Mixing method and method for producing lower olefin composition

Abstract

To provide a method of blending two or more kinds of naphtha having different characteristics, such as naphtha derived from a biomass raw material and naphtha derived from a fossil fuel, to use as naphtha for manufacturing a lower olefin, so as to obtain naphtha capable of producing a lower olefin having a low methanol formation concentration at a high olefin yield.SOLUTION: A blending method is for blending naphtha derived from a biomass raw material and naphtha derived from a fossil fuel so that a content of an ether having an asymmetric structure contained in naphtha after the blending becomes a prescribed threshold value or less as a content in terms of an ether oxygen atom. A blending method is for blending two or more kinds of naphtha having different characteristics so that a content ratio of hydrocarbon having 7 or more carbon atoms included in the naphtha after blending is 14.0 mass% or more based on a total mass 100% of the naphtha after blending, and that a content of an ether having an asymmetric structure contained in naphtha after the blending becomes a prescribed threshold value or less as a content in terms of an ether oxygen atom.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a mixing method for mixing two or more types of naphtha with different properties, for example, naphtha derived from bio-based raw materials and naphtha derived from fossil fuels. Furthermore, the present invention relates to a method for producing a lower olefin composition, which includes thermally decomposing the naphtha obtained by the above mixing method.

[0002] In the present invention, "lower olefin" means an unsaturated hydrocarbon having 2 to 4 carbon atoms and containing one or two unsaturated bonds in one molecule, specifically including ethylene, propylene, butene (1-butene, 2-butene, isobutene), and butadiene (1,2-butadiene and 1,3-butadiene). [Background technology]

[0003] A typical method for producing lower olefins involves the thermal decomposition (steam cracking) of naphtha derived from fossil fuels (a mixture of hydrocarbons derived from crude oil with a boiling point range of approximately 30 to 230°C) in the presence of water vapor (see, for example, Patent Document 1).

[0004] On the other hand, 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), and the use of biomass-derived raw materials has been proposed as one means to achieve this. However, the technology for using biomass-derived raw materials, such as biomass-derived naphtha, in the naphtha cracking process is not well understood in detail. Furthermore, in the steam cracking method, once the raw material naphtha is selected, specific thermal decomposition conditions and equipment are basically required depending on the composition and properties of that raw material naphtha and the requirements of the product. Therefore, it has the drawback of having limited selectivity for raw material naphtha and products, and lacking flexibility. In other words, since naphtha derived from biomass differs in composition and properties from naphtha derived from fossil fuels, when biomass-derived naphtha is pyrolyzed using the steam cracking method with existing pyrolysis equipment, there is a need to improve the production yield of lower olefins from the viewpoint of improving energy intensity, etc.

[0005] From the perspective of raw material costs, it is conceivable that biomass-derived naphtha would be mixed with fossil fuel-derived naphtha before being supplied to ethylene plants to produce petrochemical products such as ethylene and propylene, and then used as a raw material for the manufacture of various petrochemical products. In this case, since the composition and properties of naphtha derived from biomass differ depending on its origin, and naphtha derived from fossil fuels differs depending on its source, it is assumed that in the above petrochemical product manufacturing process, it is necessary to mix naphtha derived from biomass and naphtha derived from fossil fuels in an appropriate mixing ratio.

[0006] Naphtha contains oxygen-containing compounds, and when naphtha is thermally decomposed to produce various lower olefins, methanol may be generated from the thermal decomposition products of these oxygen-containing compounds. While naphtha contains various oxygen-containing compounds, the proportion of methanol produced from these compounds is not constant, and the details of this process are not yet clear. Methanol derived from the thermal decomposition products of oxygen-containing compounds, when mixed with lower olefin products such as propylene, has the problem of reducing the performance of catalysts used in the polymerization of these lower olefins.

[0007] For this reason, the concentration of oxygen-containing compounds in naphtha is used as a criterion for judging the quality of naphtha. Typically, naphtha purchasers blend naphtha with a high concentration of oxygen-containing compounds with naphtha with a low concentration of oxygen-containing compounds to reduce the concentration of oxygen-containing compounds in the naphtha before using it in the production of lower olefins. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2009-40913 [Overview of the project] [Problems that the invention aims to solve]

[0009] As mentioned above, the relationship between the types of oxygen-containing compounds contained in naphtha and the amount of methanol produced from the thermal decomposition of these oxygen-containing compounds had not been clearly defined until now. Therefore, even if the quality of naphtha was determined by the concentration of oxygen-containing compounds it contained, the methanol production concentration when lower olefins were actually produced by thermal decomposition did not necessarily correlate with that concentration. In other words, a method for accurately obtaining high-quality naphtha with a low methanol production concentration had not been known until now.

[0010] The present invention aims to solve these problems. Specifically, the present invention aims to provide a method for mixing two or more naphthas with different properties, for example, naphtha derived from bio-based raw materials and naphtha derived from fossil fuels, to obtain naphtha that can produce lower olefins with a low methanol production concentration and a high olefin yield when used as naphtha for lower olefin production. Furthermore, the present invention aims to provide a method for producing a lower olefin composition with a low methanol content using naphtha obtained by the mixing method. [Means for solving the problem]

[0011] The present inventors, after conducting extensive research to solve the above problems, have found that certain ethers having an asymmetric structure with respect to the oxygen atom of the ether bond are particularly prone to selective decomposition of specific bonds in the molecule during the thermal decomposition process of naphtha, and in particular, readily produce methanol through decomposition. Furthermore, they have found that the quality of naphtha for lower olefin production can be determined by the content of oxygen atoms derived from ethers 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 is greater than or equal to a predetermined value. Moreover, they have found that this effect becomes even more pronounced when naphtha derived from bio-based raw materials is used as the raw material naphtha, and based on this finding, the present invention has been completed.

[0012] In other words, the gist of this invention is as follows:

[0013] [1] A method for mixing naphtha derived from biomaterials and naphtha derived from fossil fuels, A mixing method comprising mixing the naphtha such that the content of asymmetric ethers in the naphtha after mixing is below a predetermined threshold, expressed as the content of ether oxygen atoms.

[0014] [2] The mixing method according to [1], wherein the naphtha after mixing is mixed such that the content of hydrocarbons having 7 or more carbon atoms is 14.0% by mass or more with respect to 100% of the total mass of the naphtha after mixing.

[0015] [3] A method of mixing two or more naphthas with different properties, The proportion of hydrocarbons with 7 or more carbon atoms in the naphtha after mixing is 14.0% by mass or more, relative to 100% of the total mass of the naphtha after mixing, and A mixing method comprising mixing the naphtha such that the content of asymmetric ethers in the naphtha after mixing is below a predetermined threshold, expressed as the content of ether oxygen atoms.

[0016] [4] The mixing method according to [3], wherein the two or more types of naphtha include at least naphtha derived from bio-based raw materials and naphtha derived from fossil fuels.

[0017] [5] The mixing method according to any one of [1] to [4], wherein the content of the ether contained in the naphtha after mixing is 20,000 mass ppm or less in terms of ether oxygen atoms.

[0018] [6] The mixing method according to any one of [1] to [5], wherein the naphtha after mixing contains a sulfur-containing compound, and the content of the sulfur-containing compound contained in the naphtha after mixing is 180 mass ppm or less in terms of sulfur atoms.

[0019] [7] The mixing method according to any one of [1] to [6], wherein the average molecular weight of the hydrocarbons contained in the naphtha after mixing is 80.0 g / mol or more.

[0020] [8] The mixing method according to any one of [1] to [7], wherein the specific gravity of the naphtha after mixing is 0.6640 g / cm 3 or more and 0.6700 g / cm 3 or less.

