JPH0663361A - Concentration method of carbon 13 by using laser - Google Patents

Abstract

PURPOSE:To concentration carbon 13 at high selectivity by irradiating a satd. cyclic ether being a starting raw material with infrared laser to generate selective infrared polyphoton decomposition, and separating the carbon 13-containing product from the decomposition product. CONSTITUTION:A carbon 13-containing stad. cyclic ether (e.g. propylene oxide) of a starting raw material is irradiated with infrared laser to generate selective infrared polyphoton decomposition. Then, the carbon 13-containing product is separated by fractional distillation, etc., from the infrared polyphoton decomposition product produced in the decomposition process. In such a way, carbon 13 is concentrated at high selectivity, and the carbon 13-containing product can be obtained at high yield.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to separation / concentration of carbon 13 by laser, and more particularly to a method for concentrating carbon 13 using selective infrared multiphoton decomposition of carbon 13 by laser irradiation of saturated cyclic ether. .

[0002]

2. Description of the Related Art Carbon is a central element existing on the earth,
Natural carbon is mainly composed of two isotopes, namely 98.9%.
Carbon 12 and 1.1% carbon 13. Concentrated carbon 13 is an isotope that is in high demand and is used as a tracer in a wide range of fields, and its application to medical treatment is particularly increasing. Therefore, inexpensively enriching carbon 13 and supplying it in large quantities leads to great benefits and progress in society.

At present, a large-scale concentration of carbon 13 is carried out by a distillation method, but enlarging the apparatus is unavoidable, the efficiency of carbon 13 concentration is low, and the concentration of carbon 13 takes a long time. There were drawbacks such as cost. In comparison with this, the laser isotope enrichment method can downsize the device, can perform highly selective enrichment in one step, and require a short time for the enrichment. Furthermore, the economical efficiency of the laser method is improved by increasing the output and repetition rate of the laser used. Therefore, if the development of a reaction system effective for carbon 13 concentration advances, the laser method is very promising as a new carbon 13 production process.

The problem in laser isotope separation / concentration is to increase the selectivity of carbon 13 and simultaneously increase the decomposition / production yield. In general, when the decomposition / production yield is high, the selectivity of carbon 13 decreases. Usually, the optimization of the laser isotope separation / concentration method is achieved by optimizing the starting materials and irradiation conditions. When a gas is irradiated with intense infrared laser pulsed light, infrared multiphoton decomposition occurs after absorbing several tens of infrared photons per molecule. Since it is possible to cause extremely high isotope-selective decomposition by selecting the starting material and irradiation conditions, the application of infrared multiphoton decomposition to isotope separation / concentration is drawing attention. Among the commercially available infrared pulsed lasers, TEAC which is powerful and easy to operate
Laser isotope separation / concentration using O ₂ laser
A particularly well-studied compound as a starting material containing carbon-13 is CF ₃ Cl [P. Hackett, M. Gauthei
r, C. Willis, and M. Drouin, J. Quantum Elec., QE-1
6 , 143 (1980)], CF ₂ Cl ₂ [P. Fettweiss and M.
Neve de Mevergnies, J. Appl. Phys., 49 , 5699 (197
8)], CCl ₄ [RV Ambartzumian, YA Gorokhov,
VS Letokhov, and GN Makarav, and AA Puret
zki, Phys. Lett., 56A , 183 (1976)], CF ₃ Br [
PA Hackett, V. Malatesta, WS Nip, C. Willis,
and PB Corkum, J. Phys. Chem., 85, 1152 (198
1)], CF ₃ I [CN Plum and PL Houston, Appl.
Phys., 24 , 143 (1981)], CF ₂ Br ₂ [JJ Ritte
r, J. Am. Chem. Soc., 100 , 2441 (1978)], C ₂ F ₅
Cl [E. Borsella, R. Fantoni, and A. Giardini-Guid
oni, Chem. Phys. Lett., 84 , 313 (1981)], C ₂ F ₅
I [E. Weinberg, M. Gautheir, PA Hackett, and C.
Willis, Can. J. Chem., 59 , 1307 (1981)], C ₃ F
₆ [WS Nip, M. Drouin, PA Hackett, and C. Willi
s, J. Phys. Chem., 84 , 932 (1980)], CF ₃ COCF
₃ [PA Hackett, C. Willis, and M. Gauthier, J. C
hem. Phys., 71 , 546 (1979)] was used. These fluorine-substituted compounds have infrared absorption due to stretching vibration of C—F bond in the TEA CO ₂ laser oscillation region, and by irradiating the TEA CO ₂ laser beam on the low wavenumber side of this absorption, carbon 13 selective infrared light is emitted. Can cause multiphoton decomposition. However, in the laser isotope separation / concentration method using the above-mentioned starting material, the raw material gas is expensive, the decomposition threshold value is high, the decomposition / production yield is low, and the raw material gas causes environmental damage. There were drawbacks such as being connected.

