Method for producing hydrocarbon-containing composition

Abstract

A method for producing a hydrocarbon-containing composition in which the hydrocarbon-containing composition containing ethylene is produced includes a heating step for heating, in an inert gas atmosphere, a raw material containing at least one substance selected from the group consisting of polyolefin-containing plastics and decomposition products thereof, and a catalyst containing 30 mass% to 100 mass% of lanthanum oxide while in contact with each other.

Description

Method for producing hydrocarbon-containing composition

[0001] The present disclosure relates to a method for producing a hydrocarbon-containing composition.

[0002] Conventionally, waste plastics have been disposed of by landfilling or incineration, but it is becoming increasingly difficult to secure landfill sites, and landfilled plastics end up in the ocean, where they do not decompose and remain as microplastics, creating environmental problems. Furthermore, while waste plastics can be used to generate heat by incineration, the carbon dioxide emissions contribute to global warming.

[0003] Therefore, in recent years, with the growing awareness of environmental issues, there has been a need for recycling, such as reusing and regenerating waste plastics, and research and development into this area has been actively carried out. Furthermore, since most plastics are produced using fossil fuels, there is a strong demand for the development of recycling methods from the perspective of effective resource utilization.

[0004] Among plastic materials, hydrocarbon-based plastic materials such as polyethylene (PE), polypropylene (PP), and polystyrene (PS) are widely used in beverage and food containers, packaging materials, molded products, films, etc., due to their excellent properties such as heat resistance, weather resistance, mechanical strength, transparency, chemical resistance, and gas barrier properties. Therefore, these hydrocarbon-based plastic materials account for the majority of the plastic materials that make up waste plastic materials.

[0005] One method for recycling these plastic materials is chemical recycling through oil-gasification, which converts waste plastics into low-molecular-weight hydrocarbons through thermal decomposition. Many studies have been conducted on methods that use solid catalysts to improve reactivity and product selectivity.

[0006] For example, it has been proposed to apply a catalyst comprising a heat transfer medium, a first active component, a second active component, and a third active component to the decomposition of waste plastics to produce low-carbon olefins and aromatic hydrocarbons, wherein the heat transfer medium comprises an oxide of at least one element selected from Si, Al, alkali metals, and alkaline earth metals; the first active component comprises an oxide of at least one element selected from Zn, Cu, Ni, Mn, La, Ce, and Ti; the second active component is selected from an oxide of an alkali metal and / or an oxide of an alkaline earth metal; and the third active component is selected from an oxide of at least one element selected from Zn, Ga, P, Cr, Ag, and K (see Patent Document 1).

[0007] Chinese Patent Publication No. 112316986

[0008] However, the catalysts disclosed in the prior art documents have a problem of low ethylene selectivity.

[0009] An object of the present disclosure is to provide a method for producing a hydrocarbon-containing composition having a high selectivity for ethylene and a good O / P ratio of hydrocarbons having two carbon atoms and three carbon atoms.

[0010] Means for solving the above problems are as follows. That is, <1> A method for producing a hydrocarbon-containing composition for producing an ethylene-containing hydrocarbon-containing composition, comprising a heating step of heating a raw material containing at least one selected from the group consisting of polyolefin-containing plastics and decomposition products thereof under an inert gas atmosphere while contacting the raw material with a catalyst containing 30% by mass to 100% by mass of lanthanum oxide. <2> A method for producing a hydrocarbon-containing composition according to <1>, wherein the catalyst further contains an alkaline earth metal oxide. <3> A method for producing a hydrocarbon-containing composition according to <2>, wherein the mass ratio of the lanthanum oxide to the alkaline earth metal oxide [lanthanum oxide:alkaline earth metal oxide] in the catalyst is 30:70 to 99:1. <4> A method for producing a hydrocarbon-containing composition according to <2> or <3>, wherein the alkaline earth metal oxide is magnesium oxide. <5> The method for producing a hydrocarbon-containing composition according to any one of <1> to <4>, wherein the heating step is a step of heating while contacting (A) a raw material containing at least one selected from the group consisting of the plastics and their decomposition products with (B) a mixture of the catalyst and heat transfer medium particles, and wherein the mass ratio of the catalyst to the heat transfer medium particles [catalyst:heat transfer medium particles] in the mixture is 1:1 to 1:100. <6> The method for producing a hydrocarbon-containing composition according to any one of <1> to <5>, wherein the plastic contains 50% by mass to 80% by mass of the polyolefin. <7> The method for producing a hydrocarbon-containing composition according to any one of <1> to <6>, wherein the heating step is carried out at 300°C to 800°C.

