KR102687312B1 - Method of Preparing Highly Mesoporous Activated Carbon - Google Patents

Abstract

The present invention relates to a method for producing activated carbon, and more specifically, by easily producing activated carbon with developed mesopores using pitch as a raw material using low-cost by-products of petrochemical and refining processes, thereby reducing the unit cost of raw material supply and demand. Activated carbon produced economically has a high total pore volume and mesopore fraction, and is manufactured by a method for producing activated carbon with developed mesopores that can be usefully used for water purification, capacitors, CDI, etc., and the above production method. It is about activated carbon.

Description

Method of producing activated carbon with developed mesoporous {Method of Preparing Highly Mesoporous Activated Carbon}

The present invention relates to a method of producing activated carbon, and more specifically, to a method of producing activated carbon capable of producing activated carbon with developed mesopores using pitch as a raw material using low-cost by-products of petrochemical and refining processes, and the production thereof. It relates to activated carbon produced by a method.

Activated carbon has different industrial applications depending on its pore characteristics. Activated carbon with developed micropores is widely used as gas-phase activated carbon. Gas-phase activated carbon is commonly used for the purpose of adsorbing harmful gases, and activated carbon with developed mesopores is used for liquid-phase activated carbon. Liquid-phase activated carbon is used for water purification, capacitors, and CDI (capacitive deionization). It is used, etc.

Such activated carbon can be manufactured from various precursors, and precursor materials include palm shells, wood, and coal. Recently, as the supply of existing precursor materials for activated carbon (such as palm shells, wood, and coal) has become difficult, materials different from existing precursors are being researched. In particular, biomass-based activated carbons are being studied a lot, but they have a high impurity content and are difficult to control pores, so much research is needed before they can be used in industry.

Pitch is a soft material obtained through polymerization of organic compounds containing petroleum and coal residues at 300 ℃ to 500 ℃. It is a carbon material intermediate in which crystals are formed during the heat treatment process. In addition, it is a thermoplastic material with a wide molecular weight range and has the advantage of making it easy to control the pore structure by utilizing these characteristics.

However, when manufacturing activated carbon using conventional technology, only activated carbon with developed micropores can be manufactured. Because pitch contains a high proportion of carbon due to its nature, crystallinity of carbon develops upon activation at the activation temperature. Therefore, there were limitations in producing activated carbon with developed mesopores.

Korean Patent Publication No. 2022-0085479 (Publication date: 2022.06.22.) Korean Patent No. 10-2037463 (Announcement date: 2019.11.26.)

The main purpose of the present invention is to solve the above-mentioned problems, a method for producing activated carbon with developed mesopores that can easily produce activated carbon with developed mesopores using pitch as a raw material, and the manufacturing method. The purpose is to provide activated carbon with developed mesopores manufactured by .

In order to achieve the above object, one embodiment of the present invention includes the steps of (a) heat treating pitch in an oxidizing gas atmosphere; and (b) activating the heat-treated pitch using an activator in an oxidizing gas atmosphere.

In a preferred embodiment of the present invention, step (a) may be characterized in that heat treatment is performed at 200°C to 400°C for 5 minutes to 30 hours.

In a preferred embodiment of the present invention, the oxidizing gas in step (a) may be one or more selected from the group consisting of air, O2, NOx, SOx, CO, CO2, and H2O.

In a preferred embodiment of the present invention, the activator may be one or more selected from the group consisting of KOH, NaOH, ZnCl ₂ and H ₃ PO ₄ .

In a preferred embodiment of the present invention, the weight ratio of pitch and activator in step (b) may be 1:0.5 to 4.

In a preferred embodiment of the present invention, step (b) may be characterized in that the activation is performed at 600°C to 900°C in an oxidizing gas atmosphere.

In a preferred embodiment of the present invention, the oxidizing gas in step (b) may be one or more selected from the group consisting of air, O ₂ , NOx, SOx, CO, CO ₂ and H ₂ O. .

In a preferred embodiment of the present invention, the pitch may be selected from the group consisting of petroleum-based pitch, coal-based pitch, and mixtures thereof, and may be characterized as having a softening point of 70°C to 350°C.

