Method for producing olefins

Abstract

This reduces the possibility of solid material precipitation during the olefin manufacturing process. [Solution] A method for producing olefins using PET-containing plastic as a raw material, comprising a thermal decomposition step and a heat recovery step. In the heat recovery step, f(x) = -12.57 × (X1) 2 Heat recovery is performed at a temperature at least 5°C higher than the temperature f(x)[°C] derived from +1.941×(X2)+274.13, and at a temperature of 450°C or lower. X1 is the molar ratio [-] of the metal compound to the PET contained in the plastic, and X2 is the proportion [wt%] of PET in the plastic.

Description

[Technical Field]

[0001] This invention relates to a method for producing olefins. [Background technology]

[0002] There is a technology that uses plastic as a raw material, and after thermally decomposing the plastic, obtains a gas containing a large amount of lower olefins through gas-liquid separation or distillation. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] International Patent Application No. WO2023 / 047951 [Overview of the project] [Problems that the invention aims to solve]

[0004] In the conventional techniques described above, if the raw material plastic contains polyethylene terephthalate, a solid substance containing terephthalic acid may precipitate during the cooling process.

[0005] One aspect of the present invention aims to reduce the possibility of solid matter precipitation during the manufacturing process of olefins. [Means for solving the problem]

[0006] A method for producing an olefin according to one aspect of the present disclosure includes a thermal decomposition step of thermally decomposing a raw material containing a plastic to obtain a thermal decomposition product, and a heat recovery step of recovering heat from the thermal decomposition product, wherein the plastic contains polyethylene terephthalate, and in the heat recovery step, the following formula (1); f(x) = -12.57 × (X1) 2 +1.941 × (X²) + 274.13 (1) A method for producing olefins, wherein heat recovery is performed at a temperature at least 5°C higher than the temperature f(x)[°C] derived from, and at a temperature of 450°C or lower, In the above formula (1), X1 is the molar ratio [-] of the metal compound to the polyethylene terephthalate contained in the plastic, and X2 is the proportion [wt%] of polyethylene terephthalate in the plastic.

[0007] A method for producing an olefin according to another aspect of the present disclosure includes a pyrolysis step of pyrolyzing a raw material containing a plastic to obtain a pyrolysis product, and a cooling step of cooling the pyrolysis product, wherein the plastic contains polyethylene terephthalate, and the temperature of the pyrolysis product in a pipe supplying the pyrolysis product to the cooling step is given by the following formula (1); f(x) = -12.57 × (X1) 2 +1.941 × (X²) + 274.13 (1) A method for producing olefins, wherein the temperature is maintained at a range of 5°C or more higher than the temperature f(x)[°C] derived from and 450°C or less, In the above formula (1), X1 is the molar ratio [-] of the metal compound to polyethylene terephthalate contained in the plastic, and X2 is the proportion [wt%] of polyethylene terephthalate in the plastic. [Effects of the Invention]

[0008] According to one aspect of this disclosure, the possibility of solid matter precipitation during the olefin manufacturing process can be reduced. [Brief explanation of the drawing]

[0009] [Figure 1] This flowchart shows an example of a method for producing an olefin according to Embodiment 1 of this disclosure. [Figure 2] This diagram schematically shows the main configuration of the manufacturing system according to Embodiment 1 of this disclosure. [Figure 3] This is a schematic diagram of the experimental apparatus used in the demonstration test. [Figure 4] It is a graph comparing the measured value of the solid precipitation temperature and the approximate curve. [Figure 5] It is a flowchart showing an example of a method for producing an olefin according to Embodiment 2 of the present disclosure. [Figure 6] It is a system diagram schematically showing the main configuration of the production system according to Embodiment 2 of the present disclosure.

MODE FOR CARRYING OUT THE INVENTION

[0010] 〔Embodiment 1〕 Hereinafter, an embodiment of the present disclosure will be described in detail.

[0011] Hereinafter, a method for producing an olefin according to an embodiment of the present disclosure will be described in detail with reference to the drawings together with the production system used therefor.

[0012] The method for producing an olefin according to the present disclosure is a method for producing a lower olefin capable of carbon circulation as a plastic raw material using a plastic such as waste plastic as a raw material. The method for producing an olefin according to the present disclosure includes a pyrolysis step of pyrolyzing a raw material containing plastic to obtain a pyrolysis product, and a heat recovery step of recovering heat from the pyrolysis product.

[0013] FIG. 1 is a flowchart showing an example of the method for producing an olefin according to the present embodiment. As shown in FIG. 1, the method for producing an olefin of the present embodiment includes a pretreatment step S11, a first pyrolysis step S12, a catalytic cracking step S13, a heat recovery step S14, a cooling step S15, and a purification step S16. Each step will be described in detail below.

[0014] In the present embodiment, as an example, a flowchart shown in FIG. 1 and an olefin production system (FIG. 2: production system 100) that realizes the production flow shown in the flowchart will be described. However, the systems described in this specification and the drawings are merely typical examples and do not limit the scope of the present disclosure in any way. This also applies to the following other embodiments.

