JP5788352B2 - Reforming catalyst for hydrogen production, hydrogen production apparatus and fuel cell system using the catalyst - Google Patents

Description

  The present invention relates to a reforming catalyst for hydrogen production and a hydrogen production apparatus using the catalyst, and in particular, a reforming catalyst for hydrogen production used in hydrogen production in a fuel cell system using a hydrogen source such as hydrocarbon as a raw material. The present invention relates to a hydrogen production apparatus and a fuel cell system using the catalyst.

  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. As a reforming catalyst for hydrogen production, a noble metal catalyst in which a noble metal such as ruthenium or rhodium is supported on a support such as alumina, and a nickel catalyst in which nickel is supported are known as conventional techniques. In recent years, noble metal catalysts using noble metals such as ruthenium and rhodium have attracted attention as reforming catalysts for hydrocarbons because they can reduce the amount of water vapor used. Examples include those in which ruthenium is supported on alumina (see Non-Patent Document 1), those in which ruthenium is supported on alumina or silica (see Patent Document 1), zirconia and ruthenium on alumina containing an alkaline earth metal aluminate. The thing which carry | supported the component (refer patent document 2) etc. are mentioned. Although these catalysts can suppress carbon deposition, there is a problem that the cost of the catalyst is high because an expensive noble metal is used. Moreover, in the nickel catalyst which carry | supported nickel, the thing which carry | supported metallic nickel on the alumina support | carrier is mentioned as an example (refer patent document 3). Nickel-based catalysts are economically preferable because they are less expensive than precious metal-based catalysts, but they have the disadvantage of easily causing a decrease in activity due to carbon deposition. To suppress carbon deposition, the steam / carbon ratio is increased. There is a problem that a reaction needs to be performed, and energy consumption increases as the steam supply amount increases. Further, when exposed to a steam atmosphere at a high temperature, there is a problem that the activity is lowered due to aggregation of nickel. Further, by utilizing the characteristics of both the noble metal catalyst and the nickel catalyst, at least an upstream catalyst layer in which at least a ruthenium component is supported on an alumina support and a downstream catalyst layer containing nickel are included. A steam reforming method (refer to Patent Document 4) characterized by the above, a so-called stacked catalyst system has been proposed. However, this stacked catalyst system has a problem that carbon deposition tends to proceed at the interface between different catalyst layers on the upstream side and the downstream side, and carbon deposition in the downstream catalyst layer is still large.

In addition, hydrogen production in a fuel cell system that uses hydrocarbons as a raw material is not limited to steady production conditions, and it is required to efficiently produce hydrogen under a wide range of production conditions that accompany system start / stop. . The reforming catalysts for hydrogen production listed above are mainly assumed to be applied to steam reforming reactions, but in the partial oxidation reaction and autothermal reaction in which oxygen coexists, oxidation and aggregation of ruthenium and nickel As the catalyst deteriorates due to hydrogen, hydrogen production is limited to the steam reforming reaction, and it is difficult to efficiently produce hydrogen under a wide range of conditions. In the hydrogen production reaction in which these oxygens coexist, rhodium may be used as a catalyst. Examples include a catalyst for reforming hydrocarbons composed of rhodium, spinel having the chemical formula MgO.xAl ₂ O ₃ and substantially free of alumina crystal structure (see Patent Document 5), and a support containing cerium oxide. An autothermal reforming catalyst that supports rhodium and defines the atomic ratio of cerium and rhodium has been proposed (see Patent Document 6).

JP-A 57-4232 Japanese Patent Laid-Open No. 5-220397 Japanese Patent Publication No.53-12917 JP 2001-342004 A JP 2001-276620 A JP 2002-336702 A

“Journal of Fuel Association”, 25, 1980, p. 59

  However, rhodium is an expensive metal, and in order to produce hydrogen at a low cost, further improvement in the activity and durability of the catalyst is required.

  The present invention relates to a reforming catalyst for hydrogen production that solves the above-described problems of the prior art and a hydrogen production apparatus using the catalyst, and in particular, in hydrogen production in a fuel cell system using a hydrogen source such as hydrocarbon as a raw material. An object of the present invention is to provide a reforming catalyst for hydrogen production that can be used for a long period of time, a hydrogen production apparatus using the catalyst, and a fuel cell system.

