Olefin production method

Abstract

Provided is an olefin production method capable of reducing deterioration of catalytic activity of zeolite even when a polyolefin containing polyethylene terephthalate is used as a raw material. A production method according to the present disclosure comprises the following steps. Step S12: A step for thermally decomposing a raw material containing polyolefin and polyethylene terephthalate to obtain a hydrocarbon. Step S13: A step for catalytically decomposing the hydrocarbon with a zeolite-containing catalyst to obtain an olefin. In step S12, the content of polyethylene terephthalate in the raw material is 0.1 mass% or more, with the total content of polyolefin and polyethylene terephthalate being 100 mass%. In step S13, the amount of acid sites in the zeolite-containing catalyst as measured at 250-650°C by an ammonia temperature-programmed desorption method is 30-800 μmol / g.

Description

Method for producing olefin

[0001] The present invention relates to a method for producing olefins.

[0002] Olefins, which are the main raw materials for plastics, are usually produced from petroleum. However, recently, technologies for producing olefins from waste plastics have been developed with the aim of realizing a carbon recycling society. For example, Patent Document 1 discloses a method for producing olefins by thermally decomposing and catalytically decomposing polyolefins as raw materials. In this document, the catalyst used for catalytic decomposition is MFI-type zeolite.

[0003] International Publication No. 2021 / 166854

[0004] It is common for plastic products used daily to contain polymers other than polyolefins. In this regard, according to the findings of the present inventors, when the technology described in Patent Document 1 is used in the case where the raw material is a mixture, the catalytic activity of the zeolite may decrease. Specifically, it has been found that when the technology described in Patent Document 1 is used with a raw material in which polyethylene terephthalate is mixed into polyolefin, the catalytic activity decreases depending on the amount of acid sites of the zeolite.

[0005] One aspect of the present invention aims to provide a method for producing olefins that can reduce the decrease in the catalytic activity of zeolite even when using polyolefin containing polyethylene terephthalate as a raw material.

[0006] The present invention includes the following aspects: <1> A method for producing an olefin, comprising the following steps S12 and S13: Step S12: A step of thermally decomposing a raw material containing polyolefin and polyethylene terephthalate to obtain a hydrocarbon; Step S13: A step of catalytically decomposing the hydrocarbon with a catalyst containing zeolite to obtain an olefin; where, in step S12, the content of polyethylene terephthalate in the raw material is 0.1% by mass or more, with the total content of polyolefin and polyethylene terephthalate being 100% by mass; and in step S13, the amount of acid sites of the catalyst containing zeolite, measured at 250 to 650°C by ammonia thermal desorption, is 30 to 800 μmol / g. <2> The method for producing an olefin according to <1>, wherein the hydrocarbon obtained in step S12 is a gas and / or liquid. <3> The manufacturing method according to <1> or <2>, wherein the olefin obtained in step S13 comprises one or more selected from the group consisting of ethylene, propylene, butene, and pentene. <4> The manufacturing method according to any one of <1> to <3>, wherein in step S13, the zeolite has an MFI structure. <5> The manufacturing method according to any one of <1> to <4>, wherein in step S13, the zeolite contains phosphorus. <6> The manufacturing method according to any one of <1> to <5>, wherein step S13 is carried out under conditions satisfying (i) and (ii) below: (i) in the presence of a carrier gas supplied to the reaction system; (ii) the reaction temperature is 400 to 800°C. <7> The manufacturing method according to <6>, wherein the carrier gas is water vapor and / or nitrogen gas. <8> The manufacturing method according to <6> or <7>, wherein the flow rate of the carrier gas is 0.05 to 1.0 parts by mass, where the flow rate of the hydrocarbon supplied to step S13 is 1.

[0007] According to one aspect of the present invention, a method for producing olefins is provided that can reduce the decrease in the catalytic activity of zeolite even when using polyolefins containing polyethylene terephthalate as raw materials.

[0008] This is a flowchart illustrating an example of a manufacturing method according to one aspect of the present invention. This is a block diagram illustrating an implementation example of a manufacturing method according to one aspect of the present invention.

[0009] One embodiment of the present invention is described below. However, the present invention is not limited to the configurations described below. The present invention can be modified in various ways within the scope of the claims. The technical scope of the present invention also extends to embodiments or examples obtained by appropriately combining the multiple technical means disclosed herein. In this case, the multiple technical means may be disclosed across multiple embodiments or examples.

[0010] Unless otherwise specified in this specification, "A to B" representing a numerical range means "greater than or equal to A and less than or equal to B".

[0011] [1. Method for Producing Olefins] A method for producing olefins according to one embodiment of the present invention will be described below with reference to the exemplary Figure 1. In the production method shown in Figure 1, steps S11, S12, S13, and S14 are carried out in this order. Of these, steps S11 and S14 are optional steps and may or may not be carried out.

[0012] According to this manufacturing method, polyolefins are decomposed to obtain an olefin-rich gas that is rich in olefins (particularly lower olefins with 2 to 5 carbon atoms). The following describes each step in detail.

[0013] [1.1. Process S11: Pretreatment] In process S11, the plastic is pretreated. The pretreated plastic becomes a feed material M mainly containing polyolefins and is sent to process S12. The plastic supplied to process S11 is, for example, waste plastic and contains polyolefins (polyethylene, polypropylene, etc.). When comparing the plastic supplied to process S11 with the feed material M sent to process S2, the latter usually has a higher polyolefin content.

