JP2001213612A - Process of producing hydrogen containing gas for fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a process of producing hydrogen containing gas for a fuel cell having an appropriate concentration of oxygen to oxidize CO on the platinum electrode catalyst at the introduction of hydrogen containing gas in a fuel cell of a solid polymer type and the like capable of defending against the poisoning of the electrode catalyst. SOLUTION: In this process of producing hydrogen containing gas for a fuel cell, CO in a hydrogen containing gas is selectively oxidized by O2 and removed, and O2 concentration in the hydrogen containing gas after the selective oxidation and removal of CO is adjusted in the range of 0.05 to 1.5% by volume.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a hydrogen-containing gas for a fuel cell, and more particularly to a method for producing a hydrogen-containing gas for a fuel cell in which the O ₂ concentration is suitably adjusted.

[0002]

2. Description of the Related Art In recent years, power generation by a fuel cell has attracted particular attention in recent years because it has various advantages such as low pollution, low energy loss, and advantages in terms of installation location selection, expansion, operability, and the like. I have. Various types of fuel cells are known depending on the type of fuel or electrolyte, operating temperature, and the like. Among them, hydrogen is used as a reducing agent (active material) and oxygen (air or the like) is used as an oxidizing agent. The development of a hydrogen-oxygen fuel cell (low-temperature operation type fuel cell) is the most advanced, and it is expected that the hydrogen-oxygen fuel cell will become more popular in the future.

There are various types of such hydrogen-oxygen fuel cells depending on the type of electrolyte, the type of electrodes, and the like. Representative examples thereof include a phosphoric acid type fuel cell, a KOH type fuel cell, There is a polymer electrolyte fuel cell 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 (a platinum catalyst) is used for an electrode. However, since the platinum used for the electrode is easily poisoned by CO, C
When O is contained at a certain level or more, there is a serious problem that the power generation performance is reduced or power cannot be generated at all depending on the concentration.

Accordingly, 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 which are inexpensive and have excellent storage properties or are already equipped with a public supply system [for example, methane or natural gas (LNG), propane,
Petroleum gas (LPG) such as butane, naphtha, gasoline, kerosene, light oil, etc., various hydrocarbon fuels, alcohol fuels such as methanol, city gas, and other fuels for hydrogen production). It has become common to use such hydrogen-containing gas, and fuel cell power generation systems incorporating such reforming equipment have been widely used. However, since such a reformed gas generally contains a considerable concentration of CO in addition to hydrogen, this CO is converted into CO ₂ 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 set at 1,0.
It is said that it is desirable to reduce the concentration to a low concentration of 00 vol ppm or less, preferably 100 vol ppm or less, more preferably 10 vol ppm or less.

In order to solve the above problem, as one of means for reducing the concentration of CO in a fuel gas (hydrogen-containing gas in a reformed gas), a shift reaction represented by the following formula (1) is used. A technique using (water gas shift reaction) has been proposed. CO + H ₂ O = CO ₂ + H ₂ (1) However, in the reaction using only this shift reaction, there is a limit to the reduction of the CO concentration due to restrictions on chemical equilibrium. In general, the CO concentration is reduced to 1% by volume or less. It is difficult to do.

Accordingly, as a means for reducing the CO concentration to a lower concentration, a method has been proposed in which oxygen or an oxygen-containing gas (air or the like) is introduced into the reformed gas to convert CO into CO ₂ . However, in this case, since a large amount of hydrogen is present in the reformed gas, when oxidizing CO, the hydrogen is also oxidized, and the CO concentration may not be sufficiently reduced. As a solution to this problem,
CO or C is introduced by introducing oxygen or oxygen-containing gas into the reformed gas.
When oxidizing to O ₂ , a method using a catalyst that selectively oxidizes only CO can be considered.

Conventionally, CO oxidation catalysts include Pt / alumina, Pt / SnO ₂ , Pt / C, Co / TiO ₂ ,
Although catalyst systems such as popcalite and Pd / alumina are known, these catalysts are not sufficiently resistant to humidity, have a low and narrow reaction temperature range, and have low selectivity for CO oxidation. At the same time, large amounts of hydrogen must be sacrificed by oxidation in order to reduce the small amount of CO in the presence of large amounts of hydrogen such as gas to a low concentration of 10 ppm by volume or less.

Japanese Patent Application Laid-Open No. Hei 5-201702 discloses a method for producing a CO-free hydrogen-containing gas for selectively removing CO from the hydrogen-enriched CO-containing gas and supplying the CO to an automotive fuel cell system. I have. A catalyst in which Rh or Ru is supported on an alumina carrier is used as a catalyst, but has a problem that it can be applied only to a low CO concentration.

[0009]

Problems to be Solved by the Invention
Publications such as No. 6 disclose various oxidation catalysts. These catalysts solve the above-mentioned problems, but if CO cannot be removed at the time of load fluctuation, the platinum-based electrode catalyst is poisoned. In addition, since CO is expected to be generated by the reverse shift reaction, O ₂
Is left in an appropriate amount to oxidize CO (C
O + 1 / 2O ₂ → CO ₂ ) was found to be preferable.

