Catalyst, method for producing catalyst, and method for producing hydrogen and carbon using catalyst

Abstract

Provided is a catalyst for obtaining hydrogen and carbon by pyrolyzing hydrocarbon, the catalyst comprising a carrier containing alumina as a main component, and an iron oxide carried on the carrier, wherein, when the temperature of the catalyst is raised from 20°C to 1000°C at 10°C / min in a hydrogen atmosphere, the accumulative hydrogen consumption from 600°C to 1000°C is 50 or greater, assuming that the accumulative hydrogen consumption from 20°C to 1000°C is 100.

Description

Catalyst, catalyst manufacturing method, and catalyst-based hydrogen and carbon manufacturing method

[0001] The present invention relates to a catalyst, a method for producing a catalyst, and a method for producing hydrogen and carbon using a catalyst.

[0002] BACKGROUND ART Conventionally, a process for obtaining hydrogen and carbon by thermal decomposition of hydrocarbons using a catalyst has been known.

[0003] For example, Patent Document 1 discloses a catalyst for thermal decomposition of hydrocarbons that contains iron, rare earth elements, and aluminum.

[0004] Japanese Patent Application Laid-Open No. 2021-58848

[0005] However, there is room for improvement in the catalytic activity of conventional catalysts for thermal cracking.

[0006] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a highly active catalyst for obtaining hydrogen and carbon by thermal decomposition of hydrocarbons, a method for producing the same, and a method for producing hydrogen and carbon using the same.

[0007] [1] A catalyst for obtaining hydrogen and carbon by thermal decomposition of hydrocarbons, comprising a support mainly composed of alumina and iron oxide supported on the support, wherein, when the catalyst is heated from 20°C to 1000°C at a rate of 10°C / min under a hydrogen atmosphere, the cumulative hydrogen consumption from 600°C to 1000°C is 50 or more, where the cumulative hydrogen consumption from 20°C to 1000°C is 100. [2] The catalyst according to [1], when the catalyst is heated from 20°C to 1000°C at a rate of 10°C / min under a hydrogen atmosphere, has at least one hydrogen consumption peak in each of the temperature ranges from 300°C to 550°C and from 600°C to 1000°C. [3] The catalyst according to [1] or [2], wherein the alumina is α-alumina. [4] The catalyst according to any one of [1] to [3], wherein the iron oxide is iron(III) oxide. [5] The catalyst according to any one of [1] to [4], wherein the iron oxide contains 100 to 550 parts by mass of iron atoms per 100 parts by mass of aluminum atoms of the support. [6] The catalyst according to any one of [1] to [5], wherein the support is porous.

[0008] [7] A method for producing the catalyst according to any one of [1] to [6], comprising the steps of: mixing an aqueous solution containing iron ions with porous particles mainly composed of γ-alumina to obtain a mixture in which the porous particles are impregnated with the aqueous solution; drying the mixture to obtain a dried product; and calcining the dried product. [8] The method for producing the catalyst according to [7], wherein the calcination temperature is 500°C or higher.

[0009] [9] The method for producing a catalyst according to [7] or [8], wherein the aqueous solution containing iron ions is an aqueous solution of iron (III) nitrate.

[0010]

[10] A method for producing hydrogen and carbon, comprising a step of thermally decomposing a hydrocarbon using the catalyst according to any one of [1] to [6] above to obtain carbon and hydrogen.

[11] The method according to

[10] , wherein the hydrocarbon contains methane.

[12] The method according to claim 11, wherein the carbon contains carbon nanotubes.

[0011] According to the present invention, there are provided a highly active catalyst for obtaining hydrogen and carbon by thermal decomposition of hydrocarbons, a method for producing the same, and a method for producing hydrogen and carbon using the same.

[0012] 1 is a graph showing the results of measurements of hydrogen by a temperature-programmed reduction method in Examples and Comparative Examples, where (a) is a high-magnification TEM image of the carbon obtained in Example 1, and (b) is a low-magnification TEM image of the carbon obtained in Example 1.