Another embodiment of the present invention provides activated carbon with developed mesopores, which is produced by the above production method.

In another preferred embodiment of the present invention, the activated carbon has a total pore volume of 0.60 cm ³ /g or more, a specific surface area of 2000 m ² /g or less, and a micropore volume of 0.45 cm ³ /g with a pore size of less than 2 nm. g or less, and the fraction of micropores with a pore size of less than 2 nm may be less than 80.0%.

The method for producing activated carbon according to the present invention is to easily produce activated carbon with developed mesopores by using pitch as a raw material using low-cost by-products from petrochemical and refining processes, thereby producing active carbon that is economical in terms of raw material supply and demand costs. Carbon has a high total pore volume and mesopore fraction, so it can be usefully used for water purification, capacitors, and CDI (Capacitive Deionization).

1 is a schematic flowchart of a method for producing activated carbon according to an embodiment of the present invention.
Figure 2 is a graph of the nitrogen adsorption and desorption isotherm measurement results of activated carbon prepared in Examples 1 to 3 and Comparative Examples 1 and 2.
Figure 3 is a graph of the pore size distribution measurement results of activated carbon prepared in Examples 1 to 3 and Comparative Examples 1 and 2.

Unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as commonly understood by a person skilled in the art to which the present invention pertains. In general, the nomenclature used herein is well known and commonly used in the art.

Terms such as “comprises,” “comprises,” or “has” used in the specification refer to the presence of features, values, steps, operations, components, parts, or combinations thereof described in the specification. It does not exclude the possibility that other features, values, steps, operations, components, parts, or combinations thereof that are not described may exist or be added.

The pore size described in this specification is based on the pore diameter standards of the International Union of Pure and Applied Chemistry (IUPAC): less than 2 nm is a micropore, 2 nm to 50 nm is a mesopore, and more than 50 nm is an atmospheric pore. It means macropore.

The present invention includes the steps of (a) heat treating pitch in an oxidizing gas atmosphere; and (b) activating the heat-treated pitch using an activator in an oxidizing gas atmosphere. A method for producing activated carbon with developed mesopores, and a meso-porous material produced by the method. It is about activated carbon with developed pores.

Generally, in the production of activated carbon using petroleum-based and/or coal-based pitch, the gas used for activation is an inert gas such as nitrogen or argon to maintain an inert atmosphere. However, during this process, pitch is dehydrogenated by heat, forming more crystalline activated carbon, which results in most of the micropores having a pore diameter of less than 2 nm.

Accordingly, in the present invention, in the production of activated carbon using pitch, heat treatment is performed in an oxidizing gas atmosphere before activation using an activator, and at the same time, activation is performed in an oxidizing gas atmosphere, so that many benzene rings inside are connected by strong covalent bonds. By introducing various oxygen functional groups to the surface of the pitch forming the laminated structure, cross-linking during activation is prevented and crystallization can be prevented, thereby increasing the mesopore (mesopore) ratio of the activated carbon produced. .

Hereinafter, preferred embodiments of the method for producing activated carbon according to the present invention will be described in detail with reference to the attached drawings. 1 is a schematic process diagram of a method for producing activated carbon according to an embodiment of the present invention.

Referring to Figure 1, in the method for producing activated carbon with developed mesopores according to an embodiment of the present invention, pitch, which is a raw material, is first heat-treated in an oxidizing gas atmosphere [step (a)].

The pitch is a by-product from petroleum and coal-based oils, and can be easily and inexpensively obtained by polymerizing organic compounds containing petroleum-based and coal-based residues at 300°C to 500°C, thereby reducing manufacturing costs and reducing carbon It has a high content and low volatility, so it can be preferably used as a raw material for activated carbon. Moreover, the pitch enables higher activation yield and pore property control than conventional activated carbon manufacturing technology through the oxidation process.

