JP5759922B2 - Method for producing hydrogen - Google Patents

Description

  The present invention relates to a method for producing hydrogen, and more particularly to a method for producing hydrogen in a fuel cell system using a hydrogen source such as a hydrocarbon as a raw material.

  In recent years, with increasing environmental awareness, attention has been focused on energy using hydrogen, which has a low environmental impact. As one of the energy technologies using hydrogen, fuel cells that can extract electric energy from the reaction of hydrogen and oxygen without causing the direct emission of carbon dioxide, which is the cause of global warming, and the destruction of the ozone layer, have attracted attention. ing. Various raw materials such as natural gas, liquid fuel, and petroleum-based hydrocarbons have been studied as hydrogen sources for fuel cells. Especially, hydrocarbons represented by city gas, LP gas, naphtha, gasoline, kerosene, The supply infrastructure has been established and is widely distributed in large quantities, so it is considered promising as a hydrogen source. Hydrogen production in fuel cell systems using these hydrocarbons as raw materials is required to be efficiently performed in various states including starting and stopping of the system.

  In order to obtain hydrogen from the hydrocarbon, it is common to perform a steam reforming reaction in the presence of a reforming catalyst for producing hydrogen. Nickel catalysts and noble metal catalysts are known as reforming catalysts for hydrogen production (see Patent Documents 1 and 2). These catalysts are subjected to catalyst poisoning by sulfur and the catalytic function is lowered. In particular, noble metal catalysts are susceptible to sulfur poisoning. In order to prevent this, the sulfur content in the raw fuel is usually reduced to 0.05 ppm or less in a desulfurization process using a desulfurization catalyst before hydrogen production.

JP-A 57-4232 Japanese Patent Publication No.53-12917

  However, the function of the desulfurization catalyst in the desulfurization process may gradually deteriorate, and the sulfur content may not be completely removed in the desulfurization process. Also, in hydrogen production systems that frequently start and stop like fuel cells, the desulfurization process frequently becomes unsteady when starting and stopping, so there are frequent occurrences of periods when hydrogen raw material is not sufficiently desulfurized. There are things to do. In this case, temporary or continuous sulfur slip occurs, and sulfur poisoning of the reforming catalyst proceeds. In order to avoid this, there are methods such as increasing the amount of desulfurization catalyst and installing a guard reactor, but these lead to an increase in cost and installation space.

  In the present invention, a steam reforming reaction using a reforming catalyst for hydrogen production using a hydrogen source such as hydrocarbon as a raw material may cause a case where the function of the desulfurization process is lowered and the sulfur content cannot be removed temporarily or continuously. Even so, an object of the present invention is to provide a method for producing hydrogen that is capable of continuing the production of hydrogen and has excellent sulfur resistance.

  As a result of intensive investigations in view of the problems of the prior art, the present inventors have included a platinum group metal and nickel on the same specific carrier, the platinum group metal contains rhodium, and rhodium It has been found that the reforming catalyst for producing hydrogen distributed on the surface layer of the carrier can efficiently produce hydrogen even in a steam reforming reaction using a raw material containing sulfur, and has completed the present invention.

That is, the present invention has a step of obtaining hydrogen by reforming a hydrogen raw material containing hydrocarbon compounds with a reforming catalyst for hydrogen production,
A reforming catalyst for hydrogen production comprising an alumina, an inorganic composite oxide support supporting a rare earth metal oxide and an alkaline earth metal oxide, and a nickel and platinum group metal supported on the support In the catalyst, nickel and a platinum group metal are supported on the same carrier, rhodium is contained as the platinum group metal, and rhodium in the carrier diameter direction passing through the center of the catalyst cross section by an electron probe microanalyzer (EPMA). The ratio of the characteristic X-ray intensity of rhodium detected in the range of a distance within 10% of the carrier diameter from the outer surface of the carrier to the characteristic X-ray intensity of all the rhodium detected was 90%. The ratio of the characteristic X-ray intensity of rhodium detected in the range of the distance within 20% of the carrier diameter from the outer surface of the carrier is 95% or more,
The period for reforming the hydrogen raw material whose sulfur compound content concentration is 0.3 ppm or more in terms of sulfur atom mass, and / or the cumulative amount of the supplied sulfur compound is 1 mg or more in terms of sulfur atom mass per 1 g of catalyst. A method for producing hydrogen is provided, which includes a period for reforming a hydrogen raw material with the reforming catalyst for hydrogen production.

  In the hydrogen production reforming catalyst, the supported amount of nickel is 1 to 30 parts by mass in terms of nickel atoms with respect to 100 parts by mass of alumina, and the supported amount of rhodium is 0 in terms of rhodium atoms with respect to 100 parts by mass of alumina. It is preferable that it is 0.01-3 mass parts.

  In the above reforming catalyst for hydrogen production, the supported amount of platinum group metal is preferably 0.01 to 3 parts by mass in terms of platinum group metal atoms with respect to 100 parts by mass of alumina.

  Further, in the hydrogen production reforming catalyst, the rare earth metal oxide is preferably cerium oxide, the alkaline earth metal oxide is strontium oxide, and the platinum group metal is preferably rhodium and platinum.

  According to the present invention, in the steam reforming reaction by the reforming catalyst for hydrogen production using a hydrogen source such as hydrocarbon as a raw material, the function of the desulfurization step is reduced and the sulfur content cannot be removed temporarily or continuously. Even if this occurs, it is possible to provide a method for producing hydrogen that is capable of continuing production of hydrogen and that is excellent in sulfur resistance.

