Deuterium synthesis method and deuterium synthesis apparatus

Abstract

Provided is a deuterium synthesis method capable of efficiently producing highly pure deuterium D2 or partially deuterated deuterium HD. 【Solution means】The deuterium synthesis method according to the present invention applies an aqueous gas shift equilibrium reaction using formic acid as a reaction intermediate, and provides a step of extracting formic acid, which is a reaction intermediate, and performs separation by utilizing the difference in solubility of carbon dioxide, hydrogen, carbon monoxide, and formic acid in a solvent (water) to synthesize highly pure 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 us humans. However, since fossil fuels may be depleted, there is a pressing 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 conducted, and nuclear fusion requires tritium and deuterium as its fuel sources. To date, the inventors have studied the organic synthesis from carbon dioxide and water, and from a physical and chemical perspective, have elucidated the reaction mechanism and studied the improvement of reaction efficiency. Among them, the inventors first announced in the world the reversibility of the water-gas shift reaction (water-gas shift equilibrium reaction) and the fact that the reaction intermediate is formic acid. Technologies that utilize the reversibility of the water-gas shift reaction and formic acid as the reaction intermediate are, for example, Patent Document 1 below. Also, regarding the production of deuterium 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] In the technology for producing deuterium, which is a fuel source for nuclear fusion energy, there is still much room for improvement in terms of purity.

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

Means for Solving the Problems

[0006] [Summary of Findings on the Water-Gas Shift Equilibrium Reaction Using Formic Acid as a Reaction Intermediate] The water-gas shift reaction is a reaction that produces carbon dioxide and hydrogen from carbon monoxide and water, and has been known for a long time. The inventors confirmed that in the hydrothermal decomposition reaction of formic acid, there are both reactions that decompose into carbon monoxide and water and reactions that decompose into carbon dioxide and hydrogen, and they are competitive reactions. Hitherto, only the decomposition of formic acid into carbon dioxide and hydrogen has been known, so it was confirmed that by controlling the reaction conditions, it can be decomposed into carbon monoxide and water, and this was reported for the first time in the world. Furthermore, it was predicted that the water-gas shift reaction, which has been known for a long time, is related to formic acid, and the water-gas shift reaction is a reversible reaction using formic acid as an intermediate, and this was confirmed by experiments and reported at a society. It was found that by controlling the reaction conditions, the abundance ratios of carbon monoxide and water, or carbon dioxide and hydrogen, can be freely controlled, and methods for obtaining only carbon monoxide and methods for obtaining only carbon dioxide and hydrogen were established. Also, although formic acid is a reaction intermediate, it is an organic compound that can be stably extracted. Therefore, in the present invention, by successfully controlling the reaction conditions and the stability of formic acid and applying them to "hydrogen separation", the invention was completed. Figure 1 summarizes the characteristics of the water-gas shift equilibrium reaction, formic acid as the reaction intermediate, and two reaction pathways. Centering on formic acid, it is a competitive reaction between the reaction that decomposes into carbon dioxide and hydrogen and the reaction that decomposes into carbon monoxide and water. For each reaction, the former is thermodynamically dominant and the latter is kinetically dominant. By controlling the reaction temperature, each reaction can be promoted or suppressed. Also, since carbon dioxide, hydrogen, and carbon monoxide are gases at normal temperature and pressure, each reaction can also be promoted or suppressed by controlling the pressure of the reaction field. Furthermore, each reaction can be controlled by using the difference in reaction rate constants, acid catalysts, and the catalytic action of the reaction vessel surface, and in fact, only one of the reactions can proceed. Since it is an equilibrium reaction, by controlling the above reaction conditions, the forward and reverse reactions can be preferentially promoted or suppressed. Figure 1 is a simple summary of these concepts, and the details are described in Patent No. 7288484. Furthermore, carbon dioxide, hydrogen, and carbon monoxide are gases at normal temperature and pressure, and formic acid is a liquid at normal temperature and pressure. Also, since the solubilities of these substances in a solvent are different, utilizing the separation of substances using this property is also a feature of the present invention. When water is used as the solvent, the solubilities of carbon dioxide, hydrogen, and carbon monoxide are low, while conversely, the solubility of formic acid is high. Substances can be separated using this solubility difference, and it is possible to increase the purity. By setting the conditions well, in fact, a substance with a purity almost approaching 100% can be obtained. The present invention is an excellent method for preparing the desired substance and separating substances. From the above, controlling the reaction conditions of the water-gas shift equilibrium reaction using formic acid as the reaction intermediate, providing a step of extracting formic acid, a relatively stable substance as the reaction intermediate, and utilizing the separation of substances using the solubility difference, especially when the solvent is water, are the features of the present invention. Thereby, it becomes possible to increase the purity of deuterium, which is the object of the present invention, and extract only deuterium through the above separation process. In the method for synthesizing deuterium according to the present invention, it preferably includes a synthesis step of reacting carbon monoxide with heavy water D2O to synthesize formic acid, and a hydrogenation step of decomposing the formic acid synthesized in the synthesis step into carbon dioxide and deuterium. Further, in the method for synthesizing deuterium according to the present invention, it preferably includes a preparation step of decomposing formic acid into carbon monoxide and water, a synthesis step of reacting the carbon monoxide generated by decomposition in the preparation step with heavy water to synthesize formic acid, and a hydrogenation step of decomposing the formic acid synthesized in the synthesis step into carbon dioxide and deuterium.

