JPS58183932A - Concentration of carbon 13 isotope - Google Patents

Abstract

PURPOSE:To stepwisely concentrate a carbon 13 molecule, by irradiating carbon dioxide laser beam to at least one among plural halogenated methane molecules in the coexistence of oxygen to decompose and remove a carbon 12 molecule. CONSTITUTION:A mixed gas consisting of CF3I and O2 (CF3I/O2=1/9) is introduced into a stock gas sump (1-A) and sent to a reaction tower 3 while the pressure in a reactor is controlled by evacuating the same by an oil rotary pump 7. As laser 4, CO2 pulse laser is used. The gas passing through the reactor is passed through an adsorbing column filled with soda lime particles to remove decomposition product such as difluorocarbonyl. In the next step, trifluoroiodomethane is collected by a cold trap (1-B) held at the temp. of liquified nitrogen. When the sending of the stock gas in the gas sump is completed, the cold trap is returned to a room temp. while the stock mixed gas is regenerated by the addition of oxygen to be again sent to the reactor. The stock gas sump (1-A) and the cold trap (1-B) are connected by a pipe so as to exchange the function with each other.

Description

[Detailed description of the invention] The present invention relates to a method for enriching carbon isotopes.

In recent years, environmental pollution caused by chemical substances has become pervasive, causing unexpected disasters in various situations. In order to prevent these disasters from occurring, it is necessary to clarify the circulation mechanism of chemical substances in the ecosystem, and safety tests are being conducted vigorously in limited areas such as foods, pesticides, and pharmaceuticals. Techniques using isotopes are essential for elucidating the causal relationship between metabolism in living organisms and environmental pollutants, but radioactive isotopes have traditionally been used exclusively. However, due to its radioactivity, its range of use is limited, and special legal measures are taken against its use. Therefore, the non-radioactive Yasu isotope is used.
However, enriching stable isotopes that contain only trace amounts is extremely difficult and too expensive to promote widespread use. The stable isotopes used for this purpose are carbon-13 (natural abundance 1.1%), nitrogen-15 (natural abundance 0.37%), and oxygen-18 (natural abundance 0.20%).
, value number 34 (4.2%), etc. Among them, demand for carbon-13, which is the central element of organic compounds, is extremely large.

The conventional method for concentrating carbon-13 is low-7m precision distillation of carbon monoxide, but this method requires a large investment in equipment for distillation columns and requires sophisticated technology to control the extremely low temperature of -200°C. Moreover, the separation efficiency is very poor. The purpose of the present invention is to overcome the deficiencies and inadequacies of the conventional methods, and to efficiently separate C compounds of high purity using extremely simple equipment and techniques.

The present inventor has been conducting research to achieve the above objective, and in this research, he utilized the principle that molecules absorb light of slightly different wavelengths depending on the isotope contained in them, and With the appearance of lasers, we were able to obtain strong, monochromatic light, which led us to think that it might be possible to selectively decompose specific isotope molecules.As a result of further research, we discovered that the pulsed light of a specific laser The present inventors have discovered that the desired objective can be achieved by using the molecule and selectively using a specific molecule, and have thus completed the present invention.

That is, the present invention is characterized in that 12 carbon molecules are decomposed and removed by irradiation with trifluorofluoride and acid gas pulsed laser light in the coexistence of oxygen, and 13 carbon molecules are concentrated stepwise. This relates to a method for concentrating 13 isotopes.

Examples of the ionized methane include trino-D-iodomethane and trifluoro-D-iodomethane, with trifluoro-D-iodomethane being preferred. In addition, examples of difluorocarbon compounds used in the present invention include
Examples include o-difluoro-methane, difluoroiodomethane, difluoro-short-methane, difluoro-diku-Oo-methane, and 'difluoro-dipro-7-methane.

