JP2000264603A - Hydrogen generator - Google Patents

Abstract

(57) [Summary] [PROBLEMS] Even in applications where operation is repeatedly stopped and started, or where there is severe vibration, the performance of the catalyst body can be fully exhibited and its life can be completed, so that it can operate stably for a long period of time. To provide a hydrogen generator. SOLUTION: Fuel supply unit, fuel reforming water supply unit, CO
A purification air supply unit, a reforming catalyst, and a CO conversion catalyst and / or a CO purification catalyst, and a reforming catalyst, a CO conversion catalyst toward the downstream side from the fuel supply unit,
A hydrogen generator comprising: a CO purification catalyst arranged in the order of: a catalyst wherein each of the catalysts is supported on a carrier having a honeycomb structure, a foam structure or a corrugated structure to carry a catalyst component. .

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydrogen generator for generating hydrogen used for fuel such as a fuel cell.

[0002]

2. Description of the Related Art Conventionally, hydrogen used for vehicle-mounted and household fuel cells has been developed from hydrocarbon fuels such as methane, propane, gasoline, and kerosene; alcohol fuels such as methanol;
Alternatively, ether fuels such as dimethyl ether are generated by contact with a reforming catalyst heated by adding steam. Usually, hydrocarbon-based fuel is reformed at a temperature of about 500 to 800 ° C, and alcohol and ether-based fuels are reformed at a temperature of about 200 to 400 ° C. At this time, the higher the reaction temperature, the higher the concentration of carbon monoxide (CO) generated. Therefore, particularly when a hydrocarbon fuel is used, CO and steam are reduced by using a CO shift catalyst to reduce the CO concentration. Is reacting. Furthermore, in the case of a fuel cell that operates at a low temperature of about 100 ° C., such as a polymer electrolyte fuel cell, it is necessary to remove the CO concentration to a level of several ppm. It uses a CO purification catalyst that oxidizes. These catalysts have been used as catalyst bodies having a pellet shape such as a columnar shape or a spherical shape. However, when using a pellet-shaped catalyst body, the catalyst body collapses due to thermal shock at every start-up of the fuel cell or vibrations during vehicle mounting, so it is necessary to replace it with a new catalyst body. There was a problem that it could not be used until the life of the component. Further, there has been a possibility that a problem that the catalyst powder generated by the collapse of the catalyst clogs the fuel passage of the fuel cell may occur.

[0003]

That is, the conventional hydrogen generator performs only a steady operation in a chemical plant or the like.
There is no major problem in applications that do not require frequent start-up operations, but there is a problem in applications such as in-vehicle or household fuel cells where the operation is repeatedly stopped and started or in which there is severe vibration. In view of the above facts, an object of the present invention is to sufficiently exhibit the performance of the catalyst body even in applications in which the operation is repeatedly stopped and started or in which there is severe vibration,
An object of the present invention is to provide a hydrogen generator which can operate stably for a long period of time by being able to complete its life.

[0004]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a fuel supply unit, a fuel reforming water supply unit (hereinafter, also simply referred to as a "water supply unit"), and a CO purification unit. An air supply unit (hereinafter, also simply referred to as “air supply unit”), a reforming catalyst, a CO conversion catalyst and / or a CO purification catalyst, and a reforming catalyst is provided downstream from the fuel supply unit. A hydrogen generator comprising a medium, a CO conversion catalyst, and a CO purification catalyst arranged in this order, wherein the catalyst has a catalyst component supported on a carrier having a honeycomb structure, a foam structure, or a corrugated structure. Provided is a hydrogen generator configured. In this hydrogen generator,
It is preferable that the fuel supply unit supplies a hydrocarbon-based, alcohol-based, or ether-based fuel. Further, it is preferable that the water supply unit supplies air or only air together with water vapor. Preferably, the carrier is made of a heat-resistant inorganic material. Preferably, the carrier is made of a metal or a thermally conductive inorganic material. Further, it is preferable that the carrier is formed by compounding a heat-resistant inorganic material and a metal or a thermally conductive inorganic material.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention provides a fuel supply unit, a fuel reforming water supply unit, a CO purification air supply unit, a reforming catalyst, and a CO conversion catalyst and / or a CO purification catalyst. A hydrogen generator comprising a reforming catalyst body, a CO conversion catalyst body, and a CO purification catalyst body arranged in this order from a fuel supply section toward a downstream side, wherein the catalyst body has a honeycomb structure, a foam structure, or a corrugated structure. The present invention relates to a hydrogen generator constituted by coating a carrier having a catalyst component with a catalyst component.