[0014] The polyolefin content in the plastic supplied to process S11 may be 60% by mass or more, 80% by mass or more, or 90% by mass or more, based on 100% by mass of the total amount of plastic. The polyolefin content in the supply M may be 80% by mass or more, 90% by mass or more, or 95% by mass or more, based on 100% by mass of the total amount of supply M.

[0015] The supply material M contains polyethylene terephthalate in addition to polyolefin. The lower limit of the polyethylene terephthalate content in supply material M is 0.1% by mass or more, and may be 0.5% by mass or more, or 1% by mass or more, based on the total content of polyolefin and polyethylene terephthalate as 100% by mass. The upper limit of the polyethylene terephthalate content in supply material M may be 25% by mass or less, 20% by mass or less, or 15% by mass or less, based on the total content of polyolefin and polyethylene terephthalate as 100% by mass. Furthermore, the lower limit of the polyethylene terephthalate content in supply material M may be 0.05% by mass or more, 0.1% by mass or more, 0.25% by mass or more, 0.5% by mass or more, 0.75% by mass or more, or 1% by mass or more, based on the total amount of supply material M as 100% by mass. The upper limit of the polyethylene terephthalate content in the supply M may be 25% by mass or less, 22.5% by mass or less, 20% by mass or less, 17.5% by mass or less, 15% by mass or less, 12.5% ​​by mass or less, or 10% by mass or less, with the total content of polyolefin and polyethylene terephthalate being 100% by mass.

[0016] [1.2. Step S12: Thermal Decomposition] In step S12, the feed material M is thermally decomposed. The first product P1 obtained by thermal decomposition mainly contains hydrocarbons and is sent to step S13. The number of carbon atoms in the hydrocarbons contained in the first product P1 may be 1 to 30. The average number of carbon atoms in the hydrocarbons contained in the first product P1 may be 8 to 30. The hydrocarbons contained in the first product P1 may be gases, liquids, or mixtures thereof. In one embodiment, the hydrocarbons contained in the first product P1 include one or more selected from the group consisting of normal paraffins, cycloparaffins, isoparaffins, olefins, cycloolefins, and isoolefins.

[0017] The thermal decomposition temperature in step S12 may be set based on the composition of the feed material M. A higher thermal decomposition temperature results in a faster decomposition rate of the plastic, but if it is too high, it will carbonize. Taking this into consideration, the upper limit of the thermal decomposition temperature may be 800°C or less, 595°C or less, or 550°C or less. The lower limit of the thermal decomposition temperature may be 350°C or higher, 380°C or higher, or 400°C or higher.

[0018] At least a portion of the heat source required in step S12 may be supplied by combustion. Examples of fuels used in combustion include the pyrolysis residue in step S12, a hydrocarbon-containing liquid and / or lower paraffin gas in step S14, and fuels introduced from outside the system (natural gas, kerosene, etc.). Alternatively, at least a portion of the heat source required in step 12 may be supplied by electric heating or microwave irradiation.

[0019] The heating method can be either direct heating or indirect heating. An example of direct heating is a method in which microwave energy is directly supplied to the supply M via a microwave-absorbing material (susceptor). An example of indirect heating is a method in which heat obtained by an electric heater or combustion is supplied via the heat transfer surface of the device, or by using a high-temperature gas (water vapor, nitrogen gas, CO2). ２Methods include introducing gases or other substances into the apparatus, and introducing heated solid particles (mainly composed of iron, iron oxide, alumina, silica, etc.) into the apparatus. For preheating the gases or solid particles introduced into the apparatus, the same apparatus used in process S12 may be used, or an apparatus combined with the apparatus used in process S12 may be used. The gases or solid particles introduced into the apparatus may be circulated.

[0020] In step S12, a low pressure is desirable because the number of moles increases due to the thermal decomposition reaction. The lower limit of the gauge pressure in step S12 may be -80 kPaG or higher, -10 kPaG or higher, or 0 kPaG or higher. The upper limit of the gauge pressure may be 1000 kPaG or lower, 300 kPaG or lower, or 100 kPaG or lower.

[0021] In step S12, a catalyst may be used to promote thermal decomposition. An example of a catalyst to be used is a silicate catalyst. 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. In one embodiment, the silicate catalyst is a zeolite. In one embodiment, the zeolite is an MFI-type zeolite. The zeolite may be one of those described in step S13.

[0022] Step S12 may be carried out in the presence or absence of a carrier gas. A carrier gas is a gas introduced into the reaction system to fluidize the decomposition products. The carrier gas may be introduced in step S12, or in a step prior to step S12. On the other hand, gases generated in steps S12 and S13 are not included in the definition of a carrier gas. Examples of carrier gases include inert gases (such as nitrogen gas and argon gas), water vapor, and CO2. ２Examples include gases. In one embodiment, the carrier gas is nitrogen gas and / or water vapor.

[0023] The flow rate of the carrier gas can be adjusted as appropriate so that the concentration of hydrocarbons in the first product P1 sent to step S13 is within an appropriate range. The lower limit of the mass of the carrier gas sent to step S13 may be 0.05 or more, 0.1 or more, or 0.15 or more, when the mass of hydrocarbons sent to step S13 is taken as 1. The lower limit of the mass of the carrier gas sent to step S13 may be 1 or less, 0.75 or less, or 0.5 or less, when the mass of hydrocarbons sent to step S13 is taken as 1.

