Process for producing ethylene oxide

Abstract

[Task] The present invention provides a method for producing ethylene oxide that can reduce carbon dioxide emissions. [Solution] The method for producing ethylene oxide includes: an ethylene oxide production step 1, wherein a raw material containing ethylene and oxygen is reacted in the presence of a diluent gas to obtain a first mixture containing ethylene oxide; a gas-liquid separation step 2, wherein the first mixture is gas-liquid separated into a second mixture and a third mixture, the second mixture being a gas component containing ethylene, oxygen and carbon dioxide, and the third mixture being a liquid component containing ethylene oxide and water; a carbon dioxide separation step 3, wherein carbon dioxide is separated from the second mixture; and an electrolytic reduction step 4, wherein carbon dioxide is electrolytically reduced to obtain a fourth mixture containing ethylene, methane and carbon dioxide, and oxygen is obtained. In the carbon dioxide separation step, carbon dioxide is separated from the fourth mixture. In the ethylene oxide production step, the second mixture and the fourth mixture from which carbon dioxide has been removed, and the oxygen obtained in the electrolytic reduction step are used as raw materials and diluent gases.

Description

Technical Field

[0001] The present invention relates to a method for producing ethylene oxide. Background Art

[0002] As shown in Patent Document 1, there is a known method for producing ethylene oxide by catalytic oxidation of ethylene in a gas using silver as a catalyst. In this production method, ethylene is completely burned and a side reaction of producing carbon dioxide occurs. When the ethylene conversion rate is high, this side reaction is more likely to occur. Therefore, in the production method of ethylene, most of them adopt a circulation method that reduces the conversion rate of ethylene, recovers ethylene oxide from the reaction product, and then uses the unreacted ethylene, oxygen, etc. as raw materials again.

[0003] Prior art documents

[0004] Patent Documents

[0005] Patent Document 1: JP2001-172272A Summary of the invention

[0006] The task to be accomplished by the present invention

[0007] The carbon dioxide contained in the reaction product is separated from ethylene oxide, ethylene, oxygen, etc., and then a part of it is collected and used for food manufacturing, but most of it is released into the atmosphere. The amount of carbon dioxide emitted from the ethylene oxide production process is large, and from the viewpoint of global environmental protection, it is desired to reduce the amount of carbon dioxide.

[0008] In view of the above background, an object of the present invention is to provide a method for producing ethylene oxide which can reduce carbon dioxide emissions.

[0009] How to complete the task

[0010] To achieve the above-mentioned object, one aspect of the present invention is a method for producing ethylene oxide, comprising: an ethylene oxide generation step (1), wherein a raw material containing ethylene and oxygen is reacted in the presence of a diluent gas to obtain a first mixture containing ethylene oxide; a gas-liquid separation step (2), wherein the first mixture is gas-liquid separated into a second mixture and a third mixture, the second mixture being a gas component containing ethylene, oxygen and carbon dioxide, and the third mixture being a liquid component containing ethylene oxide and water; a carbon dioxide separation step (3), wherein carbon dioxide is separated from the second mixture; and an electrolytic reduction step (4), wherein the carbon dioxide separated from the second mixture is electrolytically reduced to obtain a fourth mixture containing ethylene, methane and unreacted carbon dioxide at a cathode and oxygen at an anode, wherein in the carbon dioxide separation step, carbon dioxide is further separated from the fourth mixture, and in the ethylene oxide generation step, the second mixture and the fourth mixture from which carbon dioxide has been removed in the carbon dioxide separation step and the oxygen obtained in the electrolytic reduction step are used as at least a part of the raw materials and the diluent gas.

[0011] According to this aspect, by using the carbon dioxide generated when producing ethylene oxide, ethylene and oxygen used as raw materials of ethylene oxide can be generated. Therefore, the emission of carbon dioxide as a greenhouse gas can be significantly reduced. In addition, the cost of raw materials in the method for producing ethylene oxide can be reduced. In addition, the methane generated as a by-product when ethylene is generated by carbon dioxide can be used as a diluent gas to reduce the oxygen concentration during the reaction of ethylene oxide, thereby reducing the cost of the diluent gas. In addition, by using a carbon dioxide separation step, it is possible to remove carbon dioxide from the fourth mixture generated by the cathode in the electrolytic reduction step.

[0012] In the above aspect, preferably, the fourth mixture is mixed into the second mixture before being treated in the carbon dioxide separation step.

[0013] According to this aspect, by utilizing the carbon dioxide separation step, unreacted carbon dioxide can be removed from the fourth mixture generated in the electrolytic reduction step.

