Process for the production of butadiene

Abstract

This invention provides a method for manufacturing butadiene that can reduce carbon dioxide emissions. The method includes: an electrolytic reduction step 2, which produces ethylene and oxygen from carbon dioxide and water as raw materials through electrolytic reduction; a butene generation step 3, which generates butene by dimerizing the ethylene generated in the electrolytic reduction step; a mixing step 4, which prepares a mixed gas by mixing oxygen generated in the electrolytic reduction step, butene generated in the butene generation step, and air; and a butadiene generation step 5, which produces butadiene by heating the mixed gas and oxidizing and dehydrogenating the butene, wherein the carbon dioxide produced as a byproduct in the butadiene generation step is used as part of the raw material in the electrolytic reduction step.

Description

Technical Field

[0001] This invention relates to a method for manufacturing butadiene. Background Technology

[0002] In recent years, ethylene production methods have shifted from those using pyrolysis of naphtha to those using ethane obtained from shale gas and other sources as feedstock. When using ethane as feedstock, the amount of butadiene produced as a byproduct of ethylene production decreases compared to when naphtha is used. This leads to an increased supply-demand gap for butadiene. To address this issue, Patent Documents 1 and 2 disclose methods for preparing butadiene by dimerizing ethylene to produce butene, followed by oxidative dehydrogenation of the butene. Existing technical documents Patent documents

[0003] Patent Document 1: JP2014-62094A Patent Document 2: JP2011-148720A Summary of the Invention The task to be accomplished by this invention

[0004] However, in the process of butene oxidative dehydrogenation to produce butadiene, the complete combustion reaction generates a large amount of carbon dioxide as a side reaction, which is a problem. Previously, the generated carbon dioxide was released into the atmosphere, but from the perspective of global environmental protection, there is a desire to reduce carbon dioxide emissions.

[0005] In view of the above background, the object of the present invention is to provide a method for manufacturing butadiene that can reduce carbon dioxide emissions. means of completing the task

[0006] To achieve this objective, one aspect of the present invention provides a method for manufacturing butadiene, the method comprising: an electrolytic reduction step (2) which produces ethylene and oxygen from carbon dioxide and water as raw materials by electrolytic reduction; a butene generation step (3) which generates butene by dimerizing the ethylene generated in the electrolytic reduction step; a mixing step (4) which prepares a mixed gas by mixing the oxygen generated in the electrolytic reduction step, the butene generated in the butene generation step, and air; and a butadiene generation step (5) which manufactures butadiene by heating the mixed gas and oxidizing and dehydrogenating the butene, wherein the carbon dioxide byproduct of the butadiene generation step is used as part of the raw materials in the electrolytic reduction method.

[0007] Based on this, carbon dioxide produced during the butadiene production process via oxidative dehydrogenation can be used to generate ethylene, a feedstock for butadiene, and oxygen, which is required for oxidative dehydrogenation. Therefore, emissions of carbon dioxide, a greenhouse gas, can be reduced. Furthermore, the cost of raw materials can be lowered in the butadiene production method.

[0008] In the foregoing, preferably, the method for manufacturing butadiene comprises: a heat exchange step (6) for cooling a gaseous composition containing butadiene and carbon dioxide flowing out in the butadiene generation step; a butadiene separation step (7) for separating butadiene from the gaseous composition cooled in the heat exchange step; and a carbon dioxide separation step (8) for separating carbon dioxide from the gaseous composition from which butadiene was separated in the butadiene separation step, wherein the carbon dioxide separated in the carbon dioxide separation step is used as part of the raw material in the electrolytic reduction step.

[0009] In this respect, carbon dioxide is concentrated and supplied to the electrolytic reduction process. Therefore, the efficiency of electrolytic reduction can be improved.

[0010] In the above aspects, preferably, in the heat exchange step, the gas composition flowing out of the butadiene generation step and containing the butadiene and the carbon dioxide is cooled by heat exchange with the gas composition (from which the carbon dioxide is separated in the carbon dioxide separation step).

[0011] Based on this, energy efficiency can be improved.

[0012] In the above manner, preferably, the gaseous composition from which the carbon dioxide is separated in the carbon dioxide separation step is heat-exchanged with the gaseous composition containing the butadiene and the carbon dioxide that flows out in the butadiene generation step in the heat exchange step, and then mixed with the mixed gas in the mixing step.

[0013] According to this aspect, the gaseous composition from which carbon dioxide is separated in the carbon dioxide separation process is heated in a heat exchange process and then supplied to the butadiene generation process via a mixing process. Therefore, the energy consumption of the reactor used to heat the butadiene generation process can be reduced.

