JP2018134628A - Catalyst structure for producing hydrogen from ammonia, method for manufacturing catalyst structure and method for producing hydrogen - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a catalyst structure that uses a catalyst structure coated with a catalyst powder on a metal base material structure, is excellent in adhesion of the catalyst powder to the metal base material structure, suppresses deterioration in performance due to peeling at the interface and can stably produce a high-concentration hydrogen, to provide a method for manufacturing the catalyst structure and to provide a method for producing hydrogen.SOLUTION: According to an aspect of the present invention, there is provided a catalyst structure which comprises: a metal base material structure having a distribution channel for ammonia gas and composed of a metal base material; and an outer surface layer present on the surface of the metal base material structure and including a ruthenium-supported catalyst having ruthenium supported on one kind of carrier selected from the group consisting of aluminum oxide, cerium oxide, magnesium oxide, silicon oxide, and zirconium oxide.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a catalyst structure for stably producing hydrogen from a gas containing ammonia, a method for producing the catalyst structure, and a method for producing hydrogen.

The coke oven gas (COG) generated from the coke oven contains 6 to 10 g / Nm ³ of ammonia, but the ammonia corrodes the piping and causes NOx when burning with COG as fuel. Therefore, it is necessary to remove it in advance. As a method for removing ammonia from COG, a method is generally employed in which COG is washed with dilute sulfuric acid and ammonium sulfate (ammonium sulfate) is recovered. However, with this method, the demand for ammonium sulfate tends to be greatly influenced by market conditions. Therefore, as other ammonia treatment methods, for example, a fossum method for producing high-purity liquid ammonia, a Coppers method in which ammonia is directly burned after separation, a Karl-still method in which it is burned in the presence of a catalyst, and the like are also employed.

On the other hand, in view of the recent global warming, efforts toward a hydrogen society focusing on using hydrogen as a fuel source are in full swing. Here, as a method for producing hydrogen, in addition to a method for reforming fossil resources such as natural gas, oil, and coal, a method such as electrolysis of water has been studied. However, both methods have a problem that a large amount of CO ₂ is generated because heat and electric power are required in addition to using hydrocarbon as a raw material. Under these circumstances, efforts for hydrogen production by dehydrogenation from various hydrogen-containing compounds are being promoted, and attention is particularly focused on ammonia having a large hydrogen content per unit volume and unit mass. Since ammonia is composed only of hydrogen atoms and nitrogen atoms, it does not emit CO ₂ in the decomposition reaction. Therefore, if ammonia can be decomposed with high efficiency, CO ₂ emission is zero and there is no environmental burden. It can be a hydrogen production method.

  The dehydrogenation reaction using a catalyst from ammonia has been studied for a long time because it is integrated with the ammonia synthesis reaction, and the catalyst components (that is, the catalytically active species and the catalyst carrier) have been studied extensively. . As the catalytically active species, for example, a group 8-10 metal element described in Patent Document 1 and a platinum group element described in Patent Document 2 are known. Further, as a catalyst carrier, not only alumina but also silica, zirconia, titania, ceria and the like described in Patent Document 3, and rare earth oxides described in Patent Document 4 are known. When a large amount of ammonia gas is processed in a short period of time using a reactor filled with these catalyst components in the form of general particles (that is, when a large flow rate of ammonia gas is allowed to flow through the reactor), the catalyst layer The gas diffusion at this rate is rate limiting, and sufficient catalytic activity cannot be obtained. For this reason, as described in Patent Document 5, it has been proposed to form a catalyst molded body in which particles of a catalyst component are supported on a honeycomb base material in which many flow paths are formed using cordierite as a component. Under these circumstances, as described in Patent Document 6, catalyst component particles are supported on a metal honeycomb having a large number of flow paths, which is made of a metal having a higher thermal conductivity and a smaller heat capacity than ceramics such as cordierite. It has also been proposed to form a catalyst molded body. In the catalyst molded body described in Patent Document 6, hydrogen can be efficiently produced by treating a large amount of ammonia in a short period of time, and the catalyst carrier can be heated quickly and efficiently. It is said that it can be downsized.

JP 2010-207783 A JP 2009-254979 A JP 2010-240644 A JP 2011-56488 A JP 2012-5926 A JP 2010-195642 A JP 2009-297691 A

  However, the metal portion constituting the metal honeycomb is often a thin plate. When the catalyst particles are supported on the metal thin plate, the smoothness of the surface of the thin plate is high, so that the adhesion with the catalyst particles is not always sufficient. As a result, separation occurs at the interface between the metal thin plate and the catalyst particles, and the catalyst There was a problem that the performance deteriorated. For such problems, a method of forming a coating layer of activated alumina having a specific geometric roughness on the surface of a thin plate as described in Patent Document 7 has been proposed. There was room for improvement.

  Accordingly, the present invention has been made in view of the above problems, and an object of the present invention is to provide a metal substrate structure as a catalyst used when producing hydrogen with high production efficiency from a gas containing ammonia. Using a catalyst structure coated with a catalyst powder on top, the catalyst powder has excellent adhesion to the metal substrate structure, suppresses performance degradation due to separation at the interface, and a large amount of high-concentration hydrogen It aims at providing the catalyst structure which can be manufactured stably, the manufacturing method of the said catalyst structure, and the manufacturing method of hydrogen.

  In order to solve the above problems, the present inventors have intensively studied a catalyst for producing hydrogen using ammonia as a raw material. As a result, the inventor cleans the surface of the metal substrate structure composed of the metal substrate, and forms an underlayer containing aluminum oxide on the structure as necessary (the formation of the underlayer is And an outer surface layer containing a ruthenium-supported catalyst in which ruthenium is supported on one kind of support selected from an aluminum oxide, a cerium oxide, a magnesium oxide, a silicon oxide, and a zirconium oxide. It has been found that when the formed catalyst structure is used, peeling of the ruthenium-supported catalyst is suppressed as compared with the case where the ruthenium-supported catalyst layer is directly formed on the metal substrate. Furthermore, the present inventor forms through channels having a regular shape over the entire plane perpendicular to the direction in which ammonia flows in the metal substrate structure, and covers the above-described layers on these through channels. It has also been found that hydrogen can be produced by reforming ammonia stably with high efficiency without increasing pressure loss even when a raw material gas is flowed at a large flow rate.

  In addition, as a result of further intensive studies by the inventors, after degreasing the metal substrate structure, the metal substrate structure is immersed in an acidic aqueous solution and an alkaline aqueous solution to make the metal substrate structure uneven, Then, the method of coat | covering the gel solution of the aluminum hydroxide prepared by the sol-gel method and the ruthenium carrying | support catalyst in order on the uneven surface was discovered. Based on these findings, the present inventor has arrived at the present invention. The gist of the present invention is as described below.

(1) a metal substrate structure having a distribution path of ammonia gas and composed of a metal substrate;
Ruthenium was supported on one type of support selected from the group consisting of aluminum oxide, cerium oxide, magnesium oxide, silicon oxide, and zirconium oxide, present on the surface of the metal base structure. A catalyst structure for producing hydrogen from ammonia, comprising an outer surface layer containing a ruthenium-supported catalyst.
(2) a metal substrate structure having a distribution path of ammonia gas and composed of a metal substrate;
Present on the surface of the metal substrate structure, and an underlayer containing aluminum oxide;
A ruthenium-supported catalyst in which ruthenium is supported on one type of support selected from the group consisting of aluminum oxide, cerium oxide, magnesium oxide, silicon oxide, and zirconium oxide, present on the surface of the underlayer. And a catalyst structure for producing hydrogen from ammonia.

  (3) The ruthenium-supported catalyst forming the outer surface layer of the catalyst structure contains one or more selected from the group consisting of potassium, cesium, and sodium as a promoter. A catalyst structure for producing hydrogen from ammonia according to 1) or (2).

  (4) The ammonia gas flow path of the metal substrate structure includes a through-flow path having a regular shape over the entire plane perpendicular to the direction in which ammonia flows. A catalyst structure for producing hydrogen from ammonia according to any one of (3).

