Method for replacing oxygen isotope from carbon monoxide

Abstract

The invention provides a method for simultaneously producing heavy oxygen water, carbon-enriched heavy isotopes and oxygen-16 carbon monoxide. The method comprises the following steps: carrying out low-temperature rectification on a carbon monoxide raw material to obtain carbon monoxide rich in carbon-13 and / or carbon-14 and oxygen-18; performing methanation reaction on the carbon monoxide rich in carbon-13 and / or carbon-14 and oxygen-18 and hydrogen to obtain heavy oxygen water rich in oxygen-18 and methane rich in carbon-13 and / or carbon-14; and partially oxidizing the methane rich in carbon-13 and / or carbon-14 to obtain carbon monoxide rich in oxygen-16 and carbon-13 and / or carbon-14. According to the method, oxygen isotopes and carbon isotopes in carbon monoxide can be separated, carbon monoxide rich in oxygen-16 and carbon-13 and / or carbon-14 and heavy-oxygen water rich in oxygen-18 can be prepared respectively, the process is simple, and the production cost is low.

Description

Technical Field

[0001] The invention relates to the technical field of isotope separation and enrichment, and in particular to a method for replacing oxygen isotopes from carbon monoxide. Background Art

[0002] Oxygen has three stable isotopes: oxygen-16, oxygen-17, and oxygen-18, with natural abundances of 99.76%, 0.04%, and 0.2%, respectively. Oxygen-18 is a stable isotope of oxygen. Heavy oxygen water is a colorless, odorless, and tasteless water containing oxygen-18.

[0003] Oxygen-18 is a basic material for tracing human physiological processes. It is widely used in the study of drug metabolism, energy metabolism and PET (positron emission tomography) imaging agent precursor synthesis. Among them, since oxygen-18 isotopes can obtain fluorine-18 ions through medical cyclotron bombardment, its labeled positron imaging drug 18F-FDG is mainly used in nuclear medicine positron emission computed tomography diagnostic technology (Positron Emission Computed Tomography, PET). Among the four medical imaging examination methods, PET-CT can detect abnormal lesions six months in advance, and can examine the whole body in one positioning. It has high sensitivity to various tumors and has an accuracy rate of more than 95%. Therefore, domestic PET has developed rapidly. With the continuous development of PET technology for early detection of cancer, the market demand for heavy oxygen water (oxygen-18 water) formed by the combination of oxygen-18 and hydrogen is increasing. Heavy oxygen water also has important uses in health care, oxygen therapy, health and beauty products, chemical reaction mechanism research, biomedicine and environmental monitoring.

[0004] At present, the separation of oxygen isotopes includes cryogenic distillation of oxygen or nitric oxide, chemical exchange, membrane separation, thermal diffusion, and water distillation. Cryogenic distillation of nitric oxide was once the main method for producing oxygen-18 abroad. This method mainly produces nitrogen isotope nitrogen-15, and oxygen-18 is the main by-product; but nitric oxide is flammable, explosive and highly toxic, and it corrodes equipment seriously, posing a great safety hazard. The membrane separation technology is not yet mature, and the thermal diffusion method is difficult to mass produce. Neither of these two methods has been industrially applied. The cryogenic distillation of oxygen uses oxygen separated from the air as a raw material to extract oxygen-18 through cryogenic distillation, but the content of oxygen-18 in natural oxygen is too low, and the one-step method only enriches a product with an oxygen-18 abundance of 25%. Due to the technical difficulty and high cost of extracting oxygen-18 by cryogenic distillation, the more advanced and newly built oxygen isotope production facilities currently generally use water distillation. This method uses natural water as a raw material and achieves the purpose of producing heavy oxygen water through a multi-stage cryogenic distillation cascade. Water distillation is also the main method for producing oxygen-18 isotopes in China, but this method has extremely low raw material abundance, high production energy consumption, and a low separation coefficient. The main domestic heavy oxygen water producers are Shanghai Chemical and Changshu Huayi. They use a water distillation method that takes 11 months to produce heavy oxygen water, and their production capacity is far from meeting the domestic market. The typical separation factor for separating oxygen-18 and oxygen-16 by water distillation is 1.006. In order to obtain heavy oxygen water with an oxygen-18 abundance of 97%, more than 2,000 cascade towers are required to operate in series, which is very difficult to separate and consumes a lot of energy. At the same time, deuterium and oxygen-18 are enriched simultaneously during the water distillation production process. The increase in deuterium content reduces the separation factor between oxygen-18 water and oxygen-16 water, increasing the difficulty of separation.

