Naphtha for lower olefin production and method for producing same, method for determining naphtha for lower olefin production, lower olefin composition and method for producing same, and polyolefin polymer

Abstract

Specifically disclosed is a naphtha for producing a lower olefin, which contains an ether that contains a hydrocarbon having 7 or more carbon atoms and has an asymmetric structure with respect to oxygen atoms constituting an ether bond, the content of the ether being less than or equal to 100% of the total mass of the naphtha for producing a lower olefin, and the content of the ether being less than or equal to 100% of the total mass of the naphtha for producing a lower olefin. The content ratio of the hydrocarbon having 7 or more carbon atoms is 14.0 mass% or more, and the content of the ether is 20,000 mass ppm or less in terms of ether oxygen atoms.

Description

Technical Field

[0001] The present invention relates to naphtha for producing lower olefins used for producing lower olefins and a method for producing the same.

[0002] Furthermore, the present invention relates to a method for producing a lower olefin composition, comprising producing the lower olefin composition from the above-mentioned naphtha for producing lower olefins.

[0003] Furthermore, the present invention relates to a lower olefin composition obtained from the above-mentioned naphtha for producing lower olefins.

[0004] Furthermore, the present invention relates to a polyolefin polymer obtained by polymerizing the above-mentioned lower olefin composition.

[0005] Furthermore, the present invention relates to a method for determining naphtha for producing lower olefins.

[0006] In the present invention, "lower olefin" refers to an unsaturated hydrocarbon having 2 to 4 carbon atoms and containing one or two unsaturated bonds in one molecule, and specific examples thereof include ethylene, propylene, butene (1-butene, 2-butene, isobutylene), and butadiene (1,2-butadiene and 1,3-butadiene). Background Art

[0007] As a typical method for producing lower olefins, there is known a method of thermally decomposing (steam cracking) fossil fuel-derived naphtha (a hydrocarbon mixture derived from crude oil having a boiling point range of about 30 to 230° C.) in the presence of steam (for example, Patent Document 1).

[0008] In recent years, efforts have been made to use renewable organic resources (such as plants) other than fossil fuels as raw materials for industrial products in order to achieve the Sustainable Development Goals (SDGs). As one of the means, effective utilization of raw materials from biomass has been proposed. However, the technology of using raw materials from biomass, such as naphtha from biomass, in the cracking process of naphtha is not yet known in detail.

[0009] In the steam cracking method, once the raw material naphtha is selected, specific thermal decomposition conditions and specific thermal decomposition equipment are basically required according to the composition, properties and product requirements of the raw material naphtha. Therefore, there are disadvantages such as poor selectivity between raw material naphtha and products and lack of flexibility.

[0010] That is, naphtha from biomass is different from naphtha from fossil fuel in composition and properties. Therefore, when a single naphtha from biomass or a naphtha mixture containing naphtha from biomass raw materials and naphtha from fossil fuel is thermally decomposed by steam cracking using an existing thermal decomposition device, it is required to increase the production yield of lower olefins from the viewpoint of improving specific energy consumption.

[0011] Naphtha contains oxygen-containing compounds. When naphtha is thermally decomposed to produce various lower olefins, methanol may be generated as a thermal decomposition product of the oxygen-containing compounds.

[0012] There are many types of oxygen-containing compounds contained in naphtha, but the ratio of methanol generated from these oxygen-containing compounds is not fixed, and the details are not yet clear.

[0013] If methanol derived from the thermal decomposition product of the oxygen-containing compound is mixed into the product lower olefins such as propylene, there is a problem that the performance of the catalyst used for polymerizing the lower olefins such as propylene is degraded.

[0014] Therefore, the content concentration of oxygen-containing compounds in naphtha is regarded as a criterion for determining whether the quality of naphtha is good or not.

[0015] Normally, a buyer of naphtha purchases the naphtha after checking the content concentrations of various oxygen-containing compounds present in the naphtha.

[0016] The concentration of oxygen-containing compounds in naphtha is also reflected in the price of naphtha. Compounds with high oxygen-containing compound concentrations are cheap, while compounds with low oxygen-containing compound concentrations are sold at high prices.

[0017] Under the above background, naphtha buyers usually blend purchased naphtha with a high oxygen-containing compound content with naphtha with a low oxygen-containing compound concentration to reduce the oxygen-containing compound content in the naphtha and then use the mixture to produce lower olefins.

[0018] Prior art literature

[0019] Patent Literature

[0020] Patent Document 1: Japanese Patent Application Publication No. 2009-40913 Summary of the invention

[0021] Problems to be solved by the invention

[0022] As described above, conventionally, the details of the relationship between the types of oxygen-containing compounds contained in naphtha and the amount of methanol produced from the thermal decomposition of the oxygen-containing compounds have not been clearly understood.

[0023] Therefore, even if the quality of naphtha is determined based on the content concentration of oxygen-containing compounds in naphtha, the concentration of methanol produced when lower olefins are actually produced by thermal decomposition is not necessarily proportional to the content concentration.

[0024] That is, a method for accurately identifying high-quality naphtha having a low methanol production concentration has not been known so far.

[0025] Furthermore, a method for accurately identifying high-quality naphtha having a low methanol production concentration using naphtha derived from biomass raw materials that differs in composition and properties from conventional naphtha derived from fossil fuels has not been known to date.

[0026] The present invention aims to solve these problems.

[0027] That is, an object of the present invention is to provide naphtha for lower olefin production which can produce a lower olefin composition having a low methanol production concentration at a high olefin yield, a production method thereof, and a determination method thereof.

[0028] Another object of the present invention is to provide a method for producing a lower olefin composition using the naphtha for producing lower olefins. Furthermore, another object of the present invention is to provide a lower olefin composition having a low methanol content produced by the method for producing a lower olefin composition, and a polyolefin polymer obtained by polymerizing the lower olefin composition.

[0029] Methods for solving problems

[0030] The present inventors have conducted extensive studies to solve the above-mentioned problems and, as a result, have obtained the following findings.

[0031] (1) Among oxygen-containing compounds, specific ethers having an asymmetric structure with respect to the oxygen atom of the ether bond are likely to selectively decompose specific bonds in the molecule in the thermal decomposition step of naphtha, and are particularly likely to produce methanol by decomposition.

[0032] (2) By using naphtha for producing low olefins in which the absolute value ΔE [unit: e] of the difference in charge values ​​between two carbon atoms bonded to the oxygen atom of the ether bond in the specific ether having an asymmetric structure is greater than a predetermined value, more preferably the content of oxygen atoms derived from the ether is less than a predetermined value, and the content ratio of hydrocarbons having 7 or more carbon atoms is greater than a predetermined value, a low olefin composition with a low methanol formation concentration can be obtained with a high olefin yield.

[0033] (3) This effect is particularly remarkable in the case of naphtha for producing lower olefins using naphtha derived from biomass raw materials as raw material naphtha.

[0034] The present inventors have completed the present invention based on this finding.

[0035] That is, the gist of the present invention is as follows.

[0036] [1] A naphtha for producing lower olefins, which is a naphtha for producing lower olefins containing ether,

[0037] The naphtha for producing lower olefins contains hydrocarbons having 7 or more carbon atoms.

[0038] The ether has an asymmetric structure with respect to the oxygen atom constituting the ether bond.

[0039] The content of the hydrocarbons having 7 or more carbon atoms is 14.0% by mass or more relative to 100% by mass of the total mass of the naphtha for producing lower olefins,

[0040] The content of the ether is 20,000 mass ppm or less in terms of ether oxygen atoms.

[0041] [2] The naphtha for producing lower olefins according to [1], wherein the average molecular weight of hydrocarbons contained in the naphtha for producing lower olefins is 80.0 g / mol or more.

[0042] [3] The naphtha for producing lower olefins according to [1] or [2], wherein the specific gravity is 0.6640 g / cm 3 above.

[0043] [4] The naphtha for lower olefin production according to any one of [1] to [3], wherein the content of the ether is 0.1 ppm by mass or more in terms of ether oxygen atoms.

[0044] [5] The naphtha for lower olefin production according to any one of [1] to [4], wherein the content of sulfur-containing compounds is 180 ppm by mass or less in terms of sulfur atoms.

[0045] [6] The naphtha for producing lower olefins according to any one of [1] to [5], wherein the content of the hydrocarbons having 7 or more carbon atoms is 42.0% by mass or less relative to 100% by total mass of the naphtha for producing lower olefins.

[0046] [7] The naphtha for lower olefin production according to any one of [1] to [6], wherein the average molecular weight of hydrocarbons contained in the naphtha for lower olefin production is 87.0 g / mol or less.

[0047] [8] The naphtha for producing lower olefins according to any one of [1] to [7], wherein the specific gravity is 0.6695 g / cm 3 the following.

[0048] [9] The naphtha for lower olefin production according to any one of [1] to [8], wherein the content of the sulfur-containing compound is 1 ppm by mass or more in terms of sulfur atoms.

[0049]

[10] The naphtha for producing lower olefins according to any one of [1] to [9], wherein the naphtha for producing lower olefins comprises naphtha derived from a bio-raw material.

[0050]

[11] The naphtha for producing lower olefins according to

[10] , wherein the naphtha for producing lower olefins is naphtha derived from biomass raw materials alone, or a naphtha mixture containing naphtha derived from biomass raw materials and naphtha derived from fossil fuels.

[0051]

[12] The naphtha for producing lower olefins according to

[10] or

[11] , wherein the naphtha derived from a biomass raw material is inedible biomass and / or naphtha derived from a non-fossil fuel.

