KR102544657B1 - The Method of Producing Active Carbon by Using Physical Activation and the Active Carbon Produced by the Same - Google Patents

Abstract

The present invention comprises the steps of (a) introducing an oxygen functional group into pitch to prepare an oxidized pitch for activation; (b) carbonizing the oxidized pitch to produce coke; (c) The coke is physically activated to have a specific surface area of 550 to 2100 m 2 /g and a micro pore volume of 0.2 cm ³ /g or more. Preparing activated carbon having a micro pore content of 82 to 99%.

Description

The Method of Producing Active Carbon by Using Physical Activation and the Active Carbon Produced by the Same}

The present invention relates to a method for producing activated carbon using physical activation and an activated carbon produced thereby, and more particularly, to produce coke for physical activation with reduced crystallinity by imparting an oxygen functional group to pitch, and then physically activating the same. It relates to a method for preparing activated carbon having a high micropore ratio and a high specific surface area.

Activated carbon is a porous carbon material produced by adsorbing substances harmful to the human body. Innumerable pores are developed inside. The internal surface area of the pore layer is remarkably large, and the surface has hydrophilicity for impurities, so it has good solubility as an adsorbed material. Removal of components is accomplished by adsorption of soluble components to the large inner surfaces of the pores.

Activated carbon is used for various purposes depending on the size of the pores. In particular, activated carbon containing a large number of microscopic pores is required to remove pollutants in the air, such as gas causing sick house syndrome and fine dust, which have recently become a problem. .

As a raw material for producing activated carbon, coal occupies 58% as of 2014, char made from trees such as sawdust accounts for 21%, coconut shells account for 19%, and other materials such as phenolic resin account for 2%. . As China (44.7%, as of 2017), which has the highest coal production in the world, has recently regulated coal production, many problems are occurring in the supply and demand of activated carbon raw materials.

Therefore, it is necessary to diversify the raw material of activated carbon. Pitch is a raw material of carbon material produced from coal tar, a by-product of petroleum residue, which is a petrochemical by-product, or a by-product of the carbonization process of coal, and can be applied as a raw material of activated carbon. Therefore, the production of activated carbon using pitch is a way to solve both the industrial by-product disposal problem and the activated carbon raw material supply and demand problem.

Activated carbon forms a wide range of pore structures including macro pores of 50 nm or more, meso pores of 2 to 50 nm, and micro pores of 2 nm or less in size through the carbonization and activation processes. will do

The activation process is classified into a chemical activation method and a physical activation method according to the type of activator. Chemical activation uses KOH, NaOH, etc. as an activator. It has a high specific surface area and can develop micropores that are easy to remove contaminants in the air. Physical activation uses CO2, water vapor, etc. as an activator, and although the specific surface area is low and it is difficult to develop micropores, the price of the activator is low, so industrial utilization is high.

As a prior art related to this, Korean Patent Publication No. 10-2020-0055698 describes activated carbon having micropores prepared using an alkali activator, and Korean Patent Publication No. 10-2020-0025804 discloses carbon such as pitch. A method for producing activated carbon having micropores through a material carbonization process and a chemical activation process using an alkali hydroxide is described.

However, in the prior literature, an expensive activator is used using a chemical activation method, and a process of removing the activator after reaction is added, so that the production cost of activated carbon is high and mass production is difficult. Therefore, activated carbon manufactured by a chemical activation method is used for special purposes such as electric double layer capacitors with low usage.

On the other hand, activated carbon for removing environmental pollutants requires a physical activation method that is inexpensive and easy to mass-produce because inexpensive activated carbon is used in large quantities. In addition, in order to purify indoor air, there is a need for activated carbon having micro pores that can easily remove contaminants in the air.

At the present time, when the problem of supply and demand of raw materials for activated carbon is emerging as in the above-mentioned issue, a physical activation method using pitch-based coke to solve the problem of supply and demand of activated carbon raw materials, industrial waste treatment, and activated carbon for indoor air quality purification. Activated carbon with micro pores is highly valuable, and the technology to implement it is very important.

Korean Patent Publication No. 10-2020-0055698 (May 21, 2020) Korean Patent Publication No. 10-2020-0025804 (2020.03.10)

An object of the present invention is to provide an efficient method for solving the problem of supply and demand of activated carbon raw materials, producing coke through a carbonization process of pitch, and mass-producing activated carbon through a physical activation method thereof.

