Treatment method and mixture

Abstract

To provide a treatment method capable of efficiently decomposing rubber in a short time and effectively utilizing the rubber, in particular, to provide a treatment method capable of efficiently producing hydrogen gas and solid carbon from a raw material containing the rubber in a short time, and to provide a mixture suitably used for producing the hydrogen gas and the solid carbon.SOLUTION: A treatment method of the present invention includes a hydrogen-carbon production step of irradiating a mixture of a raw material containing rubber and a catalyst containing an iron-based catalyst with microwaves to selectively heat and activate the iron-based catalyst, and decomposing the rubber in the presence of the iron-based catalyst to produce hydrogen gas and solid carbon.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a processing method and a mixture. [Background technology]

[0002] A wide variety of rubber products are used in a variety of fields. From the perspective of SDGs, attempts are being made to reuse various materials, but rubber materials are more difficult to reuse than other materials (e.g., metal, paper, plastic, etc.).

[0003] In order to solve such problems, a method has been proposed in which a rubber material is decomposed in a specific organic solvent in the presence of a specific acid (see, for example, Patent Document 1).

[0004] However, conventionally, rubber materials could not be decomposed efficiently in a short time, and it could not be said that they were being used effectively. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-70127 Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide a processing method that can efficiently decompose rubber in a short period of time and enable the effective use of rubber, and in particular to provide a processing method that can efficiently produce hydrogen gas and solid carbon from raw materials containing rubber in a short period of time, and to provide a mixture that can be suitably used to produce hydrogen gas and solid carbon. [Means for solving the problem]

[0007] Such an object can be achieved by the present invention described below. The treatment method of the present invention is characterized by comprising a hydrogen / carbon production step in which microwaves are applied to a mixture containing a raw material containing rubber and a catalyst containing an iron-based catalyst, thereby selectively heating and activating the iron-based catalyst, and decomposing the rubber in the presence of the iron-based catalyst to produce hydrogen gas and solid carbon.

[0008] In the present invention, the solid carbon preferably contains carbon black. In the present invention, the iron-based catalyst is FeAlO x It is preferable that the nanoparticles include nanoparticles represented by the formula:

[0009] In the present invention, the raw material preferably contains carbon black. In the present invention, the raw material preferably includes waste tires.

[0010] In the present invention, it is preferable that the raw material to be subjected to the hydrogen / carbon production step is one from which at least a portion of the metal material has been removed.

[0011] In the present invention, it is preferable that the mixture further contains at least one selected from the group consisting of polyhydric alcohol compounds, water, hydrates, and hydroxides.

[0012] In the present invention, the polyhydric alcohol compound is preferably at least one selected from the group consisting of cellulose, sucrose, and polyvinyl alcohol.

[0013] The present invention preferably further comprises a solid carbon separation step of separating the solid carbon from the iron-based catalyst by magnetic force.

[0014] The mixture of the present invention is a mixture used to produce hydrogen gas and solid carbon from a raw material containing rubber, The method is characterized by including the raw material, a catalyst including an iron-based catalyst, and at least one selected from the group consisting of a polyhydric alcohol compound, water, a hydrate, and a hydroxide. [Effects of the Invention]

[0015] According to the present invention, it is possible to provide a processing method that can efficiently decompose rubber in a short time and enable effective utilization of the rubber, in particular to provide a processing method that can efficiently produce hydrogen gas and solid carbon from raw materials containing rubber in a short time, and to provide a mixture that can be suitably used to produce hydrogen gas and solid carbon. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is a graph showing the composition ratio of the produced gas in the first cycle in Examples 1 to 4. [Figure 2] FIG. 2 is a graph showing the amount of gas produced in the first cycle in Examples 1 to 4. [Figure 3] FIG. 3 is a graph showing the composition ratio of the produced gas in the first cycle in Example 5. [Figure 4] FIG. 4 is a graph showing the amount of gas produced in the first cycle in Example 5. [Figure 5] FIG. 5 is a graph showing the Raman spectrum of the solid phase at the end of the first cycle in Example 1. [Figure 6] FIG. 6 is an SEM photograph of the solid phase at the end of the first cycle in Example 1. [Figure 7] FIG. 7 is a graph showing the amounts of gas produced in the first to third cycles in Example 1. As shown in FIG. [Figure 8] FIG. 8 is a graph showing the composition ratio of the produced gas in the first cycle in Example 1, the composition ratio of the produced gas in the first cycle when the same treatment as in Example 1 was performed except that the heating temperature (maximum temperature) was changed to 500°C, and the composition ratio of the produced gas in the first cycle when the same treatment as in Example 1 was performed except that the heating temperature (maximum temperature) was changed to 900°C. [Figure 9] FIG. 9 is a graph showing the amount of gas produced in the first cycle in Example 1, the amount of gas produced in the first cycle when the same process as in Example 1 was performed except that the heating temperature (maximum temperature) was changed to 500°C, and the amount of gas produced in the first cycle when the same process as in Example 1 was performed except that the heating temperature (maximum temperature) was changed to 900°C. [Figure 10] FIG. 10 is a photograph showing carbon black (left side in the figure) and bead wire (right side in the figure) obtained by separating the solid phase obtained in the first cycle in Example 5 using a ferrite magnet and then by sieving. DETAILED DESCRIPTION OF THE INVENTION

[0017] Preferred embodiments of the present invention will be described in detail below. It should be noted that the measurements and treatments described in this specification were carried out at room temperature (23°C) unless otherwise specified.

[0018] [1] Processing method The treatment method of the present invention is characterized by comprising a hydrogen / carbon production step in which microwaves are applied to a mixture containing a raw material containing rubber and a catalyst containing an iron-based catalyst, thereby selectively heating and activating the iron-based catalyst, and decomposing the rubber in the presence of the iron-based catalyst to produce hydrogen gas and solid carbon.

[0019] By irradiating a mixture containing a raw material including rubber and a catalyst including an iron-based catalyst with microwaves, it is possible to selectively heat a specific substance in the mixture, more specifically, the iron-based catalyst.

[0020] When heated by microwaves, the iron-based catalyst becomes more active as a catalyst, and heat conduction effectively heats the rubber in the mixture around the iron-based catalyst. When heated, the rubber undergoes thermal decomposition; in other words, the heat breaks the carbon-hydrogen bond, generating hydrogen and atomic carbon. This carbon precipitates and grows on the surface of the iron-based catalyst particles, generating solid carbon.

[0021] In particular, by selectively heating an iron-based catalyst with microwaves, a temperature difference is created between the catalyst portion and the surrounding rubber portion. In other words, the catalyst portion is hotter and the rubber portion is cooler than the catalyst portion. This temperature difference between the catalyst portion and the rubber portion creates a temperature non-equilibrium state, accelerating the thermal decomposition reaction of the rubber. This allows the thermal decomposition reaction of rubber to be carried out efficiently in a short period of time.

[0022] Microwaves can be used to directly heat the iron-based catalyst with electromagnetic energy, supplying the thermal energy required for the catalytic reaction and thereby accelerating the catalytic reaction. In particular, the temperature in the vicinity of the iron-based catalyst, where the rubber thermal decomposition reaction is likely to proceed, can be efficiently increased, while the temperature in the region away from the iron-based catalyst, where the rubber thermal decomposition reaction is less likely to proceed, can be prevented from being increased more than necessary, thereby improving the overall energy efficiency of the rubber thermal decomposition reaction. In other words, the total energy required to promote the rubber thermal decomposition reaction can be reduced. Furthermore, by directly and selectively heating the iron-based catalyst with microwaves, the temperature of the entire mixture can be kept lower than when the entire mixture is heated.

