Method for producing hydrocarbon and system for producing hydrocarbon

Abstract

The present disclosure provides a means by which resource efficiency in hydrocarbon production can be improved. Disclosed is a method for producing hydrocarbons, wherein: a CO2 hydrate and an alkali metal ion concentrated aqueous solution are obtained from a CO2-containing gas and an alkali metal ion-containing aqueous solution; the CO2 hydrate is decomposed to obtain CO2 and water (a); the alkali metal ion concentrated aqueous solution is introduced into the anode chamber of an electrolytic cell provided with a diaphragm, water for recovery is introduced into the cathode chamber, and H2 and an alkali metal hydroxide aqueous solution are obtained by electrolysis; and the CO2 and the H2 are reacted to obtain a hydrocarbon and water (b).

Description

Hydrocarbon production method and hydrocarbon production system

[0001] The present invention relates to a method and system for producing hydrocarbons.

[0002] In recent years, efforts to achieve carbon neutrality have been accelerating, and carbon dioxide (CO ２ ) and hydrogen (H ２ Synthetic fuels (e-fuels) produced from carbon dioxide (CO) are attracting attention. ２ and H from renewable energy ２ It is said that carbon neutrality can be achieved by using these as raw materials. Synthetic fuels include methane and synthetic crude oil (gasoline, jet fuel, diesel, heavy oil, etc. can be obtained by refining synthetic crude oil), and research and development into the manufacturing processes for these is underway.

[0003] Japanese Patent Application Laid-Open Publication No. 2021-116294 discloses a system for effectively utilizing recovered carbon dioxide, which includes a carbon dioxide separation and capture facility that separates and captures carbon dioxide from a gas containing carbon dioxide, a renewable energy power generation facility, a water electrolysis facility that electrolyzes water using the electricity obtained from the renewable energy power generation facility to produce hydrogen, and a methanation facility having a methanation reactor that produces methane using carbon dioxide and hydrogen. The system further includes a hydrogen storage means for storing hydrogen produced by the water electrolysis facility and a carbon dioxide storage means for storing carbon dioxide captured by the carbon dioxide separation and capture facility. The hydrogen filling rate in the hydrogen storage means and the carbon dioxide filling rate in the carbon dioxide storage means are adjusted to fall within predetermined ranges, and the hydrogen and carbon dioxide filling rates are adjusted to be supplied to the methanation reactor when the hydrogen and carbon dioxide filling rates are equal to or greater than predetermined values. According to this document, the above configuration makes it possible to stabilize the flow rates of hydrogen and carbon dioxide supplied to the methanation facility.

[0004] In the synthetic fuel manufacturing process, the raw material CO ２ and H ２In the above document, the carbon dioxide separation and capture equipment includes a water vapor removal device and a CO ２ It describes the use of a liquefaction compressor in combination, and the use of an alkaline electrolytic cell or a polymer electrolyte membrane (PEM) electrolytic cell as the water electrolysis equipment.

[0005] However, the system described in the above document has a problem of low resource efficiency (low amounts of useful material and energy produced per amount of material and energy input).

[0006] Therefore, an object of the present invention is to provide a means for improving resource efficiency in the production of hydrocarbons.

[0007] The present inventors have conducted extensive research to solve the above problems. ２ The CO ion-containing gas and the alkali metal ion-containing aqueous solution are used as starting materials. ２ Hydrate formation and decomposition leads to CO ２ and obtaining an aqueous solution of concentrated alkali metal ions; and performing electrolysis using the aqueous solution of concentrated alkali metal ions to obtain H ２ and obtaining an aqueous alkali metal hydroxide solution; and ２ and the above H ２ to obtain hydrocarbons; and the inventors have found that the above-mentioned problems can be solved by reacting the above-mentioned compounds, thereby completing the present invention.

[0008] That is, in one aspect of the present invention, a method for producing hydrocarbons is ２ CO from the CO-containing gas and the alkali metal ion-containing aqueous solution ２ obtaining a CO hydrate and alkali metal ion enriched aqueous solution; ２ Decomposing hydrate to CO ２ and water (a); introducing the concentrated aqueous solution of alkali metal ions into the anode chamber of an electrolytic cell equipped with a diaphragm, introducing recovery water into the cathode chamber, and generating H by electrolysis. ２ and obtaining an aqueous alkali metal hydroxide solution; ２ and the above H ２ to obtain hydrocarbon and water (b).

