Hydrogencarbonate production method and organic compound production method

Abstract

The purpose of the present invention is to provide a hydrogencarbonate production method capable of efficiently producing a high-purity hydrogencarbonate. The hydrogencarbonate production method of the present disclosure involves a step for generating a hydrogencarbonate by bringing carbon dioxide and a solution containing a base into contact with each other in a gas-liquid contactor while supplying carbon dioxide and the solution containing the base to the gas-liquid contactor. The flow rate of carbon dioxide supplied to the gas-liquid contactor is 30 L / min or more, and a ratio of said flow rate of carbon dioxide to a flow rate of the solution containing the base supplied to the gas-liquid contactor is 1.00-4.00.

Description

Method for producing hydrogen carbonate, and method for producing organic compound

[0001] The present invention relates to a method for producing hydrogen carbonate and a method for producing an organic compound.

[0002] In recent years, global warming caused by the increase in greenhouse gases has been one of the important issues. Carbon dioxide is a greenhouse gas that has a large impact on global warming. Carbon dioxide is a combustion product of fossil fuels, and is abundantly contained in exhaust gas discharged from thermal power plants, cement factories, ironworks, and the like. Therefore, various techniques for separating or recovering carbon dioxide contained in such exhaust gas have been proposed. For example, Patent Document 1 discloses a method of recovering carbon dioxide as an insoluble compound (e.g., sodium carbonate) which is a reaction product of an absorbent and carbon dioxide by causing an alkaline absorbent (e.g., aqueous sodium carbonate solution) to absorb carbon dioxide contained in exhaust gas.

[0003] Japanese Unexamined Patent Application Publication No. 2005-8478

[0004] In conventional methods using exhaust gas, even if carbonates such as sodium carbonate are produced, hydrogen carbonates such as sodium hydrogen carbonate may not be produced. Even when hydrogen carbonate is produced, its purity is generally low. Further, when exhaust gas is used, the amount of carbon dioxide contained in the exhaust gas fluctuates, so the production efficiency of hydrogen carbonate decreases depending on the flow rate of carbon dioxide.

[0005] Accordingly, an object of the present invention is to provide a method for producing hydrogen carbonate that can efficiently produce high-purity hydrogen carbonate.

[0006] The present invention provides a method for producing hydrogen carbonate, comprising: a step of producing hydrogen carbonate by bringing a solution containing a base into contact with carbon dioxide in a gas-liquid contactor while supplying the solution containing the base and carbon dioxide to the gas-liquid contactor, wherein a flow rate at which the carbon dioxide is supplied to the gas-liquid contactor is 30 L / min or more, and a ratio of the flow rate of the carbon dioxide to a flow rate at which the solution is supplied to the gas-liquid contactor is 1.00 or more and 4.00 or less.

[0007] According to the present invention, a method for producing bicarbonate that can efficiently produce high-purity bicarbonate is available.

[0008] This is a schematic diagram showing an example of a manufacturing apparatus suitable for the method of producing bicarbonate according to this embodiment. This is a schematic diagram showing a modified example of a manufacturing apparatus suitable for the method of producing bicarbonate according to this embodiment.

[0009] A manufacturing method according to a first aspect of the present invention includes the step of producing a bicarbonate by supplying a solution containing a base and carbon dioxide to a gas-liquid contactor and bringing the solution and carbon dioxide into contact in the gas-liquid contactor, wherein the flow rate of carbon dioxide supplied to the gas-liquid contactor is 30 L / min or more, and the ratio of the flow rate of carbon dioxide to the flow rate of the solution supplied to the gas-liquid contactor is 1.00 or more and 4.00 or less.

[0010] In a second embodiment of the present invention, for example, in the manufacturing method according to the first embodiment, the gas-liquid contactor is a tubular reactor.

[0011] In a third embodiment of the present invention, for example, in the manufacturing method according to the first or second embodiment, the base includes an alkali metal element.

[0012] In a fourth aspect of the present invention, for example, in the manufacturing method according to any one of the first to third aspects, the concentration of the base in the solution is 1 mol / L or more.

