JP5105937B2 - Method for reducing carbon monoxide concentration - Google Patents

Description

  The present invention relates to a method of selectively oxidizing carbon monoxide in a raw material gas containing carbon monoxide and hydrogen to reduce the concentration of carbon monoxide, and a fuel cell system using the method.

  A fuel cell has a feature that high efficiency can be obtained because a free energy change caused by a combustion reaction of fuel can be directly taken out as electric energy. In addition to the fact that it does not emit harmful substances, it is being developed for various uses. In particular, solid polymer fuel cells are characterized by high power density, compactness, and operation at low temperatures.

In general, as a fuel gas for a fuel cell, a gas containing hydrogen as a main component is used, and the raw materials thereof include natural gas, hydrocarbons such as LPG, naphtha and kerosene, alcohols such as methanol and ethanol, dimethyl ether and the like. Of ether or the like is used.
However, since elements other than hydrogen exist in these raw materials, it is inevitable that impurities derived from carbon are mixed in the fuel gas to the fuel cell. Among these, carbon monoxide poisons platinum-based noble metals used as electrode catalysts for fuel cells. Therefore, if carbon monoxide is present in the fuel gas, sufficient power generation characteristics cannot be obtained. In particular, a fuel cell operated at a low temperature has a stronger carbon monoxide adsorption and is more susceptible to poisoning. Therefore, in a system using a polymer electrolyte fuel cell, it is indispensable that the concentration of carbon monoxide in the fuel gas is reduced.

  As a method for reducing the concentration of carbon monoxide, a method in which carbon monoxide in the reformed gas obtained by reforming the raw material is reacted with water vapor and converted into hydrogen and carbon dioxide, so-called water gas shift reaction is used. However, normally, this method can reduce the carbon monoxide concentration only to about 0.5 to 1 vol%. However, although the carbon monoxide resistance of the catalyst used for the fuel cell electrode depends on the metal species used, the carbon monoxide concentration in the fuel gas is preferably 100 volppm or less in order for the fuel cell to operate efficiently. The water gas shift reaction alone is not sufficient. Therefore, it is required to further reduce the carbon monoxide concentration lowered to about 0.5 to 1 vol% by the water gas shift reaction.

As a method for further reducing the carbon monoxide concentration, a method of adsorptive separation of carbon monoxide and a method of membrane separation can be considered. However, although the hydrogen purity obtained by these methods is high, there are problems that the apparatus cost is high and the apparatus size is large, which is not practical. On the other hand, the chemical method is a more realistic method. As a chemical method, a method of methanating carbon monoxide, a method of oxidizing to carbon dioxide, and the like can be considered. In addition, a two-stage treatment method in which methanation is performed in the former stage and oxidation is performed in the latter stage has been proposed (see Patent Document 1).
JP-A-11-86892

  However, the method of methanating carbon monoxide is not suitable in terms of efficiency because hydrogen used as fuel for the fuel cell is lost. Even in the two-stage treatment method, loss of hydrogen in the previous stage is inevitable. Therefore, it is appropriate to employ a method in which carbon monoxide is oxidized to carbon dioxide. The point in this method is how to selectively oxidize carbon monoxide mixed in a trace amount or a small amount in a large excess of hydrogen.

In a fuel cell system, when reforming a raw material to obtain hydrogen, a step of removing sulfur content in the raw material in desulfurization is required. In this desulfurization process, there is an option to recycle part of the generated hydrogen in order to perform hydrogen co-desulfurization for the purpose of improving desulfurization efficiency. At this time, in order to avoid clogging due to condensation of water in the recycle line, a method of reducing moisture in the off-gas after the shift reaction with a heat exchanger is known (for example, Patent Document 2).
JP 2003-012302 A

  However, when moisture is reduced by a heat exchanger, the gas temperature is lowered. In the case of a catalyst in which a relatively large amount of Ru is supported, the catalyst operates even when the gas temperature is low in exchange for the narrowness of the usable window, but a catalyst having a wide usable window cannot secure a sufficient temperature.