[0023] In addition, adjusting the microwave output and heating time makes it easier to control the temperature of the iron-based catalyst.

[0024] In addition, the application of microwave heating as a source of thermal energy will contribute significantly to reducing CO2 emissions during heating processes, i.e., decarbonization (carbon neutrality).

[0025] As described above, the processing method of the present invention can efficiently decompose raw materials containing rubber in a short time, and instead of disposing of them or simply recycling them as in the past, it is possible to obtain hydrogen gas, which is attracting attention as a fuel, and recover carbon (C) contained in the raw materials as a solid, thereby suppressing the emission of carbon dioxide, a substance that causes global warming.

[0026] The excellent effects of the present invention can be obtained by the processing method having the above-mentioned configuration, and cannot be obtained if the processing method does not have the above-mentioned configuration.

[0027] For example, if the catalyst does not contain an iron-based catalyst, even if the mixture is irradiated with microwaves, the catalyst cannot be selectively heated and activated, and the thermal decomposition reaction of the rubber cannot be sufficiently promoted.

[0028] Furthermore, for example, if the mixture is heated by a method other than microwave irradiation, the catalyst cannot be selectively heated and activated, and the thermal decomposition reaction of the rubber cannot proceed favorably.

[0029] Furthermore, if a catalyst other than an iron-based catalyst is used instead of an iron-based catalyst, the above-mentioned microwave-assisted catalytic reaction cannot be favorably promoted. For example, if a nickel-based catalyst is used instead of an iron-based catalyst, the catalyst cannot be selectively heated by microwaves, and the above-mentioned temperature non-equilibrium state cannot be favorably promoted. For example, even when a nickel-based catalyst is used, it is possible to heat the catalyst by placing a member made of a material that favorably absorbs microwaves (e.g., silicon carbide) in contact with the catalyst. However, in such a case, the catalyst is indirectly heated by heat conduction from the member, rather than being selectively or directly heated. Therefore, the above-mentioned temperature non-equilibrium state cannot be achieved, and therefore the above-mentioned temperature non-equilibrium state cannot be favorably promoted.

[0030] [1-1] Hydrogen and carbon generation process In the hydrogen and carbon production process, microwaves are applied to a mixture containing a raw material containing rubber and a catalyst containing an iron-based catalyst, selectively heating and activating the iron-based catalyst, and the rubber is decomposed in the presence of the iron-based catalyst to produce hydrogen gas and solid carbon.

[0031] [1-1-1]Mixture The mixture includes a raw material including rubber and a catalyst including an iron-based catalyst.

[0032] [1-1-1-1] Rubber-containing raw materials As the rubber, for example, various natural rubbers and synthetic rubbers can be used. Examples of rubber include diene rubber and non-diene rubber.

[0033] Examples of diene rubbers include isoprene rubber, butadiene rubber, acrylonitrile-butadiene rubber (NBR), chloroprene rubber (CR), butyl rubber (IIR), and styrene-isoprene-butadiene copolymer rubber (SIBR).

[0034] The isoprene-based rubber refers to a rubber containing units derived from isoprene as monomer units, and the butadiene-based rubber refers to a rubber containing units derived from butadiene as monomer units.

[0035] Examples of isoprene-based rubbers include natural rubber (NR), synthetic isoprene rubber (IR), modified natural rubber (modified NR), modified natural rubber (modified NR), and modified synthetic isoprene rubber (modified IR).

[0036] Examples of natural rubber (NR) include RSS#3 and TSR20 (for example, SIR20 and STR20).

[0037] The origin of natural rubber (NR) is not particularly limited, and examples thereof include those derived from Hevea brasiliensis, guayule, and Russian dandelion.

[0038] An example of synthetic isoprene rubber (IR) is IR2200. Examples of modified NR include deproteinized natural rubber (DPNR) and highly purified natural rubber (UPNR).

[0039] Examples of modified NR include epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), and grafted natural rubber.

[0040] Examples of modified IR include epoxidized synthetic isoprene rubber, hydrogenated synthetic isoprene rubber, and grafted synthetic isoprene rubber.

[0041] Examples of butadiene rubbers include butadiene rubber (BR) and aromatic vinyl compound-butadiene copolymer rubber (such as styrene-butadiene rubber (SBR)).

[0042] Examples of the butadiene rubber (BR) include high cis content butadiene rubber, low cis content butadiene rubber, and butadiene rubber containing syndiotactic polybutadiene crystals.

[0043] Examples of aromatic vinyl compound-butadiene copolymer rubbers (e.g., SBR) include emulsion-polymerized aromatic vinyl compound-butadiene copolymer rubbers (e.g., emulsion-polymerized styrene-butadiene rubber (E-SBR)), solution-polymerized aromatic vinyl compound-butadiene copolymer rubbers (e.g., solution-polymerized styrene-butadiene rubber (S-SBR)), and the like.

[0044] In the aromatic vinyl compound-butadiene copolymer rubber, examples of the aromatic vinyl compound (aromatic vinyl monomer) include styrene, vinylnaphthalene, and divinylnaphthalene.

[0045] Examples of non-diene rubbers include ethylene propylene diene rubber (EPDM), ethylene propylene rubber (EPM), and butyl rubber (IIR).

[0046] The rubber may be crosslinked or non-crosslinked. The rubber may be modified by, for example, introducing a functional group such as an amino group, an amide group, an isocyanate group, an imino group, an imidazole group, a urea group, an ammonium group, an imide group, a hydrazo group, an azo group, a diazo group, a carboxyl group, a nitrile group, a pyridyl group, an alkoxy group, a hydroxyl group, an oxy group, an epoxy group, an ether group, a carbonyl group, an oxycarbonyl group, a silyl group, an alkoxysilyl group, a mercapto group, a sulfide group, a disulfide group, a sulfonyl group, a sulfinyl group, or a thiocarbonyl group.

[0047] The rubber-containing raw material used in the present invention may suitably contain at least one of the above-mentioned materials.

[0048] The rubber-containing raw material used in the present invention is not particularly limited, but preferably includes waste rubber such as rubber products discarded after use, rubber dregs generated in the manufacturing process, and waste containing rubber as a main component.

[0049] Although some waste rubber has been recycled, products containing recycled waste rubber generally have inferior properties compared to those made with virgin resin materials and are not suitable for producing high-value-added products. Furthermore, waste rubber can sometimes contain relatively high levels of impurities, making the above-mentioned problems more pronounced. In contrast, the present invention can utilize waste rubber as a source of hydrogen gas, which is highly useful as a fuel that does not generate carbon dioxide and as a raw material for chemical synthesis, and as a raw material for solid carbon. Therefore, the effects of the present invention are more pronounced when the rubber-containing raw material used in the present invention contains waste rubber.

[0050] When using waste rubber as the rubber-containing raw material, it is preferable to subject the raw material to pretreatment, such as washing, removal of impurities, crushing, cutting, etc. This allows the thermal decomposition reaction of the rubber to proceed more efficiently.

[0051] The rubber-containing raw material may be contained in any form in the mixture. More specifically, the rubber-containing raw material may be contained in the mixture in the form of, for example, a sheet, a strip, a pellet, a powder, a fiber, a fabric, or the like.

