JPS6320563B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a novel method for separating carbon isotopes. Naturally occurring carbon has a mass number of 12 (carbon
^12C ) approximately 98.89% by weight and carbon with mass number 13 ( ^13C ) approx.
It is a 1.11% by weight mixture. Because ¹³ C is non-radioactive, it is suitable for use as a label for compounds in various fields such as clinical medicine, pharmacy, biochemistry, and agriculture, so it is expected that recent advances in mass spectrometers will make quantitative methods easier. Therefore, the demand for ^13C is increasing significantly. Therefore, it has become important to develop a technology to separate and obtain ¹³ C in a highly concentrated state. The main ^13C separation method currently in use is the cold distillation method, and other known methods include the thermal diffusion method, the chemical exchange method, and the laser method. Among these, the chemical exchange method utilizes a carbon isotope exchange reaction between different carbon-containing chemical species.
That is, when the carbon isotope exchange reaction shown in the following formula (1) occurs between different carbon-containing chemical species CX and CY, and the equilibrium constant K deviates from 1, when both chemical species are brought into contact, one side ^13C can be concentrated into the following chemical species: Until now, various combinations of chemical species that cause such isotopic effects have been known. However, all previous reactions have been limited to gas-liquid or liquid-liquid exchange reactions. The present invention has higher separation efficiency than conventional methods.
This provides a chemical exchange method that can concentrate ^13C . The present inventors have discovered that in the above formula (1), CX and CY
If the adsorption characteristics of the ion exchange resins are different,
In the following formula (2), K′ deviates from 1, (However, C is the concentration of carbon in the solution, and is the concentration of carbon in the resin phase.) As a result, it was discovered that ¹³ C was efficiently concentrated in the resin phase or solution phase, and this led to the present invention. . That is, the present invention is a method for separating carbon isotopes by an isotope exchange reaction between an acid-dissociable chemical species of a carbon-containing acid and a non-dissociable chemical species, the method comprising: By bringing an aqueous solution containing a non-dissociated chemical species into contact with an anionic resin as a solid phase, a carbon isotope exchange reaction between the acid-dissociated chemical species and the non-dissociated chemical species is carried out, and the acid dissociates. type chemical species is adsorbed on an anion exchange resin, ¹² C,
and ¹³ C into a solution phase and a solid phase, or a solid phase and a solution phase, respectively, and ¹³ C is concentrated in the phase from which ¹³ C is separated. The present invention will be specifically explained below. The two types of carbon-containing compounds in the present invention include various compounds, such as acid-dissociated type and non-dissociated type of organic acid or inorganic acid, and specific acids include H ₂ CO ₃ , HOCN, HSCN,
Examples include HCOOH. As the ion exchange resin in the present invention, an anion exchange resin is used when the acid dissociated type and non-dissociated type of the organic acid or inorganic acid are used. The anion exchange resin that can be used in the present invention can include the following as its constituent components. That is, the non-crosslinked polymerizable monomers include styrene, methylstyrene, dimethylstyrene, 3,
4,6-trimethylstyrene, methoxystyrene, promustyrene, cyanostyrene, fluorostyrene, dichlorostyrene, N,N-dimethylaminostyrene, nitrostyrene, chloromethylstyrene, trifluorostyrene, trifluoromethylstyrene, aminostyrene, etc. Styrene derivatives, vinyl sulfide derivatives such as methyl vinyl sulfide and phenyl vinyl sulfide, acrylonitrile derivatives such as acrylonitrile, methacrylonitrile, and α-acetoxyacrylonitrile, vinyl ketones such as methyl vinyl ketone and ethyl isopropyl ketone, vinylidene chloride, Vinylidene compounds such as vinylidene bromide and vinylidene cyanide, acrylamide, methacrylamide, N