When irradiation is carried out in the presence of oxygen, only 100 molecules of trifluoro-iodomethane are selectively decomposed, and the decomposition products generated by the decomposition easily and reliably react with oxygen and are more easily absorbed than undecomposed C molecules. It has become clear that it can be separated very easily from trifudio-iodomethane, which consists of

The present invention will now be explained based on the drawings. FIG. 1 is a flow sheet showing an actual example of the method of the present invention. In FIG. 1, the raw material gas reservoir (1, J) contains a mixed gas of trino-iodomethane and oxygen. Flow rate control device (2
), the mixed gas is supplied to the reactor (3) at a constant flow rate. On the other hand, the laser (4) is a carbon dioxide gas pulse laser.
The oscillation wavelength is set to 9.5 μm band oscillation line R(1) using
, 9.2714 μm and irradiate the reactor (3). At this time, the 12C molecule absorbs light, and thaifluorocarbonyl is produced by the reaction of the following formula.

12CF --1-0812CF O+ OF, (
2) 3 2 2 taifluorocarbonyl and other decomposition products of this repellent are separated and removed through an adsorption column (5).

Residual gas is 13. It becomes a mixture of trifudio-ioodomethane and oxygen, which consists of molecules, but in a cold trap (1-
By B), 1'+:ゝゝ of trifudio-iodomethane is collected. Next, the temperature of Cold Tora Two J (1-B) is raised and oxygen is added to regenerate the raw material gas. This is sent to the reactor (3) again, where it is repeatedly decomposed, and gases 1- and 4, which were previously used as gas reservoirs, are now used as cold wraps to collect them. By repeating this operation, the C molecule concentration in Trifudio 03-tomethane gradually increases from 1%, and 8-1
It increases to more than 90% in 0 cycles.

The laser used in the present invention is a carbon dioxide gas pulsed laser, which has an energy per pulse large enough to cause decomposition, and a pulse width sufficient to exhibit sufficient selective decomposition. required to have one. Now, to explain using fluence as a representative value representing 1,000 energy per pulse, fluence is 0.05.
(Joule/c-j) or more, preferably about 0.5-2 (di], -L/d), and the pulse width is usually 5O-
It is about 200 nVtt, preferably about 100 nslc. For example, the relationship between fluesis and decomposition rate is as shown in FIG.

When carrying out the method of the present invention, a laser beam is irradiated to a gas mixture of oxygen and at least one of trifluorohydride and difluoride, and the pressure and selectivity of the gas mixture at this time are The relationship is as shown in FIG. Here, β is called a separation coefficient, and is a parameter representing how much 12C molecules are selectively decomposed in the case of triflic 0-iodomethane as defined by the following equation.

As is clear from FIG. 3, when the pressure exceeds 4 torr, the selectivity decreases significantly, and it is found that about 2 torr is appropriate. The appropriate amount of oxygen to be added is about 10 times the amount of raw metal. When the amount becomes extremely small, the following reaction occurs in parallel with reaction (2).

When the amount is increased, this contribution gradually becomes smaller, and when the amount is increased by 100 times, it becomes almost negligible, but there is a tendency for the excited molecules to be deactivated by collision with oxygen, resulting in a significant decrease in decomposition efficiency.

For example, even in the case of 1:9, 10-20% of the product is
Rifugio 0 eta.

Although it must be separated in the end, the boiling point for trifluoroiodo metal is -22.5°C1 + safluoriodine metal is -79°C, so it can be fractionally distilled. In the case of difluoro 0 ha 0 geshi conversion metashi, a small amount of tetrafluoro D ethireshi can be made instead of he + safluoro D etashi, but the same is true. The feature of the TIFUL present invention is that it decomposes and removes 99% of the C molecules while leaving 1% of the C molecules that are to be concentrated. Normally, only a small amount of decomposition is required, so a method of decomposing and collecting C molecules can be considered.However, one concentration process does not result in sufficient concentration, so multi-stage concentration is required. This requires an operation to regenerate the raw material molecules from the decomposition products, making the system extremely complicated.Compared from the viewpoint of decomposition efficiency, in C decomposition, the absorption cross section is increased to increase selectivity. A small wavelength must be selected, and the deactivation effect due to the coexisting 100 molecules is large, resulting in poor efficiency.Also, the gain of the oscillation line of the carbon dioxide laser used is small, so the advantage is that the amount of decomposition is small. In contrast, with C decomposition, there is no need to regenerate, and the decomposition products can simply be removed from the system, which simplifies the system considerably.In addition, since the concentration proceeds continuously, it is extremely efficient. Even with high-purity products, the cost often increases dramatically.Even when considering the required laser performance, C
Decomposition methods are advantageous. In general, higher output and shorter pulses are more suitable for increasing isotope selectivity, and a faster repetition rate of such pulses is required to increase productivity. However, it is difficult to create a laser that satisfies this condition, and we must wait for advances in laser equipment. However, if the method of the present invention is used, the concentration will proceed sufficiently even if the selectivity is not so good, and the conditions for high output and short pulses will be relaxed to a large extent, so that it can be applied satisfactorily even to a laser of the present invention.

