Method for producing plastic decomposition products and apparatus for decomposing plastics

Abstract

To provide a method for producing plastic decomposition products and a plastic decomposition apparatus that exhibits good recovery rates of monomers, which are plastic decomposition products, excellent heating efficiency, and can suppress the generation of plastic-derived chars. [Solution] A method for producing plastic decomposition products, comprising the step of heating a plastic mixture containing a plastic and a catalyst compound, wherein at least a portion of the heating in the heating step is performed by microwave irradiation, and the catalyst compound contains potassium ferrite.

Description

Technical Field

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[0001] The present disclosure relates to a method for producing plastic decomposition products and a plastic decomposition apparatus.

Background Art

[0002] In recent years, due to the increasing awareness of environmental issues, technologies for recycling discarded plastics as useful resources have been emphasized. There is a demand for the development of technologies for chemically decomposing plastics and converting them into monomers, oils, or useful gases for reuse as raw materials.

[0003] Patent Document 1 discloses a method for recycling plastics using a molten salt as a catalyst compound. The plastics are decomposed by bringing them into contact with the molten salt. The molten salt contains at least one salt selected from the group consisting of chlorides of alkali metals, alkaline earth metals, and iron, and may contain at least one compound selected from the group consisting of hydroxides, oxides, carbonates, and nitrite compounds.

[0004] Patent Documents 2 and 3 disclose methods for decomposing plastics by irradiating a mixture of a microwave heating element and plastics with microwaves. The microwave heating element absorbs microwaves and generates heat.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0006] When alkali metals, alkaline earth metals, or iron chlorides are used as catalytic compounds in molten salts, by-products are likely to be generated during the decomposition of plastics. Therefore, the recovery rate and purity of monomers produced by the decomposition of plastics may be low. Furthermore, the production of molten salts requires melting the salt, which requires a significant amount of energy for heating.

[0007] Furthermore, when microwave irradiation is used as a heating method, it is necessary to mix a microwave heating element with the plastic. However, since the microwave heating element itself does not have a plastic-decomposing effect, the recovery rate and purity of monomers produced by the decomposition of the plastic may be low. If compounds other than microwave heating elements are further mixed in order to improve the monomer recovery rate, the mass proportion of non-plastic components increases, and these non-plastic components need to be heated further, thus requiring more energy for heating.

[0008] Furthermore, microwave heating elements readily absorb microwaves and generate heat at high temperatures, but do not generate heat easily at room temperature. Therefore, when a mixture of microwave heating elements and plastics is heated, temperature variations can occur depending on the reaction site, leading to the formation of plastic char and potentially reducing monomer recovery rates.

[0009] The present disclosure aims to provide a method for producing plastic decomposition products and a plastic decomposition apparatus that exhibits good recovery rates of monomers, which are plastic decomposition products, excellent heating efficiency, and the ability to suppress the generation of plastic-derived chars. [Means for solving the problem]

[0010] The method for producing plastic degradation products in this disclosure is: The process includes a step of heating a plastic mixture containing plastic and a catalyst compound. At least a portion of the heating in the aforementioned heating step is performed by microwave irradiation. The catalyst compound includes potassium ferrite.

[0011] The plastic decomposition apparatus disclosed herein, A plastic decomposition apparatus used in the above-mentioned method for producing plastic decomposition products, Includes a heating container for containing the aforementioned plastic mixture and heating it, The heating container is equipped with a microwave irradiation device for irradiating the plastic mixture contained within the heating container with microwaves. [Effects of the Invention]

[0012] According to this disclosure, it is possible to provide a method for producing plastic decomposition products and a plastic decomposition apparatus that have a good recovery rate of monomers, which are plastic decomposition products, excellent heating efficiency, and can suppress the generation of charred materials derived from plastics. [Brief explanation of the drawing]

[0013] [Figure 1] Figure 1 is a schematic diagram showing an example of a microwave irradiation device. [Modes for carrying out the invention]

[0014] Embodiments of this disclosure will be described below. Note that the dimensions such as length, width, thickness, and depth in the drawings have been altered for clarity and simplification and do not represent the actual dimensions.