(5) a pretreatment step of cleaning the surface of the metal substrate structure having a distribution path of ammonia gas;
A catalyst supporting step of producing a ruthenium-supported catalyst by supporting ruthenium on one support selected from the group consisting of aluminum oxide, cerium oxide, magnesium oxide, silicon oxide, and zirconium oxide;
An outer surface layer forming step in which the surface of the structure subjected to the pretreatment step is coated with the ruthenium supported catalyst prepared in the catalyst supporting step, and then dried and fired to form an outer surface layer. A method for producing a catalyst structure for producing hydrogen from ammonia.

(6) a pretreatment process for cleaning the surface of the metal substrate structure having a distribution path of ammonia gas;
An underlayer forming step of forming an underlayer containing aluminum oxide on the surface of the structure subjected to the pretreatment step;
A catalyst supporting step of producing a ruthenium-supported catalyst by supporting ruthenium on one support selected from the group consisting of aluminum oxide, cerium oxide, magnesium oxide, silicon oxide, and zirconium oxide;
An outer surface layer forming step of coating the ruthenium supported catalyst prepared in the catalyst supporting step on the under layer formed in the under layer forming step, and then drying and firing to form an outer surface layer; A method for producing a catalyst structure for producing hydrogen from ammonia, comprising:

(7) a pretreatment process for cleaning the surface of the metal substrate;
A catalyst supporting step of producing a ruthenium-supported catalyst by supporting ruthenium on one support selected from the group consisting of aluminum oxide, cerium oxide, magnesium oxide, silicon oxide, and zirconium oxide;
An outer surface layer forming step of coating the ruthenium-supported catalyst prepared in the catalyst supporting step on the surface of the metal substrate subjected to the pretreatment step, and then drying and firing to form an outer surface layer; Have
A step of making the metal base material a metal base material structure having an ammonia gas flow path at a timing after the pretreatment step and before the outer surface layer formation step or after the outer surface layer formation step. The manufacturing method of the catalyst structure for manufacturing hydrogen from ammonia characterized by performing.

(8) a pretreatment process for cleaning the surface of the metal substrate;
An underlayer forming step of forming an underlayer containing an aluminum oxide on the surface of the metal substrate subjected to the pretreatment step;
A catalyst supporting step of producing a ruthenium-supported catalyst by supporting ruthenium on one kind of support selected from the group consisting of aluminum oxide, cerium oxide, magnesium oxide, silicon oxide, and zirconium oxide;
An outer surface layer forming step of coating the ruthenium supported catalyst prepared in the catalyst supporting step on the under layer formed in the under layer forming step, and then drying and firing to form an outer surface layer; Have
At the timing after the pretreatment step and before the base layer formation step, after the base layer formation step and before the outer surface layer formation step, or after the outer surface layer formation step, the metal substrate The manufacturing method of the catalyst structure for manufacturing hydrogen from ammonia characterized by performing the process made into the metal base material structure which has the distribution channel of ammonia gas.

(9) In the pretreatment step,
A step of drying after degreasing the surface of the metal substrate or the metal substrate structure using an organic solvent, a step of drying after immersing the metal substrate or the metal substrate structure in an alkaline aqueous solution, The surface of the metal substrate or the metal substrate structure is treated by performing a step of drying after immersing the metal substrate or the metal substrate structure in an acidic aqueous solution (5 The manufacturing method of the catalyst structure for manufacturing hydrogen from ammonia in any one of (8)-(8).

  (10) A method for producing hydrogen from ammonia using the catalyst structure according to any one of (1) to (4), wherein a gas containing ammonia is circulated through the ammonia gas flow path. And hydrogen is produced by bringing ammonia in the gas into contact with the ruthenium-supported catalyst to decompose the ammonia to produce hydrogen.

  (11) A method for producing hydrogen from ammonia using the catalyst structure produced by the production method according to any one of (5) to (9), wherein a gas containing ammonia is used as the ammonia. A method for producing hydrogen, characterized by causing hydrogen to flow through a gas flow path, bringing ammonia in the gas into contact with the ruthenium-supported catalyst, decomposing the ammonia, and producing hydrogen.

  As described above, according to the present invention, it is possible to stably produce high-concentration hydrogen using ammonia as a raw material without degrading performance due to separation of the metal base structure and catalyst powder at these interfaces. It becomes.

It is a schematic diagram of the catalyst structure used in Example 1 of this embodiment.

  Exemplary embodiments of the present invention will be described below in detail with reference to the accompanying drawings. The catalyst structure for producing hydrogen from ammonia according to the present embodiment is a metal substrate structure composed of a metal substrate, and is present on the surface of the metal substrate structure, and includes aluminum oxide and cerium oxide. And an outer surface layer containing a ruthenium-supported catalyst in which ruthenium is supported on one kind of support selected from the group consisting of magnesium oxide, silicon oxide, and zirconium oxide. Alternatively, a metal base structure composed of a metal base, a base layer present on the surface of the metal base structure and containing aluminum oxide, and present on the surface of the base layer, aluminum oxide, cerium One type of support selected from the group consisting of oxides, magnesium oxides, silicon oxides, and zirconium oxides has an outer surface layer containing a ruthenium-supported catalyst in which ruthenium is supported. This will be described below in order.

(1) Metal base structure The metal base structure is composed of a metal base. As the material for the metal substrate, aluminum and stainless steel are suitable. For stainless steel, martensite, ferrite, austenite, austenite / ferrite duplex, precipitation strengthened steel, and the like are suitable. From the viewpoint of easy coating of the underlayer and the outer surface layer, a steel type containing aluminum is more preferable. Furthermore, the metal substrate structure is formed so as to have a flow path for ammonia gas. The flow path formed in the metal substrate structure preferably includes a through flow path having a regular shape over a plane perpendicular to the direction in which ammonia flows. For example, it is desirable that a honeycomb shape is formed by these through-flow passages, but other through-hole shapes may be used. Moreover, the metal base material as a base material does not contribute directly to the reaction except for imparting heat conductivity and the shape of the base material. For this reason, it is better that the volume ratio per unit volume of the catalyst structure is small, and the thickness of the metal substrate (specifically, the thickness in the direction perpendicular to the through flow path) is preferably 100 μm or less, more preferably It is desirable to be 50 μm or less. The lower limit is not particularly limited, but is preferably a thickness having a strength that can maintain the shape. Also, from the viewpoint of increasing the surface area, the cell (here, the through-flow channel) density is preferably high. For example, 100 cells / inch ² (15.5 cells / cm ² ) or more in a plane perpendicular to the cells, It is desirable that the cell density is 200 cells / inch ² (31 cells / cm ² ) or more. The upper limit value is not particularly limited, but may be 900 cells / inch ² , for example.

  The production flow for producing the catalyst structure includes a metal substrate pretreatment step → catalyst supporting step → underlayer forming step → outer surface layer forming step, and metal substrate structure forming step. The underlayer forming step may be omitted, but it is preferable to have it. The metal substrate structure forming step may be performed anywhere from before the metal substrate pretreatment step to after the outer surface layer forming step.

  That is, the metal substrate structure forming process using the metal substrate as the metal substrate structure is performed before the metal substrate pretreatment process, after the metal substrate pretreatment process, or the outer surface layer formation. Either before the step or after the outer surface layer forming step may be used. Further, when there is an underlayer forming process, it may be before the underlayer forming process or after the underlayer forming process. In the following description, the metal substrate and the metal substrate structure are collectively referred to as “metal substrate”.

(2) Pretreatment step of metal substrate In order to increase the adhesion strength between the outer surface layer (that is, the catalyst layer) formed on the metal substrate or the base layer and the outer surface layer, the surface of the metal substrate is previously treated. More preferably, it is activated. Since the metal substrate is relatively smooth, the adhesion at the interface between the surface of the metal substrate and the base layer may not be sufficient as it is. Therefore, it is preferable to perform the following pretreatment process. Specifically, first, in order to remove oil on the surface of the metal substrate, it is washed with a volatile organic solvent such as alcohol or acetone and dried. Thereafter, the metal substrate is immersed in an alkaline aqueous solution, washed with water and dried. Thereafter, the metal substrate is immersed in an acidic aqueous solution, washed with water and dried. Since a part of the metal crystal grain boundary on the surface of the metal substrate is dissolved by the above pretreatment process, irregularities are formed on the surface of the metal substrate. Note that the pretreatment process may be omitted.

