WO2014073576A1 - Oxidative decomposition catalyst for ammonia, method for producing hydrogen, and apparatus for producing hydrogen - Google Patents

Abstract

This method for producing hydrogen is characterized in that when hydrogen is produced by oxidatively decomposing ammonia by bringing a reaction gas that contains ammonia and oxygen into contact with a catalyst that comprises one or more metals selected from the group consisting of Ru, Co, Rh, Ir and Ni and a carrier that supports the metals, the oxidative decomposition reaction of ammonia is initiated by utilizing the heat generated by the catalyst.

Description

Ammonia oxidative decomposition catalyst, hydrogen production method and hydrogen production apparatus

The present invention relates to an ammonia oxidative decomposition catalyst, a hydrogen production method using an ammonia oxidative decomposition catalyst, and a hydrogen production apparatus.

An advanced energy conversion and utilization system using ammonia as a hydrogen medium has been proposed. In this system, hydrogen is produced by photolysis of water using sunlight in an area where there is a lot of sunlight. The resulting hydrogen reacts with nitrogen to convert it to ammonia, and liquid ammonia is consumed by the consumer. Then, hydrogen is utilized by decomposing ammonia to produce hydrogen.

Developed ammonia decomposition catalyst used for ammonia decomposition for practical application of the above system. Various catalysts have been proposed for ammonia decomposition catalysts (see, for example, Patent Documents 1 to 4 below).

JP 2005-246163 A JP 2006-326578 A JP 2006-346642 A JP 2007-021482 A

The ammonia decomposition reaction represented by 2NH ₃ → N ₂ + 3H ₂ is an endothermic reaction, and a temperature of 400 ° C. is required to sufficiently decompose ammonia. In a conventional hydrogen production apparatus using an ammonia decomposition catalyst, it is necessary to heat the catalyst to 400 ° C. for start-up, and it is necessary to supply heat from the outside even after start-up. There is a problem.

The present invention starts oxidative decomposition of ammonia from a low temperature such as room temperature without external heat supply or with a slight heat supply (hereinafter sometimes referred to as “cold start of oxidative decomposition of ammonia”). An object of the present invention is to provide an ammonia oxidative decomposition catalyst, a hydrogen production method and a hydrogen production apparatus using the catalyst.

In the present invention, a reaction gas containing ammonia and oxygen is brought into contact with a catalyst having at least one metal selected from the group consisting of Ru, Co, Rh, Ir and Ni, and a carrier supporting the metal. Thus, when producing hydrogen by oxidizing and decomposing ammonia, there is provided a method for producing hydrogen, characterized in that the oxidative decomposition reaction of ammonia is started using the heat generated by the catalyst.

According to the method for producing hydrogen of the present invention, by introducing oxygen into the reaction gas brought into contact with the catalyst and utilizing the heat generated by the catalyst, it is possible to quickly reach the combustion start temperature of ammonia, Hydrogen can be obtained by decomposing ammonia without heat supply from the outside due to internal heat generation due to the combustion reaction of ammonia.

In one embodiment of the method for producing hydrogen according to the present invention, the above heat generation can be obtained by contacting oxygen with a catalyst in which the metal and the carrier are in a reduced state. In this case, it is preferable that the carrier contains one or more oxides containing one or more elements selected from Ce, Zr and Pr.

Furthermore, the catalyst may be reduced by a product gas containing hydrogen produced from a reaction gas containing ammonia and oxygen. In this case, once the ammonia decomposition reaction is started, the ammonia decomposition reaction can be started repeatedly without pretreatment of the catalyst thereafter.

In another aspect of the method for producing hydrogen according to the present invention, the exothermic heat can be obtained by contacting oxygen with a catalyst in which the metal is in a reduced state. In this case, the carrier preferably contains one or more oxides selected from the group consisting of La ₂ O ₃ , MgO, and Mg—Al oxide.

Furthermore, the catalyst may be reduced by a product gas containing hydrogen produced from a reaction gas containing ammonia and oxygen. In this case, once the ammonia decomposition reaction is started, the ammonia decomposition reaction can be started repeatedly without pretreatment of the catalyst thereafter.

In another aspect of the method for producing hydrogen according to the present invention, the exotherm can be obtained by contacting ammonia with a catalyst in which the carrier has an acid point. In this case, the above heat generation can be obtained by contacting ammonia with a catalyst having a support containing one or more oxides selected from the group consisting of Al ₂ O ₃ and SiO ₂ .

Furthermore, the catalyst may have ammonia desorbed by the heat of reaction of the oxidative decomposition reaction of ammonia. In this case, once the ammonia decomposition reaction is started, the ammonia decomposition reaction can be started repeatedly without pretreatment of the catalyst thereafter.

In the above method, when the start and end of the oxidative decomposition reaction of ammonia are repeated, the catalyst at room temperature between the reactions can come into contact with oxygen.

The present invention also includes one or more metals selected from the group consisting of Ru, Co, Rh, Ir, and Ni, and a carrier supporting the metal, and the carrier is selected from Ce, Zr, and Pr. Provided is an ammonia oxidative decomposition catalyst characterized by containing one or more oxides containing one or more elements.

The present invention also includes at least one metal selected from the group consisting of Ru, Co, Rh, Ir, and Ni, and a carrier supporting the metal, wherein the carrier is La ₂ O ₃ , MgO, and Mg—. An ammonia oxidative decomposition catalyst comprising one or more oxides selected from the group consisting of Al oxides is provided.

The present invention also includes at least one metal selected from the group consisting of Ru, Co, Rh, Ir, and Ni, and a carrier supporting the metal, and the carrier is made of Al ₂ O ₃ and SiO _2. An ammonia oxidative decomposition catalyst comprising one or more oxides selected from the group is provided.

The ammonia oxidative decomposition catalyst according to the present invention can generate heat by being brought into contact with oxygen or ammonia, and thereafter, when brought into contact with a reaction gas containing ammonia and oxygen, the ammonia combustion reaction is started by self-heating. be able to. According to the oxidative decomposition catalyst for ammonia according to the present invention, it is possible to cold start the oxidative decomposition of ammonia.

The present invention also provides a hydrogen production apparatus including any one of the ammonia oxidative decomposition catalysts according to the present invention.

According to the hydrogen production apparatus according to the present invention, it is possible to suppress energy consumption for startup by including the ammonia oxidative decomposition catalyst according to the present invention, and hydrogen can be supplied without external heat supply after startup. Can be manufactured. It can be said that the hydrogen production apparatus according to the present invention is an apparatus excellent in startability and energy saving.

According to the present invention, it is possible to provide an ammonia oxidative decomposition catalyst that enables a cold start of oxidative decomposition of ammonia, a hydrogen production method and a hydrogen production apparatus using the catalyst.

It is a mimetic diagram showing one embodiment of a hydrogen production device concerning the present invention. It is a schematic diagram which shows other embodiment of the hydrogen production apparatus which concerns on this invention.

FIG. 1 is a schematic view showing an embodiment of a hydrogen production apparatus according to the present invention. A hydrogen production apparatus 1 shown in FIG. 1 includes a reactor 10, a catalyst layer 20 provided in the reactor 10, and a heat insulating material 30 provided so as to surround the reactor 10. A flow path L1 for introducing a reaction gas that is a raw material of hydrogen is connected to the inlet of the reactor 10, and a flow path L2 for taking out the product gas is connected to the outlet of the reactor 10. Furthermore, the reactor 10 is filled with an inert filler 50 on the upstream side and the downstream side of the catalyst layer 20 partitioned by the partition member 40.

FIG. 2 is a schematic view showing another embodiment of the hydrogen production apparatus according to the present invention. In the hydrogen production apparatus 2 shown in FIG. 1, the heat insulating material 30 is provided only on the downstream side of the reactor 10, and the inert filler 50 is filled only on the downstream side of the catalyst layer 20. It has the same configuration as the hydrogen production apparatus 1 of FIG.