[0014] In the foregoing, preferably, the method for manufacturing butadiene includes: measuring the oxygen concentration and flow rate of the mixed gas in the mixing process; and controlling the flow rate of the oxygen supplied from the electrolytic reduction process to the mixing process based on the oxygen concentration and the flow rate of the mixed gas.

[0015] This method allows the oxygen concentration in the mixed gas to be maintained within an appropriate range.

[0016] In the foregoing, preferably, the method for manufacturing butadiene includes: measuring the flow rate of carbon dioxide supplied from the butadiene generation step to the electrolytic reduction step; and controlling the electrolytic reduction potential in the electrolytic reduction step based on the flow rate of the carbon dioxide.

[0017] This method can improve the efficiency of electrolytic reduction.

[0018] In the foregoing, preferably, the method for producing butadiene further includes an ethylene generation step (101) of generating ethylene from ethane or naphtha as raw materials, wherein the ethylene generated in the ethylene generation step is used as part of the raw materials in the butene generation step.

[0019] Based on this, the supply of ethylene can be increased.

[0020] In the above aspects, preferably, butene produced as a byproduct of the ethylene production process is used in the butadiene production process.

[0021] Based on this, the supply of butene can be increased. The effects of the invention

[0022] Therefore, based on the above aspects, a method for manufacturing butadiene that can reduce carbon dioxide emissions can be provided. Attached Figure Description

[0023] Figure 1 This is an explanatory diagram showing a butadiene manufacturing system; Figure 2 This is an explanatory diagram showing the butadiene manufacturing system; Figure 3 This is an explanatory diagram showing an electrolytic reducer; and Figure 4 This is an explanatory diagram showing a butadiene manufacturing system according to an improved embodiment. Detailed Implementation

[0024] Hereinafter, an embodiment of the method for producing butadiene according to the present invention will be described. Figure 1 and 2 As shown, the butadiene manufacturing system 1 according to this embodiment includes an electrolytic reduction step 2, a butene generation step 3, a mixing step 4, a butadiene generation step 5, a heat exchange step 6, a butadiene separation step 7, and a carbon dioxide separation step 8.

[0025] In the electrolytic reduction process 2, ethylene and oxygen are produced from carbon dioxide and water, which are used as raw materials, through electrolytic reduction. 2CO2 + 2H2O → C2H4 + 3O2 In the electrolytic reduction process 2, an electrolytic reducer that uses a gas diffusion electrode as the cathode 16 or an electrolytic reducer that uses a solid polymer membrane as a separator can be used.

[0026] like Figure 3 As shown, the electrolytic reducer 10 used in the electrolytic reduction step 2 can be, for example, a three-chamber electrolytic reducer. More specifically, the electrolytic reducer 10 may include an electrolytic cell 14 having a cathode gas chamber 11, a cathode electrolyte chamber 12, and an anode electrolyte chamber 13 spaced apart from each other. The cathode gas chamber 11 and the cathode electrolyte chamber 12 are separated by a cathode 16, which serves as a gas diffusion electrode. The cathode electrolyte chamber 12 and the anode electrolyte chamber 13 are separated by a partition wall 17 having ion conductivity. An anode 18 is provided in the anode electrolyte chamber 13. Gaseous carbon dioxide is supplied to the cathode gas chamber 11. As described later, the carbon dioxide is supplied by a carbon dioxide separation step 8. The cathode electrolyte is supplied to the cathode electrolyte chamber 12. The anode electrolyte is supplied to the anode electrolyte chamber 13. The anode 18 and the cathode 16 are connected to a DC power supply 19.

[0027] The anolyte and catholyte are aqueous solutions in which electrolytes are dissolved. Electrolytes include at least one of potassium, sodium, lithium, and their compounds. For example, electrolytes may include at least one selected from the group consisting of LiOH, NaOH, KOH, Li₂CO₃, Na₂CO₃, K₂CO₃, LiHCO₃, NaHCO₃, and KHCO₃.

[0028] The cathode 16 is a gas diffusion electrode and includes a gas diffusion layer 21 and a microporous layer 22. The gas diffusion layer 21 is permeable to carbon dioxide-containing gas but inhibits the permeation of aqueous solutions containing cathode electrolyte. The microporous layer 22 is permeable to both carbon dioxide-containing gas and aqueous solutions containing cathode electrolyte. Both the gas diffusion layer 21 and the microporous layer 22 have flat surfaces. The gas diffusion layer 21 is disposed on one side of the cathode gas chamber 11, while the microporous layer 22 is disposed on one side of the cathode electrolyte chamber 12.

