KR100878262B1 - Production method of high performance activated carbon from soybean curd residue - Google Patents

Abstract

The present invention relates to a method for producing high-performance activated carbon using as a raw material of by-products produced by tofu, and to a low cost, high purity activated carbon production method capable of controlling specific surface area and average pore diameter, the activated carbon produced by this, and the The present invention relates to an electrode material for an electric double layer supercapacitor using busy carbon. The busy activated carbon produced by the present invention can be used as a high-performance, high-functional activated carbon such as electrode material for electric double layer supercapacitor, various odor removal, water and air purification, natural gas adsorption, catalyst carrier or molecular sieve. .

Busy, Carbonized, Activated, Activated Carbon, KOH, NaOH, Electric Double Layer Super Capacitors

Description

Production method of high performance activated carbon from soybean curd residue}

1 is a scanning electron micrograph of busy busy activated carbon prepared according to an embodiment of the present invention.

2 is a nitrogen gas adsorption isotherm curve of the busy activated carbon prepared according to an embodiment of the present invention.

Figure 3 is a nitrogen gas adsorption isotherm curve according to the ratio of the mixed activator of busy activated carbon prepared according to an embodiment of the present invention.

Figure 4 shows the capacitance of the supercapacitor using a busy activated carbon electrode and an aqueous electrolyte prepared according to an embodiment of the present invention.

5 is a CV graph of a supercapacitor using a busy activated carbon electrode and an organic electrolyte prepared according to an embodiment of the present invention.

6 is a charge / discharge graph of a supercapacitor using a busy activated carbon electrode and an organic electrolyte prepared according to an embodiment of the present invention.

7 illustrates a change in capacitance according to current density of a supercapacitor manufactured according to an embodiment of the present invention; (a) specific capacity by weight, (b) specific capacity by volume.

8 is an AC-impedance graph of a supercapacitor manufactured according to an embodiment of the present invention.

The present invention relates to a method for producing activated carbon using as a raw material a by-product produced in tofu production, a busy activated carbon prepared by the above method, and an electrode material for a high power electric double layer supercapacitor manufactured using the busy active carbon.

An electric double layer supercapacitor (EDLC) is a device that obtains energy by accumulating high-density charge in an electric double layer by using adsorption and desorption of ions during charging and discharging. The polarizable electrode material has high electrical conductivity and specific surface area so that the charge has a minimum voltage drop distribution at the electrode, and does not cause oxidation / reduction reaction under a certain potential, that is, electrochemically stable. The price of the material should be low. Active carbon-based electrode materials include materials that generally satisfy these requirements. Currently, activated carbon, which is used as a carbon material for electric double layer supercapacitors, which is industrially produced, is mainly activated by chemicals such as wood, pitch, and phenol-resin. There are many cases of using about 2000 ~ 2500m2 per g, and the electrode is manufactured by mixing them alone or two or three components. An average pore diameter of about 2 nm is known as an optimal size in aqueous solutions and organic capacitors, and the larger the ratio of mesopores, the more favorable it is for producing high-speed charge and discharge capacitors. However, in the case of the wood-based activated carbon, there is a limit to increase the specific surface area by more than 2000 m 2 per unit weight (g), and when pitch or phenol resin is used as a raw material, it is difficult to control the pore structure and to limit the supply of raw materials. It has the following disadvantages. Therefore, there is an urgent need for the development of activated carbon materials and manufacturing methods that smoothly supply raw materials and control low cost, ultra high specific surface area, and pore structure.

Activated carbon can be classified into various forms according to its final shape, activation method, use and function, and is one of the most important carbon materials industrially in all industries such as food, medicine, environment and electronic materials. As a method for producing activated carbon, a carbonized material may be heat-treated under conditions in which various activators (gases and chemicals) react with carbon.

Activated carbon is manufactured from various raw materials such as plant-based (wood, palm), coal / petroleum pitch, polymer-based, and bio-mass. Any can be used as a raw material of activated carbon. However, the production of activated carbon, which is cheaper and whose specific surface area and pore structure are effectively controlled, has an important position in the industrial field.

Soybeans produced by tofu using soybeans are about 33% of soluble protein removed and have no nutritional value, and are difficult to digest into macromolecules composed of fiber. Efforts to use 100% of soybean ingredients, such as soybean solubilization and soybean emulsification, have been very small. Therefore, recycling and high utilization of enormous amount of waste paper can be very important in terms of resource recycling and industrial purposes.