[0013] In a fifth embodiment of the present invention, for example, in a manufacturing method according to any one of the first to fourth embodiments, the supply of carbon dioxide to the gas-liquid contactor is performed by supplying a gas containing carbon dioxide to the gas-liquid contactor.

[0014] In a sixth aspect of the present invention, for example, in the manufacturing method according to the fifth aspect, the concentration of carbon dioxide in the gas is 30% by volume or more and 100% by volume or less under standard conditions.

[0015] In a seventh aspect of the present invention, for example, a manufacturing method according to any one of the first to sixth aspects includes circulating the solution by returning at least a portion of the solution discharged from the gas-liquid contactor back to the gas-liquid contactor.

[0016] A method for producing an organic compound according to the eighth aspect of the present invention includes a step of producing an organic compound using a bicarbonate produced by any one of the production methods according to the first to seventh aspects.

[0017] The details of the present invention will be described below, but the following description is not intended to limit the present invention to any particular embodiment.

[0018] [Method for producing bicarbonate] The method for producing bicarbonate according to this embodiment includes a production step in which a solution containing a base (hereinafter sometimes referred to as a basic solution) and carbon dioxide are supplied to a gas-liquid contactor and brought into contact in the gas-liquid contactor to produce bicarbonate.

[0019] In the manufacturing method of this embodiment, the flow rate of carbon dioxide supplied to the gas-liquid contactor is 30 L / min or more, and the ratio of the flow rate of carbon dioxide supplied to the gas-liquid contactor (L / min) to the flow rate of basic solution supplied to the gas-liquid contactor (L / min) is 1.00 or more and 4.00 or less. Hereinafter, the ratio of the flow rate of carbon dioxide supplied to the gas-liquid contactor to the flow rate of basic solution supplied to the gas-liquid contactor may be referred to as the "CO2 / base flow rate ratio".

[0020] Bicarbonates can be used as reaction raw materials for organic compounds such as formate salts, and can also be used as raw materials for pharmaceuticals such as antacids. Furthermore, bicarbonates have a higher molecular weight of carbon dioxide relative to metal cations compared to carbonates, making them suitable as carbon dioxide storage materials. The carbon dioxide obtained by the decomposition of bicarbonates can be used as a reaction raw material for organic compounds such as hydrocarbons. The inventors have found that high purity of bicarbonates is desirable for these applications. For example, high-purity bicarbonates allow for faster reaction when used as a reaction raw material. In addition, more carbon dioxide can be recovered from high-purity bicarbonates.

[0021] The reaction in the production process usually proceeds in two steps, as shown in equations (1) and (2) below, ultimately producing bicarbonate. Equations (1) and (2) below are examples when the base is potassium hydroxide. CO2 + 2KOH → K2CO3 + H2O ...Equation (1) CO2 + K2CO3 + H2O → 2KHCO3 ...Equation (2)

[0022] If the carbon dioxide flow rate is insufficient, and / or if the CO2 / base flow rate ratio is not appropriate, the reaction may not proceed to equation (2) above, but may stop at equation (1), resulting in no bicarbonate being produced. Furthermore, even if the reaction proceeds to equation (2), the purity of the produced bicarbonate may be low. It is conceivable to lower the base concentration of the basic solution to increase the purity of the produced bicarbonate, but in such cases, carbon dioxide loss increases, and the conversion rate from the input carbon dioxide to bicarbonate (carbon dioxide recovery rate) decreases.

[0023] In this embodiment, the manufacturing method, by ensuring that the carbon dioxide and basic solution meet the above flow rates during gas-liquid contact of carbon dioxide and a basic solution, can increase the purity of the produced bicarbonate and accelerate the rate of bicarbonate production. Therefore, this embodiment can efficiently produce high-purity bicarbonate.

[0024] High purity means, for example, that the purity of the bicarbonate is 80% or higher. Therefore, the purity of the bicarbonate produced by the manufacturing method of this embodiment is, for example, 80% or higher. Preferably, the purity of the bicarbonate produced by the manufacturing method of this embodiment is 90% or higher, more preferably 95% or higher, and even more preferably 97% or higher. The upper limit of the purity of the bicarbonate is not particularly limited, and is, for example, 100%. In this specification, "purity of bicarbonate" means the ratio of the amount of substance (mol) of bicarbonate to the total amount (mol) of the amount of substance of bicarbonate and the amount of substance of carbonate produced in the production process.