[0014] In the above aspect, preferably, in the electrolytic reduction step, the catalyst supported on the cathode is selected so that the selectivity of ethylene on the cathode is 30% or more.

[0015] According to this embodiment, the amount of methane generated can be reduced by increasing the ethylene production rate during electrolytic reduction of carbon dioxide, thereby preventing methane from being excessive relative to the amount required as a diluent gas.

[0016] In the above-mentioned manner, preferably, an electrolytic reduction device (10) is used in the electrolytic reduction step, which includes: a cathode gas chamber (11), which is supplied with carbon dioxide in gaseous form; a cathode electrolyte chamber (12), which is supplied with a cathode electrolyte; an anode electrolyte chamber (13), which is supplied with an anode electrolyte; a cathode (16), which serves as a gas diffusion electrode separating the cathode gas chamber and the cathode electrolyte chamber from each other; a partition wall (17), which has ionic conductivity and separates the cathode electrolyte chamber and the anode electrolyte chamber from each other; and an anode (18), which is arranged in the anode electrolyte chamber.

[0017] According to this aspect, the fourth mixture containing ethylene and methane and unreacted carbon dioxide generated at the cathode can be prevented from mixing with the oxygen generated at the anode. Therefore, the step of separating carbon dioxide from oxygen can be omitted.

[0018] In the above aspect, preferably, the method further comprises a carbon monoxide removal step, wherein carbon monoxide is removed from the fourth mixture produced in the electrolytic reduction step. In addition, preferably, in the carbon monoxide removal step, carbon monoxide is removed from the fourth mixture before the carbon dioxide is removed in the carbon dioxide separation step.

[0019] According to this aspect, in the case where the catalyst used in the ethylene oxide generating step is poisoned by carbon monoxide, this can be suppressed.

[0020] In the above aspect, preferably, the method further comprises an ethylene glycol production step (6), wherein ethylene glycol is produced from the ethylene oxide contained in the third mixture by a hydration method.

[0021] According to this aspect, ethylene glycol can be produced by using the produced ethylene oxide.

[0022] In the above embodiment, it is preferred that in the electrolytic reduction step (4), carbon dioxide discharged from other factories is used as a part of the carbon dioxide to be electrolytically reduced.

[0023] According to this aspect, the production amounts of ethylene and methane can be increased, and the raw materials and diluent gases can be further reduced.

[0024] In the above-mentioned embodiment, it is preferred that in the electrolytic reduction step (4), electric power generated from natural energy is used to electrolytically reduce carbon dioxide.

[0025] According to this aspect, the emission amount of carbon dioxide can be suppressed.

[0026] Effects of the Invention

[0027] According to the above aspects, a method for producing ethylene oxide capable of reducing carbon dioxide emissions can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is a schematic diagram showing a process for producing ethylene oxide and ethylene glycol; and

[0029] Figure 2 is a schematic diagram showing an electrolytic reduction device. DETAILED DESCRIPTION

[0030] Hereinafter, one embodiment of the method for producing ethylene oxide of the present invention will be described. Figure 1 As shown, the method for producing ethylene oxide according to this embodiment includes: an ethylene oxide generation step 1, wherein a raw material containing ethylene and oxygen is reacted in the presence of a diluent gas to obtain a first mixture containing ethylene oxide; a gas-liquid separation step 2, wherein the first mixture is gas-liquid separated into a second mixture and a third mixture, the second mixture being a gas component containing ethylene, oxygen and carbon dioxide, and the third mixture being a liquid component containing ethylene oxide and water; a carbon dioxide separation step 3, wherein carbon dioxide is separated from the second mixture; and a carbon dioxide electrolytic reduction step 4, wherein the carbon dioxide separated from the second mixture is electrolytically reduced to obtain a fourth mixture containing ethylene, methane and unreacted carbon dioxide at the cathode, and oxygen is obtained at the anode. In the carbon dioxide separation step 3, unreacted carbon dioxide is further separated from the fourth mixture. In addition, in the ethylene oxide generation step 1, the second mixture and the fourth mixture from which carbon dioxide is removed in the carbon dioxide separation step 3 and the oxygen obtained in the electrolytic reduction step 4 are used as at least a part of the raw material and the diluent gas.