Another object of the present invention is to provide a method for producing coke with improved isotropy by introducing an oxygen functional group into pitch.

In addition, another object of the present invention is to provide a method for preparing activated carbon having micropores that can easily remove contaminants in the air using a physical activation method.

In order to achieve the above object, the present invention comprises the steps of (a) introducing an oxygen functional group into pitch to produce oxidized pitch; (b) carbonizing the oxidized pitch to produce coke; (c) The coke is physically activated to have a specific surface area of 550 to 2100 m 2 /g and a micro pore volume of 0.2 cm ³ /g or more. It provides a method for producing activated carbon comprising the steps of preparing activated carbon having a micro pore content of 82 to 99%.

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.

In a preferred embodiment of the present invention, step (a) may be treated by selecting any one or more of thermal oxidation, acid treatment, and plasma treatment.

In a preferred embodiment of the present invention, the pitch oxidized in step (a) may have an oxygen/carbon content weight ratio greater than 0.2.

In a preferred embodiment of the present invention, step (a) may be performed by contacting the pitch with a gas containing oxygen at a temperature of 150 to 400 ° C. for 1 to 12 hours.

In a preferred embodiment of the present invention, the defect ratio [defect intensity (Ig) / crystallinity intensity (Ig) of Raman analysis] of the carbonized coke in step (b) may be greater than 0.93.

In a preferred embodiment of the present invention, step (b) may be performed by contacting the oxidized pitch with an inert gas at a temperature of 800 to 1200 ° C.

In a preferred embodiment of the present invention, step (c) may be performed by contacting the coke with a physical activator at a temperature of 800 to 1200 ° C. for 30 minutes to 5 hours.

In a preferred embodiment of the present invention, the physical activator may be selected from the group consisting of carbon dioxide (CO2), water vapor, and mixtures thereof.

In addition, another embodiment of the present invention provides activated carbon prepared by the method for preparing activated carbon.

According to the present invention, it is possible to solve the problem of supply and demand of activated carbon raw materials by using pitch as a raw material of activated carbon, and to manufacture activated carbon that is inexpensive and easy to mass-produce using a physical activation method.

In addition, by preparing activated carbon having a high micro pore ratio, activated carbon that can easily remove contaminants in the air can be prepared.

The effects of the present invention are not limited to those mentioned above, and other effects not mentioned will be clearly understood by those skilled in the art from the description below.

1 is a graph showing nitrogen adsorption isotherms of activated carbons prepared from Examples and Comparative Examples.
2 is a graph showing XRD analysis results of cokes prepared from Examples 1, 3, and Comparative Example 1.
Figure 3 is a graph showing the Raman analysis results of the coke prepared from Example 1, Example 3, Comparative Example 1.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In general, the nomenclature used herein is one well known and commonly used in the art.

Throughout the present specification, when a certain component is said to "include", it means that it may further include other components without excluding other components unless otherwise stated.

In order to manufacture activated carbon having a high specific surface area and micro pore ratio, the present invention manufactures coke for activated carbon having a high oxygen content and low crystallinity through a pitch oxidation process, and physically activating it. A manufacturing method is provided.

In one aspect of the present invention, (a) preparing an oxidized pitch by introducing an oxygen functional group into the pitch; (b) carbonizing the oxidized pitch to produce coke; (c) The coke is physically activated to have a specific surface area of 550 to 2100 m 2 /g and a micro pore volume of 0.2 cm ³ /g or more. It provides a method for producing activated carbon comprising the steps of preparing activated carbon having a micro pore content of 82 to 99%.

The pitch used in step (a) may be selected from the group consisting of petroleum-based pitch, coal-based pitch, and mixtures thereof.

The coal-based pitch is prepared using coal tar generated in the carbonization process of coal, and has the advantage of high carbonization yield when producing activated carbon due to its high aromatic compound content, but high content of impurities such as metal oxides, metals, sulfur, and nitrogen. There are restrictions on use.

On the other hand, the petroleum pitch is prepared using petroleum residue generated in the distillation process of crude oil, and has the advantage of having a relatively low content of impurities, but has the disadvantage of low carbonization yield when producing activated carbon due to the low content of aromatic compounds. .

Therefore, in order to improve the carbonization yield of petroleum pitch, an oxidation process capable of attacking the aliphatic chain of pitch to lower the hydrogen content and introducing various oxygen functional groups such as C-O, C=O, O=C-O, and C-O-C is required. .