[0029] For example, the gas diffusion layer 21 can be composed of a porous conductive substrate such as carbon paper, carbon felt, and carbon cloth, and a waterproof membrane such as polytetrafluoroethylene formed on the surface of the conductive substrate. The conductive substrate is connected to the negative terminal of the DC power supply 19 and is supplied with electrons. The microporous layer 22 is formed on the surface of the gas diffusion layer 21 using carbon black or the like, and carries a catalyst. The catalyst can be a known carbon dioxide reduction catalyst, and includes, for example, at least one of Group 11 elements such as copper, Group 12 elements such as zinc, Group 13 elements such as gallium, Group 14 elements such as germanium, and their metal compounds. The metal compounds include at least one of oxides, sulfides, and phosphides. The catalyst is preferably suitable for reducing carbon dioxide to produce ethylene, and is preferably made of a material formed by combining copper or copper compounds with metals or their metal compounds, such as those of Group 11, Group 12, Group 13, or Group 14 elements. A binder such as an ion exchange resin can be added to the microporous layer 22.

[0030] For example, the anode 18 is made of metals such as titanium, nickel, molybdenum, platinum, gold, silver, copper, iron, and lead, their metal alloys, carbon-based materials such as carbon, or conductive ceramics. The anode 18 can be formed as a flat plate, a flat plate with multiple openings, a mesh, or a porous body. The openings of the flat plate can be formed as circular, rhomboid, star-shaped, etc. The flat plate can be corrugated or curved, and its surface can be uneven. The anode 18 carries an oxygen-generating catalyst such as platinum or iridium. The anode 18 can be disposed on the surface of the anolyte chamber 13 on one side of the partition wall 17.

[0031] DC power supply 19 converts electricity obtained from thermal power generation, nuclear power generation, solar power generation, wind power generation, hydropower generation, etc., into direct current as needed, and supplies this electricity to cathode 16 and anode 18. From the viewpoint of reducing carbon dioxide emissions, it is preferable to use electricity obtained from natural energy (renewable energy) power generation such as solar power generation, wind power generation, hydropower generation, etc., as DC power supply 19. DC power supply 19 applies a voltage such that cathode 16 has a negative potential relative to anode 18. DC power supply 19 obtains the potential of cathode 16 by using a reference electrode, and preferably controls the voltage to be applied so that the potential of cathode 16 is maintained within a specified range.

[0032] The cathode gas chamber 11 includes an inlet 24 and an outlet 25. Carbon dioxide gas is supplied from the inlet 24 and discharged from the outlet 25. The outlet 25 of the cathode gas chamber 11 is connected to the inlet 24 via a gas circulation passage 26.

[0033] The cathode electrolyte chamber 12 includes an inlet 27 and an outlet 28. The inlet 27 and outlet 28 of the cathode electrolyte chamber 12 are connected via a cathode electrolyte circulation passage 29. Similarly, the anode electrolyte chamber 13 includes an inlet 31 and an outlet 32. The inlet 31 and outlet 32 ​​of the anode electrolyte chamber 13 are connected via an anode electrolyte circulation passage 33. Separators 35 and 36 are respectively provided in the cathode electrolyte circulation passage 29 and the anode electrolyte circulation passage 33. Separators 35 and 36 may include gas-liquid separators. Furthermore, electrolyte concentration controllers 37 and 38 may be respectively provided in the cathode electrolyte circulation passage 29 and the anode electrolyte circulation passage 33 for adjusting the electrolyte concentrations of the cathode electrolyte and the anode electrolyte within a specified range. Electrolyte concentration controllers 37 and 38 may include sensors for detecting the electrolyte concentration of the cathode electrolyte and the anolyte, an electrolyte supply device for supplying fresh cathode electrolyte and anolyte at a specified concentration, and a discharge device for discharging a portion of the circulating cathode electrolyte and anolyte.