[0031] In the ethylene oxide generation step 1, a first mixture containing ethylene oxide is obtained by gas-phase catalytic oxidation of ethylene gas and oxygen in the presence of a silver catalyst. Preferably, the ethylene oxidation reactor in which the ethylene oxide generation step 1 is performed is, for example, a multi-tubular reactor filled with a silver catalyst. The ethylene gas and oxygen as raw materials and the diluent gas are heated and then supplied to the ethylene oxidation reactor. The diluent gas is used to reduce the oxygen concentration in the ethylene oxidation reactor to suppress explosion. The diluent gas can be methane, nitrogen or an inert gas such as argon. As an example, methane is used as the diluent gas in this embodiment. The first mixture obtained from the ethylene oxidation reactor contains: ethylene oxide as a reaction product; unreacted ethylene and oxygen; methane as a diluent gas; and side reaction products, which include water, carbon dioxide, aldehydes such as formaldehyde and acetaldehyde, and organic acids such as acetic acid.

[0032] The silver catalyst preferably comprises an alumina carrier and silver supported on the alumina carrier. Preferably, the silver loading is, for example, 15 to 35% by weight. The silver catalyst preferably comprises a promoter, for example, cesium, rhenium, tungsten, molybdenum, etc. Preferably, the reaction conditions of the ethylene oxide generation step 1 are, for example, a temperature of 230-270° C., a pressure of 15-25 bar, and a reaction time of 3000-8000 hours. -1 In addition, in order to suppress the side reaction of generating carbon dioxide and water due to the combustion of ethylene, the conversion rate of ethylene is preferably set to 8-15%.

[0033] In the gas-liquid separation step 2, the first mixture is cooled to a temperature higher than the freezing point of water (0°C) and lower than the boiling point of ethylene oxide (10.7°C), after which it is gas-liquid separated into a second mixture as a gaseous component and a third mixture as a liquid component. The second mixture contains ethylene, oxygen and carbon dioxide. The third mixture contains water and ethylene oxide. In addition, by-products such as acetaldehyde and acetic acid are contained in the third mixture. In the gas-liquid separation step 2, a gas-liquid separation device such as a separation tank is preferably used.

[0034] In the carbon dioxide separation step 3, carbon dioxide is separated from the second mixture. Preferably, the separation of carbon dioxide is carried out by a carbon dioxide separation device based on a known method, which may be a chemical adsorption method such as the Benfield method, the MDEA (methyldiethanolamine) method, etc., a physical adsorption method such as the Selexol method, the Rectisol method, etc., a membrane separation method, a PSA method (pressure swing adsorption method), a PTSA method (pressure swing temperature adsorption method), etc. The carbon dioxide separated from the second mixture and adsorbed on various adsorbents is separated from the adsorbent during the regeneration process and becomes a highly concentrated gaseous state.

[0035] The second mixture after carbon dioxide is separated contains ethylene, oxygen and methane. The gas containing ethylene, oxygen and methane is returned to the ethylene oxide production step 1 and used as a raw material and diluent gas for producing ethylene oxide.

[0036] In the carbon dioxide electrolytic reduction step 4, the carbon dioxide separated from the second mixture in the carbon dioxide separation step 3 is electrolytically reduced. In the electrolytic reduction step 4, it is preferred to use an electrolytic reduction device using a gas diffusion electrode as a cathode, an electrolytic reduction device using a solid polymer membrane as a separator, or the like.

[0037] like Figure 2As shown, the electrolytic reduction device 10 used in the electrolytic reduction step 4 is preferably, for example, a three-chamber type electrolytic reduction device. Specifically, the electrolytic reduction device 10 preferably includes an electrolytic cell 14 having a cathode gas chamber 11, a cathode electrolyte chamber 12, and an anode electrolyte chamber 13 that are separated from each other. The cathode gas chamber 11 and the cathode electrolyte chamber 12 are separated by a cathode 16 that serves as a gas diffusion electrode. The cathode electrolyte chamber 12 and the anode electrolyte chamber 13 are separated by an ion-conductive partition wall 17. The anode 18 is disposed in the anode electrolyte chamber 13. The cathode gas chamber 11 is supplied with carbon dioxide in the form of gas separated in the gas-liquid separation step 2. The cathode electrolyte chamber 12 is supplied with a cathode electrolyte. The anode electrolyte chamber 13 is supplied with an anode electrolyte. The anode 18 and the cathode 16 are connected to a DC power supply 19.

[0038] The anolyte and the catholyte are aqueous solutions in which an electrolyte is dissolved. The electrolyte comprises at least one of potassium, sodium, lithium or a compound thereof. For example, the electrolyte preferably comprises at least one selected from LiOH, NaOH, KOH, Li2CO3, Na2CO3, K2CO3, LiHCO3, NaHCO3 and KHCO3.

