Olefin production process

Abstract

Reduces the possibility of solids depositing during the olefin production process. The method for producing olefins using PET-containing plastics as raw materials includes a thermal decomposition step and a heat recovery step. In the heat recovery step, f(x)=-12.57×(X1) 2 Heat recovery is carried out at a temperature at least 5°C higher than the temperature f(x) [°C] derived from +1.941 × (X2) + 274.13, but not higher than 450°C. 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] The present invention relates to a process for producing olefins. [Background technology]

[0002] There is a technology that uses plastic as a raw material, thermally decomposes the plastic, and then performs gas-liquid separation or distillation to obtain a gas that contains a large amount of lower olefins. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Patent Application No. WO2023 / 047951 Summary of the Invention [Problem to be solved by the invention]

[0004] In the above-mentioned conventional techniques, when the raw plastic contains polyethylene terephthalate, there is a possibility that a solid containing terephthalic acid may precipitate during the cooling operation.

[0005] One aspect of the present invention aims to reduce the possibility of solids being deposited during the production of olefins. [Means for solving the problem]

[0006] An olefin production method according to one embodiment of 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, wherein the plastic contains polyethylene terephthalate, and in the heat recovery step, a compound represented by 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 carried out at a temperature 5°C or higher than the temperature f(x) [°C] derived from the above formula and 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 embodiment 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 for supplying the pyrolysis product to the cooling step is controlled based on the following formula (1): f(x)=-12.57×(X1) 2 +1.941×(X2)+274.13 (1) A method for producing an olefin, wherein the temperature is maintained in a range of 5°C or more higher than the temperature f(x) [°C] derived from the above formula and 450°C or less, 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. [Effects of the Invention]

[0008] According to one aspect of the present disclosure, the possibility of solid matter precipitating during the olefin production process can be reduced. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a flowchart illustrating an example of a method for producing an olefin according to a first embodiment of the present disclosure. [Figure 2] 1 is a system diagram schematically illustrating a main configuration of a manufacturing system according to a first embodiment of the present disclosure. [Figure 3] FIG. 1 is a schematic diagram of the experimental device used in the demonstration test. [Figure 4] 1 is a graph comparing actual measured values ​​of solid precipitation temperature with an approximate curve. [Figure 5] 1 is a flowchart illustrating an example of a method for producing an olefin according to a second embodiment of the present disclosure. [Figure 6] FIG. 10 is a system diagram schematically illustrating the main configuration of a manufacturing system according to a second embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0010] [Embodiment 1] An embodiment of the present disclosure will be described in detail below.

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

[0012] The olefin production method according to the present disclosure is a method for producing lower olefins that can be recycled as plastic raw materials using plastics such as waste plastics as raw materials. The olefin production method according to the present disclosure includes a pyrolysis step of pyrolyzing a raw material containing plastics 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 an olefin production method according to this embodiment. As shown in Fig. 1, the olefin production method according to this embodiment includes a pretreatment step S11, a first thermal cracking 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 this embodiment, an olefin production system (production system 100 in FIG. 2) that realizes the flowchart shown in FIG. 1 and the production flow shown in the flowchart will be described as an example. 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 other embodiments described below.

[0015] <Olefin production system (production system 100)> First, an example of the configuration of the manufacturing system 100 will be described with reference to Figures 1 and 2. Figure 2 is a system diagram that schematically shows the main configuration of the manufacturing system 100 according to the first embodiment.

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

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

[0018] A raw material is supplied to the pretreatment system 10 via a path L1. The raw material supplied via the path L1 may be plastic, such as waste plastic. In addition to the raw material, an additive may also be supplied to the pretreatment system 10. The additive may be supplied to the first pyrolysis device 21 instead of the pretreatment system 10.