[0007] In the method for synthesizing deuterium according to the present invention, it preferably includes a synthesis step of reacting carbon monoxide with heavy water to synthesize formic acid, a substitution step of substituting the deuterated hydroxy group of the formic acid 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.

[0008] In the method for synthesizing deuterium according to the present invention, it preferably includes a preparation step of decomposing formic acid into carbon monoxide and water, a synthesis step of reacting the carbon monoxide generated by decomposition in the preparation step with heavy water to synthesize formic acid, a substitution step of substituting the deuterated hydroxy group of the formic acid 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.

[0009] Further, in the above method for synthesizing deuterium, at least one of the synthesis step, the hydrogenation step, and the preparation step is preferably carried out under hydrothermal conditions.

[0010] According to such a configuration, deuterium can be efficiently generated.

[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, a method for synthesizing deuterium capable of efficiently generating deuterium can be provided.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Embodiments for Carrying Out the Invention

[0015] The deuterium synthesis method according to an embodiment of the present invention includes a synthesis step of reacting carbon monoxide and 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. In addition, it 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 and 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 reacting carbon monoxide with heavy water to synthesize formic acid-d1, a substitution step of substituting the deuterohydroxy group of the formic acid-d1 synthesized in the synthesis step with a hydroxy 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 deuterated hydrogen HD. Further, it has 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 formic acid-d1, a substitution step of substituting the deuterohydroxy group of the formic acid-d1 synthesized in the synthesis step with a hydroxy 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 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 under the concept as shown in FIG. 4, for example.

[0020] [Conceptual diagram of deuterium synthesis method] Utilize the water-gas shift equilibrium reaction using formic acid as a reaction intermediate to synthesize deuterium. For the two equilibrium reactions described in FIG. 1, in order to obtain only the desired product by controlling the reaction conditions well, in fact, only one of the reactions proceeds. Further, the present invention applies the fact 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, and the difference in their solubilities.

