RU2327635C1 - Method of obtaining fullerene c60 - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention can be used in the chemical industry. An extract of a mixture of fullerenes is dissolved in several stages in o-xylol at 80-85°C until 96±2% content of C₆₀ is obtained. Dissolving and filtration of the suspension at 80-85°C is done in turns. The obtained suspension, rich in fullerene C₆₀, is dissolved in o-xylol. The obtained solution undergoes the first chromatographic cleaning on a sorbent in form of activated carbon. The separated product of the first cleaning stage is kept in a vacuum at 10^-1-10^-2 mmHg at 180-200°C for 2-4 hours and then later diluted in o-oxylol. The obtained solution undergoes second chromatographic cleaning on a sorbent in form of activated carbon and the end product is separated from the solution. The end product is then later evaporated in a rotation evaporator in a vacuum at 1-10^-1 mmHg, washed in ethanol, and treated with steam with subsequent drying. The end product has marketable appearance and purity of over 99.9%.

EFFECT: high output.

2 ex

Description

The invention relates to the chemical industry, and more particularly to methods for purification and separation of fullerenes.

Extraction of fullerenes, their separation and purification of small (gram) amounts are usually carried out by preparative liquid chromatography (see S. Saim et al. "Supercritical fluid extraction of fullerenes C ₆₀ and C ₇₀ from carbon soot", Sep. Sci. Technol., 1993, Vol. 28, No. 8, p. 1509-1525; WAScrivens et al., "Purification of gram quantities of C _60. A new inexpensive and facile method". J. Am. Chem. Soc., 1992, Vol. 114, No. 20. p. 7914-7919).

A known method of purification of fullerenes (see US patent No. 5310532, IPC B01D 15/08, published 05/10/1994) by liquid chromatography, in which activated carbon with the addition of silica gel is used as the stationary phase, and an aromatic solvent: toluene as the mobile phase , carbon tetrachloride, pyridine.

The known method allows to obtain fullerene With ₆₀ purity of not more than 95%.

A known method of purification of fullerene C ₆₀ (see US patent No. 5662876, IPC СВВ 31/00, published 02.09.1997), including chromatographic purification of the extract of fullerenes dissolved in a mixture of aromatic solvents: o-dichlorobenzene and toluene, on a mixture of activated carbon and silica gel taken in the ratio 1: 1, under nitrogen pressure.

The known method requires the use of a large amount of sorbent due to its low productivity, moreover, the process is carried out at overpressure.

A known method of purification of fullerenes (see US patent No. 5904852, IPC B01D 15/08, published 05/18/1999), in which fullerenes, including C ₆₀ , are separated on a chromatographic column using a polymer with aromatic functional groups as the stationary phase, and as a mobile phase, an organic solvent.

The disadvantage of this method is the lack of purity of the obtained fullerene C ₆₀ , the high cost of the sorbent, low productivity C ₆₀ .

A known method of purification of fullerene C ₆₀ (see JP patent No.2005082461, IPC C01B 31/02, published March 31, 2005), comprising dissolving a mixture of fullerenes and carixarene in a first solvent (toluene or benzene) to form a complex of fullerene C ₆₀ and carixarene, a drop-out into a precipitate, dissolving this precipitate in a second solvent, for example, dialkylbenzenes or trialkylbenzenes, in which C _{60 is} soluble, but does not dissolve very well or does not dissolve carixarene. The resulting C ₆₀ solution is purified from impurities by chromatography to give a product containing 98% C ₆₀ .

The disadvantage of this method is its multi-stage and insufficient purity of the obtained With ₆₀ , as well as the high cost of carixarene.

A known method for the separation of fullerenes With ₆₀ , C ₇₀ and higher fullerenes from fullerene-containing soot (see application WO No. 9204279, published March 19, 1992) by liquid chromatography. A non-polar aromatic solvent (toluene and / or benzene) is used as the main component of the eluent, and coke, anthracite and / or artificial graphite are used as the carrier material. Separation is carried out at a temperature of 20-80 ° C.

Obtained in a known manner fullerene C ₆₀ is not high enough purity.

A known method of separating fullerenes from fullerene-containing products (see patent RU No. 2107536, IPC B01D 11/02, published 03/27/1998), including extraction of the fullerene-containing product with an organic solvent, filtering the resulting solution, evaporating the solvent to obtain a solid product containing a mixture of fullerenes and the remaining solution, elution of the solid solution with an organic solvent in a chromatographic column. The evaporation of the solvent is carried out at a temperature of 80-120 ° C for 4 hours to 3 days under reduced pressure, and the remaining solution is cooled for 10-30 hours at a temperature of 15-25 ° C to obtain a solid product and the remaining solution.