The oxidation process of step (a) is a step of producing oxidized pitch by introducing an oxygen functional group into pitch, and it can be oxidized by thermal oxidation, acid treatment, ozone treatment, or plasma treatment, and in addition, these complex or step-by-step treatments It may be oxidized by a method, and preferably a thermal oxidation process may be used.

At this time, it is preferable that the gas for introducing the oxygen functional group in the thermal oxidation process proceeds in an oxygen or air atmosphere, and it is more preferable to use air industrially.

At this time, the oxygen functional group is introduced so that the oxygen / carbon content weight ratio of the oxidized pitch is greater than 0.20, and if the oxygen / carbon ratio is less than 0.20, oxygen is not sufficiently introduced, so that defects in coke do not develop, which is necessary for activation. There is a problem in that active points are reduced and activation does not occur due to this. The oxygen/carbon content weight ratio of the oxidized pitch is preferably greater than 0.2 and may be less than 0.31.

In addition, the thermal oxidation process may be performed by contacting the pitch with a gas containing oxygen for 1 to 12 hours at a temperature of 150 to 400 ° C., preferably, the pitch at a temperature of 300 to 400 ° C. for 1 to 12 hours It can be carried out by contacting with a gas containing oxygen during the process.

Here, when the temperature of the thermal oxidation process is less than 150 ° C or the reaction time is less than 1 hour, it is difficult to introduce sufficient oxygen functional groups and it is difficult to lower the crystallinity of coke for physical activation, and the treatment temperature exceeds 400 ° C or the reaction If the time exceeds 12 hours, there is a problem in that the yield of the step of introducing an oxygen functional group is lowered due to peroxidation. When the oxidation temperature exceeds 400° C., it is difficult to introduce oxygen functional groups because oxygen in the pitch and air excessively causes a combustion reaction and is converted into CO or CO 2 .

Subsequently, the carbonization process of step (b) is a step of preparing coke by heat-treating the oxidized pitch containing a large amount of oxygen functional groups.

The pitch oxidized in the carbonization process may be heat-treated to produce coke such that a defect ratio (Id/Ig) obtained from the defect strength (Ig) and crystallinity strength (Ig) of Raman analysis is greater than 0.93.

If the defect ratio is less than 0.93, the crystallinity of the coke increases and the active points for forming the micropores decrease, making it difficult to form the micropores.

The carbonization process may be performed by contacting the oxidized pitch with an inert gas at a temperature of 800 to 1200 ° C., and the temperature of the carbonization process is preferably performed at the same temperature as the physical activation.

If the temperature of the carbonization process is lower than 800 ° C, sufficient energy for activation is not supplied and micropores are not formed. There is a problem in that the yield is low because the amount of activated carbon to be out) increases.

Physical activation may be performed after cooling the coke after the carbonization process, or the physical activation process may be directly performed by changing the carbonization process atmosphere gas into an activation gas without a separate cooling process.

That is, a separate holding time is not required after reaching the target temperature of the carbonization process. Here, when the target temperature is maintained for a certain time, the crystallinity of the coke is improved, so that it is difficult to create micro pores.

In addition, the inert gas used in the carbonization process may be selected from the group consisting of nitrogen, argon, and mixtures thereof.

The step (c) is a step of physically activating coke having a defect ratio (Id/Ig) greater than 0.93, and by activating coke having a low crystallinity of the coke, the specific surface area is 550 to 2100 m/g, and the micropores ( The volume of micro pore) is 0.2 cm ³ /g or more. It is possible to manufacture activated carbon containing 82 to 99% of micropores.

Here, the activation of coke with low crystallinity begins when a chemical reaction occurs between the surface of the coke and the activator, and this chemical reaction converts carbon into CO or CO2 gas and removes it, and the removed site acts as a defect. This causes a continuous reaction to form pores. Therefore, the more defects on the surface of coke or the lower the crystallinity, the more advantageous it is to form pores.

The physical activation process may be performed by contacting the coke with a physical activator at a temperature of 800 to 1200 ° C. for 30 minutes to 5 hours, and preferably, the coke is physically activated at a temperature of 1000 to 1200 ° C. for 30 minutes to 5 hours. It can be carried out by contacting with an activator.

When the temperature of the physical activation process is less than 800 ° C or the reaction time is less than 30 minutes, there is a disadvantage in that micro pores are not sufficiently formed due to insufficient reaction and a low specific surface area, and the activation temperature is 1200 ° C. or when the reaction time exceeds 5 hours, there is a problem in that the specific surface area and yield are rather reduced because overactivation occurs and the generated pores collapse.