[0005]

Therefore, according to the present invention, a carbon 13 produced by a laser, which has a high decomposition / production yield and a high carbon 13 selectivity, is produced by using an inexpensive raw material having a low decomposition threshold. The purpose of the present invention is to provide a method for concentrating. Another object of the present invention is to provide a method for producing an olefin containing carbon 13 with high yield and selectivity by using an inexpensive raw material having a low decomposition threshold value.

Further, it is an object of the present invention to provide a method for producing an aldehyde containing carbon 13 with high yield and selectivity by using an inexpensive raw material having a low decomposition threshold value. Still another object of the present invention is to provide a method for producing CO containing carbon 13 with high yield and selectivity by using an inexpensive raw material having a low decomposition threshold value.

[0007]

As a result of intensive studies, the inventors of the present invention focused on the relatively low bond energy of the C—O bond of a saturated cyclic ether and used it as a starting material containing carbon 13. It has been found that the above object can be achieved by irradiating the saturated cyclic ether with infrared laser light to cause selective infrared multiphoton decomposition of the saturated cyclic ether containing carbon 13.

That is, the present invention provides (a) selective infrared multiphoton decomposition of a saturated cyclic ether containing carbon 13 by irradiating a saturated cyclic ether as a starting material containing carbon 13 with an infrared laser beam. And (b) a method for concentrating carbon 13 including the step of: (b) separating a product containing carbon 13 from the infrared multiphoton decomposition product generated in the step (a).

The present invention also provides a method for producing an olefin containing carbon 13 using the above-mentioned carbon 13 concentration method. Furthermore, the present invention provides the above carbon 1
Also provided is a method for producing an aldehyde containing carbon 13 using the concentration method of 3. Furthermore, the present invention also provides a method for producing CO containing carbon 13 using the above-described carbon 13 concentration method.

The saturated cyclic ether which can be used as a starting material in the present invention is not particularly limited, but includes a substituted and / or unsubstituted saturated cyclic ether having 2 to 10 carbon atoms, specifically, propylene oxide. , Tetrahydrofuran,
There may be mentioned saturated saturated cyclic ethers such as tetrahydropyran and dioxane, saturated cyclic perfluoroethers such as perfluoroethylene oxide, perfluoropropylene oxide, perfluorotetrahydrofuran, perfluorotetrahydropyran and perfluorodioxane, among which, perfluoroethylene oxide and perfluoroethylene Propylene oxide and perfluorotetrahydrofuran are preferred. Since these ethers have a relatively low threshold value for infrared multiphoton decomposition, it can be said that it is possible to increase the selectivity for carbon 13 concentration and the production yield.
The carbon isotope distribution in the main product, aldehyde, can be measured to determine the selectivity for carbon 13 enrichment.

In the present invention, an infrared laser which selectively causes infrared multiphoton decomposition can be used as a starting material containing carbon 13. For example, TEA CO ₂ laser, HB _r laser, CF ₄ laser, parahydrogen Raman laser and the like can be mentioned. Of these, TEA
A CO ₂ laser is preferred. Examples of the method for separating a desired product containing carbon 13 from the infrared multiphoton decomposition product include separation by a Tepler pump, gas chromatography method, and fractional distillation method. Separation and gas chromatography methods are preferred.

[0012]

When a gas is irradiated with intense infrared laser pulsed light, it absorbs several tens of infrared photons per molecule and then undergoes infrared multiphoton decomposition. Identification of the product of infrared multiphoton decomposition of saturated cyclic ether by CO ₂ laser irradiation revealed the following decomposition reaction mechanism.