[0015] Embodiment 1. A method for producing plastic decomposition products according to one embodiment of the present disclosure (hereinafter also referred to as "Embodiment 1") comprises a step of heating a plastic mixture containing a plastic and a catalyst compound, wherein at least a portion of the heating in the heating step is performed by microwave irradiation, and the catalyst compound contains potassium ferrite.

[0016] The method for producing a plastic decomposition product according to Embodiment 1 has a good recovery rate of monomers which are plastic decomposition products, excellent plastic decomposition efficiency, and suppressed generation of carbides derived from plastics. The reason is presumed as follows.

[0017] Potassium ferrite contained as a catalyst compound is presumed to act as a basic catalyst on plastics because its surface has basic portions. When potassium ferrite acts on plastics as a basic catalyst, carbanions are generated from the plastics, and a decomposition reaction occurs in which monomers are separated chain by chain. Therefore, when potassium ferrite is used as a catalyst compound, the recovery rate of monomers which are plastic decomposition products becomes good.

[0018] In addition, potassium ferrite has excellent microwave absorption characteristics at room temperature and can decompose plastics even with low-output microwaves. Therefore, when potassium ferrite is used as a catalyst compound, temperature unevenness due to the reaction location is unlikely to occur, the heating efficiency is excellent, and the generation of carbides derived from plastics is suppressed.

[0019] <Step of heating a plastic mixture> In the step of heating a plastic mixture, by heating the plastic mixture, the plastics are decomposed to obtain plastic decomposition products.

[0020] The plastic mixture is a mixture of plastics and a catalyst compound. In the step of heating the plastic mixture, by heating the plastic mixture, the catalyst compound generates heat, and the plastics in contact with the catalyst compound are in a high-temperature state, producing plastic decomposition products. Examples of plastic decomposition products include monomers, dimers, trimers, etc. of resins contained in the plastics, as well as derivatives thereof.

[0021] For example, if the plastic in the plastic mixture contains polystyrene, the plastic decomposition products include one or more compounds selected from the group consisting of benzene, toluene, ethylbenzene, xylene, styrene, α-methylstyrene, styrene dimer, and styrene trimer.

[0022] In the process of heating a plastic mixture, at least a portion of the heating of the plastic mixture is performed by microwave irradiation. From the viewpoint of more effectively suppressing the generation of charred material derived from the plastic, it is preferable that the entire heating of the plastic mixture is performed by microwave irradiation. Microwave irradiation can be performed, for example, using the microwave irradiation apparatus shown in Figure 1.

[0023] The microwave irradiation device 10 in Figure 1 comprises a microwave generator 1, waveguides 2 and 3, an isolator 4, a power monitor 5, an E / H tuner 6, and an applicator 7. Microwaves generated from the microwave generator 1 are incident on the plastic mixture placed in the applicator 7 through waveguides 2 and 3, and microwaves that are reflected without being absorbed by the plastic mixture are absorbed by the isolator 4. The microwave generator 1 typically uses a frequency of 2.45 GHz, but is not limited to this frequency. The power monitor 5 separates and detects the incident microwaves and the reflected microwaves. The E / H tuner 6 adjusts the microwaves based on the amount of microwaves detected by the power monitor 5 so that the reflected microwaves are minimized. The plastic mixture can be placed in the applicator 7. The applicator 7 has a through hole 8, and the temperature of the plastic mixture can be measured by passing a thermometer through the through hole 8.

[0024] As the microwave generator 1, for example, a magnetron-type microwave oscillator and a semiconductor oscillator can be used. Among these, the magnetron-type microwave oscillator is preferred because the magnetron used therein is inexpensive and can be produced in large quantities. The semiconductor oscillator is preferred because the frequency and phase can be easily controlled.

[0025] When heating by microwave irradiation, depending on the shape of the plastic mixture, the plastic mixture may be heated locally. Therefore, it is preferable to perform heating by microwave irradiation using methods such as irradiating with microwaves using multiple microwave generators, scattering microwaves using a stirrer fan, or stirring the plastic mixture.