Hereinafter, the present invention will be described. For easy understanding, the description will be made in order along the flow of fuel (source gas) in the hydrogen generator of the present invention with reference to the drawings. FIG.
It is a schematic diagram which shows the structure of one Example of the hydrogen generator of this invention. In the hydrogen generator shown in FIG. 1, fuel is introduced from a fuel supply unit 1, and steam is added from a fuel reforming water supply unit 2. The raw material gas in which the fuel and the steam are mixed is heated through a flow path having the heat exchange fins 3. Then, it contacts and reacts with the reforming catalyst body 4 heated by the heating burner 5 to generate a reformed gas. At this time, the combustion exhaust gas is exhausted from the exhaust port 6. Next, the amount of CO contained in the reformed gas is reduced by the CO conversion catalyst 7.
Furthermore, for use in polymer electrolyte fuel cells, CO
Therefore, a small amount of air is introduced from the CO purification air supply unit 8 and CO is oxidized and removed by the CO purification catalyst 9. The reformed gas from which CO has been removed is supplied from the reformed gas outlet 10 to, for example, a fuel cell.

First, the fuel introduced from the fuel supply unit 1 is not particularly limited as long as it can supply hydrogen. For example, natural gas, coal gas, liquefied petroleum gas, propane gas, kerosene, gasoline, methanol And various fuels such as hydrocarbon-based, ether-based and alcohol-based fuels such as dimethyl ether and dimethyl ether. Alternatively, city gas obtained by mixing oil gas obtained by pyrolyzing petroleum and liquefied petroleum gas can be used. Above all, 13A city gas contains methane as a main component and can be used in the same manner as natural gas.

In the present invention, hydrogen is generated by reforming the fuel. The reforming method at this time includes steam reforming by adding steam, partial reforming by adding air, and the like. Further, any reforming method such as a reforming method combining both reactions can be used. Therefore, depending on the type of the reforming method, steam may be added from the water supply unit 2, or a mixture of air and steam may be added as appropriate.

[0009] The ratio of the supply amount of fuel and steam varies depending on the type of fuel and the type of reforming method.
Any stoichiometric ratio for converting to ₂ and hydrogen or more may be used as long as the efficiency is not reduced. Specifically, the stoichiometric ratio may be 1 to 3.

When the steam reforming method is used as the reforming method, for example, it may be in the following range. Type of fuel Amount supplied to fuel 1 Natural gas (natural gas) 2-5 Propane gas 6-15 Kerosene 20-40 Gasoline 16-32 Methanol 1-2 Dimethyl ether 3-6

[0011] The term "reforming" generally refers to the generation of hydrogen from fuel and steam or an oxidizing substance (eg, oxygen) by changing the hydrocarbon composition of the fuel using heat or the power of a catalyst. An operation that improves the properties. In the present invention, this means that hydrogen is generated by a fuel and steam and / or an oxidizing substance.

The raw material (mixed) gas of the fuel and the steam introduced from the fuel supply unit 1 and the water supply unit 2 then comes into contact with the reforming catalyst 4 through a flow path provided with the heat exchange fins 3. The channel may be made of a conventionally known material such as a metal such as stainless steel (copper or aluminum may be used at a low temperature), and the heat exchange fin 1 may be a conventionally known material.