[0013] (Catalyst) The catalyst according to an embodiment of the invention is a catalyst for obtaining hydrogen and carbon by thermal decomposition of hydrocarbons.

[0014] (Catalyst Composition) The catalyst according to this embodiment includes a support containing alumina as a main component and iron oxide supported on the support.

[0015] (Carrier) The term "alumina as the main component" means that the carrier is made of alumina (Al ２ O ３The amount of alumina in the support may be 70% by mass or more, 80% by mass or more, 90% by mass or more, 95% by mass or more, or 99% by mass or more.

[0016] The alumina constituting the support generally has a crystalline structure, and although there are no particular limitations on the crystalline structure, it may be, for example, γ-alumina or α-alumina. In particular, it is preferable that the alumina is α-alumina.

[0017] The components other than alumina in the carrier include, for example, silica (SiO ２ ) may be.

[0018] The support does not have to have pores, but it is preferable that the support has pores, that is, is porous.

[0019] (Iron oxide) The iron oxide is in the form of particles and is supported in the pores of the support and / or on the surface of the support. There is no particular limitation on the iron oxide, and examples thereof include iron (III) oxide (hematite: Fe ２ O ３ ), black iron oxide (magnetite: Fe ３ O ４ ), and iron (II) oxide (wustite: FeO).

[0020] Iron oxide is iron(III) oxide, i.e., Fe ２ O ３ The crystal structure of iron(III) oxide is not limited, and may be an α-phase, β-phase, or γ-phase.

[0021] There is no particular limitation on the average particle size of the iron oxide, but it is preferable that the crystallite size is 50 nm or less as measured by X-ray diffraction.

[0022] (Hydrogen reduction characteristics) When this catalyst is heated from 20°C to 1000°C at a rate of 10°C / min in a hydrogen atmosphere, the cumulative hydrogen consumption from 600°C to 1000°C is 50 or more, assuming that the cumulative hydrogen consumption from 20°C to 1000°C is 100.

[0023] This type of measurement is called the temperature programmed reduction method, and makes it possible to grasp the temperature characteristics of the hydrogen reduction reaction of iron oxide.

[0024] This catalyst can have at least one hydrogen consumption peak in the temperature ranges of 300°C to 550°C and 600°C to 1000°C when the temperature is increased from 20°C to 1000°C at a rate of 10°C / min in a hydrogen atmosphere.

[0025] (Amount of Iron Oxide Supported in Catalyst) The catalyst may contain 10 to 550 parts by mass of iron atoms per 100 parts by mass of aluminum atoms of the carrier.

[0026] (Operation and Effect) The catalyst according to this embodiment can enhance the activity of obtaining hydrogen and carbon by thermal decomposition of hydrocarbons. The reason for this is not clear, but the following is thought to be the reason.

[0027] In the catalyst according to this embodiment, iron oxide is supported on a carrier mainly composed of alumina, and the iron oxide has a stable structure that is not easily reduced by hydrogen unless the temperature is high, at least 600°C. This is thought to be why the active sites of the catalyst are less likely to be deactivated during the thermal decomposition of hydrocarbons.

[0028] (Method for Producing Catalyst) Next, an example of a method for producing the above catalyst will be described. The method for producing the catalyst according to this embodiment includes Step 1 of mixing an aqueous solution containing iron ions with porous particles mainly composed of γ-alumina to obtain a mixture in which the porous particles are impregnated with the aqueous solution, Step 2 of drying the mixture to obtain a dried product, and Step 3 of calcining the dried product.

[0029] (Step 1) In step 1, an aqueous solution containing iron ions is mixed with porous particles containing γ-alumina as a main component to obtain a mixture in which the porous particles are impregnated with the aqueous solution.

[0030] There is no particular limitation on the counter ions in the aqueous solution containing iron ions. Examples of counter ions include nitrate ions, chloride ions, sulfate ions, and acetate ions.

[0031] Specifically, an aqueous solution containing iron ions can be obtained by dissolving a water-soluble iron salt in water.

[0032] Examples of water-soluble iron salts are iron chloride, iron sulfate, iron nitrate, and iron acetate.

[0033] The iron ion is preferably iron(III) ion.