The reactor 10 is preferably a fixed bed flow reactor. The reactor may be a single reactor or a plurality of reactors arranged in series or in parallel. Moreover, the catalyst bed provided in a reactor may be single, and may be divided into plurality.

The catalyst layer 20 is filled with the ammonia oxidative decomposition catalyst according to the present invention.

As the heat insulating material 30, a general heat insulating material having low heat conductivity and sufficient heat resistance at the ammonia oxidation decomposition reaction temperature can be used. For example, ceramic, rock wool, calcium silicate hydrate system and the like can be used.

The partition material 40 is for preventing the catalyst from mixing with the inert filler, and for example, quartz wool, a metal mesh, or a punching metal plate can be used.

As the inert filler 50, for the purpose of fixing the catalyst layer 20 and rectifying the reaction fluid, for example, α-Al ₂ O ₃ balls, ceramic balls, silicon carbide, or the like, a molded product or granular material that is inert to the reaction is used. Can be used.

The hydrogen production method according to the present invention can be implemented by the hydrogen production apparatuses 1 and 2 described above.

In the method for producing hydrogen according to the present invention, ammonia and oxygen are added to a catalyst having at least one metal selected from the group consisting of Ru, Co, Rh, Ir, and Ni, and a carrier supporting the metal. When hydrogen is produced by oxidizing and decomposing ammonia by bringing the reaction gas into contact therewith, the oxidative decomposition reaction of ammonia is started using the heat generated by the catalyst. Hereinafter, preferred embodiments of the method for producing hydrogen according to the present invention and the oxidative decomposition catalyst for ammonia according to the present invention used for the method will be described.

(First embodiment)
In the method for producing hydrogen according to the first embodiment, a catalyst having one or more metals selected from the group consisting of Ru, Co, Rh, Ir and Ni, and a carrier supporting the metal, ammonia and Oxidative decomposition of ammonia using the heat generated by contacting oxygen with a catalyst in which the metal and the carrier are in a reduced state when producing hydrogen by oxidizing and decomposing ammonia by contacting a reaction gas containing oxygen Start the reaction.

In the present embodiment, it is preferable that the carrier has redox ability. The carrier preferably contains, for example, one or more oxides containing one or more elements selected from Ce, Zr and Pr.

Examples of the oxide include CeO ₂ , Pr ₆ O ₁₁ , Ce _x Zr _y O _z (0.0 <x ≦ 0.75, 0.25 ≦ y <1.0, 0.0 <z ≦ 2). 0.0, where x + y = 1).

The method for preparing the support containing the oxide is not particularly limited. For example, a known method, for example, calcination in the air, using Ce, Pr or Zr nitrate, hydroxide or oxide as a starting material. The carrier containing the oxide can be obtained by treating, or using an aqueous solution alone or after mixing, and then applying hydrothermal treatment, neutralization, calcination and the like alone or in combination.

The carrier can contain compounds other than the above oxides. For example, alumina or the like can be used as a binder component for the purpose of maintaining mechanical strength as a molded body.

The shape of the carrier can be cylindrical, pellet, spherical, lump, or powder. In the present embodiment, a cylindrical shape, a pellet, a spherical shape are used so that the gap between the catalysts is not blocked due to powdering of the carrier or mixing of foreign matters, and the flow of the reaction fluid is not hindered or the differential pressure is not generated. It is desirable to have any shape of a lump.

In the catalyst according to this embodiment, the content of the active metal is preferably 0.1 to 50.0% by mass, and preferably 0.5 to 40.0% by mass based on the total mass of the catalyst. More preferably, the content is 1.0 to 30.0% by mass.

The method for supporting the metal on the carrier is not particularly limited, and can be easily performed by applying a known method. For example, an impregnation method, a deposition method, a coprecipitation method, a kneading method, an ion exchange method, a pore filling method and the like can be mentioned, and the impregnation method is particularly desirable. The metal starting material for producing the catalyst differs depending on the above-mentioned supporting method and can be appropriately selected. Usually, organic acid salts such as chloride, nitrate and acetic acid, and carbonylates can be used. Specifically, Ru (C ₅ H ₇ O ₂ ) ₃ , RuCl ₃ , Ru (NO) (NO ₃ ) _x (OH) _y , Rh (NO ₃ ) ₃ .2H ₂ O, Ru ₃ (CO) ₁₂ , [(CH 3 COO) ₂ Rh ₂ ], [Rh (C ₇ H ₁₅ COO) ₂ ] ₂ , RhCl ₃ · nH ₂ O, Rh (NO ₃ ) ₃ , Rh (C ₂ H ₄ O ₂ ) x · nH ₂ O, C ₁₅ H ₂₁ IrO ₆ , IrCl ₃ .nH ₂ O, Ni (NO ₃ ) ₂ .6H ₂ O, (CH ₃ COO) ₂ Ni.4H ₂ O, NiCl ₂ .6H ₂ O, Ni (O ₂ C ₅ H ₇ ) ₂ · nH ₂ O, Co (NO ₃ ) ₂ · 6H ₂ O, (CH ₃ COCHCOCH ₃ ) ₂ Co · 2H ₂ O, Co ₂ (CO) ₈ , CoCl ₂ · 6H ₂ O are used. be able to.

When applying the impregnation method, for example, prepare a solution in which an organic acid salt such as chloride, nitrate, acetic acid or the like, a carbonylated product is added to water or an organic solvent, impregnate the carrier, and then dry, if necessary. A method of firing can be exemplified.

The calcination is usually performed in an air or nitrogen atmosphere, and the temperature is not particularly limited as long as it is equal to or higher than the decomposition temperature of the organic acid salt or carbonyl compound such as chloride, nitrate and acetic acid. C., preferably 200 to 900.degree. C., more preferably 250 to 800.degree. C. is desirable.

Next, a specific procedure of the hydrogen production method according to this embodiment will be described.

In this embodiment, it is preferable to perform a pretreatment for reducing the catalyst.

The conditions for the pretreatment can be appropriately set according to the oxidation-reduction characteristics of the catalyst. For example, after the catalyst is filled in the reactor and the catalyst layer is provided, the temperature is room temperature to 800 ° C., preferably 100 to 700 ° C. More preferably, it is carried out by circulating hydrogen gas or a gas containing hydrogen at a catalyst layer temperature of 200 to 600 ° C. for 5 minutes to 5 hours, preferably 10 minutes to 3 hours, more preferably 30 minutes to 2 hours. be able to.

As the oxide contained in the support, CeO ₂ or Ce _x Zr _y O _z (0.0 <x ≦ 0.75, 0.25 ≦ y <1.0, 0.0 <z ≦ 2.0, provided that When x + y = 1) is used, a pretreatment for reducing the catalyst can be performed by circulating hydrogen gas or a gas containing hydrogen at a catalyst layer temperature lower than room temperature (25 ° C.). In this case, energy for heating can be reduced.

When the pretreatment of the catalyst is completed, heating of the catalyst layer can be stopped while flowing an inert gas such as He, and the catalyst layer can be kept at room temperature.

Next, oxygen is brought into contact with the catalyst in which the metal and support are in a reduced state. In the present embodiment, it is preferable to heat the catalyst by supplying a reaction gas containing ammonia and oxygen (preferably air) to the catalyst layer. In this case, when the temperature of the catalyst reaches the combustion start temperature of ammonia, the combustion reaction of ammonia can be started. When the temperature of the catalyst reaches the oxidative decomposition reaction start temperature of ammonia due to the heat generated by the combustion reaction of ammonia, the oxidative decomposition reaction of ammonia can be started.

The volume ratio of ammonia and oxygen in the reaction gas is preferably 1.0: 0.095 to 0.5, and more preferably 1.0: 0.2 to 0.4. When air is used, the amount of air can be adjusted so that the above-mentioned ratio of ammonia and oxygen is obtained. The reactive gas can be accompanied by an inert gas such as helium in order to adjust the calorific value.