[0011] According to an embodiment of the present disclosure, a method for producing a hydrocarbon-containing composition having a high selectivity for ethylene and a good O / P ratio of hydrocarbons having two carbon atoms and three carbon atoms can be provided.

[0012] Hereinafter, embodiments of the present disclosure will be described in detail. Note that the embodiments are not limited by the following description and can be modified as appropriate within the scope of the present disclosure. Furthermore, in this specification, unless otherwise specified, the term "to" indicating a range of values ​​means that the values ​​before and after it are included as the lower and upper limits.

[0013] (Method for Producing Hydrocarbon-Containing Composition) A method for producing a hydrocarbon-containing composition according to one embodiment is a method for producing a hydrocarbon-containing composition containing ethylene, and includes a heating step of heating a raw material containing at least one selected from the group consisting of polyolefin-containing plastics and decomposition products thereof (hereinafter, may be referred to as "raw material plastic") in an inert gas atmosphere while bringing them into contact with a catalyst containing 30% by mass to 100% by mass of lanthanum oxide, and further includes other steps as necessary.

[0014] The inventors conducted extensive research and found that the composition ratio of olefins in a hydrocarbon-containing composition obtained by decomposing raw plastics varies depending on the type of metal oxide. They also found that using a catalyst containing lanthanum oxide, particularly 30% by mass to 100% by mass of a metal oxide, not only enables raw plastics to be decomposed effectively, but also results in a high selectivity for ethylene, which is useful for recycling plastic materials, among the olefins contained in the hydrocarbon-containing composition obtained by decomposing raw plastics, and a good O / P ratio of olefins having two carbon atoms and three carbon atoms. Therefore, a method for producing a hydrocarbon-containing composition according to one embodiment is also useful for reducing the environmental impact.

[0015] <Heating Step> The heating step is a step of heating a raw material containing at least one selected from the group consisting of polyolefin-containing plastics and decomposition products thereof while contacting it with a catalyst containing lanthanum oxide in an inert gas atmosphere, thereby obtaining a hydrocarbon-containing composition containing ethylene.

[0016] The heating step is a step of heating (A) a raw material containing at least one selected from the group consisting of the plastics and their decomposition products while bringing them into contact with (B) a mixture of the catalyst and heat transfer medium particles, and it is preferable that the mass ratio of the catalyst to the heat transfer medium particles [catalyst:heat transfer medium particles] in the mixture is 1:1 to 1:100.

[0017] The heating step is carried out under an inert gas atmosphere. The inert gas is not particularly limited and can be appropriately selected depending on the purpose. Examples include nitrogen gas, water vapor, and argon gas, and preferably one selected from the group consisting of nitrogen gas and water vapor. These may be used alone or in combination of two or more.

[0018] Since lanthanum oxide is a solid, the heating step may be a batch reaction or a continuous reaction. When a continuous reaction is performed, a fixed-bed reactor or a fluidized-bed reactor may be used. When a continuous reaction is performed using a fixed-bed reactor, a catalyst containing 30% to 100% by mass of lanthanum oxide is placed as a fixed bed in a reaction tube, and raw plastic is added onto the catalyst layer while an inert gas is circulated. When a continuous reaction is performed, it is preferable to use a particulate catalyst to prevent the catalyst from being washed away. It is also preferable to use heat transfer medium particles to distribute the catalyst uniformly in the reactor and stabilize the catalyst temperature.

[0019] The heating temperature in the heating step is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 300° C. to 1,100° C., more preferably 300° C. to 800° C., and even more preferably 350° C. to 500° C. When the heating temperature is 300° C. to 1,100° C., the ethylene yield is good.

[0020] The heating time in the heating step is not particularly limited and can be appropriately selected depending on the purpose.

[0021] In the heating step, the mass ratio of the raw plastic to the catalyst is not particularly limited and can be selected appropriately depending on the purpose. However, in a batch reaction, i.e., when the raw plastic is charged all at once, the catalyst is preferably 20 to 500 parts by mass, more preferably 35 to 300 parts by mass, and even more preferably 50 to 100 parts by mass, per 100 parts by mass of the raw plastic. By contacting 20 to 500 parts by mass of the catalyst with 100 parts by mass of the raw plastic, a hydrocarbon-containing composition with a high ethylene selectivity and a good O / P ratio of carbon atoms having 2 and 3 carbon atoms can be suitably produced. Furthermore, in a continuous reaction, i.e., when the raw plastic is charged intermittently or continuously, the catalyst (layer) is preferably 0.05 to 15,000 parts by mass, more preferably 30 to 800 parts by mass, per 100 parts by mass of the raw plastic per minute.