[0024] In the embodiment where step S12 is carried out using a fluidized bed reactor, the greater the amount of fluidized gas, the lower the hydrocarbon concentration in the gas phase, and therefore the easier it is for the decomposed components to vaporize. Based on this, the lower limit of the linear velocity of the fluidized gas in the fluidized bed reactor may be 0.1 cm / s or more, 0.5 cm / s or more, or 0.8 cm / s or more. The upper limit of the linear velocity of the fluidized gas in the fluidized bed reactor may be 100 cm / s or less, 75 cm / s or less, or 20 cm / s or less.

[0025] In this embodiment, the lower limit of the ratio of the fluidizing gas supply rate (NmL / min) to the supply rate (g / min) of the feed M supplied to the fluidized bed reactor may be 10 NmL / g or more, 50 NmL / g or more, or 200 NmL / g or more. The upper limit of the ratio of the fluidizing gas supply rate (NmL / min) to the supply rate (g / min) of the feed M supplied to the fluidized bed reactor may be 2000 NmL / g or less, 1500 NmL / g or less, or 1200 NmL / g or less.

[0026] In this embodiment, the lower limit of the ratio of the fluidizing gas supply rate (NmL / min) to the amount of fluidizing medium (g) present in the fluidized bed reactor may be 1.0 NmL / g·min or higher, 2.0 NmL / g·min or higher, or 3.0 NmL / g·min or higher. The upper limit of the ratio of the fluidizing gas supply rate (NmL / min) to the amount of fluidizing medium (g) present in the fluidized bed reactor may be 100 NmL / g·min or lower, 50 NmL / g·min or lower, or 25 NmL / g·min or lower.

[0027] [1.3. Step S13: Catalytic Decomposition] In step S13, the first product P1 is catalytically decomposed in the presence of a catalyst containing zeolite. The second product P2 obtained by catalytic decomposition mainly contains olefins and is sent to step S14. The number of carbon atoms in the olefins contained in the second product P2 can be 2 to 5.

[0028] In one embodiment, the second product P2 contains one or more hydrocarbons selected from the group consisting of ethylene, propylene, butene, and pentene. The proportion of ethylene, propylene, butene, and pentene in the second product P2 may be 32% by mass or more, 35% by mass or more, or 40% by mass or more.

[0029] The catalytic decomposition temperature in step S13 may be set based on the composition of the first product P1. The lower limit of the catalytic decomposition temperature may be 400°C or higher, 450°C or higher, or 500°C or higher. The upper limit of the catalytic decomposition temperature may be 800°C or lower, 650°C or lower, or 600°C or lower. The heat source required for step S13 may be supplied in the same manner as in step S12.

[0030] The lower limit of the gauge pressure in process S13 may be -80 kPaG or higher, -10 kPaG or higher, or 0 kPaG or higher. The upper limit of the gauge pressure may be 1000 kPaG or lower, 300 kPaG or lower, or 100 kPaG or lower.

[0031] Step S13 may be carried out in the presence or absence of a carrier gas. The definition and examples of the carrier gas are as described in relation to step S12. The carrier gas may be introduced in step 13 or in a step prior to step 13. In one embodiment, the carrier gas is nitrogen gas and / or water vapor.

[0032] The flow rate of the carrier gas can be adjusted as appropriate so that the concentration of olefin in the second product P2 sent to step S14 is within an appropriate range. The lower limit of the mass of the carrier gas sent to step S14 may be 0.05 or more, 0.1 or more, or 0.15 or more, when the mass of olefin sent to step S14 is taken as 1. The lower limit of the mass of the carrier gas sent to step S14 may be 1 or less, 0.75 or less, or 0.5 or less, when the mass of olefin sent to step S14 is taken as 1.

[0033] The lower limit of the contact time in step S13 may be 200 seconds or more, 300 seconds or more, or 400 seconds or more. The upper limit of the contact time in step S13 may be 1000 seconds or less, 900 seconds or less, or 800 seconds or less. The contact time in step S13 is the value obtained by dividing the mass-based flow rate (g / sec) of the hydrocarbon supplied to step S13 by the mass (g) of the catalyst containing zeolite.

[0034] [1.3.1. Catalyst containing zeolite] In step S13, hydrocarbons are catalytically cracked with a catalyst containing zeolite. Zeolites typically contain silicon atoms, aluminum atoms, oxygen atoms, and hydrogen atoms. In addition to the atoms mentioned above, zeolites may also contain atoms such as 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, sodium atoms, and gallium atoms.

[0035] Examples of zeolites include beta-type zeolite, faujasite-type zeolite, L-type zeolite, ferrielite-type zeolite, mordenite-type zeolite, and MFI-type zeolite.

[0036] In one embodiment, the zeolite includes or consists of MFI-type zeolite. MFI-type zeolite refers to a crystalline aluminosilicate having an MFI structure according to the structural code of IZA (International Zeolite Association), and is also called ZSM-5. A specific example of MFI-type zeolite is H ＋ -ZSM-5, NH４ ＋ -ZSM-5, Na ＋ -ZSM-5, Ca ２＋ -ZSM-5 is one example.

