Method for producing light olefin

Abstract

To provide a method for producing light olefin, which reduces treatment energy in cryogenic separation.SOLUTION: A method for producing light olefins comprises: a cracking process in which naphtha feedstock is introduced into a cracker to obtain naphtha cracking products; an ethanol conversion process in which a feedstock containing ethanol is introduced into a reactor and contacted with a catalyst to obtain an ethanol conversion product containing ethylene and propylene; a merging process in which at least a portion of the naphtha cracking product or a derivative thereof is combined with at least a portion of the ethanol conversion product or a derivative thereof to obtain a merged product; and a cryogenic separation process in which the merged product or a derivative thereof is introduced into a cryogenic separation facility to separate ethylene and propylene. The relationship between the ratio OE of the amount of hydrogen and methane to the total amount of ethylene and propylene in the ethanol conversion product and the ratio OC of the amount of hydrogen and methane to the total amount of ethylene and propylene in the naphtha cracking product satisfies OE<OC.SELECTED DRAWING: Figure 2

Description

Technical Field

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

Background Art

[0002] By cracking naphtha obtained from crude oil, various chemicals such as monomer raw materials have been produced. Among these chemicals, light olefins such as ethylene and propylene have particularly high demand because they have a wide variety of uses. In particular, since propylene has high value, methods for selectively producing propylene from naphtha have been studied, and steam cracking is known as a typical example (for example, Patent Document 1).

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

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the method for producing light olefins by cracking, various components are separated and purified from the naphtha cracking fraction obtained by cracking naphtha to obtain light olefins. At this time, various processes can be applied. As the separation and purification step, first, the naphtha cracking fraction is cooled to remove high-boiling components, and finally, by cryogenic separation, the fraction from which the high-boiling components have been removed is liquefied, and off-gases such as hydrogen and methane are removed to produce light olefins such as ethylene and propylene. In this case, since the fraction introduced into the cryogenic separation contains a large amount of by-products such as off-gases, there is a problem that the processing energy load of the cryogenic separation increases.

[0006] An object of the present invention is to provide a method for producing light olefins that reduces the processing energy in cryogenic separation.

Means for Solving the Problems

[0007] The inventors of the present invention have found that in the method for producing light olefins, 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 the ratio O of the amount of hydrogen and methane to the total amount of ethylene and propylene in the naphtha cracking fraction C satisfy the relationship of formula (1): O E < O C ···(1), and have found that the above-mentioned problems can be solved.

[0008] The present invention includes the following embodiments. <1> A cracking step of introducing a naphtha raw material into a cracking furnace to obtain a naphtha cracking fraction, An ethanol conversion step of introducing a raw material containing ethanol into a reactor and bringing it into contact with a catalyst to obtain an ethanol conversion fraction containing ethylene and propylene, A merging step of merging at least a part of the naphtha cracking fraction or a fraction derived therefrom and at least a part of the ethanol conversion fraction or a fraction derived therefrom to obtain a merged fraction, Introduce the combined fraction or a fraction derived therefrom into a cryogenic separation facility, and include a cryogenic separation step of separating ethylene and propylene. The ratio O of the amounts of hydrogen and methane to the total amount of ethylene and propylene in the ethanol conversion fraction E and the ratio O of the amounts of hydrogen and methane to the total amount of ethylene and propylene in the naphtha cracking fraction C The relationship between them is given by the formula (1): O E < O C ···(1) satisfies A method for producing light olefins. <2> The ratio O' of the amounts of hydrogen and methane to the total amount of ethylene and propylene in the ethanol conversion fraction or a fraction derived therefrom in the combining step E and the ratio O' of the amounts 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 them is given by the formula (1-1): O' E < O' C ···(1-1) satisfies The method for producing light olefins according to <1>. <3> The propylene / ethylene mass ratio P / E in the ethanol conversion fraction E and the propylene / ethylene mass ratio P / E in the naphtha cracking fraction C The relationship between them is given by the formula (2): |P / E C - P / E E | < 0.3 ···(2) satisfies The method for producing light olefins according to <1> or <2>. <4> The content C of ethylene and propylene in the ethanol conversion fraction or a fraction derived therefrom in the combining step E and the content C of ethylene and propylene in the naphtha cracking fraction or a fraction derived therefrom C The relationship between them is given by the formula (3): CE >C C ···(3) satisfying The method for producing a light olefin according to any one of <1> to <3>. <5> The content ratio C E and the content ratio C C The difference (C E -C C ) is 5% by mass or more, The method for producing a light olefin according to <4>. <6> The content ratio C E is higher than the content ratio C C and further includes a purification step of purifying the ethanol conversion fraction to obtain a purified ethanol conversion fraction, The method for producing a light olefin according to <4> or <5>. <7> The purification step is introducing the ethanol conversion fraction into a third cooling tower to obtain a cooled ethanol conversion fraction mainly containing olefins having 6 or less carbon atoms, including a third cooling step, The method for producing a light olefin according to <6>. <8> The purification step is pressurizing the cooled ethanol conversion fraction with a compressor to obtain a light ethanol conversion fraction mainly containing olefins having 3 or less carbon atoms as a gas component and a heavy ethanol conversion fraction mainly containing olefins having 4 or more carbon atoms as a liquid component, including a compression separation step, The method for producing a light olefin according to <7> or <8>. <9> including a recycling step of introducing at least a part of the heavy ethanol conversion fraction into the reactor as a part of the raw material, The method for producing a light olefin according to <8>. <10> including a washing step of introducing the combined fraction into a soda washing tower after the combining step to obtain a washed fraction, The method for producing a light olefin according to any one of <1> to <9>. <11> After the washing step, by introducing the washing fraction into the first distillation column, a distillation step is performed to obtain an introduction fraction that is introduced into the cryogenic separation step and a bypass fraction that bypasses the cryogenic separation step and is introduced into subsequent equipment. The method includes this distillation step. The method for producing light olefins according to any one of <1> to <10>.

Advantages of the Invention

[0009] According to the present invention, a method for producing light olefins that reduces the processing energy in cryogenic separation can be provided.

Brief Description of the Drawings

[0010]

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Embodiments for Carrying Out the Invention

[0011] The present invention will be specifically described below. Note that the present invention is not limited to the following embodiments (the present embodiment), and various modifications can be made within the scope of the gist thereof.

[0012] The numerical range indicated by using "~" indicates a range including the numerical values described before and after "~" as the minimum value and the maximum value, respectively. In the numerical ranges described step by step in this specification, the upper limit value or the lower limit value of a numerical range at a certain step can be arbitrarily combined with the upper limit value or the lower limit value of a numerical range at another step.

[0013] Modifying terms such as "first" and "second" may be used to distinguish elements, but such modifying terms do not necessarily indicate any specific order.

[0014] First, the method for producing light olefins according to the present embodiment will be outlined. FIG. 1 is a block diagram showing an outline of the method for producing light olefins according to the present embodiment. As shown in FIG. 1, the production method according to the present embodiment includes a naphtha cracking process N and an ethanol conversion process E.

[0015] In naphtha cracking process N, after pyrolyzing naphtha in cracking N1, the naphtha cracked fraction is subjected to a purification process N2, and ethylene and propylene are separated by cryogenic separation N3. In cryogenic separation N3, the treated fraction is cooled to liquefy ethylene and propylene, separating gaseous methane and hydrogen from liquid olefins. In cryogenic separation N3, since liquefaction of a relatively light fraction in the naphtha cracked fraction is required in this way, boosting of the fraction and cooling of the fraction are required, and a large amount of energy is required for the treatment.

[0016] In naphtha cracking process N, existing naphtha cracker equipment may be used. For example, an ethanol conversion fraction obtained by the ethanol conversion process described later is introduced into the naphtha cracker equipment.

[0017] Ethanol conversion process E includes, for example, a step of converting a raw material containing ethanol into an ethanol conversion fraction containing ethylene and propylene, etc. In ethanol conversion process E, by using bioethanol as the raw material, an ethanol conversion fraction derived from plants can be obtained. By connecting ethanol conversion process E to the existing equipment for performing naphtha cracking process N, a part of the petroleum-derived raw material can be replaced with a plant-derived raw material. Also, for example, by controlling the operating conditions of ethanol conversion process E, the raw material can be converted to a plant-derived one without changing the production amount of the target compound.

[0018] In the present embodiment, by introducing the ethanol conversion fraction obtained by ethanol conversion process E or a fraction derived therefrom into naphtha cracking process N, the load on cryogenic separation N3 is reduced.

[0019] Naphtha cracking process N may include any steps, but in the steps described later, for example, a cracking step, a first cooling step, a second cooling step, a merging step, a first compression step, a washing step, and a cryogenic separation step are included.

[0020] As the ethanol conversion process E, any process may be included, but in the processes described below, for example, an ethanol conversion process, a purification process, a third cooling process, a second compression process, a distillation process, and a recycling process are included.

[0021] "Light olefins" are at least one selected from the group consisting of ethylene and propylene. Light olefins are the target compounds in the production method according to the present embodiment, but from the viewpoint of making the most of the features of the production method according to the present embodiment, propylene is preferred.

[0022] In relation to a specific fraction, "the fraction derived therefrom" means a fraction obtained by subjecting the specific fraction to any process such as distillation, cooling, compression, etc.

[0023] "Mainly containing" with respect to the components of a fraction means containing more than 50% by mass in that fraction.

[0024] The method for producing light olefins according to the present embodiment is a cracking step of introducing a naphtha raw material into a cracking furnace to obtain a naphtha cracked fraction, and an ethanol conversion step of introducing a raw material containing ethanol into a reactor and bringing it into contact with a catalyst to obtain an ethanol conversion fraction containing ethylene and propylene, and a merging step of merging at least a part of the naphtha cracked fraction or a fraction derived therefrom and at least a part of the ethanol conversion fraction or a fraction derived therefrom to obtain a merged fraction, and a cryogenic separation step of introducing the merged fraction or a fraction derived therefrom into a cryogenic separation facility to separate ethylene and propylene, and the ratio O of the amounts of hydrogen and methane to the total amount of ethylene and propylene in the ethanol conversion fraction E and the ratio O of the amounts of hydrogen and methane to the total amount of ethylene and propylene in the naphtha cracked fraction C are in the relationship of formula (1): O E < O C ···(1) is satisfied. According to the above embodiments, a method for producing light olefins that reduces the processing energy in cryogenic separation can be provided.

[0025] In the naphtha cracking process, after cracking naphtha, through a purification process, light olefins are obtained from the cryogenic separation process. In the cryogenic separation process, the fraction introduced into the cryogenic separation process is pressurized by a compressor, and the fraction is cooled to a temperature below the boiling point of ethylene at the said pressure to liquefy the light olefins in the fraction, and the off-gases such as hydrogen and methane and the light olefins are separated by gas-liquid separation. In this pressurization and cooling process, the consumed energy increases according to the flow rate of the fraction introduced into the cryogenic separation process. That is, 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 the ratio O 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 with the above-mentioned range, the ratio of hydrogen and methane in the fraction introduced into the cryogenic separation process can be lowered. Therefore, when the production amount of light olefins is constant, the flow rates of hydrogen and methane in the introduced fraction are reduced, and thus cryogenic separation can be performed more efficiently.

[0026] In the method for producing light olefins according to this embodiment, the ratio O C and the ratio O E The difference (O C -O E ) is preferably 5% by mass or more, more preferably 10% by mass or more, and still more preferably 20% by mass or more from the viewpoint of excellent purification efficiency. By having the said difference (O C -O E ), the ratio of hydrogen and methane in the fraction introduced into the cryogenic separation process can be lowered, and thus cryogenic separation can be performed efficiently. Note that the upper limit of the difference (O C -O E ) is not particularly limited, but it may be 70% by mass or less.

[0027] In the method for producing light olefins according to this embodiment, the propylene / ethylene mass ratio P / E in the ethanol conversion fraction E and the propylene / ethylene mass ratio P / E in the naphtha cracking fraction C are related by the formula (2): |P / E C - P / E E | < 0.3 ···(2) It is preferable to satisfy this. By satisfying the formula (2), the propylene / ethylene mass ratio in the fraction can be made approximately the same, so that it is not necessary to modify the purification equipment in the existing cracker and it can be used as it is. Also, when connecting the ethanol conversion process by making the propylene / ethylene mass ratio in the fraction approximately the same, the production amounts of each product in the naphtha cracking process do not change significantly. |P / E C - P / E E | is preferably 0.2 or less, more preferably 0.1 or less, and still more preferably 0.05 or less. |P / E C - P / E E | has no particular limitation on its lower limit value and may be, for example, 0 or more (i.e., the same ratio).

[0028] The ratio O' of the amounts of hydrogen and methane to the total amount of ethylene and propylene in the ethanol conversion fraction or a fraction derived therefrom in the merging step E and the ratio O' of the amounts of hydrogen and methane to the total amount of ethylene and propylene in the naphtha cracking fraction or a fraction derived therefrom C are related by the formula (1-1): O' E <O' C ···(1-1) is preferably satisfied.

[0029] In the method for producing light olefins according to this embodiment, the ratio O' C and the ratio O' E The difference (O' C -O' E ) is preferably 5% by mass or more, more preferably 10% by mass or more, and still more preferably 20% by mass or more. The difference (O' C-O’ E ) By having this, the ratio of hydrogen and methane in the fraction introduced into the cryogenic separation process can be lowered, so that the cryogenic separation can be efficiently performed. Note that the difference (O’ C -O’ E ) has no particular upper limit, but may be 70% by mass or less.

[0030] In the merging step, the propylene / ethylene mass ratio P’ / E’ in the ethanol conversion fraction E and the propylene / ethylene mass ratio P’ / E’ in the naphtha cracking fraction C are related by the formula (2-1): |P’ / E’ C - P’ / E’ E | < 0.3 ···(2-1) It is preferable to satisfy this. By satisfying the formula (2-1), the propylene / ethylene mass ratio in the fraction can be made approximately the same, so that it is not necessary to modify the purification equipment in the existing cracker and it can be used as it is. |P’ / E’ C - P’ / E’ E | is preferably 0.2 or less, more preferably 0.1 or less, and still more preferably 0.05 or less. |P’ / E’ C - P’ / E’ E | has no particular lower limit and may be, for example, 0 or more (i.e., the same ratio).

[0031] In the merging step, the ethylene and propylene content C in the ethanol conversion fraction or a fraction derived therefrom E and the ethylene and propylene content C in the naphtha cracking fraction or a fraction derived therefrom C are related by the formula (3): C E >C C ···(3) It is preferable to satisfy this. By satisfying the formula (3) in this way, the energy load in the cryogenic separation step can be particularly reduced.

[0032] In the method for producing light olefins according to this embodiment, the content C E and the content CC The difference from C E -C C ) is preferably 5% by mass or more, more preferably 10% by mass or more, and still more preferably 20% by mass or more. The difference (C E -C C ) has no particular upper limit, but may be, for example, 70% by mass or less.

[0033] Hereinafter, each step of the method for producing light olefins according to this embodiment will be described.

[0034] The method for producing light olefins according to this embodiment uses, as the naphtha cracking process N described above, a cracking step of introducing a naphtha raw material into a cracking furnace to obtain a naphtha cracked fraction, and a cryogenic separation step of introducing the fraction into a cryogenic separation facility to separate ethylene and propylene.

[0035] In addition, the method for producing light olefins according to this embodiment may optionally use, as the naphtha cracking process N described above, 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. It may have. By providing the first cooling step and / or the second cooling step prior to the washing step described later, the fraction introduced into the soda washing tower can be reduced, and the washing efficiency in the soda washing tower can be improved. In addition, by providing the cooling step in two stages, it becomes easy to control the temperature and composition of the fraction obtained in the cooling step.