[0025] Typically, a gas G containing carbon dioxide and a basic solution are supplied to a gas-liquid contactor, and a bicarbonate can be produced by bringing the carbon dioxide and basic solution into gas-liquid contact. The manufacturing method of this embodiment may include a step of bringing the gas G and basic solution into gas-liquid contact to absorb the carbon dioxide into the basic solution.

[0026] The gas-liquid contactor is not limited in shape or other respects, as long as it can bring carbon dioxide and a basic solution into contact. The gas-liquid contactor is, for example, a through-type or power-driven mixing mixer. A through-type mixing mixer is, for example, a tubular reactor (plug flow reactor), preferably a static mixer as described later. An example of a power-driven mixing mixer is a stirrer with power-driven blades.

[0027] The concentration of carbon dioxide in gas G is preferably 30% by volume or more and 100% by volume or less under standard conditions, more preferably 40% by volume or more and 100% by volume or less. In this specification, "standard conditions" means a temperature of 0°C and a pressure of 1 atmosphere (101 kPa). Gas G may be a mixed gas of carbon dioxide and other gases, and the concentration of carbon dioxide in the mixed gas may be 90% by volume or less, 80% by volume or less, 70% by volume or less, or 60% by volume or less under standard conditions. In the manufacturing method of this embodiment, for example, when a mixed gas with a carbon dioxide concentration of 50% by volume is used as gas G, the flow rate of supplying gas G becomes 30 L / min or more by setting the flow rate of supplying gas G to 60 L / min or more.

[0028] Gas G includes combustion gases produced by the combustion of fuel. In this specification, "fuel" is a material that generates energy such as heat and light when burned, and is a concept that includes not only fossil fuels such as petroleum, coal, and natural gas, but also biofuels other than fossil fuels, such as fuels made from forest waste, agricultural waste, and livestock waste. Gas G may be exhaust gas or gas derived from exhaust gas emitted from thermal power plants, cement plants, steel mills, etc. Gas G may be concentrated exhaust gas or gas derived from exhaust gas.

[0029] The flow rate of carbon dioxide supplied to the gas-liquid contactor may be 35 L / min or more, or 40 L / min or more. The upper limit of the carbon dioxide flow rate is not particularly limited, but may be, for example, 1000 L / min or less, or 500 L / min or less. In this specification, the carbon dioxide flow rate is an actual measured value.

[0030] The supply pressure of carbon dioxide to the gas-liquid contactor is preferably 0.1 MPa or higher, and more preferably 0.3 MPa or higher and 5.0 MPa or lower.

[0031] The temperature of the carbon dioxide supplied to the gas-liquid contactor may be between 0°C and 100°C.

[0032] There are no particular restrictions on the solvent of the basic solution used in the production process, but it is preferable that it contains water, and more preferably water.

[0033] The base used in the basic solution preferably contains an alkali metal element. The base is not particularly limited as long as it can react with carbon dioxide to produce a carbonate and then a bicarbonate, but it is preferably a hydroxide. Examples include lithium bicarbonate, sodium bicarbonate, potassium bicarbonate, cesium bicarbonate, potassium hydroxide, sodium hydroxide, diazabicycloundecene, and triethylamine. Among the above, it is preferable that the base is a hydroxide containing an alkali metal element, more preferably potassium hydroxide and sodium hydroxide, and even more preferably potassium hydroxide.

[0034] The concentration of the base in the basic solution is not particularly limited, as long as it can produce carbonate and subsequently bicarbonate. From the viewpoint of ensuring the amount of bicarbonate produced, the concentration of the base is preferably 0.1 mol or more, more preferably 0.5 mol or more, even more preferably 1 mol or more, and particularly preferably 2.5 mol or more, per liter of solvent. Also, from the viewpoint of reaction efficiency, the concentration is preferably 30 mol or less, more preferably 20 mol or less, and even more preferably 15 mol or less, per liter of solvent. However, if the concentration exceeds the solubility of the solvent, the solution will be suspended.