  As a result of intensive studies in view of the problems of the prior art, the present inventors show that a catalyst in which rhodium and cobalt are supported on the same specific support exhibits high catalytic activity in a hydrocarbon steam reforming reaction. At the same time, it has been found that the catalyst has high catalytic activity even after the heat deterioration treatment, and has completed the present invention.

  That is, the present invention relates to a reforming catalyst for producing hydrogen comprising an inorganic composite oxide support containing alumina and supporting a rare earth metal oxide and an alkaline earth metal oxide, and cobalt and rhodium supported on the support. I will provide a.

  In the hydrogen production reforming catalyst according to the present invention, the supported amount of cobalt is 0.1 to 10 parts by mass in terms of cobalt atom with respect to 100 parts by mass of alumina, and the supported amount of rhodium is based on 100 parts by mass of alumina. It is preferable that it is 0.01-3 mass parts in conversion of a rhodium atom.

  In the hydrogen production reforming catalyst according to the present invention, the alkaline earth metal oxide is preferably strontium oxide, and the rare earth metal oxide is preferably cerium oxide.

  In the reforming catalyst for hydrogen production according to the present invention, the supported amount of the rare earth metal oxide is preferably 2 to 30 parts by mass with respect to 100 parts by mass of alumina.

  In the reforming catalyst for hydrogen production according to the present invention, the supported amount of the alkaline earth metal oxide is preferably 1 to 10 parts by mass with respect to 100 parts by mass of alumina.

  The present invention is a method for producing a reforming catalyst for hydrogen production according to the present invention, wherein the inorganic composite oxide support or its precursor is impregnated with a solution containing a cobalt compound and a rhodium compound. A method for producing a reforming catalyst for production is provided.

  The present invention provides a hydrogen production method for obtaining hydrogen by reforming a hydrogen raw material containing hydrocarbon compounds with the above-described reforming catalyst for production of hydrogen according to the present invention.

  The present invention includes a reforming unit having the reforming catalyst for hydrogen production according to the present invention, a gas containing at least one selected from oxygen and steam, and hydrocarbon compounds in the reforming unit. And a hydrogen supply unit that supplies a hydrogen-containing product from at least one reaction selected from a partial oxidation reaction, an autothermal reforming reaction, and a steam reforming reaction. Providing equipment.

  The present invention provides a fuel cell system comprising the hydrogen production apparatus according to the present invention.

  ADVANTAGE OF THE INVENTION According to this invention, the reforming catalyst for hydrogen production excellent in the catalyst activity and long-term durability which can be used for a long period in the hydrogen production in the fuel cell system which uses hydrogen sources, such as hydrocarbon, as a raw material, and A manufacturing method thereof can be provided. Moreover, according to this invention, the hydrogen production method using the reforming catalyst for hydrogen production of this invention, a hydrogen production apparatus, and a fuel cell system can be provided.

It is a conceptual diagram which shows an example of the fuel cell system which concerns on embodiment of this invention. 3 is a graph showing a relative value of a reaction rate in a steam reforming reaction using a catalyst A or a catalyst B.

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

  The reforming catalyst for hydrogen production of the present embodiment comprises an inorganic composite oxide support containing alumina and supporting a rare earth metal oxide and an alkaline earth metal oxide, and cobalt and rhodium supported on the support. It is a catalyst provided.

  The reforming catalyst for producing hydrogen according to the present embodiment can exhibit high catalytic activity in a reforming reaction for obtaining hydrogen from a hydrogen source such as hydrocarbon, and performance when exposed to a steam atmosphere at a high temperature. Is difficult to decrease.

  The cause of the high activity of the catalyst and the effect of suppressing its performance degradation is not clear, but the presence of cobalt and rhodium on the same specific support described above increases (1) the dispersibility of rhodium atoms. (2) It is considered that the reason is that (2) cobalt strongly binds to the support alumina, which acts as an anchor effect and suppresses thermal aggregation of rhodium atoms on the surface of the support alumina.

  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 B.I. can be sufficiently dispersed so that the supported rhodium and cobalt can be dispersed. 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, rhodium and cobalt cannot be sufficiently dispersed on the support surface layer, making it difficult to obtain a predetermined catalytic 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 1 to 10 parts by mass, more preferably 1 to 8 parts by mass, and 1 to 8 parts by mass with respect to 100 parts by mass of alumina. Even more preferred. 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, when the amount of the alkaline earth metal oxide supported is less than 1 part by mass, the effect of addition is reduced, 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 cobalt is preferably 0.1 to 10 parts by mass in terms of cobalt atom, more preferably 0.2 to 5 parts by mass, and 0.2 to 2 parts by mass with respect to 100 parts by mass of alumina. Even more preferably, it is part. When the amount of cobalt supported is more than 10 parts by mass, it is not preferable because it is present in excess with respect to alumina and the effect of addition compared to the content cannot be obtained. On the other hand, if the supported amount of cobalt is less than 0.1 parts by mass, the effect of addition becomes low, which is not preferable.