[0026] The step of heating the plastic mixture may include heating methods other than microwave irradiation. Examples of heating methods other than microwave irradiation include firing, wet heating, hot air heating, and infrared heating. Firing is performed using heaters and boilers. Wet heating includes boiling, which is heating in hot water, and steam heating, which is heating with hot steam. Hot air heating is performed by blowing hot air. Infrared heating is performed by irradiating with infrared rays. Heating methods other than microwave irradiation may be used individually or in combination. Heating methods other than microwave irradiation may be performed before or after microwave irradiation of the plastic mixture.

[0027] The step of heating the plastic mixture is preferably carried out under an atmospheric gas to suppress further decomposition of plastic decomposition products. The atmospheric gas can be any commonly used atmospheric gas. Examples of atmospheric gases include non-oxidizing gases such as nitrogen, argon, and helium; reducing gases such as hydrogen, carbon monoxide, and hydrocarbon gases; oxidizing gases such as oxygen and water vapor; and nitriding gases such as ammonia gas. The atmospheric gases may be used individually or in combination. Among these, the step of heating the plastic mixture is more preferably carried out under a non-oxidizing gas atmosphere, and even more preferably under a nitrogen gas atmosphere.

[0028] In the step of heating the plastic mixture, the reaction temperature of the plastic mixture is preferably 300°C to 700°C, and more preferably 400°C to 600°C, from the viewpoint of improving the recovery rate of monomers, which are plastic decomposition products.

[0029] (Potassium ferrite) Potassium ferrite is included in catalytic compounds and plays a role in promoting the decomposition of plastics. Potassium ferrite has the chemical formula KFeO2 or K2Fe2O4. It is a complex oxide composed of iron oxide and potassium oxide.

[0030] Potassium ferrite can be produced by mixing an iron compound and a potassium compound and heating the mixture. For example, it can be obtained by mixing a powder mixture of α-iron(III) oxide and potassium carbonate (K2CO3) using an agate mortar and pestle, and then calcining the powder mixture in the atmosphere. The calcination temperature may be, for example, 900°C.

[0031] With regard to the production of potassium ferrite, the mixing ratio of iron compounds and potassium compounds is not particularly limited as long as potassium ferrite can be produced. To efficiently produce potassium ferrite, the molar ratio of iron atoms to potassium atoms is preferably 10 / 1 to 1 / 10, more preferably 5 / 1 to 1 / 5, even more preferably 2 / 1 to 1 to 2, and most preferably 1 / 1.

[0032] Examples of iron compounds used in the production of potassium ferrite include iron(II) nitrate, iron(II) hydroxide, iron(II) oxide, iron(II) carbonate, iron(II) oxalate, iron(III) nitrate, iron(III) hydroxide, iron(III) oxide, iron(III) carbonate, and iron(III) oxalate.

[0033] Examples of potassium compounds used in the production of potassium ferrite include potassium nitrate, potassium hydroxide, potassium oxide, potassium carbonate, and potassium oxalate.

[0034] Regarding the production of potassium ferrite, heating methods for calcining the above powder mixture include calcination heating, wet heating, hot air heating, infrared heating, and microwave heating.

[0035] The shape of potassium ferrite may be in the form of lumps such as spheres, ellipses, hollows, squares, and cylinders, or it may be in powder form. From the viewpoint of further improving the recovery rate of monomers, which are plastic decomposition products, and heating efficiency, the shape of potassium ferrite is preferably in powder form. This is preferable because the surface area in which the plastic comes into contact with the potassium ferrite in the plastic mixture increases. Potassium ferrite can be made into lumps or powder by using a known crusher.

[0036] Potassium ferrite may be potassium ferrite produced by mixing and calcining the iron and potassium compounds mentioned above, or it may be recycled potassium ferrite. Recycled potassium ferrite is potassium ferrite whose catalytic activity has been restored by reheating the potassium ferrite residue after the process of heating a plastic mixture. Potassium ferrite may decompose into raw material compounds due to carbon dioxide and other substances generated during the process of heating the plastic mixture. The decomposed raw material compounds can be used as raw materials for recycled potassium ferrite, as described above.