[0039] The cathode 16 is a gas diffusion electrode, including a gas diffusion layer 21 and a microporous layer 22. The gas diffusion layer 21 allows a gas containing carbon dioxide to pass therethrough, but inhibits an aqueous solution containing a cathode electrolyte from passing therethrough. The microporous layer 22 allows both a gas containing carbon dioxide and an aqueous solution containing a cathode electrolyte to pass therethrough. The gas diffusion layer 21 and the microporous layer 22 are each formed in a planar shape. The gas diffusion layer 21 is disposed on the cathode gas chamber 11 side, and the microporous layer 22 is disposed on the cathode electrolyte chamber 12 side.

[0040] The gas diffusion layer 21 can be formed by forming a waterproof coating made of a material such as polytetrafluoroethylene on the surface of a porous conductive substrate such as carbon paper, carbon felt or carbon cloth. The conductive substrate is connected to the negative electrode of the DC power supply 19 and receives electron supply. A microporous layer 22 is formed on the surface of the gas diffusion layer 21 using carbon black or the like, and a catalyst is loaded thereon. The catalyst can be a well-known carbon dioxide reduction catalyst, and for example contains at least one of an 11th group element such as copper, a 12th group element such as zinc, a 13th group element such as gallium, a 14th group element such as germanium, or a metal compound thereof. The metal compound contains at least one of an oxide, a sulfide and a phosphide. Preferably, the catalyst is a catalyst suitable for reducing carbon dioxide to produce ethylene, for example, preferably copper or a copper compound. A binder such as an ion exchange resin can be added to the microporous layer 22.

[0041] Anode 18 is, for example, a metal material such as titanium, nickel, molybdenum, platinum, gold, silver, copper, iron, lead, or an alloy material thereof, a carbon-based material such as carbon, or a conductive ceramic. The shape of anode 18 can be a flat plate, a flat plate with a plurality of openings, a mesh, or a porous body. The shape of the opening formed on the above-mentioned flat plate can be circular, rhombus, star-shaped, etc. The above-mentioned flat plate can be formed into a waveform or a curve, or it can have an irregular shape on the surface. Anode 18 has an oxygen generation catalyst such as platinum or iridium loaded thereon. Anode 18 can be arranged on the side surface of anolyte chamber 13 of partition wall 17.

[0042] The DC power source 19 converts the power obtained by thermal power generation, nuclear power generation, solar power generation, wind power generation, hydroelectric power generation, etc. into DC power as needed, and supplies it to the cathode 16 and the anode 18. From the viewpoint of reducing the emission of carbon dioxide, it is preferred to use power obtained by solar power generation, wind power generation, hydroelectric power generation, etc. that utilize natural energy (renewable energy) as the DC power source 19. The DC power source 19 applies a voltage so that the cathode 16 has a negative potential relative to the anode 18. Preferably, the DC power source 19 obtains the potential of the cathode 16 by using a reference electrode, and controls the applied voltage so that the potential of the cathode 16 is within a predetermined range.

[0043] The cathode gas chamber 11 has an inlet 24 and an outlet 25. The carbon dioxide gas supplied from the carbon dioxide separation step 3 is supplied through the inlet 24 and discharged from the outlet 25. The outlet 25 of the cathode gas chamber 11 is connected to the inlet 24 through a gas circulation passage 26.

[0044] The cathode electrolyte chamber 12 has an inlet 27 and an outlet 28. The inlet 27 and the outlet 28 of the cathode electrolyte chamber 12 are connected by a cathode electrolyte circulation passage 29. Similarly, the anode electrolyte chamber 13 has an inlet 31 and an outlet 32. The inlet 31 and the outlet 32 ​​of the anode electrolyte chamber 13 are connected by an anode electrolyte circulation passage 33. The cathode electrolyte circulation passage 29 is provided with a cathode-side gas-liquid separation device 35. The anode electrolyte circulation passage 33 is provided with an anode-side gas-liquid separation device 36. In addition, the cathode electrolyte circulation passage 29 and the anode electrolyte circulation passage 33 are preferably provided with electrolyte concentration control devices 37 and 38 for adjusting the electrolyte concentrations in the cathode electrolyte and the anode electrolyte within a predetermined range, respectively. The electrolyte concentration control devices 37, 38 preferably include sensors for detecting the electrolyte concentrations in the cathode electrolyte and the anode electrolyte, electrolyte suppliers for providing new cathode electrolyte and anode electrolyte having predetermined concentrations, and discharge devices for discharging partially circulated cathode electrolyte and anode electrolyte, respectively.