In the present invention, there is no particular limitation on the types of petroleum-based pitch and coal-based pitch, and all petroleum-based pitch and coal-based pitch used in the technical field can be used. However, preferably, pitch having a softening point of 70°C to 350°C may be used in terms of thermal oxidation. In the case of pitch with a softening point of less than 70 ℃, the pitch may be softened during the process of introducing oxygen functional groups, which may cause a problem of lower yield. In the case of pitch with a softening point of more than 350 ℃, the introduction of functional groups is significantly reduced, leading to an increase in the mesoporous ratio. Problems may arise where it is difficult to manufacture activated carbon.

The pitch is heat treated in an oxidizing gas atmosphere before the activation step using an activator to form various oxygen functional groups on the pitch surface, making it easy to activate during the activation step and preventing crystallization, thereby increasing the mesoporous ratio of activated carbon. there is.

The heat treatment can be performed in an oxidizing gas atmosphere at 200°C to 400°C for 5 minutes to 30 hours, and is preferably performed at 200°C to 300°C for 1 hour to 24 hours.

If the heat treatment temperature is less than 200 ℃, sufficient oxidation does not occur and mesopores in the range of 2 nm to 50 nm are not formed on the pitch surface during the activation stage. If the heat treatment temperature exceeds 400 ℃, the pitch is damaged due to excessive oxidation reaction. Sintering (burn off) may cause a problem in which yield is significantly reduced.

In addition, if the heat treatment time is less than 5 minutes, sufficient oxidation does not occur and macropores cannot be formed in the activation step, and if it exceeds 30 hours, the pitch is sintered due to excessive oxidation reaction, resulting in a significant decrease in yield. Problems may arise.

The heat treatment is performed in an atmosphere in which an oxidizing gas is supplied, and the oxidizing gas is one selected from the group consisting of oxidizing gases such as air, O ₂ , NOx, SOx, CO, CO ₂ and H ₂ O (water vapor). It may be more than that, and preferably it may be air.

The amount of oxidizing gas supplied during the heat treatment may be 50 cc/min to 500 cc/min based on a 1L reactor. If the oxidizing gas supply amount is less than 50 cc/min, the oxidizing gas content capable of reacting with pitch is insufficient and the reaction must take a long time, resulting in an increase in process cost, and if it exceeds 500 cc/min, there is a problem with yield. This may occur.

Thereafter, the pitch heat-treated in the oxidizing gas atmosphere is activated using an activator in the oxidizing gas atmosphere [step (b)].

The activation step is a step of producing activated carbon by forming pores in the oxidized pitch and activating it at the same time. It is a generally known physical activation method using an activator such as carbon dioxide or steam, or a chemical activation method using an activator such as potassium hydroxide. It may be performed by an activation method, but is preferably performed by a chemical activation method using an activator such as potassium hydroxide.

The chemical activation method using an activator such as potassium hydroxide has a simpler manufacturing process than the physical activation method and can form a higher specific surface area while improving yield, and the pitch heat-treated in an oxidizing gas atmosphere has developed mesopores. It can be manufactured from activated carbon.

At this time, the activator that can be used may be potassium hydroxide (KOH), sodium hydroxide (NaOH), phosphoric acid (H ₃ PO ₄ ), zinc chloride (ZnCl ₂ ), etc., and preferably potassium hydroxide (KOH). .

The content ratio of the activator to the pitch heat-treated in an oxidizing gas atmosphere can be mixed at a weight ratio of 1:0.5 to 4 (pitch heat-treated in an oxidizing gas atmosphere: activator), preferably 1:1 to 2. there is. As the ratio of the activator increases, higher specific surface area characteristics can be imparted, but if mixed beyond the above numerical range, it may cause collapse of the pitch pore structure. In addition, if the ratio of the activator is less than the above numerical range, pore formation may be difficult, which may result in the inability to manufacture activated carbon with developed medium pores.

Meanwhile, the activation step can be performed by supplying an activator to pitch heat-treated in an oxidizing gas atmosphere at 600 ° C to 900 ° C for 30 minutes to 3 hours, but considering the content of heat-treated pitch, degree of oxidation, etc. This allows you to control the activation temperature and time range. If the activation step is performed under the conditions within the above range, activated carbon with high yield and developed mesoporosity can be easily produced without excessive energy consumption.