  Therefore, when the particles (catalyst particles or alumina particles of the underlayer) are applied to the surface of the metal substrate, the particles adhere more firmly to the surface of the metal substrate due to the anchor effect. That is, the adhesion can be further improved. Here, as the alkaline aqueous solution, common ones such as sodium hydroxide can be used. The pH of the alkaline aqueous solution is not particularly limited, but is preferably 9 or more, for example. The acidic aqueous solution may be a general one such as hydrochloric acid or nitric acid. Further, the pH is not particularly limited, but is preferably 6 or less, for example. In the pretreatment step, the metal substrate is first immersed in an alkaline aqueous solution for a certain time. Then, in order to remove the alkaline aqueous solution adhering to the surface of the metal substrate, the metal substrate is washed with pure water. At this time, an ultrasonic generator can be appropriately used in order to increase the cleaning effect. Thereafter, similarly, the metal substrate is immersed in an acidic aqueous solution for a predetermined time. Then, in order to remove the acidic aqueous solution adhering to the surface of the metal substrate, the operation is completed by washing the metal substrate with pure water. The immersion time in each aqueous solution is not particularly limited because it can be appropriately determined in consideration of the steel type of the metal base to be used, the thickness, the degree of unevenness, the efficiency of a series of operations, etc. It can be about 1 hour. In addition, the temperature of each aqueous solution at the time of immersion can be appropriately determined in consideration of the steel type of the metal substrate, the thickness, the degree of unevenness, the efficiency of a series of operations, etc., for example, room temperature to 90 ° C. The temperature can be up to. Here, the catalyst or catalyst particles refers to the ruthenium-supported catalyst described in the catalyst support step described in (3).

(3) Catalyst supporting step Ruthenium supporting catalyst used for the outer surface layer (that is, ruthenium supported on one kind of carrier selected from aluminum oxide, cerium oxide, magnesium oxide, silicon oxide and zirconium oxide) ) Is produced as follows. That is, in the ruthenium-supported catalyst, it is preferable that the ruthenium particles are uniformly and highly dispersed on one kind of support selected from aluminum oxide, cerium oxide, magnesium oxide, silicon oxide, and zirconium oxide. The ruthenium-supported catalyst is produced, for example, by bringing a solution containing a ruthenium compound into contact with porous carrier particles, followed by drying and firing. Details will be described later. Here, when the carrier particles are porous, the ruthenium particles can be carried on the wall surfaces of the open pores that exist inside the carrier particles and are connected to the outer surface. Here, the characteristic of the carrier is not particularly limited as long as it is porous, but for example, it is preferable that the specific surface area is large to some extent because the amount of catalyst supported can be increased. However, if the specific surface area is too large, the carrier itself becomes brittle. Specifically, when the specific surface area is less than 10 m ² / g, the ruthenium particles supported on the support aggregate and become coarse, which may make it difficult to obtain sufficient catalytic activity. On the other hand, when the specific surface area exceeds 600 m ² / g, the support itself is brittle and the strength is insufficient, and the production is complicated, which is uneconomical. Therefore, the specific surface area is preferably 10~600m ² / g, more preferably 20~550m ² / g. The average particle diameter of the carrier may be appropriately selected depending on the surface shape of the metal substrate itself, the shape of the reactor, the reaction conditions, and the like, and is not particularly limited. However, the average particle diameter is, for example, preferably 0.1 μm to 10 mm, more preferably 1 μm to 5 mm. When the average particle size is less than 0.1 μm, ruthenium supported on the surface tends to be inhomogeneous, or the carriers are likely to coalesce and become coarse in the supporting step. On the other hand, when the average particle diameter exceeds 10 mm, it is difficult to finely disperse ruthenium and it may be difficult to obtain sufficient activity. Here, the average particle diameter of the carrier can be measured in the same manner as in the case of the aluminum oxide particles of the underlayer. The specific surface area can be evaluated by a BET method using nitrogen.

  Further, the ruthenium compound used for the preparation of the ruthenium supported catalyst is not particularly limited, but ruthenium halide, ruthenium nitrate compound, ruthenium carbonylated compound, ruthenium anminated compound, ruthenium nitrosylated compound, perruthenic acid compound, ruthenium water. A Japanese thing etc. can be used conveniently. The ruthenium compound can be supported on the carrier in an appropriately dissolved state in water or an organic solvent.

  In the production of a ruthenium-supported catalyst, ruthenium is supported on a carrier using the above-described ruthenium compound. Specifically, each compound is supported on the surface of the support by a normal impregnation method such as an incipient wetness method and evaporation to dryness method, a precipitation method, an ion exchange method, etc., and then the support is dried and fired. The ruthenium-supported catalyst particles used in forming the outer surface layer can be obtained. Here, with respect to drying, the drying time is not particularly limited, but may be, for example, 0.5 to 20 hours. Although a drying temperature is not specifically limited, For example, it can be set as 50-150 degreeC. Furthermore, regarding firing, the firing time is not particularly limited, but can be, for example, 0.5 to 20 hours. Although a calcination temperature can be suitably determined so that the supported metal particle may not become coarse, it can be 200-1000 degreeC, for example.

  Here, the supported amount of ruthenium is not less than the minimum amount for exhibiting the activity, and it may be less than the supported amount in which the dispersibility of the supported ruthenium is extremely lowered and the reaction contribution efficiency of ruthenium is decreased. The content is preferably 0.1 to 50% by mass, and more preferably 0.5 to 20% by mass. If the content is below this range, the activity may not be sufficiently exhibited. If the content is above this range, the degree of dispersion may be reduced and the utilization efficiency of the supported ruthenium may be reduced, which is not preferable. The supported amount here does not necessarily mean that the supported ruthenium is finally reduced by 100%, so the mass of metal ruthenium when considered to be reduced by 100% is the total mass of the catalyst (ruthenium converted to metal and The ratio to the total mass) of the carrier. Further, these masses can be measured by a general elemental analysis technique, and as described later, for example, an ICP-AES method after pretreatment such as acid decomposition or alkali melting can be suitably used. .

  Furthermore, in the production of a ruthenium-supported catalyst to which a cocatalyst is added, a metal component described later can be supported along with the ruthenium compound described above. Specifically, in addition to the ruthenium compound, either a potassium compound, a cesium compound or a sodium compound is supported on the support surface by the same conventional impregnation method, precipitation method, ion exchange method, etc., followed by drying and firing. By doing so, ruthenium-supported catalyst particles can be obtained. The potassium compound, cesium compound, and sodium compound used here are not particularly limited, but are nitrate, chloride, fluoride, iodide, bromide, acetate, carbonate, sulfide, hydroxide. Organic materials and the like can be suitably used. These compounds can be supported on a carrier in an appropriately dissolved state in water or an organic solvent. Here, when the promoter compound is impregnated and supported, it can be supported simultaneously with ruthenium (co-impregnation), or can be separately supported before or after ruthenium is supported (sequential impregnation).

  Here, the amount of the cocatalyst supported is at least the minimum amount for developing the function as a cocatalyst, the degree of dispersion of the supported cocatalyst component is extremely reduced, and the reaction contribution efficiency of the cocatalyst is reduced. It is sufficient that the amount is less than or equal to the supported amount, preferably 0.1 to 30% by mass, and more preferably 0.5 to 20% by mass. Below this range, the function as a co-catalyst may not be sufficiently developed, and when it exceeds this range, the dispersibility decreases, and the utilization efficiency of the supported promoter component decreases, and the utilization efficiency of ruthenium. May be uneconomical. The amount of the promoter supported here refers to the ratio of the mass of the metal as the promoter to the total mass of the catalyst (the total mass of the promoter element, ruthenium and support converted to metal). Moreover, these masses can also be measured by a general elemental analysis technique. For example, an ICP-AES method after pretreatment such as acid decomposition or alkali melting can be suitably used.

