Method for producing olefins

Abstract

The present invention provides a method for producing olefins that can achieve both improved olefin yield and reduced by-product generation. [Solution] The manufacturing method of the present disclosure comprises the following steps: Step S13: A step of catalytically decomposing a mixed gas of hydrocarbons and a carrier gas with a catalyst containing zeolite to obtain an olefin. The amount of acid sites of the catalyst containing zeolite, measured at 250 to 650°C by the ammonia temperature-controlled desorption method, is greater than 0 and 800 μmol / g or less. Divide the mass (g) of the catalyst containing zeolite by the mass-based flow rate (g / sec) of the hydrocarbon. The required contact time is 200 to 1000 seconds. In the gas mixture, the mass of the carrier gas is 0.05 to 1, assuming the mass of the hydrocarbons is 1.

Description

Technical Field

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

Background Art

[0002] One of the methods for producing olefins (especially lower olefins), which are the main raw materials such as plastics, is a method of catalytic cracking of hydrocarbons. For example, Patent Document 1 discloses a method for producing olefins by thermally decomposing polyolefins to obtain a decomposition product containing hydrocarbons and then catalytically cracking this decomposition product. In this document, the catalyst used for catalytic cracking is MFI-type zeolite.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The production of olefins by catalytic cracking of hydrocarbons often involves problems of yield and selectivity. That is, there is a need for a production method that improves the yield of olefins while reducing the production of by-products such as benzene, toluene, and xylene.

[0005] One aspect of the present invention aims to provide a method for producing olefins that can achieve both an improvement in the yield of olefins and a reduction in the production of by-products.

Means for Solving the Problems

[0006] The present invention includes the following aspects. <1> A method for producing olefins having the following step S13: Step S13: A step in which a mixed gas of hydrocarbons and a carrier gas is catalytically cracked with a catalyst containing zeolite to obtain an olefin; Here, The amount of acid sites in the catalyst containing the above zeolite, as measured by the ammonia heating desorption method at 250-650°C, is greater than 0 and less than or equal to 800 μmol / g. The contact time, obtained by dividing the mass-based flow rate (g / sec) of the above hydrocarbon by the mass (g) of the catalyst containing the above zeolite, is 200 to 1000 seconds. In the above mixed gas, the mass of the carrier gas is 0.05 to 1, where the mass of the hydrocarbon is 1. <2> The above olefin comprises one or more selected from the group consisting of ethylene, propylene, butene, and pentene. <1> The manufacturing method described above. <3> The above zeolite has an MFI structure. <1> or <2> The manufacturing method described above. <4> The carrier gas mentioned above is water vapor and / or nitrogen. <1> ~ <3> A manufacturing method described in any of the following. <5> The average number of carbon atoms in the above hydrocarbons is 8 to 30. <1> ~ <4> A manufacturing method described in any of the following. <6> The above-mentioned hydrocarbons contained in the mixed gas include one or more selected from the group consisting of normal paraffins, cycloparaffins, isoparaffins, olefins, cycloolefins, and isoolefins. In step S13 described above, an olefin having 2 to 5 carbon atoms is obtained. <5> The manufacturing method described above. [Effects of the Invention]

[0007] According to one aspect of the present invention, a method for producing olefins is provided that can achieve both an improvement in the yield of olefins and a reduction in the generation of by-products. [Brief explanation of the drawing]

[0008] [Figure 1] It is a flowchart showing an example of a manufacturing method according to an aspect of the present invention. [Figure 2] It is a block diagram showing an implementation example of a manufacturing method according to an aspect of the present invention. [Figure 3] It is a flowchart showing an example in which the flow of FIG. 1 is incorporated into the production of olefins from hydrocarbons. [Figure 4] It is a block diagram showing an example in which the block of FIG. 2 is incorporated into the production of olefins from hydrocarbons.

MODE FOR CARRYING OUT THE INVENTION

[0009] An embodiment of the present invention will be described below. However, the present invention is not limited to each configuration described below. The present invention can be variously modified within the scope shown in the claims. The technical scope of the present invention also extends to embodiments or examples obtained by appropriately combining a plurality of technical means disclosed in this specification. At this time, the plurality of technical means may be disclosed over a plurality of embodiments or examples.

[0010] Unless otherwise specified in this specification, "A~B" representing a numerical range is intended to mean "A or more and B or less".