[0034] Among the above iron salts, iron(III) chloride, iron(III) sulfate, iron(III) nitrate, and iron(III) acetate are preferred. Among these, iron(III) nitrate is preferred, and iron(III) nitrate nonahydrate (Fe(NO)) is particularly preferred. ３ ) ３ ・9H ２ O) is preferred.

[0035] There are no particular limitations on the concentration of iron ions in the aqueous solution, but it can be, for example, 0.1 to 10 mol / L.

[0036] The porous particles contain γ-alumina as a main component. "Containing γ-alumina as a main component" means that the particles contain γ-alumina at a concentration of 50% by mass or more. The amount of γ-alumina may be 70% by mass or more, 80% by mass or more, 90% by mass or more, or 99% by mass or more. An example of another component is silica. The BET specific surface area of ​​the porous particles containing γ-alumina as a main component is 10 m ２ / g or more is preferable, and 100m ２ / g or more, and ２ / g or more.

[0037] The mixing method is not particularly limited, and stirring or the like may be used.

[0038] This produces a mixture in which porous particles mainly composed of γ-alumina are impregnated with an aqueous solution containing iron ions.

[0039] (Drying step) The mixture is then dried to obtain a dried product. The drying method is not particularly limited, and heat drying, vacuum drying, natural drying, or a combination of these methods may be used as appropriate. This produces an iron salt on the gamma-alumina support.

[0040] (Firing step) Subsequently, the dried product is fired. There are no limitations on the firing temperature, but from the viewpoint of converting the iron salt to iron oxide, it is preferably 500°C or higher, and from the viewpoint of suppressing excessive sintering reactions of iron oxide and alumina, it may be 1000°C or lower. There are no particular limitations on the time for which the firing temperature is maintained, but it can be 30 minutes to 6 hours.

[0041] The firing atmosphere is not particularly limited, but a non-reducing atmosphere, that is, an oxidizing atmosphere such as air, an inert atmosphere such as argon gas, or a vacuum atmosphere is preferred.

[0042] This makes it possible to obtain the above-mentioned catalyst.

[0043] (Method of Using the Catalyst) The obtained catalyst can be used as a catalyst for thermally decomposing hydrocarbons to obtain hydrogen and carbon.

[0044] Specifically, after the catalyst is filled into a vessel, a hydrocarbon is fed into the vessel. There are no particular limitations on the hydrocarbon, and methane or natural gas may be used.

[0045] There is no particular limitation on the temperature of the pyrolysis, ie, the catalyst temperature, but it may be 500 to 900°C.

[0046] There is no particular limitation on the pressure for pyrolysis, but it may be 0.1 to 5 MPa.

[0047] Pyrolysis of hydrocarbons produces hydrogen gas and solid carbon materials, which may be carbon fibers.

[0048] The catalyst may be in the form of a fixed bed or a fluidized bed.

[0049] The catalyst may be subjected to a pre-reduction treatment before contacting with hydrocarbons. The pre-reduction treatment is carried out by contacting the catalyst with a gas containing a reducing gas such as hydrogen at 400°C or higher.

[0050] Example 1 Catalyst A used in Example 1 was synthesized according to the following procedure.

[0051] 36.2 g of iron (III) nitrate nonahydrate (manufactured by Kanto Chemical Co., Inc.) was dissolved in 14.0 g of pure water, and then 5 g of a porous γ-alumina carrier (manufactured by Sumitomo Chemical Co., Ltd. (γ-alumina content 96 wt % and silica content 4 wt %)) was added to the solution, and the solution was kept at 80°C for 3 hours while stirring with a stirrer. The γ-alumina carrier was crushed in a mortar and then sieved with metal sieves having openings of 45 μm and 90 μm to separate the carrier into particle sizes ranging from 45 μm to 90 μm.

[0052] Thereafter, the solvent was evaporated using a rotary evaporator, and the resulting powder was placed in a polytetrafluoroethylene beaker and dried in an oil bath at 120° C. for 3 hours.

