JP2001327868A - Oxidation catalyst for co and method for producing hydrogen-containing gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an oxidation catalyst for CO which can efficiently and selectively oxidize and remove CO in hydrogen-containing gas in a wide reaction temperature range and to provide a method for producing hydrogen-containing gas by using the catalyst, especially hydrogen-containing gas preferably suitable for a fuel cell. SOLUTION: The oxidation catalyst for CO having at least a ruthenium component deposited on an inorganic refractory carrier has the following features. In the graph (not shown) giving the relation of the distance r in the width direction of the cross section (distance from the center to the catalyst surface) and the intensity I of x-rays, wherein r is obtained by the measurement of the line analysis for the ruthenium atom in one direction by using an electron probe microanalysis (EPMA) device, the integral value N0 of I (r) from one catalyst surface -r0 to the other catalyst surface r0 and the integral value N1 of I (r) from -2/3r0 to 2/3r0 satisfy S=(N.N0×100>=50, wherein N=N0-N1. The method for preparing hydrogen-containing gas is carried out by using the oxidation catalyst for CO to remove CO in the hydrogen containing gas.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a catalyst for selectively oxidizing and removing CO from a hydrogen-containing gas, and more particularly to a catalyst containing ruthenium as an active component and containing C from hydrogen-containing gas.
The present invention relates to a CO oxidation catalyst for improving the selective oxidation activity of O, and a method for producing a hydrogen-containing gas using the catalyst.

[0002]

2. Description of the Related Art In recent years, new energy technologies have been spotlighted due to environmental problems, and fuel cells have attracted attention as one of the new energy technologies. This fuel cell converts chemical energy into electric energy by electrochemically reacting hydrogen and oxygen, and has the feature of high energy use efficiency.
Practical research is being actively conducted for industrial or automotive use. As the fuel cell, types such as a phosphoric acid type, a molten carbonate type, a solid oxide type, and a solid polymer type are known according to the type of electrolyte used. on the other hand,
As a hydrogen source, liquefied natural gas mainly composed of methanol and methane, city gas mainly composed of natural gas, synthetic liquid fuel composed of natural gas as raw material, and petroleum LP
The use of petroleum hydrocarbons such as G, naphtha, and kerosene is being studied. When fuel cells are used for consumer or automotive applications, the petroleum hydrocarbons described above are easy to store and handle, and have an excellent supply system, such as gas stations and dealers. It is. When hydrogen is produced using this petroleum hydrocarbon, a method is generally used in which the hydrocarbon is subjected to steam reforming or partial oxidation reforming treatment in the presence of a reforming catalyst. The hydrogen-containing gas obtained in these reactions usually contains CO together with the intended hydrogen gas.

[0003] Such a CO gas is liable to poison platinum (platinum catalyst) used as an electrode in a fuel cell, particularly in a low-temperature operation type fuel cell such as the above-mentioned polymer electrolyte fuel cell. If it 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 electrocatalyst. However, as described above, a significant concentration of CO in addition to hydrogen is generally contained in the reformed gas.
Therefore, there is a strong demand for the development of a technology for converting this CO into CO ₂ or the like harmless to the platinum-based electrode catalyst and reducing the CO concentration in the fuel of the fuel cell. At that time, CO
Is usually 100 ppm or less, preferably 10 pp
It is considered desirable to reduce the concentration to a low concentration of m or less. In order to solve the above problem, as one of means for reducing the concentration of CO in the fuel gas (hydrogen-containing gas in the reformed gas) of the fuel cell, 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 in reducing the CO concentration due to restrictions on chemical equilibrium. In general, the CO concentration is reduced to 1% or less. It is difficult.

Therefore, 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 a fuel gas to convert CO into CO ₂ . However, in this case, since a large amount of hydrogen is present in the fuel gas, when oxidizing CO, the hydrogen is also oxidized, and the CO concentration may not be sufficiently reduced. In order to solve this problem, when introducing oxygen or an oxygen-containing gas into the fuel gas to oxidize CO into CO ₂ , a method using a catalyst that selectively oxidizes only CO can be considered. As a CO oxidation catalyst, conventionally, Pt
/ Alumina, Pt / SnO ₂ , Pt / C, Co / TiO
_2. Catalyst systems such as popcalite and Pd / alumina are known, but these catalysts are not sufficiently resistant to humidity.
Since the reaction temperature range is low and narrow, and the selectivity for CO oxidation is low, a small amount of CO in a large amount of hydrogen such as fuel gas of a fuel cell is reduced to a low concentration of 10 ppm or less. To this end, large amounts of hydrogen must also be sacrificed by oxidation. JP-A-5-2017
No. 02 discloses a method for producing a CO-free hydrogen-containing gas for selectively removing CO from a hydrogen-enriched CO-containing gas and supplying the CO to an automotive fuel cell system. Here, a catalyst in which Rh or Ru is supported on an alumina carrier is used as a catalyst, but there is a problem that it can be applied only to a low CO concentration. Also, Japanese Patent Application Laid-Open No.
No. 31,531 discloses that a titania carrier contains ruthenium,
A catalyst for removing CO in a hydrogen-containing gas, which carries an alkali metal compound and / or an alkaline earth metal compound, is disclosed.

