JPH082902A - Production of hydrogen-containing gas for fuel cell - Google Patents

Abstract

PURPOSE:To extend the life-time of a cell and improve stability of the power output by using a catalyst exhibiting a CO selective oxidation activity within wide-ranging temperatures and efficiently producing a hydrogen-containing gas satisfactorily reduced in CO concentration. CONSTITUTION:This production of a hydrogen-containing gas for a fuel cell is carried out by bringing a mixture gas composed mainly of hydrogen and containing CO2 in an amount of 17 to 40vol.% into contact with a catalyst composed of a platinum-containing compound selected from platinum tetraammine chloride, chloroplatinic acid, a chloroplatinic acid salt, platinum tetraammine hydroxide and dinitrodiaminoplatinum or such a platinum- containing compound and a halogen-containing compound selected from hydrogen chloride, ammonium chloride, hydrogen fluoride, ammonium fluoride, hydrogen iodide, ammonium iodide, hydrogen bromide and ammonium bromide respectively supported on L-form zeolite and selectively oxidizing CO to CO2 at 60 to 200 deg.C. The amount of the supported platinum-containing compound is 0.1 to 5.0wt.% on platinum base based on the total weight of the catalyst.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a hydrogen-containing gas for a fuel cell, and more specifically to various hydrogen producing fuels such as methane or natural gas (LN).
G), propane, butane or petroleum gas (LPG),
CO is selectively catalytically oxidized from reformed gas obtained by steam reforming of hydrocarbon fuels such as naphtha, kerosene, light oil, synthetic petroleum, alcohol fuels such as methanol and mixed alcohols, or city gas. The present invention relates to a method for producing a hydrogen-containing gas for a fuel cell, which can be removed and can prevent poisoning of an electrode of the fuel cell.

A hydrogen-containing gas for a fuel cell having a low CO concentration obtained by this method is an H ₂ combustion type fuel cell (phosphoric acid type fuel cell, which uses platinum (platinum catalyst) for an electrode of a fuel electrode (negative electrode), When used as a fuel for low-temperature fuel cells such as KOH fuel cells and solid polymer electrolyte fuel cells), the poisoning and deterioration of the platinum electrode catalyst is suppressed to prevent the voltage drop of the fuel cell. And can be advantageously used as fuel for fuel cells.

The process for producing a hydrogen-containing gas by the method of the present invention can be suitably used in the form of being incorporated in a fuel cell power generation system together with the reforming process.

[0004]

2. Description of the Related Art Power generation by a fuel cell has various advantages such as low pollution, low energy loss, selection of installation place, expansion, operability, etc. There is. Various types of fuel cells are known depending on the type of fuel or electrolyte, operating temperature, etc. Among them, hydrogen is used as a reducing agent (active material) and oxygen (air, etc.) is used as an oxidizing agent. Hydrogen-oxygen fuel cells (low-temperature operation fuel cells) have been most developed and put into practical use, and are expected to become even more popular in the future.

There are various types of such hydrogen-oxygen fuel cells depending on the type of electrolyte and the configuration of electrodes, etc., and typical examples thereof include phosphoric acid fuel cells, KOH type fuel cells, and solid state fuel cells. There are polymer electrolyte fuel cells and the like. In the case of such a fuel cell, particularly a low temperature operation type fuel cell such as a polymer electrolyte fuel cell, platinum (platinum catalyst) is used for an electrode. However, the platinum (platinum catalyst) used in the electrodes is easily poisoned by CO, so if the fuel contains CO above a certain level, the power generation performance will decline, or depending on the concentration, power generation will not be possible at all. There is a serious problem that it ends up. Since the deterioration of the catalytic activity due to the CO poisoning is remarkable especially at low temperatures,
This problem is particularly serious in the case of a low temperature operation type fuel cell.

Therefore, pure hydrogen is preferable as a fuel for a fuel cell using such a platinum-based electrode catalyst,
From a practical point of view, various fuels that are cheap and have excellent storage properties, or have already been equipped with a public supply system [eg, methane or natural gas (LNG), petroleum gas (LPG) such as propane, butane, etc.] , Hydrocarbons such as naphtha, kerosene, and light oil, alcohol-based fuels such as methanol, city gas, and other fuels for hydrogen production] The fuel cell power generation system incorporating such a reforming facility is being widely spread. However, since such reformed gas generally contains a considerable concentration of CO in addition to hydrogen, this CO is converted into CO ₂ which is harmless to the platinum-based electrode catalyst, and the CO concentration in the fuel is reduced. There is a strong demand for the development of a technology for reducing this. At that time, the concentration of CO is usually 100 ppm
It is said that it is desirable to reduce the concentration to the low level below.

