JPH0748101A - Method for producing hydrogen-containing gas for fuel cell - Google Patents

Abstract

(57) [Abstract] [Purpose] Selectivity of CO in reformed gas containing hydrogen as a main component obtained by steam reforming of various hydrogen producing fuels to CO ₂ which is harmless to electrodes of fuel cells. Well catalytically oxidized,
A technique for easily reducing the CO concentration to a low concentration of 100 ppm or less has been developed, and when used as a fuel for a fuel cell, poisoning and deterioration of a platinum electrode catalyst can be suppressed to significantly improve the power generation performance of the fuel cell. A method for efficiently producing a hydrogen-containing gas having a high hydrogen content and a sufficiently reduced CO concentration. An oxygen-containing gas is added to a reformed gas containing hydrogen as a main component and containing CO, which is obtained by reforming a hydrogen-producing fuel that can be converted into a fuel gas containing at least hydrogen by a reforming reaction. In a method for producing a hydrogen-containing gas for a fuel cell by contacting a mixed gas formed by mixing with a catalyst to selectively oxidize and remove CO, the oxidation-removal reaction of CO is performed in the presence of a gold-containing catalyst, Pressure 2kg / cm
Method for producing hydrogen-containing gas for fuel cell under conditions of ² G or more and less than 10 kg / cm ² G

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, 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. Fuels for fuel cells that have been removed, in particular, various types of H ₂ combustion fuel cells (phosphoric acid fuel cells, KOH fuel cells, solid fuel cells) of the type in which platinum (platinum catalyst) is used at least for the electrode of the fuel electrode (negative electrode) It can be advantageously used as a supply fuel to low-temperature operation fuel cells such as polymer electrolyte fuel cells).
The present invention relates to a method for efficiently producing a hydrogen-containing gas having a sufficiently reduced CO concentration.

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

[0003]

2. Description of the Related Art Power generation by a fuel cell has attracted particular attention in recent years because it has various advantages such as low pollution, little energy loss, and advantages such as selection of installation site, expansion, and operability. . 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),
The so-called hydrogen-oxygen fuel cell (low-temperature operation type fuel cell) that uses oxygen (air or the like) as an oxidant has been most developed and put into practical use, and is expected to become more and more popular in the future.

There are various types of such hydrogen-oxygen fuel cells depending on the type of electrolyte and the structure of the electrodes. 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 such a fuel cell, especially in the case of a low temperature operation type fuel cell, platinum (platinum catalyst) is used for the electrode. However, the platinum (platinum catalyst) used for the electrodes is C
Since CO is liable to be poisoned by O, if CO is contained in the fuel at a certain level or more, the power generation performance is lowered, or depending on the concentration, power generation cannot be performed at all, which is a serious problem. The deterioration of catalytic activity due to this CO poisoning is
This problem is particularly serious in the case of a fuel cell that operates at a low temperature, since the problem is remarkable at a low temperature.

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

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

Therefore, as a means for reducing the CO concentration to a lower concentration, oxygen or a gas containing oxygen (such as air) is introduced (added) into the reformed gas, and a C is selectively used by using a catalyst.
Method for converting O to CO ₂ (CO selective oxidation removal method)
Or ideas have been proposed.

For example, Japanese Unexamined Patent Publication (Kokai) No. 3-276577 describes that an oxygen introduction device and a CO oxidation device are installed between the reformer and the fuel cell. But,
In this publication, there is no clear description of the selective oxidation method of CO [what kind of conditions (catalyst, reaction conditions, etc.) should be actually used for oxidation], and specific examples (CO Data, such as how much the concentration of can be reduced and how much hydrogen consumption can be suppressed at that time) is not shown. Therefore, this publication merely shows the concept (concept) of removing CO by oxidation, and specifically describes a hydrogen-containing gas production technology (CO selective removal technology) suitable for fuel for fuel cells. It is not presented in. This is because with an ordinary oxidation catalyst, hydrogen will also be oxidized when trying to oxidize CO, and if the reaction conditions are unsuitable even if a catalyst is selected, it is possible to oxidize CO selectively and to a low concentration. Because you can't.

In fact, as a CO oxidation catalyst,
Various transition metal-based catalysts such as Pt catalysts and Pd catalysts are known, but these catalysts have the drawback that they are susceptible to self-poisoning effects at low temperatures, and even if they have high activity, they are
Due to insufficient selectivity for O 2 oxidation, it is not practical for this purpose because a large amount of hydrogen must be sacrificed by oxidation at the same time to reduce the CO concentration to a low concentration of, for example, 100 ppm or less. .