The known method improves the performance of the process of separation of fullerenes from fullerene-containing products and separation into individual fullerenes through a regulated process of evaporation and cooling, which leads to an increase in the speed and volume of released homologs of fullerenes. However, the resulting C ₆₀ fullerene is of insufficient purity.

A known method of producing fullerene C ₆₀ (see patent RU No. 2259942, IPC СВВ 31/02, published September 10, 2005), in which fullerene-containing soot is extracted in a Soxhlet apparatus with an aromatic solvent — toluene. To do this, use an excessive amount of soot in relation to a saturated solution of a mixture of fullerenes in toluene. On the hot bottom of the apparatus, an extract is precipitated from a solution containing up to 95% C ₆₀ . then C ₆₀ fullerene and separated on a chromatographic column using charcoal activated carbon as the stationary phase, toluene or chlorobenzene as the mobile phase, the target product is crystallized. The desired product, if necessary, is subjected to further purification by recrystallization or sublimation in vacuum.

The known method allows to achieve a purity of fullerene C _{60 of} 99.9 +%. However, the known method is excessively expensive and also leads to significant product losses both in the Soxhlet apparatus and during sublimation.

A known method of producing fullerene C ₆₀ (see patent RU No. 2224714, IPC C01B 31.02, published 02.27.2004), in which the extract of a mixture of fullerenes is dissolved in several stages in o-xylene at a temperature of 80-85 ° C until reaching a content of C ₆₀ on level 96 ± 2%, alternating with the dissolution and filtration of the precipitate at a temperature of 80-85 ° C. The obtained precipitate, enriched in C ₆₀ fullerene, is dissolved in o-xylene, the resulting solution is subjected to chromatographic purification on a sorbent in the form of activated nitrogen-containing granular coal, and the final product is isolated from the solution with a content of 99.53%.

The known method does not provide a final product with a content of more than 99.6%, moreover, it is intended only to obtain small amounts of C ₆₀ fullerene for use in analytical chemistry. The relatively high cost of granulated coal brand SKN leads to the need for regeneration of the sorbent. However, during regeneration, the effective capacity of such a sorbent drops sharply, which entails a decrease in the efficiency of the cleaning process and increases the time spent.

The task to which the claimed technical solution is directed was the development of such a method of producing C ₆₀ , which would ensure the purity of the resulting product to 99.9+% and have increased productivity.

The problem is solved in that the method for producing C ₆₀ involves dissolving the extract of the fullerene mixture in several stages in o-xylene at a temperature of 80-85 ° C until reaching a C ₆₀ content of 96 ± 2%, alternating with the dissolution and filtration of the precipitate at a temperature 80-85 ° С, dissolution of the obtained precipitate enriched in С ₆₀ fullerene in o-xylene, first chromatographic purification on a sorbent in the form of activated carbon, isolation of С ₆₀ fullerene from the obtained solution. The new is the exposure obtained after chromatographic purification of fullerene C ₆₀ in a vacuum of 10 ^-1 -10 ^-2 mm RT.article for 2-4 hours at a temperature of 180-200 ° C, its subsequent dissolution in o-xylene, chromatographic purification of the resulting solution on a sorbent in the form of activated carbon and isolation of the final product from the solution.

The disadvantage of the chromatographic method is the inability to achieve a purity of the resulting product of more than 99.8%. This is due to the presence of an inseparable chromatographic impurity of fullerene epoxide C ₆₀ : C ₆₀ O with a content of 3.0-0.2%.

In the inventive method, the fullerene C _{60 having a} purity of 97-99.8% obtained after the first chromatographic purification is subjected to heat treatment in a vacuum of 10 ^-1 -10 ^-2 mm Hg. at a temperature of 180-200 ° C for 2-4 hours. In this case, the C ₆₀ O epoxide interacts with the C ₆₀ molecule to form the C ₁₂₀ O compound, which, when using reverse phase high performance liquid chromatography (HPLC), has a doubled output time compared to C ₆₀ fullerene and is very sorbed by activated carbon. As a result, after the second chromatographic purification, fullerene C ₆₀ freed from epoxide is obtained with a purity of 99.9% or more.

When heat treatment is less than 2 hours and at a temperature of less than 180 ° C, epoxide C ₆₀ O does not fully react. At a pressure of more than 10 ^-1 mm RT.article the oxygen contained in the air will oxidize C ₆₀ at a high temperature to C ₆₀ O epoxide, which, in turn, will react with the new C ₆₀ molecule to form C ₁₂₀ O, which is impractical.