[0009] Fig. 1 is a flow chart showing a hydrocarbon production method according to one embodiment of the present invention. Fig. 2 is a cross-sectional view schematically showing an electrolytic cell used in the electrolysis step (3) in the hydrocarbon production method according to one embodiment of the present invention.

[0010] <Method for Producing Hydrocarbons> One aspect of the present invention is a method for producing hydrocarbons, ２ CO from the CO-containing gas and the alkali metal ion-containing aqueous solution ２ obtaining a hydrate and an alkali metal ion-enriched aqueous solution (hereinafter also referred to as "hydrate production step (1)" or "step (1)"); ２ Decomposing hydrate to CO ２ and obtaining water (a) (hereinafter also referred to as "hydrate decomposition step (2)" or "step (2)"); introducing the concentrated aqueous solution of alkali metal ions into the anode chamber of an electrolytic cell equipped with a diaphragm, introducing recovery water into the cathode chamber, and generating H by electrolysis. ２ and obtaining an aqueous alkali metal hydroxide solution (hereinafter also referred to as "electrolysis step (3)" or "step (3)"); ２ and the above H ２ to obtain hydrocarbons and water (b) (hereinafter also referred to as "hydrocarbon synthesis step (4)" or "step (4)"). The hydrocarbon production method according to this embodiment makes it possible to improve resource efficiency in hydrocarbon production (increase the amount of useful materials and energy produced per input amount of materials and energy).

[0011] As described above, according to the technology described in JP 2021-116294 A, a carbon dioxide separation and capture system (a water vapor removal device and a CO ２ Carbon dioxide is separated from a gas containing carbon dioxide by a liquefaction compressor, and hydrogen is produced from water by a water electrolysis facility (an alkaline electrolytic cell or a polymer electrolyte membrane (PEM) electrolytic cell). ２ CO ２ , H２ and an aqueous alkali metal hydroxide solution are produced. More specifically, CO ２ CO from contained gas ２ At the same time, in step (1), the water in the alkali metal ion-containing aqueous solution is separated into CO ２ When forming the hydrate, the alkali metal ions are concentrated to obtain an alkali metal ion concentrated aqueous solution. ２ By using an aqueous solution of concentrated alkali metal ions in electrolysis, the solution resistance can be reduced, and the overvoltage can be reduced. ２ The production efficiency of alkali metal hydroxide can be improved. Furthermore, an alkali metal hydroxide aqueous solution is obtained in the cathode chamber by step (3). The alkali metal ions contained in the alkali metal hydroxide aqueous solution can be recovered as an alkali metal compound by subsequent treatment and reused as a raw material. In other words, the production method according to this embodiment can be said to be a technique that is superior in resource efficiency compared to conventional techniques in that an alkali metal hydroxide aqueous solution can also be obtained from an alkali metal ion-containing aqueous solution by steps (1) to (3).

[0012] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. In the description of the drawings, the same elements are designated by the same reference numerals, and duplicate explanations will be omitted. Furthermore, the dimensional proportions in the drawings are exaggerated for the convenience of explanation and may differ from the actual proportions.

[0013] 1 is a flowchart showing a hydrocarbon production method according to one embodiment of the present invention. As shown in FIG. 1, in the hydrocarbon production method of this embodiment, CO ２ A CO ion-containing gas and an alkali metal ion-containing aqueous solution are introduced as raw materials. ２ The CO hydrate and alkali metal ion-enriched aqueous solution are obtained. ２ The hydrate is introduced into the hydrate decomposition step (2) through a pipe 101, and CO ２On the other hand, the concentrated aqueous solution of alkali metal ions obtained in step (1) is decomposed into CO ２ CO dissolved in the concentrated aqueous solution of alkali metal ions introduced into the removal step (1a) (hereinafter also referred to as "step (1a)") ２ The CO obtained in step (1a) is removed. ２ The concentrated aqueous solution of alkali metal ions after the removal is introduced through a pipe 103 into a precipitated salt removal step (1b), where precipitated salts present in the concentrated aqueous solution of alkali metal ions are removed. In the subsequent electrolysis step (3), the concentrated aqueous solution of alkali metal ions after the removal of precipitated salts obtained in step (1b) is introduced through a pipe 104 into an anode chamber of an electrolytic cell equipped with a diaphragm, and recovery water is introduced into a cathode chamber. Then, H ２ and an aqueous alkali metal hydroxide solution are obtained. Then, in the hydrocarbon synthesis step (4), the CO obtained in the step (2) is ２ passes through the pipe 105 and is supplied to the H obtained in the above step (3). ２ is introduced through a pipe 106. Then, hydrocarbons and water (b) are obtained by a hydrocarbon synthesis reaction. The water (a) obtained in the step (2) may be passed through a pipe 107 and used as recovery water for the electrolysis step (3). Similarly, the water (b) obtained in the step (4) may be passed through a pipe 108 and used as recovery water for the electrolysis step (3). Each step of the hydrocarbon production method according to this embodiment will be described in detail below.

