Method for producing light olefin

Abstract

Disclosed is a method for producing a light olefin, the method comprising: a cracking step for introducing a naphtha starting material into a cracking furnace so as to obtain a naphtha cracking fraction; an ethanol conversion step for introducing a starting material that contains ethanol into a reactor and bringing the starting material into contact with a catalyst so as to obtain an ethanol conversion fraction that contains ethylene and propylene; a merging step for merging at least some of the naphtha cracking fraction or a fraction derived therefrom with at least some of the ethanol conversion fraction or a fraction derived therefrom so as to obtain a combined fraction; and a cryogenic separation step for introducing the combined fraction or a fraction derived therefrom into a cryogenic separation facility so as to separate ethylene and propylene. In the merging step, the content CE of ethylene and propylene in the ethanol conversion fraction or a fraction derived therefrom and the content CC of ethylene and propylene in the naphtha cracking fraction or a fraction derived therefrom satisfy the relational expression (A): CE > CC.

Description

Light olefin production method

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

[0002] Cracking naphtha obtained from crude oil has been used to produce a variety of chemical products, including raw materials for monomers. Among these chemical products, light olefins such as ethylene and propylene are in particularly high demand due to their wide variety of uses. Since propylene is particularly valuable, research has been conducted into methods for selectively producing propylene from naphtha, and steam cracking is a known representative example (see, for example, Patent Document 1).

[0003] As a method for obtaining light olefins from alcohols, a method using a catalyst such as zeolite has been reported. For example, Patent Document 2 proposes a method for producing propylene efficiently and stably by contacting at least one raw material selected from ethylene and ethanol with a catalyst containing a medium pore size zeolite in a fluidized bed reactor.

[0004] Japanese Patent Application Laid-Open No. 2016-117800 International Publication No. WO2009 / 037992

[0005] An object of the present invention is to provide a method for producing light olefins, which can efficiently purify olefins having 2 or 3 carbon atoms.

[0006] The present inventors have found that the above-mentioned problems can be solved by controlling the composition of each fraction in a process for producing light olefins.

[0007] The present invention includes the following embodiments: <1> A method for producing a naphtha cracked fraction comprising: a cracking step of introducing a naphtha feedstock into a cracking furnace to obtain a naphtha cracked fraction; an ethanol conversion step of introducing an ethanol-containing feedstock into a reactor and contacting it with a catalyst to obtain an ethanol-converted fraction containing ethylene and propylene; a combining step of combining at least a portion of the naphtha cracked fraction or a fraction derived therefrom with at least a portion of the ethanol-converted fraction or a fraction derived therefrom to obtain a combined fraction; and a cryogenic separation step of introducing the combined fraction or a fraction derived therefrom into cryogenic separation equipment to separate ethylene and propylene, wherein the ethylene and propylene content C of the ethanol-converted fraction or a fraction derived therefrom in the combining step is 0.05%. Ｅ and the content C of ethylene and propylene in the naphtha cracking fraction or a fraction derived therefrom. Ｃ The relationship is expressed by the formula (A): Ｅ >C Ｃ <2> A method for producing a light olefin that satisfies the above condition (A). Ｅ and the content C Ｃ The difference between Ｅ -C Ｃ <3> The method for producing light olefins according to <1>, wherein the propylene / ethylene mass ratio P / E in the ethanol-converted fraction is 5% by mass or more. Ｅ and P / E in the naphtha cracking fraction. Ｃ The relationship is expressed by the formula (α): −0.25<(P / E Ｅ -P / E Ｃ <4> The method for producing a light olefin according to <1> or <2>, wherein the ethylene and propylene contents C in the ethanol-converted fraction satisfy the following condition: <0.30 ... (α) Ｅ＿ＡＰ and the content C of ethylene and propylene in the naphtha cracking fraction Ｃ＿ＡＰ The relationship is expressed by the formula (β-1): |C Ｅ＿ＡＰ -C Ｃ＿ＡＰ<5> A method for producing light olefins according to any one of <1> to <3>, which satisfies the following condition: |<20 mass% ... (β-1) <5> A method for producing light olefins according to any one of <1> to <3>, which comprises: a cracking step of introducing a naphtha feedstock into a cracking furnace to obtain a naphtha cracked fraction; an ethanol conversion step of introducing an ethanol-containing feedstock into a reactor and bringing it into contact with a catalyst to obtain an ethanol-converted fraction containing ethylene and propylene; a combining step of combining at least a portion of the naphtha cracked fraction or a fraction derived therefrom with at least a portion of the ethanol-converted fraction or a fraction derived therefrom to obtain a combined fraction; and a cryogenic separation step of introducing the combined fraction or a fraction derived therefrom into cryogenic separation equipment to separate ethylene and propylene, wherein the propylene / ethylene mass ratio P / E in the ethanol-converted fraction is 0.05 to 0.15. Ｅ and P / E in the naphtha cracking fraction. Ｃ The relationship is expressed by the formula (α): −0.25<(P / E Ｅ -P / E Ｃ ) < 0.30 ... (α), and the ethylene and propylene contents C in the ethanol-converted fraction are Ｅ＿ＡＰ and the content C of ethylene and propylene in the naphtha cracking fraction Ｃ＿ＡＰ The relationship is expressed by the formula (β-1): |C Ｅ＿ＡＰ -C Ｃ＿ＡＰ <6> A method for producing a light olefin, wherein the ethylene and propylene contents C in the ethanol-converted fraction satisfy the following relationship: |<20 mass% ... (β-1). Ｅ＿ＡＰ and the content C of ethylene and propylene in the naphtha cracking fraction Ｃ＿ＡＰ The relationship is expressed by the formula (β-2): 0≦(C Ｅ＿ＡＰ -C Ｃ＿ＡＰ) <20% by mass ... (β-2). <7> A method for producing light olefins according to any one of <1> to <6>, comprising a first cooling step of introducing the naphtha cracked fraction or the combined fraction into a first cooling tower to obtain a first cooled fraction mainly containing olefins having 6 or less carbon atoms. <8> A method for producing light olefins according to any one of <1> to <7>, comprising a second cooling step of introducing the naphtha cracked fraction, the combined fraction, or a fraction derived therefrom into a second cooling tower to obtain a second cooled fraction mainly containing olefins having 4 or less carbon atoms. <9> A method for producing light olefins according to any one of <1> to <8>, comprising a third cooling step of introducing the ethanol converted fraction into a third cooling tower to obtain a cooled ethanol converted fraction mainly containing olefins having 6 or less carbon atoms. <10> The method for producing light olefins according to <9>, comprising a compression separation step of pressurizing the cooled ethanol-converted fraction with a compressor to obtain a light ethanol-converted fraction mainly containing olefins having 3 or less carbon atoms as a gas component, and a heavy ethanol-converted fraction mainly containing olefins having 4 or more carbon atoms as a liquid component. <11> The method for producing light olefins according to <10>, comprising a recycling step of introducing at least a portion of the heavy ethanol-converted fraction into the reactor as part of the raw material. <12> The method for producing light olefins according to any one of <1> to <11>, comprising a washing step of introducing the combined fraction or a fraction derived therefrom into a soda wash tower after the combining step to obtain a washed fraction. <13> The method for producing light olefins according to any one of <1> to <12>, comprising a first compression step of pressurizing the fraction after the second cooling step and before the cryogenic separation step. <14> The method for producing light olefins according to any one of <1> to <12>, comprising a first compression step of pressurizing the fraction after the second cooling step and before the cryogenic separation step. <15> The method for producing light olefins according to <1>, comprising a first compression step of compressing the fraction after the second cooling step and before the cryogenic separation step. <16> The method for producing light olefins according to <1>, comprising a first compression step of compressing the fraction after the second cooling step and before the cryogenic separation step. <17> The method for producing light olefins according to <1>, comprising a first compression step of compressing the fraction after the second cooling step and before the cryogenic separation step. <18> The method for producing light olefins according to <1>, comprising a first compression step of compressing the fraction after the second cooling step and before the cryogenic separation step. <19> The method for producing light olefins according to <10>, comprising a first compression step of compressing the fraction after the second cooling step and before the cryogenic separation step. <20> The Ｅ and a ratio O of the amount of hydrogen and methane to the total amount of ethylene and propylene in the naphtha cracking fraction. Ｃ The relationship is expressed by the formula (1): Ｅ <O Ｃ...(1) <15> A method for producing light olefins according to any one of <1> to <14>, which satisfies any one of the following (1) to (5): (1) A first cooling step of introducing the naphtha cracked fraction into a first cooling tower to obtain a first cooled fraction mainly containing olefins having 6 or less carbon atoms, and a second cooling step of introducing the first cooled fraction into a second cooling tower to obtain a second cooled fraction mainly containing olefins having 4 or less carbon atoms, wherein in the combining step, at least a portion of the second cooled fraction and at least a portion of the ethanol converted fraction or a fraction derived therefrom are combined. (2) A first cooling step of introducing the naphtha cracking fraction into a first cooling tower to obtain a first cooled fraction mainly containing olefins having a carbon number of 6 or less; and a second cooling step of introducing the combined fraction or a fraction derived therefrom into a second cooling tower to obtain a second cooled fraction mainly containing olefins having a carbon number of 4 or less, wherein at least a portion of the first cooled fraction and at least a portion of the ethanol conversion fraction or a fraction derived therefrom are combined in the combining step. (3) The method includes: a first cooling step of introducing the naphtha cracked fraction into a first cooling tower to obtain a first cooled fraction mainly containing olefins having a carbon number of 6 or less; a second cooling step of introducing the first cooled fraction into a second cooling tower to obtain a second cooled fraction mainly containing olefins having a carbon number of 4 or less; a circulation step of introducing at least a portion of the second heavy fraction obtained in the second cooling step, the second heavy fraction mainly containing hydrocarbons having a carbon number of 5 or more, into the second cooling tower; and a first introducing step of introducing the combined fraction into the second cooling tower, wherein in the combining step, at least a portion of the second heavy fraction and at least a portion of the ethanol converted fraction or a fraction derived therefrom are combined. (4) A first cooling step of introducing the combined fraction or a fraction derived therefrom into a first cooling tower to obtain a first cooled fraction mainly containing olefins having a carbon number of 6 or less; and a second cooling step of introducing the first cooled fraction into a second cooling tower to obtain a second cooled fraction mainly containing olefins having a carbon number of 4 or less, wherein at least a portion of the naphtha cracked fraction and at least a portion of the ethanol converted fraction or a fraction derived therefrom are combined in the combining step.(5) The method includes: a first cooling step of introducing the naphtha cracked fraction into a first cooling tower to obtain a first cooled fraction mainly containing olefins having a carbon number of 6 or less; a second cooling step of introducing the first cooled fraction into a second cooling tower to obtain a second cooled fraction mainly containing olefins having a carbon number of 4 or less; a circulation step of introducing at least a portion of the second heavy fraction obtained in the second cooling step, which mainly contains hydrocarbons having a carbon number of 5 or more, into the first cooling tower; and a second introducing step of introducing the combined fraction into the first cooling tower, wherein in the combining step, at least a portion of the second heavy fraction and at least a portion of the ethanol converted fraction or a fraction derived therefrom are combined.

[0008] According to the present invention, a method for producing light olefins, which can efficiently purify olefins having 2 or 3 carbon atoms, can be provided.

[0009] FIG. 1 is a block diagram showing an outline of the method for producing light olefins according to this embodiment. FIG. 2 is a schematic configuration diagram of production equipment used in the method for producing light olefins according to this embodiment. FIG. 3 is a schematic configuration diagram of a fixed-bed single-stage adiabatic reactor. FIG. 4 is a schematic configuration diagram of production equipment used in the method for producing light olefins according to this embodiment. FIG. 5 is a schematic configuration diagram of production equipment used in the method for producing light olefins according to this embodiment. FIG. 6 is a schematic configuration diagram of production equipment used in the method for producing light olefins according to this embodiment. FIG. 7 is a schematic configuration diagram of production equipment used in the method for producing light olefins according to this embodiment. FIG. 8 is a schematic configuration diagram of production equipment used in the method for producing light olefins according to this embodiment. FIG. 9 is a schematic configuration diagram of production equipment used in the method for producing light olefins according to this embodiment. FIG. 10 is a schematic configuration diagram of production equipment used in the method for producing light olefins according to this embodiment. FIG. 11 is a schematic configuration diagram of production equipment used in the method for producing light olefins according to this embodiment. FIG. 12 is a schematic configuration diagram of production equipment used in the method for producing light olefins according to this embodiment. FIG. 13 is a schematic configuration diagram of production equipment used in the method for producing light olefins according to this embodiment. FIG. 14 is a schematic configuration diagram of production equipment used in a conventional front-end demethanolizer type production method for light olefins. FIG. 15 is a schematic configuration diagram of production equipment used in a light olefin production method according to this embodiment. FIG. 16 is a schematic configuration diagram of production equipment used in a light olefin production method according to this embodiment. FIG. 17 is a schematic configuration diagram of production equipment used in a light olefin production method according to this embodiment. FIG. 18 is a schematic configuration diagram of production equipment used in a light olefin production method according to this embodiment. FIG. 19 is a schematic configuration diagram of production equipment used in a light olefin production method according to this embodiment. FIG. 20 is a schematic configuration diagram of production equipment used in a light olefin production method according to this embodiment. FIG. 21 is a schematic configuration diagram of production equipment used in a light olefin production method according to this embodiment. FIG. 22 is a schematic configuration diagram of production equipment used in a light olefin production method according to this embodiment.Fig. 23 is a schematic configuration diagram of production equipment used in the method for producing light olefins according to this embodiment. Fig. 24 is a schematic configuration diagram of production equipment used in the method for producing light olefins according to this embodiment. Fig. 25 is a schematic configuration diagram of production equipment used in the method for producing light olefins according to this embodiment. Fig. 26 is a schematic configuration diagram of production equipment used in a conventional front-end depropanizer type method for producing light olefins.

[0010] The present invention will be described in detail below. Note that the present invention is not limited to the following embodiments (present embodiments), and can be practiced in various modifications within the scope of the gist thereof.

[0011] Numerical ranges indicated using "to" indicate ranges that include the numerical values ​​before and after "to" as the minimum and maximum values, respectively. In the numerical ranges described in stages in this specification, the upper limit or lower limit of a numerical range in one stage can be arbitrarily combined with the upper limit or lower limit of a numerical range in another stage.

[0012] Although modifiers such as "first" and "second" may be used to distinguish elements, such modifiers do not necessarily indicate any particular order.

[0013] First, the method for producing light olefins according to this embodiment will be outlined. Fig. 1 is a block diagram showing an outline of the method for producing light olefins according to this embodiment. As shown in Fig. 1, the production method according to this embodiment includes a naphtha cracking process N and an ethanol conversion process E.

[0014] In the naphtha cracking process N, naphtha is thermally cracked in cracking N1, then subjected to naphtha cracked fraction refining process N2, and ethylene and propylene are separated by cryogenic separation N3. In cryogenic separation N3, the treated fraction is cooled, ethylene and propylene are liquefied, and gaseous methane and hydrogen are separated from liquid olefins. In cryogenic separation N3, it is necessary to liquefy a relatively light fraction among the naphtha cracked fraction, so that the fraction must be pressurized and cooled, and a large amount of energy is required for the process.

[0015] An existing naphtha cracker facility may be used in the naphtha cracking process N. For example, an ethanol-converted fraction obtained by the ethanol conversion process described below is introduced into the naphtha cracker facility.

[0016] The ethanol conversion process E includes, for example, a step of converting a raw material containing ethanol into an ethanol conversion fraction containing ethylene, propylene, and the like. In the ethanol conversion process E, by using bioethanol as a raw material, a plant-derived ethanol conversion fraction can be obtained. By connecting the ethanol conversion process E to an existing facility that performs the naphtha cracking process N, a portion of the petroleum-derived raw material can be replaced with a plant-derived raw material. Furthermore, for example, by controlling the operating conditions of the ethanol conversion process E, the raw material can be converted to a plant-derived raw material without changing the production amount of the target compound.

[0017] In this embodiment, the ethanol converted fraction obtained by the ethanol conversion process E or a fraction derived therefrom is introduced into the naphtha cracking process N, thereby reducing the load on the cryogenic separation N3.

[0018] The naphtha cracking process N may include any steps, and includes, for example, the cracking step, the first cooling step, the second cooling step, the combining step, the first compression step, the washing step, and the cryogenic separation step, which will be described later.

[0019] The ethanol conversion process E may include any steps, and includes, for example, the ethanol conversion step, the purification step, the third cooling step, the second compression step, the distillation step, and the recycling step, which will be described later.

[0020] The "light olefin" refers to at least one selected from the group consisting of ethylene and propylene. The light olefin is the target compound in the production method according to this embodiment, and from the viewpoint of utilizing the characteristics of the production method according to this embodiment, propylene is preferred.

[0021] In relation to a specific fraction, "a fraction derived therefrom" means a fraction that has undergone some process, such as distillation, cooling, or compression, with respect to the specific fraction.

[0022] With respect to a component of a fraction, the term "mainly comprise" means that the fraction contains more than 50 mass % of the component.

[0023] The content of ethylene and propylene in the ethanol-converted fraction or the fraction derived therefrom in the combining step is defined as C Ｅ The content of ethylene and propylene in the ethanol-converted fraction obtained from the reaction step and not subjected to a separation process is represented by C Ｅ＿ＡＰ The content of ethylene and propylene in the naphtha cracking fraction or the fraction derived therefrom in the combining step is expressed as C Ｃ The content of ethylene and propylene in the naphtha cracked fraction obtained from the cracking process and not subjected to a separation process is expressed as C Ｃ＿ＡＰ It is expressed as:

[0024] The method for producing light olefins of this embodiment includes Embodiment A and Embodiment B shown below.

[0025] In general, in a method for producing light olefins by cracking, various components are separated and purified from a naphtha cracked fraction obtained by cracking naphtha to obtain light olefins. Various processes can be applied to this process, and one method for producing light olefins is to finally liquefy the fraction from which high-boiling components have been removed by cryogenic separation, and remove off-gases such as hydrogen and methane to obtain olefins having 2 or 3 carbon atoms, such as ethylene and propylene. In this case, further improvement in processing efficiency is required.

[0026] An object of embodiment A is to provide a method for producing light olefins that improves the processing efficiency of olefins having 2 or 3 carbon atoms.

[0027] The present inventors have found that the above-mentioned problems can be solved by controlling the composition of each fraction in a process for producing light olefins.

[0028] In the light olefin production method according to embodiment A, the content C of ethylene and propylene in the ethanol-converted fraction or a fraction derived therefrom in the confluence step is Ｅ and the content C of ethylene and propylene in the naphtha cracking fraction or a fraction derived therefrom. Ｃ The relationship is expressed by the formula (A): C Ｅ >C Ｃ ...(A) is satisfied. By satisfying formula (A) in this way, the efficiency of treating olefins having 2 or 3 carbon atoms can be increased. Furthermore, by satisfying formula (A), the energy load in the cryogenic separation step in particular can be reduced. In order to satisfy formula (A), for example, a step of cooling the ethanol-converted fraction prior to joining the naphtha cracked fraction can be provided, thereby reducing the C Ｅ It is preferable to design it so as to increase

[0029] In the naphtha cracking process, naphtha is cracked, then refined, and light olefins are obtained in a cryogenic separation process. In the cryogenic separation process, the fraction introduced into the cryogenic separation process is pressurized by a compressor and cooled to below the boiling point of ethylene to liquefy the light olefins, and the light olefins are separated from off-gases such as hydrogen and methane. In this pressurization and cooling process, the energy consumption increases depending on the flow rate of the fraction introduced into the cryogenic separation process. In other words, the ethylene and propylene content C of the ethanol conversion fraction is Ｅ and the content C of ethylene and propylene in the naphtha cracking fraction Ｃ By setting the relationship between and within the above range, the amount of compounds other than light olefins introduced into the cryogenic separation step can be reduced, and the contents of ethylene and propylene in the fraction introduced into the cryogenic separation step can be increased. When the production amount of light olefins is constant, the flow rate of the fraction introduced can be reduced, thereby making it possible to perform cryogenic separation more efficiently. Furthermore, although the maximum throughput of a compressor is determined by its size, by increasing the content of light olefins in the fraction introduced into the cryogenic separation step, it is possible to increase the production amount of light olefins without, for example, changing the size of the compressor or performing modification work.

[0030] From the viewpoint of light olefin production efficiency, the naphtha cracking fraction in the combining step preferably has a high content of light olefins, for example, C Ｃ is preferably 10% by mass or more, more preferably 20% by mass or more, and even more preferably 30% by mass or more.

[0031] In the light olefin production method according to embodiment A, the content C Ｅ and content C Ｃ The difference between Ｅ -C Ｃ ) is preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 20% by mass or more. Ｅ -C Ｃ The upper limit of the content of the hydroxybenzoate is not particularly limited, but may be, for example, 70 mass % or less.

[0032] Generally, in the production of light olefins by cracking, various components are separated and purified from naphtha cracked fractions obtained by cracking naphtha to obtain light olefins. The production volume of light olefins fluctuates due to the conversion of naphtha into ethanol, and if the operating rate of the refining system fluctuates, operating efficiency will be significantly reduced due to compressor surging and distillation column flooding.

[0033] In the light olefin production method according to embodiment B, the propylene / ethylene mass ratio P / E in the ethanol-converted fraction is Ｅ and the propylene / ethylene mass ratio P / E in the naphtha cracking fraction Ｃ The relationship is expressed by the formula (α): −0.25<(P / E Ｅ -P / E Ｃ ) < 0.30 ... (α) and the ethylene and propylene contents C in the ethanol-converted fraction are Ｅ＿ＡＰ and the content C of ethylene and propylene in the naphtha cracking fraction Ｃ＿ＡＰ The relationship is expressed by the formula (β-1): |C Ｅ＿ＡＰ -C Ｃ＿ＡＰ|<20 mass% ... (β-1) is satisfied. In this way, by simultaneously satisfying formula (α) and formula (β-1), the operating rate of the purification system can be stabilized. In order to simultaneously satisfy formula (α) and formula (β-1), it is preferable to adjust the reaction temperature (particularly the reactor outlet temperature), the amount of catalyst, and the catalyst in the ethanol conversion step. Compared to the naphtha cracking step, the ethanol conversion step has a higher degree of variation in each variable (P / E) due to changes in these conditions. Ｅ ), C Ｅ＿ＡＰ Since the range of fluctuations in the ethanol conversion process is large, it is more effective to change the conditions of the ethanol conversion process.