[0037] The lower limit of the amount of acid sites in the zeolite-containing catalyst used in step S13 is 30 μmol / g or more, and may be 40 μmol / g or more or 50 μmol / g or more. The upper limit of the amount of acid sites in the zeolite-containing catalyst used in step S13 is 800 μmol / g or less, and may be 700 μmol / g or less, 600 μmol / g or less, 500 μmol / g or less, 400 μmol / g or less or 300 μmol / g or less.

[0038] In this specification, the amount of acid sites in the catalyst is measured by the ammonia adsorption desorption method. An example of a measuring device is the TPD-1-Atw temperature rise desorption apparatus (Microtrac Bell Co., Ltd.). The specific measurement method is as follows (this method was also adopted in the embodiment of the present application described later). 1. Weigh 50 mg of catalyst and pass helium through it at 500°C for 60 minutes. The flow rate is 50 mL / min. 2. Cool the catalyst to 100°C. Pass 0.5% ammonia / helium through it at 100°C for 30 minutes. The flow rate is 100 mL / min. This adsorbs ammonia onto the catalyst surface. 3. Pass helium through it at 100°C for 30 minutes. The flow rate is 50 mL / min. 4. The temperature is increased from 100°C to 800°C at a rate of 10°C / min, and the amount of ammonia desorbed between 250°C and 650°C is measured using a quadrupole mass spectrometer. 5. From the obtained TPD spectrum, the area value is calculated using the absolute calibration curve method. The obtained area force and the amount of ammonia desorbed per unit mass are calculated. This desorption amount is taken as the amount of acid sites per unit mass of catalyst.

[0039] The catalyst used in step S13 may contain components other than zeolite. Examples of such components include carriers and binders (matrix materials). Examples of carriers include silica, alumina, silica-alumina, silica-titania, silica-thoria, silica-magnesia, silica-zirconia, silica-beryllia, and ternary compositions of silica and other refractory oxides. Examples of binders (matrix materials) include clays (montmorillonite, kaolin, bentonite, halloysite, dickite, nacrite, anaxite, etc.). In the catalyst used in step S13, the mass ratio occupied by zeolite can be 50% by mass or more, 70% by mass or more, or 90% by mass or more. In one embodiment, the catalyst used in step S13 consists only of zeolite.

[0040] (Method for producing zeolite) The zeolite used in step S13 can be produced by a conventional method. Hereinafter, an example of a method for producing MFI-type zeolite will be shown. MFI-type zeolite can be produced by crystallizing a mixture containing a silicon source, an aluminum source, a templating agent, and an alkali metal source. Here, the templating agent is a substance that forms a pore structure in the crystalline aluminosilicate.

[0041] The silicon source may be a conventionally known silica-containing material used in the production of zeolite. Specific examples of the silica-containing material include tetraethyl orthosilicate, colloidal silica, silica gel dry powder, and silica hydrogel.

[0042] The aluminum source may be a conventionally known aluminum source used in the production of zeolite. Specific examples of the aluminum source include aluminum nitrate, aluminum chloride, and sodium aluminate. Among these aluminum sources, aluminum nitrate and sodium aluminate are preferred.

[0043] The mold agent may be a conventionally known mold agent used for MFI zeolite synthesis. Specific examples of the mold agent include tetrapropylammonium salt, tetraethylammonium salt, propanolamine, ethanolamine, n-propylamine, morpholine, 1,5-diaminopentane, 1,6-diaminohexane, dipropylenetetramine, and triethylenetetramine. Among these mold agents, tetrapropylammonium salt is preferred.

[0044] Examples of the alkali metal source include hydroxides containing an alkali metal, chlorides containing an alkali metal, bromides containing an alkali metal, and sulfides containing an alkali metal. Examples of the alkali metal include sodium and potassium.

[0045] When the alkali metal is sodium, the sodium source is a compound containing sodium. Examples of the compound containing sodium include compounds containing sodium as a counter cation. More specifically, sodium hydroxide, sodium chloride, sodium bromide, sodium sulfate, sodium silicate, and sodium aluminate can be mentioned.

[0046] When the alkali metal is potassium, the potassium source is a compound containing potassium. Examples of the compound containing potassium include compounds containing potassium as a counter cation. More specifically, potassium hydroxide, potassium chloride, potassium bromide, potassium sulfate, potassium silicate, and potassium aluminate can be mentioned.

[0047] The ratio of the number of moles of silicon atoms to the number of moles of aluminum atoms in the mixture before crystallization can be 10 to 1000.

[0048] The number of moles of the mold agent, alkali source, and water contained in the mixture before crystallization is preferably in the following ranges when the number of moles of silicon atoms is set to 1. - Mold agent: 0.02 - 5.0 - Alkali source: 0.01 - 0.2 - Water: 2 - 100

[0049] MFI-type zeolite can be prepared by crystallizing the above-mentioned mixture in a sealed pressure vessel. The reaction temperature is, for example, 100°C to 200°C. The reaction time is, for example, 1 to 120 hours. The MFI-type zeolite obtained by crystallization is usually washed and then dried. The drying temperature is, for example, 100°C to 150°C. The dried MFI-type zeolite may be further calcined. The calcination temperature is, for example, 300°C to 700°C.

[0050] For example, the amount of acid sites in MFI-type zeolite can be altered by adding phosphorus. Generally, a higher phosphorus content tends to result in a lower amount of acid sites. To add phosphorus to MFI-type zeolite, a phosphorus source may be added to the mixture before crystallization, or the crystallized MFI-type zeolite may be calcined together with the phosphorus source. Examples of phosphorus sources include phosphates.