[0014] [Hydrate Production Step (1)] In step (1), CO ２ CO from the CO-containing gas and the alkali metal ion-containing aqueous solution ２ A concentrated aqueous solution of hydrate and alkali metal ions is obtained.

[0015] CO ２ The contained gas is carbon dioxide (CO ２ There are no particular limitations on the gas as long as it contains CO, but examples include exhaust gases emitted from power plants and factories, and the atmosphere. ２ Carbon dioxide (CO ２The concentration of the hydroxybenzoate is not particularly limited, and is, for example, 400 ppm by volume (0.04% by volume) or more and 100% by volume or less, preferably 0.1% by volume or more and 20% by volume or less, more preferably 1% by volume or more and 19% by volume or less, even more preferably 5% by volume or more and 18% by volume or less, and particularly preferably 10% by volume or more and 17% by volume or less.

[0016] The alkali metal ion-containing aqueous solution is not particularly limited as long as at least one alkali metal (e.g., lithium (Li), sodium (Na), potassium (K), rubidium (Rb), or cesium (Cs)) is present in the form of an ion in the aqueous solution. According to the hydrocarbon production method of this embodiment, not only hydrocarbons but also an alkali metal hydroxide aqueous solution is obtained as a product. From the alkali metal hydroxide aqueous solution, it is possible to recover an alkali metal compound by subsequent treatment. Considering the rarity and industrial usefulness of alkali metal compounds, the alkali metal ions contained in the alkali metal ion-containing aqueous solution preferably contain at least one of lithium ions, rubidium ions, and cesium ions, and preferably contain lithium ions. That is, according to one embodiment of the present invention, the alkali metal ion-containing aqueous solution contains lithium ions (is a lithium ion-containing aqueous solution).

[0017] The lithium ion-containing aqueous solution can be any water containing dissolved lithium ions, such as brine (e.g., seawater, salt lake water, geothermal brine, hot spring water, etc.), lithium ion-containing aqueous solutions obtained during the recycling process of lithium-containing products (e.g., lithium ion batteries (LiBs)), concentrated seawater that is a by-product of seawater desalination, and concentrated water that is a by-product of soda salt production. The following is an example of a method for obtaining a lithium ion-containing aqueous solution from LiBs. First, the LiBs are deactivated and crushed to remove the casing, resin, and current collector metal. The remaining black mass (concentrated slag containing nickel, manganese, cobalt, lithium, etc.) is brought into contact with water to dissolve the lithium in the water, thereby obtaining a lithium ion-containing aqueous solution. Since elements other than lithium, such as nickel, manganese, and cobalt, are insoluble in water, they are separately recovered by hydrometallurgy, in which the black mass obtained after dissolving lithium in water is dissolved in an acid solution to extract the metal ions.

[0018] The concentration of lithium ions contained in the lithium ion-containing aqueous solution is not particularly limited, but from the viewpoint of improving the efficiency of electrolysis in the step (3) described below, it is preferably 0.17 ppm by mass or more, more preferably 0.5 ppm by mass or more, even more preferably 1 ppm by mass or more and 1000 ppm by mass or less, and particularly preferably 5 ppm by mass or more and less than 100 ppm by mass.

[0019] In step (1), CO ２ By applying low temperature and high pressure conditions in the presence of a CO-containing gas and an alkali metal ion-containing aqueous solution, ２ Generate hydrate. ２ Hydrate is a water molecule cage structure containing CO ２ It is an ice-like solid substance with molecules trapped inside.