[0036] In addition, the method for producing light olefins according to this embodiment may optionally use, as the naphtha cracking process N described above, before introducing the fraction into the cryogenic separation facility, a first compression step of boosting the pressure of the fraction, and a washing step of introducing the fraction into a soda washing tower to obtain a washed fraction. It may have. In the soda scrubber tower, by removing acid components such as carbon dioxide gas contained in the fraction, the separation efficiency in the cryogenic separation process can be improved. Further, by providing the first compression step prior to the washing step, the volume of the fraction introduced into the soda scrubber tower can be compressed, and the operating efficiency in the soda scrubber tower can be improved.

[0037] On the other hand, the method for producing light olefins according to the present embodiment includes, as the ethanol conversion process E described above, an ethanol conversion step of introducing a raw material containing ethanol into a reactor and bringing it into contact with a catalyst to obtain an ethanol conversion fraction containing ethylene and propylene.

[0038] On the other hand, the method for producing light olefins according to the present embodiment may optionally include, as the ethanol conversion process E described above, a purification step of purifying the ethanol conversion fraction to obtain a purified ethanol conversion fraction. By providing the purification step, the concentration of the target compound contained in the ethanol conversion fraction can be increased, and the purification efficiency in the cryogenic separation process is improved.

[0039] On the other hand, the method for producing light olefins according to the present embodiment may optionally include, as the purification step in the ethanol conversion process E described above, a third cooling step of introducing the ethanol conversion fraction into a third cooling tower to obtain a cooled ethanol conversion fraction mainly containing olefins having 6 or less carbon atoms; It may have. By providing the third cooling step, the amount of hydrocarbons having 7 or more carbon atoms contained in the ethanol conversion fraction or a fraction derived therefrom can be reduced, and the purification efficiency in the cryogenic separation process is improved.

[0040] On the other hand, the method for producing light olefins according to the present embodiment may optionally include, as the purification step in the ethanol conversion process E described above, The step of compression and separation may be included, in which the cooled ethanol conversion fraction is pressurized by a compressor to obtain a light ethanol conversion fraction mainly containing olefins having 3 or less carbon atoms as a gas component and a heavy ethanol conversion fraction mainly containing olefins having 4 or more carbon atoms as a liquid component. By providing the compression and separation step, the amount of hydrocarbons having 4 or more carbon atoms contained in the ethanol conversion fraction or a fraction derived therefrom can be reduced, and the purification efficiency in the cryogenic separation step is improved.

[0041] The method for producing light olefins according to the embodiment optionally uses, as the aforementioned ethanol conversion process E, The method may have a recycling step of introducing at least a part of the above-mentioned heavy ethanol conversion fraction into the reactor as a part of the raw material. By providing the recycling step, the olefins contained in the heavy ethanol conversion fraction can be converted into target compounds, and the production efficiency of ethylene and propylene per unit of raw material ethanol is improved.

[0042] The method for producing light olefins according to the present embodiment includes a merging step of merging at least a part of the naphtha cracking fraction or a fraction derived therefrom and at least a part of the ethanol conversion fraction or a fraction derived therefrom to obtain a merged fraction. That is, by merging at least a part of the ethanol conversion fraction or a fraction derived therefrom into the naphtha cracking process, while using a raw material derived from ethanol, cryogenic separation is efficiently performed. As will be described later, the merging step is performed at any stage in the naphtha cracking process.

[0043] In the description of the above embodiment, for the sake of organizing the description of each step, the naphtha cracking N and the ethanol conversion process E in the technical field are divided into general categories for description. However, each step according to the present embodiment may belong to either the naphtha cracking N or the ethanol conversion process E.

[0044] The method for producing light olefins according to this embodiment is realized by, for example, the production equipment shown in FIG. 2. The light olefin production equipment includes a cracking furnace 11, a first cooling tower 12, a second cooling tower 13, a first compressor 14, a soda washing tower 15, and a cryogenic separation facility 16. Further, the light olefin production equipment includes a reactor 21 and a third cooling tower 22. Hereinafter, taking the case of using the production equipment as an example, each step according to this embodiment will be described in detail.

[0045] <Cracking step> In the cracking furnace 11, the above-described cracking step is performed.

[0046] (Naphtha raw material) In the method for producing light olefins according to this embodiment, a naphtha raw material is used. The naphtha raw material contains at least naphtha. Naphtha is a mixture of hydrocarbons with a boiling point range of about 30 to 230°C, and is divided into light naphtha and heavy naphtha according to its boiling point range, and either can be used. The naphtha raw material preferably contains hydrocarbons having 2 to 40 carbon atoms, more preferably contains hydrocarbons having 2 to 30 carbon atoms, and still more preferably contains hydrocarbons having 5 to 12 carbon atoms. The boiling point of the naphtha raw material may be, for example, in the range of 30 to 230°C. The naphtha raw material is not particularly limited, but generally, it is derived from fossil resources obtained from petroleum. Also, bio-naphtha obtained by decomposing vegetable oils and animal fats can be used.

[0047] From the viewpoint of reducing the by-production amount of coke, the naphtha raw material preferably contains dilution steam. The supply amount of the dilution steam is preferably 0.1 to 1.0 in terms of mass ratio to naphtha, and more preferably 0.3 to 0.6.

[0048] In the cracking process, the decomposition method is not particularly limited, but examples include the steam cracking method in which heated naphtha is thermally decomposed by contacting it with steam heated to 950 °C or higher, and the moving bed method in which a granular heat medium heated to a high temperature and naphtha are brought into contact in a moving bed for thermal decomposition. Examples of the steam cracking method include the tubular heating method in which naphtha and steam are circulated through a heating tube and thermally decomposed by heating from the tube wall. Also, in each method, a catalyst may be used to promote thermal decomposition.

[0049] Into the cracking furnace 11, the above-described naphtha raw material is introduced, and steam may be further introduced together with the naphtha raw material. At this time, the introduction amount of steam is preferably 20 to 100 parts by mass, more preferably 30 to 70 parts by mass, and still more preferably 35 to 60 parts by mass with respect to 100 parts by mass of the naphtha raw material. By setting the introduction amount of steam within the above range, the generation of carbonaceous substances can be suppressed.

[0050] The treatment temperature in the cracking furnace is preferably 700 to 1000 °C, more preferably 750 to 950 °C, and still more preferably 800 to 900 °C. By setting the temperature within this range, the thermal decomposition of naphtha proceeds favorably, and the generation of light components such as methane can be suppressed. Also, by controlling the treatment temperature according to the boiling point of the naphtha raw material, 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.

[0051] The reaction pressure in the cracking furnace is preferably 0.01 to 1.5 MPaG, more preferably 0.05 to 0.5 MPaG, and still more preferably 0.07 to 0.2 MPaG.

[0052] <First cooling step> The naphtha cracked fraction obtained in the cracking furnace 11 is introduced into the first cooling tower 12. Also, before being introduced into the first cooling tower 12, light olefins such as ethane and propane recycled from the subsequent purification facility may be mixed with the naphtha cracked fraction. In the first cooling tower 12, the aforementioned first cooling step is performed 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, the progress of excessive cracking can be suppressed, and furthermore, at least a part of the olefins having more than 6 carbon atoms is removed.

[0053] In the first cooling tower 12, it is preferable to cool by bringing heavy oil, cracked gasoline, or a mixture thereof into contact with the naphtha cracked fraction.

[0054] The pressure of the first cooled fraction after being treated by the first cooling tower 12 is preferably 0.01 to 1.5 MPaG, more preferably 0.05 to 0.5 MPaG, and still more preferably 0.07 to 0.2 MPaG.

[0055] The temperature of the first cooled fraction after being treated in the first cooling tower 12 is preferably 50 to 300 °C, more preferably 100 to 200 °C, and still more preferably 105 to 160 °C from the viewpoint of excellent removal efficiency of olefins having more than 6 carbon atoms.

[0056] <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 aforementioned second cooling step is performed. By cooling the first cooled fraction, at least a part of the olefins having more than 4 carbon atoms is removed, and a second cooled fraction mainly containing olefins having 4 or less carbon atoms is obtained. At this time, from the bottom of the tower, a second heavy fraction mainly containing hydrocarbons having 5 or more carbon atoms and water are mainly obtained.

[0057] In the second cooling tower 13, it is preferable to cool by bringing water into contact with the first cooled fraction.

[0058] The pressure of the second cooled fraction after treatment by 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.

[0059] 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 removal efficiency of olefins having more than 4 carbon atoms.

[0060] <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 above-described compression step is performed to increase the pressure of the second cooled fraction. In the first compressor 14, for example, the pressure of the second cooled fraction may be increased by one compressor, or the pressure of the second cooled fraction may be increased stepwise by, for example, 2 to 4 plural compressors. In the first compression step, in addition to increasing the pressure of the second cooled fraction as a gas component, a liquid component in which a high-boiling component such as a hydrocarbon having 5 or more carbon atoms contained in the second cooled fraction is liquefied may be obtained. Thus, by removing the high-boiling component by increasing the pressure, the concentration of olefins having 3 or less carbon atoms in the second cooled fraction can be improved.

[0061] 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.

[0062] <First Circulation Step> The method for producing light olefins according to this embodiment may include a first circulation step of introducing at least a part of a second heavy fraction mainly containing hydrocarbons having 5 or more carbon atoms in the second cooling step into a first cooling tower. The second heavy fraction contains heavy target compounds such as aromatic compounds. When the circulation amount of the second heavy fraction to the first cooling tower in the first circulation step is increased, the production efficiency of these heavy target compounds decreases. On the other hand, when the circulation amount is increased, since a part of the olefins having 4 or less carbon atoms contained in the second heavy fraction can be introduced into the cryogenic separation step, the production efficiency of these olefins is improved. Therefore, it is preferable that the circulation amount in the first circulation step is determined 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 production efficiency of propylene, the circulation amount in the first circulation step is preferably 20 to 90% by mass, more preferably 30 to 90% by mass, and still more preferably 40 to 90% by mass with respect to the second heavy fraction.

[0063] <Second Circulation Step> The method for producing light olefins according to this embodiment may have a second circulation step of introducing at least a part of a second heavy fraction mainly containing hydrocarbons having 5 or more carbon atoms in the second cooling step into a second cooling tower. In this circulation step, in the above-mentioned first compression step, the generated liquid components may be combined and introduced into the second cooling tower. The second heavy fraction contains heavy target compounds such as aromatic compounds. Increasing the circulation amount of the second heavy fraction 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 enables part of the olefins having 4 or fewer 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 that the circulation amount in the second circulation step is determined in consideration of the production balance between heavy target compounds such as aromatic compounds and olefins having 4 or fewer carbon atoms. From the viewpoint of excellent production efficiency of propylene, the circulation amount in the second circulation step is preferably 20 to 90% by mass, more preferably 30 to 90% by mass, and still more preferably 40 to 90% by mass with respect to the total amount of the liquid component and the second heavy fraction in the first compression step.

[0064] <Washing step> In the washing step, a washed fraction is obtained by introducing the fraction into the soda washing tower 15 before introducing it into the cryogenic separation equipment. In the washing step, acidic components such as carbon dioxide in the fraction can be removed by the treatment in the soda washing tower 15. Since the boiling point of carbon dioxide is higher than that of ethylene, it becomes difficult to separate olefins from carbon dioxide when carbon dioxide is introduced into cryogenic separation. Therefore, it is preferable to remove carbon dioxide in the fraction before introducing it into the cryogenic separation equipment.

[0065] In the soda washing tower 15, it is preferable to obtain a washed fraction by bringing the fraction into contact with an aqueous sodium hydroxide solution. The amount of sodium hydroxide can be appropriately selected so that acidic components such as carbon dioxide in the fraction can be removed.

[0066] <Cryogenic separation step> In the cryogenic separation process, the fraction is introduced into the cryogenic separation facility to separate ethylene and propylene. Here, the fraction introduced in the washing process or the cryogenic separation process is preferably the combined fraction or a fraction derived therefrom. The "combined fraction" is the fraction obtained by the above-described combining process. Further, here, the "fraction derived therefrom" means a fraction obtained by further purifying the combined fraction with a purification facility such as a soda washing tower.

[0067] Cryogenic separation generally separates components by performing a distillation operation under extremely low temperature and high pressure conditions. For example, under extremely low temperature and high pressure conditions, the fraction is liquefied to separate hydrogen and methane from light olefins.

[0068] In the cryogenic separation process, light olefins such as ethylene and propylene are separated through a demethanizer, a deethanizer, an ethylene rectification column, a depropanizer, a propylene rectification column, etc.

[0069] The purification system of the naphtha cracker has a front-end demethanizer method and a front-end depropanizer method. Hereinafter, an example of the apparatus configuration in each method will be described, but the presence or absence and the order of each separation column are not limited thereto.

[0070] In the purification system of the front-end demethanizer method, for example, light olefins are purified by the following procedure. First, the introduced fraction compressed by a compressor is introduced into a cooler to liquefy at least a part of the light olefins in the introduced fraction and at the same time remove at least a part of the hydrogen. The fraction is introduced into a demethanizer column to obtain a demethanized fraction mainly containing light olefins from the bottom of the column and an off-gas fraction containing hydrogen and methane from the top of the column. The obtained demethanized fraction is introduced into a deethanizer column to obtain an ethylene fraction mainly containing ethylene from the top of the column and a deethanized fraction mainly containing olefins having 3 or more carbon atoms from the bottom of the column. The obtained ethylene fraction is introduced into an ethylene rectification column to obtain purified ethylene by separating ethylene and ethane. The obtained deethanized fraction is introduced into a depropanizer column to obtain a propylene fraction mainly containing propylene from the top of the column and a depropanized fraction mainly containing olefins having 4 or more carbon atoms from the bottom of the column. The obtained propylene fraction is introduced into a propylene rectification column to obtain purified propylene by separating propylene and propane. The obtained depropanized fraction is introduced into a debutanizer column to obtain olefins having 4 carbon atoms.

[0071] In a purification system using the front-end depropanizer method, for example, light olefins are purified through the following procedure. In the purification system using the front-end depropanizer method, by separating the fraction into an introduced fraction mainly containing hydrocarbons with 3 or fewer carbon atoms and a bypass fraction mainly containing hydrocarbons with 3 or more carbon atoms, the amount introduced into the cryogenic separation process can be reduced, and the energy consumption related to cryogenic separation can be reduced. That is, for example, as shown in FIG. 15, in the purification system using the front-end depropanizer method, the fraction is introduced into the first distillation column 17 to separate the introduced fraction introduced into the cryogenic separation process. Also, from the bottom of the first distillation column 17, a bypass fraction is obtained that bypasses the cryogenic separation process and is introduced into the subsequent equipment. In the first distillation column 17, for example, the separation operation may be carried out by a single distillation column, or for example, the separation operation may be carried out step by step by a plurality of distillation columns of 2 to 4 towers. Then, after compressing the obtained introduced fraction with a compressor and introducing it into a cooler, at least a part of the light olefins in the introduced fraction is liquefied, and at the same time, at least a part of the hydrogen is removed. After cooling and compressing the introduced fraction, the target compound can be separated from the introduced fraction by treating it in the same manner as in the purification system using the front-end demethanizer method. Also, in the purification system using the front-end depropanizer method, the introduced 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 process. In this way, by adding the first distillation column 17 and performing the purification of the introduced fraction, the energy consumption related to the cryogenic separation process can be reduced.

[0072] <Ethanol conversion process> On the other hand, a raw material containing ethanol is introduced into the reactor 21. In the reactor 21, the aforementioned ethanol conversion process is carried out. By bringing the raw material containing ethanol into contact with a catalyst in the reactor 21, an ethanol conversion fraction containing ethylene and propylene is obtained.