[0015] <Olefin production system (Production system 100)> First, an example of the configuration of the production system 100 will be described using FIGS. 1 and 2. FIG. 2 is a system diagram schematically showing the main configuration of the production system 100 according to Embodiment 1.

[0016] The production system 100 of the present embodiment is a system that decomposes plastics, particularly plastics containing polyethylene terephthalate (PET), to obtain lower olefins. As the raw material used in the olefin production method of the present embodiment, for example, waste plastics can be used.

[0017] As shown in FIG. 2, the production system 100 of the present embodiment is schematically configured to include a pretreatment system 10, a first pyrolysis device 21, a catalytic cracking device 22, a heat recovery device 31, a cooling device 40, a purification device 50, and respective paths L1 to L5.

[0018] The raw material is supplied to the pretreatment system 10 through the path L1. The raw material supplied through the path L1 may be plastics such as waste plastics. In addition to the raw material, additives may be supplied to the pretreatment system 10. The additives may be supplied to the first pyrolysis device 21 instead of the pretreatment system 10.

[0019] The discharge port of the pretreatment system 10 and the supply port of the first pyrolysis unit 21 are connected by a path L2. The feed material M, which has been pretreated by the pretreatment system 10, is supplied to the first pyrolysis unit 21 via path L2. The first pyrolysis unit 21 and the catalytic cracking unit 22 are connected by a path L3. The feed material M supplied to the first pyrolysis unit 21 is pyrolyzed and supplied to the catalytic cracking unit 22 as a first product P1 via path L3. The first product P1 may be a gas, a liquid, or a mixture of gas and liquid. The catalytic cracking unit 22 and the cooling unit are connected by a path L4. The first product P1 supplied to the catalytic cracking unit 22 is catalytically cracked and supplied to the cooling unit 40 as a second product P2. The second product P2 is an example of a pyrolysis product according to this disclosure.

[0020] The cooling device and the purification device 50 are connected by a path L5. The secondary product P2 supplied to the cooling device 40 is cooled and supplied to the purification device 50. The secondary product P2 supplied to the purification device 50 is purified by the purification device 50 to obtain a final product containing lower olefins.

[0021] The pre-treatment system 10 is a system that processes plastics such as waste plastics to make them suitable feed material M for decomposition treatment. In other words, the pre-treatment system 10 is a system that carries out the pre-treatment process S11. The pre-treatment system 10 may include multiple devices that perform different treatments. For example, the pre-treatment system 10 may include one or more devices from among a sorting device, a crushing device, a washing device, a drying device, a melting device, or a dechlorination device. A sorting device is a device that sorts polyolefin plastics from raw materials such as waste plastics. As a sorting device, one or more devices such as an optical sorting device or a specific gravity separation device can be used. A crushing device is a device that crushes the sorted plastics. A washing device is a device that washes the crushed plastics. A drying device is a device that dries the washed plastics. A melting device is a device that heats the plastics to make them liquid. A dechlorination device is a device that removes chlorine contained in the plastics.

[0022] The first pyrolysis apparatus 21 is an apparatus capable of carrying out the first pyrolysis step S12 of this embodiment. The first pyrolysis apparatus 21 may be, for example, an apparatus that decomposes and vaporizes a substance by heating. The first pyrolysis apparatus 21 may be an apparatus that performs pyrolysis continuously, and for example, an extruder, a stirring tank, a rotary kiln, or a fluidized bed can be used. As the fluidized bed, an internal circulating fluidized bed or an external circulating fluidized bed can be used.

[0023] Furthermore, the first pyrolysis apparatus 21 may be equipped with a dust collector, either inside or outside the apparatus, for removing solid matter from the first product P1. For example, one or more of the following can be used as the dust collector: a cyclone, a ceramic filter, an electrostatic precipitator, and a bag filter. Multiple dust collectors may be used, and these may be connected in parallel or directly. The dust collector may be equipped with piping for discharging the collected solid matter to the outside of the apparatus. It may also be equipped with piping for returning a portion of the collected solid matter back into the apparatus.

[0024] Furthermore, multiple of the above-described apparatuses may be used as the first pyrolysis apparatus 21, and the multiple reactors may be connected in parallel or in series. As the heat source required in the first pyrolysis step S12, heat obtained by burning one or more of the following can be used: the pyrolysis residue generated in the first pyrolysis apparatus 21, the hydrocarbon-containing liquid and / or lower paraffin gas obtained in the purification step S16, or hydrocarbon fuels such as natural gas or kerosene. Alternatively, heat obtained by electric heating or microwave irradiation can also be used as a heat source. Alternatively, electric heating, microwave irradiation, and two or more of the heat obtained from the above-described combustion may be used in combination.

[0025] The heating method may be either direct heating or indirect heating. Direct heating methods include supplying microwave energy to waste plastics through a microwave-absorbing susceptor within the apparatus. Indirect heating methods include supplying heat obtained by burning an electric heater or hydrocarbon fuel via the heat transfer surface of the apparatus, or preheating water vapor or an inert gas such as nitrogen or CO2 gas to a high temperature using a heat source before introducing it into the apparatus. Alternatively, a method may be used in which a solid mainly composed of iron, iron oxide, alumina, silica, etc., is preheated to a high temperature using a heat source before introducing it into the apparatus. Preheating of gases or solid particles using a heat source may be performed in combination with the first pyrolysis apparatus 21, either by using a portion of the first pyrolysis apparatus 21 or a similar apparatus, circulating the gases or solids from these devices.