[0020] CO ２ The specific method for generating hydrate is not particularly limited, and may be ２ Any known method for producing hydrate can be used. For example, CO ２ and an aqueous solution containing alkali metal ions to prepare a mixed solution. Next, the mixed solution is subjected to low-temperature and high-pressure conditions to produce CO２ At this time, CO hydrate is generated in the mixed solution. ２ The low-temperature, high-pressure condition may be subjected to a low-temperature, high-pressure condition while continuing to supply CO ２ In the phase equilibrium diagram of a hydrate system, there are no particular limitations as long as the temperature and pressure are lower than the phase equilibrium conditions. ２ , gaseous CO ２ , CO ２ The quadruple point at which the four phases of hydrate can coexist is a temperature of 10.5°C and a pressure of 4.46 MPa (44.0 atm).

[0021] In addition, CO under higher temperature and lower pressure conditions (mild conditions) ２ Since hydrate generation is possible, CO ２ When producing a hydrate, a help guest substance such as cyclopentane, cyclopentanone, fluorocyclopentane, tetrahydrofuran, or methylcyclohexane may be present in the system.

[0022] Step (1) produces sherbet-like CO ２ A mixture of hydrate and an aqueous solution of concentrated alkali metal ions is produced. ２ These can be easily separated by removing the hydrate or by withdrawing the concentrated aqueous alkali metal ion solution from the bottom of the mixture.

[0023] [CO ２ Removal step (1a)] The concentrated aqueous solution of alkali metal ions obtained in the step (1) is ２ After removing the dissolved CO, the resulting solution is preferably subjected to the electrolysis step (3) described below. ２ By removing CO to the anode in the electrolysis step (3), ２This can suppress the adhesion of alkaline earth metal ions and the deposition of carbonates on the anode side, thereby improving the efficiency of electrolysis. In particular, when the alkali metal ion-containing aqueous solution that is the raw material in step (1) contains alkaline earth metal ions, alkaline earth metal carbonates are likely to be produced in the electrolysis step (3), so it is effective to perform step (1a). That is, in a hydrocarbon production method according to one embodiment of the present invention, CO is extracted from the alkali metal ion-enriched aqueous solution before the alkali metal ion-enriched aqueous solution is introduced into the anode chamber. ２

[0033] The method further comprises removing

[0024] CO from concentrated aqueous solutions of alkali metal ions ２ The method for removing CO is not particularly limited, and known methods such as reducing pressure, increasing temperature, ultrasonic treatment, and bubbling with air or an inert gas can be appropriately adopted. Two or more of the above methods may be combined. For example, a concentrated aqueous solution of alkali metal ions is heated under pressure of more than 2 MPa to remove CO. ２ After gradually removing CO ２ The pressure may be reduced to 0.1 MPa or less.

[0025] [Precipitated Salt Removal Step (1b)] The alkali metal ion-enriched aqueous solution obtained in the above step (1) is preferably subjected to the electrolysis step (3) described below after removing precipitated salts (e.g., carbonates formed in the step (1)). Removal of precipitated salts can improve the efficiency of electrolysis in the electrolysis step (3). In particular, when the alkali metal ion-containing aqueous solution used as the raw material in the step (1) contains alkaline earth metal ions, alkaline earth metal carbonates are likely to be formed in the step (1), so it is effective to perform the step (1b). That is, a hydrocarbon production method according to one embodiment of the present invention further comprises removing precipitated salts from the alkali metal ion-enriched aqueous solution before introducing the alkali metal ion-enriched aqueous solution into the anode chamber.

[0026] The method for removing precipitated salts from the concentrated aqueous solution of alkali metal ions is not particularly limited, and known methods such as filtration, centrifugation, etc. may be appropriately employed. Furthermore, the removal of precipitated salts is preferably carried out at a low temperature of −10° C. or lower and under a pressure of more than 2 MPa in order to remove as much precipitated salt as possible while preventing the water from freezing.