[0052] The rubber content in the rubber-containing raw material is preferably 30% by mass or more, more preferably 40% by mass or more, and even more preferably 45% by mass or more.

[0053] This makes it possible to suppress the amount of undesired products produced and to suppress the amount of unreacted components remaining after carrying out the treatment method of the present invention.

[0054] The raw materials containing rubber may contain reinforcing materials such as carbon black and silica, and plastics.

[0055] It is particularly preferable that the raw materials containing rubber contain carbon black as a reinforcing material, since this promotes the production of solid carbon (particularly carbon black) in the hydrogen / carbon production step.

[0056] Furthermore, even if a reinforcing material other than carbon black (e.g., silica) is contained in the raw material containing rubber, the reinforcing material can be relatively easily separated from the solid carbon and iron-based catalyst produced after the hydrogen / carbon production process.

[0057] Furthermore, when plastics are contained in raw materials containing rubber, the plastics also function favorably as raw materials for hydrogen gas and solid carbon. Furthermore, many composite products of rubber and plastic, such as tires, are in circulation. According to the present invention, since rubber and plastics can be processed without separating them, waste products derived from such composite products can also be processed with excellent efficiency. Plastics will be described in detail later.

[0058] In the present invention, the raw material containing rubber is not particularly limited, but preferably contains waste tires.

[0059] For this reason, tires are distributed in particularly large quantities among various products containing rubber, and recycling them after disposal is a particular problem. Tires also contain components other than rubber, such as bead wires, making them particularly difficult to reuse. In contrast, the present invention can suitably process even such waste tires. In other words, the effects of the present invention are more pronounced when the rubber-containing raw material is waste tires.

[0060] It is preferable that at least a portion of the metal material has been removed in advance from the rubber-containing raw material to be subjected to the hydrogen / carbon production step.

[0061] This allows hydrogen gas and solid carbon to be purified more efficiently, and also makes it easier to purify solid carbon, for example.

[0062] The rubber content in the mixture is preferably 10% by mass to 90% by mass, more preferably 20% by mass to 80% by mass, and even more preferably 30% by mass to 70% by mass. This allows the desired reaction to proceed more efficiently.

[0063] [1-1-1-2] Catalyst The catalyst preferably comprises, and is preferably composed primarily of, an iron-based catalyst. This makes it possible to more significantly exhibit the above-described effects of the present invention.

[0064] In this specification, the term "mainly" refers to the component that has the highest content among the target components.

[0065] Iron-based catalysts have two main roles in the thermal decomposition of rubber: they function as a catalyst to decompose the constituent molecules of rubber on the surface, and as a heating element that effectively absorbs microwaves and converts their energy into heat.

[0066] This allows the entire mixture to heat faster and more uniformly, resulting in fewer by-products being generated from the thermal cracking reaction of the rubber.

[0067] The iron-based catalyst may be any catalyst containing Fe, but FeAlO x It is preferable that the nanoparticles include nanoparticles represented by the formula:

[0068] This allows the iron-based catalyst to be more selectively and more efficiently heated and activated by microwave irradiation, allowing the thermal decomposition reaction of rubber to proceed more favorably.

[0069] Furthermore, since the catalyst is nanoparticles, solid carbon grows from each nano-sized catalyst particle, so solid carbon can be produced efficiently even with a small amount of catalyst particles used. Furthermore, since nano-sized catalyst particles are used, the surface area per unit amount of catalyst particles used is large. Therefore, solid carbon can be produced efficiently.

[0070] Such FeAlO x The nanoparticles represented by the formula (I) can be synthesized by the sol-gel method using, for example, Fe(NO3)3·9H2O, Al(NO3)3·9H2O, and citric acid as raw materials.

[0071] In this specification, the term "nanoparticles" refers to particles having an average particle size of 1 nm to 100 nm, the average particle size being determined by dynamic light scattering.

[0072] The catalyst may be contained in the mixture in any form. More specifically, the catalyst may be contained in the mixture in the form of, for example, a sheet, a strip, a pellet, or a powder.

[0073] In the mixture, the ratio of the raw material containing rubber to the iron-based catalyst is, by mass, raw material containing rubber: catalyst (FeAlO x ) is preferably 1:2 or more and 6:2 or less.

[0074] This allows the entire mixture to be heated more quickly and more uniformly, and the thermal decomposition reaction of the rubber can proceed more favorably.

[0075] [1-1-1-3] Iron-based catalyst reduction inhibitor The mixture used in the treatment method of the present invention may contain a raw material containing rubber and a catalyst containing an iron-based catalyst, and may further contain an iron-based catalyst reduction inhibitor, which is at least one selected from the group consisting of polyhydric alcohol compounds, water, hydrates, and hydroxides. In other words, the mixture of the present invention (a mixture used to produce hydrogen gas and solid carbon from a raw material containing rubber) may contain the raw material, a catalyst containing an iron-based catalyst, and an iron-based catalyst reduction inhibitor, which is at least one selected from the group consisting of polyhydric alcohol compounds, water, hydrates, and hydroxides.

[0076] This provides the following effects: In other words, by heating the iron-based catalyst with microwaves, the temperature of the iron-based catalyst rises to several hundred degrees Celsius. x When a catalyst contains iron-based oxides such as those listed above, repeated microwave heating can reduce and even carbonize the iron-based oxides at high temperatures. If this phenomenon continues, the catalytic activity will decrease significantly.

[0077] In contrast, by adding at least one selected from the group consisting of polyhydric alcohol compounds, water, hydrates, and hydroxides to the mixture, the oxidation state of the iron-based catalyst can be favorably maintained, catalyst degradation can be suppressed, and catalytic activity can be stably maintained at an excellent level over a long period of time. Furthermore, the catalyst life is extended, which is advantageous in terms of cost. The following reasons are believed to be the reason for this effect. By adding at least one selected from the group consisting of polyhydric alcohol compounds, water, hydrates, and hydroxides to the mixture, oxygen atoms (O) are present around the iron-based oxide, preventing the thermal reduction of the iron-based oxide and maintaining the oxidation state. In particular, adding at least one selected from the group consisting of polyhydric alcohol compounds, hydrates, and hydroxides can stably exhibit the function of preventing reduction.

[0078] In particular, since polyhydric alcohols contain hydrogen atoms (H) and carbon atoms (C) as well as oxygen atoms (O), polyhydric alcohols themselves also function as raw materials for hydrogen gas and solid carbon, just like rubber.

[0079] In this specification, the term "polyhydric alcohol compound" refers to a compound having multiple alcoholic hydroxyl groups in the molecule, but does not include plastics, which will be described in detail later.

[0080] Typical examples of polyhydric alcohol compounds include sugars, polyphenols, and polyvinyl alcohol polymers. Examples of sugars include the monosaccharide glucose, the disaccharide sucrose, fructose, and maltose, the oligosaccharide raffinose and dextrin, and the polysaccharide cellulose, hemicellulose, starch, and pectin. Examples of polyphenols include catechin, persimmon tannin, and bituminous coal. Examples of polyvinyl alcohol polymers include polyvinyl alcohol and vinylon. One or a combination of two or more selected from these can be used, but at least one selected from the group consisting of cellulose, sucrose, and polyvinyl alcohol is preferred. This makes it possible to more significantly exhibit the above-mentioned effects.

