Deuterium synthesis method and deuterium synthesis apparatus

Abstract

This invention provides a deuterium synthesis method that can efficiently produce high-purity deuterium D2 or partially deuterated deuterium HD. [Solution] The deuterium synthesis method according to the present invention applies a water-gas shift equilibrium reaction with formic acid as a reaction intermediate, and includes a step to isolate the formic acid, which is the reaction intermediate. Separation is performed by utilizing the difference in solubility of carbon dioxide, hydrogen, carbon monoxide, and formic acid in the solvent (water), thereby synthesizing high-purity deuterium.

Description

Technical Field

[0001] The present invention relates to a method for synthesizing deuterium, and more particularly to a method for synthesizing deuterium that utilizes the fact that the intermediate of the water-gas shift equilibrium reaction is formic acid.

Background Art

[0002] Most of the energy sources relied on to date are fossil fuels, which are indispensable resources for humanity. However, since fossil fuels may be depleted, there is an urgent need to consider the reuse and regeneration of fossil fuels and to efficiently obtain energy from sunlight, wind power, etc. On the other hand, research and development on energy acquisition by nuclear fusion are being carried out, and nuclear fusion requires tritium and deuterium as its fuel sources. To date, the inventors have studied organic synthesis from carbon dioxide and water, and from a physical and chemical perspective, have elucidated the reaction mechanism and studied reaction efficiency improvement. Among them, the inventors first announced worldwide the reversibility of the water-gas shift reaction (water-gas shift equilibrium reaction) and that the reaction intermediate is formic acid. A technique that makes use of the reversibility of the water-gas shift reaction and the reaction intermediate formic acid is, for example, Patent Document 1 below. Also, regarding deuterium production using formic acid, it is Non-Patent Document 1 below.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Non-Patent Documents

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Regarding the production technology for deuterium, the fuel source for nuclear fusion energy, there is still much room for improvement in terms of purity.

[0005] In view of the above problems, the object of the present invention is to provide a method for increasing the purity of deuterium. [Means for solving the problem]

[0006] [Summary of findings on the water-gas shift equilibrium reaction using formic acid as a reaction intermediate] The water-gas shift reaction, which produces carbon dioxide and hydrogen from carbon monoxide and water, has been known for a long time. The inventors confirmed that in the hydrothermal decomposition reaction of formic acid, both reactions exist: one that decomposes into carbon monoxide and water, and another that decomposes into carbon dioxide and hydrogen, indicating that these are competing reactions. Until then, only the decomposition of formic acid into carbon dioxide and hydrogen was known. Therefore, they confirmed that it can also decompose into carbon monoxide and water by controlling the reaction conditions, and published this finding for the first time in the world. Furthermore, relating the long-known water-gas shift reaction to formic acid, they predicted that the water-gas shift reaction is a reversible reaction with formic acid as an intermediate, confirmed this experimentally, and reported it at an academic conference. They found that by controlling the reaction conditions, the abundance ratio of carbon monoxide and water, or carbon dioxide and hydrogen, could be freely manipulated, and established methods for obtaining only carbon monoxide or only carbon dioxide and hydrogen. In addition, although formic acid is a reaction intermediate, it is a stable organic compound that can be extracted. Therefore, in this invention, they considered how to apply the control of reaction conditions and the stability of formic acid to "selectively produce hydrogen," leading to the completion of the invention. Figure 1 summarizes the characteristics of the water-gas shift equilibrium reaction, the reaction intermediate formic acid, and the two reaction pathways. Centered around formic acid, it is a competitive reaction between the decomposition of carbon dioxide and hydrogen, and the decomposition of carbon monoxide and water. The former is thermodynamically controlled, and the latter kinetically controlled, and by controlling the reaction temperature, each reaction can be promoted or inhibited. Furthermore, since carbon dioxide, hydrogen, and carbon monoxide are gases at room temperature and pressure, each reaction can also be promoted or inhibited by controlling the pressure of the reaction field. In addition, each reaction can be controlled by using differences in reaction rate constants, acid catalysts, and catalytic action of the reaction vessel surface, effectively allowing only one reaction to proceed. As it is an equilibrium reaction, by controlling the reaction conditions described above, the forward and reverse reactions can be preferentially promoted or inhibited. Figure 1 is a simplified summary of these concepts, and more details are described in Japanese Patent No. 7288484. Furthermore, carbon dioxide, hydrogen, and carbon monoxide are gases at room temperature and pressure, while formic acid is a liquid at room temperature and pressure. Also, since these substances have different solubility in solvents, utilizing this property for substance separation is a key feature of the present invention. When water is used as the solvent, carbon dioxide, hydrogen, and carbon monoxide have low solubility, while formic acid has high solubility. This difference in solubility allows for the separation of substances, thereby increasing purity. By carefully setting the conditions, it is possible to obtain substances with a purity virtually indistinguishable from 100%. The present invention offers an excellent method for selectively producing desired substances and for substance separation. In summary, the features of this invention are: controlling the reaction conditions of the aqueous-gas shift equilibrium reaction with formic acid as a reaction intermediate; providing a step to isolate formic acid, a relatively stable substance among the reaction intermediates; and utilizing substance separation using the difference in solubility of the solvent, particularly when the solvent is water. This makes it possible to increase the purity of deuterium, which is the objective of this invention, and to isolate only deuterium through the separation process described above. In the deuterium synthesis method according to the present invention, it is preferable to include a synthesis step of reacting carbon monoxide with heavy water (D2O) to synthesize diutemic acid, and a hydrogenation step of decomposing the diutemic acid synthesized in the synthesis step into carbon dioxide and deuterium. Furthermore, in the deuterium synthesis method according to the present invention, it is preferable to include a preparation step of decomposing formic acid into carbon monoxide and water, a synthesis step of reacting the carbon monoxide produced by the decomposition in the preparation step with heavy water to synthesize diutemic acid, and a hydrogenation step of decomposing the diutemic acid synthesized in the synthesis step into carbon dioxide and deuterium.