[0051] The alkali source (sodium and / or potassium) content may be reduced in the crystallized MFI-type zeolite. For example, the alkali source content can be reduced by contacting the MFI-type zeolite with an aqueous solution of an ammonium salt. The amount of acid sites in the MFI-type zeolite can be changed by adjusting the alkali source content. Generally, a lower alkali source content tends to result in a higher amount of acid sites.

[0052] Examples of ammonium salts include ammonium salts of inorganic acids (ammonium sulfate, ammonium hydrogen sulfate, ammonium carbonate, ammonium bicarbonate, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, ammonium phosphate, ammonium hydrogen pyrophosphate, ammonium pyrophosphate, ammonium chloride, ammonium nitrate, etc.) and ammonium salts of organic acids (ammonium acetate, etc.). Among these, ammonium sulfate, ammonium chloride, and ammonium nitrate are preferred.

[0053] Specifically, the alkali source can be reduced by mixing an aqueous solution of ammonium salt with MFI-type zeolite. The mixing temperature is, for example, 50°C to 200°C. The mixing time is, for example, 1 to 48 hours. The MFI-type zeolite with reduced alkali source is usually washed and then dried. The drying temperature is, for example, 60°C to 150°C. The dried MFI-type zeolite may be further calcined. The calcination temperature is, for example, 300°C to 700°C.

[0054] [1.4. Step S14: Purification] In step S14, the secondary product P2 is purified. In one embodiment, in step S14, the secondary product P2 is separated into olefins and other hydrocarbons (such as paraffins). In one embodiment, in step S14, olefins with a small number of carbon atoms (such as olefins with 2 to 5 carbon atoms) are separated from other hydrocarbons (such as paraffins and olefins with 6 or more carbon atoms). Step S14 separates an olefin-rich gas that is rich in olefins. The olefin content in the olefin-rich gas may be 90% by mass or more. The olefin-rich gas may contain one or more selected from the group consisting of ethylene, propylene, butene, and pentene.

[0055] At least a portion of the components other than the olefin-rich gas separated in step S14 may be refluxed to step S12 or step S13. With this configuration, the yield of olefins can be further improved.

[0056] Alternatively, at least a portion of the components other than the olefin-rich gas separated in step S14 may be burned and used as a heat source in step S12 or step S13. Such a configuration can reduce the environmental impact of the olefin manufacturing method.

[0057] [2. Olefin Manufacturing System] The olefin manufacturing method described above can be implemented by the olefin manufacturing system illustrated in Figure 2. The manufacturing system 100 shown in Figure 2 comprises a pre-processing unit 10, a thermal decomposition unit 21, a catalytic decomposition unit 22, and a purification unit 30. These components are connected by pathways L1 to L4.

[0058] Plastics such as waste plastics are supplied to the pre-processing unit 10 from the path L1. The discharge port of the pre-processing unit 10 is connected to the pyrolysis unit 21 by the path L2. The plastic supplied to the pre-processing unit 10 is pre-treated to become feed material M, which is supplied to the pyrolysis unit 21 via the path L2. The discharge port of the pyrolysis unit 21 is connected to the supply port of the catalytic decomposition unit 22 by the path L3. The feed material M supplied to the pyrolysis unit 21 is pyrolyzed to become the first product P1, which is supplied to the catalytic decomposition unit 22 via the path L3. The catalytic decomposition unit 22 and the purification unit 30 are connected by the path L4. The first product P1 supplied to the catalytic decomposition unit 22 is catalytically decomposed to become the second product P2, which is supplied to the purification unit 30 via the path L4. The second product P2 supplied to the purification unit 30 is purified to become olefin, which is removed from the manufacturing system 100. Each part will be described in detail below.

[0059] The pre-treatment unit 10 is a component that pre-treats plastics such as waste plastics to provide a feed material M suitable for decomposition. In other words, process S11 is carried out in the pre-treatment unit 10. The pre-treatment unit 10 may be equipped with multiple devices that perform different processes. For example, the pre-treatment unit 10 may be equipped with one or more devices selected from the group consisting of a sorting device, a crushing device, a washing device, a drying device, a melting device, and a dechlorination device. A sorting device is a device that sorts polyolefins from plastics such as waste plastics. Examples of sorting devices include optical sorting devices and specific gravity separation devices. A crushing device is a device that crushes plastics. A washing device is a device that washes plastics. A drying device is a device that dries plastics. A melting device is a device that heats plastics to make them liquid. A dechlorination device is a device that removes chlorine contained in plastics.

[0060] The pyrolysis unit 21 is a component that decomposes the feed material M by heating. In other words, process S12 is carried out in the pyrolysis unit 21. The decomposed feed material M becomes a first product P1 containing gaseous and / or liquid hydrocarbons. The pyrolysis unit 21 may be a device that performs pyrolysis continuously. Specific examples include an extruder, a stirring tank, a rotary kiln, and a fluidized bed. Examples of fluidized beds include an internal circulating fluidized bed and an external circulating fluidized bed. Multiple of the above-mentioned devices may be used as the pyrolysis unit 21. Multiple devices may be connected in parallel or in series.

[0061] The catalytic cracking section 22 is a component that decomposes the first product P1 by contacting it with a catalyst. In other words, step S13 is carried out in the catalytic cracking section 22. The decomposed first product P1 becomes a second product P2 containing an olefin. An example of the catalytic cracking section 22 is a reactor including a fixed bed, a moving bed, or a fluidized bed. Multiple reactors described above may be used as the catalytic cracking section 22. Multiple reactors may be connected in parallel or in series.