[0022] In the case of industrial waste, relatively homogeneous waste plastic materials consisting of specific plastic components and having a molecular weight distribution within a certain range can be obtained. In such cases, it is preferable to set the treatment conditions of the heating process according to the type and molecular weight of the plastic components constituting the waste plastic material. Note that when separating inorganic substances from waste plastic materials that are general waste, a laboratory-scale separation device can be used, but it can also be carried out on an industrial level using methods such as magnetic separation or electrostatic separation in various plants, for example, in refineries and plastic material recycling plants.

[0023] The heat source for the heating step is not particularly limited, and external heating or internal heating can be used.

[0024] <<Raw Material Plastic>> The raw material plastic contains at least one selected from the group consisting of polyolefin-containing plastics and decomposition products thereof, and further contains other components as necessary.

[0025] -Plastic containing polyolefin- The polyolefin is not particularly limited and can be appropriately selected depending on the purpose. However, polyethylene (PE), polypropylene (PP), etc., which are widely used for beverage and food containers, packaging materials, molded products, films, etc., are preferred.

[0026] The polyolefin content in polyolefin-containing plastics is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 50% by mass to 80% by mass, and more preferably 60% by mass to 80% by mass, relative to the total mass of the polyolefin-containing plastic. When the polyolefin content in polyolefin-containing plastics is 50% by mass to 80% by mass, easily available mixed plastics can be used without sorting, and a hydrocarbon-containing composition with a high selectivity for lower olefins such as ethylene can be suitably obtained.

[0027] The polyolefin-containing plastic may include, in addition to polyolefin, other plastics such as polystyrene (PS), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), polycarbonate (PC), polyvinyl chloride (PVC), polyvinylidene chloride, chlorinated polyethylene, polyamide, polyurethane, acrylonitrile-butadiene-styrene copolymer, and polymethyl methacrylate.

[0028] The content of plastics other than polyolefins in a plastic containing polyolefin is not particularly limited and can be selected appropriately depending on the type of plastic used, etc., but from the viewpoint of ethylene yield, it is preferably less than 50 mass % of the total mass of the plastic containing polyolefin, more preferably 45 mass % or less, and even more preferably 40 mass % or less.

[0029] The polyolefin-containing plastic preferably contains waste plastic from the viewpoint of reducing the environmental load.

[0030] When the polyolefin-containing plastic is waste plastic, the composition and composition ratio are not particularly limited and can be selected appropriately depending on the purpose, but it preferably contains at least one selected from the group consisting of PE and PP, more preferably 20% by mass to 80% by mass of PE and 20% by mass to 80% by mass of PP, and even more preferably 20% by mass to 40% by mass of PE, 20% by mass to 40% by mass of PP, and 10% by mass to 30% by mass of PS.

[0031] The state of the polyolefin-containing plastic in the heating step is not particularly limited, and examples thereof include crystalline, glassy, ​​rubbery, and liquid states.

[0032] When the polyolefin-containing plastic is crystalline or glassy, ​​its form is not particularly limited, and examples include crushed plastic, pellets of crushed plastic, chips of crushed plastic, and the like.

[0033] The crushed plastic material is not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include powder and flake forms.

[0034] A rubbery or liquid polyolefin-containing plastic refers to a plastic that is in a fluid state at a temperature equal to or higher than the melting point of the polyolefin-containing plastic and lower than the thermal decomposition temperature of the polyolefin-containing plastic. A rubbery or liquid polyolefin-containing plastic is also called a "melt of a polyolefin-containing plastic."

[0035] These various forms of raw material plastics may be used after being treated separately from the method for producing a hydrocarbon-containing composition of one embodiment, or may be treated in a pretreatment step described below.

[0036] The molecular weight of plastics containing rubbery or liquid polyolefins is the same as that of plastics containing crystalline or glassy polyolefins of the same composition. Therefore, plastics containing polyolefins and decomposition products of polyolefin-containing plastics can be distinguished by molecular weight. As the molecular weight decreases due to decomposition, the melting point decreases, so in practice, the melting temperature can be used to determine the melting point. The melting temperature is measured using the method specified in the heat flux differential scanning calorimetry (DSC) method of JIS K7121-2012.

[0037] The melting temperature of the polyolefin-containing plastic is not particularly limited and can be appropriately selected depending on the raw material used, but is preferably 80°C to 200°C, more preferably 90°C to 190°C.

[0038] -Decomposition products of polyolefin-containing plastics- Decomposition products of polyolefin-containing plastics are materials obtained by lowering the molecular weight of polyolefin-containing plastics, and it is preferable that the molecular weight of the decomposition products of the raw plastics in the hydrocarbon-containing composition is larger than that of the decomposition products of the raw plastics.