[0034] In the naphtha cracking process, as described above, light olefins are purified by cryogenic separation. If the ratio of propylene, ethylene, and other components introduced into the cryogenic separation step is significantly different from the ratio before the ethanol conversion fraction or at least a portion of the fraction derived therefrom is introduced, problems such as compressor surging and distillation column flooding occur due to fluctuations in the operating rate of each refining equipment. Therefore, in order to efficiently refine light olefins, it is necessary to keep the operating rate of each refining equipment constant. In other words, the propylene / ethylene mass ratio P / E in the ethanol conversion fraction is Ｅ and the propylene / ethylene mass ratio P / E in the naphtha cracking fraction Ｃ and the content C of ethylene and propylene in the ethanol-converted fraction is set to the range as shown in the above formula (α), Ｅ＿ＡＰ and the content C of ethylene and propylene in the naphtha cracking fraction Ｃ＿ＡＰ By setting the relationship between the above and the above in the range of the above formula (β-1), it is possible to efficiently carry out the purification of light olefins.

[0035] Among the methods for producing light olefins according to embodiment B, the method according to embodiment B has excellent purification efficiency of light olefins, and therefore, the content C of ethylene and propylene in the ethanol conversion fraction is Ｅ＿ＡＰ and the content C of ethylene and propylene in the naphtha cracking fraction Ｃ＿ＡＰ The relationship is expressed by the formula (β-2): 0≦(C Ｅ＿ＡＰ -C Ｃ＿ＡＰ ) < 20 mass % (β-2) is preferably satisfied.

[0036] In the method for producing light olefins according to embodiment A, the load of the propylene purification facility or the ethylene purification facility is kept constant so as not to impair the purification efficiency of light olefins. Therefore, the propylene / ethylene mass ratio P / E in the ethanol-converted fraction is preferably kept constant. Ｅ and the propylene / ethylene mass ratio P / E in the naphtha cracking fraction Ｃ It is preferable that the relationship between the ethylene and propylene contents C in the ethanol-converted fraction satisfies the above-mentioned formula (α). Ｅ＿ＡＰ and the content C of ethylene and propylene in the naphtha cracking fraction Ｃ＿ＡＰ It is preferable that the relationship satisfies the above-mentioned formula (β-1).

[0037] By replacing the naphtha cracked fraction produced by the naphtha cracking process N with the ethanol converted fraction produced by the ethanol conversion process E, it is possible to convert petroleum feedstocks to biomass feedstocks, particularly when bioethanol is used as a feedstock. On the other hand, as the substitution rate with the ethanol converted fraction increases, the production volume of each product fluctuates, and problems such as compressor surging and distillation column flooding occur in the refining equipment. When the above formula (α) or the above formula (β-1) is satisfied, the substitution rate of the ethanol converted fraction can be increased while suppressing the occurrence of the above problems. Because of its excellent environmental friendliness, the substitution rate of the ethanol converted fraction is preferably 10% by mass or more, more preferably 20% by mass or more, and even more preferably 30% by mass or more. The substitution rate of the ethanol converted fraction is calculated using the following formula: (Substitution rate of the ethanol converted fraction) = (Amount of ethylene produced in the ethanol converted fraction) / [(Amount of ethylene produced in the ethanol converted fraction) + (Amount of ethylene produced in the naphtha cracked fraction)]

[0038] Embodiments A and B relate to the composition of the product in either the cracking step or the ethanol conversion step, but the purification step of each fraction having such a composition, i.e., how the fraction derived from the cracking step and the fraction derived from the ethanol conversion step are joined and purified, is not particularly limited, and can be arbitrarily combined with, for example, the first, second, third, fourth, and fifth embodiments shown below.

[0039] The method for producing light olefins according to the first embodiment includes: a cracking step of introducing a naphtha feedstock into a cracking furnace to obtain a naphtha cracked fraction; a first cooling step of introducing the naphtha cracked fraction into a first cooling tower to obtain a first cooled fraction mainly containing olefins having 6 or fewer carbon atoms; a second cooling step of introducing the first cooled fraction into a second cooling tower to obtain a second cooled fraction mainly containing olefins having 4 or fewer carbon atoms; an ethanol conversion step of introducing an ethanol-containing feedstock into a reactor and contacting it with a catalyst to obtain an ethanol-converted fraction containing ethylene and propylene; a combining step of combining at least a portion of the second cooled fraction with at least a portion of the ethanol-converted fraction or a fraction derived therefrom to obtain a combined fraction; and a cryogenic separation step of introducing the combined fraction or a fraction derived therefrom into cryogenic separation equipment to separate ethylene and propylene.

[0040] In the method for producing light olefins according to the first embodiment, the content C of ethylene and propylene in the ethanol-converted fraction or a fraction derived therefrom in the confluence step is Ｅ and the content C of ethylene and propylene in the naphtha cracking fraction or a fraction derived therefrom. Ｃ The relationship is expressed by the formula (A): C Ｅ >C Ｃ It is preferable that the following expression (A) is satisfied. As a result, according to the method for producing light olefins according to the first embodiment, the efficiency of treating olefins having 2 or 3 carbon atoms can be improved. The expression (A) and preferred aspects are as shown in the above-mentioned embodiment A.

[0041] In the method for producing light olefins according to the first embodiment, the propylene / ethylene mass ratio P / E in the ethanol-converted fraction is Ｅ and the propylene / ethylene mass ratio P / E in the naphtha cracking fraction Ｃ The relationship is expressed by the formula (α): −0.25<(P / E Ｅ -P / E Ｃ ) < 0.30 ... (α) and the ethylene and propylene contents C in the ethanol-converted fraction are Ｅ＿ＡＰ and the content C of ethylene and propylene in the naphtha cracking fraction Ｃ＿ＡＰ The relationship is expressed by the formula (β-1): |C Ｅ＿ＡＰ -C Ｃ＿ＡＰ It is preferable that the following relationship is satisfied: |<20 mass% ... (β-1). As a result, according to the method for producing light olefins according to the first embodiment, the availability of the refining system can be stabilized. Formula (α), Formula (β-1) and preferred aspects are as shown in the above-mentioned embodiment B.

[0042] As shown in the combining step in the first embodiment, after producing a naphtha cracked fraction, components having a carbon number of more than 6 are removed in a first cooling step, and components having a carbon number of more than 4 are further removed in a second cooling step to produce a second cooled fraction, which is then combined with the ethanol converted fraction or a fraction derived therefrom. When light olefins produced by naphtha cracking are replaced by ethanol conversion and combined in this manner, the mass flow rates introduced into the first and second cooling steps can be reduced compared to before the replacement, and the amount of contact refrigerant required for cooling can be reduced, thereby reducing the energy required for the treatments in these steps. Furthermore, when combined in this manner in addition to the light olefins produced by naphtha cracking, the production amount of light olefins can be increased without increasing the load on the first and second cooling steps.

[0043] The method for producing light olefins according to the second embodiment includes: a cracking step of introducing a naphtha feedstock into a cracking furnace to obtain a naphtha cracked fraction; a first cooling step of introducing the naphtha cracked fraction into a first cooling tower to obtain a first cooled fraction mainly containing olefins having 6 or fewer carbon atoms; an ethanol conversion step of introducing an ethanol-containing feedstock into a reactor and contacting it with a catalyst to obtain an ethanol-converted fraction containing ethylene and propylene; a combining step of combining at least a portion of the first cooled fraction with at least a portion of the ethanol-converted fraction or a fraction derived therefrom to obtain a combined fraction; a second cooling step of introducing the combined fraction or a fraction derived therefrom into a second cooling tower to obtain a second cooled fraction mainly containing olefins having 4 or fewer carbon atoms; and a cryogenic separation step of introducing the combined fraction or a fraction derived therefrom into cryogenic separation equipment to separate ethylene and propylene.

[0044] In the method for producing light olefins according to the second embodiment, the content C of ethylene and propylene in the ethanol-converted fraction or a fraction derived therefrom in the confluence step is Ｅ and the content C of ethylene and propylene in the naphtha cracking fraction or a fraction derived therefrom. Ｃ The relationship is expressed by the formula (A): C Ｅ >C Ｃ It is preferable that the following expression (A) is satisfied. As a result, according to the method for producing light olefins according to the second embodiment, the efficiency of treating olefins having 2 or 3 carbon atoms can be improved. The expression (A) and preferred aspects are as shown in the above-mentioned embodiment A.

[0045] In the method for producing light olefins according to the second embodiment, the propylene / ethylene mass ratio P / E in the ethanol-converted fraction is Ｅ and the propylene / ethylene mass ratio P / E in the naphtha cracking fraction Ｃ The relationship is expressed by the formula (α): −0.25<(P / E Ｅ -P / E Ｃ ) < 0.30 ... (α) and the ethylene and propylene contents C in the ethanol-converted fraction are Ｅ＿ＡＰ and the content C of ethylene and propylene in the naphtha cracking fractionＣ＿ＡＰ The relationship is expressed by the formula (β-1): |C Ｅ＿ＡＰ -C Ｃ＿ＡＰ |<20 mass% ... (β-1) is preferably satisfied. As a result, according to the method for producing light olefins according to the second embodiment, the availability of the refining system can be stabilized. Formula (α), Formula (β-1) and preferred aspects are as shown in the above-mentioned embodiment B.

[0046] In the second embodiment of the light olefin production method, at least a portion of the first cooled fraction is combined with at least a portion of the ethanol-converted fraction or a fraction derived therefrom before being introduced into the second cooling tower. At least a portion of the components having a carbon number of more than 4 contained in the fraction derived from the ethanol-converted fraction is removed in the second cooling step, thereby further increasing the proportion of ethylene and propylene in the fraction introduced into the cryogenic separation. Furthermore, for example, if the ethanol-converted fraction or a fraction derived therefrom contains hydrophilic by-products such as ethanol, the hydrophilic by-products can be extracted by introducing the ethanol-converted fraction or a fraction derived therefrom into the second cooling tower using water as the contact refrigerant, thereby improving the purity of the light olefins.

[0047] The method for producing light olefins according to the third embodiment includes: a cracking step of introducing a naphtha feedstock into a cracking furnace to obtain a naphtha cracked fraction; a first cooling step of introducing the naphtha cracked fraction into a first cooling tower to obtain a first cooled fraction mainly containing olefins having a carbon number of 6 or less; a second cooling step of introducing the first cooled fraction into a second cooling tower to obtain a second cooled fraction mainly containing olefins having a carbon number of 4 or less; a circulation step of introducing at least a portion of the second heavy fraction obtained in the second cooling step, the second heavy fraction mainly containing hydrocarbons having a carbon number of 5 or more, into the second cooling tower; an ethanol conversion step of introducing an ethanol-containing feedstock into a reactor and contacting it with a catalyst to obtain an ethanol-converted fraction containing ethylene and propylene; a combining step of combining at least a portion of the second heavy fraction with at least a portion of the ethanol-converted fraction or a fraction derived therefrom to obtain a combined fraction; and a first introducing step of introducing the combined fraction into a second cooling tower. and a cryogenic separation step of introducing the second cooled fraction or a fraction derived therefrom into cryogenic separation equipment to separate ethylene and propylene.

[0048] In the method for producing light olefins according to the third embodiment, the content C of ethylene and propylene in the ethanol-converted fraction or a fraction derived therefrom in the confluence step is Ｅ and the content C of ethylene and propylene in the naphtha cracking fraction or a fraction derived therefrom. Ｃ The relationship is expressed by the formula (A): C Ｅ >C Ｃ It is preferable that the following expression (A) is satisfied. As a result, according to the method for producing light olefins according to the third embodiment, the efficiency of treating olefins having 2 or 3 carbon atoms can be improved. The expression (A) and preferred aspects are as shown in the above-mentioned embodiment A.

[0049] In the light olefin production method according to the third embodiment, the propylene / ethylene mass ratio P / E in the ethanol-converted fraction is Ｅ and the propylene / ethylene mass ratio P / E in the naphtha cracking fraction Ｃ The relationship is expressed by the formula (α): −0.25<(P / E Ｅ -P / E Ｃ) < 0.30 ... (α) and the ethylene and propylene contents C in the ethanol-converted fraction are Ｅ＿ＡＰ and the content C of ethylene and propylene in the naphtha cracking fraction Ｃ＿ＡＰ The relationship is expressed by the formula (β-1): |C Ｅ＿ＡＰ -C Ｃ＿ＡＰ It is preferable that the following relationship is satisfied: |<20 mass% ... (β-1). As a result, according to the method for producing light olefins according to the third embodiment, the availability of the refining system can be stabilized. Formula (α), Formula (β-1) and preferred aspects are as shown in the above-mentioned embodiment B.

[0050] In the third embodiment of the light olefin production method, at least a portion of the second heavy fraction in the recycling step is combined with at least a portion of the ethanol-converted fraction or a fraction derived therefrom. At least a portion of the components having a carbon number of more than 4 contained in the fraction derived from the ethanol-converted fraction is removed in the second cooling step after the combining step, thereby further increasing the proportions of ethylene and propylene in the fraction introduced into cryogenic separation. By combining at least a portion of the second heavy fraction with at least a portion of the ethanol-converted fraction or a fraction derived therefrom in the recycling step, the temperature difference between the two components can be reduced, and volume fluctuations due to liquefaction of the second heavy fraction can be suppressed, compared to when at least a portion of the first cooled fraction is combined with at least a portion of the ethanol-converted fraction or a fraction derived therefrom.

[0051] The method for producing light olefins according to the fourth embodiment includes: a cracking step of introducing a naphtha feedstock into a cracking furnace to obtain a naphtha cracked fraction; an ethanol conversion step of introducing an ethanol-containing feedstock into a reactor and contacting it with a catalyst to obtain an ethanol-converted fraction containing ethylene and propylene; a combining step of combining at least a portion of the naphtha cracked fraction with at least a portion of the ethanol-converted fraction or a fraction derived therefrom to obtain a combined fraction; a first cooling step of introducing the combined fraction or a fraction derived therefrom into a first cooling tower to obtain a first cooled fraction mainly containing olefins having 6 or less carbon atoms; a second cooling step of introducing the first cooled fraction into a second cooling tower to obtain a second cooled fraction mainly containing olefins having 4 or less carbon atoms; and a cryogenic separation step of introducing the second cooled fraction into cryogenic separation equipment to separate ethylene and propylene.

[0052] In the method for producing light olefins according to the fourth embodiment, the content C of ethylene and propylene in the ethanol-converted fraction or a fraction derived therefrom in the confluence step is Ｅ and the content C of ethylene and propylene in the naphtha cracking fraction or a fraction derived therefrom. Ｃ The relationship is expressed by the formula (A): C Ｅ >C Ｃ It is preferable that the following formula (A) is satisfied. As a result, according to the method for producing light olefins according to the fourth embodiment, the efficiency of treating olefins having 2 or 3 carbon atoms can be increased. Formula (A) and preferred aspects are as shown in the above-mentioned embodiment A.

[0053] In the method for producing light olefins according to the fourth embodiment, the propylene / ethylene mass ratio P / E in the ethanol-converted fraction is Ｅ and the propylene / ethylene mass ratio P / E in the naphtha cracking fraction Ｃ The relationship is expressed by the formula (α): −0.25<(P / E Ｅ -P / E Ｃ ) < 0.30 ... (α) and the ethylene and propylene contents C in the ethanol-converted fraction are Ｅ＿ＡＰ and the content C of ethylene and propylene in the naphtha cracking fraction Ｃ＿ＡＰThe relationship is expressed by the formula (β-1): |C Ｅ＿ＡＰ -C Ｃ＿ＡＰ It is preferable that the following relationship is satisfied: |<20 mass% ... (β-1). As a result, according to the method for producing light olefins according to the fourth embodiment, the availability of the refining system can be stabilized. Formula (α), Formula (β-1) and preferred aspects are as shown in the above-mentioned embodiment B.

[0054] In the fourth embodiment of the light olefin production method, at least a portion of the naphtha cracked fraction and at least a portion of the ethanol-converted fraction or a fraction derived therefrom are combined before being introduced into the first cooling tower. Components with a carbon number greater than 4 contained in the fraction derived from the ethanol-converted fraction are removed in the first and second cooling steps after the combining step, thereby further increasing the proportion of ethylene and propylene in the fraction introduced into the cryogenic separation. Furthermore, for example, if the ethanol-converted fraction or a fraction derived therefrom contains lipophilic by-products, introducing the ethanol-converted fraction or a fraction derived therefrom into the first cooling tower using heavy oil, cracked gasoline, or a mixture thereof as the contact refrigerant can extract the lipophilic by-products and improve the purity of the light olefins. Furthermore, for example, if the ethanol-converted fraction or a fraction derived therefrom contains hydrophilic by-products such as ethanol, introducing the ethanol-converted fraction or a fraction derived therefrom into the second cooling tower using water as the contact refrigerant can extract the hydrophilic by-products and improve the purity of the light olefins.

[0055] The method for producing light olefins according to the fifth embodiment includes: a cracking step of introducing a naphtha feedstock into a cracking furnace to obtain a naphtha cracked fraction; a first cooling step of introducing the naphtha cracked fraction into a first cooling tower to obtain a first cooled fraction mainly containing olefins having a carbon number of 6 or less; a second cooling step of introducing the first cooled fraction into a second cooling tower to obtain a second cooled fraction mainly containing olefins having a carbon number of 4 or less; a circulation step of introducing at least a portion of the second heavy fraction obtained in the second cooling step, the second heavy fraction mainly containing hydrocarbons having a carbon number of 5 or more, into the first cooling tower; an ethanol conversion step of introducing an ethanol-containing feedstock into a reactor and contacting it with a catalyst to obtain an ethanol-converted fraction containing ethylene and propylene; a combining step of combining at least a portion of the second heavy fraction with at least a portion of the ethanol-converted fraction or a fraction derived therefrom to obtain a combined fraction; and a second introducing step of introducing the combined fraction into the first cooling tower. and a cryogenic separation step of introducing the second cooled fraction or a fraction derived therefrom into cryogenic separation equipment to separate ethylene and propylene. Ｅ and the content C of ethylene and propylene in the naphtha cracking fraction or a fraction derived therefrom. Ｃ The relationship is expressed by the formula (A): C Ｅ >C Ｃ It is preferable that the following expression (A) is satisfied. As a result, according to the method for producing light olefins according to the fifth embodiment, the efficiency of treating olefins having 2 or 3 carbon atoms can be improved. The expression (A) and preferred aspects are as shown in the above-mentioned embodiment A.

[0056] In the light olefin production method according to the fifth embodiment, the propylene / ethylene mass ratio P / E in the ethanol-converted fraction is Ｅ and the propylene / ethylene mass ratio P / E in the naphtha cracking fraction Ｃ The relationship is expressed by the formula (α): −0.25<(P / E Ｅ -P / E Ｃ) < 0.30 ... (α) and the ethylene and propylene contents C in the ethanol-converted fraction are Ｅ＿ＡＰ and the content C of ethylene and propylene in the naphtha cracking fraction Ｃ＿ＡＰ The relationship is expressed by the formula (β-1): |C Ｅ＿ＡＰ -C Ｃ＿ＡＰ |<20 mass% ... (β-1) is preferably satisfied. As a result, according to the method for producing light olefins according to the fifth embodiment, the availability of the refining system can be stabilized. Formula (α), Formula (β-1) and preferred aspects are as shown in the above-mentioned embodiment B.

[0057] In the light olefin production method according to the fifth embodiment, at least a portion of the second heavy fraction is combined with at least a portion of the ethanol-converted fraction or a fraction derived therefrom in the recycling step. By combining at least a portion of the second heavy fraction with at least a portion of the ethanol-converted fraction or a fraction derived therefrom in the recycling step, the temperature difference between the two components is reduced, thereby suppressing volume fluctuations due to liquefaction of the second heavy fraction, compared to connecting at least a portion of the naphtha cracked fraction. Components with a carbon number greater than 4 contained in the fraction derived from the ethanol-converted fraction are removed in the first and second cooling steps, thereby further increasing the proportions of ethylene and propylene in the fraction introduced into cryogenic separation. Furthermore, for example, if the ethanol-converted fraction or a fraction derived therefrom contains lipophilic by-products, the lipophilic by-products can be extracted by introducing the ethanol-converted fraction or a fraction derived therefrom into a first cooling tower using heavy oil, cracked gasoline, or a mixture thereof as a contact refrigerant, thereby improving the purity of the light olefins. Furthermore, for example, when the ethanol-converted fraction or a fraction derived therefrom contains hydrophilic by-products such as ethanol, the hydrophilic by-products can be extracted by introducing the ethanol-converted fraction or a fraction derived therefrom into a second cooling tower using water as a contact refrigerant, thereby improving the purity of the light olefins.

[0058] In the light olefin production method according to this embodiment, when the first compression step is performed after the second cooling step and before the cryogenic separation step, the combining step according to this embodiment allows the pressure of the ethanol-converted fraction or a fraction derived therefrom to be increased in the first compression step, thereby reducing the equipment installation load when introducing the ethanol-converted fraction into a naphtha cracking process. Furthermore, by increasing the pressure of the naphtha cracked fraction or a fraction derived therefrom and the ethanol-converted fraction or a fraction derived therefrom in the same compression step, it becomes easy to adjust the pressure of the combined fraction.

[0059] In this embodiment, the compound represented by formula (1): O Ｅ <O Ｃ ...When the relationship (1) is satisfied, the amount of off-gas from the ethanol-converted fraction is small, so that the purification load of the ethanol-converted fraction can be reduced, and the ethanol-converted fraction or a fraction derived therefrom can be introduced into the naphtha cracking process with simple purification.