[0019] The outlet of the pretreatment system 10 is connected to the inlet of the first thermal cracking device 21 via a path L2. The feed M pretreated by the pretreatment system 10 is supplied to the first thermal cracking device 21 via the path L2. The first thermal cracking device 21 and the catalytic cracking device 22 are connected via a path L3. The feed M supplied to the first thermal cracking device 21 is thermally cracked and supplied to the catalytic cracking device 22 via the path L3 as a first product P1. The first product P1 may be a gas, a liquid, or a mixture of gas and liquid. The catalytic cracking device 22 and the cooling device are connected via a path L4. The first product P1 supplied to the catalytic cracking device 22 is catalytically cracked and supplied to the cooling device 40 as a second product P2. The second product P2 is an example of a thermal cracking product according to the present disclosure.

[0020] The cooling device and the purification device 50 are connected by a path L5. The second product P2 supplied to the cooling device 40 is cooled and supplied to the purification device 50. The second 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 pretreatment system 10 processes plastics, such as waste plastics, to produce a feedstock M suitable for decomposition. In other words, the pretreatment system 10 is a system that performs the pretreatment step S11. The pretreatment system 10 may include multiple devices that perform different processes. For example, the pretreatment system 10 may include one or more devices selected from the group consisting of a sorting device, a crushing device, a cleaning device, a drying device, a melting device, and a dechlorination device. The sorting device is a device that separates polyolefin-based plastics from raw materials, such as waste plastics. The sorting device may include one or more devices, such as an optical sorting device or a gravity separator. The crushing device is a device that crushes sorted plastics. The cleaning device is a device that cleans crushed plastics. The drying device is a device that dries cleaned plastics. The melting device is a device that heats plastics to liquefy them. The dechlorination device is a device that removes chlorine from plastics.

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

[0023] The first pyrolysis device 21 may also include a dust collector attached to the inside or outside of the device for removing solids from the first product P1. For example, one or more of a cyclone, a ceramic filter, an electrostatic precipitator, and a bag filter may be used as the dust collector. A plurality of such dust collectors may be used, and the plurality of dust collectors may be connected in parallel or in series. The dust collector may also include a pipe for discharging the collected solids to the outside of the device. The dust collector may also include a pipe for returning a portion of the collected solids to the inside of the device.

[0024] Furthermore, a plurality of the above-described devices may be used as the first pyrolysis device 21, and the plurality of reactors may be connected in parallel or in series. Heat obtained by burning one or more of the pyrolysis residue generated in the first pyrolysis device 21, the hydrocarbon-containing liquid and / or lower paraffin gas obtained in the refining step S16, or a hydrocarbon fuel such as natural gas or kerosene may be used as the heat source required in the first pyrolysis step S12. Alternatively, heat obtained by electrical heating or microwave irradiation may also be used as the heat source. Alternatively, two or more of electrical heating, microwave heating, and the heat obtained from the above-described combustion may be used in combination.

[0025] The heating method may be either direct or indirect. Direct heating involves placing a microwave-absorbing material (susceptor) inside the device and supplying microwave energy to the waste plastic through it. Indirect heating involves supplying heat from an electric heater or the combustion of hydrocarbon fuel through the device's heat transfer surface, or by preheating inert gases such as steam, nitrogen gas, or CO2 gas to a high temperature using a heat source before introducing them into the device. Alternatively, solids primarily composed of iron, iron oxide, alumina, or silica may be preheated to a high temperature using a heat source before being introduced into the device. Preheating of gases or solid particles using a heat source may be performed using a portion of the interior of the first pyrolysis device 21 or a device similar to the pyrolysis device, combined with the first pyrolysis device 21, to circulate the gases and solids from these devices.

[0026] The catalytic cracking unit 22 is a unit that performs the catalytic cracking step S13. Specifically, the catalytic cracking unit 22 is a unit that cracks substances by bringing the first product P1 into contact with a catalyst. As the catalytic cracking unit 22, for example, a fixed bed, a moving bed, or a fluidized bed can be used. Furthermore, as the catalytic cracking unit 22, a plurality of these exemplified reactors may be used, and the plurality of reactors may be connected in parallel or in series.