[0005] Carbon isotope carbon-13 can be used as an isotope marker. Carbon is one of the most common elements in living organisms and organic compounds. Therefore, carbon-13 is widely used in research fields such as life sciences and chemistry. For example, it is increasingly widely used in carbon-13 breath tests to detect human Helicobacter pylori. At present, the method for enriching carbon-13 isotopes usually adopts carbon monoxide cryogenic distillation, which is also the main method for industrial separation of carbon isotopes. However, the primary product obtained by the cryogenic distillation separation method usually also contains a high abundance of heavy oxygen isotopes (oxygen-18), and the heavy isotopes of oxygen will interfere with the separation of heavy isotopes of carbon (carbon-13 or carbon-14) and carbon-12. Therefore, in the process of producing carbon-13 isotopes by carbon monoxide cryogenic distillation, it is also necessary to remove the heavy isotope of oxygen, oxygen-18.

[0006] To this end, it is necessary to establish a method to separate carbon isotopes and oxygen isotopes in carbon monoxide. Summary of the invention

[0007] In view of this, the main object of the present invention is to provide a method for simultaneously producing heavy oxygen water and carbon monoxide enriched with oxygen-16 and heavy isotopes of carbon.

[0008] To this end, the present invention provides a method for simultaneously producing heavy oxygen water and carbon monoxide enriched in oxygen-16 and heavy isotopes of carbon, comprising subjecting a carbon monoxide raw material to cryogenic distillation to obtain carbon monoxide enriched in carbon-13 and / or carbon-14 and oxygen-18; mixing the carbon monoxide enriched in carbon-13, carbon-14 and / or oxygen-18 with hydrogen, and subjecting the mixture to a methanation reaction in the presence of a catalyst to obtain heavy oxygen water enriched in oxygen-18 and methane enriched in carbon-13 and / or carbon-14; and partially oxidizing the methane enriched in carbon-13 and / or carbon-14 to obtain carbon monoxide enriched in carbon-13 and / or carbon-14 and oxygen-16.

[0009] In some embodiments, the carbon monoxide enriched in carbon-13 and / or carbon-14 and oxygen-18 has an oxygen-18 abundance of 5%-25%, and a carbon-13 or carbon-14 abundance of 5-100%.

[0010] In some embodiments, the catalyst includes an active metal component supported on a carrier, wherein the active metal component is one or more selected from Ru, Fe, Ni, Co, Rh, Pd, Pt and Ir, and the carrier is one or more selected from Al2O3, SiO2, TiO2, ZrO2, CeO2 and foamed Ni.

[0011] In some embodiments, in the methanation reaction, the molar ratio of carbon monoxide rich in carbon-13 and / or carbon-14 and oxygen-18 to hydrogen is 1:3 to 1:8.

[0012] In some embodiments, the mixed gas of carbon monoxide and hydrogen rich in carbon-13 and / or carbon-14 and oxygen-18 passes through the catalyst at a gas rate of 1600-2400 L / h.

[0013] In some embodiments, the temperature of the methanation reaction is 280°C-320°C.

[0014] In some embodiments, the partially oxidized methane rich in carbon-13 and / or carbon-14 uses oxygen, or an oxygen-containing gas mixed with an inert gas, as an oxidant. Preferably, the molar ratio of the methane rich in carbon-13 and / or carbon-14 to the oxygen-containing gas is 1:1.2 to 1:1.5.

[0015] In some embodiments, the partial oxidation is performed at 50°C-1500°C.

[0016] In some embodiments, the heavy oxygen water rich in oxygen-18 is electrolyzed to obtain oxygen rich in oxygen-18.