(4) Outer surface layer forming step In the outer surface layer forming step, an outer surface layer containing a ruthenium-supported catalyst is formed on a metal substrate. The outer surface layer forming step is not particularly limited as long as the outer surface layer can be formed on the metal substrate with a uniform thickness. The outer surface layer forming step is, for example, creating a solution tank in which ruthenium-supported catalyst particles are dispersed in a liquid solvent at a highly volatile room temperature such as alcohol, and then cleaning the surface of the metal substrate or cleaning Then, the ruthenium-supported catalyst particles can be attached to the surface of the metal substrate by immersing and pulling up the metal substrate coated with the base layer. Moreover, a binder component can also be added suitably and an organic binder and an inorganic binder can be used suitably. Here, when the adhesion amount does not reach the predetermined ratio, the adhesion amount, that is, the thickness of the outer surface layer can be adjusted by repeating this operation. In addition, the amount of ruthenium-supported catalyst particles attached can be adjusted by applying a solution containing catalyst particles on a metal substrate by a wash coat method and then blowing off excess solution by air blowing. Here, the amount of the ruthenium-supported catalyst to be coated on the metal substrate, that is, the coating amount is preferably 1 to 500 g (hereinafter referred to as g / L), more preferably 10 to 400 g / L, per liter of the metal substrate. It is. If the coating amount is less than 1 g / L, the catalyst component is small and the inner wall of the cell may not be sufficiently coated. Further, when the coating amount exceeds 500 g / L, the cell may be filled with the catalyst component, and the gas flow path may be blocked. The outer surface layer is preferably uniformly coated on the surface of the metal substrate, but is not necessarily uniformly coated as long as the catalytic activity required under the assumed reaction conditions can be exhibited. For example, the outer surface layer may be covered only on a part of the metal substrate.

  In addition, when forming the foundation layer of the following (5) after the (2) pretreatment process of the metal substrate, before the (4) outer surface layer formation process, the following (6) foundation layer formation process To implement.

(5) Underlayer The underlayer containing aluminum oxide is formed on a metal substrate in order to improve the adhesion between an outer surface layer and a metal substrate, which will be described later. That is, since the surface of the metal substrate is relatively smooth and lacks irregularities, a ruthenium-supported catalyst (that is, one type of support selected from aluminum oxide, cerium oxide, magnesium oxide, silicon oxide, and zirconium oxide) When ruthenium was supported on the surface of the metal substrate, the contact point with the metal substrate was few, the adhesion strength was insufficient, and the catalyst layer was easily peeled off. Therefore, in this embodiment, the surface of the metal substrate is coated with particles that are smaller than the particle size of the catalyst powder and do not adversely affect the catalyst activity, so that an intermediate layer (lower layer) is formed between the catalyst particles and the metal substrate. Formation). Thereby, the adhesion strength of the whole catalyst layer can be improved while maintaining the activity of the catalyst particles themselves.

  Here, the underlayer is a layer containing aluminum oxide, but is preferably made of aluminum oxide. In addition, it is desirable that the base layer is uniformly coated on the surface of the metal substrate, but if the outer surface layer can be coated on the surface of the metal substrate with good adhesion, it is not necessarily coated uniformly. For example, the base layer may be covered only on a part of the metal substrate. The particle diameter of the aluminum oxide constituting the underlayer (that is, in direct contact with the metal substrate) is not particularly limited, but the adhesion strength with the catalyst powder coated on the underlayer is increased (that is, the catalyst powder) From the viewpoint of increasing the contact point with the catalyst powder, it is preferable to have a particle size smaller than that of the catalyst powder. Specifically, the average particle size, which is the average value of the particle sizes of aluminum oxide, is preferably 100 μm or less, and more preferably 0.001 to 50 μm. Here, the particle diameter of the aluminum oxide is a so-called equivalent sphere diameter, and the average particle diameter is an arithmetic average value of the particle diameter. The average particle diameter can be evaluated by a calculation formula from the diffraction peak profile of aluminum oxide obtained from the X-ray diffraction measurement. In addition to the evaluation method based on X-ray diffraction measurement, the average particle diameter can also be evaluated by an evaluation method using a laser diffraction particle size distribution measuring device or an evaluation method directly observed with an electron microscope.

  Moreover, as a method of adjusting the average particle diameter of aluminum oxide to the said range, the method of adjusting the hydrolysis temperature at the time of preparing the sol solution mentioned later, the temperature at the time of aging, and time is mentioned, for example. When aluminum oxide is produced by solid phase sintering, the obtained aluminum oxide sintered mass is pulverized by a dry method using a mortar or the like or a wet method using a planetary ball mill or the like. At this time, the average particle diameter can be adjusted by adjusting the pulverization time. Further, particles that are too large relative to the average particle size, that is, particles that exceed the upper limit particle size may be removed by sieving or the like. The upper limit particle diameter is not particularly limited, and may be set according to characteristics required for the underlayer.

(6) Underlayer Formation Step Further, as a method for forming an underlayer containing aluminum oxide on the surface of the metal substrate, a method using a sol solution containing aluminum oxide is suitable. In this method, first, a sol solution containing an aluminum oxide is prepared using a sol-gel method. Specifically, an alcohol is eliminated from the aluminum alkoxide by subjecting an aluminum alkoxide (eg, aluminum isopropoxide) to hydrolysis and polycondensation reaction under acidic conditions. Thereby, a gel solution in which homogeneous and fine aluminum hydroxide particles are dispersed is prepared. The gel solution is aged for a desired time at a desired temperature. Here, the acidic condition is not particularly limited as long as the pH is lower than the neutral condition (pH is 7 to 8). For example, the pH is preferably 6 or less. Moreover, the average particle diameter and particle diameter distribution of an aluminum oxide can be adjusted by adjusting a hydrolysis temperature and the temperature and time at the time of aging. Specifically, the sol solution contains aluminum oxide as a main component. Here, the main component means that 50% by mass or more of aluminum oxide is contained with respect to the total mass of the sol solution. Although it is preferable that the ratio of the aluminum oxide in the sol solution is large, it may contain aluminum oxide or the like mixed during the production of the sol solution.

  Subsequently, a metal base material is immersed in a gel solution, or a coating solution is formed on a metal base material by apply | coating a gel solution on a metal base material. Next, the coating layer is dried and fired as necessary. The foundation layer is formed on the metal substrate through the above steps. Here, although drying time is not specifically limited, For example, it can be set as 0.5 to 20 hours. Although a drying temperature is not specifically limited, For example, it can be set as 50-150 degreeC. Furthermore, regarding firing, the firing time is not particularly limited, and can be, for example, 0.5 to 20 hours. Although a calcination temperature is not specifically limited, For example, it can be 200-1000 degreeC.

(7) Method for Producing Hydrogen Next, a method for producing hydrogen from ammonia according to the present embodiment will be described. In the method for producing hydrogen according to this embodiment, hydrogen is produced from ammonia gas in the reactor using the catalyst for producing hydrogen from ammonia according to this embodiment described above. Hydrogen can be produced by bringing a raw material gas containing ammonia into contact with the catalyst according to the present embodiment.

The raw material gas containing ammonia used for the production of hydrogen is not particularly limited. For example, a gas containing 50% by volume or more of ammonia is preferable from the viewpoint of productivity. For example, a gas obtained by concentrating ammonia from COG is preferably used. In addition to ammonia, hydrocarbons such as methane, H ₂ , CO, CO ₂ , N ₂ , H ₂ S, HCN, SCN, and the like are included. Also good. The source gas containing ammonia is not limited to the coke oven and may be produced by any route.

  Further, the reactor used for contacting the gas containing ammonia and the catalyst according to the present embodiment is not particularly limited. For example, a reactor for a general gas phase synthesis process such as a fixed bed and a microchannel reactor. Etc.

  Here, the shape of the reactor is not particularly limited as long as the catalyst structure is stable and can be filled without a gap in consideration of the shape of the catalyst structure. It is desirable to have a cylindrical or prismatic space. When filling the inside of the reactor with the catalyst structure, a plurality of them may be arranged in series along the gas flow path, or in a direction perpendicular to the gas flow path in relation to the dimensions inside the reactor. A plurality may be arranged. Further, in the case of serial arrangement along the gas flow path, the catalyst structures having different cell shapes or cell densities may be arranged. Furthermore, from the viewpoint of improving the diffusion of the source gas and the heat supply, the plurality of catalyst structures can be arranged with a certain distance therebetween.

  As a material for the reactor, any material having required strength, rigidity, durability, and corrosion resistance in an environment from room temperature to a high temperature of about 900 ° C. can be used. For example, when using deformable parts, heat resistant stainless steel such as SUS310S, or metal such as heat resistant nickel alloy such as Inconel or Hastelloy, etc., in addition to the above materials, silica, alumina General heat-resistant ceramics such as can be used. In addition, when using a material with low oxidation resistance, these materials can be applied by maintaining the inside of the furnace in a non-oxidizing atmosphere, for example, a nitrogen atmosphere.