The reforming catalyst 4 plays a role of heating the raw material gas by the heating burner 5 and further bringing the raw material gas into contact with the reforming catalyst to reform the fuel and generate hydrogen gas. The present invention has the greatest feature in the structure of the reforming catalyst. That is, in order to solve the problem that the conventionally used pellet-shaped catalyst body is likely to collapse, the present inventors have conducted intensive studies and found a reforming catalyst body having a structure as described below. It is. That is, the reforming catalyst 4 is configured by supporting a catalyst component on a carrier having a honeycomb structure, a foam structure, or a corrugated structure.

By adopting such a configuration, the catalyst does not collapse as in the case of the conventional catalyst, and can maintain stable characteristics for a long time. Further, as compared with the conventional pellet-shaped catalyst body, the contact area with the raw material gas is increased, so that the reaction can be performed efficiently, the amount of the catalyst can be reduced, and the heat capacity of the catalyst body can be reduced. There is an advantage. Further, since the surface area per volume is large, there is an advantage that heat radiation due to radiation and convection is large and heat conductivity is high. In addition, heat from the heating burner 5 is uniformly transmitted to the entire reforming catalyst body, and the Heat can be removed quickly.

Next, a method for producing the reforming catalyst body 4 will be described. The reforming catalyst 4 can be manufactured by mixing a powder of the reforming catalyst (catalyst component) with a dispersion medium to prepare a slurry, and then applying (coating) the slurry to a carrier and drying the slurry. .

As the reforming catalyst, fuel, steam and / or
There is no particular limitation as long as it has a function of generating hydrogen by oxygen, and examples thereof include a Ni-based catalyst such as nickel supported on alumina and a noble metal catalyst such as ruthenium supported on alumina and rhodium supported on alumina.

In the present invention, the reforming catalyst is pulverized by a conventional method into a powder. The particle size of the powder is not particularly limited as long as it does not hinder the dispersibility of the slurry when it is manufactured and does not peel off when the slurry is carried on a carrier. Specifically, for example, it may be 0.1 to 2 μm. The dispersion medium for dispersing the reforming catalyst powder is not particularly limited as long as it can be easily blown off after the obtained slurry is applied to the carrier. Specifically, for example, water, alcohol and the like can be mentioned.

The carrier used in the present invention has a honeycomb structure, a foam structure or a corrugated structure. This is because the contact area with the source gas is increased as described above. In the foam structure, since the raw material gas is difficult to pass if the individual bubbles are independent, it is preferable that the individual bubbles be connected. The material of the carrier is not particularly limited as long as it is stable in a hydrogen-rich atmosphere and high-temperature use conditions. For example, heat-resistant inorganic materials such as cordierite, alumina, silica alumina, and mullite, and high heat conductive materials such as carbon silicon And various metallic materials such as stainless steel.

The heat-resistant inorganic material has an advantage that it maintains (holds) a stable function when used under a high-temperature condition for a long time. The high thermal conductive material has an advantage that the temperature distribution of the obtained reforming catalyst body 4 is made uniform, the temperature control thereof is easy, and the reaction efficiency can be increased. In addition, when the above-mentioned metal material is used, there is an advantage that molding is easy and extremely high resistance to vibration. Further, such a carrier may be manufactured from the above-described materials by a conventionally known method such as extrusion molding or brazing.

The slurry can be applied to the carrier by a known method conventionally used in the field of paints and the like, and examples thereof include a spray method and a roll method.
Drying may be natural drying or heat drying. It should be noted that if the heating temperature is too high, the function of the catalyst may be impaired. The amount of the reforming catalyst component applied to the carrier depends on the type of the catalyst component, the type of the fuel gas, and the like, but can be appropriately selected by those skilled in the art.

The heating temperature when the raw material gas of the reforming support 4 obtained as described above passes varies depending on the type of fuel, the type of reforming catalyst, and the like. Any temperature may be used as long as the temperature rises to generate hydrogen gas.

