Method for determining manufacturing process of molecule to be determined

Abstract

This method for determining a manufacturing process of a molecule to be determined includes: a step for acquiring an isotope ratio δD of deuterium to protium contained in a molecule to be determined; and a step for determining, when the isotope ratio δD is equal to or less than a prescribed threshold, that the molecule to be determined was manufactured by means of a method including an electrolysis step for generating hydrogen molecules through the electrolysis of a water-containing liquid.

Description

Method for determining manufacturing process of molecule to be determined

[0001] The present disclosure relates to a method for determining a manufacturing process of a molecule to be determined.

[0002] Carbon dioxide is considered a problem as a cause of global warming, and there has been an active movement worldwide to curb carbon dioxide emissions. On the other hand, hydrogen, which produces only water and no carbon dioxide when burned, has attracted attention as a clean, next-generation energy source. An alkaline water electrolysis device disclosed in Patent Document 1 is known as a method for producing hydrogen.

[0003] International Publication No. 2019 / 181662

[0004] Hydrogen can be classified as gray hydrogen, blue hydrogen, green hydrogen, etc. depending on the production method. Gray hydrogen is hydrogen produced from fossil fuels. Blue hydrogen is hydrogen produced by capturing, storing, or reusing the carbon dioxide produced during the gray hydrogen production process, rather than releasing it into the atmosphere. Green hydrogen is hydrogen produced by electrolyzing a liquid containing water. However, until now, there has been no known method for determining whether the hydrogen molecule being evaluated was produced by a method that includes an electrolysis process.

[0005] Therefore, an object of the present disclosure is to provide a manufacturing process determination method for determining whether a molecule to be determined is a molecule produced by a method including an electrolysis process or a molecule produced using fossil fuels as raw materials.

[0006] The manufacturing process determination method for a molecule to be determined according to the present disclosure includes the steps of: acquiring an isotope ratio δD of deuterium to proton contained in the molecule to be determined; and, if the isotope ratio δD is equal to or less than a predetermined threshold, determining that the molecule to be determined is a molecule that was manufactured by a method that includes an electrolysis step of generating hydrogen molecules by electrolysis of a liquid containing water.

[0007] The manufacturing process determination method for a molecule to be determined according to the present disclosure includes the steps of acquiring an isotope ratio δD of deuterium to proton contained in the molecule to be determined, and determining that the molecule to be determined is a molecule produced using a fossil fuel as a raw material if the isotope ratio δD is greater than a predetermined threshold.

[0008] The determination step may determine that the molecule to be determined is a molecule produced by a method including an electrolysis step of producing hydrogen molecules by electrolysis of a water-containing liquid if the isotope ratio δD is equal to or less than a predetermined threshold, and may determine that the molecule to be determined is a molecule produced using a fossil fuel as a raw material if the isotope ratio δD is greater than the predetermined threshold.

[0009] The molecule to be determined may be hydrogen, ammonia, or a hydrocarbon.

[0010] The electrolysis may be at least one of anion exchange membrane water electrolysis and proton exchange membrane water electrolysis.

[0011] The predetermined threshold value may be a value determined based on a first fitting curve obtained by creating a first histogram with classes based on the isotope ratio δD of molecules to be evaluated that are produced under a plurality of conditions by a method including an electrolysis step of generating hydrogen molecules by electrolysis of a water-containing liquid, and performing fitting on the first histogram.

[0012] The predetermined threshold value may be a value determined based on a second fitting curve obtained by creating a second histogram in which the isotope ratios δD of the molecules to be evaluated that are produced using fossil fuels as raw materials are classified under a plurality of conditions and performing fitting on the second histogram.

[0013] The predetermined threshold may be the intersection of a first fitting curve obtained by creating a first histogram with classes based on the isotope ratio δD of molecules to be determined that are produced under a plurality of conditions by a method including an electrolysis step of generating hydrogen molecules by electrolysis of a water-containing liquid and fitting the first histogram, and a second fitting curve obtained by creating a second histogram with classes based on the isotope ratio δD of molecules to be determined that are produced under a plurality of conditions using fossil fuels as raw materials and fitting the second histogram.