In this case, the physical activator may be selected from the group consisting of carbon dioxide (CO 2 ), water vapor, and mixtures thereof, and may preferably be carbon dioxide (CO 2 ).

The volume of the micropores of the activated carbon prepared in step (c) may be 0.2 cm ³ /g or more, preferably 0.6 cm ³ /g or more.

In addition, the activated carbon prepared in step (c) may have a micro pore content of 82 to 99%.

In addition, the present invention provides activated carbon having a very large specific surface area and a very high content of micropores, prepared by the method for preparing activated carbon.

Therefore, the activated carbon according to the present invention has a very large specific surface area and a high micropore content, so it can be used for adsorbing/absorbing harmful organic or gaseous molecules or metal elements. Specifically, it can be used for water treatment and purification, air/gas treatment and It can be used for refining, cosmetics, gold recovery, and mercury removal.

In addition, the activated carbon according to the present invention can be used as a catalyst support supporting a large amount of catalytic nanoparticles in addition to applications for chemical adsorption/conversion of harmful substances, and can also be applied to medical and fuel cells.

Hereinafter, the present invention will be described in more detail through examples. However, the following examples are merely illustrative of the present invention, and the present invention is not limited by the following examples.

Example 1

To prepare activated carbon, isotropic pitch with a softening point of 250 ° C was selected as a raw material and three-step treatment was performed. The first step of introducing an oxygen functional group into the pitch was performed by heat-treating the pitch while flowing air at a flow rate of 100 cc / min at 320 ° C. for 8 hours, and oxidized pitch was prepared through the first step treatment. Step 2 was carried out by heating the oxidized pitch at a rate of 10 ° C per minute to 1000 ° C in an inert atmosphere and then cooling without holding time to prepare coke for activated carbon. In the third step, CO2 was used as an activator, and the activating gas was injected at a flow rate of 100 cc/min. Step 3 was performed by heat-treating the coke at 900 ° C. for 3 hours in an activated gas atmosphere, and activated carbon having a high specific surface area and micropore ratio was prepared.

Example 2

Activated carbon was prepared in the same manner as in Example 1, except that the pitch activation temperature was set to 900 ° C in Example 1.

Example 3

Activated carbon was prepared in the same manner as in Example 1, except that the oxidation temperature of the pitch was set to 240 ° C and the activation temperature was set to 900 ° C in Example 1.

Example 4

Activated carbon was prepared in the same manner as in Example 1, except that the pitch activator in Example 1 was used as steam and the activation temperature was set to 900 ° C.

Example 5

Activated carbon was prepared in the same manner as in Example 1, except that the oxidation temperature of the pitch was set to 400 ° C. in Example 1.

Comparative Example 1

A carbon material for an anode material was prepared in the same manner as in Example 1, except that the step of introducing an oxygen functional group into the pitch was omitted in Example 1.

Comparative Example 2

Activated carbon was prepared in the same manner as in Example 1, except that the oxidation temperature of the pitch was set to 120 ° C in Example 1.

Comparative Example 3

Activated carbon was prepared in the same manner as in Example 1, except that the pitch activation temperature was set to 1300 ° C in Example 1.

Comparative Example 4

Activated carbon was prepared in the same manner as in Example 1, except that the pitch activation temperature was set to 700 ° C in Example 1.

Experimental example

(1) The pore characteristics of the activated carbons prepared in Examples and Comparative Examples were measured with a specific surface area analyzer (Brunauer-Emmett-Teller Analyzer, BET, ASAP 2420).

(2) The carbon, hydrogen, and oxygen content ratios of the thermally oxidized pitch were measured using an Elemental Analyzer (EA, Thermo Scientific Flash 2000).

(3) The crystallinity and defect ratio (Id/Ig) of coke is measured with an X-ray Diffractometer (XRD, Rigaku D/Max 2200V) and Raman spectroscopy (Bruker FRA 106/S) did

Hereinafter, characteristics of activated carbon prepared according to Examples and Comparative Examples will be compared and evaluated.