[0052]

[13] According to the naphtha for low olefin production described in any one of [1] to

[12] , in the above-mentioned ether, the absolute value ΔE (ΔE=|E1-E2|) of the difference between the charge E1 of one carbon atom and the charge E2 of the other carbon atom calculated by density functional theory for two carbon atoms bonded to the oxygen atom constituting the ether bond is greater than 0.05 [unit: e].

[0053] Where e represents the elementary charge, e = 1.602176634 × 10 -19 [Unit: C].

[0054]

[14] The naphtha for lower olefin production according to any one of [1] to

[13] , wherein the ether is a monoether.

[0055]

[15] The naphtha for producing lower olefins according to any one of [1] to

[14] , wherein one of the two carbon atoms bonded to the oxygen atom constituting the ether bond is a carbon atom of a methyl group.

[0056]

[16] The naphtha for producing lower olefins according to any one of [1] to

[15] , wherein the lower olefin is propylene.

[0057]

[17] A method for producing a lower olefin composition, comprising the step of decomposing the lower olefin producing naphtha according to any one of [1] to

[16] .

[0058]

[18] The method for producing a lower olefin composition according to

[17] , wherein the lower olefin producing naphtha is decomposed to produce a lower olefin composition containing lower olefins and methanol.

[0059]

[19] The method for producing a lower olefin composition according to

[18] , wherein the lower olefin contained in the lower olefin composition includes propylene.

[0060]

[20] A lower olefin composition comprising a lower olefin and / or a derivative thereof which is a decomposition product of the naphtha for lower olefin production described in any one of [1] to

[16] .

[0061]

[21] The lower olefin composition according to

[20] , wherein the lower olefin contained in the lower olefin composition is an unsaturated hydrocarbon having 2 to 4 carbon atoms and containing one or two unsaturated bonds in one molecule.

[0062]

[22] The lower olefin composition according to

[20] or

[21] , further comprising methanol.

[0063]

[23] A polyolefin polymer obtained by polymerizing the lower olefin and / or its derivative contained in the lower olefin composition according to any one of

[20] to

[22] .

[0064]

[24] A method for producing naphtha for producing lower olefins, comprising: mixing naphtha derived from a biomass raw material with naphtha derived from a fossil fuel to obtain the naphtha for producing lower olefins according to any one of [1] to

[16] .

[0065]

[25] A method for determining a naphtha composition for use in the production of lower olefins, which is a method for determining a naphtha composition for use in the production of lower olefins, comprising: mixing naphtha from a biological raw material with naphtha from a fossil fuel to obtain a mixed naphtha; when the mixed naphtha obtained is equivalent to the naphtha for use in the production of lower olefins described in any one of [1] to

[16] , determining that the naphtha composition is qualified as the naphtha composition for use in the production of lower olefins and providing it for thermal decomposition treatment.

[0066] Effects of the Invention

[0067] Since the amount of methanol generated during thermal decomposition is small, the naphtha for producing lower olefins of the present invention can produce a lower olefin composition having a low methanol content at a high olefin yield.

[0068] According to the present invention, in naphtha for producing low olefins, especially containing naphtha from bio-raw materials as raw material naphtha, based on the content of ether-derived oxygen atoms, where the absolute value ΔE (ΔE = |E1-E2|) of the difference between the charge E1 of one carbon atom and the charge E2 of the other carbon atom obtained by density functional method for two carbon atoms bonded to a specific ether in the naphtha for producing low olefins, specifically, to oxygen atoms constituting an ether bond, is 0.05 [unit: e] or more, it is possible to accurately judge whether the naphtha is good as a low olefin raw material, and such naphtha for producing low olefins can be easily achieved.

[0069] Therefore, for example, it is possible to select a naphtha having a low content of ether-derived oxygen atoms of ΔE of 0.05 [unit: e] or more from naphtha that is inexpensive due to its high oxygen-containing compound content, thereby suppressing the methanol production concentration and producing high-purity lower olefins while using inexpensive raw material naphtha. In addition, even naphtha having a high oxygen-containing compound content can be used as a raw material naphtha without blending it with naphtha having a low oxygen-containing compound content, as long as it has a low content of ether-derived oxygen atoms of ΔE of 0.05e [unit: e] or more. BRIEF DESCRIPTION OF THE DRAWINGS

[0070] [ Figure 1 ] Figure 1 This is a graph showing the relationship between ΔE [unit: e] and the methanol formation ratio B of various ethers. DETAILED DESCRIPTION

[0071] The present invention will be described in detail below. The present invention is not limited to the following description, and can be arbitrarily modified and implemented without departing from the gist of the present invention.

[0072] Unless otherwise specified, the numerical range expressed using "to" in the present specification means a range including the numerical values ​​described before and after "to" as the lower limit and the upper limit. "A to B" means A or more and B or less.

[0073] In the present invention, "lower olefin" refers to an unsaturated hydrocarbon having 2 to 4 carbon atoms and containing one or two unsaturated bonds in one molecule. Specifically, lower olefins refer to ethylene, propylene, butene (1-butene, 2-butene, isobutylene) and butadiene (1,2-butadiene and 1,3-butadiene).

[0074] [Naphtha for the production of lower olefins]

[0075] The naphtha for producing lower olefins of the present invention is characterized in that it contains ether and hydrocarbons having 7 or more carbon atoms, the ether having an asymmetric structure with respect to oxygen atoms constituting ether bonds (hereinafter, such ethers may be referred to as "asymmetric ethers"), the content ratio of the hydrocarbons having 7 or more carbon atoms relative to 100% of the total mass of the naphtha for producing lower olefins is 14.0% by mass or more, and the content of the ether is 20,000 ppm by mass or less in terms of ether oxygen atoms.

[0076] Such naphtha for producing lower olefins produces less methanol during thermal decomposition, and thus can produce a lower olefin composition having a low methanol concentration at a high olefin yield. The naphtha for producing lower olefins of the present invention is particularly suitable for producing propylene as a lower olefin.

[0077] Here, the "ether oxygen atom" refers to an oxygen atom participating in an ether bond contained in ether.

[0078] <Hydrocarbons with 7 or more carbon atoms>

[0079] The hydrocarbons having 7 or more carbon atoms contained in the naphtha for producing lower olefins of the present invention are mainly aromatic hydrocarbons such as ethylbenzene and styrene contained in naphtha derived from biomass; aliphatic hydrocarbons such as n-heptane, n-octane, and n-decane; cycloalkanes such as methylcyclohexane and ethylcyclohexane, etc. The upper limit of the carbon number of these hydrocarbons is usually 15 or less.

[0080] The naphtha for producing lower olefins of the present invention may contain only one of these hydrocarbons having 7 or more carbon atoms, or may contain two or more of them.

[0081] In the naphtha for producing lower olefins of the present invention, the content ratio of these hydrocarbons having 7 or more carbon atoms is 14.0 mass % or more relative to 100% of the total mass of the naphtha for producing lower olefins. When the content ratio of the hydrocarbons having 7 or more carbon atoms is 14.0 mass % or more, the effect of specifying the upper limit of the content of the asymmetric ether in the naphtha for producing lower olefins can be effectively obtained, and specifically, a lower olefin composition having a lower methanol content concentration can be produced at a higher olefin yield.

[0082] From this viewpoint, the lower limit of the content of hydrocarbons having 7 or more carbon atoms in the naphtha for producing lower olefins of the present invention is 14.0 mass % or more, preferably 16.0 mass % or more, more preferably 18.0 mass % or more, and further preferably 20.0 mass % or more.

[0083] On the other hand, if the proportion of high carbon atoms in naphtha increases excessively, there is a problem that the yield of lower olefins such as ethylene and propylene decreases. From this viewpoint, the upper limit of the content of hydrocarbons with 7 or more carbon atoms in the naphtha for producing lower olefins of the present invention is preferably 42.0 mass % or less, more preferably 38.0 mass % or less, and further preferably 35.0 mass % or less.

[0084] The above upper and lower limits may be combined arbitrarily. That is, the content ratio of hydrocarbons having 7 or more carbon atoms in the naphtha for producing lower olefins of the present invention is preferably 14.0 mass % to 42.0 mass %, more preferably 16.0 mass % to 38.0 mass %, further preferably 18.0 mass % to 35.0 mass %, particularly preferably 20.0 mass % to 35.0 mass %.

[0085] In the naphtha for producing lower olefins of the present invention, if the content ratio of hydrocarbons having 7 or more carbon atoms is 14.0 mass % or more and the content of asymmetric ethers is 20,000 mass ppm or less in terms of ether oxygen atoms, a lower olefin composition having a low methanol content can be produced with a high olefin yield. The reason for this is not yet clear, but is presumed as follows.

[0086] That is, by including hydrocarbons with a large molecular weight such as hydrocarbons with a carbon number of 7 or more in naphtha, there is a tendency for the partial pressure of the hydrocarbons to decrease. As a result, the side reaction of producing methanol from the asymmetric ether is suppressed. Therefore, it is presumed that the amount of methanol produced during thermal decomposition can be reduced.

[0087] The content ratio of hydrocarbons having 7 or more carbon atoms in the lower olefin producing naphtha can be analyzed by the method described in Example 1 described later.

[0088] The lower limit of the average molecular weight of hydrocarbons in the naphtha for the manufacture of lower olefins of the present invention is not particularly limited. From the viewpoint of manufacturing a lower olefin composition containing low concentration of methanol with a high olefin yield, it is preferably 80.0 g / mol or more, more preferably 81.5 g / mol or more, and further preferably 83.0 g / mol or more. On the other hand, the upper limit of the above-mentioned average molecular weight is not particularly limited. If the proportion of high carbon atoms in naphtha increases excessively, there is a tendency for the yield of lower olefins such as ethylene and propylene to decrease. Therefore, its upper limit is preferably 87.0 g / mol or less, more preferably 86.5 g / mol or less, and further preferably 86.0 g / mol or less.

