JP2010279911A - Catalyst for manufacturing hydrogen, manufacturing method of the catalyst, and manufacturing method of hydrogen using the catalyst - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a catalyst for manufacturing hydrogen which has long term durability to poisoning by a sulfur compound included in a hydrocarbon group compound that is the raw material, the transformation of catalyst components and coking by temperature and environment change due to repetition of the operational breakdown of a fuel cell system. <P>SOLUTION: The catalyst for manufacturing hydrogen, which is a catalyst used in manufacturing hydrogen to produce hydrogen by reforming the hydrocarbon group compound, includes a catalyst composition which contains activated alumina and cerium based densely mixed oxide and is carried by a honeycomb carrier. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a hydrogen production catalyst for producing a hydrogen-containing gas by reforming a hydrocarbon compound, and a method for producing the catalyst.

  Hydrogen-containing gas (syngas) mainly composed of hydrogen and carbon monoxide is widely used as a reducing gas in addition to hydrogen gas production, and as a raw material for various chemical products. Recently, it is used for fuel cells. Research into practical use is also in progress as a fuel. It is known that such a hydrogen-containing gas can be obtained by steam reforming of a hydrocarbon compound. The steam reforming reaction when methane, the main component of natural gas, is used as a raw material is shown in the following equation.

天然ガスの水蒸気改質によって工業的に水素を製造する水素製造用触媒としては主にニッケル系触媒が使用されている。しかしながら家庭用燃料電池システムにおいては、電力および熱需要の状況への対応によりシステムの稼動停止を頻繁に実施される。この際、改質器内部に水および未改質燃料が存在したままシステムを停止すると、触媒の劣化、再起動性の悪化、燃料の漏洩等の原因となる。そこで燃料電池システムを停止する場合は、燃料を停止して水蒸気のみを流通させて改質器内部を不活性なガスでパージしてから停止する方法が採用されている。水素製造用触媒として工業的に実績があるニッケル系触媒は高温の水蒸気雰囲気にてニッケルが酸化されてシンタリングし失活することが知られており、家庭用燃料電池システムの水素製造用触媒としては白金族であるルテニウム系触媒が一般的に使用されている。パージガスとしては水蒸気以外に窒素や空気などが考えられ、特に空気が好ましいがルテニウム系触媒は高温の酸化雰囲気で昇華性が高いことが知られており、耐酸化性の優れた触媒開発が望まれている。

Nickel-based catalysts are mainly used as hydrogen production catalysts for industrially producing hydrogen by steam reforming of natural gas. However, in a domestic fuel cell system, the system is frequently shut down in response to the situation of power and heat demand. At this time, if the system is stopped while water and unreformed fuel are present inside the reformer, it may cause deterioration of the catalyst, deterioration of restartability, fuel leakage, and the like. Therefore, when the fuel cell system is stopped, a method is adopted in which the fuel is stopped, only water vapor is circulated, and the interior of the reformer is purged with an inert gas and then stopped. Nickel-based catalysts that have an industrial track record as a catalyst for hydrogen production are known to be oxidized and deactivated by oxidation of nickel in a high-temperature steam atmosphere. As a catalyst for hydrogen production in home fuel cell systems A ruthenium-based catalyst which is a platinum group is generally used. As the purge gas, nitrogen and air can be considered in addition to water vapor, and air is particularly preferable. However, ruthenium-based catalysts are known to have high sublimation properties in a high-temperature oxidizing atmosphere, and development of a catalyst with excellent oxidation resistance is desired. ing.

  The hydrocarbon compounds used as the raw material for the reforming reaction include methanol, LP gas, natural gas, gasoline, light oil, kerosene, etc., but especially as a hydrogen source for household fuel cells, in terms of infrastructure. Preference is given to using city gas, LP gas and kerosene. However, only a very small amount of sulfur compounds such as mercaptans contained in city gas and LP gas as odorants and sulfur compounds contained in kerosene are catalyst poisons for steam reforming catalysts and subsequent CO conversion catalysts. Therefore, it is desired to improve sulfur poisoning resistance of the catalyst. Therefore, as a means of avoiding deterioration of the catalyst for hydrogen production due to sulfur compounds contained in the raw material, a pretreatment desulfurization device is installed in front of the reformer to remove the sulfur content from the raw material gas before reforming. Preventive measures such as use for reaction have been proposed. However, when these preventive measures are taken, a new problem arises in that the cost of hydrogen production rises because of the expense of installing and maintaining the pretreatment desulfurization apparatus.

  On the other hand, a catalyst containing platinum and rhodium has been proposed as a catalyst that suppresses catalyst deterioration due to sulfur poisoning in a reforming reaction of a raw material containing a sulfur compound (Patent Document 1). This document discloses that rhodium is particularly effective in improving sulfur poisoning resistance. Similarly, a steam reforming catalyst containing rhodium in addition to ruthenium has been proposed as a means for ensuring long-term catalyst stability even when a sulfur compound is contained in a raw material of hydrocarbon compounds above a certain concentration. (Patent Document 2).

  The rhodium-containing catalyst is excellent in sulfur poisoning resistance and oxidation resistance. However, rhodium is a very expensive noble metal among platinum group metals, which may cause a significant increase in the unit cost of the catalyst.

Japanese Patent Laid-Open No. 04-281845 Japanese Patent Publication No. 42277779

  Since the catalyst for hydrogen production is used under high-temperature and high-humidity conditions, thermal deterioration due to sintering of catalyst components and poisoning deterioration due to sulfur compounds contained in the raw material gas occur, so that improvement in durability is desired. Further, the catalyst life depends on the reaction temperature at the time of reforming, and if the reforming reaction proceeds efficiently at a low temperature, the catalyst life can be extended.

  The present invention has been made in view of the above circumstances, and its purpose is due to changes in temperature and atmosphere due to poisoning by sulfur compounds contained in the hydrocarbon-based compounds as raw materials and repeated shutdown of the fuel cell system. It is to provide a hydrogen production catalyst having long-term durability against catalyst component alteration and coking, and a method for producing the catalyst.

  As a result of detailed investigations on the reforming reaction of hydrocarbon compounds, the present inventors have found that sulfur resistance is improved by using a catalyst in which a catalyst composition containing activated alumina and a cerium-based dense mixed oxide is supported on a honeycomb carrier. The present inventors completed the present invention by finding that the poisoning is improved and the thermal load is suppressed by the improvement of the low temperature activity and the catalyst life can be greatly extended. The cerium-based dense mixed oxide is a complex oxide, solid solution or mixed oxide of cerium and at least one transition metal selected from manganese, iron, cobalt, nickel, copper, zinc, yttrium, and zirconium (hereinafter referred to as a “mixed oxide”). These are collectively referred to as a cerium-based dense mixed oxide).

  According to the hydrogen production catalyst of the present invention, even when the raw material gas contains a sulfur compound, the reforming reaction can be performed at a low temperature, and poisoning by the sulfur compound can be suppressed. Therefore, the hydrogen production catalyst of the present invention can be used for fuel cells, and is suitable for incorporation into, for example, household polymer electrolyte fuel cells and solid oxide fuel cells.