As a method for removing moisture, a method of removing moisture by permeating it from an organic solvent such as ethanol using a zeolite membrane is also known (see Patent Document 3). Compared to the distillation methods used in the past, the energy saving is significant and the system is simple to operate.
Japanese Patent Laying-Open No. 2005-074382

The zeolite membrane is a coating of zeolite crystals on the outer surface of a porous ceramic tube, and types such as A type, Y type, T type, and ZSM-5 type are known depending on the type of zeolite. (For example, Patent Documents 4 to 7). Since separation is performed by passing only molecules smaller than the diameter of the pores of the zeolite, normally, small molecules such as hydrogen and carbon monoxide are permeated.
Japanese Patent Laid-Open No. 7-089714 JP-A-7-185275 Japanese Patent Laid-Open No. 2001-240411 JP 2002-18247 A

  The key point in the method of selectively oxidizing carbon monoxide in a gas containing hydrogen and carbon monoxide using a catalyst is an industrially satisfactory catalyst replacement frequency, and a trace amount in hydrogen present in a large excess. This is how the carbon monoxide mixed in a small amount can be selectively oxidized.

  As a result of diligent research on these problems, the present inventors have an important role in reducing the water concentration in the introduced gas by a separation membrane using a zeolite membrane in the method of selectively oxidizing carbon monoxide. And the present invention has been completed.

That is, the present invention uses a catalyst in which Ru is supported on a carrier made of an inorganic oxide containing at least one selected from alumina, silica, zirconia, and titania, and uses a catalyst in a source gas containing hydrogen and carbon monoxide. In the selective oxidation of carbon oxide, the water concentration in the raw material gas is reduced by a separation membrane consisting of a zeolite membrane , and then the selective oxidation reaction is performed. The water concentration in the raw material gas is controlled by the sweep gas flow rate. The present invention also relates to a method for reducing the concentration of carbon monoxide in a source gas, wherein the moisture concentration in the source gas is reduced to 15 vol% or less .

Further, the present invention provides at least one metal selected from Pt, Pd, Au, Ag, Rh and Ir and Ru on a support made of an inorganic oxide containing at least one selected from alumina, silica, zirconia and titania. In selective oxidation of carbon monoxide in a raw material gas containing hydrogen and carbon monoxide using a supported catalyst, the water concentration in the raw material gas is reduced by a separation membrane consisting of a zeolite membrane , and then a selective oxidation reaction The concentration of carbon monoxide in the source gas is reduced by controlling the moisture concentration in the source gas by the sweep gas flow rate and reducing the moisture concentration in the source gas to 15 vol% or less. Regarding the method.

  Further, the present invention is characterized in that the separation membrane is a separation membrane selected from a mordenite membrane, a ZSM-5 type zeolite membrane, an A type zeolite membrane, a Y type zeolite membrane, a T type zeolite membrane and a ZSM-35 type zeolite membrane. To the method described above.

  The present invention also relates to the above-described method, wherein the raw material gas is obtained by subjecting a hydrocarbon, alcohol or ether to a reforming reaction and a water gas shift reaction.

  The present invention also relates to the above method, wherein the raw material gas is obtained by subjecting hydrocarbon, alcohol or ether to desulfurization reaction, reforming reaction and water gas shift reaction.

The present invention, the permeate side of the environment of the separation membrane, flowing the Air as scan Ipugasu, flowing product gas after the selective oxidation reaction of carbon monoxide as a sweep gas, a reforming earlier feed gas as sweep gas A portion that flows Air as a sweep gas and a portion that flows a raw material gas before reforming, and a generated gas after a selective oxidation reaction of carbon monoxide and a raw material gas before reforming as a sweep gas The method described above, wherein the environment is selected from the group consisting of flowing parts.

  The present invention also relates to an apparatus for producing a high-concentration hydrogen-containing gas by reducing the carbon monoxide concentration in the raw material gas by the method described above.

  The present invention also relates to a fuel cell system that supplies a high-concentration hydrogen-containing gas obtained from the above-described apparatus as a cathode-side fuel.

  In the method of selectively oxidizing carbon monoxide by contacting a catalyst containing a raw material gas containing carbon monoxide and hydrogen with a catalyst according to the method of the present invention, the concentration of carbon monoxide in the raw material gas is reduced over a long period of time. Is possible. The resulting product gas can be suitably employed as a fuel gas for a fuel cell system using a solid polymer fuel cell.