[0027] The catalytic cracking unit 22 may also be provided with a dust collector attached to the inside or outside of the unit for removing catalyst from the second product P2. For example, one or more of a cyclone, a ceramic filter, an electrostatic precipitator, and a bag filter can be used as the dust collector. A plurality of such dust collectors may be used, and the plurality of dust collectors may be connected in parallel or in series. The dust collector may also be provided with a pipe for discharging the recovered catalyst outside the unit. The dust collector may also be provided with a pipe for returning at least a portion of the recovered catalyst to the unit where catalytic cracking is performed.

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

[0029] The heating method may be either direct or indirect. Direct heating involves placing a microwave-absorbing material (susceptor) inside the device and supplying microwave energy to the waste plastic through it. Indirect heating involves supplying heat from an electric heater or hydrocarbon fuel combustion through the device's heat transfer surface, or heating inert gases such as steam, nitrogen gas, or CO2 gas to a high temperature using a heat source before introducing them into the device. Alternatively, solids primarily composed of iron, iron oxide, alumina, or silica may be preheated to a high temperature using a heat source before being introduced into the device. The solid particles may be the catalyst. Preheating of gases or solid particles using a heat source may be performed using a portion of the interior of the first pyrolysis device 21 or a device similar to the first pyrolysis device 21, combined with the first pyrolysis device 21, to circulate the gases and solids from these devices.

[0030] The heat recovery device 31 is provided on 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 performing the heat recovery step S14 of this embodiment. As the heat recovery device 31, for example, a shell-and-tube heat exchanger or a plate-type heat exchanger can be used.

[0031] The cooling device 40 is a device that cools the second product P2 after heat recovery. In other words, the cooling device 40 is a device that can perform the cooling step S15 of this embodiment. As the cooling device, for example, a spray tower, a plate tower, a packed tower, or a cooling can (submerged cooling using an immersion tube) can be used.

[0032] The purification apparatus 50 is an apparatus capable of separating the mixture supplied thereto by a known gas-liquid separation operation, distillation operation, or the like. In other words, the purification apparatus 50 is an apparatus capable of performing the purification step S16 of this embodiment. The purification apparatus 50 can be, for example, a gas-liquid separation apparatus or a distillation apparatus. These apparatuses may also be combined, or a plurality of these apparatuses may be connected. Note that, in order to increase the purity of the olefins obtained in the purification apparatus 50 to an olefin having a desired carbon number, a distillation apparatus may be optionally installed downstream of the purification apparatus 50.

[0033] <Olefin production method> The olefin production method according to the first embodiment is carried out, for example, according to the flowchart shown in Fig. 1. Note that the flowchart shown in Fig. 1 is an example and is not limiting. Each step in the olefin production method according to the first embodiment will be described in detail.

[0034] (About ingredients) Before describing each step, the raw material used in the present 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 or the like. The plastic is preferably primarily composed of polyolefins such as polyethylene or polypropylene, but may also contain other plastics. The other plastics may include, for example, chlorinated plastics (e.g., 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 olefin production method according to the present disclosure is particularly suitable for applications in which the plastic used as the raw material contains 0.01 wt% to 10 wt% PET. Furthermore, the waste plastic may include virgin mixed plastics or post-consumer mixed plastics. The polyolefin-based plastic content in the raw plastic is preferably 60 wt% or more, more preferably 80 wt% or more, and even more preferably 90 wt% or more.