[0037] Potassium ferrite may be used in which potassium ferrite is supported on a heat-resistant oxide such as alumina, silica, or titanium oxide.

[0038] From the viewpoint of further improving heating efficiency and suppressing the generation of carbides derived from plastic, potassium ferrite is preferably included in the plastic mixture at a concentration of 1% to 200% by mass, more preferably at a concentration of 5% to 50% by mass, and even more preferably at a concentration of 10% to 30% by mass, based on the mass of plastic in the plastic mixture.

[0039] (catalyst compound) The catalyst compound contains potassium ferrite. The catalyst compound is a catalyst that promotes the decomposition of plastics and may contain other catalysts besides potassium ferrite. The other catalyst may be present in the catalyst compound in amounts of 90% by mass or less, or 10% by mass or less. Examples of other catalysts include acid catalysts, oxide catalysts, alkali metal catalysts, magnesium catalysts, and alkaline earth metal catalysts.

[0040] Examples of acid catalysts include crystalline silica-alumina compounds, amorphous silica-alumina compounds, aluminum oxide, silicon oxide, silica-magnesia compounds, bauxite, natural soils such as activated clay and acid clay, sulfated zirconia, sulfated nanographene, and activated carbon.

[0041] Examples of oxide catalysts include lithium oxide, sodium oxide, potassium oxide, rubidium oxide, magnesium oxide, calcium oxide, strontium oxide, barium oxide, chromium oxide, iron oxide, copper oxide, nickel oxide, cobalt oxide, and zinc oxide.

[0042] Examples of alkali metal catalysts include lithium chloride, sodium chloride, potassium chloride, rubidium chloride, lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide, lithium carbonate, sodium carbonate, potassium carbonate, and rubidium carbonate.

[0043] Examples of magnesium-based catalysts include magnesium chloride, magnesium hydroxide, and magnesium carbonate.

[0044] Examples of alkaline earth metal catalysts include calcium chloride, strontium chloride, barium chloride, calcium hydroxide, strontium hydroxide, barium hydroxide, calcium carbonate, strontium carbonate, and barium carbonate.

[0045] The shape of the other catalyst may be a lump such as a sphere, ellipse, hollow, square, or cylindrical shape, or it may be in powder form. From the viewpoint of further improving heating efficiency, the shape of the other catalyst is preferably in powder form.

[0046] (plastic) The plastic can be any material that is widely used as a polymer material, and is not limited by molecular weight, degree of polymerization, etc. Examples of elements constituting the plastic include polypropylene, polyethylene, polystyrene, poly(α-methylstyrene), poly(p-methylstyrene), poly(m-methylstyrene), poly(o-methylstyrene), poly(pt-butylstyrene), poly(mt-butylstyrene), poly(ot-butylstyrene), poly(p-chlorostyrene), poly(o-chlorostyrene), polymethyl methacrylate, polyisoprene, polybutadiene, polyacrylate, polycarbonate, polyester, polyamide, polystyrene-acrylonitrile copolymer, polystyrene-butadiene copolymer, and polystyrene-acrylonitrile-butadiene copolymer. These plastics may be used individually or in combination of two or more. In this embodiment, from the viewpoint of further improving the recovery rate of monomers, which are plastic decomposition products, the plastic preferably contains polystyrene, polypropylene, and polyethylene, and more preferably contains polystyrene.

[0047] The plastic may contain fillers such as fibers, talc, carbon black, and titanium dioxide, as well as additives such as antioxidants, UV absorbers, plasticizers, and waxes.

[0048] It is preferable that the plastic is free of contaminants. Therefore, it is preferable to further include a step of removing contaminants from the plastic before preparing the plastic mixture. The plastic can be cleaned to remove contaminants by a washing operation. The washing operation is not particularly limited, but examples include ultrasonic washing, spray washing, shower washing, and degassing washing.