[0089] The above upper and lower limits may be combined arbitrarily. That is, the average molecular weight of the hydrocarbons in the naphtha for producing lower olefins of the present invention is not particularly limited, but is preferably 80.0 g / mol to 87.0 g / mol, more preferably 81.5 g / mol to 86.5 g / mol, and further preferably 83.0 g / mol to 86.0 g / mol.

[0090] The average molecular weight of hydrocarbons in the lower olefin producing naphtha can be analyzed by the method described in Example 1 described later.

[0091] <Asymmetric ether>

[0092] The content of the asymmetric ether having an asymmetric structure with respect to the oxygen atom constituting the ether bond (hereinafter sometimes referred to as "ether oxygen atom") in the naphtha for producing lower olefins of the present invention is 20,000 mass ppm or less in terms of ether oxygen atom.

[0093] When the content of the asymmetric ether in the lower olefin producing naphtha is 20,000 mass ppm or less in terms of ether oxygen atoms, the content of methanol in the lower olefin composition obtained by thermally decomposing the lower olefin producing naphtha can be reduced for the reasons described below.

[0094] In the present invention, the absolute value ΔE (ΔE = |E1-E2|) of the difference between the charge E1 [unit: e] of one carbon atom and the charge E2 [unit: e] of the other carbon atom, calculated by density functional theory for the two carbon atoms bonded to the asymmetric ether and the ether oxygen atom, is set to 0.05 [unit: e] or more, and the content of the asymmetric ether is set to 20,000 mass ppm or less in terms of ether oxygen atoms. For the reasons described below, the content of methanol in the lower olefins obtained by thermal decomposition of naphtha for the production of lower olefins of the present invention can be more effectively reduced.

[0095] In this specification, "e" refers to the elementary charge, e = 1.602176634 × 10 -19 [Unit: C].

[0096] The values ​​of the charges of the two carbon atoms are calculated by density functional theory (DFT) calculation of the molecular structure of the ether. In the DFT calculation conditions, def-TZVP can be used as the basis set, COSMO solvation model (Conductor like Screening Model) can be used as the solvent effect, and Mulliken's charge density analysis method (Population Analysis) can be used as the analysis method.

[0097] For the calculation of ΔE, the quantum chemical calculation software "TURBOMOLE" (manufactured by TURBOMOLE) and the graphical user interface "TmoleX" for TURBOMOLE (manufactured by TURBOMOLE) can be used.

[0098] Generally, the ether having a large ΔE is an asymmetric ether having an asymmetric structure with respect to the ether oxygen atom. The present inventors have found that asymmetric ethers tend to be easily thermally decomposed under thermal decomposition conditions to generate methanol.

[0099] Furthermore, the present inventors have found that the larger the ΔE of an ether is, the greater the charge deviation between the two carbon atoms bonded to the ether oxygen atom is, and therefore such an ether tends to be easily thermally decomposed under thermal decomposition conditions to produce methanol.

[0100] Furthermore, the present inventors have found that the concentration of methanol in a lower olefin composition obtained by thermally decomposing the naphtha can be reduced by using an asymmetric ether, more preferably an asymmetric ether having a ΔE [unit: e] of 0.05 or more, as the ether and by setting the content of the asymmetric ether contained in the naphtha to 20,000 ppm by mass or less in terms of ether oxygen atoms.

[0101] For example, as asymmetric ethers having an asymmetric structure with respect to the ether oxygen atom, ΔE [unit: e] of 2-methoxybutane (CH3CH2CH(CH3)-O-CH3), methoxycyclopentane (C5H9-O-CH3), and 1-methoxypropane (CH3CH2CH2-O-CH3) are 0.181, 0.151, and 0.084, respectively. The large ΔE means a large deviation in charge. Therefore, specific bonds in the molecule are easily decomposed selectively. As a result, in the thermal decomposition process of naphtha containing these ethers, the above ethers easily generate methanol.

[0102] On the other hand, as ethers having a symmetrical structure with respect to the ether oxygen atom (hereinafter referred to as "symmetrical ethers"), ΔE [unit: e] of dimethyl ether (CH3-O-CH3), diethyl ether (CH3-CH2-O-CH2-CH3), diisopropyl ether ((CH3)2CH-O-CH(CH3)2), and dipropyl ether (CH3-CH2-CH2-O-CH2-CH2-CH3) are 0.004, 0.001, 0.010, and 0.000, respectively. ΔE is small and the deviation of the charge is small. Therefore, it is difficult for a specific bond in the molecule to be selectively decomposed. As a result, in the thermal decomposition process of naphtha containing these symmetrical ethers, the above-mentioned symmetrical ethers are difficult to produce methanol.

[0103] Since the naphtha for producing lower olefins of the present invention has an asymmetric ether content of a predetermined value or less, the content of produced methanol in the lower olefin composition obtained by thermally decomposing the naphtha can be reduced.

[0104] The asymmetric ether is preferably a monoether having only one ether oxygen atom in the molecule, from the viewpoint of being able to effectively reduce the content of produced methanol in the obtained lower olefin composition.

[0105] The asymmetric ether having a ΔE [unit: e] of 0.05 or more has a ΔE value of 0.05 or more for at least one ether bond in the molecule. The ΔE value has a high correlation with the amount of methanol produced. From the perspective of being able to effectively reduce the content of produced methanol in the obtained lower olefin composition, a monoether having only one ether oxygen atom in the molecule is preferred.

[0106] The asymmetric ether, preferably the asymmetric ether having a ΔE of 0.05 or more, is preferably a carbon atom in which one of the two carbon atoms bonded to the ether oxygen atom is a methyl group, such as 2-methoxybutane, methoxycyclopentane, and 1-methoxypropane. Such an asymmetric ether can more effectively reduce the content of the produced methanol in the obtained lower olefin composition.

[0107] When an ether has two or more ether bonds in one molecule, ΔE of each ether bond portion can be calculated as the absolute value of the difference in charge between two carbon atoms bonded to each ether oxygen atom. The ΔE of the ether is the maximum value among the two or more ΔEs.

[0108] In the naphtha for producing lower olefins of the present invention, from the viewpoint of suppressing the amount of methanol produced in the lower olefin composition obtained by thermal decomposition of the naphtha, the upper limit of the content of the asymmetric ether is 20,000 mass ppm or less, preferably 10,000 mass ppm or less, more preferably 1,000 mass ppm or less, further preferably 100 mass ppm or less, particularly preferably 50 mass ppm or less, and most preferably 30 mass ppm or less, in terms of ether oxygen atoms.

[0109] The lower limit of the content of the asymmetric ether contained in the naphtha for producing lower olefins of the present invention is not particularly limited, but from the viewpoint of reducing the production cost of the asymmetric ether and the viewpoint of quantitative accuracy of measurement based on GC and GC / MS, which are general analytical instruments, is usually 0.1 mass ppm or more, preferably 0.3 mass ppm or more, more preferably 1.0 mass ppm or more, further preferably 3.0 mass ppm or more, particularly preferably 7.0 mass ppm or more, and most preferably 12.0 mass ppm or more, in terms of ether oxygen atom.

[0110] The above upper and lower limits may be combined arbitrarily. That is, the content of the asymmetric ether contained in the naphtha for producing lower olefins of the present invention is not particularly limited, but is usually 0.1 mass ppm to 20,000 mass ppm, preferably 0.3 mass ppm to 10,000 mass ppm, more preferably 1.0 mass ppm to 1,000 mass ppm, further preferably 3.0 mass ppm to 100 mass ppm, particularly preferably 7.0 mass ppm to 50 mass ppm, and most preferably 12.0 mass ppm to 30 mass ppm.

[0111] The content of the asymmetric ether in the lower olefin producing naphtha in terms of ether oxygen atom can be determined based on the asymmetric ether contained in the naphtha by measurement using a general analytical instrument such as GC or GC / MS.

[0112] <Sulfur compounds>

[0113] Naphtha generally contains sulfur-containing compounds such as disulfide compounds, sulfide compounds, and mercaptan compounds. In the naphtha for producing lower olefins of the present invention, the upper limit of the content of sulfur-containing compounds is not particularly limited, but from the perspective of being able to produce a lower olefin composition having a low methanol content with a high olefin yield, the content is preferably 180 mass ppm or less, more preferably 150 mass ppm or less, further preferably 100 mass ppm or less, particularly preferably 30 mass ppm or less, and most preferably 10 mass ppm or less in terms of sulfur atom conversion.

[0114] The lower the content of the sulfur-containing compound, the better. The lower limit is not particularly limited, but from the viewpoint of reducing the production cost of the above-mentioned sulfur-containing compound, it is usually preferably 1 mass ppm or more, more preferably 3 mass ppm or more, further preferably 5 mass ppm or more, and particularly preferably 7 mass ppm or more.

[0115] The reason why a lower olefin composition having a low methanol content can be produced at a higher olefin yield as the content of the sulfur-containing compound decreases is not clear, but it is presumed that this is because the sulfur-containing compound promotes side reactions.

[0116] The above upper and lower limits may be combined arbitrarily. That is, the content of sulfur-containing compounds in the naphtha for producing lower olefins of the present invention is not particularly limited, but is preferably 1 mass ppm to 180 mass ppm in terms of sulfur atom, more preferably 3 mass ppm to 150 mass ppm, further preferably 5 mass ppm to 100 mass ppm, particularly preferably 7 mass ppm to 30 mass ppm, and most preferably 7 mass ppm to 10 mass ppm.