It is a conceptual diagram which shows an example of the fuel cell system which concerns on embodiment of this invention. It is a figure which shows the relationship between the elapsed time of the steam reforming reaction using the catalyst A or the catalyst B, and a propane reaction rate.

  Hereinafter, the present invention will be described in more detail.

  The method for producing hydrogen according to the present embodiment includes a step of obtaining hydrogen by reforming a hydrogen raw material containing hydrocarbon compounds with a reforming catalyst for hydrogen production, and the content concentration of the sulfur compound is in terms of sulfur atom mass. (A) for reforming a hydrogen raw material having a concentration of 0.3 ppm or more and / or reforming for hydrogen production in which the cumulative amount of supplied sulfur compound is 1 mg or more in terms of the mass of sulfur atom per gram of catalyst. A period (b) for reforming the hydrogen raw material with the catalyst is included.

  A sulfur compound refers to a compound containing a sulfur atom in a molecule contained in a hydrogen raw material.

  The content concentration of the sulfur compound in the hydrogen raw material refers to the mass value of sulfur atoms measured by GC-SCD analysis. Further, the cumulative amount of sulfur compound supplied to the reforming catalyst for hydrogen production refers to the cumulative value when the sulfur atom mass measured by GC-SCD analysis is supplied to the reforming catalyst for hydrogen production.

  First, the reforming catalyst for hydrogen production used in the method of this embodiment will be described.

  The reforming catalyst for hydrogen production according to the present embodiment includes an inorganic composite oxide carrier containing alumina and supporting a rare earth metal oxide and an alkaline earth metal oxide, and nickel and a platinum group metal supported on the carrier. The catalyst has nickel and a platinum group metal supported on the same carrier, contains rhodium as the platinum group metal, and has a carrier diameter passing through the center of the catalyst cross section by an electron probe microanalyzer (EPMA). The ratio of the characteristic X-ray intensity of rhodium detected within a distance within 10% of the carrier diameter from the outer surface of the carrier to the characteristic X-ray intensity of all rhodium detected when the rhodium line analysis measurement was performed in the direction Is 90% or more and the ratio of the characteristic X-ray intensity of rhodium detected in the range of the distance from the carrier outer surface within 20% of the carrier diameter is 95% or more And features.

  The reforming catalyst for hydrogen production of the present embodiment has nickel and rhodium-containing platinum group metal supported on the same carrier, and further, rhodium is distributed on the surface layer of the carrier at a specific ratio or more, so that expensive rhodium While suppressing the amount of the catalyst used, it is possible to suppress a decrease in the performance of the catalyst when a hydrogen raw material containing a sulfur compound is supplied.

  Although the cause of the effect of suppressing the catalyst performance degradation is not clear, the presence of nickel and a platinum group metal containing rhodium on the same support, (1) the coexisting nickel is sulfur to the platinum group metal. Suppresses adhesion of platinum group metal due to sulfur by suppressing adhesion. (2) Sulfur poisoning of nickel by supplying hydrogen molecules activated on platinum group metal containing rhodium by spillover to adjacent nickel. It is thought that this is because the composite action such as alleviating the decrease in the hydrogenation ability of nickel due to is promoted.

  In order to efficiently obtain the above-described effect, of the total rhodium content carried on the carrier, 90 mass is formed on the carrier surface layer at a distance within 10% of the carrier diameter from the outer surface of the carrier toward the center of the carrier. % Or more of rhodium is preferably distributed, and 95% by mass or more of rhodium is preferably distributed in the carrier surface layer within a distance of 20% or less. When the ratio of rhodium contained in the carrier surface layer part within the distance of 10% or less is less than 90% by mass, or the ratio of rhodium contained in the carrier surface layer part within the distance of 20% or less is less than 95% by mass, the carrier The ratio of rhodium present inside the carrier which does not function easily for the catalytic reaction on the surface layer becomes too large, and the above-described effects are hardly obtained, and the amount of expensive rhodium used cannot be suppressed, which is not preferable.

The mass distribution of rhodium contained in the support is the characteristic X-ray intensity of rhodium detected when the rhodium is analyzed by electron probe microanalyzer (EPMA) in the diameter direction of the support passing through the center of the catalyst cross section. It can be obtained from the distribution of. Specifically, the characteristic X-ray intensity (cps) of all rhodium detected when rhodium was analyzed in the diameter direction of the carrier passing through the center of the catalyst cross section is I ₁₀₀ , and the carrier diameter from the outer surface of the carrier is 10 The characteristic X-ray intensity (cps) of rhodium detected within a range of distance within ₁₀ % is I ₁₀ , and the characteristic X-ray intensity (cps) of rhodium detected within a distance within 20% of the carrier diameter from the outer surface of the carrier Is I ₂₀ , the distribution ratio of rhodium supported on the carrier can be calculated by the following formula. Incidentally, R ₁₀ represents a content of rhodium from the outer surface of the support toward the center of the carrier contained in the carrier surface part of the distance of within 10% of the carrier diameter (mass%), R ₂₀ is a carrier The content ratio (% by mass) of rhodium contained in the surface layer of the carrier at a distance within 20% of the carrier diameter from the outer surface toward the center of the carrier.
R ₁₀ = I ₁₀ ÷ I ₁₀₀ × 100
R ₂₀ = I ₂₀ ÷ I ₁₀₀ × 100

  The carrier in the reforming catalyst for hydrogen production of this embodiment is an inorganic composite oxide carrier containing alumina and supporting a rare earth metal oxide and an alkaline earth metal oxide.