  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 reforming catalyst for hydrogen production of the present embodiment can also contain one or more platinum group metals selected from ruthenium, palladium, platinum and the like. In this case, the supported amount of the platinum group metal other than rhodium is preferably 0.01 to 3 parts by mass, and 0.05 to 2 parts by mass in terms of platinum group atoms with respect to 100 parts by mass of alumina. More preferred is 0.1 to 1 part by mass.

  The reforming catalyst for hydrogen production of the present embodiment contains a metal such as an alkali metal, an alkaline earth metal, and a rare earth metal in addition to cobalt, rhodium, and the platinum group metal as long as the effects according to the present invention are not impaired. You can also.

  In the reforming catalyst for hydrogen production according to the present embodiment, the method for supporting cobalt, rhodium, rare earth metal oxide, and alkaline earth metal oxide on the support is not particularly limited, and a normal impregnation method, a pore fill method, etc. A known 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. Cobalt and rhodium are preferably dissolved in the same solvent and then simultaneously contained in the catalyst. That is, it is preferable to impregnate an inorganic composite oxide carrier or a precursor thereof with a solution containing a cobalt compound and a rhodium compound. As the cobalt compound and rhodium compound, the above-mentioned chloride, nitrate, sulfate, acetate, acetoacetate can be used, and preferred compounds are from the viewpoint of ease of solution preparation due to high solubility, Examples include cobalt nitrate and rhodium nitrate.

  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 the present embodiment, from the viewpoint of suppressing thermal aggregation of rhodium atoms, which are active metals, by high-temperature baking treatment, before introducing cobalt and rhodium into the catalyst, more specifically, containing alumina, rare earth metal Before impregnating a solution containing a cobalt compound and a rhodium compound into an inorganic composite oxide support or precursor thereof supporting an oxide and an alkaline earth metal oxide, the inorganic composite oxide support or precursor thereof is It is preferable to perform a pre-baking treatment at a temperature of 650 to 1200 ° C. in the presence of oxygen. 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-described firing treatment, rhodium introduced together with cobalt into the catalyst is easily distributed on the surface of the support in the diameter direction of the inorganic composite oxide support, and the sintering of the inorganic composite oxide support is triggered. Thus, the decrease in 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 cobalt and rhodium, the introduced cobalt and rhodium are deposited 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 thereof. Distributed and fixed. When drying or firing is performed at a temperature higher than the firing temperature of the inorganic composite oxide support after the introduction of cobalt and rhodium, the sintering of the inorganic composite oxide support triggers the distribution on the surface of the inorganic composite oxide support. This is not preferable because the aggregation of rhodium proceeds and the catalyst performance decreases. The drying or firing temperature after the introduction of cobalt and rhodium can be set based on the aforementioned firing temperature of the inorganic composite oxide support or its precursor, 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 the desorption of moisture is insufficient and the introduced cobalt and rhodium are not immobilized on the surface of the inorganic composite oxide support.

  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.

  As a preferred method for producing the reforming catalyst for hydrogen production according to the present embodiment, for example, a predetermined amount of rare earth metal oxide and alkaline earth metal oxide is introduced into alumina to form an inorganic composite oxide support. Then, after performing a baking treatment at 650 to 1200 ° C. in an air atmosphere, cobalt and rhodium are introduced into the inorganic composite oxide carrier after the baking treatment, and then the above-described drying or baking treatment is 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.

  Next, the hydrogen production method according to this embodiment will be described. The hydrogen production method of this embodiment is a method for obtaining hydrogen by reforming a hydrogen raw material containing hydrocarbon compounds with the above-described reforming catalyst for hydrogen production of this embodiment.

  Specifically, for example, in the presence of the reforming catalyst for hydrogen production described above, a gas containing at least one selected from oxygen and steam and a hydrogen raw material containing hydrocarbon compounds are supplied, Examples thereof include 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.

  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.