[0039] The decomposition product of the polyolefin-containing plastic is not particularly limited and can be appropriately selected depending on the raw material used, but from the viewpoint of transportation and storage, it is preferably a liquid at 25° C., and more preferably has an initial boiling point of 30° C. or higher. The initial boiling point is measured in accordance with the atmospheric pressure method of JIS K2254:2018.

[0040] The decomposition product of the polyolefin-containing plastic may be decomposed separately from the method for producing a hydrocarbon-containing composition of one embodiment and used, or may be decomposed in the decomposition step described below.

[0041] Other Components There are no particular limitations on the other components in polyolefin-containing plastics and they can be selected appropriately depending on the purpose. Examples of such other components include materials other than plastics or additives. Examples of materials other than plastics include materials that are typically contained in waste plastics, etc. Specific examples of materials other than plastics include paper and metal.

[0042] There are no particular restrictions on the content of materials other than plastics or additives in the raw plastic material.

[0043] <<Catalyst>> The catalyst is lanthanum oxide (La ２ O ３ ) in an amount of 30% by mass to 100% by mass, and further contains other components as necessary.

[0044] -Lanthanum oxide-Lanthanum oxide is an inorganic compound containing the rare earth element lanthanum and oxygen. ２ O ３ is.

[0045] The content of lanthanum oxide in the catalyst is 30% by mass to 100% by mass, preferably 30% by mass to 90% by mass, more preferably 30% by mass to 70% by mass, and even more preferably 40% by mass to 60% by mass, relative to the total mass of the catalyst. If the content of lanthanum oxide in the catalyst is less than 30% by mass, the selectivity for ethylene decreases, and the O / P ratio of carbon atoms having 2 and carbon atoms decreases.

[0046] Other Components The other components in the catalyst are not particularly limited and can be selected appropriately depending on the purpose, but the catalyst preferably further contains an alkaline earth metal oxide. The catalyst may also contain a binder, a granulation aid, etc. as necessary.

[0047] The alkaline earth metal oxide in the other components is not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include beryllium oxide (BeO), magnesium oxide (MgO), calcium oxide (CaO), strontium oxide (SrO), barium oxide (BaO), and radium oxide (RaO). These may be used alone or in combination of two or more. Among these, magnesium oxide is preferred as the alkaline earth metal oxide, since it can improve the O / P ratio of carbon atoms having two and three carbon atoms.

[0048] The content of alkaline earth metal oxide in the catalyst is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 30% by mass to 70% by mass, more preferably 40% by mass to 65% by mass, and even more preferably 40% by mass to 60% by mass, relative to the total mass of the catalyst.

[0049] When the catalyst contains an alkaline earth metal oxide, the mass ratio of lanthanum oxide to the alkaline earth metal oxide [lanthanum oxide: alkaline earth metal oxide] in the catalyst is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 30:70 to 99:1, more preferably 30:70 to 70:30, and even more preferably 40:60 to 60:40.

[0050] <<Heat Medium Particles>> Heat medium particles are preferably used to maintain the temperature of the reaction system at a constant temperature in the heating step.

[0051] The heat transfer medium particles are not particularly limited and can be appropriately selected depending on the purpose, but those having sufficient heat resistance and chemical stability in the heating process are preferred. Specific examples of heat transfer medium particles include silicon carbide, iron, alumina, zirconia, silica, ceramics, glass, carbon, boron carbide, etc. These may be used alone or in combination of two or more. Among these, silicon carbide is preferred as the heat transfer medium particles. The heat transfer medium particles may be surface-treated from the above materials for purposes such as surface inactivation and improving the flow of molten plastic and decomposition products.

[0052] The size of the heat transfer medium particles is not particularly limited and can be appropriately selected depending on the purpose, but a nominal opening of 4.75 mm to 275 mm is preferred, and 2.36 mm to 38 mm is more preferred. The size of the heat transfer medium particles is measured in accordance with JIS Z 8801-1:2019.

[0053] The shape and structure of the heat transfer medium particles are not particularly limited and can be appropriately selected depending on the purpose.

[0054] In the heating step, the heat transfer medium particles are preferably used as a mixture of catalyst and heat transfer medium particles. The mass ratio of the catalyst to the heat transfer medium particles in the mixture [catalyst:heat transfer medium particles] is not particularly limited and can be selected appropriately depending on the purpose, but is preferably 1:1 to 1:100, more preferably 1:1 to 1:50, even more preferably 1:1 to 1:20, and particularly preferably 1:1 to 1:10. When the mass ratio [catalyst:heat transfer medium particles] is 1:1 or more, the heating temperature is easily maintained. Furthermore, when the mass ratio [catalyst:heat transfer medium particles] is 1:100 or less, the catalyst and the raw plastic can be in good contact with each other.