  In the hydrogen production catalyst of the present invention, a catalyst composition containing activated alumina and a cerium-based dense mixed oxide is supported on a honeycomb carrier, and the cerium-based dense mixed oxide is manganese, iron, cobalt, nickel, A catalyst for hydrogen production, which is a complex oxide, solid solution or mixed oxide of at least one transition metal selected from copper, zinc, yttrium and zirconium and cerium. The present hydrogen production catalyst can generate hydrogen from a hydrocarbon compound by a reforming reaction. The present invention is described in detail below.

  The hydrogen production catalyst used in the present invention contains activated alumina and a cerium-based dense mixed oxide. The ratio of the cerium-based homogeneous mixed oxide is 10 to 200 parts by mass, more preferably 30 to 150 parts by mass, and particularly preferably 50 to 100 parts by mass with respect to 100 parts by mass of the activated alumina. It is preferable to add to the catalyst composition. When the content of the cerium-based dense mixed oxide is less than 10 parts by mass, the initial performance and durability of the catalyst for hydrogen production become insufficient, and even if it exceeds 200 parts by mass, a performance improvement effect commensurate with the cost is obtained. Absent. Compared with commonly used cerium dioxide, the cerium-based dense mixed oxide can greatly increase the content in the catalyst composition, and can thereby provide a significant durability improvement effect. . By adding the cerium-based dense mixed oxide at such a high content rate, not only the thermal catalytic activity decrease suppression effect, but also the poisoning reduction by sulfur and other catalyst poison components and the carbon deposition suppression Can effectively act, and can maintain an excellent catalytic action stably for a long period of time.

  The cerium-based dense mixed oxide used in the present invention is composed of at least one transition metal selected from manganese, iron, cobalt, nickel, copper, zinc, yttrium and zirconium, and preferably cerium. And a transition oxide of the transition metal or a solid solution of cerium and the transition metal. The fact that cerium and transition metal form a complex oxide can be confirmed by the fact that the peak of the oxide with the lower content ratio is not detected or is a very amorphous peak in X-ray diffraction analysis. it can. In addition, when cerium and a transition metal form a solid solution, it can be confirmed by a shift of the X-ray diffraction peak depending on the content ratio. Moreover, in addition to the X-ray diffraction peak of the complex oxide or solid solution, a mixed oxide in which a single oxide peak is detected may be used. In the case of a mixed oxide, the intensity ratio of the diffraction peak of the single oxide to the main peak of X-ray diffraction of the composite oxide or solid solution is 70% or less, preferably 50% or less.

  Specifically, the cerium-based dense mixed oxide is a cerium-manganese dense mixed oxide, a cerium-iron dense mixed oxide, a cerium-cobalt dense mixed oxide, a cerium-nickel dense mixed oxide, and cerium. -Two-component systems such as copper dense mixed oxide, cerium-zinc dense mixed oxide, cerium-yttrium dense mixed oxide, cerium-zirconium dense mixed oxide, and cerium-manganese-copper dense mixed oxide And cerium-manganese-iron dense mixed oxide, cerium-nickel-yttrium dense mixed oxide, and cerium-zirconium-yttrium dense mixed oxide. Preferred cerium-based dense mixed oxides are cerium-manganese dense mixed oxide, cerium-nickel dense mixed oxide, cerium-zirconium dense mixed oxide and cerium-zirconium-yttrium dense mixed oxide, Of these, cerium-zirconium dense mixed oxide and cerium-zirconium-yttrium dense mixed oxide are preferable.

  The cerium-based dense mixed oxide is prepared by a solid-phase reaction method, a coprecipitation method, a deposition method, a chemical solution mixing method, an impregnation method, or the like of a cerium compound and a transition metal element-containing compound. It is preferable that it is -98 mol%. More preferably, the content of cerium is 50 to 90 mol%, more preferably 60 to 85 mol%. When the cerium content in the cerium-based dense mixed oxide is less than 30 mol%, the cerium content in the catalyst composition is decreased, sulfur poisoning resistance is reduced and coking is likely to occur. When it exceeds 98 mol%, the content of other elements decreases and a sufficient durability performance improvement effect cannot be obtained.

The specific surface area of the cerium-based dense mixed oxide is preferably 20 to 100 m ² / g, more preferably 30 to 70 m ² / g. When the specific surface area is smaller than 20 m ² / g, the contact efficiency with the reaction gas is lowered and sufficient initial activity cannot be obtained. When the specific surface area exceeds 100 m ² / g, it is easy to sinter in a high temperature reaction, resulting in rapid performance due to use. There is a possibility of degrading. Particularly preferably, the catalyst composition contains a cerium-based dense mixed oxide having a specific surface area of 30 m ² / g or more after calcination at 700 ° C. for 5 hours or longer in the preparation of the cerium-based dense mixed oxide. preferable.

Next, examples of the activated alumina used in the present invention include γ-alumina, δ-alumina, θ-alumina, and η-alumina. Among these, γ-alumina or δ-alumina having a specific surface area of 50 to 250 m ² / g is preferably used. In particular, γ-alumina is particularly preferably used because it has a large BET specific surface area and a large contact area with the reaction gas, so that the reforming reaction is promoted and the high temperature heat resistance is excellent.

  As the activated alumina, commercially available aluminum oxide powder can be used. Alternatively, boehmite that becomes activated alumina by firing, alumina hydrate in a pseudo boehmite state, aluminum hydroxide, or the like may be used. Alternatively, activated alumina obtained by adding an alkaline compound to an aluminum salt aqueous solution such as aluminum nitrate to form a precipitate of hydroxide, and drying and firing the precipitate may be used. Alternatively, activated alumina obtained by a sol-gel method in which an alkoxide such as aluminum isopropoxide is hydrolyzed to prepare an alumina gel, which is dried and fired may be used. Further, it may be added to the catalyst composition as a precursor of activated alumina such as boehmite, aluminum nitrate or alumina sol and supported on the honeycomb carrier, and then calcined to be converted into activated alumina.

  Moreover, alkaline earth metals such as magnesium, calcium and barium, and rare earth elements such as lanthanum, cerium and neodymium can be added to the activated alumina to improve the thermal stability of the activated alumina. As an element to be added to the activated alumina, it is preferable to add 1 to 20 parts by mass, preferably 3 to 10 parts by mass of the above element as an oxide with respect to 100 parts by mass of activated alumina. In particular, addition of barium and lanthanum is preferable, and the heat-stabilized activated alumina can suppress the crystal change to inactive α-alumina even when exposed to a high temperature atmosphere of 800 ° C. or higher.

  The catalyst for hydrogen production of the present invention contains at least one platinum group metal element selected from the group consisting of palladium, platinum, rhodium, ruthenium, osmium and iridium in addition to activated alumina and a cerium-based dense mixed oxide. It is preferable. At this time, the platinum group metal content per unit volume of the honeycomb carrier is 0.2 to 20 g / L, and more preferably 0.3 to 10 g / L. By using the cerium-based dense mixed oxide of the present invention, the dispersibility and heat resistance of the platinum group metal are remarkably improved, and the amount of platinum group metal used can be greatly reduced. Also, against platinum poisoning of platinum group metals, the synergistic effect of cerium dense mixed oxides and platinum group metals enables high activity at low temperatures with a small amount of platinum group metals used and long-term durability. be able to.