Thus, a product gas containing hydrogen can be obtained from a reaction gas containing ammonia.

According to the hydrogen production method of the present embodiment, for example, in a hydrogen production apparatus as shown in FIGS. 1 and 2, after the reaction is stopped and the catalyst layer is cooled, the reaction is performed under a reducing atmosphere (for example, under a hydrogen atmosphere) or not. By maintaining the catalyst system under an active atmosphere, the second start-up can be performed without performing the pretreatment (heating before start, hydrogen reduction treatment, etc.) as described above. Specifically, for example, the heat generation of the catalyst layer is stopped by circulating an inert gas such as He, and the catalyst layer can be restarted by supplying the reaction gas after the temperature of the catalyst layer is lowered to room temperature. At this time, before supplying the reaction gas, a mixed gas of ammonia and helium may be supplied, and then oxygen may be supplied.

The above effect is considered to be due to the in-situ reduction of the metal and the carrier by hydrogen generated by the oxidative decomposition reaction of ammonia.

In the present embodiment, at the second or third start-up, a reaction gas containing ammonia and oxygen (preferably air) is supplied, or a reaction gas containing oxygen (preferably air) is supplied after ammonia is supplied first. It is desirable to supply. In addition, a reaction gas can be supplied after supplying a mixed gas of ammonia and helium and then supplying oxygen.

In this embodiment, when CeO ₂ is used as the oxide contained in the support, the catalyst layer temperature is 800 ° C. or less, preferably room temperature (about 25 ° C.) to 800 ° C., more preferably 100 ° C. to 600 ° C. Then, the He gas is circulated, the catalyst is heat-treated with He, and then ammonia is brought into contact with the catalyst, whereby the oxidative decomposition reaction of ammonia can be started. In the present embodiment, it is preferable to heat the catalyst by supplying a reaction gas containing ammonia and oxygen (preferably air) to the catalyst layer. In this case, when the temperature of the catalyst reaches the combustion start temperature of ammonia, the combustion reaction of ammonia can be started. When the temperature of the catalyst reaches the oxidative decomposition reaction start temperature of ammonia due to the heat generated by the combustion reaction of ammonia, the oxidative decomposition reaction of ammonia can be started.

In addition, it is thought that the heat_generation | fever obtained by making ammonia contact a catalyst is based on ammonia adsorb | sucking to the acid point of the said oxide. Further, the above metal is easily highly dispersed on CeO ₂ , and the activity is enhanced. Therefore, it is considered that the oxidative decomposition reaction of ammonia is enabled by the heat of adsorption.

(Second Embodiment)
In the method for producing hydrogen according to the second embodiment, a catalyst having one or more metals selected from the group consisting of Ru, Co, Rh, Ir and Ni, and a carrier supporting the metal, ammonia and When producing hydrogen by oxidizing and decomposing ammonia by contacting a reaction gas containing oxygen, the exothermicity can be obtained by bringing oxygen into contact with a catalyst in which the metal is in a reduced state. In this case, the carrier preferably contains one or more oxides selected from the group consisting of La ₂ O ₃ , MgO, and Mg—Al oxide.

The carrier preferably contains, for example, one or more oxides selected from the group consisting of La ₂ O ₃ , MgO, and Mg—Al oxide.

The method for preparing the support containing the oxide is not particularly limited. For example, La, Mg or Al nitrate, hydroxide or oxide is used as a starting material, and a known method, for example, firing in air. The carrier containing the oxide can be obtained by treating, or using an aqueous solution alone or after mixing, and then applying hydrothermal treatment, neutralization, calcination and the like alone or in combination.

The carrier can contain compounds other than the above oxides. For example, alumina or the like can be used as a binder component for the purpose of maintaining mechanical strength as a molded body.

The shape of the carrier can be cylindrical, pellet, spherical, lump, or powder. In the present embodiment, a cylindrical shape, a pellet, a spherical shape are used so that the gap between the catalysts is not blocked due to powdering of the carrier or mixing of foreign matters, and the flow of the reaction fluid is not hindered or the differential pressure is not generated. It is desirable to have any shape of a lump.

In the catalyst according to this embodiment, the content of the active metal is preferably 0.1 to 50.0% by mass, and preferably 0.5 to 40.0% by mass based on the total mass of the catalyst. More preferably, the content is 1.0 to 30.0% by mass.

The method for supporting the metal on the carrier is not particularly limited, and can be easily performed by applying a known method. For example, an impregnation method, a deposition method, a coprecipitation method, a kneading method, an ion exchange method, a pore filling method and the like can be mentioned, and the impregnation method is particularly desirable. The metal starting material for producing the catalyst differs depending on the above-mentioned supporting method and can be appropriately selected. Usually, organic acid salts such as chloride, nitrate and acetic acid, and carbonylates can be used. Specifically, Ru (C ₅ H ₇ O ₂ ) ₃ , RuCl ₃ , Ru (NO) (NO ₃ ) _x (OH) _y , Rh (NO ₃ ) ₃ .2H ₂ O, Ru ₃ (CO) ₁₂ , [(CH 3 COO) ₂ Rh ₂ ], [Rh (C ₇ H ₁₅ COO) ₂ ] ₂ , RhCl ₃ · nH ₂ O, Rh (NO ₃ ) ₃ , Rh (C ₂ H ₄ O ₂ ) x · nH ₂ O, C ₁₅ H ₂₁ IrO ₆ , IrCl ₃ .nH ₂ O, Ni (NO ₃ ) ₂ .6H ₂ O, (CH ₃ COO) ₂ Ni.4H ₂ O, NiCl ₂ .6H ₂ O, Ni (O ₂ C ₅ H ₇ ) ₂ · nH ₂ O, Co (NO ₃ ) ₂ · 6H ₂ O, (CH ₃ COCHCOCH ₃ ) ₂ Co · 2H ₂ O, Co ₂ (CO) ₈ , CoCl ₂ · 6H ₂ O are used. be able to.

When applying the impregnation method, for example, prepare a solution in which an organic acid salt such as chloride, nitrate, acetic acid or the like, a carbonylated product is added to water or an organic solvent, impregnate the carrier, and then dry, if necessary. A method of firing can be exemplified.

The calcination is usually performed in an air or nitrogen atmosphere, and the temperature is not particularly limited as long as it is equal to or higher than the decomposition temperature of the organic acid salt or carbonyl compound such as chloride, nitrate and acetic acid. C., preferably 200 to 900.degree. C., more preferably 250 to 800.degree. C. is desirable.

Next, a specific procedure of the hydrogen production method according to this embodiment will be described.

In this embodiment, it is preferable to perform a pretreatment for reducing the catalyst.

The conditions for the pretreatment can be appropriately set according to the oxidation-reduction characteristics of the catalyst. For example, after the catalyst is filled in the reactor and the catalyst layer is provided, the temperature is 100 to 800 ° C., preferably 400 to 700 ° C. More preferably, it is carried out by circulating hydrogen gas or a gas containing hydrogen at a catalyst layer temperature of 500 to 700 ° C. for 5 minutes to 5 hours, preferably 10 minutes to 3 hours, more preferably 30 minutes to 2 hours. be able to.

When the pretreatment of the catalyst is completed, heating of the catalyst layer can be stopped while flowing an inert gas such as He, and the catalyst layer can be kept at room temperature.

Next, oxygen is brought into contact with the catalyst in which the metal and the carrier are in a reduced state. In the present embodiment, it is preferable to heat the catalyst by supplying a reaction gas containing ammonia and oxygen (preferably air) to the catalyst layer. In this case, when the temperature of the catalyst reaches the combustion start temperature of ammonia, the combustion reaction of ammonia can be started. When the temperature of the catalyst reaches the oxidative decomposition reaction start temperature of ammonia due to the heat generated by the combustion reaction of ammonia, the oxidative decomposition reaction of ammonia can be started.