[0017] In the present invention, carbon monoxide containing heavy isotopes of carbon and / or oxygen is enriched by cryogenic distillation, and then carbon monoxide rich in carbon-13 and / or carbon-14 and oxygen-18 is subjected to a methanation reaction to prepare heavy oxygen water rich in oxygen-18, and carbon monoxide rich in oxygen-16, carbon-13 and / or carbon-14 is obtained by partial oxidation of methane rich in carbon-13 and / or carbon-14. The technical scheme of the present invention is simple, the difficulty of separating oxygen-18 is low, and the safety is high. The abundance of oxygen-18 in the raw material is high, and the production cost is low. In addition, the method of the present invention prepares the carbon isotopes and oxygen isotopes in the carbon monoxide rich in carbon-13 and / or carbon-14 and oxygen-18 into a carbon isotope-rich carbon monoxide product and an oxygen isotope-rich heavy oxygen water product, respectively, optimizes the utilization rate of the isotope products, and achieves greater economic value. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The present invention is a process flow chart of one embodiment of the present invention. DETAILED DESCRIPTION

[0019] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in combination with the embodiments of the present invention and the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0020] Throughout the specification, unless otherwise specifically stated, the terms used herein should be understood as meanings commonly used in the art. Therefore, unless otherwise defined, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art to which the present invention belongs. In the event of a conflict, the present specification takes precedence.

[0021] It should be noted that, in the embodiments of the present invention, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a method or device including a series of elements includes not only the elements explicitly stated, but also other elements not explicitly listed, or also includes elements inherent to the implementation of the method or device. In the absence of further restrictions, an element defined by the sentence "includes a ..." does not exclude the existence of other related elements in the method or device including the element.

[0022] It should be noted that the terms "first\second\third" involved in the embodiments of the present invention are only used to distinguish similar objects, and do not represent a specific order for the objects. It is understandable that the specific order or sequence of "first\second\third" can be interchanged where permitted. It should be understood that the objects distinguished by "first\second\third" can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein.

[0023] The existing technology for producing heavy oxygen water rich in oxygen-18 has problems such as high technical difficulty, high separation cost, and low abundance of oxygen-18 in the product. The carbon monoxide product enriched in carbon isotopes obtained by the low-temperature distillation of carbon monoxide is usually also enriched in oxygen isotopes, which has an adverse effect on the subsequent use of the carbon isotope-enriched carbon monoxide product.

[0024] In view of this, the present invention provides a method for simultaneously producing heavy oxygen water and carbon monoxide enriched in oxygen-16 and heavy isotopes of carbon, comprising subjecting a carbon monoxide raw material to cryogenic distillation to obtain carbon monoxide enriched in carbon-13 and / or carbon-14 and oxygen-18; mixing the carbon monoxide enriched in carbon-13 and / or carbon-14 and oxygen-18 with hydrogen, and subjecting the mixture to a methanation reaction in the presence of a catalyst to obtain heavy oxygen water enriched in oxygen-18 and methane enriched in carbon-13 and / or carbon-14; and partially oxidizing the methane enriched in carbon-13 and / or carbon-14 to obtain carbon monoxide enriched in carbon-13 and / or carbon-14 and oxygen-16.

[0025] In the present invention, the low temperature distillation of the carbon monoxide raw material can be carried out by a method known to those skilled in the art, and the present invention does not impose any particular limitation thereto.

[0026] The inventors have found that in the existing process of extracting carbon-13 by low-temperature distillation of carbon monoxide, oxygen-18, whose abundance is increased to 10%-25%, is basically ignored and even needs to be removed. With the widespread application of carbon-13, factories that have been built or are under construction in China to extract carbon-13 by low-temperature distillation of carbon monoxide will greatly increase the output of carbon monoxide products rich in oxygen-18.

[0027] In order to efficiently utilize oxygen-18 enriched in the low-temperature distillation process of carbon monoxide, the present invention further prepares heavy oxygen water rich in oxygen-18 by methanation reaction of carbon monoxide rich in carbon-13 and / or carbon-14 and oxygen-18, and obtains carbon monoxide rich in carbon-13 and / or carbon-14 and oxygen-16 by partially oxidizing methane rich in carbon-13 and / or carbon-14. The method of the present invention prepares carbon isotopes and oxygen isotopes in carbon monoxide raw materials rich in carbon-13, carbon-14 and oxygen-18 into carbon isotope-rich carbon monoxide products and oxygen isotope-rich heavy oxygen water products, respectively. The technical solution of the present invention is simple, the difficulty of separating oxygen-18 is low, and the safety is high. The abundance of oxygen-18 in the raw material is high and the production cost is low. In addition, the utilization rate of isotope products is optimized to achieve greater economic value. Through the method of the present invention, heavy oxygen water with an oxygen-18 abundance of 5%-30% can be obtained.