[0007] In the deuterium synthesis method according to the present invention, it is preferable that the method includes a synthesis step of reacting carbon monoxide with heavy water to synthesize formic acid, a substitution step of replacing the dihydroxyl group of the formic acid synthesized in the synthesis step with a hydroxyl group in water to form partially deuterated formic acid DCOOH, and a hydrogenation step of decomposing the partially deuterated formic acid substituted in the substitution step into carbon dioxide and partially deuterium HD.

[0008] In the deuterium synthesis method according to the present invention, it is preferable that the method includes: a preparation step of decomposing formic acid into carbon monoxide and water; a synthesis step of reacting the carbon monoxide produced by the decomposition in the preparation step with heavy water to synthesize diutemic acid; a substitution step of substituting the dihydroxyl group of the diutemic acid synthesized in the synthesis step with a hydroxyl group in water to form partially deuterated formic acid DCOOH; and a hydrogenation step of decomposing the partially deuterated formic acid substituted in the substitution step into carbon dioxide and partially dehydrogen dioxide HD.

[0009] Furthermore, in the above-described deuterium synthesis method, it is preferable that at least one of the synthesis step, the hydrogenation step, and the preparation step be carried out under hydrothermal conditions.

[0010] With this configuration, deuterium can be produced efficiently.

[0011] In addition, in the above method for synthesizing deuterium, it is preferable that at least one of the synthesis step, the hydrogenation step, and the preparation step is carried out in an ionic liquid.

[0012] According to such a configuration, deuterium can be efficiently generated.

Advantages of the Invention

[0013] As described above, according to the present invention, it is possible to provide a method for synthesizing deuterium that can efficiently generate deuterium.

Brief Description of the Drawings

[0014] [Figure 1] A schematic diagram related to the present invention, showing the water-gas shift equilibrium reaction in which the reaction intermediate is formic acid and the reaction conditions. [Figure 2] Reaction scheme (D2) of the method for synthesizing deuterium according to an embodiment of the present invention. [Figure 3] Reaction scheme (HD) of the method for synthesizing deuterium according to an embodiment of the present invention. [Figure 4] Schematic cross-sectional view of the apparatus used in the method for synthesizing deuterium according to an embodiment of the present invention. [Figure 5] Raman spectrum observing D2 and HD related to the present invention.