  When carrying out the reaction for producing hydrogen from ammonia, it is necessary that the ruthenium supported on the carrier be reduced metal ruthenium. Therefore, when there is a possibility that ruthenium is oxidized by the operation end operation or facility maintenance operation, a reducing gas such as hydrogen gas is circulated before the reaction to reduce the ammonia dehydrogenation catalyst. It is possible to start up to a smooth and early hydrogen production state. Such a reduction treatment is not particularly limited, but can be performed at a temperature of 300 to 500 ° C. for 0.1 to 20 hours, for example, 450 ° C. for 1 hour.

The reaction conditions during the production of hydrogen are not particularly limited, and conventionally applied conditions can be set according to the type of the reactor. For example, the reaction temperature is preferably 300 to 900 ° C. When the reaction temperature is less than 300 ° C., the catalytic activity is hardly exhibited and the target hydrogen gas cannot be obtained, which is not preferable. On the other hand, when the reaction temperature exceeds 900 ° C., it is economically disadvantageous because the reformer becomes expensive, for example, a heat-resistant structure of the reactor is required. The reaction temperature is more preferably 350 to 800 ° C. The reaction pressure is preferably 0.002 to 2 MPa, more preferably 0.004 to 1 MPa. The space velocity of the reaction gas with respect to the catalyst is 100 to 300,000 h ⁻¹ , preferably 1,000 to 200,000 h ⁻¹ . In the present embodiment, hydrogen gas can be efficiently generated from ammonia gas even at a high space velocity. That is, even at a high space velocity of 1000 h ⁻¹ or more, hydrogen gas can be efficiently generated from ammonia gas.

EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples.

Example 1
[Creation of metal base structure]
A 100 μm-thick thin plate of stainless steel (steel type: YUS205M1, schematic component: 20Cr-5Al, aluminum containing about 5% by mass) was used as the metal substrate. The numbers in the outline components indicate the mass% of each metal element contained in the steel. First, a thin plate having a size as shown in FIG. 1 was cut out and repeatedly bent in the order of a mountain fold, a mountain fold, and a valley fold at intervals of 18 equal parts to obtain a shape as shown on the right in FIG. Thereby, a metal substrate structure was produced. Hereinafter, this structure is referred to as a metal substrate structure A. As another metal base structure, a cylindrical metal honeycomb (steel type: YUS205M1, plate thickness: 30 or 50 μm, fin (wave foil) shape: sign 19 mmφ, length 50 mm, 100 to 900 cells / inch ² Wave). Hereinafter, this structure is referred to as a metal base structure B. The metal substrate structure B is used in some other examples described later.

[Pretreatment of metal substrate structure (activation treatment)]
Next, the surface of the metal substrate structure was degreased by immersing the metal substrate structure A in acetone at room temperature, pulling it up and drying it. Thereafter, the metal substrate structure was immersed in an alkaline solution in which 1.5 g of NaOH (Wako Pure Chemical Industries, 198-13765) was dissolved in 37.5 mL of pure water at about 80 ° C., and held for 1 hour. Thereafter, the operation of immersing the metal substrate structure in 500 mL of distilled water and irradiating with ultrasonic waves for 2.5 minutes was repeated twice. Thereafter, the metal substrate structure was immersed in an acidic solution obtained by diluting 12.5 mL of hydrochloric acid (Wako Pure Chemical Industries, Ltd., 080-01061) twice with pure water at room temperature, and held for 15 minutes. Thereafter, the metal substrate structure was immersed in 500 mL of distilled water and cleaned by irradiating ultrasonic waves for about 2 hours. In other examples described later, the metal substrate structure B was used instead of the metal substrate structure A. In the case of using the metal substrate structure B, the outer cylinder was pre-coated with parafilm and then the treatment was performed.

[Preparation of aluminum oxide sol solution]
Next, a sol solution (aluminum sol) for forming an aluminum oxide underlayer was prepared. Specifically, 3.0 g of aluminum triisopropoxide (Nacalai Tesque, 01842-05) was put in a beaker, 20 mL of distilled water kept at 55 ° C. in a thermostatic bath was added thereto, and the aluminum triisopropoxide was completely removed. Stir with a stir bar until dissolved. Thereafter, 1.5 mL of nitric acid (Wako Pure Chemical Industries, 141-01361) was added and stirred, and then 1 mL of formaldehyde (Wako Pure Chemical Industries, 664-00406) was added and further stirred. Thereafter, in order to stabilize the sol, aging was performed in an incubator maintained at 27 ° C. for 48 hours. A sol solution was prepared by the above steps.

[Preparation of underlayer]
Next, the pre-treated metal substrate structure was dipped in the sol solution prepared above and pulled up several times to apply the sol solution. Thereafter, the metal substrate structure was rotated at 180 rpm for about 5 seconds so that the sol solution was uniformly applied onto the metal substrate structure, and then held at 100 ° C. for 30 minutes to be dried. Thereafter, the metal substrate structure was continuously held at 500 ° C. for 1 hour, and fired on the metal substrate structure. Then, the alumina layer of about 240 mg was formed on the substrate by holding at 800 ° C. for 1 hour and performing final firing. The average particle diameter of the alumina particles thus prepared was about 0.003 μm as a result of obtaining from the X-ray diffraction measurement.

[Preparation of ruthenium supported catalyst]
Alumina powder (JRC-ALO-8, specific surface area 148 m ² / g, average particle size 2.2 μm) (In some other examples described later, instead of alumina powder, magnesium oxide powder (JRC-MGO) -3, specific surface area 36 m ² / g, average particle diameter 8.0 μm), cerium oxide powder (JRC-CEO-2, specific surface area 173 m ² / g, average particle diameter 4.5 μm), silicon oxide powder (JRC-SIO) -4, specific surface area 347 m ² / g, average particle diameter 3 μm) or zirconium oxide powder (JRC-ZRO-3, specific surface area 98 m ² / g, average particle diameter 3.4 μm) was dispersed in distilled water Then, the mixture was stirred at room temperature for 12 hours while being deaerated using an aspirator. Then, ruthenium (III) chloride n hydrate (Wako Pure Chemical Industries, 186-02633) (in some other examples described later, a ruthenium (III) nitrate solution (Tanaka Kikinzoku) instead of ruthenium chloride) Were used and weighed so as to be 3% by mass in terms of ruthenium with respect to the carrier powder, and further stirred at room temperature for 2 hours. In some other examples described later, a promoter is further supported on the oxide carrier. When the promoter was supported on the oxide carrier, a predetermined amount of an aqueous solution of potassium nitrate, cesium nitrate, or magnesium nitrate was mixed with the ruthenium (III) nitrate solution, and mixed and stirred with each carrier. The resulting slurry suspension was evaporated to dryness at 80 ° C. and dried at 120 ° C. for 2 hours. Thereafter, the powder of ruthenium supported catalyst was prepared by calcining at 500 ° C. for 5 hours.

[Creation of catalyst slurry]
40 ml of 2-propanol (Wako Pure Chemical Industries, 166-04831) was placed in a polyethylene container, and 1.0 g of the catalyst powder was added and dispersed therein. The catalyst powder was ground in advance with an agate mortar to have the same particle size.

[Application of catalyst slurry to metal base structure coated with underlayer]
The metal substrate structure coated with the underlayer was immersed in the catalyst slurry solution and pulled up to apply the catalyst onto the underlayer. Thereafter, the metal base structure was held at 100 ° C. for 30 minutes and dried to form an outer surface layer on the base layer of the metal base structure. In addition, when using metal base-material structure B, after a series of processes were complete | finished, after removing the parafilm which coat | covered the outer cylinder, it used for the below-mentioned catalytic activity evaluation.

[Evaluation of catalytic activity]
Through the above-described steps, a catalyst structure in which 100 mg of the ruthenium-supported catalyst was supported on the underlayer was obtained. This catalyst structure 9.4 cm ³ was fixed to the center of a quartz reaction tube having an inner diameter of 21.5 mmφ with quartz wool, and a thermocouple was inserted at the center of the catalyst layer. Subsequently, these fixed bed reaction tubes were set at predetermined positions.