[0045] In addition, a gas circulation flow rate regulating device 40 for discharging a portion of the gas circulating inside the gas circulation passage 26 is provided. The outlet of the gas circulation flow rate regulating device 40 is connected to the first gas return passage 41. The gas discharge passage of the cathode-side gas-liquid separation device 35 is connected to the first gas return passage 41. The gas circulation flow rate regulating device 40 adjusts the flow rate and pressure of the gas circulating in the gas circulation passage 26 and the cathode gas chamber 11 by discharging the gas to the first gas return passage 41. By the gas circulation flow rate regulating device 40, the gas pressure in the cathode gas chamber 11 is maintained to be higher than the liquid pressure in the cathode electrolyte chamber 12 by a predetermined value. Therefore, the cathode electrolyte in the cathode electrolyte chamber 12 is prevented from passing through the cathode 16 and flowing into the cathode gas chamber 11. Part 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 inside of the cathode gas chamber 11 to the cathode electrolyte chamber 12 is small.

[0046] The carbon dioxide in the cathode gas chamber 11 diffuses into the interior of the gas diffusion layer 21 of the cathode 16 and is reduced in the microporous layer 22, thereby obtaining a fourth mixture. The fourth mixture contains ethylene and methane as main products, and contains a small amount of by-products such as hydrogen, carbon monoxide, formic acid, etc. Most of the fourth mixture is produced on the cathode gas chamber 11 side of the cathode 16. Note that part of the fourth mixture is produced on the cathode electrolyte chamber 12 side of the cathode 16. Unreacted carbon dioxide flowing into the cathode electrolyte chamber 12 is mixed into the fourth mixture in the cathode electrolyte chamber 12. Similarly, unreacted carbon dioxide is mixed into the fourth mixture in the cathode gas chamber 11.

[0047] In the fourth mixture generated on the cathode electrolyte chamber 12 side of the cathode 16, ethylene and methane as well as byproduct hydrogen and carbon monoxide are gases, and are separated from the cathode electrolyte together with unreacted carbon dioxide by the cathode side gas-liquid separation device 35 in the cathode electrolyte circulation passage 29 so that they flow into the first return gas channel 41. Formic acid in the fourth mixture is liquid, circulates in the cathode electrolyte circulation passage 29 together with the cathode electrolyte, and is discharged from the electrolyte concentration control device 37 together with the cathode electrolyte.

[0048] In the fourth mixture generated on the cathode gas chamber 11 side of the cathode 16, ethylene and methane and byproducts of hydrogen and carbon monoxide circulate in the gas circulation passage 26 together with unreacted carbon dioxide, and are discharged from the gas circulation flow regulating device 40 to the first return gas channel 41. The fourth mixture containing ethylene and methane generated on the cathode electrolyte chamber 12 side of the cathode 16, byproducts of hydrogen and carbon monoxide, and unreacted carbon dioxide flows from the cathode side gas-liquid separation device 35 and the gas circulation flow regulating device 40 to the first return gas channel 41.

[0049] At the anode 18 , water and hydroxide ions in the anolyte are oxidized to generate oxygen. Oxygen is a gas and is separated from the anolyte by the anode-side gas-liquid separator 36 in the anolyte circulation passage 33 , so that the separated oxygen flows toward the second gas return passage 42 .

[0050] In the electrolytic reduction step 4, the catalyst supported on the cathode 16 is preferably selected so that the selectivity for producing ethylene at the cathode 16 is 30% or more.

[0051] The fourth mixture containing ethylene and methane generated at the cathode 16 in the carbon dioxide electrolytic reduction step 4 is supplied to the carbon dioxide separation step 3 via the first return gas channel 41, and carbon dioxide is removed therefrom. The fourth mixture containing ethylene and methane may contain carbon monoxide and hydrogen, in which case the fourth mixture may be supplied to the carbon monoxide removal step 5 to remove carbon monoxide therefrom before being supplied to the carbon dioxide separation step 3. In the carbon monoxide removal step 5, carbon monoxide may be adsorbed by using an adsorbent such as zeolite. Note that the carbon monoxide removal step 5 is not a necessary configuration and may be omitted. In addition, the fourth mixture containing ethylene and methane may be supplied to the hydrogen removal step to remove hydrogen therefrom, and then supplied to the carbon dioxide separation step 3. As a hydrogen removal step, for example, pressure swing adsorption (PSA) or the like may be applied. Note that the hydrogen removal step is not a necessary configuration and may be omitted. Preferably, the fourth mixture supplied by the first return gas channel 41 is mixed with the second mixture supplied to the carbon dioxide separation step 3 by the gas-liquid separation step 2. Thus, after carbon dioxide is removed in the gas-liquid separation step 2, the fourth mixture is returned to the ethylene oxide production step 1 together with the second mixture, and is used as a raw material and a part of the diluent gas.