[0060] In the method for producing a light olefin according to the present embodiment, preferably, the ethylene and propylene content C Ｅ１ and a purification step of purifying the ethanol-converted fraction to obtain a purified ethanol-converted fraction so that the ethylene and propylene contents are higher than those of the naphtha cracked fraction or a fraction derived therefrom in the combining step. By including this step, the ethylene and propylene contents C Ｅ１ The production method according to the present embodiment preferably includes a purification step after the ethanol conversion step and before the combining step.

[0061] The purification step preferably includes a third cooling step of introducing the ethanol-converted fraction into a third cooling tower to obtain a cooled ethanol-converted fraction mainly containing olefins having 6 or less carbon atoms. The cooled ethanol-converted fraction is a fraction from which heavy components have been removed by the third cooling tower, and is preferably a fraction obtained from the top of the third cooling tower, for example. By including the third cooling step, the ethylene and propylene contents C Ｅ１ This can increase the amount of material that undergoes a phase transition from gas to liquid in the cryogenic separation process, thereby preventing the generation of condensation heat and reducing the energy load required for cooling in the cryogenic separation process.

[0062] The purification step preferably includes a compression separation step in which the cooled ethanol-converted fraction is pressurized by a compressor to obtain a light ethanol-converted fraction containing mainly olefins having a carbon number of 3 or less as a gas component, and a heavy ethanol-converted fraction containing mainly olefins having a carbon number of 4 or more as a liquid component. By including the compression separation step, the ethylene and propylene contents C Ｅ１ This can increase the amount of material that undergoes a phase transition from gas to liquid in the cryogenic separation step, thereby preventing the generation of condensation heat and reducing the energy load required for cooling in the cryogenic separation step. In addition, the inclusion of the compression separation step can reduce the amount of fraction derived from the ethanol converted fraction that is combined in the combining step, reducing the flow rate to be pressurized and cooled in the cryogenic separation step and reducing the energy load in the cryogenic separation step.

[0063] The method for producing light olefins according to this embodiment preferably includes a recycling step in which at least a portion of the heavy ethanol-converted fraction is introduced into the reactor as part of the feedstock. By introducing the heavy ethanol-converted fraction, which mainly contains olefins having 4 or more carbon atoms, into the reactor used in the ethanol conversion step, the amount of ethanol introduced in the ethanol conversion step can be reduced. In particular, since the heavy ethanol-converted fraction contains highly reactive olefins having 4 or more carbon atoms, these components can undergo further conversion reactions in the presence of a catalyst in the ethanol conversion step, and can also be converted into ethylene and propylene. Furthermore, since the heavy ethanol-converted fraction has been subjected to the third cooling step to remove heavy components having 9 or more carbon atoms, even when introduced into the reactor used in the ethanol conversion step, it is unlikely to cause coke generation in the reactor, and the feedstock can be effectively utilized while maintaining catalyst activity.

[0064] The method for producing light olefins according to this embodiment preferably includes a washing step in which the combined fraction is introduced into a soda wash tower after the combining step to obtain a wash fraction. The wash fraction is a fraction from which components eluted into the wash liquid side by the soda wash tower have been removed, and is preferably, for example, a fraction obtained from the top of the soda wash tower. By performing this step and then a cryogenic separation step, acidic gases such as carbon dioxide and hydrogen sulfide contained in the combined fraction can be removed, and the purity of the light olefins obtained in the cryogenic separation step can be improved.

[0065] Hereinafter, each step of the method for producing light olefins according to this embodiment will be described.

[0066] The method for producing light olefins according to this embodiment includes, as the naphtha cracking process N described above, a cracking step in which naphtha feedstock is introduced into a cracking furnace to obtain a naphtha cracked fraction, and a cryogenic separation step in which the naphtha feedstock is introduced into a cryogenic separation facility to separate ethylene and propylene.

[0067] Furthermore, the method for producing light olefins according to this embodiment may optionally include, as the naphtha cracking process N, a first cooling step in which the naphtha cracked fraction is introduced into a first cooling tower to obtain a first cooled fraction mainly containing olefins having a carbon number of 6 or less, and a second cooling step in which the first cooled fraction is introduced into a second cooling tower to obtain a second cooled fraction mainly containing olefins having a carbon number of 4 or less. By providing the first cooling step and / or the second cooling step prior to the washing step described below, the fraction introduced into the soda wash tower can be reduced, thereby improving the efficiency of washing in the soda wash tower. Furthermore, by providing the cooling step in two stages, it becomes easier to control the temperature and composition of the fraction obtained in the cooling step.

[0068] Furthermore, the light olefin production method according to this embodiment may optionally include, as the naphtha cracking process N described above, a first compression step of pressurizing the fraction before introduction into the cryogenic separation facility, and a scrubbing step of introducing the fraction into a soda wash tower to obtain a scrubbed fraction. In the soda wash tower, acid components such as carbon dioxide gas contained in the fraction are removed, thereby improving the separation efficiency in the cryogenic separation step. Furthermore, by providing the first compression step prior to the scrubbing step, the volume of the fraction introduced into the soda wash tower can be compressed, thereby improving the operating efficiency of the soda wash tower.

[0069] On the other hand, the method for producing light olefins according to this embodiment includes, as the ethanol conversion process E, an ethanol conversion step of introducing an ethanol-containing raw material into a reactor and bringing it into contact with a catalyst to obtain an ethanol-converted fraction containing ethylene and propylene.

[0070] Meanwhile, the method for producing light olefins according to this embodiment may optionally include a purification step of purifying the ethanol-converted fraction to obtain a purified ethanol-converted fraction as the ethanol conversion process E. By providing this purification step, the concentration of the target compound contained in the ethanol-converted fraction can be increased, and the purification efficiency in the cryogenic separation step can be improved.

[0071] Meanwhile, the method for producing light olefins according to this embodiment may optionally include, as a purification step in the ethanol conversion process E, a third cooling step of introducing the ethanol-converted fraction into a third cooling tower to obtain a cooled ethanol-converted fraction mainly containing olefins having 6 or fewer carbon atoms. By providing the third cooling step, the amount of hydrocarbons having 7 or more carbon atoms contained in the ethanol-converted fraction or a fraction derived therefrom can be reduced, thereby improving the purification efficiency in the cryogenic separation step.

[0072] On the other hand, the method for producing light olefins according to this embodiment may optionally include, as a purification step in the ethanol conversion process E, a compression separation step in which the cooled ethanol converted fraction is pressurized by a compressor to obtain a light ethanol converted fraction containing mainly olefins having 3 or less carbon atoms as a gas component, and a heavy ethanol converted fraction containing mainly olefins having 4 or more carbon atoms as a liquid component. By providing the compression separation step, the amount of hydrocarbons having 4 or more carbon atoms contained in the ethanol converted fraction or fractions derived therefrom can be reduced, thereby improving the purification efficiency in the cryogenic separation step.

[0073] The method for producing light olefins according to the embodiment may optionally include a recycle step of introducing at least a portion of the heavy ethanol-converted fraction into the reactor as part of the raw material, as part of the ethanol conversion process E. By providing the recycle step, the olefins contained in the heavy ethanol-converted fraction can be converted into target compounds, thereby improving the production efficiency of ethylene and propylene per unit of raw material ethanol.

[0074] The method for producing light olefins according to this embodiment includes a combining step of combining at least a portion of a naphtha cracking fraction or a fraction derived therefrom with at least a portion of an ethanol conversion fraction or a fraction derived therefrom to obtain a combined fraction. In other words, by combining at least a portion of the ethanol conversion fraction or a fraction derived therefrom with a naphtha cracking process, an ethanol-derived raw material is used and cryogenic separation is efficiently performed. The combining step is performed at any stage in the naphtha cracking process, as described below.

[0075] In the above description of the embodiment, in order to explain and organize the steps, the steps have been described as being divided into the general categories of naphtha cracking N and ethanol conversion process E in this technical field. However, each step according to the present embodiment may belong to either naphtha cracking N or ethanol conversion process E.

[0076] The method for producing light olefins according to this embodiment is realized, for example, by the production facility shown in Fig. 2. The light olefin production facility includes a cracking furnace 11, a first cooling tower 12, a second cooling tower 13, a first compressor 14, a soda wash tower 15, and a cryogenic separation facility 16. The light olefin production facility also includes a reactor 21 and a third cooling tower 22. Each step according to this embodiment will be described in detail below using the production facility as an example.

[0077] <Cracking Step> In the cracking furnace 11, the above-mentioned cracking step is carried out.

[0078] (Naphtha Feedstock) In the light olefin production method according to this embodiment, a naphtha feedstock is used. The naphtha feedstock includes at least naphtha. Naphtha is a mixture of hydrocarbons with a boiling point range of approximately 30 to 230°C. Naphtha is divided into light naphtha and heavy naphtha depending on the boiling point range, but either may be used. The naphtha feedstock preferably contains hydrocarbons having 2 to 40 carbon atoms, more preferably hydrocarbons having 2 to 30 carbon atoms, and even more preferably hydrocarbons having 5 to 12 carbon atoms. The boiling point of the naphtha feedstock may be, for example, in the range of 30 to 230°C. The naphtha feedstock is not particularly limited, but is generally derived from fossil resources obtained from petroleum. Bionaphtha obtained by cracking animal and vegetable oils can also be used.

[0079] The naphtha feedstock preferably contains dilution steam from the viewpoint of reducing the amount of coke by-product. The amount of dilution steam supplied is preferably 0.1 to 1.0, more preferably 0.3 to 0.6, in terms of mass ratio relative to the naphtha.

[0080] The cracking method used in the cracking step is not particularly limited, but examples include a steam cracking method in which heated naphtha is contacted with steam heated to 950°C or higher to perform thermal decomposition, and a moving bed method in which naphtha is contacted with a granular heat transfer medium heated to a high temperature in a moving bed to perform thermal decomposition. Examples of steam cracking methods include a tubular heating method in which naphtha and steam are circulated through a heating tube and thermally decomposed by heat from the tube wall. In each method, a catalyst may be used to promote thermal decomposition.

[0081] The naphtha feedstock described above is introduced into the cracking furnace 11, and steam may also be introduced together with the naphtha feedstock. In this case, the amount of steam introduced is preferably 20 to 100 parts by mass, more preferably 30 to 70 parts by mass, and more preferably 35 to 60 parts by mass, per 100 parts by mass of the naphtha feedstock. By setting the amount of steam introduced within the above range, it is possible to suppress the generation of carbonaceous substances.

[0082] The treatment temperature in the cracking furnace is preferably 700 to 1000°C, more preferably 750 to 950°C, and even more preferably 800 to 900°C. By setting the temperature within this range, the thermal cracking of naphtha proceeds smoothly and the production of light components such as methane can be suppressed. Furthermore, by controlling the treatment temperature according to the boiling point of the naphtha feedstock, the cracking severity can be controlled and the ratio of ethylene to propylene can be set within a suitable range. The mass ratio of ethylene to propylene (P / E mass ratio) in naphtha cracking is not particularly limited, but is preferably 0.3 to 1.0.

[0083] The reaction pressure in the cracking furnace is preferably 0.01 to 1.5 MPaG, more preferably 0.05 to 0.5 MPaG, and even more preferably 0.07 to 0.2 MPaG.

[0084] <First Cooling Step> The naphtha cracked fraction obtained in the cracking furnace 11 is introduced into the first cooling tower 12. Furthermore, before being introduced into the first cooling tower 12, light olefins such as ethane and propane recycled from downstream refining equipment may be mixed with the naphtha cracked fraction. In the first cooling tower 12, the above-mentioned first cooling step is carried out to obtain a first cooled fraction mainly containing olefins having 6 or less carbon atoms. In the first cooling tower 12, by cooling the naphtha cracked fraction, excessive cracking can be suppressed, and further, at least a portion of the olefins having more than 6 carbon atoms can be removed.

[0085] In the first cooling tower 12, it is preferable to cool the naphtha cracked fraction by bringing the heavy oil, cracked gasoline, or a mixture thereof into contact with the naphtha cracked fraction.

[0086] The pressure of the first cooled fraction after treatment in the first cooling tower 12 is preferably 0.01 to 1.5 MPaG, more preferably 0.05 to 0.5 MPaG, and even more preferably 0.07 to 0.2 MPaG.

[0087] The temperature of the first cooled fraction after treatment in the first cooling tower 12 is preferably 50 to 300°C, more preferably 100 to 200°C, and even more preferably 105 to 160°C, from the viewpoint of excellent removal efficiency of olefins having more than 6 carbon atoms.

[0088] <Second Cooling Step> The first cooled fraction obtained in the first cooling tower 12 is introduced into the second cooling tower 13. In the second cooling tower 13, the second cooling step described above is carried out, and by cooling the first cooled fraction, at least a portion of the olefins having more than 4 carbon atoms are removed, and a second cooled fraction mainly containing olefins having 4 or less carbon atoms is obtained. At this time, a second heavy fraction mainly containing hydrocarbons having 5 or more carbon atoms and water are mainly obtained from the bottom of the tower.

[0089] In the second cooling tower 13, it is preferable to cool the first cooled fraction by bringing it into contact with water.

[0090] The pressure of the second cooled fraction after treatment in the second cooling tower 13 is preferably 0.01 to 1.5 MPaG, more preferably 0.05 to 0.5 MPaG, and even more preferably 0.07 to 0.2 MPaG.

[0091] The temperature of the second cooled fraction after treatment in the second cooling tower 13 is preferably 10 to 100°C, more preferably 30 to 90°C, from the viewpoint of excellent efficiency in removing olefins having more than 4 carbon atoms.

[0092] <First Compression Step> The second cooled fraction obtained in the second cooling tower 13 is introduced into the first compressor 14. In the first compressor 14, the aforementioned compression step is performed to increase the pressure of the second cooled fraction. The first compression step may be performed before introduction into the cryogenic separation equipment, but it is preferable that the fraction containing the second cooled fraction be introduced into the first compressor 14 after the second cooling step. In the first compressor 14, for example, the second cooled fraction may be pressurized using a single compressor, or the second cooled fraction may be pressurized in stages using multiple compressors, for example, two to four compressors. In the first compression step, the second cooled fraction can be pressurized as a gas component, and a liquid component may be obtained by liquefying high-boiling-point components contained in the second cooled fraction, such as hydrocarbons with 5 or more carbon atoms. In this way, by removing high-boiling-point components by pressurization, the concentration of olefins with 3 or less carbon atoms in the second cooled fraction can be increased.

[0093] The pressure of the second cooled fraction after treatment by the first compressor 14 is preferably 0.10 to 10.0 MPaG, more preferably 0.20 to 5.0 MPaG, and even more preferably 0.50 to 1.5 MPaG.

[0094] <First Circulation Step> The light olefin production method according to this embodiment may include a first circulation step in which at least a portion of the second heavy fraction, which is obtained in the second cooling step and mainly contains hydrocarbons having 5 or more carbon atoms, is introduced into a first cooling tower. The second heavy fraction contains heavy target compounds such as aromatic compounds. Increasing the amount of the second heavy fraction circulated to the first cooling tower in the first circulation step reduces the production efficiency of these heavy target compounds. On the other hand, increasing the circulation amount allows some of the olefins having 4 or less carbon atoms contained in the second heavy fraction to be introduced into the cryogenic separation step, thereby improving the production efficiency of these olefins. Therefore, it is preferable to determine the circulation amount in the first circulation step in consideration of the production balance between heavy target compounds such as aromatic compounds and olefins having 4 or less carbon atoms. From the viewpoint of achieving excellent propylene production efficiency, the circulation amount in the first circulation step is preferably 20 to 90 mass% of the second heavy fraction, more preferably 30 to 90 mass%, and even more preferably 40 to 90 mass%.

[0095] <Second Circulation Step> The light olefin production method according to this embodiment may include a second circulation step in which at least a portion of the second heavy fraction, which is obtained in the second cooling step and mainly contains hydrocarbons having 5 or more carbon atoms, is introduced into a second cooling tower. In this circulation step, the liquid components generated in the first compression step may be combined and introduced into the second cooling tower. The second heavy fraction contains heavy target compounds such as aromatic compounds. Increasing the amount of the second heavy fraction circulated to the first cooling tower in the first circulation step reduces the production efficiency of these heavy target compounds. On the other hand, increasing the circulation amount allows some of the olefins having 4 or less carbon atoms contained in the second heavy fraction to be introduced into the cryogenic separation step, thereby improving the production efficiency of these olefins. Therefore, it is preferable to determine the circulation amount in the second circulation step in consideration of the production balance between heavy target compounds such as aromatic compounds and olefins having 4 or less carbon atoms. From the viewpoint of excellent propylene production efficiency, the circulation amount in the second circulation step is preferably 20 to 90 mass% relative to the total amount of the liquid component in the first compression step and the second heavy fraction, more preferably 30 to 90 mass%, and even more preferably 40 to 90 mass%.

[0096] <Washing Step> In the washing step, the fraction is introduced into a soda wash tower 15 before being introduced into the cryogenic separation equipment to obtain a washed fraction. In the washing step, acidic components such as carbon dioxide in the fraction can be removed by treatment in the soda wash tower 15. Since carbon dioxide has a higher boiling point than ethylene, if carbon dioxide is introduced into the cryogenic separation, it becomes difficult to separate the olefins from the carbon dioxide. Therefore, it is preferable to remove carbon dioxide from the fraction before being introduced into the cryogenic separation equipment. The washing step may be performed before being introduced into the cryogenic separation equipment, but it is preferable to provide it after the first compression step because this makes it easier to operate the soda wash tower.

[0097] In the soda wash tower 15, the distillate is preferably brought into contact with an aqueous sodium hydroxide solution to obtain a washed distillate. The amount of sodium hydroxide can be appropriately selected so as to remove acidic components such as carbon dioxide from the distillate.

[0098] <Cryogenic separation step> In the cryogenic separation step, the fraction is introduced into a cryogenic separation facility to separate ethylene and propylene. Here, the fraction introduced in the washing step or cryogenic separation step is preferably a combined fraction or a fraction derived therefrom. The "combined fraction" refers to a fraction obtained by the above-mentioned combining step. Here, the "fraction derived therefrom" refers to a fraction obtained by further refining the combined fraction using a refining facility such as a soda washing tower.

[0099] Cryogenic separation generally involves separating components by distillation at extremely low temperatures and high pressures. For example, by liquefying fractions at extremely low temperatures and high pressures, hydrogen and methane are separated from light olefins.

[0100] In the cryogenic separation step, light olefins such as ethylene and propylene are separated through a demethanizer, a deethanizer, an ethylene fractionator, a propanizer, a propylene fractionator, etc.

[0101] The refining system of a naphtha cracker is classified into a front-end demethanolizer system and a front-end depropanizer system. An example of the device configuration for each system will be described below, but the presence or absence of each separation tower and the order in which they are used are not limited to these.

[0102] In a front-end demethanizer purification system, for example, light olefins are purified by the following procedure. First, an input fraction compressed by a compressor is introduced into a cooler, thereby liquefying at least a portion of the light olefins in the input fraction and simultaneously removing at least a portion of the hydrogen. The fraction is introduced into a demethanizer, and a demethanized fraction containing mainly light olefins is obtained from the bottom of the column, and an off-gas fraction containing hydrogen and methane is obtained from the top of the column. The obtained demethanized fraction is introduced into a deethanizer, and an ethylene fraction containing mainly ethylene is obtained from the top of the column, and an ethane-depleted fraction containing mainly olefins having 3 or more carbon atoms is obtained from the bottom of the column. The obtained ethylene fraction is introduced into an ethylene fractionator, and ethylene and ethane are separated to obtain purified ethylene. The obtained ethane-depleted fraction is introduced into a depropanizer, and a propylene fraction containing mainly propylene is obtained from the top of the column, and a propane-depleted fraction containing mainly olefins having 4 or more carbon atoms is obtained from the bottom of the column. The resulting propylene fraction is introduced into a propylene fractionator to separate propylene from propane to obtain purified propylene, and the resulting depropanized fraction is introduced into a debutanizer to obtain olefins having four carbon atoms.

[0103] In a front-end depropanizer purification system, for example, light olefins are purified by the following procedure. In a front-end depropanizer purification system, a fraction is separated into an inlet fraction containing mainly hydrocarbons with a carbon number of 3 or less and a bypass fraction containing mainly hydrocarbons with a carbon number of 3 or more, thereby reducing the amount of fraction introduced into the cryogenic separation step and reducing energy consumption related to the cryogenic separation. That is, for example, as shown in FIG. 15 , in a front-end depropanizer purification system, the fraction is introduced into a first distillation column 17, thereby separating the inlet fraction to be introduced into the cryogenic separation step. In addition, a bypass fraction that bypasses the cryogenic separation step and is introduced into downstream equipment is obtained from the bottom of the first distillation column 17. In the first distillation column 17, the separation operation may be performed, for example, using a single distillation column, or the separation operation may be performed in stages using multiple distillation columns, for example, two to four columns. The resulting input fraction is then compressed by a compressor and introduced into a cooler, thereby liquefying at least a portion of the light olefins in the input fraction and simultaneously removing at least a portion of the hydrogen. After cooling and compressing the input fraction, the target compound can be separated from the input fraction by treating it in the same manner as in a front-end demethanolizer purification system. In addition, in a front-end depropanizer purification system, the input fraction obtained from the first distillation column 17 can be further purified by introducing it into a deethanizer and then introduced into the cryogenic separation step. In this way, by purifying the input fraction in addition to the first distillation column 17, energy consumption related to the cryogenic separation step can be reduced.

[0104] <Ethanol Conversion Step> On the other hand, a raw material containing ethanol is introduced into the reactor 21. The above-described ethanol conversion step is carried out in the reactor 21. In the reactor 21, the raw material containing ethanol is brought into contact with a catalyst to obtain an ethanol-converted fraction containing ethylene and propylene.