[0034] Furthermore, a gas circulation flow regulator 34 is provided in the gas circulation passage 26 to discharge a portion of the gas circulating within it. The outlet of the gas circulation flow regulator 34 is connected to the first gas passage 39. The gas discharge passage of the separator 35 is connected to the first gas passage 39. The gas circulation flow regulator 34 regulates the flow rate and pressure of the gas circulating in the gas circulation passage 26 and the cathode gas chamber 11 by discharging gas into the first gas passage 39. The gas pressure in the cathode gas chamber 11 is maintained by the gas circulation flow regulator 34 at a value higher than the liquid pressure in the cathode electrolyte chamber 12 by a predetermined value, thereby suppressing the flow of cathode electrolyte from the cathode gas chamber 12 into the cathode gas chamber 11 through the cathode 16. A portion of the gas in the cathode gas chamber 11 passes through the cathode 16 and flows into the cathode electrolyte chamber 12. Preferably, the amount of gas flowing from the cathode gas chamber 11 into the cathode electrolyte chamber 12 is small.

[0035] Carbon dioxide in the cathode gas chamber 11 diffuses within the gas diffusion layer 21 of the cathode 16 and is reduced in the microporous layer 22 to obtain a first product. The first product contains ethylene as the main product and byproducts such as methane, hydrogen, carbon monoxide, and formic acid. Most of the first product is generated on the cathode gas chamber 11 side of the cathode 16. A portion of the first product is generated on the cathode electrolyte chamber 12 side of the cathode 16. The first product in the cathode electrolyte chamber 12 mixes with unreacted carbon dioxide flowing into the cathode electrolyte chamber 12. Similarly, the first product in the cathode gas chamber 11 mixes with unreacted carbon dioxide.

[0036] The first product generated at one side of the cathode electrolyte chamber 12 of cathode 16 contains ethylene, methane, and byproducts hydrogen and carbon monoxide as gases. These gases, along with unreacted carbon dioxide, are separated from the cathode electrolyte by separator 35 in the cathode electrolyte circulation passage 29 and then flow into the first gas passage 39. The first gas passage 39 may be equipped with a separator to separate ethylene from the first product. The separator may be a combination of a distillation unit, an extraction unit, and an adsorption unit.

[0037] In the first product composition generated at the cathode gas chamber 11 side of cathode 16, ethylene, methane, and byproducts hydrogen and carbon monoxide, along with unreacted carbon dioxide, circulate through gas circulation passage 26 and are discharged from gas circulation flow regulator 34 into first gas passage 39. The first product, including unreacted carbon dioxide and the ethylene, methane, and byproducts hydrogen and carbon monoxide generated at the cathode electrolyte chamber 12 side of cathode 16, flows into first gas passage 39 from separator 35 and gas circulation flow regulator 34.

[0038] At anode 18, water and hydroxide ions in the anolyte are oxidized to produce gaseous oxygen. The oxygen is separated from the anolyte by separator 36 in the anolyte circulation path 33. Oxygen, being a gas, is separated from the anolyte by separator 36 in the anolyte circulation path 33 and flows into the second gas passage 40.

[0039] In the electrolytic reduction step 2, the potentials of the cathode 16 and the catalyst supported on the cathode 16 can be set such that the Faradaic efficiency for ethylene production at the cathode 16 is 30% or higher, preferably 50% or higher. The Faradaic efficiency is defined as the ratio of the current contributing to the production of each product to the total current flowing through the electrolytic cell 14. In the electrolytic reduction step 2, the catalyst supported on the cathode 16 can be selected such that the selectivity for ethylene production at the cathode 16 is 30% or higher.

[0040] Ethylene produced in the electrolytic reduction step 2 is supplied to the butene generation step 3 via the first gas passage 39 and the first pipeline 41. In addition, oxygen produced in the electrolytic reduction step 2 is supplied to the mixing step 4 via the second gas passage 40 and the second pipeline 42.

[0041] In the butene production step 3, the ethylene produced in the electrolytic reduction step 2 is dimerized to produce butene. 2C2H4→C4H8 In step 3 of the butene formation process, butene is produced, and the main product is n-butene. For example... Figure 2 As shown, the butene generation step 3 includes a dimerization reactor 44 and a first separator 45.

[0042] The dimerization reactor 44 can be, for example, a fixed-bed flow reactor packed with an ethylene dimerization catalyst. The ethylene dimerization catalyst contains nickel, alumina, and silica. The ethylene dimerization catalyst can be, for example, a catalyst in which alumina and nickel are supported on a silica support, or a catalyst in which nickel is supported on a silica support containing alumina. The nickel content of the ethylene dimerization catalyst is 0.0001% to 1% by weight, preferably 0.0001% to 0.5%, more preferably 0.0001% to 0.05%.