[0026] The catalytic cracking apparatus 22 is an apparatus that carries out the catalytic cracking process S13. Specifically, the catalytic cracking apparatus 22 is an apparatus that decomposes a substance by bringing the first product P1 into contact with a catalyst. As the catalytic cracking apparatus 22, for example, a fixed bed, a moving bed, or a fluidized bed can be used. Furthermore, multiple of these reactors exemplified above may be used as the catalytic cracking apparatus 22, and the multiple reactors may be connected in parallel or in series.

[0027] Furthermore, the catalytic cracking apparatus 22 may be equipped with a dust collector for removing the catalyst from the second product P2, either inside or outside the apparatus. One or more of the following can be used as the dust collector: a cyclone, a ceramic filter, an electrostatic precipitator, and a bag filter. Multiple dust collectors may be used, and multiple dust collectors may be connected in parallel or directly. The dust collector may be equipped with piping for discharging the recovered catalyst to the outside of the apparatus. It may also be equipped with piping for returning at least a portion of the recovered catalyst to the apparatus where catalytic cracking is performed.

[0028] In the catalytic cracking step S13, the heat source required can be the heat obtained by burning one or more of the following: coke generated in the catalytic cracking apparatus 22 and adhering to the catalyst surface, a hydrocarbon-containing liquid and / or lower paraffin gas obtained in the refining step S16, or hydrocarbon fuels such as natural gas or kerosene. Alternatively, heat obtained by electric heating or microwave irradiation can also be used as a heat source. Or, electric heating, microwave irradiation, and two or more of the heat obtained from the aforementioned combustion methods may be used in combination.

[0029] The heating method may be either direct heating or indirect heating. A direct heating method involves holding a microwave-absorbing material (susceptor) within the apparatus and supplying microwave energy to the waste plastic through it. An indirect heating method involves supplying heat obtained by burning an electric heater or hydrocarbon fuel through the heat transfer surface of the apparatus, or by preheating steam or an inert gas such as nitrogen or CO2 gas to a high temperature using a heat source before introducing it into the apparatus. Alternatively, a method may be used in which a solid mainly composed of iron, iron oxide, alumina, silica, etc., is preheated to a high temperature using a heat source before introducing it into the apparatus. The solid particles may also be the catalyst mentioned above. Preheating of the gas or solid particles using a heat source may be performed in combination with the first pyrolysis apparatus 21, either using a part of the interior of the first pyrolysis apparatus 21 or using a similar apparatus, circulating the gas or solid from these devices.

[0030] The heat recovery device 31 is installed in the path L4 and is capable of recovering heat from the second product P2, which is a pyrolysis product. In other words, the heat recovery device 31 is capable of carrying out the heat recovery process S14 of this embodiment. For example, a multi-tube heat exchanger or a plate heat exchanger can be used as the heat recovery device 31.

[0031] The cooling device 40 is a device for cooling the second product P2 after heat recovery. In other words, the cooling device 40 is a device capable of carrying out the cooling process S15 of this embodiment. As the cooling device, for example, a spray tower, a tray tower, a packed tower, or a cooler (liquid cooling by immersion tubes) can be used.

[0032] The purification apparatus 50 is capable of separating the mixture supplied to the apparatus by known gas-liquid separation operations or distillation operations. In other words, the purification apparatus 50 is capable of carrying out the purification process S16 of this embodiment. The purification apparatus 50 can, for example, be a gas-liquid separation apparatus or a distillation apparatus. These apparatuses may also be combined, or multiple apparatuses may be connected together. In addition, a distillation apparatus may be optionally installed downstream of the purification apparatus 50 in order to increase the purity of the olefin obtained in the purification apparatus 50 to an olefin purity of any desired number of carbon atoms.

[0033] <Method for producing olefins> The method for producing olefins according to Embodiment 1 is carried out, for example, according to the flowchart shown in Figure 1. Note that the flowchart shown in Figure 1 is an example and is not limited thereto. Each step in the method for producing olefins according to Embodiment 1 will be described in detail.

[0034] (Regarding raw materials) Prior to describing each step, the raw materials used in this disclosure will be described. Plastic can be used as the raw material supplied to the pretreatment system 10. The plastic may be waste plastic contained in municipal solid waste, etc. The plastic is preferably mainly composed of polyolefins such as polyethylene or polypropylene, but may also contain other plastics. Other plastics may include, for example, chlorinated plastics (such as chlorinated polyethylene), polyvinyl chloride (PVC), polyvinylidene chloride (PVDC), non-chlorinated plastics (e.g., polyethylene, polypropylene, polyethylene terephthalate (PET), polybutylene terephthalate, polystyrene, nylon 66, etc.), or mixtures thereof. The method for producing olefins according to this disclosure can be particularly suitably applied to embodiments in which the plastic used as a raw material contains 0.01 wt% to 10 wt% of PET. The waste plastic may also include unused mixed plastics or used mixed plastics. The polyolefin-based plastic content in the raw material plastic is preferably 60% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more.