[0105] (Raw material: ethanol conversion process) In the ethanol conversion process, a raw material containing ethanol is used. Ethanol produced by various methods can be used. Among these, it is preferable to use bioethanol from the viewpoint of environmental friendliness. In recent years, the importance of replacing fossil resources such as crude oil with renewable plant-derived resources has been recognized anew in order to realize a sustainable society or to reduce greenhouse gas emissions. Therefore, it is possible to produce chemical products that have traditionally been produced using fossil resources such as crude oil by using bioethanol obtained from renewable plant-derived resources.

[0106] The content of ethanol in the raw materials is preferably 30 to 100% by mass, more preferably 40 to 100% by mass, and even more preferably 50 to 100% by mass, based on the total amount of the raw materials.

[0107] The raw material may contain ethylene and ethanol. By using such a raw material, propylene can be produced with a high yield by using an adiabatic reactor and controlling the temperature inside the reactor. The raw material may also contain an olefin having 4 to 6 carbon atoms.

[0108] In the raw materials, the molar ratio of ethylene to ethanol is preferably 0.05 to 2.5, more preferably 0.20 to 2.0, even more preferably 0.30 to 1.8, and still more preferably 0.30 to 1.5.

[0109] In the ethanol conversion step, the raw material may contain an olefin having 4 to 6 carbon atoms and an oxygen-containing compound having 1 to 6 carbon atoms other than ethanol. Examples of oxygen-containing compounds having 1 to 6 carbon atoms other than ethanol include methanol, propanol, dimethyl ether, and diethyl ether. These compounds can be brought into contact with a catalyst in a reactor to produce target compounds such as ethylene and propylene.

[0110] The raw material may contain saturated aliphatic hydrocarbons such as paraffin, olefins having 7 or more carbon atoms, and oxygen-containing compounds having 7 or more carbon atoms. When these saturated aliphatic hydrocarbons, olefins having 7 or more carbon atoms, and oxygen-containing compounds having 7 or more carbon atoms are brought into contact with a catalyst in the same manner as ethylene and ethanol, they can be converted into target compounds such as propylene through a combination of dehydrogenation and dehydration reactions, but their reactivity is lower than that of the above-mentioned olefins having 4 to 6 carbon atoms and oxygen-containing compounds having 1 to 6 carbon atoms other than ethanol.

[0111] The raw material may also include olefins having 4 or more carbon atoms that have been separated in whole or in part from a reaction gas containing olefins having 3 or more carbon atoms obtained in the ethanol conversion step. In this way, the use of a so-called recycle reaction system makes it possible to effectively utilize the olefin raw material.

[0112] The feedstock may contain inert gases such as nitrogen in addition to the above-mentioned feedstocks that can be converted into target compounds such as propylene in the ethanol conversion process. The feedstock may also contain hydrogen or methane as a diluent gas, but it is preferable not to dilute with hydrogen. Hydrogen may be used to suppress coking degradation of the catalyst.

[0113] In the ethanol conversion process, the raw material may contain water. Since the ethylene and ethanol contained in the mixed raw material are produced by various production methods, the mixed raw material may contain "water generated in the production process." Here, "water generated in the production process" refers to water that is generated during the production process of ethylene and / or ethanol and has not been removed.

[0114] In the ethanol conversion process, steam can be added to the mixed feedstock in addition to the "water generated in the production process." Steam has the effect of suppressing coking degradation by lowering the olefin partial pressure and improving the yield of light olefins. However, steam may promote dealumination of zeolite, so it is preferable not to add steam to the mixed feedstock in addition to the "water generated in the production process."

[0115] In the method for producing light olefins according to the present embodiment, the ratio of the amount of hydrogen and methane to the total amount of ethylene and propylene in the ethanol-converted fraction is 0.05 to 0.05. Ｅ and the ratio of the amount of hydrogen and methane to the total amount of ethylene and propylene in the naphtha cracking fraction. Ｃ The relationship is expressed by the formula (1): Ｅ <O Ｃ It is preferable to satisfy the following condition (1): By satisfying this condition, it is possible to provide a method for producing light olefins that reduces the processing energy required for cryogenic separation.

[0116] In the naphtha cracking process, naphtha is cracked, then refined, and then cryogenically separated to obtain light olefins. In the cryogenic separation process, the fraction introduced into the cryogenic separation process is pressurized by a compressor, and the fraction is cooled to below the boiling point of ethylene at that pressure to liquefy the light olefins in the fraction. Off-gases such as hydrogen and methane are separated from the light olefins by gas-liquid separation. In this pressurization and cooling process, the energy consumption increases depending on the flow rate of the fraction introduced into the cryogenic separation process. In other words, the ratio of the amount of hydrogen and methane to the total amount of ethylene and propylene in the ethanol conversion fraction is 0. Ｅ and the ratio of the amount of hydrogen and methane to the total amount of ethylene and propylene in the naphtha cracking fraction. Ｃ By setting the relationship between the above and the ratio of hydrogen and methane in the fraction introduced into the cryogenic separation step to within the above range, the proportions of hydrogen and methane in the fraction introduced can be reduced. Therefore, when the production amount of light olefins is constant, the flow rates of hydrogen and methane in the fraction introduced can be reduced, thereby enabling more efficient cryogenic separation.

[0117] In the light olefin production method according to this embodiment, the ratio O Ｃ and ratio O Ｅ The difference between Ｃ -O Ｅ From the viewpoint of excellent purification efficiency, the difference (O Ｃ -O Ｅ), the ratio of hydrogen and methane in the fraction introduced into the cryogenic separation step can be reduced, so that cryogenic separation can be carried out efficiently. Ｃ -O Ｅ The upper limit of the content of ) is not particularly limited, but may be 70 mass % or less.

[0118] In the light olefin production method according to this embodiment, the propylene / ethylene mass ratio P / E in the ethanol-converted fraction is Ｅ and the propylene / ethylene mass ratio P / E in the naphtha cracking fraction. Ｃ Difference with P / E Ｃ - P / E Ｅ is preferably 0.2 or less, more preferably 0.1 or less, and even more preferably 0.05 or less. Ｃ - P / E Ｅ The lower limit of | is not particularly limited, and may be, for example, 0 or more (that is, the same ratio).

[0119] (Adiabatic Reactor) In the ethanol conversion process, the reactor is not particularly limited, but an adiabatic reactor is preferred because it consumes less energy. For details on adiabatic reactors, see Adiabatic Fixed-Bed Reactors (Elsevier, 2014, Ch. 1, P. 4, L. 5-24, ISBN: 978-0-12-801306-9). Examples of adiabatic reactors include fixed-bed adiabatic reactors, moving-bed adiabatic reactors, and fluidized-bed adiabatic reactors. However, a fixed-bed adiabatic reactor is preferred for the method of this embodiment. Among fixed-bed adiabatic reactors, a fixed-bed single-stage adiabatic reactor having only one fixed catalyst bed is more preferred. Since carbonaceous matter (coke) accumulates on the catalyst during the reaction, a multi-column switching type fixed-bed single-stage adiabatic reactor is preferred, as it allows for the combustion and removal of this carbonaceous matter while the reaction continues.

[0120] 3 is a schematic diagram of a fixed-bed, single-stage adiabatic reactor. The fixed-bed, single-stage adiabatic reactor 211 includes a reaction casing 212 with a heat insulating material 216 provided on the outer periphery, a catalyst bed 213, a reactor inlet 214, and a reactor outlet 215. The reaction casing 212 is provided with the heat insulating material 216 on the outer periphery, thereby preventing heat from escaping from the reactor to the outside. In the production method according to this embodiment, the temperature inside the reactor can be controlled by the heat generation and heat absorption caused by the reaction.

[0121] The catalyst bed 213 is filled with a catalyst, which will be described later. A first sheathed thermocouple 217 is provided in the catalyst bed 213 just before it contacts the catalyst bed inlet 219a. A second sheathed thermocouple 218 is provided in the catalyst bed 213 just after it passes through the catalyst bed outlet 219b. These thermocouples measure the temperature of the mixed feedstock just before it contacts the catalyst bed inlet 219a and the reaction gas just after it passes through the catalyst bed outlet 219b. The catalyst bed 213 may be of a multi-stage type, but is preferably of a single stage type as shown in FIG. 3 .

[0122] In the fixed-bed single-stage adiabatic reactor 211 , a mixed raw material is introduced from a reactor inlet 214 and brought into contact with a catalyst bed 213 , and a reaction gas is taken out from a reactor outlet 215 .

[0123] The reaction temperature in the ethanol conversion step is preferably 300 to 600°C, more preferably 450 to 590°C, and even more preferably 500 to 580°C, from the viewpoint of suppressing coking degradation while increasing reactivity. The reaction temperature is a value calculated using the formula: [catalyst bed inlet temperature + catalyst bed outlet temperature] / 2. The catalyst bed inlet temperature is the temperature of the mixed raw material immediately before the raw material fluid comes into contact with the catalyst bed packed in the adiabatic reactor. The catalyst bed outlet temperature is the temperature of the reaction gas immediately after the reaction gas has passed through the catalyst bed. The temperatures of the mixed raw material and the reaction gas referred to here refer to temperatures between 0d and 0.8d in a plane perpendicular to the fluid flow direction, where 0 is the center of the reactor and d is the distance from the center of the reactor to the inner wall surface of the reactor.

[0124] The reaction pressure in the ethanol conversion step is preferably 0.01 to 3.0 MPaG, more preferably 0.01 to 1.0 MPaG.

[0125] The feed rate of the raw material in the ethanol conversion step is preferably 0.1 to 1000 hr in terms of the mass-based space velocity (WHSV) of the catalyst. －１ and more preferably 0.1 to 500 hours. －１ and more preferably 0.5 to 100 hours. －１ In the ethanol conversion process, the WHSV is calculated by converting ethanol into ethylene as shown in the following formula.

[0126] WHSV (hr －１ ) = mass flow rate of raw material supply (kg / hr) / catalyst amount (kg) Mass flow rate of raw material supply (kg / hr) = ethylene flow rate (kg / hr) + ethylene-equivalent ethanol flow rate (kg / hr) + C4-C6 olefin flow rate (kg / hr) + C1-C6 oxygenated compound flow rate other than ethanol (kg / hr) Ethylene-equivalent ethanol flow rate (kg / hr) = ethanol flow rate (kg / hr) × ethylene molecular weight (g / mol) / ethanol molecular weight (g / mol)

[0127] (Catalyst) The catalyst used in the ethanol conversion process is a solid catalyst that exhibits catalytic activity for converting olefins and ethanol into target compounds such as propylene. Zeolite-containing catalysts are preferred as such catalysts because of their excellent thermal durability and propylene selectivity. A common issue in conventional olefin production using zeolites is coking, in which heavy carbonaceous material (coke) accumulates inside the zeolite pores due to reaction with hydrocarbons, deactivating the catalyst. To regenerate the catalyst, it is preferable to burn and remove the coke in an atmosphere containing oxygen molecules. However, this coke combustion causes structural collapse of the zeolite, leading to permanent deterioration of the catalyst, which is difficult to regenerate. The ethanol conversion process can suppress coke formation, making it easier to maintain activity even when using a zeolite-containing catalyst.

[0128] <Zeolite-Containing Catalyst> A zeolite-containing catalyst is a catalyst powder or molded body containing zeolite as an active species. In the ethanol conversion process, it is preferable to use a so-called intermediate pore size zeolite having a pore size of 5 to 6 Å as the zeolite in the zeolite-containing catalyst. An intermediate pore size zeolite means "a zeolite whose pore size range is intermediate between the pore size of small pore size zeolites, such as A-type zeolites, and the pore size of large pore size zeolites, such as mordenite, X-type zeolites, and Y-type zeolites." An "intermediate pore size zeolite" has a so-called 10-membered oxygen ring in its crystal structure.

[0129] Examples of intermediate pore size zeolites include MFI zeolites such as ZSM-5, ZSM-8, ZSM-11, ZSM-12, ZSM-21, ZSM-23, ZSM-35, ZSM-38, LZ-105, FZ-1, TS-1, and silicate. Of these, MFI zeolites are preferred, and ZSM-5 is more preferred. Zeolites similar to ZSM-5 and ZSM-11 described in Stud. Surf. Sci. Catal. 1987, 33, 167-215 can also be used. Of these, MFI zeolites are preferred, and ZSM-5 is more preferred, from the viewpoint of excellent catalytic performance (catalytic activity and durability against coking).

[0130] The silica / alumina (SiO ２ / Al ２ O ３ The silica / alumina (SiO ) molar ratio of the zeolite contained in the zeolite-containing catalyst can be appropriately selected, but from the viewpoint of excellent catalytic activity and propylene selectivity, it is preferably 20 to 2000, and from the viewpoint of improving the durability of the catalyst, it is more preferably 100 to 1500, even more preferably 300 to 1200, and still more preferably 800 to 1200. ２ / Al ２ O ３The silica / alumina molar ratio may be 20 to 400, or may be 100 to 300. The silica / alumina molar ratio of the zeolite can be measured by a known method, for example, by completely dissolving the zeolite in an alkaline aqueous solution and analyzing the resulting solution by plasma emission spectrometry or the like.

[0131] The zeolite synthesis method of the present embodiment is not particularly limited, but can be produced by optimizing various conditions of a conventionally known hydrothermal synthesis method for MFI zeolite. Generally, means for efficiently obtaining MFI zeolite by hydrothermal synthesis include a method of hydrothermal synthesis using an appropriate organic structure-directing agent (SDA), a method of hydrothermal synthesis in which hydrothermally synthesized MFI zeolite is added as seed crystals, or a method of hydrothermal synthesis in which MFI zeolite is added as a seed slurry in the crystalline stage. Examples of organic structure-directing agents (SDAs) used here include ammonium salts, urea compounds, amines, and alcohols. It is known that not only organic SDAs but also inorganic cations and anions are involved in the structure, and zeolite synthesis depends on the combined functions of each component. In the hydrothermal synthesis method of MFI zeolite as described above, a suitable catalyst can be obtained by appropriately optimizing synthesis conditions such as the raw material charge composition (e.g., the type of raw material and additive (SDA), the amount of additive, pH, silica / alumina molar ratio, medium, cation and anion abundance ratio), synthesis temperature, and synthesis time.

[0132] Specific examples include the synthesis method using a seed slurry described in Japanese Patent No. 5,426,983 and the method exemplified in The Hydrothermal Synthesis of Zeolites (Chemical Reviews, 2003, 103, 663-702).

[0133] Furthermore, commercially available zeolites can also be used as long as they are MFI zeolites having the above-mentioned specific physical properties and composition.

[0134] The zeolite-containing catalyst in this embodiment preferably contains elemental phosphorus or elemental silver.

[0135] The form of phosphorus element is a polymer of phosphorus (e.g., polyphosphoric acid), an oxide of phosphorus (e.g., P ２ O ５ ), compounds in which phosphorus is added to the aluminum of zeolite, etc. In addition, a plurality of these may be contained. When the zeolite contains aluminum, elemental phosphorus has the effect of suppressing dealumination of the zeolite and, in some cases, the effect of improving the propylene yield. In particular, in applications where the zeolite is exposed to a high-temperature steam atmosphere, the properties of the zeolite-containing catalyst are likely to change due to dealumination, so the effect of suppressing dealumination is further improved.

[0136] The content of elemental phosphorus contained in the zeolite-containing catalyst is preferably 0.01 to 2.0 mass % relative to the mass of the entire catalyst, and from the viewpoint of achieving an excellent effect of suppressing dealumination, is more preferably 0.05 to 2.0 mass %.

[0137] In this embodiment, the content of phosphorus in the catalyst is a value measured using an X-ray fluorescence analyzer. The content of phosphorus can be measured using a commercially available X-ray fluorescence analyzer under normal conditions in accordance with the instruction manual. For example, when using a Rigaku product under the trade name "RIX3000," the measurement conditions can be P-Kα radiation, a tube voltage of 50 kV, and a tube current of 50 mA.

[0138] In this embodiment, phosphoric acid and / or a phosphate (hereinafter also referred to as a "phosphorus raw material") is used as a raw material for the phosphorus element contained in the zeolite-containing catalyst. Phosphates are more preferred as the phosphorus raw material, and among phosphates, compounds showing a solubility of 1 g or more in 100 g of water at 25°C are more preferred.

[0139] Examples of phosphoric acid include phosphoric acid and pyrophosphoric acid, and examples of phosphates include ammonium phosphate salts such as ammonium phosphate, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, and sodium ammonium hydrogen phosphate, as well as potassium hydrogen phosphate, aluminum hydrogen phosphate, sodium phosphate, and potassium phosphate. Among these, ammonium phosphate salts having relatively high solubility in water are preferred, and more preferred is at least one selected from the group consisting of ammonium phosphate, diammonium hydrogen phosphate, and ammonium dihydrogen phosphate. These may be used alone or in combination of two or more.

[0140] The silver element may be in the form of, for example, silver ions, which have the effect of improving the hydrothermal resistance of zeolite by controlling the acid sites of the zeolite.

[0141] The content of silver element contained in the zeolite-containing catalyst is preferably 0.01 to 2.0 mass% relative to the mass of the entire catalyst, and from the viewpoint of excellent effect of improving hydrothermal resistance per content, it is more preferably 0.05 to 2.0 mass%.

[0142] In this embodiment, the silver content in the catalyst is a value measured using an X-ray fluorescence analyzer. The silver content can be measured using a commercially available X-ray fluorescence analyzer under normal conditions in accordance with the instruction manual. For example, when using a Rigaku product under the trade name "RIX3000," the measurement conditions can be P-Kα radiation, a tube voltage of 50 kV, and a tube current of 50 mA.

[0143] In this embodiment, silver nitrate can be used as a source of elemental silver contained in the zeolite-containing catalyst. A zeolite-containing catalyst containing sodium as a counter cation is ion-exchanged with silver nitrate, followed by sintering, to obtain a zeolite-containing catalyst containing elemental silver. The ion exchange between sodium, the counter cation in the zeolite, and silver nitrate can be performed by immersing the zeolite or the zeolite-containing catalyst in an aqueous solution of silver nitrate, followed by washing with water. The ion exchange rate can be improved by repeating the immersion and washing steps multiple times. Furthermore, a zeolite-containing catalyst containing elemental silver can also be obtained by treating a proton-type or ammonium-type zeolite with silver nitrate.

[0144] The zeolite-containing catalyst of this embodiment can be produced by molding a zeolite having the specific physical properties and composition described above, for example, as follows. The molding method is not particularly limited, and a common method can be used. Specific examples include a method of compression molding or extrusion molding of the catalyst components, and a spray-dry molding method that is optimal for a fluidized bed reaction system.

[0145] A binder can be used for molding. The binder is not particularly limited, and for example, silica, alumina, and kaolin can be used alone or in combination. Commercially available binders can be used. The mass ratio of zeolite to binder is preferably in the range of 10 / 90 to 90 / 10, more preferably in the range of 20 / 80 to 80 / 20. From the viewpoint of suppressing coking, a silica binder is preferred.

[0146] In the ethanol conversion process, a pretreatment process may be performed on the zeolite-containing catalyst prior to contacting the catalyst with the raw material. A preferred pretreatment process is a heat treatment process at a temperature of 300°C or higher in the presence of steam. Pretreatment tends to more significantly suppress catalyst degradation and improve selectivity. In the above method, the process is preferably performed at a temperature of 300°C or higher and 900°C or lower, in an atmosphere that is not particularly limited, but in which a mixed gas of air or an inert gas such as nitrogen and steam (water vapor) is circulated, with a water vapor partial pressure of 0.01 atmosphere or higher. The heat treatment temperature is more preferably 400°C or higher and 700°C or lower. This pretreatment process can also be performed using a reactor for converting ethanol.

[0147] (Product: Ethanol-Converted Fraction Containing Ethylene and Propylene) In the ethanol conversion step, the raw material is brought into contact with a catalyst to obtain an ethanol-converted fraction containing ethylene and propylene. The ethanol-converted fraction may contain hydrogen, aliphatic hydrocarbons having 1 to 3 carbon atoms, aliphatic hydrocarbons having 4 to 8 carbon atoms, aromatic compounds, and hydrocarbons having 9 or more carbon atoms.

[0148] The total content of ethylene and propylene in the ethanol-converted fraction is preferably 15% by mass or more, more preferably 20% by mass or more, and even more preferably 25% by mass or more, from the viewpoint of excellent production efficiency of the target compound. The P / E mass ratio, which represents the mass ratio of ethylene to propylene, can be appropriately adjusted depending on the reaction conditions, but from the viewpoint of excellent purification efficiency of the target compound, it is preferably 0.40 to 1.0, more preferably 0.45 to 0.80, and even more preferably 0.50 to 0.70.

[0149] <Purification step> The method for producing light olefins may include a purification step of separating target compounds such as ethylene and propylene from the ethanol conversion fraction. In the purification step, the ethylene and propylene contents C Ｅ１ However, it is preferable to purify the ethanol-converted fraction so that the ethylene and propylene contents are higher than those of the naphtha cracked fraction or a fraction derived therefrom in the combining step, thereby obtaining a purified ethanol-converted fraction.

[0150] (Third Cooling Step) The purification step preferably includes a third cooling step in which the ethanol-converted fraction is introduced into a third cooling tower 22 to obtain a cooled ethanol-converted fraction mainly containing olefins having 6 or less carbon atoms.

[0151] The ethanol-converted fraction obtained in the reactor 21 is introduced into the third cooling tower 22. In the third cooling tower 22, the aforementioned third cooling step is carried out to obtain a cooled ethanol-converted fraction containing mainly olefins having a carbon number of 6 or less. In the third cooling tower 22, the ethanol-converted fraction is cooled to remove hydrocarbons having a carbon number of more than 6 and water.

[0152] In the third cooling tower 22, the ethanol-converted fraction is preferably cooled by contacting it with water. The pH of the water used in the third cooling tower 22 can be adjusted appropriately for the purpose of suppressing corrosion of the equipment.