First, the decomposition reaction of an unsubstituted saturated cyclic ether is initiated by C--O bond cleavage, and a biradical is initially formed (formula 1). Secondary decomposition of the biradical produces carbene (CH ₂ , CHR) and formaldehyde (H ₂ CO) and alkyl aldehyde (RCHO) (Equation 2). Carbene dimerizes to an olefin (formula 3). Further, a part of the aldehyde is further decomposed to generate CO (formula 4).

[0014]

[Chemical 1]

O (CH ₂ ) _x CHR ・ → CH ₂ , CHR + H ₂ CO, RCHO (2) 2CH ₂ or 2CHR → C ₂ H ₄ + CHRCHR (3) RCHO (+1 hν) → CO + RH ( 4) (In the formula, R represents an alkyl group, and x represents an integer of 1 to 4.) In the formula 1, if the C—O bond of the saturated cyclic ether containing carbon 13 is selectively cleaved, the final product Carbon 13 is concentrated in the olefins, aldehydes and CO. However, since CO is obtained through a secondary decomposition process of aldehydes, there is a possibility that not only aldehydes containing carbon 13 but also aldehydes containing carbon 12 may be decomposed, and the selectivity for the concentration of carbon 13 in CO is reduced. It may be lower than it actually is.

In the infrared multiphoton decomposition of the saturated cyclic perfluoroether as well as the infrared multiphoton decomposition of the unsubstituted saturated cyclic ether by CO ₂ laser irradiation, the C—O bond having the lowest energy is found. It is thought to start upon cleavage. A reaction similar to that of Formulas 1-4 proceeds and the final product is a perfluoroaldehyde (RCFO: R = C
_n F _{2n + 1} ) and CO are expected to be obtained. Therefore, selective cleavage of the C—O bond of a saturated cyclic ether containing carbon 13 should concentrate carbon 13 in the final products aldehyde and CO.

[0017]

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 is a schematic view of an apparatus for carrying out the carbon 13 concentration method of the present invention.
In FIG. 1, the apparatus for carrying out the method for concentrating carbon 13 of the present invention comprises an irradiation reaction vessel 15, a raw material ether supply system 21, and a TEA CO ₂ laser oscillator 11. The irradiation reaction container 15 and the raw material ether supply system 21 are connected so as to be communicable with each other, for example, by a supply pipe formed of a gas distribution device having a valve. Also,
A gas handling system 20 is connected to the raw material ether supply system 21, and the gas handling system 20 includes an exhaust device 22 and a sample separation system 18.
And are connected. Further, a gas chromatograph-mass spectrometer 19 is connected to the sample separation system 18.

The beam 12 from the pulsed TEA CO ₂ laser oscillator 11 passes through the diaphragm plate 13, is gently narrowed by the infrared light lens 14, and is introduced into the irradiation reaction container 15 placed near the focal point. TEA to irradiate a starting material containing saturated cyclic ether containing carbon-13
The CO ₂ laser oscillator 11 is installed. When the carbon 13 is concentrated by the apparatus configured as described above, first, the irradiation reaction container 15 is removed by the exhaust device 22.
The inside pressure is reduced to 10 ^-3 Torr or less.

After that, the valve is opened, and saturated cyclic ether as a starting material containing carbon 13 is introduced into the irradiation reaction vessel 15. The starting material may be introduced into the irradiation reaction vessel in a batch system or may be circulated in the irradiation reaction vessel (flow method). However, in the case of introduction in a batch system, 0.3 to 20 Torr,
Preferably 0.5 to 5 Torr of starting material is introduced, and when introduced by the flow method, 10 ^-1 to 10 ³ ml / min, for example,
When the pressure of the starting material is 1 Torr and the repetition rate of the laser pulse is 1 Hz, the starting material can be circulated in the irradiation reaction vessel at a constant flow rate of preferably 1 to 10 ml / min.
Further, the starting material may be converted into a molecular beam and introduced into the irradiation reaction vessel. Alternatively, the starting material may be injected from a nozzle into a vacuum cell and introduced into the irradiation reaction container as a supersonic beam.