Hereinafter, the present invention will be described in detail.
The present invention relates to a method for selectively oxidizing carbon monoxide in a raw material gas containing hydrogen and carbon monoxide in the presence of a catalyst.
The catalyst used in the present invention is a catalyst in which Ru is supported on a support made of an inorganic oxide containing at least one selected from alumina, silica, zirconia and titania, or at least one selected from alumina, silica, zirconia and titania. It is a catalyst in which at least one metal selected from Pt, Pd, Au, Ag, Rh and Ir and Ru are supported on a support made of an inorganic oxide.

  As the carrier, an inorganic oxide containing at least one selected from alumina, silica, zirconia and titania is used. Among these, alumina (α-alumina, θ-alumina, γ-alumina, etc.) is more preferable. As alumina, γ-alumina is particularly preferable. The shape, size, and molding method of the carrier are not particularly limited. Further, at the time of molding, an appropriate binder may be added to improve moldability.

The metal to be supported is Ru, or at least one metal selected from the group consisting of Pt, Pd, Ru, Au, Ag, Rh and Ir and Ru. Of these, Ru, or Pt and Ru are preferable.
The supported amount of the supported metal is not particularly limited, but regarding Ru, 0.05 to 2% by mass is preferable and 0.2 to 1% by mass is particularly preferable based on the total amount of the catalyst. Regarding other metals, 0.005 to 1% by mass is preferable, and 0.01 to 0.5% by mass is particularly preferable based on the total amount of the catalyst.

  The supporting method is not particularly limited, and an impregnation method or an equilibrium adsorption method using a metal solution in which a metal salt of the metal to be supported is dissolved in a solvent is preferably used. The solvent used in the metal solution is not particularly limited as long as it can dissolve the metal salt, but water or ethanol is preferable. There is no particular limitation on the number of times of loading, and it is preferable to load all at the same time or in several times in the loading step.

The metal salt is not particularly limited as long as it is soluble in a solvent. For example, in the case of Pt, PtCl ₂ , K ₂ PtCl ₄ , K ₂ PtCl ₆ , H ₂ PtCl ₆ , (NH ₄ ) ₂ PtCl ₆ , Pt (NH ₃ ) ₄ Cl ₂ .H ₂ O and Pt (C ₅ H ₇ O ₂ ) ₂ are preferred. Pd is preferably Na ₂ PdCl ₆ .nH ₂ O, (NH ₄ ) ₂ PdCl ₆ , Pd (NH ₃ ) ₄ Cl ₂ .H ₂ O and Pd (C ₂ H ₅ CO ₂ ) ₂ . In Ru, RuCl ₃ .nH ₂ O, Ru (NO ₃ ) ₃ , K ₂ (RuCl ₅ (H ₂ O)), (NH ₄ ) ₂ RuCl ₆ , (Ru (NH ₃ ) ₆ ) Br ₃ , Ru ( _{NH 3) 6 Cl 3, Na} 2 RuO 4, K 2 RuO 4, Ru (CO) 5, [Ru (NH 3) 5 Cl] Cl 3, Ru 3 (CO) 12 and _{Ru (C 5} H 7 _{O 2 2} is preferred. For Au, AuBr ₃ , AuCl ₃ , KAuBr ₄ and Au (OH) ₃ are preferred. In Ag, AgNO ₃ , AgBF ₄ , AgPF ₆ , Ag (CF ₃ SO ₃ ), and Ag (CH ₃ COO) ₂ are preferable. In Rh, Na ₃ RhCl ₆ , RhCl ₃ · nH ₂ O, [Rh (NH ₃ ) ₅ Cl] Cl ₃ , Rh (NO ₃ ) ₃ and Rh (C ₅ H ₇ O ₂ ) ₂ are preferable. In _{Ir, Na 2 IrCl 6 · nH} 2 O, Na 2 IrBr 6, [Ir (NH 3) 5 Cl] Cl 3, IrCl 4 · nH 2 O and _{Ir (C 5 H 7 O 2} ) 3 are preferable. Moreover, even if it is the same kind of metal, you may mix a some metal salt.