[0005]

However, since ruthenium used for a ruthenium-based catalyst is a noble metal, a catalyst using the same as a supporting component is generally expensive, so that a catalyst containing a ruthenium component is industrially used. In order to make the catalyst useful, it is necessary to reduce not only the catalyst performance but also the catalyst price. On the other hand, the above-mentioned conventional ruthenium-based catalyst has practically insufficient catalytic activity per supported ruthenium, and a catalyst with higher activity has been desired. Therefore,
A catalyst capable of efficiently and selectively oxidizing and removing CO in a hydrogen-containing gas over a wide reaction temperature range and having extremely excellent catalytic activity per supported ruthenium, and a hydrogen-containing gas using the same, particularly for a fuel cell There has been a demand for a method for producing a hydrogen-containing gas that can be suitably applied to a gas. The present invention has been made under such circumstances, and uses a ruthenium component as an active component and is capable of efficiently and selectively oxidizing and removing CO in a hydrogen-containing gas over a wide reaction temperature range. An object of the present invention is to provide a method for producing a hydrogen-containing gas using the same, particularly a hydrogen-containing gas which can be suitably applied to a fuel cell.

[0006]

Means for Solving the Problems The present inventors have intensively studied to achieve the above object. As a result, in the conventional ruthenium-based oxidation catalyst, the ruthenium component is relatively uniformly dispersed in the support, but the ruthenium component that contributes to the reaction during the reaction is only the one existing near the outer surface of the support. It was found that the ruthenium component present inside hardly contributed to the reaction. In addition, ruthenium, which is an active component in the carrier, which is largely distributed on the outer surface side of the carrier, is remarkably excellent in catalytic activity even with the same loading amount, and can be adapted to the purpose as a CO oxidation catalyst. In addition, it has been found that by performing the CO oxidation removal treatment using this catalyst, a hydrogen-containing gas suitably applicable to a fuel cell can be efficiently obtained. The present invention has been completed based on such findings. That is, the present invention relates to a CO oxidation catalyst comprising at least a ruthenium component supported on an inorganic refractory carrier, by using an electron probe microanalysis (EPMA) apparatus to cross-section the cross section of the catalyst in one direction for ruthenium atoms. In the diagram showing the relationship between the cross-sectional width direction distance r (distance from the center to the catalyst surface) obtained by analytical measurement and the X-ray intensity I, r is one catalyst surface -r
Integrated values N ₀ of the I (r) between the other catalyst surface r ₀ from _0, the value obtained by subtracting the integration value N ₁ of the I (r) in between -2 / 3r ₀ of 2 / 3r ₀ N Wherein the _value of the ratio of N to N ₀ S = (N / N ₀ ) × 100 is 50 or more, and CO in the hydrogen-containing gas is reduced by using the catalyst. A method for producing a hydrogen-containing gas, which is characterized in that it is removed.

[0007]

FIG. 1 is a cross-sectional view of an example of the catalyst of the present invention and the relationship between the distance in the width direction and the X-ray intensity. The CO oxidation catalyst for hydrocarbons of the present invention is a CO oxidation catalyst comprising at least a ruthenium component supported on an inorganic refractory carrier, wherein the cross section of the catalyst is unidirectionally measured using an electron probe microanalysis (EPMA) apparatus. In the diagram showing the relationship between the cross-sectional width direction distance r (the distance from the center to the catalyst surface) and the X-ray intensity I obtained by performing a line analysis measurement on ruthenium atoms, r is one catalyst surface -r
Integrated values N ₀ of the I (r) between the other catalyst surface r ₀ from _0, the value obtained by subtracting the integration value N ₁ of the I (r) in between -2 / 3r ₀ of 2 / 3r ₀ N The ratio of N to N _0, S = (N / N ₀ ) × 100, is 50 or more, preferably 55 or more, and more preferably 70 or more. By having the above-mentioned ruthenium distribution, that is, by distributing a large amount of ruthenium components on the outer surface side of the support, a CO oxidation catalyst having extremely excellent catalytic activity per supported ruthenium can be obtained.

