KR102318843B1 - Method for the production of kenaf activationcarbon - Google Patents

Abstract

Hibiscus cannabinus activated carbon produced in the present invention has a light mass to volume than other plant-based activated carbon and thus exhibits a packing density less than twice or more thereof. In addition, the Hibiscus cannabinus activated carbon exhibits strong antioxidant activity greatly to the extent of 5 times difference. The method of the present invention comprises: a step of carbonizing Hibiscus cannabinus chips; a step of activating the carbonized product; and a step of cooling the same.

Description

Method for producing kenaf activated carbon {Method for the production of kenaf activationcarbon}

The present invention relates to a method for producing activated carbon, and more particularly, to a method for producing kenaf activated carbon.

As global environmental problems such as air pollution and water pollution become more serious, the demand for activated carbon is rapidly increasing. Activated carbon is a porous carbon body in which pores of a fixed carbon body obtained by carbonizing an organic material are further enlarged through an activation process.

The raw materials used in the manufacture of activated carbon can be broadly divided into plant, animal, and mineral. Dependence on the supply and demand is unstable. In addition, the supply and demand of oaks and other trees also takes a long period of growth, so there is concern about environmental pollution due to the smooth supply and production of wooden plant-based and mineral-based activated carbon raw materials.

Activated carbon can be classified into a liquid type for water treatment, liquid decolorization and purification, and a gaseous type suitable for gas adsorption, depending on the use, and can be divided into granular, powder, molded, activated fiber, etc. . In general, activated carbon for gas phase has developed micropores, and plant material made of cellulose is used as the main raw material. Activated carbon for liquid phase uses a material made from coal or plant as a raw material and mixes it with a binder and then goes through the activation process again. Compared to dragons, the middle and macropores are more developed.

Activated carbon is a material with excellent adsorption performance and has the ability to absorb chemicals, metals, and toxins. Therefore, it is most used to adsorb and remove organic substances in aqueous and gaseous phases. , CO ₂ separation, use and recovery treatment, in addition to decolorization, deodorization, solvent recovery, etc., are actively used in all industrial fields.

In addition, plant-based activated carbon has been used as a medicinal or cosmetic material since ancient times, and has anti-inflammatory, digestive and antioxidant properties, whitening teeth, resolving abdominal distension and gas problems, alcohol detoxification and toxin discharge, skin improvement, aging prevention, and cholesterol removal , immunity enhancement, and prevention of pests and diseases have been reported. However, when used on the human body, activated carbon from which harmful substances such as tar have been removed through the activation process must be used, and eating is prohibited in Korea. In addition, activated carbon is widely used as a building material or other industrial material by using various functions such as removal or prevention of harmful substances.

The adsorption capacity and application form of activated carbon depends on the physical properties such as pore structure, surface area, density, and surface chemistry. Activated carbon is produced through the carbonization and activation process of raw materials.

Carbonization refers to the process of heating organic raw materials to a temperature of about 900° C. or lower in an inert atmosphere. First, a drying process in which moisture is removed and pyrolysis of volatile matter occurs, and then the internal carbon reacts with some of the product gas and only the fixed carbon remains.

Activation is a process of developing a micropore structure by eroding the surface of carbide by oxidation reaction of carbon occurring at a temperature of 800 to 1100 °C. The activation method includes a physical activation method of fine porous adsorbed carbon by reacting the carbonized raw material with an oxidizing gas such as steam and carbon dioxide, which are oxidizing gases, at high temperature, and a chemical activation method using _{KOH, ZnCl 2} , H ₃ PO _{4 , etc.} .

Although the chemical activation method has the advantage of obtaining activated carbon with a very large surface area, the manufacturing process is complicated, and it has problems such as device corrosion, secondary pollution, and economic feasibility. Since the physical activation method can easily change the pore size, activated carbon suitable for various purposes can be produced. However, the enlargement of the structure results in a decrease in output and is expensive because it requires extra heat. Therefore, it is important to select a process for producing the most economically efficient activated carbon in consideration of the use.

Rodriquez-Reinoso reported _{that, through a comparative study on the role of water vapor and CO 2 as} an activator, expansion occurred at an early stage of the activation process when water vapor was used as an activator at 800 °C. On the other hand, it is reported that microporosity expansion occurs in the second half when _{CO 2 is used as an activator.} In addition, it is reported that water vapor produces a wider range of pore size distributions with more development of mesopores and macropores than _{CO 2 (Rodriquez-Reinoso (1995), The Use of steam and CO 2} as activating agents). in the preparation of activated carbon. Carbon. 33. pp. 15-23).