[0081] Among polyhydric alcohols, cellulose is the main component of plant cell walls and plant fibers and is widely found in plant-derived materials, particularly in cotton, hemp, and wood, making it the most abundant biomass on Earth. Cellulose is also found in waste products made from plant-derived materials (e.g., paper products, building materials, etc.), inedible parts of plants such as grains and vegetables, food waste, and weeds. Effective utilization of this abundant cellulose is extremely important from the perspective of the SDGs and other goals.

[0082] As the raw material containing cellulose, it is preferable to use, for example, plants, products produced from plants, waste paper, livestock excrement, food waste, wood generated from construction, or waste containing sewage sludge.

[0083] This will reduce waste and CO2 emissions during waste incineration, thereby easing the burden on the environment.

[0084] When using the above waste materials as a raw material containing cellulose, it is preferable to subject the raw material to pretreatment, such as washing, removal of impurities, and cutting. This allows the thermal decomposition reaction of cellulose to proceed more efficiently.

[0085] The cellulose-containing raw material may contain components other than cellulose as a chemical substance (compound), such as hemicellulose and lignin.

[0086] For example, when wood is used as a raw material containing cellulose, the wood contains hemicellulose and lignin in addition to cellulose, which is the main component.

[0087] Hemicellulose is not a single compound, but a general term for polysaccharides extracted from plants with alkali, and has a more complex structure than cellulose. Hemicellulose binds cellulose fibers and mediates the bond with lignin.

[0088] Although the details of lignin are not fully understood, it has a very complex chemical structure. Lignin is the main component of wood and acts as an adhesive between cells.

[0089] In a raw material containing cellulose and lignin, if the proportion of cellulose is high, the amount of hydrogen gas produced increases but the amount of solid carbon produced decreases, whereas if the proportion of lignin is high, the amount of solid carbon produced increases but the amount of hydrogen gas produced decreases.

[0090] In this way, by adjusting the ratio of cellulose to lignin, it is possible to adjust the ratio of hydrogen gas and solid carbon produced.

[0091] More specifically, for example, by using chemical pulp (including waste paper, etc.) from which lignin has been removed by refining as a raw material containing cellulose, and applying the processing method of the present invention, hydrogen gas can be obtained more efficiently.

[0092] Furthermore, solid carbon can be obtained more efficiently by mixing lignin removed during the chemical pulp production process with raw materials with a high cellulose content, such as wood, waste paper, and scraps of paper products, to produce a mixture with an increased lignin content. In particular, although some of the lignin removed during the chemical pulp production process is used as fuel (lignin-containing waste liquid), as a raw material for vanillin flavoring, or as a component of adhesives, it cannot be said that it is being fully utilized. It would be a great advantage if such lignin could be suitably utilized to produce solid carbon with higher added value (e.g., carbon black, carbon nanotubes, etc.).

[0093] When the cellulose-containing raw material also contains lignin, the mass ratio of cellulose:lignin is preferably 75:25 or more and 25:75 or less.

[0094] This makes it possible to make both the amount of hydrogen gas produced and the amount of solid carbon produced suitable.

[0095] The cellulose-containing raw material may be contained in any form in the mixture. More specifically, the cellulose-containing raw material may be contained in the mixture in the form of, for example, a sheet, a strip, a pellet, a powder, or the like. The cellulose-containing raw material may also be contained in a defibrated state.

[0096] When the mixture used in the treatment method of the present invention contains cellulose, the ratio of cellulose to rubber is preferably cellulose:rubber=40:60 or more and 60:40 or less by mass ratio.

[0097] This makes it possible to make the above-mentioned effects more pronounced, and in particular to improve the amount of solid carbon produced.

[0098] By including water in the mixture, for example, carbon adhering to the catalyst surface can be removed, keeping the catalyst surface clean and extending its life.

[0099] In particular, by including water in the mixture together with the polyhydric alcohol compound as described above, the evaporation of water during microwave heating can be effectively suppressed, and the above-mentioned effects can be more significantly exhibited.

[0100] Examples of the hydrates include iron(III) oxide monohydrate. Examples of the hydroxide include iron (II) hydroxide, iron (III) hydroxide, and aluminum hydroxide, and one or more selected from these can be used in combination.

[0101] The polyhydric alcohol compound, hydrate, and hydroxide may be contained in the mixture in any form, more specifically, the polyhydric alcohol compound, hydrate, and hydroxide may be contained in the mixture in the form of, for example, a sheet, a strip, a pellet, a powder, or a fiber.

[0102] Rubber typically contains less oxygen atoms (O) than iron-based catalyst reduction-inhibitors. Therefore, when the rubber content in the mixture used in the treatment method of the present invention is high, reduction of the iron-based catalyst, in other words, deterioration of the iron-based catalyst, is more likely to proceed, and the effect of using an iron-based catalyst reduction-inhibitor is more pronounced.

[0103] More specifically, when the rubber content in the mixture used in the treatment method of the present invention is 40% by mass or more, the effect of using an iron-based catalyst reduction inhibitor is more pronounced.

[0104] In the mixture, the mass ratio of the rubber-containing raw material to the iron-based catalyst reduction inhibitor is preferably rubber-containing raw material:iron-based catalyst reduction inhibitor=25:75 or more and 75:25 or less. This makes the above-mentioned effects more pronounced.

[0105] [1-1-1-4] Plastic The mixture used in the treatment method of the present invention may further contain a plastic.

[0106] This allows, for example, the production ratio of hydrogen gas and solid carbon to be more suitably adjusted. Similarly to rubber, plastics are also materials for which effective utilization is desired. Therefore, by subjecting a material containing plastics together with rubber to the treatment method of the present invention, both can be treated simultaneously, which is more suitable.

[0107] Examples of plastics include polyethylenes such as low-density polyethylene, linear polyethylene, medium-density polyethylene, high-density polyethylene, and very low-density polyethylene; polypropylenes such as random copolymer polypropylene, block copolymer polypropylene, and homopolypropylene; polyolefin resins such as polybutene, polybutadiene, and polymethylpentene; ionomers such as ethylene-vinyl acetate copolymers, zinc ion crosslinkers, and sodium ion crosslinkers; olefin copolymers such as ethylene-(meth)acrylic acid copolymers, ethylene-(meth)acrylic acid ester (random, alternating) copolymers, ethylene-propylene copolymers, ethylene-butene copolymers, and ethylene-hexene copolymers; polyester resins such as polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, and polybutylene naphthalate; polyurethanes; polyimides; polyamides; polyether ketones such as polyether ether ketones; polyethersulfones; and polystyrenes. Examples of suitable materials include fluororesins such as poly(tetrafluoroethylene) homopolymer (PTFE), poly(hexafluoroethylene), poly(tetrafluoroethylene-hexafluoroethylene), and poly(tetrafluoroethylene-ethylene-propylene); chlorinated resins such as chlorinated polyethylene, chlorinated polypropylene, chlorinated ethylene-propylene copolymer, polyvinyl chloride, and polyvinylidene chloride; thermoplastic resins such as acrylonitrile-butadiene-styrene copolymer (ABS resin), silicone resin, cellulose resin, (meth)acrylic resin, polyester-based thermoplastic elastomer, polyvinyl isoprene, polycarbonate, polyacetal, polyphenylene oxide, and polyphenylene sulfide; and thermosetting resins such as polyimide resin, polyamide resin, epoxy resin, phenolic resin, amino resin, unsaturated polyester resin, cation exchange resins mainly containing sulfonic acid groups, Nafion, anion exchange resins mainly containing quaternary ammonium groups, and thermosetting elastomers. Biomass-derived plastics are also acceptable. As the plastic, at least one of the above can be suitably used.