The volume ratio of ammonia and oxygen in the reaction gas is preferably 1.0: 0.095 to 0.5, and more preferably 1.0: 0.2 to 0.4. When air is used, the amount of air can be adjusted so that the above-mentioned ratio of ammonia and oxygen is obtained. The reactive gas can be accompanied by an inert gas such as helium in order to adjust the calorific value.

Thus, a product gas containing hydrogen can be obtained from a reaction gas containing ammonia.

According to the hydrogen production method of the present embodiment, for example, in a hydrogen production apparatus as shown in FIGS. 1 and 2, after the reaction is stopped and the catalyst layer is cooled, the reaction is performed under a reducing atmosphere (for example, under a hydrogen atmosphere) or not. By maintaining the catalyst system under an active atmosphere, the second start-up can be performed without performing the pretreatment (heating before start, hydrogen reduction treatment, etc.) as described above. Specifically, for example, the heat generation of the catalyst layer is stopped by circulating an inert gas such as He, and the catalyst layer can be restarted by supplying the reaction gas after the temperature of the catalyst layer is lowered to room temperature. At this time, before supplying the reaction gas, a mixed gas of ammonia and helium may be supplied, and then oxygen may be supplied.

The above effect is considered to be due to in-situ reduction of the metal by hydrogen generated by the oxidative decomposition reaction of ammonia.

In the present embodiment, at the second or third start-up, a reaction gas containing ammonia and oxygen (preferably air) is supplied, or a reaction gas containing oxygen (preferably air) is supplied after ammonia is supplied first. It is desirable to supply. In addition, a reaction gas can be supplied after supplying a mixed gas of ammonia and helium and then supplying oxygen.

(Third embodiment)
In the method for producing hydrogen according to the third embodiment, a catalyst having one or more metals selected from the group consisting of Ru, Co, Rh, Ir and Ni, and a carrier supporting the metal, ammonia and In producing hydrogen by oxidizing and decomposing ammonia by contacting a reaction gas containing oxygen, ammonia is added to a catalyst having a support containing one or more oxides selected from the group consisting of Al ₂ O ₃ and SiO _2. The above heat generation can be obtained by contact.

Examples of the oxide include γ-Al ₂ O ₃ , SiO ₂ and SiO ₂ —Al ₂ O ₃ .

From the viewpoint of startability, the support preferably contains one or more of Al ₂ O ₃ and SiO ₂ . By including these oxides in the support, the combustion start temperature of ammonia can be lowered.

Also, in that repeated activation of the can be easily without external heating, it is preferred that the carrier comprises Al ₂ O _3. Further, Al ₂ O ₃ is more preferably γ-Al ₂ O ₃ .

The method for preparing the support containing the oxide is not particularly limited. For example, an aluminum hydroxide gel is prepared using an aluminum aqueous solution prepared from nitrate, sulfate, etc. as a raw material for Al ₂ O _3. In addition, a commercially available aluminum oxide intermediate or boehmite powder may be used. As a raw material of SiO ₂ , silicic acid, water glass, silica sol and the like can be used. When combining Al ₂ O ₃ and SiO ₂ , an Si raw material may be added in the aluminum raw material solution or in the kneading step, and it is more preferable that the Al raw material is mixed in advance before the kneading step. After these are prepared, for example, in the air, or after being singly or mixed using an aqueous solution, the above oxides are contained by applying the steps such as hydrothermal treatment, neutralization, and calcination alone or in combination. A carrier can be obtained.

The carrier can contain compounds other than the above oxides. For example, alumina or the like can be used as a binder component for the purpose of maintaining mechanical strength as a molded body.

The shape of the carrier can be cylindrical, pellet, spherical, lump, or powder. In the present embodiment, a cylindrical shape, a pellet, a spherical shape are used so that the gap between the catalysts is not blocked due to powdering of the carrier or mixing of foreign matters, and the flow of the reaction fluid is not hindered or the differential pressure is not generated. It is desirable to have any shape of a lump.

In the catalyst according to this embodiment, the content of the active metal is preferably 0.1 to 50.0% by mass, and preferably 0.5 to 40.0% by mass based on the total mass of the catalyst. More preferably, the content is 1.0 to 30.0% by mass.

The method for supporting the metal on the carrier is not particularly limited, and can be easily performed by applying a known method. For example, an impregnation method, a deposition method, a coprecipitation method, a kneading method, an ion exchange method, a pore filling method and the like can be mentioned, and the impregnation method is particularly desirable. The metal starting material for producing the catalyst differs depending on the above-mentioned supporting method and can be appropriately selected. Usually, organic acid salts such as chloride, nitrate and acetic acid, and carbonylates can be used. Specifically, Ru (C ₅ H ₇ O ₂ ) ₃ , RuCl ₃ , Ru (NO) (NO ₃ ) _x (OH) _y , Rh (NO ₃ ) ₃ .2H ₂ O, Ru ₃ (CO) ₁₂ , [(CH 3 COO) ₂ Rh ₂ ], [Rh (C ₇ H ₁₅ COO) ₂ ] ₂ , RhCl ₃ · nH ₂ O, Rh (NO ₃ ) ₃ , Rh (C ₂ H ₄ O ₂ ) x · nH ₂ O, C ₁₅ H ₂₁ IrO ₆ , IrCl ₃ .nH ₂ O, Ni (NO ₃ ) ₂ .6H ₂ O, (CH ₃ COO) ₂ Ni.4H ₂ O, NiCl ₂ .6H ₂ O, Ni (O ₂ C ₅ H ₇ ) ₂ · nH ₂ O, Co (NO ₃ ) ₂ · 6H ₂ O, (CH ₃ COCHCOCH ₃ ) ₂ Co · 2H ₂ O, Co ₂ (CO) ₈ , CoCl ₂ · 6H ₂ O are used. be able to.

When applying the impregnation method, for example, prepare a solution in which an organic acid salt such as chloride, nitrate, acetic acid or the like, a carbonylated product is added to water or an organic solvent, impregnate the carrier, and then dry, if necessary. A method of firing can be exemplified.

The calcination is usually performed in an air or nitrogen atmosphere, and the temperature is not particularly limited as long as it is equal to or higher than the decomposition temperature of the organic acid salt or carbonyl compound such as chloride, nitrate and acetic acid. C., preferably 200 to 900.degree. C., more preferably 250 to 800.degree. C. is desirable.

Next, a specific procedure of the hydrogen production method according to this embodiment will be described.

In the present embodiment, it is preferable to perform a pretreatment for expressing the acid sites of the carrier.

In the pretreatment, for example, after a catalyst is charged into a reactor and a catalyst layer is provided, the catalyst layer heated to 10 to 800 ° C., preferably 50 to 700 ° C., more preferably 100 to 500 ° C. is used as an inert gas. For example, He gas can be circulated for 5 minutes to 5 hours, preferably 10 minutes to 3 hours, more preferably 30 minutes to 2 hours, and then the temperature of the catalyst layer is lowered to, for example, 100 ° C. to room temperature. When the temperature of the catalyst layer is lowered, it is preferable to purge with He in order to maintain the acid sites on the catalyst.

When the support contains γ-Al ₂ O ₃ , pretreatment can be performed with a gas containing oxygen. In this case, if there is air, ammonia, and a slight heat source, it is possible to repeatedly start the hydrogen production apparatus, and it is preferable because hydrogen can be easily obtained.

Next, ammonia is brought into contact with the catalyst. In the present embodiment, it is preferable to heat the catalyst by supplying a reaction gas containing ammonia and oxygen (preferably air) to the catalyst layer. In this case, when the temperature of the catalyst reaches the combustion start temperature of ammonia, the combustion reaction of ammonia can be started. When the temperature of the catalyst reaches the oxidative decomposition reaction start temperature of ammonia due to the heat generated by the combustion reaction of ammonia, the oxidative decomposition reaction of ammonia can be started.