[0043] The carrier preferably has a high specific surface area and a high pore volume. The preferred specific surface area of ​​the carrier is 200 m². 2 / g to 1200m 2 The pore volume of the support is preferably from 0.4 cc / g to 2 cc / g. The silica support can be made of amorphous silica or mesoporous silica. The support containing silica and alumina can be Y-type zeolite, X-type zeolite, mordenite, β-type zeolite, L-type zeolite or MFI-type zeolite.

[0044] In the dimerization reactor 44, the reaction temperature for the ethylene dimerization reaction is set to 150°C to 400°C, preferably 200°C to 350°C. Below 150°C, the catalyst activity decreases. Above 400°C, branched olefins increase rapidly, nickel tends to aggregate on the catalyst, and coke byproducts are generated. Therefore, the catalyst may deteriorate. The reaction pressure for ethylene dimerization is preferably 0.1 MPa to 50 MPa. Above 50 MPa, byproducts tend to be generated. Below 0.1 MPa, the catalyst activity decreases. The ethylene feed rate (weight hourly space velocity: WHSV) per unit weight of catalyst can be 0.1 h⁻¹. -1 Up to 50h -1 Preferably 0.5h -1 Up to 40h -1 More preferably 0.5h -1 Up to 30 hours -1 When the ethylene feed rate is less than 0.1 h⁻¹ -1 Under these conditions, the yield decreases. Furthermore, as the oligomerization reaction proceeds continuously, the selectivity for dimers and trimers decreases. When the ethylene feed rate is greater than 40 h⁻¹, the yield decreases. -1 Under these conditions, the conversion rate of ethylene decreases.

[0045] The dimerization of ethylene produces n-butene as the main product, including 1-butene, cis-2-butene, and trans-2-butene. Additionally, hexenes such as 1-hexene, 2-hexene, and 3-hexene can be produced as byproducts.

[0046] The first separator 45 separates n-butene from unreacted ethylene and the reaction products obtained by ethylene dimerization in the dimerizing reactor 44. The first separator 45 is connected to the dimerizing reactor 44 via a third line 47. The first separator 45 can be a combination of known distillation, extraction, and adsorption devices. Furthermore, the first separator 45 separates unreacted ethylene from the reaction products and returns it to the dimerizing reactor 44 via a return line 48. Hydrocarbons such as hexene separated by the first separator 45 can be fed into the oxygen combustion unit 60 (mentioned later) and used as fuel.

[0047] In mixing step 4, oxygen generated in electrolytic reduction step 2, butene generated in butene generation step 3, and air are mixed to prepare a mixed gas. Mixing step 4 includes a gas mixer 51. The gas mixer 51 is supplied with n-butene via a fourth line 52 from the first separator 45 of butene generation step 3, air via an air line 53, oxygen via a second line 42 from the separator 36 of electrolytic reduction step 2, and recycled gas mainly containing nitrogen and oxygen from the carbon dioxide separation step 8 via a sixth line 55. Air, oxygen from electrolytic reduction step 2, and recycled gas are used to adjust the oxygen concentration in the oxidative dehydrogenation reactor 67 mentioned later. The mixed gas is prepared such that the molar ratio of oxygen to n-butene is maintained in the range of 1:0.5 to 1:3, preferably in the range of 1:0.8 to 1:2.

[0048] Air line 53 is equipped with a first flow control valve 57 to control the flow rate of air supplied to gas mixer 51. Second line 42 is equipped with a second flow control valve 58 to control the flow rate of oxygen supplied to gas mixer 51. The second flow control valve 58 is connected via a seventh line 59 to an oxygen combustion device 60, such as a boiler, that uses oxygen. The heat energy generated in the oxygen combustion device 60 can be recovered and used to heat the gas flowing out of gas mixer 51. Furthermore, the carbon dioxide produced in the combustion of oxygen in the oxygen combustion device 60 can be recovered and used as part of the raw material in the electrolytic reduction process 2.

[0049] Gas mixer 51 supplies a mixture of ethylene, oxygen, air, and recirculated gas to butadiene production step 5 via eighth line 61. A first gas flow meter 63 for measuring the flow rate of the mixed gas and an oxygen concentration meter 64 for measuring the oxygen concentration of the mixed gas are installed at the outlet of gas mixer 51 or eighth line 61. Additionally, a pressurization pump 65 for pressurizing the mixed gas and a preheating furnace 66 for preheating the mixed gas are installed on eighth line 61. Oxygen can be supplied to the furnace 66 from second line 42 or seventh line 59.