[0117] Specific examples of the disulfide compound include dimethyl disulfide, methyl ethyl disulfide, and diethyl disulfide.

[0118] Examples of the sulfide compound include diethyl sulfide and dipropyl sulfide.

[0119] Examples of the thiol compound include thiol compounds having 2 to 10 carbon atoms, such as ethyl mercaptan, propyl mercaptan, and butyl mercaptan.

[0120] The naphtha for lower olefin production may contain only one of these sulfur-containing compounds, or may contain two or more of them.

[0121] <Specific Gravity>

[0122] The specific gravity of the naphtha for producing low olefins of the present invention is not particularly limited. It is known that there is a correlation between the density of naphtha and the composition of naphtha. From the perspective of being able to produce a low methanol concentration low olefin composition with a high olefin yield, the lower limit of the specific gravity is preferably 0.6640 g / cm 3 More preferably 0.6650 g / cm 3 above.

[0123] From the viewpoint of being able to maintain a good yield of lower olefins such as ethylene and propylene, the upper limit of the specific gravity is preferably 0.6695 g / cm 3 Below, more preferably 0.6680 g / cm 3 the following.

[0124] The above upper and lower limits may be combined arbitrarily. That is, the specific gravity of the naphtha for producing lower olefins of the present invention is not particularly limited, but is preferably 0.6640 g / cm 3 Above 0.6695g / cm 3 Below, more preferably 0.6650 g / cm 3 Above 0.6680g / cm 3 the following.

[0125] The reason why a lower olefin composition having a low methanol concentration can be produced at a higher olefin yield when the specific gravity of the naphtha for producing lower olefins is within the above numerical range is not yet clear, but it is presumed that this is because the higher the density of the naphtha, the more the number of carbon atoms of the hydrocarbons contained in the naphtha tends to increase, and as a result, the naphtha is efficiently decomposed into olefins.

[0126] The specific gravity of naphtha can be measured according to JIS K2249-1:2011.

[0127] <Raw material naphtha>

[0128] The naphtha for producing lower olefins of the present invention preferably contains naphtha derived from a bio-raw material, from the viewpoint of being able to suppress the production of methanol generated from the asymmetric ether contained as an impurity and to obtain a high yield of lower olefins.

[0129] From the viewpoint of being able to suppress the production of methanol generated from asymmetric ethers contained as impurities and to obtain a high yield of lower olefins, the naphtha for producing lower olefins of the present invention is preferably naphtha derived from a bio-raw material alone, or a naphtha mixture containing naphtha derived from a bio-raw material and naphtha derived from a fossil fuel.

[0130] Herein, naphtha from biomass refers to naphtha from non-edible biomass and / or non-fossil fuels.

[0131] In the present invention, non-edible biomass refers to resources made from non-edible grasses and trees. Specifically, examples include cellulose, hemicellulose, lignin, etc. obtained from woody biomass such as conifers and broad-leaved trees; bioethanol and biodiesel obtained from herbaceous biomass such as corn, sugarcane stems, soybeans, and rapeseed; and waste oils from plants, but are not limited to these.

[0132] In the present invention, non-fossil fuel refers to, for example, hydrogen, or organic matter from animals and plants that is not derived from fossil fuels or inedible biomass. Specifically, methane, sugar ethanol, etc. obtained from firewood, charcoal, dried livestock manure, etc. can be cited. However, it is not limited to these.

[0133] In the present invention, naphtha derived from fossil fuels refers to at least one selected from the group consisting of naphtha derived from petroleum, naphtha derived from coal, and naphtha derived from natural gas.

[0134] <Method for producing naphtha for producing lower olefins>

[0135] The method for producing the naphtha for producing lower olefins of the present invention is not particularly limited. As a specific embodiment, there can be mentioned a method of mixing naphtha derived from a biomass raw material and naphtha derived from a fossil fuel.

[0136] More specifically, the following method can be cited: naphtha derived from a bio-raw material is mixed with naphtha derived from a fossil fuel to obtain a mixed naphtha, and the mixed naphtha is used to produce the naphtha for producing lower olefins of the present invention, that is, the mixed naphtha contains an asymmetric ether having an asymmetric structure with respect to an oxygen atom constituting an ether bond as an ether, and the content of the asymmetric ether, the content ratio of hydrocarbons having 7 or more carbon atoms, and more preferably the specific gravity of the naphtha and the content of sulfur-containing compounds are within the above-mentioned preferred ranges.

[0137] In this case, as a method for adjusting the content of the asymmetric ether to the above-mentioned preferred range, the following method can be mentioned.

[0138] (1) Purchase or obtain naphtha derived from fossil fuels or naphtha derived from biomass raw materials, the naphtha having an asymmetric ether content of 20,000 ppm by mass or less in terms of ether oxygen atoms.

[0139] (2) When the purchased or obtained naphtha has a high asymmetric ether content, the asymmetric ether content may be reduced by mixing the purchased or obtained naphtha with a low asymmetric ether content.

[0140] In order to adjust the content of hydrocarbons having 7 or more carbon atoms to the above-mentioned preferred range, naphtha derived from fossil fuels may be appropriately mixed with naphtha derived from biomass raw materials.

[0141] In order to adjust the specific gravity of the naphtha for lower olefin production to the above preferred range, naphtha derived from fossil fuels may be appropriately mixed with naphtha derived from biomass raw materials.

[0142] In order to adjust the content of the sulfur-containing compound to the above preferred range, naphtha derived from fossil fuels may be appropriately mixed with naphtha derived from biomass raw materials.

[0143] [Determination method of naphtha for lower olefin production]

[0144] A method for determining naphtha for producing low-olefins as one embodiment of the present invention is the following method for determining naphtha, which comprises: when producing the naphtha for producing low-olefins of the present invention, mixing naphtha from biological raw materials with naphtha from fossil fuels to obtain a mixed naphtha, and then, when the obtained mixed naphtha is equivalent to the naphtha for producing low-olefins of the present invention, determining that the mixed naphtha is qualified as a naphtha composition used in the production of low-olefins and providing it for thermal decomposition treatment.

[0145] More specifically, the method for determining naphtha comprises: the mixed naphtha contains an asymmetric ether having an asymmetric structure with respect to oxygen atoms constituting ether bonds as an ether, and when the content of the asymmetric ether, the content ratio of hydrocarbons having 7 or more carbon atoms, and more preferably the specific gravity of the naphtha and the content of sulfur-containing compounds are within the above-mentioned preferred ranges, the mixed naphtha is determined to be qualified as a naphtha composition used in the production of lower olefins and is subjected to thermal decomposition treatment.

[0146] [Method for producing lower olefin composition]

[0147] The method for producing a lower olefin composition of the present invention comprises the step of decomposing the lower olefin producing naphtha of the present invention.

[0148] By thermally decomposing naphtha for lower olefin production, a lower olefin composition containing lower olefins and methanol can be produced.

[0149] In the method for producing a lower olefin composition, by using the lower olefin producing naphtha of the present invention as the lower olefin producing naphtha to be subjected to thermal decomposition, the amount of methanol produced can be significantly reduced as described above.

[0150] The method for producing a lower olefin composition of the present invention can produce a lower olefin composition by a conventional method except for using the naphtha for producing lower olefins of the present invention.

[0151] That is, the lower olefin composition is obtained by thermally decomposing (steam cracking) the naphtha for producing lower olefins of the present invention (hereinafter sometimes simply referred to as "naphtha") at a temperature of 700 to 1000° C. in the presence of water vapor.

[0152] In the conditions of thermal decomposition, regarding the ratio of naphtha to water vapor, the water vapor is preferably 20 to 100 parts by mass, more preferably 30 to 70 parts by mass, and particularly preferably 35 to 60 parts by mass relative to 100 parts by mass of naphtha. When the amount of water vapor is less than 20 parts by mass, there is a tendency for the carbonaceous material to deposit more on the pipes for decomposition reaction provided in the thermal decomposition furnace. On the other hand, when the amount of water vapor is greater than 100 parts by mass, the heat applied to the water vapor increases, and the energy load applied to the device becomes too large.

[0153] The reaction temperature of the thermal decomposition is usually 700 to 1000° C., preferably 750 to 950° C. When the reaction temperature is lower than 700° C., the thermal decomposition of naphtha cannot be fully carried out, and the yield of the target lower olefins is reduced. When the reaction temperature is higher than 1000° C., the thermal decomposition of naphtha becomes excessive, the generation of undesirable by-products such as methane increases, and there is a tendency for the yield of the target lower olefins to decrease.

[0154] The reaction time of the thermal decomposition is preferably 0.01 to 1 second, more preferably 0.04 to 0.7 seconds. When the reaction time is less than 0.01 seconds, the thermal decomposition of naphtha cannot be fully carried out, and there is a tendency for the yield of the target lower olefins to decrease. When the reaction time is greater than 1 second, the thermal decomposition of naphtha becomes excessive, the generation of undesirable by-products such as methane increases, and there is a tendency for the yield of the target lower olefins to decrease.

[0155] The reaction pressure of the thermal decomposition is preferably 0.01 to 1.5 MPa (gauge pressure), more preferably 0.05 to 0.5 MPa (gauge pressure), and further preferably 0.07 to 0.2 MPa (gauge pressure).