[0028] In the present invention, the source of the carbon monoxide raw material is not particularly limited, for example, it can be waste gas from a nuclear power plant, or it can be waste gas generated after absorbing neutrons. In the present invention, the carbon monoxide raw material includes carbon-13 and / or carbon-14 isotopes and oxygen-18 isotopes.

[0029] The following will be combined Figure 1 The process flow chart of one embodiment of the present invention is shown to describe the method of the present invention in detail. It should be understood that the following description of the drawings and specific embodiments is only exemplary and is not intended to limit the scope of the present invention.

[0030] In some embodiments, the method for simultaneously producing heavy oxygen water and carbon isotope-enriched carbon monoxide includes subjecting a carbon monoxide raw material to cryogenic distillation to obtain carbon monoxide rich in carbon-13 and / or carbon-14 and oxygen-18; mixing the carbon monoxide rich in carbon-13 and / or carbon-14 and oxygen-18 with hydrogen, and subjecting the mixture to a methanation reaction in the presence of a catalyst to obtain heavy oxygen water rich in oxygen-18 and methane rich in carbon-13 and / or carbon-14; and partially oxidizing the methane rich in carbon-13 and / or carbon-14 to obtain carbon monoxide rich in carbon-13 and / or carbon-14 and oxygen-16.

[0031] The carbon monoxide rich in carbon-13 and / or carbon-14 and oxygen-18 prepared by the carbon monoxide low-temperature distillation process has a high oxygen-18 concentration and lower overall cost. As the carbon monoxide production capacity increases, the potential production capacity of oxygen-18 will also increase significantly.

[0032] In some embodiments, the abundance of oxygen-18 in the carbon monoxide rich in carbon-13 and / or carbon-14 and oxygen-18 is 5%-25%; the abundance of carbon-13 and / or carbon-14 is 5-100%. Using carbon monoxide with an abundance of oxygen-18 within the above range as a raw material is conducive to obtaining heavy oxygen water rich in oxygen-18 with better purity, saving production costs and energy consumption.

[0033] In some embodiments, the catalyst includes an active metal component supported on a carrier, the active metal component is one or more selected from Ru, Fe, Ni, Co, Rh, Pd, Pt and Ir, and the carrier is one or more selected from Al2O3, SiO2, TiO2, ZrO2, CeO2 and foamed Ni. The use of the above catalyst is conducive to improving the efficiency of the methanation reaction, achieving the separation of carbon isotopes and oxygen isotopes, and obtaining carbon isotope products and oxygen isotope products respectively. In some preferred embodiments, the catalyst is selected from one or more of Ni / SiO2, Ru / SiO2, Ru / Al2O3, Ru / TiO2 or mixtures thereof.

[0034] In some embodiments, in the methanation reaction, the molar ratio of carbon monoxide rich in carbon-13 and / or carbon-14 and oxygen-18 to hydrogen is 1:3 to 1:8. By making the molar ratio of carbon monoxide rich in carbon-13, carbon-14 and oxygen-18 to hydrogen within the above range, it is beneficial for the carbon monoxide raw material to fully react to achieve the separation of carbon isotopes and oxygen isotopes, and it is beneficial to save production costs. Exemplarily, the molar ratio of carbon monoxide rich in carbon-13, carbon-14 and oxygen-18 to hydrogen can be 1:3, 1:4, 1:5, 1:6, 1:7, 1:8 or a value between the range composed of any two of them.

[0035] In some embodiments, the mixed gas of carbon monoxide and hydrogen rich in carbon-13, carbon-14 and oxygen-18 passes through the catalyst at a gas velocity of 1600-2400 L / h. By making the gas velocity of the mixture other within the above range, it is beneficial for carbon monoxide and hydrogen rich in carbon-13, carbon-14 and oxygen-18 to fully contact and react with the catalyst, thereby improving the reaction efficiency. Exemplarily, the gas velocity of the mixed gas can be 1600 L / h, 1800 L / h, 2000 L / h, 2200 L / h, 2400 L / h or a value between the ranges consisting of any two of them.