Alumina is not particularly limited by composition or structure, and includes α-alumina, γ-alumina, and a mixture of these aluminas and inorganic metal oxides selected from silica, titania, zirconia, and the like. . B. of alumina E. T.A. The specific surface area is not particularly limited, but it may be necessary to disperse the supported nickel and platinum group metals sufficiently. E. T.A. The specific surface area is preferably ³ to 200 m ² / g. B. E. T.A. When the specific surface area is less than 3 m ² / g, nickel and platinum group metals cannot be sufficiently dispersed on the support surface layer, making it difficult to obtain a predetermined catalyst activity and catalyst life. E. T.A. When the specific surface area is larger than 200 m ² / g, the void ratio on the surface is high, and it is difficult to obtain a sufficient carrier strength.

  Examples of the rare earth metal oxide include oxides of one or more rare earth metals selected from lanthanum, cerium, praseodymium, neodymium, promethium, samarium, ytterbium, and the like. The rare earth metal is particularly preferably lanthanum or cerium. These rare earth metal oxides can be obtained by firing using rare earth metal compounds such as chlorides, nitrates and acetates as precursors.

  The supported amount of the rare earth metal oxide is preferably 2 to 30 parts by mass, more preferably 5 to 20 parts by mass, and even more preferably 10 to 18 parts by mass with respect to 100 parts by mass of alumina. preferable. When the loading amount of the rare earth metal oxide is more than 30 parts by mass, it is not preferable because it exists in an excess amount with respect to alumina and an effect of addition relative to the content cannot be obtained. On the other hand, if the supported amount of the rare earth metal oxide is less than 2 parts by mass, the effect of addition becomes low, which is not preferable.

  Examples of the alkaline earth metal oxide include oxides of one or more alkaline earth metals selected from magnesium, calcium, strontium, barium and the like. The alkaline earth metal is particularly preferably magnesium, strontium, or barium. These alkaline earth metal oxides can be obtained by firing with an alkaline earth metal compound such as chloride, nitrate, acetate, etc. as a precursor.

  The supported amount of the alkaline earth metal oxide is preferably 0.1 to 10 parts by weight, more preferably 0.5 to 8 parts by weight, and 1 to 8 parts by weight with respect to 100 parts by weight of alumina. Even more preferably. When the supported amount of the alkaline earth metal oxide is more than 10 parts by mass, it is not preferable because it is present in an excessive amount with respect to alumina and the effect of addition relative to the content cannot be obtained. On the other hand, if the supported amount of the alkaline earth metal oxide is less than 0.1 parts by mass, the effect of addition becomes low, which is not preferable.

  The combination of the rare earth element contained in the rare earth metal oxide and the alkaline earth element contained in the alkaline earth metal oxide in this embodiment is strontium and cerium, magnesium and cerium, barium and cerium, strontium and lanthanum, and barium. And at least one selected from lanthanum. Particularly preferred is a combination of strontium and cerium, or barium and cerium.

  The supported amount of nickel is preferably 1 to 30 parts by mass, more preferably 3 to 25 parts by mass, and further preferably 5 to 20 parts by mass in terms of nickel atoms with respect to 100 parts by mass of alumina. More preferred. When the amount of nickel supported is more than 30 parts by mass, it is not preferable because it is present in an excessive amount with respect to alumina and the effect of addition relative to the content cannot be obtained. On the other hand, if the supported amount of nickel is less than 1 part by mass, the effect of addition becomes low, which is not preferable.

  The reforming catalyst for hydrogen production of this embodiment contains rhodium as a platinum group metal. That is, at least nickel and rhodium are supported on the inorganic composite oxide carrier. The supported amount of rhodium is preferably 0.01 to 3 parts by mass, more preferably 0.05 to 1 part by mass, and more preferably 0.05 to 0. Even more preferably 5 parts by weight. If the supported amount of rhodium is more than 3 parts by mass, the expensive rhodium metal is present in an excessive amount with respect to alumina, and not only the addition effect compared with the content cannot be obtained, but also the catalyst price is high. This is not preferable. On the other hand, if the amount of rhodium supported is less than 0.01 parts by mass, the effect of addition is reduced, which is not preferable.

  In addition to rhodium, the platinum group metal can also contain one or more platinum group metals selected from ruthenium, palladium, platinum and the like. The total supported amount of platinum group metal including rhodium is preferably 0.01 to 3 parts by mass in terms of platinum group atoms with respect to 100 parts by mass of alumina. If the total supported amount of platinum group atoms is more than 3 parts by mass, it will be present in excess with respect to alumina, and not only will the effect of addition relative to the content not be obtained, but also the catalyst price will be high. It is not preferable. On the other hand, if the total supported amount of platinum group atoms is less than 0.01 parts by mass, the effect of addition becomes low, which is not preferable.

  The reforming catalyst for hydrogen production of this embodiment preferably contains palladium and / or platinum as a platinum group metal. In this case, these metals function as a stabilizer and can improve the stability of nickel. The supported amount of palladium and / or platinum is preferably 0.005 to 0.2 parts by mass, and 0.01 to 0.1 parts by mass in terms of platinum group atoms with respect to 100 parts by mass of alumina. More preferred.