  The sulfur concentration contained in the hydrocarbon compound used as a raw material is preferably 50 mass ppb or less, more preferably 20 mass ppb or less, and still more preferably 10 mass ppb or less as the mass of sulfur atoms. If the sulfur concentration exceeds 50 mass ppb, poisoning of the reforming catalyst with sulfur proceeds and carbon deposition is promoted, which is not preferable. If necessary, it is preferable to desulfurize the raw material to reduce the sulfur concentration as a pretreatment for the hydrogen production reaction. There are no particular limitations on the raw material desulfurization method, and one or more known techniques such as hydrodesulfurization and adsorption separation, which are generally used industrially, can be used. For example, a method of performing hydrodesulfurization treatment in the presence of a predetermined desulfurization catalyst and hydrogen and removing the produced hydrogen sulfide with an absorbent can be exemplified. There is no restriction | limiting in particular also in the implementation method of a desulfurization process, For example, you may implement just before hydrogen production reaction, and you may use the raw material which processed beforehand by the independent desulfurization process.

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 300 to 800 ° 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 set to be in the range of 0.3 to 10, more preferably 0.5 to 5, and further preferably 1.5 to 3.5. 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, hydrogen is a main component from hydrocarbon fuels such as city gas, natural gas, LPG, naphtha, and kerosene by a hydrogen production reaction by the reforming catalyst for hydrogen production according to this embodiment. The reformed gas contained as 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 according to this embodiment 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.

  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.

  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)>
A γ-alumina carrier (pore volume 0.43 ml / g, BET specific surface area 182 m ² / g) molded into a spherical shape having a diameter of 2 to 3 mm was dried in air at 150 ° C. for 6 hours, and then nitric acid. It was impregnated with an aqueous solution containing cerium, dried at 150 ° C. for 4 hours, and then calcined at 400 ° C. for 4 hours in air. This was impregnated with an aqueous solution containing strontium nitrate, dried at 150 ° C. for 4 hours, and then fired at 800 ° C. for 4 hours in air to carry cerium oxide on 100 parts by mass of the γ-alumina carrier. An oxide carrier A having an amount of 12 parts by mass and a supported amount of strontium oxide of 5 parts by mass was obtained.

  The oxide carrier A was impregnated with an aqueous solution containing cobalt nitrate and rhodium nitrate, dried at 150 ° C. for 4 hours, and then fired at 600 ° C. for 3 hours in the air. 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 cobalt is 1 part by mass in terms of cobalt atom, and the supported amount of rhodium is 100 parts by mass of γ-alumina. A catalyst having a ratio of 0.2 parts by mass in terms of rhodium atoms was obtained. This was designated as “catalyst A”.

<Comparative Example 1 (Catalyst B)>
An oxide carrier A produced in the same manner as in Example 1 was impregnated with an aqueous solution containing rhodium nitrate, dried at 150 ° C. for 4 hours, and then fired at 600 ° C. for 3 hours in air. 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, and the supported amount of rhodium is 0.2 parts by mass in terms of rhodium atoms with respect to 100 parts by mass of γ-alumina. A catalyst was obtained. This was designated as “catalyst B”.

[Evaluation of catalytic activity by steam reforming reaction]
The catalyst was evaluated in a steam reforming reaction using a fixed bed microreactor. 1 ml of catalyst is filled into a reaction tube (inner diameter of about 15 mm), which is placed in a tubular electric furnace, and propane is used under atmospheric pressure, reaction temperature of 350 ° C., and steam / carbon ratio (molar ratio) of 2.5. Gas was introduced as a raw material at GHSV 2,200 h ⁻¹ .

  The reaction product gas is analyzed for its composition using a gas chromatogram, and the propane conversion rate obtained by the following formula (1) is calculated based on the number of moles of the carbon component contained in the reaction product gas. Conversion was determined. This was designated as “initial propane conversion”.

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 .

Based on the propane conversion obtained above, the reaction rate obtained by the following formula (2) was calculated. This was defined as “initial reaction rate”.
Reaction rate (mol / sec / ml) = propane feed molar rate (mol / sec) × propane conversion (%) ÷ 100 ÷ catalyst amount (ml) Formula (2)

  After this, steam was passed through the catalyst filled in the reaction tube at 800 ° C. for 4 hours to perform heat deterioration treatment, and then propane gas was introduced under the same conditions as described above. The reaction rate was calculated. These were defined as “post-degradation propane conversion” and “degradation reaction rate”, respectively.