[0050] In the butadiene production step 5, the mixed gas is heated to oxidize and dehydrogenate the butene, thereby producing butadiene. C4H8 + 1 / 2O2 → C4H6 + H2O

[0051] The butadiene production step 5 includes an oxidative dehydrogenation reactor 67. The oxidative dehydrogenation reactor 67 can be any reactor, such as a fixed-bed reactor, a fluidized-bed reactor, or a moving-bed reactor. The oxidative dehydrogenation reactor 67 is filled with an oxidative dehydrogenation catalyst. The oxidative dehydrogenation catalyst can be a composite metal oxide catalyst containing molybdenum and bismuth, an iron oxide catalyst, a vanadium oxide catalyst, etc. Preferably, the oxidative dehydrogenation catalyst also contains iron and cobalt in addition to molybdenum and bismuth. Besides composite metal oxides, the oxidative dehydrogenation catalyst may also contain silicon dioxide.

[0052] In the oxidative dehydrogenation reactor 67, the oxidative dehydrogenation reaction is carried out at 300-600°C, preferably 300-500°C, and more preferably 320-460°C. Furthermore, the oxidative dehydrogenation reaction is carried out at 0-2 MPa, preferably 0-0.5 MPa. Additionally, the feed rate of n-butene per unit weight of catalyst can be 0.1 h⁻¹. -1 Up to 10h -1 More preferably 0.2h -1 Up to 5 hours -1 Butadiene is produced as the main product from n-butene through an oxidative dehydrogenation reaction. Additionally, carbon dioxide is produced as a byproduct through the complete combustion of n-butene.

[0053] The outlet of the oxidative dehydrogenation reactor 67 is connected to the butadiene separation process 7 via a ninth pipeline 69. A gas composition containing butadiene, carbon dioxide, and unreacted gas flows out of the outlet of the oxidative dehydrogenation reactor 67. A heat exchanger 71 constituting the heat exchange process 6 is installed in the ninth pipeline 69. The gas composition flowing through the ninth pipeline 69 is cooled in the heat exchanger 71.

[0054] A gaseous composition is supplied to butadiene separation step 7 via a ninth pipeline 69, where butadiene is separated from the gaseous composition. Butadiene separation step 7 includes a second separator 72. The second separator 72 can, for example, liquefy the butadiene by cooling the gaseous composition and separate liquid butadiene from the gaseous composition by gas-liquid separation.

[0055] The gaseous composition from which butadiene is separated in butadiene separation step 7 primarily contains nitrogen, carbon dioxide, and oxygen. This gaseous composition, from which butadiene has been separated, is supplied via a tenth line 74 to carbon dioxide separation step 8, where carbon dioxide is separated from the gaseous composition. Carbon dioxide separation step 8 may include a third separator 75, which operates using known methods, such as chemisorption methods like the Benfield method and the MDEA (methyldiethanolamine) method, physisorption methods like the Selexol method and the Rectisol method, membrane separation methods, PSA (pressure swing adsorption), PTSA (pressure swing temperature adsorption), electrochemical separation methods using quinone, etc. The carbon dioxide separated from the gaseous composition and adsorbed by various adsorbents is separated from the adsorbents through a regeneration process and converted into a high-concentration gaseous state.

[0056] The carbon dioxide separated in carbon dioxide separation step 8 is supplied from the third separator 75 to the cathode gas chamber 11 of the electrolytic reduction step 2 via the eleventh line 76. Therefore, the carbon dioxide byproduct of the butadiene generation step 5 is used as part of the raw material in the electrolytic reduction step 2. Furthermore, the eleventh line 76 is connected to a carbon dioxide line 77 that supplies carbon dioxide gas to the eleventh line 76. A third flow control valve 78 is installed in the carbon dioxide line 77. A carbon dioxide concentration meter 79 is installed in the eleventh line 76 to measure the concentration of carbon dioxide passing through the eleventh line 76. Additionally, a second gas flow meter 80 is installed in the eleventh line 76 to measure the flow rate of carbon dioxide passing through the eleventh line 76.

[0057] The gaseous composition from which carbon dioxide has been separated mainly contains nitrogen and oxygen, and is returned as a recirculated gas to the gas mixer 51 of mixing step 4 via the sixth pipeline 55. The sixth pipeline 55 passes through the heat exchanger 71 of heat exchange step 6, where the recirculated gas exchanges heat with the gaseous composition passing through the ninth pipeline 69. Therefore, at the outlet of the heat exchanger 71, the temperature of the recirculated gas passing through the sixth pipeline 55 increases, while the temperature of the gaseous composition passing through the ninth pipeline 69 decreases.