Embodiments for Carrying Out the Invention

[0015] The method for synthesizing deuterium according to an embodiment of the present invention includes a synthesis step of reacting carbon monoxide with heavy water to synthesize heavy formic acid, and a hydrogenation step of decomposing the heavy formic acid synthesized in the synthesis step into carbon dioxide and deuterium. It also includes a preparation step of decomposing formic acid into carbon monoxide and water, a synthesis step of reacting the carbon monoxide generated by the decomposition in the preparation step with heavy water to synthesize heavy formic acid, and a hydrogenation step of decomposing the heavy formic acid synthesized in the synthesis step into carbon dioxide and deuterium.

[0016] Alternatively, it has a synthesis step of synthesizing formic acid-d by reacting carbon monoxide with heavy water, a substitution step of substituting the heavy hydroxy group of the formic acid-d synthesized in the synthesis step with a hydroxy group in water to obtain partially deuterated formic acid DCOOH, and a hydrogenation step of decomposing the partially deuterated formic acid substituted in the substitution step into carbon dioxide and partially deuterated hydrogen HD. Further, it has a preparation step of decomposing formic acid into carbon monoxide and water, a synthesis step of synthesizing formic acid-d by reacting the carbon monoxide generated by the decomposition in the preparation step with heavy water, a substitution step of substituting the heavy hydroxy group of the formic acid-d synthesized in the synthesis step with a hydroxy group in water to obtain partially deuterated formic acid DCOOH, and a hydrogenation step of decomposing the partially deuterated formic acid substituted in the substitution step into carbon dioxide and partially deuterated hydrogen HD.

[0017] Alternatively, at least one of the synthesis step, the hydrogenation step, and the preparation step is carried out under hydrothermal conditions.

[0018] Alternatively, at least one of the synthesis step, the hydrogenation step, and the preparation step is carried out in an ionic liquid. Hereinafter, "relating to an embodiment of the present invention" is simply referred to as "relating to the present embodiment".

[0019] The deuterium synthesis method according to the present embodiment is implemented, for example, under the concept as shown in FIG. 4.

[0020] [Conceptual diagram related to deuterium synthesis method] Utilize the water gas shift equilibrium reaction with formic acid as the reaction intermediate to synthesize deuterium. Regarding the two equilibrium reactions described in FIG. 1, in order to obtain only the desired product by properly controlling the reaction conditions, in fact, only one of the reactions proceeds. Further, the present invention applies the differences in solubility that carbon dioxide, hydrogen, and carbon monoxide are gases at normal temperature and pressure, and formic acid is a liquid at normal temperature and pressure.

