JPH0834601A - Production of hydrogen-containing gas for fuel cell - Google Patents

Abstract

PURPOSE:To efficiently produce a hydrogen-containing gas suppressing a poisoning and a deterioration of a platinum electrode catalyst when used as a fuel of a H2 combustion type fuel cell using platinum for the electrode of the fuel cell to prevent a voltage drop of the fuel cell and favorably usable as the fuel of the fuel cell. CONSTITUTION:In a modified gas obtained by modifying the fuel for producing hydrogen which is convertible to a fuel gas containing at least hydrogen by a modifying reaction, and in a producing method of the hydrogen containing gas for the fuel cell by oxidizing selectively CO to convert to CO2 by mixing the modified gas consisting essentially of the hydrogen and containing CO2 and CO and oxygen-containing gas and by passing through a catalyst layer, a part of the oxygen-containing gas is mixed in the modified gas divided into several times in midway of the catalyst layer.

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. The present invention relates to a method for efficiently producing a hydrogen-containing gas which can be removed and advantageously used as a fuel for a fuel cell.

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 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 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 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 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)
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.

When the selective oxidation of CO is carried out, the following both primary and secondary reactions occur. (Main reaction) CO + 1 / 2O ₂ → CO ₂ + H ₂ (Sub reaction) In order to selectively react H ₂ + 1 / 2O ₂ → H ₂ O CO, the main reaction is efficient while suppressing the above-mentioned side reaction. It is necessary to carry out the reaction under the reaction conditions that proceed to. That is, it is necessary to limit the temperature so that the reaction rate of the main reaction is significantly higher than the reaction rate of the side reaction.
However, since both reactions are extremely exothermic reactions, if the reaction is carried out in an adiabatic reactor, the temperature may increase by several hundreds of degrees Celsius depending on the conditions. Therefore, effective cooling is required to maintain the catalyst layer at a temperature suitable for the selective oxidation reaction. For cooling the reactor, a system in which a cooling pipe is installed in the catalyst layer and a cooling medium (for example, water) is circulated can also be used.

As a prior art relating to the selective oxidation of CO, for example, Japanese Patent Laid-Open No. 376577/1990 describes that an oxygen introduction device and a CO oxidation device are installed between a reformer and a fuel cell. There is. However, in this publication, there is no clear explanation about the selective oxidation method of CO, that is, what kind of conditions (catalyst, reaction conditions, etc.) should actually be used for the oxidation.

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.

Further, in Japanese Unexamined Patent Publication (Kokai) No. 5-201102, a reaction of oxidizing and removing CO is carried out using a catalyst composed of Rh and Ru at a reaction temperature of 120.degree.
It is described that the O molar ratio is smaller than 1, but there is a description about the reaction temperature, the reaction pressure, and the oxygen / CO ratio, but there is no description about the temperature control method.

[0013]

The object of the present invention is to provide a fuel electrode.
H type that uses platinum (platinum catalyst) for the (negative electrode) electrode
₂Combustion fuel cell (phosphoric acid fuel cell, KOH fuel cell
Low temperature operation including ponds and solid polymer electrolyte fuel cells
When used as fuel for a dynamic fuel cell, etc.
Control the poisoning and deterioration of the electrode catalyst to reduce the voltage of the fuel cell.
Can be prevented and can be used as fuel for fuel cells.
The hydrogen-containing gas can be used to maximize the temperature distribution in the catalyst layer.
To provide a method for efficiently manufacturing by controlling to appropriate conditions.
It is in.

[0014]

As a result of intensive studies to achieve the above object, the present inventor divided a part of the oxygen-containing gas to be reacted with the reformed gas into several times in the middle of the catalyst layer. It was found that the selective oxidation of CO can be effectively carried out even in high GHSV by mixing them, and the present invention has been completed based on these findings.

That is, the present invention is a reformed gas obtained by reforming a hydrogen-producing fuel that 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 A reformed gas containing CO ₂ and CO and an oxygen-containing gas are mixed and passed through a catalyst layer to form C
In a method for producing a hydrogen-containing gas for a fuel cell by selectively oxidizing O and converting it to CO ₂ , a part of the oxygen-containing gas is divided into several times in the middle of the catalyst layer to obtain a reformed gas. The present invention provides a method for producing a hydrogen-containing gas for a fuel cell, characterized in that

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
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.