[0010] Further, US Pat.
Indicates that O in the hydrogen-containing gas_TwoTo 2-4capacity% Added, C
O oxidation reaction occurs on the platinum catalyst of the fuel electrode (negative electrode)
A method is disclosed. But that O_TwoContains a large amount of
When the fuel is directly introduced into the fuel cell, the fuel electrode (negative
The oxidation reaction of hydrogen (H_Two+1/2
O _Two→ H_TwoO) also occurs and the reaction is exothermic and
As a result, sintering of the platinum electrode catalyst occurs (battery
Polymer electrolyte)
It is also found that there is a problem that it is easily damaged
Was.

The present invention has been made in view of the above, and
When introducing a hydrogen-containing gas to the polymer electrolyte fuel cell or the like, by causing an oxidation reaction of CO on the platinum electrode catalyst, suppression of poisoning of the electrode catalyst is capable, O ₂ concentration suitable amount It is an object of the present invention to provide a method for producing a hydrogen-containing gas for a fuel cell.

[0012]

Means for Solving the Problems As a result of earnest studies, the present inventors have adjusted the O ₂ concentration in the hydrogen-containing gas after the selective oxidation removal of CO to 0.05 to 1.5% by volume. It has been found that the object of the invention can be effectively achieved, and the present invention has been completed. That is, the gist of the present invention is as follows. 1. The CO in the hydrogen-containing gas to a method for selective oxidation is removed by O _2, and characterized in adjusting the O ₂ concentration in the hydrogen-containing gas after CO selective oxidation removal 0.05-1.5 volume% Of producing a hydrogen-containing gas for a fuel cell. 2. 2. The method for producing a hydrogen-containing gas for a fuel cell according to the above item 1, wherein the selective oxidation and removal of CO is performed using a catalyst in which ruthenium is supported on a carrier composed of titania and alumina. 3. 2. The method for producing a hydrogen-containing gas for a fuel cell according to the above item 1, wherein the selective oxidative removal of CO is performed using a catalyst comprising ruthenium and an alkali metal and / or an alkaline earth metal supported on a carrier comprising titania and alumina. 4. The method for producing a hydrogen-containing gas for a fuel cell according to any one of the above 1 to 3, wherein the hydrogen-containing gas is a gas obtained by reforming or partially oxidizing a raw material for hydrogen production.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. The present invention will be described in the order of (1) a step of reforming or partially oxidizing a raw material for hydrogen production, and (2) a step of selectively oxidizing and removing CO. (1) Step of reforming or partially oxidizing a hydrogen-producing material In this step, CO contained in a reformed gas or the like obtained by reforming various hydrogen-producing materials is selectively oxidized and removed using a catalyst. Then, a desired hydrogen-containing gas having a sufficiently reduced CO concentration is produced. As shown below, this step can be performed by any method such as a method implemented or proposed in a conventional hydrogen production step, particularly a hydrogen production step in a fuel cell system. Therefore, in a fuel cell system provided with a reformer or the like in advance, a reformed gas or the like may be prepared by using the reformer as it is.

First, reforming or partial oxidation of a raw material for hydrogen production will be described. As raw materials for hydrogen production, hydrocarbons capable of producing a hydrogen-rich gas by steam reforming or partial oxidation, specifically, hydrocarbons such as methane, ethane, propane, butane, natural gas (LNG), and naphtha , Hydrocarbon fuels such as gasoline, kerosene, light oil, heavy oil, and asphalt; alcohols such as methanol, ethanol, propanol and butanol; oxygen-containing compounds such as methyl formate, methyl tertiary butyl ether (MTBE) and dimethyl ether; Various city gas, synthesis gas, coal and the like can be mentioned. Among these, what kind of fuel for hydrogen production is 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 usually, methanol, methane or LNG, propane, etc. Alternatively, LPG, naphtha or lower saturated hydrocarbon, city gas and the like are preferably used.

[0015] The technology belonging to the reforming or partial oxidation (hereinafter referred to as "reforming")
It is called a reforming reaction. Examples of (2) include steam reforming, partial oxidation, a combination of steam reforming and partial oxidation, autothermal reforming, and other reforming reactions. Usually, steam reforming (steam reforming) is the most common reforming reaction, but depending on the raw material, partial oxidation or other reforming reactions (for example, thermal reforming reaction such as thermal decomposition, contact reforming) Various catalytic reforming reactions such as decomposition and shift reaction) can also be appropriately applied.

At this time, different types of reforming reactions may be used in combination as appropriate. For example, since the steam reforming reaction is generally an endothermic reaction, a steam reforming reaction and a partial oxidation may be combined (autothermal reforming) to compensate for the endothermic component, or C by-produced by the steam reforming reaction or the like.
Various combinations are possible, such as by reacting O with H ₂ O using a shift reaction to convert a part of the O to CO ₂ and H ₂ in advance to reduce it. After the partial oxidation is performed without a catalyst or in a catalytic manner, steam reforming can be performed in a subsequent stage. In this case, the heat generated by the partial oxidation can be used as it is for the steam reforming in the subsequent stage, which is an endothermic reaction.