Korean Patent Laid-Open No. 1020150025183 (published on March 10, 2015) discloses a bamboo charcoal manufacturing step (step S1) of heating and carbonizing pieces of bamboo to obtain bamboo charcoal having micropores; a bamboo charcoal washing step (step S2) of thoroughly washing the bamboo charcoal prepared in the bamboo charcoal production step (step S1) with distilled water; a charcoal powder manufacturing step (step S3) of grinding the bamboo charcoal that has undergone the step S2 with a blender to make charcoal powder; an organic impurity removal step (step S4) of immersing the charcoal powder obtained in the charcoal powder manufacturing step (step S3) in 3M HCL to remove organic impurities; a filtering step (step S5) of filtering the charcoal powder from which organic impurities have been removed through the organic impurity removal step (step S4) by a vacuum filter method; A mixing step (step S6) of making a mixture by grinding KOH and bamboo charcoal powder that has undergone the filtering step (step S5) to be well mixed in a ratio of 1:1 to 10:1; a first heating step (step S7) of heating the mixture mixed in the mixing step (step S6) at 200 to 500° C. for 5 minutes or more; A method for producing bamboo activated carbon comprising a second heating step (step S8) of heating the mixture that has undergone the first heating step (step S7) at 800° C. or higher for 5 minutes or more is described.

The present invention aims to develop and provide a method for making activated carbon using kenaf.

The present invention comprises the steps of carbonizing a kenaf chip while raising the temperature to 350 ~ 450 ℃ under anaerobic conditions (a); (b) raising the temperature of the kenaf chip carbonized in step (a) under anoxic conditions to 800 to 1,000° C., and injecting carbon dioxide gas and water vapor while maintaining this temperature condition when this temperature is reached (b); After the activation step of step (b) has elapsed, the supply of carbon dioxide gas, water vapor, and a heat source is stopped, and the step (c) of cooling below 200° C. under anoxic conditions; A manufacturing method is provided.

In the method for producing kenaf activated carbon of the present invention, in step (c), it is preferable to store the cooled activated carbon at room temperature in a sealed condition.

In the method for producing kenaf activated carbon of the present invention, the anaerobic condition is preferably implemented by injecting nitrogen gas. In this case, the nitrogen gas is preferably injected at a rate of 100 to 1,200 ml/min.

In the method for producing activated kenaf carbon according to the present invention, in step (a), it is preferable that the kenaf chip reach 350 to 450° C. at a temperature increase rate of 10° C./min.

In the method for producing kenaf activated carbon of the present invention, the carbon dioxide gas is preferably injected at a rate of 100 to 1,200 ml/min.

In the method for producing kenaf activated carbon according to the present invention, the water vapor is preferably injected at a rate of 10 to 100 ml/hr.

Kenaf activated carbon prepared in the present invention boasted a packing density that was less than twice that of other plant-based activated carbons by having a lighter mass to volume ratio. In addition, it boasted a strong antioxidant activity with a significant difference of 5 times. Based on these results, Kenaf activated carbon can be used as a variety of industrial materials, functional foods, and cosmetic materials. In particular, it is used for filter materials, building materials, bio-composites, and various other industrial materials to reduce the weight of materials and store them through antioxidant and anti-inflammatory effects. Distribution and quality increase can be expected.

1 is a schematic diagram of an apparatus capable of making kenaf activated carbon of the present invention.
2 is a kenaf thermal decomposition characteristic analysis result (TGA test).
3 is a measurement (%) result of antioxidant activity according to the concentration of kenaf activated carbon of the present invention.
Figure 4 is a photograph visually showing the color change (antioxidant ability) when the present invention kenaf activated carbon, oak activated carbon, and bamboo activated carbon are reacted with DPPH.