In addition, it is thought that the heat generated by contacting ammonia with the catalyst is due to adsorption of ammonia on the acid sites of the oxide.

The volume ratio of ammonia and oxygen in the reaction gas is preferably 1.0: 0.095 to 0.5, and more preferably 1.0: 0.2 to 0.4. When air is used, the amount of air can be adjusted so that the above-mentioned ratio of ammonia and oxygen is obtained. The reactive gas can be accompanied by an inert gas such as helium in order to adjust the calorific value.

Thus, a product gas containing hydrogen can be obtained from a reaction gas containing ammonia.

According to the hydrogen production method of the present embodiment, for example, in a hydrogen production apparatus as shown in FIGS. 1 and 2, after the reaction is stopped and the temperature of the catalyst layer is lowered, an inert atmosphere or a reducing atmosphere (for example, hydrogen By maintaining the catalyst system in the atmosphere), the second start-up is possible without performing the pretreatment as described above (heating before starting, hydrogen reduction treatment, etc.). At this time, even if the catalyst touches a gas containing oxygen, if a sufficient adsorption point of ammonia remains, the second activation can be performed without pretreatment. Specifically, for example, the heat generation of the catalyst layer is stopped by circulating an inert gas such as He, and the catalyst layer can be restarted by supplying the reaction gas after the temperature of the catalyst layer is lowered to room temperature. At this time, oxygen may be supplied before the reaction gas is supplied.

The above effect is thought to be due to the fact that ammonia adsorbed by the heat of reaction of the oxidative decomposition reaction of ammonia is desorbed in-situ from the carrier, and the acid sites are developed again.

In this embodiment, at the second or third start-up, a reaction gas containing ammonia and oxygen (preferably air) is supplied, or oxygen (preferably air) is supplied first and then a reaction gas containing ammonia is supplied. It is desirable to supply.

In this embodiment, when Al ₂ O ₃ is used as the oxide contained in the support, it is 800 ° C. or less, preferably room temperature (about 25 ° C.) to 800 ° C., more preferably room temperature (about 25 ° C.) to 600. A pretreatment for reducing the catalyst can be performed by circulating hydrogen gas or a gas containing hydrogen at a catalyst layer temperature of ° C. Thereafter, the oxygen oxidative decomposition reaction can be started by bringing oxygen into contact with the catalyst in which the metal and the carrier are in a reduced state. In the present embodiment, it is preferable to heat the catalyst by supplying a reaction gas containing ammonia and oxygen (preferably air) to the catalyst layer. In this case, when the temperature of the catalyst reaches the combustion start temperature of ammonia, the combustion reaction of ammonia can be started. When the temperature of the catalyst reaches the oxidative decomposition reaction start temperature of ammonia due to the heat generated by the combustion reaction of ammonia, the oxidative decomposition reaction of ammonia can be started.

Example A-1
A solution of Ru ₃ (CO) ₁₂ (Tanaka Kikinzoku Kogyo Co., Ltd.) dissolved in tetrahydrofuran was impregnated with CeO ₂ particles (prepared by a precipitation method and baked at 700 ° C. in air for 5 hours), then rotary Evaporation to dryness was carried out using an evaporator, and loading was carried out so that the loading amount of Ru was 5% by mass based on the total mass of the catalyst. Next, the obtained impregnated product was heat-treated at 350 ° C. for 5 hours under a flow of He to obtain an oxidative decomposition catalyst A-1 for ammonia.

Example A-2
Instead of CeO ₂ particles, Ce _0.5 Zr _0.5 O ₂ particles (prepared by a precipitation method and calcined in air at 700 ° C. for 5 hours) were used in the same manner as in Example A-1. Thus, an oxidative decomposition catalyst A-2 of ammonia was obtained.

Example A-3
Oxidative decomposition of ammonia in the same manner as in Example A-1, except that Pr ₆ O ₁₁ particles (prepared by a precipitation method and calcined in air at 700 ° C. for 5 hours) were used instead of CeO ₂ particles. Catalyst A-3 was obtained.

A reaction apparatus having the same configuration as in FIG. 1 was prepared. The reactor has a cylindrical normal pressure fixed bed flow reactor having a diameter of 7 mm, and a ceramic heat insulating material provided so as to surround the vessel, and upstream of the catalyst layer partitioned by quartz wool. The side and downstream side are filled with α-Al ₂ O ₃ balls. A thermocouple that reaches the catalyst layer is provided inside the reaction apparatus, whereby the temperature of the catalyst layer can be measured. Further, the catalyst layer, quartz wool, and α-Al ₂ O ₃ balls can be heated by an electric furnace provided outside the reactor.

Hydrogen was produced by the following procedure using the above reactor. First, as a pretreatment, the catalyst layer filled with 0.2 g of catalyst was heated, and the catalyst was reduced by flowing hydrogen gas at 600 ° C. for 1 hour. Thereafter, the heating of the catalyst layer was stopped and purged with He. After the temperature of the catalyst layer was lowered to room _temperature, the reaction NH 3, and a reaction _{gas O 2} and He are mixed at a ratio of _NH 3 _/ O 2 _{/He=150/37.5/20.8(ml/} min) The product gas was supplied from the inlet of the apparatus at room temperature, and the generated gas was analyzed by GC-TCD (GC-8A, manufactured by Shimadzu Corporation).

Further, when the oxygen absorption amount of the pretreated catalysts A-1 to A-3 was measured, it was confirmed that oxygen was absorbed into the reduced Ru, and a part of Ru was reduced by the pretreatment. It was confirmed that

When the ammonia oxidative decomposition catalyst A-1 was used, it was confirmed that the upstream side of the catalyst layer started to red heat 5 seconds after the start of the supply of the reaction gas, and one minute after the start of the supply of the reaction gas, the thermoelectric inserted into the catalyst layer The temperature of the pair reached 424 ° C., and it was confirmed that the subsequent product gas contained 21% yield of hydrogen. At this time, the conversion rates of ammonia and oxygen were 54% and 100%, respectively.

When the ammonia oxidative decomposition catalyst A-2 was used, it was confirmed that the upstream side of the catalyst layer started to red heat 5 seconds after the start of the supply of the reaction gas, and the thermoelectric power inserted into the catalyst layer 1 minute after the start of the supply of the reaction gas. It was confirmed that the temperature of the pair reached 596 ° C., and the subsequent product gas contained hydrogen in a yield of 36%. At this time, the conversion rates of ammonia and oxygen were 70% and 100%, respectively.

In addition, when the ammonia oxidative decomposition catalyst A-2 was used, it was confirmed that the reaction could be restarted by introducing the reaction gas without performing external heating after the reaction was temporarily stopped, even after the fourth restart. It was confirmed that the same hydrogen yield as in the initial stage and the conversion rates of ammonia and oxygen were maintained.

In the case of using the ammonia oxidative decomposition catalyst A-3, it was confirmed that the upstream side of the catalyst layer started to red heat after 5 seconds from the start of the supply of the reaction gas, and one minute after the start of the supply of the reaction gas, The temperature of the pair reached 358 ° C., and it was confirmed that the subsequent product gas contained 45% hydrogen. At this time, the conversion rates of ammonia and oxygen were 79% and 100%, respectively.

As described above, it was found that according to the oxidative decomposition catalysts A-1 to A-3 of ammonia, a cold start of oxidative decomposition of ammonia was possible. As a mechanism for obtaining such an effect, the reduced carrier and Ru are oxidized by oxygen in the reaction gas, the catalyst layer temperature rises rapidly, reaches the combustion start temperature of ammonia, and further the combustion of ammonia. It is conceivable that the oxidative decomposition reaction of ammonia proceeds without heating from the outside by continuing the reaction due to heat generated by the reaction.