[0035] In the olefin production method according to the present disclosure, an additive may be added to the raw material supplied to the pretreatment step or to the feed M after the pretreatment step. In other words, the additive may be added in the pretreatment step S11 or in the first pyrolysis step S12. A metal compound may be used as the additive. The metal compound may be, for example, an alkali metal compound, an alkaline earth metal compound, or a mixture 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] (Pretreatment step S11) The pretreatment step S11 is a step in which the plastic is pretreated to obtain a feed material M to be supplied to the first pyrolysis step S12. The plastic undergoes the pretreatment step S11 and can be supplied to the first pyrolysis step S12 as a feed material M containing mainly polyolefin-based plastics. As a result of the pretreatment step S11, the polyolefin-based plastic content in the raw plastics is preferably 80% by mass or more, 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 supply M is decomposed by heating to obtain a first product P1. In other words, the first pyrolysis step S12 is included in the pyrolysis step according to the present disclosure. By the pyrolysis in the first pyrolysis step S12, the carbon compounds contained in the supply M are decomposed into smaller molecules, primarily into hydrocarbons having approximately 1 to 30 carbon atoms. In other words, the average carbon number of 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 supply M. A high pyrolysis temperature is desirable because it accelerates the decomposition rate of plastics. However, if the temperature is too high, carbonization will occur. Therefore, the pyrolysis temperature may be, for example, 450°C to 900°C, 500°C to 750°C, or 500°C to 650°C. Regarding the pressure in the first pyrolysis step S12, low pressure is desirable 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 or more and 1000 kPaG or less, −10 kPaG or more and 300 kPaG or less, or 0 kPaG or more and 100 kPaG or less.

[0038] In addition, a catalyst may be optionally used in the first pyrolysis step S12 to promote 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. The silicate catalyst may typically contain silicon, aluminum, oxygen, and hydrogen atoms. The silicate catalyst may also contain atoms such as sodium, titanium, chromium, manganese, iron, cobalt, nickel, copper, ruthenium, rhodium, palladium, silver, iridium, platinum, boron, nitrogen, magnesium, phosphorus, zinc, and gallium.

[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 a fluidizing gas or carrier gas for the fluidized bed. When a fluidized bed reactor is used in the first pyrolysis step S12, these carrier gases may be used as a fluidizing gas. The more fluidizing gas there is, the lower the hydrocarbon concentration in the gas phase, and the more likely the cracked components are to be vaporized. The linear velocity of the fluidizing gas in the fluidized bed reactor may be 0.1 cm / s or more and 500 cm / s or less.

[0040] If a dust collector is attached inside or outside the apparatus performing the first pyrolysis step, solid matter can 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 and discharged by the dust collector 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 cracked in the presence of a catalyst to produce a second product P2 in which the first product P1 is decomposed into hydrocarbons having approximately 1 to 20 carbon atoms. The catalytic cracking step S13 is included in the thermal cracking step according to the present disclosure. The cracking temperature in the catalytic cracking step S13 can 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, -80 kPaG to 1000 kPaG, -10 kPaG to 300 kPaG, or 0 kPaG to 100 kPaG.

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

[0043] In the catalytic cracking step S13, a gas containing at least one of an inert gas such as nitrogen gas or argon gas, water (steam), CO2 gas, methane, or ethane may be introduced into the reaction system. In other words, in the catalytic cracking step S13, at least one of an inert gas such as nitrogen gas or argon gas, water (steam), CO2 gas, methane, or ethane may be allowed to coexist, and these gases may be used as carrier gases (fluidizing gases) for the fluidized bed.

[0044] If a dust collector is provided inside or outside the apparatus performing the catalytic cracking step, the catalyst may be removed from the second product P2 by the dust collector in the catalytic cracking step 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 to the outside of the apparatus.

[0045] (Heat recovery process S14) The heat recovery step S14 is a step of recovering heat from the second product P2, which is a pyrolysis product, using a heat recovery device 31. If the pyrolysis product is quenched as is, the difference in sensible heat between the pyrolysis product after the catalytic cracking step S13 and the pyrolysis product after quenching is large, resulting in a large amount of sensible heat loss. By providing the heat recovery step S14 between the catalytic cracking step S13 and the cooling step S15, heat can be used effectively.

[0046] On the other hand, when the raw plastic contains PET, terephthalic acid may be produced during the pyrolysis process. When the pyrolysis product is cooled, a solid containing mainly terephthalic acid precipitates and solidifies in the piping, which may cause problems in the routes and / or equipment in the olefin production system.