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 decomposition or 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, the 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 obtain the yield of hydrogen and suppress 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 various conditions should be selected so that the reaction 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.

Furthermore, even if CO is modified and reformed by utilizing the shift reaction represented by the above formula (1), since this shift reaction is an equilibrium reaction, a considerable amount of CO remains. 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. 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 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 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 reformed gas obtained as described above is mixed with an oxygen-containing gas, and the mixed gas is passed through a catalyst layer to select CO in the reformed gas. However, it is important to mix a part of the oxygen-containing gas with the reformed gas in the middle of the catalyst layer several times. Therefore,
A flow path for the oxygen-containing gas is installed in the middle of the catalyst layer so that the oxygen-containing gas can be mixed.

When the oxygen-containing gas is completely mixed just before the catalyst layer, the oxygen concentration becomes higher from the inlet portion to the middle portion of the catalyst layer than in the latter half portion. In the portion where the oxygen concentration is high, the oxidation reaction rapidly occurs, the temperature of the catalyst rises, and not only CO but also hydrogen is often burned, so that the outlet CO concentration may not be sufficiently reduced. By introducing the oxygen-containing gas into several portions in small portions and introducing it into the oxidation catalyst layer in the CO oxidation reactor, the temperature of the catalyst layer can be selectively oxidized by CO without biasing the oxygen concentration in the reactor. High GHS because it is possible to maintain the optimum temperature evenly.
It becomes possible to selectively oxidize and remove CO while maintaining V.

As the oxygen-containing gas mixed with the reformed gas, pure oxygen (O ₂ ), air or oxygen-enriched air is usually preferably used. The mixing amount of the oxygen-containing gas is preferably adjusted so that oxygen / CO (molar ratio) is preferably 0.5 to 5, more preferably 1 to 3.
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.

As a reactor used for the selective oxidation reaction,
There is no particular limitation, and various types can be applied as long as the oxygen-containing gas can be supplied from the middle of the catalyst layer.However, since this oxidation reaction is an exothermic reaction, the reaction is performed to facilitate temperature control. It is desirable to use a reaction device or a reactor having a good heat removal property. Specifically, for example, a multi-tube type or a plate fin type heat exchange type reactor is preferably used. The oxygen-containing gas, which is supplied from the middle, is preferably supplied to the catalyst layer filled in the tubular reactor, for example, from the center of the tube or from several points in the middle of the tube. The amount of the oxygen-containing gas supplied from the middle is preferably 20 to 80% with respect to the total amount of the oxygen-containing gas.

The catalyst used in the method of the present invention is not particularly limited and is preferably Pt, Au or Rh.
A catalyst containing at least one metal selected from Ru and Ru is preferably used. Among these, a gold-containing catalyst is preferably used. 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 immobilizing gold or the metal oxide used as a mixture or composition with gold (ultrafine particles or the like) is itself inert to hydrogen oxidation under the above-mentioned 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, and 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 which will be 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
No. 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.

The shape of the metal oxide for fixing gold (catalyst carrier) used in the preparation of the catalyst is not particularly limited, and for example, it can 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 preparation of the above catalyst, the gold-immobilized metal oxide (precipitate or the like) deposited by the coprecipitation method or the gold-immobilized metal oxide carrier immobilized on the gold-immobilized metal oxide carrier is immobilized. 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, based on 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, a 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 reaction pressure is usually atmospheric pressure to 10 kg / cm.
Perform within ² G pressure range. 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 kg / cm
^If it exceeds ² G, it will be subject to the regulations of the High Pressure Gas Control Law, and the explosion limit will be widened, which will cause a problem of reduced safety.

In the oxidation reaction, GHSV (supply volume velocity in standard state of supply gas and apparent volume-based space velocity of oxidation catalyst layer to be used) is usually 1000 to 50.
It is preferable to select it in the range of 000 h ^-1 . Here, decreasing GHSV increases the size of the device, while
If GHSV is too large, the CO removal rate may decrease.

