JP2005035852A - Hydrogen producing equipment and method for manufacturing hydrogen-rich gas using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide hydrogen producing equipment that obtains the sufficient reaction rate even at a low temperature and that obtains a hydrogen-rich gas including a lower concentration of carbon monoxide. <P>SOLUTION: The hydrogen producing equipment for manufacturing the hydrogen-rich gas from a hydrocarbonaceous fuel and water or a molecular oxygen-containing gas has a power source, a plurality of electrodes connected with the power source and a catalyst layer filled between the electrodes. The catalyst layer comprises a fuel reforming catalyst containing one or two or more metal elements selected from the group consisting of copper, palladium and zinc. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a hydrogen production apparatus for producing a hydrogen rich gas from a hydrocarbon fuel and a hydrogen production system in which the apparatus is arranged. The present invention also relates to a method for producing a hydrogen rich gas that produces a hydrogen rich gas using a hydrogen production apparatus or a hydrogen production system.

Solid polymer fuel cells are expected to be used as power sources for automobiles and the like because a high current density can be obtained even at a relatively low temperature. Various proposals have been made for the supply source of the hydrogen-containing gas to the solid polymer fuel cell. For example, steam reforming methods and autothermal reforming methods have been developed as technologies for reforming organic compounds such as hydrocarbons to convert them into synthesis gas (H ₂ + CO) or hydrogen, and various improvements are being considered. Has been.

  In recent years, unlike these, a method for producing hydrogen from a hydrogen-containing compound using low-temperature plasma has been proposed.

  For example, Patent Document 1 discloses a method for producing hydrogen, which is characterized by decomposing a hydrogen-containing compound with low-temperature plasma. According to the method of the document 1, by continuously decomposing a hydrocarbon such as methane, an alcohol such as methanol, and a compound such as water under a low temperature plasma, hydrogen can be stably stably produced with high selectivity and high yield. It is supposed to be generated. Here, in the method of Document 1, it is not essential that the raw material compound is brought into contact with the catalyst, and there is a description that the catalyst may be used, but the effect in that case is not described and is not clear.

On the other hand, as a method of decomposing a raw material compound by low-temperature plasma in the presence of a catalyst, for example, Patent Document 2 discloses that hydrocarbon and water vapor are excited by low-temperature plasma, and metal Ni supported on alumina is applied to the hydrocarbon and water vapor. And producing a synthesis gas (H ₂ + CO) from hydrocarbons and water vapor is disclosed. According to the method of Document 2, synthesis gas is selectively generated from hydrocarbons and water vapor, and the yield is also improved.

Furthermore, as a device for producing hydrogen-rich gas from hydrocarbon fuel using a plasma reactor filled with catalyst, it was announced at the 35th Autumn Meeting of the Chemical Engineering Society (2002) (lecture number: X216). There is. The apparatus is filled with silica beads carrying Ni between a cylindrical outer electrode and an inner electrode on the concentric axis, and an AC voltage of several tens of kHz and several kV is applied between both electrodes. A mixed gas of methane and water vapor is supplied into a reaction tube filled with the beads to produce a hydrogen rich gas.
JP 2002-338203 A JP 2002-241774 A

  However, when Ni is used as the catalytic metal element, it has been necessary to increase the temperature to about 400 to 500 ° C. even when using low temperature plasma in order to obtain a sufficient reaction rate. Further, as the reaction temperature increases, the concentration of carbon monoxide in the resulting hydrogen-rich gas increases. Therefore, in the case of using Ni, in order to remove carbon monoxide, the load on the shift reaction apparatus, the carbon monoxide selective oxidation apparatus, etc. disposed in the latter stage increases, resulting in an increase in the size of the apparatus and an increase in cost. It was a problem.

  Accordingly, an object of the present invention is to provide a hydrogen production apparatus capable of obtaining a sufficient reaction rate even at a low temperature and obtaining a hydrogen rich gas having a lower carbon monoxide concentration.

  The present invention exists between one electrode, another electrode, a power source that generates low-temperature plasma between the one electrode and the other electrode, and the one electrode and the other electrode. , A hydrogen production apparatus comprising a hydrocarbon fuel and a catalyst layer including a fuel reforming catalyst that promotes a reaction from water to hydrogen-rich gas, wherein the fuel reforming catalyst is selected from the group consisting of copper, palladium, and zinc. This is a hydrogen production apparatus containing one or more selected metal elements.