[0153] The pressure of the cooled ethanol-converted fraction after treatment in the third cooling tower 22 is preferably 0.01 to 1.5 MPaG, more preferably 0.05 to 0.5 MPaG, and even more preferably 0.07 to 0.2 MPaG.

[0154] The temperature of the cooled ethanol-converted fraction after treatment in the third cooling tower 22 is preferably 5 to 200°C, more preferably 10 to 100°C.

[0155] The method for producing light olefins according to this embodiment preferably includes a recycle step of introducing at least a portion of the cooled ethanol-converted fraction as part of the raw material into the reactor 21. By supplying the cooled ethanol-converted fraction to the reactor 21 in this manner, it can be converted into ethylene or propylene.

[0156] <Compression Separation Step> The method for producing light olefins according to this embodiment may include a compression separation step in which the cooled ethanol converted fraction is pressurized using a compressor to obtain a light ethanol converted fraction containing mainly olefins having 3 or less carbon atoms as a gas component, and a heavy ethanol converted fraction containing mainly olefins having 4 or more carbon atoms as a liquid component.

[0157] The compression separation step may include: a second compression step of pressurizing the cooled ethanol-converted fraction with a compressor; and a distillation step of obtaining, using a distillation column, a light ethanol-converted fraction containing mainly olefins having 3 or less carbon atoms as a gas component, and a heavy ethanol-converted fraction containing mainly olefins having 4 or more carbon atoms as a liquid component.

[0158] More specifically, as shown in FIG. 4, the cooled ethanol-converted fraction obtained in the third cooling step may be pressurized by a second compressor 23 and introduced into a distillation column 24.

[0159] In the distillation column 24, a light ethanol-converted fraction containing mainly olefins having a carbon number of 3 or less as a gas component and a heavy ethanol-converted fraction containing mainly hydrocarbons having a carbon number of 4 or more as a liquid component are obtained. As described above, the distillation process is carried out in the second compressor 23 and the distillation column 24.

[0160] The obtained light ethanol-converted fraction may be introduced into a condenser 25, and a portion thereof may be liquefied and refluxed to the distillation column to obtain a cooled light ethanol-converted fraction. By providing a distillation step in this manner, it is possible to reduce the amounts of hydrocarbons having 4 or more carbon atoms and water in the fraction derived from the ethanol-converted fraction, and to increase the proportions of ethylene and propylene.

[0161] The pressure of the cooled light ethanol converted fraction is preferably 0.5 to 3.0 MPaG, more preferably 1.0 to 2.5 MPaG, and even more preferably 1.1 to 2.0 MPaG.

[0162] The temperature of the cooled light ethanol converted fraction is preferably 0 to 50°C, more preferably 5 to 30°C, and even more preferably 10 to 20°C.

[0163] In the refining process including the distillation process, the ethylene and propylene content C after the refining Ｅ１ The ethanol-converted fraction is purified so that the ethylene and propylene contents are higher than those of the naphtha cracked fraction or a fraction derived therefrom in the combining step, thereby obtaining a purified ethanol-converted fraction.

[0164] In this way, when the ethanol-converted fraction that has undergone the compression separation step is combined in the combining step described below, a fraction with a high content of olefins having a carbon number of 3, from which hydrocarbons having a carbon number of 4 or more have been removed, is combined with a fraction derived from naphtha cracking fraction, thereby reducing the content of hydrocarbons having a carbon number of 4 or more in the combined fraction and increasing the proportions of ethylene and propylene. This makes it possible to reduce the processing energy required in cryogenic separation.

[0165] The method for producing light olefins according to this embodiment preferably includes a recycling step in which at least a portion of the heavy ethanol-converted fraction is introduced as part of the raw material into the reactor 21. By supplying the heavy ethanol-converted fraction to the reactor 21 in this manner, the olefins contained in the heavy ethanol-converted fraction are converted into ethylene or propylene, thereby improving the efficiency of producing light olefins from ethanol.

[0166] The compression separation step may involve liquefying a portion of the fraction by increasing the pressure with a compressor, and treating the fraction with a gas-liquid separator to obtain a light ethanol-converted fraction containing mainly olefins having 3 or less carbon atoms as a gas component, and a heavy ethanol-converted fraction containing mainly olefins having 4 or more carbon atoms as a liquid component. Use of a gas-liquid separator can reduce energy consumption in the compression separation step compared to using a distillation column.

[0167] More specifically, as shown in FIG. 5, the cooled ethanol-converted fraction obtained in the third cooling step may be pressurized by a second compressor 23 and introduced into a gas-liquid separation drum 26 .

[0168] In this way, when the ethanol-converted fraction that has undergone the compression separation step using the gas-liquid separator is combined in the combining step described below, the fraction that has a high content of olefins with a carbon number of 3, from which hydrocarbons with a carbon number of 4 or more have been removed, is combined with the fraction derived from the naphtha cracking fraction, thereby reducing the content of hydrocarbons with a carbon number of 4 or more in the combined fraction and increasing the proportions of ethylene and propylene. This makes it possible to reduce the processing energy required for cryogenic separation.

[0169] The method for producing light olefins according to this embodiment preferably includes a recycle step in which at least a portion of the heavy ethanol-converted fraction that has been subjected to the compression separation step using a gas-liquid separator is introduced as part of the raw material into the reactor 21. By supplying the heavy ethanol-converted fraction to the reactor 21 in this manner, the olefins contained in the heavy ethanol-converted fraction are converted to ethylene or propylene, thereby improving the efficiency of producing light olefins from ethanol.

[0170] <Combining Step> In the combining step, at least a portion of the naphtha cracked fraction or a fraction derived therefrom and at least a portion of the ethanol converted fraction or a fraction derived therefrom are combined to obtain a combined fraction.

[0171] The term "naphtha cracked fraction" refers to a fraction obtained by the cracking process described above. The term "fraction derived therefrom" refers to a fraction obtained by further refining the naphtha cracked fraction. The naphtha cracked fraction may be mixed with a hydrocarbon-containing gas to adjust its properties before refining.

[0172] The "ethanol-converted fraction" refers to a fraction obtained by the above-mentioned ethanol conversion step. Furthermore, the "fraction derived therefrom" refers to a fraction obtained by further refining the ethanol-converted fraction.

[0173] The joining step in the light olefin production method according to this embodiment will be described using a specific example.

[0174] In the first embodiment, the confluence step is performed after the second cooling step, as shown in Figures 4, 5, 16, and 17. By including the confluence step, the flow rate of the fraction introduced into the cryogenic separation step can be reduced, and the load on the cryogenic separation step can be alleviated.

[0175] The above-described production method may further include a first compression step in which the second cooled fraction is pressurized, and at least a portion of the naphtha cracked fraction or a fraction derived therefrom in the combining step may be the compressed second cooled fraction. In this case, the ethanol converted fraction or a fraction derived therefrom is preferably a fraction pressurized by a compression separation step or the like. By combining the naphtha cracked fraction or a fraction derived therefrom pressurized by the first compression step with the ethanol converted fraction or a fraction derived therefrom, i.e., by eliminating the first pressurization step for the ethanol converted fraction or a fraction derived therefrom, the pressure increase load in the naphtha cracking process can be reduced, facilitating the connection between the ethanol conversion process and the naphtha cracking process. Furthermore, when the pressure of the ethanol converted fraction or a fraction derived therefrom is higher than that of the naphtha cracked fraction or a fraction derived therefrom, the pressure can be reduced, facilitating the connection between the ethanol conversion process and the naphtha cracking process.

[0176] In the second embodiment, the combining step is performed after the first cooling step, as shown in, for example, Figures 6, 7, 9, 18, 19, and 21. In the second embodiment, at least a portion of the first cooled fraction is combined with at least a portion of the ethanol-converted fraction or a fraction derived therefrom before being introduced into the second cooling tower. At least a portion of the components having a carbon number of more than 4 contained in the fraction derived from the ethanol-converted fraction combined in the combining step is removed in the second cooling step, thereby further increasing the proportions of ethylene and propylene in the fraction introduced into cryogenic separation. Furthermore, for example, if the ethanol-converted fraction or a fraction derived therefrom contains hydrophilic by-products such as ethanol, the hydrophilic by-products can be extracted by introducing the ethanol-converted fraction or a fraction derived therefrom into the second cooling tower using water as a contact refrigerant, and the purity of the light olefins can be improved.

[0177] In the third embodiment, the joining step is performed so as to join the fraction in the circulation step of circulating the fraction to the second cooling tower, as shown in Figures 8 and 20. In this embodiment, the load on the cryogenic separation step can be reduced, as in the above-described embodiment.

[0178] In the fourth embodiment, the combining step is performed before introduction into the first cooling tower, as shown in, for example, Figures 10, 11, 13, 22, 23, and 25. In the fourth embodiment, at least a portion of the naphtha cracked fraction and at least a portion of the ethanol converted fraction or a fraction derived therefrom are combined before being introduced into the first cooling tower. Components with a carbon number greater than 6 contained in the fraction derived from the ethanol converted fraction, which are combined in the combining step, are removed by the third cooling tower 22 and then combined with the naphtha cracked fraction, thereby increasing the proportions of ethylene and propylene in the combined fraction. Furthermore, components with a carbon number greater than 4 contained in the fraction derived from the ethanol converted fraction are removed in the second cooling step, thereby further increasing the proportions of ethylene and propylene in the fraction introduced into cryogenic separation. Furthermore, for example, when the ethanol-converted fraction or a fraction derived therefrom contains lipophilic by-products, the lipophilic by-products can be extracted and the purity of light olefins can be improved by introducing the ethanol-converted fraction or a fraction derived therefrom into a first cooling tower using heavy oil, cracked gasoline, or a mixture thereof as a contact refrigerant.Furthermore, for example, when the ethanol-converted fraction or a fraction derived therefrom contains hydrophilic by-products such as ethanol, the hydrophilic by-products can be extracted and the purity of light olefins can be improved by introducing the ethanol-converted fraction or a fraction derived therefrom into a second cooling tower using water as a contact refrigerant.

[0179] In the fifth embodiment, as shown in, for example, FIGS. 12 and 24 , the confluence step combines the fraction introduced into the first cooling tower with a fraction in a circulation step, which circulates the fraction. In the fifth embodiment, at least a portion of the second heavy fraction in the circulation step is combined with at least a portion of the ethanol-converted fraction or a fraction derived therefrom. In this embodiment, as in the above-described embodiment, the load on the cryogenic separation step can be reduced. Furthermore, by combining at least a portion of the second heavy fraction with at least a portion of the ethanol-converted fraction or a fraction derived therefrom in the circulation step, the temperature difference between the two components can be reduced and volume fluctuations due to liquefaction of the second heavy fraction can be suppressed compared to when the second heavy fraction is connected with at least a portion of the naphtha cracked fraction.

[0180] The ratio O' of the amount of hydrogen and methane to the total amount of ethylene and propylene in the ethanol-converted fraction or a fraction derived therefrom in the combining step Ｅ and the ratio O' of the amount of hydrogen and methane to the total amount of ethylene and propylene in the naphtha cracking fraction or a fraction derived therefrom. Ｃ The relationship between these is represented by the formula (1-1): O' Ｅ <O' Ｃ ...It is preferable to satisfy (1-1).

[0181] In the light olefin production method according to this embodiment, the ratio O' Ｃ and ratio O' Ｅ The difference between (O' Ｃ -O' Ｅ The difference (O') is preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 20% by mass or more. Ｃ -O' Ｅ By having the difference (O'), the proportions of hydrogen and methane in the fraction introduced into the cryogenic separation step can be reduced, so that cryogenic separation can be carried out efficiently. Ｃ -O' Ｅ The upper limit of the content of ) is not particularly limited, but may be 70 mass % or less.

[0182] Propylene / ethylene mass ratio P' / E' in the ethanol-converted fraction in the combining step Ｅand the propylene / ethylene mass ratio P' / E' in the naphtha cracking fraction. Ｃ The relationship is expressed by the formula (2-1): |P' / E' Ｃ - P' / E' Ｅ It is preferable to satisfy | < 0.3 (2-1). By satisfying formula (2-1), the propylene / ethylene mass ratio in the fraction can be made approximately the same, so that there is no need to modify the refining equipment in the existing cracker, and it can be used as is. | P' / E' Ｃ - P' / E' Ｅ is preferably 0.2 or less, more preferably 0.1 or less, and even more preferably 0.05 or less. Ｃ - P' / E' Ｅ The lower limit of | is not particularly limited, and may be, for example, 0 or more (that is, the same ratio).

[0183] <Light Olefins> According to the production method of this embodiment, light olefins are obtained. The light olefins are obtained by the cryogenic separation step described above. In the olefin production method of this embodiment, the light olefin may be either ethylene or propylene, but is preferably propylene. Furthermore, according to the production method of this embodiment, propylene derived from bioresources can also be produced by using bioresources such as bioethanol as the raw material used in the ethanol conversion step.

[0184] The present invention will be described in more detail below by showing examples, but the present invention is not limited to the examples described below.

[0185] [Methods for measuring various physical properties] The methods for measuring various physical properties are as follows.

[0186] (Silica / alumina molar ratio of zeolite in zeolite-containing catalyst) Zeolite was completely dissolved in a sodium hydroxide solution to prepare a solution. The amount of Si and Al contained in the solution was measured by a conventional method using an ICP (inductively coupled plasma) emission spectrometer (manufactured by Rigaku, product name "JY138"), and the silica / alumina molar ratio was derived from the results. The measurement conditions were set as follows: high-frequency power: 1 kW, plasma gas: 13 L / min, sheath gas: 0.15 L / min, nebulizer gas: 0.25 L / min, Si measurement wavelength: 251.60 nm, Al measurement wavelength: 396.152 nm.

[0187] (Zeolite Structure Type) The structure type of the zeolite in the zeolite-containing catalyst was identified by measuring the X-ray diffraction pattern of the zeolite using an X-ray analyzer (manufactured by Rigaku, trade name "RINT") and referring to the diffraction patterns of known zeolites. The measurement conditions were as follows: Cu cathode, tube voltage: 40 kV, tube current: 30 mA, scan speed: 1 deg / min.

[0188] [Method for preparing zeolite-containing catalyst] Clay obtained from 70 parts by mass of proton-type ZSM-5 (silica / alumina molar ratio 980), a medium pore size zeolite, and 30 parts by mass of silica (water content adjusted using colloidal silica and fumed silica) was kneaded and then extruded to obtain an extruded molded body adjusted to a diameter of 2.1 mm and a length of 4 to 6 mm. The obtained molded body was calcined for 5 hours to obtain a proton-type zeolite-containing catalyst (ZSM-5). Furthermore, the proton-type zeolite-containing catalyst was impregnated with ammonium dihydrogen phosphate so that the P / Al molar ratio was 0.7, and calcined for 5 hours to obtain a phosphorus-added zeolite-containing catalyst (P-ZSM-5).

[0189] [Method of Ethanol Conversion] (Feedstock) In the examples and comparative examples, a feedstock mainly containing ethanol, ethylene, and olefins having 4 to 6 carbon atoms is used for ethanol conversion. The ethylene / ethanol molar ratio was calculated according to the following formula: Ethylene / ethanol molar ratio (mol / mol) = ethylene molar flow rate (mol / hr) / ethanol molar flow rate (mol / hr)

[0190] (Temperature Measurement) The temperatures at the catalyst bed inlet and outlet are measured using thermocouples inserted from outside the reactor. Specifically, as shown in Figure 3, in a plane perpendicular to the fluid flow direction, the center of the reactor is set to 0 and the distance from the center of the reactor to the inner wall surface of the reactor is set to d, and the temperature is measured at 0.5d to 0.6d. Note that the effect of heat radiation due to the insertion of these thermocouples is negligibly small.

[0191] (Reaction Evaluation) According to the following Examples and Comparative Examples, the reaction is carried out so that the average inlet and outlet reaction temperature is 540°C. A portion of each fraction is sampled every 3 hours from the start of the reaction and introduced into a gas chromatograph (hereinafter simply referred to as "GC", TCD, FID detector) for composition analysis. The average inlet and outlet reaction temperature is calculated according to the following formula: Average inlet and outlet reaction temperature (°C) = [catalyst bed inlet temperature (°C) + catalyst bed outlet temperature (°C)] / 2

[0192] (Distillate Gas Analysis) Apparatus: GC-2030 manufactured by Shimadzu Corporation Column: Custom capillary column SPB-1 manufactured by SUPELCO, USA (inner diameter 0.25 mm, length 60 m, film thickness 3.0 μm) Sample gas amount: 1 mL (sampling line kept at 200°C to 300°C) Heating program: Maintain at 40°C for 12 minutes, then heat to 200°C at 5°C / min, and then maintain at 200°C for 22 minutes. Split ratio: 200:1 Carrier gas (nitrogen) flow rate: 120 mL / min FID detector: Air supply pressure 50 kPa (approximately 500 mL / min), hydrogen supply pressure 60 kPa (approximately 50 mL / min) Measurement method: The TCD detector and FID detector were connected in series, and composition analysis was performed based on data detected by the TCD detector for hydrogen and data detected by the FID detector for oxygenated substances such as hydrocarbons and ethanol, and the calibration curve method was used to determine the concentration of the target compound in the reaction gas, and the mass per hour produced by the reaction.

[0193] (C2-3 Olefin Treatment Efficiency) The C2-3 olefin efficiency is calculated from the fraction introduced into the cryogenic separation step using the following formula: C2-3 olefin efficiency (mass %)=(mass of ethylene+mass of propylene) / mass of introduced fraction×100

[0194] (C2-3 olefin treatment efficiency index) In Examples A1 to A13, the C2-3 olefin treatment efficiency index was calculated by dividing the above-mentioned olefin treatment efficiency by the treatment efficiency of Reference Example A1. In Examples B1 to B13, the C2-3 olefin treatment efficiency index was calculated by dividing the above-mentioned olefin treatment efficiency by the treatment efficiency of Reference Example B1.

[0195] (C3L Volumetric Efficiency) The C3L volumetric efficiency is calculated from the fraction introduced into the cryogenic separation step using the following formula: C3L volumetric efficiency (mol %) = (molar amount of ethylene + mole amount of propylene) / (molar amount of hydrogen + mole amount of methane + mole amount of acetylene + mole amount of ethylene + mole amount of ethane + mole amount of propylene + mole amount of propane) × 100

[0196] (C3L volume efficiency index) In Examples A1 to A13, the C3L volume efficiency index was determined by dividing the above-mentioned C3L volume efficiency by the C3L volume efficiency of Reference Example A1. In Examples B1 to B13, the C3L volume efficiency index was determined by dividing the above-mentioned C3L volume efficiency by the C3L volume efficiency of Reference Example B1.

[0197] (Off-gas ratio in each fraction) The off-gas ratio in each fraction is the ratio of the amount of hydrogen and methane to the total amount of ethylene and propylene in the fraction, and is calculated from the composition of each fraction using the following formula. Ｅ , the off-gas ratio in the naphtha cracking fraction is O Ｃ and the off-gas ratio in the ethanol-converted fraction or a fraction derived therefrom in the combining step is O'. Ｅ , the off-gas ratio in the naphtha cracking fraction or the fraction derived therefrom in the combining step is O' Ｃ Off-gas ratio in each fraction (mass%) = (hydrogen mass + methane mass) / (ethylene mass + propylene mass) x 100

[0198] (Ethylene and propylene content in each fraction) Content C of ethylene and propylene in the ethanol converted fraction or a fraction derived therefrom in the combining step Ｅ The content of ethylene and propylene in the naphtha cracking fraction or the fraction derived therefrom in the combining step is C ＣThe content of ethylene and propylene in the ethanol-converted fraction obtained from the reaction step and not subjected to a separation process is represented by C. Ｅ＿ＡＰ The content of ethylene and propylene in the naphtha cracked fraction obtained from the cracking process and not subjected to a separation process is C Ｃ＿ＡＰ is calculated from the composition of each fraction using the following formula: Content of ethylene and propylene in each fraction (mass%) = (mass of ethylene + mass of propylene) / mass of each fraction × 100

[0199] (Product Ratio in Recycle Fraction) When a portion of the ethanol-converted fraction is recycled to the reaction step as a recycled fraction, the product ratio in the recycled fraction is calculated from the composition of the recycled fraction using the following formula: Product ratio in recycled fraction (mass %) = (Ethylene mass + Propylene mass) / Recycle fraction mass × 100

[0200] (Propylene to Ethylene Mass Ratio P / E) The propylene to ethylene mass ratio P / E in each fraction is calculated from the composition of each fraction using the following formula: P / E(-) = propylene mass / ethylene mass

[0201] [Naphtha Cracking Method] In the examples and comparative examples, naphtha and diluted steam at a mass ratio of 0.5 to the naphtha are co-fed into a heated tubular reactor to obtain naphtha cracked gas. The obtained naphtha cracked fraction is analyzed in the same manner as in the ethanol conversion method. Prior to the downstream process, the naphtha cracked fraction is mixed with light gas recycled from the downstream refining equipment to adjust its temperature.

[0202] Reference Example A1 Reference Example A1 is carried out using a front-end demethanolizer-type light olefin production facility shown in FIG. 14. A naphtha feedstock containing 357.3 ton / y of heavy naphtha and dilution steam at a mass ratio of 0.5 to the naphtha is introduced into a cracking furnace under cracking conditions of 0.17 MPaG and 825 ° C. to obtain a naphtha cracked fraction. The naphtha cracked fraction is introduced into a first cooling tower and cooled to 110 ° C. by contacting it with a mixture of heavy oil and cracked gasoline to obtain a first cooled fraction. Subsequently, the first cooled fraction is introduced into a second cooling tower and contacted with cooling water to obtain a second cooled fraction at 0.11 MPaG and 41 ° C. The second cooled fraction is pressurized to 0.99 MPaG by a compressor and introduced into a soda wash tower to obtain an introduced fraction to be introduced into the cryogenic separation process. The compositions of the naphtha cracking fraction and the feed fraction are shown in Table 1.