[0021] Figure 1 summarizes the characteristics of the water-gas shift equilibrium reaction, the reaction intermediate formic acid, and the two reaction pathways. Centered around formic acid, the reaction involves a competition between the decomposition of carbon dioxide and hydrogen, and the decomposition of carbon monoxide and water. The former is thermodynamically controlled, while the latter is kinetically controlled. By controlling the reaction temperature, each reaction can be promoted or inhibited. Furthermore, since carbon dioxide, hydrogen, and carbon monoxide are gases at room temperature and pressure, each reaction can also be promoted or inhibited by controlling the pressure in the reaction field. In addition, each reaction can be controlled by using differences in reaction rate constants, acid catalysts, and catalytic activity on the reaction vessel surface, effectively allowing only one reaction to proceed. As it is an equilibrium reaction, by controlling the reaction conditions described above, the forward and reverse reactions can be preferentially promoted or inhibited. Figure 1 provides a simplified summary of these concepts. Furthermore, carbon dioxide, hydrogen, and carbon monoxide are gases at room temperature and pressure, while formic acid is a liquid at room temperature and pressure. Also, since these substances have different solubility in solvents, utilizing this property for substance separation is a key feature of this invention. When water is used as the solvent, carbon dioxide, hydrogen, and carbon monoxide have low solubility, while formic acid has high solubility. This difference in solubility allows for the separation of substances, thereby increasing purity. By carefully setting the conditions, it is possible to obtain substances with a purity virtually indistinguishable from 100%. This invention provides a method that considers both the selective production of desired substances and their separation. In summary, the features of this invention are: controlling the reaction conditions of the aqueous-gas shift equilibrium reaction with formic acid as a reaction intermediate; providing a step to isolate formic acid, a relatively stable substance among the reaction intermediates; and utilizing substance separation using the difference in solubility of the solvent, particularly when the solvent is water. This makes it possible to increase the purity of deuterium, which is the objective of this invention, and to isolate only deuterium through the separation process described above. Figure 2 shows the steps for the production of deuterium D2. The procedure is described starting with formic acid, but carbon monoxide may also be used as the starting material. The procedure is described using water as the solvent, but other solvents may also be used. First, the formic acid is decomposed into carbon monoxide and water (1). For the decomposition method, please refer to Japanese Patent No. 7288484. Since the product carbon monoxide is a gas at room temperature and pressure, only carbon monoxide can be isolated. If degassing is performed when injecting formic acid and water into the reaction vessel, only carbon monoxide can be isolated after the reaction. On the other hand, even if nitrogen or oxygen is present, for example, degassing is not always necessary as only carbon monoxide needs to be reacted in the next step. In the next step, the isolated carbon monoxide and heavy water are injected into the reaction vessel and the reaction proceeds to produce deuterium formic acid DCOOD (2). The generated deuterium formic acid is dissolved in deuterium acid at room temperature and pressure after the reaction, so it can be easily separated from the starting material carbon monoxide. The reason is that carbon monoxide has extremely low solubility in water. For the next step, only the formic acid aqueous solution is taken out and decomposed into carbon dioxide and deuterium D2 in a separate reaction vessel 10 (3). Alternatively, degassing may be performed before decomposition into carbon dioxide and deuterium, as in step (1). Deuterium and carbon dioxide may be separated using a metal container or the like. In step (3), only the formic acid may be taken out and other solvents (organic solvents such as benzene or ionic liquids, etc.) may be used. Figure 3 shows the steps for producing partially deuterated HD. The only difference from deuterium D2 shown in Figure 2 is step 2'; otherwise, it is the same. Also, similar to the production of D2, HD may be produced by starting with carbon monoxide. Step 2' is the step of substituting the hydroxyl groups OD of deuterium DCOOD with OH in water (light water, H2O). When deuterium DCOOD is dissolved in a large amount of H2O compared to deuterium DCOOD, theoretically, almost all of the hydroxyl groups of deuterium will be replaced with OH groups. Of course, care must be taken with the concentration of deuterium so that almost all of them become OH groups. From the above, by adding the step of producing partially deuterated deuterium DCOOH, it is possible to produce HD with nearly 100% purity. Using these findings, we disclose a method for synthesizing deuterium.

[0022] [Deuterium synthesis apparatus] The deuterium synthesis method according to this embodiment is the same as that described in Japanese Patent No. 7288484, and is carried out, for example, under an apparatus as shown in Figure 4. The apparatus 1 for carrying out the method for accelerating the formic acid synthesis reaction according to this embodiment is a batch reactor having a containment space S capable of accommodating a reaction solvent (or a solution in which the reaction substrate to be reacted is dissolved). Here, a batch reactor is used as an example, but a flow reactor may also be used. Specifically, the apparatus 1 for carrying out the method for accelerating the formic acid synthesis reaction according to this embodiment comprises a reaction vessel 10 formed in a cylindrical shape and having a containment space S inside that can accommodate a solvent (solution), a jacket 20 covering the outer surface and bottom surface of the reaction vessel 10, and a reaction medium storage tank 30 for storing the reaction medium containing the solvent (solution). Furthermore, the apparatus 1 for carrying out the deuterium synthesis method according to this embodiment includes a pipe L for connecting the reaction vessel 10 and the reaction medium storage tank 30, and a valve V for adjusting the open / closed state of the pipe L. Furthermore, the apparatus 1 for carrying out the deuterium synthesis method according to this embodiment preferably includes an inert gas storage tank (not shown) in which an inert gas such as nitrogen gas, helium gas, or argon gas is stored, piping connecting the inert gas storage tank and the reaction tank 10, and a valve for adjusting the open / closed state of the piping.