Further, Japanese Patent Application Laid-Open No. 2-153801 discloses a technique in which the oxidation removal reaction of CO is carried out using an Au catalyst at a reaction temperature of 200 ° C. or lower. However, in the case of this conventional technique, the catalyst activity is insufficient and the conditions such as the reaction pressure are also inadequate, so it is necessary to lower the space velocity (SV) in order to obtain a high CO conversion rate. Moreover, since the selectivity of CO oxidation is not sufficient, the CO concentration cannot be sufficiently reduced if hydrogen oxidation is suppressed.

On the other hand, relatively recently, ultrafine gold particles having a particle size of 10 nm or less are treated with cobalt oxide (Co ₃ O ₄ ) or iron oxide (F).
e ₂ O ₃ or Fe ₃ O ₄ ), further MgO, TiO ₂ ,
A catalyst supported on an oxide carrier such as Al ₂ O ₃ or SiO ₂ is
It has been found and reported to have high activity for the oxidation of CO and the oxidation of H ₂ or hydrocarbons [for example, Haruta, Sukai, Vol. 28 (5), pp. 333-342
(1990), etc.]. However, in these reports, such a supported gold catalyst is used to produce a fuel for a fuel cell as described above (selective oxidation of CO from a hydrogen-containing gas such as a reformed gas containing hydrogen as a main component and CO as an impurity). There is no description about the application to the removal reaction). In fact, as far as these reports are seen, the supported gold ultrafine particle catalyst has a high activity for the oxidation of CO as described above, but exhibits an extremely high activity for the oxidation of hydrogen alone.
Mixed gas of hydrogen and CO (especially the above reformed gas)
Whether or not CO in it can be preferentially oxidized preferentially, and whether there are such reaction conditions, cannot be predicted at all.

[0013]

SUMMARY OF THE INVENTION An object of the present invention is to convert CO in a reformed gas containing hydrogen as a main component, which is obtained by steam reforming of various fuels for producing hydrogen, into an electrode of a fuel cell (platinum). We have developed a technology to catalytically oxidize CO ₂ which is harmless to the system electrode catalyst) with high selectivity and easily reduce the CO concentration to a low concentration of 100 ppm or less, and to add platinum (platinum catalyst) to the electrode of the fuel electrode (negative electrode). The platinum electrode catalyst when used as a fuel for a type of H ₂ combustion fuel cell to be used (phosphoric acid fuel cell, KOH fuel cell, low-temperature fuel cell including solid polymer electrolyte fuel cell, etc.) It is possible to significantly improve the power generation performance of a fuel cell by suppressing the poisoning and deterioration of hydrogen, and therefore, it can be advantageously used as a fuel of such a fuel cell, and the hydrogen content is high.
It is to provide a method for efficiently producing a hydrogen-containing gas in which the O concentration is sufficiently reduced.

[0014]

In order to achieve the above object, the present inventors selectively oxidize CO in the reformed gas (preferentially) and sufficiently suppress the consumption of hydrogen. In order to reduce the CO concentration to a sufficiently low concentration, intensive research has been conducted focusing on what kind of catalyst should be used under what reaction conditions. As a result, an appropriate amount of oxygen-containing gas (oxygen, air, oxygen-enriched air, etc.) is mixed with the reformed gas, and this is contacted with a specific gold-containing catalyst at an appropriate temperature and a reaction pressure within a specific range. By letting
It is easily reduced the CO concentration after having been able to selectively oxidize efficiently CO ₂ to CO in the reformed gas is suitably suppressed consumption by oxidation of hydrogen to a significantly low concentration of 100ppm or less I found what I could do. That is, it was found that this method can efficiently obtain a hydrogen-containing gas suitable as a fuel for a low temperature operation type fuel cell using a platinum electrode catalyst as described above,
The present invention has been completed based on these findings and facts.