[0027] In the hydrocarbon production method shown in FIG. 1 , the concentrated alkali metal ion aqueous solution obtained in step (1) is sequentially subjected to step (1a) and step (1b) before being subjected to step (3). Performing step (1a) and step (1b) in this order can further improve the efficiency of electrolysis in the electrolysis step (3). However, the embodiment is not limited to the one shown in FIG. 1 . The concentrated alkali metal ion aqueous solution obtained in step (1) may be immediately subjected to step (3); the concentrated alkali metal ion aqueous solution obtained in step (1) may be treated in step (1a) and then immediately subjected to step (3); the concentrated alkali metal ion aqueous solution obtained in step (1) may be treated in step (1b) and then immediately subjected to step (3); or the concentrated alkali metal ion aqueous solution obtained in step (1) may be treated in step (1b) and then immediately subjected to step (3).

[0028] [Hydrate Decomposition Step (2)] In step (2), the CO obtained in step (1) is decomposed. ２ Decomposing hydrate to CO ２ and water (a).

[0029] CO ２ The specific means for decomposing the hydrate is not particularly limited, and may be CO ２ By setting the temperature and pressure conditions higher than the hydrate phase equilibrium conditions, CO ２ Hydrates can be easily decomposed.

[0030] The water (a) obtained in the step (2) may be used as recovery water for the electrolysis step (3) described below.

[0031] [Electrolysis Step (3)] In step (3), the concentrated aqueous solution of alkali metal ions obtained in step (1) is introduced into the anode chamber of an electrolytic cell equipped with a diaphragm, and recovery water is introduced into the cathode chamber. ２ and an aqueous alkali metal hydroxide solution is obtained.

[0032] FIG. 2 is a cross-sectional view schematically illustrating an electrolytic cell used in the electrolysis step (3) in a method for producing hydrocarbons according to one embodiment of the present invention. As shown in FIG. 2, the electrolytic cell 20 includes a cation exchange membrane (preferably a lithium ion conductor) 21, which is a diaphragm. A cathode 23 is disposed on one side of the cation exchange membrane 21, and an anode 25 is disposed on the other side. The cathode 23 and the anode 25 are connected to an external power source. In the electrolytic cell 20, recovery water 31 is poured into the cathode chamber 27 on the cathode 23 side, and an alkali metal ion concentrated aqueous solution (e.g., lithium ion concentrated aqueous solution) 33 is poured into the anode chamber 29 on the anode 25 side. When a voltage is applied from the external power source, electrons are supplied to the cathode 23, and the water (H ２ O) is electrolyzed to produce hydrogen (H ２ ) and hydroxide ions (OH － ) is produced. The reaction on the cathode side is ２ O + 2e － →H ２ +2OH － In addition, alkali metal ions (preferably lithium ions) 35 present in the alkali metal ion concentrated aqueous solution 33 pass through the cation exchange membrane 21 and move to the recovered water 31. As a result, on the cathode 23 side, H ２ and an aqueous solution of alkali metal hydroxide (preferably an aqueous solution of lithium hydroxide). On the other hand, the reaction on the anode 25 side varies depending on the anions contained in the aqueous solution of concentrated alkali metal ions. When the aqueous solution of concentrated alkali metal ions is neutral to alkaline, hydroxide ions (OH － ) emits electrons to the anode 25, and oxygen (O ２ In this case, the reaction on the anode side is 4OH － →O ２ +2H ２ O+4e －Step (3) will be described in detail below.

[0033] The electrolytic cell used in step (3) is equipped with a diaphragm. The presence of the diaphragm makes it possible to obtain an aqueous alkali metal hydroxide solution on the cathode side. The diaphragm is not particularly limited, and any diaphragm used in diaphragm electrolysis can be used without limitation. From the viewpoint of improving the recovery efficiency of the aqueous hydroxide solution, the diaphragm is preferably a cation exchange membrane. Furthermore, from the viewpoint of recovering a highly pure aqueous lithium hydroxide solution, the diaphragm is more preferably a membrane that selectively allows lithium ions to pass through (also referred to as a "lithium ion conductor").

[0034] As the lithium ion conductor, for example, a lithium ion conductor represented by Formula 1: (Li ｘ , La ｙ ) TiO ｚ (where x=3a-2b, y=2 / 3-a, z=3-b, 0<a≦1 / 6, 0≦b≦0.06, x>0) or lithium lanthanum titanate (LLTO) having a composition of formula 2: Li １＋ｘ＋ｙ Al ｘ (Ti, Ge) ２－ｘ Si ｙ P ３－ｙ O １２ (where 0≦x≦0.6, 0≦y≦0.6) Li-substituted NASICON (Na Super Ionic Conductor) crystals having the composition are known. ０．２９ La ０．５７ TiO ３ LLTO having the composition (in the above formula 1, a≈0.1, b≈0) is preferred.