[0073] (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, from the perspective of excellent environmental compatibility, it is preferable to use bioethanol. In recent years, for the realization of a sustainable society or for the suppression of greenhouse gas emissions, the importance of replacing fossil resources such as crude oil with renewable plant-derived resources has been re-recognized. Therefore, it becomes possible to produce chemicals that have conventionally been produced using fossil resources such as crude oil by using bioethanol obtained from renewable plant-derived resources.

[0074] In the raw material, the ethanol content is preferably 30 to 100% by mass, more preferably 40 to 100% by mass, and still more preferably 50 to 100% by mass with respect to the total amount of the raw material.

[0075] As the raw material, a raw material containing ethylene and ethanol may be used. By using this raw material, an adiabatic reactor can be used to control the temperature inside the reactor and produce propylene with good yield. Further, the raw material may contain olefins having 4 to 6 carbon atoms.

[0076] In the raw material, the molar ratio of ethylene / ethanol is preferably 0.05 to 2.5, more preferably 0.20 to 2.0, still more preferably 0.30 to 1.8, and even more preferably 0.30 to 1.5.

[0077] In the ethanol conversion process, the raw material may contain olefins having 4 to 6 carbon atoms and oxygen-containing compounds having 1 to 6 carbon atoms other than ethanol. Examples of the oxygen-containing compounds having 1 to 6 carbon atoms other than ethanol include methanol, propanol, dimethyl ether, and diethyl ether. These compounds can give target compounds such as ethylene and propylene by contacting with the catalyst inside the reactor.

[0078] The raw materials 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. These saturated aliphatic hydrocarbons, olefins having 7 or more carbon atoms, and oxygen-containing compounds having 7 or more carbon atoms can be converted into target compounds such as propylene by dehydrogenation reaction or a combination of dehydration reactions by contacting with a catalyst in the same manner as ethylene and ethanol. However, they are less reactive than the aforementioned olefins having 4 to 6 carbon atoms and oxygen-containing compounds having 1 to 6 carbon atoms other than ethanol.

[0079] In addition, the raw materials can include those obtained by separating all or part of the olefins having 4 or more carbon atoms from the reaction gas containing olefins having 3 or more carbon atoms obtained from the ethanol conversion step by a separation step. In this way, by using a so-called recycle reaction system, effective utilization of olefin raw materials can be achieved.

[0080] In addition to the above-mentioned raw materials that can be converted into target compounds such as propylene by the ethanol conversion step, the raw materials may contain inert gases such as nitrogen. In addition, the raw materials may contain hydrogen and methane as dilution gases, but it is preferable not to perform hydrogen dilution. Hydrogen may be used to suppress coking deterioration of the catalyst.

[0081] In the ethanol conversion step, the raw materials may contain water. Since ethylene and ethanol contained in the mixed raw materials are produced by various production methods, they may contain "water generated in the production process". Here, "water generated in the production process" refers to moisture generated in the production process of ethylene and / or ethanol and not removed.

[0082] In the ethanol conversion step, in addition to "water generated in the production process", water vapor can be included in the mixed raw materials. Water vapor has the effect of suppressing coking deterioration by reducing the olefin partial pressure and improving the yield of lower olefins. On the other hand, since water vapor may promote dealumination of zeolite, it is preferably not to include water vapor in the mixed raw materials in addition to "water generated in the production process".

[0083] (Insulated Reactor) In the ethanol conversion step, the reactor is not particularly limited, but an insulated reactor is preferred because it consumes less energy. Regarding insulated reactors, reference can be made to the description in Adiabatic Fixed-Bed Reactors (Elsevier, 2014, Ch.1, P.4, L.5~24 ISBN: 978-0-12-801306-9). Examples of insulated reactors include fixed-bed insulated reactors, moving-bed insulated reactors, and fluidized-bed insulated reactors. Among them, a fixed-bed insulated reactor is preferred for the method of this embodiment. Among fixed-bed insulated reactors, a single-stage fixed-bed adiabatic reactor with only one fixed catalyst bed is more preferred. Since carbonaceous matter (coke) accumulates on the catalyst during the reaction, a multi-column switching type single-stage fixed-bed adiabatic reactor capable of burning and removing this carbonaceous matter while continuing the reaction is preferred.

[0084] FIG. 3 is a schematic configuration diagram of a single-stage fixed-bed adiabatic reactor. The single-stage fixed-bed adiabatic reactor 211 includes a reaction housing 212 provided with a heat insulating material 216 on the outer periphery, a catalyst bed 213, a reactor inlet 214, and a reactor outlet 215. The reaction housing 212 is provided with a heat insulating material 216 on the outer periphery to prevent the heat inside the reactor from escaping to the outside. In the manufacturing method according to this embodiment, the temperature inside the reactor can be controlled by the heat generation and heat absorption due to the reaction.

[0085] The catalyst bed 213 is filled with a catalyst described later. A first sheathed thermocouple 217 is provided immediately before contacting the catalyst bed inlet 219a of the catalyst bed 213. A second sheathed thermocouple 218 is provided immediately after passing through the catalyst bed outlet 219b of the catalyst bed 213. These thermocouples measure the temperature of the mixed raw material immediately before contacting the catalyst bed inlet 219a and the reaction gas immediately after passing through the catalyst bed outlet 219b. The catalyst bed 213 may be multi-stage, but is preferably single-stage as shown in FIG. 3.

[0086] In the single-stage fixed-bed adiabatic reactor 211, the mixed raw material is introduced from the reactor inlet 214, brought into contact with the catalyst bed 213, and the reaction gas is taken out from the reactor outlet 215.

[0087] In the ethanol conversion step, the reaction temperature is preferably 300 to 600 °C, more preferably 450 to 590 °C, and still more preferably 500 to 580 °C, from the viewpoint of enhancing reactivity while suppressing coking deterioration. The reaction temperature is the value calculated by the formula: [inlet temperature of the catalyst bed + outlet temperature of the catalyst bed] / 2. The inlet temperature of the catalyst bed is the temperature of the mixed raw material immediately before the raw material fluid contacts the catalyst bed filled in the adiabatic reactor. The outlet temperature of the catalyst bed 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 mean the temperatures in the range of 0d to 0.8d, 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 in a plane perpendicular to the flow direction of the fluid.

[0088] In the ethanol conversion step, the reaction pressure is preferably 0.01 to 3.0 MPaG, more preferably 0.01 to 1.0 MPaG.

[0089] In the ethanol conversion step, the supply rate of the raw material is the space velocity (WHSV) based on the mass of the catalyst, and is preferably 0.1 to 1000 h -1 -1, more preferably 0.1 to 500 h -1 -1, and still more preferably 0.5 to 100 h -1 -1. In the ethanol conversion step, WHSV is calculated after converting ethanol to ethylene as shown by the following formula.

[0090] WHSV (h -1 -1) = mass flow rate of raw material supply (kg / h) / amount of catalyst (kg) Mass flow rate of raw material supply (kg / h) = ethylene flow rate (kg / h) + ethanol flow rate in terms of ethylene (kg / h) + olefin flow rate having 4 to 6 carbon atoms (kg / h) + oxygen-containing compound flow rate having 1 to 6 carbon atoms other than ethanol (kg / h) Ethanol flow rate in terms of ethylene (kg / h) = ethanol flow rate (kg / h) × ethylene molecular weight (g / mol) / ethanol molecular weight (g / mol)

[0091] (Catalyst) The catalyst in the ethanol conversion step is a solid catalyst that exhibits the catalytic ability to convert olefins and ethanol into target compounds such as propylene. From the viewpoint of excellent thermal durability and propylene selectivity of the catalyst, a zeolite-containing catalyst is preferable. As a common problem in the production of olefins using conventional zeolites, there is coking deterioration in which heavy carbonaceous substances (coke) accumulate inside the zeolite pores due to reaction with hydrocarbons and deactivate. In order to regenerate the catalyst performance, it is preferable to burn and remove the coke in an atmosphere containing oxygen molecules. However, with this coke combustion, the structural collapse of the zeolite progresses, leading to permanent deterioration of the catalyst that is difficult to regenerate. According to the ethanol conversion step, since the generation of coke can be suppressed, it becomes easier to maintain the activity even when using a zeolite-containing catalyst.

[0092] ≪Zeolite-Containing Catalyst≫ A zeolite-containing catalyst refers to a catalyst powder or molded body that contains zeolite as an active species. In the ethanol conversion step, as the zeolite in the above zeolite-containing catalyst, it is preferable to use a so-called intermediate pore diameter zeolite having a pore diameter of 5 to 6 Å. The intermediate pore diameter zeolite means "a zeolite whose pore diameter range is intermediate between the pore diameter of small pore diameter zeolites typified by A-type zeolites and the pore diameter of large pore diameter zeolites typified by mordenite, X-type, and Y-type zeolites". The "intermediate pore diameter zeolite" has a so-called oxygen 10-membered ring in its crystal structure.

[0093] Examples of intermediate pore size zeolites include MFI type 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, Silicate, etc. Among them, MFI type zeolites are preferred, and ZSM-5 is more preferred. In addition, zeolites similar to ZSM-5 and ZSM-11 described in Stud. Surf. Sci. Catal. 1987, 33, 167-215 can be used. Among them, from the viewpoint of excellent catalytic performance (catalytic activity and durability against coking), MFI type zeolites are preferred, and ZSM-5 is more preferred.

[0094] The silica / alumina (SiO 2 / Al 2 O 3 ) molar ratio of the zeolite contained in the zeolite-containing catalyst of this embodiment can be appropriately selected. From the viewpoint of excellent catalytic activity and propylene selectivity, it is preferably 20 to 2000, more preferably 100 to 1500 from the viewpoint of enhancing the durability of the catalyst, still more preferably 300 to 1200, and even more preferably 800 to 1200. The silica / alumina (SiO 2 / Al 2 O 3 ) molar ratio of the zeolite contained in the zeolite-containing catalyst 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, the zeolite can be completely dissolved in an aqueous alkali solution, and the resulting solution can be analyzed by inductively coupled plasma optical emission spectrometry or the like to obtain it.

[0095] The synthesis method of the zeolite of the present embodiment is not particularly limited, but it can be produced by optimizing various conditions of the conventionally known hydrothermal synthesis method of MFI-type zeolite. Generally, as a means of efficiently obtaining MFI-type zeolite by the hydrothermal synthesis method, there are a method of hydrothermal synthesis using an appropriate organic structure-directing agent (SDA), a method of hydrothermal synthesis by adding hydrothermally synthesized MFI zeolite as a seed crystal, or a method of hydrothermal synthesis by adding it as a seed slurry in the crystal stage. Here, examples of the organic structure-directing agent (SDA) used include ammonium salts, urea compounds, amines, and alcohols. It is also known that not only organic SDA but also inorganic cations and anions are involved in the structure, and zeolite synthesis depends on the complex action of each component. In the hydrothermal synthesis method of MFI-type zeolite as described above, the raw material charge composition such as the type of raw material and additive (SDA), the amount of additive, pH, silica / alumina molar ratio, medium, cation, and anion abundance ratio, and the synthesis conditions such as synthesis temperature and synthesis time are appropriately optimized to obtain a suitable catalyst.

[0096] Specifically, for example, there are a method of synthesis using the seed slurry described in Japanese Patent No. 5426983 and the method exemplified in The Hydrothermal Synthesis of Zeolites (Chemcal Reviews, 2003, 103, 663-702).

[0097] Also, as long as it is an MFI zeolite having the specific physical properties and composition described above, commercially available zeolite can also be used.

[0098] The zeolite-containing catalyst in the present embodiment preferably contains a phosphorus element or a silver element.

[0099] As the form of the phosphorus element, polymers of phosphorus (for example, polyphosphoric acid), oxides of phosphorus (for example, P 2 O 5) Compounds in which phosphorus is added to the aluminum of zeolite, etc. may be mentioned. Also, a plurality of them may be included. When the zeolite contains aluminum, the phosphorus element has the effect of suppressing dealumination of the zeolite, and in some cases, the effect of improving the propylene yield. In particular, in the case of applications exposed to a high-temperature steam atmosphere, since the properties of the zeolite-containing catalyst are likely to change due to dealumination, the effect of suppressing dealumination is further improved.

[0100] The content of the phosphorus element contained in the zeolite-containing catalyst is preferably 0.01 to 2.0% by mass, more preferably 0.05 to 2.0% by mass, based on the mass of the entire catalyst, from the viewpoint of excellent dealumination suppression effect.

[0101] In the present embodiment, the content of the phosphorus element in the catalyst indicates the value measured using a fluorescent X-ray analyzer. The measurement of the content of the phosphorus element may be performed using a commercially available fluorescent X-ray analyzer under normal conditions in accordance with the instruction manual. For example, when using a Rigaku product with the trade name "RIX3000", the measurement conditions can be set to use the P-Kα line, with a tube voltage of 50 kV and a tube current of 50 mA.

[0102] In the present embodiment, phosphoric acid and / or phosphate (hereinafter also referred to as "phosphorus raw material") is used as the raw material of the phosphorus element contained in the zeolite-containing catalyst. As the phosphorus raw material, phosphate is more preferable, and among phosphates, a compound showing a solubility of 1 g or more in 100 g of water at 25°C is more preferable.

[0103] Examples of the phosphoric acid include phosphoric acid and pyrophosphoric acid. Examples of the phosphate include ammonium phosphate salts such as ammonium phosphate, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, and ammonium sodium hydrogen phosphate, potassium hydrogen phosphate, aluminum hydrogen phosphate, sodium phosphate, potassium phosphate, and the like. Among them, ammonium phosphate salts having a relatively high solubility in water are preferable, and more preferably, 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.

[0104] The form of the silver element is, for example, silver ions. The silver element has an effect of improving the hydrothermal resistance of the zeolite by controlling the acid sites of the zeolite.

[0105] The content of the silver element contained in the zeolite-containing catalyst is preferably 0.01 to 2.0% by mass based on the mass of the entire catalyst, and more preferably 0.05 to 2.0% by mass from the viewpoint of excellent effect of improving the hydrothermal resistance per content.

[0106] In the present embodiment, the content of the silver element in the catalyst indicates the value measured using a fluorescent X-ray analyzer. The measurement of the content of the silver element may be performed using a commercially available fluorescent X-ray analyzer under normal conditions in accordance with the instruction manual. For example, when using the product name "RIX3000" manufactured by Rigaku, the measurement conditions may be using the P-Kα line, a tube voltage of 50 kV, and a tube current of 50 mA.

[0107] In this embodiment, silver nitrate can be mentioned as a raw material of the silver element contained in the zeolite-containing catalyst. By using a zeolite-containing catalyst containing sodium as a counter cation, performing ion exchange with silver nitrate, and sintering, a zeolite-containing catalyst containing a silver element can be obtained. The ion exchange between sodium, which is a counter cation in the zeolite, and silver nitrate can be carried out by immersing the zeolite or the zeolite-containing catalyst in an aqueous solution of silver nitrate and then washing with water. At this time, the ion exchange rate can be improved by performing the immersion and the water washing a plurality of times. Further, a zeolite-containing catalyst containing a silver element can also be obtained by treating a proton-type or ammonium-type zeolite with silver nitrate.

[0108] The zeolite-containing catalyst of this embodiment can be produced, for example, by molding as follows using a zeolite having the specific physical properties and composition described above. The molding method is not particularly limited, and a general method can be used. Specifically, methods such as compression molding, extrusion molding, and spray drying molding, which is optimal for the fluidized bed reaction method, can be mentioned.

[0109] Further, 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 products of these binders can be used. The mass ratio of zeolite / binder is preferably in the range of 10 / 90 to 90 / 10, and more preferably in the range of 20 / 80 to 80 / 20. From the viewpoint of suppressing coking, it is preferable that the binder is a silica binder.