[0156] By quenching the reaction product from the reaction zone of the thermal decomposition, the progress of excessive decomposition can be suppressed. The cooling temperature is not particularly limited, and for example, when implemented on an industrial scale, it is preferably 200 to 700° C., and more preferably 250 to 650° C. When implemented on a small scale such as a pilot plant or a laboratory, it is preferably 0 to 100° C., and more preferably 3 to 40° C.

[0157] The reaction product containing lower olefins thus obtained can be subjected to purification, classification, and other treatments according to conventional methods. Thus, lower olefins such as ethylene, propylene, butene, butadiene, and the like, aromatic hydrocarbons, and other hydrocarbons can be obtained.

[0158] Saturated hydrocarbons such as ethane and propane can be recovered and supplied to thermal decomposition again.

[0159] Butene and butadiene among the lower olefins are usually obtained as a mixture with butane. Therefore, butadiene is separated by solvent extraction in another process. The mixture of butene and butane as the extraction residue is preferably utilized and classified by polymerization, distillation, etc. in another process.

[0160] In the method for producing a lower olefin composition of the present invention, it is preferred that the above ΔE [unit: e] and the methanol formation ratio B in the obtained lower olefins satisfy the following formulas (1) and (2). Thus, by thermal decomposition of the naphtha for producing lower olefins of the present invention, a lower olefin composition having a further reduced methanol content can be obtained.

[0161] 0.05≤ΔE Formula (1)

[0162] B≤1.25×ΔE+0.10 Formula (2)

[0163] As described above, methanol has an adverse effect on the polymerization catalyst when polymerizing lower olefins. The content of methanol in the lower olefins obtained by thermally decomposing naphtha under the conditions satisfying the above formulas (1) and (2) is reduced. Therefore, it is effective in the case of producing lower olefins such as propylene.

[0164] The above formula (2) more preferably satisfies the condition of B≤1.25×ΔE+0.05.

[0165] The methanol formation ratio B is an index showing the production ratio of methanol generated when naphtha is thermally decomposed, and refers to the ratio of "the number of oxygen atoms in methanol contained in condensed water" to "the number of oxygen atoms in ether contained in naphtha".

[0166] The specific method for measuring the methanol formation ratio B is described in Example 1 described later.

[0167] According to the method for producing a lower olefin composition using the naphtha for producing lower olefins of the present invention, it is possible to produce a lower olefin composition containing lower olefins and in which the formation of methanol is suppressed, that is, a lower methanol content.

[0168] By using the method for producing a lower olefin composition of the present invention, a propylene composition containing propylene and methanol can be produced.

[0169] More specifically, by using the method for producing a lower olefin composition of the present invention, it is possible to produce a propylene composition containing propylene and in which the production of methanol is suppressed, that is, a propylene composition having a low methanol content.

[0170] As described above, methanol has an adverse effect on the polymerization catalyst when polymerizing lower olefins or propylene. Therefore, the method for producing a lower olefin composition of the present invention is effective when producing lower olefins such as propylene.

[0171] <Lower Olefin Composition>

[0172] The lower olefin composition of the present invention is a composition containing the decomposition product of the naphtha for producing lower olefins of the present invention, that is, lower olefins and / or their derivatives.

[0173] The above-mentioned "lower olefin" refers to an unsaturated hydrocarbon having 2 to 4 carbon atoms and containing one or two unsaturated bonds in one molecule. Specifically, ethylene, propylene, butene (1-butene, 2-butene, isobutylene) and butadiene (1,2-butadiene and 1,3-butadiene) can be mentioned. Among them, at least one selected from the group consisting of ethylene, propylene, 1-butene and 2-butene is preferred.

[0174] The above-mentioned "derivatives thereof", i.e., "derivatives of lower olefins" may be compounds generated when the naphtha for producing lower olefins of the present invention is decomposed, or may be compounds obtained using lower olefins which are decomposition products of the naphtha for producing lower olefins of the present invention.

[0175] The above-mentioned "lower olefin derivatives" are not particularly limited, and examples thereof include the following ethylene derivatives, propylene derivatives, and butene derivatives.

[0176] a) Ethylene derivatives:

[0177] Ethylene oxide, ethylene glycol, ethanolamine, glycol ether, etc. produced by the oxidation reaction of ethylene,

[0178] Vinyl chloride monomer, 1,1,1-trichloroethane, vinylidene chloride, polyvinyl chloride, etc. produced by chlorination of ethylene,

[0179] α-olefins obtained by polymerization of ethylene, and higher alcohols obtained by subjecting the α-olefins as raw materials to carbonylation reaction and subsequent hydrogenation reaction, etc.,

[0180] Low-density or high-density polyethylene obtained by polymerization of ethylene,

[0181] Vinyl acetate obtained by the reaction of ethylene and acetic acid, etc.

[0182] Acetaldehyde obtained by Wacker reaction of ethylene and ethyl acetate as its derivative, etc.

[0183] b) Propylene derivatives:

[0184] Acrylonitrile obtained by ammoxidation of propylene, etc.

[0185] Acrolein, acrylic acid, and acrylic esters obtained by selective oxidation of propylene,

[0186] Oxo alcohols such as n-butyraldehyde and 2-ethylhexanol obtained by carbonylation of propylene,

[0187] Polypropylene obtained by polymerization of propylene, etc.

[0188] Propylene oxide and propylene glycol produced by selective oxidation of propylene, isopropanol produced by hydration of propylene, etc.

[0189] Acetone obtained by Wacker reaction of propylene, methyl isobutyl ketone and acetone cyanohydrin obtained from acetone, methyl methacrylate obtained from acetone cyanohydrin, and the like.

[0190] c) Butene derivatives:

[0191] Butadiene obtained by oxidative dehydrogenation of butene,

[0192] 1,4-Butanediol obtained by acetoxylation, hydrogenation and hydrolysis of butadiene, γ-butyrolactone obtained as a raw material, pyrrolidones such as N-methylpyrrolidone, etc.,

[0193] Tetrahydrofuran, polytetramethylene glycol, etc. obtained by dehydration reaction of pyrrolidones,

[0194] Various synthetic rubbers obtained using butadiene.

[0195] By using the naphtha for producing lower olefins of the present invention, it is possible to produce a lower olefin composition containing lower olefins and in which the production of methanol is suppressed, that is, a lower methanol content.

[0196] In the lower olefin composition of the present invention, the ether contained in the naphtha for lower olefin production is an asymmetric ether having an asymmetric structure with respect to the ether oxygen atom.

[0197] In the lower olefin composition of the present invention, the ether contained in the naphtha for lower olefin production is preferably a monoether having only one ether oxygen atom in the molecule, from the viewpoint of being able to more effectively reduce the content of produced methanol in the obtained lower olefins.

[0198] In the low olefin composition of the present invention, from the perspective of being able to more effectively reduce the content of produced methanol in the obtained low olefins, the above-mentioned ether contained in the above-mentioned naphtha for producing low olefins is preferably an ether in which one of the two carbon atoms bonded to the ether oxygen atom is a methyl group, such as 2-methoxybutane, methoxycyclopentane, and 1-methoxypropane.

[0199] When the ether is an ether in which one of the two carbon atoms bonded to the ether oxygen atom is a methyl group, the lower olefin composition of the present invention contains methanol.

[0200] The content ratio of the lower olefins in the lower olefin composition is not particularly limited, but is preferably 70% by mass or more, more preferably 80% by mass or more, further preferably 90% by mass or more, particularly preferably 95% by mass or more, and particularly preferably 98% by mass or more, relative to 100% of the total mass of the lower olefin composition. The content ratio of the lower olefins in the lower olefin composition may be 100% by mass.

[0201] The content of methanol in the above-mentioned lower olefin composition is not particularly limited, but is preferably 10,000 mass ppm or less, more preferably 1,000 mass ppm or less, further preferably 100 mass ppm or less, particularly preferably 10 mass ppm or less, particularly preferably 5 mass ppm or less, and most preferably 1 mass ppm or less, relative to the total mass of the above-mentioned lower olefin composition.

[0202] The content of methanol in the lower olefins can be measured by gas chromatography.

[0203] Such a lower olefin composition can be obtained by cracking the naphtha for lower olefin production of the present invention.

[0204] <Polyolefin polymer>

[0205] The polyolefin polymer of the present invention is a polyolefin polymer obtained by polymerizing the lower olefin and / or its derivative contained in the lower olefin composition of the present invention using a known polymerization method. The polyolefin polymer of the present invention comprises repeating units derived from olefins (hereinafter referred to as "lower olefin units") or repeating units derived from their derivatives (hereinafter referred to as "lower olefin derivative units").

[0206] The polyolefin polymer of the present invention may be a polymer consisting only of lower olefin units, a polymer consisting of lower olefin units and lower olefin derivative units, or a polymer consisting only of lower olefin derivative units.

[0207] The above-mentioned "repeating unit" refers to a unit directly formed by the polymerization reaction of a lower olefin and / or its derivative, and may be a unit in which a part of the unit is converted into another structure by treating the polymer.

[0208] The polyolefin polymer of the present invention may be a polymer obtained by polymerizing a product obtained by removing methanol contained in the lower olefin composition of the present invention by a known methanol separation method such as distillation.

[0209] Alternatively, the polyolefin polymer of the present invention may also be a polyolefin polymer directly polymerized from the lower olefin composition of the present invention. In this case, for the above reasons, the methanol content in the above lower olefin composition is low, so the performance of the catalyst used in polymerizing the lower olefin is not substantially impaired by methanol, and the obtained polyolefin polymer is excellent in quality from the viewpoints of molecular weight distribution, impurities, etc.