[0108] When the mixture used in the present invention contains a plastic, the plastic preferably contains at least one selected from the group consisting of polyolefin resin, polyester resin, polycarbonate, and phenol resin. This makes it possible to more suitably obtain hydrogen gas and carbon nanotubes.

[0109] In particular, when the mixture used in the present invention contains a polyolefin resin, since the polyolefin resin does not contain oxygen O as a constituent element, when the reaction is carried out in an atmosphere that is substantially free of oxygen (for example, an atmosphere in which the oxygen partial pressure is 0.1 kPa or less), it is possible to suitably prevent carbon C from being emitted as a greenhouse gas, and to produce a larger number of carbon nanotubes.

[0110] When the mixture used in the present invention contains a polyester resin, oxygen O is contained in the constituent elements, and therefore the carbonization reaction and reduction reaction of the iron-based catalyst can be suitably prevented, and the catalytic activity can be suitably maintained for a longer period of time.

[0111] Furthermore, when the mixture used in the present invention contains polycarbonate, oxygen O is included as a constituent element, and therefore, the carbonization reaction and reduction reaction of the iron-based catalyst can be suitably prevented, and the catalytic activity can be suitably maintained for a longer period of time.

[0112] Furthermore, when the mixture used in the present invention contains a thermosetting resin, the following effects can be obtained. That is, thermosetting resins are more difficult to recycle than thermoplastic resins, and have traditionally been incinerated or disposed of in landfills. However, in the present invention, even when a thermosetting resin is used as the plastic, hydrogen gas and carbon nanotubes can be efficiently produced. In other words, since the present invention can effectively utilize even thermosetting resins, the effects of the present invention are more pronounced when the mixture used in the present invention contains a thermosetting resin.

[0113] In particular, when the mixture used in the present invention contains a phenolic resin, oxygen O is included in the constituent elements, so that the carbonization reaction and reduction reaction of the iron-based catalyst can be suitably prevented, and the catalytic activity can be suitably maintained for a longer period of time.

[0114] The mixture used in the present invention is not particularly limited, but preferably contains waste plastics such as plastic products discarded after use, plastic dregs generated during the manufacturing process, and waste containing plastic as the main component.

[0115] Although some waste plastics have been recycled, products containing recycled waste plastics generally have inferior properties compared to those made from virgin resin materials and are not suitable for producing high-value-added products. Furthermore, waste plastics can sometimes contain relatively high levels of impurities, making the above-mentioned problems more pronounced. In contrast, the present invention enables waste plastics to be used as a raw material for high-value carbon nanotubes and hydrogen gas, which is highly useful as a carbon dioxide-free fuel and a raw material for chemical synthesis.

[0116] The plastic may be contained in the mixture in any form. More specifically, the plastic may be contained in the mixture in the form of, for example, a sheet, a strip, a pellet, a powder, a fiber, a fabric, or the like.

[0117] The content of plastic in the mixture is preferably 1% by mass or more and 60% by mass or less, more preferably 2% by mass or more and 50% by mass or less, and even more preferably 3% by mass or more and 40% by mass or less. This makes the above-mentioned effects more pronounced.

[0118] [1-1-1-5] Other ingredients The mixture may also contain components other than those mentioned above. However, the content of components other than those mentioned above in the mixture used in the treatment method of the present invention is preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 3% by mass or less.

[0119] [1-1-2] Microwave When the mixture is irradiated with microwaves, the iron-based catalyst contained in the mixture is directly and selectively heated and activated.

[0120] By using microwaves, it is not necessary to heat the entire reaction vessel in which the reaction is carried out to a high temperature, which makes it possible to simplify the process and the equipment and make them less expensive, and also allows for more efficient use of energy, which is preferable from the viewpoints of energy conservation and reducing the environmental load.

[0121] The frequency of microwaves is generally between 300 MHz and 300 GHz, but it is preferable to use a frequency band permitted for industrial use as the ISM band (Industrial Scientific and Medical Band), and the peak frequency is preferably between 900 MHz and 30 GHz, more preferably between 2.40 GHz and 2.50 GHz, and even more preferably 2.45 GHz.

[0122] This makes it possible to suppress deterioration of the iron-based catalyst due to heat, while also allowing the catalyst to be sufficiently heated and activated, allowing the thermal decomposition reaction of rubber and the like to proceed more efficiently.

[0123] The microwave output per unit mass of the mixture is preferably 10 W / g or more and 1500 W / g or less, more preferably 100 W / g or more and 850 W / g or less, and even more preferably 300 W / g or more and 750 W / g or less.

[0124] This makes it possible to suppress deterioration of the iron-based catalyst due to heat, while also allowing the catalyst to be sufficiently heated and activated, allowing the thermal decomposition reaction of rubber and the like to proceed more efficiently.

[0125] The heating time using microwaves is preferably from 30 seconds to 30 minutes, more preferably from 1 minute to 20 minutes, and even more preferably from 3 minutes to 10 minutes.

[0126] The temperature of the mixture during microwave irradiation is preferably 100°C or higher and 1300°C or lower, more preferably 300°C or higher and 1000°C or lower, and even more preferably 400°C or higher and 900°C or lower.

[0127] This makes it possible to sufficiently heat and activate the iron-based catalyst while suppressing thermal degradation of the catalyst, allowing the thermal decomposition reaction of rubber and the like to proceed more efficiently, improving the yield of hydrogen and solid carbon, and more effectively preventing a decrease in productivity of hydrogen and solid carbon due to an unnecessarily long treatment time.

[0128] The mixture may be irradiated with microwaves in either single mode or multimode, but multimode irradiation is preferred.

[0129] Compared with single-mode microwave irradiation, multi-mode microwave irradiation allows for easier catalyst temperature management and microwave output control, making it easier to maintain stable thermal decomposition reactions of rubber, etc. Furthermore, multi-mode microwave irradiation allows for the processing of many mixtures at once, and also makes the mixtures and products easier to handle.

[0130] Furthermore, when flammable gas such as hydrogen and solid carbon are produced, if the atmosphere contains oxidizing gases such as air and oxygen, the quality and yield of the product will decrease until the oxygen is consumed by the combustion reaction. Therefore, it is preferable to irradiate the mixture with microwaves in an inert gas atmosphere, such as nitrogen, helium, neon, argon, or carbon dioxide.

[0131] This allows the growth of solid carbon to proceed smoothly, and also makes it possible to easily recover the hydrogen gas and solid carbon as products from the residue after the reaction.

[0132] Microwave irradiation may be carried out in multiple steps. In such a case, it is preferable that the sum of the times of the multiple microwave treatments satisfies the above-mentioned condition for the microwave heating time.

[0133] Furthermore, the microwave irradiation conditions (for example, microwave frequency, output, mode, and atmosphere during microwave irradiation) may be changed midway.

[0134] For example, when irradiating the mixture with microwaves, the microwave irradiation conditions may be constant, or the microwave irradiation conditions may be controlled so that the temperature rise rate and heating temperature of the mixture are constant.