In the present invention, it is preferable that the carrier has a spherical or columnar shape. Therefore, r (distance from the center to the catalyst surface) in the present invention refers to the radius of the support when it is spherical, and refers to the radius of a cross section cut parallel to the bottom surface when the support is cylindrical. Spherical and cylindrical shapes include not only strictly spherical and cylindrical shapes but also those which can be regarded as substantially spherical and cylindrical although some of the shapes are deformed.
The ruthenium distribution of the present invention can also be achieved by preparing a catalyst in a carrier having a shape other than the spherical and cylindrical shapes according to the above-mentioned spherical and cylindrical shapes. The CO oxidation catalyst used in the present invention usually has a diameter or a cross-sectional diameter of 1 to 10 mm, and more preferably 2 to 10 mm.
It is preferably 6 mm. If the diameter of the catalyst is smaller than the above range, the effect of supporting the outer surface is not sufficient,
If it is larger than the above range, the catalytic activity may not be sufficient and may not be preferable.

The carrier used in the CO oxidation catalyst of the present invention
Thus, inorganic refractory carriers are preferred. Like this
Is selected from, for example, alumina, titania and silica.
Can be mentioned. These can be used alone
It is also possible to use two or more kinds in combination. In the present invention
In particular, the catalyst consisting of alumina and titania
It is preferably used from the viewpoint of activity. Carry on these carriers
The ruthenium component is indispensable as the metal component
You. In the present invention, much of this ruthenium component is
Although it exists on the surface side, as a ruthenium source, for example,
For example, RuCl_Three・ NH_TwoO, Ru (NO_Three)_Three, Ru_Two
(OH)_TwoCl_Four・ 7NH_Three・ 3H_TwoO, K_Two(RuC
l_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 such as water,
Using a catalyst preparation obtained by dissolving
The ruthenium component can be supported on a carrier. Lute above
Of the sodium salts, RuCl is preferable in terms of handling.
_Three・ NH_TwoO, Ru (NO_Three)_Three, Ru_Two(OH)_TwoC
l_Four・ 7NH_Three・ 3H_TwoO is used.

The loading of the ruthenium component on the carrier can be carried out using the catalyst preparation solution by a usual impregnation method, coprecipitation method or competitive adsorption method. At this time, the processing conditions may be appropriately selected according to various methods, and are usually from room temperature to 90 ° C.
The carrier may be contacted with the catalyst preparation solution at a temperature of 1 minute to 10 hours. In particular, by immediately impregnating the carrier with an aqueous solution having a water absorption of the carrier or less, the ruthenium component of the present invention can be unevenly distributed on the outer surface side. The loading amount of the ruthenium component is not particularly limited, but is usually preferably 0.05 to 10% by weight as Ru relative to the carrier, and particularly preferably 0.1 to 0.1% by weight.
The range of 5 to 5% by weight is optimal. If the content of ruthenium is less than the lower limit, the conversion activity of CO becomes insufficient. On the other hand, if the loading is too high, the amount of the ruthenium component used becomes excessively large and the catalyst cost increases.
After supporting the ruthenium component on the carrier, drying is performed. As the drying method, for example, any of natural drying, evaporation to dryness, and drying with a rotary evaporator or a blow dryer can be used. After drying, usually 350-550
C., preferably at a temperature of 380 to 500.degree. C. for 2 to 6 hours, preferably 2 to 4 hours.

