Method for producing carbamic acid compound

Abstract

To provide a method for producing a carbamic acid compound which can efficiently absorb carbon dioxide contained in a composition containing carbon dioxide to efficiently produce a carbamic acid compound.SOLUTION: There is provided a method for producing a carbamic acid compound, which comprises a step of continuously obtaining a carbamic acid compound by continuously contacting an amino compound having two or more amino groups in the molecule with a composition containing carbon dioxide. In the step, it is preferable to continuously contact an amino compound solution obtained by dissolving the amino compound in a solvent with the composition containing carbon dioxide by continuously supplying the amino compound solution from the top to the bottom of the reaction vessel and continuously supplying the composition containing carbon dioxide from the bottom to the top of the reaction vessel.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for producing a carbamic acid compound. [Background technology]

[0002] In recent years, the greenhouse effect caused by carbon dioxide has been pointed out as one of the causes of global warming, and measures to combat this have become an urgent international issue in order to protect the global environment.

[0003] In particular, since the majority of the energy required for social activities is obtained from fossil fuels such as coal, oil, and natural gas, the amount of carbon dioxide generated from these fossil fuels is enormous, and reducing this energy-derived carbon dioxide is effective in curbing global warming.

[0004] Therefore, methods for removing and capturing carbon dioxide from combustion exhaust gases generated and emitted by combustion in combustion facilities such as factories and thermal power plants are being actively researched.

[0005] For example, Patent Document 1 discloses a method for removing and recovering carbon dioxide in a combustion exhaust gas by using an aqueous solution of an amine compound as an absorption liquid and bringing the combustion exhaust gas into contact with the absorption liquid, and a method for storing the recovered carbon dioxide without releasing it into the atmosphere.

[0006] However, the method described in Patent Document 1 has problems in that the absorption of carbon dioxide into the mixed aqueous solution cannot be performed sufficiently efficiently, resulting in a high proportion of carbon dioxide not being absorbed into the mixed aqueous solution, and in that a long processing time is required to absorb a unit substance amount of carbon dioxide. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent No. 2871335 Summary of the Invention [Problem to be solved by the invention]

[0008] An object of the present invention is to provide a method for producing a carbamic acid compound, which can efficiently absorb carbon dioxide contained in a carbon dioxide-containing composition and efficiently produce a carbamic acid compound. [Means for solving the problem]

[0009] These objects can be achieved by the present invention as set forth in (1) to (7) below. (1) A method for producing a carbamic acid compound, comprising a step of continuously contacting an amino compound having two or more amino groups in the molecule with a composition containing carbon dioxide to continuously obtain a carbamic acid compound.

[0010] (2) In the above step, An amino compound solution obtained by dissolving the amino compound in a solvent is continuously supplied from the top to the bottom of the reaction vessel, and The composition containing carbon dioxide is continuously supplied from the bottom to the top of the reaction vessel, The method for producing a carbamic acid compound according to (1) above, which comprises continuously contacting the amino compound solution with the composition containing carbon dioxide.

[0011] (3) The method for producing a carbamic acid compound according to (2) above, wherein the amino compound solution recovered from the bottom of the reaction vessel is fed back into the reaction vessel.

[0012] (4) The method for producing a carbamic acid compound according to (3) above, wherein the carbon dioxide-containing composition is supplied to the reaction vessel from a position higher than a position where the amino compound solution is recovered from the reaction vessel.

[0013] (5) The method for producing a carbamic acid compound according to any one of (2) to (4) above, wherein the reaction vessel used in the step is cylindrical and arranged so that its longitudinal direction is vertical.

[0014] (6) The method for producing a carbamic acid compound according to any one of (2) to (5) above, wherein in the step, at least a part of the carbamic acid compound is precipitated from the amino compound solution.

[0015] (7) The method for producing a carbamic acid compound according to any one of (1) to (6) above, wherein the carbon dioxide-containing composition is air or an exhaust gas from a factory or a thermal power plant. [Effects of the Invention]

[0016] According to the present invention, it is possible to provide a method for producing a carbamic acid compound, which can efficiently absorb carbon dioxide contained in a carbon dioxide-containing composition and efficiently produce a carbamic acid compound. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a diagram schematically illustrating an example of the configuration of a reaction apparatus used in the method for producing a carbamic acid compound of the present invention. [Figure 2] 1 is a photograph showing the production of 6-aminohexylcarbamic acid in a reaction vessel in the first step of Example 1. [Figure 3] 1 shows IR spectra of 6-aminohexylcarbamic acid obtained in the first step and the white solid obtained in the second step in Example 1. [Figure 4] 1 shows IR spectra of 3-aminomethylcyclohexylmethylcarbamate obtained in the first step and the white solid obtained in the second step in Example 2. [Figure 5]1 shows IR spectra of 5-amino-1,3,3-trimethylcyclohexylmethylcarbamic acid obtained in the first step and the white solid obtained in the second step in Example 3. [Figure 6] FIG. 1 shows the thermogravimetric changes of 6-aminohexylcarbamic acid obtained in the first step and the white solid obtained in the second step in Example 1. [Figure 7] FIG. 2 is a graph showing the thermogravimetric changes of 3-aminomethylcyclohexylmethylcarbamic acid obtained in the first step and the white solid obtained in the second step in Example 2. [Figure 8] FIG. 1 shows the thermogravimetric changes of 5-amino-1,3,3-trimethylcyclohexylmethylcarbamic acid obtained in the first step and the white solid obtained in the second step in Example 3. DETAILED DESCRIPTION OF THE INVENTION

[0018] Preferred embodiments of the present invention will be described in detail below. [1] Method for producing carbamic acid compounds The method for producing the carbamic acid compound of the present invention will be described below.

[0019] The method for producing a carbamic acid compound of the present invention is characterized by comprising a step of continuously contacting an amino compound having two or more amino groups in the molecule with a composition containing carbon dioxide to continuously obtain a carbamic acid compound.

[0020] According to the method for producing a carbamic acid compound of the present invention, by continuously contacting an amino compound having two or more amino groups in the molecule with a composition containing carbon dioxide, the carbon dioxide contained in the composition can be continuously and efficiently absorbed into the amino compound.

[0021] Specifically, the amino compound is reacted with carbon dioxide continuously to produce the carbamic acid compound continuously and efficiently.

[0022] As described above, according to the method for producing a carbamic acid compound of the present invention, by continuously contacting the amino compound with a composition containing carbon dioxide in the step, it is possible to achieve high efficiency, simplification, and energy savings in the process.