Hereinafter, steam reforming will be mainly described as a typical reforming reaction. In such a reforming reaction, catalysts and reaction conditions are generally selected so that the yield of hydrogen is as large as possible. However, it is difficult to completely suppress CO by-products. Even if it is used, there is a limit to the reduction of the CO concentration in the reformed gas. In fact, for the steam reforming reaction of hydrocarbons such as methane, the hydrogen yield and C
For O-product inhibition, the following formula (2) or the formula _{(3): CH 4 + 2H} 2 O → 4H 2 + CO 2 (2) C n H m + 2nH 2 O → (2n + m / 2 It is preferable to select various conditions so that the reaction represented by H ₂ + nCO ₂ (3) takes place with as high selectivity as possible.

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 preferable to select the conditions to occur. Further, CO is added to the above (1)
The metamorphic reforming may be performed by utilizing the shift reaction represented by the formula. However, since this shift reaction is an equilibrium reaction, a considerable concentration of CO remains. Thus, the reformed gas or the like by such reaction (of the present invention is a starting material gas containing mainly hydrogen, hereinafter the same) during normal, the CO ₂ and unreacted another large amount of hydrogen water vapor or the like and slightly CO will be included.

A wide variety of catalysts are known as effective catalysts for the reforming reaction, depending on the type of raw material, the type of reaction, the reaction conditions and the like. Specific examples of some of them include catalysts effective for steam reforming of hydrocarbons and methanol, for example, Cu-ZnO-based catalysts, Cu
-Cr ₂ O ₃ catalyst, supported Ni-based catalyst, Cu-Ni-Z
nO-based catalyst, Cu-Ni-MgO-based catalyst, Pd-ZnO
And the like.Examples of catalysts effective for catalytic reforming reaction and partial oxidation of hydrocarbons include, for example,
Supported Pt-based catalysts, supported Ni-based catalysts, supported Ru-based catalysts, and the like can be given.

The reforming apparatus is not particularly limited, and any type of apparatus such as those commonly used in conventional fuel cell systems and the like can be applied. However, many reforming apparatuses such as a steam reforming reaction and a decomposition reaction can be used. Since the reaction is an endothermic reaction, generally, a reactor or a reactor having a good heat supply property (a heat exchanger type reactor or the like) is suitably used. Examples of such a reactor include a multitubular reactor, a plate-fin reactor, and the like. Examples of the heat supply method include heating using a burner, a method using a heat medium, and a catalyst using partial oxidation. Examples include, but are not limited to, heating by combustion.

The reaction conditions for the reforming reaction may vary depending on the raw materials used, the reforming reaction, the catalyst, the type of the reaction apparatus, the reaction system, and other conditions, and may be appropriately determined. In any case, it is desirable to select various conditions so that the conversion of the raw material is sufficiently increased (preferably to 100% or nearly 100%) and the yield of hydrogen is as large as possible. If necessary, a method of separating and recycling unreacted hydrocarbons and alcohols may be adopted.
Also, if necessary, the produced or unreacted CO ₂
And moisture or the like may be removed as appropriate.

(2) Step of selectively oxidizing and removing CO As described above, a desired reformed gas having a large hydrogen content and a sufficiently reduced amount of raw material components other than hydrogen such as hydrocarbons and alcohols can be obtained. obtain. In the present invention, this CO
Various catalysts can be used as the selective oxidation-removal catalyst of the above. However, in terms of hydrogen purity, ruthenium, an alkali metal compound and / or an alkali metal compound can be added to the refractory inorganic oxide carrier described in JP-A-9-131531. A catalyst supporting an earth metal compound can be suitably used, and a catalyst in which ruthenium is supported on a carrier composed of titania and alumina described below, or ruthenium on a carrier composed of titania and alumina, and alkali metal and / or alkaline earth are described below. Those supporting a class of metals are particularly preferred.

The above-mentioned catalyst in which ruthenium is supported on a carrier composed of titania and alumina, or the catalyst in which ruthenium and an alkali metal and / or an alkaline earth metal are supported on a carrier composed of titania and alumina will be described in detail. The carrier used for the catalyst is composed of titania and alumina. The catalyst of the present invention using a carrier composed of titania and alumina is disclosed in
Compared to a catalyst in which ruthenium or ruthenium and an alkali metal compound and / or an alkaline earth metal compound are supported on a titania carrier or an alumina carrier as disclosed in Japanese Patent No.
It has an excellent effect on the oxidative removal of CO, particularly the oxidative removal of CO at a relatively high temperature. Further, as compared with the titania carrier catalyst, the alumina / titania catalyst is excellent in ease of manufacture such as moldability and the like, and has high utility such as excellent catalyst strength, abrasion resistance, strength at use temperature, and the like.

As a method for producing a carrier composed of titania and alumina, any method can be used as long as a carrier composed of both can be produced. For example, a method of mixing titania and alumina, a method of producing an alumina molded body (including alumina particles and powder), and the like. A method of attaching titania is preferably used.
As a method for mixing titania and alumina, there is a method in which titania powder and alumina powder or pseudo-boehmite alumina are mixed with water, followed by molding, drying, and firing. Extrusion may be usually used for molding, and at that time, an organic binder can be added to improve moldability. Suitable carriers can also be obtained by mixing titania with an alumina binder. In addition, titanium alkoxide and aluminum alkoxide are hydrolyzed by adding water to a mixed solution obtained by dissolving the same in a solvent such as alcohol, and the coprecipitated precipitate is formed, dried, and calcined in the same manner as described above. Good. In this case, the obtained titania / alumina mass ratio is preferably 10/90 to 90/10.