[0053] 24.2 g of the dried sample was placed on a porcelain dish and placed in a muffle furnace, and the temperature was increased from room temperature to 900° C. at a rate of 10° C. / min without introducing air from the outside, and then maintained at 900° C. for 5 hours. After cooling to room temperature, the solid matter was recovered, yielding 9.0 g of catalyst A.

[0054] The theoretical composition of catalyst A synthesized as described above was Fe:Al:Si:O=41.2:20.9:0.8:37.2 by mass percentage. When the structure of the catalyst was confirmed by X-ray diffraction (XRD), the main components were iron(III) oxide and α-alumina.

[0055] Using the obtained catalyst A, temperature programmed reduction measurements were carried out using hydrogen under the following conditions, and the cumulative hydrogen consumption between 600°C and 1000°C and the peak temperature of hydrogen consumption were calculated from the hydrogen consumption at each temperature, with the cumulative hydrogen consumption between 20°C and 1000°C being set at 100. The relationship between hydrogen consumption and temperature is shown in Figure 1.

[0056] Measurement by temperature-programmed reduction method using hydrogen Measurement was performed using a catalyst analyzer BELCAT-A Microtrack (manufactured by BEL Corporation) under the following conditions: Amount of catalyst sample: 50 mg Measurement conditions: Temperature increased from 20°C to 1000°C at a rate of 10°C / min Gas amount detection method: Hydrogen consumption detected with a quadrupole mass spectrometer Measurement atmosphere: 5% hydrogen and helium mixed gas supplied at 50 ml / min at normal pressure Detected fragment: m / z 2

[0057] X-ray Diffraction Method (XRD) Measurement was performed using an X-ray diffraction analyzer MiniFlex II (manufactured by Rigaku) ​​under the following conditions: X-ray tube: Cu-Kα, scan range: 10-90 deg, scan step: 0.04 deg

[0058] BET specific surface area: Measured using a BELSORP-mini manufactured by Japan BEL Co., Ltd. under the following treatment conditions. Pretreatment device: BELPREP-vac2 manufactured by Japan BEL Co., Ltd. Pretreatment conditions: 2 hours at 120°C, vacuum degassing Measurement conditions: Measurement of adsorption / desorption isotherm with nitrogen using a constant volume method. Adsorption temperature: 77K Adsorbate: Nitrogen Saturated vapor pressure: Actual measurement Adsorbate cross-sectional area: 0.162 nm ２ Sample amount: 50 mg

[0059] (Evaluation as a hydrocarbon thermal cracking catalyst) The synthesis reaction of hydrogen and carbon was carried out according to the following procedure. 0.05 g of catalyst A was dispersed in a 2.0 cm x 7.7 cm quartz sample dish and introduced into a quartz tube with a diameter of 36.0 cm. While flowing methane at a rate of 15 ml / min, the temperature was raised to 700°C from the outside using an electric furnace, and after the internal temperature reached 700°C, it was maintained for 6 hours. After the reaction, the solid matter in the reactor was collected and weighed. The weight increase obtained by subtracting the weight of catalyst A from the weight of the recovered solid matter was calculated as the produced carbon, and the weight ratio to the introduced catalyst A was calculated to be 14.7 (carbon-g / catalyst-g).

[0060] The results of TEM observation of the obtained carbon are shown in Figure 2. The obtained carbon had a carbon nanotube structure.

[0061] Example 2 Catalyst B used in Example 2 was synthesized according to the following procedure.

[0062] 36.2 g of iron (III) nitrate nonahydrate (Kanto Chemical Co., Ltd.) was dissolved in 14.0 g of pure water, and then the solution was mixed with a porous γ-alumina support (Mizusawa Chemicals Co., Ltd. (γ-alumina content 96 wt %, silica content 4 wt %, average particle diameter 45 μm, BET specific surface area 263 m)). ２ 5.0 g of 1.0 g of PEG-400 / g) was added, and the mixture was kept at 80° C. for 3 hours while stirring with a stirrer.

[0063] Thereafter, the solvent was evaporated using a rotary evaporator, and the resulting powder was placed in a polytetrafluoroethylene beaker and dried at 120° C. for 3 hours.