[0021] [9] The mixing method according to any one of [1], [2] or [4] to [8], wherein the naphtha derived from bio-based raw materials is naphtha derived from non-edible biomass and / or non-fossil fuels.

[0022]

[10] The mixing method according to any one of [1] to [9], wherein the content of the ether contained in the naphtha after mixing is 0.1 mass ppm or more in terms of ether oxygen atoms.

[0023]

[11] The mixing method according to any one of [1] to

[10] , wherein the ether has an 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, determined by density functional theory for the two carbon atoms bonded to the oxygen atom constituting the ether bond, which is 0.05 [unit: e] or more. However, e represents the elementary electron weight, and e = 1.602176634 × 10⁻¹⁴ -19 [Unit: C]

[0024]

[12] The mixing method according to any one of [1] to

[11] , wherein the ether is a monoether.

[0025]

[13] The mixing method according to any one of [1] to

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

[0026] A method for producing a lower olefin composition, comprising thermally decomposing the naphtha after mixing obtained by any of the mixing methods described in [1] to

[13] .

[0027]

[15] A method for producing the lower olefin composition according to

[14] , wherein the lower olefin comprises propylene. [Effects of the Invention]

[0028] According to the present invention, by mixing two or more naphthas with different properties, for example, naphtha derived from bio-based raw materials and naphtha derived from fossil fuels, naphtha with a low methanol production rate during thermal decomposition can be more accurately obtained, and lower olefins with a low methanol content can be produced with a high olefin yield using such naphtha. In other words, by mixing two or more types of naphtha with different properties, such as naphtha derived from bio-based raw materials and naphtha derived from fossil fuels, so that the content of oxygen atoms derived from specific ethers in the naphtha, specifically ethers with an asymmetric structure, is below a predetermined threshold, high-quality raw material naphtha with a low methanol production concentration can be accurately obtained for use in the production of lower olefins.

[0029] Furthermore, according to the present invention, in a mixed naphtha obtained by mixing two or more naphthas with different properties as raw material naphtha, for example, naphtha derived from bio-based raw materials and naphtha derived from fossil fuels, by controlling the content of oxygen atoms derived from a specific ether in the mixed naphtha, specifically, an ether whose 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, determined by density functional theory, is 0.05 [unit: e] or more, it is possible to more accurately obtain a high-quality mixed naphtha with a low methanol production concentration as naphtha for lower olefin production. Therefore, for example, by selecting naphtha with a low content of oxygen atoms derived from ethers with a ΔE of 0.05 [unit: e] or higher from among inexpensive naphtha with a high concentration of oxygen-containing compounds, it is possible to produce high-purity lower olefins using inexpensive raw material naphtha while suppressing methanol production concentration. Furthermore, even if naphtha has a high concentration of oxygen-containing compounds, if it has a low content of oxygen atoms derived from ethers with a ΔE of 0.05e [unit: e] or higher, it can be used as raw material naphtha without blending it with naphtha with a low concentration of oxygen-containing compounds. [Brief explanation of the drawing]

[0030] [Figure 1] This graph shows the relationship between the ΔE [unit: e] of various ethers and the methanol production ratio B. [Modes for carrying out the invention]

[0031] The present invention will be described in detail below, but the present invention is not limited to the following description and can be modified and implemented as such without departing from the spirit of the invention.

[0032] Unless otherwise specified, numerical ranges represented using "~" in this specification mean a range that includes the numbers before and after "~" as the lower and upper limits, respectively, and "A~B" means A or greater and B or less.

[0033] In the present invention, "lower olefin" means an unsaturated hydrocarbon having 2 to 4 carbon atoms and containing one or two unsaturated bonds in one molecule, specifically referring to ethylene, propylene, butene (1-butene, 2-butene, isobutene), and butadiene (1,2-butadiene and 1,3-butadiene).

[0034] [Mixing method] A mixing method according to one embodiment of the present invention is a method for mixing naphtha derived from biomaterials and naphtha derived from fossil fuels, the method comprising mixing such that the content of asymmetric ethers (hereinafter sometimes referred to as "asymmetric ethers") contained in the mixed naphtha is less than or equal to a predetermined threshold (hereinafter sometimes simply referred to as "threshold") in terms of ether oxygen atom content.

[0035] Furthermore, another mixing method according to a different embodiment of the present invention is a method for mixing two or more naphthas with different properties, wherein the content of hydrocarbons having 7 or more carbon atoms in the mixed naphthas is 14.0% by mass or more based on 100% of the total mass of the mixed naphthas, and the content of asymmetric ethers having an asymmetric structure in the mixed naphthas is below a predetermined threshold when expressed as the content in terms of ether oxygen atoms. In this mixing method, it is preferable to mix at least two types of naphtha with different properties, such as naphtha derived from bio-based raw materials and naphtha derived from fossil fuels.

[0036] In this invention, "ether oxygen atom" refers to an oxygen atom in the ether that is involved in ether bonding. In the following, the mixing method of the present invention will be described using an example of mixing naphtha derived from biomaterials and naphtha derived from fossil fuels. However, the mixing method of the present invention is not limited in any way to mixing naphtha derived from biomaterials and naphtha derived from fossil fuels. For example, it may be a method of mixing naphtha derived from biomaterials with different properties or compositions, or naphtha derived from fossil fuels with different properties, compositions, origins, etc. Furthermore, in the following, the naphtha obtained by mixing according to the mixing method of the present invention may be referred to as "the mixed naphtha of the present invention." Also, the content of asymmetric ether in terms of ether oxygen atoms may be referred to as "the content of asymmetric ether oxygen atoms."

[0037] In the present invention, the embodiments of "mixing naphtha derived from bio-based raw materials and naphtha derived from fossil fuels" are not particularly limited. For example, this includes mixing transported naphtha with naphtha previously stored in a tank in an appropriate mixing ratio, or mixing naphtha stored in two or more tanks in an appropriate mixing ratio, where one of the mixtures is derived from bio-based raw materials.

[0038] <Mechanism> Ether is a compound found in naphtha. In the present invention, the asymmetric ether has an asymmetric structure with respect to the ether oxygen atom.

[0039] Among the aforementioned asymmetric ethers, those in which 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, determined by density functional theory for the two carbon atoms bonded to the ether oxygen atom, is 0.05 [unit: e] or greater, can be mixed based on the threshold, thereby more effectively reducing the methanol content in the lower olefin composition obtained by thermal decomposition of the naphtha after mixing. In this specification, "e" represents the elementary electron quantity, where e = 1.602176634 × 10⁻¹⁴ -19 [Unit: C] The charge values ​​of the two carbon atoms are calculated by performing density functional theory (DFT) calculations on the molecular structure of the ether. The DFT calculation conditions use def-TZVP as the basis set, employ the COSMO solvation model (Conductor-like Screening Model) as the solvent effect, and Mulliken's charge density analysis (Population Analysis) as the analysis method. The aforementioned ΔE can be calculated using the quantum chemistry calculation software "TURBOMOLE" (manufactured by TURBOMOLE Inc.) and its graphical user interface "TmoleX" (manufactured by TURBOMOLE Inc.).

[0040] Generally, ethers with a large ΔE are asymmetric ethers, having an asymmetric structure with respect to the ether oxygen atom. The inventors have found that asymmetric ethers tend to readily decompose under thermal decomposition conditions to produce methanol. Furthermore, the inventors have found that the larger the ΔE of the ether, the greater the charge imbalance between the two carbon atoms bonded to the ether oxygen atom, and therefore such ethers tend to decompose more readily under thermal decomposition conditions to produce methanol.