[0021] Figure 1 summarizes the characteristics of the aqueous gas shift equilibrium reaction, formic acid as a reaction intermediate, and two reaction pathways. Centered around formic acid, it is a competitive reaction between the reaction of decomposing into carbon dioxide and hydrogen and the reaction of decomposing into carbon monoxide and water. The former is a thermodynamically dominant reaction, and the latter is a kinetically dominant reaction. By controlling the reaction temperature, each reaction can be promoted or suppressed. Also, since carbon dioxide, hydrogen, and carbon monoxide are gases at normal temperature and pressure, each reaction can also be promoted or suppressed by controlling the pressure of the reaction field. Furthermore, by using the differences in reaction rate constants, acid catalysts, and the catalytic action on the surface of the reaction vessel, each reaction can be controlled, and in fact, only one of the reactions can proceed. Since it is an equilibrium reaction, by controlling the above reaction conditions, the forward and reverse reactions can be preferentially promoted or suppressed. Figure 1 is a simple summary of these concepts. Furthermore, carbon dioxide, hydrogen, and carbon monoxide are gases at normal temperature and pressure, and formic acid is a liquid at normal temperature and pressure. Also, since the solubilities of these substances in solvents are different, using the separation of substances utilizing this property is also a feature of the present invention. When water is used as the solvent, the solubilities of carbon dioxide, hydrogen, and carbon monoxide are low, while conversely, the solubility of formic acid is high. Substances can be separated using this solubility difference, and it is possible to increase the purity. By setting the conditions well, it is possible to obtain substances with a purity almost approaching 100% in fact. The present invention is a method considering the preparation and separation of the substances to be obtained. From the above, controlling the reaction conditions of the aqueous gas shift equilibrium reaction using formic acid as a reaction intermediate, providing a step of extracting formic acid, a relatively stable substance as a reaction intermediate, and utilizing the separation of substances using the solubility difference, especially when the solvent is water, are the features of the present invention. Thereby, it becomes possible to increase the purity of deuterium, which is the object of the present invention, and extract only deuterium through the above separation process. Figure 2 shows the steps for generating deuterium D2. Starting from the case where formic acid is used as the starting material is described, but carbon monoxide may also be used as the starting point. Also, the case where water is selected as the solvent is described, but another solvent may be used. First, formic acid is decomposed into carbon monoxide and water (1). The decomposition method can refer to Patent No. 7288484. Since the carbon monoxide in the product is a gas at normal temperature and pressure, only carbon monoxide can be taken out. If degassing is performed when injecting formic acid and water into the reaction vessel, only carbon monoxide can also be taken out after the reaction. On the other hand, even in a situation where, for example, nitrogen or oxygen is mixed in, since only carbon monoxide needs to react in the next step, it is not always necessary to perform degassing. As the next step, the extracted carbon monoxide and heavy water are injected into the reaction vessel, and the reaction is allowed to proceed to generate deuterated formic acid DCOOD (2). The generated deuterated formic acid is dissolved in deuterated formic acid at normal temperature and pressure after the reaction, so it is easy to separate from the starting carbon monoxide. The reason is that the solubility of carbon monoxide in water is extremely low. For the next step, only the deuterated formic acid heavy aqueous solution is taken out, and in another reaction tank 10 (reaction vessel), the deuterated formic acid is decomposed into carbon dioxide and deuterium D2 (3). It may be decomposed into carbon dioxide and deuterium after degassing in the same manner as in step (1). Carbon dioxide and deuterium may be separated using a metal container or the like. In step (3), only deuterated 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 generating HD where a part is deuterated. The difference from D2 shown in Figure 2 is step 2’, and the rest is the same. Also, similar to the generation of D2, carbon monoxide may be used as the starting point to generate HD. Step 2’ is the step of substituting the hydroxy group OD of deuterated formic acid DCOOD with OH in water (light water, H2O). When deuterated formic acid DCOOD is dissolved in a large amount of H2O compared to deuterated formic acid DCOOD, theoretically, almost all of the hydroxy groups of deuterated formic acid are substituted with OH groups. Of course, it is necessary to pay attention to the concentration of deuterated formic acid so that almost all of them become OH groups. From the above, by adding the step of generating deuterated formic acid DCOOH where a part is deuterated, HD with a purity of approximately 100% can be generated. Using these findings, a method for synthesizing deuterium is disclosed.

[0022] [Deuterium synthesis device] The deuterium synthesis method according to this embodiment is the same as that of Patent No. 7288484, and is carried out, for example, under the apparatus as shown in FIG. 4. The apparatus 1 for carrying out the method for promoting the formic acid synthesis reaction according to this embodiment is a batch reactor having an accommodation space S capable of accommodating a reaction solvent (or a solution in which a reaction substrate to be reacted is dissolved) therein. Here, a batch reactor is described as an example, but a flow reactor may also be used. Specifically, the apparatus 1 for carrying out the method for promoting the formic acid synthesis reaction according to this embodiment includes a reaction tank 10 formed in a cylindrical body and having an accommodation space S capable of accommodating a solvent (solution) therein, a jacket 20 covering the outer surface and the bottom surface of the reaction tank 10, and a reaction medium storage tank 30 for storing a reaction medium containing the solvent (solution). Further, the apparatus 1 for carrying out the deuterium synthesis method according to this embodiment includes a pipe L for connecting the reaction tank 10 and the reaction medium storage tank 30, and a valve V for adjusting the opening and closing 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) storing an inert gas such as nitrogen gas, helium gas, or argon gas, a pipe connecting the inert gas storage tank and the reaction tank 10, and a valve for adjusting the opening and closing state of the pipe.