[0035] The electrodes (cathode and anode) used in step (3) are also not particularly limited as long as they are made of a highly conductive material (e.g., a metal, a carbon material, a conductive polymer, etc.). From the viewpoint of improving the efficiency of electrolysis, the electrodes are preferably porous (e.g., a mesh, a felt, etc.). In particular, by using an electrode made of a porous material as the cathode and arranging the cathode so that it is in contact with the surface of a cation exchange membrane (preferably a lithium ion conductor) on the cathode chamber side, the ion migration rate can be significantly improved, and therefore the efficiency of electrolysis can be further improved. That is, in a method for producing hydrocarbons according to one embodiment of the present invention, the cathode in the electrolytic cell is made of a porous material, and the cation exchange membrane (preferably a lithium ion conductor) and the cathode are in contact with each other.

[0036] In step (3), the concentrated aqueous solution of alkali metal ions is introduced into the anode chamber of the electrolytic cell, recovery water is introduced into the cathode chamber, and a voltage is applied between the anode and cathode to perform electrolysis. Here, from the viewpoint of obtaining a highly pure aqueous solution of alkali metal hydroxide, the recovery water is preferably water containing little or no impurities (pure water (resistivity of about 1 to 10 MΩ cm), preferably ultrapure water (resistivity of more than about 10 MΩ cm)). The pure water (preferably ultrapure water) may be RO water, deionized water, or distilled water. Furthermore, the pure water (preferably ultrapure water) used as the recovery water preferably contains water (a) obtained in the hydrate decomposition step (2) described above or water (b) obtained in the hydrocarbon synthesis step (4) described below. This eliminates the need to separately procure recovery water, thereby further improving resource efficiency. The water (a) or the water (b) may be reused as recovery water in its original form, or may be purified as necessary to remove impurities (particularly divalent metal ions such as magnesium ions and calcium ions) before being reused as recovery water.

[0037] One of the features of the hydrocarbon production method according to this embodiment is that the concentrated alkali metal aqueous solution obtained in the step (1) (and optional steps (1a) and / or (1b)) is used in the step (3). This configuration, using an aqueous solution with a high ion concentration, makes it possible to reduce the solution resistance when a voltage is applied. This reduces the overvoltage when the same current is applied, thereby improving the efficiency of electrolysis. According to a preferred embodiment, the alkali metal ion-containing aqueous solution used as the raw material in the step (1) contains lithium ions (it is a lithium ion-containing aqueous solution). In this case, a concentrated lithium ion aqueous solution is obtained in the step (1), and this is introduced into the anode chamber of the electrolytic cell in the step (3). The lithium ion concentration in the concentrated lithium ion aqueous solution in this case is preferably 100 ppm by mass or more, more preferably 100 ppm by mass to 6% by mass, even more preferably 200 ppm by mass to 4% by mass, and particularly preferably 400 ppm by mass to 1% by mass. By carrying out electrolysis using a lithium ion concentrated aqueous solution having a concentration within the above range, it is possible to further improve the efficiency of the electrolysis.

[0038] Furthermore, step (3) produces an aqueous alkali metal hydroxide solution in the cathode chamber. The alkali metal contained in the aqueous alkali metal hydroxide solution can be recovered as an alkali metal compound through subsequent treatment and reused as a raw material. In particular, by using a membrane (lithium ion conductor) that selectively allows lithium ions to pass through as the diaphragm, a high-purity aqueous lithium hydroxide solution can be obtained from the cathode chamber. The aqueous lithium hydroxide solution can be recovered as a lithium compound through subsequent treatment and reused as a raw material for batteries, etc. That is, in a hydrocarbon production method according to one embodiment of the present invention, the aqueous alkali metal hydroxide solution is an aqueous lithium hydroxide solution.

[0039] [Hydrocarbon synthesis step (4)] In step (4), the CO obtained in step (2) is ２ and H obtained in the above step (3). ２are reacted to obtain a hydrocarbon and water (b).