[0062] The purification unit 30 is a component that separates and purifies the second product P2 to obtain olefin. In other words, step S14 is carried out in the purification unit 30. Examples of the purification unit 30 include a gas-liquid separator and a distillation apparatus. Multiple of the above-mentioned apparatuses may be used as the purification unit 30. Multiple apparatuses may be connected in parallel or in series.

[0063] [Example 1] An olefin was produced from a mixture of polyolefin and polyethylene terephthalate by a manufacturing method according to one embodiment of the present invention.

[0064] [Example 1-1] (Preparation of catalyst) 1 g of ammonium-type ZSM-5 (CBV28014, Zeolyst) was calcined in a muffle furnace to obtain catalyst A. The calcination conditions were an air atmosphere, 550°C, and 5 hours. The amount of acid sites (solid acid amount) of catalyst A, measured at 250-650°C by ammonia thermal desorption, was 66 μmol / g.

[0065] (Olefin Production) Olefins were produced using catalyst A according to the following procedure. 1. Two glass reaction tubes connected in series were prepared. The upstream reaction tube was filled with 0.95 g of polyethylene (Sumikasen G201F, Sumitomo Chemical Co., Ltd.) and 0.05 g of polyethylene terephthalate (Teijin Limited) as raw materials (polyethylene terephthalate content: 5% by mass). The downstream reaction tube was filled with 0.05 g of catalyst A. 2. A cooling trap was connected further downstream of the downstream reaction tube. A 5 L gas bag was connected further downstream of the cooling trap. 3. While circulating nitrogen gas from the upstream side of the reaction tube (flow rate: 10 mL / min), only the downstream reaction tube was heated at 550 °C for 1 hour to pre-treat the catalyst. Next, the downstream reaction tube was cooled to 525 °C. 4. The upstream reaction tube was heated to 455°C while circulating nitrogen gas (flow rate: 10 mL / min) to thermally decompose the sample into hydrocarbons. The obtained hydrocarbons were supplied to the downstream reaction tube and brought into contact with the catalyst at 525°C for catalytic decomposition. 5. Of the catalytic decomposition products obtained 103 minutes from the start of heating of the raw materials, the liquid products were collected in a cooling trap, and the gaseous products were collected in a gas bag.

[0066] Analysis of the liquid and gaseous catalytic decomposition products by gas chromatography revealed that the yield of olefins with 2 to 5 carbon atoms was 50.6%, relative to the mass of polyethylene used as the raw material.

[0067] [Example 1-2] (Preparation of Catalyst) Catalyst B was prepared according to the following procedure. 1. 16.4 g of aqueous solution of tetrapropylammonium hydroxide (22.3% by mass), 15.0 g of tetraethyl orthosilicate, and 4.1 g of deionized water were placed in a 200 mL inner cylinder container made of PTFE. Next, the inner cylinder container was loaded into a SUS autoclave. 2. The contents of the container were homogenized at room temperature. Next, it was heated at 80°C for 24 hours with stirring. 3. After the contents of the container were cooled, the entire volume was transferred to a glass flask. Next, the contents of the flask were evaporated using an evaporator at 80°C for 2 hours. 4. The entire volume of the mixture remaining in the flask was transferred to a PTFE container, and 0.18 g of aluminum nitrate nonahydrate, 0.29 g of sodium hydroxide, and 0.60 g of deionized water were added. Next, the contents of the container were uniformly stirred using a stirring bar at room temperature. 5. The entire amount of the obtained mixture was transferred to a 200 mL PTFE inner cylinder container. Next, the inner cylinder container was loaded into a SUS autoclave. 6. The cylindrical container was heated at 170°C for 24 hours. Next, it was cooled with ice water. 7. The obtained suspension was centrifuged and the supernatant was removed. Water was added to the precipitated residue to resuspend it, and the supernatant was removed again by centrifuging. This operation was repeated until the pH of the supernatant was 8 or less. 8. The precipitated residue was dried at 120°C for 8 hours. 9. The obtained solid was ground in a mortar. Next, the ground material was calcined in a muffle furnace. The calcination conditions were an air atmosphere, 550°C, and 6 hours. In this way, 2.9 g of calcined material was obtained. 10. 2.0 g of the calcined material and 100 mL of ammonium nitrate aqueous solution (0.5 M) were placed in a resin container and left to stand at 60°C for 6 hours. Next, the obtained mixture was filtered by suction using a Buchner funnel to recover the solids. This treatment with ammonium nitrate was repeated a total of three times. 11. The recovered solids were washed with 150 g of water. Next, they were dried at 90°C for 12 hours. 12. The obtained solids were calcined in a muffle furnace. The calcination conditions were an air atmosphere, 550°C, and 5 hours. In this way, 1.3 g of catalyst B was obtained. The amount of acid sites (solid acid content) of catalyst B, measured at 250-650°C by ammonia temperature-controlled desorption, was 89 μmol / g.

[0068] (Olefin Production) The following changes were made to the olefin production method of Example 1-1. Otherwise, the olefin was produced in the same manner as in Example 1-1. - In step 1, the catalyst packed into the downstream reaction tube was changed from catalyst A to catalyst B. - In step 5, the recovery time of the catalytic cracking product was changed from 103 minutes to 102 minutes from the start of heating of the raw materials.