  According to the present invention, in a hydrogen production apparatus using low temperature plasma, a hydrogen rich gas can be produced at a lower temperature than in the prior art by providing a catalyst layer containing a fuel reforming catalyst containing a predetermined metal element. . Therefore, the carbon monoxide concentration in the obtained hydrogen-rich gas can be reduced, and the load on the carbon monoxide concentration reducing means disposed in the subsequent stage can be reduced. In some cases, the shift reactor can be omitted. Therefore, the apparatus can be reduced in size and cost. Therefore, it is particularly useful when applied to a vehicle such as an automobile.

  In the first aspect of the present invention, one electrode, another electrode, a power source for generating low-temperature plasma between the one electrode and the other electrode, and between the one electrode and the other electrode A hydrogen production apparatus having a hydrocarbon fuel and a catalyst layer containing a fuel reforming catalyst that promotes a reaction from water to hydrogen-rich gas, wherein the fuel reforming catalyst is made of copper, palladium, and zinc. A hydrogen production apparatus comprising one or more metal elements selected from the group consisting of:

  FIG. 1 shows a preferred embodiment of the hydrogen production apparatus of the present invention. FIG. 1 shows a cross section of the hydrogen production apparatus. Here, in FIG. 1, 1 is a hydrogen production apparatus, 2 is a hydrocarbon fuel, 3 is water, 4 is a molecular oxygen-containing gas, 5 is a hydrogen-rich gas, 10 is a reactor, 20 is an external electrode, 30 is an internal An electrode, 40 is a catalyst layer, and 50 is a power source.

  The hydrogen production apparatus 1 includes a cylindrical reactor 10 that forms a flow path for hydrocarbon fuel. An external electrode 20 is disposed on the inner periphery of the reactor 10 and is grounded. The reactor 10 may be formed of a conductor and may also be used as the external electrode 20. The hydrogen production apparatus 1 has an internal electrode 30. The internal electrode 30 has a rod shape and is disposed on the central axis of the reactor 10. The internal electrode 30 is electrically insulated from the external electrode 20 and fixed. A space surrounded by the external electrode 20 and the internal electrode 30 in the reactor 10 is filled with a catalyst layer 40. The hydrogen production apparatus 1 further includes a power supply 50. The power supply 50 applies a high voltage between the external electrode 20 and the internal electrode 30 to generate low temperature plasma.

  Hereinafter, the hydrogen production apparatus of the present invention will be described in more detail.

  In the hydrogen production apparatus of the present invention, when a high voltage is applied between the external electrode and the internal electrode by the power source, low temperature plasma is generated in the catalyst layer. The power source used here is not particularly limited, and a conventionally known power source can be used. In the present specification, “low temperature plasma” refers to non-equilibrium plasma in which electrons, radicals, ions and neutral molecules are not in a thermal equilibrium state. In this low-temperature plasma state, only some of the electrons have acquired extremely high energy. Therefore, only the electron temperature is extremely high, for example, reaching 5000 to 10000 ° C. On the other hand, components such as radicals, ions and neutral molecules are maintained at about room temperature. As a result, unlike ordinary gas phase reactions and catalytic reactions, even if the temperature of the supplied gas is about room temperature, the fuel reforming reaction proceeds by ions and radicals generated by collision of molecules with high-temperature electrons. . Accordingly, the concentration of by-produced carbon monoxide is reduced. Moreover, since it is excellent in startability and energy efficiency, it is useful especially when applied to vehicles, such as a motor vehicle.

  The form, size, electrode material and the like of one electrode and the other electrode are not particularly limited, and conventionally known forms can be preferably used. The number of each electrode is not particularly limited, and a plurality of other electrodes may be arranged in addition to one electrode. Preferably, one electrode is cylindrical as described above, and the other electrode is disposed on the central axis of the one electrode.

  The hydrocarbon fuel supplied to the water production apparatus of the present invention is not particularly limited as long as it can generate hydrogen by low-temperature plasma. Examples thereof include hydrocarbons such as methane, ethane and propane, alcohols such as methanol and ethanol, ethers such as dimethyl ether and diethyl ether, naphtha and gasoline. Here, when priority is given to the ease of reforming, methane or methanol is preferably used. On the other hand, liquid energy such as gasoline is preferably used when priority is given to energy density, such as mounting in an automobile.