With a shutter speed of more than 4 hours, heat treatment is not economically feasible, since the entire epoxide has time to react. At temperatures above 200 ° C, an irreversible loss of the product occurs due to the thermal oligomerization of C ₆₀ , and at low temperatures the heat treatment time is greatly increased, or the process does not proceed at all. Apply a pressure of less than 10 ^-2 mm Hg it is not economically feasible, since the oxygen content is reduced so much that C ₆₀ practically does not oxidize during the heat treatment.

The final product can be isolated from the solution by evaporation, for example, in a rotary evaporator in a vacuum of 1-10 ^-1 mm Hg

The final product can be treated with ethyl alcohol for 1.0-1.5 hours, and after treatment with ethyl alcohol, water vapor is used, followed by drying to remove residual organic solvents. Processing with alcohol gives the final product a presentation. With less processing time, the product is not a shiny black powder; a brown powder without gloss, in which particles tend to stick together. A longer treatment with alcohol is not economically feasible.

The method is as follows. By evaporating graphite electrodes in an electric arc discharge in an inert gas environment, fullerene-containing soot is obtained. Extraction of fullerenes from fullerene-containing soot yields a fullerene extract (a mixture of fullerenes), which is dissolved in several stages in o-xylene at a temperature of 80-85 ° C until a C ₆₀ content of 96 ± 2% is reached. This process, called fractional concentration of the C ₆₀ fullerene extract, is described in the literature (see X. Zhou, J. Liu, Z. Jin, Z. Gu, Y. Wu, Y.Sun. "Solubility of fullerenes C ₆₀ and C ₇₀ in toluene, o-xylene and carbon disulfide at various temperatures. "- Fullerene Science and Technology, 1997, 5 (1), p. 285-290). Fractional concentration is based on the difference in solubility of fullerenes with different molecular weights depending on temperature. The solubility of fullerene C ₆₀ in o-xylene decreases significantly with increasing temperature from 30 ° C to 85 ° C, while the solubility of fullerene C ₇₀ , on the contrary, increases. As a result, in the temperature range of 80-85 ° С, the remainder of the fullerene extract, which did not dissolve in o-xylene, will be enriched in C ₆₀ fullerene, and the solution in C ₇₀ fullerene. The number of stages of fractional concentration depends on the composition of the initial fullerene extract. The volume of solvent is selected so that the loss of component C _{60 is the} smallest. Carrying out fractional concentration at a temperature below 80 ° C leads to a decrease in the overall productivity of the method. At temperatures above 85 ° C, hardly soluble forms of fullerenes are formed due to thermally induced oligomerization, which subsequently complicates the dissolution of the precipitate. The obtained precipitate, enriched in C ₆₀ fullerene, is dissolved in o-xylene, the first chromatographic purification on the sorbent in the form of activated carbon is carried out, and C ₆₀ fullerene is isolated from the resulting solution. The fullerene C ₆₀ obtained after the first chromatographic purification is kept in a vacuum of 10 ^-1 -10 ^-2 mm Hg. within 2-4 hours at a temperature of 180-200 ° C. After exposure to vacuum, the fullerene C ₆₀ obtained after the first chromatographic purification is dissolved in o-xylene, a second chromatographic purification of the obtained solution on the sorbent in the form of activated carbon is carried out, and the final product is isolated from the solution with a purity of 99.9% or more.