[0041] Furthermore, the inventors have found that by using an asymmetric ether, more preferably an asymmetric ether with a ΔE [unit: e] of 0.05 or more, as the ether, and by mixing the ether so that the content of asymmetric ether oxygen atoms in the naphtha after mixing is below a predetermined value, preferably below 20,000 ppm by mass, the methanol content in the lower olefin obtained by thermal decomposition of the naphtha after mixing can be reduced.

[0042] For example, as asymmetric ethers having an asymmetric structure with respect to the ether oxygen atom, 2-methoxybutane (CH3CH2CH(CH3)-O-CH3), methoxycyclopentane (C5H9-O-CH3), and 1-methoxypropane (CH3CH2CH2-O-CH3) have ΔE [unit: e] values ​​of 0.181, 0.151, and 0.084, respectively. Because ΔE is large and the charge imbalance is large, specific bonds in the molecule are easily selectively decomposed. As a result, in the thermal decomposition process of naphtha containing these ethers, the ethers readily produce methanol.

[0043] On the other hand, 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), which have a symmetric structure with respect to the ether oxygen atom (hereinafter referred to as "symmetric ethers"), have ΔE [unit: e] values ​​of 0.004, 0.001, 0.010, and 0.000, respectively. Because ΔE is small and the charge imbalance is small, selective decomposition of specific bonds in the molecule is unlikely to occur. As a result, in the thermal decomposition process of naphtha containing these symmetric ethers, the symmetric ethers are less likely to produce methanol.

[0044] In the mixing method of the present invention, naphtha derived from bio-based raw materials and naphtha derived from fossil fuels are mixed such that the content of asymmetric ether oxygen atoms in the naphtha after mixing is below a predetermined value. This suppresses methanol production in the lower olefin manufacturing process, which involves thermal decomposition of the mixed naphtha of the present invention after mixing, making it possible to produce a lower olefin composition with a low methanol content and high product value.

[0045] According to the present invention, a specific method for mixing naphtha such that the content of asymmetric ether oxygen atoms in the mixed naphtha is below a threshold is as follows: (1) If the asymmetric ether oxygen atom content of naphtha derived from biomaterials exceeds the threshold, naphtha derived from fossil fuels with an asymmetric ether oxygen atom content below the threshold is mixed in so that the asymmetric ether oxygen atom content of the mixed naphtha is below the threshold. (2) If the asymmetric ether oxygen atom content of naphtha derived from biomaterials is below the threshold, naphtha derived from fossil fuels, which also has an asymmetric ether oxygen atom content below the threshold, is mixed in such a way that the asymmetric ether oxygen atom content of the mixed naphtha is below the threshold. (3) If the asymmetric ether oxygen atom content of naphtha derived from biomaterials is below the threshold, naphtha derived from fossil fuels, which has an asymmetric ether oxygen atom content exceeding the threshold, is mixed in such an amount that the asymmetric ether oxygen atom content of the mixed naphtha becomes below the threshold.

[0046] The asymmetric ether oxygen atom content of naphtha can be determined based on the asymmetric ether contained in the naphtha, using common analytical instruments such as GC and GC / MS measurements.

[0047] Therefore, by providing a measuring means for measuring the asymmetric ether oxygen atom content of naphtha derived from bio-based materials and naphtha derived from fossil fuels, and a control device that calculates and adjusts the selection of naphtha derived from bio-based materials and naphtha derived from fossil fuels to be mixed, as well as their mixing ratio, based on these measured values, so that the asymmetric ether oxygen atom content of the mixed naphtha is below a threshold, it is possible to automatically mix naphtha derived from bio-based materials and naphtha derived from fossil fuels.

[0048] For example, when there are multiple types of naphtha derived from biomaterials, a storage tank into which naphtha derived from fossil fuels is added can be selected based on the asymmetric ether oxygen atom content of the naphtha derived from fossil fuels, so as to be mixed using one of the methods (1) to (3) above, and the amount added can be controlled so that the asymmetric ether oxygen atom content of the mixed naphtha is below a threshold. Furthermore, when there are multiple types of naphtha derived from fossil fuels, it is possible to select the naphtha derived from bio-based raw materials to be mixed based on the asymmetric ether oxygen atom content of each fossil fuel-derived naphtha, and then switch the storage tanks to which each type is added.

[0049] <Raw material: naphtha> The mixing method of the present invention is preferable from the viewpoint of suppressing the generation of methanol produced from asymmetric ethers contained as impurities, and obtaining a high yield of lower olefins, by mixing naphtha derived from bio-based raw materials and naphtha derived from fossil fuels to obtain the mixed naphtha of the present invention.

[0050] Here, naphtha derived from bio-based raw materials refers to naphtha derived from non-edible biomass and / or non-fossil fuels. In this invention, non-edible biomass refers to resources derived from non-edible grasses and trees. Specifically, this includes, but is not limited to, cellulose, hemicellulose, and lignin obtained from woody biomass such as coniferous and broad-leaved trees, as well as bioethanol, biodiesel, and plant-derived waste oil obtained from herbaceous biomass such as corn and sugarcane stalks, soybeans, and rapeseed. In this invention, non-fossil fuels refer to, for example, hydrogen, or organic matter derived from plants and animals that does not originate from fossil fuels or non-edible biomass. Specifically, examples include, but are not limited to, methane and sugar ethanol obtained from firewood, charcoal, dried livestock manure, etc. Furthermore, in this invention, fossil fuel-derived naphtha refers to at least one selected from petroleum-derived naphtha, coal-derived naphtha, and natural gas-derived naphtha.

[0051] <threshold> In the present invention, the mixed naphtha obtained by mixing is mixed such that the asymmetric ether oxygen atom content of the mixed naphtha is below a predetermined threshold. The threshold is not particularly limited, but from the viewpoint of suppressing the amount of methanol produced in the lower olefin obtained by thermal decomposition of the naphtha after mixing, it is preferably 20,000 ppm by mass or less, more preferably 1,000 ppm by mass or less, even more preferably 100 ppm by mass or less, and particularly preferably 50 ppm by mass or less in terms of ether oxygen atoms.

[0052] On the other hand, the lower limit of the threshold is not particularly limited, but usually, from the viewpoint of the manufacturing cost for reducing the asymmetric ether and the quantitative accuracy by GC and GC / MS measurements, which are common analytical instruments, it is 0.1 mass ppm or more, preferably 0.2 mass ppm or more, more preferably 0.5 mass ppm or more, even more preferably 1 mass ppm or more, particularly preferably 10 mass ppm or more, and most preferably 20 mass ppm or more, in terms of ether oxygen atoms.

[0053] <Asymmetric Ether> As described above, in the asymmetric ether according to the present invention, it is preferable that 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, determined by density functional theory for the two carbon atoms bonded to the ether oxygen atom, is 0.05 [unit: e] or more, from the viewpoint of being able to more effectively reduce the methanol content in the lower olefin obtained by thermal decomposition of the naphtha after mixing according to the present invention.

[0054] Examples of asymmetric ethers according to the present invention include, but are not limited to, 2-methoxybutane (CH3CH2CH(CH3)-O-CH3), methoxycyclopentane (C5H9-O-CH3), and 1-methoxypropane (CH3CH2CH2-O-CH3).

[0055] The aforementioned asymmetric ether is preferably a monoether having only one ether oxygen atom in its molecule, because it can effectively reduce the amount of methanol produced in the lower olefin obtained by thermal decomposition of the naphtha after mixing according to the present invention.

[0056] Furthermore, the asymmetric ether with a ΔE [unit: e] of 0.05 or more is one in which the ΔE value of at least one ether bond in the molecule is 0.05 or more. However, because there is a high correlation between the ΔE value and the amount of methanol produced, the amount of methanol produced in the resulting lower olefin can be effectively reduced. Therefore, it is preferable that the monoether has only one ether oxygen atom in the molecule.