  Examples of platinum group metal element compounds include ruthenium compounds, ruthenium chloride aqueous solutions, ruthenium nitrate aqueous solutions, rhodium compounds, rhodium chloride aqueous solutions, rhodium nitrate aqueous solutions, iridium compounds, iridium chloride aqueous solutions, iridium nitrate aqueous solutions, platinum compounds, chloroplatinic acid aqueous solutions. Dinitrodiaminoplatinum nitric acid aqueous solution or the like can be used.

  The platinum group metal element to be added preferably contains at least ruthenium. Further, by using a combination of ruthenium and other platinum group metals, further improvement in low temperature activity and improvement in sulfur poisoning resistance can be obtained. As other platinum group metals, addition of platinum, palladium or rhodium is preferred. The mass ratio of ruthenium and platinum group metal elements other than ruthenium is 100: 0 to 70:30, preferably 97: 3 to 90:10. An increase in the ratio of platinum group metal elements other than ruthenium is not preferable because it may lead to a decrease in selectivity to hydrogen in the reforming reaction and an increase in catalyst material costs. The platinum group metal may be supported on either activated alumina or cerium-based dense mixed oxide. For example, a powder in which a platinum group metal is supported on activated alumina and / or a cerium dense mixed oxide in advance is wet pulverized to coat a honeycomb carrier, or an aqueous solution of a platinum group metal is added to a slurry during wet pulverization. The platinum carrier metal may be supported after the honeycomb carrier is coated by adding to the honeycomb carrier, or after the honeycomb carrier is coated with activated alumina or a cerium-based dense mixed oxide.

As described above, the catalyst for hydrogen production of the present invention is formed by supporting a catalyst composition containing activated alumina, a cerium-based intimate mixed oxide or a platinum group metal on a honeycomb carrier. As the honeycomb carrier that can be used in the present invention, a ceramic honeycomb carrier such as cordierite or mullite, a stainless metal honeycomb, or the like can be used. In particular, it is preferable to use a metal honeycomb carrier in which flat plates and corrugated plates made of a ferritic stainless steel (Fe—Cr—Al) thin steel sheet containing aluminum are alternately stacked and stacked in a spiral shape. The fuel cell system based on the steam reforming reaction requires the catalyst to be heated to 500 ° C. or more by external heating at the start, but the catalyst temperature is quickly raised by using a lightweight and good heat transfer metal honeycomb carrier as the carrier. This makes it possible to start up in a short time and is suitable as a hydrogen production catalyst for reforming reactions. The number of cells of the metal honeycomb carrier is 100 to 600 cells / inch ² (number of cells per square inch), and the foil thickness of the stainless steel sheet is preferably 10 to 50 μm. More preferably, the number of cells is 200 to 400 cells / inch ² , and the foil thickness of the stainless steel sheet is 20 to 30 μm. When the number of cells of the metal honeycomb carrier is 100 cells / inch ² or less, the contact area with the gas per unit volume is small, so that it is difficult to obtain a sufficient reaction rate. When the number of cells exceeds 600 cells / inch ² , the catalyst Since clogging is likely to occur during loading of the composition, it is not preferable. Further, when the foil thickness of the stainless steel sheet is less than 10 μm, the mechanical strength of the honeycomb may be lowered, and when it exceeds 50 μm, the catalyst weight becomes heavier and the heat conductivity is lowered, which is not preferable.

By using the metal honeycomb carrier as described above as a carrier, the geometric surface area is remarkably larger than that of a pellet-shaped catalyst generally used as a catalyst for industrial hydrogen production, so the contact efficiency with gas is high. It is possible to increase the hydrogen production rate per unit volume of the catalyst. The geometric surface area of the metal honeycomb carrier is preferably 1500 m ² / m ³ or more, more preferably 2500 m ² / m ³ or more.

  Moreover, it is preferable that the average particle diameter which measured the catalyst coat layer formed by coat | covering a catalyst composition on a metal honeycomb support | carrier using EPMA is 0.5-10 micrometers. More preferably, the average particle diameter is 1 to 5 μm. In addition, the average particle diameter of a catalyst coat layer can be calculated | required with the following measuring methods.

<Method for Measuring Average Particle Diameter of Catalyst Coat Layer>
Using EPMA (Electron Probe Micro Analyzer), the catalyst coat layer of the finished catalyst was taken at a magnification of 5000 times, and 30 X-ray images of the constituent elements of the catalyst composition such as alumina, cerium, transition metal, etc. were taken at random. Each particle diameter is measured from the distribution of the element in the photograph, and the average particle diameter is obtained based on the measured value.

  When the average particle diameter of the catalyst coat layer thus stopped is less than 0.5 μm, cracks are likely to occur in the coat layer during drying and firing in the catalyst composition supporting step, and the catalyst component may be peeled off during use. Further, the stability of the slurry may become insufficient, causing gelation and a decrease in adhesiveness with the metal honeycomb carrier. On the other hand, when the average particle size of the coat layer exceeds 10 μm, it is difficult to form a dense coat layer and sufficient adhesion to the metal honeycomb carrier cannot be obtained.

  The catalyst composition is supported at 100 to 300 g (g / L: mass per liter of catalyst, hereinafter the same) per unit volume of the honeycomb carrier, more preferably 150 to 250 g / L. Is preferred. When the supported amount per unit volume of the catalyst composition is less than 100 g / L, the thickness of the catalyst coat layer becomes thin, gas diffusion becomes insufficient, and the reaction efficiency is lowered, which is not preferable. On the other hand, if it exceeds 300 g / L, it is difficult to produce the catalyst, and there is a possibility that problems such as an increase in pressure loss due to cell blockage and carbon deposition during use are likely to occur. Furthermore, the average thickness of the catalyst coat layer supported on the honeycomb carrier is preferably 50 to 200 μm, and more preferably 80 to 150 μm. The average thickness of the catalyst coat layer can be measured using EPMA as described above.

(Method for producing a catalyst for hydrogen production)
The method for producing a catalyst for hydrogen production of the present invention comprises a step of coating a honeycomb carrier with a slurry obtained by mixing activated alumina and a cerium-based intimate mixed oxide and wet-grinding. First, a method for preparing a cerium-based dense mixed oxide, which is a feature of the present hydrogen production catalyst, will be described. As a method for preparing the cerium-based dense mixed oxide, various cerium compounds and transition metal element-containing compounds can be prepared by a solid phase reaction method, a coprecipitation method, a deposition method, a chemical solution mixing method, an impregnation method, and the like. Hereinafter, specific preparation examples will be described by taking the case of a cerium-zirconium homogeneous mixed oxide as an example.
(1) After mixing cerium oxide and zirconium oxide, firing and solid phase reaction.
(2) After mixing a cerium salt aqueous solution and a zirconium salt aqueous solution, drying and baking.
(3) A cerium salt aqueous solution and a zirconium salt aqueous solution are mixed, an ammonium compound or the like is added and coprecipitated by hydrolysis, and then dried and fired.
(4) After immersing and mixing the zirconium salt aqueous solution in cerium oxide, drying and firing, or immersing and mixing the cerium salt aqueous solution in zirconium oxide, followed by drying and firing.
(5) After immersing the zirconium salt aqueous solution in the cerium oxide precursor, mixing, drying and firing, or immersing the cerium salt aqueous solution in the zirconium oxide precursor, then mixing, drying and firing.