[0035] The method for producing olefins according to this disclosure may include the addition of additives to the raw materials supplied to the pretreatment step or to the feed product M after the pretreatment step. In other words, the additives may be added in the pretreatment step S11 or in the first pyrolysis step S12. Metal compounds may be used as additives. The metal compounds may be, for example, alkali metal compounds, alkaline earth metal compounds, or mixtures thereof. More specifically, the metal compound may be a calcium compound, and the calcium compound may be calcium oxide, calcium carbonate, or a mixture thereof.

[0036] (Pre-treatment step S11) The pretreatment step S11 is a step of pretreatment of the plastic to obtain a feed material M to be used in the first pyrolysis step S12. The plastic can be supplied to the first pyrolysis step S12 as a feed material M mainly containing polyolefin plastics after going through the pretreatment step S11. It is preferable that the polyolefin plastic content in the raw material plastic becomes 80% by mass or more after the pretreatment step S11, more preferably 90% by mass or more, and even more preferably 95% by mass or more.

[0037] (First pyrolysis step S12) The first pyrolysis step S12 is a step in which the feed material M is decomposed by heating to obtain the first product P1. In other words, the first pyrolysis step S12 is included in the pyrolysis step of this disclosure. By thermal decomposition in the first pyrolysis step S12, the carbon compounds contained in the feed material M are reduced in molecular weight and decomposed mainly into hydrocarbons with about 1 to 30 carbon atoms. In other words, the average number of carbon atoms in the hydrocarbons contained in the first product P1 may be 30 or less. The pyrolysis temperature (°C) in the first pyrolysis step S12 can be set based on the composition of the feed material M. The pyrolysis temperature is preferably high because it allows for a fast decomposition rate of the plastic, but if the temperature is too high, carbonization will occur, so it may be, for example, 450°C to 900°C, 500°C to 750°C, or 500°C to 650°C. As for the pressure in the first pyrolysis step S12, a low pressure is preferable because the decomposition reaction is a reaction in which the number of moles increases. The pressure in the first pyrolysis step S12 may be, for example, -80 kPaG to 1000 kPaG, -10 kPaG to 300 kPaG, or 0 kPaG to 100 kPaG.

[0038] Furthermore, in the first pyrolysis step S12, a catalyst may be optionally used to accelerate decomposition. Examples of catalysts used in the first pyrolysis step S12 include, but are not limited to, silicate catalysts, preferably zeolite catalysts, and more preferably MFI-type zeolite catalysts. Silicate catalysts typically contain silicon atoms, aluminum atoms, oxygen atoms, and hydrogen atoms. Silicate catalysts may also contain atoms such as sodium atoms, titanium atoms, chromium atoms, manganese atoms, iron atoms, cobalt atoms, nickel atoms, copper atoms, ruthenium atoms, rhodium atoms, palladium atoms, silver atoms, iridium atoms, platinum atoms, boron atoms, nitrogen atoms, magnesium atoms, phosphorus atoms, zinc atoms, and gallium atoms.

[0039] In the first pyrolysis step S12, an inert gas such as nitrogen gas, water vapor, or CO2 gas may be present, and these gases may be used as the fluidizing gas or carrier gas in the fluidized bed. When a fluidized bed reactor is used in the first pyrolysis step S12, these carrier gases may be used as the fluidizing gas. The more fluidizing gas there is, the lower the hydrocarbon concentration in the gas phase becomes, and the more easily the decomposed components tend to vaporize. The linear velocity of the fluidizing gas in the fluidized bed reactor may be between 0.1 cm / s and 500 cm / s.

[0040] If a dust collector is attached inside or outside the apparatus performing the first pyrolysis step, solid matter may be removed from the first product P1 by the dust collector in the first pyrolysis step S12. The particle size of the removed solid matter is, for example, 0.1 μm to 200 μm, 1 μm to 100 μm, or 5 μm to 50 μm. At least a portion of the solid matter removed by the dust collector may be discharged outside the apparatus. The solid matter removed by the dust collector and discharged is, for example, inorganic components contained in the plastic of the feed material M, and / or the additives.

[0041] (Catalytic cracking process S13) The catalytic cracking step S13 is a step in which the first product P1 is decomposed in the presence of a catalyst to produce a second product P2, which is a hydrocarbon with approximately 1 to 20 carbon atoms. The catalytic cracking step S13 is included in the thermal cracking step according to this disclosure. The cracking temperature in the catalytic cracking step S13 may be set based on the composition of the first product P1. The cracking temperature may be, for example, 450°C to 900°C, 500°C to 750°C, or 500°C to 650°C. The cracking pressure in the catalytic cracking step S13 may be, for example, -80kPaG to 1000kPaG, -10kPaG to 300kPaG, or 0kPaG to 100kPaG.