  After the metal is supported on the carrier, the solvent needs to be removed, and any method of natural drying in air, heat drying, and deaeration drying under reduced pressure can be employed. In addition, although it is also preferably performed after drying, it is preferably performed at a temperature of 300 to 800 ° C. for 1 to 5 hours in a hydrogen atmosphere. In the prepared catalyst, chloride ions derived from a carrier or a supported metal salt may remain, but the chloride ion concentration is preferably 100 ppm by mass or less. More preferably, it is 80 mass ppm or less, Most preferably, it is 50 mass ppm or less. When the chloride ion concentration is higher than 100 ppm by mass, the aggregation of the supported metal is promoted and the carbon monoxide selective oxidation activity is lowered. When the catalyst prepared by the above method is put to practical use, hydrogen reduction is usually performed as a pretreatment. The conditions are 100 to 800 ° C., preferably 180 to 250 ° C. for 1 to 5 hours, preferably 1 to 3 hours.

  As the raw material gas containing carbon monoxide and hydrogen used in the present invention, a hydrocarbon or oxygen-containing compound usually used as a starting material (raw fuel) of fuel gas for a fuel cell is subjected to a reforming reaction by various methods. A gas containing hydrogen as a main component is obtained. Examples of the hydrocarbon include natural gas, LPG, naphtha, kerosene, gasoline or various equivalents thereof, and hydrocarbons such as methane, ethane, propane, and butane. Examples of the oxygen-containing compound include various alcohols such as methanol and ethanol, and various ethers such as dimethyl ether.

  The method for reforming the raw fuel is not particularly limited, and various methods such as a steam reforming method, a partial oxidation reforming method, and autothermal reforming can be used. Any of these methods can be employed in the present invention.

If the raw fuel containing sulfur is supplied to the reforming process as it is, the reforming catalyst will be poisoned, the activity of the reforming catalyst will not be expressed, and the life will be shortened. Prior to this, it is preferable to desulfurize the raw fuel.
The conditions for the desulfurization reaction vary depending on the state of the raw fuel and the sulfur content, and thus cannot be generally stated, but the reaction temperature is usually preferably from room temperature to 450 ° C, particularly preferably from room temperature to 300 ° C. The reaction pressure is preferably from normal pressure to 1 MPa, and particularly preferably from normal pressure to 0.2 MPa. Preferably in the range of 0.01～15H ^-1 when SV raw materials is a liquid, more preferably in the range of 0.05～5H ^-1, range 0.1～3H ^-1 are particularly preferred. When using a gas precursor is preferably in the range of 100～10,000H ^-1, more preferably in the range of 200～5,000H ^-1, range 300～2,000H ^-1 are particularly preferred.

Further, although the reforming reaction conditions are not necessarily limited, usually, the reaction temperature is preferably 200 to 1,000 ° C, particularly preferably 500 to 850 ° C. The reaction pressure is preferably from normal pressure to 1 MPa, and particularly preferably from normal pressure to 0.2 MPa. GHSV is preferably from 100～100,000H ^-1, more preferably 300~50,000h ^-1, 500~30,000h ^-1 is particularly preferred.
The gas (reformed gas) obtained by the reforming reaction contains hydrogen as a main component, but other components include carbon monoxide, carbon dioxide, water vapor, and the like.

In the present invention, it is possible to directly use the reformed gas as a raw material gas, but it is also possible to use a gas obtained by pretreating the reformed gas in advance to reduce the carbon monoxide concentration to some extent.
Examples of such pretreatment include a method of reacting carbon monoxide in the reformed gas with water vapor to convert it into hydrogen and carbon dioxide in order to reduce the concentration of carbon monoxide in the reformed gas, so-called water gas shift reaction. . Examples of the pretreatment other than the water gas shift reaction include a method of adsorptive separation of carbon monoxide or a method of membrane separation.

In the present invention, in order to reduce carbon monoxide in the reformed gas and increase hydrogen, it is preferable that the reformed gas is further subjected to a water gas shift reaction as a raw material gas, whereby the carbon monoxide concentration Can be made more effective.
The reaction conditions for the water gas shift reaction are not necessarily limited depending on the composition of the reformed gas and the like, but the reaction temperature is usually preferably 120 to 500 ° C, and particularly preferably 150 to 450 ° C. The reaction pressure is preferably from normal pressure to 1 MPa, and particularly preferably from normal pressure to 0.2 MPa. SV is preferably 100~50,000h ^-1, especially 300～10,000H ^-1 are preferred.