[0210] Examples

[0211] Hereinafter, experimental examples and comparative experimental examples instead of the examples are listed to more specifically illustrate the present invention. They are only for illustration and do not impose any limitation on the present invention.

[0212] The names of the compounds used in the experimental examples and comparative experimental examples are as follows.

[0213] 2-Methoxybutane (manufactured by Tokyo Chemical Industry Co., Ltd.)

[0214] Methoxycyclopentane (manufactured by Tokyo Chemical Industry Co., Ltd.)

[0215] 1-Methoxypropane (manufactured by Tokyo Chemical Industry Co., Ltd.)

[0216] Dimethyl ether (manufactured by Koike Chemical Co., Ltd.)

[0217] Diethyl ether (manufactured by Tokyo Chemical Industry Co., Ltd.)

[0218] Diisopropyl ether (manufactured by Tokyo Chemical Industry Co., Ltd.)

[0219] Dipropyl ether (manufactured by Tokyo Chemical Industry Co., Ltd.)

[0220] <Evaluation method>

[0221] (1) Determination of the content ratio of hydrocarbons having 7 or more carbon atoms in naphtha

[0222] The content ratio of hydrocarbons having 7 or more carbon atoms in naphtha is measured using a gas chromatography measuring device (GC device) under the following conditions.

[0223] <GC measurement conditions>

[0224] GC device: GC-2010Plus (device name, manufactured by Shimadzu Corporation)

[0225] Detector: Flame ionization detector (FID)

[0226] Carrier gas: Nitrogen (flow rate 0.8 ml / minute)

[0227] Column: Capillary column CBP1-M50-025 (manufactured by Shimadzu Corporation, size: Film thickness: 0.25 μm)

[0228] Column temperature: 0°C (holding time 5 minutes) → heating at 3°C / min → 200°C (no holding time) → heating at 10°C / min → 250°C (holding time 10 minutes)

[0229] Inlet temperature: 250℃

[0230] Detector temperature: 250°C

[0231] Sample volume: 0.5 μL (split ratio: 1 / 60)

[0232] Quantitative method: Absolute calibration curve method

[0233] As a sample for GC measurement, naphtha was used directly without any pretreatment.

[0234] A calibration curve for calculating the hydrocarbon content ratio from the peak area of ​​a gas chromatogram is prepared as follows: For each component of hydrocarbons having 1 to 15 carbon atoms identified by the gas chromatogram, compounds previously separated and purified from naphtha, commercially available compounds, and pre-synthesized compounds are accurately weighed, diluted, and used in a standard solution to prepare the curve.

[0235] As an example of a gas chromatogram of naphtha, the retention time (minutes), type, and carbon number of each hydrocarbon component contained in the naphtha identified by the gas chromatogram of a mixture of petroleum-derived naphtha and bio-raw material-derived naphtha used in Experiment C-1 are shown in Table A.

[0236] As shown in Table A, all hydrocarbon components were observed between retention times of 3.570 and 39.021 minutes, and the carbon number of the hydrocarbons was in the range of 3 to 10.

[0237] Here, the naphtha mixture of Experimental Example C-1 is used as an example, and the results shown in Table A are obtained. However, the types and carbon numbers of the hydrocarbon components contained in the naphtha vary depending on the source, production area, or production conditions of the naphtha.

[0238] [Table A]

[0239]

[0240] The content ratio of hydrocarbons having 7 or more carbon atoms in naphtha was calculated according to the following procedure.

[0241] First, in the gas chromatogram obtained using the above-mentioned GC measurement conditions, the peak area of ​​each component of hydrocarbons having a carbon number of 1 to 15 is read based on the peaks observed between retention times of 1 minute and 100 minutes, and the content ratio of each of the above-mentioned components (unit: mass %) is calculated by the absolute calibration curve method.

[0242] Next, the total value of the content ratio of each component of hydrocarbons with carbon atoms of 1 to 15 is set to B1, and the total value of the content ratio of each component of hydrocarbons with carbon atoms of 7 to 15 is set to A1, and the content ratio of hydrocarbons with carbon atoms of 7 or more in naphtha is calculated by the following formula.

[0243] Content ratio of hydrocarbons with carbon number of 7 or more (mass %) = A1 / B1×100

[0244] A1: Total value of the content ratio of each component of hydrocarbons having 7 to 15 carbon atoms (mass %)

[0245] B1: Total value of the content ratio of each component of hydrocarbons having 1 to 15 carbon atoms (mass %)

[0246] (2) Calculation of the average molecular weight of hydrocarbons in naphtha

[0247] The average molecular weight of hydrocarbons in naphtha is calculated by the following formula using B1 calculated by the measurement method of "(1) Content ratio of hydrocarbons having 7 or more carbon atoms in naphtha" and the content ratio Sn and relative molecular mass Mn of each component of hydrocarbons having 1 to 15 carbon atoms.

[0248] Average molecular weight of hydrocarbons in naphtha = (S1×M1+S2×M2+····S15×M15) / B1

[0249] Sn (n is an integer of 1 to 15): content ratio of hydrocarbons having n carbon atoms (mass %)

[0250] Mn (n is an integer from 1 to 15): relative molecular mass of the hydrocarbon with n carbon atoms

[0251] B1: Total value of the content ratio of each component of hydrocarbons having 1 to 15 carbon atoms (mass %)

[0252] Relative molecular mass is the ratio of the mass of one molecule of a substance to the unified atomic mass unit, and refers to the sum of the atomic weights contained in the molecule.

[0253] Hydrocarbons with a certain number of carbon atoms may also be composed of multiple hydrocarbon components with different relative molecular masses. For example, hydrocarbons with 5 carbon atoms are composed of six hydrocarbons: isopentane, 2-methyl-1-butene, n-pentane, 2-pentene, 2-methyl-2-butene, and cyclopentane.

[0254] (3) Analysis of the content of sulfur compounds in naphtha

[0255] As the sulfur content of the sulfur-containing compounds in the naphtha, the content of the sulfur-containing compounds converted to sulfur atoms (sulfur atom-converted content) was measured using inductively coupled plasma optical emission spectrometry (ICP-OES).

[0256] First, a sample for ICP-OES measurement was prepared according to the following procedure.

[0257] In a Teflon container, 1 ml of the above naphtha was mixed with 8 ml of nitric acid, and then subjected to thermal decomposition treatment using a microwave decomposition device (device name: MultiwavePRO, manufactured by Anton Paar) under the following conditions. The mixture was then made up to 25 ml with ultrapure water and used as a sample for ICP-OES measurement.

[0258] Microwave decomposition conditions: Ramp (500W / 10 minutes) → Hold (500W / 10 minutes) → Ramp (1300W / 10 minutes) → Hold (1300W / 30 minutes)

[0259] The sulfur atom content (unit: mass ppm) in the naphtha was measured for the measurement sample using ICP-OES (apparatus name: iCAP6500, manufactured by Thermo Fischer, wavelength: S=180.731 nm) and the result was taken as the content of sulfur-containing compounds in terms of sulfur atoms.

[0260] The calibration curve was prepared by an absolute calibration curve method using Sulfur Standard for ICP (product name, manufactured by Aldrich).

[0261] (4) Calculation method of ΔE

[0262] For the ethers used in the experimental examples and comparative experimental examples, the absolute value ΔE [unit: e] of the difference in charge between two carbon atoms bonded to the ether oxygen atom in the ether was calculated according to the following procedure.

[0263] Density functional theory (DFT) calculations were performed on the molecular structure of the above ether to calculate the charge values ​​of the above two carbon atoms. In the DFT calculation conditions, def-TZVP was used as the basis set, and the COSMO solvation model (Conductor like Screening Model) was used as the solvent effect. The analysis method used Mulliken's charge density analysis (Population Analysis).

[0264] Next, for the two carbon atoms bonded to the oxygen atom of the ether bond in the ether, the absolute value ΔE (ΔE=|E1-E2|) (unit: e) of the difference between the charge E1 of one carbon atom and the charge E2 of the other carbon atom is calculated.

[0265] "e" represents the elementary charge, e = 1.602176634 × 10 -19[Unit: °C]. For example, when ΔE is 0.05 [unit: eV], if it is expressed in SI unit system, then ΔE = 0.05 × 1.602176634 × 10 -19 [Unit: °C].

[0266] In the calculation of the above ΔE, the quantum chemistry calculation software “TURBOMOLE ver7.2” (manufactured by TURBOMOLE GmbH) and the graphical user interface for TURBOMOLE “TmoleX ver4.4.1” (manufactured by TURBOMOLE GmbH) are used.

[0267] (5) Calculation of methanol production ratio B

[0268] The methanol produced by the thermal decomposition of naphtha is substantially contained in the condensed water obtained in the experimental examples and comparative experimental examples and not contained in the gas components and oil components. Therefore, using a gas chromatography-mass spectrometry measurement device (GC / MS device) (device name: GCMS-QP2010 Ultra, manufactured by Shimadzu Corporation), the methanol production ratio B of the condensed water obtained in the experimental examples and comparative experimental examples is measured under the following conditions.

[0269] It was confirmed in advance that methanol is not produced from the blank naphtha used in the experimental examples and comparative experimental examples.