Example A-4
A reactor having the same configuration as that shown in FIG. 2 was prepared. The reactor has a cylindrical normal pressure fixed bed flow reactor having a diameter of 7 mm and a ceramic heat insulating material provided so as to surround a downstream portion from the catalyst layer of the vessel, and is partitioned by quartz wool. The downstream side of the catalyst layer is filled with α-Al ₂ O ₃ balls. A thermocouple that reaches the catalyst layer is provided inside the reaction apparatus, whereby the temperature of the catalyst layer can be measured. Further, the catalyst layer, quartz wool, and α-Al ₂ O ₃ balls can be heated by an electric furnace provided outside the reactor.

Hydrogen was produced by the following procedure using the oxidative decomposition catalyst A-1 of ammonia obtained in the same manner as in Example A-1 and the above reaction apparatus.

First, as a pretreatment, the catalyst layer filled with 0.2 g of catalyst was heated, and the catalyst was reduced by flowing hydrogen gas at room temperature (less than 25 ° C.) for 1 hour. Thereafter, the heating of the catalyst layer was stopped and purged with He. After the temperature of the catalyst layer was lowered to room _temperature, the reaction NH 3, and a reaction _{gas O 2} and He are mixed at a ratio of _NH 3 _/ O 2 _{/He=150/37.5/20.8(ml/} min) The product gas was supplied from the inlet of the apparatus at room temperature, and the generated gas was analyzed by GC-TCD (GC-8A, manufactured by Shimadzu Corporation).

It was confirmed that the product gas 30 minutes after the start of driving contained hydrogen with a yield of 63%. At this time, the conversion rates of ammonia and oxygen were 96% and 100%, respectively.

Further, it was confirmed that the reaction can be restarted without external heating by introducing a reaction gas after the reaction is temporarily stopped by purging with He and the catalyst layer is allowed to cool to room temperature. Moreover, it was confirmed that the same hydrogen yield as that of the initial stage and the conversion ratios of ammonia and oxygen were maintained even after the fourth restart, and repeated normal temperature startup was possible.

Also, it was confirmed that hydrogen can be produced even when the temperature in the pretreatment is changed to 25 ° C. or 100 ° C.

Example A-5
Production of hydrogen in the same manner as in Example A-4, except that ammonia oxidative decomposition catalyst A-2 obtained in the same manner as in Example A-2 was used instead of ammonia oxidative decomposition catalyst A-1. Went.

It was confirmed that hydrogen produced at a yield of 54% was contained in the product gas 30 minutes after the start of driving. At this time, the conversion rates of ammonia and oxygen were 87% and 100%, respectively.

Also, it was confirmed that hydrogen can be produced even when the temperature in the pretreatment is changed to 25 ° C.

(Example A-6)
The ammonia oxidative decomposition catalyst A-3 obtained in the same manner as in Example A-3 was used in place of the ammonia oxidative decomposition catalyst A-1, and the catalyst was reduced by flowing hydrogen gas at 200 ° C. for 1 hour. Except for the above, hydrogen was produced in the same manner as in Example A-4.

It was confirmed that the product gas 30 minutes after the start of driving contained hydrogen with a yield of 66%. At this time, the conversion rates of ammonia and oxygen were 99% and 100%, respectively.

(Example A-7)
Hydrogen was produced according to the following procedure using the ammonia oxidative decomposition catalyst A-1 obtained in the same manner as in Example A-1 and a reactor having the same configuration as in FIG.

First, as a pretreatment, the catalyst layer filled with 0.2 g of catalyst was heated, and helium gas was circulated at 200 ° C. for 0.5 hour. Thereafter, heating of the catalyst layer was stopped and purged with He. After the temperature of the catalyst layer was lowered to room _temperature, the reaction NH 3, and a reaction _{gas O 2} and He are mixed at a ratio of _NH 3 _/ O 2 _{/He=150/37.5/20.8(ml/} min) The product gas was supplied from the inlet of the apparatus at room temperature, and the generated gas was analyzed by GC-TCD (GC-8A, manufactured by Shimadzu Corporation).

It was confirmed that the product gas 30 minutes after the start of driving contained hydrogen with a yield of 62%. At this time, the conversion rates of ammonia and oxygen were 94% and 100%, respectively.

Example B-1
After impregnating a solution of Ru ₃ (CO) ₁₂ (Tanaka Kikinzoku Kogyo Co., Ltd.) in tetrahydrofuran with La ₂ O ₃ particles (prepared by precipitation and baked in air at 700 ° C. for 5 hours) The mixture was evaporated to dryness on a rotary evaporator, and supported so that the supported amount of Ru was 5% by mass based on the total mass of the catalyst. Next, the obtained impregnated product was heat-treated at 350 ° C. for 5 hours under a flow of He to obtain an ammonia oxidative decomposition catalyst B-1.

Example B-2
Instead of La ₂ O ₃ particles, MgO particles (manufactured by Ube Material (JRC-MgO-3), fired at 700 ° C. in air for 5 hours) were used in the same manner as in Example B-1. Thus, an oxidative decomposition catalyst B-2 of ammonia was obtained.

Example B-3
Instead of La ₂ O ₃ particles, Mg—Al oxide particles (hydrotalcite (Mg: Al = 3: 1), which is a clay-like compound, prepared by a precipitation method and calcined at 700 ° C. in air for 5 hours) Ammonia oxidative decomposition catalyst B-3 was obtained in the same manner as in Example B-1, except that was used.

A reaction apparatus having the same configuration as in FIG. 1 was prepared. The reactor has a cylindrical normal pressure fixed bed flow reactor having a diameter of 7 mm, and a ceramic heat insulating material provided so as to surround the vessel, and upstream of the catalyst layer partitioned by quartz wool. The side and downstream side are filled with α-Al ₂ O ₃ balls. A thermocouple that reaches the catalyst layer is provided inside the reaction apparatus, whereby the temperature of the catalyst layer can be measured. Further, the catalyst layer, quartz wool, and α-Al ₂ O ₃ balls can be heated by an electric furnace provided outside the reactor.

Hydrogen was produced by the following procedure using the above reactor. First, as a pretreatment, the catalyst layer filled with 0.2 g of catalyst was heated, and the catalyst was reduced by flowing hydrogen gas at 600 ° C. for 1 hour. Thereafter, the heating of the catalyst layer was stopped and purged with He. After the temperature of the catalyst layer was lowered to room _temperature, the reaction NH 3, and a reaction _{gas O 2} and He are mixed at a ratio of _NH 3 _/ O 2 _{/He=150/37.5/20.8(ml/} min) The product gas was supplied from the inlet of the apparatus at room temperature, and the generated gas was analyzed by GC-TCD (GC-8A, manufactured by Shimadzu Corporation).

Further, when the oxygen absorption amount of the pretreated catalysts B-1 to B-3 was measured, it was confirmed that oxygen was absorbed into the reduced Ru, and a part of Ru was reduced by the pretreatment. It was confirmed that As specific values, in the case of catalyst B-1, an oxygen absorption amount of 286 μmol / g was measured after the pretreatment, and a value of 58% with respect to the theoretical value of 495 μmol / g when all of Ru was reduced. Met.

When the ammonia oxidative decomposition catalyst B-1 was used, it was confirmed that the upstream side of the catalyst layer started to red heat after 5 seconds from the start of the supply of the reaction gas, and one minute after the start of the supply of the reaction gas, The temperature of the pair reached 515 ° C., and it was confirmed that the subsequent product gas contained 59% hydrogen. At this time, the conversion rates of ammonia and oxygen were 92% and 100%, respectively.

When the ammonia oxidative decomposition catalyst B-2 was used, it was confirmed that the upstream side of the catalyst layer started to red heat 5 seconds after the start of supply of the reaction gas, and the thermoelectric power inserted into the catalyst layer 2 minutes after the start of supply of the reaction gas. The temperature of the pair reached 338 ° C., and it was confirmed that the subsequent product gas contained 47% yield of hydrogen. At this time, the conversion rates of ammonia and oxygen were 80% and 100%, respectively.