Kenaf ( Hibiscus cannabinus L. ) is an annual herbaceous plant and is a plant of the genus Mallow family Mugunghwa that is native to India and Africa. Many studies on kenaf have been conducted in the United States and Japan, and products made from wood are being replaced with kenaf raw materials. In addition to the traditional products such as ropes, sacks, and rugs, it has been developed and produced as high-quality printing and copying paper, recycled paper, and newspaper by replacing wood in the pulp and paper field. It is being used in a variety of ways, including pet mats, carpets, insulation materials, wallpaper, various sidewalks, and textile composites, other than building interior materials. In addition, the use of eco-friendly products is expanding throughout the industry, such as oil absorbents, hamburger covers, disposable containers, automobile parts, and fuel pellets. As kenaf is used in industry, a significant amount is processed and treated, but stems are mostly used as raw materials, and leaves and seeds are generated in large amounts as by-products.

Kenaf is a biomass resource that can be produced every year compared to other wood or mineral materials because it has a faster production rate and better absorption of carbon dioxide than wood materials. In addition, since it can be grown domestically, it can be supplied stably regardless of fluctuations in the international market price by utilizing domestic resources. In addition, it has the advantage of being very light in weight to volume compared to wood or mineral materials and its activated carbon, so the development of various industrial materials is expected, and it has strengths in transportation convenience and economic feasibility of raw materials and products. With the improvement of varieties and the development of cultivation methods, kenaf raw materials with superior productivity and lignification than the existing kenaf varieties are produced, and thus economic efficiency and quality of kenaf activated carbon are expected. By adding or replacing Kenaf activated carbon to industrial materials, it is possible to reduce the weight of the material and increase the storage and distribution and quality due to its antioxidant and anti-inflammatory functions.

In the present invention, a method for producing kenaf activated carbon was developed. The present invention comprises the steps of carbonizing a kenaf chip while raising the temperature to 350 ~ 450 ℃ under anaerobic conditions (a); (b) heating the kenaf chip carbonized in step (a) under anaerobic conditions to 800 to 1,000° C. and activating it using carbon dioxide gas and water vapor while maintaining this temperature condition when this temperature is reached; After the activation step of step (b) has elapsed, the supply of carbon dioxide gas, water vapor, and a heat source is stopped, and the step (c) of cooling below 200° C. under anoxic conditions; A manufacturing method is provided.

Hereinafter, the method for producing kenaf activated carbon of the present invention will be subdivided into each step and described in detail. For the apparatus used in the method for producing kenaf activated carbon of the present invention, reference may preferably be made to FIG. 1 .

<Step (a): Carbonization process>

This step (a) is a process of carbonizing the kenaf chip while raising the temperature to 350 ~ 450 ℃ under anoxic conditions. This step (a) is a process of putting a kenaf chip in a cage (or chamber) and carbonizing it by applying high heat.

This step (a) should be performed under an anaerobic condition, which is preferably implemented by injecting nitrogen gas. Nitrogen gas is preferably injected into the chamber or cage at a rate of 100 to 1,200 ml/min (preferably 1,000 ml/min). Through this, the inside of the cage is implemented under anaerobic conditions. The most important thing in carbonization is to create anaerobic conditions, and the rate of nitrogen injection depends on the amount of activated carbon and the internal volume of the machine and container. It can be injected slowly, and it is better to make an anaerobic condition in advance by injecting nitrogen gas before temperature rise.

In addition, in this step (a), it is good to sequentially apply heat to the kenaf chips to raise the temperature to 350 ~ 450 ℃ (preferably 400 ℃), in this case, the temperature increase is preferably performed at a rate of 10 ℃ / min.

In addition, in this step (a), the carbonization is preferably performed for 8 to 40 minutes (more preferably 10 minutes).

After step (a) of this process, the weight of the kenaf chip is rapidly reduced (about 75%), and carbonization is completed.

<Step (b): Activation process>

This step is a process of activating the kenaf chip carbonized in step (a) by injecting carbon dioxide gas and water vapor while maintaining the temperature condition when the temperature is raised to 800 ~ 1,000 ° C under anaerobic conditions, and when this temperature is reached.

In this step (b), as an activation process, the carbonized kenaf chip is further heated and activated by injecting carbon dioxide gas and water vapor. The temperature increase is preferably performed at a rate of 10° C./min.

In this step (b), the carbon dioxide gas is preferably injected at a rate of 100 to 1,200 ml/min (more preferably 1,000 ml/min). In addition, the water vapor is preferably injected at a rate of 10 to 100 ml/hr (more preferably 30 ml/hr). At this time, the water vapor has a relatively slow transfer speed, and it is also good to inject it with carbon dioxide gas to facilitate transfer. In this way, the injection rate of carbon dioxide is accompanied by water vapor so that it can be transported quickly.