[0057] Furthermore, the asymmetric ether, preferably the asymmetric ether with a ΔE of 0.05 or higher, is preferable because one of the two carbon atoms bonded to the ether oxygen atom is the carbon atom of the methyl group, such as 2-methoxybutane, methoxycyclopentane, or 1-methoxypropane, can more effectively reduce the amount of methanol produced in the lower olefin composition obtained by thermal decomposition of the naphtha after mixing according to the present invention.

[0058] Furthermore, if an asymmetric ether has two or more ether bonds in one molecule, the ΔE of each ether bond is determined as the absolute value of the charge difference between the two carbon atoms bonded to each ether oxygen atom, and the ΔE of the ether is the largest value among the two or more ΔEs.

[0059] <Hydroxides with 7 or more carbon atoms> In the present invention, it is preferable that the content of hydrocarbons having 7 or more carbon atoms in the mixed naphtha of the present invention obtained by mixing is 14.0% by mass or more, based on 100% of the total mass of the mixed naphtha of the present invention.

[0060] Hydrocarbons with 7 or more carbon atoms mainly include aromatic hydrocarbons such as ethylbenzene and styrene found in biomass-derived naphtha, aliphatic hydrocarbons such as n-heptane, n-octane, and n-decane, and naphthenes such as methylcyclohexane and ethylcyclohexane. There is no particular upper limit on the number of carbon atoms in these hydrocarbons, but it is usually 15 or less.

[0061] The mixed naphtha of the present invention may contain only one of these hydrocarbons having 7 or more carbon atoms, or it may contain two or more.

[0062] In the mixing method of the present invention, it is preferable to mix the hydrocarbons having 7 or more carbon atoms such that their content is 14.0% by mass or more relative to 100% of the total mass of the mixed naphtha of the present invention. If the naphtha has a content of 14.0% by mass or more of hydrocarbons having 7 or more carbon atoms, the effects of defining the content of the asymmetric ether in the mixed naphtha of the present invention can be more effectively obtained, and specifically, a lower olefin composition with a lower methanol content can be produced with a higher olefin yield. From this viewpoint, in the mixing method of the present invention, it is preferable to mix the naphtha so that the lower limit of the content of hydrocarbons having 7 or more carbon atoms in the mixed naphtha is 14.0% by mass or more, more preferably 16.0% by mass or more, even more preferably 18.0% by mass or more, and particularly preferably 20.0% by mass or more. On the other hand, if the proportion of high carbon numbers in the naphtha increases too much, there is a problem that the yield of lower olefins such as ethylene and propylene decreases. Therefore, in the mixing method of the present invention, it is preferable to mix the naphtha so that the upper limit of the content of hydrocarbons having 7 or more carbon atoms in the obtained mixed naphtha is 90.0% by mass or less, more preferably 85.0% by mass or less, even more preferably 80.0% by mass or less, and particularly preferably 60.0% by mass or less. The above upper and lower limits can be combined in any way. That is, in the mixing method of the present invention, the content of hydrocarbons having 7 or more carbon atoms in the mixed naphtha is preferably 14.0% to 90.0% by mass, more preferably 16.0% to 85.0% by mass, even more preferably 18.0% to 80.0% by mass, and particularly preferably 20.0% to 60.0% by mass.

[0063] The reason why the mixed naphtha of the present invention, in which the content of hydrocarbons with 7 or more carbon atoms in the mixed naphtha is 14.0% by mass or more, exhibits the remarkable effect of enabling the production of lower olefin compositions with lower methanol content and higher olefin yields using the mixed naphtha of the present invention, in which the content of asymmetric ethers is below the threshold, is not entirely clear, but it is presumed to be as follows. In other words, the presence of hydrocarbons with seven or more carbon atoms, which are relatively large molecular weight hydrocarbons, in naphtha tends to lower the partial pressure of these hydrocarbons. As a result, it is presumed that the side reaction that produces methanol from asymmetric ethers is suppressed, thus reducing the amount of methanol produced during thermal decomposition.

[0064] The content of hydrocarbons having 7 or more carbon atoms in the mixed naphtha of the present invention can be analyzed by the method described in the Examples section below.

[0065] Furthermore, in the mixing method of the present invention, the lower limit of the average molecular weight of hydrocarbons in the obtained mixed naphtha is not particularly limited, but from the viewpoint of producing a lower olefin composition with a low methanol content in a high olefin yield, it is preferably 80.0 g / mol or more, more preferably 82.0 g / mol or more, and even more preferably 84.0 g / mol. On the other hand, the upper limit of the average molecular weight is not particularly limited, but since the yield of lower olefins such as ethylene and propylene tends to decrease if the proportion of high carbon numbers in the naphtha increases too much, it is preferably 150.0 g / mol or less, more preferably 130.0 g / mol or less, and even more preferably 100.0 g / mol or less. The above upper and lower limits can be combined in any way. That is, in the mixing method of the present invention, the average molecular weight of hydrocarbons in the mixed naphtha is not particularly limited, but is preferably 80.0 to 150.0 g / mol, more preferably 82.0 to 130.0 g / mol, and even more preferably 84.0 to 100.0 g / mol.

[0066] The average molecular weight of hydrocarbons in the mixed naphtha can be analyzed by the method described in the Examples section below.

[0067] <Sulfur-containing compounds> Naphtha typically contains sulfur-containing compounds such as disulfide compounds, sulfide compounds, and thiol compounds. In this invention, the upper limit of the sulfur-containing compound content in the resulting mixed naphtha is not particularly limited. However, since a lower olefin composition with a low methanol content can be produced with a high olefin yield, it is preferable to mix the compounds so that the sulfur content is 180 ppm by mass or less, more preferably 150 ppm by mass or less, even more preferably 100 ppm by mass or less, particularly preferably 30 ppm by mass or less, and most preferably 10 ppm by mass or less. A lower content of sulfur-containing compounds is preferable, and there is no particular lower limit. However, from the viewpoint of reducing the manufacturing cost of the sulfur-containing compounds, it is usually 1 ppm by mass or more. The above upper and lower limits can be combined arbitrarily. That is, in the mixing method of the present invention, the content of the sulfur-containing compound in the mixed naphtha is not particularly limited, but is preferably 1 ppm to 180 ppm by mass, more preferably 1 ppm to 150 ppm by mass, even more preferably 1 ppm to 100 ppm by mass, particularly preferably 1 ppm to 30 ppm by mass, and most preferably 1 ppm to 10 ppm by mass in terms of sulfur atoms.

[0068] Specific examples of the above-mentioned disulfide compounds include dimethyl disulfide, methyl ethyl disulfide, and diethyl disulfide. Other examples of sulfide compounds include diethyl sulfide and dipropyl sulfide. Other examples of thiol compounds include ethyl thiols, propanethiols, and butanethiols, which have 2 to 10 carbon atoms. The mixed naphtha of the present invention may contain only one of these sulfur-containing compounds, or it may contain two or more of them.

[0069] <Specific gravity> In the mixing method of the present invention, the specific gravity of the resulting mixed naphtha is not particularly limited, but is 0.6640 g / cm³. 3 More than 0.6700g / cm 3 It is preferable to mix them in the following manner. It is known that there is a correlation between naphtha density and naphtha composition. From the viewpoint of being able to produce lower olefins in the present invention, i.e., unsaturated hydrocarbons with 2 to 4 carbon atoms containing one or two unsaturated bonds in one molecule, in high yield while suppressing the formation of by-products, the specific gravity of naphtha is preferably within the above range, which is 0.6650 g / cm³. 3 More than 0.6700g / cm 3 The following is more preferable: The reason why a lower olefin composition with a low methanol content can be produced with a higher olefin yield when the specific gravity of naphtha for lower olefin production is within the aforementioned numerical range is not entirely clear, but it is presumed that the higher the naphtha density, the more carbon atoms in the hydrocarbons contained in the naphtha tend to increase, and as a result, the naphtha is efficiently decomposed into olefins. The specific gravity of naphtha can be measured using JIS K2249-1:2011.