On the other hand, the method of adhering titania to the alumina compact may be as follows. In an organic solvent, a titania powder (the titania powder may be a titania powder supporting a metal to be described later), and if necessary, an organic binder and pseudo-boehmite alumina powder are added and dispersed well. The alumina molded body is immersed in the mixed liquid (usually in a slurry form), the mixed liquid is sufficiently immersed, and titania powder is adhered to the alumina molded body, and then the alumina molded body is taken out. The alumina compact may be dried and fired. Alternatively, titanium alkoxide or titanium tetrachloride and an alumina compact are added to alcohol, water is added to this solution to hydrolyze the titanium alkoxide or titanium tetrachloride, and titanium hydroxide is formed on the alumina compact. The precipitate may be dried and fired. As can be seen from these attaching methods, titania may be adhered in a manner of supporting titania on the alumina molded body. In the case of a method in which titania is adhered to an alumina molded body, the mass ratio of the obtained titania / alumina is 0.1 / 99.9 to 50/5.
0, preferably 0.5 / 99.5 to 50/50, and more preferably 1/99 to 50/50. Including both methods, the titania / alumina weight ratio is 0.1 / 99.9 to 90/10, preferably 0.5 /
99.5 to 90/10, more preferably 1/99 to 9
Desirably, it is 0/10.

The alumina raw material used in the above-mentioned method for producing a carrier may contain aluminum atoms. Examples of commonly used materials include aluminum nitrate, aluminum hydroxide, aluminum alkoxide, pseudoboehmite alumina, α-alumina, and γ-alumina. Pseudo-boehmite alumina, α-alumina,
Gamma alumina and the like can be made from aluminum nitrate, aluminum hydroxide, aluminum alkoxide, and the like. What is necessary is just to select these raw materials which are easy to use according to a manufacturing method etc.

The titania raw material may be any one containing a titanium atom, and usually includes titanium alkoxide, titanium tetrachloride, amorphous titania powder, anatase type titania powder, rutile type titania powder and the like. Amorphous titania powder, anatase-type titania powder, rutile-type titania powder and the like can be made of titanium alkoxide, titanium tetrachloride or the like.
What is necessary is just to select these raw materials which are easy to use according to a manufacturing method etc.

The carrier may be composed of titania and alumina, but may contain other refractory inorganic oxides. For example, it may contain zirconia, silica, or the like. Any zirconia source may be used as long as it contains a zirconium atom, and zirconium hydroxide, zirconium oxychloride, zirconium oxynitrate, zirconium tetrachloride, zirconia powder, and the like can be used. Zirconia powder is zirconium hydroxide, zirconium oxychloride,
It can be made from zirconium oxynitrate, zirconium tetrachloride. Any silica source may be used as long as it contains a silicon atom, and silicon tetrachloride, sodium silicate, ethyl silicate, silica gel, silica sol and the like can be used. Silica gel can be made from silicon tetrachloride, sodium silicate, ethyl silicate, silica sol, and the like.

Next, the loading of ruthenium on a carrier will be described.
I will tell. To support ruthenium on a carrier, for example, R
uCl_Three・ NH_TwoO, Ru (NO_Three)_Three, Ru_Two(O
H)_TwoCl_Four・ 7NH_Three・ 3H_TwoO, K_Two(RuCl_Five
(H_TwoO)), (NH_Four)_Two(RuCl_Five(H
_TwoO)), K_Two(RuCl_Five(NO)), RuBr_Three・
nH_TwoO, Na_TwoRuO_Four, Ru (NO) (N
O_Three)_Three, (Ru_ThreeO (OAc)₆(H_TwoO)_Three) OA
c ・ nH_TwoO, K_Four(Ru (CN)₆) · NH_TwoO, K
_Two(Ru (NO_Two)_Four(OH) (NO)), (Ru (N
H_Three) ₆) Cl_Three, (Ru (NH_Three)₆) Br_Three, (R
u (NH_Three)₆) Cl_Two, (Ru (NH_Three)₆) B
r_Two, (Ru_ThreeO_Two(NH_Three)₁₄) Cl₆・ H_TwoO,
(Ru (NO) (NH_Three)_Five) Cl_Three, (Ru (OH)
(NO) (NH_Three)_Four) (NO _Three)_Two, RuCl_Two(P
Ph_Three)_Three, RuCl_Two(PPh_Three)_Four, (RuClH
(PPh_Three)_Three) ・ C₇H₈, RuH_Two(PP
h_Three)_Four, RuClH (CO) (PPh_Three)_Three, RuH
_Two(CO) (PPh_Three)_Three, (RuCl_Two(Cod))
_n, Ru (CO)₁₂, Ru (acac)_Three, (Ru (H
COO) (CO)_Two)_n, Ru_TwoI_Four(P-cymen
e)_TwoRuthenium salts are dissolved in water, ethanol, etc.
The resulting catalyst preparation is used. Preferably, the
RuCl in terms of handling_Three・ NH_TwoO, Ru (N
O_Three)_Three, Ru_Two(OH)_TwoCl_Four・ 7NH_Three・ 3H _Two
O is used.