[0055] <<Hydrocarbon-Containing Composition>> The hydrocarbon-containing composition obtained by the method for producing a hydrocarbon-containing composition according to one embodiment contains at least ethylene, and preferably further contains an olefin having a carbon number of 3 to 5. Note that the hydrocarbon-containing composition obtained by the method for producing a hydrocarbon-containing composition according to one embodiment may contain by-products other than the lower olefins.

[0056] - Ethylene - Ethylene is an olefin having two carbon atoms.

[0057] The ethylene content in the hydrocarbon-containing composition is not particularly limited and can be selected appropriately depending on the purpose, but is preferably 20 mol% or more, more preferably 22 mol% or more, even more preferably 24 mol% or more, and particularly preferably 27 mol% or more, relative to the total carbon moles of the hydrocarbon-containing composition. The upper limit of the ethylene content in the hydrocarbon-containing composition is not particularly limited, as a higher content is more preferable, but is preferably 50 mol% or less, more preferably 40 mol% or less, and even more preferably 35 mol% or less. The lower and upper limits of the ethylene content in the hydrocarbon-containing composition can be appropriately combined, and is preferably 20 mol% to 50 mol%, more preferably 22 mol% to 40 mol%, even more preferably 24 mol% to 40 mol%, and particularly preferably 27 mol% to 35 mol%.

[0058] —Olefins Having 3 to 5 Carbon Atoms— The olefins having 3 to 5 carbon atoms are preferably at least one selected from the group consisting of alkenes having 3 to 5 carbon atoms and dienes having 3 to 5 carbon atoms, and more preferably alkenes having 3 to 5 carbon atoms.

[0059] An example of an olefin having 3 carbon atoms is propylene. The method for producing a hydrocarbon-containing composition according to one embodiment has the advantage that the selectivity of propylene is also high in addition to the high selectivity of ethylene.

[0060] Examples of the olefin having 4 carbon atoms include 1-butene, cis-2-butene, trans-2-butene, and 2-methylpropene.

[0061] Examples of the olefin having 5 carbon atoms include 1-pentene, cis-2-pentene, trans-2-pentene, 2-methyl-1-butene, and 2-methyl-2-butene.

[0062] The total content of ethylene and propylene in the hydrocarbon-containing composition is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 50 mol% to 80 mol%, more preferably 50 mol% to 70 mol%, based on the total number of carbon moles in the hydrocarbon-containing composition.

[0063] The total content of olefins having 2 to 5 carbon atoms in the hydrocarbon-containing composition is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 50 mol% to 90 mol%, more preferably 60 mol% to 80 mol%, based on the total carbon moles of the hydrocarbon-containing composition.

[0064] In the present disclosure, olefins having 2 to 5 carbon atoms, including ethylene, may be referred to as "lower olefins" or "useful components."

[0065] Lower olefins are used as raw materials for polyolefins, which can be suitably used as raw materials in various fields such as plastic bags, plastic wrap films, straws, medical devices, housings for home appliances, erasers, hoses, tires, tubes, CD cases, food trays, food containers, plastic bottles, and fibers.

[0066] By-products Examples of by-products include aromatic compounds and paraffins.

[0067] --Aromatic Compound-- The aromatic compound is not particularly limited, but is preferably benzene, toluene, ethylbenzene, three positional isomers of xylene (p-xylene, m-xylene, and o-xylene), styrene, or cumene.

[0068] The content of aromatic compounds in the hydrocarbon-containing composition is not particularly limited and can be appropriately selected depending on the purpose.

[0069] Aromatic compounds can be used as raw materials for resins, and resins can be suitably used as raw materials in various fields such as CD cases, food trays, food containers, PET bottles, and fibers.

[0070] --Paraffin-- The paraffin is not particularly limited, but is preferably an aliphatic saturated hydrocarbon having 2 to 5 carbon atoms, more preferably a chain aliphatic saturated hydrocarbon having 2 to 5 carbon atoms, and even more preferably a chain aliphatic saturated hydrocarbon having 2 or 3 carbon atoms. Specific examples of paraffins include methane, ethane, propane, isobutane, n-butane, and n-pentane. Among these, the selectivity for methane in the method for producing a hydrocarbon-containing composition according to one embodiment is low.

[0071] The lower the methane content in the hydrocarbon-containing composition, the better, but it is more preferably 20 mol% or less, even more preferably 15 mol% or less, and particularly preferably 10 mol% or less, based on the total carbon moles of the hydrocarbon-containing composition.

[0072] The total content of ethane and propane in the hydrocarbon-containing composition is preferably 30 mol % or less, more preferably 25 mol % or less, and even more preferably 20 mol % or less, based on the total number of carbon moles in the hydrocarbon-containing composition.