  In this case, as a cerium compound as a raw material, in addition to commercially available cerium oxide, water-soluble cerium salt compounds such as cerium nitrate, cerium chloride, cerium sulfate, cerium acetate, cerium oxide sol which is a precursor of the cerium oxide, water Cerium oxide, cerium carbonate, or the like can be used.

  In addition to commercially available zirconium oxide, zirconium compounds include water-soluble zirconium salts such as zirconium tetrachloride, zirconyl chloride (zirconium oxychloride), zirconyl sulfate, zirconium nitrate, zirconyl nitrate, zirconium acetate, zirconyl acetate, and zirconyl oxalate. Carbonates such as zirconium oxide sol, zirconium carbonate, zirconyl carbonate, and partial hydrolysis products can be used as the compound and the precursor of the zirconium oxide.

  In the above methods (1) to (5), other cerium-based intimate mixing is similarly performed by selecting a transition metal element compound containing manganese, iron, cobalt, nickel, copper, zinc or yttrium instead of the zirconium compound. Oxides can be easily prepared. In addition, the addition ratio of a cerium compound and a transition metal element compound is mix | blended so that the content rate of the cerium oxide in the mixed oxide after preparation may be 30-98 mol%.

  The calcination in the above (1) to (5) is carried out, for example, in the air at 500 to 1000 ° C., preferably 600 to 800 ° C. for about 5 to 10 hours. Mixed oxides can be obtained. The cerium homogeneous mixed oxide thus obtained is thermally stable, maintains a high specific surface area after heat treatment compared to single cerium dioxide, and suppresses particle growth at high temperatures. It has excellent physical properties. In particular, by using the cerium-based dense mixed oxide obtained by the coprecipitation method (3) and the impregnation method (4) and (5), a highly active and durable catalyst for hydrogen production is produced. can do. In particular, the solid-liquid impregnation method in which the powdered oxide precursor shown in (5) is impregnated with an aqueous metal salt solution can easily prepare complex oxides and solid solutions having excellent characteristics with simple manufacturing equipment. For example, there is no need for a pH control facility or a large amount of cleaning wastewater treatment facility required in the coprecipitation method.

  A typical production of a catalyst for hydrogen production according to the present invention, comprising a step of coating a honeycomb carrier with a slurry obtained by mixing activated alumina and a cerium-based dense mixed oxide obtained by the above method and wet-grinding the resulting mixture. The method will be described below.

<Catalyst production method 1>
There is a step of mixing activated alumina and a cerium-based dense mixed oxide, supplying the mixture to a pulverizer such as a ball mill, preparing a slurry by wet pulverization, and coating the slurry on a honeycomb carrier. After coating the catalyst component, it may be dried and fixed, and calcination and / or reduction treatment may be performed as necessary.

  When preparing the slurry, in addition to the above catalyst components, in order to adjust the viscosity and improve the stability of the slurry, acidic compounds such as hydrochloric acid, sulfuric acid, nitric acid, acetic acid, oxalic acid, basic compounds such as ammonia and tetraammonium hydroxide Further, a polymer compound such as polyacrylic acid or polyvinyl alcohol may be added as necessary. When the honeycomb carrier is a metal honeycomb carrier, the average particle size of the slurry is preferably 0.5 to 10 μm. More preferably, the average particle diameter is 1 to 5 μm. Even if the average particle diameter of the slurry is smaller than 0.5 μm or exceeds 10 μm, the adhesion to the metal honeycomb carrier is lowered and the slurry is easily peeled off.

  The method for coating the honeycomb carrier with the slurry is not particularly limited, and methods such as an impregnation method, a suction method, a wet adsorption method, a spray method, and a coating method can be applied. Moreover, the conditions at the time of slurry coating can also be changed suitably. For example, the impregnation operation can be carried out under atmospheric pressure or reduced pressure, and a homogeneous coat layer can be easily formed by carrying out under reduced pressure. The temperature at the time of slurry coating is not particularly limited, and may be heated if necessary, and preferably within a range of room temperature to 90 ° C. In the case of using a metal honeycomb carrier, the catalyst component can be uniformly supported when the slurry is sucked and impregnated under reduced pressure. Therefore, this suction impregnation method is preferably used. After the coating, it is preferable to dry after removing excess slurry (for example, slurry remaining in the cells) adhering to the honeycomb carrier by a method such as air blowing.

  There is no restriction | limiting in particular also about the drying method, As long as the conditions which can remove the water | moisture content of a slurry, all can be used. Drying may be performed by passing hot air at room temperature or 50 to 200 ° C. into the cell. By baking after drying, the catalyst composition can be firmly fixed to the honeycomb carrier. About baking conditions, what is necessary is just to bake at 400-800 degreeC in air or a reducing atmosphere, for example. When a required amount of the catalyst composition cannot be supported by a single operation, the above impregnation-drying-calcination operation may be repeated.

<Catalyst production method 2>
An aqueous platinum group metal solution, activated alumina and a cerium-based dense mixed oxide are supplied to a pulverizer such as a ball mill, wet pulverized to prepare a slurry, and the slurry is coated on a honeycomb carrier. In the same manner as in the catalyst production method 1, the catalyst composition is coated and then dried, and calcining and / or reduction treatment can be performed as necessary.

  In this production method, the production process can be simplified because the platinum group metal is added to the slurry as an aqueous solution. In addition, since platinum group metal ions are free in the solution, the platinum group metal element can be supported on the surface of the catalyst coat layer by adjusting the ventilation drying conditions in the cell, and the platinum group metal can be used effectively. Can do. In addition, platinum group metal elements can be chemically converted into active alumina and / or cerium oxide in the slurry by appropriately selecting platinum group metal salt aqueous solution species, activated alumina source, cerium-based dense mixed oxide source, pH adjuster, etc. It can also be fixed to.

<Catalyst production method 3>
This is a method for producing a catalyst for producing hydrogen, comprising a step of supporting and fixing a part or all of a platinum group metal element in advance on activated alumina and / or a cerium-based dense mixed oxide. In addition, a manufacturing method process can be manufactured according to the said catalyst manufacturing method 1 or 2.

  In order to support and fix the platinum group element on the activated alumina by this method, the platinum group metal source aqueous solution is brought into contact with the activated alumina, and then dried and fired. Specifically, a platinum group metal aqueous solution is prepared so that a desired amount of platinum group metal is supported, activated alumina is contact-mixed, dried at 50 to 150 ° C., and then in air or in a reducing atmosphere. For example, activated alumina carrying a platinum group metal element is obtained by firing at a temperature in the range of 300 to 700 ° C. for about 2 to 6 hours.

  In this production method, the effect of improving the heat resistance can be obtained by supporting and fixing the platinum group metal element to a part of the activated alumina at a high supporting rate of 3 to 30% by mass, more preferably 5 to 20% by mass. Sometimes. When the platinum group metal is supported on the activated alumina at such a high loading rate, the platinum group metal exists in a specific range of particle diameters, and the solid activated alumina on which the platinum group metal is not supported is in the coating layer. By interposing in the vicinity, it is presumed that aggregation of platinum group metals is prevented and durability is improved.