In the case of using the ammonia oxidative decomposition catalyst B-3, it was confirmed that the upstream side of the catalyst layer started to red heat 5 seconds after the start of the reaction gas supply, and the thermoelectric power inserted into the catalyst layer 3 minutes after the start of the reaction gas supply. It was confirmed that the temperature of the pair reached 339 ° C., and the subsequent product gas contained hydrogen in a yield of 25%. At this time, the conversion rates of ammonia and oxygen were 58% and 100%, respectively.

As described above, according to the oxidative decomposition catalysts B-1 to B-3 of ammonia, it was found that cold start of oxidative decomposition of ammonia is possible. As a mechanism for obtaining such an effect, the reduced Ru is oxidized by oxygen in the reaction gas, the catalyst layer temperature rapidly increases, reaches the combustion start temperature of ammonia, and further due to the combustion reaction of ammonia. It is conceivable that the oxidative decomposition reaction of ammonia proceeds without heating from the outside as the reaction continues with exotherm.

Example B-4
A reactor having the same configuration as that shown in FIG. 2 was prepared. The reactor has a cylindrical normal pressure fixed bed flow reactor having a diameter of 7 mm and a ceramic heat insulating material provided so as to surround a downstream portion from the catalyst layer of the vessel, and is partitioned by quartz wool. The downstream side of the catalyst layer is filled with α-Al ₂ O ₃ balls. A thermocouple that reaches the catalyst layer is provided inside the reaction apparatus, whereby the temperature of the catalyst layer can be measured. Further, the catalyst layer, quartz wool, and α-Al ₂ O ₃ balls can be heated by an electric furnace provided outside the reactor.

Hydrogen was produced according to the following procedure using the ammonia oxidative decomposition catalyst B-1 obtained in the same manner as in Example B-1 and the above reaction apparatus.

First, as a pretreatment, the catalyst layer filled with 0.2 g of the catalyst was heated, and the catalyst was reduced by flowing hydrogen gas at 500 ° C. for 1 hour. Thereafter, the heating of the catalyst layer was stopped and purged with He. After the temperature of the catalyst layer was lowered to room _temperature, the reaction NH 3, and a reaction _{gas O 2} and He are mixed at a ratio of _NH 3 _/ O 2 _{/He=150/37.5/20.8(ml/} min) The product gas was supplied from the inlet of the apparatus at room temperature, and the generated gas was analyzed by GC-TCD (GC-8A, manufactured by Shimadzu Corporation).

It was confirmed that the product gas 30 minutes after the start of driving contained hydrogen with a yield of 63%. At this time, the conversion rates of ammonia and oxygen were 96% and 100%, respectively.

Example C-1
In a solution of Ru ₃ (CO) ₁₂ (Tanaka Kikinzoku Kogyo Co., Ltd.) dissolved in tetrahydrofuran, γ-Al ₂ O ₃ particles (Sumitomo Chemical Co., Ltd., high-purity alumina AKP-G15 (JRC-ALO-8)), Impregnated with 700 ° C. in air for 5 hours) and then evaporated to dryness in a rotary evaporator, and supported so that the supported amount of Ru becomes 5% by mass based on the total mass of the catalyst. Next, the obtained impregnated product was heat-treated at 350 ° C. for 5 hours under a flow of He to obtain an ammonia oxidative decomposition catalyst C-1.

Example C-2
An ammonia oxidative decomposition catalyst C-2 was obtained in the same manner as in Example C-1, except that SiO ₂ particles (AEROSIL 300, used unfired) were used instead of γ-Al ₂ O ₃ particles.

Example C-3
Instead of γ-Al ₂ O ₃ particles, SiO ₂ —Al ₂ O ₃ particles (manufactured by Catalyst Kasei Co., Ltd., IS-28E, used unfired) were used in the same manner as in Example C-1, An ammonia oxidative decomposition catalyst C-3 was obtained.

A reactor having the same configuration as that shown in FIG. 2 was prepared. The reactor has a cylindrical normal pressure fixed bed flow reactor having a diameter of 7 mm and a ceramic heat insulating material provided so as to surround a downstream portion from the catalyst layer of the vessel, and is partitioned by quartz wool. The downstream side of the catalyst layer is filled with α-Al ₂ O ₃ balls. A thermocouple that reaches the catalyst layer is provided inside the reaction apparatus, whereby the temperature of the catalyst layer can be measured. Further, the catalyst layer, quartz wool, and α-Al ₂ O ₃ balls can be heated by an electric furnace provided outside the reactor.

Hydrogen was produced by the following procedure using the above reactor. First, as a pretreatment, the catalyst layer filled with 0.2 g of catalyst was heated, and helium gas was circulated at 350 ° C. for 0.5 hour. Thereafter, the heating of the catalyst layer was stopped and purged with He. After the temperature of the catalyst layer was lowered to room _temperature, the reaction NH 3, and a reaction _{gas O 2} and He are mixed at a ratio of _NH 3 _/ O 2 _{/He=150/37.5/20.8(ml/} min) The product gas was supplied from the inlet of the apparatus at room temperature, and the generated gas was analyzed by GC-TCD (GC-8A, manufactured by Shimadzu Corporation).

When the ammonia oxidative decomposition catalyst C-1 was used, the temperature of the thermocouple inserted into the catalyst layer reached 359 ° C. 2 minutes after the start of the supply of the reaction gas. Was confirmed to be included. At this time, the conversion rates of ammonia and oxygen were 96% and 100%, respectively.

In addition, when the ammonia oxidative decomposition catalyst C-1 was used, it was confirmed that the reaction can be restarted by introducing the reaction gas without performing external heating after the reaction is temporarily stopped, even after the fourth restart. It was confirmed that the same hydrogen yield as in the initial stage and the conversion rates of ammonia and oxygen were maintained. Even when the catalyst touched the oxygen-containing gas and Ru was oxidized during the suspension of the reaction, restarting by introduction of the reaction gas without external heating was possible.

When the ammonia oxidative decomposition catalyst C-2 was used, the temperature of the thermocouple inserted into the catalyst layer reached 390 ° C. 2 minutes after the start of the supply of the reaction gas, and the yield of 58% in the subsequent product gas It was confirmed that hydrogen was contained. At this time, the conversion rates of ammonia and oxygen were 92% and 100%, respectively.

In the case of using the ammonia oxidative decomposition catalyst C-3, the temperature of the thermocouple inserted into the catalyst layer reached 330 ° C. 2 minutes after the start of the supply of the reaction gas, and the yield of 56% in the subsequent product gas It was confirmed that hydrogen was contained. At this time, the conversion rates of ammonia and oxygen were 89% and 100%, respectively.

As described above, it was found that according to the ammonia oxidative decomposition catalysts C-1 to C-3, cold start of oxidative decomposition of ammonia was possible. As a mechanism for obtaining such an effect, ammonia in the reaction gas is adsorbed on the acid point of the carrier, the temperature of the catalyst layer rapidly rises due to the heat of adsorption, reaches the combustion start temperature of ammonia, and further the ammonia It is conceivable that the oxidative decomposition reaction of ammonia proceeds without heating from the outside by continuing the reaction due to heat generated by the combustion reaction. Moreover, it is considered that the effect of reducing the combustion start temperature of ammonia by the above carrier also contributes to the cold start.

Example C-4
Except that an ammonia oxidative decomposition catalyst C-1 obtained in the same manner as in Example C-1 was prepared and provided with a cylindrical atmospheric pressure fixed bed flow reactor having a diameter of 9 mm, it was used in Example C-1. Hydrogen was produced by the following procedure using an apparatus having the same configuration as the reaction apparatus. First, as a pretreatment, the catalyst layer filled with 0.4 g of catalyst was heated, and a mixed gas of oxygen and helium (volume ratio O ₂ / He = 1/4) was circulated at 120 ° C. for 0.5 hour. Thereafter, the heating of the catalyst layer was stopped and purged with He. After the temperature of the catalyst layer was lowered to room _temperature, the reaction NH 3, and a reaction _{gas O 2} and He are mixed at a ratio of _NH 3 _/ O 2 _{/He=250/62.5/34.7(ml/} min) The product gas was supplied from the inlet of the apparatus at room temperature, and the generated gas was analyzed by GC-TCD (GC-8A, manufactured by Shimadzu Corporation).