That is, the present invention contains hydrogen as a main component and contains CO, which is obtained by reforming a fuel (fuel for hydrogen production) that can be converted into a fuel gas containing at least hydrogen by a reforming reaction. In the method for producing a hydrogen-containing gas for a fuel cell by bringing a mixed gas obtained by mixing an oxygen-containing gas into a reformed gas into contact with a catalyst to selectively oxidize and remove CO, a reaction for oxidizing and removing CO is performed. , 2 kg / cm ² G or more and 10 kg / c in the presence of a gold-containing catalyst
The present invention provides a method for producing a hydrogen-containing gas for a fuel cell, which is carried out under a condition of less than m ² G.

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) is selectively oxidized under the specific reaction conditions (specific reaction pressure range) using the specific catalyst (gold-containing catalyst), and the CO concentration is sufficiently reduced. The desired hydrogen-containing gas is produced, and the reforming step (reforming reaction) for obtaining the reformed gas is performed by any method such as the method carried out or proposed in the conventional fuel cell system, as shown below. Can be performed by the method of. 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
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.

In order to prevent the poisoning of the reforming reaction catalyst and the electrode catalyst of the fuel cell, and the suppression of pollution, it is desirable and necessary to use the reforming reaction raw material having a low sulfur content. If desired, a desulfurization step may be provided before the reforming step. Depending on the case, this desulfurization may be performed simultaneously with or after the reforming reaction.

The steam reforming reaction (steam reforming) is the most common reforming reaction, 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 CO by-product, and even if the shift reaction However, there is a limit to the reduction of CO concentration in the reformed gas.

In practice, 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 obtain a hydrogen yield and suppress CO by-product. 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 reformed 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.

Various catalysts are known as effective catalysts for the reforming reaction depending on the type of raw material (fuel), the type of reaction, the reaction conditions, etc., and some of them are specifically described. For example, as a catalyst effective for steam reforming of hydrocarbons and methanol, for example, Cu-Zn
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 conventional fuel cell systems 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 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 hydrocarbons 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.

2. CO Selective Oxidation Removal Step In the method of the present invention, the oxygen-containing gas is mixed with the reformed gas obtained as described above, and the mixed gas is brought into contact with a predetermined oxidation catalyst to remove CO in the reformed gas. Selective (priority)
In this case, a specific catalyst called a gold-containing catalyst is used as the oxidation catalyst, and the catalytic oxidation reaction is performed for 2 k.
It is important to carry out in a specific pressure range of g / cm ² G or more and less than 10 kg / cm ² G.

As the oxygen-containing gas to be added to and mixed with the reformed gas, pure oxygen (O ₂ ), air or oxygen-enriched air is usually preferably used. The amount of the oxygen-containing gas added is such that the concentration of oxygen (O ₂ ) in the mixed gas (the supply gas used for the oxidation reaction) after mixing is sufficient to completely oxidize CO to CO _2. The oxygen concentration is usually 1 to 10% by volume.
It is suitable to adjust it to about 2 to 5% by volume. If the oxygen concentration is less than 1% by volume, the CO removal rate may be insufficient. On the other hand, if it is higher than 10% by volume, the CO removal rate can be further improved, but in general, It is not preferable because it consumes a large amount.

As described above, the mixed gas obtained by mixing the reformed gas and the oxygen-containing gas is brought into contact with the gold-containing catalyst to carry out a predetermined oxidation reaction (selective oxidation removal reaction of CO). The catalytic oxidation reaction is carried out in a certain pressure range of and 10 kg / cm ² less than G at 2 kg / cm ² G or more as described above. Here, if the reaction pressure is less than ² kg / cm ² G, CO cannot be selectively oxidized (removed) to a sufficiently low concentration. That is, in such a low-pressure reaction, the consumption of hydrogen is sufficiently suppressed, and then CO
It becomes difficult to reduce the concentration of 100 to a sufficiently low concentration of 100 ppm or less. On the other hand, if the reaction pressure is set too high, it is economically disadvantageous because the power for increasing the pressure needs to be increased by that amount, and especially 10 k
When it is more than g / cm ² G, there is a problem that the high pressure gas control law regulates it and the explosion limit is widened so that the safety is lowered.

The above-mentioned oxidation reaction can be suitably carried out usually at a temperature of 0 to 150 ° C, preferably 40 to 100 ° C. If the reaction temperature is lower than 0 ° 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. On the other hand, the reaction temperature is 1
If it exceeds 50 ° C., the selectivity of CO oxidation becomes insufficient, hydrogen is likely to be preferentially oxidized, and problems such as a reduction in CO removal rate tend to occur.