In the present invention, the ruthenium component
And further, an alkali metal and / or an alkali
Lithium metal can be used. As alkali metal
Is potassium, sodium, lithium, cesium, or
Rubidium is preferably used. These are used alone
Can also be used in combination of two or more
it can. As the alkali metal source, K_TwoB_TenO₁₆, KB
r, KBrO_Three, KCN, K_TwoCO_Three, KCl, KCl
O_Three, KCLO_Four, KF, KHCO_Three, KHF_Two, KH
_TwoPO_Four, KH_Five(PO_Four)_Two, KHSO_Four, KI, K
IO_Three, KIO_Four, K_FourI_TwoO₉, KN_Three, KNO_Two,
KNO_Three, KOH, KPF₆, K_ThreePO_Four, KSCN,
K_TwoSO_Three, K_TwoSO_Four, K_TwoS_TwoO_Three, K_TwoS
_TwoO_Five, K_TwoS_TwoO₆, K_TwoS_TwoO₈, K (CH_ThreeCO
K) salts such as O); CsCl, CsClO_Three, CsCl
O_Four, CsHCO_Three, CsI, CsNO_Three, Cs_TwoSO
_Four, Cs (CH_ThreeCOO), Cs_TwoCO_Three, CsF etc.
Cs salt; Rb_TwoB_TenO₁₆, RbBr, RbBrO_Three, R
bCl, RbClO_Three, PbCLO_Four, RbI, RbN
O_Three, Rb_TwoSO_Four, Rb (CH_ThreeCOO)_Two, Rb_Two
CO_ThreeRb salt; Na_TwoB_FourO₇, NaB_TenO₁₆, N
aBr, NaBrO_Three, NaCN, Na_TwoCO_Three, Na
Cl, NaClO, NaClO_Three, NaClO_Four, Na
F, NaHCO_Three, NaHPO_Three, Na_TwoHPO_Three, N
a_TwoHPO_Four, NaH_TwoPO_Four, Na_ThreeHP_Two0₆, N
a _TwoH_TwoP_TwoO₇, NaI, NaIO_Three, NaIO_Four,
NaN_Three, NaNO_Two, NaNO_Three, NaOH, Na_Two
PO_Three, Na_ThreePO_Four, Na_FourP_TwoO₇, Na_TwoS, N
aSCN, Na_TwoSO_Three, Na_TwoSO_Four, Na_TwoS_TwoO
_Five, Na_TwoS_TwoO₆, Na (CH_ThreeNa such as COO)
Salt; LiBO_Two, Li_TwoB_FourO₇, LiBr, LiBr
O_Three, Li_TwoCO_Three, LiCl, LiClO_Three, LiC
10_Four, LiHCO_Three, Li_TwoHPO_Three, LiI, Li
N_Three, LiNH_FourSO_Four, LiNO_Two, LiNO_Three, L
iOH, LiSCN, Li_TwoSO_Four, Li_ThreeVO_FourEtc.
Li salts are used and these are dissolved in water, ethanol, etc.
The above alkali metal component using the catalyst preparation solution obtained by
Can be carried on a carrier.

Further, as the alkaline earth metal, barium
Calcium, magnesium, and strontium
It is preferably used. These can be used alone
However, two or more kinds can be used in combination. Al
As a potassium earth metal source, BaBr_Two, Ba (Br
O_Three)_Two, BaCl_Two, Ba (ClO_Two)_Two, Ba (C
10_Three)_Two, Ba (ClO_Four)_Two, BaI_Two, Ba (N
_Three)_Two, Ba (NO_Two)_Two, Ba (NO_Three)_Two, Ba
(OH)_Two, BaS, BaS_TwoO₆, BaS_FourO₆, B
a (SO_ThreeNH_Two)_TwoSuch as Ba salt; CaBr_Two, CaI
_Two, CaCl_Two, Ca (ClO_Three)_Two, Ca (IO_Three)
_Two, Ca (NO_Two)_Two, Ca (NO_Three)_Two, CaS
O_Four, CaS_TwoO_Three, CaS_TwoO₆, Ca (SO_ThreeNH
_Two)_Two, Ca (CH_ThreeCOO)_Two, Ca (H_TwoPO_Four)
_TwoCa salt, etc .; MgBr_Two, MgCO_Three, MgCl_Two,
Mg (ClO_Three)_Two, MgI_Two, Mg (IO_Three)_Two, M
g (NO_Two)_Two, Mg (NO_Three)_Two, MgSO_Three, Mg
SO_Four, MgS_TwoO₆, Mg (CH_ThreeCOO)_Two, Mg
(OH)_Two, Mg (ClO _Four)_TwoMg salt such as SrBr
_Two, SrCl_Two, SrI_Two, Sr (NO_Three)_Two, Sr
O, SrS_TwoO_Three, SrS_TwoO₆, SrS_FourO₆, Sr
(CH_ThreeCOO)_Two, Sr (OH)_TwoSr salt is used
Are obtained by dissolving them in water, ethanol, etc.
Using the catalyst preparation solution, the alkaline earth metal component is
You can have.