The present invention is characterized in that, in selectively oxidizing carbon monoxide in a raw material gas containing hydrogen and carbon monoxide, a selective oxidation reaction is performed after the moisture concentration in the raw material gas is reduced by a separation membrane. To do.
The separation membrane used in the present invention is preferably a zeolite membrane. The zeolite membrane is obtained by forming zeolite crystals on the surface of a porous ceramic support or a metal support such as a sintered metal. The material of the porous support is appropriately selected from, for example, alumina, metal, organic polymer material, inorganic polymer material such as glass, ceramics such as mullite crystal, etc. according to the type of the target zeolite membrane. However, it is not limited to these. For example, a pipe having an outer diameter of about 10 mm and a length of about 20 cm to 100 cm, or a cylinder having an outer diameter of 30 mm to 100 mm and a length of 20 cm to 100 cm and a larger number of holes having an inner diameter of about 2 mm to 12 mm in the axial direction or a lotus root shape Or a 30 mm square plate is preferable. The membrane area is appropriately determined as an area necessary for achieving a predetermined moisture reduction amount.
The type of the zeolite membrane is not particularly limited, and examples thereof include zeolite membranes such as mordenite membrane, ZSM-5 type zeolite membrane, A type zeolite membrane, Y type zeolite membrane, T type zeolite membrane, and ZSM-35 type zeolite membrane. It is done.

  In the present invention, the moisture concentration in the raw material gas containing carbon monoxide and hydrogen is reduced by the separation membrane such as the zeolite membrane, and the carbon monoxide is selectively oxidized in the presence of the catalyst. For example, a reforming reaction is performed using a hydrocarbon such as LPG as a raw material at a steam / carbon molar ratio of 3.0, and the moisture concentration in the gas subjected to the shift reaction is about 20 vol%. This is preferably reduced to 15 vol% or less, more preferably to 12 vol% or less by the zeolite membrane.

In the present invention, conditions selected from the following (1) to ( 5 ) can be preferably adopted as the environment on the permeation side of the separation membrane, but are not limited to these environments.
( 1 ) Flowing Air as a sweep gas ( 2 ) Flowing a product gas after selective oxidation of carbon monoxide as a sweep gas ( 3 ) Flowing a raw material gas before reforming as a sweep gas ( 4 ) Sweep gas ( 5 ) As a sweep gas, from a portion where the product gas after the selective oxidation reaction of carbon monoxide and the material gas before the reforming flow. Composed

  In the present invention, the raw material gas used for the selective oxidation reaction contains carbon monoxide and hydrogen, and the carbon monoxide concentration is usually 0.1 to 2 vol%, preferably 0.5 to 1 vol%. On the other hand, the hydrogen concentration is usually 40 to 85 vol%. Moreover, nitrogen, carbon dioxide, etc. may be contained as components other than carbon monoxide and hydrogen, for example.

  In the present invention, an oxygen-containing gas is added to the source gas in order to remove carbon monoxide from the source gas by an oxidation reaction. Although it does not specifically limit as oxygen-containing gas, Air and oxygen are mentioned. For example, when the concentration of carbon monoxide is 0.5 vol%, the oxygen-containing gas to be introduced has a total oxygen amount to carbon monoxide concentration ratio (molar ratio) in the raw material gas in the range of 0.5 to 4.0. In particular, 0.5 to 2.5 is preferable. When the concentration ratio is less than 0.5, oxygen is not stoichiometrically sufficient, so that the oxidation reaction with carbon monoxide does not proceed sufficiently. On the other hand, when the concentration ratio is greater than 3.0, side reactions such as a decrease in hydrogen concentration due to hydrogen oxidation, a rise in reaction temperature due to the heat of oxidation of hydrogen, and methane formation are likely to occur.

The reaction pressure during the oxidation reaction of carbon monoxide is preferably in the range of normal pressure to 1 MPa, particularly preferably normal pressure to 0.2 MPa in consideration of the economics and safety of the fuel cell system. The reaction temperature is not particularly limited as long as it lowers the carbon monoxide concentration. However, the reaction rate is slow at low temperatures and the selectivity decreases at high temperatures. 100-280 degreeC is preferable. If GHSV is too high, the oxidation reaction of carbon monoxide will not proceed easily. On the other hand, if it is too low, the apparatus will be too large. Therefore, the range of 1,000 to 50,000 h ⁻¹ is preferable, particularly 3,000 to 30. A range of 1,000,000 ⁻¹ is preferred.