[0203] In Reference Example A2, a naphtha cracked fraction was obtained in the same manner as in Reference Example A1, except that the temperature of the cracking furnace was changed to 840°C and the amount of naphtha fed was adjusted in accordance with the amount of ethylene produced. The composition of the naphtha cracked fraction is shown in Table 1.

[0204] In Reference Example A3, a naphtha cracked fraction was obtained in the same manner as in Reference Example A1, except that the heavy naphtha was changed to light naphtha and the amount of naphtha fed was adjusted in accordance with the amount of ethylene produced. The composition of the naphtha cracked fraction is shown in Table 1.

[0205] In Reference Example A4, a naphtha cracked fraction was obtained in the same manner as in Reference Example A3, except that the temperature of the cracking furnace was changed to 840°C and the amount of naphtha fed was adjusted in accordance with the amount of ethylene produced. The composition of the naphtha cracked fraction is shown in Table 1.

[0206] From Reference Examples A1 to A4, it can be seen that the yield of methane and hydrogen varies depending on the type of naphtha raw material used in naphtha cracking and the temperature of the cracking furnace. However, the highest yield was obtained when the cracking process was carried out at 825°C using heavy naphtha as the raw material. Ｃ It can be seen that the value of becomes smaller.

[0207] Reference Example A5 A raw material containing 23.6 mass% of ethanol, 15.1 mass% of ethylene, and 16.0 mass% of olefins having 4 to 6 carbon atoms was heated and supplied to a reactor packed with a zeolite-containing catalyst so as to have a WHSV of 3.8, and an ethanol-converted fraction was obtained by carrying out an ethanol conversion reaction. In addition to the above, the raw material also contained paraffins, olefins having 7 or more carbon atoms, and water. The heater temperature was adjusted so that the average reaction temperature at the inlet and outlet was 540°C. The ethanol conversion reaction was carried out for 48 hours, and the composition of the ethanol-converted fraction 24 hours after the start of the reaction is shown in Table 1, converted into an ethylene production rate of 100.0 ton / y. The ethanol-converted fraction was 0.001% throughout the 48 hours. Ｅ The value of was constant at 0.6.

[0208] Comparison of Reference Examples A1 to A5 with Reference Example A5 reveals that when light olefins are obtained from a raw material containing ethanol, the yields of methane and hydrogen are lower than when the same amount of ethylene is obtained by naphtha cracking.

[0209]

[0210] In the following Examples A1 to A13 and Examples B1 to B13, the purification step of the ethanol-converted fraction and the position of the combining step in the naphtha cracking process will be discussed. In Examples A1 to A13 and Examples B1 to B13, the ethanol conversion step was carried out in the same manner as in Reference Example A5, and the cracking step was carried out in the same manner as in Reference Example A1. At this time, (P / E Ｅ -P / E Ｃ ) is 0.01, |C Ｅ＿ＡＰ -C Ｃ＿ＡＰ | is 0.8 mass%, satisfying the formula (α) and formula (β-1). The raw material composition for ethanol conversion is shown in Example A1.

[0211] Example A1 This example was carried out using the light olefin production facility shown in Figure 2. (Ethanol Conversion) A feedstock containing 209.2 ton / y of ethanol (23.6 mass%), 15.1 mass% ethylene, 16.0 mass% C4-6 olefins, 13.6 mass% C4-6 paraffins, 4.2 mass% aromatic compounds, and 16.7 mass% water was heated and fed to a reactor 21 packed with a zeolite-containing catalyst so that the WHSV was 3.8. An ethanol conversion reaction was carried out at a reaction temperature of 540°C to obtain an ethanol-converted fraction. The ethanol-converted fraction was introduced into a third cooling tower 22 and contacted with cooling water to obtain a cooled ethanol-converted fraction at 35°C and 0.15 MPaG at a rate of 123.0 ton / y. 40.9 ton / y of the cooled ethanol-converted fraction was recycled as a mixed feedstock without undergoing processes such as separation and purification. At this time, the product ratio in the recycled fraction was 49.4 mass %.

[0212] (Naphtha Cracking) A naphtha feedstock containing 266.5 ton / y of heavy naphtha and dilution steam at a mass ratio of 0.5 to the naphtha is introduced into a cracking furnace 11 under cracking conditions of 0.17 MPaG and 825°C to obtain a naphtha cracked fraction. The naphtha cracked fraction is introduced into a first cooling tower 12 and cooled to 110°C by contacting it with a mixture of heavy oil and cracked gasoline to obtain a first cooled fraction, which is then introduced into a second cooling tower 13 and contacted with cooling water to obtain a second cooled fraction at 0.11 MPaG and 41°C. The second cooled fraction is introduced into a pressure booster 14 and pressurized to 0.99 MPaG.

[0213] (Combination of Ethanol Conversion and Naphtha Cracking) A combined fraction is prepared by mixing the pressurized second cooled fraction at 253.2 ton / y with the cooled ethanol conversion fraction at 82.1 ton / y. The combined fraction is introduced into a soda wash tower 15 where it is contacted with aqueous sodium hydroxide to obtain a washed fraction. The washed fraction is introduced into the cryogenic separation step as an introduced fraction. In this example, the amount of ethylene produced is 100.0 ton / y contained in the introduced fraction. The composition of the introduced fraction is shown in Table 2. The value of the C2-3 olefin treatment efficiency index indicates that the treatment efficiency of light olefins in the cryogenic step is improved. In addition, the value of the C3L volumetric efficiency index indicates that the treatment efficiency of light olefins per volume of the fraction introduced into the cryogenic step is improved.

[0214] Example A2 This example was carried out using the light olefin production facility shown in Figure 4. (Ethanol Conversion) 139.7 ton / y of raw material was heated and fed to a reactor 21 packed with a zeolite-containing catalyst so that the WHSV was 3.8. An ethanol conversion reaction was carried out at a reaction temperature of 540°C to obtain an ethanol-converted fraction. The ethanol-converted fraction was introduced into a third cooling tower 22 and contacted with cooling water to obtain a cooled ethanol-converted fraction at 45°C. The cooled ethanol-converted fraction was pressurized using a pressure booster 23 and introduced into a second distillation tower 24, thereby obtaining a light ethanol-converted fraction from the top of the second distillation tower 24. The light ethanol-converted fraction was introduced into a condenser 25, and a portion was liquefied and refluxed to the second distillation tower 24. The cooled light ethanol-converted fraction was obtained as a gas at 1.90 MPaG and 15°C. At this time, the heavy ethanol converted fraction of 47.5 ton / y obtained from the bottom of the second distillation column 24 is used as a recycled fraction to be reused as the raw material introduced into the reactor 21 without undergoing additional steps such as purification. At this time, the product ratio in the recycled fraction is 0.7 mass%.

[0215] (Naphtha Cracking) A naphtha feedstock containing 266.5 ton / y of heavy naphtha and dilution steam at a mass ratio of 0.5 to the naphtha is introduced into a cracking furnace 11 under cracking conditions of 0.17 MPaG and 825°C to obtain a naphtha cracked fraction. The naphtha cracked fraction is introduced into a first cooling tower 12 and cooled to 110°C by contacting it with a mixture of heavy oil and cracked gasoline to obtain a first cooled fraction, which is then introduced into a second cooling tower 13 and contacted with cooling water to obtain a second cooled fraction at 0.11 MPaG and 41°C. The second cooled fraction is introduced into a pressure booster 14 and pressurized to 0.99 MPaG.

[0216] (Combination of Ethanol Conversion and Naphtha Cracking) A combined fraction is prepared by mixing 253.2 ton / y of the second cooled fraction with 45.4 ton / y of the cooled light ethanol converted fraction. The combined fraction is introduced into the soda wash tower 15, where it is contacted with aqueous sodium hydroxide to obtain a washed fraction. The washed fraction is further pressurized and introduced into the cryogenic separation step as an introduced fraction. In this example, the ethylene produced is 100.0 ton / y contained in the introduced fraction. The flow rate and composition of the introduced fraction are shown in Table 2-1. A comparison of this example with Example A1 reveals that by introducing the fraction obtained by ethanol conversion into the second distillation tower 24 and providing a distillation step to separate the fraction into a light ethanol converted fraction and a heavy ethanol converted fraction, the amount of fraction introduced into the cryogenic separation step can be reduced and the energy efficiency of the cryogenic separation can be improved. Furthermore, by providing a distillation step, the product ratio in the recycled fraction recycled as a mixed feedstock can be reduced, and light olefins such as ethylene and propylene can be produced efficiently from a smaller amount of the mixed feedstock.

[0217] Example A3 The procedure of Example A3 was repeated except that the naphtha cracking-derived fraction and the ethanol-converted fraction were combined in such amounts that, of the 100.0 ton / y of ethylene introduced into the cryogenic separation step, 50.0 ton / y of ethylene was obtained by ethanol conversion and 50.0 ton / y of ethylene was obtained by naphtha cracking. The flow rates and compositions of the introduced fractions are shown in Table 2.

[0218] Example A4 The procedure of Example A2 was repeated except that the naphtha cracking-derived fraction and the ethanol-converted fraction were combined in such amounts that, of the 100.0 ton / y of ethylene introduced into the cryogenic separation step, 75.0 ton / y of ethylene was obtained by ethanol conversion and 25.0 ton / y of ethylene was obtained by naphtha cracking. The flow rates and compositions of the introduced fractions are shown in Table 2.

[0219] Example A5 This example was carried out using the light olefin production facility shown in FIG. 5. (Ethanol Conversion) 145.6 ton / y of raw material was heated and fed to reactor 21 packed with a zeolite-containing catalyst so that WHSV = 3.8. An ethanol conversion reaction was carried out at a reaction temperature of 540°C to obtain an ethanol-converted fraction. The ethanol-converted fraction was introduced into a third cooling tower 22 and contacted with cooling water to obtain a cooled ethanol-converted fraction at 45°C. The cooled ethanol-converted fraction was pressurized using a pressure booster 23 and introduced into a gas-liquid separation drum, yielding a light ethanol-converted fraction of 51.3 ton / y as a gas at 1.90 MPaG and 40°C. At this time, 49.5 ton / y of heavy ethanol-converted fraction obtained as a liquid in gas-liquid separation drum 26 was used as a recycled fraction to be reused as raw material introduced into reactor 21 without undergoing additional purification or other processes. At this time, the product ratio in the recycled fraction was 11.3 mass%. (Naphtha Cracking) A naphtha feedstock containing 266.5 ton / y of heavy naphtha and dilution steam at a mass ratio of 0.5 to the naphtha is introduced into a cracking furnace 11 under cracking conditions of 0.17 MPaG and 825°C to obtain a naphtha cracked fraction. The naphtha cracked fraction is introduced into a first cooling tower 12 and cooled to 110°C by contacting it with a mixture of heavy oil and cracked gasoline to obtain a first cooled naphtha cracked fraction. The first cooled naphtha cracked fraction is introduced into a second cooling tower 13 and contacted with cooling water to obtain a second cooled naphtha cracked fraction at 0.11 MPaG and 41°C. The second cooled naphtha cracked fraction is introduced into a pressure booster 14 and pressurized to 0.99 MPaG. (Combination of Ethanol Conversion and Naphtha Cracking) A combined fraction is prepared by mixing 253.2 ton / y of the second cooled naphtha cracking fraction with 51.3 ton / y of the light ethanol conversion fraction. The combined fraction is introduced into a soda wash tower 15 where it is contacted with an aqueous sodium hydroxide solution to obtain a washed fraction. The washed fraction is introduced into the cryogenic separation step as an introduced fraction. The amount of ethylene produced in this example is the sum of the amounts of ethylene contained in the introduced fractions, and is 100.0 ton / y. The flow rate and composition of the introduced fraction are shown in Table 2.

[0220]

[0221]

[0222] [Example A6] This example was carried out using the light olefin production facility shown in Figure 6. (Ethanol Conversion) 209.2 ton / y of raw material was heated and fed to a reactor 21 packed with a zeolite-containing catalyst so that the WHSV was 3.8. The ethanol conversion reaction was carried out at a reaction temperature of 540°C to obtain an ethanol-converted fraction. The ethanol-converted fraction was introduced into a third cooling tower 22 and contacted with cooling water to obtain a cooled ethanol-converted fraction at 45°C and 0.15 MPaG at a rate of 138.6 ton / y. Of the cooled ethanol-converted fraction, 46.1 ton / y was used as a recycled fraction, which was reused as a mixed feedstock without undergoing processes such as separation and purification. At this time, the product ratio in the recycled fraction was 43.8 mass%.

[0223] (Naphtha Cracking) A naphtha feedstock containing 266.5 ton / y of heavy naphtha and dilution steam at a mass ratio of 0.5 to the naphtha is introduced into a cracking furnace 11 under cracking conditions of 0.17 MPaG and 825°C to obtain a naphtha cracked fraction. The naphtha cracked fraction is introduced into a first cooling tower 12 and cooled to 110°C by contacting it with a mixture of heavy oil and cracked gasoline to obtain a first cooled fraction.

[0224] (Combination of Ethanol Conversion and Naphtha Cracking) A combined fraction is prepared by mixing 474.1 ton / y of the first cooled fraction with 92.5 ton / y of the cooled ethanol conversion fraction. The combined fraction is introduced into a second cooling tower 13 and contacted with cooling water to obtain a second cooled fraction at 41°C. The second cooled fraction is introduced into a pressure booster 14 and pressurized to 0.99 MPaG. The pressurized second cooled fraction is introduced into a soda wash tower 15 and contacted with aqueous sodium hydroxide to obtain a wash fraction. The wash fraction is further pressurized and introduced into the cryogenic separation step as an input fraction. In this example, the ethylene produced is 100.0 ton / y contained in the input fraction. The flow rate and composition of the input fraction are shown in Table 3.

[0225] Example A7 This example was carried out using the light olefin production facility shown in Figure 7. (Ethanol Conversion) 139.7 ton / y of raw material was heated and fed to a reactor 21 packed with a zeolite-containing catalyst so that the WHSV was 3.8. An ethanol conversion reaction was carried out at a reaction temperature of 540°C to obtain an ethanol-converted fraction. The ethanol-converted fraction was introduced into a third cooling tower 22 and contacted with cooling water to obtain a cooled ethanol-converted fraction at 45°C. The cooled ethanol-converted fraction was pressurized using a pressure booster 23 and introduced into a second distillation tower 24, thereby obtaining a light ethanol-converted fraction from the top of the second distillation tower 24. The light ethanol-converted fraction was introduced into a condenser 25, and a portion was liquefied and refluxed to the second distillation tower 24. The cooled light ethanol-converted fraction was obtained as a gas at 1.90 MPaG and 15°C. At this time, the heavy ethanol converted fraction of 47.5 ton / y obtained from the bottom of the second distillation column 24 is used as a recycled fraction to be reused as a mixed feedstock without undergoing additional steps such as purification, etc. At this time, the product ratio in the recycled fraction is 0.7 mass%.

[0226] (Naphtha Cracking) A naphtha feedstock containing 266.5 ton / y of heavy naphtha and dilution steam at a mass ratio of 0.5 to the naphtha is introduced into a cracking furnace 11 under cracking conditions of 0.17 MPaG and 825°C to obtain a naphtha cracked fraction. The naphtha cracked fraction is introduced into a first cooling tower 12 and cooled to 110°C by contacting it with a mixture of heavy oil and cracked gasoline to obtain a first cooled fraction.

[0227] (Combination of Ethanol Conversion and Naphtha Cracking) A combined fraction is prepared by mixing 474.1 ton / y of the first cooled fraction with 45.4 ton / y of the cooled light ethanol conversion fraction. The combined fraction is introduced into a second cooling tower 13 and contacted with cooling water to obtain a second cooled fraction at 41°C. The second cooled fraction is introduced into a pressure booster 14 and pressurized to 0.99 MPaG. The pressurized second cooled fraction is introduced into a soda wash tower 15 and contacted with aqueous sodium hydroxide to obtain a wash fraction. The wash fraction is further pressurized and introduced into the cryogenic separation step as an input fraction. In this example, the ethylene produced is 100.0 ton / y contained in the input fraction. The flow rate and composition of the input fraction are shown in Table 3.

[0228] Example A8 This example is carried out using the light olefin production facility shown in FIG. 8 . This example is carried out in the same manner as Example A7, except for changing the connection points. In this example, a combined fraction is prepared by combining a cooled light ethanol-converted fraction at 15°C with a second bottom reflux fraction at 68°C, which contains a fraction obtained from the bottom of the second cooling tower 13 and is refluxed into the second cooling tower 13. The amount of the second bottom reflux fraction is determined based on the production balance of the target compounds, but in this example, the second bottom reflux fraction is set to 52.6 ton / y. By combining the second bottom reflux fraction with the ethanol-converted fraction, the ethanol-converted fraction is introduced into the second cooling tower 13. Therefore, the composition and flow rate of the introduced fraction obtained in Example A7 and this example are the same. At this point, the naphtha cracking fraction and the ethanol conversion fraction are merged, thereby reducing the temperature difference between the fractions to 53 K, which is smaller than the 96 K in Example A7, and making it possible to suppress the volume change associated with the liquefaction of the high-temperature fraction.

[0229] Example A9 This example was carried out using the light olefin production facility shown in Figure 9. (Ethanol Conversion) 145.6 ton / y of feedstock was heated and fed to reactor 21 packed with a zeolite-containing catalyst so that WHSV = 3.8. An ethanol conversion reaction was carried out at a reaction temperature of 540°C to obtain an ethanol-converted fraction. The ethanol-converted fraction was introduced into third cooling tower 22 and contacted with cooling water to obtain a cooled ethanol-converted fraction at 45°C. The cooled ethanol-converted fraction was pressurized using booster 23 and introduced into gas-liquid separation drum 26, yielding a light ethanol-converted fraction of 51.3 ton / y as a gas at 1.90 MPaG and 40°C. At this time, 49.4 ton / y of heavy ethanol-converted fraction obtained as a liquid in gas-liquid separation drum 26 was used as a recycled fraction to be reused as feedstock introduced into reactor 21 without undergoing additional purification or other processes. At this time, the product ratio in the recycled fraction is 11.3 mass%. (Naphtha Cracking) A naphtha feedstock containing 266.5 ton / y of heavy naphtha and dilution steam at a mass ratio of 0.5 to the naphtha is introduced into a cracking furnace 11 under cracking conditions of 0.17 MPaG and 825°C to obtain a naphtha cracked fraction. The naphtha cracked fraction is introduced into a first cooling tower 12 and cooled to 110°C by contacting it with a mixture of heavy oil and cracked gasoline to obtain a first cooled naphtha cracked fraction. (Combination of Ethanol Conversion and Naphtha Cracking) A combined fraction is prepared by mixing 474.1 ton / y of the first cooled naphtha cracked fraction with 51.3 ton / y of the light ethanol converted fraction. The combined fraction is introduced into a second cooling tower 13 and brought into contact with cooling water to obtain a second cooled naphtha cracked fraction at 0.11 MPaG and 41°C. The second cooled naphtha cracked fraction is introduced into a pressure booster 14 and pressurized to 0.99 MPaG. The combined fraction is introduced into a soda wash tower where it is brought into contact with aqueous sodium hydroxide solution to obtain a wash fraction. The wash fraction is further pressurized and introduced into the cryogenic separation step as an input fraction. The composition of the input fraction is shown in Table 3. The amount of ethylene produced in this example is the total amount of ethylene contained in the input fractions, and is 100.0 ton / y.

[0230]

[0231]

[0232] [Example A10] This example was carried out using the light olefin production facility shown in Figure 10. (Ethanol Conversion) 209.2 ton / y of raw material was heated and fed to a reactor 21 packed with a zeolite-containing catalyst so that the WHSV was 3.8. The ethanol conversion reaction was carried out at a reaction temperature of 540°C to obtain an ethanol-converted fraction. The ethanol-converted fraction was introduced into a third cooling tower 22 and contacted with cooling water to obtain a cooled ethanol-converted fraction at 45°C and 0.15 MPaG at a rate of 138.6 ton / y. Of the cooled ethanol-converted fraction, 46.1 ton / y was used as a recycled fraction, which was reused as a mixed feedstock without undergoing processes such as separation and purification. At this time, the product ratio in the recycled fraction was 43.8 mass%.

[0233] (Naphtha Cracking) A naphtha feedstock containing 266.5 ton / y of heavy naphtha and dilution steam at a mass ratio of 0.5 to the naphtha is introduced into the cracking furnace 11 under cracking conditions of 0.17 MPaG and 825°C to obtain a naphtha cracked fraction.

[0234] (Combination of Ethanol Conversion and Naphtha Cracking) A combined fraction is prepared by mixing 417.2 ton / y of naphtha cracked fraction at 360°C with 92.5 ton / y of cooled ethanol conversion fraction. The combined fraction is introduced into a first cooling tower 12 and contacted with a mixture of heavy oil and cracked gasoline to cool to 110°C, thereby obtaining a first cooled fraction. The first cooled fraction is introduced into a second cooling tower 13 and contacted with cooling water to obtain a second cooled fraction at 41°C. The second cooled fraction is introduced into a pressure booster 14 and pressurized to 0.99 MPaG. The pressurized second cooled fraction is introduced into a soda wash tower 15 and contacted with aqueous sodium hydroxide solution to obtain a washed fraction. The washed fraction is further pressurized and introduced into the cryogenic separation step as an introduced fraction. In this example, the ethylene produced was contained in the introduced fraction at a rate of 100.0 ton / y. The flow rate and composition of the introduced fraction are shown in Table 4.