Next, the TEA CO ₂ laser oscillator 1
After passing through the diaphragm plate 13, the laser beam 12 from 1 is gently narrowed down by the lens 14 for infrared light and irradiated with the saturated cyclic ether which is the starting material in the irradiation reaction vessel 15 placed near the focus. , Causes selective infrared multiphoton decomposition of saturated cyclic ethers containing carbon-13. The laser used in the present invention may be continuously irradiated, but pulse irradiation is preferable. In this case, the irradiation pulse number is 1 to 10
⁴ pulse is preferred. If the pulse number is smaller than this range, the decomposition rate of the starting material is low and a sufficient amount of product cannot be obtained. If the pulse number is larger than this range, secondary photolysis of the product will occur. Of the above ranges, especially 100
~ 2000 pulses are preferred.

The pulse time width is 1 to 1000 ns.
Is preferred. If the time width is smaller than this range, a sufficient laser output cannot be obtained, and a sufficient amount of product cannot be obtained. Further, if the time width is larger than this range, the contribution of the thermal reaction increases, so that the selectivity for carbon 13 concentration decreases.
Of the above range, 50 to 200 ns is particularly preferable. Furthermore, the laser pulse repetition rate is 0.1 to 100.
Hz is preferred. If the repetition rate is slower than this range, the reaction amount decreases, and a sufficient amount of product cannot be obtained.
If the repetition rate is higher than this range, the window plate may be damaged or a secondary reaction may be induced. Of the above range, 0.5 to 10 ns is particularly preferable.

The wavelength of the laser is 930 to 1100 cm
It is preferable to select a wavelength within the range of ⁻¹ that is expected to have an absorption of saturated cyclic ether containing carbon 13 on the low wave number side of about 10 to 30 cm ⁻¹ of the absorption of ether. When the laser wavelength is longer than this range, the absorption of the saturated cyclic ether used as a starting material is weak, and when the laser wavelength is shorter than this range, the decomposition rate of the saturated cyclic ether becomes low. Depending on the type of saturated cyclic ether used as a starting material, a specific example is an oscillation line between 930 and 980 cm ^-1 .

The laser fluence is ^{2 to} 50 J · cm ^-2
Is preferred. If the fluence is larger than this range, carbon 1
The selectivity of 3 enrichment is reduced, and if the fluence is smaller than this range, the yield of the infrared multiphoton decomposition product containing carbon 13 is reduced. Of the above range, 3 to 6 J · cm ⁻² is particularly preferable. Laser irradiation is preferably performed at a temperature of -50 to 100 ° C. When the temperature is higher than this range, the saturated cyclic ether of the starting material is thermally decomposed, and when the temperature is lower than this range, the vapor pressure of the saturated cyclic ether of the starting material is decreased, and an arbitrary pressure cannot be obtained. Occurs. Of the above temperature range, −20 to 50 ° C. is particularly preferable.

The reaction mixture after irradiation with laser light is guided to 15 → 21 → 20 → 18 in FIG. In FIG. 1, the reaction mixture after laser light irradiation is transferred from the irradiation reaction container 15 to the raw material ether supply system 21 by a normal valve operation, and is further guided to the sample separation system 18 via the gas handling system 20.
This series of operations can be performed by the function of the gas handling system 20 connected to the exhaust device 22. First, the components (ether and product) that are trapped at the liquid nitrogen temperature (-196 ° C.) and the components that are not trapped (mainly C
O), and in some cases, it may be further separated into components that are captured at −95 ° C. and components that are not captured (mainly aldehydes). Each component is measured by the gas chromatograph-mass spectrometer 19, and the amount of decomposed raw materials, the amount of each product produced, and the concentration of carbon 13 in CO and aldehyde can be quantified.

In the present invention, the products produced by laser irradiation include olefins, aldehydes, and CO
Can be. In addition, alcohols, ketones, and alkanes can be produced. By separating the product containing the desired carbon 13 from these reaction products, carbon 13
Can be concentrated. When carrying out laser concentration of carbon 13 on a large scale, an aldehyde or CO enriched with carbon 13 can be obtained by separating the mixture after laser light irradiation by a column chromatography method, a fractional distillation method or the like.