[0070] [Method for producing lower olefin compositions] The method for producing the lower olefin composition of the present invention includes thermal decomposition of the mixed naphtha of the present invention obtained by the mixing method of the present invention. By thermal decomposition of naphtha, a lower olefin composition containing a lower olefin and methanol is produced, but as described above, by using the mixed naphtha of the present invention, the amount of methanol produced can be significantly reduced.

[0071] The method for producing the lower olefin composition of the present invention can be carried out according to conventional methods, except that the mixed naphtha of the present invention is used. Specifically, a lower olefin composition is obtained by thermally decomposing (steam cracking) the mixed naphtha of the present invention (hereinafter sometimes simply referred to as "naphtha") in the presence of water vapor at a temperature of 700 to 1000°C.

[0072] In the pyrolysis conditions, the ratio of naphtha to steam is preferably 20 to 100 parts by mass of steam per 100 parts by mass of naphtha, more preferably 30 to 70 parts by mass, and particularly preferably 35 to 60 parts by mass. If the amount of steam is less than 20 parts by mass, there is a tendency for more carbonaceous material to be deposited on the piping used for the decomposition reaction installed in the pyrolysis furnace. On the other hand, if the amount of steam exceeds 100 parts by mass, the amount of heat supplied to the steam increases, resulting in an excessive energy load on the equipment.

[0073] Furthermore, the reaction temperature for thermal decomposition is usually 700 to 1000°C, preferably 750 to 950°C. If the reaction temperature is below 700°C, the thermal decomposition of naphtha does not proceed sufficiently, and the yield of the target lower olefin decreases. On the other hand, if the reaction temperature exceeds 1000°C, the thermal decomposition of naphtha becomes excessive, increasing the generation of undesirable by-products such as methane, and tends to decrease the yield of the target lower olefin.

[0074] Furthermore, the reaction time for thermal decomposition is preferably 0.01 to 1 second, more preferably 0.04 to 0.7 seconds. If the reaction time is less than 0.01 seconds, the thermal decomposition of naphtha does not proceed sufficiently, and the yield of the target lower olefin tends to decrease. On the other hand, if the reaction time exceeds 1 second, the thermal decomposition of naphtha becomes excessive, and the generation of undesirable by-products such as methane increases, which tends to decrease the yield of the target lower olefin.

[0075] Furthermore, the reaction pressure for thermal decomposition is preferably 0.01 to 1.5 MPa (gauge pressure), more preferably 0.05 to 0.5 MPa (gauge pressure), and even more preferably 0.07 to 0.2 MPa (gauge pressure).

[0076] The reaction product, once it has left the thermal decomposition reaction range, can be rapidly cooled to suppress excessive decomposition. The cooling temperature is not particularly limited, but for example, when carried out on an industrial scale, it is preferably 200 to 700°C, more preferably 250 to 650°C, and when carried out on a small scale such as in a pilot or laboratory, it is preferably 0 to 100°C, more preferably 3 to 40°C.

[0077] The reaction products containing the lower olefins obtained in this way can be purified, fractionated, and subjected to other treatments according to conventional methods. This yields lower olefins such as ethylene, propylene, butene, and butadiene, as well as aromatic hydrocarbons and other hydrocarbons. Saturated hydrocarbons such as ethane and propane can be recovered and subjected to further thermal decomposition. Of the lower olefins, butene and butadiene are usually obtained as mixtures with butane. Therefore, it is preferable to isolate butadiene by solvent extraction in a separate step, and then utilize or fractionate the resulting mixture of butene and butane by polymerization, rectification, or other methods in a separate step.

[0078] Furthermore, in the method for producing the lower olefin composition of the present invention, it is preferable that ΔE [unit: e] and the methanol production ratio B in the obtained lower olefin composition satisfy the following formulas (1) and (2), thereby enabling the thermal decomposition of the mixed naphtha of the present invention to yield a lower olefin composition with a further reduced methanol content. 0.05≦ΔE Formula (1) B≦1.25×ΔE+0.10 Formula (2)

[0079] As mentioned above, methanol adversely affects polymerization catalysts when polymerizing lower olefins. Lower olefin compositions obtained by thermally decomposing naphtha under conditions satisfying formulas (1) and (2) have a reduced methanol content and are therefore effective in producing lower olefins such as propylene.

[0080] It is more preferable that equation (2) satisfies the condition B ≤ 1.25 × ΔE + 0.05.

[0081] The methanol production ratio B is an indicator of the proportion of methanol produced when naphtha is thermally decomposed, and represents the ratio of the number of oxygen atoms in methanol contained in condensate to the number of oxygen atoms in ether contained in naphtha. The specific method for measuring methanol production ratio B is described in the Examples section below.

[0082] The present invention provides a method for producing a lower olefin composition using mixed naphtha, which allows for the production of a lower olefin composition containing a lower olefin and having suppressed methanol production, i.e., a lower olefin composition with a low methanol content.

[0083] Furthermore, by using the method for producing the lower olefin composition of the present invention, a propylene composition containing propylene and methanol can be produced. More specifically, by using the method for producing the lower olefin composition of the present invention, it is possible to produce a propylene composition that contains propylene and further suppresses methanol production, that is, a propylene composition with a low methanol content.

[0084] As mentioned above, methanol adversely affects polymerization catalysts when polymerizing lower olefins or propylene; therefore, the method for producing lower olefin compositions of the present invention is effective when producing lower olefins such as propylene.

[0085] The content of the lower olefin in the lower olefin composition produced by the method for producing the lower olefin composition of the present invention is not particularly limited, but is preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, particularly preferably 95% by mass or more, and especially preferably 98% by mass or more, based on 100% of the total mass of the lower olefin composition. The content of the lower olefin in the lower olefin composition may be 100% by mass.

[0086] The methanol content in the lower olefin composition produced by the method for producing the lower olefin composition of the present invention is not particularly limited, but is preferably 10,000 ppm by mass or less, more preferably 1,000 ppm by mass or less, even more preferably 100 ppm by mass or less, particularly preferably 10 ppm by mass or less, most preferably 5 ppm by mass or less, and most preferably 1 ppm by mass or less, relative to the total mass of the lower olefin composition. Here, the methanol content in the lower olefin can be measured by gas chromatography.

[0087] Such lower olefin compositions can be obtained by cracking the mixed naphtha of the present invention. [Examples]

[0088] The present invention will be described in more detail below with reference examples, comparative examples, and alternative experimental examples provided below, but these are for illustrative purposes only and do not limit the present invention in any way.

[0089] The names of the compounds used in the experimental examples, reference experimental examples, and comparative experimental examples are as follows: 2-Methoxybutane (manufactured by Tokyo Chemical Industry Co., Ltd.) Methoxycyclopentane (manufactured by Tokyo Chemical Industry Co., Ltd.) 1-Methoxypropane (manufactured by Tokyo Chemical Industry Co., Ltd.) Dimethyl ether (manufactured by Koike Chemical Co., Ltd.) Diethyl ether (manufactured by Tokyo Chemical Industry Co., Ltd.) Diisopropyl ether (manufactured by Tokyo Chemical Industry Co., Ltd.) Dipropyl ether (manufactured by Tokyo Chemical Industry Co., Ltd.)