The range of the heating temperature for each type of fuel will be described below. Type of fuel Heating temperature range (℃) Natural gas (city gas) 500-800 Propane gas 500-800 Kerosene 500-800 Gasoline 500-800 Methanol, dimethyl ether 200-400

When the raw material gas passes through the reforming catalyst 4, it becomes a reformed gas, which usually contains CO in addition to hydrogen (for example, natural gas is used as a fuel and reformed at 500 to 800 ° C.). Contains about 10% CO). On the other hand, when hydrogen obtained by the hydrogen generator of the present invention is used in, for example, a fixed polymer fuel cell, the CO concentration is several thousand ppm to 1 ppm.
% Need to be reduced to about%. Therefore, the reformed gas is passed through the CO conversion catalyst 7, and the CO concentration in the reformed gas is reduced to several thousands ppm to about 1%.

The method of producing the CO conversion catalyst 7 is the same as that of the reforming catalyst 4 except that the type of the catalyst used is different. The CO conversion catalyst used here is not particularly limited as long as it has a function of reacting CO with water vapor to convert CO ₂ and hydrogen. For example, generally used Cu-Zn catalysts, Fe-Cr catalysts And so on. In other words, "CO metamorphosis" here
Means that CO and water vapor are reacted to form CO ₂ and hydrogen, and a high CO concentration (for example, 10%) is reduced to a low concentration (for example, 1 to 2).
% Or less). Further, when methanol or dimethyl ether is used as the fuel, the reforming can be performed at a relatively low heating temperature, and the CO concentration of the reformed gas is relatively low. In some cases, only the CO purification catalyst 9 may be provided.

Further, when hydrogen is used in a polymer electrolyte fuel cell, it is desirable to reduce the CO concentration to a level of several ppm. Therefore, in the hydrogen generator of the present invention, the reformed gas that has passed through the CO conversion catalyst 7 is led to the CO purification catalyst 9 through the flow path c to oxidize and remove a small amount of contained CO. At this time, C
Since oxygen is required to oxidize O, a purification air supply unit 8 is provided in the middle of the flow path c, and the reformed gas passing through the CO conversion catalyst 7 is brought into contact with the CO conversion catalyst 7 together with air. .

The method of manufacturing the CO purifying catalyst 9 is the same as that of the reforming catalyst 4 except that the type of the catalyst used is different. The CO purification catalyst used here is not particularly limited as long as it has a function of selectively oxidizing CO contained in the reformed gas or a function of reacting CO with hydrogen to methanate. Supported Pt-based catalysts, Ru-based catalysts and the like can be mentioned. In addition,
When hydrogen obtained by the hydrogen generator of the present invention is used for a fuel cell that operates even when containing hundreds to thousands of ppm of CO, the CO purification catalyst 9 can be omitted.

The thus obtained CO purification catalyst 9
Can be taken out from the reformed gas outlet 10 and supplied to, for example, a fuel cell or the like.

Here, in the hydrogen generator of the present invention, it is preferable to cover the outside of the chamber, the flow path and the like provided with each catalyst body with a heat insulating material. In addition, since the reforming catalyst 4, the CO conversion catalyst 7, and the CO purifying catalyst 9 have different optimum temperature distributions and heat transfer conditions, the reforming catalyst 4 has a metal honeycomb structure having excellent thermal conductivity. CO conversion catalyst 7 and CO purification catalyst 9
It is also effective to select and use different materials from heat-resistant inorganic materials, metallic materials, and high-thermal-conductivity inorganic materials, such as using a honeycomb structure carrier made of cordierite. Furthermore, when using a carrier with a honeycomb structure, metal rods are installed at the center of the carrier, and the upstream and downstream parts are made of different materials. Is an effective means for

When partial reforming is performed by adding air instead of steam from the water supply unit 2, the proportion of hydrogen contained in the reformed gas decreases. As a result, heating of the catalyst body becomes easy. Also in this case, by using the carrier having the honeycomb structure, the contact area between the raw material gas and the reforming catalyst is increased, and an efficient reaction is enabled. When air and steam are added at the same time, an intermediate property between steam reforming and partial reforming is obtained.
In addition, the chamber and the flow path including the respective catalyst bodies therein can be manufactured from a material such as stainless steel by a conventional method. Hereinafter, the present invention will be described with reference to Examples, but the present invention is not limited thereto.