  According to the method of the present invention, the carbon monoxide concentration in the raw material gas can be reduced to 100 volppm or less, preferably 50 volppm or less, and most preferably 10 volppm or less. Can be maintained. Therefore, the fuel gas with a reduced carbon monoxide concentration obtained by the method of the present invention is capable of suppressing the poisoning and deterioration of the noble metal catalyst used for the electrode of the fuel cell, while maintaining high power generation efficiency. The lifetime can be maintained.

  The present invention also provides an apparatus for producing a high-concentration hydrogen-containing gas by reducing the carbon monoxide concentration in the raw material gas using the method described above.

Furthermore, the present invention provides a fuel cell system characterized in that a high-concentration hydrogen-containing gas obtained from the above-described apparatus is supplied as a cathode-side fuel.
The fuel cell system of the present invention will be described below. FIG. 2 is a schematic view showing an example of the fuel cell system of the present invention. The raw fuel in the fuel tank 3 flows into the desulfurizer 5 through the fuel pump 4. At this time, if necessary, the hydrogen-containing gas from the selective oxidation reactor 11 can be added. The desulfurizer 5 can be filled with, for example, a copper-zinc-based or nickel-zinc-based sorbent. The raw fuel desulfurized by the desulfurizer 5 is mixed with water from the water tank 1 through the water pump 2, then introduced into the vaporizer 6 and fed into the reformer 7.

The reformer 7 is heated by a heating burner 18. As the fuel for the heating burner 18, the anode off gas of the fuel cell 17 is mainly used, but the fuel discharged from the fuel pump 4 can be supplemented as necessary. As the catalyst filled in the reformer 7, a nickel-based, ruthenium-based, or rhodium-based catalyst can be used.
The raw material gas containing hydrogen and carbon monoxide produced in this way undergoes a reforming reaction by the high temperature shift reactor 9 and the low temperature shift reactor 10. The high temperature shift reactor 9 is filled with an iron-chromium catalyst, and the low temperature shift reactor 10 is filled with a catalyst such as a copper-zinc catalyst.

  The gas reformed by the high temperature shift reactor 9 and the low temperature shift reactor 10 is led to the selective oxidation reactor 11 after the moisture concentration is reduced by the moisture reducing device 19 using a separation membrane. The selective oxidation reactor 11 includes a catalyst in which Ru is supported on a support made of an inorganic oxide containing at least one selected from alumina, silica, zirconia and titania, or at least one selected from alumina, silica, zirconia and titania. A support made of an inorganic oxide containing seeds is packed with a catalyst supporting Ru and at least one metal selected from Pt, Pd, Au, Ag, Rh and Ir. The reformed gas is mixed with the air supplied from the air blower 8, and carbon monoxide is selectively oxidized in the presence of the catalyst, and the carbon monoxide concentration is reduced to a level that does not affect the characteristics of the fuel cell. The

  The polymer electrolyte fuel cell 17 includes an anode 12, a cathode 13, and a solid polymer electrolyte 14, and a fuel gas containing high-purity hydrogen with a reduced carbon monoxide concentration obtained by the above method on the anode side. However, the air sent from the air blower 8 is introduced to the cathode side after appropriate humidification treatment (a humidifier is not shown) if necessary. At this time, a reaction in which hydrogen gas becomes protons and emits electrons proceeds at the anode, and a reaction in which oxygen gas obtains electrons and protons to become water proceeds at the cathode. In order to promote these reactions, platinum black and Pt catalyst or Pt-Ru alloy catalyst supported on activated carbon are used for the anode, and platinum black and Pt catalyst supported on activated carbon are used for the cathode. In general, both the anode and cathode catalysts are formed into a porous catalyst layer together with polytetrafluoroethylene, a low molecular weight polymer electrolyte membrane material, activated carbon and the like as necessary.