  Furthermore, from the viewpoint of improving the stability of nickel, the reforming catalyst for hydrogen production preferably contains platinum as a platinum group metal. In this case, the molar ratio of platinum to rhodium (Pt / Rh) is preferably 0.05 to 0.5 mol / mol. By supporting platinum so that the molar ratio is within such a range, the amount of platinum group metal to be introduced can be suppressed.

  In the reforming catalyst for hydrogen production of this embodiment, as a combination that can achieve the invention effect more effectively, the rare earth metal oxide is cerium oxide, the alkaline earth metal oxide is strontium oxide, and a platinum group metal Is preferably rhodium and platinum.

  In the reforming catalyst for hydrogen production according to the present embodiment, the method for supporting nickel, platinum group metal, rare earth metal oxide and alkaline earth metal oxide on the support is not particularly limited, and is a normal impregnation method or pore fill. Known methods such as the method can be used. Usually, it is dissolved in a solvent containing water or an organic substance as a metal salt or metal complex, and then impregnated on a carrier containing alumina. As the metal salt or metal complex to be contained, chloride, nitrate, sulfate, acetate, acetoacetate and the like can be used. There is no restriction | limiting in particular regarding the frequency | count of an impregnation, or a process, It can be made to divide once or several times. Nickel and rhodium are preferably dissolved in the same solvent and then simultaneously contained in the catalyst. Moreover, when the reforming catalyst for hydrogen production contains a metal other than rhodium as the platinum group metal, it is preferable that nickel, rhodium and other platinum group metal are dissolved in the same solvent and then simultaneously contained in the catalyst.

  The drying treatment after the inclusion of each metal is not particularly limited with respect to the conditions, but for example, it may be performed in air at 100 ° C. or higher.

  In order for the reforming catalyst for hydrogen production of this embodiment to have a predetermined X-ray intensity distribution in the above-mentioned rhodium line analysis measurement by EPMA, before introducing rhodium into the catalyst, specifically, rhodium is supported on the support. A method of previously calcining an inorganic composite oxide carrier containing alumina and carrying a rare earth metal oxide and an alkaline earth metal oxide or a precursor thereof in the presence of oxygen at a temperature of 650 to 1200 ° C. Is mentioned. The firing temperature is preferably 700 ° C. or higher, more preferably 750 ° C. or higher, preferably 1000 ° C. or lower, and more preferably 900 ° C. or lower.

  As a precursor of the inorganic composite oxide carrier, for example, a carrier containing alumina impregnated with the rare earth metal compound is fired at 400 to 800 ° C. in the presence of oxygen, and this is impregnated with the alkaline earth metal compound. And a carrier containing alumina impregnated with the rare earth metal compound and the alkaline earth metal compound.

  By performing the above-mentioned calcination treatment, rhodium introduced into the catalyst later is easily distributed on the surface of the support with respect to the diameter direction of the inorganic composite oxide support, and the sintering of the inorganic composite oxide support is triggered. The decrease in the catalyst performance due to the aggregation of rhodium can be suppressed. At a temperature lower than 650 ° C., not only rhodium is likely to be distributed in the internal direction of the inorganic composite oxide support after rhodium is introduced, but also thermal aggregation of alumina contained in the inorganic composite oxide support is likely to proceed, It is not preferable because it tends to cause aggregation of rhodium. On the other hand, when the baking treatment is performed at a temperature higher than 1200 ° C., the BET specific surface area of the inorganic composite oxide carrier is decreased, which is not preferable.

  After the introduction of rhodium, the introduced rhodium is distributed and immobilized on the surface of the inorganic composite oxide support by drying or firing at a temperature lower than the firing temperature of the inorganic composite oxide support or precursor described above. Is done. When rhodium is introduced and dried or calcined at a temperature higher than the firing temperature of the inorganic composite oxide support, rhodium distributed on the surface of the inorganic composite oxide support is triggered by sintering of the inorganic composite oxide support. Aggregation progresses and catalyst performance decreases, which is not preferable. The drying or firing temperature after the introduction of rhodium can be set based on the firing temperature of the inorganic composite oxide carrier or the precursor thereof, but is preferably in the range of 100 ° C. or more and less than 650 ° C., more preferably It is the range of 130-600 degreeC. A temperature lower than 100 ° C. is not preferable because rhodium introduced due to insufficient moisture desorption is not immobilized on the surface of the inorganic composite oxide carrier.

  The reforming catalyst for hydrogen production according to the present embodiment can be subjected to reduction treatment or metal immobilization treatment as necessary. The treatment method is not particularly limited, and for example, gas phase reduction treatment or liquid phase reduction treatment under hydrogen flow can be performed.

  There is no restriction | limiting in particular about the form of the reforming catalyst for hydrogen production which concerns on this embodiment, For example, the shape of the support | carrier containing an alumina can be utilized as it is. Alternatively, it can be used as a catalyst formed by tableting and pulverized and sized within a predetermined range, a powder or a catalyst formed into a spherical shape, ring shape, tablet shape, cylindrical shape or the like.

  The reforming of the hydrogen raw material is performed, for example, by supplying a gas containing at least one selected from oxygen and steam and a hydrogen raw material containing hydrocarbon compounds in the presence of the reforming catalyst for hydrogen production. And a method of obtaining a product containing hydrogen from a hydrogen raw material by at least one hydrogen production reaction selected from a partial oxidation reaction, an autothermal reforming reaction and a steam reforming reaction.