[0042] The catalyst used in the catalytic cracking step S13 may include, but is not limited to, a silicate catalyst, preferably a zeolite catalyst, and more preferably an MFI-type zeolite catalyst. Silicate catalysts may typically contain silicon atoms, aluminum atoms, oxygen atoms, and hydrogen atoms. Silicate catalysts may also contain atoms such as sodium atoms, titanium atoms, chromium atoms, manganese atoms, iron atoms, cobalt atoms, nickel atoms, copper atoms, ruthenium atoms, rhodium atoms, palladium atoms, silver atoms, iridium atoms, platinum atoms, boron atoms, nitrogen atoms, magnesium atoms, phosphorus atoms, zinc atoms, and gallium atoms.

[0043] In catalytic cracking step S13, a gas containing at least one of the following may be introduced into the reaction system: nitrogen gas or argon gas, water (water vapor), CO2 gas, methane, or ethane. In other words, in catalytic cracking step S13, at least one of the following may be present: nitrogen gas or argon gas, water (water vapor), CO2 gas, methane, or ethane, and these gases may be used as carrier gases (fluidizing gases) in the fluidized bed.

[0044] If a dust collector is attached inside or outside the apparatus performing the catalytic cracking process, the catalyst may be removed from the second product P2 by the dust collector in the catalytic cracking process S13. At least a portion of the removed catalyst may be returned to the apparatus. Alternatively, at least a portion of the removed catalyst may be discharged outside the apparatus.

[0045] (Heat recovery process S14) The heat recovery step S14 is a step in which heat is recovered from the second product P2, which is a pyrolysis product, using a heat recovery device 31. If the pyrolysis product is rapidly cooled as is, the difference in sensible heat between the pyrolysis product after the catalytic decomposition step S13 and the pyrolysis product after rapid cooling is large, resulting in a large loss of sensible heat. By providing the heat recovery step S14 between the catalytic decomposition step S13 and the cooling step S15, heat can be utilized effectively.

[0046] On the other hand, if the raw material plastic contains PET, terephthalic acid may be produced during the thermal decomposition process. When the thermal decomposition products are cooled, a solid mainly containing the produced terephthalic acid precipitates and solidifies in the piping, potentially causing problems in the pathways and / or equipment of the olefin manufacturing system.

[0047] The inventors have found that when the pyrolysis product contains a metal compound, the PET content in the raw material and the amount of metal compound added affect the solid deposition temperature. Specifically, they found that when a feed containing a PET-containing plastic raw material with a metal compound added is pyrolyzed and the resulting pyrolysis product is cooled, the solid deposition temperature is approximated by the following equation (1).

[0048] f(x) = -12.57 × (X1) 2 +1.941 × (X²) + 274.13 (1) In equation (1) above, X1 is the molar ratio [-] of the metal compound added as an additive to the PET contained in the plastic supplied as a raw material. X2 is the percentage [wt%] of PET contained in the plastic supplied as a raw material. Note that if the raw material does not contain PET, then X1 = X2 = 0.

[0049] Based on the above findings, the heat recovery step S14 in this disclosure is performed at a temperature at which heat recovery is 5°C or more higher than the temperature f(x)[°C] derived from formula (1) above, and at a temperature of 450°C or lower. This configuration makes it possible to recover heat while reducing the possibility of solids containing terephthalic acid precipitation in the heat recovery step S14.

[0050] (Cooling process S15) The cooling step S15 is a step in which the secondary product P2 is cooled using the cooling device 40. In the cooling step, the secondary product P2 after heat recovery is cooled to approximately 0 to 100°C.

[0051] (Purification step S16) The purification step S16 is a step for separating and purifying the secondary product P2. The purification step S16 may be a step that separates the secondary product P2 into a gas containing at least one type of hydrocarbon with a small number of carbon atoms (e.g., C1-4) and a liquid containing at least one type of hydrocarbon with a large number of carbon atoms (e.g., C5 or more). Furthermore, the gas may be an olefin-rich gas containing 90% by mass or more of lower olefins. The lower olefin may contain at least one of ethylene, propylene, or butene. In addition, a purification step may be optionally added downstream of the purification step S16 in order to increase the purity of olefins with a specific number of carbon atoms in the olefin-rich gas obtained in the purification step S16.

[0052] The proportion of lower olefins having 2 and 3 carbon atoms obtained by the purification process S16 is 20 wt% or more relative to the raw material.

[0053] Furthermore, at least a portion of the hydrocarbon-containing liquid obtained in the purification step S16 may be supplied to the first pyrolysis unit 21 or the catalytic cracking unit 22. This can further improve the yield of olefins.

[0054] Alternatively, the hydrocarbon-containing liquid and / or lower paraffin gas obtained in the purification step S16 may be burned and used as a heat source in any of the steps from the pretreatment step S11 to the purification step S16. This reduces the environmental impact of the entire olefin manufacturing system.