[0052] The oxygen supplied by the second gas return passage 42, i.e., the oxygen generated from the anode 18 in the electrolytic reduction step 4, is returned to the ethylene oxide production step 1 and used as a part of the raw material. Preferably, the oxygen generated from the anode 18 in the electrolytic reduction step 4 is mixed with the second mixture and the fourth mixture from which the carbon dioxide has been removed in the carbon dioxide separation step 3, and then returned to the ethylene oxide production step 1.

[0053] A sensor 51 may be provided to detect the flow rate of each component of the gas supplied from the carbon dioxide separation step 3 and the second gas return passage 42. In addition, a control device not shown in the figure may control flow control valves 52, 53, 54 based on the detection value of the sensor 51, and these flow control valves respectively control the flow rates of ethylene, oxygen and methane newly supplied to the ethylene oxide production step 1, thereby adjusting the respective flow rates of ethylene, oxygen and methane supplied to the ethylene oxidation reactor in the ethylene oxide production step 1.

[0054] In the ethylene glycol production step 6, the third mixture containing ethylene oxide and water separated from the first mixture in the gas-liquid separation step 2 is used as a raw material. In the ethylene glycol production step 6, ethylene oxide is hydrolyzed in the presence of a catalyst, that is, according to a hydration method, to produce ethylene glycol. Preferably, the catalyst is a resin catalyst, such as "Amberlist" (registered trademark), "Doulit" (registered trademark), "DOWEX" (registered trademark), etc. In the ethylene glycol production reaction, the reaction temperature is preferably 100 to 120°C and the reaction pressure is 20 to 35 bar.

[0055] The effects of the above-described embodiments will be described. According to the method for producing ethylene oxide of the present embodiment, ethylene and oxygen as raw materials of ethylene oxide can be generated by using the carbon dioxide generated when producing ethylene oxide. Therefore, the emission of carbon dioxide as a greenhouse gas can be reduced. In addition, the cost of raw materials in the method for producing ethylene oxide can be reduced. In addition, the methane generated as a by-product when ethylene is generated from carbon dioxide can be used as a diluent gas to reduce the oxygen concentration during the reaction of ethylene oxide, thereby reducing the cost of the diluent gas.

[0056] In the carbon dioxide electrolytic reduction step 4, by making the Faraday efficiency of ethylene production at the cathode 16 30% or more, it is possible to reduce the amount of methane generated during carbon dioxide electrolytic reduction, thereby preventing methane from being excessive relative to the necessary amount as a diluent gas.

[0057] Next, examples of the above-described embodiment will be described.

[0058] (Example 1)

[0059] An example of ethylene oxide production step 1 will be described. A fixed bed reactor filled with about 30 cc of a catalyst prepared by supporting 20 wt% silver on α alumina and further adding 3 wt% rhenium as a promoter was used. The reaction mixture was heated to 100 ℃ and heated to 400 ℃ at a temperature of 250° C., a pressure of 20 bar, and a GHSV of 5000 hours. -1 Under the condition of , a gas containing 25 mol% of ethylene, 10 mol% of oxygen and 65 mol% of methane was supplied to the reactor. The proportions of the reaction products obtained from the reactor outlet were 22.6 mol% of ethylene, 3.7 mol% of oxygen, 65.9 mol% of methane, 2.1 mol% of ethylene oxide, 2.3 mol% of carbon dioxide and 3.4 mol% of water.

[0060] (Example 2)

[0061] An embodiment of the carbon dioxide absorption method in the carbon dioxide separation step 3 will be described below. A glass gas absorption bottle is immersed in a constant temperature water bath set at a liquid temperature of 40°C, and 50 ml of an aqueous solution containing 18.8% by weight of N-methyldiethanolamine and 31.2% by weight of piperazine is filled therein. A mixed gas containing 20% ​​by weight of dicarbon dioxide and 80% by weight of nitrogen is dispersed in the form of bubbles at 0.7 liters / minute at atmospheric pressure for absorption. The carbon dioxide concentration in the gas is measured at the absorption liquid inlet and the absorption liquid outlet, and the carbon dioxide absorption amount is measured by the carbon dioxide flow rate difference between the inlet and the outlet. The saturated absorption amount is measured as the amount at the time point when the carbon dioxide concentration at the absorption liquid outlet matches the carbon dioxide concentration at the inlet. The carbon dioxide saturated absorption amount is 115.7 g / L. Subsequently, the liquid temperature is raised to 70°C in the same gas flow within a few minutes, and the desorption amount and desorption rate of carbon dioxide from the liquid are measured. The desorption amount of carbon dioxide is 25.4 g / L, and the desorption rate is 2.05 g / L / min.