[0023] Furthermore, according to the method for producing a carbamic acid compound of the present invention, for example, the obtained carbamic acid compound can be polymerized by subjecting the carbamic acid compound to the second step described below, thereby suitably producing polyurea. In this way, by using a carbamic acid compound as a raw material for polyurea, absorbed carbon dioxide can be effectively utilized without separation, allowing polyurea to be efficiently produced. Furthermore, since the carbon dioxide absorbed by the amino compound is incorporated into the skeleton of the polyurea, the absorbed carbon dioxide is suitably immobilized and suitably prevented from unintentional separation and volatilization.

[0024] In the present invention, the term "continuous" is used in the sense of corresponding to "continuous system" as opposed to "batch system," and does not necessarily mean that the supply of the amino compound and carbon dioxide, the contact of the amino compound with the composition containing carbon dioxide, the reaction to produce the carbamic acid compound, etc. are carried out continuously. For example, a composition containing carbon dioxide (carbon dioxide-containing gas 30) may be intermittently supplied into a reaction vessel 10 as described below.

[0025] In the present invention, the term "carbamic acid compound" refers to a compound having an NHCOOH chemical structure in the molecule. The NHCOOH group constituting the carbamic acid compound may be in the form of a salt.

[0026] In the following description, the process of continuously obtaining a carbamic acid compound by continuously contacting an amino compound having two or more amino groups in the molecule with a composition containing carbon dioxide is also referred to as the "first process."

[0027] [1-1] First step In the first step, an amino compound having two or more amino groups in the molecule is continuously contacted with a composition containing carbon dioxide to continuously obtain a carbamic acid compound.

[0028] [1-1-1] Amino compounds The amino compound is not particularly limited as long as it has two or more amino groups in the molecule, and examples thereof include linear diamines having a linear structure, branched diamines having a branched structure, alicyclic diamines, diamines having an aromatic ring, ether-containing diamines having an ether bond in the linear chain, and diamines having a nitrogen atom in the linear chain.

[0029] Examples of the linear diamine include 1,6-hexamethylenediamine, ethylenediamine, and 1,3-propanediamine.

[0030] Examples of branched diamines include 1,2-propanediamine and 2-methylpentamethylenediamine.

[0031] Examples of the alicyclic diamine include 1,3-cyclohexyldiamine, 1,3-bisaminomethylcyclohexane, hexahydrometaphenylenediamine, isophoronediamine, and 4,4'-methylenebis(cyclohexylamine).

[0032] Examples of diamines having an aromatic ring include p-xylylenediamine and m-xylylenediamine.

[0033] Examples of ether-containing diamines include polyether diamines such as compounds represented by the following formula (3).

[0034] [ka]

[0035] Examples of diamines having a nitrogen atom in a linear chain include compounds represented by the following formula (4).

[0036] [ka]

[0037] As the amino compound, in addition to the above-mentioned diamines, compounds having three or more amino groups in the molecule may also be used.

[0038] [1-1-2] Composition containing carbon dioxide Examples of compositions containing carbon dioxide include gases containing carbon dioxide, carbon dioxide solutions in which carbon dioxide is dissolved in a solvent, and dispersions in which minute bubbles containing carbon dioxide (such as so-called microbubbles or nanobubbles) are dispersed.

[0039] The size (diameter) of the bubbles contained in the dispersion is not particularly limited, but can be several tens of nanometers or more and several millimeters or less.

[0040] The carbon dioxide-containing gas is not particularly limited as long as it is a gaseous component containing carbon dioxide, and examples thereof include air, exhaust gases discharged from boilers and gas turbines of factories or thermal power plants, gases contained in coal gasification gas, synthetic gas, coke oven gas, petroleum gas, natural gas, etc. Among these, the carbon dioxide-containing gas is preferably air or exhaust gas from factories or thermal power plants.

[0041] This allows carbon dioxide to be easily removed from the target gas, and the carbon dioxide can be effectively utilized as a raw material for the carbamic acid compound.

[0042] In particular, since air exists in a variety of environments (for example, various environments on Earth, and enclosed spaces such as space stations and submarines), when the target gas is air, it is possible to suitably use carbon dioxide to produce a carbamic acid compound in such a variety of environments. Furthermore, in enclosed spaces such as space stations and submarines, if the carbon dioxide concentration in the air increases, it could endanger the lives of people staying in the space. However, when the carbon dioxide-containing gas is the air in an enclosed space, it is possible to rapidly decrease the carbon dioxide concentration in the space, thereby more suitably ensuring the safety of the lives of people and others in the space.

[0043] Furthermore, when the carbon dioxide-containing gas is exhaust gas from a factory or a thermal power plant, the carbon dioxide in the exhaust gas from the factory or the thermal power plant can be removed, and the recovered carbon dioxide can be effectively utilized as a raw material for a carbamic acid compound, which can also contribute to reducing the carbon dioxide emitted into the atmosphere from the factory or the thermal power plant.

[0044] The concentration of carbon dioxide contained in the carbon dioxide-containing gas is preferably 0.001% by volume or more and 20.0% by volume or less, more preferably 0.5% by volume or more and 15.0% by volume or less, and even more preferably 1.0% by volume or more and 10.0% by volume or less.

[0045] This allows the carbon dioxide contained in the gas to come into contact with the amino compound more efficiently, and allows the reaction of the amino compound and carbon dioxide to produce the carbamic acid compound to proceed more favorably.

[0046] [1-1-3] Reaction in the first step As described above, in the first step, an amino compound having two or more amino groups in the molecule is continuously contacted with a composition containing carbon dioxide to continuously obtain a carbamic acid compound.

[0047] In the first step, examples of the method for contacting an amino compound having two or more amino groups in the molecule with a composition containing carbon dioxide include gas-liquid contact, gas-solid contact, and liquid-liquid contact, with gas-liquid contact being preferred.

[0048] This allows the amino compound to come into contact with the composition containing carbon dioxide more efficiently.

[0049] Specific examples of the gas-liquid contact method include a method of contacting an amino compound solution prepared by dissolving an amino compound in a solvent with a gas containing carbon dioxide, and a method of contacting an amino compound that has been melted into a liquid state with a gas containing carbon dioxide. Of these, the method of contacting an amino compound solution prepared by dissolving an amino compound in a solvent with a gas containing carbon dioxide is preferred.