-butoxymethylacrylamide, N-phenylacrylamide, diacetone acrylamide,
Acrylamide derivatives such as N,N-dimethylaminoethyl acrylamide, N-vinylsuccinimide, N-vinylpyrrolidone, N-vinylphthalimide, N-vinylcarbazole, vinylfuran, 2-vinylbenzofuran, vinylthiophenone, vinylimidazole, methyl Vinylimidazole, vinylpyrazole, vinyloxazolidone, vinylthiazole, vinyltetrazole, vinylpyridine, methylvinylpyridine, 2,4-
These include dimethyl-6-vinyltriazine, vinylquinoline, and epoxybutadiene. Examples of crosslinking polymerizable monomers include divinylbenzene, divinyltoluene, divinylxylene, divinylnaphthalene, divinylethylbenzene, divinylphenanthrene, trivinylbenzene, divinyldiphenyl, divinyldiphenylmethane, divinylbenzyl, divinyl phenyl ether, Divinyldiphenyl sulfide, divinyldiphenylamine, divinylsulfone, divinylketone, divinylfuran, divinylpyridine, divinylquinoline, diallyl phthalate, diallyl maleate,
Diallyl fumarate, diallyl succinate, diallyl oxalate, diallyl adipate, diallylamine, triallylamine, N,N'-ethylene diacrylamide, N,N'-methylene diacrylamide, N,N'-methylene dimethacrylamide,
Examples include ethylene glycol dimethacrylate, triethylene glycol dimethacrylate, and polyethylene glycol dimethacrylate. Preferred compositions of the resin that can be used in the present invention include chloromethylated and aminated polymer crosslinked products synthesized by addition copolymerization using divinylbenzene such as styrene, vinyltoluene, and ethylvinylbenzene as the main component; Aminated addition copolymers mainly composed of monomers with active groups such as styrene, epoxybutadiene, acrylamide, and crosslinking monomers such as divinylbenzene and triallyl isocyanurate, N-vinylphthalimide, Examples include those whose main component is a monomer having nitrogen that can be used as an exchange group, such as vinyl imidazole, vinyl pyridine, vinyl tetrazole, vinyl quinoline, divinyl pyridine, etc., and which are copolymerized with a crosslinkable monomer as necessary. . Amines that can be used for amination include triethanolamine, triethylamine, trimethylamine, triallylamine, diethanolamine,
Aliphatic amines such as diallylamine, diethylamine, dimethylamine, 2-aminoethanol, ethylamine, methylamine, ethanolamine,
Aniline, o-aminophenol, N,N-dimethylaniline, N-methylaniline, m-toluidine, p-toluidine, p-aminophenol,
Aromatic amines such as diphenylamine, pyridine,
r-picoline, piperidine, pyrazine, piperazine, indoline, indole, imidazole, 2
-methylimidazole, quinoline, 2,6-lutidine, 1,2,3,4-tetrahydroquinoline,
These include heterocyclic amines such as N-methylpyrrolidine and benzotriazole. In order to produce the anion exchange resin used in the method of the present invention from each of the above-mentioned components, a commonly used method can be adopted, but a more specific explanation will be as follows. Contains 6 to 98%, preferably 10 to 90% by weight, more preferably 20 to 80% by weight of non-crosslinked polymerizable monomer, based on the total weight of non-crosslinked polymerizable monomer and crosslinked polymerizable monomer. A polymerization initiator is added to the mixture containing 2 to 94% by weight of a crosslinkable monomer to carry out a polymerization reaction. As a polymerization initiator, peroxides such as benzoyl peroxide and methyl ethyl ketone peroxide, azobisisobutyronitrile, 2-
Contains azo compounds such as cyano-2-propylazoformamide. The amount of the polymerization initiator added is 0.01 to 12% by weight, preferably 0.1 to 5% by weight, and more preferably 0.2 to 3% by weight based on the total weight of the monomers. The polymerization temperature is usually in the range of 0°C to 200°C, preferably in the range of 15°C to 160°C, more preferably 30°C.
It ranges from ℃ to 130℃. The polymerization time is generally 30 minutes to 50 hours, preferably 1 hour to 30 hours, and more preferably 2 hours to 20 hours. After polymerization, it is cooled, washed with methanol and a large excess of water, dried, and then poured into chloromethyl ether to perform chloromethylation. The reaction temperature for chloromethylation is usually 2°C to 10°C, and the reaction time is 1 hour to 80 hours.
Preferably it is from 10 hours to 60 hours. When carrying out amination, the polymer prepared as described above is mixed with 5% of the amine used in the amination.
Perform the amination reaction in ~40% ethanol solution.