Further, in order to increase the purity of carbon 13,
Further concentrates carbon 13 of aldehyde and CO of reaction products
You may. As a method, there is aldehyde itself
Or aldehyde or CO was converted by chemical method
TEA CO to the appropriate compound ₂Laser irradiates carbon
13 There is a laser concentration method that causes selective decomposition.
it can.

[0027]

EFFECT OF THE INVENTION According to the method for concentrating carbon 13 of the present invention, carbon 13 is highly selectively concentrated and a product containing carbon 13 is obtained in a high yield.

[0028]

The present invention will be described in more detail with reference to the following examples. The scope of the invention is not limited by this example. The experiments described in the examples were conducted at room temperature. The irradiation reaction container 15 is moved to 10 by the exhaust device 22.
^The pressure was reduced to ^-3 Torr or less, and then 0.3 to 20 Torr of perfluoropropylene oxide (manufactured by PCR) was introduced into the irradiation reaction container 15.

After the beam 12 from the pulse oscillation TEA CO ₂ laser oscillator 11 has passed through the diaphragm plate 13, the infrared reaction lens 14 having a focal length of 80 cm or 150 cm gently narrows the beam 12, and the irradiation reaction container 15 is placed near the focal point. The perfluoropropylene oxide inside was irradiated. TEA CO ₂
In oscillation line of the laser was about 40-50 cm ^-1 wave number side lower absorption of ether (1020cm ^-1), primarily selects the oscillation line of 969-976Cm ^-1 that are expected to be absorbed ethers containing carbon 13 did. Calculated from the beam area at the focal point, the laser fluence at the focal point is 4.6 to 4.7 J · cm ^-2.
Met. The laser pulse repetition rate was 0.7 Hz, and the pulse number was 500 to 2000. The irradiation reaction vessel is made of cylindrical glass with a diameter of 2 cm and a length of 65 cm.
An aCl window plate 17 was attached, the irradiation light path length was 65 cm, and the internal volume of the container was 220 cm ³ .

A sample gas 16 which is a reaction mixture after laser light irradiation is first separated by a separation system 1 such as a Tepler pump.
8 (Components (ether and product)) and components (mainly C) that are trapped at the liquid nitrogen temperature (-196 ° C.)
O), and in some cases, it was further separated into a component that was captured at -95 ° C and a component that was not captured (mainly an aldehyde). Each component was measured by a gas chromatograph-mass spectrometer 19 to quantify the decomposition amount of the raw material, the production amount of each product, and the concentration of carbon 13 in CO and aldehyde.

As a result, the final product is CF₂O, CF₃
CFO and C₂F_FourI found out. Product
Since the cloth is simple, it is possible to
Equations 5 and 6 are involved in the initial decomposition process of ropylene oxide.
it seems to do. CF ₃CF is isomerized to C₂F
_Four(Equation 7), CF₂Is dimerized to C₂F_Four(Equation 8)
To generate. CF₂O and CF₃The ratio of the amount of CFO produced is calculated by the formula
5 means the branching ratio between Equation 5 and Equation 6, and changes depending on the irradiation conditions.
To do. CF under most conditions₂CF than O₃CF
Since more O is generated, if Equation 6 occurs preferentially,
I can say.

[0032]

[Chemical 2]

[0033]

[Chemical 3]

CF ₃ CF → C ₂ F ₄ (7) 2 ・ CF ₂ → C ₂ F ₄ (8) CF ₂ O, CF ₃ produced by irradiation with laser light having a wavenumber on the low wavenumber side of absorption at 1020 cm ^-1 The isotope distribution in CFO and C ₂ F ₄ was investigated. That is, m / e of CO ₂ produced by hydrolysis of CF ₂ O = 44 ( ¹² C ¹⁶ O ¹⁶ O ⁺ ), 45 ( ¹³ C ¹⁶ O
¹⁶ O ⁺ ), and m / e of CF ₃ CFO = 47 ( ¹² CF ¹⁶ O ⁺ ), 48 (
¹³ CF ¹⁶ O ⁺ ), 50 ( ¹² CF ₂ ⁺ ), 51 ( ¹³ CF ₂ ⁺ ), and
C ₂ F ₄ m / e = 50 ( ¹² CF ₂ ⁺ ) and 51 ( ¹³ CF ₂ ⁺ ) were measured. Table 1 shows the resulting selectivity for carbon 13 enrichment (selectivity (α ₁₃ ) = (carbon 13 in product / carbon 12) / (natural carbon 13 / carbon 12)).