Activation in this step (b) is preferably performed for 20 to 60 minutes (more preferably for 30 minutes). The most important thing in activation is sufficient contact between the activated carbon and the activator, which depends on the amount of activated carbon and the internal volume of the machine and container. can react.

<Step (c): Cooling process>

This step is a process of stopping the supply of carbon dioxide gas, water vapor, and a heat source after the activation step of step (b) has elapsed, and cooling it to below 200° C. under anoxic conditions.

This step (c) is a process of cooling after the activation of step (b), and the activated kenaf activated carbon through this step is cooled to below 200°C, preferably not to below 0°C. .

The anaerobic condition of this step is for oxidation prevention, and it is preferably carried out while injecting nitrogen as in step (a) or (b).

In this step (c), it is preferable to store the cooled activated carbon at room temperature under sealed conditions.

[Example 1: Preparation of Kenaf Activated Carbon]

(1) Materials and devices

For the production of activated carbon, the stems of kenaf grown and harvested in 2018 at Sindong-myeon Farm in Chuncheon were used by removing the fibrous skins, drying them, and then cutting or pulverizing them. In the case of kenaf used in the experiment, the pulverized kenaf chips were separated into a particle size of 2.35 mm or more using a mesh network, and this separation process can be omitted in the actual production of activated carbon. As a control group, oak chips separated to a particle size of 2.35 mm or more were used.

The manufacturing equipment was modified and used by WOONGIN's A-WJC003, which is capable of temperature control. In Fig. 1, '7' is a carbonization container, which is used by stacking two saggars with an inner diameter of 230mm*230mm*100mm that are modified to make good contact with gas in a mechanical device with an inner diameter of 300mm*300mm*330mm or A stainless steel mesh container was put and used as a carbonization container. When using saggar as a carbonization container, ceramic beads of about 5 mm can be filled in the lower part to ensure good contact with the gas. '8' and '9' may be omitted as devices for obtaining liquefaction and wood vinegar by vacuum cooling the discharged gas. 1 is a schematic diagram of an example of an apparatus capable of making activated carbon using kenaf of the present invention.

(2) Manufacturing method

① First, the kenaf chips were carbonized for 10 minutes after reaching 400°C at a temperature increase rate of 10°C/min under nitrogen gas conditions (1,000ml/min).

② The primary carbonized kenaf chips were heated under nitrogen conditions to the set activation temperature of 900℃, and when the activation temperature was reached, carbon dioxide gas (1,000ml/min) and water vapor (30ml/min) and water vapor (30ml/min) while maintaining the 900℃ temperature condition hr) for 30 min.

③ After the activation period had elapsed, the supply of carbon dioxide, water vapor, and heat source was stopped, and nitrogen was injected to prevent oxidation, and the activated carbon was cooled to 200° C. or less to prepare activated carbon.

④ The cooled activated carbon was cooled to room temperature under sealed conditions and used.

(3) Experimental results

(A) Carbonization of Kenaf

The change in the weight of kenaf during carbonization was observed using a thermogravimetric analyzer, and the results are shown in FIG. 2 . It can be seen from FIG. 2 that the mass of the sample is reduced by evaporation of moisture up to about 100°C. In general, volatiles are vaporized at 200 ~ 300 ℃, and then vaporization starts after about 200 ℃ It was confirmed that the mass decreases rapidly. Therefore, it was confirmed that the carbonization reaction started from about 200°C to the thermal decomposition reaction of the organic components contained in the kenaf. lost. In addition, the thermal decomposition reaction was almost completed at 887°C. There is a difference in the change time of vaporization according to the temperature increase rate. 2 is a kenaf thermal decomposition characteristic analysis result (TGA test).

On the other hand, when activated carbon was prepared by activating kenaf and oak chips, the weight change of the two materials was compared. The weights of kenaf and oak chips, which were 350 g and 800 g, respectively, were 73.7 g and 176.9 g after carbonization. Although there was no significant difference in weight change, kenaf basically has a porous structure, so even when the packing density is compared, kenaf activated carbon is 0.0616 g/mL and oak activated carbon is 0.1402 g/mL per volume It was about 2.3 times lighter in weight.