[0035] The flow rate of the basic solution supplied to the gas-liquid contactor can be appropriately changed in relation to the flow rate of carbon dioxide, and is 7.5 L / min or more, preferably 10 L / min or more, and more preferably 15 L / min or more. The upper limit of the flow rate of the basic solution is not particularly limited as long as the CO2 / base flow rate ratio satisfies the above range, but may be, for example, 500 L / min or less, or 250 L / min or less.

[0036] The CO2 / base flow rate ratio is preferably 1.10 or higher, more preferably 1.20 or higher, even more preferably 1.30 or higher, and particularly preferably 1.33 or higher, from the viewpoint of the purity of the bicarbonate and the reaction efficiency. The CO2 / base flow rate ratio may also be 1.00 or higher and less than 4.00, 1.10 or higher and 3.90 or lower, 1.20 or higher and 3.80 or lower, and even 1.33 or higher and 3.70 or lower.

[0037] In the production process, the reaction temperature in the reaction between carbon dioxide and a base to produce carbonate and subsequently bicarbonate is not particularly limited, but it is preferably 0°C or higher and preferably 100°C or lower, as carbon dioxide is dissolved in a basic solvent (typically an aqueous solvent).

[0038] Carbonates and bicarbonates produced by the reaction of carbon dioxide with a base can be used, for example, as reaction raw materials to be reacted with hydrogen for the synthesis of organic compounds.

[0039] The method for producing bicarbonate in this embodiment preferably includes circulating the basic solution by returning at least a portion of the basic solution discharged from the gas-liquid contactor to the gas-liquid contactor. In other words, the method for producing bicarbonate in this embodiment is preferably a circulating method. With such a configuration, high-purity bicarbonate can be produced efficiently. The basic solution discharged from the gas-liquid contactor is an absorbent liquid which is a gas-liquid two-phase flow obtained by gas-liquid contact between carbon dioxide and the basic solution, or a solution obtained by separating and removing the gas from the absorbent liquid. The above solution typically contains bicarbonate. In other words, the basic solution discharged from the gas-liquid contactor is typically a reaction liquid containing reaction products.

[0040] The manufacturing method of this embodiment will be further explained below using a schematic diagram showing an example of a manufacturing apparatus.

[0041] [Bicarbonate Production Apparatus] Figure 1 is a schematic diagram showing an example of a production apparatus suitable for the production method according to this embodiment. The production apparatus 100 according to this embodiment is equipped with a gas-liquid contactor 1. The gas-liquid contactor 1 brings carbon dioxide and a basic solution into gas-liquid contact to produce an absorbent liquid A1 which is a two-phase gas-liquid flow. In the absorbent liquid, carbonate is first produced, and then bicarbonate is produced by the reaction of carbonate with carbon dioxide. In other words, the absorbent liquid is a reaction solution for bicarbonate production.

[0042] A gas containing carbon dioxide G is supplied to the gas-liquid contactor 1 through flow paths L1 and L2. A basic solution tank 2 is connected to flow path L2 via flow path L4. The basic solution tank 2 is supplied with basic solution L B A flow path L6 for introducing the solution may also be connected. The basic solution discharged from the basic solution tank 2 into flow path L2 is pumped by the pump 3 and introduced into the gas-liquid contactor 1 together with the gas G.

[0043] The gas-liquid contactor 1 sufficiently disperses the fine carbon dioxide bubbles contained in the gas G into the basic solution to produce the absorbent solution A1. The gas-liquid contactor 1 is not particularly limited as long as it can produce the absorbent solution A1, but is preferably a through-type or power-driven mixing mixer. A through-type mixing mixer is, for example, a tubular reactor, and is preferably a static mixer. A static mixer comprises a cylindrical body and a spiral blade structure provided inside the body along the longitudinal direction. The spiral blade structure has a structure in which counterclockwise spiral blades and clockwise spiral blades are arranged alternately. The basic solution and the fine carbon dioxide bubbles are stirred as they pass through the spiral blade structure, thereby bringing the mixture into gas-liquid contact. An example of a power-driven mixing mixer is a stirrer with power-driven blades.