The alkali metal component and the alkaline earth metal component can be prepared by using the above-mentioned catalyst preparation solution by the usual impregnation method, coprecipitation method,
It can be supported on a carrier by a competitive adsorption method. At this time, the treatment conditions may be appropriately selected according to various methods, but usually, the treatment can be performed by bringing the carrier into contact with the catalyst preparation solution at a temperature of room temperature to 90 ° C. 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. The amount of alkali metal or alkaline earth metal supported is not particularly limited,
Each is usually preferably 0.01 to 10% by weight as a metal relative to the carrier, and most preferably 0.03 to 3% by weight. If the content of these metals is less than the lower limit, C
The selective oxidation activity of O 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 excessively large, so that the catalyst cost increases. After the above-mentioned alkali metal and alkaline earth metal are supported on the carrier, drying is performed. As a drying method,
For example, natural drying, evaporation to dryness, drying with a rotary evaporator or a blow dryer can be performed. After drying, it is usually 350 to 550 ° C, preferably 38 ° C.
2 to 6 hours at a temperature of 0 to 500 ° C, preferably 2 to 4 hours
Perform firing for a time. The catalyst of the present invention may be formed by, for example, extruding the catalyst itself or by a method of attaching the catalyst to a honeycomb or ring-shaped substrate, and the method is not particularly limited.

Next, carbon monoxide in a gas containing hydrogen as a main component is oxidized with oxygen using the catalyst of the present invention,
A method for producing a hydrogen-containing gas with reduced carbon monoxide will be described. Since the catalyst prepared as described above is usually calcined, the supported metal exists in an oxide state. Usually, this catalyst is reduced by hydrogen reduction before use. Hydrogen reduction is usually carried out under a hydrogen stream at 250 to 550.
C., preferably at a temperature of 300 to 530.degree. C., for 1 to 5 hours, preferably for 1 to 2 hours. The catalyst obtained as described above contains hydrogen as a main component and at least C
Oxygen is added to the hydrogen-containing gas containing O to perform a selective oxidation reaction of CO with oxygen. The CO oxidation method of the present invention selectively removes CO in a gas containing hydrogen as a main component obtained by reforming or partially oxidizing a raw material for hydrogen production (hereinafter referred to as a reformed gas or the like). It is preferably used for the production of a hydrogen-containing gas for a fuel cell, but is not limited thereto.

1. Reforming or Partial Oxidation Step of Hydrogen Production Raw Material In the present invention, CO contained in a reformed gas or the like obtained by reforming various hydrogen production raw materials is selectively oxidized and removed by oxygen using a catalyst. , To produce the desired hydrogen-containing gas with sufficiently reduced CO concentration. The step of obtaining the reformed gas or the like can be performed by any method such as a conventional hydrogen production step, particularly a conventionally practiced or proposed method in a hydrogen production step in a fuel cell system, as described below. . 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. Hydrogen production raw materials are hydrocarbons that can produce gas rich in hydrogen by steam reforming or partial oxidation, that is, methane, ethane,
Hydrocarbons such as propane and butane, or natural gas (L
NG), naphtha, gasoline, kerosene, light oil, heavy oil, asphalt and other hydrocarbon-based raw materials, methanol, ethanol,
Alcohols such as propanol and butanol, oxygen-containing compounds such as methyl formate, methyl tertiary butyl ether and dimethyl ether, and various city gases, L
PG, synthesis gas, coal and the like. Among these, what kind of raw material 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 supply of the raw material, but usually, methanol, methane or LNG, propane, etc. Alternatively, LPG, naphtha, kerosene or lower saturated carbon, city gas and the like are suitably used.

In general, when sulfur is present in these raw material hydrocarbons, desulfurization is preferably performed through the desulfurization step until the sulfur content is generally about 0.1 ppm or less. When the sulfur content in the raw material hydrocarbon is more than about 0.1 ppm, it may cause the deactivation of the reforming catalyst. Although the desulfurization method is not particularly limited, hydrodesulfurization, adsorption desulfurization and the like can be used as appropriate. Techniques belonging to reforming or partial oxidation (hereinafter referred to as reforming reaction, etc.) include:
Examples 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 appropriate combination. 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 kerosene, the following equation (2) or equation (3): CH ₄ + 2H ₂ O → 4H, in order to suppress the yield of hydrogen and the by-product of CO. ₂ + CO ₂ (2) Cn Hm + 2nH ₂ O → (2n + m / 2) H ₂ + nCO ₂ (3) It is preferable to select various conditions so that the reaction occurs as efficiently as possible.