(B) Antioxidant activity

The DPPH test is widely used to evaluate the free radical scavenging ability of extracts or specific mixtures from plants or foods. DPPH radical scavenging activity was measured by modifying the method of Blois. Prepared by pulverizing activated carbon of kenaf, oak, and bamboo, and 0.15 mM DPPH (α,α-diphenyl-β-picrylhydrazyl, Sigma-Aldrich Co.) methanol in 0.01 g, 0.05 g, 0.025 g, and 0.1 g of each sample. By adding 10 ml of the solution, each 0.1 0.25, 0.5, and 1% concentration was prepared. The prepared sample was stirred under Wise stirring (Vison Scientific co. KMC-130SH) at room temperature and in the dark at 100 rpm for 30 minutes. After stirring, centrifugation was performed at 5000 rpm for 10 minutes, and the supernatant was filtered with a 0.45 μm membrane filter, and absorbance was measured at 517 nm using a spectrophotometer (Hitachi U-2001). The negative control had a value of 1.534abs, and the activity was calculated by the formula "DPPH radical scavenging ability (%)=100-[(OD of sample/OD of control)×100]", and the average was repeated three times. saved

3 is a measurement (%) result of antioxidant activity according to the concentration of kenaf activated carbon, and Table 1 summarizes the results in a table.

Measurement of antioxidant activity according to the concentration of kenaf activated carbon (%) Concentration (%) Kenaf charcoal Oak charcoal bamboo charcoal 0.1 36.03 ±0.20 12.95 ±0.51 8.45 ±0.69 0.25 58.67 ±0.11 21.38 ±0.28 9.56 ±0.21 0.5 69.77 ±0.57 23.36 ±0.14 12.34 ±0.33 One 72.38 ±0.15 27.44 ±0.24 13.04 ±0.79

As a result of confirming the antioxidant activity by reacting DPPH with kenaf, oak, and bamboo activated carbon at various concentrations, as shown in FIG. 3 and Table 1, the DPPH free radical scavenging activity became stronger as the content of activated carbon increased, and kenaf activated carbon 1 % concentration showed the strongest activity at 72.38%, and there was a big difference of 2.6 times and 5.6 times, respectively, when compared with the activated carbon of oak and bamboo at the same concentration. According to the analysis results, the kenaf activated carbon of the present invention is considered to have strong antioxidant activity compared to other activated carbons.

On the other hand, DPPH is a water-soluble substance with chemically stable free radicals and is a purple indicator. It is reduced to yellow by ascorbic acid, tocopherol, and polyhydroxy aromatic compounds. That is, the color of DPPH is changed by reacting with a substance having antioxidant activity. As shown in FIG. 4 , it was visually confirmed that the kenaf activated carbon of the present invention exhibited superior antioxidant activity compared to oak activated carbon or bamboo activated carbon. Figure 4 is a photograph visually showing the color change (antioxidant ability) when the present invention kenaf activated carbon, oak activated carbon, and bamboo activated carbon are reacted with DPPH.

Claims (7)

In anoxic conditions, Kenaf ( Hibiscus cannabinus L. ) Carbonizing the chip while raising the temperature to 350 ~ 450 ℃ (a);
(b) raising the temperature of the kenaf chip carbonized in step (a) under anoxic conditions to 800~1,000°C, and injecting carbon dioxide gas and water vapor while maintaining this temperature condition when this temperature is reached (b);
After the activation step of step (b) has elapsed, the supply of carbon dioxide gas, water vapor, and a heat source is stopped, and the step (c) of cooling below 200° C. under anoxic conditions includes;
The carbon dioxide gas and water vapor of step (b) are respectively injected at a rate of 100 to 1,200 ml/min and 10 to 100 ml/hr at the same time.
According to claim 1,
The step (c) is,
A method for producing kenaf activated carbon with enhanced antioxidant activity, characterized in that the cooled activated carbon is stored at room temperature under sealed conditions.
According to claim 1,
The anaerobic conditions are
A method for producing kenaf activated carbon with enhanced antioxidant activity, characterized in that it is implemented by injecting nitrogen gas.
4. The method of claim 3,
The nitrogen gas is
A method for producing activated kenaf activated carbon with enhanced antioxidant activity, characterized in that it is injected at a rate of 100 to 1,200 ml/min.
According to claim 1,
The step (a) is,
A method for producing kenaf activated carbon with enhanced antioxidant activity, characterized in that the kenaf chip reaches 350 to 450 °C at a temperature increase rate of 10 °C/min.
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