The oxidation reaction is usually 0 to 200.
It can be suitably carried out at a temperature of 50 ° C, preferably 50 to 90 ° 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, if the reaction temperature exceeds 200 ° C., the selectivity of CO oxidation becomes insufficient, hydrogen is apt to be preferentially oxidized, and the CO removal rate is lowered, which is likely to cause problems.

In the oxidation reaction, GHSV (the supply volume velocity in the standard state of the supply gas and the apparent space-based space velocity of the oxidation catalyst layer used) is usually 1000 to 50.
It is preferable to select it in the range of 000 h ^-1 . Here, decreasing GHSV increases the size of the device, while
If GHSV is too large, the CO removal rate may decrease.

As described above, the hydrogen-containing gas produced by the method of the present invention has a sufficiently low CO concentration, and can 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.

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 at least for 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.

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 device according to the method of 1), it becomes possible to construct a fuel cell system far superior to the conventional one.

[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 Fe ₂ O ₃ -supported alumina obtained by impregnating 100 g of alumina pellets having a particle diameter of 3 mm with a 0.5 M ferric nitrate aqueous solution at 400 ° C. for 5 hours was treated with chloroauric acid. It was immersed in 300 ml of an aqueous potassium carbonate solution having a pH of 10 such as 1 g. 20 ml of 3.7% formalin aqueous solution
Was gradually added dropwise over 50 minutes. The obtained pellets were washed with water, dried under vacuum, and calcined in air at 400 ° C. to obtain a gold-containing catalyst (Au / Fe ₂ O ₃ catalyst). The gold content in the catalyst after calcination was 0.5% by weight, which corresponded to 4 g per liter of catalyst.

Gold-containing catalyst (catalyst A) 16 to 3 obtained above
1 cc of pulverized to 2 mesh was filled in a tubular reactor to form a catalyst layer having a length of about 3.5 cm. This catalyst layer was filled with hydrogen-containing gas (hydrogen: 74% by volume, CO: 1% by volume,
CO ₂ : 25% by volume) and air were passed through. Air is supplied so that the total supply amount becomes O ₂ / CO molar ratio = 2, and the reformed gas is mixed with an amount of air so that O ₂ / CO molar ratio = 1 before the reformed gas contacts the catalyst. Then, the remaining air was mixed from the central portion of the catalyst layer. The reaction conditions are GHSV: 16
The reaction was carried out at 000 h ^-1 , reaction pressure: 3.5 kg / cm ² G, reaction temperature: 55 ° C. As a result of the reaction, the CO concentration at the reactor outlet could be reduced to 2 to 9 ppm even at high GHSV. FIG. 1 shows the temperature distribution in the catalyst layer.

Comparative Example 1 The same amount of air was supplied as in Example 1, and the CO oxidation reaction was carried out under the same conditions as in Example except that the reforming gas was mixed at the inlet of the reactor. As a result, the CO concentration at the outlet of the reactor could only be reduced to 100 ppm. FIG. 1 shows the temperature distribution in the catalyst layer.

As can be seen from FIG. 1, in Comparative Example 1, GH
Since the SV is high, the temperature of the catalyst layer is considerably higher than the set temperature of 55 ° C., and it is considered that the selectivity of CO oxidation is lowered accordingly. In Example 1, it is considered that the temperature rise is small even under the same conditions, and therefore the selectivity of CO oxidation can be kept high.

Example 2 A double-tube type reaction tube having a reaction tube diameter of 1 inch and an outer cooling chamber diameter of 4 inches was produced (see FIG. 2).
150cc as it is without crushing catalyst A (3mm spherical)
It filled and formed the catalyst layer of about 25 cm in length. Two reactors were produced, both were similarly charged with a catalyst, and then connected in series. Then, a hydrogen-containing gas (hydrogen: 74% by volume, CO: 1% by volume, CO ₂ : 25% by volume) and air were passed. Air is supplied so that the total supply amount becomes O ₂ / CO molar ratio = 2, and O is supplied before the hydrogen-containing gas comes into contact with the catalyst.
_{The 2} / CO molar ratio = 1 was mixed, and the remaining air was mixed just before the second stage reactor. The amount of supply gas was such that the total gas GHSV was 2500 h ⁻¹ with respect to the catalyst amount for the two stages of the reactor. The reaction pressure is normal pressure, and the supply gas is at a gas temperature of 7 at the entrance of the first catalyst layer.
It was preheated with an electric heater so as to reach 0 ° C. Tap water (about 15 ° C.) for cooling was circulated at 2 liter / min in the cooling chamber outside the reaction tube.