[Measurement of metal dispersion by CO adsorption]
Before the evaluation of the catalytic activity and after the evaluation after the thermal deterioration treatment, the metal dispersibility was measured, and the “initial metal dispersity” and the “post-degradation metal dispersity” were obtained respectively. .

The metal dispersity is measured by measuring the CO adsorption amount V ₅₀ adsorbed on the catalyst by a gas adsorption analysis method using carbon monoxide (CO) (using a metal dispersity measuring device BEL-METAL-3SP (manufactured by Nippon BEL)). And it calculated according to following formula (3) using those values.
Metal dispersity (%) = (number of moles of CO molecules adsorbed per gram of catalyst / number of moles of noble metal contained per gram of catalyst) × 100 Formula (3)

In the formula (3), “the number of moles of CO molecules adsorbed per 1 g of catalyst” is obtained by measuring the catalyst sample at 200 ° C. for 60 minutes under a hydrogen stream of 50 ml / min, and subsequently under a helium stream of 50 ml / min. After pretreatment at 200 ° C. for 30 minutes, rhodium is supported as a sphere on the support surface based on the CO adsorption amount V ₅₀ when CO pulses are injected at 50 ° C. in a helium gas stream. Assuming that one CO molecule is adsorbed on the rhodium atom, the following formula (4) was used.
Number of moles of CO molecules adsorbed per 1 g of catalyst (mol / g) = V ₅₀ /W×(273/(273+t))×(P/102.906)/(22.4×10 ³ ) Formula (4)
V ₅₀ : CO adsorption amount (ml) at a measurement temperature of 50 (° C.)
W: Sample amount of catalyst (g)
P: Pressure during measurement (kPa)
t: Measurement temperature (° C)

  These results are shown in Table 1. The unit of the catalyst composition in Table 1 is the content based on the total mass of the catalyst. Further, with respect to the “initial reaction rate” and “post-degradation reaction rate” of the catalysts A and B, the relative ratio of the reaction rates when the initial reaction rate of the catalyst B is 1 is shown in FIG.

  The catalyst A to which cobalt is added together with rhodium has a reaction rate of about 20% higher than that of the catalyst B to which no cobalt is added in both the initial reaction rate and the post-degradation reaction rate. This result shows that the reforming catalyst for hydrogen production provided by the present invention has high catalytic activity even after being subjected to thermal degradation treatment, and can efficiently proceed with the steam reforming reaction of hydrocarbons. Suggest.

  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 (9)

An inorganic composite oxide support containing alumina and supporting a rare earth metal oxide and an alkaline earth metal oxide; and cobalt and rhodium supported on the support ;
A reforming catalyst for hydrogen production , wherein the alkaline earth metal oxide contains strontium oxide .   The supported amount of cobalt is 0.1 to 10 parts by mass in terms of cobalt atom with respect to 100 parts by mass of alumina, and the supported amount of rhodium is 0.01 to in terms of rhodium atom with respect to 100 parts by mass of alumina. The reforming catalyst for hydrogen production according to claim 1, wherein the reforming catalyst is 3 parts by mass.   The reforming catalyst for hydrogen production according to claim 1 or 2, wherein the alkaline earth metal oxide is strontium oxide and the rare earth metal oxide is cerium oxide.   The reforming catalyst for hydrogen production according to any one of claims 1 to 3, wherein an amount of the rare earth metal oxide supported is 2 to 30 parts by mass with respect to 100 parts by mass of the alumina.   The reforming catalyst for hydrogen production according to any one of claims 1 to 4, wherein the supported amount of the alkaline earth metal oxide is 1 to 10 parts by mass with respect to 100 parts by mass of the alumina. A method for producing a reforming catalyst for hydrogen production according to any one of claims 1 to 5,
A method for producing a reforming catalyst for hydrogen production, comprising a step of impregnating the inorganic composite oxide support or a precursor thereof with a solution containing a cobalt compound and a rhodium compound.   A hydrogen production method wherein hydrogen is obtained by reforming a hydrogen raw material containing hydrocarbon compounds with the reforming catalyst for hydrogen production according to any one of claims 1 to 5. A reforming unit having the reforming catalyst for hydrogen production according to any one of claims 1 to 5, a gas containing at least one selected from oxygen and steam in the reforming unit, and hydrocarbon compounds A supply unit for supplying a hydrogen raw material containing
An apparatus for producing hydrogen, wherein a product containing hydrogen is obtained 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.   A fuel cell system comprising the hydrogen production apparatus according to claim 8.

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