[0023] The reaction tank 10 includes a cylindrical side wall portion 10a, a bottom wall portion 10b closing the bottom surface side of the cylindrical side wall portion 10a, and a top wall portion 10c closing the top surface side of the cylindrical side wall portion 10a. In the reaction tank 10, as described above, the cylindrical side wall portion 10a is closed by the bottom wall portion 10b and the top wall portion 10c, so that the accommodation space S is a sealed space. The solvent (solution) is accommodated in the accommodation space S of the reaction tank 10 from the reaction medium storage tank 30 via the pipe L. The accommodation of the reaction medium into the accommodation space S may be carried out after reducing the pressure in the accommodation space S using a vacuum pump (not shown), or may be carried out under atmospheric pressure (1.01325×105 Pa (0.101325 MPa)) without reducing the pressure in the accommodation space S. It is preferable that the accommodation of the reaction medium into the accommodation space S is carried out under atmospheric pressure without reducing the pressure in the accommodation space S. In the reaction tank 10, after the reaction medium is accommodated in the accommodation space S, the inert gas stored in the inert gas storage tank may be enclosed in the accommodation space S, and at least a part of the air contained in the gas phase part of the accommodation space S may be replaced with the inert gas, or all of the air contained in the gas phase part of the accommodation space S may be replaced with the inert gas. Replacement with an inert gas is the best mode and is not essential. In this state, carbon monoxide may be enclosed in the accommodation space S. Each gas to be enclosed is enclosed in a predetermined amount at a pressure higher than the pressure in the accommodation space S. The specific configuration of the apparatus and the method of enclosure are the same as those for the inert gas. Further, in addition to connecting a gas storage tank to the pipe L for gas injection as described above, a gas recovery tank may be connected to the pipe L for gas recovery. Note that the reaction tank 10 may be provided with a stirring device (not shown) for stirring the reaction medium accommodated in the accommodation space S. By providing the reaction tank 10 with the stirring device, the reaction can be carried out while stirring the reaction medium accommodated in the accommodation space S with the stirring device. Thereby, the deuterium synthesis reaction contained in the reaction medium can be carried out more efficiently.

[0024] As described above, since the apparatus 1 for carrying out the deuterium synthesis method according to the present embodiment is a batch-type reaction apparatus, the reaction tank 10 is a batch-type container. Note that the batch-type container means one that can hermetically accommodate the reaction medium and the reaction substrate used in a single treatment. Since the reaction tank 10 has an inner wall surface in contact with the accommodated reaction medium and reaction substrate, when it is preferable that the inner wall surface is made of a non-metal, it is used. Preferred substances for forming the inner wall surface include resin, glass, ceramic, diamond-like carbon, and the like.

[0025] The 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.), polyarylene sulfide (PAS), etc., or may be a general rubber or the like. In this embodiment, from the viewpoint of stability against hydrothermal reaction, the resin is preferably a silicone resin, silicone rubber, fluororesin, fluororubber, epoxy resin, or the like. Among these resins, the resin is preferably a fluororesin. Examples of the fluororesin include polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), polychlorotrifluoroethylene (PCTFE), tetrafluoroethylene-ethylene copolymer (ETFE), polyvinylidene fluoride (PVdF), and the like. The resin may be used alone as a constituent material of the inner wall surface, or a mixture of two or more kinds may be used as a constituent material of the inner wall surface.

[0026] Examples of the glass include soda glass, borosilicate glass, quartz glass, crystal glass, and the like.

[0027] Examples of the ceramic 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 (3Al203·2SiO2), cordierite (2MgO·2Al2O3·5SiO2), and the like. The ceramic may be used alone as a constituent material of the inner wall surface, or a mixture of two or more kinds may be used as a constituent material of the inner wall surface.

[0028] The entire wall defining the accommodation space S of the reaction tank 10 may be made of the above material, or only the surface layer (the surface layer forming the inner wall surface of the reaction tank 10) may be made of the above material. The above material may be formed into a plurality of layers. The reaction tank 10 may have, for example, a metal body, and a glass layer and a resin layer may be laminated in a double layer on the inner wall surface of the body. Note that the reaction tank 10 may be replaced for each reaction step.