[0058] The controller 85 controls the first flow control valve 57 and the second flow control valve 58 based on signals from the first gas flow meter 63 and the oxygen concentration meter 64. The controller 85 can increase the opening of the first flow control valve 57 as the flow rate of the mixed gas decreases, based on the signal from the first gas flow meter 63. Therefore, the amount of air supplied to the gas mixer 51 increases, and thus the flow rate of the mixed gas increases. Furthermore, the controller 85 can adjust the opening of the second flow control valve 58 based on the signal from the oxygen concentration meter 64, and increase the flow rate of oxygen from the second flow control valve 58 to the gas mixer 51 as the oxygen concentration of the mixed gas decreases. Therefore, the oxygen concentration of the mixed gas can be maintained within an appropriate range.

[0059] Furthermore, the controller 85 can control the potential of the DC power supply 19 based on signals from the carbon dioxide concentration meter 79 and the second gas flow meter 80. Therefore, the efficiency of electrolytic reduction is improved. In addition, the controller 85 controls the third flow control valve 78 based on signals from the carbon dioxide concentration meter 79 and the second gas flow meter 80, and regulates the amount of carbon dioxide supplied to the carbon dioxide separation process 8.

[0060] The effects of the above embodiments will be described. The butadiene manufacturing system 1 and the butadiene manufacturing method utilize the carbon dioxide generated during the butadiene production process via oxidative dehydrogenation to generate ethylene as a butadiene feedstock and oxygen required for oxidative dehydrogenation. Therefore, emissions of carbon dioxide, a greenhouse gas, generated during the butadiene production process can be reduced. Furthermore, the cost of raw materials can be reduced in the butadiene manufacturing method.

[0061] The carbon dioxide produced in the butadiene formation step 5 is concentrated through heat exchange step 6, butadiene separation step 7, and carbon dioxide separation step 8, and then supplied to the electrolytic reduction step 2. Therefore, the efficiency of the electrolytic reduction can be improved. The gaseous composition from which carbon dioxide is separated in the carbon dioxide separation step 8 is heat-exchanged with the gaseous composition containing butadiene and carbon dioxide flowing out of the butadiene formation step 5 in heat exchange step 6, and then mixed with the mixed gas in mixing step 4. Therefore, the energy consumption of the oxidative dehydrogenation reactor 67 used to heat the butadiene formation step 5 can be reduced. Furthermore, since the gaseous composition containing butadiene and carbon dioxide flowing out of the butadiene formation step 5 can be cooled, energy efficiency can be improved.

[0062] like Figure 4As shown, the butadiene manufacturing system 1 may further include an ethylene generation process 101 for producing ethylene from ethane or naphtha as feedstock. The ethylene generation process 101 can generate ethylene by cracking ethane or naphtha as feedstock. A portion of the ethylene generated in the ethylene generation process 101 can be supplied to the butene generation process 3 via the twelfth pipeline 102 for use as part of the feedstock for the butene generation process 3.

[0063] Furthermore, the butene produced as a byproduct in the ethylene generation process 101 can be supplied to the mixing process 4 via the thirteenth pipeline 103, and then used in the butadiene generation process 5. In this case, the twelfth pipeline 102 can be omitted. Additionally, with the ethylene generation process 101 provided, the carbon dioxide pipeline 77 can be omitted because the amount of ethylene required to be produced in the electrolytic reduction process 2 is reduced.

[0064] As an example, in a three-chamber electrolytic cell 14 consisting of a cathode gas chamber 11, a cathode electrolyte chamber 12, and an anode electrolyte chamber 13, the cathode 16 is formed of a gas diffusion electrode supported on a copper-zinc composite catalyst, and the anode 18 is formed of a Pt mesh. (At 265 mA / cm²) 2 The current was applied for 6 hours, while 1M (1mol / L) potassium bicarbonate aqueous solution was supplied to both the cathode electrolyte chamber 12 and the anode electrolyte chamber 13 at a rate of 1ml / min, and carbon dioxide was supplied to the cathode gas chamber 11 at a rate of 100ml / min. Analysis of the products in the gas showed that the cathode 16 produced 37% ethylene, 1% methane, and 25% hydrogen at a Faraday efficiency, while the anode 18 produced a gas containing 99% oxygen at a Faraday efficiency.