[0110] In the ethanol conversion step, prior to bringing the zeolite-containing catalyst into contact with the raw material, a pretreatment step may be performed on the zeolite-containing catalyst. Preferred pretreatment steps include a heat treatment step at a temperature of 300 °C or higher in the presence of steam. When pretreatment is performed, the effects of suppressing catalyst deterioration and improving selectivity tend to become more prominent. In the case of the above method, at a temperature of 300 °C or higher and 900 °C or lower, the atmosphere is not particularly limited, but it is preferable to flow a mixed gas of air or an inert gas such as nitrogen and steam (water vapor) and perform the treatment under the condition that the water vapor partial pressure is 0.01 atm or higher. As the heat treatment temperature, a temperature of 400 °C or higher and 700 °C or lower is more preferable. Further, this pretreatment step can be carried out using a reactor for converting ethanol.

[0111] (Product: Ethanol conversion fraction containing ethylene and propylene) In the ethanol conversion step, an ethanol conversion fraction containing ethylene and propylene is obtained by bringing the raw material into contact with the catalyst. The ethanol conversion 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.

[0112] From the viewpoint of excellent production efficiency of the target compound, the total content of ethylene and propylene in the ethanol conversion fraction is preferably 15% by mass or more, more preferably 20% by mass or more, and still more preferably 25% by mass or more. Further, the P / E mass ratio representing the mass ratio of ethylene to propylene can be appropriately adjusted according to 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 still more preferably 0.50 to 0.70.

[0113] <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 content C after purification E1 is the ethylene and propylene content C in the second cooling fractionC2 It is preferable to purify the ethanol conversion fraction so as to be higher than that, and obtain a purified ethanol conversion fraction.

[0114] (Third cooling step) In the purification step, it is preferable to have a third cooling step in which the ethanol conversion fraction is introduced into a third cooling tower 22 to obtain a cooled ethanol conversion fraction mainly containing olefins having 6 or less carbon atoms.

[0115] The ethanol conversion 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 performed to obtain a cooled ethanol conversion fraction mainly containing olefins having 6 or less carbon atoms. In the third cooling tower 22, by cooling the ethanol conversion fraction, hydrocarbons having more than 6 carbon atoms and water are removed.

[0116] In the third cooling tower 22, it is preferable to cool by bringing water into contact with the ethanol conversion fraction. The water used in the third cooling tower 22 can be appropriately adjusted in pH for the purpose of suppressing equipment corrosion.

[0117] The pressure of the cooled ethanol conversion fraction after the treatment by the third cooling tower 22 is preferably 0.01 to 1.5 MPaG, more preferably 0.05 to 0.5 MPaG, and still more preferably 0.07 to 0.2 MPaG.

[0118] The temperature of the cooled ethanol conversion fraction after the treatment in the third cooling tower 22 is preferably 5 to 200 °C, more preferably 10 to 100 °C.

[0119] The method for producing light olefins according to this embodiment preferably has a recycling step of introducing at least a part of the cooled ethanol conversion fraction into the reactor 21 as a part of the raw material. By supplying the cooled ethanol conversion fraction to the reactor 21 in this way, it can be converted into ethylene or propylene.

[0120] <Compression separation step> The method for producing light olefins according to this embodiment may include a compression separation step of boosting the pressure of the cooled ethanol conversion fraction by a compressor to obtain a light ethanol conversion fraction mainly containing olefins having 3 or less carbon atoms as a gas component and a heavy ethanol conversion fraction mainly containing olefins having 4 or more carbon atoms as a liquid component.

[0121] As the compression separation step, a second compression step of boosting the pressure of the cooled ethanol conversion fraction by a compressor, and a distillation step of obtaining a light ethanol conversion fraction mainly containing olefins having 3 or less carbon atoms as a gas component and a heavy ethanol conversion fraction mainly containing olefins having 4 or more carbon atoms as a liquid component by a distillation column may be included.

[0122] More specifically, as shown in FIG. 4, the cooled ethanol conversion fraction obtained by the third cooling step may be boosted in pressure by a second compressor 23 and introduced into a distillation column 24.

[0123] In the distillation column 24, a light ethanol conversion fraction mainly containing olefins having 3 or less carbon atoms as a gas component and a heavy ethanol conversion fraction mainly containing hydrocarbons having 4 or more carbon atoms as a liquid component are obtained. As described above, the distillation step is performed in the second compressor 23 and the distillation column 24.

[0124] The obtained light ethanol conversion fraction may be introduced into a condenser 25, and a part thereof may be liquefied and refluxed to the distillation column to obtain a cooled light ethanol conversion fraction. By providing the distillation step in this way, hydrocarbons having 4 or more carbon atoms and water in the fraction derived from the ethanol conversion fraction can be reduced, and the ratios of ethylene and propylene can be increased.

[0125] The pressure of the cooled light ethanol conversion fraction is preferably 0.5 to 3.0 MPaG, more preferably 1.0 to 2.5 MPaG, and still more preferably 1.1 to 2.0 MPaG.

[0126] The temperature of the cooled light ethanol conversion fraction is preferably 0 to 50°C, more preferably 5 to 30°C, and even more preferably 10 to 20°C.

[0127] In the purification process including a distillation process or the like, the ethylene and propylene content C E1 in the purified ethanol conversion fraction is higher than the ethylene and propylene content C C2 in the second cooling fraction, and the ethanol conversion fraction is purified to obtain a purified ethanol conversion fraction.

[0128] Thus, when the ethanol conversion fraction that has undergone the compression separation process is merged in the merging process described later, it is merged with a fraction having a high content ratio of olefins having 3 carbon atoms from which hydrocarbons having 4 or more carbon atoms have been removed and a fraction derived from the naphtha cracking fraction. Therefore, the content of hydrocarbons having 4 or more carbon atoms in the merged fraction can be reduced, and the ratio of ethylene and propylene can be increased. As a result, the processing energy in the cryogenic separation can be reduced.

[0129] Note that the method for producing light olefins according to the present embodiment preferably has a recycling process in which at least a part of the heavy ethanol conversion fraction is introduced into the reactor 21 as a part of the raw material. By supplying the heavy ethanol conversion fraction to the reactor 21 in this way, the olefins contained in the heavy ethanol conversion fraction are converted into ethylene or propylene, so that the production efficiency of light olefins from ethanol can be improved.

[0130] In the compression separation process, a part of the fraction is liquefied by boosting the pressure with a compressor, and the fraction is processed by a gas-liquid separation device to obtain a light ethanol conversion fraction mainly containing olefins having 3 or less carbon atoms as a gas component and a heavy ethanol conversion fraction mainly containing olefins having 4 or more carbon atoms as a liquid component. By using a gas-liquid separation device, the energy consumption related to the compression separation process can be suppressed as compared with the case of using a distillation column.

[0131] More specifically, as shown in FIG. 5, the cooled ethanol conversion fraction obtained in the third cooling step may be pressurized by the second compressor 23 and introduced into the gas-liquid separation drum 26.

[0132] In this way, when the ethanol conversion fraction that has undergone the compression separation step by the gas-liquid separation device is merged in the merging step described below, it is merged with the fraction having a high content ratio of olefins having 3 carbon atoms from which hydrocarbons having 4 or more carbon atoms have been removed and the fraction derived from the naphtha cracking fraction. Therefore, the content of hydrocarbons having 4 or more carbon atoms in the merged fraction can be reduced, and the ratios of ethylene and propylene can be increased. As a result, the processing energy in the cryogenic separation can be reduced.

[0133] Note that the method for producing light olefins according to the present embodiment preferably has a recycling step of introducing at least a part of the heavy ethanol conversion fraction that has undergone the compression separation step by the gas-liquid separation device into the reactor 21 as a part of the raw material. By supplying the heavy ethanol conversion fraction to the reactor 21 in this way, the olefins contained in the heavy ethanol conversion fraction are converted into ethylene or propylene, so that the production efficiency of light olefins from ethanol can be improved.

[0134] <Merging step> In the merging step, at least a part of the naphtha cracking fraction or a fraction derived therefrom and at least a part of the ethanol conversion fraction or a fraction derived therefrom are merged to obtain a merged fraction.

[0135] The "naphtha cracking fraction" is the fraction obtained by the above-described cracking step. The "fraction derived therefrom" means a fraction obtained by further purifying the naphtha cracking fraction. The naphtha cracking fraction may be mixed with a gas containing hydrocarbons in order to adjust the properties before purification.

[0136] The "ethanol conversion fraction" is the fraction obtained by the above-described ethanol conversion step. The "fraction derived therefrom" means a fraction obtained by further purifying the ethanol conversion fraction.

[0137] In the method for producing light olefins according to this embodiment, the merging step may be merged at any stage. However, specific examples of the merging step will be taken and described below.

[0138] The merging step may be performed, for example, after the aforementioned second cooling step, as shown in FIGS. 2, 4, 5, 15, 16, and 17. In this case, the method for producing light olefins according to this embodiment includes a first cooling step of introducing a naphtha cracking fraction into a first cooling tower to obtain a first cooling fraction mainly containing olefins having 6 or less carbon atoms, a second cooling step of introducing the first cooling fraction into a second cooling tower to obtain a second cooling fraction mainly containing olefins having 4 or less carbon atoms, and at least a part of the naphtha cracking fraction or a fraction derived therefrom in the merging step is the second cooling fraction. By having the merging step, the flow rate of the fraction introduced into the cryogenic separation step can be reduced, and the load of the cryogenic separation step can be reduced.

[0139] Further, the above manufacturing method further includes a first compression step of boosting the pressure of the second cooling fraction, and at least a part of the naphtha cracking fraction or a fraction derived therefrom in the merging step may be the compressed second cooling fraction. In this case, it is preferable that the ethanol conversion fraction or a fraction derived therefrom is a fraction boosted by a compression separation step or the like. In this way, by merging the naphtha cracking fraction or a fraction derived therefrom boosted by the first compression step with the ethanol conversion fraction or a fraction derived therefrom, that is, by the ethanol conversion fraction or a fraction derived therefrom not undergoing the first boosting step, the boosting load in the naphtha cracking process can be reduced, and the connection between the ethanol conversion process and the naphtha cracking process becomes easy. Also, when the pressure of the ethanol conversion fraction or a fraction derived therefrom is higher than the pressure of the naphtha cracking fraction or a fraction derived therefrom, the connection between the ethanol conversion process and the naphtha cracking process becomes easy by reducing the pressure.

[0140] The merging process may be performed, for example, as shown in FIGS. 6, 7, 9, 18, 19, and 21, after the aforementioned first cooling process. In this case, the method for producing light olefins according to this embodiment a first cooling step of introducing a naphtha cracked fraction into a first cooling tower to obtain a first cooling fraction mainly containing olefins having 6 or less carbon atoms; a second cooling step of introducing a merged fraction or a fraction derived therefrom into a second cooling tower to obtain a second cooling fraction mainly containing olefins having 4 or less carbon atoms, and further includes at least a part of the naphtha cracked fraction or a fraction derived therefrom in the merging process is at least a part of the first cooling fraction.

[0141] As described above, before introducing into the second cooling tower, at least a part of the first cooling fraction and at least a part of the ethanol conversion fraction or a fraction derived therefrom are merged. Since at least a part of the components having more than 4 carbon atoms contained in the fraction derived from the ethanol conversion fraction merged in the merging process are removed in the second cooling step, the ratios of ethylene and propylene in the fraction introduced into the cryogenic separation can be further increased. Further, for example, when the ethanol conversion fraction or a fraction derived therefrom contains hydrophilic by-products such as ethanol, by introducing the ethanol conversion fraction or a fraction derived therefrom into a second cooling tower using water as a contact refrigerant, the hydrophilic by-products can be extracted and the purity of the light olefins can be improved.

[0142] The merging process may be performed, for example, as shown in FIGS. 8 and 20, by merging with the fraction in the circulation process of circulating the fraction to the aforementioned second cooling tower. In this case, the method for producing light olefins according to this embodiment a first cooling step of introducing a naphtha cracked fraction into a first cooling tower to obtain a first cooling fraction mainly containing olefins having 6 or less carbon atoms; Introduce the first cooling fraction into the second cooling tower to obtain a second cooling fraction mainly containing olefins having 4 or less carbon atoms and a second heavy fraction mainly containing hydrocarbons having 5 or more carbon atoms, and a second cooling step; A second circulation step of introducing at least a part of the second heavy fraction mainly containing hydrocarbons having 5 or more carbon atoms in the second cooling step into the second cooling tower; A first introduction step of introducing the combined fraction into the second cooling tower; further comprising; At least a part of the naphtha cracking fraction or a fraction derived therefrom in the combining step is at least a part of the second heavy fraction. Also in this embodiment, the load of the cryogenic separation step can be reduced in the same manner as in the above-described aspect.

[0143] The combining step may be performed, for example, as shown in FIGS. 10, 11, 13, 22, 23, and 25, before introducing it into the above-described first cooling tower. In this case, the method for producing light olefins according to the present embodiment a first cooling step of introducing the combined fraction or a fraction derived therefrom into the first cooling tower to obtain a first cooling fraction mainly containing olefins having 6 or less carbon atoms; a second cooling step of introducing the first cooling fraction into the second cooling tower to obtain a second cooling fraction mainly containing olefins having 4 or less carbon atoms; further comprising a cryogenic separation step of introducing the second cooling fraction or a fraction derived therefrom into a cryogenic separation facility to separate ethylene and propylene.

[0144] As described above, at least a part of the naphtha cracking fraction and at least a part of the ethanol conversion fraction or a fraction derived therefrom are merged before being introduced into the first cooling tower. In the merging step, the fraction having more than 6 carbon atoms contained in the fraction derived from the ethanol conversion fraction to be merged is removed by the aforementioned third cooling tower 22 and then merged with the naphtha cracking fraction, so that the proportions of ethylene and propylene in the merged fraction can be increased. Moreover, since the fraction having more than 4 carbon atoms contained in the fraction derived from the ethanol conversion fraction is removed in the second cooling step, the proportions of ethylene and propylene in the fraction introduced into the cryogenic separation can be further increased. Further, for example, when the ethanol conversion fraction or a fraction derived therefrom contains lipophilic by-products, the ethanol conversion fraction or a fraction derived therefrom is introduced into the first cooling tower using heavy oil, cracked gasoline, or a mixture thereof as a contact refrigerant, whereby the lipophilic by-products can be extracted and the purity of the light olefins can be improved. Furthermore, for example, when the ethanol conversion fraction or a fraction derived therefrom contains hydrophilic by-products such as ethanol, the ethanol conversion fraction or a fraction derived therefrom is introduced into the second cooling tower using water as a contact refrigerant, whereby the hydrophilic by-products can be extracted and the purity of the light olefins can be improved.

[0145] The merging step may be performed, for example, as shown in FIGS. 12 and 24, by merging with the fraction in the circulation step of circulating the fraction to be introduced into the aforementioned first cooling tower. In this case, the method for producing light olefins according to the present embodiment a first cooling step of introducing a naphtha cracking 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 and a second heavy fraction mainly containing hydrocarbons having 5 or more carbon atoms; a first circulation step of introducing at least a part of the second heavy fraction mainly containing hydrocarbons having 5 or more carbon atoms in the second cooling step into the first cooling tower; A merging step of merging at least a part of the second heavy fraction and at least a part of the ethanol conversion fraction or a fraction derived therefrom to obtain a merged fraction; A second introducing step of introducing the merged fraction into a first cooling tower; Further including a cryogenic separation step of introducing the second cooled fraction or a fraction derived therefrom into a cryogenic separation facility to separate ethylene and propylene. At least a part of the naphtha cracking fraction or a fraction derived therefrom in the merging step is at least a part of the second heavy fraction.