Pore characteristics and specific surface areas of the activated carbons prepared in the above Examples and Comparative Examples were evaluated using nitrogen adsorption isotherms, and the results are shown in Figure 1 and Table 1. The activated carbon prepared in Example 1 had a high specific surface area of 1519.6 m2/g and a high micropore ratio of 95.6%. Compared to Example 1, in the case of Example 2 activated at a lower temperature, the specific surface area was reduced to 729.6 m / g, but a high micropore ratio (98.7%) was maintained. In the case of Example 3 in which the oxidation temperature was 240° C., the ratio of micropores was maintained while the specific surface area was reduced to 553.3 m/g. In the case of Comparative Example 1, it was confirmed that pores were not formed with a specific surface area of 1.9 m2/g.

In addition, in order to confirm the effect of the pitch oxidation process on the defects of coke, the oxidized pitch and coke prepared from Examples 1, 3, and Comparative Example 1 were analyzed.

[Table 1] Specific surface area and pore characteristics of the prepared activated carbon

The characteristics of the oxidized pitch (pitch with an oxygen functional group introduced) prepared in Examples 1, 3, and Comparative Example 1 were evaluated for the content of oxygen using elemental analysis, and the results are shown in Table 2 . The carbon content of the pitch of Comparative Example 1 without oxidation treatment was the highest at 94.1%, and contained 5.7% of hydrogen and 0.2% of oxygen. As the thermal oxidation treatment temperature increased, the content of carbon and hydrogen decreased while the ratio of oxygen increased. Example 1, which had the highest thermal oxidation treatment temperature, had the highest oxygen content.

[Table 2] Results of oxygen content element analysis of thermally oxidized pitch

The characteristics of the cokes prepared through Example 1, Example 3, and Comparative Example 1 were evaluated for crystallinity using XRD and Raman, and the respective results are shown in FIGS. 2 and 3. From the Raman results, Id/Ig representing the degree of defect was calculated, which is shown in Table 3.

Figure 2 shows the XRD results of the cokes prepared through Example 1, Example 3, and Comparative Example 1, and it was confirmed that the intensity of the peak representing the 002 plane decreased as the thermal oxidation treatment temperature increased. A decrease in the intensity of the peak means that the crystallinity is poor, and accordingly, the crystallinity of Example 1 was the lowest.

3 and Table 3 show the results of Raman analysis of coke prepared through Example 1, Example 3, and Comparative Example 1. As a result of Raman analysis, Example 1 showed the highest Id/Ig, indicating the ratio of defects, and Comparative Example 1 showed the lowest. It was confirmed that the coke prepared from Example 1 had the most defects.

[Table 3] Coke defects

Having described specific parts of the present invention in detail above, it will be clear to those skilled in the art that these specific descriptions are only preferred embodiments, and the scope of the present invention is not limited thereby. will be. Accordingly, the substantial scope of the present invention will be defined by the appended claims and their equivalents.

Claims (10)

(a) preparing an oxidized pitch for activation by introducing an oxygen functional group into the pitch;
(b) carbonizing the oxidized pitch to produce coke;
(c) The coke is physically activated to have a specific surface area of 550 to 2100 m2/g and a micro pore volume of 0.2 cm3/g or more. Preparing activated carbon having a micro pore content of 82 to 99% with respect to the total pore volume;
Step (a) is carried out by contacting the pitch with a gas containing oxygen at a temperature of 150 to 400 ° C. for 1 to 12 hours,
Step (c) is a method for producing activated carbon, characterized in that carried out by contacting the coke with a physical activator at a temperature of 800 to 1200 ° C. for 30 minutes to 5 hours.
According to claim 1,
The pitch is a method for producing activated carbon, characterized in that selected from the group consisting of petroleum-based pitch, coal-based pitch and mixtures thereof.
According to claim 1,
The step (a) is a method for producing activated carbon, characterized in that the treatment by selecting at least one of thermal oxidation, acid treatment, and plasma treatment.
According to claim 1,
The pitch oxidized in step (a) is a method for producing activated carbon, characterized in that the content weight ratio of oxygen / carbon is greater than 0.2.
delete According to claim 1,
The defect ratio of the carbonized coke in step (b) [defect strength (Ig) / crystallinity strength (Ig) of Raman analysis] is greater than 0.93 A method for producing activated carbon, characterized in that.
According to claim 1,
Step (b) is a method for producing activated carbon, characterized in that carried out by contacting the oxidized pitch with an inert gas at a temperature of 800 to 1200 ° C.
delete According to claim 1,
The method for producing activated carbon, characterized in that the physical activator may be selected from the group consisting of carbon dioxide (CO2), water vapor and mixtures thereof.
Activated carbon prepared by the method of any one of claims 1 to 7 and 9.

Images