[0014] According to the present disclosure, it is possible to provide a manufacturing process determination method for determining whether a molecule to be determined is a molecule produced by a method including an electrolysis process or a molecule produced using fossil fuels as raw materials.

[0015] Figure 1 shows a histogram of the δD of hydrogen gas produced by various methods, with fitting curves added to the histogram in Figure 2.

[0016] Hereinafter, several exemplary embodiments will be described with reference to the drawings. Note that the dimensional proportions of the drawings are exaggerated for the convenience of explanation and may differ from the actual proportions.

[0017] The method for determining the manufacturing process of a molecule to be determined according to this embodiment includes an isotope ratio acquisition step and a determination step.

[0018] The isotope ratio acquisition step is a step of acquiring the isotope ratio δD of hydrogen contained in the molecule to be determined. The molecule to be determined is a hydrogen-containing molecule containing a hydrogen element, and may be a liquid, solid, or gas. As will be described later, the molecule to be determined is not particularly limited as long as it contains a hydrogen element, and may be a hydrogen molecule or a hydrogen-containing compound. The hydrogen-containing compound may be, for example, ammonia or a hydrocarbon. In other words, the molecule to be determined may be hydrogen, ammonia, or a hydrocarbon. Since this determination method makes a determination using the hydrogen isotope ratio δD, it is not limited to cases where the molecule to be determined is hydrogen, and can also be used when the molecule to be determined is, for example, a hydrogen-containing compound.

[0019] Since the amount of isotope variation in natural substances is usually very small, it is expressed in ‰ units as a relative value δD to Vienna Standard Mean Seawater (VSMOW). In other words, the hydrogen isotope ratio δD indicates the amount by which the molar ratio of deuterium to protons contained in the target molecule changes relative to the molar ratio of deuterium to protons contained in the reference VSMOW. The hydrogen isotope ratio δD of a target molecule is defined by the following formula (1):

[0020]

[0021] In the above formula (1), δD is the isotope ratio of deuterium to protium contained in the molecule to be determined, (D / H) ｔａｒｇｅｔ is the molar ratio of deuterium to protium contained in the molecule to be determined, (D / H) ＶＳＭＯＷ represents the molar ratio of deuterium to hydrogen contained in VSMOW. (D / H) ＶＳＭＯＷ is 155.76±0.1 ppm.

[0022] Here, hydrogen elements that exist in nature include protium ( １ H or H), deuterium ( ２ H or D) and tritium (tritium: ３ It is known that hydrogen exists in three isotopes: H, D, or T. Hydrogen is the most abundant isotope of hydrogen in nature. Deuterium is a stable isotope of hydrogen. Tritium is a radioactive isotope and exists in very small amounts in nature. There are several methods for electrolyzing water, but in any electrolysis method, due to the isotope effect, the amount of HD gas and D produced is greater than the amount of hydrogen gas produced. ２ Therefore, the isotope ratio δD of the hydrogen molecules produced by electrolysis is smaller than the isotope ratio δD of the water used as a raw material in electrolysis.

[0023] The molar ratio of deuterium to protons (D / H) can be obtained by calculating the molar ratio of deuterium to protons contained in the molecule to be determined. The molar ratio of deuterium to protons (D / H) can be obtained using a mass spectrometer. The molar ratio of deuterium to protons (D / H) may also be obtained using a mass spectrometer combined with a separation device such as a gas chromatograph.

[0024] The determination step may be a step of determining that the molecule to be determined is a molecule produced by a method including an electrolysis step when the acquired isotope ratio δD is equal to or less than a predetermined threshold. The electrolysis step is specifically a step of generating hydrogen molecules by electrolysis. The liquid to be electrolyzed may be a liquid containing water. Hydrogen can be generated by electrolyzing a liquid containing water. The liquid containing water may specifically be an aqueous solution containing an electrolyte. The aqueous solution may be hydrochloric acid, a sodium chloride aqueous solution, an alkaline aqueous solution, or the like. The alkaline aqueous solution may contain an aqueous solution of an alkali metal hydroxide. The alkali metal hydroxide may contain, for example, at least one of sodium hydroxide and potassium hydroxide. In this specification, electrolysis of a liquid containing water is also referred to as water electrolysis.