[0069] Analysis of the liquid and gaseous catalytic decomposition products by gas chromatography revealed that the yield of olefins with 2 to 5 carbon atoms was 53.5%, relative to the mass of polyethylene used as the raw material.

[0070] [Examples 1-3] (Preparation of catalyst) 1 g of ammonium-type ZSM-5 (CBV8014, Zeolyst) was calcined in a muffle furnace to obtain catalyst C. The calcination conditions were an air atmosphere, 550°C, and 5 hours. The amount of acid sites (solid acid amount) of catalyst C, measured at 250-650°C by ammonia thermal desorption, was 279 μmol / g.

[0071] (Olefin Production) In step 1 of the olefin production method of Example 1-1, the catalyst packed into the downstream reaction tube was changed from catalyst A to catalyst C. Otherwise, the olefin was produced in the same manner as in Example 1-1.

[0072] Analysis of the liquid and gaseous catalytic decomposition products by gas chromatography revealed that the yield of olefins with 2 to 5 carbon atoms was 51.0%, relative to the mass of polyethylene used as the raw material.

[0073] [Example 1-4] (Preparation of Catalyst) Catalyst D was prepared according to the following procedure. 1. 12.0 g of deionized water and 0.03 g of diammonium hydrogen phosphate were added to a glass round-bottom flask and stirred at room temperature for 5 minutes. Next, 5.0 g of ammonium type ZSM-5 (CBV28014, Zeolyst) was added to the flask. 2. The deionized water in the flask was evaporated using an evaporator at 60°C for 2 hours. 3. The entire residue was transferred to a magnetic dish and dried at 110°C for 12 hours. 4. The obtained solid was calcined in a muffle furnace. The calcination conditions were an air atmosphere, 600°C, and 4 hours. In this way, 4.9 g of catalyst D was obtained. The amount of acid sites (solid acid amount) of catalyst D, measured at 250-650°C by ammonia heating desorption, was 57 μmol / g.

[0074] (Olefin Production) In step 1 of the olefin production method of Example 1-1, the catalyst packed into the downstream reaction tube was changed from catalyst A to catalyst D. Otherwise, the olefin was produced in the same manner as in Example 1-1.

[0075] Analysis of the liquid and gaseous catalytic decomposition products by gas chromatography revealed that the yield of olefins with 2 to 5 carbon atoms was 55.7%, relative to the mass of polyethylene used as the raw material.

[0076] [Example 1-5] (Preparation of catalyst) The same catalyst A as in Example 1-1 was prepared.

[0077] (Olefin Production) In step 1 of the olefin production method of Example 1-1, the composition of the raw materials to be filled into the upstream reaction tube was changed to 0.90 g of polyethylene (Sumikasen G201F, Sumitomo Chemical Co., Ltd.) and 0.10 g of polyethylene terephthalate (Teijin Limited) (polyethylene terephthalate content: 10% by mass). Otherwise, the olefin was produced in the same manner as in Example 1-1.

[0078] Analysis of the liquid and gaseous catalytic decomposition products by gas chromatography revealed that the yield of olefins with 2 to 5 carbon atoms was 37.9%, relative to the mass of polyethylene used as the raw material.

[0079] [Example 1-6] (Preparation of catalyst) The same catalyst A as in Example 1-1 was prepared.

[0080] (Olefin Production) In step 1 of the olefin production method of Example 1-1, the composition of the raw materials to be filled into the upstream reaction tube was changed to 0.85 g of polyethylene (Sumikasen G201F, Sumitomo Chemical Co., Ltd.) and 0.15 g of polyethylene terephthalate (Teijin Limited) (polyethylene terephthalate content: 15% by mass). Otherwise, the olefin was produced in the same manner as in Example 1-1.

[0081] Analysis of the liquid and gaseous catalytic decomposition products by gas chromatography revealed that the yield of olefins with 2 to 5 carbon atoms was 33.6%, relative to the mass of polyethylene used as the raw material.

[0082] [Example 1-7] (Preparation of catalyst) The same catalyst B as in Example 1-2 was prepared.

[0083] (Olefin Production) The following changes were made to the olefin production method of Example 1-1. Otherwise, the olefin was produced in the same manner as in Example 1-1. - In step 1, the catalyst packed into the downstream reaction tube was changed from catalyst A to catalyst B. - In step 1, the composition of the raw materials packed into the upstream reaction tube was changed to 0.90 g of polyethylene (Sumikasen G201F, Sumitomo Chemical Co., Ltd.) and 0.10 g of polyethylene terephthalate (Teijin Limited) (polyethylene terephthalate content: 10% by mass). - In step 5, the recovery time of the catalytic decomposition product was changed from 103 minutes to 102 minutes from the start of heating of the raw materials.

[0084] Analysis of the liquid and gaseous catalytic decomposition products by gas chromatography revealed that the yield of olefins with 2 to 5 carbon atoms was 39.6%, relative to the mass of polyethylene used as the raw material.

[0085] [Example 1-8] (Preparation of catalyst) The same catalyst B as in Example 1-2 was prepared.