  In the hydrogen production apparatus of the present invention, the catalyst layer contains a fuel reforming catalyst containing one or more metal elements selected from the group consisting of copper, palladium and zinc. The form of the fuel reforming catalyst contained in the catalyst layer is not particularly limited as long as the metal element is contained. As a result, the hydrocarbon fuel can be reformed and hydrogen can be produced even under a low temperature condition of about room temperature. In the present invention, the shape of the catalyst layer is not particularly limited, and includes a plate shape and a shape in which the portion where the fuel reforming catalyst is present has a certain thickness as described in the preferred embodiment. .

  Hereinafter, preferred embodiments of the fuel reforming catalyst will be described.

The fuel reforming catalyst contained in the catalyst layer is preferably formed by supporting the metal element on a base material. The base material is not particularly limited, and a conventionally known base material for the fuel reforming catalyst can be used. For example, zinc oxide, cerium oxide, aluminum oxide, zirconium oxide, titanium oxide, and complex oxides thereof can be used. Of these, zinc oxide can be preferably used. When a catalytically active metal element is supported using these as a base material, a hydrogen production apparatus having excellent fuel reforming performance at a lower temperature can be obtained. Incidentally, BET specific surface area of the substrate of the fuel reforming catalyst is preferably 10 to 500 m ² / g, more preferably 100 to 300 m ² / g, particularly preferably 200 to 300 m ² / g. The average particle size of the substrate is preferably 1 to 10 μm, more preferably 1 to 3 μm, and particularly preferably 2 to 3 μm.

The catalytically active metal element supported on the substrate is not limited to one or more metal elements selected from the group consisting of copper, palladium, and zinc, and may include other metal elements. For example, noble metal elements such as rhodium, platinum, and ruthenium, aluminum, nickel, zirconium, titanium, cerium, cobalt, manganese, silver, gold, barium, iron, and the like can be used. In addition to the copper, palladium and zinc elements, only one of these metal elements may be used, or two or more of them may be used in combination. Preferably, a noble metal element is contained in terms of excellent steam reforming reaction (for example, CH ₃ OH + H ₂ O → 3H ₂ + CO ₂ ). More preferably, a rhodium element is contained in that the catalytic activity is particularly high and the durability is excellent.

  Furthermore, the fuel reforming catalyst used in the present invention may further contain an alkali metal element, an alkaline earth metal element, a rare earth element, or the like.

  As the alkali metal element, sodium, potassium, rubidium, cesium and the like are preferable. Further, as the alkaline earth metal element, magnesium, calcium, strontium, barium and the like are preferable. As the rare earth element, lanthanum, cerium, praseodymium, neodymium and the like are preferable. The loading of these components may be performed simultaneously with the loading of the noble metal element or additive, or may be performed separately.

  The fuel reforming catalyst of the present invention may contain necessary additives in addition to the base material and the metal element. Examples of the additive include a suitable binder.

  The fuel reforming catalyst used in the present invention contains a base material, a metal element supported on the base material, and other necessary additives, but the content of each of these components is not particularly limited, It can be determined appropriately according to. Preferably, the total amount of the fuel reforming catalyst is 100% by mass, the base material is 50 to 95% by mass, the catalytically active metal element is 5 to 50% by mass in terms of metal, and 0 to 5% by mass of other necessary additives. In addition, the total content in the fuel reforming catalyst of one or more metal elements selected from the group consisting of copper, palladium and zinc is preferably 10 to 50% by mass in terms of metal. Preferably it is 30-50 mass%, Most preferably, it is 40-50 mass%.

  In the present invention, the aspect in which the fuel reforming catalyst is filled in the catalyst layer is not particularly limited. For example, the form filled with lump shape, such as a pellet form, the granulated shape, the cylindrical shape formed by tableting, or Rachel ring, is illustrated. Moreover, the aspect filled with the monolith support | carriers, such as a honeycomb or foam, is also illustrated. In these embodiments, one type can be used alone, or two or more types can be used in combination.

  Here, the fuel reforming catalyst used in the present invention is not particularly limited and can be prepared using a conventionally known technique. Hereinafter, preferred embodiments of the method for preparing the fuel reforming catalyst will be described.

  First, a base material for supporting a catalytically active metal element is prepared. Next, using the catalyst preparation solution containing the metal element to be supported on the base material, the metal element is supported on the base material using various techniques such as an impregnation method, a coprecipitation method, and a competitive adsorption method. Thereafter, the catalyst active powder can be prepared by firing and grinding to a desired particle size.

