The method of inoculation porous carbon material

 

The invention is intended for the adsorption engineering, electrical engineering and electronics and can be used to obtain active carbon electrode materials. Powder nanoporous carbon material with a volume of nanopores of 0.49 cm³/g and a specific surface area of 1330 m²/g is impregnated with a liquid oxidizing agent, for example, nitric acid with a concentration of 30-65%. Incubated at room temperature and a residual pressure of not more than 100 PA 15 minutes Impregnated powder is placed in a flask and poured acid. The mass ratio of acid : carbon material is 10:1. After incubation in a water bath at 80^o2 h acid is drained. The powder is washed from acid to a pH of not less than 3, dried at 1105)^oC. Determine the content of functional groups. It should be at least 1.0 mmol/g Heat treatment is carried out in argon at 300-800^oWith heating rate 20^oC/min, Incubated 1 h Cycle oxidation - heat treatment is repeated until reaching the desired size and pore volume. The invention allows to expand the range of absorbed substances to adjust the porous structure of the carbon material, to increase the volume and dimensions of the nanopores. 4 C.p. f-crystals, 1 Il., table 1. the particular active carbons, and can be used in the adsorption engineering, electrical engineering, electronics and other fields.

Active carbons are characterized by a high content of pores of size less thandue to which they have a high adsorption capacity. In practice, especially abroad, now for then, less thancommon is the term "nanopores". Therefore, active carbons can be considered carbon nanoporous materials. In practical application for these materials are important parameters of the porous structure. The parameters of the porous structure include the volume of the nanopores, their size distribution, specific surface area. The terms used to disclose the invention.

The use of nanoporous carbon materials in modern engineering fields, such as electronics, electronics and so on, requires the directed modification of the parameters of the porous structure, providing a carbon material with a variable volume, the average size of the nanopores, their size distribution.

A known method of modifying the pore structureid carbon or water vapor at a temperature of 850-900^oWith [1]. This method achieved the development of the porous structure due to the chemical interaction of gaseous oxidizing agents carbon frame. Parameters of porous structure of carbon materials obtained in this way, substantially depend on the process conditions and raw material quality. Due to the fact that the process is carried out in the gas phase, diffusion factors have a great influence on the course of chemical reactions which result is the formation of nanoporosity. This makes it difficult to obtain materials with desired parameters of the porous structure. To exclude the effect of diffusion is preferable to carry out the process in the liquid phase.

There is a method of modifying carbon nanoporous materials by oxidation with nitric acid, which is the closest to the claimed solution [2]. The method includes processing a porous carbon material with concentrated nitric acid at 80^oC for 2 h, washing and drying at 200^oC for 4 hours. This method allows you to create on the surface of the nanopore acidic functional group and is used to obtain materials with improved sorption capacity in relation to Katie is ACA of the invention is to develop a method, enabling directional modifying the pore structure of nanoporous carbon material and ensure the expansion of the range of applications for which this material can be used effectively.

The technical result of the proposed method is to increase the amount and size of the nanopores, as well as expanding the range of absorbed substances.

The technical result is achieved due to the fact that the modification of carbon material containing pores with a size less than, exercise cycles, each of which comprises oxidizing in the liquid oxidants and subsequent processing in a non-oxidizing atmosphere at high temperature. The number of cycles is determined by the required volumetric content of nanopores or the size of the nanopores in the final product.

More preferably phase oxidation of carbon nanoporous material be done by processing it 30-65% nitric acid. As a non-oxidizing atmosphere, preferably argon, and the heat treatment be carried out in the temperature range 300-800^oC.

When carrying out the oxidation with nitric acid of a concentration lower than 30%, there is no Tr is lateline, because difficulties arise when working with it because of the formation of gaseous oxides of nitrogen.

Heat treatment at temperatures below 300^oWith no leads to changes in the porous structure of the material and at a temperature of 800^oWith the inoculation process was completed.

The invention consists in the following. The oxidation of liquid oxidants such as nitric acid, is a chemical interaction of the surface carbon atoms with a hydrogen peroxide solution, which are formed of oxygen-containing functional groups. These groups can be phenoliccarboxylcarbonyllactonaseThe advantage of nitric acid as the liquid oxidizer is that this reagent acts on the basal plane graphite-like fragments that form the walls of the nanopores carbon nanoporous materials that can deliberately create functional groups formed on the defects on these planes.