[0062] (Example 3)

[0063] An embodiment of the carbon dioxide electrolytic reduction step 4 will be described below. An electrolytic reduction device 10 including the above-mentioned cathode gas chamber 11, cathode electrolyte chamber 12 and anode electrolyte chamber 13 is used. The catalyst in the gas diffusion layer 21 of the cathode 16 is a copper-zinc complex catalyst. The anode 18 is a titanium plate on which an iridium oxide catalyst is supported. A 1M potassium bicarbonate solution flowing at 1 ml / min is used as the anode electrolyte and the cathode electrolyte. Carbon dioxide is made to flow in the cathode gas chamber 11 at a rate of 100 ml / min, while at 300 mA / cm 2 The current of 1000 Ω was passed for 6 hours. The composition analysis of the gas generated from the cathode electrolyte chamber 12 showed that the ethylene selectivity at the cathode 16 was 53%, the methane selectivity was 18%, and the hydrogen selectivity was 20%. The composition analysis of the gas generated from the anode electrolyte chamber 13 showed that the oxygen selectivity at the anode 18 was 99%.

[0064] (Example 4)

[0065] The calculation results of the mass balance when ethylene glycol is produced at a rate of 100 tons / hour in a factory using the above-mentioned method for producing ethylene oxide are shown in the following Table 1. Figure 1As shown, the composition of the raw material newly added from outside the system for the ethylene oxide production step 1 is represented by C1, the composition of the product of the ethylene glycol production step 6 is represented by C2, the composition of the raw material supplied from the carbon dioxide separation step 3 to the electrolytic reduction step 4 is represented by C3, the composition of the mixture of the oxygen supplied from the electrolytic reduction step 4 and the second mixture and the fourth mixture from which carbon dioxide is removed by the carbon dioxide separation step 3 is represented by C4, the composition of the raw material supplied to the ethylene glycol production step 6 is represented by C5, and the composition of the dilution gas newly added from outside the system for the ethylene oxide production step 1 is represented by C6. As the calculation conditions of the mass balance, the outlet temperature of the ethylene oxidation reactor in the ethylene oxide production step 1 is set to 250°C and the outlet pressure is set to 20 bar. In addition, in the absorption of carbon dioxide in the carbon dioxide separation step 3, a chemical absorption method using an aqueous solution containing 18.8% by weight of N-methyldiethanolamine and 31.2% by weight of piperazine is adopted. The reaction conditions of the reactor in the ethylene glycol production step 6 are a reaction temperature of 100°C and a pressure of 25 bar. The reaction conditions of the carbon dioxide electrolytic reduction step 4 are as follows: the carbon dioxide conversion rate is 70%, the ethylene selectivity of the cathode 16 is 80%, and the methane selectivity of the cathode 16 is 20%.

[0066] [Table 1]

[0067] (Unit: tons / hour)

[0068] No. C1 C2 C3 C4 C5 C6 <![CDATA[CH4]]> 0 0 0.1 0.1 0 2.4 <![CDATA[H2O]]> 0 0 0 0 34 0 <![CDATA[C2H4]]> 51.9 0 0 3.4 0 0 <![CDATA[O2]]> 29.2 0 0 15.7 0 0 <![CDATA[CO2]]> 0 0 17.5 0 0 0 Ethylene oxide 0 0 0 0 3.2 0 Acetaldehyde 0 0 0 0 0 0 Ethylene glycol 0 100 0 0 0 0 Diethylene glycol 0 3.2 0 0 0 0 Triethylene glycol 0 0.2 0 0 0 0 total 81.1 103.4 17.6 19.2 37.2 2.4

[0069] The above is a description of a specific embodiment, but the present invention is not limited to the above embodiment and can be variously modified. The second gas return channel 42 can be connected to the first gas return channel 41. In this case, the oxygen generated by the anode 18 is mixed with the fourth mixture generated by the cathode 16, and after the carbon dioxide is separated in the carbon dioxide separation step 3, it is returned to the ethylene oxide production step 1.

[0070] As the electrolytic reduction device 10, various known electrolytic reduction devices can be used. For example, in the electrolytic reduction device 10, the cathode gas chamber 11 can be omitted, and the cathode 16 can be provided in the cathode electrolyte chamber 12. In this case, the carbon dioxide gas can be blown into the cathode electrolyte by bubbling near the cathode 16. In addition, the carbon dioxide gas can be dissolved in the cathode electrolyte.