[0023] The reaction vessel 10 comprises a cylindrical side wall portion 10a, a bottom wall portion 10b that closes the bottom side of the cylindrical side wall portion 10a, and a top wall portion 10c that closes the top side of the cylindrical side wall portion 10a. In the reaction vessel 10, as described above, the containment space S is made into a sealed space by closing the cylindrical side wall portion 10a with the bottom wall portion 10b and the top wall portion 10c. The solvent (solution) is contained in the containment space S of the reaction vessel 10 via piping L from the reaction medium storage tank 30. The containment of the reaction medium into the containment space S may be carried out after reducing the pressure inside the containment space S using a vacuum pump (not shown), or it may be carried out under atmospheric pressure (1.01325 × 10⁵ Pa (0.101325 MPa)) without reducing the pressure inside the containment space S. It is preferable to contain the reaction medium in the containment space S under atmospheric pressure conditions without reducing the pressure inside the containment space S. In the reaction vessel 10, after the reaction medium is contained in the containment space S, the inert gas stored in the inert gas storage tank is sealed into the containment space S, so that at least a portion of the air contained in the gas phase portion of the containment space S is replaced with the inert gas, or all of the air contained in the gas phase portion of the containment space S is replaced with the inert gas. Replacement with inert gas is the best mode, but not essential. In this state, carbon monoxide may be sealed into the containment space S. Each gas to be sealed is sealed in a predetermined amount at a pressure higher than the pressure inside the containment space S. The specific configuration of the apparatus and the sealing method are the same as for inert gas. In addition to connecting a gas storage tank to the piping L for gas injection as described above, a gas recovery tank may also be connected to the piping L for gas recovery. The reaction vessel 10 may also be equipped with a stirring device (not shown) for stirring the reaction medium contained within the containment space S. Since the reaction vessel 10 is equipped with the stirring device, the reaction can be carried out while stirring the reaction medium contained in the containment space S with the stirring device. This makes it possible to carry out the deuterium synthesis reaction contained in the reaction medium more efficiently.

[0024] As described above, the apparatus 1 for carrying out the deuterium synthesis method according to this embodiment is a batch reactor, and therefore the reaction vessel 10 is a batch container. A batch-type container refers to a container that can contain the reaction medium and reaction substrate used in a single-process treatment in a sealed manner. Since the reaction vessel 10 has an inner wall surface that comes into contact with the reaction medium and reaction substrate it contains, it is preferable to use a non-metallic material for the inner wall surface if possible. Preferred materials for forming the inner wall surface include resin, glass, ceramic, and diamond-like carbon.

[0025] The aforementioned resin may be, for example, a plastic such as polyimide (PI), polyamide (PA), polyamideimide (PAI), polyethersulfone (PES), polyetherimide (PEI), polyetheretherketone (PEEK), aromatic polyester (PET, PEN, etc.), or polyallylen sulfide (PAS), or it may be a general rubber. In this embodiment, from the viewpoint of stability against hydrothermal reactions, the resin is preferably a silicone resin, silicone rubber, fluororesin, fluororubber, epoxy resin, etc. Among these resins, the aforementioned resin is preferably a fluororesin. Examples of the aforementioned fluororesins include polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), polychlorotrifluoroethylene (PCTFE), tetrafluoroethylene-ethylene copolymer (ETFE), and polyvinylidene fluoride (PVdF). The aforementioned resin may be used as a single component of the inner wall surface, or as a mixture of two or more resins.

[0026] Examples of the aforementioned glass include soda-lime glass, borosilicate glass, quartz glass, and crystal glass.

[0027] Examples of the aforementioned ceramics include alumina (Al2O3), zirconia (ZrO2), titania (TiO2), silica (SiO2), silicon carbide (SiC), silicon nitride (Si3N4), zircon (ZrO2·SiO2), aluminosilicate (Al2O3·SiO2), barium titanate (BaTiO3), aluminum nitride (AlN), steatite (MgO·SiO2), forsterite (2MgO·SiO2), mullite (3Al2O3·2SiO2), and cordierite (2MgO·2Al2O3·5SiO2). The aforementioned ceramic may be used as a single component of the inner wall surface, or as a mixture of two or more types of ceramics.