[0055] (Summary of Embodiment 1) As described above, the exemplary method for producing an olefin of this disclosure comprises a pyrolysis step of pyrolyzing a raw material containing plastic to obtain a pyrolysis product, The process includes a heat recovery step for recovering heat from the thermal decomposition products, The aforementioned plastic contains polyethylene terephthalate, In the heat recovery process described above, the following equation (1); f(x) = -12.57 × (X1) 2 +1.941 × (X²) + 274.13 (1) A method for producing olefins, wherein heat recovery is performed at a temperature at least 5°C higher than the temperature f(x)[°C] derived from, and at a temperature of 450°C or lower, In the above equation (1), X1 is the molar ratio [-] of the metal compound to polyethylene terephthalate contained in the plastic, X2 is the proportion [wt%] of polyethylene terephthalate in the aforementioned plastic.

[0056] This configuration reduces the possibility of solid precipitation in the manufacturing process of producing olefins from plastics including PET.

[0057] In Embodiment 1, an example was described in which the pyrolysis process according to this disclosure includes two pyrolysis steps: a first pyrolysis step and a catalytic cracking step. However, the pyrolysis process is not limited to this configuration. For example, the pyrolysis process according to this disclosure may be, for example, an oil conversion step that converts to oil by pyrolysis, or a catalyst-free high-temperature pyrolysis step performed at a high temperature without a catalyst. Alternatively, it may be a combination of the various pyrolysis steps described above.

[0058] [Demonstration Test] The following describes the tests that demonstrated the method for producing the olefin related to this disclosure.

[0059] (Experimental apparatus) Figure 3 is a schematic diagram of the experimental apparatus used in this demonstration test. The experimental apparatus includes a reaction tube 101, a first electric furnace 102, a second electric furnace 103, a sheath tube 104, a first thermocouple 105, a second thermocouple 106, a cooling trap 107, and a gas bag 108.

[0060] The reaction tube 101 is made of glass, and the constricted section in the middle is filled with a catalyst. The upstream part of the reaction tube, located below the catalyst-filled section, functions as a pyrolysis section where thermal decomposition takes place. A first electric furnace 102, which is an electric furnace for thermal decomposition, is arranged around the pyrolysis section. The catalyst-filled section, located downstream of the pyrolysis section, functions as a catalytic decomposition section where catalytic decomposition takes place. A second electric furnace 103, which is an electric furnace for catalytic decomposition, is arranged around the catalytic decomposition section. Nitrogen gas is supplied to the pyrolysis section as a carrier gas. A first thermocouple 105 for measuring the catalytic decomposition temperature is located in the catalyst-filled section, and a second thermocouple 106 for measuring the deposition temperature is located inside the reaction tube above the catalyst-filled section.

[0061] (Experiment 1) The pyrolysis section of reaction tube 101 was filled with 1.82 g of polyethylene (Sumitomo Chemical: Sumikasen® G201F), 0.18 g of polyethylene terephthalate (Teijin TRN-TRJ), and 0.11 g of calcium oxide (Ube Materials). In addition, an MFI type zeolite catalyst (Si / Al=400) was filled into the constricted section downstream of the pyrolysis section to form the catalytic decomposition section (catalyst-filled section).

[0062] As a preliminary step to the reaction, nitrogen gas was flowed through the upstream side of the reaction tube at a rate of 10 mL / min, and only the catalyst-packed section was heated to 550°C for 1 hour to pre-treat the MFI-type zeolite catalyst. After that, the downstream side of the reaction tube was cooled to 525°C.

[0063] In the first stage of thermal decomposition, the decomposition product was obtained by maintaining the temperature T1:450°C in the thermal decomposition section while flowing nitrogen gas at a rate of 10 mL / min. In the second stage of thermal decomposition (catalytic decomposition), the decomposition product obtained as described above was introduced into a catalytic decomposition section at a temperature T2:525°C and brought into contact with an MFI-type zeolite catalyst. The entire amount of liquid catalytic decomposition product obtained 2 hours after the start of heating of the polyolefin plastic was collected in a cooling trap 107 cooled with ice water, and the entire amount of gaseous catalytic decomposition product was collected in a gas bag 108.

[0064] The molar ratio of calcium oxide to polyethylene terephthalate was calculated by dividing the added weight by the molecular weight of calcium oxide (56) and the molecular weight of PET (192), respectively, to determine the amount of substance (mol) added, and then dividing the amount of added calcium oxide by the amount of added polyethylene terephthalate.

[0065] The solid deposition temperature was measured using the following procedure. First, during the thermal decomposition reaction, when the temperature was stable, the first thermocouple 105 was lowered to the bottom of the sheath tube 104 (reference point), and while it was being gradually raised upwards, the distance from the reference point and the temperature measured at each point were recorded. From the obtained data, a graph showing the relationship between the distance from the reference point and the temperature data was created. The first thermocouple 105 was kept lowered to the bottom of the sheath tube 104 during the thermal decomposition reaction, except for the measurement operation of the temperature distribution. Immediately after the end of the thermal decomposition reaction, the distance from the reference point to the lower end of the solid deposited on the first thermocouple 105 was checked, and the solid deposition temperature was determined by comparing it with the created graph. The obtained solid deposition temperature (measured value) was 236.11°C.

[0066] Analysis of the recovered liquid and gaseous catalytic degradation products by gas chromatography revealed that the yield of lower olefins (C2-C3 olefins) based on the mass of the input plastic was 38.0% by mass.