[0064] 34.0 g of the dried sample was placed in a quartz tubular furnace having an inner diameter of 36.0 cm, and the temperature was raised from room temperature to 900° C. while introducing air at a rate of 100 ml / min, and then maintained at 900° C. for 5 hours. After cooling to room temperature, the solid matter was recovered, yielding 11.6 g of catalyst B.

[0065] The theoretical composition of the catalyst B synthesized as described above was Fe:Al:Si:O=41.2:20.9:0.8:37.2 by mass percentage. When the structure of the catalyst was confirmed by XRD, the main components were iron(III) oxide and α-alumina.

[0066] Using the obtained catalyst B, a temperature-programmed reduction measurement using hydrogen was carried out under the same conditions as in Example 1. From the hydrogen consumption at each temperature, the cumulative hydrogen consumption between 600°C and 1000°C and the peak temperature of hydrogen consumption were calculated, assuming that the cumulative hydrogen consumption between 20°C and 1000°C was 100.

[0067] When a hydrocarbon cracking reaction was carried out using catalyst B under the same conditions as in Example 1, the ratio of the weight increase to the catalyst amount was 12.6 (carbon-g / catalyst-g).

[0068] Example 3 Catalyst C used in Example 3 was synthesized according to the following procedure.

[0069] 36.2 g of iron (III) nitrate nonahydrate (Kanto Chemical Co., Ltd.) was dissolved in 14.0 g of pure water, and the solution was then mixed with a porous γ-alumina support (Sumitomo Chemical Co., Ltd.) NKHO-24 (γ-alumina content 99.7 wt%, particle size range 45 to 90 μm, BET specific surface area 170 m ２ 5.0 g of 100% ammonium hydroxide (100% ammonium hydroxide / g) was added, and the mixture was stirred with a stirrer while being maintained at 80° C. for 3 hours. The alumina carrier was crushed in a mortar and then sieved with metal sieves having openings of 45 μm and 90 μm to separate carriers in the particle size range of 45 μm to 90 μm.

[0070] The solvent was then evaporated using a rotary evaporator, and the resulting powder was dried in a polytetrafluoroethylene beaker at 120° C. for 3 hours.

[0071] 22.8 g of the dried sample was placed on a porcelain dish and placed in a muffle furnace, and the temperature was increased from room temperature to 900° C. at a rate of 10° C. / min without introducing air from the outside, and then maintained at 900° C. for 5 hours. After cooling to room temperature, the solid matter was recovered, yielding 10.9 g of catalyst C.

[0072] The theoretical composition of catalyst C synthesized as described above was Fe:Al:Si:O=41.2:21.8:0.0:37.0 by mass percentage. When the structure of the catalyst was confirmed by XRD, the main components were iron(III) oxide and α-alumina.

[0073] Using the obtained catalyst, a temperature-programmed reduction measurement using hydrogen was carried out under the same conditions as in Example 1. From the hydrogen consumption at each temperature, the cumulative hydrogen consumption between 600°C and 1000°C and the peak temperature of hydrogen consumption were calculated, assuming that the cumulative hydrogen consumption between 20°C and 1000°C was 100.

[0074] When a hydrocarbon cracking reaction was carried out using catalyst C under the same conditions as in Example 1, the ratio of the weight increase to the catalyst amount was 7.5 (carbon-g / catalyst-g).

[0075] Example 4 Catalyst D used in Example 4 was synthesized according to the following procedure.

[0076] 36.2 g of iron (III) nitrate nonahydrate (Kanto Chemical Co., Ltd.) was dissolved in 14.0 g of pure water, and then the solution was mixed with a porous γ-alumina support (Sumitomo Chemical Co., Ltd. (γ-alumina content 99.99 wt %, particle size 100 μm or less, BET specific surface area 164 m)). ２5.0 g of 100% ethanol (1 / g) was added and stirred with a stirrer while maintaining the temperature at 80°C for 3 hours. Thereafter, the solvent was evaporated using a rotary evaporator. The obtained powder was dried in a polytetrafluoroethylene beaker at 120°C for 3 hours. 26.3 g of the dried sample was placed in a quartz tubular furnace with an inner diameter of 36.0 cm, and the temperature was raised from room temperature to 900°C while introducing air at a rate of 100 ml / min, and then maintained at 900°C for 5 hours. The mixture was cooled to room temperature, and the solid matter was recovered to obtain 10.7 g of catalyst D.