  Here, the method for preparing the catalytically active powder will be described step by step.

  First, the processing conditions for supporting the metal element can be appropriately selected according to various methods. Usually, a base material and a catalyst preparation solution are made to contact at 20-90 degreeC for 1 minute-10 hours. For example, a catalyst preparation solution in which a compound containing a metal element is dissolved or dispersed is used, the substrate is impregnated therein, and the metal element is supported on the substrate. As a solvent for the catalyst preparation solution, a solvent capable of dissolving a compound containing the preceding element such as water, alcohols such as methanol and ethanol, ethers such as diethyl ether, carboxylic acids and the like can be widely used.

  Thereafter, the substrate on which the metal element is supported is dried. As the drying method, for example, natural drying, evaporation to dryness, rotary evaporator, spray dryer, drying with a drum dryer, or the like can be used. Thereafter, firing may be performed. As firing conditions, a firing temperature of 200 to 1000 ° C. and a firing time of 30 to 480 minutes are usually sufficient. Finally, the calcined product is pulverized to a desired particle size to obtain a catalytically active powder. Here, the pulverization method is not particularly limited, and a conventionally known method can be used. For example, a ball type vibration mill can be used. The particle size of the obtained catalytically active powder is not particularly limited, but is preferably 1 to 10 μm, more preferably 1 to 3 μm. If the particle size is too small, the cost increases. On the other hand, when the particle size is 10 μm or less, the catalytically active metal element supported in the deep part of the pores can be effectively used even when the substrate is porous.

The catalytically active powder obtained above is molded into a desired shape by a conventionally known method to obtain a fuel reforming catalyst. The shape at this time is not particularly limited as described above, and may be a conventionally known shape. Here, for example, when it is formed as a lump such as a pellet, the size is not particularly limited. Here, the volume per lump is preferably 0.1 to ² cm ² , more preferably 0.5 to ¹ cm ² . When the volume is 0.1 cm ² or more, an increase in pressure loss can be prevented. On the other hand, when the volume is 2 cm ² or less, the interval between the pellets does not become too large, and plasma can be generated effectively.

  When a monolith catalyst is used, an appropriate amount of water is added to the obtained catalyst active powder to form a catalyst slurry, which is applied to the monolith support by a conventionally known method, dried and fired to obtain a fuel reforming catalyst. .

  In the hydrogen production apparatus of the present invention, the mechanism for producing hydrogen from hydrocarbon fuel by low-temperature plasma is assumed as follows. The technical scope of the present invention should be determined based on the description of the scope of claims, and even if the following mechanism is different from the fact, the technical scope of the present invention is not limited at all.

  In a low-temperature plasma state generated by applying a high voltage, electrons in a high-temperature state move while being accelerated in the catalyst layer by an electric field formed between the electrodes. The electrons collide with molecules in the supplied hydrocarbon fuel and supply bond dissociation energy necessary for breaking the bonds in the molecules.

Here, generally, the bond dissociation energy of the covalent bond in the hydrocarbon molecule is smaller in the C—C bond than in the C—H bond. Accordingly, for example, n-octane (n-C ₈ H ₁₈ ) is exemplified as a hydrocarbon.

Seems to be happening. Here, CH ₃ and CH ₂ produced in the above (1) are relatively stable so that they are not further decomposed and combined with the OH produced in the above (2), and the following reaction

Produces CH ₃ OH and CH ₂ OH. These are in contact with the fuel reforming catalyst packed in the catalyst layer of the hydrogen production apparatus of the present invention, and the following reaction

This is considered to generate a hydrogen-rich gas mainly composed of H ₂ and CO. Here, “(s)” means that molecules or atoms are adsorbed on the catalyst surface. The series of reactions generally do not have a large reaction barrier, and thus the reaction proceeds at a low temperature.

  In the hydrogen production apparatus of the present invention, carbon dioxide is also generated. Here carbon dioxide is the following reaction

It is thought that it generates. Here, the equilibrium of the above formulas (12) and (13) is close to the product side (the right side of the formula) at low temperatures. Therefore, in order to further reduce the carbon monoxide concentration in the hydrogen-rich gas, it is preferable to lower the reaction temperature.