At this time, the activating atmosphere is performed in an atmosphere in which an oxidizing gas is supplied, and the oxidizing gas is one selected from the group consisting of oxidizing gases such as air, O ₂ , NOx, SOx, CO, CO ₂ and H ₂ O (water vapor). It may be more than one species, and preferably air.

The oxidizing gas supply amount may be 50 cc/min to 500 cc/min based on a 1L reactor. If the oxidizing gas supply amount is less than 50 cc/min, it is insufficient to form mesopores due to insufficient oxygen content introduced into the pitch, and if it exceeds 500 cc/min, yield problems may occur due to burn-off of the pitch. there is.

In the present invention, by performing the activation in an oxidizing gas atmosphere, crystalline growth can be inhibited and carbonaceous materials having a structure favorable for mesopore formation can be formed.

The activated carbon produced thereafter can be dried to remove moisture after repeated washing and filtration steps. The washing and filtration can be repeated until the pH of the produced activated carbon reaches 7, and drying can be performed in a dryer at a temperature of 80°C to 200°C for 10 to 15 hours. At this time, if the drying temperature is less than 80°C, drying may not be sufficient, and if it exceeds 200°C, the pore structure may be affected due to changes in the surface chemical properties of the activated carbon.

Activated carbon produced by this manufacturing method has a total pore volume of 0.60 m ³ /g or more, preferably 0.63 cm ³ /g to 0.90 cm ³ /g, and a specific surface area of 2000 m ² /g or less. is 1000 m ² /g to 1200 m ² /g, the volume of micropores with a pore size of less than 2 nm is 0.45 cm ³ /g or less, 0.10 cm ³ /g to 0.45 cm ³ /g, and the volume of micropores with a pore size of less than 2 nm is 0.45 cm 3 /g or less. With a micropore fraction of 80.0% or less, preferably 10.0% to 70.0%, mesopores are developed and can be usefully used for water purification, capacitors, CDI (Capacitive Deionization), etc.

Hereinafter, for a more detailed description of the present invention, examples will be given. However, the following examples are only preferred examples of the present invention and the present invention is not limited to the following examples.

<Examples 1 to 3>

After preparing 20 g of petroleum pitch with a softening point of 250°C, the heat treatment step and the activation step were sequentially performed under the conditions shown in Table 1 below to obtain activated carbon, and the obtained activated carbon was washed with water until the pH reached 7. and filtration were repeated, and then dried at 100° C. to prepare activated carbon. At this time, in the activation step, KOH was used as an activator, and the content ratio of pitch and KOH was 1:1 based on weight ratio.

<Comparative Examples 1 and 2>

Activated carbon was prepared in the same manner as in Example 1, but under the conditions shown in Table 1 below.

division (a) Heat treatment step (b) Activation phase gas
type gas
Injection amount
(cc/min) heat treatment
temperature
(℃) heat treatment
hour
(h) gas
type gas
Injection amount
(cc/min) heat treatment
temperature
(℃) heat treatment
hour
(h) Example 1 air 100 300 6 air 100 800 One Example 2 air 100 300 12 air 100 800 One Example 3 air 100 300 24 air 100 800 One Comparative Example 1 - - - - N ₂ 100 800 One Comparative Example 2 - - - - air 100 800 One

<Experimental Example 1: Measurement of physical properties of activated carbon>

The specific surface area, total pore volume, micropore volume, and micropore fraction of the activated carbon prepared in Examples 1 to 3 and Comparative Examples 1 and 2 were measured by the following methods, and the results are shown in Table 2 and Figures 2 and 3. .

(1) Specific surface area (BET Surface area)

The specific surface area, total pore volume, micropore volume, and micropore fraction of the activated carbon prepared in Examples 1 to 3 and Comparative Examples 1 and 2 were measured by the following methods, and the results are shown in Table 2 and Figures 2 and 3. .