[0025] The electrolysis may be, for example, PEM (Proton Exchange Membrane) water electrolysis, alkaline water electrolysis, AEM (Anion Exchange Membrane) water electrolysis, SOEC (Solid Oxide Electrolysis Cell) water electrolysis, PCEC (Protonic Ceramic Electrolysis Cell) water electrolysis, or a combination thereof. More specifically, the electrolysis may be at least one of anion exchange membrane water electrolysis and proton exchange membrane water electrolysis.

[0026] The predetermined threshold may be a value determined based on a first fitting curve obtained by creating a first histogram in which the isotope ratios δD of the target molecules produced by a method including an electrolysis step are classified under a plurality of conditions and fitting the first histogram. The predetermined threshold may be a value determined based on a second fitting curve obtained by creating a second histogram in which the isotope ratios δD of the target molecules produced using a fossil fuel as a raw material are classified under a plurality of conditions and fitting the second histogram. The predetermined threshold may be an intersection of the first fitting curve and the second fitting curve.

[0027] The predetermined threshold in the determination step may be a numerical value of -375‰ or less. By setting the predetermined threshold to -375‰ or less, it is possible to more clearly determine that the molecule to be determined is a molecule produced by a method including an electrolysis step. The predetermined threshold may be a numerical value of -436.1‰ or less, a numerical value of -448.2‰ or less, or a numerical value of -510.1‰ or less. The predetermined threshold may be a numerical value of 0‰ or more, a numerical value of -903.5‰ or more, or a numerical value of -721.3‰ or more.

[0028] In the determination step, if the isotope ratio δD is greater than a predetermined threshold, the determination target molecule may be determined to be a molecule produced using a fossil fuel as a raw material. This makes it possible to determine that the determination target molecule is a molecule produced using a fossil fuel as a raw material.

[0029] The determination step may determine that the target molecule is a molecule produced by a method including an electrolysis step if the acquired isotope ratio δD is equal to or less than a predetermined threshold, and determine that the target molecule is a molecule produced using a fossil fuel as a raw material if the acquired isotope ratio δD is greater than the predetermined threshold. This makes it possible to determine not only whether the target molecule is a molecule produced by a method including an electrolysis step, but also whether the target molecule is a molecule produced using a fossil fuel as a raw material.

[0030] For example, if the target molecule is a hydrogen molecule and it is determined that the hydrogen molecule was produced using a method including an electrolysis process, the hydrogen molecule can be estimated to be hydrogen produced using renewable energy. When electrolysis is performed using electricity generated from fossil fuels, the Gibbs free energy ΔG is considered to be too high a cost and the process is not feasible, so this hydrogen may be green hydrogen. Although green hydrogen is expensive to produce, it does not produce carbon dioxide during the hydrogen production process, not just when hydrogen is burned, and therefore can contribute to reducing carbon dioxide emissions.

[0031] On the other hand, if the target molecule is a hydrogen molecule and it is determined that the hydrogen molecule is hydrogen produced using a fossil fuel as a raw material, it can be estimated to be gray hydrogen or blue hydrogen produced from fossil fuels by, for example, steam reforming, thermal decomposition, or partial oxidation. While the production cost of such hydrogen is low, carbon dioxide is emitted during the hydrogen production process, making it undesirable from the perspective of carbon dioxide emissions. The fossil fuel may include, for example, at least one selected from the group consisting of coal, petroleum, and natural gas.

[0032] The molecule to be determined may be hydrogen, ammonia, or a hydrocarbon. Compounds such as ammonia and hydrocarbons can be produced using hydrogen molecules produced by electrolysis as a raw material. Ammonia can be produced, for example, by the Haber-Bosch process using hydrogen molecules as a raw material. Hydrocarbons may contain at least one of methane and olefins. Methane can be produced by a methanation reaction using hydrogen molecules as a raw material. Olefins (alkenes) can be produced by a Fischer-Tropsch reaction using hydrogen molecules as a raw material. Because this determination method makes use of the hydrogen isotope ratio δD, it is not limited to cases where the molecule to be determined is hydrogen, and can also be used when the molecule is a hydrogen-containing compound such as ammonia or hydrocarbons produced as described above.