Example 1. By fractional concentration, a fullerene concentrate C ₆₀ 94% was prepared. To this was placed 450 grams of the extract with a content of the fullerene C ₆₀ 60% in a sealed vessel equipped with a stirrer, thermostatically controlled jacket and thermostated filter. It was poured with 8 liters of o-xylene and the suspension was intensively stirred at a temperature of 80 ° C for 5 hours. In this case, the solution is enriched in terms of fullerene C ₇₀ and higher fullerenes, and the insoluble precipitate is enriched in terms of fullerene C ₆₀ . Then the solution was pressurized with compressed air through a filter. The finished concentrate C ₆₀ 88% remained on the filter. By repeated fractional concentration procedure, the purity of fullerene C _{60 was} increased to 94%. Further purification was carried out by chromatographic method. For this purpose, a loading solution was prepared by dissolving 200 grams of C ₆₀ concentrate with stirring for 1 hour in 40 liters of o-xylene. 2.8 kg of NORIT-AZO activated carbon was filled with a dry steel chromatographic column using a vibrodrive using a 140 × 650 mm column. Pure o-xylene was fed to the column using an isocratic pump from the bottom up at a speed of about 500 ml / min for 0.5 hours in order to remove air from the coal. After this, a prepared solution of fullerene C ₆₀ concentrate in o-xylene was passed through the column at the same speed and then the column was washed with 30 liters of pure o-xylene. At the outlet of the column, 20 liters of pure o-xylene were first collected, and then 50 liters of a purified fullerene C ₆₀ solution were collected. The solution of purified fullerene C _{60 was} evaporated to dryness on a rotary evaporator. A dry product of fullerene C _{60 with a} purity of 98% with an admixture of fullerene epoxide C ₆₀ O up to 2% was obtained. Fullerene C ₇₀ and higher fullerenes contained in the initial concentrate remained sorbed on activated carbon. Fullerene C _{60 with a} purity of 98% was subjected to heat treatment in a vacuum of 10 ^-1 mm Hg. at 200 ° C for 2 hours. In this case, the C ₆₀ O epoxide reacted with the C ₆₀ molecule and transferred to the C ₁₂₀ O compound, which on the reversed-phase high-performance liquid chromatographic column has a doubled exit time compared to C ₆₀ and is very sorbed by activated carbon. Prepared loading solution in o-xylene with a concentration of heat-treated With ₆₀ 4.5 g / L. A suspension of activated carbon NORIT-AZO was prepared. To do this, it was poured with o-xylene and subjected to ultrasonic treatment during pumping out in order to remove the air contained in the pores of activated carbon. The suspension was placed on a 85 × 185 mm column. A solution of heat-treated C ₆₀ with a volume of 100 l was passed through a prepared column. The solution obtained from the column was evaporated in vacuo using a rotary evaporator to dryness. The product was treated with ethanol for 1 hour. Then the product was subjected to steam treatment to remove residual organic solvents, and then dried in an oven. Got a marketable product with a content of C ₆₀ 99.9 +% according to HPLC analysis.

Example 2. By the method of fractional concentration, a fullerene concentrate C ₆₀ 96% was prepared. To this end, 500 grams of fullerene extract with a content of _{60 to} 80% were placed in an airtight container equipped with a stirrer, a thermostatic jacket and a thermostatic filter. Pour 9 l of o-xylene and intensively stirred the suspension at a temperature of 85 ° C for 4 hours. Then the solution was pressurized with compressed air through a filter. The finished concentrate C ₆₀ 92% remained on the filter. By repeated procedure, the purity of fullerene C _{60 to} 96% was achieved. Further purification of fullerene C _{60 was} carried out by chromatographic method. For this, a loading solution was prepared by dissolving 250 grams of C ₆₀ concentrate with stirring for 1 hour in 50 liters of o-xylene. After filling the steel chromatographic column 140 × 650 mm with activated carbon NORIT-AZO and removing air from it, the prepared solution of fullerene concentrate C ₆₀ in o-xylene was passed through the column and the column was washed with 30 liters of pure o-xylene after it. At the column outlet, 60 liters of purified fullerene C ₆₀ solution were collected. The solution was evaporated to dryness on a rotary evaporator. Received a dry product of fullerene C _{60 with a} purity of 99% with an admixture of fullerene epoxide C ₆₀ O up to 1%. Fullerene C _{60 with a} purity of 99% was subjected to heat treatment in a vacuum of 10 ^-2 mm Hg. at 200 ° C for 4 hours. After that, a loading solution in o-xylene with a concentration of heat-treated With ₆₀ 5 g / L was prepared. A solution of heat-treated C ₆₀ with a volume of 120 liters was passed through a prepared column. The resulting solution was evaporated to dryness in vacuo. The product was treated with ethyl alcohol for 1.5 hours, then with water vapor and dried in an oven. Got a marketable product - fullerene C _{60 with a} purity of 99.9+% according to HPLC analysis.

The inventive method allows the use of high-performance equipment for fractional concentration and chromatographic primary purification.

Claims (1)

A method of producing fullerene C ₆₀ , which consists in the fact that the extract of a mixture of fullerenes is dissolved in several stages in o-xylene at a temperature of 80-85 ° C until reaching a C ₆₀ content of 96 ± 2%, alternating with the dissolution and filtration of the precipitate at a temperature 80-85 ° С, the obtained precipitate enriched in С ₆₀ fullerene is dissolved in o-xylene, the obtained solution is subjected to the first chromatographic purification on a sorbent in the form of activated carbon, the first purification product is isolated from the solution, it is kept in vacuum 10 ^-1 -10 ^-2 mmHg for 2-4 hours at a temperature of 180-200 ° C, then it is dissolved in o-xylene, the resulting solution is subjected to second chromatographic purification on a sorbent in the form of activated carbon, the final product is isolated from the solution, the final product is evaporated in a rotary evaporator in vacuum 1 -10 ^-1 mm RT.article, washed with ethyl alcohol, and after washing with ethyl alcohol is treated with water vapor, followed by drying.