[0235] [Example A11] This example was carried out using the light olefin production facility shown in Figure 11. (Ethanol Conversion) 139.7 ton / y of raw material was heated and fed to a reactor 21 packed with a zeolite-containing catalyst so that the WHSV was 3.8. An ethanol conversion reaction was carried out at a reaction temperature of 540°C to obtain an ethanol-converted fraction. The ethanol-converted fraction was introduced into a third cooling tower 22 and contacted with cooling water to obtain a cooled ethanol-converted fraction at 45°C. The cooled ethanol-converted fraction was pressurized using a pressure booster 23 and introduced into a second distillation tower 24, thereby obtaining a light ethanol-converted fraction from the top of the second distillation tower 24. The light ethanol-converted fraction was introduced into a condenser 25, and a portion was liquefied and refluxed to the second distillation tower 24. The cooled light ethanol-converted fraction was obtained as a gas at 1.90 MPaG and 15°C. At this time, the heavy ethanol converted fraction of 47.5 ton / y obtained from the bottom of the second distillation column 24 is used as a recycled fraction to be reused as a mixed feedstock without undergoing additional steps such as purification, etc. At this time, the product ratio in the recycled fraction is 0.7 mass%.

[0236] (Naphtha Cracking) A naphtha feedstock containing 266.5 ton / y of heavy naphtha and dilution steam at a mass ratio of 0.5 to the naphtha is introduced into the cracking furnace 11 under cracking conditions of 0.17 MPaG and 825°C to obtain a naphtha cracked fraction.

[0237] (Combination of Ethanol Conversion and Naphtha Cracking) A combined fraction is prepared by mixing 417.2 ton / y of naphtha cracked fraction at 360°C with 45.4 ton / y of cooled light ethanol conversion fraction. The combined fraction is introduced into a first cooling tower 12 and contacted with a mixture of heavy oil and cracked gasoline to cool to 110°C, thereby obtaining a first cooled fraction. The first cooled fraction is introduced into a second cooling tower 13 and contacted with cooling water to obtain a second cooled fraction at 41°C. The second cooled fraction is introduced into a pressure booster 14 and pressurized to 0.99 MPaG. The pressurized second cooled fraction is introduced into a soda wash tower 15 and contacted with aqueous sodium hydroxide solution to obtain a washed fraction. The washed fraction is further pressurized and introduced into the cryogenic separation step as an introduced fraction. In this example, the ethylene produced was contained in the introduced fraction at a rate of 100.0 ton / y. The flow rate and composition of the introduced fraction are shown in Table 4.

[0238] [Example A12] This example is carried out using the light olefin production facility shown in Figure 12. This example is carried out in the same manner as Example A9, except for changing the connection points. In this example, a cooled light ethanol-converted fraction at 15°C is combined with a first bottom reflux fraction at 80°C obtained from the bottom of the second cooling tower 13 and refluxed to the first cooling tower 12, to prepare a combined fraction. By combining the first bottom reflux fraction and the ethanol-converted fraction, the ethanol-converted fraction is introduced into the first cooling tower 12, so the composition and flow rate of the introduced fraction obtained in Example A9 and Example A10 are unchanged. By combining the naphtha cracked fraction and the ethanol-converted fraction at this point, the temperature difference between the fractions is reduced to 65 K, which is smaller than the 345 K in Example A9, and volume change associated with liquefaction of the high-temperature fraction can be suppressed.

[0239] Example A13 This example was carried out using the light olefin production facility shown in FIG. 13 . (Ethanol Conversion) 145.6 ton / y of mixed feed gas was heated and supplied to reactor 21 packed with a zeolite-containing catalyst so that WHSV = 3.8. An ethanol conversion reaction was carried out at a reaction temperature of 540°C to obtain an ethanol-converted fraction. The ethanol-converted fraction was introduced into third cooling tower 22 and contacted with cooling water to obtain a cooled ethanol-converted fraction at 45°C. The cooled ethanol-converted fraction was pressurized using booster 23 and introduced into gas-liquid separation drum 26, yielding a light ethanol-converted fraction of 51.3 ton / y as a gas at 1.90 MPaG and 40°C. The heavy ethanol-converted fraction of 49.4 ton / y obtained as a liquid in gas-liquid separation drum 26 was used as a recycled fraction to be reused as the feedstock introduced into reactor 21 without undergoing additional purification or other processes. At this time, the product ratio in the recycled fraction is 11.3 mass%. (Naphtha Cracking) Naphtha feedstock containing 266.5 ton / y of heavy naphtha and dilution steam at a mass ratio of 0.5 to the naphtha is introduced into the cracking furnace 11 under cracking conditions of 0.17 MPaG and 825°C to obtain a naphtha cracked fraction. (Combined Ethanol Conversion and Naphtha Cracking) A combined fraction is prepared by mixing 417.2 ton / y of naphtha cracked fraction with 51.3 ton / y of light ethanol converted fraction. The combined fraction is introduced into the first cooling tower 12 and cooled to 110°C by contacting with a mixture of heavy oil and cracked gasoline to obtain a first cooled naphtha cracked fraction. The combined fraction is introduced into the first cooling tower 12 and contacted with cooling water to obtain a second cooled naphtha cracked fraction at 0.11 MPaG and 41°C. The second cooled naphtha cracked fraction is introduced into a pressure booster 14 and pressurized to 0.99 MPaG. The pressurized second cooled naphtha cracked fraction is introduced into a soda wash tower 15 where it is contacted with an aqueous sodium hydroxide solution to obtain a washed fraction. The composition of the introduced fraction is shown in Table 4. The combined washed fraction is further pressurized and introduced into the cryogenic separation step as an introduced fraction. The amount of ethylene produced in this example is the total amount of ethylene contained in the introduced fractions, and is 100.0 ton / y.

[0240]

[0241] Reference Example B1 Reference Example B1 is carried out using a front-end depropanizer type light olefin production facility shown in FIG. 26. A naphtha feedstock containing 357.3 ton / y of heavy naphtha and dilution steam at a mass ratio of 0.5 to the naphtha is introduced into a cracking furnace 11 under cracking conditions of 0.17 MPaG and 825 ° C. to obtain a naphtha cracked fraction. The naphtha cracked fraction is introduced into a first cooling tower 12 and cooled to 110 ° C. by contacting it with a mixture of heavy oil and cracked gasoline to obtain a first cooled naphtha cracked fraction. The first cooled naphtha cracked fraction is introduced into a second cooling tower 13 and contacted with cooling water to obtain a second cooled naphtha cracked fraction at 0.11 MPaG and 41 ° C. The second cooled naphtha cracked fraction of 339.5 ton / y is introduced into a pressure booster 14, where it is pressurized to 0.99 MPaG and introduced into a soda wash tower 15 to obtain a wash fraction. The wash fraction is further pressurized to 1.82 MPaG and then introduced into a first distillation tower 17, where an inlet fraction is obtained at -18°C from the top of the tower and introduced into the cryogenic separation process. A bypass fraction is obtained from the bottom of the tower, bypassing the cryogenic separation process and being introduced into downstream equipment. The compositions of the inlet fraction and the bypass fraction are shown in Table 5. In the front-end depropanizer system, the naphtha cracked fraction is separated into an inlet fraction containing primarily hydrocarbons with a carbon number of 3 or less and a bypass fraction containing primarily hydrocarbons with a carbon number of 3 or more, thereby reducing the amount introduced into the cryogenic separation process and reducing energy consumption related to the cryogenic separation.

[0242] [Example B1] This example is carried out using the light olefin production facility shown in Figure 15. (Ethanol Conversion) 209.2 ton / y of raw material is heated and fed to a reactor 21 filled with a zeolite-containing catalyst so that the WHSV is 3.8. An ethanol conversion reaction is carried out at a reaction temperature of 540°C to obtain an ethanol-converted fraction. The ethanol-converted fraction is introduced into a third cooling tower 22 and contacted with cooling water to obtain a cooled ethanol-converted fraction at 35°C and 0.15 MPaG at a rate of 123.0 ton / y. The cooled ethanol-converted fraction is used as a recycled fraction, with 40.9 ton / y being reused as raw material introduced into the reactor 21 without undergoing processes such as separation and purification. At this time, the product ratio in the recycled fraction is 49.4 mass%. (Naphtha Cracking) A naphtha feedstock containing 266.5 ton / y of heavy naphtha and dilution steam at a mass ratio of 0.5 to the naphtha is introduced into a cracking furnace 11 under cracking conditions of 0.17 MPaG and 825°C to obtain a naphtha cracked fraction. The naphtha cracked fraction is introduced into a first cooling tower 12 and cooled to 110°C by contacting it with a mixture of heavy oil and cracked gasoline to obtain a first cooled naphtha cracked fraction. The first cooled naphtha cracked fraction is introduced into a second cooling tower 13 and contacted with cooling water to obtain a second cooled naphtha cracked fraction at 0.11 MPaG and 41°C. The second cooled naphtha cracked fraction is introduced into a booster and pressurized to 0.99 MPaG. (Combination of Ethanol Conversion and Naphtha Cracking) A combined fraction is prepared by mixing the pressurized second cooled naphtha cracking fraction (253.2 ton / y) with the cooled ethanol conversion fraction (82.1 ton / y). The combined fraction is introduced into a soda wash tower 15 where it is contacted with aqueous sodium hydroxide to obtain a washed fraction. The washed fraction is pressurized to 1.82 MPaG and then introduced into a first distillation tower 17. An introduced fraction is obtained from the top of the tower at −18°C to be introduced into the cryogenic separation step. A bypass fraction is obtained from the bottom of the tower at 16°C to bypass the cryogenic separation step and be introduced into downstream equipment. The compositions of the introduced fraction and the bypass fraction are shown in Table 5. The amount of ethylene produced in this example is the sum of the amounts of ethylene contained in the introduced fraction and the bypass fraction, and is 100.0 ton / y.

[0243] [Example B2] This example is carried out using the light olefin production facility shown in Figure 16. (Ethanol Conversion) 139.7 ton / y of raw material is heated and fed to a reactor 21 packed with a zeolite-containing catalyst so that the WHSV is 3.8. An ethanol conversion reaction is carried out at a reaction temperature of 540°C to obtain an ethanol-converted fraction. The ethanol-converted fraction is introduced into a third cooling tower 22 and contacted with cooling water to obtain a cooled ethanol-converted fraction at 45°C. The cooled ethanol-converted fraction is pressurized using a pressure booster 23 and introduced into a second distillation tower 24, thereby obtaining a light ethanol-converted fraction from the top of the second distillation tower 24. The light ethanol-converted fraction is introduced into a condenser 25, and a portion is liquefied and refluxed to the second distillation tower 24. The cooled light ethanol-converted fraction is obtained as a gas at 1.90 MPaG and 15°C. At this time, the heavy ethanol conversion fraction of 47.5 ton / y obtained from the bottom of the second distillation column 24 is used as a recycled fraction to be reused as a mixed feedstock without undergoing additional purification or other processes. The product ratio in the recycled fraction is 0.7 mass%. (Naphtha Cracking) A naphtha feedstock containing 266.5 ton / y of heavy naphtha and dilution steam at a mass ratio of 0.5 to the naphtha is introduced into the cracking furnace 11 under cracking conditions of 0.17 MPaG and 825°C to obtain a naphtha cracked fraction. The naphtha cracked fraction is introduced into the first cooling tower 12 and cooled to 110°C by contacting it with a mixture of heavy oil and cracked gasoline to obtain a first cooled naphtha cracked fraction. The first cooled naphtha cracked fraction is introduced into the second cooling tower 13 and contacted with cooling water to obtain a second cooled naphtha cracked fraction at 0.11 MPaG and 41°C. The second cooled naphtha cracked fraction is introduced into the pressure booster 14 and pressurized to 0.99 MPaG. (Combination of Ethanol Conversion and Naphtha Cracking) A combined fraction is prepared by mixing 253.2 ton / y of the second cooled naphtha cracked fraction with 45.4 ton / y of the cooled light ethanol conversion fraction. The combined fraction is introduced into the soda wash tower 15, where it is contacted with aqueous sodium hydroxide to obtain a washed fraction. The washed fraction is pressurized to 1.82 MPaG and then introduced into the first distillation tower 17, where an introduced fraction is obtained at -18°C from the top of the tower and introduced into the cryogenic separation step. In addition, a bypass fraction is obtained at 16°C from the bottom of the tower, bypassing the cryogenic separation step and being introduced into downstream equipment. The compositions of the introduced fraction and the bypass fraction are shown in Table 5.The amount of ethylene produced in this example is the sum of the amounts of ethylene contained in the introduced fraction and the bypassed fraction, and is 100.0 ton / y. A comparison of this example with Example B1 shows that by distilling and separating a fraction containing mainly lighter olefins than the ethanol-converted fraction before the ethanol-converted fraction and the naphtha cracked fraction are combined, the amount of fraction introduced into the cryogenic separation step can be reduced, improving the energy efficiency of purification. A comparison of this example with Example B1 shows that if the cooled ethanol-converted fraction is used as a recycle fraction without undergoing additional steps such as separation and purification, the product ratio in the recycle fraction will be high, more raw materials will be required for production, and the ethylene production efficiency per raw material will be reduced.

[0244] [Example B3] The procedure of Example B2 was repeated except that the naphtha cracking-derived fraction and the ethanol-converted fraction were combined in such amounts that, of the 100.0 ton / y of ethylene produced, 50.0 ton / y of ethylene was obtained by ethanol conversion and 50.0 ton / y of ethylene was obtained by naphtha cracking. The compositions of the introduced fraction and the bypassed fraction are shown in Table 5.

[0245] [Example B4] The procedure of Example B2 was repeated except that the naphtha cracking-derived fraction and the ethanol-converted fraction were combined in such amounts that, of the 100.0 ton / y of ethylene produced, 75.0 ton / y of ethylene was obtained by ethanol conversion and 25.0 ton / y of ethylene was obtained by naphtha cracking. The compositions of the introduced fraction and the bypassed fraction are shown in Table 5.

[0246] Example B5 This example was carried out using the light olefin production facility shown in FIG. 17 . (Ethanol Conversion) 145.6 ton / y of feedstock was heated and fed to reactor 21 packed with a zeolite-containing catalyst so that WHSV was 3.8. An ethanol conversion reaction was carried out at a reaction temperature of 540°C to obtain an ethanol-converted fraction. The ethanol-converted fraction was introduced into third cooling tower 22 and contacted with cooling water to obtain a cooled ethanol-converted fraction at 45°C. The cooled ethanol-converted fraction was pressurized using booster 23 and introduced into gas-liquid separation drum 26, yielding a light ethanol-converted fraction of 51.3 ton / y as a gas at 1.90 MPaG and 40°C. The heavy ethanol-converted fraction of 49.5 ton / y obtained as a liquid in gas-liquid separation drum 26 was used as a recycled fraction to be reused as the feedstock introduced into reactor 21 without undergoing additional purification or other processes. At this time, the product ratio in the recycled fraction is 11.3 mass%. (Naphtha Cracking) A naphtha feedstock containing 266.5 ton / y of heavy naphtha and dilution steam at a mass ratio of 0.5 to the naphtha is introduced into a cracking furnace 11 under cracking conditions of 0.17 MPaG and 825°C to obtain a naphtha cracked fraction. The naphtha cracked fraction is introduced into a first cooling tower 12 and contacted with a mixture of heavy oil and cracked gasoline to cool to 110°C to obtain a first cooled naphtha cracked fraction. The first cooled naphtha cracked fraction is introduced into a second cooling tower 13 and contacted with cooling water to obtain a second cooled naphtha cracked fraction at 0.11 MPaG and 41°C. The second cooled naphtha cracked fraction is introduced into a pressure booster 14 and pressurized to 0.99 MPaG. (Combination of Ethanol Conversion and Naphtha Cracking) A combined fraction is prepared by mixing 253.2 ton / y of the second cooled naphtha cracking fraction with 51.3 ton / y of the light ethanol conversion fraction. The combined fraction is introduced into a soda wash tower 15, where it is contacted with aqueous sodium hydroxide to obtain a washed fraction. The washed fraction is pressurized to 1.82 MPaG and then introduced into a first distillation tower 17, where an introduced fraction is obtained at -18°C from the top of the tower and introduced into the cryogenic separation step. In addition, a bypass fraction is obtained at 16°C from the bottom of the tower, bypassing the cryogenic separation step and being introduced into downstream equipment. The compositions of the introduced fraction and the bypass fraction are shown in Table 5.The amount of ethylene produced in this example is the sum of the amounts of ethylene contained in the introduced fraction and the bypassed fraction, and is 100.0 ton / y.

[0247]

[0248]

[0249] [Example B6] This example is carried out using the light olefin production facility shown in Figure 18. (Ethanol Conversion) 209.2 ton / y of raw material is heated and fed to a reactor 21 filled with a zeolite-containing catalyst so that the WHSV is 3.8. An ethanol conversion reaction is carried out at a reaction temperature of 540°C to obtain an ethanol-converted fraction. The ethanol-converted fraction is introduced into a third cooling tower 22 and contacted with cooling water to obtain a cooled ethanol-converted fraction at 45°C and 0.15 MPaG at a rate of 138.6 ton / y. The cooled ethanol-converted fraction is used as a recycled fraction, with 46.1 ton / y being reused as raw material introduced into the reactor 21 without undergoing processes such as separation and purification. At this time, the product ratio in the recycled fraction is 43.8 mass%. (Naphtha Cracking) A naphtha feedstock containing 266.5 ton / y of heavy naphtha and dilution steam at a mass ratio of 0.5 to the naphtha is introduced into a cracking furnace 11 under cracking conditions of 0.17 MPaG and 825°C to obtain a naphtha cracked fraction. The naphtha cracked fraction is introduced into a first cooling tower 12 and cooled to 110°C by contact with a mixture of heavy oil and cracked gasoline to obtain a first cooled naphtha cracked fraction. (Combination of Ethanol Conversion and Naphtha Cracking) A combined fraction is prepared by mixing 474.1 ton / y of the first cooled naphtha cracked fraction with 92.5 ton / y of the cooled ethanol converted fraction. The combined fraction is introduced into a second cooling tower 13 and contacted with cooling water to obtain a second cooled naphtha cracked fraction at 0.11 MPaG and 41°C. The second cooled naphtha cracking fraction is introduced into a pressure booster 14, where it is pressurized to 0.99 MPaG, and then introduced into a soda wash tower 15 where it is contacted with aqueous sodium hydroxide to obtain a wash fraction. The wash fraction is pressurized to 1.82 MPaG and then introduced into a first distillation tower 17, where an inlet fraction is obtained at −18°C from the top of the tower and introduced into the cryogenic separation step. A bypass fraction is obtained at 16°C from the bottom of the tower, bypassing the cryogenic separation step and being introduced into downstream equipment. The compositions of the inlet fraction and the bypass fraction are shown in Table 6. The amount of ethylene produced in this example is the sum of the amounts of ethylene contained in the inlet fraction and the bypass fraction, and is 100.0 ton / y.

[0250] Example B7 This example is carried out using the light olefin production facility shown in Figure 19. (Ethanol Conversion) 139.7 ton / y of raw material is heated and fed to a reactor 21 packed with a zeolite-containing catalyst so that the WHSV is 3.8. An ethanol conversion reaction is carried out at a reaction temperature of 540°C to obtain an ethanol-converted fraction. The ethanol-converted fraction is introduced into a third cooling tower 22 and contacted with cooling water to obtain a cooled ethanol-converted fraction at 45°C. The cooled ethanol-converted fraction is pressurized using a pressure booster 23 and introduced into a second distillation column 24, thereby obtaining a light ethanol-converted fraction from the top of the second distillation column 24. The light ethanol-converted fraction is introduced into a condenser 25, and a portion is liquefied and refluxed to the second distillation column 24. The cooled light ethanol-converted fraction is obtained as a gas at 1.90 MPaG and 15°C. At this time, 47.5 ton / y of heavy ethanol-converted fraction obtained from the bottom of the second distillation column 24 is used as a recycled fraction to be reused as the raw material introduced into the reactor 21 without undergoing additional purification or other processes. The product ratio in the recycled fraction is 0.7 mass%. (Naphtha Cracking) A naphtha feedstock containing 266.5 ton / y of heavy naphtha and dilution steam at a mass ratio of 0.5 relative to the naphtha is introduced into the cracking furnace 11 under cracking conditions of 0.17 MPaG and 825°C to obtain a naphtha cracked fraction. The naphtha cracked fraction is introduced into the first cooling tower 12 and cooled to 110°C by contacting it with a mixture of heavy oil and cracked gasoline to obtain a first cooled naphtha cracked fraction. (Combination of Ethanol Conversion and Naphtha Cracking) A combined fraction is prepared by mixing 474.1 ton / y of the first cooled naphtha cracking fraction with 45.4 ton / y of the cooled light ethanol conversion fraction. The combined fraction is introduced into a second cooling tower 13 and contacted with cooling water to obtain a second cooled fraction at 41 ° C. The second cooled fraction 13 is introduced into a pressure booster 14 and pressurized to 0.99 MPaG. The pressurized second cooled fraction is introduced into a soda wash tower where it is contacted with aqueous sodium hydroxide to obtain a wash fraction. The wash fraction is pressurized to 1.82 MPaG and then introduced into the first distillation tower 12, where an introduced fraction is obtained at -18 ° C from the top of the tower and introduced into the cryogenic separation step. In addition, a bypass fraction is obtained at 16 ° C from the bottom of the tower that bypasses the cryogenic separation step and is introduced into downstream equipment. The compositions of the introduced fraction and the bypass fraction are shown in Table 6.The amount of ethylene produced in this example is the sum of the amounts of ethylene contained in the introduced fraction and the bypassed fraction, and is 100.0 ton / y.

[0251] Example B8 This example is carried out using the light olefin production facility shown in FIG. 20 . This example is carried out in the same manner as Example B7, except for changing the connection points. In this example, a combined fraction is prepared by combining a cooled light ethanol-converted fraction at 15°C with a second bottom reflux fraction at 68°C, which contains a fraction obtained from the bottom of the second cooling tower 13 and is refluxed into the tower. The amount of the second bottom reflux fraction is determined based on the production balance of the target compounds, and in this example, the second bottom reflux fraction is set to 52.6 ton / y. By combining the second bottom reflux fraction with the ethanol-converted fraction, the ethanol-converted fraction is introduced into the second cooling tower 13. Therefore, the composition and flow rate of the introduced fraction and the bypassed fraction obtained in this example and Example B7 are unchanged. However, the temperature difference between the naphtha cracked fraction and the ethanol-converted fraction is reduced to 53 K, which makes it possible to suppress volume changes associated with cooling and liquefaction of the high-temperature naphtha fraction.