[0135] Furthermore, the mixture may be subjected to a treatment such as stirring during microwave irradiation or between multiple microwave irradiation treatments.

[0136] [1-2] Solid carbon separation process The treatment method of the present invention is sufficient as long as it includes at least the hydrogen and carbon production step described above, but may further include other steps.

[0137] Specifically, it is preferable to further include a solid carbon separation step of separating solid carbon from the iron-based catalyst by magnetic force.

[0138] This allows the solid carbon and the iron-based catalyst to be suitably separated, and the unintended incorporation of the iron-based catalyst into the recovered solid carbon can be suitably prevented, resulting in solid carbon with a low impurity content. As a result, the separated solid carbon and iron-based catalyst can each be suitably utilized. More specifically, the separated solid carbon can be suitably utilized as a high-purity industrial product or a raw material thereof, and the separated iron-based catalyst can be suitably utilized again in the above-mentioned hydrogen / carbon production process.

[0139] In this step, for example, a permanent magnet such as a ferrite magnet or a neodymium magnet may be used, or an electromagnet may be used.

[0140] Furthermore, when the solid obtained after the hydrogen / carbon production step contains solid components other than the solid carbon and the iron-based catalyst (hereinafter also referred to as "other solid components"), in this step, the solid carbon may be separated not only from the iron-based catalyst but also from the other solid components.

[0141] [1-3] Other processes The processing method of the present invention may include steps other than those described above.

[0142] For example, when the treatment method of the present invention includes the above-mentioned solid carbon separation step, if the solid obtained after the hydrogen-carbon production step contains other solid components, the treatment method may include a step of separating the other solid components from the solid carbon and the iron-based catalyst before the solid carbon separation step, or may include a step of separating the other solid components from the solid carbon or the iron-based catalyst after the solid carbon separation step. In other words, the other solid components may be separated from the solid carbon-iron-based catalyst in a step different from the solid carbon separation step.

[0143] Furthermore, the residue remaining in the reaction vessel after the hydrogen and carbon production step may be washed with an acid or the like.

[0144] This allows the solid carbon to be suitably recovered. In particular, by performing acid washing, catalyst particles adhering to the outside of the solid carbon can be easily and reliably dissolved and removed, thereby increasing the purity of the solid carbon.

[0145] Furthermore, when the solid carbon produced by the treatment method of the present invention contains single-walled carbon nanotubes as described below, the purity of the single-walled carbon nanotubes can be suitably increased by using an organic solvent such as N-methyl-2-pyrrolidone (NMP) or benzene.

[0146] [2] Product Next, the product obtained by the treatment method of the present invention will be described.

[0147] The products obtained by the treatment method of the present invention include a product gas containing hydrogen gas and solid carbon. Because the produced hydrogen is gaseous and the solid carbon is solid, they can be suitably separated and recovered without complex treatment.

[0148] [2-1] Solid carbon The solid carbon obtained by the treatment method of the present invention may be any solid carbon material, and examples thereof include amorphous carbon material such as carbon black, crystalline carbon material such as graphite, diamond, fullerene, carbon nanotube (including Ketjenblack), carbon nanofiber, and carbon nanohorn.

[0149] In particular, the solid carbon obtained by the treatment method of the present invention preferably contains carbon black.

[0150] The present invention makes it possible to obtain high-quality carbon black having the same shape and size as commercially available carbon black. Carbon black is a material that is widely used as a pigment and is in high demand.

[0151] When the solid carbon obtained by the treatment method of the present invention is carbon black, the average particle size of the carbon black is preferably 5 nm or more and 1000 nm or less, more preferably 10 nm or more and 700 nm or less, and even more preferably 15 nm or more and 500 nm or less.

[0152] Carbon black having an average particle size within this range is in particularly high demand. Furthermore, when the average particle size of the carbon black obtained in the present invention is within the above range, the particle size distribution is very sharp, and high-quality carbon black can be obtained.

[0153] In this specification, the average particle size refers to the median diameter (D50 value of cumulative 50% frequency) unless otherwise specified. The average particle size can be determined, for example, by measurement using a Microtrac UPA (manufactured by Nikkiso Co., Ltd.).

[0154] When the solid carbon obtained by the treatment method of the present invention is carbon black, the carbon black is preferably substantially spherical.

[0155] Nearly spherical carbon black is in particularly high demand. Furthermore, when the carbon black obtained in the present invention is nearly spherical, the particle size distribution is very sharp, and high-quality carbon black can be obtained.

[0156] The solid carbon obtained by the processing method of the present invention may contain carbon nanotubes. Carbon nanotubes are seamless cylindrical materials made from graphene. Generally, single-walled carbon nanotubes are those with a single layer of cylinder, while multi-walled carbon nanotubes are those with multiple cylinders of different diameters stacked in layers.

[0157] When the solid carbon obtained by the processing method of the present invention contains carbon nanotubes, the carbon nanotubes preferably include single-walled carbon nanotubes.

[0158] Single-walled carbon nanotubes have been attracting attention as an extremely superior material, exhibiting significantly higher performance than multi-walled carbon nanotubes, for example, being lightweight with a density half that of aluminum, yet 20 times stronger than steel, 10 times more thermally conductive than copper, and 1,000 times more electrically conductive than copper. For example, single-walled carbon nanotubes are highly transparent and have excellent electrical conductivity, making them suitable for use in transparent conductive films, etc.

[0159] Furthermore, such single-walled carbon nanotubes are soluble in organic solvents such as N-methyl-2-pyrrolidone (NMP) and benzene, and can therefore be easily extracted and purified from a product obtained as a mixture of multiple compounds.

[0160] This makes it possible to obtain single-walled carbon nanotubes of higher purity and better quality, and thus makes them even more valuable.

[0161] According to the present invention, as described above, by optimizing the various conditions in the treatment method, it is possible to obtain such high-quality single-walled carbon nanotubes in high yield.

[0162] [2-2] Produced gas The product gas obtained by the treatment method of the present invention contains hydrogen gas (H2).

[0163] The product gas obtained by the treatment method of the present invention may contain other gas components in addition to hydrogen gas. Such gas components include, for example, carbon monoxide gas (CO).

[0164] Hydrogen gas can be suitably used, for example, as a clean fuel that does not emit carbon dioxide. Hydrogen can also be suitably used, for example, as a reducing agent or a raw material for various chemical syntheses.

[0165] Carbon monoxide gas can also be suitably used as a raw material for synthesizing chemical products such as alcohols and carboxylic acids, and plastics such as polycarbonate.

[0166] Hydrogen and carbon monoxide may also be used in applications such as SynGas, methanation, etc.

[0167] SynGas is a mixture of hydrogen and carbon monoxide, and is a basic feedstock in C1 chemistry, as well as being used as jet fuel and fuel for power generation.

[0168] Methanation is a technology that synthesizes methane (CH4) by reacting carbon monoxide with hydrogen, and can be carried out using conventional natural gas facilities as is.

[0169] The gas components contained in the produced gas may be separated as needed. Examples of methods for separating the gas components contained in the produced gas include cryogenic separation, adsorption separation, and membrane separation.

[0170] Cryogenic separation is a method of fractionating a mixed gas by cooling it to a low temperature of around -200°C. With cryogenic separation, since the boiling points of each gas component in the mixed gas are different (H2: -252.9°C, CO: -191.5°C), multiple gas components can be separated and recovered.

