JP6902091B2 - How to obtain heavy oxygen water and equipment for its production - Google Patents

Description

The present invention relates to the production of oxygen-18 for PET tomography and can be used to produce water rich in oxygen-18 isotopes (heavy oxygen water, H2O-18).

Water rich in isotope oxygen-18 (H2O-18) is now widely used in medicine, pesticides and biochemistry. Oxygen-18 was first concentrated to 99.5% in 1943 using the thermal diffusion method (Non-Patent Document 1). So far, electrolysis, chemical isotope exchange, gas diffusion, oxygen rectification, nitrogen oxides, and the use of water have been described to concentrate water to oxygen-18. Among them, the water rectification method (Non-Patent Document 2), which was first demonstrated in 1944, is currently being used successfully in industry.

The oxygen isotope effect during electrolysis was discovered at the same time as the hydrogen isotope effect (Non-Patent Document 3). However, attempts to generate oxygen-18 by this method have not been successful (Non-Patent Documents 4 and 5). Similarly, attempts to enrich oxygen-18 by the method of chemical isotope exchange in the exchange reaction between CO2 and H2O were unsuccessful. The separation coefficient of this reaction is as high as 1.046, but the reaction rate is too slow to streamline the process on an industrial scale (Non-Patent Document 6).

The method of chemical isotope exchange for obtaining H2O-18 was carried out based on the exchange reaction between nitrogen oxide NO and nitric acid (Non-Patent Document 7). By this method, H2O-18 could be obtained with an enrichment of about 15%. The low technical and economic indicators of the process are related to the difficulty of quantitatively converting nitric oxide to nitric acid: some of the products are elemental nitrogen or nitrogen oxides in a highly oxidized state. The background is that it is irreversibly converted to.

Even if the gas diffusion method is used to obtain oxygen-18, satisfactory results cannot be obtained because the concentration coefficient is low (Non-Patent Document 8).

Thermal diffusion is more effective, but the process is so slow that it is not suitable for the production of large amounts of concentrated H2O-18. For example, in order to obtain 250 ml of oxygen-18, it was necessary to operate a cascade of columns having a total length of 59 meters for 1.5 years or more (Non-Patent Document 9). Using some of the more modern methods of this process makes things a little faster. For example, in a 4-stage cascade device using a column with dimensions of 3.4 m x 9.2 mm, after 3 weeks of work with an initial intermediate product with an oxygen-18 content of 1.5-2%, an 81% enrichment A product could be obtained (Non-Patent Document 10). Using each of the raw materials with an oxygen-18 content of about 40% in a three-stage cascade with three columns, a product with a concentration of 85-90% can be produced up to 30 ml per day (Non-Patent Documents). 11). However, these quantities are far from the industrial quantities required to produce the product. Moreover, in any case, a pre-concentrated material is required.

The process of distilling water is much more efficient. This method was first implemented in 1937 and was able to obtain 200 ml of H2O-18 at a concentration of 0.85% (Non-Patent Document 12). In the subsequent period, this method was improved, and in 1956, a rectified water concentration unit capable of producing 24% O-18 and 1.7% O-17 water was created (Non-Patent Document 13). The most perfect process underlying all modern processes for producing oxygen-18 by the water rectification method was carried out in the late 1950s (Non-Patent Document 14). It is possible to obtain H2O-18 with an enrichment of 99% or more, which is a characteristic process with high efficiency and reliability.

The method described in Non-Patent Document 15 is the closest to the proposed invention regarding a method for producing oxygen-rich water. The method selected as a prototype is oxygen from natural water with an oxygen-18 content of 0.2% and a deuterium content of 0.015% through a two-step process of pre-concentration by rectification and final concentration by chemical isotope exchange. -18 is to obtain 90% concentrated water.

The raw material used is ordinary natural water with an oxygen-18 content of about 0.2% and a deuterium content of about 0.015%. The presence of deuterium in natural water leads to the fact that the concentration of deuterium occurs at the same time as the concentration of oxygen-18 (at a column operating temperature of 65 ° C, the concentration factor αo- of the H2O-18 / H2O-16 system. 18 / O-16 is about 1.005, and the enrichment factor αD / H of the HDO / H2O system is about 10 times larger, about 1.045). As a result, the composition of the final product, H2O-18, is almost 100% D2O-18. However, medical applications require products that naturally contain hydrogen isotopes, and the deuterium content of the product must not exceed 0.015%. Therefore, products obtained according to the prototype scheme must always undergo additional treatment (so-called isotopic composition normalization process) to remove deuterium. The normalization process is, in principle, carried out by electrolysis of water followed by combustion of oxygen-18 in hydrogen of natural isotopic composition. At this stage, losses and wastes inevitably occur, which affects production costs.

The same article describes equipment for obtaining oxygen-rich water (Figure 1) that is closest to what is claimed. Prototype equipment includes:
Preliminary concentration unit of H2O-18 consisting of a distillation column consisting of a distillation column that performs type 1 extraction and operates simultaneously in an open circuit (no discharge): The resulting intermediate concentrate is sent to the final concentration unit without flow feedback. Be done.
・ Final concentration unit consisting of 3 H2O-18 concentration columns and 1 H2O-16 removal column

Thanks to the mechanism adopted, each pre-concentration column is not backflow connected to subsequent stages of the cascade and operates independently.