[0047] The present inventors have found that when a pyrolysis product contains a metal compound, the PET content in the raw material and the amount of metal compound added affect the solid precipitation temperature. Specifically, when a pyrolysis product obtained by pyrolyzing a feedstock in which a metal compound is added to a plastic raw material containing PET is cooled, the solid precipitation temperature can be approximated by the following formula (1).

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

[0049] Based on the above findings, in the heat recovery step S14 of the present disclosure, heat recovery is performed at a temperature that is 5°C or higher than the temperature f(x) [°C] derived from the above formula (1) and is 450°C or lower. With this configuration, heat recovery can be performed while reducing the possibility of precipitation of a solid containing terephthalic acid in the heat recovery step S14.

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

[0051] (Purification step S16) The purification step S16 is a step of separating and purifying the second product P2. The purification step S16 may be, for example, a step of separating the second product P2 into a gas containing at least one hydrocarbon with a low carbon number (e.g., C1-4) and a liquid containing at least one hydrocarbon with a high carbon number (e.g., C5 or higher). Furthermore, the gas may be an olefin-rich gas containing 90 mass% or more of lower olefins. The lower olefins may include at least one of ethylene, propylene, and butene. Note that, in order to increase the purity of olefins with a desired carbon number in the olefin-rich gas obtained in the purification step S16, an optional purification step may be added downstream of the purification step S16.

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

[0053] At least a portion of the liquid containing hydrocarbons obtained in the refining step S16 may be supplied to the first thermal cracking 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 refining step S16 may be combusted and used as a heat source in any of the steps from the pretreatment step S11 to the refining step S16, thereby reducing the environmental load of the entire olefin production system.

[0055] (Summary of embodiment 1) As described above, an exemplary method for producing olefins according to the present disclosure includes a pyrolysis step of pyrolyzing a raw material containing plastic to obtain a pyrolysis product; a heat recovery step of recovering heat from the pyrolysis product, the plastic contains polyethylene terephthalate; 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 carried out at a temperature 5°C or higher than the temperature f(x) [°C] derived from the above formula and 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, X2 is the proportion [wt%] of polyethylene terephthalate in the plastic.

[0056] This configuration can reduce the possibility of solids precipitating in the manufacturing process for producing olefins from plastics including PET.

[0057] In the first embodiment, the thermal decomposition process according to the present disclosure includes two thermal decomposition processes, a first thermal decomposition process and a catalytic decomposition process. However, the thermal decomposition process is not limited to this configuration. For example, the thermal decomposition process according to the present disclosure may be, for example, an oil-reducing process in which oil is produced by thermal decomposition, or a non-catalytic high-temperature thermal decomposition process carried out at high temperatures without a catalyst. Alternatively, the thermal decomposition process may be a combination of the various thermal decomposition processes described above.

[0058] [Demonstration test] The following describes tests that demonstrated the process for producing olefins according to the present disclosure.

[0059] (Experimental equipment) 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 cold trap 107, and a gas bag 108.

[0060] The reaction tube 101 is made of glass, and the narrowed section located in the middle is filled with a catalyst. The upstream reaction tube located below the catalyst-filled section functions as the thermal cracking section where thermal cracking takes place. A first electric furnace 102, which is an electric furnace for thermal cracking, is arranged around the thermal cracking section. The catalyst-filled section located downstream of the thermal cracking section functions as the catalytic cracking section where catalytic cracking takes place. A second electric furnace 103, which is an electric furnace for catalytic cracking, is arranged around the catalytic cracking section. Nitrogen gas is supplied to the thermal cracking section as a carrier gas. A first thermocouple 105 for measuring the catalytic cracking 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) 1.82 g of polyethylene (Sumikathene (registered trademark) G201F manufactured by Sumitomo Chemical Co., Ltd.), which is a polyolefin-based plastic, 0.18 g of polyethylene terephthalate (TRN-TRJ manufactured by Teijin Co., Ltd.), and 0.11 g of calcium oxide (manufactured by Ube Materials, Inc.) were packed into the thermal cracking section of the reaction tube 101. In addition, an MFI-type zeolite catalyst (Si / Al=400) was packed into the narrowed section downstream of the thermal cracking section to form a catalytic cracking section (catalyst-packed section).