  In the present embodiment, steam is improved by supplying a gas containing steam and a hydrogen raw material containing hydrocarbon compounds in that more hydrogen can be efficiently produced from the same hydrocarbon. It is preferable to carry out a quality reaction.

  Examples of the reaction format using the reforming catalyst for hydrogen production include a fixed bed type, a moving bed type, and a fluidized bed type, and are not particularly limited. Also, the reactor using the reforming catalyst for hydrogen production is not particularly limited.

  Hydrocarbon compounds as raw materials in the hydrogen production reaction contain an organic compound having 1 to 40 carbon atoms, preferably 1 to 30 carbon atoms, more preferably 1 to 6 carbon atoms. Specific examples include saturated aliphatic hydrocarbons, unsaturated aliphatic hydrocarbons, aromatic hydrocarbons, and the like, and saturated aliphatic hydrocarbons and unsaturated aliphatic hydrocarbons are linear or cyclic. Any shape can be used. Such hydrocarbon compounds can contain substituents. As the substituent, either a chain or a ring can be used, and examples thereof include an alkyl group, a cycloalkyl group, an aryl group, an alkylaryl group, and an aralkyl group. These hydrocarbon compounds may be substituted with a substituent containing a hetero atom such as a hydroxy group, an alkoxy group, a hydroxycarbonyl group, an alkoxycarbonyl group, or a formyl group.

  Specific examples of the hydrocarbon compounds include chain saturated aliphatic hydrocarbons such as methane, ethane, propane, butane, pentane, hexane, heptane, and octane and their structural isomers, ethylene, propylene, butene, pentene, hexene. Chain unsaturated aliphatic hydrocarbons such as heptene and octene and their structural isomers, cyclic hydrocarbons such as cyclopentane, cyclohexane, cycloheptane and cyclooctane and their structural isomers, benzene, toluene, xylene, naphthalene, And aromatic hydrocarbons such as biphenyl. Moreover, the material which contains these as a single item or a mixture can be used. Examples thereof include city gas, natural gas, LPG, naphtha, gasoline, kerosene, and light oil.

  In addition, as hydrocarbon compounds having a substituent containing a hetero atom, raw materials containing alcohols, ethers, biofuels and the like can be used. Examples of the alcohols include methanol and ethanol. Examples of the ethers include dimethyl ether. Examples of the biofuel include biogas, bioethanol, biodiesel, and biojet. And so on.

  In addition, a raw material containing hydrogen, water, carbon dioxide, carbon monoxide, oxygen, nitrogen or the like as the above raw material can also be used. For example, when hydrodesulfurization is performed as a pretreatment of the raw material, the hydrogen residue used in the reaction can be used as it is without being particularly separated.

  In the present embodiment, by using the above reforming catalyst for hydrogen production, there is a period (a) for reforming a hydrogen raw material having a sulfur compound content concentration of 0.3 ppm or more in terms of sulfur atom mass. Hydrogen can be produced efficiently. From the viewpoint of achieving both sulfur resistance and stability of hydrogen production, the content concentration of the sulfur compound of the hydrogen raw material supplied in the period (a) is preferably 0.3 ppm or more and 8 ppm or less in terms of sulfur atom mass, More preferably, it is 0.3 ppm or more and 3 ppm or less.

  Further, by using the above-described reforming catalyst for hydrogen production, the efficiency of hydrogen is improved even after the cumulative amount of sulfur compounds supplied to the reforming catalyst for hydrogen production becomes 1 mg or more in terms of the mass of sulfur atom per 1 g of the catalyst. Can be manufactured well. From the viewpoint of achieving both sulfur resistance and hydrogen production stability, the integrated amount is preferably from 1 mg to 3000 mg, and more preferably from 1 mg to 2000 mg.

  In hydrogen production of a fuel cell, hydrogen is usually produced by steam reforming after desulfurizing sulfur in the raw material in a desulfurization step. When the method for producing hydrogen according to the present embodiment is applied to such a fuel cell, the function of the desulfurization process occurs due to a decrease in the function of the desulfurization catalyst or an unsteady state (starting or stopping of the fuel cell) during the desulfurization process. Even if a case where the sulfur content cannot be removed temporarily / continuously occurs, hydrogen production can be continued with a small amount of noble metal. As a result, it is not necessary to provide additional equipment such as a catalyst increase or a guard reactor to compensate for the desulfurization agent function deterioration, and the cost of hydrogen production can be reduced.

In this embodiment, the space velocity of the flow material introduced into the reforming catalyst for hydrogen production is preferably a gas space velocity (hereinafter referred to as GHSV), preferably 10 to 10,000 h ⁻¹ , more preferably 50 to 5, 000h ^-1, more preferably in the range of 100~3,000h ^-1. If the GHSV is higher than 10,000 h ^−1, the contact time between the raw material and the catalyst cannot be secured sufficiently, and the reaction conversion does not proceed, which is not preferable. On the other hand, if GHSV is lower than 10 h ^−1, it is not preferable because the amount of hydrogen production relative to the amount of catalyst is small and the hydrogen production efficiency is low. The liquid space velocity (hereinafter referred to as LHSV) is preferably 0.05 to 5.0 h ⁻¹ , more preferably 0.1 to 2.0 h ⁻¹ , and still more preferably 0.2 to 1.0 h ⁻¹ . It is a range. When LHSV is higher than 5.0 h ^−1, the contact time between the raw material and the catalyst cannot be ensured sufficiently, so that the reaction conversion does not proceed and it is not preferable. On the other hand, if LHSV is lower than 0.05 h ^−1, it is not preferable because the amount of hydrogen production relative to the amount of catalyst is small and the hydrogen production efficiency is low.