[0028] The reaction vessel 10 may be composed of the above material for the entire wall defining the containment space S, or only the surface layer (the surface layer forming the inner wall surface of the reaction vessel 10) may be composed of the above material. The above material may be formed in multiple layers. The reaction vessel 10 may, for example, have a metal body with a double layer of glass and resin laminated on the inner wall surface of the body. The reaction vessel 10 may be replaced after each reaction step.

[0029] The material forming the inner wall surface is preferably such that the amount of metal ions eluted by formic acid at room temperature (23±2℃) is 1000 ppm or less. The amount of metal ions eluted can be measured by methods such as ICP.

[0030] As described above, by constructing the inner wall surface of the reaction vessel 10 from a nonmetallic material, the inner wall surface of the reaction vessel 10 becomes acid-resistant. Furthermore, if the inner wall surface is made of a metal such as stainless steel, there is a concern that the carboxyl group (COOH) contained in formic acid (HCOOH) may form ionic bonds with the metal. However, if the inner wall surface is made of a nonmetal, the formation of ionic bonds can be suppressed as described above. In other words, the adsorption of the formic acid onto the inner wall surface can be suppressed by forming an ionic bond with the inner wall surface via the carboxyl group. This allows for the more efficient production of formic acid from carbon dioxide and hydrogen.

[0031] The jacket 20 is equipped with a heating device (not shown), such as a heater. The jacket 20 heats the reaction vessel 10 using a heating device such as a heater.

[0032] Any tank having a storage space S for containing the reaction medium can be used as the reaction medium storage tank 30. On the other hand, since the reaction medium storage tank 30 has an inner wall surface that comes into contact with the stored reaction medium, it is preferable that the inner wall surface be made of a nonmetal. Preferred materials for forming the inner wall surface include resin, glass, ceramic, and diamond-like carbon. The same materials as those described above can be used as the resin, glass, and ceramic. [Examples]

[0033] The present invention will be further described in detail below with reference to examples. The following examples are provided to further explain the present invention and do not limit its scope. The examples disclose a part of the method using the findings described in the above-mentioned [Summary of Knowledge on Water-Gas Shift Equilibrium Reaction Using Formic Acid as a Reaction Intermediate] and [Conceptual Diagram of Deuterium Synthesis Method]. The reaction solvent may be water, heavy water, ionic liquid, or organic compound, and a solvent suitable for promoting the reaction should be selected. The reaction temperature should also be appropriately selected to promote the reaction. In the case of a batch reaction vessel, the pressure during the reaction can be controlled by adjusting the amount of starting material and solvent charged into the reaction vessel. The pressure value can be calculated. In the case of a flow reaction, the pressure can be adjusted by controlling the flow pressure.

[0034] Example 1: In the reaction vessel 10 shown in Figure 4, a 3.0 M (mol / L) formic acid aqueous solution (heavy water solution) was added to a packing density of 70%. After degassing with a vacuum pump, nitrogen gas was introduced at atmospheric pressure. After closing the connection valve to seal the reaction vessel, the reaction vessel 10 was heated to 250°C. After 12 hours, the mixed gas of carbon monoxide and nitrogen gas produced at room temperature was removed. The removed carbon monoxide and nitrogen gas were separated using a separation column or similar method, and the carbon monoxide was collected. Then, heavy water was added to the reaction vessel 10 to a packing density of 50%, and the separated carbon monoxide was injected into the (separately prepared) reaction vessel 10. The reaction vessel 10 was then heated to 400°C. After 2 hours, the carbon dioxide and deuterium D2 produced at room temperature were collected (recovered) in a metal container. Subsequently, carbon dioxide and deuterium D2 may be separated using a separation column, or deuterium D2 may be extracted from the carbon dioxide and deuterium D2 in the metal container using the metal permeability of hydrogen. The extracted deuterium gas was subjected to 1H-NMR, 2H-NMR, or Raman NMR. The product was confirmed, and the conversion rate of hydrogen to deuterium (D2) was confirmed by 2H-NMR. As a result, D2 with a conversion rate of nearly 100% was obtained. Figure 5 shows the results of Raman measurement of carbon dioxide and deuterium D2 without separation. For comparison, the reaction conditions and setup were manipulated to set conditions in which only D2 is produced and conditions in which HD and D2 coexist. (a) shows the conditions in which D2 and HD are produced, (b) shows the conditions in which almost only D2 is produced, and (c) shows the case where the initial concentration of formic acid is higher than in (a) and the series of steps are followed.