As a result of the reaction, the maximum temperature of the first-stage catalyst layer was suppressed to 120 ° C., the maximum temperature of the second-stage catalyst layer was suppressed to 100 ° C., the CO concentration was 1500 ppm at the first-stage outlet, and the second-stage outlet was The CO concentration could be reduced to 10 ppm.

Example 3 The reactor and the amount of catalyst were the same as in Example 2, the total supply amount of air to be introduced was O ₂ / CO molar ratio = 1.5, and O was added before the hydrogen-containing gas contacted the catalyst. _{The 2} / CO molar ratio = 1 was mixed, and the remaining air was mixed just before the second reactor.

As a result, the maximum temperature of the first stage and the CO concentration at the outlet were the same as in Example 2, but the maximum temperature of the second stage was 50.
The temperature was suppressed to 0 ° C., and the CO concentration at the outlet of the second stage was 25 ppm. Comparative Example 2 The catalyst A was crushed in one reactor used in Example 2 in 3 units.
The catalyst layer was filled with 00 cc to form a catalyst layer having a length of 50 cm. Then, a hydrogen-containing gas (hydrogen: 74% by volume, CO: 1% by volume, CO ₂ : 25% by volume) and air were passed. All of the air was mixed before the hydrogen-containing gas came into contact with the catalyst so that the supply amount was O ₂ / CO molar ratio = 2. The amount of supply gas was the same as in Example 2 such that the total gas GHSV was 2500 h ⁻¹ with respect to the catalyst amount. Other conditions are the same as those in the second embodiment.

As a result, the catalyst temperature rapidly increased near the entrance of the catalyst layer, and the maximum temperature reached 230 ° C. As the catalyst temperature increased, the selectivity for CO decreased,
The CO concentration at the outlet was 2000 ppm.

As can be seen from the comparison between Example 2 and Comparative Example 2, by introducing the feed air by dividing it into two portions, it is possible to suppress the local heat generation of the catalyst layer. As a result, with the same catalyst amount, the CO concentration at the outlet was 2000 ppm in Comparative Example 2.
In contrast, in Example 2, the outlet CO concentration is 10 pp.
It can be seen that m can be effectively reduced.

From the third embodiment, in the second and subsequent stages,
It can be seen that CO can be considerably reduced even if the amount of air introduced is reduced. By thus introducing the air by dividing it into several times, it is possible to reduce the total air supply amount, suppress wasteful consumption of hydrogen serving as the fuel of the fuel cell, and improve the efficiency of the system.

[0063]

According to the present invention, the fuel electrode (negative electrode) is used as an electrode.
Type H using platinum (platinum catalyst) ₂Combustion fuel cell
(Phosphoric acid fuel cell, KOH fuel cell, polymer electrolyte
Low temperature operating fuel cells such as degradable fuel cells
Poisoning of the platinum electrocatalyst when used as fuel
And deterioration can be prevented to prevent a fuel cell voltage drop.
Can be advantageously used as fuel for fuel cells
The hydrogen-containing gas is controlled to optimize the temperature distribution in the catalyst layer.
Can be manufactured efficiently.

That is, according to the method of the present invention, the temperature distribution of the catalyst layer can be controlled to the optimum conditions for the selective oxidation of CO, so that the selective oxidation of CO can be performed effectively even at high GHSV. The oxidation reactor can be downsized, and the fuel cell system can be downsized.

[Brief description of drawings]

FIG. 1 is a graph showing a temperature change in a catalyst layer.

2 is an explanatory view of the reactor used in Example 2. FIG.

Claims (1)

[Claims] 1. A reformed gas obtained by reforming a hydrogen-producing fuel that 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 and CO 2. In the method for producing a hydrogen-containing gas for a fuel cell by mixing a reformed gas containing oxygen with an oxygen-containing gas, selectively passing CO through a catalyst layer to convert CO into CO _2. A method for producing a hydrogen-containing gas for a fuel cell, wherein a part of the gas is divided into several times in the middle of the catalyst layer and mixed with the reformed gas.