The productivity of equipment with the above specifications is 4 kg per year with 90% concentrated H2O-18. More productive devices that work with this method and mechanism are currently in operation in the United States, Europe, Israel, and China, supplying more than 50% of the global market (about 1500 kg per year) of heavy oxygen water (about 1500 kg per year). Non-Patent Document 16).

Clusius, Dickel and Becker, Naturwiss, 31, 210, 1943 H.G. Thode, S.R. Smith, F.D. Walkling, The Separation Of The Oxygen Isotopes By The Distillation Of Water, Canadian Journal of Research, 1944, 22b (4): 127-136, 10.1139 / cjr44b-016 E. W. Washburn, E. R. Smith and M. Frandsen, J. Chem. Phys. 1, 288, 1933 H.L. Johnston, J. Am. Chem. Soc., 57, 484, 1935 H. Anbar, H. Taube, J. Am. Chem. Soc. 78, 3252, 1956 W. T. Boyd, R. R. White, Ind. Eng. Chem. 44, 2202, 1952 T. I. Taylor, J. Chim. Phys. 60, 154, 1963 R. Sherr, J. Chim. Phys. 6, 251, 1938 Clusius, Dickel and Becker, Naturwiss, 31, 210, 1943 K. Clusius and K. Schleich, Helv. Chim. Acta, 45, N5, 1702, 1962 E. P. Ageev and G. M. Panczenkov, Atomnaja Energia, 14, No. 5, 494, 1963 Huffman and Urey, Ind. Eng. Chem. 29, 531, 1937 O. W. Umarov, W. A. Sokolski and N. M. Zavoronkov, Chim. Promyszi, 404, 1956 Dostrovsky, Llewellyn, Vromen, J. Chem. Soc. 3517, 1952; Dostrovsky ref. Proc. 2nd Intern. Conf. Peaceful Uses Atomic Energy, Geneva, 1958, p. 605 Dostrovsky, I., Raviv, A .: "Proc. Int. Symp. Isotope Separation (Amsterdam, 1957)", p. 336, (1958), North-Holland, Amsterdam Oxygen-18 (CAS 32767-18-3), Market Research Report 2015, BAC Reports

Table 1 shows the specifications of the prototype device (see Figure 4).

Since the prototype device uses natural water with a natural deuterium content of 0.015% as a raw material, deuterium accumulates in products and intermediate products (process medium of the final concentrated column). The presence of a significant amount of deuterium (50% or more) in the intermediate product sharply reduces the efficiency of the enrichment process in the instrument. This is due to the fact that the separation coefficient αO-18 / O-16 of the H2O-18 / H2O-16 system is about 1.005 (65 ° C) and decreases sharply with the accumulation of heavy water: HDO-18. The αO-18 / O-16 for the / HDO-16 system is 1.0041 and the D2O-18 / D2O-l6 for the D2O-18 / D2O-16 system is 1.0034. Therefore, the efficiency (productivity) of the process decreases in inverse proportion to the separation coefficient.

The proposed inventions are intended to eliminate the following disadvantages:
· Improve product quality and reduce losses associated with the need for additional operations to remove deuterium in prototype-based methods and equipment;
-Because deuterium accumulates in the process stream, prototype methods and installations have limitations in improving process efficiency (productivity).

To solve the set challenges, such as reducing product loss and improving process efficiency, the patented method is pre-concentration of H20-18 in the pre-concentration unit and final in the final concentration unit. A method of obtaining oxygen-18 concentrated water by rectifying water under vacuum in a rectification column, including concentration, the flowchart and equipment of which further supplies the raw material, i.e. natural water. A chemical isotope exchange unit is installed in the water-carbon dioxide system on the line. Natural water is a source of oxygen-18. In the prototype mechanism, water enters the rectification column cascade directly, and at the same time as oxygen-18, deuterium contained in natural water is introduced into the process stream. According to the claims solution, oxygen-18 contained in the raw natural water is transported by carbon dioxide to the supply line of the equipment, and this carbon dioxide functions as a transport agent for the raw water which is the supply flow of the equipment. The chemical isotope exchange unit incorporates two chemical isotope exchange columns: a column for raw materials perfused with natural water and a column for supply in which the supply flow to the cascade of rectified columns circulates. Is. These columns are interconnected via a line of carbon dioxide that circulates in a closed loop, transporting oxygen-18 from the raw material to the supply flow. At that time, deuterium is not transported by carbon dioxide, so it does not enter the equipment. Carbon dioxide circulates in the pre-purification column in a countercurrent manner with respect to the water stream, reliably transporting oxygen-18 from the raw material flow to the supply flow of the pre-concentration unit.

A feature of the proposed method lies in the principle of raw material supply to the equipment: oxygen-18 from natural water is supplied to the cascade via a chemical isotope exchange unit with carbon dioxide, so it is deuterium from the process stream. The elimination of hydrogen improves equipment productivity and eliminates product loss.