[0270] <GC / MS measurement conditions>

[0271] Carrier gas: helium, linear velocity 40 cm / sec

[0272] Column: SUPELCOWAX-10 (manufactured by Supelco, inner diameter 0.32 mm × length 60 m × film thickness 0.25 μm)

[0273] Temperature (temperature rising condition): 50 °C (holding time 5 minutes) → rising temperature at 20 °C / minute → 200 °C (holding time 2.5 minutes)

[0274] Inlet temperature: 200 °C

[0275] MS interface temperature: 200 °C

[0276] Ion source temperature: 200 °C

[0277] Sample volume: 0.5 μL

[0278] Split ratio: 1:5

[0279] Measurement mode: SIM (m / z = 31)

[0280] The amount of methanol generated as a thermal decomposition product was quantitatively determined from the condensed water obtained in the experimental examples and the comparative experimental examples, and the methanol generation ratio B relative to the added ether was determined from the following formula based on a calibration curve prepared in advance using a standard solution of methanol of known concentration.

[0281] [Methanol generation ratio B] = [Number of oxygen atoms in methanol in condensed water] ÷ [Number of oxygen atoms in ether added to blank naphtha]

[0282] That is, when the methanol generation ratio B is 1.00, it means that all the added ether is quantitatively converted into methanol.

[0283] The number of oxygen atoms contained in the ether added here is 1 oxygen atom per 1 molecule of the ether compound.

[0284] (6) Determination of lower olefin yield

[0285] The lower olefin yield when the raw material naphtha was thermally decomposed was measured by the following method using a naphtha flow evaluation device equipped with a SUS310S reaction tube.

[0286] As described above, the "lower olefins" refer to ethylene, propylene, butenes (1-butene, 2-butene and isobutylene), butadiene (1,2-butadiene and 1,3-butadiene).

[0287] From the lower part of the reaction tube, naphtha and steam of the experimental examples and comparative experimental examples described later were supplied to the reaction tube (4 mm inner diameter×6 mm outer diameter), and the naphtha was thermally decomposed under the conditions of a reaction temperature of 810°C, a reaction pressure of 0.1 MPaG, a residence time of 0.6 seconds, and a steam / naphtha mass ratio (S / O ratio) of 0.4, and the product was extracted from the upper part of the reaction tube. The obtained thermal decomposition product was quenched at 5°C, and gas-liquid separation was performed using a gas-liquid separator under the conditions of 0.1 MPaG and 5°C to obtain a separated gas and a separated liquid.

[0288] For the obtained separated gas, a separate gas chromatography measuring apparatus is used to quantify hydrogen, carbon monoxide and carbon dioxide which are thermal decomposition products of naphtha, and methane, ethane, ethylene, propane, propylene, propadiene, isobutane, n-butane, propadiene, 1-butene, 2-butene, isobutene, 1,2-butadiene, 1,3-butadiene, methylacetylene, isopentane, n-pentane, 1-pentene, 2-pentene, cyclopentane, 2-methyl-1-butene, 2-methyl-2-butene, cyclopentene, isoprene, pentadiene, cyclopentadiene, benzene, toluene, xylene, n-hexane, ethylbenzene, styrene, n-heptane and n-octane (hereinafter referred to as "hydrocarbons") which are hydrocarbons.

[0289] Specifically, a gas chromatograph (model: GC-8A, manufactured by Shimadzu Corporation) was used for the quantitative determination of hydrogen.

[0290] A gas chromatograph (model: GC-2014, manufactured by Shimadzu Corporation) was used for the quantitative determination of carbon monoxide, carbon dioxide, and the above-mentioned hydrocarbons.

[0291] The quantitative values ​​of hydrogen, carbon monoxide, carbon dioxide, hydrocarbons and lower olefins thus measured are denoted as X (hydrogen), X (carbon monoxide), X (carbon dioxide), X (hydrocarbons) and X (lower olefins) (unit: g), respectively.

[0292] For the separated liquid separated in the form of oil by oil-water separation, a gas chromatography measuring apparatus (model: GC-2014, manufactured by Shimadzu Corporation) is used to quantify the lower olefins contained in the separated liquid on the oil side as thermal decomposition products of naphtha, and the quantitative value is set to Y (lower olefins) (unit: g).

[0293] The above hydrocarbons and hydrocarbons having a boiling point of 150° C. or higher and 280° C. or lower were quantitatively determined, and their quantitative values ​​were combined as Y (hydrocarbon compounds) (unit: g).

[0294] The lower olefin yield (unit: mass %) was calculated by the following formula using X (hydrogen), X (carbon monoxide), X (carbon dioxide), X (lower olefins), X (hydrocarbons), Y (lower olefins) and Y (hydrocarbon compounds) measured by the above method between 60 and 420 minutes after the start of thermal decomposition of naphtha.

[0295] Lower olefin yield (unit: weight %) = (X (lower olefin) + Y (lower olefin)) / (X (hydrogen) + X (carbon monoxide), X (carbon dioxide) + X (hydrocarbons) + Y (hydrocarbon compounds)) × 100

[0296] [Comparative Experimental Example A-1-1]

[0297] The content of hydrocarbons with 7 or more carbon atoms is 13.1% by mass, the average molecular weight of hydrocarbons is 79.2 g / mol, and the specific gravity is 0.6636 g / cm 3 , the content of sulfur-containing compounds (sulfur atom conversion): 190 mass ppm), 2-methoxybutane was added in such a way that the content of oxygen atoms from ether was 50 mass ppm, and then thermal decomposition was carried out in the presence of water vapor using a thermal decomposition furnace under the following thermal decomposition conditions. The obtained thermal decomposition product was quenched at 5°C, and gas-liquid separation was carried out using a gas-liquid separator at 0.1 MPa (gauge pressure) and 5°C to obtain a gas component and a separated liquid.

[0298] Furthermore, the separated liquid was separated into oil and condensed water using a separatory funnel under atmospheric pressure and room temperature.

[0299] <Thermal Decomposition Conditions>

[0300] Naphtha flow rate: 83.1g / hr

[0301] Steam / naphtha mass ratio: 0.4

[0302] Retention time: 0.6 seconds

[0303] Thermal decomposition temperature: 810℃

[0304] Thermal decomposition pressure: 0.1MPa (gauge pressure)

[0305] The methanol generation ratio B of the condensed water was measured by the above method and is shown in Table 1 together with the value of ΔE. In addition, the relationship between ΔE and the methanol generation ratio B is shown in Table 1. Figure 1 .

[0306] [Comparative Experimental Examples A-1-2 to A-1-3]

[0307] The evaluation was performed under the same conditions as in Comparative Experimental Example A-1-1 except that the content in terms of ether oxygen atoms was changed as described in Table 1. The evaluation results are shown in Table 1.

[0308] [Comparative Experimental Example A-0]

[0309] The evaluation results are shown in Table 1.

[0310] [Comparative Experimental Examples A-2 to A-7]

[0311] Evaluation was performed under the same conditions as in Comparative Experimental Example A-1 except that the type of ether and the content of the ether oxygen atom conversion of the ether were changed as described in Table 1. The evaluation results are shown in Table 1.

[0312] Comparative Experimental Example A-1 is Comparative Experimental Example A-1-1 to Comparative Experimental Example A-1-3 described in Table 1.

[0313] Comparative Experimental Example A-2 is Comparative Experimental Example A-2-1 to Comparative Experimental Example A-2-3 described in Table 1.

[0314] Comparative Experimental Example A-3 is Comparative Experimental Example A-3-1 to Comparative Experimental Example A-3-3 described in Table 1.

[0315] In the following Tables 1 to 3, the content of the added ether in terms of ether oxygen atoms is described as "oxygen atom concentration".

[0316] [Table 1]

[0317]

[0318] [Experimental Examples B-1 to B-3, Comparative Experimental Examples B-4 and B-7]

[0319] In place of the petroleum naphtha in Comparative Experiment A-1, a biomass-derived naphtha (manufactured by AltAir Paramount, with a content of hydrocarbons with a carbon number of 7 or more: 43.9% by mass, an average molecular weight of hydrocarbons: 88.3 g / mol, and a specific gravity: 0.6700 g / cm 3 , the content of sulfur-containing compounds (sulfur atom conversion): 1 mass ppm), and the type of ether and the content of ether oxygen atom conversion derived from the ether were changed as described in Table 2. The evaluation was carried out under the same conditions as Comparative Experimental Example A-1. The evaluation results are shown in Table 2.

[0320] Experimental Example B-2 is Experimental Example B-2-1 to Experimental Example B-2-3 described in Table 1.

[0321] [Experimental Example B-0]

[0322] The evaluation results are shown in Table 2.

[0323] [Table 2]

[0324]

[0325] [Experimental Example C-1]

[0326] Instead of the petroleum-derived naphtha in Comparative Experiment A-1, a mixture of the petroleum-derived naphtha and the above-mentioned biomass-derived naphtha (mass ratio 1:1) (content ratio of hydrocarbons with a carbon number of 7 or more: 30.6% by mass, average molecular weight of hydrocarbons: 84.14 g / mol, specific gravity: 0.6667 g / cm 3 , the content of sulfur-containing compounds (sulfur atom conversion): 100 mass ppm), and the type of ether and the content of ether oxygen atom conversion derived from the ether were changed as described in Table 3. The evaluation was carried out under the same conditions as Comparative Experimental Example A-1. The evaluation results are shown in Table 3.

[0327] [Experimental Example C-0]

[0328] The evaluation results are shown in Table 3.

[0329] [Table 3]

[0330]

[0331] exist Figure 1 , Experimental Examples B-1, B-2-1, B-3, and Experimental Example C-1, and Comparative Experimental Examples A-1-1, A-2-1, A-3-1, A-4, A-7, B-4, and B-7 are plotted.

[0332] From the comparison between Experimental Examples B-1 to B-3 and Comparative Experimental Examples B-4 and B-7 and Comparative Experimental Examples A-1 to A-7, it can be seen that naphtha from biomass raw materials has a lower methanol production ratio B than naphtha from fossil fuels, and is less likely to produce methanol.