[0030]

EXAMPLES Example 1 Pellet catalysts for reforming, CO conversion, and CO purification were each pulverized (particle size: about 1 μm).
m), a catalyst component: water = 1: 2 (weight), and dispersed in water to form a slurry. These slurries were coated on a carrier having a honeycomb structure made of cordierite to prepare a reforming catalyst 4, a CO conversion catalyst 7, and a CO purification catalyst 9. These catalysts were incorporated in the hydrogen generator shown in FIG. The desulfurized city gas is supplied from the fuel supply unit 1 at 50 liters per minute, and the steam is supplied from the water supply unit 2 at 150 liters per minute.
The reforming catalyst 4 was heated to about 800 ° C. by the heating burner 5 and reacted. The composition of the product gas after passing through the reforming catalyst 4 was measured by gas chromatography, excluding water vapor, and was found to be about 80% hydrogen, about 12% CO, about 8% carbon dioxide, and 500 ppm methane. When the reformed gas passed through the CO conversion catalyst 7, air was introduced from the air supply unit 8 so that the CO concentration became approximately 3000 ppm and further 2% oxygen concentration, and the CO purification catalyst 9 reacted. , CO
The concentration was 5 ppm. The hydrogen generator was stopped once and then started. Stop and start operation for 150
When the composition of the reformed gas was measured 0 times, the methane concentration after passing through the reforming catalyst 4 was 800 ppm, about 4500 ppm after passing through the CO conversion catalyst 7, and the CO purification catalyst 9
After passing, it was 7 ppm.

Example 2 The hydrogen generator, the fuel cell and the driving motor obtained in Example 1 were connected and mounted on a passenger car, and a 100,000 km running test was performed. After running, when the composition of the reformed gas was measured by gas chromatography in the same manner as in Example 1, the methane concentration was 1000 ppm after passing through the reforming catalyst 4, the CO concentration was about 4800 ppm after passing through the CO conversion catalyst 7, After passing through the CO purification catalyst 9, C
The O concentration was 9 ppm.

Example 3 A hydrogen generator was operated in the same manner as in Example 1 except that cordierite was used instead of cordierite as a material of a carrier having a honeycomb structure. . The composition of the product gas after passing through the reforming catalyst 4 was measured by gas chromatography, excluding water vapor, and was found to be about 80% hydrogen, about 12% CO, about 8% carbon dioxide, and 300 ppm methane. After passing through the CO conversion catalyst 7, the CO concentration becomes about 2500 ppm, and air is introduced from the air supply unit 8 so that the oxygen concentration becomes further 2%, and the CO purification catalyst 9 reacts. It became. The hydrogen generator was stopped once and then started. Stop and start operation by 1
When the reformed gas composition was measured 500 times,
The methane concentration after passing through the reforming catalyst 4 is 700 ppm,
It was about 4000 ppm after passing through the shift catalyst 7 and 6 ppm after passing through the CO purification catalyst 9.