[0146] As described above, at least a part of the second heavy fraction in the circulation step is merged with at least a part of the ethanol conversion fraction or a fraction derived therefrom. Also in this embodiment, the load of the cryogenic separation step can be reduced in the same manner as the above-described aspect. Further, in the circulation step, by merging at least a part of the second heavy fraction and at least a part of the ethanol conversion fraction or a fraction derived therefrom, compared with the case of connecting with at least a part of the naphtha cracking fraction, the temperature difference between the two components can be reduced and the volume fluctuation due to the liquefaction of the second heavy fraction can be suppressed.

[0147] <Light Olefins> According to the production method according to this embodiment, light olefins can be obtained. The light olefins are obtained by the above-described cryogenic separation step. In the olefin production method according to this embodiment, the light olefins may be any of ethylene and propylene, but propylene is preferable. Further, according to the production method according to this embodiment, by using a bioresource such as bioethanol as a raw material used in the ethanol conversion step, propylene derived from the bioresource can also be produced.

Examples

[0148] Examples are shown below to explain the present invention in more detail, but the present invention is not limited by the examples described below.

[0149] [Measurement Methods for Various Physical Properties] The measurement methods of various physical properties are as follows.

[0150] (Silica / alumina molar ratio of zeolite in the zeolite-containing catalyst) A solution in which zeolite was completely dissolved in a sodium hydroxide solution was prepared. The amounts of Si and Al contained in the solution were measured by a conventional method using an ICP (inductively coupled plasma) emission spectrometer (manufactured by Rigaku, trade 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 / mim, nebulizer gas: 0.25 L / min, Si measurement wavelength: 251.60 nm, Al measurement wavelength: 396.152 nm.

[0151] (Structure type of zeolite) The structure type of zeolite in the zeolite-containing catalyst was identified by measuring the X-ray diffraction pattern of zeolite using an X-ray analyzer (manufactured by Rigaku, trade name "RINT") and referring to the diffraction patterns of known zeolites. The measurement conditions are as follows. Cu cathode Tube voltage: 40 kV Tube current: 30 mA Scan speed: 1 deg / min

[0152] [Method for preparing zeolite-containing catalyst] 70 parts by mass of proton-type ZSM-5 (silica / alumina molar ratio 980), which is a medium-pore zeolite, and clay obtained from 30 parts by mass of silica (adjusting the water content using colloidal silica and fumed silica) were kneaded and then extrusion molding was carried out to obtain an extruded body adjusted to a diameter of 2.1 mm and a length of 4 - 6 mm. The obtained molded body was calcined for 5 hours to obtain a zeolite-containing catalyst.

[0153] [Method for ethanol conversion] (Raw materials) In the examples and comparative examples, raw materials mainly containing ethanol, ethylene, and olefins having 4 to 6 carbon atoms are used for ethanol conversion. The molar ratio of ethylene / ethanol was calculated according to the following formula. Molar ratio of ethylene / ethanol (mol / mol) = ethylene molar flow rate (mol / hr) / ethanol molar flow rate (mol / hr)

[0154] (Temperature measurement) The temperature at the inlet of the catalyst bed and the temperature at the outlet of the catalyst bed are measured by a thermocouple inserted from outside the reactor. Specifically, as shown in Figure 3, in a plane perpendicular to the fluid flow direction, with the center of the reactor being 0 and the distance from the center of the reactor to the inner wall surface of the reactor being d, the temperature at 0.5d to 0.6d is measured. The heat dissipation effect due to the insertion of this thermocouple is negligibly small.

[0155] (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 part of each fraction is sampled every 3 hours from the start of the reaction and introduced into a gas chromatograph (hereinafter also 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

[0156] (Fraction gas analysis) Apparatus: GC-2030 manufactured by Shimadzu Corporation Column: Custom capillary column SPB-1 (inner diameter 0.25 mm, length 60 m, film thickness 3.0 μm) manufactured by SUPELCO, USA Sample gas volume: 1 mL (the sampling line is kept warm at 200°C to 300°C) Temperature rising program: Hold at 40°C for 12 minutes, then rise the temperature to 200°C at 5°C / min, and then hold at 200°C for 22 minutes. Split ratio: 200 to 1 Carrier gas (nitrogen) flow rate: 120 mL / min FID detector: Air supply pressure 50 kPa (about 500 mL / min), hydrogen supply pressure 60 kPa (about 50 mL / min) Measurement method: The TCD detector and the FID detector are connected in series. For hydrogen, the data detected by the TCD detector, and for oxygen-containing substances such as hydrocarbons and ethanol, the data detected by the FID detector are used for composition analysis. The calibration curve method is used to determine the concentration of the target compound in the reaction gas, and the mass per unit time generated by the reaction is determined.

[0157] (C2-3 olefin treatment efficiency) The C2-3 olefin efficiency is calculated from the introduced fraction into the cryogenic separation process using the following calculation formula. C2-3 olefin efficiency (mass%) = (ethylene mass + propylene mass) / introduced fraction mass × 100

[0158] (C2-3 olefin treatment efficiency index) In Examples A1 to A13, the value obtained by dividing the above-mentioned olefin treatment efficiency by the treatment efficiency of Reference Example A1 is defined as the C2-3 olefin treatment efficiency index. In Examples B1 to B13, the value obtained by dividing the above-mentioned olefin treatment efficiency by the treatment efficiency of Reference Example B1 is defined as the C2-3 olefin treatment efficiency index.

[0159] (C3L volume efficiency) The C3L volume efficiency is calculated from the introduced fraction into the cryogenic separation process using the following calculation formula. C3L volume efficiency (mol%) = (ethylene molar amount + propylene molar amount) / (hydrogen molar amount + methane molar amount + acetylene molar amount + ethylene molar amount + ethane molar amount + propylene molar amount + propane molar amount) × 100

[0160] (C3L volume efficiency index) In Examples A1 to A13, the value obtained by dividing the above-mentioned C3L volume efficiency by the C3L volume efficiency of Reference Example A1 is defined as the C3L volume efficiency index. In Examples B1 to B13, the value obtained by dividing the above-mentioned C3L volume efficiency by the C3L volume efficiency of Reference Example B1 is defined as the C3L volume efficiency index.

[0161] (Off-gas ratio in each fraction) The off-gas ratio in the fraction is the ratio of the amounts of hydrogen and methane to the total amount of ethylene and propylene in the fraction, and is calculated from the composition of each fraction by the following calculation formula. The off-gas ratio in the ethanol conversion fraction is O E , the off-gas ratio in the naphtha cracking fraction is O C , and the off-gas ratio in the ethanol conversion fraction or the fraction derived therefrom in the merging step is O' E , and the off-gas ratio in the naphtha cracking fraction or the fraction derived therefrom in the merging step is O' C are respectively represented. Off-gas ratio in each fraction (mass%) = (hydrogen mass + methane mass) / (ethylene mass + propylene mass) × 100

[0162] (Ethylene and propylene content rates in each fraction in the merging step) The content rates of ethylene and propylene in the ethanol conversion fraction or the fraction derived therefrom in the merging step are C E , and the content rates of ethylene and propylene in the naphtha cracking fraction or the fraction derived therefrom are C C are calculated from the composition of each fraction by the following calculation formula. Content rate of ethylene and propylene in each fraction (mass%) = (ethylene mass + propylene mass) / mass of each fraction × 100

[0163] (Product ratio in the recycle fraction) When a part of the ethanol conversion fraction is recycled to the reaction step as the recycle fraction, the product ratio in the recycle fraction is calculated from the composition of the recycle fraction by the following calculation formula. Product ratio in the recycle fraction (mass%) = (ethylene mass + propylene mass) / mass of recycle fraction × 100

[0164] [Method of naphtha cracking] In the examples and comparative examples, naphtha cracking gas is obtained by co-feeding naphtha and a dilution stream with a mass ratio of 0.5 to naphtha into a heated tubular reactor. The obtained naphtha cracking fraction is analyzed in the same manner as the method for ethanol conversion. Note that the temperature of the naphtha cracking fraction is adjusted by mixing it with a light gas recycled from the downstream purification facility prior to the downstream process.

[0165] [Reference Example A1] Reference Example A1 is carried out using a front-end demethanizer type light olefin production facility shown in FIG. 14. A naphtha raw material containing 357.3 ton / y of heavy naphtha and a dilution stream with a mass ratio of 0.5 to naphtha is introduced into a cracking furnace under cracking conditions of 0.17 MPaG and 825 °C to obtain a naphtha cracking fraction. The naphtha cracking 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 washing tower to obtain an introduced fraction that is introduced into a cryogenic separation process. The compositions of the naphtha cracking fraction and the introduced fraction are shown in Table 1.

[0166] [Reference Example A2] Reference Example A2 obtains a naphtha cracking fraction in the same manner as the method shown in Reference Example A1, except that the temperature of the cracking furnace is changed to 840 °C and the supply amount of naphtha is adjusted according to the ethylene production amount. The composition of the naphtha cracking fraction is shown in Table 1.

[0167] [Reference Example A3] Reference Example A3 obtains a naphtha cracking fraction in the same manner as the method shown in Reference Example A1, except that heavy naphtha is changed to light naphtha and the supply amount of naphtha is adjusted according to the ethylene production amount. The composition of the naphtha cracking fraction is shown in Table 1.

[0168] [Reference Example A4] In Reference Example A4, a naphtha cracking fraction is obtained in the same manner as in Reference Example A3, except that the temperature of the cracking furnace is changed to 840°C and the supply amount of naphtha is adjusted according to the ethylene production amount. The composition of the naphtha cracking fraction is shown in Table 1.

[0169] From Reference Examples A1 to A4, it can be seen that the yields of methane and hydrogen change depending on the type of naphtha raw material used for naphtha cracking and the temperature of the cracking furnace. However, when the cracking process is carried out at 825°C using heavy naphtha as the raw material, the value of O C becomes the smallest.

[0170] [Reference Example A5] A raw material containing 23.6% by mass of ethanol, 15.1% by mass of ethylene, and 16.0% by mass of olefins having 4 to 6 carbon atoms is heated and supplied to a reactor filled with a zeolite-containing catalyst so that WHSV = 3.8 to carry out an ethanol conversion reaction to obtain an ethanol conversion fraction. In addition to the above, the raw material contains paraffin, olefins having 7 or more carbon atoms, and water. At this time, the heater temperature was adjusted so that the average reaction temperature of the inlet and outlet was 540°C. The ethanol conversion reaction was carried out for 48 hours, and the composition of the ethanol conversion fraction 24 hours after the start of the reaction is shown in Table 1 in terms of an ethylene production amount of 100.0 ton / y. During the 48 hours, the value of O E was constant at 0.6.

[0171] From the comparison between Reference Examples A1 to A4 and Reference Example A5, it can be seen that when obtaining light olefins from a raw material containing ethanol, the yields of methane and hydrogen are lower than those when obtaining the same amount of ethylene by naphtha cracking.

[0172]

Table 1

[0173] In the following examples, an ethanol conversion step is carried out in the same manner as in Reference Example A5, and a cracking step is carried out in the same manner as in Reference Example A1. The raw material composition in the ethanol conversion is shown in Example A1.

[0174] [Example A1] This example is implemented by the light olefin production facility shown in FIG. 2. (Ethanol conversion) A raw material containing 209.2 tons / y of ethanol at 23.6% by mass, ethylene at 15.1% by mass, olefins having 4 to 6 carbon atoms at 16.0% by mass, paraffins having 4 to 6 carbon atoms at 13.6% by mass, aromatic compounds at 4.2% by mass, and water at 16.7% by mass is heated and supplied to a reactor 21 filled with a zeolite-containing catalyst so that WHSV = 3.8, and an ethanol conversion reaction is carried out at a reaction temperature of 540°C to obtain an ethanol conversion fraction. The ethanol conversion fraction is introduced into a third cooling tower 22 and brought into contact with cooling water to obtain a cooled ethanol conversion fraction at 45°C and 0.15 MPaG at 138.6 tons / y. The cooled ethanol conversion fraction is used as a recycle fraction for recycling 46.1 tons / y to the mixed raw material without going through processes such as separation and purification. At this time, the product ratio in the recycle fraction is 43.8% by mass.

[0175] (Naphtha cracking) A naphtha raw material containing 266.5 tons / y of heavy naphtha and a dilution steam having a mass ratio of 0.5 to naphtha is introduced into a cracking furnace 11 under cracking conditions of 0.17 MPaG and 825°C to obtain a naphtha cracking fraction. The naphtha cracking 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 fraction, and then introduced into a second cooling tower 13 and brought into contact with cooling water to obtain a second cooled fraction at 0.11 MPaG and 41°C. The second cooled fraction is introduced into a booster 14 and pressurized to 0.99 MPaG.

[0176] (Confluence of ethanol conversion and naphtha cracking) A combined fraction is prepared by mixing the pressurized second cooling fraction of 253.2 ton / y and the cooled ethanol conversion fraction of 92.5 ton / y. The combined fraction is introduced into the soda washing tower 15 to contact with an aqueous sodium hydroxide solution, and a washed fraction is obtained. The washed fraction is introduced into the cryogenic separation process as an introduced fraction. In this example, the ethylene produced is 100.0 ton / y contained in the introduced fraction. The composition of the introduced fraction is shown in Table 2. It can be seen from the value of the C2-3 olefin treatment efficiency index that the treatment efficiency of light olefins in the cryogenic process is improved. In addition, it can be seen from the value of the C3L volume efficiency index that the treatment efficiency of light olefins per volume of the fraction introduced into the cryogenic process is improved.

[0177] [Example A2] This example is implemented by the light olefin production equipment shown in FIG. 4. (Ethanol conversion) 139.7 ton / y of raw material is heated and supplied to the reactor 21 filled with a zeolite-containing catalyst so that WHSV = 3.8, and an ethanol conversion reaction is carried out at a reaction temperature of 540 °C to obtain an ethanol conversion fraction. The ethanol conversion fraction is introduced into the third cooling tower 22 and contacted with cooling water to obtain a cooled ethanol conversion fraction at 45 °C. The cooled ethanol conversion fraction is pressurized by a booster 23 and introduced into the second distillation tower 24, and a light ethanol conversion fraction is obtained from the top of the second distillation tower 24. The light ethanol conversion fraction is introduced into a condenser 25, and a part of it is liquefied and refluxed to the second distillation tower 24, and a cooled light ethanol conversion 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 tower 24 is used as a recycle fraction that is reused as a raw material introduced into the reactor 21 without passing through additional purification and other processes. At this time, the product ratio in the recycle fraction is 0.7 mass%.

[0178] (Naphtha cracking) A naphtha feedstock containing 266.5 tons / y of heavy naphtha and a dilution steam with a mass ratio of 0.5 to 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, cooled to 110 °C by contacting with a mixture of heavy oil and cracked gasoline to obtain a first cooled fraction, and then introduced into the 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 booster 14 and pressurized to 0.99 MPaG.

[0179] (Confluence of ethanol conversion and naphtha cracking) A confluent fraction is prepared by mixing 253.2 tons / y of the second cooled fraction and 45.4 tons / y of the cooled light ethanol conversion fraction. The confluent fraction is introduced into a soda washing tower 15 to contact with an aqueous sodium hydroxide solution to obtain a washed fraction. The washed fraction is further pressurized and introduced into a cryogenic separation process as an introduced fraction. In this example, the ethylene produced is 100.0 tons / y contained in the introduced fraction. The flow rate and composition of the introduced fraction are shown in Table 2-1. From the comparison between this example and Example A1, it can be seen that by introducing the fraction obtained by ethanol conversion into the second distillation tower 24 and providing a distillation process to separate it into a light ethanol conversion fraction and a heavy ethanol conversion fraction, the amount of the fraction introduced into the cryogenic separation process can be reduced, and the energy efficiency related to cryogenic separation can be improved. Also, by providing the distillation process, 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 efficiently produced from a smaller amount of mixed feedstock.