[0029] The material for forming the inner wall surface preferably has an elution amount of metal ions by formic acid at room temperature (23 ± 2°C) of 1000 ppm or less. The elution amount of the metal ions can be measured by an ICP method or the like.

[0030] As described above, by configuring the inner wall surface of the reaction tank 10 with a non-metal, the inner wall surface of the reaction tank 10 has acid resistance. Furthermore, when the inner wall surface is made of a metal such as stainless steel, although there is a concern that the carboxyl group (COOH) contained in formic acid (HCOOH) forms an ionic bond with the metal, when the inner wall surface is made of a non-metal, formation of the ionic bond as described above can be suppressed. That is, by suppressing the formic acid from forming an ionic bond with the inner wall surface via a carboxyl group, it is possible to suppress the adsorption of the formic acid on the inner wall surface. Thereby, it is possible to produce formic acid from the carbon dioxide and hydrogen more efficiently.

[0031] The jacket 20 is provided with a heating device (not shown) such as a heater. The jacket 20 heats the reaction tank 10 by a heating device such as a heater.

[0032] The reaction medium storage tank 30 can be any tank as long as it has a storage space S for storing the reaction medium inside. On the other hand, since the reaction medium storage tank 30 has an inner wall surface in contact with the stored reaction medium, it is preferable that the inner wall surface is made of a non-metal. Preferred substances for constituting the inner wall surface include resin, glass, ceramic, diamond-like carbon, and the like. As the resin, the glass, and the ceramic, the same ones as those described above can be used.

Example

[0033] The present invention will be described in more detail with reference to the following examples. The following examples are for further explaining the present invention and do not limit the scope of the present invention. In the examples, a part of the method using the findings described in the above [Summary of findings on the water gas shift equilibrium reaction using formic acid as a reaction intermediate] and [Conceptual diagram regarding the method for synthesizing deuterium] is disclosed. As the reaction solvent, water, heavy water, ionic liquid, and organic compounds may be used, and a solvent suitable for promoting the reaction is selected. Further, the reaction temperature is appropriately selected to promote the reaction. The pressure during the reaction can be controlled by adjusting the amounts of the starting materials charged into the reaction vessel and the solvent in the case of a batch reaction vessel. The value of the pressure can be obtained from calculations. In the case of a flow-type reaction, it can be adjusted by controlling the pressure during flowing.

[0034] Example 1: The reaction vessel 10 shown in Fig. 4 was filled with an aqueous formic acid solution (heavy water solution) with a concentration of 3.0 M (mol / L) to a filling ratio of 70%. After degassing with a vacuum pump, nitrogen gas was introduced at the same pressure as atmospheric pressure. After closing the connection valve to make the reaction vessel airtight, the reaction vessel 10 was heated to 250 °C. After 12 hours, the mixed gas of carbon monoxide and nitrogen gas generated at room temperature was taken out. The taken-out carbon monoxide and nitrogen gas were separated by a separation column or the like, and carbon monoxide was collected. Then, heavy water was put into the reaction vessel 10 to a filling ratio of 50%, and the separated carbon monoxide was injected into the reaction vessel 10 (prepared separately). Then, the reaction vessel 10 was heated to 400 °C. After 2 hours, the carbon dioxide and deuterium D2 generated at room temperature were collected (recovered) in a metal container. Then, carbon dioxide and deuterium D2 may be separated using a separation column, or deuterium D2 may be taken out from the carbon dioxide and deuterium D2 in the metal container using the metal permeability of hydrogen. The taken-out deuterium gas was measured by, for example, 1H-NMR measurement or 2H-NMR measurement. Or Raman measurement was performed. While confirming the product, the deuteration rate of hydrogen was confirmed by 2H-NMR measurement. As a result, D2 with an almost 100% deuteration rate was obtained. Fig. 5 shows the result of Raman measurement without separating carbon dioxide and deuterium D2. For comparison, the reaction conditions and charges were manipulated to set conditions where only D2 is generated and conditions where HD and D2 coexist. (a) shows the conditions where D2 and HD are generated, (b) shows the conditions where almost only D2 is generated, and (c) shows the case where a series of steps were taken with a higher initial concentration of formic acid than (a).