The oxidation reaction is usually performed by GHSV.
(Supply volume velocity in standard state of feed gas and apparent volume-based space velocity of oxidation catalyst layer used) is 100
It is preferable to select it in the range of 0 to 50,000 h ⁻¹ . Here, reducing GHSV means reducing the amount of gas supplied per unit time or increasing the amount of catalyst. Therefore, if this GHSV is set to a too small value, the amount of gas processed per unit time is reduced. (The amount of hydrogen-containing gas supplied to the fuel cell) becomes insufficient, or the amount of catalyst becomes excessive, and the reactor becomes larger than necessary. In some cases, problems such as an increase in oxidation (consumption) of hydrogen due to oxygen remaining after the oxidation of CO may occur. From this point of view, in general, it is practically disadvantageous if GHSV is smaller than 1000 h ^-1 . On the other hand, if GHSV is too large, the CO removal rate becomes insufficient.

The reactor used for the oxidation reaction is
There is no particular limitation, and various types can be applied as long as they satisfy the above reaction conditions.However, since this oxidation reaction is an exothermic reaction, it is necessary to remove the heat of reaction in order to facilitate temperature control. It is desirable to use a good reactor or reactor. Specifically, for example, a multi-tube type or a plate fin type heat exchange type reactor is preferably used.

Next, the gold-containing catalyst used in the method of the present invention will be described in detail. The selective CO oxidation is achieved by using a specific catalyst called a gold-containing catalyst,
As this gold-containing catalyst, a catalyst composed of gold and a suitable metal oxide is preferably used, and this catalyst is a mixture of gold and a metal oxide, or gold is immobilized or supported on a suitable metal oxide. (Hereinafter, this form is referred to as a gold-immobilized metal oxide, the metal oxide used for immobilizing or supporting the gold is referred to as a gold-immobilizing metal oxide), and further, gold and a metal oxide. It can be used as a catalyst in various forms such as a mixture of products and / or the gold-immobilized metal oxide supported on another carrier.

The gold in such a gold-containing catalyst is preferably in the form of ultrafine particles (highly dispersed state), and particularly, the particle size is 10 nm or less, and further, the particle size is 1 to 5 nm.
It is preferable that they are carried (immobilized) or contained in the above state. Here, since large gold particles having a particle size of more than 10 nm generally do not show sufficient catalytic activity for a predetermined oxidation reaction, those containing only such large gold particles have insufficient catalytic activity. However, even if the catalyst containing a large amount of such large gold particles satisfies the catalytic activity, expensive gold is wasted and the catalyst cost increases.

The metal oxide for fixing gold or the metal oxide used as a mixture or composition with gold (ultrafine particles or the like) is itself inactive to oxidize hydrogen under the predetermined reaction conditions. Or, those having an activity but exhibiting no extreme activity are preferably used, and specific examples thereof include iron oxide, manganese oxide, cobalt oxide, zinc oxide, nickel oxide, magnesium oxide, magnesium hydroxide, tin oxide. , Oxides of single metals such as titanium oxide, aluminum oxide, beryllium oxide, zirconium oxide, silicon oxide, lanthanum oxide, or iron, manganese, cobalt, zinc, nickel, magnesium, tin, titanium, aluminum, beryllium, zirconium Oxides consisting of two or more metal elements such as nickel, silicon and lanthanum Etc. can be mentioned. Further, these single metal oxides and complex oxides may be mixed or used as a complex, if necessary.

In the present invention, among the various types of gold-containing catalysts described above, a catalyst comprising a gold-immobilized metal oxide as described above (that is, a gold-immobilized metal oxide catalyst or other catalysts described later). A catalyst supported on a suitable carrier or support is preferably used. This is because gold immobilized on metal oxide (supported) is supported on the metal oxide surface in ultrafine particle form with good dispersibility as compared to that prepared by mixing gold and metal oxide. This is because it is easy to carry out, the effective surface area of gold becomes large, and the contact area between the gold particles and the metal oxide also becomes large, so that excellent catalytic performance is exhibited.

Various methods are known as a method for preparing such a gold-immobilized metal oxide catalyst or a method for immobilizing gold in the form of ultrafine particles on a metal oxide. Specifically, for example, (1) Coprecipitation method (method described in Japanese Patent Publication No. 12934/1993), (2) Uniform precipitation method (JP-A-62-1
155937), (3) drop neutralization precipitation method (method described in JP-A-63-252908), (4) pH control neutralization precipitation method (JP-A 63- 25
2908), (5) carboxylic acid metal salt addition method (such as the method described in JP-A-2-252610), and (6) reducing agent addition method (JP-A-63-25290).
8), (7) precipitation-precipitation method (method described in JP-A-3-97623, etc.), and (8) impregnation method.

