RU2701908C2 - Method of producing carbon material - Google Patents

Abstract

FIELD: chemistry.SUBSTANCE: invention can be used in production of capacitors and supercapacitors. First, initial carbon material with high specific surface area is not less than 300 m/g is impregnated on moisture capacity with concentrated solution of alkali or soda, or salts of alkali metal. Thermochemical activation is then carried out in the presence of air at temperature of 60–300 °C for 2–50 h prior to ignition of material, that is sudden uncontrolled heating. Activated material is quickly isolated from air atmosphere, cooled to room temperature, washed with distilled water or diluted acid solutions in volume ratio of 0.3–30 and dried at temperature not higher than 100 °C for prevention of repeated spontaneous ignition.EFFECT: obtained carbon material is characterized by high pseudo-electrical capacity.4 cl, 2 dwg, 2 tbl, 2 ex

Description

The invention relates to the field of production of carbon materials ... Modern carbon materials for capacitors and supercapacitors put forward requirements for carbon carriers associated with high electrical conductivity and stability to redox processes under cycling current-voltage charging / discharging materials.

The most suitable and widely used materials in this area are carbon materials of the Vulcan, Ketjen black, Black Pearls brands. However, the prices of these carbon materials are very high. This is mainly due to the method of their preparation, because all of the carbon materials listed are carbon blacks, i.e. thermal decomposition products of high-purity hydrocarbon feedstocks. Their limited production and narrow-profile application also contribute.

The carbon blacks described in the inventions US 9,793,555, US 9,790,076, US 9,742,010, US 9,793,576, US 9,793,550, US 9,786,953, US 9,775,235, US 9,724,940 and many others are analogues of the invention according to the method of use. However, due to the fundamentally different raw materials for producing the carbon material, it makes sense to consider other analogues in order to emphasize the fundamental novelty of the method of activation of the carbon material.

In the invention RU 2,467,798, the carbon material is modified with heteroatomic metal particles by impregnation from solutions of precursors, which is associated with this invention only by the presence of a carbon carrier.

In work RU 2,625,671, a hydrothermal treatment of a carbon material was carried out without the addition of an activating component, alkali, at temperatures much lower, which did not significantly improve the activation of the material, but led to its granulation.

In the invention RU 2,556,011, the modification of the carbon material was carried out with non-stoichiometric phosphate salts, which does not correlate with this invention.

The method described in RU 2,436,625, offers the thermal activation of wood precursor in an inert atmosphere at a temperature of 300-800 ° C, followed by the use of alkali with heat treatment at 800 ° C and washing the resulting material after cooling. The key difference in this case is the use of an inert atmosphere and high temperature values.

However, the most technically closest way to activate carbon material is described in RU 2,583,026, СВВ 31/02, 04/27/2010, where activated carbon from a precursor is obtained at a temperature of at least 700 ° C in the presence of alkalis in an inert atmosphere, followed by heat treatment in the presence of CO ₂ .

The invention solves the problem of simplifying the production of carbon materials with high and stable electrical intensity ..

EFFECT: high pseudoelectric power, the proposed method does not require such high temperatures and specific processing conditions.

A method for producing carbon material is proposed, characterized in that the initial high-surface carbon material is subjected to moderate thermochemical activation by impregnation of moisture content with a concentrated solution of alkali or soda, go alkali metal salt, followed by drying of the carbon material in the presence of air, cooling in an inert atmosphere, leaching alkali, re-drying the activated material to remove excess water.

Drying is carried out at a temperature of 60-300 ° C for 2-50 hours or until the material ignites, i.e. sudden uncontrolled heating, followed by rapid isolation of the carbon material from the atmosphere and its cooling to room temperature.

The solution of alkali or soda or alkali metal salt after activation is removed with distilled water or dilute acid solutions in a volume ratio of 0.3-30.

Re-drying of the activated material is carried out at a temperature not exceeding 100 ° C to prevent re-ignition.

The essence of the invention lies in the special thermochemical processing of industrially available carbons, including stone activated carbons of Russian origin. The activation method requires coal with a specific surface area of at least 300 m ² / g. Coal is soaked in moisture capacity with a concentrated alkali solution (including soda and other alkali metal salts), dried in air at temperatures of 60-300 ° C for 2-50 hours or until self-ignition begins, then it is isolated from the environment or placed in an inert atmosphere, followed by cooling. In the process of thermal drying, the surface of the coal is activated into the grafting of stable active quinone-hydroquinone groups on the surface of the carbon material, which are responsible for the high pseudo-capacity. The final stage of preparation consists in leaching alkali from the pores of the carbon material with distilled water (or a purer analogue) in an amount of 0.3-30 volumes of the volume of the carbon material and final drying from water with moderate heat treatment to 100 ° C. In the activation process, alkali is both a catalyst for the activation process, lowering the activation barrier for surface oxidation, and a stabilizer of surface groups, forming salts with oxidation products. Thus, it is possible to significantly reduce the cost of carbon materials for the electrochemical field.