[0171] Adsorption separation is a method of removing specific gas components (for example, carbon monoxide gas) using a porous adsorbent, and can be carried out by a relatively simple process. Examples of porous adsorbents include activated carbon, zeolite, and metal catalysts.

[0172] Furthermore, the pressure swing adsorption (PSA) method makes it possible to concentrate and extract specific gas components (such as carbon monoxide gas) through a pressurization and decompression process.

[0173] Membrane separation is a method of separating a specific gas component (e.g., hydrogen gas) from a mixed gas using a metal membrane or a polymer membrane, thereby separating that gas component from other gas components (e.g., other carbon monoxide gases).

[0174] As described above, according to the treatment method of the present invention, the rubber can be suitably pyrolyzed to produce hydrogen gas and solid carbon simply by heating a mixture of a raw material containing rubber and a catalyst containing an iron-based catalyst with microwaves.

[0175] In other words, the processing method of the present invention can also be applied as a method for producing hydrogen gas and solid carbon.

[0176] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these. [Example]

[0177] The present invention will be described in detail below based on specific examples, but the present invention is not limited thereto. Treatments and measurements in the following examples, for which no temperature conditions are specified, were carried out at room temperature (23°C).

[0178] [3] Processing of raw materials containing rubber The rubber-containing feedstock was treated as follows.

[0179] Example 1 A tire manufactured by Bridgestone Corporation was prepared and cut to obtain a large number of blocks of the portion not containing bead wires. In this example, these blocks were used as the "raw material containing rubber."

[0180] The above rubber-containing raw material: 2.0 g, and FeAlO as an iron-based catalyst x Nanoparticles represented by the formula: 2.0 g were weighed and mixed to obtain a mixture.

[0181] The resulting mixture was sealed in a quartz test tube. The mixture was fixed by sandwiching it between quartz wool from above and below. After creating a nitrogen gas atmosphere inside the test tube, the tube was capped with a silicone rubber stopper.

[0182] The sample prepared above was heated by microwave irradiation. Microwave irradiation was performed using a Shikoku Instruments Corporation "μReactor Ex" microwave heating device in multimode. The microwave frequency was 2.45 GHz. First, the microwave output was controlled to maintain a constant heating rate (approximately 60°C / min) until the mixture temperature rose from 100°C to 700°C. After that, the microwave output was controlled to maintain the mixture at 700°C for 20 minutes. The mixture was then allowed to cool to 100°C.

[0183] The above thermal cycle was counted as one cycle and this cycle was repeated 10 times. From the second cycle onwards, 2.0 g of the above-mentioned rubber-containing raw material (a block of a tire manufactured by Bridgestone Corporation that does not include bead wires) was added to the product obtained in the previous cycle, and the heat treatment was repeated under the same conditions.

[0184] Example 2 The same treatment as in Example 1 was carried out, except that a block of a portion of a tire manufactured by Dunlop Co., Ltd. that did not contain a bead wire was used as the rubber-containing raw material instead of a block of a portion of a tire manufactured by Bridgestone Co., Ltd. that did not contain a bead wire.

[0185] Example 3 The same treatment as in Example 1 was carried out, except that a block of a portion of a tire manufactured by Yokohama Rubber Co., Ltd. that did not contain bead wires was used as the rubber-containing raw material instead of a block of a portion of a tire manufactured by Bridgestone Corporation that did not contain bead wires.

[0186] Example 4 The same treatment as in Example 1 was carried out, except that a block of a portion of a tire manufactured by Toyo Tire Corporation that did not contain a bead wire was used as the rubber-containing raw material instead of a block of a portion of a tire manufactured by Bridgestone Corporation that did not contain a bead wire.

[0187] Example 5 The tire was cut into a number of blocks containing bead wires, and these blocks were used as the "rubber-containing raw material" in this example.

[0188] The above raw material containing rubber (raw material containing bead wire): 2.0 g, and FeAlO as an iron-based catalyst x Nanoparticles represented by the formula: 2.0 g were weighed and mixed to obtain a mixture.

[0189] The resulting mixture was sealed in a quartz test tube. The mixture was fixed by sandwiching it between quartz wool from above and below. After creating a nitrogen gas atmosphere inside the test tube, the tube was capped with a silicone rubber stopper.

[0190] The sample prepared above was heated by microwave irradiation. Microwave irradiation was performed using a Shikoku Instruments Corporation "μReactor Ex" microwave heating device in multimode. The microwave frequency was 2.45 GHz. First, the microwave output was controlled to maintain a constant heating rate (approximately 60°C / min) until the mixture temperature rose from 100°C to 700°C. After that, the microwave output was controlled to maintain the mixture at 700°C for 20 minutes. The mixture was then allowed to cool to 100°C.

[0191] The above thermal cycle was counted as one cycle and this cycle was repeated 10 times. From the second cycle onwards, 2.0 g of the above-mentioned rubber-containing raw material (raw material containing bead wire) was further added to the product obtained in the previous cycle, and the heat treatment was repeated under the same conditions.

[0192] [4] Analysis The products obtained by the treatment methods of the above examples were subjected to the following analyses.

[0193] [4-1] Analysis by gas chromatography The products obtained by the treatment methods of the above examples were analyzed by gas chromatography.

[0194] Gas chromatography was performed using a Shimadzu GC-2014. Argon gas was used as the carrier gas, the flow rate was 50 mL / min, the column temperature was increased from 40°C to 200°C at a rate of 10°C / min, and the detector temperature was 200°C, and a gas chromatogram was obtained.

[0195] As a result, it was confirmed that hydrogen gas was produced in each of the above examples. In particular, in each of the above examples, most of the gas obtained was hydrogen gas. Although it was confirmed that carbon monoxide gas, methane, ethane, and carbon dioxide gas were also produced as by-products, the production of methane, ethane, and carbon dioxide gas was significantly suppressed.

[0196] Fig. 2 is a graph showing the amount of gas produced in the first cycle in Examples 1 to 4. Fig. 3 is a graph showing the composition ratio of gas produced in the first cycle in Example 5. Fig. 4 is a graph showing the amount of gas produced in the first cycle in Example 5. Note that Fig. 4 shows the amount of gas produced when converted to a weight of 2 g obtained by subtracting the mass of the bead wire from the raw material containing the rubber (raw material containing the bead wire).

[0197] [4-2] Raman Spectroscopic Analysis The products obtained by the treatment methods of the above examples were analyzed by Raman spectroscopy.

[0198] A Raman spectrum was obtained by measurement using a Raman spectrometer ("LabRAM HR-800" manufactured by HORIBA Jobin Yvon) at a laser wavelength of 633 nm.

[0199] The Raman spectrum of carbon black is usually assigned to two modes: the D-band and the G-band.

[0200] From the measurement results, peaks specific to carbon black were observed in each of the above examples, which confirmed that carbon black was produced.

[0201] From the above results, in each of the above examples, hydrogen gas and carbon black could be produced simultaneously by activating the iron-based catalyst through microwave irradiation and pyrolyzing the rubber.

[0202] FIG. 5 is a graph showing the Raman spectrum of the solid phase at the end of the first cycle in Example 1.

[0203] [5] SEM image of the solid phase after the hydrogen and carbon generation process FIG. 1 is a graph showing the composition ratio of the produced gas in the first cycle in Examples 1 to 4.