[0044] As shown in Fig. 1, the manufacturing apparatus 100 is configured such that the absorption liquid A1 produced in the gas-liquid contactor 1 is returned to the basic solution tank 2. That is, after passing through the gas-liquid contactor 1, the basic solution discharged from the basic solution tank 2 is returned to the basic solution tank 2 via the flow path L3, so that the basic solution circulates between the gas-liquid contactor 1 and the basic solution tank 2. This enables efficient acquisition of high-purity bicarbonate.

[0045] The basic solution tank 2 is, for example, a gas-liquid separation tank including a supply port and a discharge port provided below the supply port. In the gas-liquid separation tank, after the absorption liquid A1 supplied from the supply port descends and reaches the discharge port, bubbles of excess carbon dioxide D rise due to buoyancy and are separated from the absorption liquid A1. As a result, the excess carbon dioxide D is discharged to the outside via the flow path L5 provided at the upper part of the basic solution tank 2. Accordingly, what is discharged from the discharge port to the flow path L4 is the absorption liquid A2 from which excess carbon dioxide bubbles have been separated (typically a solution containing bicarbonate and / or base). That is, the basic solution tank 2 also functions as a gas-liquid separation device.

[0046] In the present embodiment, excess carbon dioxide D is also separated from the absorption liquid A1 in the basic solution tank 2. However, after separating excess carbon dioxide D from the absorption liquid A1 by a gas-liquid separation device constituted by a separate element from the basic solution tank 2, the absorption liquid A2 may be sent to the basic solution tank 2. In addition, in the present embodiment, the configuration is such that the absorption liquid A1 is returned from the gas-liquid contactor 1 to the basic solution tank 2, that is, the basic solution circulates between the gas-liquid contactor 1 and the basic solution tank 2. However, the absorption liquid A1 obtained by the gas-liquid contactor 1 may be sent out. Further, in the present embodiment, the gas-liquid contactor 1 and the gas-liquid separation device (the basic solution tank 2) are constituted by separate elements, but the gas-liquid contactor 1 and the gas-liquid separation device may be constituted by one element having both functions. An example of such an element is a bubble column. However, it is preferable to use a circulating manufacturing apparatus for the manufacturing method of the present embodiment.

[0047] Figure 2 is a schematic diagram showing a modified example of a production apparatus suitable for the method for producing a hydrogen carbonate according to the present embodiment. A production apparatus 110 shown in FIG. 2 includes basic solution tanks 2A and 2B. For example, using the basic solution tank 2A, circulation of feeding a basic solution and recovering an absorption liquid A1 from a gas-liquid contactor 1, that is, circulation of the basic solution between the basic solution tank 2A and the gas-liquid contactor 1, is repeated. Then, the flow path is switched by operating a valve to circulate the basic solution between the basic solution tank 2B and the gas-liquid contactor 1. While the basic solution is circulated between the basic solution tank 2B and the gas-liquid contactor 1, a reaction liquid (absorption liquid A2) containing hydrogen carbonate generated in the basic solution tank 2A is discharged through a flow path L7 and recovered. After recovering the reaction liquid from the basic solution tank 2A, a new basic solution is charged into the basic solution tank 2A. Thereafter, the flow path is switched by operating a valve to circulate the basic solution between the basic solution tank 2A and the gas-liquid contactor 1 again, and during that time the reaction liquid is recovered from the basic solution tank 2B. By preparing two or more basic solution tanks in this manner, for example, the time for replacing the raw material (basic solution) can be shortened, which can be advantageous from the viewpoints of scale-up and cost.

[0048] [Method for producing organic compound] The method for producing an organic compound according to the present embodiment includes a step of producing an organic compound using the hydrogen carbonate produced by the above-described method for producing a hydrogen carbonate. Examples of the organic compound produced in this manner include formate. For example, formate can be obtained by reacting hydrogen carbonate with hydrogen using a metal catalyst in the presence of a solvent. Formic acid produced from formate, for example by using electrodialysis, requires low energy for the dehydrogenation reaction and can be handled easily, so it is an excellent compound as a storage material for hydrogen or carbon dioxide.

[0049] Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

[0050] Using the manufacturing apparatus 100 shown in Figure 1, the above-described method for producing bicarbonate was used to carry out the examples and comparative examples and obtain bicarbonate. In the following examples and comparative examples, a static mixer (manufactured by Noritake Corporation) was used as the gas-liquid contactor 1.