[0180] [Example A3] Among the 100.0 tons / y of ethylene introduced into the cryogenic separation process, except for combining a naphtha cracking-derived fraction and an ethanol conversion fraction in an amount such that 50.0 tons / y of ethylene is obtained by ethanol conversion and 50.0 tons / y of ethylene is obtained by naphtha cracking, it is carried out in the same manner as in Example A2. The flow rate and composition of the introduced fraction are shown in Table 2.

[0181] [Example A4] Among 100.0 ton / y of ethylene introduced into the cryogenic separation process, a fraction derived from naphtha cracking and an ethanol conversion fraction in an amount such that 75.0 ton / y of ethylene is obtained by ethanol conversion and 25.0 ton / y of ethylene is obtained by naphtha cracking are combined. The process is carried out in the same manner as in Example A2 except for this combination. The flow rate and composition of the introduced fractions are shown in Table 2.

[0182] [Example A5] This example is carried out using the light olefin production facility shown in Fig. 5. (Ethanol conversion) 145.6 ton / y of raw material is heated and fed to reactor 21 filled with a zeolite-containing catalyst so that WHSV = 3.8, and an ethanol conversion reaction is carried out at a reaction temperature of 540 °C to obtain an ethanol conversion fraction. The ethanol conversion fraction is introduced into the third cooling tower 22 and contacted with cooling water to obtain a cooled ethanol conversion fraction at 45 °C. The cooled ethanol conversion fraction is pressurized by a booster 23 and introduced into a gas-liquid separation drum to obtain 51.3 ton / y of a light ethanol conversion fraction as a gas at 1.90 MPaG and 40 °C. At this time, 49.5 ton / y of a heavy ethanol conversion fraction obtained as a liquid in the gas-liquid separation drum 26 is used as a recycle fraction that is reused as raw material introduced into reactor 21 without going through additional purification processes or the like. At this time, the product ratio in the recycle fraction is 11.3 mass%. (Naphtha cracking) A naphtha raw material containing 266.5 ton / y of heavy naphtha and a dilution steam with a mass ratio of 0.5 to naphtha is introduced into a cracking furnace 11 under cracking conditions of 0.17 MPaG and 825 °C to obtain a naphtha cracking fraction. The naphtha cracking fraction is introduced into the first cooling tower 12 and contacted with a mixture of heavy oil and cracked gasoline to cool it to 110 °C to obtain a first cooled naphtha cracking fraction. The first cooled naphtha cracking fraction is introduced into the second cooling tower 13 and contacted with cooling water to obtain a second cooled naphtha cracking fraction at 0.11 MPaG and 41 °C. The second cooled naphtha cracking fraction is introduced into a booster 14 and pressurized to 0.99 MPaG. (Combination of ethanol conversion and naphtha cracking) A combined fraction is prepared by mixing a second cooled naphtha cracked fraction of 253.2 ton / y and a light ethanol conversion fraction of 51.3 ton / y. The combined fraction is introduced into a soda washing tower 15 to contact with an aqueous sodium hydroxide solution, and a washed fraction is obtained. The washed fraction is introduced into a cryogenic separation process as an introduced fraction. The amount of ethylene produced in this example is the total amount of ethylene contained in the introduced fraction, which is 100.0 ton / y. The flow rate and composition of the introduced fraction are shown in Table 2.

[0183]

Table 2-1

[0184]

Table 2-2

[0185] [Example A6] This example is implemented by a light olefin production facility shown in Figure 6. (Ethanol conversion) 209.2 ton / y of raw materials are heated and fed to a reactor 21 filled with a zeolite-containing catalyst so that WHSV = 3.8, and an ethanol conversion reaction is carried out at a reaction temperature of 540 °C to obtain an ethanol conversion fraction. The ethanol conversion fraction is introduced into a third cooling tower 22 and contacted with cooling water to obtain a cooled ethanol conversion fraction at 45 °C and 0.15 MPaG at 138.6 ton / y. The cooled ethanol conversion fraction is used as a recycle fraction to recycle 46.1 ton / y to the mixed raw materials without passing through processes such as separation and purification. At this time, the product ratio in the recycle fraction is 43.8 mass%.

[0186] (Naphtha cracking) A naphtha raw material containing 266.5 ton / y of heavy naphtha and a dilution steam with a mass ratio of 0.5 to 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 be cooled to 110 °C to obtain a first cooled fraction.

[0187] (Confluence of Ethanol Conversion and Naphtha Cracking) A confluent fraction is prepared by mixing a first cooled fraction of 474.1 ton / y and a cooled ethanol conversion fraction of 92.5 ton / y. The confluent fraction is introduced into a second cooling tower 13 and brought into contact with cooling water to obtain a second cooled fraction at 41°C. The second cooled fraction is introduced into a booster 14 and pressurized to 0.99 MPaG. The pressurized second cooled fraction is introduced into a soda washing tower 15 to be brought into contact with an aqueous sodium hydroxide solution, obtaining a washed fraction. The washed fraction is further pressurized and introduced as an introduced fraction into a cryogenic separation process. 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 3.

[0188] [Example A7] This example is implemented by the light olefin production facility shown in FIG. 7. (Ethanol Conversion) 139.7 ton / y of raw material is heated and supplied to a reactor 21 filled with a zeolite-containing catalyst so that WHSV = 3.8, and an ethanol conversion reaction is carried out at a reaction temperature of 540°C to obtain an ethanol conversion fraction. The ethanol conversion fraction is introduced into a third cooling tower 22 and brought into contact with cooling water to obtain a cooled ethanol conversion fraction at 45°C. The cooled ethanol conversion fraction is pressurized by a booster 23 and introduced into a second distillation tower 24, and a light ethanol conversion fraction is obtained from the top of the second distillation tower 24. The light ethanol conversion fraction is introduced into a condenser 25, and part of it is liquefied and refluxed to the second distillation tower 24, and the cooled light ethanol conversion 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 tower 24 is used as a recycle fraction that is reused in the mixed raw material without going through additional purification and other processes. At this time, the product ratio in the recycle fraction is 0.7 mass%.

[0189] (Naphtha Cracking) A naphtha raw material containing 266.5 tons / y of heavy naphtha and a dilution steam with a mass ratio of 0.5 to naphtha is introduced into the cracking furnace 11 under cracking conditions of 0.17 MPaG and 825 °C to obtain a naphtha cracking fraction. The naphtha cracking 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 fraction.

[0190] (Confluence of ethanol conversion and naphtha cracking) A confluent fraction is prepared by mixing 474.1 tons / y of the first cooled fraction and 45.4 tons / y of the cooled light ethanol conversion fraction. The confluent fraction is introduced into the second cooling tower 13 and cooled to 41 °C by contacting it with cooling water to obtain a second cooled fraction. The second cooled fraction is introduced into a booster 14 and pressurized to 0.99 MPaG. The pressurized second cooled fraction is introduced into a soda washing tower 15 to contact it with an aqueous sodium hydroxide solution to obtain a washed fraction. The washed fraction is further pressurized and introduced as an introduced fraction into a cryogenic separation process. In this example, the ethylene produced is 100.0 tons / y contained in the introduced fraction. The flow rate and composition of the introduced fraction are shown in Table 3.

[0191] [Example A8] This example is implemented by the light olefin production equipment shown in Figure 8. This example is implemented in the same manner as Example A7 except that the connection points are changed. In this example, a cooled light ethanol conversion fraction at 15 °C is combined with a second bottom reflux fraction at 68 °C that is refluxed within the second cooling tower 13 and contains the fraction obtained from the bottom of the second cooling tower 13 to prepare a confluent fraction. The amount of the second bottom reflux fraction is determined by the production balance of the target compound. In this example, 52.6 tons / y is used as the second bottom reflux fraction. By merging the second bottom reflux fraction and the ethanol conversion fraction, since the ethanol conversion fraction is introduced into the second cooling tower 13, there is no change in the composition and flow rate of the introduced fraction obtained in Example A7 and this example. At this point, by merging the naphtha cracking fraction and the ethanol conversion fraction, the temperature difference between the fractions can be made smaller than 53K in this example compared to 96K in Example A7, and the volume change associated with the liquefaction of the high-temperature fraction can be suppressed.

[0192] [Example A9] This example is implemented by the light olefin production facility shown in FIG. 9. (Ethanol conversion) Heat 145.6 ton / y of raw material and supply it to the reactor 21 filled with a zeolite-containing catalyst so that WHSV = 3.8, and carry out an ethanol conversion reaction at a reaction temperature of 540°C to obtain an ethanol conversion fraction. Introduce the ethanol conversion fraction into the third cooling tower 22 and contact it with cooling water to obtain a cooled ethanol conversion fraction at 45°C. The cooled ethanol conversion fraction is pressurized by a booster 23 and introduced into a gas-liquid separation drum 26 to obtain 51.3 ton / y of a light ethanol conversion fraction as a gas at 1.90 MPaG and 40°C. At this time, the 49.4 ton / y of the heavy ethanol conversion fraction obtained as a liquid in the gas-liquid separation drum 26 is used as a recycle fraction that is reused as a raw material introduced into the reactor 21 without going through additional purification and other processes. At this time, the product ratio in the recycle fraction is 11.3 mass%. (Naphtha cracking) Introduce a naphtha raw material containing 266.5 ton / y of heavy naphtha and a dilution steam with a mass ratio of 0.5 to naphtha into the cracking furnace 11 under cracking conditions of 0.17 MPaG and 825°C to obtain a naphtha cracking fraction. Introduce the naphtha cracking fraction into the first cooling tower 12 and contact it with a mixture of heavy oil and cracked gasoline to cool it to 110°C to obtain a first cooled naphtha cracking fraction. (Confluence of ethanol conversion and naphtha cracking) A combined fraction is prepared by mixing a first cooled naphtha cracked fraction of 474.1 ton / y and a light ethanol conversion fraction of 51.3 ton / y. 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 booster 14 and pressurized to 0.99 MPaG. The combined fraction is introduced into a soda washing tower to be brought into contact with an aqueous sodium hydroxide solution to obtain a washed fraction. The washed fraction is further pressurized and then introduced into a cryogenic separation process as an introduced fraction. The composition of the introduced fraction is shown in Table 3. The amount of ethylene produced in this example is the total amount of ethylene contained in the introduced fraction, which is 100.0 ton / y.

[0193]

Table 3-1

[0194]

Table 3-2

[0195] [Example A10] This example is implemented by the light olefin production facility shown in Figure 10. (Ethanol conversion) 209.2 ton / y of raw material is heated and supplied to a reactor 21 filled with a zeolite-containing catalyst so that WHSV = 3.8, and an ethanol conversion reaction is carried out at a reaction temperature of 540°C to obtain an ethanol conversion fraction. The ethanol conversion fraction is introduced into a third cooling tower 22 and brought into contact with cooling water to obtain 138.6 ton / y of a cooled ethanol conversion fraction at 45°C and 0.15 MPaG. The cooled ethanol conversion fraction is used as a recycle fraction for recycling 46.1 ton / y to the mixed raw material without going through processes such as separation and purification. At this time, the product ratio in the recycle fraction is 43.8 mass%.

[0196] (Naphtha cracking) A naphtha feedstock containing 266.5 tons / year of heavy naphtha and a dilution steam with a mass ratio of 0.5 to naphtha is introduced into the cracking furnace 11 under cracking conditions of 0.17 MPaG and 825 °C to obtain a naphtha cracking fraction.

[0197] (Confluence of ethanol conversion and naphtha cracking) A confluent fraction is prepared by mixing 417.2 tons / year of the naphtha cracking fraction at 360 °C and 92.5 tons / year of the cooled ethanol conversion fraction. The confluent 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 fraction. The first cooled fraction is introduced into the 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 booster 14 and pressurized to 0.99 MPaG. The pressurized second cooled fraction is introduced into a soda washing tower 15 to contact it with an aqueous sodium hydroxide solution to obtain a washed fraction. The washed fraction is further pressurized and introduced into the cryogenic separation process as an introduced fraction. In this example, the ethylene produced is 100.0 tons / year contained in the introduced fraction. The flow rate and composition of the introduced fraction are shown in Table 4.

[0198] [Example A11] This example is implemented by the light olefin production facility shown in Figure 11. (Ethanol conversion) 139.7 tons / y of raw materials were heated and fed to reactor 21 filled with a zeolite-containing catalyst at a WHSV of 3.8, and an ethanol conversion reaction was carried out at a reaction temperature of 540 °C to obtain an ethanol conversion fraction. The ethanol conversion fraction was introduced into the third cooling tower 22 and brought into contact with cooling water to obtain a cooled ethanol conversion fraction at 45 °C. The cooled ethanol conversion fraction was pressurized by a booster 23 and introduced into the second distillation column 24, and a light ethanol conversion fraction was obtained from the top of the second distillation column 24. The light ethanol conversion fraction was introduced into a condenser 25, and a part of it was liquefied and refluxed to the second distillation column 24, and a cooled light ethanol conversion fraction was obtained as a gas at 1.90 MPaG and 15 °C. At this time, the heavy ethanol conversion fraction of 47.5 tons / y obtained from the bottom of the second distillation column 24 was used as a recycle fraction that was reused in the mixed raw materials without going through additional purification processes. At this time, the product ratio in the recycle fraction was 0.7 mass%.

[0199] (Naphtha cracking) A naphtha raw material containing 266.5 tons / y of heavy naphtha and a dilution steam with a mass ratio of 0.5 to naphtha was introduced into a cracking furnace 11 under cracking conditions of 0.17 MPaG and 825 °C to obtain a naphtha cracking fraction.

[0200] (Confluence of ethanol conversion and naphtha cracking) A confluence fraction was prepared by mixing 417.2 tons / y of the naphtha cracking fraction at 360 °C and 45.4 tons / y of the cooled light ethanol conversion fraction. The confluence fraction was introduced into the first cooling tower 12 and brought into contact with a mixture of heavy oil and cracked gasoline to be cooled to 110 °C to obtain a first cooled fraction. The first cooled fraction was introduced into the second cooling tower 13 and brought into contact with cooling water to obtain a second cooled fraction at 41 °C. The second cooled fraction was introduced into a booster 14 and pressurized to 0.99 MPaG. The pressurized second cooled fraction was introduced into a soda washing tower 15 and brought into contact with an aqueous sodium hydroxide solution to obtain a washed fraction. The washed fraction was further pressurized and introduced into a cryogenic separation process as an introduced fraction. In this example, the ethylene produced was 100.0 tons / y contained in the introduced fraction. The flow rate and composition of the introduced fraction are shown in Table 4.

[0201] [Example A12] This example is implemented by the light olefin production facility shown in FIG. 12. This example is implemented in the same manner as Example A9, except that the connection points are changed. In this example, a cooled light ethanol conversion fraction at 15°C is obtained from the bottom of the second cooling tower 13 and merged with the first bottom reflux fraction at 80°C that refluxes to the first cooling tower 12 to prepare a merged fraction. By merging the first bottom reflux fraction and the ethanol conversion fraction, the ethanol conversion fraction is introduced into the first cooling tower 12, so there is no change in the composition and flow rate of the introduced fraction obtained in Example A9 and Example A10. At this point, by merging the naphtha cracking fraction and the ethanol conversion fraction, the temperature difference between the fractions can be made smaller than 65K compared to 345K in Example A9, and the volume change associated with the liquefaction of the high-temperature fraction can be suppressed.