[0049] It is preferable that the plastic is crushed. Therefore, it is preferable to further include a step of crushing the plastic before preparing the plastic mixture. This is because crushing the plastic allows it to be uniformly mixed with the catalyst compound in the plastic mixture. The plastic can be crushed by a crushing operation. The crushing operation is not particularly limited, but examples include compression, impact, shearing, and friction. Examples of crushers used to carry out the crushing operation include jaw crushers, cone crushers, impact crushers, and screw crushers. From the viewpoint of further improving the recovery rate of monomers, which are plastic decomposition products, the particle size of the plastic or its crushed material is preferably 10 mm or less, and more preferably 5 mm or less.

[0050] In this embodiment 1, it is more preferable to include either a step of removing dirt from the plastic or a step of crushing the plastic before the step of heating the plastic mixture, and the order of the steps of removing dirt from the plastic and crushing the plastic is not important. For example, the dirt may be removed from the plastic before crushing, or the dirt may be removed from the plastic after crushing, or the washing and crushing of the plastic may be performed simultaneously.

[0051] The plastic may be rigid waste plastic such as containers, home appliances, and bathtubs, or flexible waste plastic such as polystyrene foam, packaging film, and trays, or a mixture thereof. The flexible waste plastic may be further compressed into ingots, blocks, etc., before the crushing process described above. The plastic may be used plastic or unused plastic, or a mixture thereof.

[0052] (Plastic mixture) The plastic mixture contains plastic and a catalyst compound. The content of the catalyst compound in the plastic mixture may be 1% by mass or more and 250% by mass or 5% by mass or 10% by mass or 50% by mass or more, based on the mass of plastic in the plastic mixture.

[0053] The plastic mixture may be in the form of a solid mixture containing plastic fragments and a catalyst compound, or in the form of a solid-liquid mixture containing molten plastic and a catalyst compound. When the plastic mixture is in the form of a solid-liquid mixture, the plastic surrounds the catalyst compound, making it easier for the plastic and the catalyst compound to come into contact with each other compared to when the plastic is in the form of a solid mixture, and thus improving the recovery rate of monomers, which are plastic decomposition products. For this reason, it is preferable for the plastic mixture to be in the form of a solid-liquid mixture.

[0054] The plastic mixture may contain other substances besides plastic and catalyst compounds. Examples of other substances include microwave heating elements and solid particles. These other substances may be contained in the plastic mixture in a solid mixture state or in the plastic mixture state.

[0055] Plastic mixtures can be transformed into solid-liquid mixtures by heating them from a solid state. The heating temperature is preferably such that the plastic does not undergo thermal decomposition; for example, it is preferably between 150°C and 350°C. Note that the term "plastic mixture in a solid state" also includes plastic mixtures that have been cooled or otherwise transformed back into a solid state.

[0056] The particle size of the plastic mixture may be between 100 μm and 50 mm, or between 1 mm and 5 mm.

[0057] The plastic mixture may further contain a microwave heating element, as this allows for more uniform and rapid heating of the plastic mixture. Preferably, the microwave heating element is a material with a large product of dielectric constant (ε) and loss coefficient (tanδ), or a large product of permeability (μ) and loss coefficient, thereby improving the heating efficiency using microwave irradiation. Examples of microwave heating elements include carbon materials such as graphite, carbon black, activated carbon, carbonate fiber, and boron carbide, as well as metallic materials such as silicon, silicon carbide, iron oxide, iron, aluminum, copper oxide, silver sulfide, copper bromide, copper chloride, cobalt, tricobalt tetroxide, nickel oxide, manganese dioxide, molybdenum, molybdenum sulfide, lead sulfide, titanium boride, vanadium, tungsten, tungsten trioxide, zinc, and zinc chloride. These microwave heating elements may be used individually or in combination.

[0058] The content of the above microwave heating element may be 1% by mass or more and 90% by mass or less, 5% by mass or more and 50% by mass or less, or 10% by mass or more and 30% by mass or less, based on the mass in the plastic mixture.

[0059] The shape of the microwave heating element may be a lump, such as a sphere, ellipse, hollow, square, or cylindrical shape, or it may be in powder form. From the viewpoint of improving heating efficiency, the microwave heating element is preferably in powder form. This is preferable because the surface area in which the plastic in the plastic mixture contacts the microwave heating element increases. The microwave heating element can be made into a lump or powder by using a known crusher.