Further, CO may be reformed and reformed by utilizing the shift reaction represented by the above formula (1). However, since this shift reaction is an equilibrium reaction, a certain 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 according to the type of raw materials, the type of reaction, the reaction conditions, and the like. Specific examples of some of them include catalysts effective for catalytic reforming reaction and partial oxidation of hydrocarbons, for example, supported Ru-based catalyst, supported Pt-based catalyst, supported Ni-based catalyst, and the like. it can. Since the conditions of the reforming reaction vary depending on the conditions such as the raw material used, the reforming reaction, the catalyst, the type of the reaction apparatus, the reaction system, and the like, they may be appropriately determined. In any case, the conversion of the raw material should be sufficient (preferably 100
% Or nearly 100%), and various conditions are desirably selected so that the yield of hydrogen is as large as possible. If necessary, a method of separating and recycling unreacted hydrocarbons and alcohols may be adopted. If necessary, generated or unreacted CO ₂ and water may be appropriately removed.

2. Selective Oxidation (Conversion) Removal Step of CO As described above, it is possible to obtain 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. it can. In the method for producing a hydrogen-containing gas of the present invention, 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 containing a small amount of CO. Therefore, oxidation of hydrogen must be suppressed as much as possible. 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 catalyst of the present invention is generally used in a reduced state, it is preferable to perform a reduction operation with hydrogen when the catalyst is not in a reduced state. By using the catalyst of the present invention, CO ₂
It shows good results in the selective oxidation and removal of CO with respect to the raw material gas having a low content, and also obtains good results even under the condition where the CO ₂ content is high. Normally, in a fuel cell system, a reformed gas having a general concentration of CO ₂ , that is, a gas containing ₅ to 33% by volume, preferably 10 to 25% by volume, more preferably 15 to 20% by volume of CO ₂ 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, it is contained in an amount of about 5 to 30%. When the catalyst of the present invention is used, the CO concentration is low (0.6% by volume).
Hereinafter, the CO concentration in the source gas can also 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 be suitably reduced. In the present invention, by using the catalyst of the present invention, C
O ₂ is from 60 to 3 in conditions such that there more than 15% volume
CO2 in a temperature range including a relatively high temperature of 00 ° C.
Can be efficiently removed. Also, C
The conversion and removal reaction of O is an exothermic reaction like the oxidation reaction of hydrogen, which is a concurrent side reaction, and recovering the generated heat and utilizing it in the fuel cell is effective in improving the power generation efficiency. When adding oxygen gas to reformed gas, etc.
Usually, pure oxygen (O ₂ ), air or oxygen-enriched air is preferably used. The added amount of the oxygen gas is oxygen / CO
(Molar ratio) is preferably adjusted to be 0.5 to 5, more preferably 1 to 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, it is usually from normal pressure to 1 MPa.
G, preferably in a pressure range from normal pressure to 0.5 MPa · G. If the reaction pressure is set too high, the power for pressurization must be increased accordingly, which is economically disadvantageous. In particular, if it exceeds 1 MPa · G, it is subject to the regulations of the High Pressure Gas Control Law, As the explosion limit is widened, there is also the problem of reduced safety.

The reaction is usually carried out in a very wide temperature range of 60 ° C. or higher, preferably 60 to 300 ° C.
The reaction can be suitably performed while stably maintaining the selectivity for the 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 addition, the reaction is usually performed using GHSV (value obtained by dividing the supplied volume velocity in the standard state of the supplied gas by the apparent volume of the catalyst layer to be used = gas space velocity) from 5000 to 1
It is preferable to perform the selection in the range of 00000 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. For this reason, GHSV preferably
It is selected in the range of 6000 to 60000 hr ^-1 . This C
Since the CO conversion reaction in the O conversion and removal step is an exothermic reaction, the reaction increases 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. In that sense, it may be better that the GHSV is not too large. There is no particular limitation on the reactor used for the conversion and removal of CO, and various types of reactors can be applied as long as the reaction conditions described above can be satisfied. In order to facilitate the control, it is desirable to use a reactor or a reactor having a good removal 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.