[0033] The determination step may be performed by a determination unit. The determination unit may be, for example, a computer including a CPU (central processing unit), a memory, an input unit, and an output unit. The CPU reads a determination program stored in the memory and determines whether the target molecule is a molecule produced by a method including an electrolysis process or a molecule produced using a fossil fuel as a raw material based on the acquired isotope ratio δD and a threshold value. Specifically, in the determination step, the determination unit may determine that the target molecule is a molecule produced by a method including an electrolysis process if the isotope ratio δD input to the input unit is equal to or less than a predetermined threshold. Furthermore, in the determination step, the determination unit may determine that the target molecule is hydrogen produced using a fossil fuel as a raw material if the acquired isotope ratio δD is greater than a predetermined threshold. The result determined by the determination unit may be output to an output unit such as a monitor.

[0034] As described above, the manufacturing process determination method for a molecule to be determined according to this embodiment includes a step of acquiring the isotope ratio δD of deuterium to proton contained in the molecule to be determined. If the isotope ratio δD is equal to or less than a predetermined threshold, the determination method includes a step of determining that the molecule to be determined is a molecule produced by a method including an electrolysis step of producing hydrogen molecules by electrolysis of a water-containing liquid.

[0035] Furthermore, the manufacturing process determination method for a molecule to be determined according to this embodiment includes the steps of acquiring an isotope ratio δD of deuterium to proton contained in the molecule to be determined, and determining that the molecule to be determined is a molecule produced using fossil fuel as a raw material if the isotope ratio δD is greater than a predetermined threshold value.

[0036] Hydrogen produced by electrolysis has a small isotope ratio δD due to the isotope effect. On the other hand, hydrogen produced by, for example, steam reforming of fossil fuels has a small isotope effect, and the difference from the natural isotope ratio δD is not as great as in the case of electrolysis. Therefore, in the manufacturing process determination method according to this embodiment, if the isotope ratio δD of the hydrogen contained in the target molecule is equal to or less than a predetermined threshold, it is determined that the hydrogen contained in the target molecule is derived from hydrogen produced by electrolysis of a liquid containing water. Therefore, the manufacturing process determination method according to this embodiment can determine whether the target molecule was produced by a method including an electrolysis step. Alternatively, in the manufacturing process determination method according to this embodiment, if the isotope ratio δD of the hydrogen contained in the target molecule is greater than a predetermined threshold, it is determined that the hydrogen contained in the target molecule is derived from hydrogen produced from a fossil fuel. Therefore, the manufacturing process determination method according to this embodiment can determine that the target molecule was produced using a fossil fuel as a raw material. As described above, the manufacturing process determination method according to this embodiment can meet the needs for evaluation of environmental impact.

[0037] Furthermore, the manufacturing process determination method according to this embodiment can determine whether hydrogen contained in a molecule to be determined originates from a manufacturing process that involves the generation of carbon dioxide. Therefore, for example, it is possible to ensure that hydrogen provided to the market is derived from hydrogen produced by electrolysis, rather than from hydrogen derived from fossil fuels. Furthermore, hydrogen-containing compounds such as ammonia and hydrocarbons can be produced using hydrogen as a raw material. Therefore, this determination method can ensure that not only hydrogen but also hydrogen-containing compounds such as ammonia or hydrocarbons originate from hydrogen produced by electrolysis, rather than from hydrogen derived from fossil fuels.

[0038] The present embodiment will be described in further detail below, but the present embodiment is not limited to these examples.

[0039] Isotope ratio δD of hydrogen gas produced by electrolysis of water ｇａｓ , isotope ratio δD of hydrogen gas produced from liquefied natural gas (LNG)ｇａｓ First, the isotope ratio δD ｇａｓ The procedure for obtaining this will be explained.

[0040] Isotope separation factor α of hydrogen gas produced during water electrolysis ｇ is defined as the following formula (2) (H. Sato et al. Int. Journal Hydrogen Energy, October 2021, Vol. 46, Issue 68, pp. 33689-33695).