In order to solve the above problems, as one of means for reducing the concentration of CO in fuel gas (hydrogen-containing gas such as reformed gas), a shift reaction represented by the following formula (1) A technique utilizing (water gas shift reaction) has been proposed.

CO + H ₂ O = CO ₂ + H ₂ (1) However, in the method using only this shift reaction, there is a limit to the reduction of the CO concentration due to restrictions on chemical equilibrium, and in general, the CO concentration is 1%. It is difficult to

Therefore, as a means for reducing the CO concentration to a lower concentration, a method has been proposed in which oxygen or a gas containing oxygen (such as air) is introduced (added) into the reformed gas to convert CO into CO _2. ing. However, in this case, since a large amount of hydrogen is present in the reformed gas, when attempting to oxidize CO, hydrogen is also oxidized, and the CO concentration may not be sufficiently reduced.

As a method for solving this problem,
When oxygen or a gas containing oxygen is introduced into the reformed gas to oxidize CO into CO ₂ , a method of using a catalyst that selectively oxidizes only CO can be considered.

As a CO oxidation catalyst, catalyst systems such as Pt / alumina and Pd / alumina have been conventionally known. However, since these catalysts have low selectivity for CO oxidation, they can be used like a reformed gas. In order to reduce a small amount of CO in a large amount of hydrogen to a low concentration of 100 ppm or less, a large amount of hydrogen must be sacrificed by oxidation at the same time.

Japanese Examined Patent Publication No. 39-21742 describes a method of selectively oxidizing CO from ammonia synthesis gas using a catalyst in which platinum, ruthenium, rhodium are supported on silica, alumina or the like. According to the method described in the publication, at a slightly higher pressure of about 5 kg / cm ² G or more, C in hydrogen-containing gas in a temperature range of 60 to 160 ° C.
O is selectively oxidized to reduce the CO concentration to 2 to 650 ppm. However, in this publication, in order to obtain a very low CO concentration at the outlet, the carbon dioxide content in the introduced gas needs to be 1% or less, and in the hydrogen-containing gas containing more carbon dioxide than that. It is stated that the outlet CO concentration cannot be reduced sufficiently. The publication also states that the amount of carbon dioxide in the introduced gas may be 1% or more if the CO content is not targeted to be 10 ppm or less, but the carbon dioxide concentration is actually 17%. Looking at the example in which the gas of 100% is introduced, the outlet CO
The concentration is 1000 ppm or more. In the fuel cell system, the carbon dioxide concentration is at least 17% or more, usually about 20 to 30%, and the outlet CO concentration is 100 p.
Considering that it is necessary to reduce to pm or less, it is understood that the technique described in this publication cannot be directly applied to this fuel cell system. Further, in the fuel cell system, it is desirable to operate at a low pressure of about atmospheric pressure to about 4 kg / cm ² G in order to improve power generation efficiency, and in this respect, the technique of the publication is difficult to apply.

In Japanese Patent Laid-Open No. 53-53596, CO is selectively oxidized in a reformed gas for synthesizing ammonia by using a noble metal catalyst such as platinum and the steam content in the introduced gas is adjusted. , A method for preventing deterioration of catalyst performance is described. In the examples described in this publication, 20 to 6
Since the reaction is performed at a very low temperature of 0 ° C., maintaining a low catalyst layer temperature in the fuel cell system requires a large cooling device, which is disadvantageous in terms of compactness and cost. Is. This is because the selective oxidation reaction of CO is an exothermic reaction, and unless a special cooling mechanism is provided, the temperature of the catalyst layer rises significantly with the progress of the reaction. When the temperature of the catalyst actually rises, the rate of hydrogen oxidation reaction also generally increases, so that the selectivity of CO oxidation tends to decrease, and as a result, the outlet CO concentration cannot be sufficiently reduced. In order to prevent this, a method of controlling the temperature of the catalyst layer by circulating a cooling medium may be considered, but the optimum temperature range for the selective oxidation of CO has a narrow width of 40 ° C. in the above example. It is difficult to maintain the catalyst temperature at a narrow temperature.