In the hydrogen production apparatus of the present invention, the catalyst layer may contain other components in addition to the fuel reforming catalyst. Preferably, the catalyst layer contains a high dielectric compound. In the present specification, the “high dielectric compound” refers to a compound having a relative dielectric constant of 1000 or more. Here, examples of the high dielectric compound include barium titanate, strontium titanate, and lead titanate. Here, the relative dielectric constant (epsilon _r), dielectric constant of a substance of (epsilon), the ratio of the substance to air dielectric constant in the case of a (may be considered a vacuum in the standard _state) (ε ₀₎ (ε / Ε ₀ ). The relative dielectric constant can be measured, for example, by a method defined in JIS K 6911 (1993).

  The aspect in which a high dielectric compound is contained in the catalyst layer is not particularly limited. Here, for example, a preparation method when the fuel reforming catalyst is filled in the catalyst layer in a pellet form will be described. In this case, when a pellet-shaped fuel reforming catalyst is produced by the above-described method, a catalytically active powder and a high dielectric compound are mixed, and the mixture may be formed into a desired shape to form a pellet catalyst. In addition to the pellet-shaped fuel reforming catalyst, a high dielectric compound may be formed into a pellet. In this case, the obtained pellets can be filled in the catalyst layer in a mixed state.

  When the fuel reforming catalyst is supported on a monolith support, for example, a catalyst active powder and a high dielectric compound are mixed, and water is added to the mixture to form a catalyst slurry. Thus, a monolith-supported catalyst can be obtained. Further, when a monolith-supported catalyst is used, each slurry of a catalytically active powder and a high dielectric compound is prepared, one is applied to a monolith support, dried and fired, and then the other is applied and dried and fired. The monolith-supported catalyst can also be prepared. In this case, any slurry may be applied first, and the number of times of application is not particularly limited.

  Furthermore, in the method for preparing the fuel reforming catalyst, a high dielectric compound can be used instead of the base material. In this case, a catalytically active powder in which a catalytic metal element is supported on a high dielectric compound can be prepared by the same method as described above. A fuel reforming catalyst can be prepared by forming this catalytically active powder by the above-described method, for example, by forming it into pellets or by supporting it on a monolith support.

  Here, it is generally known that a high dielectric compound undergoes a large dielectric polarization when a voltage is applied. In the present invention, the high dielectric compound is preferably contained in the catalyst layer of the hydrogen production apparatus for the following reason.

  Here, consider a case where the catalyst layer is filled with a mixture of a fuel reforming catalyst and a high dielectric compound in the form of pellets. In this case, when a high voltage is applied between the external electrode and the internal electrode, the high dielectric compound is greatly dielectrically polarized. As a result, the potential difference between the pellets becomes extremely large, and low temperature plasma is generated.

  At this time, low-temperature plasma can be generated without containing a high dielectric compound. In this case, however, the distance between the external electrode and the internal electrode that can generate low-temperature plasma is limited to several millimeters, and the flow path of the hydrocarbon-based fuel becomes narrow. For this reason, the production amount of the hydrogen rich gas per volume of the hydrogen production apparatus decreases.

  On the other hand, when a high dielectric compound is contained in the catalyst layer, low temperature plasma can be generated even when the electrode spacing is large. For this reason, the amount of hydrogen rich gas produced per volume of the hydrogen production apparatus increases, and the hydrogen production apparatus can be downsized.

  The second aspect of the present invention is to reduce the concentration of carbon monoxide in the hydrogen-rich gas produced by the hydrogen production apparatus of the first aspect of the invention, a fuel supply apparatus that supplies the hydrocarbon fuel to the apparatus, and the hydrogen production apparatus. And a carbon monoxide selective oxidation reaction apparatus. Hereinafter, a preferred embodiment of the present invention will be described with reference to FIG.

  FIG. 2 is a block diagram showing a schematic configuration of the hydrogen production system of the present invention. In FIG. 2, 2 is a hydrocarbon-based fuel, 3 is water, 4 is a molecular oxygen-containing gas, 110 is a fuel evaporator, 120 is a water evaporator, 130 is a hydrogen production device, and 140 is carbon monoxide selective oxidation. The reactor 150 is a fuel cell.