The hydrogen-containing gas produced by the method of the present invention has a sufficiently reduced CO concentration as described above, so that the poisoning and deterioration of the platinum electrode catalyst of the fuel cell can be sufficiently reduced. , Its life, power generation efficiency and 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. The hydrogen-containing gas obtained according to the present invention can be suitably used as a fuel for various types of H ₂ combustion type fuel cells. In particular, a type using platinum (platinum catalyst) for at least the fuel electrode (negative electrode) is used. can be advantageously utilized as a fuel supply for various into H ₂ combustion fuel cell (phosphoric acid fuel cell, KOH-type fuel cell, such as low temperature operation type fuel cell including a polymer electrolyte fuel cell). In addition,
Oxygen introduction according to the method of the present invention between a reformer of a conventional fuel cell system (if a reformer is provided after the reformer, the reformer is also regarded as a part of the reformer) and the fuel cell. By incorporating equipment and reactors, or
In those already equipped with an oxygen introduction device and a conversion reaction device, by using the catalyst as a CO conversion removal catalyst and adjusting the reaction conditions as described above, it is possible to configure a fuel cell system superior to the conventional one. It becomes possible.

[0022]

EXAMPLES Next, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples. The S of the catalyst obtained in each example was
And the CO concentration after the selective oxidation reaction were measured by the following methods. <Measurement of S> In a cross section passing through the center of the sphere of the spherical catalyst or a cross section cut in parallel with the bottom surface of the columnar catalyst,
The value obtained by linearly analyzing the amount of Ru metal contained in the outer peripheral portion up to a distance of one third of the radius from the catalyst surface using an electron beam microanalyzer (EPMA) is defined as N, and is included in the entire catalyst. S when the line analysis value of Ru metal is No
Was determined from the equation of S = (N / No) × 100 (%). <Measurement of CO concentration> 10 cc of each catalyst was filled in a quartz reaction tube having an inner diameter of 25 mm. After reducing the catalyst with hydrogen in a reaction tube at 500 ° C. for 1 hour, GHSV: 100
Under the conditions of 00h ^-1, the following hydrogen-containing gases A and B were introduced at an inlet temperature of 100 ° C. to perform a CO selective oxidation reaction. The obtained gas was sampled, and the CO concentration was measured by gas chromatography. The results are shown in Table 1. Hydrogen-containing gas A; CO / O ₂ / CO ₂ / H ₂ O / N ₂ / H ₂ = 0.6 / 0.6 / (volume%) 15/20 / 2.4 / Balance Hydrogen-containing gas B; CO / O ₂ / CO ₂ / H ₂ O / N ₂ / H ₂ = 0.6 / 1.5 / (volume%) 15/20 / 6.0 / Balance

Example 1 2 ml of an aqueous ruthenium nitrate (Ru (NO ₃ ) ₃ ) solution (50 g / l as Ru metal) was placed in a 50 ml beaker, and 1.6 ml of ion-exchanged water was added thereto and stirred until uniform. did. In another 50 ml beaker, 10 g of alumina carrier KHD24 (manufactured by Sumitomo Chemical Co., Ltd., spherical shape having a diameter of 2 to 4 mm) was weighed. Ruthenium nitrate aqueous solution prepared above on the alumina carrier,
After the carrier was added dropwise with good stirring with a glass rod, the mixture was further stirred well for about 1 minute. Next, the mixture was allowed to stand at room temperature for 3 hours, then placed in a drier, and dried at 120 ° C. for 24 hours to obtain a catalyst in which Ru was supported on an alumina carrier at 1.0% by weight. Comparative Example 1 5 ml of an aqueous ruthenium nitrate (Ru (NO ₃ ) ₃ ) solution (50 g / l as Ru metal) was placed in a 50 ml beaker, and 10 ml of ethanol and 10 ml of water were added thereto and stirred. In another 50 ml beaker, 10 g of alumina carrier KHD24 (manufactured by Sumitomo Chemical Co., Ltd., spherical shape having a diameter of 2 to 4 mm) was weighed.
The alumina carrier was immersed in the ruthenium nitrate solution prepared above, and left as it was for about 12 hours. The obtained catalyst was taken out of the beaker, left at room temperature for 3 hours, then put in a drier and dried at 120 ° C. for 24 hours.
Thus, a catalyst carrying 1.1% by weight of u was obtained.