[0051] (Example 1) 5 L of potassium hydroxide aqueous solution, adjusted to a concentration of 5.0 mol / L, was added to the basic solution tank as a basic solution. Carbon dioxide gas was supplied to the production apparatus at a flow rate of 55 L / min and 0.3 MPa. The flow rate of carbon dioxide gas was measured. The above potassium hydroxide aqueous solution was circulated within the system at a liquid temperature of 19.3°C and a flow rate of 30 L / min (i.e., circulated between the basic solution tank and the static mixer), and an absorption solution was prepared by repeatedly bringing the gas-liquid into contact. The carbon dioxide gas was passed through in one pass without circulation, and the excess unreacted carbon dioxide was discharged to the outside. Ten minutes after the start of operation, the absorption solution was collected from the basic solution tank and the concentration of potassium bicarbonate was measured. In addition, the liquid temperature in the basic solution tank and the carbon dioxide gas discharge flow rate were observed during the operation of the apparatus, and the point at which the liquid temperature decreased and the carbon dioxide gas discharge flow rate increased sharply was defined as the reaction endpoint, and the time from the start of operation of the apparatus to the reaction endpoint was defined as the reaction time. From this reaction time and the amount of potassium hydroxide used, the reaction time per mole of base (potassium hydroxide) was calculated.

[0052] [Method for Calculating the Concentration of Potassium Bicarbonate] 500 μL of DMSO (dimethyl sulfoxide) was added to 5 mL of the collected absorption solution and dissolved in 500 μL of heavy water. NMR measurements were performed on the sample prepared in this way. The integral value was determined from the obtained NMR spectrum, and the concentration of the generated potassium bicarbonate (mol / L) was calculated using a calibration curve of the previously prepared NMR spectrum and the molar ratio of potassium bicarbonate:DMSO. Similarly, the concentration of potassium carbonate (mol / L) was also calculated by NMR measurement. Based on the calculated concentrations of potassium bicarbonate and potassium carbonate, the purity of potassium bicarbonate was calculated and expressed as the purity of the bicarbonate salt (%).

[0053] (Example 2) Except for setting the flow rate of the potassium hydroxide aqueous solution to 20 L / min, potassium bicarbonate of Example 2 was obtained by the same method as in Example 1, and the reaction time was measured. In addition, the purity of the bicarbonate in the absorption solution 10 minutes after the start of operation was determined by the same method as in Example 1.

[0054] (Example 3) Except for using a potassium hydroxide aqueous solution with a concentration of 2.5 mol / L and a carbon dioxide gas flow rate of 40 L / min, potassium bicarbonate was obtained in the same manner as in Example 1, and the reaction time was measured. Also, 7 minutes after the start of operation, the absorption solution (reaction solution) was taken from the basic solution tank and the concentration of potassium bicarbonate was measured, and the purity of the bicarbonate was determined in the same manner as in Example 1.

[0055] (Example 4) Except for setting the carbon dioxide gas flow rate to 55 L / min, potassium bicarbonate of Example 4 was obtained using the same method as in Example 3, and the reaction time was measured. Also, the purity of the bicarbonate in the absorbent solution 7 minutes after the start of operation was determined using the same method as in Example 3.

[0056] (Example 5) Except for setting the flow rate of the potassium hydroxide aqueous solution to 15 L / min, potassium bicarbonate of Example 5 was obtained by the same method as in Example 3, and the reaction time was measured. In addition, the purity of the bicarbonate in the absorbent solution 7 minutes after the start of operation was determined by the same method as in Example 3.

[0057] (Example 6) Except for setting the carbon dioxide gas flow rate to 55 L / min, potassium bicarbonate of Example 6 was obtained using the same method as in Example 5, and the reaction time was measured. In addition, the purity of the bicarbonate in the absorbent solution 7 minutes after the start of operation was determined using the same method as in Example 3.

[0058] (Comparative Example 1) Potassium bicarbonate for Comparative Example 1 was obtained using the same method as in Example 1, except that the flow rate of carbon dioxide gas was set to 15 L / min, and the reaction time was measured. In addition, absorption liquid was collected from the basic solution tank 7 minutes and 10 minutes after the start of operation, and the concentration of potassium bicarbonate was measured, and the purity of the bicarbonate was determined using the same method as in Example 1.