[0073] The total content of paraffins having 2 to 5 carbon atoms in the hydrocarbon-containing composition is preferably 35 mol% or less, more preferably 30 mol% or less, and even more preferably 25 mol% or less, based on the total carbon moles of the hydrocarbon-containing composition.

[0074] --O / P Ratio-- In the present disclosure, a low content of paraffins, a minor component, can be evaluated by determining the ratio of the total content (%) of olefins in the hydrocarbon-containing composition to the total content (%) of paraffins in the hydrocarbon-containing composition, i.e., the ratio [total content (%) of olefins / total content (%) of paraffins] (hereinafter, sometimes referred to as the "O / P ratio"). In the ratio [total content (%) of olefins / total content (%) of paraffins], the O / P ratio is evaluated by the ratio [total content (%) of olefins having 2 and 3 carbon atoms / total content (%) of paraffins having 2 and 3 carbon atoms] or the ratio [total content (%) of olefins having 2 to 5 carbon atoms / total content (%) of paraffins having 2 to 5 carbon atoms].

[0075] The O / P ratio is not particularly limited for the O / P ratios of those having 2 and 3 carbon atoms, and for those having 2 to 5 carbon atoms, and can be appropriately selected depending on the purpose, but is preferably 1.0 or more, more preferably 2.0 or more, and even more preferably 3.0 or more. The higher the O / P ratio, the better, so there is no particular upper limit, but it is preferably 50 or less, and more preferably 20 or less.

[0076] The content of ethylene and other olefins contained in the hydrocarbon-containing composition, as well as the O / P ratio, can be determined by analyzing the hydrocarbon-containing composition obtained in the cracking step, specifically the gaseous product, using a gas chromatograph (GC) equipped with a flame ionization detector under the analytical conditions described in the Examples, and quantifying each component using the internal standard method based on the ratio of the peak area of ​​each component to that of the internal standard. The internal standard is not particularly limited as long as it is stable under analytical conditions and can be easily separated from the components to be analyzed, and examples include cyclopentane. In the present disclosure, the content based on the number of moles of carbon may be expressed as "C mol%".

[0077] When analyzing aromatic compounds as the olefin-containing composition obtained in the cracking step, in the recovery step described below, a liquid substance containing aromatic compounds is separated from the gaseous product by, for example, providing a liquid trap filled with tetrahydrofuran (THF) between the reactor and the gas recovery section, and the tetrahydrofuran (THF)-soluble product (hereinafter sometimes referred to as the "THF-soluble product") is analyzed using a gas chromatograph (GC) equipped with a flame ionization detector under the following analytical conditions, and each component can be quantified using the internal standard method from the ratio of the peak area of ​​each component to that of the internal standard. In this case, the C5 olefins 1-pentene, cis-2-pentene, trans-2-pentene, 2-methyl-1-butene, and 2-methyl-2-butene, as well as n-pentane, the C2 to C5 chain aliphatic saturated hydrocarbon, are also separated as liquid substances. Therefore, in order to calculate the total content of olefins having 2 to 5 carbon atoms or the O / P ratio of olefins having 2 to 5 carbon atoms, it is necessary to combine the analysis results of the liquid substance and the gaseous product. The internal standard used in the analysis of the liquid substance is not particularly limited as long as it is stable under the analysis conditions and can be easily separated from the component to be analyzed, and an example of such an internal standard is t-butylbenzene. [GC analysis conditions for THF-soluble products] Apparatus: Nexis GC-2030 (Shimadzu Corporation) Column: DB-1 (diameter: 0.25 mm, length: 30 m, Agilent Technology) Carrier gas type: He Carrier gas flow rate: 97 mL / min Injection temperature: 350°C Sample injection amount: 1 μL Split ratio: 1 / 50 Column temperature: The temperature rise program was set in the following order: 35°C (10 min) → temperature rise (5°C / min) → 350°C (10 min) Detector: Hydrogen flame ionization detector (FID) Detector temperature: 350°C

[0078] <Other Steps> Other steps in the method for producing a hydrocarbon-containing composition are not particularly limited and can be selected appropriately depending on the purpose. Examples include a pretreatment step for raw plastics, a decomposition step for raw plastics, a recovery step for useful components obtained in the heating step, and a separation step for useful components.

[0079] <<Pretreatment Step>> The pretreatment step is a step of pretreating a polyolefin-containing plastic before subjecting it to a heating step. In the pretreatment step, the polyolefin-containing plastic is put into a form or state that is easy to decompose, so that the polyolefin-containing plastic can be decomposed more efficiently in the heating step.

[0080] Examples of pretreatments include pulverizing the polyolefin-containing plastic, pelletizing (chipping) the pulverized polyolefin-containing plastic, and melting the polyolefin-containing plastic.