  Next, the aforementioned porous catalyst layer is laminated on both sides of a polymer electrolyte membrane known by a trade name such as Nafion (DuPont), Gore (Gore), Flemion (Asahi Glass), Aciplex (Asahi Kasei). Then, a MEA (Membrane Electrode Assembly) is formed. Further, the fuel cell is assembled by sandwiching the MEA with a separator having a gas supply function, a current collecting function, particularly an important drainage function in the cathode, and the like made of a metal material, graphite, carbon composite and the like. The electric load 15 is electrically connected to the anode and the cathode. The anode off gas is consumed in the heating burner 18. The cathode off gas is discharged from the exhaust port 16.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

[catalyst]
A catalyst in which 0.01% by mass of Pt and 0.25% by mass of Ru are supported on γ-alumina is used as a catalyst. Here, the external ratio represents a ratio to the carrier.

[Zeolite membrane]
(Mordenite film)
A seed crystal was coated on a porous alumina tube support, and mordenite was formed by a secondary growth method. First, the support was vertically immersed in a mordenite seed crystal (Si / Al = 5.1) aqueous solution (concentration 1.76 g / l), then pulled up at about 3 cm / s, and dried at 70 ° C. for 30 minutes or more. . This operation was repeated twice to coat the seed crystal on the support. Thereafter, crystallization was carried out by hydrothermal synthesis at 180 ° C. for 4 hours in a raw material gel (10Na ₂ O: 0.15Al ₂ O ₃ : 36SiO ₂ : 960H ₂ O) aged at 50 ° C. for 4 hours. Filmed. A water (10 kPa) / hydrogen (90 kPa) binary system at 150 ° C. having a water / hydrogen separation factor of 131 was used.

(ZSM-5 membrane)
A seed crystal was coated on a porous alumina tube support, and ZSM-5 was formed by secondary growth.
First, the support is vertically immersed in a slurry (concentration of 2.4 g / l) of Na-ZSM-5 seed crystal (Si / Al = 12), then pulled up at about 3 cm / s, and at 70 ° C. for 30 minutes or more. Dried. This operation was repeated twice to carry seed crystals on the support. Thereafter, using a raw material (10Na ₂ O: 0.15Al ₂ O ₃ : 36SiO ₂ : 1200H ₂ O) aged at 50 ° C. for 4 hours, crystallization is performed by a hydrothermal synthesis method at 180 ° C. for 12 hours to form a film. did. A water (10 kPa) / hydrogen (90 kPa) binary system at 150 ° C. having a water / hydrogen separation factor of 75 was used.

(Y-type film)
A seed crystal was coated on a porous alumina tube support, and a Y-type zeolite was formed by secondary growth. First, the support was vertically immersed in an aqueous seed crystal (Si / Al = 2.8) solution, then pulled up at about 0.1 cm / s and dried at 70 ° C. for 30 minutes or more. This operation was repeated twice to coat the seed crystal on the support. Thereafter, in a raw material gel (22Na ₂ O: Al ₂ O ₃ : 25SiO ₂ : 990H ₂ O) aged at 20 ° C. for 4 hours, crystallization was performed by a hydrothermal synthesis method at 100 ° C. for 4 hours to form a film. . A water (10 kPa) / hydrogen (90 kPa) binary system at 150 ° C. having a water / hydrogen separation factor of 10 was used.

[Experimental conditions]
Each catalyst tube was filled with 24 cc and reduced at 200 ° C. for 1 hour in a hydrogen stream, and then the following carbon monoxide removal reaction was evaluated.
As the test gas, a raw material gas obtained by steam reforming kerosene and a water gas shift reaction (composition: hydrogen 61.5 vol%, carbon monoxide 0.5 vol%, carbon dioxide 18.1 vol%, water 19.7 vol) %, Methane 0.2 vol%), and passed through the zeolite membrane as shown in FIG. At that time, air was circulated as a sweep gas on the permeate side, and the flow rate of the sweep gas was controlled so that the water concentration at the outlet of the zeolite membrane was 12%.
A gas in which air was added to the gas on the non-permeate side of the zeolite membrane so that the O ₂ / CO ratio was 1.0 was introduced into a reaction tube filled with a catalyst, and the carbon monoxide removal reaction was evaluated. The reaction evaluation conditions are normal pressure and GHSV = 5,000 h ⁻¹ .
The temperature of the catalyst layer is set to 80 ° C. in a state where a test gas into which air has not been introduced is circulated. Subsequently, air is introduced, and the introduction of air is stopped after 1 hour. Repeat this operation once. The number of cycles until the carbon monoxide concentration of the reaction product gas exceeds 10 volppm is determined.