[0067] (Other experiments) Experiments 2 through 6 were conducted using the same procedure as in Experiment 1 described above.

[0068] The various conditions and results for Experiments 1-6 are shown in Table 1 below. [Table 1]

[0069] (Regarding the approximate formula for solid precipitation temperature) Figure 4 is a graph showing the following approximate formula f(x) for the solid deposition temperature discovered by the inventors, and the solid deposition temperatures measured in Experiments 1 to 6. f(x) = -12.57 × (X1) 2 +1.941 × (X²) + 274.13 As shown in the graph in Figure 4, it has been demonstrated that the above equation f(x) can closely approximate the measured values. Note that the R of this model... 2 The score was 0.972.

[0070] Therefore, it was demonstrated that by performing heat recovery in the heat recovery process at a temperature at least 5°C higher than the initial temperature, but below 450°C, the possibility of solid precipitation can be significantly reduced.

[0071] [Embodiment 2] Other embodiments of this disclosure are described below. For the sake of clarity, components having the same function as those described in the above embodiments are denoted by the same reference numerals, and their descriptions are not repeated.

[0072] Figure 5 is a flowchart showing an example of an olefin manufacturing method according to Embodiment 2. As shown in Figure 1, the olefin manufacturing method of this embodiment includes a pretreatment step S11, a first pyrolysis step S12, a catalytic cracking step S13, a cooling step S15, and a purification step S16. The olefin manufacturing method according to Embodiment 2 differs from Embodiment 1 in that it does not include a heat recovery step S14. Each step other than the heat recovery step S14 may be the same as in Embodiment 1.

[0073] Figure 2 is a schematic diagram showing the main components of the manufacturing system 100A according to Embodiment 2. The manufacturing system 100A differs from the manufacturing system 100 of Embodiment 1 in that it has a heat retention configuration 32 instead of a heat recovery device 31. Other than that, it may be the same as the manufacturing system 100 of Embodiment 1.

[0074] The heat retention configuration 32 is provided in the pathway L4 and maintains the temperature of the second product P2 in the pathway L4 at a temperature at least 5°C higher than the temperature f(x)[°C] derived from the following equation (1), and within a range of 450°C or less. Equation (1) below is as described in Embodiment 1. f(x) = -12.57 × (X1) 2 +1.941 × (X²) + 274.13 (1) The thermal insulation configuration 32 may consist of, for example, temperature sensors, heat traces, and, if necessary, insulating material. One or more temperature sensors are installed inside and / or on the outer surface of the path L4 to measure the temperature of the path L4. As the heat trace, for example, an electric heater, steam piping, etc., can be used. The heat trace is installed along the path L4 to regulate the temperature of the path L4.

[0075] The heat retention configuration 32 can maintain the temperature of the second product P2 in path L4 within the above range by acquiring temperature data from a temperature sensor in real time and continuously adjusting the output of the heat trace based on the acquired data. Alternatively, the heat retention configuration 32 can maintain the temperature of the second product P2 in path L4 within the above range by increasing the output of the heat trace when the temperature in path L4 falls below a set value.

[0076] The heat retention configuration 32 may further include insulating material on the outside of the heat trace and temperature sensor. For example, glass wool or rock wool can be used as the insulating material. This can reduce heat dissipation and suppress temperature drop.

[0077] The above configuration makes it possible to reduce the possibility of solid precipitation in the manufacturing process of producing olefins from plastics including PET.

[0078] (summary) (1) A method for producing an olefin according to Embodiment 1 of the present disclosure includes a thermal decomposition step of thermally decomposing a raw material containing a plastic to obtain a thermal decomposition product, and a heat recovery step of recovering heat from the thermal decomposition product, wherein the plastic contains polyethylene terephthalate. In the heat recovery process described above, the following equation (1); f(x) = -12.57 × (X1) 2 +1.941 × (X²) + 274.13 (1) A method for producing olefins, wherein heat recovery is performed at a temperature at least 5°C higher than the temperature f(x)[°C] derived from, and at a temperature of 450°C or lower, In the above formula (1), X1 is the molar ratio [-] of the metal compound to the polyethylene terephthalate contained in the plastic, and X2 is the proportion [wt%] of polyethylene terephthalate in the plastic.

[0079] (2) In the method for producing an olefin according to Embodiment 2 of the present disclosure, the plastic contains 0.01 wt% to 10 wt% of polyethylene terephthalate in Embodiment 1.

[0080] (3) In the method for producing an olefin according to aspect 3 of the present disclosure, the pyrolysis step is carried out in the presence of a carrier gas introduced into the reaction system and under conditions of 450°C to 900°C.

[0081] (4) The method for producing an olefin according to Embodiment 4 of the present disclosure is, in any of Embodiments 1 to 3 above, the metal compound is an alkali metal compound, an alkaline earth metal compound, or a mixture thereof.

[0082] (5) The method for producing an olefin according to aspect 5 of the present disclosure is, in any of aspects 1 to 4 above, wherein the metal compound is a calcium compound.

[0083] (6) The method for producing an olefin according to aspect 6 of the present disclosure is, in aspect 5 above, the calcium compound is any of calcium oxide, calcium carbonate, or a mixture thereof.