[0065] exist Figure 4 In the butadiene manufacturing system shown, process calculations are performed for a butadiene production rate of 100 kg / hr. In butadiene generation step 5, when butadiene is produced at a rate of 100 kg / hr, 12 kg / hr of ethylene is supplied from electrolytic reduction step 2 to butadiene generation step 3, 250 kg / hr of ethylene is supplied from ethylene generation step 101 to butadiene generation step 3, 205 kg / hr of butadiene is supplied from butadiene generation step 3 to mixing step 4, air containing 10 kg / hr of oxygen is supplied from air line 53 to mixing step 4, 56 kg / hr of oxygen is supplied from electrolytic reduction step 2 to mixing step 4, and 50 kg / hr of carbon dioxide is supplied from butadiene generation step 5 to electrolytic reduction step 2. That is, 50 kg / hr of carbon dioxide is generated in butadiene generation step 5, and 12 kg / hr of ethylene and 56 kg / hr of oxygen are generated in electrolytic reduction step 2 using this carbon dioxide as feedstock. In this case, the ethylene selectivity in electrolytic reduction step 2 is set to 80%.

[0066] The specific embodiments of the present invention have been described above, but the present invention is not limited to the above embodiments, and various changes and modifications can be made within the scope of the present invention. Glossary

[0067] 1: Butadiene Manufacturing System 2: Electrolytic reduction process 3: Butene production process 4: Mixing process 5: Butadiene production process 6: Heat exchange process 7: Butadiene separation process 8: Carbon dioxide separation process 10: Electrolytic Reducer 44: Dimerization Reactor 51: Gas mixer 57: First flow control valve 58: Second flow control valve 61: Oxygen combustion device 63: First gas flow meter 64: Oxygen concentration meter 67: Oxidative Dehydrogenation Reactor 71: Heat exchanger 72: Second separator 75: Third Separator 79: Carbon Dioxide Concentration Meter 80: Second gas flow meter 85: Controller 101: Ethylene production process 102: Twelfth Pipeline 103: Thirteenth Pipeline

Claims

1. A method for manufacturing butadiene, comprising: The electrolytic reduction process produces ethylene and oxygen from carbon dioxide and water, which are used as raw materials, through electrolytic reduction. The butene generation process generates butene by dimerizing the ethylene generated in the electrolytic reduction process. A mixing process, which prepares a mixed gas by mixing oxygen generated in the electrolytic reduction process, butene generated in the butene formation process, and air; and The butadiene production process involves heating the mixed gas and oxidizing and dehydrogenating the butene to produce butadiene. In this process, the carbon dioxide produced as a byproduct in the butadiene generation process is used as part of the raw material in the electrolytic reduction process.

2. The method for manufacturing butadiene according to claim 1, comprising: A heat exchange process that cools the gaseous composition containing butadiene and carbon dioxide flowing out from the butadiene generation process. A butadiene separation process that separates butadiene from the gaseous composition cooled in the heat exchange process; and A carbon dioxide separation process that separates carbon dioxide from a gaseous composition from which butadiene was separated in the butadiene separation process. The carbon dioxide separated in the carbon dioxide separation process is used as part of the raw material in the electrolytic reduction process.

3. The method for producing butadiene according to claim 2, wherein In the heat exchange process, the gaseous composition that flows out in the butadiene generation process and contains the butadiene and the carbon dioxide is cooled by exchanging heat with the gaseous composition from which the carbon dioxide is separated in the carbon dioxide separation process.

4. The method for producing butadiene according to claim 3, wherein The gaseous composition that separates carbon dioxide in the carbon dioxide separation step is then mixed with the gaseous composition containing butadiene and carbon dioxide that flows out in the butadiene generation step in the heat exchange step.

5. A method for producing butadiene according to any one of claims 1 to 4, comprising: Measure the oxygen concentration and flow rate of the mixed gas during the mixing process; as well as The flow rate of oxygen supplied from the electrolytic reduction process to the mixing process is controlled based on the oxygen concentration and the flow rate of the mixed gas.

6. A method for producing butadiene according to any one of claims 1 to 4, comprising: Measure the flow rate of the carbon dioxide supplied from the butadiene generation process to the electrolytic reduction process; as well as The electrolytic reduction potential in the electrolytic reduction process is controlled based on the flow rate of the carbon dioxide.

7. The method for producing butadiene according to any one of claims 1 to 4 further includes an ethylene generation step of generating ethylene from ethane or naphtha as a raw material. wherein, The ethylene produced in the ethylene generation process is used as part of the raw material in the butene generation process.

8. The method for producing butadiene according to claim 7, wherein The butadiene production process uses butene that is a byproduct of the ethylene production process.

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