Use for oxidation of liquid oxidizer, in particular nitric acid, provides a uniform oxidation of the entire surface the pressure is ensured regardless of the size of the sample including when processing large phone during subsequent heat treatment in an inert environment is the destruction of functional groups. This destruction begins at a temperature of approximately 300^oWith, the sustainability of the groups depends on their structure. The least stable are carboxyl groups. Important is that the destruction occurs with the formation of gaseous carbon oxides co and CO₂, i.e., during desorption of oxygen at the same time removed the carbon atoms from the surface of the nanopore. Thus there is an increase in the volume and size of the nanopores of the carbon material. After the first loop, if necessary, carried out the second and subsequent cycles to achieve the desired size and volume of the nanopores.

The invention is illustrated by the following examples.

Example 1. A portion of nanoporous carbon material in the form of a powder, the characteristics of which are presented in the table, soaked in nitric acid having a concentration of 65 wt.%. The impregnation is carried out at a residual pressure of not more than 100 PA at room temperature for 15 min to ensure penetration of the acid into all the nanoporous material. Then soaked in acid powder poured what about the flask is placed in a thermostatted water bath, heated to 80^oC and maintained for 2 hours Then the acid is drained and washed the powder with distilled water to achieve a pH of wash water at least 3. Then the powder is dried at 1105)^oC. Then determine the content of functional groups on the surface of the material. The material is then placed in a quartz flow reactor and carry out its processing argon by heating in the temperature range 300-800^oWith heating rate 20^oC/min, Then at a temperature of 800^oWith stand for 1 hour. The specified processing, including phase oxidation with nitric acid and heat treatment in an inert atmosphere are repeated 3 times. After each treatment cycle to determine the parameters of the porous structure of the material.

The values obtained are given in the table.

Example 2. As the source material used nanoporous carbon material made in the form of discs with a diameter of 20 mm and a thickness of 1 mm Treatment is carried out analogously to example 1. Parameters of porous structure are presented in the table and in the drawing.

Material properties were determined by the following methods.

The content of functional groups after the stage of oxidation was determined what slotow, described in [2]. The volume of the nanopores was determined executory method for the adsorption of benzene in static conditions [3].

Specific surface area was determined from low-temperature nitrogen adsorption.

The distribution of the pore sizes were determined from the isotherms of low-temperature adsorption of nitrogen.

The presented data allow us to conclude that the proposed method modification leads to an increase in volume and size of the nanopores of the carbon material. Products according to the invention can find application for the absorption of organic substances, as electrode materials. The inventive method allows to expand the range of absorbed substances and to use high adsorption properties of carbon materials in areas that were previously inaccessible due to the large size of the molecules adsorbed substances. The proposed method allows you to adjust the porous structure of materials depending on the particular application and to create high-performance materials on the basis of cheap feedstock.

Sources of information 1. Calcev N. In. Fundamentals of adsorption technique. - M.: Chemistry, S. 262-264.

2. Jan Pawlaczyk, Halina Sobczak Badaniasorpcyjnychleczni coal. IV. The influence of oxidation on the sorption properties of carbo medicinalis // Acta polon. Pharm., XXXVII, No. 6, 1980 (Polska., RES eng., eng.), S. 655-661.

3. Calcev N. In. Fundamentals of adsorption technique. - M.: Chemistry, S. 33.

Claims

1. The method of inoculation porous carbon material mainly containing pores of a size less thanincludes treatment of the material in liquid oxidizers and heat treatment in a non-oxidizing atmosphere, wherein the first conducting processing in liquid oxidizers, and then heat treatment of the material at 300-800^oC.

2. The method according to p. 1, characterized in that the cycle of oxidation - heat treatment is repeated until reaching the desired size and pore volume.

3. The method according to p. 1, characterized in that at the stage of oxidation of the carbon material as a liquid oxidizing agent, nitric acid concentration of 30-65%.

4. The method according to any of paragraphs. 1-3, characterized in that the treatment is carried out before formation of the functional groups on the surface of the carbon material is not less than 1.0 mmol/g

5. The method according to any of paragraphs. 1-4, characterized in that before heat treatment the material washed from the liquid oxidizer.