The loading of ruthenium on a carrier may be carried out by using the catalyst preparation solution by a usual impregnation method, coprecipitation method or competitive adsorption method. The treatment conditions may be appropriately selected according to various methods, but usually, the carrier may be brought into contact with the catalyst preparation solution at room temperature to 90 ° C. for 1 minute to 10 hours. The amount of ruthenium supported is not particularly limited, but is usually preferably 0.05 to 10% by mass as ruthenium with respect to the carrier, particularly preferably 0.3 to 10% by mass.
The range of 3% by mass is optimal. When the content of ruthenium is less than the lower limit, the conversion activity of CO becomes insufficient,
On the other hand, if the loading ratio is too high, the amount of ruthenium used becomes excessively large and the catalyst cost increases.

After supporting ruthenium on the carrier, the carrier is dried. As a drying method, for example, natural drying, evaporation to dryness,
Drying is performed by a rotary evaporator or a blow dryer. After drying, usually at 350 to 550 ° C, preferably 380 to 500 ° C, for 2 to 6 hours, preferably 2 to 6 hours.
Bake for ~ 4 hours.

Next, an alkali metal and / or alkaline earth
The loading of a class of metal on a carrier will be described. First, the alkali
The loading of the metal on the carrier will be described. As an alkali metal
Potassium, cesium, rubidium, sodium
And lithium are preferably used. Carry alkali metal
To do, K_TwoB_TenO₁₆, KBr, KBrO_Three, KC
N, K_TwoCO_Three, KCl, KCLO_Three, KCLO_Four, K
F, KHCO_Three, KHF_Two, KH_TwoPO_Four, KH_Five(P
O_Four)_Two, KHSO_Four, KI, KIO_Three, KIO_Four, K
_FourI_TwoO₉, KN_Three, KNO_Two, KNO_Three, KOH, K
PF₆, K_ThreePO_Four, KSCN, K_TwoSO_Three, K_TwoSO
_Four, K_TwoS_TwoO_Three, K_TwoS_TwoO_Five, K_TwoS_TwoO ₆, K_Two
S_TwoO₈, K (CH_ThreeCO salts such as COO); CsCl, C
sCLO_Three, CsCLO_Four, CsHCO_Three, CsI, C
sNO_Three, Cs_TwoSO_Four, Cs (CH_ThreeCOO), Cs
_TwoCO_Three, CsF and the like; Rb_TwoB_TenO₁₆, RbB
r, RbBrO_Three, RbCl, RbClO_Three, PbCl
O_Four, RbI, RbNO_Three, Rb _TwoSO_Four, Rb (CH
_ThreeCOO)_Two, Rb_TwoCO_ThreeRb salt; Na_TwoB_FourO
₇, NaB_TenO₁₆, NaBr, NaBrO_Three, NaC
N, Na_TwoCO_Three, NaCl, NaClO, NaClO
_Three, NaClO_Four, NaF, NaHCO_Three, NaHPO
_Three, Na_TwoHPO_Three, Na_TwoHPO_Four, NaH_TwoP
O_Four, Na_ThreeHP_Two0₆, Na_TwoH_TwoP_TwoO₇, Na
I, NaIO_Three, NaIO_Four, NaN_Three, NaNO_Two,
NaNO_Three, NaOH, Na_TwoPO_Three, Na_ThreePO_Four,
Na_FourP_TwoO₇, Na _TwoS, NaSCN, Na_TwoS
O_Three, Na_TwoSO_Four, Na_TwoS_TwoO_Five, Na_TwoS
_TwoO₆, Na (CH_ThreeNa salt such as COO); LiB
O_Two, Li_TwoB_FourO₇, LiBr, LiBrO_Three, Li
_TwoCO_Three, LiCl, LiClO_Three, LiClO_Four, L
iHCO_Three, Li_TwoHPO_Three, LiI, LiN_Three, Li
NH_FourSO_Four, LiNO _Two, LiNO_Three, LiOH, L
iSCN, Li_TwoSO_Four, Li_ThreeVO_FourLi salt such as
Use a catalyst preparation solution obtained by dissolving in water, ethanol, etc.
Can be.

The theory of supporting alkaline earth metals on carriers
I will tell. Barium and calcium are the alkaline metal earths.
, Magnesium and strontium are preferably used
Can be To support the alkaline earth metal, BaB
r_Two, Ba (BrO_Three)_Two, BaCl_Two, Ba (ClO
_Two)_Two, Ba (ClO_Three)_Two, Ba (ClO_Four)_Two, B
aI _Two, Ba (N_Three)_Two, Ba (NO_Two)_Two, Ba (N
O_Three)_Two, Ba (OH)_Two, BaS, BaS_TwoO₆, B
aS_FourO₆, Ba (SO_ThreeNH_Two)_TwoBa salt such as Ca;
Br_Two, CaI_Two, CaCl_Two, Ca (ClO_Three)_Two,
Ca (IO_Three)_Two, Ca (NO_Two)_Two, Ca (NO_Three)
_Two, CaSO_Four, CaS_TwoO_Three, CaS_TwoO₆, Ca
(SO_ThreeNH_Two)_Two, Ca (CH_ThreeCOO)_Two, Ca
(H_TwoPO_Four)_TwoCa salt, etc .; MgBr_Two, MgC
O_Three, MgCl_Two, Mg (ClO_Three)_Two, MgI _Two, M
g (IO_Three)_Two, Mg (NO_Two)_Two, Mg (N
O_Three)_Two, MgSO_Three, MgSO_Four, MgS_TwoO₆, M
g (CH_ThreeCOO)_Two, Mg (OH)_Two, Mg (ClO
_Four)_TwoMg salt such as SrBr_Two, SrCl_Two, Sr
I_Two, Sr (NO_Three)_Two, SrO, SrS_TwoO_Three, Sr
S_TwoO₆, SrS_FourO₆, Sr (CH_ThreeCOO) _Two, S
r (OH)_TwoIs dissolved in water, ethanol, etc.
Can be used.