[0036] In some embodiments, the temperature of the methanation reaction is 280° C.-320° C. By making the temperature of the methanation reaction within the above range, it is beneficial for carbon monoxide and hydrogen to fully react to obtain methane and heavy oxygen water rich in oxygen-18. Exemplarily, the temperature of the methanation reaction can be 280° C., 290° C., 300° C., 310° C., 320° C., or a value between the ranges consisting of any two of them.

[0037] In some embodiments, the partial oxidation of methane rich in carbon-13 and / or carbon-14 uses oxygen, or an oxygen-containing gas mixed with an inert gas as an oxidant. Preferably, the molar ratio of the methane rich in carbon-13 and / or carbon-14 and oxygen or the oxygen in the oxygen-containing gas is 1:1.2 to 1:1.5. By having the molar ratio of the methane rich in carbon-13 and / or carbon-14 and oxygen in the above range, it is beneficial to achieve partial reaction to generate carbon monoxide rich in carbon-13 and / or carbon-14, and avoid excessive oxidation of methane. Exemplarily, the molar ratio of the methane rich in carbon-13 and / or carbon-14 and oxygen or the oxygen in the oxygen-containing gas can be 1:1.2, 1:1.3, 1:1.4, 1:1.5 or a value between the ranges consisting of any two of them. In some embodiments, the oxygen-containing gas includes at least 1% oxygen. In some embodiments, the mixed gas containing at least 1% oxygen is a mixed gas of one or more selected from air and an inert gas and oxygen. In some embodiments, the inert gas is helium or argon. Exemplarily, the mixed gas containing at least 1% oxygen can be air containing at least 1% oxygen, a mixed gas of pure oxygen and helium, or a mixed gas of pure oxygen and argon.

[0038] In some embodiments, the partial oxidation is carried out at 50°C-1500°C. By making the temperature of the partial oxidation within the above range, it is beneficial to partially oxidize methane and oxygen to generate carbon monoxide, reduce methane carbonization or other side reactions, and improve reaction efficiency. Exemplarily, the temperature of the partial oxidation can be 50°C, 100°C, 500°C, 600°C, 700°C, 800°C, 900°C, 1000°C, 1100°C, 1200°C, 1300°C, 1400°C, 1500°C or a value between the ranges consisting of any two of them.

[0039] In some embodiments, the oxygen-18-rich heavy oxygen water can be electrolyzed to obtain oxygen-18-rich oxygen. The oxygen-18-rich oxygen obtained by electrolysis can be used in the fields of isotope tracing, health care, oxygen therapy, health and beauty products, chemical reaction mechanism research, biomedicine, and environmental monitoring.

[0040] The technical solution of the present invention will be described in detail below in conjunction with specific embodiments.

[0041] Example

[0042] Example 1

[0043] The oxygen-18 abundance of 20% obtained by low-temperature distillation of carbon monoxide 13 CO and high-purity H2 were mixed in a molar ratio of 1 to 8 to obtain a mixed gas. The mixed gas was passed through a Ni / ZrO2 and Ni / SiO2 mixed catalyst at a temperature of 280°C at a gas velocity of 2000 L / h to obtain 13 CH4 and heavy oxygen water. Then the 13 CH4 and ordinary high-purity oxygen are mixed in a molar ratio of 1:1.5 and reacted at 1200°C to obtain and return oxygen-16-rich 13 CO.

[0044] Example 2

[0045] The oxygen-18 abundance of 25% obtained by low-temperature distillation of carbon monoxide 13 CO and high-purity H2 were mixed in a molar ratio of 1 to 6 to obtain a mixed gas. The mixed gas was passed through a Ni / ZrO2 and Ni / SiO2 mixed catalyst at a gas velocity of 1600 L / h at a temperature of 290°C to obtain 13 CH4 and heavy oxygen water. Then the 13 CH4 and ordinary high-purity oxygen are mixed in a molar ratio of 1:1.4 and cyclically reacted at 1300℃ to obtain and return oxygen-rich 16 13 CO.