[0041]

[0042] In the above formula (2), (D / H) ｉｎ represents the molar ratio of deuterium to hydrogen contained in the water to be electrolyzed, (D / H) ｇａｓ represents the molar ratio of deuterium to protium contained in the hydrogen gas produced by electrolysis.

[0043] The above formula (2) can be transformed into the following formula (3).

[0044]

[0045] The hydrogen isotope ratio δD of a sample ｓａｍｐｌｅ is defined by the following equation (4), similarly to the above equation (1).

[0046]

[0047] In the above formula (4), δD ｓａｍｐｌｅ represents the hydrogen isotope ratio of a sample, and (D / H) ｓａｍｐｌｅ represents the molar ratio of deuterium to hydrogen in a sample, and (D / H) ＶＳＭＯＷ represents the molar ratio of deuterium to protium contained in the VSMOW. When the sample to be measured is water to be electrolyzed, the molar ratio of deuterium to protium contained in the water to be electrolyzed can be expressed by the following formula (5).

[0048]

[0049] Substituting the formulas (4) and (5) into the formula (3), the following formula (6) is derived.

[0050]

[0051] When the sample to be measured is hydrogen gas generated by electrolysis of water, the isotope ratio δD of the hydrogen gas to be measured is expressed as δD ｇａｓ Then, the formula (4) can be expressed as the following formula (7).

[0052]

[0053] From the above formula (7), the (D / H) of hydrogen gas ｇａｓ By measuring δD ｇａｓ can be derived.

[0054] Moreover, by substituting the above-mentioned formula (6) into the above-mentioned formula (7), the following formula (8) can be derived.

[0055]

[0056] From the above formula (8), the δD of the water to be electrolyzed is ｓａｍｐｌｅ and the isotope separation factor α, which depends on the electrolysis method ｇ From this, the δD of hydrogen gas produced by water electrolysis ｇａｓ can be calculated.

[0057] (δD of hydrogen gas produced by electrolysis of water ｇａｓ Regarding the type of electrode catalyst, the isotope separation factor α of AEM and PEM reported for water electrolysis ｇ and the hydrogen isotope ratio δD of natural water in Japan ｓａｍｐｌｅ and into the above formula (8), the hydrogen isotope ratio δD of the generated hydrogen gas is ｇａｓ The isotope separation factor α ｇThe following references were used for this purpose: R. Ogawa et al. Energy, April 2018, Vol. 149, pp. 98-104; H. Sato et al. Int. Journal Hydrogen Energy, October 2021, Vol. 46, Issue 68, pp. 33689-33695; Mizota C. and Kusakabe M. Geochemical Journal, 1994, Vol. 28, pp. 387-410.

[0058] These results are shown in Tables 1 and 2. From these results, the hydrogen isotope ratio δD ｇａｓ A histogram (first histogram) was created as shown in Figure 1.

[0059]

[0060]

[0061] (δD of hydrogen gas produced from liquefied natural gas (LNG) ｇａｓ Calculation of δD of hydrogen produced by steam reforming of methane contained in LNG gas Here, in the steam reforming using methane as a raw material, the reactions shown in the following reaction formulas (1) to (3) mainly occur.

[0062] CH ４ +H ２ O → CO + 3H ２ (1) CH ４ +2H ２ O → CO2 + 4H ２ (2) CO + H ２ O → CO ２ +H ２ (3)

[0063] Reaction formulas (1) to (3) can be expressed as one reaction formula, as shown in reaction formula (4) below.

[0064] CH ４ +2H ２ O → CO ２ +4H ２ (4)

[0065] The hydrogen isotope ratio of the raw water is δD ｗ The molar ratio of deuterium to hydrogen (D / H) contained in water is a, and the molar ratio of deuterium to hydrogen contained in VSMOW is (D / H). ＶＳＭＯＷ Then, Equation (4) can be expressed as Equation (9) below. Similarly, if the hydrogen isotope ratio of the raw material methane is δD ｇ , the molar ratio of deuterium to hydrogen (D / H) contained in methane is b, and the molar ratio of deuterium to hydrogen contained in VSMOW is (D / H) ＶＳＭＯＷ Then, the formula (4) can be expressed as the following formula (10): Ｗ and δD ｇ The values ​​of a and b can be obtained by substituting the above into equations (9) and (10).