[0050] This allows the amino compound to be brought into contact with the gas containing carbon dioxide more efficiently.

[0051] The following description will mainly focus on the case where an amino compound solution in which an amino compound is dissolved in a solvent is continuously brought into contact with a gas containing carbon dioxide.

[0052] As the solvent, a liquid component that does not react with the amino compound and carbon dioxide can be used, and examples thereof include water, alcohol (e.g., methanol, ethanol, propanol, isopropanol, butanol, tert-butanol, ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, glycerin, etc.), tetrahydrofuran, dioxane, acetonitrile, N-methyl-2-pyrrolidone, dimethylformamide, dimethyl sulfoxide, benzene, toluene, xylene, pyridine, etc. These may be used alone or in combination of two or more. Among these, ethanol is preferred as the solvent.

[0053] The concentration of the amino compound in the amino compound solution is preferably 10% by mass or more and 100% by mass or less, more preferably 20% by mass or more and 80% by mass or less, and even more preferably 30% by mass or more and 75% by mass or less.

[0054] This allows the amino compound in the amino compound solution to come into contact with the carbon dioxide in the gas more efficiently, and allows the reaction of the amino compound and carbon dioxide to produce the carbamic acid compound to proceed more favorably.

[0055] Examples of methods for contacting an amino compound solution in which an amino compound is dissolved in a solvent with a gas containing carbon dioxide include a method of supplying a gas containing carbon dioxide toward the surface of the amino compound solution, a method of placing the amino compound solution in a container and supplying a gas containing carbon dioxide into the space (gas phase) within the container in which the amino compound solution is placed, and a method of blowing a gas containing carbon dioxide into the amino compound solution.

[0056] In this case, the amino compound solution may be passed or circulated within the container, or a gas containing carbon dioxide may be passed or circulated within the container.

[0057] This allows the amino compound solution to be brought into continuous contact with the gas containing carbon dioxide more suitably, and allows the reaction of obtaining a carbamic acid compound from the amino compound and carbon dioxide to proceed more suitably.

[0058] Among the above-mentioned methods, a method in which a gas containing carbon dioxide is blown into an amino compound solution in which an amino compound is dissolved in a solvent is preferred.

[0059] This allows the amino compound solution to be brought into contact with the gas containing carbon dioxide more efficiently, and allows the reaction of obtaining a carbamic acid compound from the amino compound and carbon dioxide to proceed more favorably.

[0060] In the following explanation, the case where a gas containing carbon dioxide is blown into an amino compound solution will be mainly explained.

[0061] FIG. 1 is a diagram schematically illustrating an example of the configuration of a reaction apparatus used in the method for producing a carbamic acid compound of the present invention.

[0062] In this embodiment, in the first step, an amino compound solution 20 in which an amino compound is dissolved in a solvent is continuously supplied from the top to the bottom of a reaction vessel 10, and a gas 30 which is a composition containing carbon dioxide is continuously supplied from the bottom to the top of the reaction vessel 10, thereby continuously contacting the amino compound solution 20 with the gas 30 containing carbon dioxide.

[0063] This allows the above-mentioned effects to be more effectively exhibited, and the reaction of obtaining a carbamic acid compound from an amino compound and carbon dioxide to proceed more favorably.

[0064] In particular, in this embodiment, the reaction vessel 10 used in the first step is cylindrical and is arranged so that its longitudinal direction is the up-down direction. This makes it possible to more significantly exhibit the above-mentioned effects.

[0065] Such an effect can be obtained even when the composition containing carbon dioxide is in a form other than gas (for example, in the form of a carbon dioxide solution or dispersion), but is more pronounced when it is in gas form.

[0066] The reaction apparatus 1 shown in FIG. 1 comprises a cylindrical reaction vessel 10 arranged in a vertical direction, a solution supply port 11 provided at the top of the reaction vessel 10 and supplying an amino compound solution 20 into the reaction vessel 10, a solution recovery port 12 provided at the bottom of the reaction vessel 10 and recovering a solution 20a that has passed through the reaction vessel 10, a gas supply port 13 provided at the bottom of the reaction vessel 10 and supplying a gas 30 containing carbon dioxide into the reaction vessel 10, and a gas discharge port 14 provided at the top of the reaction vessel 10 and discharging the gas 30a that has passed through the reaction vessel 10 to the outside of the reaction vessel 10.

[0067] In the example shown in the figure, the reaction apparatus 1 further has a solution supply pipe 16 connected to the solution supply port 11, a solution recovery pipe 17 connected to the solution recovery port 12, and a gas supply pipe 18 connected to the gas supply port 13.

[0068] Furthermore, as will be described later, at least a part of the carbamic acid compound produced by the reaction of the amino compound with carbon dioxide may precipitate from the solution, and therefore the reaction apparatus 1 has a solid recovery section 15 provided at the bottom of the reaction vessel 10 for recovering the precipitated solid 40 containing the carbamic acid compound.

[0069] The gas supply pipe 18 is, for example, a soft tube inserted into the reaction vessel 10 through the gas supply port 13 .

[0070] In the example shown in FIG. 1, a gas 30 containing carbon dioxide is supplied into the reaction vessel 10 through the gas supply pipe 18, but the present invention is not limited to this. Instead of the gas supply pipe 18, a gas-permeable membrane that allows gas to pass through but not liquid may be disposed at the gas supply port 13, and the gas may be supplied into the reaction vessel 10 through the gas-permeable membrane.

[0071] The amino compound solution 20 is continuously supplied into the reaction vessel 10 from the solution supply port 11 at the top of the reaction vessel 10, flows from the top to the bottom of the reaction vessel 10, and is then recovered as a solution 20a from the solution recovery port 12 at the bottom of the reaction vessel 10.

[0072] Since the amino compound reacts with carbon dioxide in the reaction vessel 10 to produce a carbamic acid compound, the solution 20a recovered from the solution recovery port 12 has a lower amino compound content than the amino compound solution 20 supplied from the solution supply port 11.

[0073] The solution 20a recovered from the solution recovery port 12 may be substantially free of an amino compound, but preferably contains an amino compound. This reduces the proportion of carbon dioxide introduced into the reaction vessel 10 that is discharged unreacted from the gas discharge port 14. More specifically, for example, the carbon dioxide content in the gas 30a discharged from the gas discharge port 14 can be set to 0 mass %.