Before starting the reforming reaction, the reactor was first heated to 450 ° C. in a nitrogen atmosphere, and then reduced for 1 hour while flowing hydrogen gas at 50 mL / min. After that, each gas is adjusted so that ammonia: helium = 1: 2, and the total space velocity is 100 to 1200 h ⁻¹ mixed with helium gas used as carrier gas and calibration gas as gas mainly composed of ammonia. Then, the catalyst performance was evaluated by analyzing the gas after reaction at each temperature of 300 to 600 ° C. under normal pressure using a TCD gas chromatograph. In addition, unreacted ammonia was collect | recovered by making the product gas discharged | emitted from the exit pass through a water trap and a sulfuric acid trap. Here, the decomposition degree of ammonia (ammonia conversion rate) was calculated by the following equation based on the ammonia concentration in the outlet gas.

  Ammonia conversion (%) = 1 − {(volume of ammonia discharged) / (volume of ammonia supplied)} × 100

While maintaining the reaction temperature at 450 ° C., the evaluation was performed under the condition that the space velocity (synonymous with the flow rate) of the source gas was 100 to 1,200 h ⁻¹ .

  As a result of Table 1, even at a relatively low temperature of 450 ° C., the ammonia decomposition reaction proceeds at a high rate, suggesting that the ammonia decomposition activity is excellent even in a relatively high space velocity region. Yes. Further, after the reaction for 1000 hours, it was found that no catalyst layer was observed for any of the catalysts, and there was no problem in adhesion. The selectivity for hydrogen and nitrogen was 100%. Here, the hydrogen selectivity is defined as (hydrogen generation amount) × (2/3) / (ammonia decomposition amount) × 100, and the nitrogen selectivity is defined as (nitrogen generation amount) × 2 / (ammonia decomposition amount) × 100. The

(Example 2)
Use of metal base structure B (plate thickness 50 μm, cell density 400 cells / inch ² ) in place of metal base structure A, outer surface layer using ruthenium nitrate solution instead of ruthenium chloride as a ruthenium compound The catalyst structure was produced by performing the same process as Example 1 except having formed. When the catalytic activity was evaluated using the catalyst structure thus obtained, all of the RUN No. of Example 1 except that the reaction temperature was 425 ° C. Evaluation was performed in the same manner as in 2. As a result, the ammonia conversion rate was 73.7%, and ammonia decomposition activity higher than that in Example 1 was obtained. Further, in the case of catalyst powder prepared using this compound as a starting material, the adhesion to the metal substrate remained high, and there was no problem even after 1000 hours of reaction. The selectivity for hydrogen and nitrogen was 100%.

(Example 3)
Except for setting the reaction temperature to 300 to 800 ° C., all of RUN No. of Example 1 were used. Evaluation was performed in the same manner as in 2.

  As a result of Table 2, if the reaction temperature is 300 ° C. or higher, it suggests that the decomposition reaction of ammonia proceeds. Further, after the reaction for 1000 hours, it was found that no catalyst layer was observed for any of the catalysts, and there was no problem in adhesion. The selectivity for hydrogen and nitrogen was 100%.

Example 4
All evaluations were made in the same manner as in Example 1 except that the space velocity was 2,000 to 200,000 h ⁻¹ .

  As a result of Table 3, even when the space velocity is high, the ammonia decomposition reaction proceeds at a high rate, suggesting that the ammonia decomposition activity is excellent. Further, after the reaction for 1000 hours, it was found that no catalyst layer was observed for any of the catalysts, and there was no problem in adhesion. The selectivity for hydrogen and nitrogen was 100%.

(Example 5)
Except for using the metal substrate structure B molded to have a metal foil thickness and cell density as shown in Table 4, all of the RUN No. of Example 1 were used. Evaluation was performed in the same manner as in 2.

  As a result of Table 4, regardless of the thickness of the metal foil and the cell density, the ammonia decomposition reaction proceeds at a high rate, suggesting that the ammonia decomposition activity is excellent. Further, after the reaction for 1000 hours, it was found that no catalyst layer was observed for any of the catalysts, and there was no problem in adhesion. The selectivity for hydrogen and nitrogen was 100%.

(Example 6)
As the metal substrate structure B, the RUN No. 24, and the basis weight of the catalyst particles is 50, 100, 200, and 400 g / L, all of the RUN No. of Example 1 are used. Evaluation was performed in the same manner as in 2.

  As a result of Table 5, when the basis weight is increased with respect to the honeycomb having the same cell density, the catalyst coating layer becomes thick so that ammonia in the layer becomes difficult to diffuse, or the decomposition reaction tends to slightly decrease. However, in all cases, the reaction proceeded at a high rate, suggesting that the decomposition activity of ammonia is excellent. Further, after the reaction for 1000 hours, it was found that no catalyst layer was observed for any of the catalysts, and there was no problem in adhesion. The selectivity for hydrogen and nitrogen was 100%.

(Example 7)
As the metal substrate, the RUN No. in Table 4 was used using the steel types shown in Table 6. Except for creating and using the structure of No. 21, all of the RUN No. of Example 1 were used. Evaluation was performed in the same manner as in 2. In addition, the number in the schematic component in a table | surface shows the mass% of each metal element contained in steel.

  As a result of Table 6, the decomposition reaction progressed at a high rate even when a honeycomb structure made of any steel type was used, suggesting that the decomposition activity of ammonia is excellent. Further, after the reaction for 1000 hours, it was found that no catalyst layer was observed for any of the catalysts, and there was no problem in adhesion. The selectivity for hydrogen and nitrogen was 100%.

(Example 8)
A catalyst structure is obtained by performing the same process as in Example 2 except that the metal base structure B, which is a cylindrical honeycomb formed to have a metal foil thickness and a cell density as shown in Table 7, is used. Was prepared. Except for the catalytic activity of this catalyst structure, the reaction temperature was set to 425 ° C., all RUN No. Evaluation was performed in the same manner as in 2.

  As a result of Table 7, regardless of the thickness of the metal foil and the cell density, the ammonia decomposition reaction proceeds at a high rate, suggesting that the ammonia decomposition activity is excellent. Further, after the reaction for 1000 hours, it was found that no catalyst layer was observed for any of the catalysts, and there was no problem in adhesion. The selectivity for hydrogen and nitrogen was 100%.

Example 9
Except for using a solution in which dodecacarbonyl triruthenium (Wako Pure Chemical Industries, 043-24051) was dissolved in tetrahydrofuran as the ruthenium compound, RUN No. 1 of Example 1 was used. Evaluation was performed in the same manner as in 2. As a result, the ammonia conversion rate was 72.0%, and a high ammonia decomposition activity similar to that of Example 1 was obtained. Further, in the case of catalyst powder prepared using this compound as a starting material, the adhesion to the metal substrate remained high, and there was no problem even after 1000 hours of reaction. The selectivity for hydrogen and nitrogen was 100%.

(Example 10)
A catalyst structure was prepared in the same manner as in Example 1 except that the average particle size of the alumina powder coated with the sol solution was adjusted as shown in Table 8, and RUN No. Evaluation was performed in the same manner as in 2.

  As a result of Table 8, regardless of the average particle diameter of any alumina particles, the ammonia decomposition reaction proceeds at a high rate, suggesting that the ammonia decomposition activity is excellent. Further, after the reaction for 1000 hours, it was found that no catalyst layer was observed for any of the catalysts, and there was no problem in adhesion. The selectivity for hydrogen and nitrogen was 100%.

(Example 11)
A catalyst structure was prepared in the same manner as in Example 1 except that the ruthenium-supporting alumina powder having the specific surface area and average particle diameter shown in Table 9 was used. Evaluation was performed in the same manner as in 2.

  As a result of Table 9, in any of the alumina carriers, the ammonia decomposition reaction proceeds at a high rate, suggesting that the ammonia decomposition activity is excellent. Further, after the reaction for 1000 hours, it was found that no catalyst layer was observed for any of the catalysts, and there was no problem in adhesion. The selectivity for hydrogen and nitrogen was 100%.