[0060] Embodiment 2. A plastic decomposition apparatus according to one embodiment of the present disclosure is a plastic decomposition apparatus used in a method for producing the above-mentioned plastic decomposition product, and includes a heating container for containing and heating the plastic mixture, wherein the heating container is equipped with a microwave irradiation device for irradiating the plastic mixture contained in the heating container with microwaves.

[0061] The heating container is a container for holding a plastic mixture to be heated and includes a microwave irradiation device for irradiating the plastic mixture contained within the heating container with microwaves. The heating container may further include other heating means other than the microwave irradiation device as means for heating the plastic mixture. Examples of other heating means include heaters, boilers, and superheated steam generators.

[0062] A microwave irradiation device is used to heat plastic mixtures. For example, the microwave irradiation device shown in Figure 1 can be used. As mentioned above, the microwave generator in the microwave irradiation device can be a magnetron-type microwave oscillator, a semiconductor oscillator, or the like.

[0063] The plastic decomposition apparatus may further include a storage container for storing the plastic mixture, a kneader for stirring the plastic mixture in the heating container, a gas generator for supplying atmospheric gas into the heating container, a storage container for storing the decomposed plastic products, and a regeneration container for regenerating the catalytic activity of the catalyst compound using the residue of the catalyst compound. The plastic decomposition apparatus may further include devices commonly combined as a plastic decomposition apparatus, such as a condenser and a cooler. [Examples]

[0064] The present disclosure will be described in detail below with reference to examples, but the present disclosure is not limited to these examples.

[0065] (Preparation of catalyst compounds) The catalyst compound containing potassium ferrite was obtained by the following procedure. 159.7 g of α-iron(III) oxide (manufactured by Fujifilm Wako Pure Chemical Industries) and 138.2 g of potassium carbonate (manufactured by Fujifilm Wako Pure Chemical Industries) were mixed using an agate mortar and calcined in air at 900°C for 6 hours to obtain a solid. This solid was ground into a powder using an agate mortar and passed through a sieve (mesh number 80, opening 180 μm). The resulting powder was used as a catalyst compound.

[0066] The obtained catalyst compound was identified by X-ray diffraction, and its crystal structure confirmed that its main component was potassium ferrite (KFeO2).

[0067] (Prepare plastic) The plastic used was plastic fragments recovered from a mixture of plastics derived from discarded used home appliances. Of these plastic fragments, more than 95% by mass was polystyrene resin. Other materials included polypropylene resin, ABS resin, and polystyrene / polyphenylene ether resin (PE / PPE resin).

[0068] (Preparation of plastic mixtures) [Manufacturing Example 1] 100 parts by mass of crushed plastic was mixed with 25 parts by mass of a catalyst compound. Then, using a small tabletop kneader (DSM Corporation, XPlore series MC15), the mixture was kneaded at 210°C for 2 minutes to obtain strands. These strands were then crushed using a crusher to obtain a plastic mixture with a particle size of 5 mm or less.

[0069] [Manufacturing Example 2] The plastic mixture for Production Example 2 was prepared in the same manner as in Production Example 1, except that 25 parts by mass of α-iron(III) oxide (α-Fe2O3, manufactured by Fujifilm Wako Pure Chemical Industries) were mixed in place of the catalyst compound.

[0070] [Manufacturing Example 3] The plastic mixture for Production Example 3 was prepared in the same manner as in Production Example 1, except that 25 parts by mass of triiron tetroxide (Fe3O4, manufactured by Fujifilm Wako Pure Chemical Industries) were mixed in place of the catalyst compound.

[0071] [Manufacturing Example 4] The plastic mixture for Production Example 4 was prepared in the same manner as in Production Example 1, except that 25 parts by mass of potassium carbonate (K2CO3, manufactured by Fujifilm Wako Pure Chemical Industries) were mixed in place of the catalyst compound.

[0072] [Manufacturing Example 5] The plastic mixture for Production Example 5 was prepared in the same manner as in Production Example 1, except that a strand consisting only of 100 parts by mass of crushed plastic was obtained.