[0062] As a preliminary preparation for the reaction, nitrogen gas was passed through the upstream of the reaction tube at 10 mL / min, and only the catalyst-packed section was heated at 550°C for 1 hour to pretreat the MFI zeolite catalyst. After that, the temperature of the downstream reaction tube was lowered to 525°C.

[0063] The first-stage thermal cracking was carried out by flowing nitrogen gas at 10 mL / min and setting the temperature of the thermal cracking section, T1, to 450°C to obtain a decomposition product. The second-stage thermal cracking (catalytic cracking) was carried out by introducing the decomposition product obtained as described above into a catalytic cracking section set to a temperature, T2, of 525°C, and bringing it into contact with an MFI zeolite catalyst. The entire liquid catalytic cracking product obtained two hours after the start of heating the polyolefin plastic was collected in a cooling trap 107 cooled with ice water, and the entire gaseous catalytic cracking 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 by the molecular weight of PET (192) to calculate the amount of substance (mol) added, and then dividing the amount of substance of calcium oxide added by the amount of substance of polyethylene terephthalate added.

[0065] The solid precipitation 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 then successively raised upward, recording the distance from the reference point and the temperature measured at each point. 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 maintained lowered to the bottom of the sheath tube 104 during the thermal decomposition reaction except for the temperature distribution measurement operation. Immediately after the end of the thermal decomposition reaction, the distance from the reference point to the bottom of the solid precipitated on the first thermocouple 105 was confirmed, and the solid precipitation temperature was calculated by comparing this with the created graph. The obtained solid precipitation temperature (actual measured value) was 236.11°C.

[0066] The recovered liquid catalytic cracking product and gaseous catalytic cracking product were analyzed by gas chromatography, and the yield of lower olefins (C2-C3 olefins) was 38.0 mass% based on the mass of the charged plastic.

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

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

[0069] (Approximate formula for solid precipitation temperature) FIG. 4 is a graph showing the following approximate formula f(x) of the solid precipitation temperature, which the present inventors have found, and the solid precipitation temperatures actually 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 formula f(x) can adequately approximate the measured values. 2 The score was 0.972.

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

[0071] [Embodiment 2] Other embodiments of the present disclosure will be described below. For ease of explanation, the same reference numerals will be used to designate components having the same functions as those described in the above embodiment, and the description thereof will not be repeated.

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

[0073] 2 is a system diagram showing a schematic diagram of the main components of a 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 system 32 instead of a heat recovery device 31. Other than that, the manufacturing system 100A may be the same as the manufacturing system 100 of embodiment 1.

[0074] The heat retention structure 32 is provided on the path L4 and maintains the temperature of the second product P2 on the path L4 within a range that is at least 5°C higher than the temperature f(x) [°C] derived from the following formula (1) and is not higher than 450°C. The following formula (1) is as described in the first embodiment. f(x)=-12.57×(X1) 2 +1.941×(X2)+274.13 (1) The heat retention structure 32 may include, for example, a temperature sensor, heat tracing, and, if necessary, an 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. The heat tracing may be, for example, an electric heater, a steam pipe, or the like. The heat tracing is installed along the path L4 to adjust the temperature of the path L4.

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

[0076] The heat retention structure 32 may further include a heat insulating material on the outside of the heat trace and temperature sensor. Examples of the heat insulating material include glass wool and rock wool. This reduces the amount of heat radiation and suppresses temperature drops.

[0077] The above-described configuration can reduce the possibility of solids precipitating in the manufacturing process for producing olefins from plastics including PET.