The temperature of the amination reaction is usually 20°C to 80°C, and the reaction time is usually 10 minutes to 10 hours. Among the methods of the present invention using a combination of an acid-dissociated type and a non-dissociated type of an organic acid or an inorganic acid and an anion exchange resin, the most advantageous carbon isotope separation method is to Taking advantage of the fact that ^tautomism occurs between the two types by changing the Adsorb it as a mold to form an adsorption zone of carbon-containing acid,
Next, H ⁺ is supplied from the top of the tower to desorb the carbon-containing number as a non-dissociated type again, and in the adsorption zone, the acid-dissociated chemical species adsorbed to the resin and the non-dissociated chemical species present in the solution phase are continuously separated. This is a method in which isotope exchange reactions are superimposed by bringing the two molecules into contact with each other. When using the above chromatography operation for CO ₂ and HCO ^- ₃ , HSCN and HOCN are added at the rear of the adsorption zone.
When using 13C, ^13C can be concentrated at the front of the adsorption zone. The catalytic exchange reaction between the anion exchange resin and the carbon-containing organic functional or inorganic acid is generally preferably carried out at a temperature range of 0°C to 150°C. Furthermore, as a result of various studies on the ionization index pKa of the carbon-containing acid used and the pKa of the ion exchange resin, it was found that pKaR>pKa′, where the pKa of the anion exchange resin is pKaR and the pKa of the carbon-containing acid used is pKa′. It has been found that in the case of the combination with the relationship -2, a particularly sharp interface is formed and a preferable structure can be obtained. Next, as a specific example of the present invention, H ₂ CO ₃ , that is, a carbon isotope exchange reaction between CO ₂ and HCO ^- ₃ will be explained. The fact that the equilibrium constant K in equation (3) is slightly larger than 1 has already been shown by H.C.
Urey et al. revealed that when an isotope conversion reaction is carried out between HCO ^- ₃ adsorbed on an anion exchange resin and dissolved CO ₂ present in the solution phase in contact with it, ¹³ C is transferred to the resin phase. Can be concentrated. In addition, CO ₂ is added to the anion exchange resin made of OH ^- adsorption type.
A dissolved liquid is supplied to adsorb HCO ^- ₃ , and then H ⁺ is released from the top of the column to be re-desorbed as CO _2. HCO ^- ₃ in the resin phase and CO ₂ in the solution phase are brought into continuous contact, and the resin Needless to say, it is possible to obtain a high concentration of H ¹³ CO ^- ₃ by superimposing phase and solution phase isotope exchange reactions. This isotope exchange reaction is a solid-liquid method, and it goes without saying that it has a higher spatial efficiency and is more advantageous than a gas-liquid method that does not use a resin phase ^.
If the amount of dissolved CO ₂ is increased by increasing the pressure above G, the separation efficiency will be further improved. The preferred reaction temperature for this system is 0 to 120°C, more preferably 20 to 90°C. Further, the above-mentioned relationship pKaR>pKa'-2 also holds true in this system. Examples are shown below. Example 1 A 10-inch four-necked flask was equipped with a stirrer and a thermometer, and 3000 g of water, 20 g of sodium polyacrylate and 82 g of salt as suspending agents, 900 g of styrene, 35 g of ethylvinylbenzene, and 65 g of divinylbenzene were added.
g, methyl benzoate 380g, isoamyl alcohol 320g, normal heptane 1100g as polymerization solvent
g, and 14 g of azobisisobutyronitrile were added and stirred thoroughly to disperse the oil droplets. This at 70℃
Polymerization was carried out for 28 hours, and after the polymerization was cooled, the resin was transferred to a washing tower with a filter and thoroughly washed with 10 parts of methanol and a large excess of water. After washing, it was dried at 2 mmHg and 40°C for 72 hours, and 300 g of the dried resin was poured into chloromethyl methyl ether kept at 5°C, and reacted with 450 g of zinc chloride as a catalyst for 48 hours to undergo chloromethylation. This was followed by amination in a 20% trimethylamine ethanol solution at 40° C. for 5 hours to obtain a strongly basic anion exchange resin (pKaR>14). Mix an aqueous solution containing HCO ^- ₃ ions and a strongly basic anion exchange resin at a weight ratio of 2:1 (resin is dry weight) and stir thoroughly (290°K). After HCO ^- ₃ reaches adsorption equilibrium, H ₂ SO ₄ is added dropwise to adjust the pH to 4. After reaching isotope exchange equilibrium, the resin phase and solution phase were separated, and the carbon isotope ratios in CO ₂ in the solution and HCO ^- ₃ in the resin were measured using an electron impact mass spectrometer. Got the value.