[0059] (Comparative Example 2) Potassium bicarbonate for Comparative Example 2 was obtained using the same method as in Example 3, except that the flow rate of carbon dioxide gas was set to 27.5 L / min, and the reaction time was measured. In addition, the purity of the bicarbonate in the absorbent solution 7 minutes after the start of operation was determined using the same method as in Example 3.

[0060] (Comparative Example 3) Potassium bicarbonate for Comparative Example 3 was obtained using the same method as in Comparative Example 2, except that the flow rate of the potassium hydroxide aqueous solution was set to 15 L / min, and the reaction time was measured. In addition, the purity of the bicarbonate in the absorbent solution 7 minutes after the start of operation was determined using the same method as in Example 3.

[0061] (Comparative Example 4) Potassium bicarbonate for Comparative Example 4 was obtained using the same method as in Comparative Example 2, except that the flow rate of carbon dioxide gas was set to 15 L / min, and the reaction time was measured. In addition, the purity of the bicarbonate in the absorbent solution 7 minutes after the start of operation was determined using the same method as in Example 3.

[0062] The measurement results are shown in Table 1. In Table 1, the CO2 / base flow rate ratio is the ratio of the flow rate of carbon dioxide gas to the flow rate of potassium hydroxide solution.

[0063]

[0064] As can be seen from Table 1, in Examples 1 and 2, the reaction time was shorter and the purity of the bicarbonate after 10 minutes of reaction was higher compared to Comparative Example 1, which used a basic solution of the same concentration. Furthermore, in Examples 3 to 6, the reaction time was shorter and the purity of the bicarbonate after 7 minutes of reaction was higher compared to Comparative Examples 2 to 4, which used a basic solution of the same concentration. Thus, in Examples 1 to 6, where the carbon dioxide supply flow rate was 30 L / min or more and the CO2 / base flow rate ratio was between 1.00 and 4.00, the base and carbon dioxide reacted at a fast reaction rate, and high-purity bicarbonate was produced. In other words, high-purity bicarbonate was efficiently produced in Examples 1 to 6.

[0065] In the above examples, potassium hydroxide was used as the base in the basic solution. However, it is presumed that if a hydroxide containing another alkali metal element, such as sodium hydroxide, is used instead of potassium hydroxide, the purity of the bicarbonate and the reaction time will show a similar trend to that in the above examples.

[0066] The method for producing bicarbonate according to this embodiment is suitable for producing bicarbonate using a raw material gas containing carbon dioxide, particularly exhaust gas.

Claims

1. A method for producing a bicarbonate, comprising the step of supplying a solution containing a base and carbon dioxide to a gas-liquid contactor, and bringing the solution and carbon dioxide into contact in the gas-liquid contactor, wherein the flow rate of the carbon dioxide supplied to the gas-liquid contactor is 30 L / min or more, and the ratio of the flow rate of the carbon dioxide to the flow rate of the solution supplied to the gas-liquid contactor is 1.00 or more and 4.00 or less.

2. The method for producing a bicarbonate according to claim 1, wherein the gas-liquid contactor is a tubular reactor.

3. The method for producing a bicarbonate according to claim 1, wherein the base contains an alkali metal element.

4. The method for producing a bicarbonate according to claim 1, wherein the concentration of the base in the solution is 1 mol / L or more.

5. The method for producing a bicarbonate according to claim 1, wherein the supply of carbon dioxide to the gas-liquid contactor is performed by supplying a gas containing carbon dioxide to the gas-liquid contactor.

6. The method for producing a bicarbonate according to claim 5, wherein the concentration of carbon dioxide in the gas is 30% by volume or more and 100% by volume or less under standard conditions.

7. A method for producing a bicarbonate according to claim 1, comprising circulating the solution by returning at least a portion of the solution discharged from the gas-liquid contactor to the gas-liquid contactor.

8. A method for producing an organic compound, comprising the step of producing an organic compound using a bicarbonate produced by the manufacturing method described in any one of claims 1 to 7.

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