[0074] Even if the solution 20a recovered from the solution recovery port 12 contains an amino compound (an amino compound solution), as will be described in detail later, it can be supplied again into the reaction vessel 10 and circulated for reuse, thereby preventing the unreacted amino compound from going to waste.

[0075] Gas 30 containing carbon dioxide is continuously supplied into the reaction vessel 10 from a gas supply port 13 at the bottom of the reaction vessel 10, flows from the bottom to the top of the reaction vessel 10, and is then discharged to the outside from a gas exhaust port 14 at the top of the reaction vessel 10.

[0076] In this way, by continuously supplying the amino compound solution 20 and the gas 30 containing carbon dioxide into the reaction vessel 10 and bringing them into contact with each other, the reaction of the amino compound and carbon dioxide to obtain the carbamic acid compound can be continuously carried out.

[0077] Furthermore, inside the reaction vessel 10, the flow of the amino compound solution 20 is downward as indicated by the arrow L, whereas the flow of the carbon dioxide-containing gas 30 is upward as indicated by the arrow G. By opposing the flow of the amino compound solution 20 to the flow of the carbon dioxide-containing gas 30 in this manner, the amino compound solution 20 and the carbon dioxide-containing gas 30 can be brought into contact with each other more efficiently, and the reaction of obtaining a carbamic acid compound from the amino compound and carbon dioxide can proceed more efficiently.

[0078] In this way, the so-called flow-type reactor 1, in which raw materials are continuously supplied to a cylindrical reaction vessel 10 and continuously subjected to a chemical reaction, can produce a carbamic acid compound more efficiently than a batch-type reactor, and also has advantages such as the reaction equipment being small and safe.

[0079] When the solution 20a recovered from the bottom of the reaction vessel 10 contains an amino compound (amino compound solution), it is preferable to supply the solution (amino compound solution) 20a again into the reaction vessel 10 from the solution supply port 11 and circulate it.

[0080] In this case, an amino compound may be further added to the solution 20a recovered from the lower part of the reaction vessel 10. In particular, it is preferable to add the amino compound so that the concentration of the amino compound solution 20 supplied from the upper part of the reaction vessel 10 falls within a predetermined range.

[0081] This allows the continuous reaction between the amino compound and carbon dioxide to be carried out more efficiently and stably.

[0082] Furthermore, if the gas supply port 13 that supplies the gas 30 containing carbon dioxide to the reaction vessel 10 is located at the same height as or lower than the solution recovery port 12 that recovers the solution 20a from the reaction vessel 10, the carbon dioxide supplied from the gas supply port 13 may flow toward the solution recovery port 12.

[0083] If a reaction between carbon dioxide and an amino compound occurs near the solution recovery port 12, the precipitated carbamic acid compound may clog the solution recovery port 12 or the solution recovery pipe 17, causing blockage of the flow path.

[0084] Therefore, it is preferable to supply the gas 30 containing carbon dioxide to the reaction vessel 10 from a position higher than the position where the amino compound solution 20 is collected from the reaction vessel 10 .

[0085] Specifically, in the reaction vessel 10, the gas supply port 13 is preferably provided at a higher position than the solution recovery port 12.

[0086] This more effectively prevents the carbon dioxide supplied from the gas supply port 13 from heading toward the solution recovery port 12, while more effectively preventing the reaction of the carbon dioxide with the amino compound near the solution recovery port 12 and the blockage of the flow path by the precipitated carbamic acid compound.

[0087] The inner diameter of the cylindrical reaction vessel 10 is preferably 1 mm or more and 300 mm or less, more preferably 5 mm or more and 150 mm or less, and even more preferably 10 mm or more and 50 mm or less.

[0088] This prevents the reaction apparatus 1 from becoming excessively large, and allows the amino compound in the amino compound solution 20 to be brought into contact with the carbon dioxide in the carbon dioxide-containing gas 30 more efficiently, allowing the reaction of obtaining a carbamic acid compound from the amino compound and carbon dioxide to proceed more efficiently.

[0089] The length of the cylindrical reaction vessel 10 is preferably 100 mm or more and 2000 mm or less, more preferably 150 mm or more and 1000 mm or less, and even more preferably 200 mm or more and 500 mm or less.

[0090] This prevents the reaction apparatus 1 from becoming excessively large, and allows the amino compound in the amino compound solution 20 to be brought into contact with the carbon dioxide in the carbon dioxide-containing gas 30 more efficiently, allowing the reaction of obtaining a carbamic acid compound from the amino compound and carbon dioxide to proceed more efficiently.

[0091] In the first step, the temperature of the amino compound solution 20 is preferably 0°C or higher and 80°C or lower, more preferably 5°C or higher and 60°C or lower, and even more preferably 10°C or higher and 40°C or lower.

[0092] This allows the reaction of the amino compound and carbon dioxide to produce the carbamic acid compound to proceed more smoothly.

[0093] In the first step, the flow rate (volume flow rate) of the amino compound solution 20 per unit time and unit area is 0.00001 mL / cm 2 ·min] or more 1.0mL / [cm 2 ·min] or less, and 0.001mL / [cm 2 ·min] or more 0.5mL / [cm 2 ·min] or less, and more preferably 0.1mL / [cm 2 ·min] or more 0.3mL / [cm 2 It is even more preferable that the time is [minutes] or less.

[0094] This allows the amino compound in the amino compound solution 20 to come into contact with the carbon dioxide in the carbon dioxide-containing gas 30 more efficiently, and allows the reaction of the amino compound and carbon dioxide to produce the carbamic acid compound to proceed more efficiently.

[0095] In the first step, the temperature of the carbon dioxide-containing gas 30 is preferably 0°C or higher and 80°C or lower, more preferably 5°C or higher and 60°C or lower, and even more preferably 10°C or higher and 40°C or lower.

[0096] This allows the reaction of the amino compound and carbon dioxide to produce the carbamic acid compound to proceed more smoothly.

[0097] In the first step, the flow rate (volume flow rate) per unit time and unit area of ​​the gas 30 containing carbon dioxide is 0.00001 L / cm 2 min] or more 0.1L / [cm 2 ·min] or less, and 0.001L / [cm 2 min] or more 0.05L / [cm 2 ·min] or less, and more preferably 0.01L / [cm 2 min] or more 0.03L / [cm 2 It is even more preferable that the time is [minutes] or less.

[0098] This allows the amino compound in the amino compound solution 20 to come into contact with the carbon dioxide in the carbon dioxide-containing gas 30 more efficiently, and allows the reaction of the amino compound and carbon dioxide to produce the carbamic acid compound to proceed more efficiently.