[0011] 〔1. Method for producing olefin〕 Hereinafter, a method for producing an olefin according to an aspect of the present invention will be described while referring to exemplary FIGS. 1 and 3. In the production method shown in FIG. 1, olefins are produced from hydrocarbons through steps S13 and S14. Among these, step S14 is an optional step and may or may not be carried out. How the hydrocarbons supplied to step S13 are generated is not particularly limited.

[0012] An example of implementing the flow of FIG. 1 in the production of olefins by plastic decomposition is shown in FIG. 3. In the production method shown in FIG. 3, olefins are produced from plastic through steps S11, S12, S13, and S14. Among these, steps S11, S12, and S14 are optional steps and may or may not be carried out.

[0013] According to this production method, hydrocarbons are decomposed to obtain an olefin-rich gas rich in olefins (particularly lower olefins having 2 to 5 carbon atoms). Hereinafter, each step will be described in detail.

[0014] [1.1. Step S11: Pretreatment] In step S11, the plastic is pretreated. The pretreated plastic becomes a feedstock M mainly containing polyolefins and is sent to step S12. The plastic supplied to step S11 is, for example, waste plastic and contains polyolefins (such as polyethylene, polypropylene, etc.). Comparing the plastic supplied to step S11 with the feedstock M sent to step 12, usually, the latter has a higher polyolefin content.

[0015] The polyolefin content in the plastic supplied to step S11 can be 60% by mass or more, 80% by mass or more, or 90% by mass or more, with the total amount of the plastic being 100% by mass. The polyolefin content in the feedstock M can be 80% by mass or more, 90% by mass or more, or 95% by mass or more, with the total amount of the feedstock M 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 process 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 may 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). Examples of indirect heating include a method in which heat obtained by an electric heater or combustion is supplied via the heat transfer surface of the device, a method in which high-temperature gas (such as steam, nitrogen gas, or CO2 gas) is introduced into the device, or a method in which high-temperature solid particles (mainly composed of iron, iron oxide, alumina, silica, etc.) are introduced into the device. For preheating the gas or solid particles introduced into the device, the same device used in process S12 may be used, or a device combined with the device used in process S12 may be used. The gas or solid particles introduced into the device 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 -80kPaG or higher, -10kPaG or higher, or 0kPaG or higher. The upper limit of the gauge pressure may be 1000kPaG or lower, 300kPaG or lower, or 100kPaG 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 12, or in a step prior to step 12. On the other hand, the gases produced in steps S12 and S13 are not included in the carrier gas. Examples of carrier gases include inert gases (such as nitrogen gas and argon gas), water vapor, and CO2 gas. 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 cracking] 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 -80kPaG or higher, -10kPaG or higher, or 0kPaG or higher. The upper limit of the gauge pressure may be 1000kPaG or lower, 300kPaG or lower, or 100kPaG 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. Catalysts containing zeolite] In step S13, hydrocarbons are catalytically decomposed using 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 greater than 0 μmol / g, and may be 5 μmol / g or more, 10 μmol / g or more, 20 μmol / g or more, 30 μmol / g or more, 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, 300 μmol / g or less, 200 μmol / g or less, or 100 μmol / g or less.

[0038] In this specification, the amount of acid sites in the catalyst is measured by ammonia adsorption desorption. An example of a measuring device is the TPD-1-Atw temperature-controlled desorption apparatus (Microtrac-Bell Co., Ltd.). The specific measurement method is as follows (this method was also adopted in the embodiments of this application described later). 1. Weigh out 50 mg of catalyst and flow helium through it at 500°C for 60 minutes. The flow rate should be 50 mL / min. 2. Cool the catalyst to 100°C. Circulate 0.5% ammonia / helium at 100°C for 30 minutes. The flow rate should be 100 mL / min. This will adsorb ammonia onto the catalyst surface. 3. Circulate helium at 100°C for 30 minutes. The flow rate should be 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 desorbed 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-tria, silica-magnesia, silica-gyronia, silica-beryllia, and ternary compositions of silica and other refractory oxides. Examples of binders (matrix materials) include viscous materials (montmorillonite, kaolin, bentonite, halloysite, dickite, nacrite, anaxite, etc.). In the catalyst used in step S13, the mass percentage of zeolite may 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 of manufacturing zeolite) The zeolite used in step S13 can be manufactured by conventional methods. Below is an example of a method for manufacturing MFI-type zeolite. MFI-type zeolite can be manufactured by crystallizing a mixture containing a silicon source, an aluminum source, a mold agent, and an alkali metal source. Here, the mold agent is a substance that forms a pore structure in crystalline aluminosilicate.