[0066]

[0067]

[0068] Here, an isotope effect appears when carbon-hydrogen bonds are broken, and cases have been reported in which the isotope effect of C-H bonds and C-D bonds is such that k / k' is 6.69 at 25 °C and 3.31 at 200 °C (Junichi Matsuo, Chemistry and Education, 2013, vol. 61, pp. 244-247). Note that k represents the rate of the reaction including the C-H bond cleavage, and k' represents the rate of the reaction including the C-D bond cleavage. The isotope effect becomes smaller as the reaction temperature increases; at very high reaction temperatures, the isotope effect does not appear, and k / k' is close to 1. The reaction temperature for typical steam reforming is estimated to be around 700 °C, and the isotope effect around this temperature is estimated to be around 1.2 to 1.3. Therefore, taking into account the above isotope effect, the molar ratio of deuterium to protium contained in methane was determined using the value of b' expressed by the following formula (11):

[0069]

[0070] where α Ｃ－Ｈ shows the isotope effect in methane steam reforming, and in this example, α Ｃ－Ｈ = 1.2 or α Ｃ－Ｈ = 1.3 and b' was calculated.

[0071] Furthermore, as shown in reaction formula (4), the product hydrogen is produced in equal amounts from the raw materials methane and water. In other words, hydrogen gas is produced by mixing equal amounts of hydrogen contained in methane and water. Therefore, if the molar ratio of deuterium to protium (D / H) in the hydrogen gas produced by the steam reforming reaction is c, c can be expressed as shown in the following formula (12). The value of c can be obtained by substituting the value of a obtained from formula (9) and the value of b obtained from formula (10) into formula (12).

[0072]

[0073] In addition, (D / H) in the above formula (7) ｇａｓ By substituting the value of c into Equation (13), the hydrogen isotope ratio δD ｇａｓ The value of can be obtained.

[0074]

[0075] That is, α shown in Table 3 Ｃ－Ｈ , δD ｇ and δD Ｗ By substituting these values ​​into Equations (9) to (13), δDgas can be calculated (MJ Whiticar, Chem. Geo. September 1999, Vol. 161, pp. 291-314). The results calculated using this method are shown in Table 3. From these results, δD ｇａｓ A histogram (second histogram) was created as shown in Figure 1.

[0076]

[0077] (δD of Reference Examples) Next, the molar ratio of deuterium to protons in the hydrogen gas of Reference Examples 1 to 4, whose production methods are known and are shown in Table 4 below, was measured using a stable isotope ratio mass spectrometer (DELTA V Advantage, manufactured by Thermo Fisher Scientific). The analysis of the molar ratio of deuterium to protons in the hydrogen gas was performed without pretreatment, by directly introducing the gas to be analyzed into the mass spectrometer, using helium gas as the flow gas, and measuring the molar ratio of deuterium to protons (D / H) by the gas bench method. ｇａｓ Then, by substituting this value into the above formula (7), δD ｇａｓ The results are shown in Table 4 and Figure 1.

[0078]

[0079] As shown in Tables 1 to 3 and FIG. ｇａｓ is different between the hydrogen gas produced by AEM and PEM and the hydrogen gas produced by methane steam reforming, and there is a clear difference in δD between the two. ｇａｓ It was confirmed that there is a region where the isotope effect does not overlap. Hydrogen gas produced by AEM and PEM is produced by a decomposition reaction using an electrode catalyst, so it has a large isotope effect. On the other hand, hydrogen gas produced by methane steam reforming has a high reaction temperature of 700 to 800°C, so the isotope effect is small. Therefore, hydrogen from water electrolysis, which has a large isotope effect, has a δD ｇａｓ The absolute value of δD for methane steam reforming is large and the isotope effect is small. ｇａｓ The absolute value of is expected to be small.