[0035] Example 2: In Example 1, a series of steps were carried out starting from formic acid. In this example, starting from carbon monoxide, the reaction conditions were the same except that the same amount of carbon monoxide as that generated when all the formic acid was decomposed into carbon monoxide and water in Example 1 was injected into the reaction vessel 10, and it was the same except that the preparatory step of decomposing the initial formic acid was skipped. Even in that case, D2 with an almost 100% deuteration rate was obtained.

[0036] Example 3: It is the same except that a substitution step of substituting the deuterated hydroxy group OD with the hydroxy group OH is added after the synthesis step of synthesizing formic acid in Example 1. In that case, almost 100% of HD was obtained.

[0037] Example 4: It is the same except that a substitution step of substituting the deuterated hydroxy group OD with the hydroxy group OH is added after the synthesis step of synthesizing formic acid in Example 2. In that case, almost 100% of HD was obtained.

[0038] The above examples are just examples, and the invention of the present application is not limited thereto. Also, in the forms and examples for implementing the above invention, a method of putting electrodes into the reaction tank 10 and not energizing them was described, but it is not limited to this, and the reaction may be promoted by energization. Further, a substance that causes a catalytic action such as a metal catalyst may be added to promote the reaction. Furthermore, the reaction may be promoted by increasing the reaction temperature to raise the energy state of the reaction substrate due to the Arrhenius effect.

Explanation of reference numerals

[0039] 1: Synthesis apparatus, 10: Reaction tank, 20: Jacket, 30: Aqueous formic acid storage tank, 10a: Side wall portion, 10b: Bottom wall portion, 10c: Top wall portion, L: Pipe, S: Accommodation space, V: Valve.

Claims

1. A synthesis step of reacting carbon monoxide with heavy water to synthesize formic acid-d1, and a hydrogenation step of decomposing the formic acid-d1 synthesized in the synthesis step into carbon dioxide and deuterium, wherein after the synthesis step under the condition that no carbon dioxide is generated, the formic acid-d1 and the carbon monoxide are separated using a solubility difference, and at least the synthesis step is carried out by enclosing it in a containment space to allow the reaction to proceed. A method for synthesizing deuterium.

2. A preparation step of decomposing formic acid into carbon monoxide and water, a synthesis step of reacting the carbon monoxide generated by decomposition in the preparation step with heavy water to synthesize formic acid-d1, a hydrogenation step of decomposing the formic acid-d1 synthesized in the synthesis step into carbon dioxide and deuterium, wherein after the synthesis step under the condition that no carbon dioxide is generated, the formic acid-d1 and the carbon monoxide are separated using a solubility difference, and at least the synthesis step is carried out by enclosing it in a containment space to allow the reaction to proceed. A method for synthesizing deuterium.

3. A synthesis step of reacting carbon monoxide with heavy water to synthesize formic acid-d1, a substitution step of substituting the deuterated hydroxy group of the formic acid-d1 synthesized in the synthesis step with a hydroxy group in water to form partially deuterated formic acid DCOOH, a hydrogenation step of decomposing the partially deuterated formic acid substituted in the substitution step into carbon dioxide and partially deuterated hydrogen HD, wherein after the synthesis step under the condition that no carbon dioxide is generated, the formic acid-d1 and the carbon monoxide are separated using a solubility difference, and at least the synthesis step is carried out by enclosing it in a containment space to allow the reaction to proceed. A method for synthesizing deuterium.

4. A preparation step of decomposing formic acid into carbon monoxide and water, a synthesis step of reacting the carbon monoxide generated by decomposition in the preparation step with heavy water to synthesize formic acid-d1, a substitution step of substituting the deuterated hydroxy group of the formic acid-d1 synthesized in the synthesis step with a hydroxy group in water to form partially deuterated formic acid DCOOH, a hydrogenation step of decomposing the partially deuterated formic acid substituted in the substitution step into carbon dioxide and partially deuterated hydrogen HD, wherein after the synthesis step under the condition that no carbon dioxide is generated, the formic acid-d1 and the carbon monoxide are separated using a solubility difference, and at least the synthesis step is carried out by enclosing it in a containment space to allow the reaction to proceed. A method for synthesizing deuterium.

5. The method for deuterium synthesis according to claim 2 or 4, wherein at least one of the synthesis step, the hydrogenation step, and the preparation step is carried out under hydrothermal conditions.

6. The method for deuterium synthesis according to claim 2 or 4, wherein 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 according to claims 1 to 4.

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