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

[0042] The aluminum source may be any conventionally known aluminum source used in the production of zeolites. Specific examples of aluminum sources 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 any conventionally known mold agent used in MFI-type zeolite synthesis. Specific examples of mold agents 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 alkali metal sources include hydroxides containing alkali metals, chlorides containing alkali metals, bromides containing alkali metals, and sulfides containing alkali metals. Examples of alkali metals include sodium and potassium.

[0045] When the alkali metal is sodium, the sodium source is a sodium-containing compound. Examples of sodium-containing compounds include those containing sodium as a countercation. More specifically, these include sodium hydroxide, sodium chloride, sodium bromide, sodium sulfate, sodium silicate, and sodium aluminate.

[0046] When the alkali metal is potassium, the potassium source is a potassium-containing compound. Examples of potassium-containing compounds include those containing potassium as a countercation. More specifically, these include potassium hydroxide, potassium chloride, potassium bromide, potassium sulfate, potassium silicate, and potassium aluminate.

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

[0048] The number of moles of the mold agent, alkali source, and water contained in the mixture before crystallization is preferably within the following range, assuming that the number of moles of silicon atoms is 1. • Mold agent: 0.02~5.0 • Alkaline source: 0.01~0.2 ·Wed: 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 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 fewer 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 substances 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. This configuration can further improve the yield of olefins.

[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 Figures 2 and 4. The manufacturing system 100 shown in Figure 2 includes a catalytic cracking unit 22 and a purification unit 30. The two components are connected by a pathway L4. Hydrocarbons, which are the raw materials, are supplied from pathway L3. How these hydrocarbons are produced is not particularly limited. It should be noted that the manufacturing method described in Section [1] can be carried out if a catalytic cracking unit 22 is available.

[0058] Figure 4 shows manufacturing system 100a, an example of implementing the manufacturing system 100 shown in Figure 2 as a system for producing olefins from plastics. Manufacturing system 100a includes a pre-processing unit 10, a pyrolysis unit 21, a catalytic cracking unit 22, and a purification unit 30. These components are connected by pathways L1 to L4. It should be noted that the manufacturing method described in Section [1] can be carried out if a catalytic cracking unit 22 is available.

[0059] 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 cracking 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 cracking unit 22 via the path L3. The catalytic cracking unit 22 and the purification unit 30 are connected by the path L4. The first product P1 supplied to the catalytic cracking unit 22 is catalytically cracked 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 is described in detail below.

[0060] 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.

[0061] 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 also 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.

[0062] 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.

[0063] The purification unit 30 is a component that separates and purifies the secondary 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. [Examples]

[0064] [Example 1] (Preparation of catalyst) Catalyst A was obtained by calcining 1 g of ammonium-type ZSM-5 (CBV28014, Zeolyst) in a muffle furnace. The calcination conditions were an air atmosphere, 550°C, and 5 hours. The amount of acid sites (solid acid content) 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. A metal reaction tube (inner diameter: 14 mm) equipped with an electric furnace for heating was filled with 3.0 g of catalyst A. 2. A cooling trap was connected further downstream of the reaction tube. A 5L gas bag was connected further downstream of the cooling trap. 3. Tetradecane (Tokyo Chemical Industries, Ltd., average carbon number: 14, flow rate: 0.3 g / min) was supplied as a hydrocarbon to a reaction tube heated to 600°C. Nitrogen gas (flow rate: 30 mL / min) and water vapor (flow rate: 0.08 g / min) were supplied as carrier gases. This caused catalytic cracking of the hydrocarbon. 4. Of the catalytic cracking products obtained between 25 and 45 minutes after the start of hydrocarbon supply, the liquid products were recovered using a cooling trap. In addition, of the catalytic cracking products obtained between 35 and 45 minutes after the start of hydrocarbon supply, the gaseous products were recovered using 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 77.5%, relative to the mass of the supplied hydrocarbon.

[0067] [Example 2] (Olefin production) In step 3 of the olefin production method of Example 1, the hydrocarbon supplied to the reaction tube was changed from tetradecane to n-octane (Tokyo Chemical Industries, Ltd., average number of carbon atoms: 8). Otherwise, the olefin was produced in the same manner as in Example 1.

[0068] 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 60.0% relative to the mass of the supplied hydrocarbon.