[0090] (1) Measurement of the content ratio of hydrocarbons having 7 or more carbon atoms in naphtha The content ratio of hydrocarbons having 7 or more carbon atoms in naphtha was measured under the following conditions using a gas chromatograph measuring device (GC device). <GC measurement conditions> GC device: GC-2010 Plus (device name, manufactured by Shimadzu Corporation) Detector: Flame ionization detector (FID) Carrier gas: Nitrogen (flow rate 0.8 ml / min) Column: Capillary column CBP1-M50-025 (manufactured by Shimadzu Corporation, size: 0.22 mmφ × 50 m, film thickness: 0.25 μm) Column temperature: 0°C (holding time 5 minutes) → temperature increase at 3°C / min → 200°C (no holding time) → temperature increase at 10°C / min → 250°C (holding time 10 minutes) Injection port temperature: 250°C Detector temperature: 250°C Sample amount: 0.5 μL (split ratio: 1 / 60) Quantification method: Absolute calibration curve method

[0091] Note that as a sample for GC measurement, naphtha was used as it was without pretreatment. In addition, a calibration curve for calculating the content ratio of hydrocarbons from the peak area of the gas chromatogram was prepared using, as standard solutions, compounds fractionated and purified from naphtha in advance, commercially available compounds, and compounds synthesized in advance, which were accurately weighed and diluted, for each component of hydrocarbons having 1 to 15 carbon atoms identified from the gas chromatogram.

[0092] As an example of the gas chromatogram of naphtha, for the mixture of petroleum-derived naphtha and biofeedstock-derived naphtha used in Experimental Example C-1, the retention time (minutes), type, and carbon number of each component of hydrocarbons contained in the naphtha identified from the gas chromatogram are shown in Table A. As shown in Table A, all hydrocarbon components were observed during retention times of 3.570 to 39.021 minutes, and the number of carbon atoms in each hydrocarbon was within the range of 3 to 10. It should be noted that this explanation uses the naphtha mixture from Experimental Example C-1 as an example, hence the results shown in Table A. However, it goes without saying that the types and carbon atoms of each hydrocarbon component contained in naphtha will differ depending on the origin, source, and manufacturing conditions of the naphtha.

[0093] [Table A]

[0094] The percentage of hydrocarbons with 7 or more carbon atoms in naphtha was calculated according to the following procedure. First, in the gas chromatogram obtained using the above GC measurement conditions, the peak area was read from the peaks observed between retention times of 1 minute and 100 minutes for each component of hydrocarbons with 1 to 15 carbon atoms, and the content percentage (unit: mass%) of each component was calculated using the absolute calibration curve method. Next, B1 was defined as the sum of the content percentages of each hydrocarbon component having 1 to 15 carbon atoms, and A1 was defined as the sum of the content percentages of each hydrocarbon component having 7 to 15 carbon atoms. The content percentage of hydrocarbons with 7 or more carbon atoms in naphtha was then calculated using the following formula.

[0095] Percentage of hydrocarbons with 7 or more carbon atoms (by mass) = A1 / B1 × 100 A1: Total percentage (by mass) of each component of hydrocarbons with 7 to 15 carbon atoms. B1: Total percentage (by mass) of each component of hydrocarbons with 1 to 15 carbon atoms.

[0096] (2) Calculation of the average molecular weight of hydrocarbons in naphtha Using the measurement method described above for "(1) Percentage of hydrocarbons with 7 or more carbon atoms in naphtha," the average molecular weight of hydrocarbons in naphtha was calculated using the following formula, along with the percentage of each hydrocarbon component (Sn) and relative molecular weight (Mn) of B1 and hydrocarbons with 1 to 15 carbon atoms.

[0097] Average molecular weight of hydrocarbons in naphtha = (S1 × M1 + S2 × M2 + ... S15 × M15) / B1 Sn (where n is an integer between 1 and 15): Percentage of hydrocarbon content (by mass) of a hydrocarbon with n carbon atoms. Mn (where n is an integer between 1 and 15): Relative molecular mass of a hydrocarbon with n carbon atoms. B1: Total percentage (by mass) of each component of hydrocarbons with 1 to 15 carbon atoms.

[0098] 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. Furthermore, hydrocarbons with a certain number of carbon atoms may be composed of multiple hydrocarbon components with different relative molecular masses. For example, a hydrocarbon with 5 carbon atoms is composed of six different hydrocarbons: isopentane, 2-methyl-1-butene, n-pentane, 2-pentene, 2-methyl-2-butene, and cyclopentane.

[0099] (3) Analysis of the content of sulfur-containing compounds in naphtha The sulfur content of sulfur-containing compounds in naphtha was measured using inductively coupled plasma atomic emission spectrometry (ICP-OES) to determine the sulfur content of the sulfur-containing compounds in terms of sulfur atoms. First, the sample for ICP-OES measurement was prepared according to the following procedure. After mixing 1 ml of naphtha and 8 ml of nitric acid in a Teflon container, the mixture was subjected to thermal decomposition using a microwave decomposition device (device name: MultiwavePRO, manufactured by Anton Paar) under the following conditions. The mixture was then diluted to a final volume of 25 ml with ultrapure water, and this was used as the sample for ICP-OES measurement. Microwave resolution conditions: Ramp (500W / 10 min) → Hold (500W / 10 min) → Ramp (1300W / 10 min) → Hold (1300W / 30 min) For the measurement sample, the concentration of sulfur atoms in naphtha (unit: mass ppm) was measured using ICP-OES (instrument name: iCAP6500 type, manufactured by Thermo Fisher Scientific, wavelength: S = 180.731 nm), and this was taken as the content of sulfur-containing compounds in terms of sulfur atoms. The calibration curve was prepared by the absolute calibration curve method using Sulfur Stndard for ICP (product name, manufactured by Aldrich).

[0100] (4) Calculation method of ΔE For the ethers used in the experimental examples, reference experimental examples, and comparative experimental examples, the absolute value of the difference in the charges of two carbon atoms bonded to the ether oxygen atom in the ether, ΔE [unit: e], was calculated according to the following procedure. Regarding the molecular structure of the ether, density functional theory (DFT) calculations were performed to calculate the charge values of the two carbon atoms. For the calculation conditions of DFT, def-TZVP was used as the basis function system, the COSMO solvation model (COnductor like Screening MOdel) was adopted as the solvent effect, and the Mulliken charge density analysis method (Population Analysis) was used as the analysis method. Next, for the two carbon atoms bonded to the oxygen atom of the ether bond in the ether, the absolute value of the difference ΔE (ΔE = |E1 - E2|) (unit: e) between the charge E1 of one carbon atom and the charge E2 of the other carbon atom was calculated. Here, "e" means the elementary charge of an electron, and e = 1.602176634×10 -19 [unit: C]. For example, when ΔE is 0.05 [unit: e], in SI units, ΔE = 0.05×1.602176634×10 -19 [unit: C].[[]END]] For the calculation of the above ΔE, the quantum chemistry calculation software "TURBOMOLE ver7.2" (manufactured by TURBOMOLE) and the graphical user interface "TmoleX ver4.4.1" for TURBOMOLE (manufactured by TURBOMOLE) were used.