Further, in Japanese Unexamined Patent Publication (Kokai) No. Hei 5-201102, the oxidation removal reaction of CO is carried out by using a catalyst composed of Rh and Ru at a reaction temperature of 120 ° C. or less and oxygen / C of feed gas
It is described that the O ratio is smaller than 1. However, even in this publication, it is described that it is desirable to maintain the catalyst temperature in the temperature range of 80 to 100 ° C.,
It is difficult to control the temperature of the catalyst layer within the range of 20 ° C. in this way, especially when the apparatus is upsized.

[0015]

An object of the present invention is to stably use CO in a reformed gas containing a large amount of carbon dioxide over a wide temperature range by using a catalyst having a CO selective oxidation ability over a wide temperature range. By developing a technology that efficiently and selectively oxidizes and changes to carbon dioxide, a hydrogen-containing gas with a sufficiently reduced CO concentration can be obtained without the need for an operation and a device for strictly controlling the temperature of the catalyst layer. It is to provide a method of efficiently manufacturing. By using the hydrogen-containing gas thus obtained as a fuel for a hydrogen-oxygen type fuel cell, it is possible to prevent the hydrogen electrode of the fuel cell of the power generator from being poisoned by CO, thereby prolonging the life of the cell and improving the output. It is possible to improve stability.

[0016]

Means for Solving the Problems As a result of intensive studies aimed at achieving the above-mentioned object, the present inventor has found that reforming containing a large amount of hydrogen can be achieved by using a platinum catalyst having L-type zeolite as a carrier. It was found that CO in gas can be selectively oxidized to CO ₂ in a wide temperature range, and the present invention has been completed based on this finding.

That is, the present invention is a reformed gas obtained by reforming a fuel for hydrogen production which can be converted into a fuel gas containing at least hydrogen by a reforming reaction, the reformed gas containing hydrogen as a main component and CO ₂ on dry basis 17-4
A mixed gas containing a 0% by volume concentration and a CO-containing reforming gas mixed with an oxygen-containing gas is brought into contact with a catalyst to selectively oxidize CO and convert it into CO ₂ to produce a fuel. A method for producing a hydrogen-containing gas for a battery, wherein the CO
The present invention provides a method for producing a hydrogen-containing gas for a fuel cell, which comprises using an L-type zeolite carrying a platinum-containing compound as the selective oxidation catalyst.

1. Reforming Step of Fuel In the method of the present invention, a reformed gas (containing hydrogen as a main component and CO
CO contained in the fuel gas containing hydrogen) is selectively oxidized using a catalyst to produce a desired hydrogen-containing gas in which the CO concentration is sufficiently reduced. A reforming step for obtaining the reformed gas The (reforming reaction) can be performed by an arbitrary method such as a method implemented or proposed in a conventional fuel cell system, as shown below. Therefore, in a fuel cell system equipped with a reforming device in advance, the reformed gas may be prepared in the same manner by using it as it is.

The fuel used as a raw material for this reforming reaction contains hydrogen as a main component and C by a suitable reforming reaction.
Various types and compositions of hydrogen-producing fuels that can be converted to a fuel gas containing O can be used, and specifically, for example, hydrocarbons such as methane, ethane, propane, butane (either alone or as a mixture). , Or natural gas (L
NG), petroleum gas (LPG), naphtha, kerosene, light oil, hydrocarbon fuels such as synthetic petroleum, methanol, ethanol,
Alcohols such as propanol and butanol (may be used alone or as a mixture), as well as various city gases, syngas,
Coal or the like can be used as appropriate. Of these,
What kind of fuel for hydrogen production should be used may be determined in consideration of various conditions such as the scale of the fuel cell system and the circumstances of fuel supply, but normally, methanol, methane or LNG, propane or LPG is used. , Naphtha or lower saturated hydrocarbon, city gas containing methane, etc. are preferably used.