[0073] [Example 1] (1) Evaluation of catalytic activity by thermal decomposition The catalytic activity of the catalyst compound was evaluated by comparing the styrene monomer recovery rate when the gas produced from a heated plastic mixture was subjected to gas chromatography-mass spectrometry (GC / MS). The method for evaluating catalytic activity is described below. 0.2 mg of the plastic mixture from Production Example 1 was subjected to a pyrolysis apparatus (Frontier Labs PY-2020iD) and heated at 500°C for 4 minutes. The gas generated from the plastic mixture was introduced into a GC / MS and separated using a gas chromatograph, and the above gas was quantitatively analyzed using a mass spectrometer. The GC and MS conditions were as follows.

[0074] (GC conditions) GC unit: Agilent Technologies 7890A Column: HP-5 column (Agilent Corporation, 60m length, 0.25mm inner diameter, 0.25μm film thickness) Column temperature: 50°C (5 min) - 10°C / min - 300°C (30 min) Inlet temperature: 300℃ Detector temperature: 250℃ Standard substance: Toluene Carrier gas: Helium Helium flow rate: 1 mL / min Ionization voltage: 70V

[0075] (MS conditions) MS analyzer: JEOL JMS-Q1000GCMK2 Ionization method: Electron ionization method Interface temperature: 250℃

[0076] The compounds detected in the above gases were quantified using toluene as a reference, based on toluene equivalent values. The styrene monomer recovery rate was calculated from the theoretical yield of styrene when the polystyrene plastic in the plastic mixture is completely decomposed into styrene monomer, and the actual styrene yield. Table 1 shows the results of the catalytic activity evaluation.

[0077] (2) Decomposition of plastics by microwave irradiation An experiment was conducted to decompose the plastic in the plastic mixture by heating the plastic mixture from manufacturing example 1 described above according to the following procedure.

[0078] The plastic mixture from Manufacturing Example 1 described above was heated using a microwave irradiation device. The microwave irradiation device used was the one shown in Figure 1. The microwave irradiation device was a waveguide type single-mode irradiation system. The microwave irradiation device was equipped with a magnetron type oscillator with a frequency of 2.45 GHz as the microwave oscillator. A radiation thermometer (FTKX manufactured by Japan Sensor Co., Ltd.) with a minimum measurable temperature of 280°C was used to measure the temperature of the plastic mixture. The temperature of the plastic mixture was measured using the radiation thermometer at the center of the vial filled with the plastic mixture. Heating using the microwave irradiation device was carried out while continuously introducing 0.4 L / min of nitrogen gas into the applicator in which the plastic mixture was placed. Microwave heating was controlled by measuring the power of the microwaves that were reflected without being incident on the plastic mixture using a power monitor, and sequentially adjusting the E / H tuner to minimize this power, thereby using most of the input microwaves for heating.

[0079] 20.0 g of the plastic mixture from Production Example 1 was transferred to quartz glass vials and heated using a microwave irradiation device. The microwave irradiation power was set to increase by 10 W per minute. When the temperature of the plastic mixture reached 500°C, the microwave irradiation power was adjusted to maintain the temperature of the plastic mixture at 500°C for 10 minutes, and microwave heating was performed. After that, microwave heating was stopped, and the plastic mixture was removed from the vials after the temperature of the vials had decreased to room temperature (25°C).

[0080] The plastic residue rate was measured by comparing the mass of plastic fragments in the heated vial with the mass of plastic fragments in the plastic mixture after complete decomposition. The presence or absence of carbides in the vial was also observed visually. Table 1 shows the results. The presence or absence of carbides was evaluated according to the following criteria. A... No carbonized material was observed. B...Carbonized material was observed.

[0081] (3) Reaction temperature of catalyst compounds by microwave irradiation To confirm the reaction temperature of the catalyst compound upon microwave irradiation, the plastic mixture from Production Example 1 was irradiated with microwaves of a constant power, and the temperature of the catalyst compound contained in the plastic mixture was observed over time.

[0082] The microwave irradiation device, vial, and plastic mixture were the same as those used in (2) above. The microwave irradiation power was 100W, and the irradiation time was 5 minutes. The temperature of the plastic mixture was measured using an infrared thermometer. The results are shown in Table 1.