[Table] As a result, the equilibrium constant K' (formula below) of isotope exchange reaction between solid and liquid between HCO ^- ₃ and CO ₂ was determined to be 1.012. Example 2 An 8 mmφ cylindrical column was filled with the strong basic ion exchange resin synthesized according to Example 1 to a height of 900 mm.
A resin bed is prepared and conditioned with alkali at 25°C to form the OH ^- form. CO ₂ 1Kg/cm ²
Supply a saturated aqueous solution at a pressure of G, and HCO ^- ₃
After forming an adsorption zone, the adsorption zone is advanced while being desorbed as CO ₂ with 0.03MH ₂ SO ₄ and the eluted
CO ₂ was collected and ^{the 13} CO ₂ / ¹² CO ₂ isotope ratio was measured using an electron impact mass spectrometer. Developing time (min) ¹³ C/ ¹² C 205.0 1.163 210.0 1.167 215.0 1.183 220.0 1.199 225.0 1.256 230.0 1.298 Example 3 An 8 mmφ cylindrical column was filled with the strong basic ion exchange resin synthesized in Example 1 to a height of 900 mm.
A resin bed is prepared and conditioned with alkali at 25°C to form the OH ^- form. 10Kg/ ^cm2 of _CO2
After supplying a pressurized dissolved aqueous solution and forming an HCO ^- ₃ adsorption zone, while desorbing _it as _CO2 with _0.2MH2SO4 ,
Advancing the adsorption zone and collecting the eluted _CO2 ,
^{The 13} CO ₂ / ¹² CO ₂ isotope ratio was measured using an electron impact mass spectrometer. The measurement results of the rear end concentration section are shown. Deployment time (min) ¹³ C/ ¹² C 42.5 1.165 43.5 1.183 44.5 1.226 45.5 1.274 46.5 1.361 47.5 1.382

Claims (1)

[Scope of Claims] 1. A method for separating carbon isotopes by an isotope exchange reaction between an acid-dissociated chemical species of a carbon-containing acid and a non-dissociable chemical species, the method comprising an acid-dissociated chemistry of a carbon-containing acid. By contacting an aqueous solution containing a species and an undissociated chemical species with an anion exchange resin as a solid phase,
A carbon isotope exchange reaction between an acid-dissociated chemical species and a non-dissociated chemical species is performed, and the acid-dissociated chemical species is adsorbed on an anion exchange resin, and ¹² C and ¹³ C
A carbon isotope separation method characterized by separating 13 C into a solution phase and a solid phase, or a solid phase and a solution phase, respectively, and concentrating ¹³ C in the phase from which ¹³ C is separated. 2 Chromatography that utilizes the fact that acid-dissociated chemical species and non-dissociated chemical species of carbon-containing organic acids or inorganic acids are tautomic by changing the pH of the solution, and refluxes both types of chemical species with acid and alkali. 2. The carbon isotope separation method according to claim 1, wherein carbon having a mass number of 13 is enriched by graphite operation. 3 Formula pKaR＞pKa'-2 [However, pKaR is the ionization index (pKa) of the anion exchange resin, and pKa' is the ionization index (pKa) of the carbon-containing organic acid or inorganic acid.
The carbon isotope separation method according to claim 1 or 2, which uses an anion exchange resin that satisfies pKa. 4. Select carbonic acid as an inorganic acid containing carbon, and utilize the carbon isotope exchange reaction between dissolved carbon dioxide as a non-dissociable chemical species and bicarbonate ion (HCO ^- ₃ ) as an acid-dissociable chemical species. Claim 1
The carbon isotope separation method according to item 2, item 3, or item 3. 5. The carbon isotope separation method according to claim 4, which increases the amount of carbon dioxide dissolved in the solution phase by pressurizing the reaction system of the resin phase and the solution phase to a pressure of 1 Kg/cm ² G or more. . 6. The carbon isotope separation method according to claim 4 or 5, wherein the reaction temperature is 20 to 90°C.