[0078] (summary) (1) A method for producing an olefin according to a first aspect of the present disclosure includes a pyrolysis step of pyrolyzing a raw material containing a plastic to obtain a pyrolysis product, and a heat recovery step of recovering heat from the pyrolysis product, wherein the plastic contains polyethylene terephthalate; 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 carried out at a temperature 5°C or higher than the temperature f(x) [°C] derived from the above formula and 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) A method for producing an olefin according to a second aspect of the present disclosure is the method for producing an olefin according to the first aspect, wherein the plastic contains 0.01 wt% or more and 10 wt% or less of polyethylene terephthalate.

[0080] (3) Aspect 3 of the present disclosure relates to a method for producing an olefin, wherein in the above-mentioned aspect 1 or 2, the pyrolysis step is carried out under conditions of 450°C or higher and 900°C or lower in the presence of a carrier gas introduced into the reaction system.

[0081] (4) A fourth aspect of the present disclosure relates to a method for producing an olefin, in any one of the first to third aspects, wherein the metal compound is an alkali metal compound, an alkaline earth metal compound, or a mixture thereof.

[0082] (5) A fifth aspect of the present disclosure relates to the method for producing an olefin, in any one of the first to fourth aspects, wherein the metal compound is a calcium compound.

[0083] (6) A sixth aspect of the present disclosure provides a method for producing an olefin according to the fifth aspect, wherein the calcium compound is calcium oxide, calcium carbonate, or a mixture thereof.

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

[0085] (8) The olefin production method according to aspect 8 of the present disclosure, in any one of aspects 1 to 7 above, further includes a purification step of purifying the pyrolysis product to obtain olefins, and the proportion of lower olefins having carbon numbers of 2 and 3 obtained after the purification step relative to the raw material is 20 wt % or more.

[0086] (9) A ninth aspect of the present disclosure provides a method for producing an olefin, comprising: 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 determined based on the following formula (1): f(x)=-12.57×(X1) 2 +1.941×(X2)+274.13 (1) A method for producing an olefin, wherein the temperature is maintained in a range of 5°C or more higher than the temperature f(x) [°C] derived from the above formula and 450°C or less, 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.

[0087] [Additional Notes] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of 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 symbols]

[0088] 100, 100A... Manufacturing System 10. Pretreatment system 21...1st pyrolysis device 22...Catalytic cracking equipment 31. Heat recovery device 32...Heat insulation configuration 50...purification equipment S11: Pretreatment process S12...First pyrolysis step S13...Catalytic cracking process S14 Heat recovery process S15...Cooling process S16...Purification process

Claims

1. a pyrolysis step of pyrolyzing a raw material containing plastic to obtain a pyrolysis product; a heat recovery step of recovering heat from the pyrolysis product, the plastic contains polyethylene terephthalate; In the heat recovery step, the following formula (1): f(x)=-12.57×(X １ ) ２ +1.941×(X ２ )+274.13 (1) A method for producing olefins, wherein heat recovery is carried out at a temperature 5°C or higher than the temperature f(x) [°C] derived from the above and 450°C or lower, In the above formula (1), X １ is the molar ratio [-] of the metal compound to the polyethylene terephthalate contained in the plastic, X ２ is the proportion [wt%] of polyethylene terephthalate in the plastic.

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

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

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; a second pyrolysis step of further pyrolyzing at least a portion of the first product to obtain the pyrolysis product; The method for producing olefins according to claim 1, wherein the second thermal cracking step is a catalytic cracking step using a catalyst.

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

9. a pyrolysis step of pyrolyzing a raw material containing plastic to obtain a pyrolysis product; a cooling step of cooling the pyrolysis product, the plastic contains polyethylene terephthalate; The temperature of the pyrolysis product in the pipe supplying the pyrolysis product to the cooling step is calculated by the following formula (1): f(x)=-12.57×(X １ ) ２ +1.941×(X ２ )+274.13 (1) A method for producing an olefin, wherein the temperature is maintained in a range of 5°C or more higher than the temperature f(x) [°C] derived from the above formula and 450°C or less, In the above formula (1), X １ is the molar ratio [-] of the metal compound to the polyethylene terephthalate contained in the plastic, X ２ is the proportion [wt%] of polyethylene terephthalate in the plastic.

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