(Comparative Example 1)
The test gas and air were directly introduced without passing through the zeolite membrane. The results are shown in Table 1.
Example 1

  Evaluation was performed using a ZSM-5 membrane as the zeolite membrane. The results are shown in Table 1.

(Example 2)
Evaluation was performed using a mordenite membrane as the zeolite membrane. The results are shown in Table 1.

(Example 3)
Evaluation was performed using a Y-type membrane as the zeolite membrane. The results are shown in Table 1.

(Examples 4 to 6)
When the product gas obtained using the carbon monoxide concentration reduction method of Example 1 was introduced into the anode electrode of the polymer electrolyte fuel cell in FIG.
When the product gas obtained using the carbon monoxide concentration reduction method of Example 2 was introduced into the anode electrode of the polymer electrolyte fuel cell of FIG.
When the product gas obtained by using the carbon monoxide concentration reduction method of Example 3 was introduced into the anode electrode of the polymer electrolyte fuel cell in FIG.

It is the schematic of the apparatus used in the Example to reduce the water | moisture content in source gas with a zeolite membrane. It is the schematic which shows an example of the fuel cell system of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Water tank 2 Water pump 3 Fuel tank 4 Fuel pump 5 Desulfurizer 6 Vaporizer 7 Reformer 8 Air blower 9 High temperature shift reactor 10 Low temperature shift reactor 11 Selective oxidation reactor 12 Anode 13 Cathode 14 Solid polymer electrolyte 15 Electrical load 16 Exhaust port 17 Polymer electrolyte fuel cell 18 Heating burner 19 Water reduction device using separation membrane

Claims (6)

Carbon monoxide in a raw material gas containing hydrogen and carbon monoxide is selectively oxidized using a catalyst in which Ru is supported on a support made of an inorganic oxide containing at least one selected from alumina, silica, zirconia and titania. In this method, the moisture concentration in the source gas is reduced by a separation membrane made of a zeolite membrane , and then a selective oxidation reaction is performed. The moisture concentration in the source gas is controlled by the sweep gas flow rate, and the moisture in the source gas is reduced. A method for reducing the concentration of carbon monoxide in a raw material gas, wherein the concentration is reduced to 15 vol% or less. A catalyst comprising at least one metal selected from Pt, Pd, Au, Ag, Rh and Ir and Ru supported on a support made of an inorganic oxide containing at least one selected from alumina, silica, zirconia and titania is used. Thus, when selectively oxidizing carbon monoxide in a raw material gas containing hydrogen and carbon monoxide, the water concentration in the raw material gas is reduced by a separation membrane made of a zeolite membrane , and then a selective oxidation reaction is performed. A method for reducing the carbon monoxide concentration in the source gas, wherein the moisture concentration in the source gas is controlled by the sweep gas flow rate, and the moisture concentration in the source gas is reduced to 15 vol% or less. Separation membrane mordenite membrane, ZSM-5 type zeolite membrane, A-type zeolite membrane, Y-type zeolite membrane, according to claim 1 or characterized in that it is a separation membrane selected from T-type zeolite membrane and ZSM-35 type zeolite membrane 2. The method according to 2 . The method according to any one of claims 1 to 3 , wherein the raw material gas is obtained by subjecting a hydrocarbon, alcohol or ether to a reforming reaction and a water gas shift reaction. The method according to any one of claims 1 to 3 , wherein the raw material gas is obtained by subjecting hydrocarbon, alcohol or ether to desulfurization reaction, reforming reaction and water gas shift reaction. Permeate side of the environment of the separation membrane, flowing the air as scan Ipugasu, flowing product gas after the selective oxidation reaction of carbon monoxide as a sweep gas, flowing a reforming earlier feed gas as sweep gas, sweep gas As a sweep gas, it consists of a part for flowing the raw material gas before reforming, and a part for flowing the product gas after the selective oxidation reaction of carbon monoxide and the raw material gas before reforming as a sweep gas the method according to any one of claims 1 to 5, which is possible, characterized in that it is a one environment selected from among which the.

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