[0099] In the first step, the size (diameter) of the bubbles when blowing the gas 30 containing carbon dioxide is preferably 0.0001 mm or more and 5 mm or less, more preferably 0.001 mm or more and 1 mm or less, and even more preferably 0.01 mm or more and 0.1 mm or less.

[0100] This allows the amino compound in the amino compound solution 20 to come into contact with the carbon dioxide in the carbon dioxide-containing gas 30 more efficiently, and allows the reaction of the amino compound and carbon dioxide to produce the carbamic acid compound to proceed more efficiently.

[0101] The carbon dioxide-containing gas 30 may be blown in through a porous body such as a sponge. The size of the bubbles can be more suitably adjusted by adjusting the pore size of the porous body.

[0102] In the above explanation, the case where the composition containing carbon dioxide is a gas containing carbon dioxide has been mainly explained. However, instead of a gas containing carbon dioxide, a carbon dioxide solution in which carbon dioxide is dissolved (dissolved) in a solvent, or a dispersion liquid in which minute bubbles containing carbon dioxide (for example, so-called microbubbles or nanobubbles) are dispersed may also be used.

[0103] As the solvent for dissolving or dispersing carbon dioxide, it is preferable to use the same type of solvent as that used for the amino compound solution.

[0104] This allows the reaction of obtaining a carbamic acid compound from an amino compound and carbon dioxide to proceed more efficiently. Furthermore, when the solution 20a (amino compound solution) recovered from the solution recovery port 12 is supplied again into the reaction vessel 10 and recycled, it is possible to preferably prevent the composition of the solvent constituting the amino compound solution from changing due to the cycle.

[0105] In the illustrated configuration, the reaction vessel 10 is disposed vertically, but the reaction vessel 10 may be disposed at an angle so that the flow direction of the amino compound solution, etc. is oblique. Even in such a case, the present specification will treat the cylindrical reaction vessel 10 as being disposed vertically.

[0106] By disposing the reaction vessel 10 at an angle in this manner, it is possible to suitably adjust, for example, the movement speed of the carbon dioxide-containing gas 30 in the reaction vessel 10. As a result, even if the length of the reaction vessel 10 is relatively short, it is possible to ensure a sufficient contact time between the amino compound and carbon dioxide, and the reaction to obtain the carbamic acid compound can proceed more suitably.

[0107] However, the inclination angle of the reaction vessel 10 with respect to the vertical direction is preferably 80° or less, more preferably 60° or less, and even more preferably 40° or less.

[0108] In the example of the reaction apparatus 1 shown in the figure, the reaction vessel 10 is cylindrical and the cross-sectional shape of the hollow portion is circular, but the shape of the reaction vessel 10 is not limited to this, and for example, the cross-sectional shape of the hollow portion of the reaction vessel 10 may be any shape, such as elliptical or polygonal. Furthermore, the reaction vessel 10 may have a hollow portion that is curved along the longitudinal direction, and specifically, may have a spiral shape, for example. Furthermore, the reaction vessel 10 may have a hollow portion whose size changes along the longitudinal direction.

[0109] Depending on the combination of the amino compound or the carbamic acid compound to be produced with the solvent, at least a portion of the carbamic acid compound produced in the first step may precipitate from the solution.

[0110] Specifically, for example, as shown in the Examples below, when a solution of 1,6-hexamethylenediamine as an amino compound dissolved in ethanol is brought into contact with a gas containing carbon dioxide, one of the amino groups of 1,6-hexamethylenediamine reacts with carbon dioxide to produce 6-aminohexylcarbamic acid as a carbamic acid compound, as shown in the following formula (1). Since 6-aminohexylcarbamic acid has extremely low solubility in ethanol, it precipitates from the solution as a solid.

[0111] [ka]

[0112] In this way, by precipitating at least a portion of the carbamic acid compound from the solution in the first step, for example, recovery of the carbamic acid compound can be facilitated and the content of impurities can be reduced. Furthermore, even when a purification treatment to increase the purity is performed, the treatment can be performed more efficiently.

[0113] In the above case, one of the two amino groups of the amino compound reacts with carbon dioxide to form a monocarbamic acid compound that is insoluble in the solvent and precipitates. In the precipitated state, however, contact between the monocarbamic acid compound and carbon dioxide is difficult, and therefore the reaction of the remaining amino group in the monocarbamic acid compound with carbon dioxide to form a dicarbamic acid compound does not easily proceed.

[0114] Furthermore, since the reaction of the dissolved unreacted amino compound with carbon dioxide occurs preferentially, most of the obtained carbamic acid compounds are monocarbamic acid compounds in which only one of the two amino groups of the amino compound has reacted with carbon dioxide.

[0115] The precipitated carbamic acid compound precipitates and accumulates at the bottom of the reaction vessel 10. A solid 40 containing the precipitated carbamic acid compound is recovered from a solid recovery section 15 provided at the bottom of the reaction vessel 10.

[0116] The precipitated carbamic acid compound may clog and block the solution recovery port 12, so it is preferable to periodically recover it.

[0117] In the above explanation, as a method for contacting an amino compound having two or more amino groups in the molecule with a gas containing carbon dioxide, the case where an amino compound solution in which an amino compound is dissolved in a solvent is continuously contacted with a gas containing carbon dioxide has been mainly explained. However, for example, a solid amino compound may be continuously contacted with a gas containing carbon dioxide, or a solid amino compound may be continuously contacted with a carbon dioxide solution.

[0118] [1-2] Other processes The method for producing a carbamic acid compound of the present invention may further include other steps in addition to the first step described above. Hereinafter, in this section, such steps will be referred to as "other steps."

[0119] Examples of other processes include various pre-processing processes and post-processing processes. More specifically, examples of the pretreatment step include an impurity removal step in which, when exhaust gas from a factory or a thermal power plant is used as the carbon dioxide-containing gas, the exhaust gas (composition containing carbon dioxide) is passed through a filter or the like to remove gas components other than carbon dioxide and fine particles contained in the gas. By carrying out such a pretreatment step, the reaction in the first step can proceed more smoothly.

[0120] Pretreatment steps also include, for example, steps of concentrating or diluting a composition containing carbon dioxide.

[0121] Furthermore, examples of the post-treatment step include a washing step in which the carbamic acid compound recovered as described above is washed.