[0202] [Example A13] This example is implemented by the light olefin production facility shown in FIG. 13. (Ethanol conversion) Heat 145.6 ton / y of mixed feed gas and supply it to the reactor 21 filled with a zeolite-containing catalyst so that WHSV = 3.8, and perform an ethanol conversion reaction at a reaction temperature of 540°C to obtain an ethanol conversion fraction. The ethanol conversion fraction is introduced into the third cooling tower 22 and brought into contact with cooling water to obtain a cooled ethanol conversion fraction at 45°C. The cooled ethanol conversion fraction is pressurized by a booster 23 and introduced into a gas-liquid separation drum 26 to obtain 51.3 ton / y of a light ethanol conversion fraction as a gas at 1.90 MPaG and 40°C. At this time, the 49.4 ton / y of the heavy ethanol conversion fraction obtained as a liquid in the gas-liquid separation drum 26 is used as a recycle fraction that is reused as a raw material introduced into the reactor 21 without passing through additional purification and other processes. At this time, the product ratio in the recycle fraction is 11.3 mass%. (Naphtha cracking) A naphtha feedstock containing 266.5 tons / year of heavy naphtha and a dilution steam with a mass ratio of 0.5 to naphtha is introduced into the cracking furnace 11 under cracking conditions of 0.17 MPaG and 825 °C to obtain a naphtha cracked fraction. (Confluence of ethanol conversion and naphtha cracking) A confluent fraction is prepared by mixing 417.2 tons / year of the naphtha cracked fraction and 51.3 tons / year of the light ethanol conversion fraction. The confluent 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. It 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 booster 14 and pressurized to 0.99 MPaG. The pressurized second cooled naphtha cracked fraction is introduced into a soda washing tower 15 to contact it with an aqueous sodium hydroxide solution to obtain a washed fraction. The composition of the introduced fraction is shown in Table 4. The washed confluent fraction is further pressurized and introduced into the cryogenic separation process as the introduced fraction. The amount of ethylene produced in this example is the total amount of ethylene contained in the introduced fraction and is 100.0 tons / year.

[0203] [Table 4]

[0204] [Reference Example B1] Reference Example B1 is carried out by the light olefin production equipment of the front-end depropanizer method shown in Fig. 26. A naphtha raw material containing 357.3 ton / y of heavy naphtha and dilution steam with a mass ratio of 0.5 to naphtha is introduced into the cracking furnace 11 under cracking conditions of 0.17 MPaG and 825 °C to obtain a naphtha cracking fraction. The naphtha cracking 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 cracking fraction. The first cooled naphtha cracking fraction is introduced into the second cooling tower 13 and contacted with cooling water to obtain a second cooled naphtha cracking fraction at 0.11 MPaG and 41 °C. 339.5 ton / y of the second cooled naphtha cracking fraction is introduced into the booster 14, pressurized to 0.99 MPaG, and introduced into the soda washing tower 15 to obtain a washed fraction. After the washed fraction is further pressurized to 1.82 MPaG, it is introduced into the first distillation tower 17 to obtain an introduced fraction introduced into the cryogenic separation process at -18 °C from the top of the tower. Also, a bypass fraction introduced into the downstream equipment bypassing the cryogenic separation process is obtained from the bottom of the tower. The compositions of the introduced fraction and the bypass fraction are shown in Table 5. In the front-end depropanizer method, by separating the naphtha cracking fraction into an introduced fraction mainly containing hydrocarbons with 3 or less carbon atoms and a bypass fraction mainly containing hydrocarbons with 3 or more carbon atoms, the amount introduced into the cryogenic separation process can be reduced, and the energy consumption related to cryogenic separation can be reduced.

[0205] [Example B1] This example is carried out by the light olefin production equipment shown in Fig. 15. (Ethanol conversion) Heat 209.2 tons / year of raw materials and supply them to reactor 21 filled with a zeolite-containing catalyst so that the WHSV is 3.8, and carry out an ethanol conversion reaction at a reaction temperature of 540 °C to obtain an ethanol conversion fraction. Introduce the ethanol conversion fraction into the third cooling tower 22 and bring it into contact with cooling water to obtain a cooled ethanol conversion fraction at 45 °C and 0.15 MPaG at 138.6 tons / year. The cooled ethanol conversion fraction is used as a recycle fraction that is recycled to the raw materials introduced into reactor 21 at 46.1 tons / year without going through processes such as separation and purification. At this time, the product ratio in the recycle fraction is 43.8 mass%. (Naphtha cracking) Introduce a naphtha raw material containing 266.5 tons / year of heavy naphtha and a dilution steam with a mass ratio of 0.5 to naphtha into the cracking furnace 11 under cracking conditions of 0.17 MPaG and 825 °C to obtain a naphtha cracking fraction. Introduce the naphtha cracking fraction into the first cooling tower 12 and bring it into contact with a mixture of heavy oil and cracked gasoline to cool it to 110 °C to obtain a first cooled naphtha cracking fraction. Introduce the first cooled naphtha cracking fraction into the second cooling tower 13 and bring it into contact with cooling water to obtain a second cooled naphtha cracking fraction at 0.11 MPaG and 41 °C. Introduce the second cooled naphtha cracking fraction into a booster and boost the pressure to 0.99 MPaG. (Confluence of ethanol conversion and naphtha cracking) Prepare a confluence fraction by mixing 253.2 tons / year of the second cooled naphtha cracking fraction after pressure boosting and 92.5 tons / year of the cooled ethanol conversion fraction. Introduce the confluence fraction into the soda washing tower 15 to bring it into contact with an aqueous sodium hydroxide solution to obtain a washed fraction. After boosting the pressure of the washed fraction to 1.82 MPaG, introduce it into the first distillation tower 17 to obtain an introduced fraction introduced into the cryogenic separation process at -18 °C from the top of the tower. Also, obtain a bypass fraction introduced into the subsequent equipment bypassing the cryogenic separation process at 16 °C from the bottom of the tower. 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 total amount of ethylene contained in the introduced fraction and the bypass fraction, which is 100.0 tons / year.

[0206] [Example B2] This example is implemented by the light olefin production facility shown in FIG. 16. (Ethanol conversion) Heat 139.7 ton / y of raw materials and supply them to the reactor 21 filled with a zeolite-containing catalyst so that WHSV = 3.8, and carry out an ethanol conversion reaction at a reaction temperature of 540 °C to obtain an ethanol conversion fraction. Introduce the ethanol conversion fraction into the third cooling tower 22 and contact it with cooling water to obtain a cooled ethanol conversion fraction at 45 °C. The cooled ethanol conversion fraction is pressurized by a booster 23 and introduced into the second distillation column 24, so as to obtain a light ethanol conversion fraction from the top of the second distillation column 24. Introduce the light ethanol conversion fraction into a condenser 25, liquefy a part of it and reflux it to the second distillation column 24, and obtain the cooled light ethanol conversion fraction 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 recycle fraction that is reused in the mixed raw materials without going through additional purification and other processes. At this time, the product ratio in the recycle fraction is 0.7% by mass. (Naphtha cracking) Introduce a naphtha raw material containing 266.5 ton / y of heavy naphtha and a dilution steam with a mass ratio of 0.5 to naphtha into a cracking furnace 11 under cracking conditions of 0.17 MPaG and 825 °C to obtain a naphtha cracking fraction. Introduce the naphtha cracking fraction into the first cooling tower 12 and contact it with a mixture of heavy oil and cracked gasoline to cool it to 110 °C to obtain a first cooled naphtha cracking fraction. Introduce the first cooled naphtha cracking fraction into the second cooling tower 13 and contact it with cooling water to obtain a second cooled naphtha cracking fraction at 0.11 MPaG and 41 °C. Introduce the second cooled naphtha cracking fraction into a booster 14 and pressurize it to 0.99 MPaG. (Confluence of ethanol conversion and naphtha cracking) A combined fraction is prepared by mixing a second cooled naphtha cracked fraction of 253.2 tons / y and a cooled light ethanol conversion fraction of 45.4 tons / y. The combined fraction is introduced into a soda washing tower 15 to contact with an aqueous sodium hydroxide solution, thereby obtaining a washed fraction. After the pressure of the washed fraction is increased to 1.82 MPaG, the washed fraction is introduced into a first distillation tower 17, and an introduced fraction introduced into a cryogenic separation process is obtained at -18 °C from the top of the tower. Further, a bypass fraction introduced into a subsequent facility bypassing the cryogenic separation process is obtained at 16 °C from the bottom of the tower. Table 5 shows the compositions of the introduced fraction and the bypass fraction. The amount of ethylene produced in this example is the total amount of ethylene contained in the introduced fraction and the bypass fraction, which is 100.0 tons / y. From the comparison between this example and Example B1, it can be seen that by distilling and separating a fraction mainly containing light olefins from the ethanol conversion fraction before merging the ethanol conversion fraction and the naphtha cracked fraction, the amount of the fraction introduced into the cryogenic separation process can be reduced, and the energy efficiency related to purification can be improved. From the comparison between this example and Example B1, it can be seen that when the cooled ethanol conversion fraction is used as a recycle fraction without passing through additional separation and purification processes, the product ratio in the recycle fraction increases, the raw materials required for production increase, and the production efficiency of ethylene per raw material decreases.

[0207] [Example B3] Among the 100.0 tons / y of ethylene produced, except for merging a naphtha cracked fraction in an amount such that the ethylene obtained by ethanol conversion is 50.0 tons / y and the ethylene obtained by naphtha cracking is 50.0 tons / y, and the ethanol conversion fraction, it is carried out in the same manner as in Example B2. Table 5 shows the compositions of the introduced fraction and the bypass fraction.

[0208] [Example B4] Among the 100.0 tons / y of ethylene produced, except for merging a naphtha cracked fraction in an amount such that the ethylene obtained by ethanol conversion is 75.0 tons / y and the ethylene obtained by naphtha cracking is 25.0 tons / y, and the ethanol conversion fraction, it is carried out in the same manner as in Example B2. Table 5 shows the compositions of the introduced fraction and the bypass fraction.

[0209] [Example B5] This example is implemented by the light olefin production facility shown in Fig. 17. (Ethanol conversion) Heat 145.6 ton / y of raw materials and supply them to the reactor 21 filled with a zeolite-containing catalyst so that WHSV = 3.8, and carry out the ethanol conversion reaction at a reaction temperature of 540 °C to obtain an ethanol conversion fraction. Introduce the ethanol conversion fraction into the third cooling tower 22 and contact it with cooling water to obtain a cooled ethanol conversion fraction at 45 °C. The cooled ethanol conversion fraction is pressurized by a booster 23 and introduced into a gas-liquid separation drum 26 to obtain 51.3 ton / y of a light ethanol conversion fraction as a gas at 1.90 MPaG and 40 °C. At this time, the 49.5 ton / y of the heavy ethanol conversion fraction obtained as a liquid in the gas-liquid separation drum 26 is used as a recycle fraction that is reused as a raw material introduced into the reactor 21 without going through additional purification processes. At this time, the product ratio in the recycle fraction is 11.3 mass%. (Naphtha cracking) Introduce a naphtha raw material containing 266.5 ton / y of heavy naphtha and a dilution steam with a mass ratio of 0.5 to naphtha into a cracking furnace 11 under cracking conditions of 0.17 MPaG and 825 °C to obtain a naphtha cracking fraction. Introduce the naphtha cracking fraction into the first cooling tower 12 and contact it with a mixture of heavy oil and cracked gasoline to cool it to 110 °C to obtain a first cooled naphtha cracking fraction. Introduce the first cooled naphtha cracking fraction into the second cooling tower 13 and contact it with cooling water to obtain a second cooled naphtha cracking fraction at 0.11 MPaG and 41 °C. Introduce the second cooled naphtha cracking fraction into a booster 14 and pressurize it to 0.99 MPaG. (Confluence of ethanol conversion and naphtha cracking) A combined fraction is prepared by mixing a second cooled naphtha cracked fraction of 253.2 ton / y and a light ethanol conversion fraction of 51.3 ton / y. The combined fraction is introduced into a soda washing tower 15 to contact with an aqueous sodium hydroxide solution, and a washed fraction is obtained. After the washed fraction is pressurized to 1.82 MPaG, it is introduced into a first distillation tower 17, and an introduced fraction to be introduced into a cryogenic separation process is obtained at -18 °C from the top of the tower. Also, a bypass fraction to be introduced into downstream equipment bypassing the cryogenic separation process is obtained at 16 °C from the bottom of the tower. 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 total amount of ethylene contained in the introduced fraction and the bypass fraction, which is 100.0 ton / y.

[0210]

Table 5-1

[0211]

Table 5-2

[0212] [Example B6] This example is carried out by a light olefin production facility shown in FIG. 18. (Ethanol conversion) 209.2 ton / y of raw material is heated and supplied to a reactor 21 filled with a zeolite-containing catalyst so that WHSV = 3.8, and an ethanol conversion reaction is carried out at a reaction temperature of 540 °C to obtain an ethanol conversion fraction. The ethanol conversion fraction is introduced into a third cooling tower 22 and contacted with cooling water to obtain a cooled ethanol conversion fraction at 45 °C and 0.15 MPaG at 138.6 ton / y. The cooled ethanol conversion fraction is used as a recycle fraction to be recycled to the raw material introduced into the reactor 21 at 46.1 ton / y without passing through processes such as separation and purification. At this time, the product ratio in the recycle fraction is 43.8 mass%. (Naphtha cracking) A naphtha feedstock containing 266.5 tons / y of heavy naphtha and a dilution steam with a mass ratio of 0.5 to 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 with a mixture of heavy oil and cracked gasoline to obtain a first cooled naphtha cracked fraction. (Confluence of ethanol conversion and naphtha cracking) A confluent fraction is prepared by mixing 474.1 tons / y of the first cooled naphtha cracked fraction and 92.5 tons / y of the cooled ethanol conversion fraction. The confluent fraction is introduced into the second cooling tower 13 and cooled to obtain a second cooled naphtha cracked fraction at 0.11 MPaG and 41 °C by contacting with cooling water. The second cooled naphtha cracked fraction is introduced into a booster 14, pressurized to 0.99 MPaG, and introduced into a soda washing tower 15 to contact with an aqueous sodium hydroxide solution to obtain a washed fraction. After the washed fraction is pressurized to 1.82 MPaG, it is introduced into the first distillation tower 17 to obtain an introduced fraction introduced into the cryogenic separation process at -18 °C from the top of the tower. Also, a bypass fraction introduced into the subsequent equipment bypassing the cryogenic separation process is obtained at 16 °C from the bottom of the tower. 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 total amount of ethylene contained in the introduced fraction and the bypass fraction, which is 100.0 tons / y.

[0213] [Example B7] This example is implemented by the light olefin production equipment shown in Figure 19. (Ethanol conversion) 139.7 ton / y of raw material is heated and supplied to a reactor 21 filled with a zeolite-containing catalyst so that WHSV = 3.8, and an ethanol conversion reaction is performed at a reaction temperature of 540 ° C. to obtain an ethanol conversion fraction. The ethanol conversion fraction is introduced into a third cooling tower 22 and contacted with cooling water to obtain a cooled ethanol conversion fraction at 45 ° C. The cooled ethanol conversion fraction is pressurized by a booster 23 and introduced into a second distillation tower 24 to obtain a light ethanol conversion fraction from the top of the second distillation tower 24. The light ethanol conversion fraction is introduced into a condenser 25, and a portion of it is liquefied to reflux the second distillation tower 24, and the cooled light ethanol conversion fraction is obtained as a gas at 1.90 MPaG and 15 ° C. At this time, 47.5 ton / y of heavy ethanol conversion fraction obtained from the bottom of the second distillation tower 24 is used as a recycled fraction to be reused as raw material to be introduced into the reactor 21 without undergoing additional purification or other processes. At this time, 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 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 with a mixture of heavy oil and cracked gasoline to obtain a first cooled naphtha cracked fraction. (Consolidation of ethanol conversion and naphtha cracking) A combined fraction is prepared by mixing a first cooled naphtha cracked fraction of 474.1 ton / y and a cooled light ethanol conversion fraction of 45.4 ton / y. The combined fraction is introduced into a second cooling tower 13 and brought into contact with cooling water to obtain a second cooled fraction at 41°C. The second cooled fraction 13 is introduced into a booster 14 and pressurized to 0.99 MPaG. The pressurized second cooled fraction is introduced into a soda washing tower to be brought into contact with an aqueous sodium hydroxide solution to obtain a washed fraction. After the washed fraction is pressurized to 1.82 MPaG, it is introduced into a first distillation tower 12 to obtain, from the top of the tower, an introduced fraction to be introduced into a cryogenic separation process at -18°C. Also, from the bottom of the tower, a bypass fraction to be introduced into subsequent equipment bypassing the cryogenic separation process is obtained at 16°C. 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 total amount of ethylene contained in the introduced fraction and the bypass fraction, which is 100.0 ton / y.