As the above-mentioned reforming reaction, the steam reforming reaction (steam reforming) is the most general, but depending on the raw material, a more general reforming reaction (for example, thermal reforming reaction such as thermal cracking, catalytic cracking). And various catalytic reforming reactions such as shift reaction, partial oxidation reforming, etc.) can be appropriately applied.
At that time, different types of reforming reactions may be appropriately combined and used. For example, since the steam reforming reaction is generally an endothermic reaction, the steam reforming reaction and partial oxidation may be combined to supplement this endothermic amount, or the CO generated by the steam reforming reaction (by-product) may be subjected to a shift reaction. Use H ₂ O
Various combinations are possible, such as reacting with and partially converting it into CO ₂ and H ₂ in advance.

In such a reforming reaction, a catalyst or reaction conditions are generally selected so that the yield of hydrogen is as large as possible, but it is difficult to completely suppress the by-product of CO, and even if the shift reaction However, there is a limit to the reduction of CO concentration in the reformed gas.

Actually, in the steam reforming reaction of hydrocarbons such as methane, the following formula (2) or (3): CH ₄ + 2H _{2 is used in} order to reduce the yield of hydrogen and the by-product of CO. O → 4H ₂ + CO ₂ (2) C _n H _m + 2nH ₂ O → (2n + m / 2) H ₂ + nCO ₂ (3) The conditions should be selected so that the reaction represented by the formula is as selective as possible. preferable.

Similarly, for the steam reforming reaction of methanol, the reaction represented by the following formula (4): CH ₃ OH + H ₂ O → 3H ₂ + CO ₂ (4) is as selective as possible. It is preferred to choose the conditions to occur.

Further, even if CO is modified and modified by utilizing the shift reaction represented by the above formula (1), a considerable concentration of CO remains because the shift reaction is an equilibrium reaction. Therefore, the reformed gas produced by such a reaction contains CO ₂ and unreacted water vapor and a small amount of CO in addition to a large amount of hydrogen.

As the catalyst effective for the reforming reaction, there are known various catalysts depending on the type of raw material (fuel), the type of reaction, the reaction conditions and the like. Specific examples of some of them include, for example, Cu-Zn as an effective catalyst for steam reforming of hydrocarbons and methanol.
O-based catalyst, Cu-Cr ₂ O ₃ -based catalyst, supported Ni-based catalyst, C
u-Ni-ZnO-based catalyst, Cu-Ni-MgO-based catalyst,
Examples thereof include Pd-ZnO-based catalysts, and examples of the catalyst effective for catalytic reforming reaction and partial oxidation of hydrocarbons include supported Pt-based catalysts and supported Ni-based catalysts. Of course, the catalyst that can be used in the reforming reaction in the method of the present invention is not limited to the above-exemplified catalysts, and may be any suitable catalyst depending on the type of raw material (fuel), the type of reaction, the reaction conditions, etc. May be appropriately selected and used. That is, also in the method of the present invention, as the reforming reaction catalyst, various known catalysts such as various known steam reforming catalysts and catalytic reforming catalysts including those exemplified above can be applied.

The reforming device is not particularly limited, and any type such as a device commonly used in a conventional fuel cell system can be applied, but many reforming processes such as steam reforming reaction and decomposition reaction are possible. Since the reaction is an endothermic reaction, generally, a reaction device or a reactor (heat exchanger type reaction device or the like) having a good heat supply property is preferably used. Examples of such a reaction device include a multi-tube reactor and a plate fin reactor, and examples of the heat supply method include heating by a burner or the like, a method using a heating medium, and a catalyst utilizing partial oxidation. The heating includes, but is not limited to, heating by combustion.

The reaction conditions for the reforming reaction differ depending on other conditions such as the raw material used, the reforming reaction, the catalyst, the type of the reaction apparatus, the reaction system, etc., and therefore may be appropriately determined. In any case, the conversion rate of the raw material (fuel) is sufficient (preferably 10%).
It is desirable to select various conditions such that the hydrogen yield rate is as high as possible and the hydrogen yield rate is as high as possible. Further, if necessary, a method of separating unreacted hydrocarbons and alcohols and recycling may be adopted. Further, if necessary, the generated or unreacted CO ₂ or water may be appropriately removed.

In this way, a desired reformed gas having a high hydrogen content and sufficiently reduced fuel components other than hydrogen such as hydrocarbon and alcohol is obtained. The CO concentration in the obtained reformed gas is usually
It is suitable to keep it at 0.02 mol or less, preferably 0.01 mol or less, and the CO concentration is adjusted to such a relatively low concentration at the stage of this reforming process to thereby prevent the subsequent oxidation. The burden of reaction becomes lighter.