[0084] (7) A method for producing an olefin according to Embodiment 7 of the present disclosure, in any of Embodiments 1 to 6 above, wherein the thermal decomposition step includes a first thermal decomposition step of thermally decomposing the raw material to obtain a first product, and a second thermal decomposition step of further thermally decomposing at least a portion of the first product to obtain the thermal decomposition product, wherein the second thermal decomposition step is a catalytic decomposition step using a catalyst.

[0085] (8) The method for producing an olefin according to Embodiment 8 of the present disclosure further includes a purification step of purifying the pyrolysis product to obtain an olefin in any of Embodiments 1 to 7 above, and the ratio of lower olefins having 2 and 3 carbon atoms obtained after the purification step to the raw material is 20 wt% or more.

[0086] (9) The method for producing an olefin according to Embodiment 9 of the present disclosure includes a pyrolysis step of pyrolyzing a raw material containing plastic to obtain a pyrolysis product, and a cooling step of cooling the pyrolysis product, wherein the plastic contains polyethylene terephthalate, and the temperature of the pyrolysis product in the pipe for supplying the pyrolysis product to the cooling step is maintained within a range of 5 °C or higher and 450 °C or lower than the temperature f(x) [°C] derived from the following formula (1); f(x)=-12.57×(X1) 2 +1.941×(X2)+274.13 (1) That is, it is a method for producing an olefin, and in the above formula (1), X1 is the molar ratio [-] of the metal compound to polyethylene terephthalate contained in the plastic, and X2 is the ratio [wt%] of polyethylene terephthalate in the plastic. In the above formula (1), X1 is the molar ratio [-] of the metal compound to polyethylene terephthalate contained in the plastic, and X2 is the ratio [wt%] of polyethylene terephthalate in the plastic.

[0087] 〔Supplementary Notes〕 The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention.

Explanation of Reference Numerals

[0088] 100, 100A... Manufacturing system 10... Pretreatment system 21... First pyrolysis device 22... Catalytic cracking device 31... Heat recovery device 32... Heat preservation structure 50... Purification device S11... Pre-treatment process S12...First pyrolysis step S13...Catalytic cracking process S14... Heat recovery process S15...Cooling process S16...Purification process

Claims

1. A thermal decomposition process in which raw materials containing plastics are thermally decomposed to obtain thermal decomposition products, The process includes a heat recovery step for recovering heat from the thermal decomposition products, The aforementioned plastic contains polyethylene terephthalate, In the heat recovery process described above, the following equation (1): f(x)=-12.57×(X １ ) ２ +1.941×(X ２ )+274.13 (1) A method for producing olefins, wherein heat recovery is performed at a temperature at least 5°C higher than the temperature f(x) [°C] derived from, and at a temperature of 450°C or lower, In the above formula (1), X １ This is the molar ratio [-] of the metal compound to the polyethylene terephthalate contained in the plastic, X ２ The method for producing an olefin, wherein the proportion [wt%] of polyethylene terephthalate in the aforementioned plastic is...

2. The method for producing an olefin according to claim 1, wherein the plastic contains 0.01 wt% to 10 wt% of polyethylene terephthalate.

3. The method for producing an olefin according to claim 1, wherein the thermal decomposition step is carried out in the presence of a carrier gas introduced into the reaction system under conditions of 450°C to 900°C.

4. The method for producing an olefin according to claim 1, wherein the metal compound is an alkali metal compound, an alkaline earth metal compound, or a mixture thereof.

5. The method for producing an olefin according to claim 1, wherein the metal compound is a calcium compound.

6. The method for producing an olefin according to claim 5, wherein the calcium compound is calcium oxide, calcium carbonate, or a mixture thereof.

7. The thermal decomposition step includes a first thermal decomposition step of thermally decomposing the raw material to obtain a first product, The process includes a second thermal decomposition step of further thermally decomposing at least a portion of the first product to obtain the thermal decomposition product, The method for producing an olefin according to claim 1, wherein the second thermal decomposition step is a catalytic decomposition step using a catalyst.

8. The process further includes a purification step of purifying the thermal decomposition product to obtain an olefin, The method for producing an olefin according to claim 1, wherein the proportion of lower olefins having 2 and 3 carbon atoms obtained after the purification step to the raw material is 20 wt% or more.

9. A thermal decomposition process in which raw materials containing plastics are thermally decomposed to obtain thermal decomposition products, The process includes a cooling step for cooling the thermal decomposition product, The aforementioned plastic contains polyethylene terephthalate, The temperature of the pyrolysis product in the piping that supplies the pyrolysis product to the cooling process is given by the following formula (1): f(x)=-12.57×(X １ ) ２ +1.941×(X ２ )+274.13 (1) A method for producing olefins, wherein the temperature is maintained at a range of 5°C or more higher than the temperature f(x) [°C] derived from and 450°C or less, In the above formula (1), X １ is the molar ratio [-] of the metal compound to polyethylene terephthalate contained in the plastic, X ２ The method for producing an olefin, wherein the proportion [wt%] of polyethylene terephthalate in the aforementioned plastic is...

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