RU2583026C2 - Method for obtaining mesoporous carbon material - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention can be used in manufacturing sorbents, catalyst carriers, and materials for electric capacitors. To obtain mesoporous carbon material with high specific surface as precursors used are mixtures of individual organic compounds, one of components of which is furfural, and second is phenol or hydroquinone. Precursors are mixed with sodium or potassium hydroxide. Obtained mixture is subjected to melting and further carbonisation at 700-900°C in medium of waste gases. Carbonisate is washed from salts, dried and activated with carbon dioxide at 800-900°C.

EFFECT: obtaining mesoporous carbon materials with specific surface larger than 2500 m²/g and capacity 2,5-4,5 cm³/g.

2 cl, 2 dwg, 8 ex

Description

The invention relates to the production of porous carbon materials from a mixture of individual organic compounds having a high specific surface area and mesoporosity, and can find application in various fields of science and technology.

Known methods for producing porous carbon materials by coking (pyrolysis) of solid organic materials, including humus coals, solid oil residues, as well as their cokes, followed by their activation with water vapor or carbon dioxide [V. B. Fenelon, Porous carbon. Novosibirsk, 1995, 513 pp.]. In the process of pyrolysis of carbon raw materials, hydrogen, methane, heterocyclic and light hydrocarbon compounds are removed to form a carbon material, the specific surface area and adsorption properties of which are controlled by activation with water vapor or carbon dioxide.

Closest to the proposed technical solution is a method for producing a mesoporous carbon material with a high specific surface area, described in SU 1836138 (CL B01J 20/20, 1993). A common feature for them is the following: use of organic compounds as precursors, carbonization, salt washing and drying.

″ 1,6 мм карбонизуют в статическом режиме на воздухе при ступенчатом, повышении температуры со скоростью 30°/ч от 180 до 350°С, а затем подвергают термической обработке при 800°С в течение 0,5 ч в токе аргона, после чего активируют в статическом режиме водяным паром при 850°С в течение 4 ч. Полученный углеродный носитель помещают в реактор с мешалкой, обрабатывают 2-кратным объемом 6 М раствора соляной кислоты и кипятят с перемешиванием в течение 6 ч. Обработку повторяют новой порцией раствора. Далее продукт нейтрализуют 3%-ным раствором едкого натра при нагревании и перемешивании раствора до pH 5 в

″ 5,5. Продукт отделяют от раствора и высушивают до воздушно-сухого состояния. В результате получают углеродный материал со следующими характеристиками: объем микропор 0,46-0,49 см³/г; объем мезопор 0,74-0,78 см³/г; удельная поверхность пор 1110-1180 м²/г. Соотношение объемов мезо- и микропор 1,6-1,7.For example, 2-methyl, 5-vinylpyridine with divinylbenzene in spherical granulation with a diameter of granules of 0.5 in

″ 1.6 mm is carbonized in static mode in air at a stepwise temperature increase at a speed of 30 ° / h from 180 to 350 ° C, and then subjected to heat treatment at 800 ° C for 0.5 h in an argon flow, after which they are activated in a static mode with water vapor at 850 ° C for 4 hours. The resulting carbon carrier is placed in a stirred reactor, treated with a 2-fold volume of a 6 M hydrochloric acid solution and boiled with stirring for 6 hours. The treatment is repeated with a new portion of the solution. Next, the product is neutralized with a 3% sodium hydroxide solution by heating and stirring the solution to a pH of 5 in

″ 5.5. The product is separated from the solution and dried to an air-dry state. The result is a carbon material with the following characteristics: micropore volume of 0.46-0.49 cm ³ / g; the volume of mesopores 0.74-0.78 cm ³ / g; the specific surface area of the pores is 1110-1180 m ² / g. The ratio of the volumes of meso- and micropores 1.6-1.7.

The problem is solved by the proposed method for producing activated carbon material with developed mesoporosity, in which individual organic compounds — phenol or various hydroquinones — are used as precursors, which are mixed with an equimolar mixture of sodium or potassium hydroxides in a ratio of 1: 2-7 by weight; the resulting mixture is subjected to melting, after which the melt is carbonized at a temperature of 700-900 ° C in the environment of the exhaust gases; the carbonate is washed with water to a neutral medium and dried to constant weight at a temperature of 105-115 ° C. The resulting product is additionally activated with carbon dioxide at a temperature of 800-900 ° C to 30-50% of the burn.