[0040] In the hydrocarbon production method according to the present embodiment, the method for obtaining hydrocarbons is not particularly limited, and known methods can be appropriately adopted. ２ +4H ２ →CH ４ +2H ２ O) is known (for example, see JP 2021-116294 A, JP 502551 A, and JP 2023-103557 A).

[0041] Another example of a method for obtaining hydrocarbons is the reverse water gas shift reaction (CO ２ +H ２ →CO+H ２ O) to obtain carbon monoxide, followed by the Fischer-Tropsch process ((2n+1)H ２ +nCO→C ｎ H ２ｎ＋２ +nH ２ Examples of methods include synthesizing hydrocarbons by the use of olefins.

[0042] <Hydrocarbon Production System> According to another aspect of the present invention, there is provided a hydrocarbon production system that is suitably used in the above-described hydrocarbon production method. ２ CO from the CO-containing gas and the alkali metal ion-containing aqueous solution ２ CO to produce hydrate and alkali metal ion enriched aqueous solutions ２ a hydrate production apparatus; and ２ Decompose the hydrate to CO ２ and water (a), ２ a hydrate decomposition device equipped with a diaphragm, which is configured to generate H by electrolysis using the concentrated aqueous solution of alkali metal ions; ２ and an electrolytic cell for producing an aqueous alkali metal hydroxide solution; ２ and the above H ２and a hydrocarbon production apparatus that reacts (a) and (b) to produce hydrocarbons and water. The hydrocarbon production system according to this embodiment makes it possible to improve resource efficiency in the production of hydrocarbons.

[0043] The hydrocarbon production system of this embodiment is ２ Between the hydrate decomposition device and the electrolytic cell, CO is generated from the concentrated aqueous solution of alkali metal ions. ２ CO ２ The system may further include a removal device and / or a precipitated salt removal device for removing precipitated salts from the concentrated aqueous alkali metal ion solution.

[0044] The following items are also included in the scope of the present invention: Item 1: A method for producing hydrocarbons, comprising: ２ CO from the CO-containing gas and the alkali metal ion-containing aqueous solution ２ obtaining a concentrated aqueous solution of hydrate and alkali metal ions; ２ Decomposing hydrate to CO ２ and water (a), and introducing the concentrated aqueous solution of alkali metal ions into the anode chamber of an electrolytic cell equipped with a diaphragm, and introducing recovery water into the cathode chamber, and generating H by electrolysis. ２ and obtaining an aqueous alkali metal hydroxide solution; ２ and the above H ２ and (b) reacting the above-mentioned aqueous solution of concentrated alkali metal ions to obtain hydrocarbons and water; Item 2: reacting the above-mentioned aqueous solution of concentrated alkali metal ions with CO 3 to obtain hydrocarbons and water (b) before introducing the above-mentioned aqueous solution of concentrated alkali metal ions into the anode chamber. ２ Item 3: The method for producing hydrocarbons according to Item 1 or 2, further comprising removing precipitated salts from the alkali metal ion concentrated aqueous solution before introducing the alkali metal ion concentrated aqueous solution into the anode chamber; Item 4: The method for producing hydrocarbons according to Item 1 or 2, further comprising removing CO from the alkali metal ion concentrated aqueous solution before introducing the alkali metal ion concentrated aqueous solution into the anode chamber. ２and removing precipitated salts from the concentrated aqueous alkali metal ion solution, in this order; Item 5: The method for producing hydrocarbons according to any one of Items 1 to 4, wherein the diaphragm is a cation exchange membrane; Item 6: The method for producing hydrocarbons according to Item 5, wherein the diaphragm is a membrane that selectively permeates lithium ions (lithium ion conductor); Item 7: The method for producing hydrocarbons according to Item 5, wherein the cathode in the electrolytic cell is made of a porous material, and the cation exchange membrane (preferably the membrane that selectively permeates lithium ions (lithium ion conductor)) and the cathode are in contact with each other; Item 8: The method for producing hydrocarbons according to any one of Items 1 to 7, wherein the recovery water is pure water; Item 9: The method for producing hydrocarbons according to Item 8, wherein the pure water contains the water (a) or the water (b); Item 10: The method for producing hydrocarbons according to any one of Items 1 to 9, wherein the alkali metal ion-containing aqueous solution contains lithium ions, and the concentration of lithium ions in the alkali metal ion-enriched aqueous solution is 100 ppm by mass or more (more preferably 100 ppm by mass or more and 6% by mass or less, even more preferably 200 ppm by mass or more and 4% by mass or less, and particularly preferably 400 ppm by mass or more and 1% by mass or less); Item 11: The method for producing hydrocarbons according to Item 6, wherein the alkali metal hydroxide aqueous solution is a lithium hydroxide aqueous solution; Item 12: A hydrocarbon production system, comprising: ２ CO from the CO-containing gas and the alkali metal ion-containing aqueous solution ２ CO to produce hydrate and alkali metal ion enriched aqueous solutions ２ a hydrate production apparatus; and ２ Decompose the hydrate to CO ２ and water (a), ２ The device is equipped with a hydrate decomposition device and a diaphragm, and generates H by electrolysis using the concentrated aqueous solution of alkali metal ions. ２ and an electrolytic cell for producing an aqueous alkali metal hydroxide solution; ２ and the above H ２ and a hydrocarbon production apparatus that reacts the above CO to produce hydrocarbons and water (b).２ Between the hydrate decomposition device and the electrolytic cell, CO is generated from the concentrated aqueous solution of alkali metal ions. ２ CO ２ The hydrocarbon production system further comprises a removal device and / or a precipitated salt removal device for removing precipitated salts from the concentrated aqueous alkali metal ion solution.