(Example 12)
A catalyst structure was prepared in the same manner as in Example 1 except that the pretreatment step was not performed, and the catalyst activity of the catalyst structure was changed to RUN No. Evaluation was performed in the same manner as in 2. As a result, the ammonia conversion rate was 70.3%, which was a slightly lower ammonia decomposition activity than that of Example 1. Further, after the reaction for 1000 hours, a portion where the catalyst layer was slightly peeled was observed, but it was found that there was almost no problem in adhesion. However, this part of peeling was presumed to be the cause of the decrease in catalyst activity. However, there was no practical problem and at least a better result than the comparative example described later was obtained. The selectivity for hydrogen and nitrogen was 100%.

(Example 13)
A catalyst structure was prepared in the same manner as in Example 1 except that each oxide shown in Table 10 was used as a carrier powder supporting ruthenium, and the catalyst activity of the catalyst structure was measured according to RUN No. Evaluation was performed in the same manner as in 2.

  As a result of Table 10, in any alumina carrier, ammonia decomposition reaction progresses at a high rate, suggesting that the ammonia decomposition activity is excellent. Further, after the reaction for 1000 hours, it was found that no catalyst layer was observed for any of the catalysts, and there was no problem in adhesion. The selectivity for hydrogen and nitrogen was 100%.

(Example 14)
A catalyst structure was prepared in the same manner as in Example 1 except that cerium oxide was used as a carrier powder for supporting ruthenium and a ruthenium-supported catalyst was prepared by supporting the ruthenium-supported amount in the ratio shown in Table 11. Except for setting the catalytic activity of the structure to a reaction temperature of 400 ° C. Evaluation was performed in the same manner as in 2.

  As a result of Table 11, as the Ru loading amount increases, the ammonia decomposition reaction proceeds at a higher rate, suggesting that the ammonia decomposition activity is excellent. Moreover, after 1000 hours reaction, performance degradation was not seen with any catalyst, peeling of the catalyst layer was not observed, and it was found that there was no problem with adhesion. The selectivity for hydrogen and nitrogen was 100%.

(Example 15)
Ruthenium 10% by weight, after preparing a supported ruthenium catalyst by supporting the 5 wt% potassium cerium oxide powder, the cell density of the ruthenium catalyst 400 cells / inch ^2, a metal substrate having a thickness 50μm A catalyst structure was prepared in the same manner as in Example 1 except that the catalyst structure was prepared by coating the surface of the structure B so that the catalyst mass was 300 mg. In addition, the catalyst activity of the catalyst structure was changed according to RUN No. of Example 1 except that the reaction temperature was 200 to 500 ° C. Evaluation was performed in the same manner as in 2.

  As a result of Table 12, if the reaction temperature is 200 ° C. or higher, it suggests that the decomposition reaction of ammonia proceeds. Further, even at a relatively low temperature of 400 ° C., the equilibrium conversion rate was reached, and almost the entire amount was decomposed. In addition, it was found that after the reaction for 1000 hours, no deterioration of the catalyst performance was observed with any catalyst, no peeling of the catalyst layer was observed, and there was no problem in adhesion. The selectivity for hydrogen and nitrogen was 100%.

(Example 16)
Ruthenium 10% by weight, after preparing a supported ruthenium catalyst by supporting the 5 wt% cesium cerium oxide powder, the cell density of the ruthenium catalyst 400 cells / inch ^2, a metal substrate having a thickness 50μm A catalyst structure was prepared in the same manner as in Example 1 except that the structure was prepared by applying the catalyst mass to the surface of structure B so that the catalyst mass was 300 mg. In addition, the catalyst activity of the catalyst structure was changed according to RUN No. of Example 1 except that the reaction temperature was 200 to 500 ° C. Evaluation was performed in the same manner as in 2.

  As a result of Table 13, if the reaction temperature is 200 ° C. or higher, it indicates that the decomposition reaction of ammonia proceeds. Further, even at a relatively low temperature of 400 ° C., the equilibrium conversion rate was reached, and almost the entire amount was decomposed. In addition, it was found that after the reaction for 1000 hours, no deterioration in performance was observed with any catalyst, no peeling of the catalyst layer was observed, and there was no problem in adhesion. The selectivity for hydrogen and nitrogen was 100%.

(Example 17)
A ruthenium-supported catalyst was prepared by supporting 10% by mass of ruthenium and 5% by mass of sodium on cerium oxide powder, and then the ruthenium-supported catalyst was mixed with a metal substrate having a cell density of 400 cells / inch ² and a plate thickness of 50 μm. The catalyst structure was prepared in the same manner as in Example 1 except that the structure was prepared by coating the surface of the material structure B so that the catalyst mass was 300 mg. In addition, the catalyst activity of the catalyst structure was changed according to RUN No. of Example 1 except that the reaction temperature was 200 to 500 ° C. Evaluation was performed in the same manner as in 2.

  As a result of Table 14, when the reaction temperature is 200 ° C. or higher, it is suggested that the decomposition reaction of ammonia proceeds. Further, even at a relatively low temperature of 400 ° C., it reached a value close to the equilibrium conversion rate and was almost decomposed. In addition, it was found that after the reaction for 1000 hours, no deterioration in performance was observed with any catalyst, no peeling of the catalyst layer was observed, and there was no problem in adhesion. The selectivity for hydrogen and nitrogen was 100%.

(Example 18)
Example 1 except that cerium oxide was used as the carrier powder for supporting ruthenium, the amount of ruthenium supported was 3% by mass, and potassium was supported on the promoter in the ratio shown in Table 15 to prepare a ruthenium supported catalyst. Thus, a catalyst structure was prepared. The catalyst activity of this catalyst structure is the same as that of RUN No. except that the reaction temperature is 400 ° C. Evaluation was performed in the same manner as in 2.

  As a result of Table 15, as the amount of potassium supported increased from 0.5 to 5% by mass, the decomposition reaction of ammonia progressed at a higher rate, and the effect of supporting potassium was significantly observed. On the other hand, when the amount of potassium supported was 10% by mass or more, although the performance improvement accompanying the addition amount was slightly seen, it was almost flat. Moreover, after 1000 hours reaction, performance degradation was not seen with any catalyst, peeling of the catalyst layer was not observed, and it was found that there was no problem with adhesion. The selectivity for hydrogen and nitrogen was 100%.

(Example 19)
A catalyst structure (catalyst carrier: alumina) was prepared by performing the same treatment as in Example 1 except that the underlayer was not formed. The catalytic activity of this catalyst structure was measured using RUN No. Evaluation was performed in the same manner as in 2. As a result, the ammonia conversion rate was 70.0%, which was a slightly lower ammonia decomposition activity than that of Example 1. Moreover, after reacting for 1000 hours, the ammonia conversion rate was reduced to 56.5%. When the catalyst structure was disassembled after the completion of the reaction, a part where the catalyst layer was slightly peeled was observed, and this part of peeling was presumed to be a cause of a decrease in catalyst activity. However, there was no practical problem and at least a better result than the comparative example described later was obtained. The selectivity for hydrogen and nitrogen was 100%.

(Example 20)
A catalyst structure (catalyst carrier: cerium oxide) was prepared in the same manner as in Examples 1 and 13 except that the underlayer was not formed. The catalytic activity of this catalyst structure was measured using RUN No. Evaluation was performed in the same manner as in 2. As a result, the ammonia conversion was 90.7%. The ammonia decomposition activity was as high as 53. Moreover, after reacting for 1000 hours, the ammonia conversion rate was maintaining a high performance of 82.3%. When the catalyst structure was disassembled after completion of the reaction, it was found that a part of the catalyst layer was partially peeled off, but the adhesion was not a problem. The selectivity for hydrogen and nitrogen was 100%.

(Example 21)
A catalyst structure (catalyst carrier: magnesium oxide) was prepared in the same manner as in Examples 1 and 13 except that the underlayer was not formed. The catalytic activity of this catalyst structure was measured using RUN No. Evaluation was performed in the same manner as in 2. As a result, the ammonia conversion was 74.1%, and RUN No. The ammonia decomposition activity was as high as 54. Moreover, after reacting for 1000 hours, the ammonia conversion rate was 66.7%, maintaining high performance. When the catalyst structure was disassembled after completion of the reaction, it was found that a part of the catalyst layer was partially peeled off, but the adhesion was not a problem. The selectivity for hydrogen and nitrogen was 100%.