The support of the alkali metal or alkaline earth metal on the carrier may be carried out using the catalyst preparation solution by a usual impregnation method, coprecipitation method or competitive adsorption method. The treatment conditions may be appropriately selected according to various methods, but are usually from room temperature to 90 ° C.
The carrier may be brought into contact with the catalyst preparation solution for 1 minute to 10 hours. The loading of ruthenium, alkali metal and alkaline earth metal may be carried out in any order, and if they can be carried out simultaneously, they may be carried out simultaneously. Further, not only a method of supporting these supported metals on the completed carrier, but also a method of supporting the titania and attaching the supported titania to alumina as described above can be used as a catalyst. As a result, any catalyst may be used as long as a supported metal such as ruthenium is supported on a titania / alumina carrier.

The amount of the alkali metal or alkaline earth metal to be carried is not particularly limited, but is usually preferably 0.01 to 10% by mass, more preferably 0.03 to 3% by mass of the metal relative to the carrier. It is. When the content of these metals is less than the lower limit, the selective oxidation activity of CO becomes insufficient,
On the other hand, when the loading ratio is too high, the selective oxidation activity of CO becomes insufficient, and the amount of metal used becomes unnecessarily excessive, so that the catalyst cost increases. The above alkali metal,
After supporting the alkaline earth metal, it is dried. As a drying method, for example, natural drying, evaporation to dryness, drying using a rotary evaporator or a blow dryer may be performed. After drying, it is usually 350 to 550 ° C, preferably 38 ° C.
Firing at 0-500 ° C for 2-6 hours, preferably 2-4 hours.

The shape and size of the catalyst prepared in this way are not particularly limited. For example, powdery, spherical, granular, honeycomb, foam, fibrous, cloth, plate, Various commonly used shapes and structures such as a ring shape can be used. The production method is not limited. For example, the catalyst itself may be formed by extrusion or the like, or a method of attaching the catalyst to a honeycomb or ring-shaped substrate may be used.

Next, a method for producing a hydrogen-containing gas with reduced carbon monoxide by oxidizing carbon monoxide in a gas containing hydrogen as a main component with oxygen using the above catalyst will be described. Since the catalyst prepared as described above is usually calcined, the supported metal exists in an oxide state. Before use, the catalyst is reduced by hydrogen reduction. The hydrogen reduction is usually carried out under a stream of hydrogen at 250 to 550 ° C, preferably 300 to 53 ° C.
The reaction is carried out at a temperature of 0 ° C. for 1 to 5 hours, preferably 1 to 2 hours.

In this step, CO is selectively oxidized (converted) to CO ₂ by adding oxygen to a raw material gas (reformed gas or the like) containing hydrogen as a main component and a small amount of CO. It is necessary to minimize the oxidation of hydrogen. It is also necessary to suppress the conversion reaction of CO ₂ generated or present in the source gas to CO (there is a possibility that a reverse shift reaction occurs because hydrogen is present in the source gas). . Since the above-mentioned catalyst is usually used in a reduced state, it is preferable to perform a reduction operation with hydrogen when it is not in a reduced state. Using the above catalyst, to exhibit good results in the CO selective oxidation removal for low feed gas of CO ₂ content, of course, good results can be obtained even in a CO ₂ content is more conditions. Normally, in a fuel cell system, a reformed gas having a general concentration of CO ₂ or the like,
A gas containing ₅ to 33% by volume of CO2, preferably 10 to 25% by volume, more preferably 15 to 20% by volume is used.

On the other hand, steam is usually present in the source gas obtained by steam reforming or the like, but the lower the steam concentration in the source gas, the better. Usually 5 to 30% by volume
There is no problem if it is included. Also,
By using the above catalyst, the CO concentration is low (0.
The CO concentration in the source gas can be effectively reduced, and the CO concentration in the source gas having a relatively high CO concentration (0.6 to 2.0% by volume) can also be suitably reduced.

In the method of the present invention, the use of various catalysts allows CO to be removed in a temperature range including a relatively high temperature of 60 to 300 ° C. even under conditions where CO ₂ is present in the raw material gas at 15% by volume or more. The selective conversion removal can be performed efficiently. In addition, the CO conversion removal reaction is an exothermic reaction, as is the simultaneous oxidation of hydrogen, which is a side reaction, and recovering the generated heat and utilizing it in the fuel cell is effective in improving the power generation efficiency. is there.

When oxygen gas is added to the reformed gas or the like, usually, pure oxygen (O ₂ ), air or oxygen-enriched air is suitably used. The added amount of the oxygen gas is preferably oxygen / CO (molar ratio) of 0.5 to 5, more preferably 1 to 5.
It is appropriate to adjust to be 4. If this ratio is small, the removal rate of CO is low, and if it is large, the consumption of hydrogen is too large, which is not preferable.