  The reaction temperature of the hydrogen production method of the present embodiment is not particularly limited, but is preferably 200 to 1000 ° C, more preferably 250 to 900 ° C, and further preferably 250 to 850 ° C. When the temperature is higher than 1000 ° C., the aggregation of the metal contained in the catalyst is likely to proceed, and the early performance deterioration of the catalyst is accompanied. On the other hand, a temperature lower than 200 ° C. is not preferable because a reaction rate sufficient for hydrogen production cannot be obtained.

  The reaction pressure of the hydrogen production method of the present embodiment is not particularly limited, but is preferably atmospheric pressure to 20 MPa, more preferably atmospheric pressure to 5 MPa, and further preferably atmospheric pressure to 1 MPa. Although it is possible to carry out at a pressure lower than the atmospheric pressure or a pressure higher than 20 MPa, in that case, it is necessary for the production equipment to cope with reduced pressure and high pressure, which is not economically preferable.

  In the present embodiment, when performing the steam reforming reaction, the amount of steam introduced into the steam reforming reaction is the ratio of the number of moles of water molecules to the number of moles of carbon atoms contained in the raw material hydrocarbon compounds (steam / carbon ratio: (Hereinafter referred to as S / C) is preferably in the range of 0.3 to 10, more preferably 0.5 to 5, further preferably 1.5 to 3.5, particularly preferably 2.0 to 3.0. Is set to be When S / C is less than 0.3, the steam required for the steam reforming reaction is insufficient, and coke deposition is promoted, so that the performance degradation of the catalyst is remarkably accelerated. On the other hand, when S / C is larger than 10, the energy required for steam supply and the cost required for generating / collecting surplus steam increase, which is not preferable.

Further, in the present embodiment, by using the hydrogen production reforming catalyst according to the present embodiment, hydrogen can be efficiently produced even in a state where oxygen coexists, such as a partial oxidation reaction and an autothermal reaction. The amount of oxygen introduced into these reactions is preferably a ratio of the number of moles of oxygen molecules to the number of moles of carbon atoms contained in the raw material hydrocarbon compounds (oxygen / carbon ratio: hereinafter referred to as O ₂ / C), preferably 0. It is 8 or less, more preferably 0.5 or less, and still more preferably 0.3 or less. A case where O ₂ / C is larger than 0.8 is not preferable because the generation reaction of carbon dioxide and water proceeds and the generation amount of hydrogen decreases.

  According to the hydrogen production method of this embodiment, from a hydrocarbon fuel such as city gas, natural gas, LPG, LNG, naphtha, gasoline, kerosene, etc., by a hydrogen production reaction by the reforming catalyst for hydrogen production according to this embodiment, A reformed gas containing hydrogen as a main component can be obtained. Moreover, the mixed gas containing hydrogen obtained by the hydrogen production reaction can be used as a fuel for a fuel cell as it is in the case of a solid oxide fuel cell. In addition, when carbon monoxide needs to be removed, such as phosphoric acid fuel cells and polymer electrolyte fuel cells, it can be suitably used as a fuel for fuel cells by using a carbon monoxide removal step in combination. Can do.

  Next, a hydrogen production apparatus and a fuel cell system in which the method for producing hydrogen according to this embodiment is implemented will be described.

  The hydrogen production apparatus of the present embodiment includes a reforming unit having the above-described reforming catalyst for hydrogen production according to the present embodiment, and a gas containing at least one selected from oxygen and steam in the reforming unit. , Comprising a supply unit for supplying a hydrogen raw material containing hydrocarbon compounds, and containing hydrogen from the hydrogen raw material by at least one reaction selected from a partial oxidation reaction, an autothermal reforming reaction and a steam reforming reaction To get things.

  In the hydrogen production apparatus of the present embodiment, when a hydrogen raw material having a sulfur compound content concentration of 0.3 ppm or more in terms of sulfur atom mass is supplied to the reforming section, and / or hydrogen production in the reforming section. There is a case where a hydrogen raw material is supplied in which the integrated amount of the sulfur compound supplied to the reforming catalyst is 1 mg or more in terms of the mass of sulfur atom per 1 g of the catalyst.

  The fuel cell system according to the present embodiment includes the hydrogen production apparatus and the fuel cell stack, and includes, for example, the configuration of FIG. FIG. 1 is a schematic view showing an example of the fuel cell system of the present embodiment.

  In FIG. 1, the fuel in the fuel tank 3 flows into the desulfurizer 5 through the fuel pump 4. The desulfurizer 5 can be filled with, for example, a copper-zinc-based or nickel-zinc-based sorbent. At this time, if necessary, a hydrogen-containing gas from at least one of the downstream of the reformer 7, the downstream of the shift reactor 9, the downstream of the carbon monoxide selective oxidation reactor 10, and the anode off-gas can be added. The fuel desulfurized in the desulfurizer 5 is mixed with water from the water tank 1 through the water pump 2, introduced into the vaporizer 6, vaporized, and sent to the reformer 7.

  The catalyst of the present embodiment is used as the catalyst of the reformer 7 and is filled in the reformer 7. The reformer reaction tube is heated by a burner 18 using fuel from the fuel tank 3 (hydrogen raw material containing hydrocarbon compounds) and anode off-gas as fuel, preferably 200 to 1000 ° C., more preferably 300 to 900. ° C, more preferably in the range of 400-800 ° C.