[0046] Example 3

[0047] The oxygen-18 abundance of 15% obtained by low-temperature distillation of carbon monoxide 13 CO and high-purity H2 were mixed in a molar ratio of 1 to 5 to obtain a mixed gas. The mixed gas was passed through a Ni / ZrO2 catalyst at a temperature of 300°C at a gas velocity of 2400 L / h to obtain 13 CH4 and heavy oxygen water. Then the 13 CH4 and ordinary high-purity oxygen are mixed in a molar ratio of 1:1.2 and cyclically reacted at 1400℃ to obtain and return oxygen-rich 16 13 CO.

[0048] Example 4

[0049] The oxygen-18 abundance of 14% is obtained by low-temperature distillation of carbon monoxide. 13 CO and high-purity H2 were mixed in a molar ratio of 1 to 3 to obtain a mixed gas. The mixed gas was passed through a Ni-Fe / AlO3 catalyst at a temperature of 320°C at a gas velocity of 2200 L / h to obtain 13CH4 and heavy oxygen water. Then the 13 CH4 and ordinary high-purity oxygen are mixed in a molar ratio of 1:1.4 and reacted at 1000℃ to obtain and return oxygen-rich 16 13 CO.

[0050] Example 5

[0051] The oxygen-18 abundance of 18% obtained by low-temperature distillation of carbon monoxide 13 CO and high-purity H2 were mixed in a molar ratio of 1 to 6 to obtain a mixed gas. The mixed gas was passed through a Ru / TiO2 mixed catalyst at a temperature of 300°C at a gas velocity of 2000 L / h to obtain 13 CH4 and heavy oxygen water. Then the 13 CH4 and ordinary high-purity oxygen are mixed in a molar ratio of 1:1.3 at 1500℃ to obtain and return oxygen-16-rich 13 CO.

[0052] The above description is only a preferred embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification and drawings under the inventive concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A method for simultaneously producing heavy oxygen water and carbon monoxide enriched in oxygen-16 and heavy isotopes of carbon, comprising subjecting a carbon monoxide raw material to cryogenic distillation to obtain carbon monoxide enriched in carbon-13 and / or carbon-14 and oxygen-18; mixing the carbon monoxide enriched in carbon-13 and / or carbon-14 and oxygen-18 with hydrogen, and subjecting the mixture to a methanation reaction in the presence of a catalyst to obtain heavy oxygen water enriched in oxygen-18 and methane enriched in carbon-13 and / or carbon-14; and partially oxidizing the methane enriched in carbon-13 and / or carbon-14 to obtain carbon monoxide enriched in carbon-13 and / or carbon-14 and oxygen-16.

2. The method according to claim 1, wherein: The carbon monoxide rich in carbon-13 and / or carbon-14 and oxygen-18 has an oxygen-18 abundance of 5%-25%, and a carbon-13 or carbon-14 abundance of 5-100%.

3. The method according to claim 1 or 2, wherein: The catalyst includes an active metal component supported on a carrier, wherein the active metal component is one or more selected from Ru, Fe, Ni, Co, Rh, Pd, Pt and Ir, and the carrier is one or more selected from Al2O3, SiO2, TiO2, ZrO2, CeO2 and foamed Ni.

4. The method according to claim 3, wherein: In the methanation reaction, the molar ratio of carbon monoxide rich in carbon-13 and / or carbon-14 and oxygen-18 to hydrogen is 1:3 to 1:

8.

5. The method according to claim 1 or 2, wherein: The mixed gas of carbon monoxide and hydrogen rich in carbon-13 and / or carbon-14 and oxygen-18 passes through the catalyst at a gas velocity of 1600-2400 L / h.

6. The method according to claim 1 or 2, wherein: The temperature of the methanation reaction is 280°C-320°C.

7. The method according to claim 1 or 2, wherein: The partial oxidation of methane rich in carbon-13 and / or carbon-14 uses oxygen, or an oxygen-containing gas mixed with an inert gas, as an oxidant. Preferably, the molar ratio of the methane rich in carbon-13 and / or carbon-14 to the oxygen in the oxygen-containing gas is 1:1.2 to 1:1.

5.

8. The method according to claim 1 or 2, wherein: The partial oxidation is carried out at 50°C-1500°C.

9. The method according to claim 1 or 2, further comprising: The heavy oxygen water rich in oxygen-18 is electrolyzed to obtain oxygen rich in oxygen-18.

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