  When hydrogen is produced using the apparatus shown in FIG. 2, the hydrocarbon-based fuel 2 is sent to the fuel evaporator 110 by a pump (not shown), vaporized by the evaporator 110, and then supplied to the hydrogen production apparatus 130. . When the hydrocarbon fuel 2 is a gas at normal temperature and normal pressure, the fuel evaporator 110 can be omitted. Similarly, the water 3 is also sent to the water evaporator 120 by a pump (not shown), vaporized by the evaporator 120, and then supplied to the hydrogen production apparatus 130. In the hydrogen production apparatus 130, hydrogen rich gas is generated. When the first apparatus of the present invention is used as the hydrogen production apparatus 130, the hydrogen rich gas contains about 1% by volume of carbon monoxide. The obtained hydrogen-rich gas is supplied to the carbon monoxide selective oxidation reactor 140, and the carbon monoxide concentration can be reduced to about several tens of ppm. The hydrogen-rich gas with a reduced carbon monoxide concentration is supplied to the polymer electrolyte fuel cell 150 and can be used for power generation.

  When producing a hydrogen rich gas using a conventional fuel reformer, the concentration of carbon monoxide in the hydrogen rich gas is reduced to about 1% by volume because a specific fuel such as methanol or dimethyl ether is used as the fuel. Only if. When other fuels are used, the carbon monoxide concentration in the hydrogen-rich gas is usually about 10% by volume. For this reason, when a conventional fuel reformer is used, it is necessary to install a shift reactor for reducing the carbon monoxide concentration by a water gas shift reaction before the carbon monoxide selective oxidation reactor.

  On the other hand, according to the hydrogen production system in which the hydrogen production apparatus of the present invention is arranged, hydrogen rich gas having an extremely low carbon monoxide concentration can be produced when any hydrocarbon-based fuel is used. For this reason, a hydrogen rich gas having a sufficiently low carbon monoxide concentration can be produced only by a selective oxidation reaction apparatus without installing a shift reaction apparatus. Thereby, size reduction and cost reduction of a hydrogen production apparatus can be achieved. Therefore, the present invention is particularly useful when applied to a vehicle such as an automobile. In the hydrogen production system of the present invention, it is not hindered to install the shift reaction apparatus, and if necessary, it can be installed in the same manner as before.

  In the hydrogen production system of the present invention, the mode of the fuel supply device and the carbon monoxide selective oxidation reaction device to be installed is not particularly limited, and a conventionally known device can be preferably used. Here, the polymer electrolyte fuel cell is configured, for example, by sandwiching a polymer electrolyte membrane that selectively permeates hydrogen ions between an anode and a cathode, and electrochemistry of fuel gas supplied by the anode and the cathode. An electromotive force is generated by the reaction, and power is generated.

  A third aspect of the present invention is a method for producing a hydrogen-rich gas using the first hydrogen production apparatus of the present invention, wherein the reaction temperature of the hydrocarbon fuel supplied to the hydrogen production apparatus is 100 to 350 ° C. A method for producing a hydrogen-rich gas.

  In the hydrogen rich gas production method of the present invention, the first hydrogen production apparatus of the present invention is used. As an aspect of these apparatuses, the aspect described above for the first aspect of the present invention can be preferably used.

  Hereinafter, a preferred embodiment of the production method of the present invention will be described in detail with reference to FIG.

  The method for producing a hydrogen-rich gas using the hydrogen production apparatus 1 of the present invention supplies a hydrocarbon-based fuel 2, water 3 and molecular oxygen-containing gas 4 from one of the reactors 10, and an external electrode 20 and an internal electrode 30. And applying a high voltage between the two. First, the reaction gas is caused to flow into the reactor 10. Thereafter, when a high voltage is applied between the external electrode 20 and the internal electrode 30 by the power supply 50, low temperature plasma is generated in the catalyst layer 40.

  The hydrocarbon fuel 2 is heated and excited by the low temperature plasma. The excited hydrocarbon fuel 2 comes into contact with the fuel reforming catalyst contained in the catalyst layer 40 and is converted to hydrogen. The hydrogen-rich gas containing hydrogen thus generated is discharged from the other side of the reactor 10.

  Here, the magnitude of the voltage applied between the external electrode and the internal electrode is not particularly limited as long as it is a voltage that can generate low-temperature plasma. Generally, it is 1-10 kV, preferably 3-7 kV, more preferably 3-4 kV. If the applied voltage is too low, low temperature plasma will not be generated. On the other hand, if the applied voltage is too high, the power consumption increases, which is disadvantageous in terms of energy efficiency, and the gas-phase insulation is completely destroyed, and a large amount of current flows in the electric circuit, which is dangerous. Examples of the applied voltage include a DC pulse voltage and an AC voltage.