  In the present embodiment, the supply unit 20 includes a water tank 1, a water pump 2, a fuel tank 3, and a desulfurizer 5, and the reforming unit 7 includes at least one selected from oxygen and steam. Any other configuration may be used as long as it supplies a gas and a hydrogen raw material containing hydrocarbon compounds.

  The reformed gas containing hydrogen and carbon monoxide produced in this way is passed through the shift reactor 9 and the carbon monoxide selective oxidation reactor 10 in order so as not to affect the characteristics of the fuel cell. The carbon monoxide concentration is reduced. Examples of the catalyst used in these reactors include an iron-chromium catalyst and / or a copper-zinc catalyst for the shift reactor 9, and a ruthenium catalyst for the carbon monoxide selective oxidation reactor 10. it can.

  According to the above-described steam reforming catalyst, hydrogen production apparatus, and fuel cell system, hydrogen production using a hydrogen source such as hydrocarbon as a raw material is inexpensive, highly durable, and efficiently produces hydrogen under a wide range of conditions. Is possible.

  In addition, the desulfurizer 5 has a reduced function of the desulfurization catalyst or an unsteady state (starting or stopping of the fuel cell), and the function of the desulfurizer 5 is reduced, so that the sulfur content cannot be removed temporarily / continuously. Even if a case occurs, hydrogen production can be continued. Therefore, according to the fuel cell system according to the present embodiment, it is not necessary to provide additional equipment such as a catalyst increase amount or a guard reactor for compensating for the function deterioration of the desulfurizer 5, and power can be supplied over a longer period.

  The effects of the present invention will be described more specifically with reference to the following examples, but the present invention is not limited to the following examples.

[Preparation of catalyst]
<Example 1 (Catalyst A)>
Pore volume 0.43 ml / g, B.I. E. T.A. The γ-alumina support formed into a spherical shape having a specific surface area of 182 m ² / g and a diameter of 2 to 3 mm was dried at 150 ° C. for 6 hours, impregnated with an aqueous solution containing cerium nitrate, and dried at 150 ° C. for 4 hours. Firing was carried out at 400 ° C. for 4 hours under air. This was impregnated with an aqueous solution containing strontium nitrate, dried at 150 ° C. for 4 hours, and then subjected to calcination treatment at 800 ° C. for 4 hours in an air atmosphere. The amount of cerium oxide supported on 100 parts by mass of the γ-alumina carrier Thus, an oxide carrier having a ratio of 12 parts by mass and a supported amount of strontium oxide of 5 parts by mass was obtained.

  Next, the obtained oxide-supported carrier was impregnated with an aqueous solution containing nickel nitrate, chloroplatinic acid and rhodium nitrate, dried at 150 ° C. for 4 hours, and then fired at 600 ° C. in the atmosphere for 3 hours. As a result, the supported amount of cerium oxide is 12 parts by mass, the supported amount of strontium oxide is 5 parts by mass, the supported amount of nickel is 10 parts by mass in terms of nickel oxide, and the supported amount of platinum with respect to 100 parts by mass of the γ-alumina carrier. Thus, a catalyst having 0.05 parts by mass in terms of platinum atoms and 0.2 parts by mass of rhodium supported in terms of rhodium atoms was obtained. This was designated as “catalyst A”.

  EPMA measurement is a sample in which the catalyst to be measured is resin-embedded, and the measurement surface is polished and then subjected to carbon vapor deposition, using an electron probe microanalyzer (Electron Beam Analyzer JXA-8900R manufactured by JEOL Ltd.) The analysis was performed under linear analysis conditions of an acceleration voltage of 20 kV, a probe current of 0.1 μA, a beam diameter of 10 μmφ, and a step width of 10 μm.

[Evaluation of rhodium distribution]
Content ratio (mass%) of rhodium contained in the surface portion of the carrier at a distance within 10% of the carrier diameter from the outer surface of the carrier toward the center of the carrier (denoted as “Rh content within 10% of the surface layer” in the table) ) R ₁₀ and the content (ratio by mass) of rhodium contained in the carrier surface layer at a distance within 20% of the carrier diameter from the outer surface of the carrier toward the center of the carrier (in the table, “within 20% of the surface layer R ₂₀ was calculated according to the following formula.
R ₁₀ = I ₁₀ ÷ I ₁₀₀ × 100
R ₂₀ = I ₂₀ ÷ I ₁₀₀ × 100
In the above formula, I ₁₀₀ represents the characteristic X-ray intensity (cps) of the total rhodium detected, and I ₁₀ is the characteristic X of the rhodium detected within a range within 10% of the carrier diameter from the outer surface of the carrier. The line intensity (cps) is indicated, and I ₂₀ indicates the characteristic X-ray intensity (cps) of rhodium detected in the range of a distance within 20% of the carrier diameter from the outer surface of the carrier.

Table 1 shows I ₁₀ , I ₂₀ , I ₁₀₀ , R ₁₀ , and R ₂₀ of Catalyst A, respectively.

<Comparative Example 1 (Catalyst B)>
Pore volume 0.43 ml / g, B.I. E. T.A. The γ-alumina support formed into a spherical shape having a specific surface area of 182 m ² / g and a diameter of 2 to 3 mm was dried at 150 ° C. for 6 hours, impregnated with an aqueous solution containing cerium nitrate, and dried at 150 ° C. for 4 hours. Firing was carried out at 400 ° C. for 4 hours under air. This was impregnated with an aqueous solution containing barium nitrate, dried at 150 ° C. for 4 hours, and then fired at 600 ° C. for 3 hours in air.