A facility for obtaining oxygen-rich water that is closest to what is claimed. It is a process drawing of the manufacturing method of _{Н 2} О-18 by this invention. Table 2 shows the characteristics of the proposed equipment according to the claimed method. Table 1 shows the characteristics of the prototype installation.

To achieve the above technical results, devices including the following are proposed:
・ Chemical isotope exchange unit;
A pre-concentration unit of H2O-18 consisting of a rectification column that operates in parallel to perform type 1 extraction in an open circuit (no discharge);
-A final concentration unit containing a complex of a column that concentrates H20-18 and a column that removes H2O-16.

Unlike the known ones, the proposed equipment (Figure 2) is additionally installed in the supply line of the pre-concentration unit with the chemical isotope exchange unit. The chemical isotope exchange unit consists of a complex of columns for chemical isotope exchange in a water-carbon dioxide system. Its purpose is to improve the quality of the product and reduce its loss, as well as to improve the efficiency and productivity of the process.

The proposed invention is attached with the following drawings:
・ Figure 1-Prototype H20-18 manufacturing process diagram;
-Fig. 2-Figure of the manufacturing process of H20-18 according to the present invention.

Equipment proposed to obtain oxygen-18-rich water (Figure 2) includes:
-Chemical isotope exchange unit consisting of chemical isotope exchange columns 15 and 16 of the water-carbon dioxide system;
Pre-concentration unit consisting of pre-concentration columns 1-10;
Final concentration unit containing concentration columns 11-13 and removal columns 14;

The device works as follows:

The stream of raw water enters the chemical isotope exchange unit in column 15. The carbon dioxide that circulates countercurrently with the inland stream of columns 15-16 maintains the transport of oxygen-18 from the raw material stream (column 16) to the supply column of cascade 15. At that time, the deuterium contained in the raw water does not enter the cascade, so that it is not accumulated in the process stream or the product.

The water from the cascade feed column 16 enters a pre-concentration unit consisting of rectification columns 1-10, which operates in parallel to perform the first type of extraction in an open circuit (no drainage), and the intermediate concentration obtained there. The material is transferred to the final enrichment unit without flow feedback.

The intermediate concentrate in the concentration column of the final concentration unit concentrates oxygen-18 to a level of at least 95%, but wastewater containing more than 99% oxygen-16 is discarded from the cycle of the waste column of the final concentration unit. Will be done.

Equipment according to this technical solution provides oxygen-18-rich water production up to 95% levels, producing products with high productivity, low levels of loss, and natural content of hydrogen isotopes. To get. The above requirements are required for market products for use in medicine and biochemistry. Table 2 shows the specifications of the proposed equipment according to the method of application.

In this design, the device has a capacity of 6 kg per year, 95% enrichment and 0.013 to 0.015% deuterium content (at the level of natural deuterium content) when implementing the proposed method. provide. Therefore, the product does not require any additional manipulation to normalize the hydrogen isotope composition.

Therefore, equipment that follows this technical solution has the following advantages over the prototype:
・ Productivity is increased by 1.5 times;
-Provide products with higher enrichment (95%);
-Provide products with a normalized hydrogen isotope composition (deuterium content 0.013-0.015%);

Furthermore, from an operational point of view, it is important that the deuterium content of treated water is lower than that of natural water, which eliminates the need for a production license according to nuclear safety standards (because deuterium is classified as a nuclear material). ).

The efficiency and economics of the proposed methods and devices demonstrate their technical and economic advantages over methods and devices with prototypes and other known technical solutions. Therefore, this equipment can be successfully used for the industrial production of oxygen-18-rich water.

The present invention relates to the production of oxygen-18 for PET tomography, and is useful as a technique for producing water rich in oxygen-18 isotopes (heavy oxygen water, H2O-18).

1-10 ... Preliminary concentration column 11-13 ... Concentration column 14 ......... Exhaust column 15, 16 ... Chemical isotope exchange column

Claims (2)

It is a method to obtain water in which oxygen-18 is concentrated by rectification under vacuum using natural water as a raw material.
In multiple pre-concentration columns operating simultaneously in an open circuit, it consists of a pre-concentration of oxygen-18 for extracting the first-class intermediate concentrate of oxygen-18, a concentration column for oxygen-18, and a removal column for oxygen-16. Containing with the final concentration of the intermediate concentrate in a cascade of final concentration columns,
Water that circulates in the pre-concentration column is used for supply, and the water that circulates in the pre-concentration column naturally contains oxygen-18 by sequentially performing chemical isotope exchange between the raw material natural water and carbon dioxide. A method characterized by maintaining quantity. A facility that produces oxygen-18-concentrated water using natural water as a raw material.
A pre-concentration unit consisting of a plurality of pre-concentration rectification columns that simultaneously extracts the first-class intermediate concentrate by an open circuit without discharge.
It is equipped with a final concentration unit consisting of an oxygen-18 concentration column and an oxygen-16 removal column.
The supply line of the pre-concentration unit is a facility characterized by further having a complex of columns for chemical isotope exchange of a water-carbon dioxide system.

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