[0077] The theoretical composition of catalyst D synthesized as described above was Fe:Al:Si:O=41.2:21.8:0.0:37.0 by mass percentage. When the structure of the catalyst was confirmed by XRD, the main components were iron(III) oxide and α-alumina.

[0078] Using the obtained catalyst D, a temperature-programmed reduction measurement using hydrogen was carried out under the same conditions as in Example 1. From the hydrogen consumption at each temperature, the cumulative hydrogen consumption between 600°C and 1000°C and the peak temperature of hydrogen consumption were calculated, assuming that the cumulative hydrogen consumption between 20°C and 1000°C was 100.

[0079] When a hydrocarbon cracking reaction was carried out using catalyst D under the same conditions as in Example 1, the ratio of the weight increase to the catalyst amount was 7.9 (carbon-g / catalyst-g).

[0080] Example 5 Catalyst E used in Example 5 was synthesized according to the following procedure.

[0081] 36.2 g of iron (III) nitrate nonahydrate (manufactured by Kanto Chemical Co., Ltd.) was dissolved in 14.0 g of pure water, and then a porous high-purity γ-alumina support (manufactured by Mizusawa Chemical Industries, Ltd. (average particle size 45 μm, BET specific surface area 194 m)) was added to the solution. ２ The mixture was stirred with a stirrer at 80° C. for 3 hours.

[0082] Thereafter, the solvent was evaporated using a rotary evaporator, and the resulting powder was dried in a polytetrafluoroethylene beaker at 120° C. for 3 hours.

[0083] 28.6 g of the dried sample was placed in a quartz tubular furnace having an inner diameter of 36.0 cm, and the temperature was raised from room temperature to 900° C. while introducing air at a rate of 100 ml / min, and then maintained at 900° C. for 5 hours. After cooling to room temperature, the solid matter was recovered, yielding 11.5 g of catalyst E.

[0084] The theoretical composition of catalyst E synthesized as described above was Fe:Al:Si:O = 41.2:21.8:0.0:37.0 by mass percentage. Confirmation of the catalyst's crystal structure by XRD revealed that the main components were iron (III) oxide and α-alumina. Using the obtained catalyst, a temperature-programmed reduction measurement was performed using hydrogen under the same conditions as in Example 1, and the cumulative hydrogen consumption between 600°C and 1000°C and the peak hydrogen consumption temperature were calculated from the hydrogen consumption at each temperature, assuming that the cumulative hydrogen consumption between 20°C and 1000°C was 100.

[0085] When a hydrocarbon cracking reaction was carried out using catalyst E under the same conditions as in Example 1, the ratio of the weight increase to the catalyst amount was 4.7 (carbon-g / catalyst-g).

[0086] Comparative Example 1 Catalyst F used in Comparative Example 1 was synthesized according to the following procedure.

[0087] 0.74 g of iron (III) oxide (manufactured by Kanto Chemical Co., Inc.) and 0.51 g of a γ-alumina carrier (manufactured by Sumitomo Chemical Co., Ltd. (γ-alumina content 96 wt %, particle size range 45 μm to 90 μm) that had been classified using a metal sieve) were physically mixed to obtain 1.25 g of catalyst F. The γ-alumina carrier was crushed in a mortar and then sieved using metal sieves with openings of 45 μm and 90 μm to separate the carrier into particles in the particle size range of 45 μm to 90 μm. The theoretical composition of catalyst F synthesized as described above was Fe:Al:Si:O=41.2:20.9:0.8:37.2 by mass percentage.

[0088] The structure of the catalyst was confirmed by XRD, and the main components were iron (III) oxide and γ-alumina. Using the obtained catalyst F, a temperature-programmed reduction measurement using hydrogen was carried out under the same conditions as in Example 1. From the amount of hydrogen consumed at each temperature, the cumulative amount of hydrogen consumed from 600°C to 1000°C and the peak temperature of hydrogen consumption were calculated, assuming that the cumulative amount of hydrogen consumed between 20°C and 1000°C was 100.