[0071] In the carbon dioxide electrolytic reduction step 4, carbon dioxide discharged from another plant can be used as a part of the carbon dioxide to be electrolytically reduced. The production amount of ethylene and methane can be increased.

[0072] Reference numerals

[0073] 1: Ethylene oxide production steps

[0074] 2: Gas-liquid separation step

[0075] 3: Carbon dioxide separation step

[0076] 4: Electrolytic reduction step

[0077] 5: Carbon monoxide separation step

[0078] 6: Ethylene glycol generation steps

[0079] 10: Electrolytic reduction device

[0080] 11: Cathode gas chamber

[0081] 12: Catholyte chamber

[0082] 13: Anolyte chamber

[0083] 14: Electrolytic Cell

[0084] 16: Cathode

[0085] 17: Partition wall

[0086] 18: Anode

[0087] 19: DC power supply

[0088] 24: Entrance

[0089] 25: Export

[0090] 26: Gas circulation pathway

[0091] 27: Entrance

[0092] 28: Exit

[0093] 29: Catholyte circulation path

[0094] 31: Entrance

[0095] 32: Export

[0096] 33: Anolyte circulation path

[0097] 35: Cathode side gas-liquid separation device

[0098] 36: Anode side gas-liquid separation device

[0099] 37: Electrolyte concentration control device

[0100] 38: Electrolyte concentration control device

[0101] 40: Gas circulation flow regulating device

[0102] 41: First air return channel

[0103] 51: Sensor

[0104] 52: Flow control valve

[0105] 53: Flow control valve

[0106] 54: Flow control valve

Claims

1. A method for producing ethylene oxide, comprising: an ethylene oxide production step, wherein a raw material containing ethylene and oxygen is reacted in the presence of a diluent gas to obtain a first mixture containing ethylene oxide; a gas-liquid separation step, wherein the first mixture is separated into a second mixture and a third mixture, wherein the second mixture is a gas component containing ethylene, oxygen and carbon dioxide, and the third mixture is a liquid component containing ethylene oxide and water; a carbon dioxide separation step, wherein carbon dioxide is separated from the second mixture; and a carbon dioxide electrolytic reduction step, wherein the carbon dioxide separated from the second mixture is electrolytically reduced to obtain a fourth mixture containing ethylene, methane and unreacted carbon dioxide at the cathode, and oxygen at the anode, Wherein, in the carbon dioxide separation step, carbon dioxide is further separated from the fourth mixture, In the ethylene oxide production step, the second mixture and the fourth mixture from which carbon dioxide has been removed in the carbon dioxide separation step and the oxygen obtained in the carbon dioxide electrolytic reduction step are used as at least a part of a raw material and a diluent gas, and The fourth mixture is mixed into the second mixture prior to processing in the carbon dioxide separation step.

2. The method for producing ethylene oxide according to claim 1, wherein in the carbon dioxide electrolytic reduction step, the catalyst supported on the cathode is selected so that the selectivity of ethylene at the cathode is 30% or more.

3. The method for producing ethylene oxide according to claim 1, wherein an electrolytic reduction device is used in the carbon dioxide electrolytic reduction step, which comprises: a cathode gas chamber which is supplied with carbon dioxide in gaseous form; a catholyte chamber supplied with a catholyte; an anolyte chamber supplied with anolyte; a cathode serving as a gas diffusion electrode separating the cathode gas chamber and the catholyte chamber from each other; a partition wall having ion conductivity and partitioning the catholyte chamber and the anolyte chamber from each other; and an anode disposed in the anolyte chamber.

4. The method for producing ethylene oxide according to claim 1, further comprising a carbon monoxide removal step, wherein carbon monoxide is removed from the fourth mixture generated in the carbon dioxide electrolytic reduction step.

5. The method for producing ethylene oxide according to claim 4, wherein: In the carbon monoxide removal step, carbon monoxide is removed from the fourth mixture before carbon dioxide is removed in the carbon dioxide separation step.

6. The method for producing ethylene oxide according to claim 1, further comprising an ethylene glycol generating step, wherein ethylene glycol is generated from the ethylene oxide contained in the third mixture by a hydration method.

7. The method for producing ethylene oxide according to claim 1, wherein in the carbon dioxide electrolytic reduction step, carbon dioxide discharged from other factories is used as a part of the carbon dioxide to be electrolytically reduced.

8. The method for producing ethylene oxide according to claim 1, wherein In the carbon dioxide electrolytic reduction step, carbon dioxide is electrolytically reduced by using electricity generated from natural energy.

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