[0086] (Olefin Production) The following changes were made to the olefin production method of Example 1-1. Otherwise, the olefin was produced in the same manner as in Example 1-1. - In step 1, the catalyst packed into the downstream reaction tube was changed from catalyst A to catalyst B. - In step 1, the composition of the raw materials packed into the upstream reaction tube was changed to 0.85 g of polyethylene (Sumikasen G201F, Sumitomo Chemical Co., Ltd.) and 0.15 g of polyethylene terephthalate (Teijin Limited) (polyethylene terephthalate content: 15% by mass). - In step 5, the recovery time of the catalytic decomposition product was changed from 103 minutes to 102 minutes from the start of heating of the raw materials.

[0087] Analysis of the liquid and gaseous catalytic decomposition products by gas chromatography revealed that the yield of olefins with 2 to 5 carbon atoms was 33.3%, relative to the mass of polyethylene used as the raw material.

[0088] [Results] The results of Example 1 are shown in Table 1. Note that the order of entries in Table 1 differs from that of the above example for ease of comparison.

[0089] In Examples 1-1 to 1-3 and Comparative Examples 1-1 to 1-2, experiments were conducted by varying the amount of acid sites in the catalyst. As can be seen from these results, the amount of acid sites in the catalyst affects the yield of olefins with 2 to 5 carbon atoms. Specifically, to increase the yield, for example, the amount of acid sites in the catalyst should be adjusted to a range of 30 to 800 μmol / g.

[0090] In Examples 1-4, the amount of acid sites was adjusted by adding phosphorus to the zeolite. Even when using zeolite with the amount of acid sites adjusted in this way as a catalyst, olefins could be successfully produced by the manufacturing method according to one embodiment of the present invention.

[0091] In Examples 1-5 to 1-8, the polyethylene terephthalate content in the raw materials was increased. Although the yield of olefins with 2 to 5 carbon atoms tended to decrease as the content increased, a sufficient yield could still be maintained according to the manufacturing method of one embodiment of the present invention.

[0092] [Example 9] An olefin was produced from a mixture containing polyolefin, polyethylene terephthalate, and other plastics using a manufacturing method according to one embodiment of the present invention.

[0093] (Preparation of catalyst) The same catalyst A as in Example 1-1 was prepared.

[0094] (Olefin Production) Olefins were produced using catalyst A according to the following procedure: 1. Two metal reactors connected in series were prepared. 2 g of catalyst A was packed into the downstream reactor. A cooling trap was connected further downstream of the downstream reactor. A gas bag was connected further downstream of the cooling trap. 2. Mixed plastic (flow rate 0.4 g / min) and nitrogen gas (flow rate: 0.06 g / min) were supplied to the upstream reactor, which was heated to 550°C, and thermal decomposition was carried out. The composition of the mixed plastic was as follows: Polyolefin and polyethylene terephthalate. The proportion of polyethylene terephthalate was 3.3% by mass. 1. The entire amount of reaction products from the upstream reactor and steam (flow rate: 0.1 g / min) were supplied to the downstream reactor heated to 525°C. This caused catalytic decomposition of hydrocarbons produced by thermal decomposition. 2. Of the catalytic decomposition products obtained between 1 hour 15 minutes and 1 hour 30 minutes after the start of supplying the mixed plastics, the liquid products were collected in a cooling trap. Furthermore, gaseous catalytic decomposition products obtained between 1 hour 20 minutes and 1 hour 30 minutes after the start of supplying the mixed plastic were recovered using a gas bag.

[0095] Analysis of the liquid and gaseous catalytic decomposition products by gas chromatography revealed that the yield of olefins with 2 to 5 carbon atoms was 51.9%, relative to the mass of the mixed plastic supplied as raw material.

[0096] Thus, according to the manufacturing method of one embodiment of the present invention, olefins could be successfully produced even from raw materials containing plastics other than polyolefins and polyethylene terephthalate.

[0097] This invention can be used in the production of olefins.

Claims

1. A method for producing an olefin comprising the following steps S12 and S13: Step S12: A step of thermally decomposing a raw material containing polyolefin and polyethylene terephthalate to obtain a hydrocarbon; Step S13: A step of catalytically decomposing the hydrocarbon with a catalyst containing zeolite to obtain an olefin; where, in step S12, the content of polyethylene terephthalate in the raw material is 0.1% by mass or more, with the total content of polyolefin and polyethylene terephthalate being 100% by mass; and in step S13, the amount of acid sites of the catalyst containing zeolite, measured at 250 to 650°C by ammonia temperature rise desorption, is 30 to 800 μmol / g.

2. The manufacturing method according to claim 1, wherein the hydrocarbon obtained in step S12 is a gas and / or a liquid.

3. The manufacturing method according to claim 1 or 2, wherein the olefin obtained in step S13 comprises one or more selected from the group consisting of ethylene, propylene, butene, and pentene.

4. The manufacturing method according to claim 1 or 2, wherein in step S13, the zeolite has an MFI structure.

5. The manufacturing method according to claim 1 or 2, wherein in step S13, the zeolite contains phosphorus.

6. The manufacturing method according to claim 1 or 2, wherein step S13 is carried out under conditions satisfying (i) and (ii) below: (i) in the presence of a carrier gas supplied to the reaction system; (ii) the reaction temperature is 400 to 800°C.

7. The manufacturing method according to claim 6, wherein the carrier gas is water vapor and / or nitrogen gas.

8. The manufacturing method according to claim 6, wherein the flow rate of the carrier gas is 0.05 to 1.0 parts by mass, with the flow rate of the hydrocarbon supplied to step S13 being 1.

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