[0122] This makes it possible to remove substances other than the carbamic acid compound, such as unreacted amino compounds, and further reduce the content of impurities.

[0123] Other steps include, for example, a purification step in which the carbamic acid compound recovered as a solid is purified to increase its purity.

[0124] Furthermore, when the produced carbamic acid compound is dissolved in the solvent and does not precipitate as a solid, other steps include a separation step in which the produced carbamic acid compound is separated from the recovered solution 20a by a method such as extraction, concentration, reprecipitation, centrifugation, filtration, or column chromatography.

[0125] [2] Uses of carbamic acid compounds The uses of the carbamic acid compound obtained as described above are not particularly limited, but examples thereof include a raw material for polyurea, a crosslinking agent for acrylic rubber, and a foaming curing agent for foamed resins, which will be described later.

[0126] Furthermore, the carbamic acid compound can be decomposed by heating or the like to release carbon dioxide. This allows carbon dioxide to be suitably stored, transported, etc., without using, for example, a gas cylinder, etc. By using the compound in such a form, it is possible to reduce the space required for storing carbon dioxide and reduce the costs of storing and transporting carbon dioxide, while eliminating the risk of gas explosions, etc.

[0127] Furthermore, the amino compound obtained by the carbamic acid compound releasing carbon dioxide can be suitably reused in the first step described above.

[0128] The heating temperature during the reaction of decomposing a carbamic acid compound to obtain carbon dioxide and an amino compound is not particularly limited, but is preferably 60°C or higher and 200°C or lower, more preferably 80°C or higher and 180°C or lower, and even more preferably 100°C or higher and 150°C or lower.

[0129] A catalyst may be used in the reaction of decomposing a carbamic acid compound to obtain carbon dioxide and an amino compound, which allows the heating temperature to be lowered, and is particularly preferred from the viewpoint of energy saving.

[0130] Examples of the catalyst include basic metal oxides such as magnesium oxide (MgO) and aluminum oxide (Al2O3), basic organic compounds such as diazabicycloundecene (also known as 1,8-diazabicyclo[5.4.0]-7-undecene, abbreviated as DBU) and diazabicyclononene (also known as 1,5-diazabicyclo[4.3.0]-5-nonene, abbreviated as DBN), and inorganic acids such as hydrochloric acid, sulfuric acid, and nitric acid.

[0131] [3] Polyurea manufacturing method Next, a method for producing polyurea using the carbamic acid compound obtained as described above as a raw material will be described.

[0132] The method for producing polyurea of ​​this embodiment includes a second step of polymerizing the carbamic acid compound obtained in the first step to obtain polyurea. In other words, polyurea can be suitably produced by carrying out the first step of continuously contacting an amino compound having two or more amino groups in its molecule with a composition containing carbon dioxide to continuously obtain a carbamic acid compound, followed by the second step of polymerizing the carbamic acid compound to obtain polyurea.

[0133] [3-1] Second step The polymerization reaction in the second step may be carried out in the absence of a solvent (solvent-free) or in the presence of a solvent.

[0134] Examples of solvents include water, alcohols (e.g., methanol, ethanol, propanol, isopropanol, butanol, tert-butanol, ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, glycerin, etc.), tetrahydrofuran, dioxane, acetonitrile, N-methyl-2-pyrrolidone, dimethylformamide, dimethyl sulfoxide, benzene, toluene, xylene, pyridine, etc. These may be used alone or in combination of two or more.

[0135] The amount of the solvent used is preferably 1,000 parts by mass or less, more preferably 100 parts by mass or more and 500 parts by mass or less, and even more preferably 200 parts by mass or more and 300 parts by mass or less, relative to 100 parts by mass of the carbamic acid compound which is the polymerization component. This allows the polymerization reaction of the carbamic acid compound to proceed more favorably.

[0136] The carbamic acid compound may be at least partially dissolved in a solvent, or may be dispersed in a solvent (dispersion medium).

[0137] The polymerization reaction may be carried out in the absence of a catalyst (catalyst-free) or in the presence of a catalyst, but is preferably carried out in the presence of a catalyst.

[0138] This can promote the polymerization reaction of the carbamic acid compound and improve the yield of polyurea.

[0139] As the catalyst, for example, a basic catalyst can be used. Examples of basic catalysts include hydroxides of alkali metals or alkaline earth metals such as sodium hydroxide, potassium hydroxide, and calcium hydroxide; carbonates such as sodium carbonate and calcium carbonate; oxides such as lime; sulfites such as sodium sulfite; phosphates such as potassium phosphate and sodium phosphate; and amines such as ammonia, trimethylamine, triethylamine, monoethanolamine, diethanolamine, triethanolamine, hexamethylenetetramine, and pyridine.

[0140] The amount of catalyst used is preferably 0.005 parts by mass or more and 20 parts by mass or less, more preferably 0.01 parts by mass or more and 15 parts by mass or less, and even more preferably 0.02 parts by mass or more and 10 parts by mass or less, relative to 100 parts by mass of the carbamic acid compound as the polymerization component.

[0141] This can more suitably promote the polymerization reaction of the carbamic acid compound, thereby further improving the yield of polyurea.

[0142] In the second step, the reaction of polymerizing the carbamic acid compound is preferably carried out in a pressure-resistant vessel.

[0143] As a result, even if CO2 is released from the carbamic acid compound when heated in the second step, for example, the released CO2 will be present in the same system of the pressure-resistant vessel, and the CO2 and the compound from which CO2 has been released from the carbamic acid compound can be reacted again to regenerate the carbamic acid compound, allowing the polymerization reaction to proceed more smoothly and resulting in a higher yield of polyurea.

[0144] In the second step, the reaction time for polymerizing the carbamic acid compound is preferably 0.5 hours or more and 24 hours or less, more preferably 1 hour or more and 12 hours or less, and even more preferably 2 hours or more and 10 hours or less.

[0145] This makes it possible to prevent the time required for producing the polyurea from becoming long, while increasing the yield of the polyurea.

[0146] In the second step, the reaction temperature when polymerizing the carbamic acid compound is preferably 0°C or higher and 300°C or lower, more preferably 50°C or higher and 250°C or lower, and even more preferably 100°C or higher and 200°C or lower. This allows the polymerization reaction of the carbamic acid compound to proceed more favorably.