[0080] Furthermore, as shown in Table 4 and FIG. 1, the δD ｇａｓ The values ​​of δD in Reference Examples 2 to 4 were in the range of hydrogen gas generated by water electrolysis. ｇａｓThe value of was in the region of hydrogen gas produced by methane steam reforming. These results show that it is possible to clearly distinguish between hydrogen derived from water electrolysis and hydrogen derived from methane steam reforming. Specifically, fitting was performed on the first histogram of AEM water electrolysis to create a first fitting curve. Similarly, fitting was performed on the first histogram of PEM water electrolysis to create a first fitting curve. Furthermore, fitting was performed on the second histogram of LNG steam reforming to create a second fitting curve. For fitting, Gaussian fitting of the histogram was performed based on the Gaussian function shown in the following equation (14). The results are shown in Figure 2 and Table 5.

[0081]

[0082] Here, in the above formula (14), x ｏ represents the average value of the hydrogen isotope ratio δD, and σ represents the variance of the hydrogen isotope ratio δD.

[0083]

[0084] From the results of FIG. 2 and Table 5, for example, the average value (δD ｇａｓ = -578.7‰) to a value 2σ (= 2 × 71.3) larger (δD ｇａｓ From the results of Figure 2, the hydrogen isotope ratio δD ｇａｓ When the ratio is large, the hydrogen gas is derived from methane steam reforming, and the hydrogen isotope ratio δD ｇａｓ If the value is small, it can be determined that the hydrogen gas is produced by electrolysis.

[0085] (δD of Test Example) Next, the (D / H) of hydrogen gas according to Test Example 1, in which the purity is specified but the hydrogen production method is unknown, ｇａｓ was measured by the same method as above, and δD ｇａｓ was calculated.

[0086]

[0087] As shown in Table 6 and FIG. 2, the isotope ratio δD ｇａｓ is smaller than the threshold value, it was determined that the hydrogen gas was produced by electrolysis of water. From this result, it can be seen that by obtaining the isotope ratio δD of hydrogen gas whose production method is unknown, it is possible to determine whether the hydrogen gas was produced by electrolysis of water or from a fossil fuel such as LNG.

[0088] In this example, it was confirmed that hydrogen gas produced by electrolysis can be distinguished from hydrogen gas produced from fossil fuels by obtaining the isotope ratio δD of the hydrogen gas. However, this determination method can be applied not only to hydrogen gas, but also to hydrogen-containing compounds that can be produced from hydrogen gas, such as ammonia gas, methane, olefins, and aviation fuel.

[0089] In other words, when hydrogen molecules are reacted with molecules other than hydrogen to produce a hydrogen-containing compound, the specific process required for the reaction is applied industrially, regardless of the hydrogen production method. Therefore, since hydrogen produced by water electrolysis and hydrogen produced by methane steam reforming undergo similar processes, the hydrogen-containing compound produced reflects the same isotope effect as hydrogen molecules. Therefore, the isotope ratio δD of hydrogen contained in the hydrogen-containing compound is calculated by multiplying the isotope ratio δD of the hydrogen in the raw material by a parameter based on the isotope effect ratio for each process, and the hydrogen isotope ratio δD of the raw material is maintained. For example, ammonia (NH ３ ) Since the hydrogen isotope ratio δD of the raw material is maintained in the hydrogen isotope ratio δD of ammonia, it is possible to distinguish between ammonia derived from water electrolysis and ammonia derived from methane steam reforming based on the hydrogen isotope ratio δD of ammonia.

[0090] Therefore, the determination methods described herein can be applied to hydrogen-containing molecules such as hydrogen, ammonia, or hydrocarbons.

[0091] In this example, a first histogram was created using classes based on the isotope ratio δD of hydrogen gas produced by PEM-type water electrolysis, and a value determined based on a first fitting curve obtained by fitting the first histogram was used as the predetermined threshold. Specifically, a value 2σ larger than the average value of the first fitting curve was set as the judgment threshold.