[0204] SEM photographs were taken of the products obtained by the treatment methods of the above-described examples and commercially available carbon black (Acetylene carbon black (100% compressed), manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.).

[0205] As a result, it was confirmed that in each of the above examples, carbon black having the same shape and size as commercially available carbon black was produced. FIG. 6 is an SEM photograph of the solid phase at the end of the first cycle in Example 1.

[0206] [6] Study on the deterioration of iron-based catalysts Next, we investigated the deterioration of iron-based catalysts when repeatedly heated by microwaves.

[0207] Specifically, the gaseous products obtained in each cycle of each of the above examples were analyzed by gas chromatography. FIG. 7 is a graph showing the amounts of gas produced in the first to third cycles in Example 1. As shown in FIG.

[0208] [7] Heating conditions for the mixture The heating conditions for the mixture were investigated.

[0209] [7-1] Examination of microwave irradiation conditions First, the microwave irradiation conditions were examined.

[0210] In each of the above examples, the microwave output was controlled so that the temperature of the mixture rose from 100°C to 700°C at a substantially constant heating rate (approximately 60°C / min), and then the microwave output was controlled so that the mixture, once it had reached 700°C, was maintained at 700°C for 20 minutes, thereby heating the mixture. In contrast, here, the microwave output was set to a constant value of 700 W, and the microwave irradiation time was set to 50 minutes, thereby heating the mixture.

[0211] For each case, graphs were created showing the change in microwave output and mixture temperature over time. In both cases, hydrogen gas and carbon black were efficiently produced. However, it was found that controlling the microwave output so that the heating temperature was constant, rather than heating the mixture at a constant microwave output, made it easier to control the mixture temperature and improve reproducibility.

[0212] [7-2] Examination of the heating temperature of the mixture The heating temperature of the mixture was examined below.

[0213] In each of the above examples, the maximum temperature of the mixture was set to 700°C and maintained at this maximum temperature for 20 minutes, whereas in this example, the maximum temperature of the mixture was changed in various ways within the range of 300°C to 900°C.

[0214] The products obtained in each case were analyzed by gas chromatography, and it was found that hydrogen gas could be produced efficiently in all cases, but the proportion of hydrogen gas in the produced gas was greatest when the heating temperature (maximum temperature) was 700°C, and the amount of hydrogen gas produced was greatest when the heating temperature (maximum temperature) was 900°C.

[0215] Fig. 8 is a graph showing the composition ratio of the produced gas in the first cycle in Example 1, the composition ratio of the produced gas in the first cycle when the same treatment as in Example 1 was performed except that the heating temperature (maximum temperature) was changed to 500°C, and the composition ratio of the produced gas in the first cycle when the same treatment as in Example 1 was performed except that the heating temperature (maximum temperature) was changed to 900°C. Fig. 9 is a graph showing the amount of gas produced in the first cycle in Example 1, the amount of gas produced in the first cycle when the same treatment as in Example 1 was performed except that the heating temperature (maximum temperature) was changed to 500°C, and the amount of gas produced in the first cycle when the same treatment as in Example 1 was performed except that the heating temperature (maximum temperature) was changed to 900°C.

[0216] [7-3] Study on the effect of including bead wire In Examples 1 to 4, a raw material not containing a bead wire was used as the raw material containing rubber, whereas in Example 5, a raw material containing a bead wire was used as the raw material containing rubber.

[0217] As described above, in each example, the microwave output was controlled so that the temperature of the mixture rose from 100°C to 700°C at a nearly constant rate (about 60°C / min), and then the microwave output was controlled so that the mixture, once it had reached 700°C, would remain at 700°C for 20 minutes. However, in Example 5, which used a raw material containing bead wire, the microwave output could be reduced compared to Examples 1 to 4, which used raw materials not containing bead wire, and the energy efficiency was particularly excellent. This is thought to be because in Example 5, not only the iron-based catalyst but also the bead wire contained in the raw material absorbed microwave energy and generated heat, thereby more effectively promoting the thermal decomposition of the rubber.

[0218] [8] Ease of separating the bead wire from the solid phase after the hydrogen-carbon generation process The solid phase obtained by the treatment method of Example 5 was used to attempt separation of the solid carbon, iron-based catalyst, and bead wire using a ferrite magnet. As a result, the solid carbon, iron-based catalyst, and bead wire could be separated satisfactorily. Furthermore, the iron-based catalyst and bead wire could also be separated satisfactorily by sieving.

[0219] FIG. 10 is a photograph showing carbon black (left side in the figure) and bead wire (right side in the figure) obtained by separating the solid phase obtained in the first cycle in Example 5 using a ferrite magnet and then by sieving.

[0220] Furthermore, when the mixture was treated in the same manner as in the above example, except that cellulose, sucrose, polyvinyl alcohol, water, hydrate (iron(III) oxide monohydrate), and hydroxide (iron(II) hydroxide, iron(III) hydroxide, aluminum hydroxide) were added as iron-based catalyst reduction inhibitors, particularly excellent results were obtained. [Industrial Applicability]

[0221] The processing method of the present invention is characterized by including a hydrogen / carbon production step in which a mixture containing a rubber-containing raw material and an iron-based catalyst is irradiated with microwaves to selectively heat and activate the iron-based catalyst, and the rubber is decomposed in the presence of the iron-based catalyst to produce hydrogen gas and solid carbon. This allows for efficient decomposition of rubber in a short period of time, providing a processing method that enables effective utilization of rubber.

[0222] The mixture of the present invention is a mixture used to produce hydrogen gas and solid carbon from a raw material containing rubber, and is characterized by containing the raw material, a catalyst containing an iron-based catalyst, and at least one selected from the group consisting of a polyhydric alcohol compound, water, a hydrate, and a hydroxide. This makes it possible to provide a mixture that can be suitably used to produce hydrogen gas and solid carbon. Therefore, the processing method and mixture of the present invention have industrial applicability.

Claims

1. A processing method characterized by comprising a hydrogen / carbon production step in which microwaves are applied to a mixture containing a raw material including rubber and a catalyst including an iron-based catalyst to selectively heat and activate the iron-based catalyst, and the rubber is decomposed in the presence of the iron-based catalyst to produce hydrogen gas and solid carbon.

2. 2. The method of claim 1, wherein the solid carbon comprises carbon black.

3. The iron-based catalyst is FeAlO ｘ The method according to claim 1 or 2, wherein the nanoparticles are represented by the formula:

4. 3. The method according to claim 1, wherein the raw material contains carbon black.

5. 3. The method according to claim 1, wherein the raw material contains waste tires.

6. 3. The processing method according to claim 1, wherein the raw material to be subjected to the hydrogen / carbon generation step is one from which at least a portion of metallic material has been removed.

7. 3. The treatment method according to claim 1, wherein the mixture further contains at least one selected from the group consisting of a polyhydric alcohol compound, water, a hydrate, and a hydroxide.

8. 8. The method according to claim 7, wherein the polyhydric alcohol compound is at least one selected from the group consisting of cellulose, sucrose, and polyvinyl alcohol.

9. 3. The method according to claim 1, further comprising a solid carbon separation step of separating the solid carbon from the iron-based catalyst by magnetic force.

10. A mixture used to produce hydrogen gas and solid carbon from a raw material containing rubber, A mixture comprising the raw material, a catalyst containing an iron-based catalyst, and at least one selected from the group consisting of a polyhydric alcohol compound, water, a hydrate, and a hydroxide.

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