<< Comparative Example 1 >> As shown in FIG.
The pelletized catalyst body for reforming, CO conversion, and CO purification used in was filled into each chamber without pulverization,
50 liters of desulfurized city gas was introduced from the fuel supply unit 11 per minute, and steam was introduced at 150 liters per minute from the water supply unit 12. In the same manner as in Example 1, the reforming catalyst 1 was heated with a heating burner.
4 was reacted by heating, and the composition of the product gas after passing through the reforming catalyst body 14 was measured by gas chromatography, excluding water vapor.
It was 2%, carbon dioxide about 8%, and methane 600 ppm. When this reformed gas passes through the CO conversion catalyst 17, C
Air is introduced from the air supply unit 18 so that the O concentration becomes about 3500 ppm and further the oxygen concentration becomes 2%.
When reacted with the purification catalyst 19, the CO concentration was 6 pp.
m. Thereafter, the hydrogen generator was stopped and subsequently started. Further, the stop and start operations were repeated 1500 times to measure the reformed gas composition. The methane concentration after passing through the reforming catalyst 14 was 9000 ppm, and the CO conversion catalyst 1
The CO concentration after passing through 7 was about 14500 ppm, and the CO concentration after passing through the CO purification catalyst 19 was 5500 ppm. When the catalyst body was taken out of the reaction chamber, the catalyst body was partially collapsed, and had a size of about three quarters of the initial size.

Comparative Example 2 A hydrogen generator, a fuel cell and a drive motor of Comparative Example 1 were connected to each other and mounted on a passenger car, and a 100,000 km running test was performed as in Example 2. After running, the composition of the reformed gas was measured by gas chromatography.
0000 ppm, the CO concentration after passing through the CO conversion catalyst 7 is about 16000 ppm, and the C concentration after passing through the CO purification catalyst 9 is C
The O concentration was 9000 ppm. When the pellet-like catalyst was taken out of the reaction chamber, it was significantly disintegrated, and had a size of about half of the initial size.

[0035]

As is clear from the comparison between the evaluation results of the above-described examples and the comparative examples, the present invention can extend the life of the catalyst, stop the operation of the apparatus, repeat the operation,
It is possible to provide a hydrogen generator that suppresses the influence of severe vibration and operates stably for a long period of time.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a configuration of an embodiment of a hydrogen generator of the present invention.

FIG. 2 is a schematic diagram showing a configuration of a comparative example of the hydrogen generator of the present invention.

[Description of Signs] 1, 11 Fuel supply unit 2, 12 Reforming water supply unit 3, 13 Heat exchange fins 4, 14 Reforming catalyst body 5, 15 Heating burner 6, 16 Exhaust port 7, 17 CO conversion catalyst body 8, 18 CO purification air supply unit 9, 19 CO purification catalyst 10, 20 Reformed gas outlet

Continued on the front page (72) Inventor Kunihiro Ukai 1006 Kazuma Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. Person Koichiro Kitagawa 6-2-61 Imafukunishi, Joto-ku, Osaka-shi, Osaka F-term in Matsushita Seiko Co., Ltd. 4G040 EA01 EA02 EA03 EA06 EA07 EC08

Claims (7)

[Claims] 1. A fuel supply section, a fuel reforming water supply section, and a CO
A purification air supply unit, a reforming catalyst, and a CO conversion catalyst and / or a CO purification catalyst, and a reforming catalyst, a CO conversion catalyst toward the downstream side from the fuel supply unit,
A hydrogen generator comprising: a CO purification catalyst arranged in the order of: a catalyst wherein each of the catalysts is supported on a carrier having a honeycomb structure, a foam structure or a corrugated structure to carry a catalyst component. . 2. The hydrogen generator according to claim 1, wherein the fuel supply unit supplies a hydrocarbon-based, alcohol-based, or ether-based fuel. 3. The hydrogen generator according to claim 1, wherein the fuel reforming water supply unit supplies air together with steam. 4. The hydrogen generator according to claim 1, wherein the fuel reforming water supply unit supplies only air. 5. The hydrogen generator according to claim 1, wherein the carrier is made of a heat-resistant inorganic material. 6. The hydrogen generator according to claim 1, wherein the carrier is made of a metal or a thermally conductive inorganic material. 7. The carrier according to claim 1, wherein the heat-resistant inorganic material is a composite of a heat-resistant inorganic material and a metal or a thermally conductive inorganic material.
7. The hydrogen generator according to any one of 6.