  On the other hand, in order to support and fix the platinum group metal element on the cerium-based dense mixed oxide, the aqueous solution of the platinum group metal source is brought into contact with the cerium-based dense mixed oxide, and then dried and fired. Specifically, a platinum group metal aqueous solution is prepared so as to have a desired amount of platinum group metal supported, contact-mixed with a cerium-based dense mixed oxide, dried at 50 to 150 ° C., and then in the air or For example, a cerium-based dense oxide carrying a platinum group metal is obtained by firing in a reducing atmosphere at a temperature in the range of 300 to 700 ° C. for about 2 to 6 hours. By supporting and fixing the platinum group metal on the cerium-based homogeneous mixed oxide, the catalytic effect of the cerium homogeneous mixed oxide is promoted, and not only the thermal catalytic activity lowering suppression effect but also the catalyst poison such as sulfur. It effectively acts to reduce poisoning due to the components and to suppress carbon deposition, and can maintain an excellent catalytic action stably for a long period of time. Specifically, the platinum group metal is preferably supported at 0.1 to 10% by mass, more preferably 0.2 to 5% by mass with respect to the cerium-based dense mixed oxide.

<Catalyst production method 4>
In the same manner as in the catalyst production method 1, the step of coating the activated alumina and the cerium-based dense mixed oxide on the honeycomb carrier, and further the honeycomb carrier coated with the activated alumina and the cerium-based dense mixed oxide is treated with a platinum group metal aqueous solution Is a method for producing a catalyst for hydrogen production, which comprises a step of impregnating a catalyst and supporting a platinum group metal.

  In this manufacturing method, first, activated alumina and cerium oxide are supplied to a pulverizer such as a ball mill, and wet pulverized to prepare a slurry. The slurry is coated on a honeycomb carrier in the same manner as in manufacturing method 1, and dried. The activated alumina and the cerium-based dense mixed oxide are fixed to the honeycomb carrier by firing in air at 400 to 800 ° C. The coated honeycomb carrier thus obtained is impregnated with a platinum group metal aqueous solution to carry the platinum group metal, dried, and then dried in air or in a reducing atmosphere at a temperature of, for example, 300 to 600 ° C. Bake for about 6 hours.

  In this production method, the slurry coating and the noble metal loading are separate processes, and therefore suitable for forming a strong coating layer of activated alumina and a cerium-based dense mixed oxide. For example, when ruthenium is used as the platinum group metal, a part of ruthenium may be scattered when fired in a high-temperature oxygen atmosphere in order to form a strong coating layer. On the other hand, in this production method, since a strong coating layer is formed and the platinum group metal is supported in the final step, the product can be processed under conditions optimal for the activation of the platinum group metal. Also, for example, by impregnating a platinum group metal with a coating layer by chemisorption, a platinum group metal-rich layer can be formed on the outermost surface of the coating layer in contact with the gas. Even if the amount is reduced, high catalytic activity can be obtained. Thus, although the typical catalyst manufacturing methods 1-4 were shown, you may combine these manufacturing methods suitably.

(Method for reforming hydrocarbon compounds)
Next, a method for producing hydrogen by reforming a hydrocarbon compound using the above-described hydrogen production catalyst will be described.

  Examples of the hydrocarbon compound used as a raw material for the reforming reaction include light hydrocarbons such as methane, ethane, propane, butane, heptane, and hexane, and petroleum hydrocarbons such as gasoline, light oil, and naphtha. , LPG, city gas, kerosene, and other industrially available raw materials can be used. However, even if hydrocarbon compounds are refined such as desulfurization treatment, sulfur compounds remain in trace amounts, or sulfur compounds such as mercaptans, thiophenes, sulfides are added as odorants to general household LPG and city gas Have been. Although sulfur compounds are known to be poisonous substances for catalysts, the hydrogen production catalyst of the present invention can also use hydrocarbon compounds containing these sulfur compounds as raw materials for the reforming reaction. By installing a desulfurizer to remove sulfur compounds contained in the raw material and then carrying out the reforming reaction using the hydrogen production catalyst of the present invention, the catalyst can be used over a long period of time, and the fuel cell system is maintained and managed. Needless to say, it becomes easier.

  In the hydrogen production method of the present invention, the hydrocarbon compound used as the raw material gas can be used by mixing with water vapor. The ratio of the number of moles of water vapor to the number of moles of carbon atoms contained in the hydrocarbon compound (S / C ratio) is 1 to 5, preferably 2 to 4, more preferably 2.5 to 3.5. . When the steam / carbon ratio is smaller than 1, coke is likely to precipitate, and when it is larger than 5, the equipment becomes larger, which is not preferable.

The pressure is normal pressure or more and 5 MPa or less, preferably 3 MPa or less. Gas space velocity (SV) is 500~100,000H ^-1, and it is preferably a 1,000~30,000H ^-1. In order to perform an efficient reforming reaction, the reaction temperature should be such that the catalyst layer temperature is in the range of 500 to 1,000 ° C., preferably 600 to 900 ° C.
The hydrogen production catalyst of the present invention is excellent in oxidation resistance, and a trace amount of oxygen may be added if necessary. With respect to the ratio of the hydrocarbon-containing gas to the oxygen-containing gas, the hydrocarbon compound generates heat due to the partial oxidation reaction due to the addition of oxygen, and the temperature of the catalyst can be raised to a predetermined temperature without heating from the outside. The ratio of the number of moles of oxygen molecules to the number of moles of atoms (oxygen / carbon ratio) can be 0 to 0.75.

  The reformed gas obtained by the hydrogen production catalyst of the present invention mainly contains hydrogen and carbon monoxide and can be used as a fuel for fuel cells and a raw material for the chemical industry. For example, molten carbonate fuel cells and solid oxide fuel cells, which are classified as high-temperature operation fuel cells, can use carbon monoxide and hydrocarbons as fuel, so the reformed gas can be used as fuel for fuel cells. A preferred application that can be made.

  In addition, the reformed gas can be reduced in carbon monoxide concentration by CO modification reaction, or impurities can be removed by cryogenic separation method, PAS method, hydrogen storage alloy or palladium membrane diffusion method, etc. It can be gas. For example, the CO modification reaction is a reaction in which carbon monoxide and water are converted into hydrogen and carbon dioxide, and the carbon monoxide concentration can be reduced to about 1%. As the catalyst used for the CO modification reaction, for example, a known catalyst mainly composed of copper or iron may be used. When it is necessary to further reduce the carbon monoxide concentration, such as the fuel of a low-temperature operation type solid polymer fuel cell, it is oxidized to carbon dioxide by a CO selective oxidation catalyst installed at the subsequent stage of the CO modification catalyst, or CO selective methane It is desirable that the carbon monoxide concentration be 10 ppm or less by converting it to methane using a catalyst.

  Hereinafter, the present invention will be described in detail with reference to examples. However, the present invention is not limited to the examples without departing from the spirit of the present invention.

Example 1
Cerium-based homogeneous mixed oxide: Nickel nitrate hexahydrate 291 g Aqueous solution of 434 g cerium nitrate hexahydrate dissolved in 5 L of pure water was gradually added dropwise with stirring and co-precipitated to a pH of 9 In that state, it was left overnight. Next, after filtration and washing with sufficient water, the precipitate is dried at 150 ° C. for 12 hours, and then calcined in an air atmosphere at 700 ° C. for 5 hours to cerium-nickel dense mixed oxide (molar ratio CeO ₂ : NiO = 50: 50). In the obtained cerium-nickel homogeneous mixed oxide, formation of a solid solution of cerium and nickel was confirmed by X-ray diffraction, and the BET specific surface area was 45 m ² / g.