Although the method of the present invention shows good results in the selective oxidation of CO even with a reformed gas having a low carbon dioxide content, the catalyst used in the present invention was used in the selective oxidation of CO. In this case, it is possible to efficiently selectively oxidize CO even under conditions where a large amount of carbon dioxide is present in the reformed gas. Therefore, in the present invention, the reformed gas having a carbon dioxide concentration that is generally used in a fuel cell system, that is, carbon dioxide, is contained in an amount of 17 to 40% by volume, preferably 20%.
A reformed gas containing 30% by volume is used. When the content of carbon dioxide is less than 17% by volume, the effect of the present invention cannot be fully utilized, and in order to reduce the carbon dioxide in the reformed gas to less than 17% by volume, gas cleaning is performed. Since it must be removed by a device or the like, there are inconveniences that the control becomes complicated, the system becomes large, and the cost increases. On the other hand, when the content of carbon dioxide exceeds 40% by volume, the hydrogen partial pressure in the resulting hydrogen-containing gas for a fuel cell becomes low and the voltage of the fuel cell is lowered.

2. CO Selective Oxidation Removal Step In the method of the present invention, the reformed gas obtained as described above is mixed with an oxygen-containing gas, and the mixed gas is brought into contact with a catalyst to selectively remove CO in the reformed gas. Oxidize to.

As the catalyst used in the method of the present invention, an L-type zeolite carrying a platinum-containing compound, or an L-type zeolite carrying a halogen-containing compound in addition to the platinum-containing compound, if necessary, is used.

L-type Zeo used as a raw material for the above catalyst
The composition of light is 0.9-1.3M _{2 / n}O ・ Al₂O₃・
5.0-7.0SiO₂・ 0-9H₂O (where M is Al
Potassium metal or alkaline earth metal, n is the source of M
Indicates the child price. ) Is represented. L-type zeolite
Is a synthetic zeolite.
The method is not particularly limited, and specifically, for example, Japanese Patent Laid-Open No.
JP-A-8-133833, pages 9-10 and JP-A-59-
In accordance with the method described in page 5 of the publication No. 80333, etc.
Those formed are preferably used. Commercial L-type Zeo
Light may be used as a raw material.

The catalyst used in the present invention is the above-mentioned raw material L.
It is prepared by supporting platinum-containing compound or platinum-containing compound and halogen-containing compound on type zeolite.

The platinum-containing compound used in the present invention is not particularly limited as long as it serves as a platinum source, but usually a platinum salt is preferably used. Specific examples of preferable platinum salts include tetraammineplatinum chloride, chloroplatinic acid, chloroplatinate, tetraammineplatinum hydroxide, and dinitrodiaminoplatinum.

As the halogen-containing compound used in the present invention, various compounds can be used.
Inorganic halogen-containing compounds are preferably used. Specific examples of the halogen-containing compound preferably used include chlorine-containing compounds such as hydrogen chloride and ammonium chloride, fluorine-containing compounds such as hydrogen fluoride and ammonium fluoride, iodine-containing compounds such as hydrogen fluoride and ammonium iodide, and odors. Examples thereof include bromine-containing compounds such as hydrogen chloride and ammonium bromide. These halogen-containing compounds may be used alone or in combination of two or more.

The method for supporting the platinum-containing compound, or the platinum-containing compound and the halogen-containing compound on the L-type zeolite is a method in which the platinum component, or the platinum component and the halogen component are supported on the starting L-type zeolite. There is no particular limitation as long as it is carried out, and it can be carried out by a normal pressure impregnation method, a vacuum impregnation method, an infiltration method, an ion exchange method or the like. When both the platinum-containing compound and the halogen-containing compound are loaded on the starting material L-type zeolite, they may be loaded simultaneously, or the platinum-containing compound may be loaded in advance and then the halogen-containing compound may be loaded, or vice versa. But it is possible.