(1) Specific surface area (BET Surface area)

ASAP2020 equipment was used for each of the activated carbons prepared in Examples 1 to 3 and Comparative Examples 1 and 2, and the amount of nitrogen gas adsorbed according to the change in relative pressure at the liquid nitrogen temperature (77 K) was measured. The specific surface area was measured using the Brunauer-Emmett-Teller equation using the nitrogen adsorption isotherm obtained through this.

(2) Micropore volume

For each of the activated carbons prepared in Examples 1 to 3 and Comparative Examples 1 and 2, the micropore volume was calculated using the t-polt method using the nitrogen adsorption isotherm.

(3) total pore volume and micropore fraction

For each of the activated carbons prepared in Examples 1 to 3 and Comparative Examples 1 and 2, the micropore fraction was measured according to the formula below, and the total porosity (%) was calculated using the mercury adsorption method.

Micropore fraction (%) = (micropore volume/total pore volume) × 100

division specific surface area
( ^m2 /g) Total pore volume
( ^cm3 /g) Micropore volume
( ^cm3 /g) Micropore fraction
(%) Example 1 1165 0.8726 0.3865 44.3 Example 2 1077 0.6388 0.3987 62.4 Example 3 1186 0.8166 0.4130 50.6 Comparative Example 1 1367 0.5105 0.4779 93.6 Comparative Example 2 1317 0.5599 0.4756 84.9

As shown in Figure 2, compared to the activated carbon prepared in Comparative Examples 1 and 2, a very large hysteresis phenomenon was observed in the activated carbon prepared in Examples 1 to 3, confirming that it was an activated carbon with mesopores formed, and Figure 3 As shown, in the case of the activated carbon prepared in Examples 1 to 3, it was confirmed that pores with a size of 4 nm to 7 nm were increased compared to the activated carbon prepared in Comparative Examples 1 and 2.

In addition, as shown in Table 2, in the case of the activated carbon prepared in Examples 1 to 3, the micropore fraction was found to be lowered from 84.9% or more to 62.4% or less.

Therefore, it was confirmed that the method for producing activated carbon according to the present invention can easily produce activated carbon with developed mesopores by using pitch, which is an inexpensive by-product of petrochemical and refining processes, as a raw material.

As described above, although the present invention has been described with limited examples and drawings, the present invention is not limited thereto, and the technical idea of the present invention will be understood by those skilled in the art to which the present invention pertains. Of course, various modifications and variations are possible within the scope of equivalency of the patent claims described in .

Claims (10)

(a) heat treating the pitch in an oxidizing gas atmosphere; and
(b) activating the heat-treated pitch using an activator in an oxidizing gas atmosphere. A method for producing activated carbon with developed mesopores, comprising:
According to paragraph 1,
Step (a) is a method of producing activated carbon with developed mesopores, characterized in that the heat treatment is performed at 200 ℃ ~ 400 ℃ for 5 minutes ~ 30 hours.
According to paragraph 1,
The oxidizing gas in step (a) is a method for producing activated carbon with developed mesopores, characterized in that at least one selected from the group consisting of air, O ₂ , NO _x , SO _x , CO, CO ₂ and H ₂ O .
According to paragraph 1,
The activator is a method of producing activated carbon with developed mesopores, characterized in that at least one selected from the group consisting of KOH, NaOH, ZnCl ₂ and H ₃ PO ₄ .
According to paragraph 1,
A method for producing activated carbon with developed mesopores, characterized in that the weight ratio of pitch and activator in step (b) is 1:0.5 to 4.
According to paragraph 1,
Step (b) is a method of producing activated carbon with developed mesopores, characterized in that the activation is performed at 600 ° C to 900 ° C in an oxidizing gas atmosphere.
According to paragraph 1,
The oxidizing gas in step (b) is a method for producing activated carbon with developed mesopores, characterized in that at least one selected from the group consisting of air, O ₂ , NO _x , SO _x , CO, CO ₂ and H ₂ O .
According to paragraph 1,
The pitch is selected from the group consisting of petroleum-based pitch, coal-based pitch and mixtures thereof, and has a softening point of 70 ° C to 350 ° C. A method of producing activated carbon with developed mesopores.
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