Metal honeycomb carrier: Fe-Cr-Al heat-resistant stainless steel plate having a foil thickness of 30 μm as a honeycomb carrier, 400 cells per square inch of cross-sectional area, an outer diameter of 20 mm, and a length of 66 mm (Geometric surface area of about 3000 m ² / m ³ ) was used.

Preparation of slurry: 75 g of activated alumina (γ-alumina) having a specific surface area of 155 m ² / g, 150 g of the cerium-nickel intimate mixed oxide, pure water and acetic acid are supplied to a ball mill and wet-ground to obtain an aqueous slurry. Prepared. When the obtained slurry was observed with a particle size distribution measuring device (laser diffraction scattering type), the average particle size was 4.5 μm.

  Production of catalyst: The carrier was immersed in the slurry to adhere the slurry, and then taken out. Then, compressed air was blown onto the carrier to remove excess slurry remaining in the cell. Next, after drying at 150 ° C., the catalyst composition was adhered to the metal honeycomb carrier by firing in air at 600 ° C. for 2 hours. The slurry support was repeated twice to obtain a finished catalyst (A). The supported amount of the catalyst composition per 1 L of the metal honeycomb carrier was 220 g / L. As a result of measuring the catalyst coat layer of the finished catalyst with EPMA, the average particle diameter was 3.9 μm, the catalyst composition was coated on the metal honeycomb carrier, and the average catalyst coat layer thickness was 130 μm.

(Example 2)
Cerium homogeneous mixed oxide: After adding an aqueous solution of zirconium oxynitrate to cerium carbonate powder and mixing uniformly, the mixture is dried at 150 ° C. to remove moisture, and then calcined at 700 ° C. for 5 hours in an air atmosphere. Thus, a cerium-zirconium homogeneous mixed oxide (molar ratio CeO ₂ : ZrO ₂ = 80: 20) was obtained. The obtained cerium-zirconium homogeneous mixed oxide formed a complex oxide having a diffraction peak of only the crystal structure of fluorite-type cerium dioxide by X-ray diffraction, and the BET specific surface area was 38 m ² / g. It was.

Preparation of slurry: A ruthenium nitrate aqueous solution containing 7.5 g of ruthenium, 150 g of activated alumina (γ-alumina) having a specific surface area of 155 m ² / g, 75 g of the cerium-zirconium homogeneous mixed oxide, pure water and acetic acid are ball milled. And wet pulverized to prepare an aqueous slurry. When the obtained slurry was observed with a particle size distribution analyzer (laser diffraction scattering type), the average particle size was 2.7 μm.

  Production of catalyst: The same metal honeycomb carrier as in Example 1 was immersed in the slurry and then taken out, and then compressed air was blown onto the carrier to remove excess slurry remaining in the cells. Next, after drying at 150 ° C. to attach the catalyst component to the carrier, reduction treatment was performed at 600 ° C. for 2 hours in a hydrogen stream (5% hydrogen / nitrogen balance) to obtain a finished catalyst (B). The finished catalyst (B) had a supported amount of catalyst composition per liter of metal honeycomb carrier of 168 g / L, and was supported at 5.4 g / L as Ru. As a result of measuring the catalyst coat layer of the finished catalyst with EPMA, the average particle diameter was 2.8 μm, the catalyst composition was coated on the metal honeycomb carrier, and the thickness of the average catalyst coat layer was 100 μm.

(Example 3)
Cerium dense mixed oxide: After adding manganese nitrate aqueous solution to cerium carbonate powder and mixing uniformly, the mixture is dried at 150 ° C. to remove moisture, and then calcined at 700 ° C. for 5 hours in an air atmosphere. A cerium-manganese dense mixed oxide (molar ratio CeO ₂ : MnO ₂ = 80: 20) was obtained. Obtained cerium - manganese intimate mixed oxide forms a complex oxide having a diffraction peak of only the crystal structure of the fluorite type cerium dioxide by X-ray diffraction, BET specific surface area was 42m 2 / ^g.

  Production of catalyst: A finished catalyst (C) was obtained in the same manner as in Example 2 except that the above cerium-based dense mixed oxide was used. In the finished catalyst (C), the supported amount of the catalyst composition per 1 L of the metal honeycomb carrier was 158 g / L, and it was supported at 5.1 g / L as Ru. As a result of measuring the catalyst coat layer of the finished catalyst with EPMA, the average particle diameter was 2.4 μm, the catalyst composition was coated on the metal honeycomb carrier, and the thickness of the average catalyst coat layer was 90 μm.

Example 4
Cerium homogeneous mixed oxide: After adding iron nitrate aqueous solution to cerium hydroxide powder and mixing uniformly, the mixture is dried at 150 ° C. to remove moisture, and then calcined at 700 ° C. for 5 hours in an air atmosphere. Thus, a cerium-iron dense mixed oxide (molar ratio CeO ₂ : Fe ₂ O ₃ = 90: 10) was obtained. The obtained cerium-iron dense mixed oxide had diffraction peaks only for fluorite-type cerium dioxide and crystal structure by X-ray diffraction, and the BET specific surface area was 35 m ² / g.

  Production of catalyst: A finished catalyst (D) was obtained in the same manner as in Example 2 except that the above cerium-based dense mixed oxide was used. In the finished catalyst (D), the supported amount of the catalyst composition per 1 L of the metal honeycomb carrier was 152 g / L, and was supported at 4.9 g / L as Ru. As a result of measuring the catalyst coat layer of the finished catalyst with EPMA, the average particle diameter was 1.8 μm, the catalyst composition was coated on the metal honeycomb carrier, and the thickness of the average catalyst coat layer was 85 μm.

(Example 5)
Cerium homogeneous mixed oxide: A cerium-zirconium homogeneous mixed oxide was obtained in the same manner as in Example 2.
Preparation of slurry: 150 g of activated alumina (γ-alumina) having a specific surface area of 155 m ² / g, 100 g of the above cerium-zirconium mixed oxide, 50 g of silica sol (SiO ₂ concentration 30 wt%), pure water and acetic acid in a ball mill An aqueous slurry was prepared by supplying and wet grinding. The average particle diameter of the obtained slurry was 3.3 μm.

  Production of catalyst: A metal honeycomb carrier was immersed in the slurry to adhere the slurry, and then taken out. Then, compressed air was blown onto the carrier to remove excess slurry remaining in the cell. Thereafter, the catalyst component was adhered to the support by drying at 150 ° C., and then calcined in air at 700 ° C. for 2 hours.