[0081] The method for obtaining pulverized polyolefin-containing plastic is not particularly limited and can be appropriately selected from conventionally known methods, such as a method in which polyolefin-containing plastic is pulverized using a pulverizer to obtain powder or flakes.

[0082] Furthermore, the method for pelletizing the pulverized material (chips) is not particularly limited and can be appropriately selected from conventionally known methods. For example, there is a method in which the pulverized material is melt-extruded and then the strand-like molten extruded material is cut to obtain chipped raw material.

[0083] The melt treatment of the polyolefin-containing plastic is not particularly limited and can be appropriately selected from conventionally known methods. However, it is preferable to treat the polyolefin-containing plastic at a temperature equal to or higher than the melting point of the polyolefin-containing plastic and lower than the thermal decomposition temperature of the polyolefin-containing plastic, and more preferably at 100°C to 300°C.

[0084] The polyolefin-containing plastic can also be supplied to the heating step as a melt, for example, by using a melt extruder to continuously supply the melt to the heating step.

[0085] <<Decomposition Step>> The decomposition step is a step of decomposing a polyolefin-containing plastic before it is subjected to a heating step. In the decomposition step, the polyolefin-containing plastic may be used as a raw material as is, or may be used after being pretreated in a pretreatment step.

[0086] The method for decomposing polyolefin-containing plastics is not particularly limited and can be appropriately selected from conventionally known methods. When decomposing polyolefin-containing plastics in the absence of the catalyst of the present disclosure, it is preferable to treat them at 300°C to 500°C. When decomposing polyolefin-containing plastics in the presence of the catalyst of the present disclosure, it is preferable to treat them at 200°C or higher but lower than 300°C.

[0087] The polyolefin-containing plastic can also be supplied to the heating step as a decomposition product, for example, by a method of continuously supplying it to the heating step using a melt extruder.

[0088] <<Recovery Step>> The recovery step is a step of recovering the gaseous product containing ethylene and other lower olefins obtained in the heating step, and further recovering liquid substances as necessary. The recovery method is not particularly limited and can be appropriately selected from known methods depending on the type of the product obtained. For example, a method can be used in which gaseous products are separated by pressurized distillation at atmospheric pressure, and liquid hydrocarbons are separated by vacuum distillation at atmospheric pressure.

[0089] <<Separation Step>> The separation step is a step of separating only useful components from the gas and liquid substance recovered in the recovery step and removing unnecessary components.

[0090] According to one embodiment of the method for producing a hydrocarbon-containing composition, in addition to useful components such as ethylene and other lower olefins, paraffins having 2 to 5 carbon atoms as minor components may be produced.

[0091] In the separation step, the method for separating the useful components from the minor components is not particularly limited, and can be appropriately selected from known methods depending on the type of product or minor component obtained.

[0092] The method for producing a hydrocarbon-containing composition according to the embodiment described above has a high selectivity for ethylene and a good O / P ratio of carbon atoms having 2 and carbon atoms having 3, and therefore can produce a raw material suitable for chemical recycling.

[0093] The present disclosure will be specifically described below with reference to examples and comparative examples, but the present disclosure is not limited to these examples and comparative examples.

[0094] Example 1: 1 g of lanthanum oxide (Kanto Chemical Co., Inc.) and 4 g of silicon carbide (Carborundum C80, Nichika Co., Ltd.) were weighed out and mixed thoroughly with a stirring rod to obtain a mixture of catalyst and heat transfer medium particles. Separately, a plastic composition was prepared by mixing polyethylene (Hi-Zex® 1300J, Prime Polymer Co., Ltd.), polypropylene (Prime Polypro® J108M, Prime Polymer Co., Ltd.), and polystyrene (PSJ-Polystyrene GPPS SGP-10, PS Japan Co., Ltd.) in a 1:1:1 (w / w) ratio. 5 g of the catalyst and heat transfer medium particle mixture was placed in a quartz test tube with an inner diameter of 18 mm, and 2.1 g of the mixed plastic composition was placed on top of the mixture and the tube was then capped. A gas bag was connected to the outlet of the quartz test tube cap. Next, the quartz test tube was placed in a tubular furnace (ARF-40KC, manufactured by Asahi Rika Seisakusho Co., Ltd.) and heated at 450° C. for 10 minutes under a nitrogen flow of 15 mL / min, while the generated gas was collected with a gas bag.

[0095] Example 2 Gas was collected in the same manner as in Example 1, except that 1 g of lanthanum oxide used as a catalyst was changed to a mixture of 0.5 g of lanthanum oxide (manufactured by Kanto Chemical Co., Inc.) and 0.5 g of magnesium oxide (special grade reagent, manufactured by Sigma-Aldrich).