[0147] In the second step, the reaction pressure (gauge pressure) when polymerizing the carbamic acid compound is preferably 0.1 MPa or more and 15.0 MPa or less, more preferably 1.0 MPa or more and 13.0 MPa or less, and even more preferably 5.0 MPa or more and 10.0 MPa or less. This allows the polymerization reaction of the carbamic acid compound to proceed more favorably.

[0148] The polyurea obtained as described above may be purified, for example, if necessary.

[0149] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these.

[0150] For example, the method for producing a carbamic acid compound of the present invention is not particularly limited as long as it is capable of continuously obtaining a carbamic acid compound by continuously contacting an amino compound with a composition containing carbon dioxide in the first step.

[0151] Specifically, for example, the above description has been given taking the case of using a flow-type reactor as an example, but the method for producing a carbamic acid compound of the present invention is not limited to this, and may use a reactor such as a continuous reactor type (CSTR), a mixed suspension mixed product discharge type (MSMPR), a Taylor vortex type, a microchannel type, or a Dean vortex type. The reaction apparatus may also be equipped with a stirring blade, a vibrating device, or the like.

[0152] Furthermore, for example, the method for producing polyurea according to the present invention may include steps other than the steps described above (for example, a pretreatment step, an intermediate treatment step, a post-treatment step, etc.).

[0153] More specifically, an intermediate treatment step or a post-treatment step for promoting a chemical reaction other than those described above may be included between Step 1 and Step 2 or after Step 2. Examples of such steps include a step of converting the functional group possessed by the carbamic acid compound obtained through Step 1 into another chemical structure when the amino compound has a functional group other than an amino group, and a step of removing the protecting group from the carbamic acid compound obtained through Step 1 or the polyurea obtained through Step 2 when the amino compound has a functional group other than an amino group and the functional group is protected with a protecting group (deprotection step).

[0154] Furthermore, for example, in the above explanation, a case has been described in which the carbamic acid compound that has precipitated from the amino compound solution is separated in the first step, but the method for producing polyurea according to the present invention is not limited to this, and for example, the carbamic acid compound that has precipitated in the first step may be polymerized in the second step while remaining precipitated (dispersed) in the solution without being separated.

[0155] Furthermore, for example, when the carbamic acid compound produced in the first step is in a state of being dissolved in a solvent, it may be polymerized in the second step while remaining dissolved in the solution. [Example]

[0156] The present invention will be described in detail below based on specific examples, but the present invention is not limited to these examples.

[0157] [4] Production of carbamic acid compounds Example 1 A carbamic acid compound was produced by carrying out a first step in which an amino compound having two or more amino groups in the molecule was continuously contacted with a composition containing carbon dioxide to continuously obtain the carbamic acid compound as follows.

[0158] First, 1,6-hexamethylenediamine as an amino compound was dissolved in ethanol to a concentration of 50% by mass to obtain an amino compound solution.

[0159] The amino compound solution was continuously fed from the top of a cylindrical reaction vessel having an inner diameter of 10 mm and a length of 300 mm at a flow rate of 1.0 mL / min. Meanwhile, the test gas was continuously supplied from the bottom of the reaction vessel at a flow rate of 0.8 L / min.

[0160] The test gas used was a model combustion exhaust gas (equivalent to LNG combustion) at 40°C with a composition of CO2: 3 mol%, O2: 16 mol%, and N2: 81 mol%. The CO2 concentration of the test gas was 30,000 ppm.

[0161] 1,6-Hexamethylenediamine in the solution reacted with carbon dioxide in the test gas to produce 6-aminohexylcarbamic acid as a carbamic acid compound.

[0162] FIG. 2 is a photograph showing the production of 6-aminohexylcarbamic acid in the reaction vessel in the first step of this example.

[0163] It can be seen from FIG. 2 that the produced 6-aminohexylcarbamic acid was at least partially precipitated as a solid, and the solution in the reaction vessel was cloudy.

[0164] The precipitated 6-aminohexylcarbamic acid was collected from the bottom of the reaction vessel and washed with ethanol.

[0165] Example 2 The amino compound solution used was a solution obtained by dissolving 1,3-bisaminomethylcyclohexane in ethanol to a concentration of 75% by mass, the test gas used was a mixed gas having a composition of 10 mol% CO2 and 90 mol% N2, the flow rate of the amino compound solution was 20 mL / min, and the flow rate of the test gas from the bottom of the reaction vessel was 3 L / min. Except for this, the treatment was carried out in the same manner as in Example 1.

[0166] In this example, 1,3-bisaminomethylcyclohexane in the solution reacted with carbon dioxide in the test gas to produce 3-aminomethylcyclohexylmethylcarbamic acid as a carbamic acid compound.

[0167] Example 3 The amino compound solution used was a solution obtained by dissolving isophoronediamine in ethanol to a concentration of 30% by mass, the test gas used was a mixed gas having a composition of CO2: 3 mol% and N2: 97 mol%, and the flow rate of the amino compound solution was set to 5 mL / min, and the flow rate of the test gas from the bottom of the reaction vessel was set to 2 L / min. Except for this, the treatment was carried out in the same manner as in Example 1.

[0168] In this example, isophoronediamine in the solution reacted with carbon dioxide in the test gas to produce 5-amino-1,3,3-trimethylcyclohexylmethylcarbamic acid as a carbamic acid compound.

[0169] [5] Polyurea manufacturing The second step of polymerizing the carbamic acid compounds obtained in the above examples was carried out as follows to obtain polyurea.

[0170] First, N-methyl-2-pyrrolidone was added as a solvent (dispersion medium) to the carbamic acid compound obtained in each of the above Examples, and potassium phosphate was further added as a catalyst, and the mixture was mixed to prepare a reaction mixture.

[0171] The amount of the solvent used was 150 parts by mass relative to 100 parts by mass of the carbamic acid compound, and the amount of the catalyst added was 10 parts by mass relative to 100 parts by mass of the carbamic acid compound.

[0172] At least a part of the carbamic acid compound was dispersed in N-methyl-2-pyrrolidone.

[0173] The reaction mixture was placed in a pressure vessel, heated to 200° C. under atmospheric pressure, and reacted for 7 hours. After the reaction was completed, a white solid was found in the pressure vessel. This white solid was scraped off and washed with water.

[0174] [6] Evaluation As shown below, for each of the above examples, the CO2 absorption ability in the first step was evaluated, and the carbamic acid compound obtained in the first step and the white solid obtained in the second step were also evaluated.

[0175] [6-1]CO2 absorption In the first step, the CO2 concentration contained in the discharged gas was measured using a CO2 analyzer (total organic carbon analyzer).