  Next, the metal honeycomb carrier coated with the catalyst component was immersed in an aqueous ruthenium nitrate solution. The impregnation liquid was maintained at 25 ° C., and the honeycomb was moved up and down to stir the impregnation liquid so that ruthenium was uniformly supported. After 1 hour, it was confirmed that the color of the impregnating liquid had disappeared, and the impregnating liquid was taken out from the impregnating liquid. After removing moisture by air blowing, it was dried at 120 ° C. The honeycomb on which ruthenium was supported was subjected to reduction treatment at 500 ° C. for 2 hours in a hydrogen stream (5% hydrogen / nitrogen balance) to obtain a finished catalyst (E). The supported amount of the catalyst composition per 1 L of the metal honeycomb carrier was 162 g / L, and it was supported at 3.0 g / L as Ru. As a result of measuring the catalyst coat layer of the finished catalyst with EPMA, the average particle diameter was 3.2 μm, the catalyst composition was coated on the metal honeycomb carrier, and the thickness of the average catalyst coat layer was 95 μm. Further, when the distribution of ruthenium in the catalyst coat layer was examined, 70% or more of the ruthenium supported on the catalyst was present in a region 20 μm from the outermost surface, and a rich layer of ruthenium was formed on the surface layer portion. It was observed.

(Example 6)
Platinum-supported activated alumina: 10 g of activated alumina (δ-alumina) having a specific surface area of 90 m ² / g was added to a dinitrodiamine platinum nitric acid aqueous solution containing 0.4 g of platinum, mixed well, and then dried at 150 ° C. Then, it was calcined in air at 600 ° C. for 2 hours to obtain activated alumina carrying platinum at 4% by mass.
Cerium-based homogeneous mixed oxide: A cerium-zirconium homogeneous mixed oxide was obtained in the same manner as in Example 2.
Preparation of slurry: ruthenium nitrate aqueous solution containing 4.0 g of ruthenium, 90 g of activated alumina (δ-alumina) having a specific surface area of 90 m ² / g, 10.4 g of platinum-supported activated alumina and 100 g of cerium-zirconium dense mixed oxide Pure water and acetic acid were supplied to a ball mill and wet pulverized to prepare an aqueous slurry. The average particle diameter of the obtained slurry was 2.8 μm.

  Production of catalyst: The carrier is immersed in the slurry to adhere the slurry, and then taken out. Then, compressed air is blown onto the carrier to remove excess slurry remaining in the cell, followed by drying at 150 ° C. After adhering the catalyst component to the carrier, the catalyst was reduced for 2 hours at 600 ° C. in a hydrogen stream (5% hydrogen / nitrogen balance) to obtain a finished catalyst (F). The supported amount of the catalyst composition per liter of the metal honeycomb carrier was 154 g / L, and Ru was supported at 3.0 g / L and Pt at 0.3 g / L. As a result of measuring the catalyst coat layer of the finished catalyst with EPMA, the average particle diameter was 2.8 μm, the catalyst composition was coated on the metal honeycomb carrier, and the average catalyst coat layer thickness was 85 μm.

(Example 7)
Palladium-supported cerium-based dense mixed oxide: After sufficiently mixing 150 g of the cerium-zirconium dense mixed oxide obtained in the same manner as in Example 2 with an aqueous palladium nitrate solution containing 0.4 g of palladium at 150 ° C. It was dried and calcined in air at 600 ° C. for 2 hours to prepare a cerium-zirconium homogeneous mixed oxide carrying 0.3% by mass of palladium.

Preparation of slurry: ruthenium nitrate aqueous solution containing 4.0 g of ruthenium, 75 g of activated alumina (δ-alumina) having a specific surface area of 90 m ² / g, 150.4 g of the palladium-supported cerium-zirconium dense mixed oxide and pure water, Acetic acid was supplied to a ball mill and wet pulverized to prepare an aqueous slurry. The average particle diameter of the obtained slurry was 3.3 μm.
Production of catalyst: The carrier is immersed in the slurry to adhere the slurry, and then taken out. Then, compressed air is blown onto the carrier to remove excess slurry remaining in the cell, followed by drying at 150 ° C. After adhering the catalyst component to the carrier, reduction treatment was performed at 600 ° C. for 2 hours in a hydrogen stream (5% hydrogen / nitrogen balance) to obtain a finished catalyst (G). The supported amount of the catalyst composition per 1 L of the metal honeycomb carrier was 175 g / L, and Ru was supported at 3.1 g / L and Pd was 0.3 g / L. As a result of measuring the catalyst coat layer of the finished catalyst with EPMA, the average particle diameter was 3.1 μm, the catalyst composition was coated on the metal honeycomb carrier, and the thickness of the average catalyst coat layer was 110 μm.

(Comparative Example 1)
Metal honeycomb carrier: The same metal honeycomb carrier as in Example 1 was used.

Cerium oxide: Commercially available cerium carbonate was calcined at 700 ° C. for 5 hours in an air atmosphere to obtain cerium oxide. The obtained cerium oxide was cerium dioxide having a fluorite-type crystal structure by X-ray diffraction, and the BET specific surface area was 13 m ² / g.
Preparation of slurry: An aqueous slurry was prepared by dispersing 75 g of activated alumina (γ-alumina) having a specific surface area of 155 m ² / g, 150 g of cerium dioxide, pure water and nitric acid with a homomixer. When the obtained slurry was observed with a particle size distribution analyzer (laser diffraction scattering type), the average particle size was 13.8 μm.

  Production of catalyst: The carrier was immersed in the slurry to adhere the slurry, and then taken out. Then, compressed air was blown onto the carrier to remove excess slurry remaining in the cell. Next, the catalyst component was adhered to the carrier by drying at 150 ° C., and then calcined in air at 700 ° C. for 2 hours to obtain a comparative catalyst (a). The supported amount of the catalyst composition per 1 L of the metal honeycomb carrier was supported at 126 g / L. As a result of measuring the catalyst coat layer of the comparative catalyst by EPMA, the catalyst composition was coated on the metal honeycomb carrier with an average particle diameter of 11.5 μm, and the thickness of the average catalyst coat layer was 75 μm.

(Comparative Example 2)
Preparation of slurry: 200 g of activated alumina (γ-alumina) having a specific surface area of 155 m ² / g, pure water and nitric acid were supplied to a high-speed circulating bead mill and wet-pulverized to prepare an aqueous slurry. The average particle diameter of the obtained slurry was 0.3 μm.

  Preparation of catalyst: A metal honeycomb carrier is immersed in the slurry and attached to the slurry, and then taken out. Then, compressed air is blown onto the carrier to remove excess slurry remaining in the cell, and then dried at 150 ° C. And baked in air at 600 ° C. for 2 hours. Activated alumina was supported at 70 g / L per 1 L of the metal honeycomb carrier. Next, a nickel honeycomb aqueous solution was impregnated with a metal honeycomb carrying activated alumina. After drying at 150 ° C., baking was performed in air at 600 ° C. for 5 hours. Thereafter, reduction treatment was performed at 500 ° C. for 2 hours in a hydrogen stream (5% hydrogen / nitrogen balance) to obtain a comparative catalyst (b). The comparative catalyst (b) was supported at 20 g / L as Ni per 1 L of the metal honeycomb carrier. As a result of measuring the catalyst coat layer of the sample with EPMA, the average particle diameter was 0.3 μm, the catalyst composition was coated on the metal honeycomb carrier, and the thickness of the average catalyst coat layer was 35 μm.