[0101] (5) Calculation of methanol production ratio B The methanol generated from the thermal decomposition of naphtha is substantially contained in the condensed water obtained in the experimental examples, reference experimental examples, and comparative experimental examples, and is not contained in the gas components and oil components. Therefore, the methanol production ratio B of the condensed water obtained in the experimental examples, reference experimental examples, and comparative experimental examples was measured under the following conditions using a gas chromatography-mass spectrometry measurement device (GC / MS device) (device name: GCMS-QP2010Ultra, manufactured by Shimadzu Corporation). It was previously confirmed that no methanol is generated from the blank naphtha used in the experimental examples, reference experimental examples, and comparative experimental examples. <GC / MS Measurement Conditions> Carrier gas: Helium, linear velocity 40 cm / sec Column: SUPELCOWAX-10 (manufactured by Supelco, inner diameter 0.32 mm × length 60 m × film thickness 0.25 μm) Temperature (temperature increase condition): 50°C (holding time 5 minutes) → temperature increase at 20°C / min → 200°C (holding time 2.5 minutes) Inlet temperature: 200°C MS interface temperature: 200°C Ion source temperature: 200°C Sample amount: 0.5 μL Split ratio: 1:5 Measurement mode: SIM (m / z = 31)

[0102] The amount of methanol, which is a pyrolysis product, generated from the condensed water obtained in the experimental examples, reference experimental examples, and comparative experimental examples was quantified, and based on the calibration curve prepared in advance using a standard solution of methanol with a known concentration, the methanol production ratio B with respect to the added ether was determined from the following formula.

[0103] [Methanol production ratio B] = [Number of oxygen atoms in methanol in condensed water] ÷ [Number of oxygen atoms in ether added to blank naphtha]

[0104] That is, when the methanol production ratio B is 1.00, it means that all of the added ether was quantified as methanol. The number of oxygen atoms contained in the ether added here is one oxygen atom per molecule of the ether compound.

[0105] (6) Measurement of lower olefin yield The yield of lower olefins obtained by thermal decomposition of raw material naphtha was measured using a naphtha flow evaluation apparatus equipped with a SUS310S reaction tube, by the following method. As mentioned above, "lower olefins" refer to ethylene, propylene, butene (1-butene, 2-butene, and isobutene), and butadiene (1,2-butadiene and 1,3-butadiene). Naphtha and steam, as described later in the experimental examples, reference experimental examples, and comparative experimental examples, were supplied to the reaction tube (inner diameter 4 mm × outer diameter 6 mm) from the bottom of the reaction tube. 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 top of the reaction tube. The obtained thermal decomposition product was rapidly cooled to 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 the separated gas and separated liquid.

[0106] The obtained separated gas was quantified using separate gas chromatographs to determine the hydrogen, carbon monoxide, and carbon dioxide, which are thermal decomposition products of naphtha, as well as the hydrocarbons methane, ethane, ethylene, propane, propylene, propadiene, isobutane, n-butane, allene, 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"). Specifically, a gas chromatograph (model: GC-8A, manufactured by Shimadzu Corporation) was used for the quantitative determination of hydrogen. A gas chromatograph (model: GC-2014, manufactured by Shimadzu Corporation) was used for the quantitative determination of carbon monoxide, carbon dioxide, and the aforementioned hydrocarbons. The quantitative values ​​of hydrogen, carbon monoxide, carbon dioxide, hydrocarbons, and lower olefins measured in this way were denoted as X (hydrogen), X (carbon monoxide), X (carbon dioxide), X (hydrocarbons), and X (lower olefins) (unit: g), respectively.

[0107] Furthermore, using a gas chromatograph (model: GC-2014, manufactured by Shimadzu Corporation), the lower olefins contained in the oily separated liquid were quantified as thermal decomposition products of naphtha, and the quantified value was defined as Y (lower olefins) (unit: g). In addition, the hydrocarbons and hydrocarbons with boiling points between 150°C and 280°C were quantified, and the combined quantified values ​​were defined as Y (hydrocarbon compounds) (unit: g).

[0108] The yield of lower olefins (unit: mass%) was calculated using the following formula, with X (hydrogen), X (carbon monoxide), X (carbon dioxide), X (lower olefins), X (hydrocarbons), Y (lower olefins), and Y (hydrocarbon compounds) measured by the method described above between 60 and 420 minutes after the start of naphtha thermal decomposition. Lower Olefin Yield (Unit: wt%) = (X (lower olefin) + Y (lower olefin)) / (X (hydrogen) + X (carbon monoxide), X (carbon dioxide) + X (hydrocarbons) + Y (hydrocarbon compounds)) × 100

[0109] [Reference Experiment Example A-1-1] The raw material used is petroleum-derived naphtha (open-spec naphtha from Saudi Arabia; content of hydrocarbons with 7 or more carbon atoms: 13.1% by mass; average molecular weight of hydrocarbons: 79.20 g / mol; content of sulfur-containing compounds (in terms of sulfur atoms): 190 ppm by mass; specific gravity: 0.6636 g / cm³). 3To the mixture, 2-methoxybutane was added to a concentration of 50 ppm by mass as the oxygen atom content derived from the ether. Then, the mixture was thermally decomposed in a pyrolysis furnace in the presence of water vapor under the following thermal decomposition conditions. The resulting thermal decomposition product was rapidly cooled to 5°C, and gas-liquid separation was performed using a gas-liquid separator at 0.1 MPa (gauge pressure) and 5°C to obtain the gaseous component and the separated liquid. Furthermore, the separated liquid was separated into oil and condensed water using a separatory funnel at atmospheric pressure and room temperature.

[0110] <Thermal decomposition conditions> Naphtha flow rate: 83.1 g / hr Water vapor / naphtha mass ratio: 0.4 Residence time: 0.6 seconds Thermal decomposition temperature: 810℃ Pyrolysis pressure: 0.1 MPa (gauge pressure)

[0111] The methanol production ratio B of the condensate was measured using the method described above and is shown in Table 1 along with the value of ΔE. The relationship between ΔE and the methanol production ratio B is shown in Figure 1.

[0112] [Reference Experiment Examples A-1-2~A-1-3] Except for changing the ether oxygen atom content as shown in Table 1, gaseous components, oil, and condensed water were obtained and evaluated under the same conditions as in Comparative Experiment Example A-1-1. The evaluation results are shown in Table 1.

[0113] [Reference Experiment Example A-0] Except for not using 2-methoxybutane, gaseous components, oil, and condensed water were obtained and evaluated under the same conditions as in Reference Experiment Example A-1-1. The evaluation results are shown in Table 1.

[0114] [Reference Experiment Examples A-2 to A-3, Comparative Experiment Examples A-4 to A-7] Except for changing the type of ether and its content (in terms of ether oxygen atoms) as shown in Table 1, gaseous components, oil, and condensed water were obtained and evaluated under the same conditions as in Reference Experiment A-1. The evaluation results are shown in Table 1.

[0115] Reference Experiment Example A-1 refers to Reference Experiment Examples A-1-1 through A-1-3 listed in Table 1. Reference Experiment Example A-2 refers to Reference Experiment Examples A-2-1 through A-2-3 listed in Table 1. Reference Experiment Example A-3 refers to Reference Experiment Examples A-3-1 through A-3-3 listed in Table 1. In Tables 1 to 3 below, the content of the added ether in terms of ether oxygen atoms is referred to as the "oxygen atom concentration".

[0116] [Table 1]

[0117] [Reference Experiment Examples B-1 to B-3, Comparative Experiment Examples B-4 and B-7] In reference experiment example A-1, bio-derived naphtha was used instead of petroleum-derived naphtha (manufactured by AltAir Paramount, containing hydrocarbons with 7 or more carbon atoms: 43.9% by mass, average molar molecular weight of hydrocarbons: 88.28 g / mol, sulfur-containing compound content (in terms of sulfur atoms): 1 ppm by mass, specific gravity: 0.6700 g / cm³). 3 Except for using the same method as in Reference Experiment A-1, and changing the type of ether and the amount of ether-derived oxygen atoms as shown in Table 2, gaseous components, oil, and condensed water were obtained and evaluated in the same manner. The evaluation results are shown in Table 2. Note that Reference Experiment Example B-2 refers to Reference Experiment Examples B-2-1 through B-2-3 listed in Table 1.

[0118] [Reference Experiment Example B-0] Except for not using 2-methoxybutane, gaseous components, oil, and condensed water were obtained and evaluated under the same conditions as in Reference Experiment Example B-1. The evaluation results are shown in Table 2.