(Example 22)
A catalyst structure (catalyst carrier: silicon oxide) was prepared in the same manner as in Examples 1 and 13 except that the underlayer was not formed. The catalytic activity of this catalyst structure was measured using RUN No. Evaluation was performed in the same manner as in 2. As a result, the ammonia conversion was 69.8%. The ammonia decomposition activity was as high as 55. Further, after reacting for 1000 hours, the ammonia conversion rate was maintained at a high performance of 58.3%. When the catalyst structure was disassembled after completion of the reaction, it was found that a part of the catalyst layer was partially peeled off, but the adhesion was not a problem. The selectivity for hydrogen and nitrogen was 100%.

(Example 23)
A catalyst structure (catalyst carrier: zirconium oxide) was prepared in the same manner as in Examples 1 and 13 except that the underlayer was not formed. The catalytic activity of this catalyst structure was measured using RUN No. Evaluation was performed in the same manner as in 2. As a result, the ammonia conversion was 66.6%, and RUN No. The ammonia decomposition activity was as high as 56. Moreover, after reacting for 1000 hours, the ammonia conversion rate maintained a high performance of 60.0%. When the catalyst structure was disassembled after completion of the reaction, it was found that a part of the catalyst layer was partially peeled off, but the adhesion was not a problem. The selectivity for hydrogen and nitrogen was 100%.

(Example 24)
Ruthenium content of 10 wt%, and supported on cerium oxide and potassium supported amount of 5 wt% creates a ruthenium supported catalyst, thickness 50μm metal substrate, a 400 cell / inch ² of the metal base structure B A catalyst structure was prepared in the same manner as in Example 1 except that the catalyst loading was 300 mg. The catalytic activity of the catalyst structure was evaluated in the same manner as in Example 1 except that the reaction temperature was 400 ° C. and the raw material gas flow rate was adjusted so that the space velocity was as shown in Table 14.

  As a result of Table 16, even under the condition where the space velocity is high, the ammonia decomposition reaction proceeds at a high rate, suggesting that the ammonia decomposition activity is excellent. Moreover, after 1000 hours reaction, performance degradation was not seen with any catalyst, peeling of the catalyst layer was not observed, and it was found that there was no problem with adhesion. The selectivity for hydrogen and nitrogen was 100%.

(Comparative Example 1)
Instead of the catalyst structure, all the same procedures as in Example 1 were conducted except that the prepared ruthenium-supported aluminum oxide catalyst was pulverized so as to have a particle diameter of 250 to 500 μm, and 100 mg of the classified particles were charged into the reactor. And evaluated.

  As a result of Table 17, in the case of catalyst particles, the decomposition reaction of ammonia progressed at a high rate under a low space velocity, but the decomposition rate decreased considerably as the space velocity increased.

The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to such examples. It is obvious that a person having ordinary knowledge in the technical field to which the present invention pertains can come up with various changes or modifications within the scope of the technical idea described in the claims. Of course, it is understood that these also belong to the technical scope of the present invention.

Claims (11)

A metal substrate structure having a distribution path of ammonia gas and composed of a metal substrate;
Ruthenium was supported on one type of support selected from the group consisting of aluminum oxide, cerium oxide, magnesium oxide, silicon oxide, and zirconium oxide, present on the surface of the metal base structure. A catalyst structure for producing hydrogen from ammonia, comprising an outer surface layer containing a ruthenium-supported catalyst. A metal substrate structure having a distribution path of ammonia gas and composed of a metal substrate;
Present on the surface of the metal substrate structure, and an underlayer containing aluminum oxide;
A ruthenium-supported catalyst in which ruthenium is supported on one type of support selected from the group consisting of aluminum oxide, cerium oxide, magnesium oxide, silicon oxide, and zirconium oxide, present on the surface of the underlayer. And a catalyst structure for producing hydrogen from ammonia.   The ruthenium-supported catalyst that forms the outer surface layer of the catalyst structure contains one or more selected from the group consisting of potassium, cesium, and sodium as a co-catalyst. 3. A catalyst structure for producing hydrogen from ammonia according to 2.   The flow path of ammonia gas of the metal substrate structure includes a through-flow path having a regular shape over the entire plane perpendicular to the direction in which ammonia flows. A catalyst structure for producing hydrogen from ammonia according to claim 1. A pretreatment step of cleaning the surface of the metal substrate structure having a flow path of ammonia gas;
A catalyst supporting step of producing a ruthenium-supported catalyst by supporting ruthenium on one support selected from the group consisting of aluminum oxide, cerium oxide, magnesium oxide, silicon oxide, and zirconium oxide;
An outer surface layer forming step in which the surface of the structure subjected to the pretreatment step is coated with the ruthenium supported catalyst prepared in the catalyst supporting step, and then dried and fired to form an outer surface layer. A method for producing a catalyst structure for producing hydrogen from ammonia. A pretreatment step of cleaning the surface of the metal substrate structure having a flow path of ammonia gas;
An underlayer forming step of forming an underlayer containing aluminum oxide on the surface of the structure subjected to the pretreatment step;
A catalyst supporting step of producing a ruthenium-supported catalyst by supporting ruthenium on one support selected from the group consisting of aluminum oxide, cerium oxide, magnesium oxide, silicon oxide, and zirconium oxide;
An outer surface layer forming step of coating the ruthenium supported catalyst prepared in the catalyst supporting step on the under layer formed in the under layer forming step, and then drying and firing to form an outer surface layer; A method for producing a catalyst structure for producing hydrogen from ammonia, comprising: A pretreatment process for cleaning the surface of the metal substrate;
A catalyst supporting step of producing a ruthenium-supported catalyst by supporting ruthenium on one support selected from the group consisting of aluminum oxide, cerium oxide, magnesium oxide, silicon oxide, and zirconium oxide;
An outer surface layer forming step of coating the ruthenium-supported catalyst prepared in the catalyst supporting step on the surface of the metal substrate subjected to the pretreatment step, and then drying and firing to form an outer surface layer; Have
A step of making the metal base material a metal base material structure having an ammonia gas flow path at a timing after the pretreatment step and before the outer surface layer formation step or after the outer surface layer formation step. The manufacturing method of the catalyst structure for manufacturing hydrogen from ammonia characterized by performing. A pretreatment process for cleaning the surface of the metal substrate;
An underlayer forming step of forming an underlayer containing an aluminum oxide on the surface of the metal substrate subjected to the pretreatment step;
A catalyst supporting step of producing a ruthenium-supported catalyst by supporting ruthenium on one support selected from the group consisting of aluminum oxide, cerium oxide, magnesium oxide, silicon oxide, and zirconium oxide;
An outer surface layer forming step of coating the ruthenium supported catalyst prepared in the catalyst supporting step on the under layer formed in the under layer forming step, and then drying and firing to form an outer surface layer; Have
At the timing after the pretreatment step and before the base layer formation step, after the base layer formation step and before the outer surface layer formation step, or after the outer surface layer formation step, the metal substrate The manufacturing method of the catalyst structure for manufacturing hydrogen from ammonia characterized by performing the process made into the metal base material structure which has the distribution channel of ammonia gas. In the pretreatment step,
A step of drying after degreasing the surface of the metal substrate or the metal substrate structure using an organic solvent, a step of drying after immersing the metal substrate or the metal substrate structure in an alkaline aqueous solution, The surface of the metal substrate or the metal substrate structure is treated by performing a step of drying after immersing the metal substrate or the metal substrate structure in an acidic aqueous solution. Item 9. The method for producing a catalyst structure for producing hydrogen from ammonia according to any one of Items 5 to 8.   A method for producing hydrogen from ammonia using the catalyst structure according to any one of claims 1 to 4, wherein a gas containing ammonia is circulated through a circulation path of the ammonia gas, and the gas is produced. A method for producing hydrogen, wherein ammonia is brought into contact with the ruthenium-supported catalyst to decompose the ammonia to produce hydrogen. A method for producing hydrogen from ammonia using the catalyst structure produced by the production method according to any one of claims 5 to 9, wherein a gas containing ammonia is introduced into a flow path of the ammonia gas. A method for producing hydrogen, characterized in that the hydrogen in the gas is brought into contact with the ruthenium-supported catalyst to decompose the ammonia to produce hydrogen.

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