(Comparative Example 3)
Production of catalyst: 75 g / L of active alumina was supported on a metal honeycomb carrier in the same manner as in Comparative Example 2 until slurry of active alumina was supported. Next, the honeycomb coated with activated alumina was immersed in an aqueous cerium nitrate solution, the excess liquid was removed and dried at 150 ° C., and then fired in air at 700 ° C. for 5 hours. Supported. Subsequently, the honeycomb was immersed in an aqueous ruthenium nitrate solution, and after removing excess liquid, the honeycomb was dried at 120 ° C. and then subjected to reduction treatment at 600 ° C. for 2 hours in a hydrogen stream (hydrogen 5% / nitrogen balance). c) was obtained. It was carried at 5.0 g / L as Ru per 1 L of the metal honeycomb carrier. As a result of measuring the catalyst coat layer of the sample with EPMA, the average particle diameter was 0.2 μm, the catalyst composition was coated on the metal honeycomb carrier, and the thickness of the average catalyst coat layer was 40 μm.

(Comparative Example 4)
Production of catalyst: In the same manner as in Comparative Example 1, a catalyst composition comprising activated alumina and cerium oxide was supported on a metal honeycomb carrier. Subsequently, the honeycomb was immersed in an aqueous ruthenium nitrate solution, and after removing excess liquid, the honeycomb was dried at 120 ° C. and then reduced at 600 ° C. for 2 hours in a hydrogen stream (5% hydrogen / nitrogen balance). (D) was obtained. The supported amount of the catalyst composition per 1 L of the metal honeycomb carrier was 121 g / L, and it was supported at 3.7 g / L as Ru. Further, as a result of measuring the catalyst coat layer of the sample by EPMA, the average particle diameter was 12.5 μm, the catalyst composition was coated on the metal honeycomb carrier, and the thickness of the average catalyst coat layer was 70 μm.

実施例１〜７及び比較例１〜４の触媒組成およびＥＰＭＡで測定したコート層の観察結果のまとめを表１に示した。

Table 1 shows a summary of the observation results of the coating compositions measured by EPMA and the catalyst compositions of Examples 1 to 7 and Comparative Examples 1 to 4.

(Initial performance test)
The initial performance of the hydrogen production catalyst was measured under the following test conditions using a laboratory activity test apparatus. The city gas 13A is used as the raw material gas without being desulfurized, and the reforming reaction is performed under the conditions of a catalyst inlet temperature of 700 ° C., a GHSV = 20,000 H ⁻¹ and a steam / carbon (S / C) ratio = 2.5. Carried out. Each concentration of the product gas was measured using gas chromatography (Shimadzu Corporation: gas chromatograph GC-8A), and the raw material conversion after 3 hours from the start of the reaction was calculated by the following formula (1).

なお、上記式において、ＣＯ濃度、ＣＯ_２濃度およびＣＨ_４濃度は、それぞれ生成ガス（触媒出口）における一酸化炭素、二酸化炭素およびメタンのガス濃度を表す。
実施例１、実施例５及び比較例１〜２の水素製造用触媒の性能試験結果を表２に示す。

In the above formula, the CO concentration, the CO ₂ concentration, and the CH ₄ concentration represent the gas concentrations of carbon monoxide, carbon dioxide, and methane in the product gas (catalyst outlet), respectively.
Table 2 shows the performance test results of the hydrogen production catalysts of Example 1, Example 5, and Comparative Examples 1-2.

（触媒成分接着性試験）
実施例１、実施例５及び比較例１〜２の触媒について触媒成分の接着性を確認するために以下の試験を実施した。試料を１時間純水に浸漬した後に１分間４０ｋＨｚの超音波洗浄を実施し、取り出して空気圧１ｋｇ／ｃｍ^２のブローし１５０℃で１時間乾燥してから、上記の初期性能試験と同じ試験条件で性能を測定し結果を表２に示した。

(Catalyst component adhesion test)
In order to confirm the adhesiveness of the catalyst components for the catalysts of Example 1, Example 5 and Comparative Examples 1-2, the following tests were conducted. The sample was immersed in pure water for 1 hour and then subjected to ultrasonic cleaning at 40 kHz for 1 minute, taken out, blown at an air pressure of 1 kg / cm ² and dried at 150 ° C. for 1 hour, and then the same test conditions as the above initial performance test The performance was measured with the results shown in Table 2.

  From the results in Table 2, the catalyst of the present invention of Example 1 has equivalent or better initial performance than the catalyst of the comparative example. The catalyst of Comparative Example 1 and Comparative Example 2 has a large performance deterioration after the adhesion test as compared with the Examples, and it is considered that the catalyst component is peeled off. On the other hand, it is clear that the catalyst of the example has higher adhesion than the comparative catalyst.

(Durability test)
For the catalysts of Examples 1 to 7 and Comparative Examples 2 to 4, the initial performance (after 3 hours) measured under the same conditions as the above initial performance test and the measured value after 40 hours of reaction are shown in Table 3 as the durability performance. Indicated. Although the performance difference is small in the initial performance, the durability of the catalyst of the present invention is better than that of the comparative catalyst. This durability performance is a performance test against complex factors such as heat resistance, water resistance, sulfur poisoning resistance, coking resistance, catalyst component peeling and scattering.

  The present invention is a hydrogen production catalyst with little performance deterioration over a long period of time when hydrogen is generated by reforming a raw material gas comprising a hydrocarbon compound, and is particularly suitable for a raw material gas containing a sulfur compound. it can.

Claims (8)

A catalyst for hydrogen production that generates hydrogen by a reforming reaction, wherein a catalyst composition containing activated alumina and a cerium-based homogeneous mixed oxide is supported on a honeycomb carrier, and the cerium-based homogeneous mixed oxide is A catalyst for hydrogen production, which is a complex oxide, solid solution or mixed oxide of at least one transition metal element selected from manganese, iron, cobalt, nickel, copper, zinc, yttrium and zirconium and cerium. The cerium-based dense mixed oxide is prepared by any one of a solid phase reaction method, a coprecipitation method, a deposition method, a chemical solution mixing method, and an impregnation method of a cerium compound and a transition metal-containing element compound, and contains cerium. The catalyst for hydrogen production according to claim 1, wherein the rate is 30 to 98 mol%. The catalyst for hydrogen production according to claim 1 or 2, wherein the catalyst composition further contains a platinum group metal element, and the platinum group metal content per unit volume of the honeycomb carrier is 0.2 to 20 g / L. 4. The honeycomb carrier is a metal honeycomb carrier, and an average particle diameter measured by EPMA of a catalyst coating layer formed by coating the catalyst composition on a metal honeycomb carrier is 0.5 to 10 μm. Catalyst for hydrogen production. The method for producing a catalyst for hydrogen production according to claim 1, further comprising a step of coating a honeycomb carrier with a slurry obtained by mixing activated alumina and a cerium-based dense mixed oxide and wet-pulverizing the honeycomb carrier. 6. The method for producing a catalyst for hydrogen production according to claim 5, further comprising the step of adding a platinum group metal element aqueous solution in the wet pulverization to prepare a slurry and coating the slurry on a honeycomb carrier. The catalyst for hydrogen production according to claim 5 or 6, further comprising a step of preliminarily immobilizing a part or all of a platinum group metal element in activated alumina and / or a cerium-based dense mixed oxide before the wet pulverization. Manufacturing method. A hydrogen production method for producing hydrogen from a hydrocarbon compound by a reforming reaction using the hydrogen production catalyst according to claim 1.