[0092] However, the predetermined threshold may be a value determined based on a second fitting curve obtained by creating a second histogram with classes based on the isotope ratio δD of hydrogen gas produced by steam reforming using LNG as a feedstock and performing fitting on the second histogram. The upper limit of the predetermined threshold may be determined based on the value of the variance σ of the hydrogen isotope ratio δD. The upper limit of the predetermined threshold may be, for example, a value 4σ smaller (−448.2‰) or a value 5σ smaller (−510.1‰) than the average value of the second fitting curve. The upper limit of the predetermined threshold may be the intersection point (−375‰) between the first fitting curve and the second fitting curve. The lower limit of the predetermined threshold may be a value determined based on the first fitting curve of AEM water electrolysis. Furthermore, the lower limit of the predetermined threshold may be, for example, −1000‰, a value (−903.5‰) that is 2σ smaller than the average value of the first fitting curve for AEM water electrolysis, or a value (−721.3‰) that is 2σ smaller than the average value of the first fitting curve for PEM water electrolysis.

[0093] The entire contents of Japanese Patent Application No. 2023-150748 (filing date: September 19, 2023) are incorporated herein by reference.

[0094] Although several embodiments have been described, the embodiments can be modified or varied based on the above disclosure. All components of the above embodiments and all features described in the claims may be individually extracted and combined as long as they are not mutually inconsistent.

[0095] The present disclosure can contribute, for example, to Goal 7 "Ensure access to affordable, reliable, sustainable and modern energy for all," Goal 12 "Ensure sustainable consumption and production patterns," and Goal 13 "Take urgent action to combat climate change and its impacts" of the Sustainable Development Goals (SDGs) led by the United Nations.

Claims

1. A method for determining the manufacturing process of a molecule to be determined, comprising: a step of acquiring an isotope ratio δD of deuterium to light hydrogen contained in the molecule to be determined; and a step of determining, when the isotope ratio δD is equal to or less than a predetermined threshold value, that the molecule to be determined is a molecule that was produced by a method including an electrolysis step of producing hydrogen molecules by electrolysis of a liquid containing water.

2. A method for determining the manufacturing process of a molecule to be determined, comprising: a step of acquiring an isotope ratio δD of deuterium to light hydrogen contained in the molecule to be determined; and a step of determining that the molecule to be determined is a molecule produced using fossil fuels as a raw material when the isotope ratio δD is greater than a predetermined threshold value.

3. The manufacturing process determination method according to claim 1 or 2, wherein the determining step determines that the molecule to be determined is a molecule produced by a method including an electrolysis step of producing hydrogen molecules by electrolysis of a liquid containing water if the isotope ratio δD is equal to or less than the predetermined threshold, and determines that the molecule to be determined is a molecule produced using a fossil fuel as a raw material if the isotope ratio δD is greater than the predetermined threshold.

4. The manufacturing process judgment method according to any one of claims 1 to 3, wherein the judgment target molecule is hydrogen, ammonia or a hydrocarbon.

5. The manufacturing process judgment method according to claim 1 or 3, wherein the electrolysis is at least one of anion exchange membrane water electrolysis and proton exchange membrane water electrolysis.

6. The manufacturing process judgment method according to any one of claims 1 to 5, wherein the predetermined threshold is a value determined based on a first fitting curve obtained by creating a first histogram classifying the isotope ratio δD of the judgment target molecule manufactured by a method including an electrolysis step of generating hydrogen molecules by electrolysis of a water-containing liquid for a plurality of conditions and performing fitting on the first histogram.

7. The manufacturing process judgment method according to any one of claims 1 to 6, wherein the predetermined threshold is a value determined based on a second fitting curve obtained by creating a second histogram in which the isotope ratio δD of the judgment target molecule produced using a fossil fuel as a raw material for a plurality of conditions is classified, and fitting the second histogram.

8. The manufacturing process judgment method according to any one of claims 1 to 7, wherein the predetermined threshold value is an intersection between a first fitting curve obtained by creating a first histogram classifying the isotope ratio δD of the target molecule produced by a method including an electrolysis step of generating hydrogen molecules by electrolysis of a water-containing liquid for a plurality of conditions and performing fitting on the first histogram, and a second fitting curve obtained by creating a second histogram classifying the isotope ratio δD of the target molecule produced using fossil fuels as a raw material for a plurality of conditions and performing fitting on the second histogram.

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