The loading amount of the platinum-containing compound and the halogen-containing compound in the loading treatment is not particularly limited, but the loading amount of the platinum-containing compound is usually 0.1 to 5.0% by weight as platinum based on the total weight of the catalyst. Is preferred, especially 0.3 to 1.5
The weight% range is optimal. If the platinum content is too low, the CO oxidation activity will be insufficient. On the other hand, if the loading rate is too high, the amount of platinum used will be unnecessarily excessive and the catalyst cost will increase. When the halogen-containing compound is supported, the supported amount of the halogen-containing compound is usually preferably 0.1 to 5% by weight, particularly 1.0 to 3.0% by weight, as halogen based on the total weight of the catalyst. Is the best. The halogen-containing compound has the effect of making platinum highly dispersed on the L-type zeolite and changing the electronic state of platinum, but in a small amount such that the amount of halogen is less than 0.1% by weight of the total weight of the catalyst. If used, the effect of supporting such a halogen-containing compound may not be obtained. Further, if the amount of the halogen-containing compound used is too large, the halogen desorbed from the catalyst may cause corrosion of the apparatus.

The conditions of the supporting treatment are not particularly limited and may be appropriately selected according to various situations, but usually from room temperature to 90 ° C.
In 1 minute to 10 hours, the L-type zeolite may be contacted with the platinum-containing compound or the platinum-containing compound and the halogen-containing compound.

Upon preparation of the catalyst used in the present invention, a natural or synthetic inorganic oxide such as alumina, silica, aluminosilicate or the like can be added as a binder, if necessary. The amount of these binders to be used is usually 5 to 90% by weight, preferably 10 to 30% by weight, based on the total weight of the catalyst.

The binder may be added before the supporting treatment of the platinum-containing compound or the platinum-containing compound and the halogen-containing compound on the L-type zeolite, or depending on the method of the supporting treatment, the addition of the binder and the supporting treatment. It is also possible to do and at the same time.

When the binder is added before the supporting treatment of the platinum-containing compound or the halogen-containing compound, a mixture (kneading) of the L-type zeolite and the binder may be added before the supporting treatment of these compounds. , Eg drying, molding,
By subjecting to various post-treatments such as firing, a product having desired properties and shapes can be obtained. When firing is performed at this stage, it is generally 400 to 600 ° C., preferably 430 to
A suitable fired product can be obtained by carrying out the treatment at a temperature of 550 ° C. for 30 minutes to 2 hours, preferably 30 minutes to 1 hour. The molding may be carried out after the platinum-containing compound or the halogen-containing compound is supported. Usually, a method in which an L-type zeolite and a binder are kneaded, molded as needed, and then subjected to a firing treatment, and then a platinum-containing compound or a halogen-containing compound is carried on the obtained molded product by an impregnation method or the like. Is preferably adopted. After the platinum-containing compound and the halogen-containing compound are supported on the L-type zeolite in this way, they may be molded or treated again into a desired shape.

After supporting the platinum-containing compound or the halogen-containing compound on the L-type zeolite, it is usually preferable to carry out a calcination treatment or a calcination treatment and hydrogen reduction before using as a catalyst. Firing at this stage is usually 200 to 50.
At a temperature of 0 ° C., preferably 250 to 350 ° C., for 30 minutes
It is suitable to carry out for 5 hours, preferably for 30 minutes to 3 hours. Hydrogen reduction is usually 400 to 600 under hydrogen flow.
C., preferably 500 to 550.degree. C., for 1 to 48 hours, preferably 1 to 24 hours.

The shape and size of the catalyst thus prepared are not particularly limited, and examples thereof include powder, sphere, granule, honeycomb, foam, fiber, cloth, plate, Various commonly used shapes and structures such as a ring shape can be used.

A mixed gas obtained by mixing a reformed gas and an oxygen-containing gas is brought into contact with the catalyst obtained as described above, and C
A selective oxidation reaction of O is performed.

As the oxygen-containing gas added to and mixed with the reformed gas, pure oxygen (O ₂ ), air or oxygen-enriched air is usually preferably used. The addition amount of the oxygen-containing gas is preferably oxygen / CO (molar ratio) of 0.5 to 5,
More preferably, it is adjusted to be 1 to 4. If this ratio is small, the CO removal rate will be low, and if it is large, the hydrogen consumption will be too large, which is not preferable.

The reaction pressure is usually atmospheric pressure to 10 kg / cm.
^The pressure is ² G, preferably atmospheric pressure to 4 kg / cm ² G, and particularly preferably ^{2 to 4} kg / cm ² G. Here, if the reaction pressure is set to be too high, it is economically disadvantageous because the power for pressurization needs to be increased by that amount, and especially when the pressure exceeds 10 kg / cm ² G There is also a problem that the safety is reduced because the regulation is legally required and the explosion limit is widened.