The reaction pressure is not particularly limited, but in the case of a fuel cell, the reaction is usually carried out within a pressure range from normal pressure to 1 MPa (Gauge), preferably from normal pressure to 0.5 MPa (Gauge). If the reaction pressure is set too high, it is necessary to increase the power for increasing the pressure, which is economically disadvantageous. In particular, if the pressure exceeds 1 MPa (Gauge), it is subject to the regulations of the High Pressure Gas Control Law. However, since the explosion limit is widened, there is also a problem that safety is reduced. The reaction is
Usually, it can be suitably carried out in a very wide temperature range of 60 ° C. or higher, preferably 60 to 300 ° C., while stably maintaining the selectivity to the CO conversion reaction. 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 within a practical range of GHSV (gas volume space velocity).

In the above reaction, the GHSV (supply volume velocity in the standard state of the supply gas and the apparent space velocity based on the apparent volume of the catalyst layer to be used) is usually 5,000 to 10.
It is preferable to perform the selection in the range of 000 hr ^-1 . Here, when the GHSV is reduced, a large amount of the catalyst is required. On the other hand, when the GHSV is excessively increased, the CO removal rate is reduced. Preferably, 6,000 to 60,00
Select within the range of ⁰ hr ^-1 . Since the CO conversion reaction in the CO conversion removal step is an exothermic reaction, the reaction raises the temperature of the catalyst layer. If the temperature of the catalyst layer is too high, the selectivity of the catalyst for CO conversion removal usually deteriorates. For this reason, it is not preferable to react too much CO on a small amount of catalyst in a short time. G from the meaning
In some cases, the HSV should not be too large.

There are no particular restrictions on the reactor used for the conversion and removal of CO, and various types of reactors can be applied as long as the above reaction conditions can be satisfied. However, this conversion reaction is an exothermic reaction. Therefore, in order to facilitate temperature control, it is desirable to use a reaction apparatus or a reactor having good removability of reaction heat. Specifically, for example, a heat exchange type reactor such as a multitube type or a plate fin type is suitably 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 be adopted.

By this step, O which is a feature of the present invention is obtained.
_{2 The} concentration is adjusted to 0.05 to 1.5% by volume, but the amount of O _{2 to be} added, the catalyst to be used, and the reaction conditions may be controlled. It is not an exaggeration to say that it depends on the catalyst used. Since the hydrogen-containing gas thus produced has a sufficiently reduced CO concentration as described above, the poisoning and deterioration of the platinum electrode catalyst of the fuel cell can be sufficiently reduced, and its life and power generation efficiency can be reduced. -Power generation performance can be greatly improved. Also, this CO
It is also possible to recover the heat generated by the conversion reaction. Further, the CO concentration in the hydrogen-containing gas containing a relatively high concentration of CO can be sufficiently reduced. The CO concentration in the hydrogen-containing gas for a fuel cell is preferably 100 ppm by volume or less, preferably 50 ppm by volume or less, more preferably 10 ppm by volume or less. It is quite possible to achieve this. On the other hand, the amount of O ₂ is also 0.05 to 1.5% by volume, causing an oxidation reaction of CO on the platinum electrode, and from this point also can contribute to the suppression of poisoning of the platinum electrode catalyst.

The hydrogen-containing gas obtained as described above contains various H
Various types of H ₂ combustion fuel cells (phosphoric acid fuel cells, KOH), which can be suitably used as a fuel for a _two- combustion fuel cell, and use platinum (platinum catalyst) for at least the fuel electrode (negative electrode) Fuel cells, low-temperature operation type fuel cells such as polymer electrolyte fuel cells, etc.), and is particularly advantageous for polymer electrolyte fuel cells.

[0047]

Next, the present invention will be described in detail with reference to examples, but the present invention is not limited to these examples. Preparation of [Ru / TiO ₂ —Al ₂ O ₃ ] (catalyst 1) Rutile type titania (TiO ₂ , CR-E, manufactured by Ishihara Sangyo Co., Ltd.)
L, surface area: 7 m ² / g) 160 g and pseudo-boehmite alumina powder (Cataloid-A, manufactured by Kako Kasei Kogyo Co., Ltd.)
P) was mixed with ion-exchanged water and sufficiently kneaded with a kneader under heating to adjust the water content to an extent suitable for extrusion molding. This was extruded with a diameter of 2 mm and a length of 0.5
It was formed into a columnar shape of 、 1 cm and dried in a dryer at 120 ° C. for 24 hours. Subsequently, the support 1 was obtained by firing in a firing furnace at 500 ° C. for 4 hours. The mass ratio of titania / alumina of the carrier 1 was 80/20.

Take 10 g of the carrier 1 and prepare ethanol solution of 5.25 cc of a ruthenium chloride solution prepared in advance (containing 0.952 g of Ru in 50 cc).
The impregnation liquid to which 75 cc was added was impregnated. After removing the ethanol by evaporation at 60 ° C., the mixture was heated at 120 ° C. in a muffle furnace.
The mixture was calcined for 2 hours at 500 ° C. for 4 hours to obtain a ruthenium-supported material. The composition of this catalyst 1 is TiO
₂ / Al ₂ O ₃ (mass ratio) = 80/20, Ru = 1.0
% By mass (based on the carrier).