2 minutes after starting the supply of the reaction gas, the temperature of the thermocouple inserted into the catalyst layer reached 342 ° C., and it was confirmed that the subsequent product gas contained 64% hydrogen. At this time, the conversion rates of ammonia and oxygen were 98% and 100%, respectively.

In addition, it was confirmed that the reaction can be restarted by introducing the reaction gas without performing external heating after the reaction is temporarily stopped, and the hydrogen yield and the conversion rates of ammonia and oxygen are the same after the fourth restart. Was confirmed to be maintained. Even when the catalyst touched the oxygen-containing gas and Ru was oxidized during the suspension of the reaction, restarting by introduction of the reaction gas without external heating was possible.

(Example C-5)
Hydrogen was produced by the following procedure using the ammonia oxidative decomposition catalyst C-1 obtained in the same manner as in Example C-1 and the reactor described above.

First, as a pretreatment, the catalyst layer filled with 0.2 g of catalyst was heated, and helium gas was circulated at 300 ° C. for 0.5 hour. Thereafter, the heating of the catalyst layer was stopped and purged with He. After the temperature of the catalyst layer was lowered to room _temperature, the reaction NH 3, and a reaction _{gas O 2} and He are mixed at a ratio of _NH 3 _/ O 2 _{/He=150/37.5/20.8(ml/} min) The product gas was supplied from the inlet of the apparatus at room temperature, and the generated gas was analyzed by GC-TCD (GC-8A, manufactured by Shimadzu Corporation).

It was confirmed that the product gas 30 minutes after the start of driving contained hydrogen with a yield of 63%. At this time, the conversion rates of ammonia and oxygen were 97% and 100%, respectively.

It was also confirmed that the reaction can be restarted without external heating by introducing a reaction gas after the reaction is temporarily stopped by purging with He and the catalyst layer is allowed to cool to room temperature. Moreover, it was confirmed that the same hydrogen yield as that of the initial stage and the conversion ratios of ammonia and oxygen were maintained even after the fourth restart, and repeated normal temperature startup was possible.

(Example C-6)
Except for using SiO ₂ —Al ₂ O ₃ particles calcined at 700 ° C. for 5 hours in air, the following oxidative decomposition catalyst of ammonia was obtained in the same manner as in Example C-3, and the following reaction apparatus was used. Hydrogen was produced according to the procedure.

First, as a pretreatment, the catalyst layer filled with 0.2 g of catalyst was heated, and helium gas was circulated at 300 ° C. for 0.5 hour. Thereafter, the heating of the catalyst layer was stopped and purged with He. After the temperature of the catalyst layer was lowered to room _temperature, the reaction NH 3, and a reaction _{gas O 2} and He are mixed at a ratio of _NH 3 _/ O 2 _{/He=150/37.5/20.8(ml/} min) The product gas was supplied from the inlet of the apparatus at room temperature, and the generated gas was analyzed by GC-TCD (GC-8A, manufactured by Shimadzu Corporation).

It was confirmed that the yield of 59% hydrogen was contained in the product gas 30 minutes after the start of driving. At this time, the conversion rates of ammonia and oxygen were 92% and 100%, respectively.

(Example C-7)
Hydrogen was produced by the following procedure using the ammonia oxidative decomposition catalyst C-1 obtained in the same manner as in Example C-1 and the reactor described above.

First, as a pretreatment, the catalyst layer filled with 0.2 g of catalyst was heated, and the catalyst was reduced by flowing hydrogen gas at 50 ° C. for 1 hour. Thereafter, the heating of the catalyst layer was stopped and purged with He. After the temperature of the catalyst layer was lowered to room _temperature, the reaction NH 3, and a reaction _{gas O 2} and He are mixed at a ratio of _NH 3 _/ O 2 _{/He=150/37.5/20.8(ml/} min) The product gas was supplied from the inlet of the apparatus at room temperature, and the generated gas was analyzed by GC-TCD (GC-8A, manufactured by Shimadzu Corporation).

It was confirmed that hydrogen produced at a yield of 64% was contained in the product gas 30 minutes after the start of driving. At this time, the conversion rates of ammonia and oxygen were 97% and 100%, respectively.

It was also confirmed that hydrogen can be produced even when the temperature in the pretreatment is changed to 400 ° C.

DESCRIPTION OF SYMBOLS 1, 2 ... Hydrogen production apparatus, 10 ... Reactor, 20 ... Catalyst layer, 30 ... Heat insulating material, 40 ... Partition material, 50 ... Inert filler.

Claims (14)

1. A catalyst having at least one metal selected from the group consisting of Ru, Co, Rh, Ir and Ni, and a carrier supporting the metal is brought into contact with a reaction gas containing ammonia and oxygen to bring the ammonia into contact. A method for producing hydrogen, characterized in that, when producing hydrogen by oxidative decomposition, an oxidative decomposition reaction of ammonia is initiated by utilizing heat generated by the catalyst.
2. The method for producing hydrogen according to claim 1, wherein the heat is obtained by contacting oxygen with the catalyst in which the metal and the support are in a reduced state.
3. 3. The method for producing hydrogen according to claim 2, wherein the carrier contains one or more oxides containing one or more elements selected from Ce, Zr and Pr.
4. The method for producing hydrogen according to claim 1, wherein the heat is obtained by bringing oxygen into contact with the catalyst in which the metal is in a reduced state.
5. 5. The method for producing hydrogen according to claim 4, wherein the carrier contains one or more oxides selected from the group consisting of La ₂ O ₃ , MgO and Mg—Al oxide.
6. The method for producing hydrogen according to any one of claims 1 to 5, wherein the catalyst is reduced by a product gas containing hydrogen produced from a reaction gas containing ammonia and oxygen.
7. The method for producing hydrogen according to claim 1, wherein the exotherm is obtained by contacting ammonia with the catalyst in a state where the carrier has an acid point.
8. 8. The hydrogen generation according to claim 7, wherein the exothermic heat is obtained by contacting ammonia with the catalyst having the support containing one or more oxides selected from the group consisting of Al ₂ O ₃ and SiO ₂ . Production method.
9. The method for producing hydrogen according to claim 7 or 8, wherein the catalyst is desorbed by heat of reaction of oxidative decomposition reaction of ammonia.
10. The hydrogen production according to any one of claims 7 to 9, wherein when the start and end of the oxidative decomposition reaction of ammonia is repeated, the catalyst at room temperature during the reaction comes into contact with oxygen. Method.
11. One or two or more metals selected from the group consisting of Ru, Co, Rh, Ir and Ni, and a carrier supporting the metal, wherein the carrier is selected from Ce, Zr and Pr. An ammonia oxidative decomposition catalyst comprising at least one oxide containing at least one kind of element.
12. One or more metals selected from the group consisting of Ru, Co, Rh, Ir and Ni, and a carrier supporting the metal, the carrier comprising La ₂ O ₃ , MgO and Mg—Al oxide. An ammonia oxidative decomposition catalyst comprising one or more oxides selected from the group.
13. One or more metals selected from the group consisting of Ru, Co, Rh, Ir and Ni, and a carrier supporting the metal, wherein the carrier is selected from the group consisting of Al ₂ O ₃ and SiO _2. A catalyst for oxidative decomposition of ammonia, comprising at least one oxide.
14. A hydrogen production apparatus comprising the ammonia oxidative decomposition catalyst according to any one of claims 11 to 13.

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