The oxidation reaction is usually performed at 60 to 200 ° C.
Preferably, it can be suitably carried out in a very wide temperature range of 60 to 180 ° C. while stably maintaining the selectivity for CO oxidation. If the reaction temperature is lower than 60 ° C., the reaction rate becomes slow, so that the CO removal rate (conversion rate) tends to be insufficient in a practical SV (space velocity) range.

Since the CO oxidation reaction in this CO selective oxidation step is an exothermic reaction, the temperature of the catalyst layer rises due to the reaction. When the temperature of the catalyst layer becomes too high, the selectivity of the catalyst for CO oxidation usually deteriorates. However, in the method of the present invention, CO can be selectively oxidized in a wide temperature range of usually 60 to 200 ° C. by using the above-mentioned catalyst, so that the catalyst temperature can be improved without strict control of the catalyst temperature. It is possible to efficiently reduce the CO concentration in the gaseous matter, and to produce a hydrogen-containing fuel gas suitable for a low temperature fuel cell using platinum as an electrode, particularly a polymer electrolyte fuel cell.

The oxidation reaction is usually performed by GHSV.
(Supply volume velocity in standard state of feed gas and apparent space-based space velocity of oxidation catalyst layer used) is 500
It is preferable to select it in the range of 0 to 50,000 h ⁻¹ . Here, if GHSV is decreased, a large reactor is required, while if GHSV is increased too much, CO
Removal rate decreases. Preferably 6000-16000
Select in the range of h ^-1 .

The reactor used for this selective oxidation reaction is not particularly limited, and various types can be applied as long as they satisfy the above reaction conditions, but since this oxidation reaction is an exothermic reaction. In order to facilitate temperature control, it is desirable to use a reaction device or a reactor having a good reaction heat removal property. Specifically, for example, a multi-tube type or a plate fin type heat exchange type reactor is preferably used. Depending on the case, a method of circulating the cooling medium in the catalyst layer or circulating the cooling medium outside the catalyst layer can also be adopted. However, as described above, the advantage of the catalyst used in the method of the present invention is that the outlet CO concentration can be sufficiently reduced over a wide temperature range, so that the catalyst layer is not cooled by the reactor so strictly. However, the flexibility of reactor design is increased.

Since the hydrogen-containing gas produced by the method of the present invention has a sufficiently reduced CO concentration as described above, poisoning and deterioration of the platinum electrode catalyst of the fuel cell can be sufficiently reduced. , Its life and power generation efficiency
The power generation performance can be greatly improved.

The hydrogen-containing gas obtained by the present invention can be suitably used as a fuel for various H ₂ combustion type fuel cells, and in particular, platinum (platinum catalyst) is used as at least the electrode of the fuel electrode (negative electrode). It is advantageously used as a fuel supply to various types of H ₂ combustion fuel cells of the type used (phosphoric acid fuel cells, KOH fuel cells, low-temperature fuel cells such as solid polymer electrolyte fuel cells). be able to.

In the conventional fuel cell system, between the reformer (when the reformer is followed by the modifier, the modifier is also regarded as a part of the reformer) and the fuel cell, the present invention is used. Incorporating an oxygen introducing device and an oxidation reaction device according to the method described above, or using a catalyst already equipped with an oxygen introducing device and an oxidation reaction device, the reaction conditions are adjusted as described above by using the catalyst as an oxidation catalyst. This also makes it possible to construct a fuel cell system that is far superior to the conventional one.

[0054]

EXAMPLES The present invention will now be described more specifically by showing examples of the present invention, but the present invention is not limited to these examples.

Example 1 L-type zeolite [manufactured by Tosoh Corporation; TSZ-500KO]
20 parts by weight of a silica binder [manufactured by Nissan Kagaku KK; Snowtex] was added to 100 parts by weight of A)], and kneading and molding were performed. After that, air calcination was performed at 500 ° C. for 2 hours to form a silica binder-molded L-type zeolite (molded product shape:
1/16 inch cylinder) was obtained. Next, 1.39 g of a 3.6 wt% hydrogen chloride aqueous solution and ammonium fluoride 0.09
7 g, tetraammine platinum chloride 0.171 g and ion-exchanged water 3.6 g were mixed to prepare an impregnation liquid. The impregnating liquid thus prepared was gradually added dropwise to 10 g of the above-mentioned silica binder-molded L-type zeolite while stirring to simultaneously carry out platinum and halogen loading treatment. Then, after drying overnight at room temperature, it was treated in air at 300 ° C. for 30 minutes (calcination).