Preparation of [Ru-K / TiO ₂ —Al ₂ O ₃ ] (catalyst 2)
10 cc of an aqueous solution containing 9 g was impregnated. 60 ℃
After evaporating and removing water, the mixture was calcined in a muffle furnace at 120 ° C. for 2 hours and at 500 ° C. for 4 hours to obtain Catalyst 1. This catalyst 2
Is TiO ₂ / Al ₂ O ₃ (mass ratio) = 80/2
0, Ru = 1.0% by mass (based on carrier), K = 0.1% by mass (based on carrier).

Preparation of [Ru-K / TiO ₂ / Al ₂ O ₃ ] (catalyst 3) 14.2 g of titanium tetraisopropoxide (TTIP, first grade reagent, manufactured by Wako Pure Chemical Industries, Ltd.) was dissolved in 97 cc of isopropyl alcohol. Then, 5.25 g of diethanolamine was added, and the mixture was stirred for 2 hours. Thereafter, a solution in which 1.8 g of water was dissolved in 3.6 cc of isopropyl alcohol was gradually added, followed by stirring for 2 hours. This solution 2
5 cc was collected, 10 g of activated alumina (KHD24, manufactured by Sumitomo Chemical Co., Ltd.) having a particle size of 16 to 32 mesh was added, and the mixture was allowed to stand for 1 hour. The particles were calcined in a muffle furnace at 120 ° C. for 2 hours and at 500 ° C. for 4 hours to obtain a carrier. The carrier is a carrier in which titania is adhered to an alumina molded body (alumina particles). The titania / alumina mass ratio of the carrier was 1/99.

10 g of the above carrier was taken, and a ruthenium chloride solution prepared in advance in ethanol (R in 50 cc) was prepared.
The sample was impregnated with 5.25 cc of ethanol and 4.75 cc of ethanol. This is 60
After removing the ethanol by evaporation at
Calcination was performed at 0 ° C. for 2 hours and at 500 ° C. for 4 hours to obtain a ruthenium carrier.

Next, the ruthenium carrier was impregnated with 10 cc of an aqueous solution containing 0.0259 g of potassium nitrate prepared in advance. After evaporating and removing the water at 60 ° C., the mixture was calcined in a muffle furnace at 120 ° C. for 2 hours and at 500 ° C. for 4 hours to obtain Catalyst 3. The composition of this catalyst 3 is TiO
₂ / Al ₂ O ₃ (mass ratio) = 1/99, Ru = 1.0 mass% (based on carrier), K = 0.1 mass% (based on carrier).

Preparation of [Pt / Al ₂ O ₃ ] (catalyst 4) 0.266 g of chloroplatinic acid (IV) hexahydrate was added to 5.0 c of water.
c to obtain an impregnating liquid. This impregnating liquid was impregnated into 10 g of commercially available alumina (KHD-24, manufactured by Sumitomo Chemical Co., Ltd.), dried at 120 ° C. for 24 hours, and calcined at 500 ° C. for 4 hours to obtain Catalyst 4. The catalyst composition was Pt = 1.0% by mass (based on the carrier).

Examples 1 to 3 and Comparative Examples 1 and 2 Catalyst (particle size: 16 to 32 mesh) in microreactor
Was filled in 1 cc or 5 cc (only in Comparative Example 2), and reacted under the following conditions. The results are shown in Table 1. Pretreatment: 500 ° C. for 1 hour in a reactor Reduction gas composition (% by volume): CO = 0.6%, CO ₂ = 15.
0%, O ₂ = 2.0% N ₂ = 8.0%, H ₂ = 74.4% GHSV: 50,000 hr ^-1 or 10,000 hr ^-1
(Only Comparative Example 2) Reaction temperature: 150 ° C, 200 ° C

[0055]

[Table 1]

When the hydrogen-containing gas of the comparative example was supplied to the fuel electrode of the polymer electrolyte fuel cell, the output voltage of the fuel cell was reduced due to the poisoning of the electrode catalyst as compared with the example.

[0057]

According to the present invention, since an appropriate amount of a hydrogen-containing gas having an O ₂ concentration is used for a fuel cell, the oxidation reaction of CO on a platinum electrocatalyst is likely to occur. Can be avoided and a high output voltage can be obtained.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) H01M 8/06 H01M 8/06 G

Claims (4)

[Claims] The CO of 1. A hydrogen-containing gas to a method for selective oxidation is removed by O _2, adjust the O ₂ concentration in the hydrogen-containing gas after CO selective oxidation removal 0.05-1.5 volume% Producing a hydrogen-containing gas for a fuel cell. 2. The method for producing a hydrogen-containing gas for a fuel cell according to claim 1, wherein the selective oxidation and removal of CO is performed using a catalyst comprising ruthenium supported on a carrier comprising titania and alumina. 3. The hydrogen-containing gas for a fuel cell according to claim 1, wherein the selective oxidative removal of CO is performed using a catalyst comprising ruthenium and an alkali metal and / or an alkaline earth metal supported on a carrier comprising titania and alumina. Manufacturing method. 4. The method for producing a hydrogen-containing gas for a fuel cell according to claim 1, wherein the hydrogen-containing gas is a gas obtained by reforming or partially oxidizing a raw material for hydrogen production.