[0035]

[Table 1] Table 1 Concentration factor of carbon 13 in the product by infrared multiphoton decomposition of perfluoropropylene oxide ─────────────────────────── ────── Pressure Laser Laser Full pulse number Carbon 13 Concentration factor (α ₁₃ ) / Torr Wavenumber / cm ^-1 ence / J cm ^-2 ─────────── CO ₂ CF ₃ CFO C ₂ F ₄ ────── CFO ^a) CF ₂ ^b) ─────────────────────────────── 2.0 973.29 4.7 500 1 45.4 7.2 6.7 2.0 969.14 4.6 1000 1 38.6 6.2 2.8 2.0 969.14 4.6 2000 1 34.2 3.5 5.7 2.0 975.93 4.7 500 1 27.7 3.4 4.0 ─────────────────────── ───────── ^{a) 12} CF ¹⁶ O ⁺ / ¹³ α ₁₆ obtained from CF ¹⁶ O ⁺ (m / e = 47/48).
^b) α ₁₃ obtained from ¹² CF ₂ ⁺ / ¹³ CF ₂ ⁺ (m / e = 50/51).

The maximum value of α ₁₃ in Table 1 is the CO derived from CF ₂ O.
In ₂ 1, CF ₃ CFO at ^{45.4 (12 CF 1 6 O +} / 13 CF 16 O + from) and ^{_{7.2 (12 CF 2 + / 13}} CF 2 + from), the C ₂ F ₄ 6. 7
Met. That, ¹³ C is ¹³ concentrated C is 34% while the carbonyl carbon in CF ₃ CFO, ¹³ C is 7% in the methyl carbon
Concentrated. Also, ¹³ C was concentrated in C ₂ F ₄ by 7%.
Therefore, it can be said that carbon 13 selective cleavage mainly occurs in the C—O bond cleavage of Formula 6.

Carbon 1 of perfluoropropylene oxide
Higher carbon 13 due to 3 selective infrared multiphoton decomposition
The enrichment selectivity and the increase of product yield could be achieved. Particularly, by adjusting the pressure of the starting material and the laser fluence, a sufficiently high carbon 13 concentration selectivity was obtained.

[Brief description of drawings]

FIG. 1 shows a schematic diagram of an apparatus used in an embodiment of the present invention.

[Explanation of symbols]

11 TEA CO ₂ Laser Oscillator 12 Laser Light 13 Aperture Plate 14 Lens for Infrared Light 15 Irradiation Reaction Container 16 Sample Gas 17 NaCl Window Plate 18 Sample Separation System 19 Gas Chromatograph-Mass Spectrometer 20 Gas Handling System 21 Raw Material Ether Supply System 22 Exhaust system

Claims (6)

[Claims] 1. (a) Carbon 13 is obtained by irradiating a saturated cyclic ether, which is a starting material containing carbon 13, with infrared laser light.
Causing a selective infrared multiphoton decomposition of a saturated cyclic ether containing (b), and (b) separating a product containing carbon 13 from the infrared multiphoton decomposition product generated in the step (a) above. Carbon 13 enrichment method including. 2. The process for concentrating carbon 13 according to claim 1, wherein the saturated cyclic ether is selected from the group consisting of propylene oxide, tetrahydrofuran, tetrahydropyran, dioxane, and mixtures thereof. 3. A method for concentrating carbon 13 according to claim 1, wherein the saturated cyclic ether is selected from the group consisting of perfluoroethylene oxide, perfluoropropylene oxide, perfluorotetrahydrofuran, perfluorotetrahydropyran, perfluorodioxane, and mixtures thereof. 4. A method for producing an olefin containing carbon 13 by using the method for concentrating carbon 13 according to claim 1. 5. A method for producing an aldehyde containing carbon 13 by using the method for concentrating carbon 13 according to claim 1. 6. A method for producing CO containing carbon 13 by using the method for concentrating carbon 13 according to claim 1.