The fired product obtained was pulverized to 16 to 32 mesh, 1 cc was filled in a tubular reactor, and then treated in a hydrogen stream at 540 ° C. for 1 hour (hydrogen reduction). Then
GHSV1000 mixed gas having the following composition was added to the catalyst layer.
Oxidation reaction was carried out by circulating in an amount of ⁰ h ⁻¹ . The reaction pressure was 3 kg / cm ² G, and the catalyst layer temperature, CO concentration at reactor inlet, oxygen concentration at reactor inlet, and nitrogen concentration at reactor inlet were shown in Table 1.
Varying as described, the CO concentration at the reactor outlet in each reaction was measured.

Supply gas composition CO: 0.6 to 1% by volume, O ₂ : 2 to 3% by volume, CO ₂ : 25% by volume, N ₂ :
7.5 to 11.3% by volume, H ₂ O: 0.7% by volume, H ₂ :
balance

[0058]

[Table 1]

[0059]

According to the method of the present invention, it is possible to efficiently and selectively oxidize CO in a hydrogen-containing reformed gas having a high CO ₂ content over a wide temperature range and convert it into CO _2. Therefore, poisoning of platinum at the hydrogen electrode of a hydrogen-oxygen type fuel cell with CO can be prevented, the life of the cell can be extended, and the output stability can be improved. In addition, since the catalyst used in the present invention has a wide temperature at which CO has a selective oxidation ability, strict temperature control of the catalyst layer in the reactor is not required, and the degree of freedom in reactor design is increased.

Claims (9)

[Claims] 1. A reformed gas obtained by reforming a fuel for producing hydrogen, which is convertible into a fuel gas containing at least hydrogen by a reforming reaction, wherein the reformed gas contains hydrogen as a main component and CO ₂ is dried. CO 2 is contained at a concentration of 17 to 40% by volume, and a mixed gas obtained by mixing an oxygen-containing gas with the reformed gas containing CO is brought into contact with a catalyst to selectively oxidize CO to produce CO ₂ In the method for producing a hydrogen-containing gas for a fuel cell by converting the hydrogen-containing gas for a fuel cell, the L-type zeolite carrying a platinum-containing compound is used as the CO selective oxidation catalyst. Production method. 2. The selective oxidation reaction of CO is performed at 60 to 200.
The method for producing a hydrogen-containing gas for a fuel cell according to claim 1, which is carried out at a reaction temperature of ° C. 3. The hydrogen for a fuel cell according to claim 1, wherein the platinum compound is selected from the group consisting of tetraammineplatinum chloride, chloroplatinic acid, chloroplatinate, tetraammineplatinum hydroxide and dinitrodiaminoplatinum. Method for producing contained gas. 4. The method for producing a hydrogen-containing gas for a fuel cell according to claim 1, 2 or 3, wherein the CO selective oxidation catalyst is L-type zeolite carrying the platinum-containing compound and the halogen-containing compound. 5. The halogen-containing compound is selected from the group consisting of hydrogen chloride, ammonium chloride, hydrogen fluoride, ammonium fluoride, hydrogen iodide, ammonium iodide, hydrogen bromide and ammonium bromide. 4. The method for producing a hydrogen-containing gas for a fuel cell according to 4. 6. The method for producing a hydrogen-containing gas for a fuel cell according to claim 1, wherein the CO selective oxidation catalyst further contains a binder. 7. The method for producing a hydrogen-containing gas for a fuel cell according to claim 1, wherein a catalyst obtained by firing and reducing with hydrogen the selective oxidation catalyst of CO is used in the selective oxidation reaction of CO. 8. The selective oxidation reaction of CO is carried out at atmospheric pressure to 10 k.
The method for producing a hydrogen-containing gas for a fuel cell according to claim 1, wherein the reaction pressure is g / cm ² G. 9. The method for producing a hydrogen-containing gas for a fuel cell according to claim 1, wherein the hydrogen-containing gas for a polymer electrolyte fuel cell is produced.