In the present invention, the hydrocarbon fuel is supplied to a hydrogen production apparatus together with water and preferably a molecular oxygen-containing gas. Here, when using a hydrocarbon-based fuel that is liquid at normal temperature and normal pressure, the fuel and water are preferably vaporized and supplied by an evaporator, respectively. Further, the molecular oxygen-containing gas is not particularly limited as long as it contains a high concentration of oxygen. For example, pure oxygen, oxygen-rich gas, or air can be used. When the hydrocarbon fuel, water vapor and molecular oxygen-containing gas are supplied to the hydrogen production apparatus, the ratio of water in these mixed gases to the carbon atom equivalent amount of the hydrocarbon fuel (so-called steam-carbon ratio) ) Is preferably 0.7 to 3.0, more preferably 0.7 to 1.5. Moreover, the ratio of oxygen in the mixed gas to the amount of carbon atom equivalent of the hydrocarbon fuel is preferably 0.2 to 0.5, more preferably 0.2 to 0.3. Further, the supply amount of the mixed gas is preferably at a space velocity (GHSV) relative to the catalyst layer 1000～10000H ^-1, more preferably 1000~3000h ^-1.

  In the present invention, the hydrocarbon-based fuel is preferably supplied together with water vapor and oxygen for the following reason. In general, hydrocarbon fuels undergo a steam reforming reaction in the presence of a catalyst to generate hydrogen. For example, when methanol is used as an example of the hydrocarbon fuel, the steam reforming reaction is represented by the following reaction formula.

  Here, the steam reforming reaction is shown as an overall reaction by the following two reactions proceeding simultaneously.

Carbon monoxide shift reaction: CO + H ₂ O═CO ₂ + H ₂ +40.5 kJ / mol
Thus, in general, the reaction for steam reforming fuel is an endothermic reaction. On the other hand, when a hydrocarbon fuel is supplied together with oxygen, in addition to the steam reforming reaction, a partial oxidation reaction represented by the following formula also occurs simultaneously.

  Thus, the partial oxidation reaction is an exothermic reaction, and the amount of heat generated by this reaction can be used for the steam reforming reaction. Therefore, since an external heating apparatus is unnecessary, the size of the hydrogen production apparatus can be reduced. In addition, it is also possible to produce hydrogen without supplying the molecular oxygen-containing gas as described above. However, in this case, particularly in a closed system such as an automobile that does not supply electricity from the outside, about 3% of the energy obtained from the hydrogen produced by the hydrogen production apparatus is used to cover the reaction heat necessary for the steam reforming reaction. One part is consumed.

  As described above, in order to produce a hydrogen-rich gas having a lower carbon monoxide concentration, it is necessary to lower the reaction temperature. On the other hand, when the reaction temperature is too low, the reaction rate between the hydrocarbon fuel and the catalyst is lowered. Therefore, considering these balances, the reaction temperature in the production method of the present invention is preferably 100 to 350 ° C, more preferably 200 to 300 ° C, and particularly preferably 250 to 300 ° C. In the present specification, the “reaction temperature” refers to the temperature of the gas in the reactor.

  In the present invention, if necessary, the mixed gas can be heated by an external heating device before being supplied to the hydrogen production device. At this time, all of the hydrocarbon fuel, the molecular oxygen-containing gas or water may be heated, or only one or two components may be heated.

  In the present invention, the reaction temperature can be adjusted by adjusting the ratio of the molecular oxygen-containing gas in the supplied mixed gas. Here, if the endothermic amount in the steam reforming reaction and the exothermic amount in the partial oxidation reaction are equal, it is apparently in a thermal equilibrium state. Therefore, when the ratio of the molecular oxygen-containing gas in the supplied mixed gas is increased, the calorific value increases due to the progress of the partial oxidation reaction, and the reaction temperature rises. Therefore, when there is a preferable temperature range for the gas supplied to the apparatus such as the carbon monoxide selective oxidation reaction apparatus used in the subsequent stage of the hydrogen production apparatus of the present invention, the molecular state in the mixed gas as described above is used. By adjusting the ratio of the oxygen-containing gas, the temperature of the gas supplied to the subsequent apparatus can be adjusted.

  Conventionally, Ni is known as a catalyst metal for producing hydrogen using low-temperature plasma. However, if only Ni is used as a catalytic metal element and a hydrogen-rich gas is produced at a low temperature of, for example, 100 to 350 ° C., a hydrogen-rich gas containing methane at a high concentration can be obtained. This is considered to be due to the following reason.