  Next, the obtained oxide-supported carrier was impregnated with an aqueous solution containing rhodium nitrate, dried at 150 ° C. for 4 hours, and then fired at 600 ° C. in the atmosphere for 3 hours. As a result, a catalyst having 12 parts by mass of cerium oxide, 4 parts by mass of barium oxide, and 0.2 parts by mass of rhodium in terms of rhodium atom with respect to 100 parts by mass of the γ-alumina carrier. Obtained. This was designated as “catalyst B”.

[Catalyst evaluation by steam reforming reaction using raw materials containing sulfur]
The catalyst was evaluated in a steam reforming reaction at 450 ° C. using a fixed bed microreactor. A catalyst tube (5 cc) was filled into a reaction tube (inner diameter of about 9.52 mm), and this was installed in a tubular electric furnace, under the conditions of a reaction temperature of 450 ° C. and a steam / carbon ratio (molar ratio) of 2.5 at atmospheric pressure. Propane gas containing 0.35 mass ppm of sulfur compound (sulfur content) as a sulfur atom mass was introduced as a raw material at GHSV 2800h- ¹ . In addition, the sulfur atom mass of the sulfur compound contained in propane gas was calculated | required by the analysis by GC-SCD (Shimadzu-ANTEK 7090 type | mold).

The reaction product gas after 0, 1, 20, 40 hours is analyzed by gas chromatogram, and the propane conversion calculated by the following formula (1) is calculated based on the number of moles of carbon components contained in the reaction product gas. Thus, the propane conversion rate of the raw material was obtained.
Propane conversion (%) = (number of moles of C1 compound contained in reaction product gas) / (total number of moles of carbon atoms contained in reaction product gas) × 100 (1)
In the formula (1), “C1 compound” is a general term for compounds having 1 carbon atom, and specifically means CO, CO ₂ , and CH ₄ .

Furthermore, based on the propane conversion obtained above, the reaction rate calculated by the following formula (2) was calculated.
Reaction rate (mol / sec / ml) = propane feed molar rate (mol / sec) × propane conversion (%) ÷ 100 ÷ catalyst amount (ml) Formula (2)

  FIG. 1 is a graph showing the relationship between the elapsed time of the steam reforming reaction using the catalyst A or the catalyst B and the propane reaction rate. As shown in FIG. 1, it can be seen that in the steam reforming reaction using the raw material containing sulfur, the catalyst A maintains a higher reaction rate than the catalyst B.

  In the steam reforming reaction by the reforming catalyst for hydrogen production using a hydrogen source such as hydrocarbon as the raw material, even if the function of the desulfurization process is lowered and the sulfur content cannot be removed temporarily / continuously, It is possible to provide a method for producing hydrogen that is excellent in sulfur resistance and capable of continuing production of hydrogen.

  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 ... Shift reactor, 10 ... One Carbon oxide selective oxidation reactor, 11 ... anode, 12 ... cathode, 13 ... solid polymer electrolyte, 14 ... electric load, 15 ... exhaust port, 16 ... solid polymer fuel cell, 17 ... heating burner, 20 ... Supply section.

Claims (3)

A step of reforming a hydrogen raw material containing hydrocarbon compounds with a reforming catalyst for hydrogen production to obtain hydrogen;
The reforming catalyst for hydrogen production contains a spherical, alumina-containing inorganic composite oxide carrier supporting rare earth metal oxide and alkaline earth metal oxide, nickel and platinum group metal supported on the carrier, In the catalyst, the nickel and the platinum group metal are supported on the same carrier, rhodium is contained as the platinum group metal, and the center of the cross section of the catalyst is measured by an electron probe microanalyzer (EPMA). The rhodium characteristic X detected within a distance within 10% of the carrier diameter from the outer surface of the carrier relative to the characteristic X-ray intensity of the total rhodium detected when the rhodium line analysis measurement was performed in the direction of the carrier diameter passing through The ratio of the characteristic X-ray intensity of rhodium detected within a range of 90% or more of the line intensity and within 20% of the carrier diameter from the outer surface of the carrier is 95%. A top, wherein a rare earth metal oxide is cerium oxide, the alkaline earth metal oxide is strontium oxide, the platinum group metal is rhodium and platinum,
The period for reforming the hydrogen raw material in which the concentration of the sulfur compound is 0.3 ppm or more in terms of sulfur atom mass and / or the cumulative amount of the supplied sulfur compound is 1 mg or more in terms of sulfur atom mass per 1 g of catalyst. A method for producing hydrogen, comprising a period of reforming the hydrogen raw material with the hydrogen production reforming catalyst.   In the reforming catalyst for hydrogen production, the supported amount of nickel is 1 to 30 parts by mass in terms of nickel atoms with respect to 100 parts by mass of alumina, and the supported amount of rhodium is rhodium with respect to 100 parts by mass of alumina. It is 0.01-3 mass parts in conversion of an atom, The manufacturing method of hydrogen of Claim 1 characterized by the above-mentioned.   3. The reforming catalyst for hydrogen production, wherein the supported amount of the platinum group metal is 0.01 to 3 parts by mass in terms of platinum group metal atoms with respect to 100 parts by mass of the alumina. A method for producing hydrogen as described in 1. above.

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