[0333] The reason for this is not yet certain, but is speculated as follows.

[0334] Compared with naphtha from fossil fuels, naphtha from biomass raw materials has a molecular weight of hydrocarbons contained in naphtha that is larger overall, and there is a tendency for the partial pressure of the hydrocarbons to be lowered. As a result, in naphtha from biomass raw materials, the side reaction of producing methanol from asymmetric ethers can be suppressed. Therefore, compared with naphtha from fossil fuels, it is difficult to produce methanol even by thermal decomposition under thermal decomposition conditions.

[0335] Furthermore, it was found that, in any type of naphtha, ethers having a ΔE of 0.05 or more tend to produce more methanol as the ΔE value increases.

[0336] From the comparison between Experimental Examples B-1 to B-3 and Comparative Experimental Examples B-4 and B-7, and the comparison between Comparative Experimental Examples A-1 to A-7, it can be seen that the ΔE value of the ether is correlated with the methanol generation ratio B, and that the ether having an asymmetric structure with respect to the ether oxygen atom has a high methanol generation ratio B and is easy to generate methanol. Furthermore, it can be seen that the ether with a ΔE of 0.05 or more tends to generate more methanol as the ΔE value increases.

[0337] According to Experimental Example B-2 in Table 2, when the concentration of the ether having an asymmetric structure with respect to the oxygen atoms constituting the ether bond was 20,000 mass ppm or less in terms of ether oxygen atoms, the values ​​of the methanol formation ratio were substantially the same when the concentration in terms of ether oxygen atoms was 50 mass ppm, 500 mass ppm, and 5,000 mass ppm.

[0338] The reason is presumably as follows.

[0339] Since ΔE is large, the ether having an asymmetric structure has a large deviation in charge between the two carbon atoms bonded to the ether oxygen atom, and is easily thermally decomposed under thermal decomposition conditions to generate methanol.

[0340] Table 4 shows the details of the lower olefin yields (unit: mass %) of Comparative Experimental Example A-1-1, Experimental Example B-1, and Experimental Example C-1.

[0341] In this evaluation, as described above, "lower olefins" refer to ethylene, propylene, butene (1-butene, 2-butene and isobutylene), butadiene (1,2-butadiene and 1,3-butadiene).

[0342] [Table 4]

[0343]

[0344] As can be seen from Table 4, the greater the content of bio-derived naphtha in naphtha, the higher the yield of any lower olefins.

[0345] Therefore, it can be seen that by using, as a raw material naphtha, naphtha containing, for example, naphtha derived from biological raw materials so that the content ratio of hydrocarbons with a carbon number of 7 or more is greater than a predetermined value, and the concentration of ether oxygen atoms converted to ethers having an asymmetric structure with respect to the ether oxygen atom in the ether is less than a predetermined value, the concentration of methanol production can be suppressed, thereby producing low olefins with high product value.

[0346] [Reference Experimental Examples D-1 to D-3]

[0347] In the mixture of naphtha derived from petroleum and naphtha derived from biomass (mass ratio 1:1) in Comparative Experiment C-1, naphtha B derived from petroleum (Japanese domestic naphtha, content of hydrocarbons with 7 or more carbon atoms: 16.3% by mass, average molecular weight of hydrocarbons: 80.4 g / mol, specific gravity: 0.6656 g / cm 3 ), and in place of the above-mentioned naphtha from bio-raw materials, naphtha B from bio-raw materials (manufactured by Alt Air Paramount, with a content of hydrocarbons with a carbon number of 7 or more: 38.6% by mass, an average molecular weight of hydrocarbons: 88.6 g / mol, and a specific gravity: 0.6712 g / cm 3 ), and the type of ether and the content of ether oxygen atoms derived from the ether were changed as described in Table 5, and in addition, a mixture of the naphtha derived from petroleum and the naphtha derived from biological raw materials (mass ratio 1:1) (content ratio of hydrocarbons with a carbon number of 7 or more: 32.1% by mass, average molecular weight of hydrocarbons: 85.0 g / mol, specific gravity: 0.6692 g / cm 3 ).

[0348] [Table 5]

[0349]

[0350] By using a mixture of naphtha derived from petroleum and naphtha derived from biomass raw materials as shown in Table 5, wherein the content ratio of hydrocarbons with a carbon number of 7 or more is greater than a predetermined value and the concentration of ether oxygen atoms of ethers having an asymmetric structure relative to the ether oxygen atom is less than a predetermined value, it can be expected that the concentration of methanol formation can be suppressed and low olefins with a high yield and high product value can be produced.

[0351] Although the present invention has been described in detail using specific embodiments, it is apparent to those skilled in the art that various modifications can be made within the scope of achieving the effects of the invention.

[0352] This application is based on Japanese Patent Application No. 2022-131236 filed on August 19, 2022, the entirety of which is incorporated by reference.

Claims

1. A naphtha for producing lower olefins, which is naphtha for producing lower olefins containing ether, The naphtha for producing lower olefins contains hydrocarbons having 7 or more carbon atoms. The ether has an asymmetric structure with respect to the oxygen atom constituting the ether bond. The content of the hydrocarbons having 7 or more carbon atoms is 14.0% by mass or more relative to 100% by mass of the total mass of the naphtha for producing lower olefins, The content of the ether is 20,000 mass ppm or less in terms of ether oxygen atoms. 2 . The naphtha for producing lower olefins according to claim 1 , wherein the average molecular weight of hydrocarbons contained in the naphtha for producing lower olefins is 80.0 g / mol or more.

3. The naphtha for producing lower olefins according to claim 1, which has a specific gravity of 0.6640 g / cm 3 above. 4 . The naphtha for producing lower olefins according to claim 1 , wherein the content of the ether is 0.1 mass ppm or more in terms of ether oxygen atoms.

5. The naphtha for producing lower olefins according to claim 1, wherein the content of the sulfur-containing compound is 180 mass ppm or less in terms of sulfur atom. 6 . The naphtha for producing lower olefins according to claim 1 , wherein a content ratio of the hydrocarbons having 7 or more carbon atoms is 42.0 mass % or less relative to 100% of the total mass of the naphtha for producing lower olefins. 7 . The naphtha for producing lower olefins according to claim 1 , wherein the average molecular weight of hydrocarbons contained in the naphtha for producing lower olefins is 87.0 g / mol or less.

8. The naphtha for producing lower olefins according to claim 1, which has a specific gravity of 0.6695 g / cm 3 the following. 9 . The naphtha for producing lower olefins according to claim 1 , wherein the content of the sulfur-containing compound is 1 ppm by mass or more in terms of sulfur atom. 10 . The naphtha for producing lower olefins according to claim 1 , wherein the naphtha for producing lower olefins comprises naphtha derived from a bio-raw material. 11 . The naphtha for producing lower olefins according to claim 10 , which is naphtha derived from a biomass raw material alone or a naphtha mixture containing naphtha derived from a biomass raw material and naphtha derived from a fossil fuel. 12 . The naphtha for producing lower olefins according to claim 10 , wherein the naphtha derived from a bio-raw material is naphtha derived from inedible biomass and / or non-fossil fuel.

13. The naphtha for producing lower olefins according to claim 1, wherein in the ether, an absolute value ΔE (ΔE=|E1-E2|) of a difference between a charge E1 of one carbon atom and a charge E2 of the other carbon atom obtained by density functional theory for two carbon atoms bonded to an oxygen atom constituting an ether bond is 0.05 or more, and the unit is e. in, e represents the elementary charge, e=1.602176634×10 -19 , unit is C.

14. The naphtha for producing lower olefins according to claim 1, wherein the ether is a monoether. 15 . The naphtha for producing lower olefins according to claim 1 , wherein one of the two carbon atoms bonded to the oxygen atom constituting the ether bond is a carbon atom of a methyl group.

16. The naphtha for producing lower olefins according to claim 1, wherein the lower olefin is propylene. 17 . A method for producing a lower olefin composition, comprising the step of decomposing the naphtha for lower olefin production according to claim 1 .

18. The method for producing a lower olefin composition according to claim 17, wherein the lower olefin production naphtha is decomposed to produce a lower olefin composition containing lower olefins and methanol. 19 . The method for producing a lower olefin composition according to claim 18 , wherein the lower olefin contained in the lower olefin composition comprises propylene.

20. A lower olefin composition comprising lower olefins and / or derivatives thereof which are decomposition products of the naphtha for producing lower olefins according to any one of claims 1 to 16. 21 . The lower olefin composition according to claim 20 , wherein the lower olefin contained in the lower olefin composition is an unsaturated hydrocarbon having 2 to 4 carbon atoms and containing one or two unsaturated bonds in one molecule.

22. The lower olefin composition according to claim 20, further comprising methanol.

23. A polyolefin polymer obtained by polymerizing the lower olefin and / or its derivative contained in the lower olefin composition according to claim 20.

24. A method for producing naphtha for producing lower olefins, comprising: The naphtha for lower olefin production according to any one of claims 1 to 16 is obtained by mixing naphtha derived from a bio-raw material with naphtha derived from a fossil fuel.

25. A method for determining naphtha for producing lower olefins, which is a method for determining naphtha for producing lower olefins used in the production of lower olefins, comprising: mixing naphtha from a bio-feedstock with naphtha from a fossil fuel to obtain a blended naphtha; When the obtained mixed naphtha corresponds to the naphtha for producing lower olefins according to any one of claims 1 to 16, the naphtha composition is judged to be acceptable as a naphtha composition used for producing lower olefins and is subjected to thermal decomposition treatment.

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