[0176] In Example 1, the CO2 contained in the test gas was removed by adsorption to 1,6-hexamethylenediamine in an ethanol solution, and the CO2 concentration in the gas was reduced from 30,000 ppm to nearly 200 ppm. The CO2 recovery rate was approximately 99%.

[0177] In Example 2, the CO2 contained in the test gas was removed by adsorption to 1,3-bisaminomethylcyclohexane in an ethanol solution, and the CO2 concentration in the gas was reduced from 100,000 ppm to nearly 600 ppm. The CO2 recovery rate was approximately 99%.

[0178] In Example 3, the CO2 contained in the test gas was removed by adsorption to isophoronediamine in an ethanol solution, and the CO2 concentration in the gas was reduced from 30,000 ppm to nearly 300 ppm. The CO2 recovery rate was approximately 99%.

[0179] [6-2]IR Spectrum The IR spectra of the carbamic acid compound obtained in the first step and the white solid obtained in the second step were measured using Fourier transform infrared spectroscopy (FT-IR), and it was confirmed that the polymerization reaction had progressed.

[0180] More specifically, in Example 1, it can be said that 6-aminohexylcarbamic acid is polymerized to produce polyurea, as shown in the following formula (2), in Example 2, it can be said that 3-aminomethylcyclohexylmethylcarbamic acid is polymerized to produce polyurea, as shown in the following formula (5), and in Example 3, it can be said that 5-amino-1,3,3-trimethylcyclohexylmethylcarbamic acid is polymerized to produce polyurea, as shown in the following formula (6). Note that in formulas (2), (5), and (6), n is an integer of 2 or greater.

[0181] [ka]

[0182] [ka]

[0183] [ka]

[0184] Figure 3 shows IR spectra of 6-aminohexylcarbamic acid obtained in the first step and the white solid obtained in the second step in Example 1. Figure 4 shows IR spectra of 3-aminomethylcyclohexylmethylcarbamic acid obtained in the first step and the white solid obtained in the second step in Example 2. Figure 5 shows IR spectra of 5-amino-1,3,3-trimethylcyclohexylmethylcarbamic acid obtained in the first step and the white solid obtained in the second step in Example 3.

[0185] [6-3] Thermogravimetry The carbamic acid compound obtained in the first step and the white solid obtained in the second step were heated from 30°C to 600°C at a rate of 10°C / min under a nitrogen atmosphere using a thermogravimetric analyzer (TG), and the weight loss was measured.

[0186] Fig. 6 is a diagram showing the thermogravimetric changes of 6-aminohexylcarbamic acid obtained in the first step and the white solid obtained in the second step in Example 1. Fig. 7 is a diagram showing the thermogravimetric changes of 3-aminomethylcyclohexylmethylcarbamic acid obtained in the first step and the white solid obtained in the second step in Example 2. Fig. 8 is a diagram showing the thermogravimetric changes of 5-amino-1,3,3-trimethylcyclohexylmethylcarbamic acid obtained in the first step and the white solid obtained in the second step in Example 3.

[0187] As shown in Figures 6 to 8, the weight of the monomeric carbamic acid compound decreased rapidly when the temperature exceeded 100°C, whereas the weight of the white solid tended to decrease gradually just before the temperature reached 100°C.

[0188] As described above, according to the method for producing a carbamic acid compound of the present invention, a composition containing carbon dioxide is used as a raw material, and an amino compound is continuously contacted with the composition containing carbon dioxide, whereby carbon dioxide contained in the gas can be continuously and efficiently recovered, and the recovered carbon dioxide can be effectively utilized to efficiently produce a carbamic acid compound.

[0189] Furthermore, the obtained carbamic acid compound can be suitably used, for example, as a raw material for polyurea. In particular, according to the method for producing polyurea of ​​the present invention, carbon dioxide absorbed by the amino compound can be incorporated and fixed in the skeleton of polyurea without separation.

[0190] Furthermore, in the second step, the same treatment as in Examples 1 to 3 was carried out except that 1,8-diazabicyclo[5.4.0]-7-undecene (DBU) was used as the catalyst instead of potassium phosphate. As a result, it was confirmed that carbon dioxide was efficiently absorbed and polyurea was produced, similar to Examples 1 to 3.

[0191] Furthermore, in the second step, the heating temperature was varied within a range of 0°C to 300°C, and the reaction time was varied within a range of 0.5 hours to 24 hours. Except for this, the same treatment as in Examples 1 to 3 was carried out, and it was confirmed that carbon dioxide was efficiently absorbed and polyurea was produced, similar to Examples 1 to 3. [Explanation of symbols]

[0192] 1: Reactor 10: Reaction vessel 11: Solution supply port 12: Solution collection port 13: Gas supply port 14: Gas outlet 15: Solid recovery section 16:Solution supply tube 17: Solution recovery tube 18: Gas supply pipe 20: Amino compound solution 20a: Solution 30: Gas containing carbon dioxide 30a: Gas 40: solid G: Arrow L: Arrow

Claims

1. A method for producing a carbamic acid compound, comprising a step of continuously contacting an amino compound having two or more amino groups in the molecule with a composition containing carbon dioxide to continuously obtain a carbamic acid compound.

2. In the above step, An amino compound solution obtained by dissolving the amino compound in a solvent is continuously supplied from the top to the bottom of the reaction vessel, and The composition containing carbon dioxide is continuously supplied from the bottom to the top of the reaction vessel, The method for producing a carbamic acid compound according to claim 1, wherein the amino compound solution is continuously contacted with the composition containing carbon dioxide.

3. 3. The method for producing a carbamic acid compound according to claim 2, wherein the amino compound solution recovered from the bottom of the reaction vessel is fed back into the reaction vessel.

4. The method for producing a carbamic acid compound according to claim 3, wherein the carbon dioxide-containing composition is supplied to the reaction vessel from a position higher than a position at which the amino compound solution is recovered from the reaction vessel.

5. 5. The method for producing a carbamic acid compound according to claim 2, wherein the reaction vessel used in the step is cylindrical and arranged so that its longitudinal direction is vertical.

6. 5. The method for producing a carbamic acid compound according to claim 2, wherein in the step, at least a part of the carbamic acid compound is precipitated from the amino compound solution.

7. 5. The method for producing a carbamic acid compound according to claim 1, wherein the composition containing carbon dioxide is air or an exhaust gas from a factory or a thermal power plant.

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