[0089] The hydrocarbon cracking reaction was carried out using catalyst F under the same conditions as in Example 1, but the ratio of the weight ratio to the catalyst charge amount was less than 0.1 (carbon-g / catalyst-g).

[0090] (Comparative Example 2) A hydrocarbon decomposition reaction was carried out using dried red mud obtained after aluminum was extracted from bauxite as catalyst G. The red mud was dried by reducing the pressure to 7 cmHg in a vacuum dryer and maintaining it at 100°C for 3 hours, and then pulverized in a mortar.

[0091] The composition of catalyst G was, in mass percentage, Fe:Al:Si:O:Na=28.0:9.8:5.8:44.1:2.0. When the structure of the catalyst was confirmed by XRD, iron(III) oxide was observed, but a clear crystal structure derived from an alumina component was not observed.

[0092] A hydrocarbon cracking reaction was carried out using catalyst G under the same conditions as in Example 1, but the ratio of the weight ratio to the catalyst charge amount was less than 0.1 (carbon-g / catalyst-g). The results are summarized in Table 1.

[0093] (Comparative Example 3) Bauxite was crushed in a mortar and sieved through metal sieves with 45 μm and 90 μm openings to obtain a particle size range of 45 μm to 90 μm. Catalyst H was used to carry out a hydrocarbon cracking reaction. Catalyst H had a composition, in mass percentage, of Fe:Al:Si:O:Na=9.9:26.0:1.5:53.2:0.0. When the crystal structure of the catalyst was confirmed by XRD, iron (III) oxide and aluminum hydroxide were observed.

[0094] The hydrocarbon cracking reaction was carried out using catalyst H under the same conditions as in Example 1, but the weight ratio to the catalyst charge was less than 0.1 (carbon-g / catalyst-g).

[0095] The results are summarized in Table 1.

[0096]

Claims

1. A catalyst for obtaining hydrogen and carbon by thermal decomposition of hydrocarbons, comprising a carrier whose main component is alumina and iron oxide supported on said carrier, wherein when said catalyst is heated from 20°C to 1000°C at a rate of 10°C / min in a hydrogen atmosphere, when the cumulative hydrogen consumption from 20°C to 1000°C is taken as 100, the cumulative hydrogen consumption from 600°C to 1000°C is 50 or more.

2. The catalyst according to claim 1, which has at least one hydrogen consumption peak in the temperature ranges of 300°C to 550°C and 600°C to 1000°C when the catalyst is heated from 20°C to 1000°C at a rate of 10°C / min in a hydrogen atmosphere.

3. The catalyst according to claim 1 or 2, wherein the alumina is alpha-alumina.

4. The catalyst according to claim 1 or 2, wherein the iron oxide is iron(III) oxide.

5. The catalyst according to claim 1 or 2, wherein the iron oxide contains 100 to 550 parts by mass of iron atoms per 100 parts by mass of aluminum atoms of the support.

6. The catalyst according to claim 1 or 2, wherein the support is porous.

7. A method for producing a catalyst according to claim 1 or 2, comprising the steps of: mixing an aqueous solution containing iron ions with porous particles mainly composed of gamma-alumina to obtain a mixture in which the porous particles are impregnated with the aqueous solution; drying the mixture to obtain a dried product; and calcining the dried product.

8. The method for producing a catalyst according to claim 7, wherein the calcination temperature is 500° C. or higher.

9. The method for producing a catalyst according to claim 7, wherein the aqueous solution containing iron ions is an aqueous solution of iron (III) nitrate.

10. A method for producing hydrogen and carbon, comprising a step of thermally decomposing a hydrocarbon using the catalyst according to claim 1 or 2 to obtain carbon and hydrogen.

11. The method of claim 10, wherein the hydrocarbon comprises methane.

12. The method of claim 11, wherein the carbon comprises carbon nanotubes.

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