[0214] [Example B8] This example is carried out by a light olefin production facility shown in Fig. 20. This example is carried out in the same manner as Example B7 except that the connection points are changed. In this example, a cooled light ethanol conversion fraction at 15°C is combined with a second bottom reflux fraction at 68°C that is obtained from the bottom of the second cooling tower 13 and refluxed into the tower to prepare a combined fraction. The amount of the second bottom reflux fraction is determined by the production balance of the target compound, and in this example, 52.6 ton / y is used as the second bottom reflux fraction. By combining the second bottom reflux fraction and the ethanol conversion fraction, since the ethanol conversion fraction is introduced into the second cooling tower 13, there is no change in the composition and flow rate of the introduced fraction and the bypass fraction obtained in this example and Example B7, but the temperature difference between the naphtha cracked fraction and the ethanol conversion fraction can be reduced to 53 K, and volume changes associated with the cooling and liquefaction of the high-temperature naphtha fraction can be suppressed.

[0215] [Example B9] This example is carried out by a light olefin production facility shown in Fig. 21. (Ethanol conversion) Heat 145.6 tons / year of raw materials and supply them to reactor 21 filled with a zeolite-containing catalyst so that the WHSV is 3.8, and carry out an ethanol conversion reaction at a reaction temperature of 540 °C to obtain an ethanol conversion fraction. Introduce the ethanol conversion fraction into the third cooling tower 22 and contact it with cooling water to obtain a cooled ethanol conversion fraction at 45 °C. The cooled ethanol conversion fraction is pressurized by a booster 23 and introduced into a gas-liquid separation drum 26 to obtain 51.3 tons / year of a light ethanol conversion fraction as a gas at 1.90 MPaG and 40 °C. At this time, the 49.4 tons / year of the heavy ethanol conversion fraction obtained as a liquid in the gas-liquid separation drum 26 is used as a recycle fraction that is reused in the raw materials introduced into the reactor 21 without going through additional purification processes. At this time, the product ratio in the recycle fraction is 11.3 mass%. (Naphtha cracking) Introduce a naphtha raw material containing 266.5 tons / year of heavy naphtha and a dilution steam with a mass ratio of 0.5 to naphtha into a cracking furnace 11 under cracking conditions of 0.17 MPaG and 825 °C to obtain a naphtha cracking fraction. Introduce the naphtha cracking fraction into the first cooling tower 12 and contact it with a mixture of heavy oil and cracked gasoline to cool it to 110 °C to obtain a first cooled naphtha cracking fraction. (Confluence of ethanol conversion and naphtha cracking) Prepare a confluence fraction by mixing 474.1 tons / year of the first cooled naphtha cracking fraction and 51.3 tons / year of the light ethanol conversion fraction. Introduce the confluence fraction into the second cooling tower 13 and contact it with cooling water to obtain a second cooled naphtha cracking fraction at 0.11 MPaG and 41 °C. Introduce the second cooled naphtha cracking fraction into a booster 14 and pressurize it to 0.99 MPaG. Introduce the confluence fraction into a soda washing tower 15 to contact it with an aqueous sodium hydroxide solution to obtain a washed fraction. After pressurizing the washed fraction to 1.82 MPaG, introduce it into a first distillation tower 17 to obtain, from the top of the tower, an introduced fraction introduced into the cryogenic separation process at -18 °C. Also, from the bottom of the tower, obtain a bypass fraction introduced into the downstream equipment bypassing the cryogenic separation process at 16 °C. 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 total amount of ethylene contained in the introduced fraction and the bypass fraction, which is 100.0 tons / year.

[0216]

Table 6-1

[0217]

Table 6-2

[0218] [Example B10] This example is implemented by the light olefin production facility shown in Fig. 22. (Ethanol conversion) 209.2 ton / y of raw material is heated and fed to the reactor 21 filled with a zeolite-containing catalyst so that WHSV = 3.8, and an ethanol conversion reaction is carried out at a reaction temperature of 540 °C to obtain an ethanol conversion fraction. The ethanol conversion fraction is introduced into the third cooling tower 22 and brought into contact with cooling water to obtain a cooled ethanol conversion fraction at 45 °C and 0.15 MPaG at 138.6 ton / y. The cooled ethanol conversion fraction is used as a recycle fraction that is recycled to the raw material introduced into the reactor 21 at 46.1 ton / y without going through processes such as separation and purification. At this time, the product ratio in the recycle fraction is 43.8 mass%. (Naphtha cracking) A naphtha raw material containing 266.5 ton / y of heavy naphtha and a dilution steam with a mass ratio of 0.5 to naphtha is introduced into the cracking furnace 11 under cracking conditions of 0.17 MPaG and 825 °C to obtain a naphtha cracking fraction. (Confluence of ethanol conversion and naphtha cracking) A combined fraction is prepared by mixing a naphtha cracking fraction of 417.2 tons / y and a cooled ethanol conversion fraction of 92.5 tons / y. The combined fraction is introduced into a first cooling tower 12 and brought into contact with a mixture of heavy oil and cracked gasoline to be cooled to 110°C, thereby obtaining a first cooled naphtha cracking fraction. The first cooled naphtha cracking fraction is introduced into a second cooling tower 13 and brought into contact with cooling water to obtain a second cooled naphtha cracking fraction at 0.11 MPaG and 41°C. The second cooled naphtha cracking fraction is introduced into a booster 14 and pressurized to 0.99 MPaG, and then introduced into a soda washing tower 15 to be brought into contact with an aqueous sodium hydroxide solution to obtain a washed fraction. After the washed fraction is pressurized to 1.82 MPaG, it is introduced into a first distillation tower 17, and from the top of the tower, an introduced fraction to be introduced into a cryogenic separation process is obtained at -18°C. Also, from the bottom of the tower, a bypass fraction to be introduced into downstream equipment bypassing the cryogenic separation process is obtained at 16°C. 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 total amount of ethylene contained in the introduced fraction and the bypass fraction, which is 100.0 tons / y.

[0219] [Example B11] This example is implemented by the light olefin production equipment shown in FIG. 23. (Ethanol conversion) Heat 139.7 tons / year of raw material gas and supply it to reactor 21 filled with a zeolite-containing catalyst so that the WHSV is 3.8, and carry out an ethanol conversion reaction at a reaction temperature of 540 °C to obtain an ethanol conversion fraction. Introduce the ethanol conversion fraction into the third cooling tower 22 and contact it with cooling water to obtain a cooled ethanol conversion fraction at 45 °C. The cooled ethanol conversion fraction is pressurized by a booster 23 and introduced into the second distillation column 24, so that a light ethanol conversion fraction is obtained from the top of the second distillation column 24. The light ethanol conversion fraction is introduced into a condenser 25, and a part of it is liquefied and refluxed to the second distillation column 24, and the cooled light ethanol conversion fraction is obtained as a gas at 1.90 MPaG and 15 °C. At this time, the heavy ethanol conversion fraction of 47.5 tons / year obtained from the bottom of the second distillation column 24 is used as a recycle fraction that is reused as a raw material introduced into the reactor 21 without going through additional purification and other processes. At this time, the product ratio in the recycle fraction is 0.7% by mass. (Naphtha cracking) Introduce a naphtha raw material containing 266.5 tons / year of heavy naphtha and a dilution steam with a mass ratio of 0.5 to naphtha into a cracking furnace 11 under cracking conditions of 0.17 MPaG and 825 °C to obtain a naphtha cracking fraction. (Confluence of ethanol conversion and naphtha cracking) Prepare a confluence fraction by mixing 417.2 tons / year of naphtha cracking fraction at 360 °C and 45.4 tons / year of cooled light ethanol conversion fraction. Introduce the confluence fraction into the first cooling tower 12 and contact it with a mixture of heavy oil and cracked gasoline to cool it to 110 °C to obtain a first cooled fraction 12. Introduce the first cooled fraction into the second cooling tower 13 and contact it with cooling water to obtain a second cooled fraction at 41 °C. Introduce the second cooled fraction into a booster 14 and pressurize it to 0.99 MPaG. Introduce the pressurized second cooled fraction into a soda washing tower 15 to contact it with an aqueous sodium hydroxide solution to obtain a washed fraction. The washed fraction is further pressurized and introduced into a cryogenic separation process as an introduced fraction. At this time, the amount of ethylene in the confluence fraction is 100.0 tons / year. The flow rate and composition of the confluence fraction are shown in Table 7.

[0220] [Example B12] Example B12 is implemented according to the process flow shown in FIG. 24. Example B12 is implemented in the same manner as Example B11, except that the connection points are changed. In Example B12, a cooled light ethanol conversion fraction at 15°C, which contains the fraction obtained from the bottom of the second cooling tower 13, is combined with a first bottom reflux fraction at 80°C that refluxes to the first cooling tower 12 to prepare a combined fraction. By combining the first bottom reflux fraction and the ethanol conversion fraction, the ethanol conversion fraction is introduced into the first cooling tower 12. Therefore, there is no change in the composition and flow rate of the introduced fraction obtained in Examples B11 and B12, but the temperature difference between the naphtha decomposition fraction and the ethanol conversion fraction can be reduced to 65 K, suppressing the cooling of the high-temperature naphtha fraction and the volume change associated with liquefaction.

[0221] [Example B13] This example is implemented using the light olefin production equipment shown in FIG. 25. (Ethanol conversion) Heat 145.6 ton / y of raw material and supply it to the reactor 21 filled with a zeolite-containing catalyst so that WHSV = 3.8, and perform an ethanol conversion reaction at a reaction temperature of 540°C to obtain an ethanol conversion fraction. The ethanol conversion fraction is introduced into the third cooling tower 22 and brought into contact with cooling water to obtain a cooled ethanol conversion fraction at 45°C. The cooled ethanol conversion fraction is pressurized by a booster 23 and introduced into a gas-liquid separation drum 26 to obtain 51.3 ton / y of a light ethanol conversion fraction as a gas at 1.90 MPaG and 40°C. At this time, the 49.4 ton / y of the heavy ethanol conversion fraction obtained as a liquid in the gas-liquid separation drum 26 is used as a recycle fraction that is reused as the raw material introduced into the reactor 21 without passing through additional purification processes. At this time, the product ratio in the recycle fraction is 11.3 mass%. (Naphtha decomposition) Introduce a naphtha raw material containing 266.5 ton / y of heavy naphtha and a dilution steam with a mass ratio of 0.5 to naphtha into the cracking furnace 11 under cracking conditions of 0.17 MPaG and 825°C to obtain a naphtha decomposition fraction. (Confluence of ethanol conversion and naphtha decomposition) A combined fraction is prepared by mixing a naphtha cracking fraction of 417.2 tons / y and a light ethanol conversion fraction of 51.3 tons / y. The combined fraction is introduced into a first cooling tower 12 and brought into contact with a mixture of heavy oil and cracked gasoline to be cooled to 110°C to obtain a first cooled naphtha cracking fraction. It is introduced into a second cooling tower 13 and brought into contact with cooling water to obtain a second cooled naphtha cracking fraction at 0.11 MPaG and 41°C. The second cooled naphtha cracking fraction is introduced into a booster 14 and pressurized to 0.99 MPaG. The pressurized second cooled naphtha cracking fraction is introduced into a soda washing tower and brought into contact with an aqueous sodium hydroxide solution to obtain a washed fraction. After the washed fraction is pressurized to 1.82 MPaG, it is introduced into a first distillation tower 17, and an introduced fraction to be introduced into a cryogenic separation process is obtained at -18°C from the top of the tower. Also, a bypass fraction to be introduced into downstream equipment bypassing the cryogenic separation process is obtained at 16°C from the bottom of the tower. 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 total amount of ethylene contained in the introduced fraction and the bypass fraction, which is 100.0 tons / y.

[0222]

Table 7

[0223] From the results of the examples and comparative examples, it can be seen that according to the method for producing light olefins according to this embodiment, the amount of off-gas such as hydrogen and methane can be reduced, and the processing energy in cryogenic separation can be reduced.

Claims

1. 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 a raw material containing ethanol into a reactor and bringing it into contact with a catalyst to obtain an ethanol conversion fraction containing ethylene and propylene; A merging step of merging at least a part of the naphtha cracked fraction or a fraction derived therefrom and at least a part of the ethanol conversion fraction or a fraction derived therefrom to obtain a merged fraction; A cryogenic separation step of introducing the merged fraction or a fraction derived therefrom into a cryogenic separation facility to separate ethylene and propylene, and Ratio O of the amounts of hydrogen and methane to the total amount of ethylene and propylene in the ethanol conversion fraction E and ratio O of the amounts of hydrogen and methane to the total amount of ethylene and propylene in the naphtha cracking fraction C are related by the formula (1): O E <O C ・・・(1) satisfying A method for producing light olefins.

2. The ratio O' of the amounts of hydrogen and methane to the total amount of ethylene and propylene in the ethanol conversion fraction or a fraction derived therefrom in the merging step E and the ratio O' of the amounts 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 with is given by formula (1-1): O’ E <O’ C ・・・(1−1) satisfying The method for producing light olefins according to Claim 1.

3. The propylene / ethylene mass ratio P / E in the ethanol conversion fraction E and the propylene / ethylene mass ratio P / E in the naphtha cracking fraction C are related by the formula (2): | P / E C - P / E E | < 0.3...(2) satisfying The method for producing light olefins according to Claim 1.

4. The content ratios C of ethylene and propylene in the ethanol conversion fraction or a fraction derived therefrom in the merging step E and the content ratios C of ethylene and propylene in the naphtha cracking fraction or a fraction derived therefrom C are related by the formula (3): C E > C C ...(3) satisfying The method for producing light olefins according to Claim 1.

5. The content ratio C E and the content ratio C C The difference from (C E - C C ) is 5% by mass or more The method for producing light olefins according to Claim 4.

6. The content ratio C E is such that the content ratio C C is purified to be higher than the ethanol conversion fraction to obtain a purified ethanol conversion fraction, including a purification step. The method for producing light olefins according to Claim 4.

7. The purification step includes a third cooling step of introducing the ethanol conversion fraction into a third cooling tower to obtain a cooled ethanol conversion fraction mainly containing olefins having 6 or less carbon atoms, The method for producing light olefins according to Claim 6.

8. The purification step includes a compression separation step of boosting the pressure of the cooled ethanol conversion fraction by a compressor to obtain a light ethanol conversion fraction mainly containing olefins having 3 or less carbon atoms as a gas component and a heavy ethanol conversion fraction mainly containing olefins having 4 or more carbon atoms as a liquid component, The method for producing light olefins according to Claim 7.

9. a recycling step of introducing at least a part of the heavy ethanol conversion fraction into the reactor as a part of the raw material, The method for producing light olefins according to Claim 8.

10. a washing step of introducing the merged fraction into a soda washing tower after the merging step to obtain a washed fraction, The method for producing light olefins according to Claim 1.

11. a distillation step of introducing the washed fraction into a first distillation tower after the washing step to obtain an introduced fraction to be introduced into the cryogenic separation step and a bypass fraction to be introduced into a subsequent facility bypassing the cryogenic separation step, The method for producing light olefins according to Claim 1.

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