EXAMPLE C was concentrated using the reaction apparatus shown in FIG. Initially, a mixed gas of CF3I and 02 (C
F31102=1/9) was added at 600CC and 12.5 torr. 2-105. by the flow control device (2). .

The mixed gas was sent to the reaction tower (3) at a flow rate of /set, and was pumped by an oil rotary pump (7) to adjust the pressure inside the reactor to about 2 Torr. The laser (4) uses a CO2 pulse laser, and the operating conditions are: incident wavelength: 9.271 μm, pulse energy: -5.6 joules/pulse, beam cross-section: 7. Oc
4. Pulse width 7 Q nxtt, repetition rate 0.5
It was 9 pulses/Klt. The length of the reactor is 1.67f
f, Yong! 3.1n stainless steel cylinder with holes on both ends.
It has a sodium chloride window that transmits e-light. The gas that passed through the reactor was passed through an adsorption column packed with soda lime granules to remove Ifluo D carbonyl and other decomposition products. The trifluoroiodomethane was then collected by a ]-rudotra'j (1-B) maintained at liquid nitrogen temperature. After sending the raw material gas from the gas reservoir, the cold trap was returned to room temperature and oxygen was added to regenerate the raw material gas mixture, which was then sent to the reactor again. (1-,4) and (1
"B) is piped so that the functions of gas reservoir and cold trap are alternately exchanged. Figure 4 shows how C is concentrated in trifluoroiodomethane collected in the cold trap. After 7 cycles, the separation factor becomes nearly 500. Repeating this cycle improves the separation factor.

FIG. 5 shows the mass spectrum of trifluoroiodomethane, and the state of concentration can be seen from the peaks of CF and radicals. (a) is 13CFii 1% before irradiation. <
b> is almost 55% after 5 cycles, and (C) is 7t
After J cycle, the purity is 83%. The irradiation time for one cycle was 20 minutes for the first cycle and about 5 minutes for the last cycle. In this example, only about 10% of the energy of the laser beam is used, but the production scale can be expanded by extending the optical path using a known method such as a reflector and by using a laser with a high repetition rate.

[Brief explanation of the drawing]

FIG. 1 is a system diagram showing an example of an embodiment of the present invention. (
・1-A/1-B) is the raw material waste reservoir/]-rudotraj, (2) is the flow rate controller, (3) is the reactor, (4) is the carbon dioxide pulse laser, and 1 (5) is the adsorption column. , (6) is a barometer, and (7) is an oil rotating position. Figure 2 shows the relationship between the fluence of laser light and the decomposition rate.
．． 11 shows the decomposition rate after irradiation with 50 pulses of light with a wavelength of 9.27 μm. FIG. 3 shows the relationship between operating pressure and separation factor. Fluence 0.6 in mixed gas of CF3I1021:9
This is the separation coefficient of decomposition products when irradiated with a pulse of dicol/cj. Figure 4 shows separation coefficient and CF collected by cold traps.
The yield of J is calculated based on the cycle of concentration operation. The yield is 10,000 based on the starting amount. Figure 5 shows the mass spectrum of concentrated CF31. (That's all) Fig. 111 113 Fushi Esis (J=-+L/1m2) Fig. 4 J-yoi 1R31 yen = 稟. Saiful Figure 5

Claims (1)

[Claims] A method for concentrating carbon-13 isotopes, which comprises decomposing and removing carbon-12 molecules by irradiating light in the coexistence of oxygen and concentrating carbon-13 molecules in stages.