The catalyst composed of the various kinds of gold-immobilized metal oxides used in the oxidation reaction in the method of the present invention can be suitably prepared by various methods including these known methods. That is, for the various types of gold-immobilized metal oxides, a metal oxide for gold immobilization is prepared or prepared in advance, and a predetermined gold compound (eg, chloroauric acid) is added to the metal oxide (catalyst carrier). Is used as a gold raw material to immobilize (carry) ultrafine gold particles, or a predetermined gold compound and an appropriate metal compound that is a raw material of a predetermined metal oxide for immobilizing gold are used as preparation raw materials. It can be prepared by various methods such as a method of obtaining a metal oxide in which ultrafine gold particles are immobilized (supported) by a precipitation method, or a method of a combination thereof.

Chloroauric acid is usually most widely used as the gold raw material used as the catalyst preparation raw material, but the gold raw material is not limited to this, and depending on the case, gold halide such as gold chloride or oxidation may be used. Various gold compounds such as gold, gold hydroxide and gold cyanide complex, gold colloid and the like are appropriately used. As a raw material of the metal oxide for immobilizing gold, for example, various compounds of a predetermined metal such as nitrate, sulfate, chloride and acetate can be used. These preparation raw materials are appropriately selected according to the preparation method and the like.

There is no particular limitation on the shape of the metal oxide for fixing gold (catalyst carrier) used in the preparation of the catalyst, and for example, it may be formed into a specific shape such as powder, gel or sol. Or not, or beads, pellets,
It can be used in various shapes or forms such as granules or the like which are molded in a desired shape in advance.

In the above catalyst preparation, gold-immobilized metal oxide (precipitate or the like) precipitated by the coprecipitation method or the like, or gold-immobilized metal obtained by immobilizing it on a metal oxide carrier for gold immobilization The metal oxide (supported material, etc.) is usually subjected to post-treatments such as washing, drying, and calcination, and if necessary, appropriately shaped to obtain a catalyst in a desired shape. Post-treatments such as drying and calcination can be performed according to a conventional method such as a known method. The firing temperature at that time is usually 2
It is suitable to select in the range of about 00 to 600 ° C, preferably 300 to 400 ° C.

The content of gold in the gold-containing catalyst such as the gold-immobilized metal oxide catalyst thus obtained is usually, relative to the total amount of gold and metal oxide (metal oxide for gold immobilization).
It is suitable to select in the range of 0.1 to 30% by weight, preferably 0.3 to 1.0% by weight. If the content of gold is too small, the oxidation activity of CO will be insufficient. On the other hand, if the supporting rate is too high, the amount of gold used will be unnecessarily excessive and the catalyst cost will increase. It may be difficult to stably fix it in the form of ultrafine particles, which may cause problems.

As described above, various desired metal oxides for immobilizing gold can be suitably obtained. The catalyst thus obtained can be preferably used as the catalyst for the oxidation reaction in the present invention, but as described above, this gold-immobilized metal oxide may be further used in another suitable carrier (or support), if necessary. It may be used by supporting it on the body. From a more practical point of view, a method in which the gold-immobilized metal oxide is supported on a carrier or support having an appropriate shape and excellent structural stability is widely used.

As such a carrier (or support), a wide variety of metal oxide carriers, metal carriers, or composites thereof are preferably used. Examples of the material of the metal oxide-based carrier include a single oxide-based material or a composite oxide-based material such as alumina, silica, titania, silica alumina, silica magnesia, alumina titania, cordierite, mullite, or zeolite. Can be illustrated. Examples of the metal-based carrier include stainless steel, iron, lead, copper, and aluminum-based single metal-based carriers and alloy-based carriers. The shape and size of these carriers (or supports) are not particularly limited, and for example, generally used such as powder, sphere, granule, honeycomb, foam, fiber, cloth, plate and ring. Various shapes and structures are available.