[0083] [Comparative Examples 1-4] The tests described in (1) to (3) above were carried out in the same manner as in Example 1, except that the plastic mixtures from Production Examples 2 to 5 were used instead of the plastic mixture from Production Example 1. The results are shown in Table 1.

[0084] [Table 1]

[0085] 65% by mass of styrene monomer was recovered from the plastic mixture in Production Example 1. This was comparable to the amount of styrene monomer recovered from the plastic mixtures in Production Examples 2-5. Since the catalytic activity does not depend on the method of heating the plastic mixture, it is expected that the same styrene monomer recovery rate can be obtained even when the plastic in the plastic mixture of Production Example 1 is decomposed by heating with microwave irradiation.

[0086] The plastic mixture in Production Example 1, when heated using a microwave irradiation device, had a plastic residue rate of 0.4% by mass after heating, and no charring was generated. This was thought to be because the plastic mixture was heated uniformly within the vial.

[0087] The plastic mixture in Production Example 1 reached a reaction temperature of 633°C within 1 minute of the start of heating when heated using a microwave irradiation device.

[0088] The embodiments and examples disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of this disclosure is indicated by the claims rather than the foregoing description, and all modifications within the meaning and scope equivalent to the claims are intended.

[0089] The various forms of this disclosure are summarized below as an appendix. (Note 1) The process includes a step of heating a plastic mixture containing plastic and a catalyst compound. At least a portion of the heating in the aforementioned heating step is performed by microwave irradiation. The catalyst compound comprises potassium ferrite. A method for producing plastic decomposition products. (Note 2) The method for producing plastic decomposition products as described in Appendix 1, wherein the aforementioned plastic includes polystyrene. (Note 3) The method for producing a plastic degradation product according to Appendix 1 or Appendix 2, wherein the plastic degradation product comprises one or more compounds selected from the group consisting of benzene, toluene, ethylbenzene, xylene, styrene, α-methylstyrene, styrene dimer, and styrene trimer. (Note 4) The method for producing plastic decomposition products according to any one of Appendix 1 to Appendix 3, wherein the heating step is performed under a non-oxidizing gas atmosphere. (Note 5) A method for producing plastic decomposition products according to any one of Appendix 1 to Appendix 4, further comprising a step of regenerating the catalyst compound after the heating step. (Note 6) A plastic decomposition apparatus used in a method for producing plastic decomposition products described in any one of Appendix 1 to Appendix 5, Includes a heating container for containing the aforementioned plastic mixture and heating it, The heating container is equipped with a microwave irradiation device for irradiating the plastic mixture contained within the heating container with microwaves, in a plastic decomposition apparatus. [Explanation of Symbols]

[0090] 1. Microwave generator, 2,3. Waveguides, 4. Isolator, 5. Power monitor, 6. E / H tuner, 7. Applicator, 8. Through hole, 10. Microwave irradiation device

Claims

1. The process includes a step of heating a plastic mixture containing plastic and a catalyst compound. At least a portion of the heating in the aforementioned heating step is performed by microwave irradiation. The catalyst compound comprises potassium ferrite. A method for producing plastic decomposition products.

2. The method for producing a plastic decomposition product according to claim 1, wherein the plastic includes polystyrene.

3. The method for producing a plastic degradation product according to claim 1 or claim 2, wherein the plastic degradation product comprises one or more compounds selected from the group consisting of benzene, toluene, ethylbenzene, xylene, styrene, α-methylstyrene, styrene dimer, and styrene trimer.

4. The method for producing plastic decomposition products according to claim 1 or claim 2, wherein the heating step is performed under a non-oxidizing gas atmosphere.

5. A method for producing a plastic decomposition product according to claim 1 or claim 2, further comprising a step of regenerating the catalyst compound after the heating step.

6. A plastic decomposition apparatus used in a method for producing plastic decomposition products according to claim 1 or claim 2, Includes a heating container for containing the aforementioned plastic mixture and heating it, The heating container is equipped with a microwave irradiation device for irradiating the plastic mixture contained within the heating container with microwaves, in a plastic decomposition apparatus.

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