[0252] Example B9 This example was carried out using the light olefin production facility shown in FIG. 21 . (Ethanol Conversion) 145.6 ton / y of feedstock was heated and fed to reactor 21 packed with a zeolite-containing catalyst so that WHSV was 3.8. An ethanol conversion reaction was carried out at a reaction temperature of 540°C to obtain an ethanol-converted fraction. The ethanol-converted fraction was introduced into third cooling tower 22 and contacted with cooling water to obtain a cooled ethanol-converted fraction at 45°C. The cooled ethanol-converted fraction was pressurized using booster 23 and introduced into gas-liquid separation drum 26, yielding a light ethanol-converted fraction of 51.3 ton / y as a gas at 1.90 MPaG and 40°C. The heavy ethanol-converted fraction of 49.4 ton / y obtained as a liquid in gas-liquid separation drum 26 was used as a recycled fraction to be reused as the feedstock introduced into reactor 21 without undergoing additional purification or other processes. At this time, the product ratio in the recycled fraction is 11.3 mass%. (Naphtha Cracking) A naphtha feedstock containing 266.5 ton / y of heavy naphtha and dilution steam at a mass ratio of 0.5 to the naphtha is introduced into a cracking furnace 11 under cracking conditions of 0.17 MPaG and 825°C to obtain a naphtha cracked fraction. The naphtha cracked fraction is introduced into a first cooling tower 12 and cooled to 110°C by contacting it with a mixture of heavy oil and cracked gasoline to obtain a first cooled naphtha cracked fraction. (Combination of Ethanol Conversion and Naphtha Cracking) A combined fraction is prepared by mixing 474.1 ton / y of the first cooled naphtha cracked fraction with 51.3 ton / y of the light ethanol converted fraction. The combined fraction is introduced into a second cooling tower 13 and contacted with cooling water to obtain a second cooled naphtha cracked fraction at 0.11 MPaG and 41°C. The second cooled naphtha cracked fraction is introduced into a pressure booster 14 and pressurized to 0.99 MPaG. The combined fraction is introduced into a soda wash tower 15 where it is contacted with aqueous sodium hydroxide to obtain a wash fraction. The wash fraction is pressurized to 1.82 MPaG and then introduced into a first distillation tower 17, where an introduced fraction is obtained from the top of the tower at -18°C to be introduced into the cryogenic separation step. In addition, a bypass fraction is obtained from the bottom of the tower at 16°C to bypass the cryogenic separation step and be introduced into downstream equipment. The compositions of the introduced fraction and the bypass fraction are shown in Table 6. The amount of ethylene produced in this example is the sum of the amounts of ethylene contained in the introduced fraction and the bypass fraction, and is 100.0 ton / y.

[0253]

[0254]

[0255] [Example B10] This example is carried out using the light olefin production facility shown in Figure 22. (Ethanol Conversion) 209.2 ton / y of raw material is heated and fed to a reactor 21 filled with a zeolite-containing catalyst so that the WHSV is 3.8. An ethanol conversion reaction is carried out at a reaction temperature of 540°C to obtain an ethanol-converted fraction. The ethanol-converted fraction is introduced into a third cooling tower 22 and contacted with cooling water to obtain a cooled ethanol-converted fraction at 45°C and 0.15 MPaG at a rate of 138.6 ton / y. The cooled ethanol-converted fraction is recycled as a recycled fraction, with 46.1 ton / y recycled as the raw material introduced into the reactor 21 without undergoing processes such as separation and purification. At this time, the product ratio in the recycled fraction is 43.8 mass%. (Naphtha Cracking) Naphtha feedstock containing 266.5 ton / y of heavy naphtha and dilution steam at a mass ratio of 0.5 to the naphtha is introduced into a cracking furnace 11 under cracking conditions of 0.17 MPaG and 825°C to obtain a naphtha cracked fraction. (Combined Ethanol Conversion and Naphtha Cracking) A combined fraction is prepared by mixing 417.2 ton / y of naphtha cracked fraction with 92.5 ton / y of cooled ethanol converted fraction. The combined fraction is introduced into a first cooling tower 12 and cooled to 110°C by contacting with a mixture of heavy oil and cracked gasoline to obtain a first cooled naphtha cracked fraction. The first cooled naphtha cracked fraction is introduced into a second cooling tower 13 and contacted with cooling water to obtain a second cooled naphtha cracked fraction at 0.11 MPaG and 41°C. The second cooled naphtha cracking fraction is introduced into a pressure booster 14, where it is pressurized to 0.99 MPaG, and then introduced into a soda wash tower 15 where it is contacted with aqueous sodium hydroxide to obtain a wash fraction. The wash fraction is pressurized to 1.82 MPaG and then introduced into a first distillation tower 17, where an inlet fraction is obtained at −18°C from the top of the tower and introduced into the cryogenic separation step. A bypass fraction is obtained at 16°C from the bottom of the tower, bypassing the cryogenic separation step and being introduced into downstream equipment. The compositions of the inlet fraction and the bypass fraction are shown in Table 7. The amount of ethylene produced in this example is the sum of the amounts of ethylene contained in the inlet fraction and the bypass fraction, and is 100.0 ton / y.

[0256] [Example B11] This example is carried out using the light olefin production facility shown in Figure 23. (Ethanol Conversion) 139.7 ton / y of feed gas is heated and supplied to a reactor 21 packed with a zeolite-containing catalyst so that the WHSV is 3.8. An ethanol conversion reaction is carried out at a reaction temperature of 540°C to obtain an ethanol-converted fraction. The ethanol-converted fraction is introduced into a third cooling tower 22 and contacted with cooling water to obtain a cooled ethanol-converted fraction at 45°C. The cooled ethanol-converted fraction is pressurized using a pressure booster 23 and introduced into a second distillation column 24, thereby obtaining a light ethanol-converted fraction from the top of the second distillation column 24. The light ethanol-converted fraction is introduced into a condenser 25, and a portion is liquefied and refluxed to the second distillation column 24. The cooled light ethanol-converted fraction is obtained as a gas at 1.90 MPaG and 15°C. At this time, 47.5 ton / y of heavy ethanol-converted fraction obtained from the bottom of the second distillation column 24 is used as a recycled fraction, which is reused as the raw material introduced into the reactor 21 without undergoing additional purification or other processes. The product ratio in the recycled fraction is 0.7 mass%. (Naphtha Cracking) A naphtha feedstock containing 266.5 ton / y of heavy naphtha and dilution steam at a mass ratio of 0.5 relative to the naphtha is introduced into the cracking furnace 11 under cracking conditions of 0.17 MPaG and 825°C to obtain a naphtha cracked fraction. (Combined Ethanol Conversion and Naphtha Cracking) A combined fraction is prepared by mixing 417.2 ton / y of naphtha cracked fraction at 360°C with 45.4 ton / y of cooled light ethanol-converted fraction. The combined fraction is introduced into a first cooling tower 12 and cooled to 110°C by contact with a mixture of heavy oil and cracked gasoline to obtain a first cooled fraction 12. The first cooled fraction is introduced into a second cooling tower 13 and contacted with cooling water to obtain a second cooled fraction at 41°C. The second cooled fraction is introduced into a pressure booster 14 and pressurized to 0.99 MPaG. The pressurized second cooled fraction is introduced into a soda wash tower 15 and contacted with an aqueous sodium hydroxide solution to obtain a wash fraction. The wash fraction is further pressurized and introduced into the cryogenic separation step as an input fraction. The amount of ethylene in the combined fraction at this time is 100.0 ton / y. The flow rate and composition of the combined fraction are shown in Table 7.

[0257] Example B12 Example B12 is carried out according to the process flow shown in FIG. 24 . Example B12 is carried out in the same manner as Example B11, except for changing the connection points. In Example B12, a combined fraction is prepared by combining a cooled light ethanol-converted fraction at 15°C with a first bottom reflux fraction at 80°C, which contains a fraction obtained from the bottom of the second cooling tower 13 and is refluxed to the first cooling tower 12. By combining the first bottom reflux fraction and the ethanol-converted fraction, the ethanol-converted fraction is introduced into the first cooling tower 12. Therefore, the composition and flow rate of the introduced fraction obtained in Example B11 and Example B12 are unchanged. However, the temperature difference between the naphtha cracked fraction and the ethanol-converted fraction is reduced to 65 K, which makes it possible to suppress volume changes associated with cooling and liquefaction of the high-temperature naphtha fraction.

[0258] Example B13 This example was carried out using the light olefin production facility shown in FIG. 25 . (Ethanol Conversion) 145.6 ton / y of feedstock was heated and fed to reactor 21 packed with a zeolite-containing catalyst so that WHSV was 3.8. An ethanol conversion reaction was carried out at a reaction temperature of 540°C to obtain an ethanol-converted fraction. The ethanol-converted fraction was introduced into third cooling tower 22 and contacted with cooling water to obtain a cooled ethanol-converted fraction at 45°C. The cooled ethanol-converted fraction was pressurized using booster 23 and introduced into gas-liquid separation drum 26, yielding a light ethanol-converted fraction of 51.3 ton / y as a gas at 1.90 MPaG and 40°C. The heavy ethanol-converted fraction of 49.4 ton / y obtained as a liquid in gas-liquid separation drum 26 was used as a recycled fraction to be reused as the feedstock introduced into reactor 21 without undergoing additional purification or other processes. At this time, the product ratio in the recycled fraction is 11.3 mass%. (Naphtha Cracking) Naphtha feedstock containing 266.5 ton / y of heavy naphtha and dilution steam at a mass ratio of 0.5 to the naphtha is introduced into the cracking furnace 11 under cracking conditions of 0.17 MPaG and 825°C to obtain a naphtha cracked fraction. (Combined Ethanol Conversion and Naphtha Cracking) A combined fraction is prepared by mixing 417.2 ton / y of naphtha cracked fraction with 51.3 ton / y of light ethanol converted fraction. The combined fraction is introduced into the first cooling tower 12 and cooled to 110°C by contact with a mixture of heavy oil and cracked gasoline to obtain a first cooled naphtha cracked fraction. The combined fraction is introduced into the second cooling tower 13 and contacted with cooling water to obtain a second cooled naphtha cracked fraction at 0.11 MPaG and 41°C. The second cooled naphtha cracked fraction is introduced into a pressure booster 14 and pressurized to 0.99 MPaG. The pressurized second cooled naphtha cracked fraction is introduced into a soda wash tower where it is contacted with aqueous sodium hydroxide to obtain a wash fraction. The wash fraction is pressurized to 1.82 MPaG and then introduced into a first distillation tower 17, where an introduced fraction is obtained from the top of the tower at −18°C to be introduced into the cryogenic separation step. In addition, a bypass fraction is obtained from the bottom of the tower at 16°C to bypass the cryogenic separation step and be introduced into downstream equipment. The compositions of the introduced fraction and the bypass fraction are shown in Table 7. The amount of ethylene produced in this example is the sum of the amounts of ethylene contained in the introduced fraction and the bypass fraction, and is 100.0 ton / y.

[0259]

[0260] From the results of the Examples and Comparative Examples, it can be seen that the method for producing light olefins according to this embodiment can reduce the amount of off-gas such as hydrogen and methane, and can reduce the processing energy required for cryogenic separation.

[0261] In Examples C1 to C5 and Comparative Examples C1 to C4, the influence of the difference in composition between the ethanol converted fraction obtained in the ethanol conversion step and the naphtha cracked fraction obtained in the naphtha cracking step on the refining equipment will be discussed.

[0262] (Production rate of each compound) In Examples C1 to C5 and Comparative Examples C1 to C4, the production volume of each product in the naphtha cracking furnace was reduced, and the reduced amount was replaced with the ethanol converted fraction. The production volume of each product after replacement with the ethanol converted fraction divided by the production volume of each product in the naphtha cracking furnace before the reduction is called the production rate. The production volume here is the total amount of each product in the ethanol converted fraction and the amount of each product in the naphtha cracking fraction.

[0263] [Examples C1 to C4, Comparative Examples C1 to C4] In Examples C1 to C4 and Comparative Examples C1 to C4, the naphtha cracking furnace, which produces 100 tons of ethylene per year, was reduced to 75 tons per year, and an ethanol conversion fraction was connected instead. In these Examples and Comparative Examples, the ethanol conversion step and the cracking step were performed under the conditions shown in Table 8, and then light olefins were purified through a combining step and a cryogenic separation step. At this time, if the production rate exceeds 100%, the purity of the product decreases, so the production amount of the ethanol conversion fraction was adjusted so that the production rate of ethylene, propylene, and hydrocarbons having 4 or more carbon atoms does not exceed 100%. Comparison between the Examples and Comparative Examples reveals that when the ethanol conversion fraction and naphtha cracking fraction are combined so as to satisfy formula (α) and formula (β-1), the production rate of ethylene, propylene, or hydrocarbons having 4 or more carbon atoms does not fall below 90%. If the production rate of each product falls below 90%, problems will arise in the refining equipment, such as surging in the compressor, which will significantly reduce the refining efficiency, which is undesirable.

[0264] Example C5 Example C5 was carried out in the same manner as Example C4, except that the ethylene production rate of the naphtha cracking furnace was reduced to 50 tons / y. The higher the replacement rate of naphtha cracking by ethanol conversion, the greater the impact on the productivity of products.

[0265]

[0266] 11... Cracking furnace, 12... Cooling tower, 13... Second cooling tower, 14... First compressor, 15... Soda washing tower, 16... Cryogenic separation equipment, 21... Reactor, 22... Third cooling tower

Claims

1. A method for producing a naphtha cracked fraction comprising: a cracking step of introducing a naphtha raw material into a cracking furnace to obtain a naphtha cracked fraction; an ethanol conversion step of introducing an ethanol-containing raw material into a reactor and contacting it with a catalyst to obtain an ethanol-converted fraction containing ethylene and propylene; a combining step of combining at least a portion of the naphtha cracked fraction or a fraction derived therefrom with at least a portion of the ethanol-converted fraction or a fraction derived therefrom to obtain a combined fraction; and a cryogenic separation step of introducing the combined fraction or a fraction derived therefrom into a cryogenic separation facility to separate ethylene and propylene, wherein the ethylene and propylene content C of the ethanol-converted fraction or a fraction derived therefrom in the combining step is Ｅ and the content C of ethylene and propylene in the naphtha cracking fraction or a fraction derived therefrom. Ｃ The relationship is represented by the formula (A): Ｅ >C Ｃ A method for producing a light olefin, which satisfies the above (A).

2. The content C in the merging step Ｅ and the content C Ｃ The difference between Ｅ -C Ｃ 2. The method for producing light olefins according to claim 1, wherein the amount of the olefin is 5 mass% or more.

3. Propylene / ethylene mass ratio P / E in the ethanol converted fraction Ｅ and the P / E ratio in the naphtha cracking fraction Ｃ The relationship is expressed by the formula (α): −0.25<(P / E Ｅ -P / E Ｃ 2. The process for producing light olefins according to claim 1 , wherein the following relationship is satisfied: α<0.30 4. The content C of ethylene and propylene in the ethanol-converted fraction Ｅ＿ＡＰ and the content C of ethylene and propylene in the naphtha cracking fraction Ｃ＿ＡＰ The relationship is expressed by the formula (β-1): |C Ｅ＿ＡＰ -C Ｃ＿ＡＰ The method for producing a light olefin according to claim 1, wherein the above-mentioned condition is satisfied: |<20 mass% ... (β-1).

5. A method for producing an ethanol-converted fraction comprising: a cracking step of introducing a naphtha raw material into a cracking furnace to obtain a naphtha cracked fraction; an ethanol conversion step of introducing an ethanol-converted fraction into a reactor and contacting it with a catalyst to obtain an ethanol-converted fraction containing ethylene and propylene; a combining step of combining at least a portion of the naphtha cracked fraction or a fraction derived therefrom with at least a portion of the ethanol-converted fraction or a fraction derived therefrom to obtain a combined fraction; and a cryogenic separation step of introducing the combined fraction or a fraction derived therefrom into a cryogenic separation facility to separate ethylene and propylene, wherein the propylene / ethylene mass ratio P / E in the ethanol-converted fraction is 0.01 to 0.

01. Ｅ and the P / E ratio in the naphtha cracking fraction Ｃ The relationship is expressed by the formula (α): −0.25<(P / E Ｅ -P / E Ｃ ) < 0.30 ... (α) is satisfied, and the ethylene and propylene contents C in the ethanol-converted fraction are Ｅ＿ＡＰ and the content C of ethylene and propylene in the naphtha cracking fraction Ｃ＿ＡＰ The relationship is expressed by the formula (β-1): |C Ｅ＿ＡＰ -C Ｃ＿ＡＰ |<20 mass% ... (β-1) 6. The content C of ethylene and propylene in the ethanol-converted fraction Ｅ＿ＡＰ and the content C of ethylene and propylene in the naphtha cracking fraction Ｃ＿ＡＰ The relationship is expressed by the formula (β-2): 0≦(C Ｅ＿ＡＰ -C Ｃ＿ＡＰ 6. The method for producing a light olefin according to claim 5, wherein the above-mentioned condition is satisfied: β-2<20% by mass.

7. A method for producing light olefins according to claim 1 or 5, comprising a first cooling step of introducing the naphtha cracking fraction or the combined fraction into a first cooling tower to obtain a first cooled fraction mainly containing olefins having a carbon number of 6 or less.

8. A method for producing light olefins according to claim 1 or 5, comprising a second cooling step of introducing the naphtha cracking fraction, or the combined fraction, or a fraction derived therefrom, into a second cooling tower to obtain a second cooled fraction mainly containing olefins having a carbon number of 4 or less.

9. A method for producing light olefins according to claim 1 or 5, comprising a third cooling step of introducing the ethanol-converted fraction into a third cooling tower to obtain a cooled ethanol-converted fraction mainly containing olefins having a carbon number of 6 or less.

10. A method for producing light olefins according to claim 9, comprising a compression separation step of pressurizing the cooled ethanol conversion fraction with a compressor to obtain a light ethanol conversion fraction containing mainly olefins having a carbon number of 3 or less as a gas component, and a heavy ethanol conversion fraction containing mainly olefins having a carbon number of 4 or more as a liquid component.

11. The method for producing light olefins according to claim 10, further comprising a recycling step of introducing at least a portion of the heavy ethanol converted fraction into the reactor as part of the feedstock.

12. A method for producing light olefins according to claim 1 or 5, comprising a washing step of introducing the combined fraction or a fraction derived therefrom into a soda washing tower after the combining step to obtain a washed fraction.

13. A method for producing light olefins according to claim 1 or 5, comprising a first compression step of increasing the pressure of the fraction after the second cooling step and before the cryogenic separation step.

14. The ratio O of the amount of hydrogen and methane to the total amount of ethylene and propylene in the ethanol conversion fraction Ｅ and a ratio O of the amount of hydrogen and methane to the total amount of ethylene and propylene in the naphtha cracking fraction. Ｃ The relationship is expressed by the formula (1): Ｅ <O Ｃ The method for producing a light olefin according to claim 1 or 5, wherein the above formula (1) is satisfied.

15. A method for producing light olefins according to claim 1 or 5, which satisfies any one of the following (1) to (5): (1) A first cooling step of introducing the naphtha cracked fraction into a first cooling tower to obtain a first cooled fraction mainly containing olefins having a carbon number of 6 or less, and a second cooling step of introducing the first cooled fraction into a second cooling tower to obtain a second cooled fraction mainly containing olefins having a carbon number of 4 or less, wherein at least a portion of the second cooled fraction is combined with at least a portion of the ethanol converted fraction or a fraction derived therefrom in the combining step. (2) A first cooling step of introducing the naphtha cracked fraction into a first cooling tower to obtain a first cooled fraction mainly containing olefins having a carbon number of 6 or less, and a second cooling step of introducing the combined fraction or a fraction derived therefrom into a second cooling tower to obtain a second cooled fraction mainly containing olefins having a carbon number of 4 or less, wherein at least a portion of the first cooled fraction is combined with at least a portion of the ethanol converted fraction or a fraction derived therefrom in the combining step. (3) A first cooling step of introducing the naphtha cracking fraction into a first cooling tower to obtain a first cooled fraction mainly containing olefins having a carbon number of 6 or less; a second cooling step of introducing the first cooled fraction into a second cooling tower to obtain a second cooled fraction mainly containing olefins having a carbon number of 4 or less; a circulation step of introducing at least a portion of the second heavy fraction mainly containing hydrocarbons having a carbon number of 5 or more in the second cooling step into the second cooling tower; and a first introducing step of introducing the combined fraction into the second cooling tower, wherein in the combining step, at least a portion of the second heavy fraction and at least a portion of the ethanol conversion fraction or a fraction derived therefrom are combined. (4) A first cooling step of introducing the combined fraction or a fraction derived therefrom into a first cooling tower to obtain a first cooled fraction mainly containing olefins having a carbon number of 6 or less; and a second cooling step of introducing the first cooled fraction into a second cooling tower to obtain a second cooled fraction mainly containing olefins having a carbon number of 4 or less, wherein at least a portion of the naphtha cracking fraction and at least a portion of the ethanol conversion fraction or a fraction derived therefrom are combined in the combining step.(5) The method includes a first cooling step of introducing the naphtha cracking fraction into a first cooling tower to obtain a first cooled fraction mainly containing olefins having a carbon number of 6 or less; a second cooling step of introducing the first cooled fraction into a second cooling tower to obtain a second cooled fraction mainly containing olefins having a carbon number of 4 or less; a circulation step of introducing at least a portion of the second heavy fraction obtained in the second cooling step, the second heavy fraction mainly containing hydrocarbons having a carbon number of 5 or more, into the first cooling tower; and a second introduction step of introducing the combined fraction into the first cooling tower, wherein in the combining step, at least a portion of the second heavy fraction and at least a portion of the ethanol conversion fraction or a fraction derived therefrom are combined.