  When only Ni is used as the catalytic metal element and a hydrogen-rich gas is produced at 100 to 350 ° C., the reactions as shown in the above (3) to (11) hardly proceed. In contrast, the following formula

It is speculated that the reaction shown in FIG.

  As described above, when a hydrogen rich gas is produced at 100 to 350 ° C. using only Ni as a catalytic metal element, a hydrogen rich gas containing methane at a high concentration can be obtained. On the other hand, in order to reduce the methane concentration in this case, the reaction temperature must be raised to about 400 to 500 ° C. However, as described above, the carbon monoxide concentration in the hydrogen-rich gas increases by increasing the reaction temperature. Therefore, when only Ni is used as a catalytic metal element when producing a hydrogen-rich gas using low-temperature plasma, it is possible to effectively reduce both the methane concentration and the carbon monoxide concentration in the obtained hydrogen-rich gas. Have difficulty.

  On the other hand, according to the present invention, the above problem can be solved by using a hydrogen production apparatus in which a catalyst layer is filled with a fuel reforming catalyst containing a predetermined metal element. That is, methane and carbon monoxide in a hydrogen-rich gas are obtained by using a hydrogen production apparatus filled with a fuel reforming catalyst containing one or more metal elements selected from the group consisting of copper, palladium and zinc. Both concentrations can be reduced efficiently.

  Conventionally, a fuel reforming catalyst containing one or more metal elements selected from the group consisting of copper, palladium and zinc is known for methanol reforming. When reforming methanol using a fuel reforming catalyst containing these elements, it is considered that hydrogen is generated by the reactions shown in the above (5) to (7).

  However, hydrogen rich gas can be produced using this fuel reforming catalyst with the conventional reformer and reforming conditions only when the fuel is methanol. For example, when ethanol, which is alcohol like methanol, is used as a fuel, the following formula

The reaction shown in FIG. That is, the reactions corresponding to the above (5) and (6) proceed, but since the aldehyde is produced, the reaction corresponding to the above (7) does not proceed and the reaction stops.

  In contrast, according to the present invention, by producing a hydrogen-rich gas using low-temperature plasma, various hydrocarbon systems can be used using a fuel reforming catalyst that has been difficult to apply to fuels other than methanol. Hydrogen rich gas can be produced from fuel.

It is a figure which shows one preferable aspect of the hydrogen production apparatus of this invention. It is a figure which shows one preferable aspect of the hydrogen production system of this invention.

Explanation of symbols

1 ... Hydrogen production equipment,
2 ... hydrocarbon fuel,
3 ... water,
4 ... molecular oxygen-containing gas,
5 ... Hydrogen rich gas,
10 ... reactor,
20 ... External electrode,
30 ... Internal electrode,
40 ... catalyst layer,
50 ... Power supply,
110 ... fuel evaporator,
120 ... water evaporator,
130 ... Hydrogen production equipment,
140 ... carbon monoxide selective oxidation reactor,
150: Solid polymer fuel cell.

Claims (5)

One electrode, another electrode, a power source for generating a low temperature plasma between the one electrode and the other electrode, and a hydrocarbon system existing between the one electrode and the other electrode A hydrogen production apparatus having a catalyst layer including a fuel reforming catalyst that promotes a reaction from fuel and water to a hydrogen-rich gas,
The hydrogen production apparatus, wherein the fuel reforming catalyst contains one or more metal elements selected from the group consisting of copper, palladium and zinc.   The hydrogen production apparatus according to claim 1, wherein the catalyst layer contains a high dielectric compound.   The hydrogen production apparatus according to claim 1, wherein the one electrode is cylindrical, and the other electrode is disposed on a central axis of the one electrode.   The hydrogen production apparatus according to any one of claims 1 to 3, a fuel supply apparatus that supplies the hydrocarbon-based fuel to the apparatus, and a carbon monoxide concentration in a hydrogen-rich gas generated by the hydrogen production apparatus. A hydrogen production system comprising a carbon monoxide selective oxidation reaction device for reduction. A method for producing a hydrogen-rich gas using the hydrogen production apparatus according to any one of claims 1 to 3,
A method for producing a hydrogen-rich gas, wherein a reaction temperature of the hydrocarbon fuel supplied to a hydrogen production apparatus is 100 to 350 ° C.

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