentration in the transferred gas, and the CO concentration is reduced based on the CO concentration. A unit for controlling the device can be provided.

Various known techniques can be used to remove the heat of reaction, for example, a method using a heat exchanger type reactor. As the structure of the heat exchanger, plate fin type,
A shell tube type or the like is given as an example. Water used as a heat exchanger type reactor and cooling the reformed gas is exemplified as water, but is not limited thereto, and the boiling point at the pressure in the heat exchanger type reactor is used. Various substances such as alcohol and oil can be used as long as they are within the activation temperature range of the CO concentration reduction catalyst. In addition, the adjustment of the cooling degree by the heat exchanger type reactor is as follows.
This is possible by controlling the flow rates of the refrigerant and the reformed gas.

[0058]

EXAMPLES Examples of the present invention and comparative examples will be described below, but the present invention is not limited to the following examples.

Example 1 Platinum was impregnated and supported on alumina using an aqueous platinum chloride solution. Platinum was impregnated so as to be 1% by mass (in terms of metal) with respect to the obtained catalyst powder. After drying, firing was performed to obtain a platinum-supported alumina catalyst powder (catalyst metal).

Next, the above platinum-carrying alumina catalyst powder, alumina sol, water, and silicon nitride (Si ₃ N ₄ : thermal conductivity 3)
0 (W · m ⁻¹ · K ⁻¹ )) was placed in a magnetic ball mill pot and mixed and pulverized for 2 hours to form a slurry. The addition of silicon nitride (Si ₃ N ₄ ) was made to be 50% by volume in the obtained catalyst coat layer. The particle diameter of the platinum-carrying alumina catalyst powder in the obtained slurry was 5 μm, and the particle diameter of silicon nitride was 8 μm.

The above slurry was applied to a plate fin type heat exchanger having about 400 channels per square inch cross section and dried by ventilation to obtain a CO concentration reduction catalyst 1.

<Example 2> A ruthenium-supported alumina-supported catalyst powder was prepared in the same manner as in Example 1 except that the platinum-supported alumina catalyst was replaced with a ruthenium-supported alumina-supported catalyst, and coated on a plate-fin type heat exchanger. did. A ruthenium chloride aqueous solution was used as a ruthenium source. The particle size of the ruthenium-supported alumina catalyst powder in the obtained slurry was 5 μm, and the particle size of silicon nitride was 8 μm.

The slurry was applied to the same plate-fin heat exchanger as in Example 1 and dried by ventilation to obtain a CO concentration reduction catalyst 2.

Example 3 A platinum-ruthenium-supported alumina-supported catalyst powder was prepared in the same manner as in Example 1 except that the platinum-supported alumina catalyst was changed to a platinum-ruthenium-supported alumina-supported catalyst. Coated to exchanger. An aqueous solution of platinum chloride was used as a platinum source, and an aqueous solution of ruthenium chloride was used as a ruthenium source. Platinum and ruthenium are each present in the resulting catalyst at 1
Impregnation was carried out so as to be mass% (in terms of metal). The particle size of the platinum-ruthenium-supported alumina catalyst in the obtained slurry was 5 μm, and the particle size of silicon nitride was 8 μm.

The slurry was applied to the same plate-fin type heat exchanger as in Example 1 and dried by ventilation to obtain a CO concentration reduction catalyst 3.

<Examples 4, 5, and 6> In Examples 1, 2, and 3, when manufacturing the slurry, silicon nitride was converted to silicon carbide (SiC: thermal conductivity 80 (W · m ⁻¹ · K ⁻¹ )). A slurry was prepared in the same manner except that the slurry was changed. The particle size of each catalyst powder in the obtained slurry is 4 μm, and the particle size of silicon carbide is 7
μm.

The slurry was applied to a plate-fin type heat exchanger in the same manner as in Example 1 and dried by ventilation to obtain CO concentration reduction catalysts 4, 5, and 6.

<Comparative Examples 1, 2, and 3> In Examples 1, 2, and 3, the silicon nitride (Si
_A slurry was prepared without mixing ₃ N ₄ : thermal conductivity 30 (W · m ⁻¹ · K ⁻¹ ). The particle size of the catalyst powder in each of the obtained slurries was 3 μm.

The above slurry was applied to a plate fin type heat exchanger in the same manner as in Example 1 and dried by ventilation to obtain CO concentration reduction catalysts 7, 8, and 9.

Comparative Example 4 In Example 3, except that silicon nitride was changed to silica (SiO ₂ : thermal conductivity 1.5 (W · m ⁻¹ · K ⁻¹ )) during slurry production. A slurry was prepared in the same manner. Platinum in the obtained slurry
The particle size of the ruthenium-supported alumina catalyst powder was 4 μm, and the particle size of silica was 6 μm.

The slurry was applied to a plate-fin heat exchanger in the same manner as in Example 3 and dried by ventilation to obtain a CO concentration reduction catalyst 10.