[0119] [Table 2]

[0120] [Experimental Example C-1] Instead of petroleum-derived naphtha in Reference Experiment Example A-1, a mixture of petroleum-derived naphtha and bio-derived naphtha (mass ratio 1:1) was used (concentration of hydrocarbons with 7 or more carbon atoms: 30.6% by mass, average molar molecular weight of hydrocarbons: 84.14 g / mol, content of sulfur-containing compounds (in terms of sulfur atoms): 100 ppm by mass, specific gravity: 0.6667 g / cm³). 3 Except for using the same method as in Reference Experiment A-1, and changing the type of ether and the amount of ether-derived oxygen atoms as shown in Table 3, gaseous components, oil, and condensed water were obtained and evaluated in the same manner. The evaluation results are shown in Table 3.

[0121] [Experimental Example C-0] Except for not using 2-methoxybutane, the gaseous components, oil, and condensed water were obtained and evaluated under the same conditions as in Experimental Example C-1. The evaluation results are shown in Table 3.

[0122] [Table 3]

[0123] Figure 1 plots experimental example C-1, as well as reference experimental examples A-1-1, A-2-1, A-3-1, B-1, B-2-1, and B-3, and comparative experimental examples A-4, A-7, B-4, and B-7.

[0124] A comparison of Reference Experiments B-1 to B-3 and Comparative Experiments B-4 and B-7 with Reference Experiments A-1 to A-3 and Comparative Experiments A-4 to A-7 reveals that naphtha derived from bio-based raw materials has a lower methanol production ratio B and is less likely to produce methanol compared to naphtha derived from fossil fuels. The reason for this is not entirely clear, but it is thought that naphtha derived from bio-based raw materials generally has a larger molecular weight of hydrocarbons and a lower partial pressure of these hydrocarbons compared to naphtha derived from fossil fuels. As a result, it is presumed that the side reaction that produces methanol from asymmetric ethers is suppressed in naphtha derived from bio-based raw materials, making it less likely to produce methanol even when thermally decomposed under thermal decomposition conditions compared to naphtha derived from fossil fuels. Furthermore, in all naphthas, ethers with a ΔE of 0.05 or higher tend to produce more methanol as the ΔE value increases.

[0125] From the comparison of reference experimental examples B-1 to B-3 and comparative experimental examples B-4 and B-7, as well as the comparison of reference experimental examples A-1 to A-3 and comparative experimental examples A-4 to A-7, it can be seen that there is a correlation between the ΔE value of ethers and the methanol production ratio B, and that ethers with an asymmetric structure with respect to the ether oxygen atom have a high methanol production ratio B and are more likely to produce methanol. Furthermore, it can be seen that ethers with a ΔE of 0.05 or higher tend to produce more methanol as the ΔE value increases.

[0126] Furthermore, as shown in Reference Experiment Example B-2 in Table 2, ethers having an asymmetric structure with respect to the oxygen atoms constituting the ether bond showed nearly identical methanol production ratios when the ether oxygen atom concentration was 50 ppm, 500 ppm, and 5,000 ppm, under conditions where the ether oxygen atom concentration was 20,000 ppm or less. The reason for this is presumed to be that ethers with an asymmetric structure have a large ΔE, resulting in a large charge imbalance between the two carbon atoms bonded to the ether oxygen atom, making them more likely to decompose under thermal decomposition conditions and produce methanol.

[0127] Table 4 shows the breakdown of lower olefin yields for Reference Experimental Examples A-0, B-0, and C-0. Lower olefins refer to ethylene, propylene, butene (1-butene, 2-butene, and isobutene), and butadiene (1,2-butadiene and 1,3-butadiene).

[0128] [Table 4]

[0129] Table 4 shows that the yield of each of the lower olefins—ethylene, propylene, butene, and butadiene—increases as the proportion of bio-derived naphtha in the naphtha increases. Therefore, when mixing two or more types of naphtha with different properties as raw materials for lower olefin production, for example, naphtha derived from bio-based raw materials and naphtha derived from fossil fuels, it is possible to produce a high-value lower olefin with suppressed methanol production using this mixed naphtha by mixing them so that the content of ethers having an asymmetric structure with respect to the ether oxygen atom is below a predetermined value, and further by mixing them so that the content of hydrocarbons with 7 or more carbon atoms is above a predetermined value.

Claims

1. A method for mixing naphtha derived from biomaterials and naphtha derived from fossil fuels, The method includes mixing the naphtha such that the content of asymmetric ethers in the mixed naphtha is 1,000 ppm by mass or less, in terms of ether oxygen atoms. The aforementioned ether is a monoether, A mixing method in which one of the two carbon atoms bonded to the oxygen atom constituting the ether bond of the ether is a carbon atom derived from a methyl group.

2. The mixing method according to claim 1, wherein the naphtha after mixing is mixed such that the content of hydrocarbons having 7 or more carbon atoms in the naphtha after mixing is 14.0% by mass or more, relative to 100% of the total mass of the naphtha after mixing.

3. A method for mixing two or more naphthas with different properties, The proportion of hydrocarbons with 7 or more carbon atoms in the naphtha after mixing is 14.0% by mass or more, relative to 100% of the total mass of the naphtha after mixing, and The method includes mixing the naphtha such that the content of asymmetric ethers in the mixed naphtha is 1,000 ppm by mass or less, in terms of ether oxygen atoms. The aforementioned ether is a monoether, A mixing method in which one of the two carbon atoms bonded to the oxygen atom constituting the ether bond of the ether is a carbon atom derived from a methyl group.

4. The mixing method according to claim 3, wherein the two or more types of naphtha include at least naphtha derived from biomaterials and naphtha derived from fossil fuels.

5. The mixing method according to claim 1 or 3, wherein the ether content in the naphtha after mixing is 100 ppm by mass or less in terms of ether oxygen atoms.

6. The mixing method according to claim 1 or 3, wherein the ether content in the naphtha after mixing is 50 ppm by mass or less in terms of ether oxygen atoms.

7. The mixing method according to claim 1 or 3, wherein the ether is any one of 2-methoxybutane, methoxycyclopentane, or 1-methoxypropane.

8. The mixing method according to claim 1 or 3, wherein the naphtha after mixing contains a sulfur-containing compound, and the naphtha after mixing is mixed such that the amount of the sulfur-containing compound contained in the naphtha after mixing is 180 ppm by mass or less in terms of sulfur atoms.

9. The mixing method according to claim 1 or 3, wherein the naphtha after mixing is mixed such that the average molecular weight of the hydrocarbons contained therein is 80.0 g / mol or more.

10. The specific gravity of the naphtha after mixing was 0.6640 g / cm³. ３ More than 0.6700g / cm ３ The mixing method according to claim 1 or 3, wherein the mixture is mixed such that the following occurs.

11. The mixing method according to claim 1 or 4, wherein the naphtha derived from the bio-raw material is naphtha derived from non-edible biomass and / or non-fossil fuels.

12. The mixing method according to claim 1 or 3, wherein the ether content in the naphtha after mixing is 0.1 ppm by mass or more in terms of ether oxygen atoms.

13. The mixing method according to claim 1 or 3, wherein the ether has an 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, determined by density functional theory for two carbon atoms bonded to the oxygen atom constituting the ether bond, which is 0.05 [unit: e] or more. However, e represents the elementary electron weight, and e = 1.602176634 × 10⁻¹⁴ －１９ [Unit: C]

14. A method for producing a lower olefin composition, comprising thermally decomposing the naphtha after mixing obtained by the mixing method described in claim 1 or 3.

15. A method for producing a lower olefin composition according to claim 14, wherein the lower olefin comprises propylene.

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