The invention is illustrated by the following examples and. FIG.

Fig 1 - Cyclic voltammograms of coal BAU-A.

FIG. 2 - XPS C1s spectrum of an AGM carbon material with various surface activation methods.

Example 1

Commercial birch coal BAU-A (manufactured by Sorbent OJSC) was impregnated with a concentrated alkali solution (15 wt.%) In terms of moisture capacity. Then the coal was loaded into a baking sheet and placed in a ventilated drying cabinet at 180 ° C for 4 hours. After coal combustion, the baking sheet was removed from the cabinet and insulated so that air exchange with the environment did not occur by wrapping the baking sheet with aluminum foil. After cooling, the carbon material was removed and washed with distilled water to remove alkali residues, dried at a relatively low temperature of 100 ° C for 24 hours. Pure coal was tested in a current – voltage cycle.

The experiment was carried out in a three-electrode cell with a liquid electrolyte in an argon atmosphere. As the electrolyte used 0.1 M HClO ₄ . The reference electrode was a reversible hydrogen electrode, the auxiliary electrode was represented by a platinum foil, and the working electrode was a glassy carbon rod with a sample deposited on it. The sample was applied from a suspension prepared as follows: 1 ml of a solution of isopropyl alcohol with water in a ratio of 3: 2 vol. and the estimated amount of ionomer binder Nafion (5 wt.%. solution in water). The potential control in the experiment was provided using the Autolab potentiostat and the Nova program.

A comparison of the starting and activated carbon is presented in Table 1. Voltammograms are shown in FIG. 1, from which there follows a sharp increase in the peak at 0.6 V (hydroquinone-quinone transition) on the direct branch of cycling.

Example 2

Commercial ATM coal (produced by Sorbent OJSC) was impregnated with a moisture capacity of 15 wt. % alkali solution. Impregnated coal was divided into 3 equal shares. The first part was placed in a baking sheet and dried in an oven at 60 ° C for 24 hours. The second part was placed in a baking sheet and dried in an oven at 100 ° C for 20 hours. The last part was also placed in a baking sheet and dried in an oven at 200 ° C for 6 hours before spontaneous combustion, then the last baking sheet was quickly removed and wrapped with aluminum foil to isolate it from the atmosphere and waited until all volumes had cooled to room temperature. Then the alkali was washed with distilled water in a volume ratio of 1:10 for each fraction and the coals were dried at 60 ° C. Carbon materials were studied by XPS using a SPECS Surface Nano Analysis GmbH (Germany) photoelectron spectrometer.

The spectrometer was equipped with a PHOIBOS-150-MCD-9 hemispherical analyzer and an XR-50M characteristic X-ray source with a double Al / Ag anode. To record the spectra, non-monochromatic radiation of Al Kα (h * = 1486.61 eV) was used. To take into account the charging effect of the samples, we used the C1s spectrum of carbon, which is part of the carrier (Esb = 284.80 eV). The relative concentrations of elements in the analysis zone were determined on the basis of the integrated intensities of the XPS lines taking into account the photoionization cross section of the corresponding terms. For a detailed analysis, the decomposition of the spectra into individual components was used. Accordingly, after subtracting the background according to the Shirley method, the experimental curve was decomposed into a series of lines corresponding to photoemission of electrons from atoms in different chemical environments. Data processing was performed using the CasaXPS software package. The peak shape of C1s was approximated by a symmetric function obtained by multiplying the Gauss and Lorentz functions. The shape of the Fe2p and S2p peaks was approximated by the asymmetric function LF based on the Lorentz and Gauss functions.

Graphic results are shown in FIG. 2. A comparative analysis of surface oxidized carbon groups to the total amount of carbon in coal is given in table 2 ..

From the data obtained it is clearly seen that thermal activation in the presence of alkali allows one to obtain activated carbon-oxygen groups according to the proposed method, corresponding to the quinone-hydroquinone type of bonds, which makes this method effective for activating any carbon materials.

Claims (4)

1. A method of producing a carbon material, characterized in that the starting carbon material with a high specific surface area of at least 300 m ² / g is impregnated according to moisture capacity with a concentrated solution of alkali or soda or alkali metal salt, after which thermochemical activation is carried out in the presence of air at temperature 60-300 ° C for 2-50 hours until the material ignites, i.e. sudden uncontrolled heating, then the activated material is quickly isolated from the atmosphere of air, cooled, washed and dried to remove excess water. 2. The method according to p. 1, characterized in that the activated material is cooled to room temperature. 3. The method according to p. 1, characterized in that for washing using distilled water or dilute solutions of acids in a volumetric ratio of 0.3-30. 4. The method according to p. 1, characterized in that the drying is carried out at a temperature not exceeding 100 ° C to prevent re-ignition.

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