[0096] Comparative Example 1 Gas was collected in the same manner as in Example 1, except that 1 g of lanthanum oxide used as the catalyst was changed to 1 g of nickel (II) oxide (special grade reagent, manufactured by Kanto Chemical Co., Inc.).

[0097] Comparative Example 2 Gas was collected in the same manner as in Example 1, except that 1 g of lanthanum oxide used as the catalyst was changed to 1 g of cerium oxide (≧99.0%, manufactured by Sigma-Aldrich).

[0098] Comparative Example 3 Gas was collected in the same manner as in Example 1, except that 1 g of lanthanum oxide used as a catalyst was changed to 1 g of magnesium oxide (special grade reagent, manufactured by Sigma-Aldrich).

[0099] <Analysis of Gas Bag Contents> In Examples 1 and 2 and Comparative Examples 1 to 3, the proportions of useful components and by-products in the pyrolysis gas collected in the gas bag were determined in terms of carbon moles (C mol %) using the following method. Specifically, 40 μL of cyclopentane (>98.0%, manufactured by Tokyo Chemical Industry Co., Ltd.) was added to each of the gas bags of Examples 1 and 2 and Comparative Examples 1 to 3. The gas bag was heated to approximately 40°C to completely vaporize the contents, and then the gas bag was gently kneaded to mix the contents. The resulting contents were analyzed by gas chromatography (GC) under the GC analysis conditions described below. The proportions (C mol %) of each component in the pyrolysis gas in the gas bag were determined from the ratio of the peak area of ​​cyclopentane to the peak area of ​​each component. The results are shown in Table 1 below. [GC analysis conditions] Apparatus: Nexis GC-2030 (Shimadzu Corporation) Column: Rt-Alumina BOND (diameter: 0.32 mm, length: 30 m, Restek) Carrier gas type: Ar Carrier gas flow rate: 360 mL / min Injection temperature: 200°C Sample injection amount: 1 mL Split ratio: 1 / 200 Column temperature: After holding at 120°C for 9 minutes, the temperature was increased to 200°C at 10°C / min and held at 200°C for 30 minutes. Detector: Flame ionization detector (FID) Detector temperature: 200°C

[0100]

[0101] In Examples 1 and 2, the yield of ethylene, a useful component, was higher than in Comparative Examples 1 to 3, and the O / P ratios of carbon atoms having 2 and carbon atoms having 3 were good.

[0102] As described above, the present disclosure has been described based on specific embodiments and examples, but these embodiments and examples are presented merely as examples, and the present disclosure is not limited to the above embodiments and examples. The above embodiments can be implemented in various other forms, and various combinations, omissions, substitutions, additions, modifications, etc. can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and spirit of the invention, and are also included in the inventions and their equivalents as set forth in the claims.

[0103] This international application claims priority based on Japanese Patent Application No. 2023-221739, filed on December 27, 2023, the entire contents of which are incorporated herein by reference.

Claims

1. In a method for producing a hydrocarbon-containing composition for producing a hydrocarbon-containing composition containing ethylene, a heating step is included in which, in an inert gas atmosphere, a raw material containing at least one selected from the group consisting of a plastic containing a polyolefin and its decomposition products is heated while being brought into contact with a catalyst containing 30% by mass to 100% by mass of lanthanum oxide. A method for producing a hydrocarbon-containing composition, characterized by the above.

2. The method for producing a hydrocarbon-containing composition according to claim 1, wherein the catalyst further contains an oxide of an alkaline earth metal.

3. The method for producing a hydrocarbon-containing composition according to claim 2, wherein the mass ratio [lanthanum oxide: oxide of alkaline earth metal] of the lanthanum oxide and the oxide of the alkaline earth metal in the catalyst is 30:70 to 99:

1.

4. The method for producing a hydrocarbon-containing composition according to claim 2 or claim 3, wherein the oxide of the alkaline earth metal is magnesium oxide.

5. The heating step is a step of heating while bringing (A) a raw material containing at least one selected from the group consisting of the plastic and its decomposition products into contact with (B) a mixture of the catalyst and heat medium particles, and in the mixture, the mass ratio [catalyst: heat medium particles] of the catalyst and the heat medium particles is 1:1 to 1:

100. The method for producing a hydrocarbon-containing composition according to any one of claims 1 to 4.

6. The method for producing a hydrocarbon-containing composition according to any one of claims 1 to 5, wherein the plastic contains 50% by mass to 80% by mass of the polyolefin.

7. The method for producing a hydrocarbon-containing composition according to any one of claims 1 to 6, wherein the heating step is performed at 300°C to 800°C.

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