The gold-immobilized metal oxide catalyst supported on such a carrier or support can be obtained by various methods. For example, the gold-immobilized metal oxide is prepared in the above-mentioned catalyst preparation. It may be obtained by previously supporting it on another suitable carrier as a carrier, or alternatively, a gold-immobilized metal oxide prepared in advance or its precursor in the preparation stage may be used as the predetermined carrier or support. For example,
It can also be suitably obtained by carrying it by various carrying methods such as a deposition method, a wash coat method and a spray coat method.

The present invention in which the catalyst containing gold in the form of ultrafine particles prepared as described above, particularly the catalyst composed of a gold-immobilized metal oxide, selectively and efficiently oxidizes CO under the above reaction conditions. Principles of important effects (Details of catalytic function)
Although it has not been sufficiently clarified at this point in time, CO is selectively activated and adsorbed on gold ultrafine particles having a particle size of 10 nm or less, and the adsorbed CO is adsorbed on the bonding surface (boundary portion) ) Or by spilling over to the surface of the metal oxide, CO can be presumed to be selectively oxidized to CO ₂ at the above low temperature.

As described above, it is possible to efficiently and easily obtain a desired hydrogen-containing gas for a fuel cell, which has a high hydrogen content and a CO concentration of 100 ppm or less and is sufficiently reduced to a low concentration. .

Since the hydrogen-containing gas produced by the method of the present invention has a sufficiently low CO concentration as described above, it is possible to sufficiently reduce the poisoning and deterioration of the platinum electrode catalyst of the fuel cell, and its life. Also, the power generation efficiency and power generation performance can be significantly improved. Moreover, since the CO concentration in the exhaust gas is sufficiently low, it is advantageous in terms of preventing pollution. Moreover, since the hydrogen content is high, it has excellent power generation performance. Therefore, this hydrogen-containing gas can be suitably used as a fuel for various H ₂ combustion fuel cells, and in particular, various types of H of the type that uses platinum (platinum catalyst) for at least the fuel electrode (negative electrode) electrode. It can be advantageously used as a fuel to be supplied to a _two- combustion fuel cell (phosphoric acid fuel cell, KOH fuel cell, low-temperature fuel cell including solid polymer electrolyte fuel cell, etc.).

It should be noted that the present invention is provided between the reformer of the conventional fuel cell system (when the reformer is followed by the modifier, the modifier is also regarded as a part of the reformer) and the fuel cell. By incorporating the oxygen introducing apparatus and the oxidation reaction apparatus according to the method of 1. or using the gold-containing catalyst as an oxidation catalyst when the reaction apparatus is already equipped with the oxygen introducing apparatus and the oxidation reaction apparatus. It is possible to configure a fuel cell system far superior to the conventional one also by adjusting to.

[0051]

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 γ-alumina beads having a specific surface area of 326 m ² / g and having a diameter of 2 mm impregnated with ferric nitrate were calcined at 400 ° C. for 4 hours to carry Fe ₂ O ₃ -supported alumina beads. Got The supported amount of Fe ₂ O ₃ was 21.8% by weight. 30 g of the Fe ₂ O ₃ -supporting alumina beads was put into 600 cc of water, and the pH was adjusted to 8.0 using a 1 mol aqueous solution of sodium carbonate. A 0.01 mol aqueous solution containing 15 g of chloroauric acid was added to this solution to deposit a precipitate on the beads, followed by aging for about 1 hour. During the precipitation and aging, the temperature of the solution was maintained at 70 to 80 ° C. and sufficient stirring was performed. Further, a sodium carbonate aqueous solution is added at a proper time to adjust the pH to 7.
As a result of being prepared between 7 and 8.5, p of this solution after aging was
H was 8.0. The catalyst precursor (γ-
Alumina carrying Fe ₂ O ₃ and a precipitate containing gold) was washed with running water for about 1 hour, dried at 120 ° C. for 12 hours, and then calcined at 400 ° C. for 4 hours. Example Catalyst A was obtained. The specific surface area of the catalyst A of this example was 220 m ² / g. The gold content was 0.5% by weight, which corresponded to 3.8 g / l of catalyst.

The gold-containing catalyst (Catalyst A) obtained above was added to
1 cc of powder pulverized to 32 mesh was filled in a tubular reactor, and a mixed gas having the following composition was passed through the catalyst layer under the following conditions to carry out a predetermined oxidation reaction.