Example 2 Rutile type titania (TiO ₂ , manufactured by Ishihara Sangyo Co., Ltd., CR
-EL, surface area: 7 m 2 / g) 160 g and pseudo-boehmite alumina powder (Catalo, manufactured by Kako Kagaku Kogyo Co., Ltd.)
59.7 g of (id-AP) were mixed and sufficiently kneaded with ion-exchanged water in a kneader under heating to adjust the water content to an extent suitable for extrusion molding. This was formed into a cylindrical shape having a diameter of 2 mm and a length of 0.5 to 1 cm using an extruder, and drying was performed using a dryer.
C. and dried for 24 hours. Then, in a firing furnace at 500 ° C., 4
Calcination for a period of time gave a titania / alumina support. The weight ratio of titania / alumina was 80/20. Ruthenium chloride (RuCl ₃ .nH ₂ O, Ru metal content: 38.0
0.263 g is weighed into a beaker. 0.259 g of potassium nitrate (KNO ₃ ) was added thereto, and 1 ml of ion-exchanged water was further added and dissolved. Another 5
In a 0 ml beaker, weigh 10 g of the carrier prepared above, pour the above-prepared ruthenium solution with stirring, and place it in a dryer without standing.
Dry at 0 ° C. overnight. Furthermore, put in a firing furnace at 500 ° C for 4 hours.
After calcination for an hour, a catalyst in which Ru and K were supported on a titania / alumina support at 1% by weight and 0.1% by weight, respectively, was obtained.

Example 3 A titania / alumina carrier was prepared in the same manner as in Example 2 except that the ruthenium- and potassium-containing solution was poured into the carrier, and then left at room temperature for 3 hours before being put into a dryer. A catalyst supporting 1% by weight of Ru and 0.1% by weight of K was obtained. Comparative Example 2 In Example 2, the amount of ion-exchanged water in which ruthenium chloride and potassium nitrate were dissolved was doubled to 2 ml,
10 g of the titania / alumina carrier prepared in Example 2 was weighed into a flask of a vacuum impregnating apparatus, and the inside of the vacuum impregnating apparatus was evacuated with a rotary pump. .
Next, the vacuum impregnating apparatus was returned to normal pressure, and left at room temperature for 3 hours. Then, drying and firing were performed in the same manner as in Example 2, and 1 wt% of Ru and 0.1 wt% of K were added to the titania / alumina carrier.
A supported catalyst was obtained.

[0026]

[Table 1]

[0027]

According to the catalyst of the present invention, the catalytic activity per supported ruthenium is remarkably excellent, and CO in a gas containing hydrogen as a main component can be efficiently converted and removed over a wide temperature range. In addition, the poisoning of platinum at the hydrogen electrode of the hydrogen-oxygen type fuel cell by CO can be prevented, the life of the battery can be prolonged, and the stability of output can be improved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an example of a CO oxidation catalyst of the present invention and a diagram showing a relationship between a distance in a width direction and an X-ray intensity.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01M 8/06 H01M 8/06 RF term (Reference) 4G040 EA02 EA03 EA06 EA07 EB31 4G069 AA03 AA08 BA01A BA02A BA04A BB04A BB06A BB06B BC01A BC02A BC03A BC04A BC05A BC06A BC08A BC09A BC10A BC12A BC13A BC50A BC70A BC70B CC32 DA06 EA02X EA04X FA02 FB67 FC08 4H060 AA01 AA04 BB08 BB11 FF02 GG02 5H027 A06

Claims (8)

[Claims] In a CO oxidation catalyst comprising at least a ruthenium component supported on an inorganic refractory carrier, a cross section of the catalyst is measured by electron probe microanalysis (E).
In a diagram showing the relationship between the cross-sectional width direction distance r (the distance from the center to the catalyst surface) and the X-ray intensity I obtained by performing line analysis measurement on ruthenium atoms in one direction using a PMA) apparatus, From the integrated value N ₀ of I (r) between one catalyst surface -r ₀ and the other catalyst surface r ₀ ,
The value obtained by subtracting the integral value N ₁ of I (r) between 2 / 3r ₀ and 2 / 3r ₀ is defined as N, and the ratio of N to N ₀ S = (N / N ₀ ) × 100 is 50. A CO oxidation catalyst characterized by the above. 2. The catalyst according to claim 1, which has a spherical or cylindrical shape. 3. The inorganic refractory carrier is at least one selected from alumina, titania and silica.
Or the catalyst according to 2. 4. The catalyst according to claim 1, wherein the carrier further supports an alkali metal component and / or an alkaline earth metal component. 5. The method according to claim 1, wherein the alkali metal is potassium, sodium, lithium, cesium or rubidium.
A catalyst according to any one of claims 1 to 4. 6. The method according to claim 1, wherein the alkaline earth metal is barium, calcium, magnesium or strontium.
The catalyst according to any one of claims 1 to 5, 7. A method for producing a hydrogen-containing gas, comprising removing CO from a hydrogen-containing gas using the catalyst according to claim 1. Description: 8. The method according to claim 7, wherein the hydrogen-containing gas is a hydrogen-containing gas for a fuel cell.