[0069] [Example 3] (Olefin production) In step 3 of the olefin production method of Example 1, the hydrocarbon supplied to the reaction tube was changed from tetradecane to decane (Tokyo Chemical Industries, Ltd., average number of carbon atoms: 10). Otherwise, the olefin was produced in the same manner as in Example 1.

[0070] 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 69.7%, relative to the mass of the supplied hydrocarbon.

[0071] [Example 4] (Olefin production) In step 3 of the olefin production method of Example 1, the hydrocarbon supplied to the reaction tube was changed from tetradecane to 1-octene (Tokyo Chemical Industries, Ltd., average number of carbon atoms: 8). Otherwise, the olefin was produced in the same manner as in Example 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 80.4% relative to the mass of the supplied hydrocarbon.

[0073] [Comparative Example 1] (Preparation of catalyst) Catalyst B was obtained by calcining 2 g of ammonium-type ZSM-5 (CBV2314, Zeolyst) in a muffle furnace. The calcination conditions were an air atmosphere, 550°C, and 5 hours. The amount of acid sites (solid acid content) of catalyst B, measured at 250-650°C by ammonia thermal desorption, was 878 μmol / g.

[0074] (Olefin production) In step 1 of the olefin production method of Example 1, the catalyst packed into the reaction tube was changed from catalyst A to catalyst B. Otherwise, the olefin was produced in the same manner as in Example 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 54.0%, relative to the mass of the supplied hydrocarbon.

[0076] [Comparative Example 2] (Olefin production) In step 1 of the olefin production method of Example 1, the amount of catalyst A packed into the reaction tube was changed from 3.0 g to 0.75 g. Otherwise, the olefin was produced in the same manner as in Example 1.

[0077] 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 48.1%, relative to the mass of the supplied hydrocarbon.

[0078] [Comparative Example 3] (Olefin production) In step 3 of the olefin production method of Example 1, the carrier gas supplied to the reaction tube was changed from nitrogen gas (flow rate: 30 mL / min) and water vapor (flow rate: 0.08 g / min) to nitrogen gas (flow rate: 10 mL / min) only. Otherwise, the olefin was produced in the same manner as in Example 1.

[0079] 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 60.3% relative to the mass of the supplied hydrocarbon.

[0080] [result] The results are shown in Table 1. Please note that the order of entries in Table 1 differs from that of the above-mentioned examples for the sake of comparison. [Table 1]

[0081] Comparative Examples 1-3 are variations of Example 1 in which the amount of acid sites in the catalyst, contact time, or carrier gas flow rate were changed. As can be seen from Table 1, each of these parameters contributes to the yield of olefins with 2-5 carbon atoms and by-products.

[0082] Examples 2 to 4 are variations of Example 1 in which the average number of carbon atoms in the raw hydrocarbon is changed. As can be seen from Table 1, according to the manufacturing method of one embodiment of the present invention, olefins can be successfully produced even if the average number of carbon atoms in the raw hydrocarbon is different. [Industrial applicability]

[0083] This invention can be used in the production of olefins.

Claims

1. A method for producing an olefin, comprising the following step S13: Step S13: A step of catalytically cracking a mixed gas of hydrocarbons and a carrier gas with a catalyst containing zeolite to obtain an olefin; Here, The amount of acid sites in the catalyst containing the above zeolite, as measured by the ammonia temperature-controlled desorption method at 250-650°C, is greater than 0 and less than or equal to 800 μmol / g. The contact time, obtained by dividing the mass-based flow rate (g / sec) of the above hydrocarbon by the mass (g) of the catalyst containing the above zeolite, is 200 to 1000 seconds. In the above mixed gas, the mass of the carrier gas is 0.05 to 1, where the mass of the hydrocarbon is 1.

2. The above olefin comprises one or more selected from the group consisting of ethylene, propylene, butene, and pentene. The manufacturing method according to claim 1.

3. The above zeolite has an MFI structure. The manufacturing method according to claim 1 or 2.

4. The carrier gas mentioned above is water vapor and / or nitrogen. The manufacturing method according to claim 1 or 2.

5. The average number of carbon atoms in the above hydrocarbons is 8 to 30. The manufacturing method according to claim 1 or 2.

6. The above-mentioned hydrocarbons contained in the mixed gas include one or more selected from the group consisting of normal paraffins, cycloparaffins, isoparaffins, olefins, cycloolefins, and isoolefins. In step S13 described above, an olefin having 2 to 5 carbon atoms is obtained. The manufacturing method according to claim 5.

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