[0035] Example 2: In Example 1, the process proceeded with a series of steps starting with formic acid. In this example, the reaction conditions were the same except that carbon monoxide was used as the starting point, and the same amount of carbon monoxide that would be produced if all the formic acid decomposed into carbon monoxide and water in Example 1 was injected into the reaction vessel 10. The only difference was that the initial preparation step to decompose the formic acid was skipped. Even in this case, D2 with a D conversion rate of nearly 100% was obtained.

[0036] Example 3: The procedure is the same as in Example 1, except that a substitution step was added after the synthesis step for formic acid synthesis, in which a deuterated hydroxyl group (OD) was replaced with a hydroxyl group (OH). In this case, nearly 100% HD was obtained.

[0037] Example 4: The procedure is the same as in Example 2, except that a substitution step was added after the synthesis step for formic acid synthesis, in which a deuterated hydroxyl group (OD) was replaced with a hydroxyl group (OH). In this case, nearly 100% HD was obtained.

[0038] The above-described embodiments are merely examples, and the present invention is not limited thereto. Furthermore, although the above embodiments and examples for carrying out the invention describe a method in which electrodes are placed in the reaction vessel 10 without applying electricity, the invention is not limited to this, and the reaction may be accelerated by applying electricity. In addition, the reaction may be accelerated by adding a catalytic substance such as a metal catalyst. Furthermore, the reaction may be accelerated by raising the reaction temperature to increase the energy state of the reaction substrate through the Arrhenius effect. [Explanation of Symbols]

[0039] 1: Synthesis apparatus, 10: Reaction vessel, 20: Jacket, 30: Formic acid aqueous solution storage tank, 10a: Side wall, 10b: Bottom wall, 10c: Top wall, L: Piping, S: Storage space, V: Valve.

Claims

1. A synthesis step involves reacting carbon monoxide with heavy water to synthesize formic acid, A hydrogenation step is performed to decompose the formic acid synthesized by the above synthesis step into carbon dioxide and deuterium, A method for synthesizing deuterium, characterized by including the following:

2. Preparation steps for decomposing formic acid into carbon monoxide and water, A synthesis step in which the carbon monoxide produced by decomposition in the above preparation step is reacted with heavy water to synthesize formic acid, A hydrogenation step is performed to decompose the formic acid synthesized by the above synthesis step into carbon dioxide and deuterium, A method for synthesizing deuterium, characterized by including the following:

3. A synthesis step involves reacting carbon monoxide with heavy water to synthesize formic acid, A substitution step is to replace the dihydroxyl group of the formic acid synthesized by the above synthesis step with a hydroxyl group in water to partially convert it into deuterated formic acid (DCOOH), A hydrogenation step is performed to decompose the partially deuterated formic acid substituted by the substitution step into carbon dioxide and partially dehydrogenated hydrogen (HD), A method for synthesizing deuterium, characterized by including the following:

4. Preparation steps for decomposing formic acid into carbon monoxide and water, A synthesis step in which the carbon monoxide produced by decomposition in the above preparation step is reacted with heavy water to synthesize formic acid, A substitution step is to replace the dihydroxyl group of the formic acid synthesized by the above synthesis step with a hydroxyl group in water to partially convert it into deuterated formic acid (DCOOH), A hydrogenation step is performed to decompose the partially deuterated formic acid substituted by the substitution step into carbon dioxide and partially dehydrogenated hydrogen (HD), A method for synthesizing deuterium, characterized by including the following:

5. The method for synthesizing deuterium according to claims 1 to 4, characterized in that at least one of the synthesis step, the hydrogenation step, and the preparation step is carried out under hydrothermal conditions.

6. The method for synthesizing deuterium according to claims 1 to 4, characterized in that at least one of the synthesis step, the hydrogenation step, and the preparation step is carried out in an ionic liquid.

7. A deuterium synthesis apparatus for synthesizing deuterium using at least one of the methods of claims 1 to 6.

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