<Comparative Example 5> In Example 3, except that silicon nitride was changed to alumina (Al ₂ O ₃ : thermal conductivity 29 (W · m ⁻¹ · K ⁻¹ )) at the time of slurry production. A slurry was prepared in the same manner. Platinum in the obtained slurry
The particle size of the ruthenium-supported alumina catalyst powder was 3 μm, and the particle size of alumina was 6 μm.

The slurry was applied to a plate fin type heat exchanger in the same manner as in Example 3, and dried by ventilation to obtain a CO concentration reduction catalyst 11.

<Examples 7 and 8> In Example 6, the amount of silicon carbide (SiC) added during slurry production was
A slurry was prepared in the same manner except that the resulting catalyst coat layer was adjusted to 30 and 80% by volume, respectively. The particle diameters of the platinum-ruthenium-supported alumina catalyst powder in the obtained slurry were 3 μm and 5 μm, respectively, and the particle diameters of silicon carbide were 6 μm and 8 μm, respectively.

The slurry was applied to a plate-fin heat exchanger in the same manner as in Example 3 and dried by ventilation to obtain CO concentration reduction catalysts 12 and 13.

<Examples 9 and 10> In Example 6, when producing the slurry, the amount of silicon carbide (SiC) added was set to 10, 95 in the obtained catalyst coat layer.
A slurry was prepared in the same manner, except that the volume was adjusted to volume%. The particle diameters of the platinum-ruthenium-supported alumina catalyst powder in the obtained slurry were 3 μm and 5 μm, respectively, and the particle diameters of silicon carbide were 5 μm and 9 μm, respectively.

The slurry was applied to a plate-fin type heat exchanger in the same manner as in Example 3 and dried by ventilation to obtain CO concentration reduction catalysts 14 and 15.

<Example 11> In Example 6, a slurry was prepared in the same manner as in Example 6, except that the mixing and pulverizing time was changed to 4 hours. The particle size of the platinum-ruthenium-supported alumina catalyst powder in the obtained slurry was 2 μm.
m and the particle size of silicon carbide were 5 μm.

The slurry was applied to a plate-fin heat exchanger in the same manner as in Example 3 and dried by ventilation to obtain a CO concentration reduction catalyst 16.

<Examples 12 and 13> In Example 6,
In the production of the slurry, the mixing and pulverizing times are each set to 0.1.
A slurry was prepared in the same manner as above except for 5 hours and 8 hours. The particle diameters of the platinum-ruthenium-supported alumina catalyst powder in the obtained slurry were 6 μm and 1.5 μm, respectively, and the particle diameters of silicon carbide were 11 μm and 4 μm, respectively.

The slurry was applied to a plate-fin heat exchanger in the same manner as in Example 3 and dried by ventilation to obtain CO concentration reduction catalysts 17 and 18.

For the CO concentration reducing catalyst (Table 1) coated on the plate fin type heat exchanger in the above Examples 1 to 13 and Comparative Examples 1 to 5, the CO reducing performance in the reformed gas under the conditions shown in Table 2 Was evaluated. In addition, after performing hydrogen reduction as a pretreatment, each CO concentration reduction catalyst was evaluated by changing the refrigerant temperature so that the reaction temperature was 80 to 160 ° C. Table 3 shows the outlet CO concentration of the plate fin type heat exchanger at each refrigerant temperature. The CO concentration reducing catalyst of the present invention had a higher CO concentration reducing effect as compared with a case where a material having a high thermal conductivity was not used. This effect was more remarkably confirmed when the refrigerant temperature was high.

[0083]

[Table 1]

[0084]

[Table 2]

[0085]

[Table 3]

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Claims (9)

[Claims] A catalyst metal and a thermal conductivity of 30 (W · m ⁻¹⁾
A CO concentration reduction catalyst for oxidizing and removing CO in fuel reformed gas, comprising a high thermal conductive material of K ^-1 or more. 2. The CO concentration reduction catalyst according to claim 1, wherein the catalyst metal is a noble metal. 3. The catalyst metal is Pt and / or R
3. C according to claim 1 or 2, wherein
O concentration reduction catalyst. 4. The CO concentration reducing catalyst according to claim 1, wherein the catalyst metal has a particle size of 2 to 5 μm. 5. The method according to claim 1, wherein the high thermal conductive material is silicon nitride or silicon carbide.
The catalyst for reducing a CO concentration according to the above item. 6. The high thermal conductive material has a particle size of 5 to 10 μm.
The CO concentration reducing catalyst according to any one of claims 1 to 5, wherein 7. The CO concentration reducing catalyst according to claim 1, wherein the high thermal conductive material is contained in an amount of 30 to 80% by volume. 8. The area ratio of the high thermal conductive material is 25 to 95%.
The CO concentration reduction catalyst according to any one of claims 1 to 7, wherein 9. The C according to claim 1, further comprising a cooling means capable of removing heat generated by the CO oxidation reaction.
A CO concentration reduction device using an O concentration reduction catalyst.