EFFECT: obtaining porous carbon materials having a high specific surface of more than 2500 m ² / g and a large capacity of 2.5-4.5 cm ³ / g.

Specific surface measurements are performed on an ASAP-2400 (Micromeritics) installation for nitrogen adsorption at 77 K after preliminary training of samples that are carried out at 200 ° C and a residual pressure of less than 0.001 mm Hg. until gas evolution ceases without contact with the atmosphere after training. According to these characteristics, the BET specific surface area is calculated. The total volume of micro- and mesopores V _Σ pores (with a characteristic size of less than 100 nm) is determined by the limiting value of nitrogen adsorption at a relative pressure P / Po = 0.98, while the error in determining the specific surface and pore volume does not exceed 5%.

The results of x-ray studies indicate a high degree of amorphism of the synthesized carbon materials.

), смещен в сторону малых углов (~22,5°) относительно типичного угла рефлекса d₀₀₂ (~26°) для идеального графита. По ширине рефлексов (002) и (100) была определена средняя слойность «пачки» (4 слоя) и ее средний размер (1,5-2 нм), соответственно.In FIG. X-ray diffraction patterns are shown in Table 1, in which strong peak broadening is observed. In this case, the d ₀₀₂ reflection corresponding to the interplanar distance between graphene-like layers in the PUM (~ 3.95

), is shifted towards small angles (~ 22.5 °) relative to the typical reflection angle d ₀₀₂ (~ 26 °) for ideal graphite. From the widths of the (002) and (100) reflections, the average layer “pack” (4 layers) and its average size (1.5–2 nm) were determined, respectively.

In FIG. Figure 2 shows a micrograph of a mesoporous carbon material obtained by high resolution electron microscopy (HREM), using a JEM-2010 transmission electron microscope with a lattice resolution of 0.14 nm and an accelerating voltage of 200 kV. The photograph shows, especially around the edges, folded sheets of graphene.

The invention is illustrated by the following examples.

Example 1

5 g of phenol is mixed with 25.132 g of sodium hydroxide and, after evaporation of water, the mixture is melted until gas evolution ceases. After that, the melt in a crucible with a lid is placed in a muffle furnace at a temperature of 700 ° C, and after 60 minutes of exposure, the crucible is removed and cooled in air to room temperature. Then the carbonate is washed with water, then acidic water, then water to a neutral environment. The resulting product is dried in an oven at a temperature of 105-115 ° C to constant weight.

The yield of porous carbon material is from 40% by weight of organics. The specific surface is evaluated by nitrogen adsorption by the BET method and it is 2500 m ² / g with a mesopore volume of 2.6 cm ³ / g.

Example 2

Similar to example 1, characterized in that instead of sodium hydroxide, potassium hydroxide in the amount of 35.185 g is taken and after evaporation the mixture is melted until gas evolution ceases. Further, as in example 1.

The yield is 35% by weight of organic matter. The specific surface is 2550 m ² / g with a mesopore volume of 2.8 cm ³ / g.

Example 3

Similar to example 1, characterized in that instead of sodium hydroxide take an equimolecular mixture of sodium hydroxide (12.568 g) and potassium (17.595 g) in an amount of 30.163 g and after evaporation the mixture is melted until gas evolution ceases. Further, as in example 1.

The yield is 36% by weight of organic matter. The specific surface area equal to 2650 m ² / g, a mesopore volume of 2.7 cm ³ / g.

Example 4

Similar to example 3, characterized in that the carbonization is carried out at a temperature of 800 ° C and after 30 minutes of exposure, the crucible is removed and cooled in air to room temperature.

Yield 30% by weight of organic matter. The specific surface is 2700 m ² / g with a mesopore volume of 2.8 cm ³ / g.

Example 5

Similar to example 3, characterized in that the carbonization is carried out at a temperature of 900 ° C and after 20 minutes of exposure, the crucible is removed and cooled in air to room temperature.

Yield 20% by weight of organic matter. The specific surface is 2800 m ² / g with a mesopore volume of 2.6 cm ³ / g.