Supply gas composition CO: 1%, O ₂ : 2
%, CO ₂ : 15%, N ₂ : 7.5%, H ₂ : balan
ce GHSV = 10000h ⁻¹ reaction temperature: 55 ° C., reaction pressure: normal pressure to 5 kg / cm ² G
(See FIG. 1) The reaction results thus obtained are shown in FIG.

As shown in FIG. 1, it can be understood that CO can be effectively removed even with a low oxygen content under the reaction conditions of the present invention.

[0056]

INDUSTRIAL APPLICABILITY In the method of the present invention, in particular, from a reformed gas containing hydrogen as a main component, which is obtained by steam reforming of hydrocarbons such as methanol and methane and various fuels for hydrogen production described above. The specific oxidization catalyst that removes CO by oxidation with an oxygen-containing gas and has high activity and high selectivity for CO oxidation (that is, gold-immobilized metal oxide containing gold in an ultrafine particle form, etc.). Since a gold-containing catalyst) is used and the reaction is carried out under appropriate reaction conditions (that is, conditions such as the above-mentioned specific reaction pressure range and the above-mentioned appropriate reaction temperature), the CO CO ₂ which is harmless to the electrode (platinum-based electrode catalyst) of the fuel cell has good selectivity to CO ₂ and can be easily oxidized and reduced to a sufficiently low concentration of 100 ppm.

Therefore, according to the present invention, since the CO concentration is sufficiently low, it is advantageous for suppressing poisoning and deterioration of the platinum-based electrode catalyst of the fuel cell, and the power generation performance (efficiency and life) can be remarkably improved. Therefore, a hydrogen-containing gas for a fuel cell that can be advantageously used as a fuel for the above-mentioned various low-temperature operation fuel cells (phosphoric acid fuel cell, KOH fuel cell, solid polymer electrolyte fuel cell, etc.) is used. It is possible to provide a method for easy manufacturing, which can significantly improve the performance and the like of the conventional fuel cell system.

[Brief description of drawings]

FIG. 1 is a graph showing the reaction results of Example 1.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical indication location H01M 8/06 RG (72) Inventor Toshio Matsuhisa 7-2-10 Hikoshimasako-cho, Shimonoseki-shi, Yamaguchi Prefecture No. Toyo CSI Co., Ltd. (72) Inventor Hiroshi Iida 1280, Kamizumi, Sodegaura-shi, Chiba Idemitsu Kosan Co., Ltd.

Claims (7)

[Claims] 1. A reformed gas containing hydrogen as a main component and containing CO, which is obtained by reforming a hydrogen-producing fuel convertible into a fuel gas containing at least hydrogen by a reforming reaction, contains oxygen. In a method for producing a hydrogen-containing gas for a fuel cell by bringing a mixed gas obtained by mixing gases into contact with a catalyst to selectively oxidize and remove CO, the oxidation-removal reaction of CO is performed in the presence of a gold-containing catalyst. And pressure 2kg /
A method for producing a hydrogen-containing gas for a fuel cell, which is carried out under the conditions of cm ² G or more and less than 10 kg / cm ² G. 2. The method for producing a hydrogen-containing gas for a fuel cell according to claim 1, wherein the gold-containing catalyst is a catalyst containing ultrafine gold particles. 3. The gold-containing catalyst according to claim 1, wherein ultrafine gold particles are immobilized on a metal oxide containing Fe ₂ O ₃ as a main component and supported on a catalyst carrier. For producing a hydrogen-containing gas for a fuel cell. 4. The method for producing a hydrogen-containing gas for a fuel cell according to claim 2, wherein the ultrafine gold particles or the immobilized ultrafine gold particles in the gold-containing catalyst have a particle size of 10 nm or less. 5. The hydrogen-containing gas for a fuel cell according to claim 1, wherein the hydrogen-producing fuel used for preparing the reformed gas is a fuel composed of hydrocarbon and / or oxygen-containing hydrocarbon. Production method. 6. The fuel for producing hydrogen used for preparing the reformed gas is methane, propane, butane, methanol, natural gas (LNG), city gas, petroleum gas (LPG), naphtha, kerosene, light oil or mixed alcohol. Claims 1-5
The method for producing a hydrogen-containing gas for a fuel cell according to any one of claims. 7. The concentration of CO in the produced gas after the oxidation removal reaction of CO is 100 ppm or less.
7. The method for producing a hydrogen-containing gas for a fuel cell according to any one of 6 to 6.