[0045] 20 Electrolytic cell, 21 Cation exchange membrane, 23 Cathode, 25 Anode, 27 Cathode chamber, 29 Anode chamber, 31 Recovery water, 33 Concentrated aqueous solution of alkali metal ions, 35 Alkali metal ions, 101, 102, 103, 104, 105, 106, 107, 108 Piping.

Claims

1. A method for producing hydrocarbons, comprising: ２ CO from the CO-containing gas and the alkali metal ion-containing aqueous solution ２ obtaining a concentrated aqueous solution of hydrate and alkali metal ions; ２ Decomposing hydrate to CO ２ and water (a); introducing the concentrated aqueous solution of alkali metal ions into an anode chamber of an electrolytic cell equipped with a diaphragm, introducing recovery water into a cathode chamber, and generating H by electrolysis. ２ and obtaining an aqueous alkali metal hydroxide solution; ２ and the H ２ to obtain hydrocarbons and water (b).

2. Before introducing the concentrated aqueous solution of alkali metal ions into the anode chamber, CO ２ The method of claim 1 further comprising removing 3. The method for producing hydrocarbons according to claim 1, further comprising removing precipitated salts from the aqueous alkali metal ion-enriched solution before introducing the aqueous alkali metal ion-enriched solution into the anode chamber.

4. The method for producing hydrocarbons according to claim 1, wherein the membrane is a cation exchange membrane.

5. The method for producing hydrocarbons according to claim 4, wherein the diaphragm is a membrane that selectively allows lithium ions to pass therethrough.

6. The method for producing hydrocarbons according to claim 4, wherein the cathode in the electrolytic cell is made of a porous material, and the cation exchange membrane and the cathode are in contact with each other.

7. The method for producing hydrocarbons according to claim 1, wherein the recovered water is pure water.

8. The method for producing hydrocarbons according to claim 7, wherein the pure water includes the water (a) or the water (b).

9. The method for producing hydrocarbons according to claim 1, wherein the alkali metal ion-containing aqueous solution contains lithium ions, and the concentration of lithium ions in the alkali metal ion-enriched aqueous solution is 100 mass ppm or more.

10. The method for producing hydrocarbons according to claim 5, wherein the aqueous alkali metal hydroxide solution is an aqueous lithium hydroxide solution.

11. A hydrocarbon production system comprising: ２ CO from the CO-containing gas and the alkali metal ion-containing aqueous solution ２ CO to produce hydrate and alkali metal ion enriched aqueous solutions ２ a hydrate production apparatus; ２ Decompose the hydrate to CO ２ and water (a), ２ a hydrate decomposition device, which is provided with a diaphragm, and which generates H by electrolysis using the concentrated aqueous solution of alkali metal ions; ２ and an electrolytic cell for producing an aqueous alkali metal hydroxide solution; ２ and the H ２ and a hydrocarbon production apparatus that reacts the above to produce hydrocarbons and water (b).

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