Example 6

Similar to example 1, characterized in that the carbonization is carried out at a temperature of 800 ° C and after 30 minutes of exposure, the crucible is removed and cooled in air to room temperature.

Yield 25% by weight of organic matter. The specific surface is 2800 m ² / g with a mesopore volume of 2.7 cm ³ / g.

Example 7

Similar to example 1, characterized in that they take 5 g of hydroquinone mixed with 24.132 g of sodium hydroxide and after evaporation of the water, the mixture is melted until gas evolution ceases. Further, as in example 1.

The yield of porous carbon material is from 30% by weight of organic matter. The specific surface area is estimated by nitrogen adsorption by the BET method, and it is 2450 m ² / g with a mesopore volume of 2.6 cm ³ / g.

Example 8

Similar to example 7, characterized in that instead of sodium hydroxide they take an equimolecular mixture of sodium hydroxide (4.189 g) and potassium (5.865 g) in an amount of 10.054 g and after evaporation the mixture is melted until gas evolution ceases. After that, the melt in a crucible with a lid is placed in a muffle furnace at a temperature of 900 ° C, and after 20 minutes of exposure, the crucible is removed and cooled in air to room temperature. Further, as in example 7.

The yield of porous carbon material is from 40% by weight of organics. The specific surface area was evaluated by BET nitrogen adsorption method, and it is 2550 m ² / g, a mesopore volume of 2.7 cm ³ / g.

As can be seen from examples 1-8, the carbon adsorbent has a high specific surface area, but a relatively small volume of mesopores.

To increase the volume of mesopores, they are treated with carbon dioxide at temperatures of 800 and 900 ° C with a supply of CO ₂ at a rate of 0.7 ml / s for 10-40 minutes; sample weight 0.2-0.3 g.

When treated with carbon dioxide at a temperature of 900 ° C with a degree of burning of 30%, the specific surface of the sample is 2750 m ² / g, the mesopore volume is 3.52 cm ³ / g, the micropore volume is 0.37 cm ³ / g.

In the treatment with carbon dioxide at a temperature of 900 ° C at 60% degree of ablation of the sample specific surface 2950 ^m2 / g, a mesopore volume of 4.47 ^cm3 / g, micropore volume 0.36 cm ³ / g.

When treated with carbon dioxide at a temperature of 800 ° C with a degree of burning of 40%, the specific surface of the sample is 2800 m ² / g, the mesopore volume is 3.44 cm ³ / g, the micropore volume is 0.36 cm ³ / g.

When treated with carbon dioxide at a temperature of 800 ° C with a degree of burning of 49%, the specific surface of the sample is 2260 m ² / g, the volume of mesopores is 3.01 cm ³ / g, and the volume of micropores is 0.23 cm ³ / g.

When treated with carbon dioxide at a temperature of 900 ° C with a degree of burning of 30%, the specific surface of the sample is 2750 m ² / g, the mesopore volume is 3.52 cm ³ / g, the micropore volume is 0.37 cm ³ / g.

As can be seen from the above examples, the proposed method allows to obtain from mesoporous carbon material from individual organic compounds, such as phenol or hydroquinone, by fusion with potassium or sodium hydroxide and subsequent carbonization at 700-900 ° C, additional activation by carbon dioxide at a temperature of 800-900 ° C allows you to increase the capacity of mesopores.

The material obtained by the proposed method can be widely used as sorbents for water purification, organic liquids as a material for electric capacitors, and also as a material for carriers of various catalysts.

Claims (2)

1. A method of obtaining a mesoporous carbon material with a high specific surface area, which consists in using as a precursor a mixture of individual organic compounds, one of the components of which is furfural, and the second component is phenol or hydroquinone, which are mixed with potassium and / or sodium hydroxide in a ratio of 1 / 2-7 by weight, the resulting mixture is subjected to melting, after which the melt is carbonized at a temperature of 700-900 ° C in the environment of the exhaust gases, the resulting carbonizate is washed from salts and dried. 2. The method according to p. 1, characterized in that the obtained carbonizate after drying is subjected to activation with carbon dioxide at a temperature of 800-900 ° C to burn 30-50%.

Images