Republic of Korea Patent No. 10-0387990 discloses a method for producing activated carbon using pulp sludge as a by-product in the manufacture of corn stalk pulp. , 10-0389556 introduces activated carbon production methods using various materials as raw materials for the purpose of recycling resources, such as the production of activated carbon using waste red pepper seeds.However, the method of having high purity and high specific surface area and easily controlling pore structure No introduction.

It is an object of the present invention to provide a production method capable of providing high-performance activated carbon for special purposes which has high purity, high specific surface area, and can control pore structure at low cost by recycling waste busy paper, and a busy activated carbon produced thereby.

In addition, an object of the present invention is to provide an electrode material for an electric double layer supercapacitor having excellent high output characteristics produced using the busy activated carbon.

The present invention

Drying the busy paper to remove moisture;

A carbonization step of carbonizing at 500 to 1000 ° C. under a vacuum or inert atmosphere to increase the content of fixed carbon; And

The present invention relates to a process for producing busy activated carbon comprising the step of high purity by removing residual ash and the like using an acidic aqueous solution and water.

In the water removal step, the water removal method may be used without limitation, a method commonly used in this field, and may be used by drying at 100 to 140 ° C. for about 24 to 48 hours.

After the water removal step, the carbonized step may be performed by grinding and / or classifying the busy paper as necessary.

In the carbonization step, the carbonization is preferably performed at 500 to 1000 ° C. for 0.5 to 4 hours. If the carbonization temperature is less than 500 ° C., the carbon crystallization is not developed and the off-system desorption of heterogeneous elements other than carbon is low. There is a problem in controlling the pore structure, and when the temperature exceeds 1000 ° C., the development of carbon crystals progresses, but it is difficult to control the pore structure upon activation.

After the carbonization step, the addition of a chemical activation step of chemically activating the mixture of inorganic salts alone or in a plurality of carbides produced in the carbonization step may produce more busy results.

The inorganic salts used in the chemical activation step may be selected from potassium hydroxide (KOH), sodium hydroxide (NaOH), zinc chloride (ZnCl ₂ ), phosphoric acid (H ₃ PO ₄ ), calcium chloride (CaCl ₂ ), and the like. The mixing ratio of the inorganic salts and the inorganic salts is preferably 1: 2 to 1: 6 by weight. When the mixing ratio of carbide and inorganic salt is out of the above range, activation progresses slowly and a difficulty in obtaining a desired specific surface area occurs.

In the chemical activation step, it is preferable to activate the mixture of carbide and inorganic salts for 0.5-1.5 hours at 500-1000 ° C. If the temperature is less than 500 ℃ the activation of the activator and the carbide does not react, the progress of the activation is difficult, if it exceeds 1000 ℃ carbonization by heat treatment rather than activation by the activator progresses the formation of coalescence and carbon crystals between the pores The specific surface area tends to decrease by.

In the high purity step, it is possible to use an aqueous solution of nitric acid (HNO ₃ ), an aqueous solution of sulfuric acid (H ₂ SO ₄ ), an aqueous solution of hydrochloric acid (HCl), and preferably use the acidic aqueous solution and water (distilled water). It is preferable to adjust the content of the residual ash to 0.0001% or less, and to adjust the pH to 6-9. If the residual ash content is out of the above range, it is not preferable in terms of high purity, and if the pH shows acidity of less than 6 or basicity of more than 9, reaction with an electrolyte when used as an electrode for water purification activated carbon or an electric double layer supercapacitor is performed. Or to corrode or decompose the electrolyte component or the electrode structure.

The present invention also relates to the busy activated carbon produced by the above production method, and the busy activated carbon of the present invention has a specific surface area of 2000 to 4000 m 2 / g and an average pore diameter of 2 to 3.5 nm. It can be used as an application.

The present invention also relates to an electrode material for an electric double layer supercapacitor manufactured by using biji activated carbon produced by the above method, and the present invention relates to biji activated carbon, PTFE binder, and carbon black (produced by the above method). An electrode material for an electric double layer supercapacitor including carbon black) is provided.

The electrode material for the electric double layer supercapacitor preferably includes a busy activated carbon, a PTFE binder, and carbon black in a weight ratio of 7-9: 0.5-1.5: 0.5-1.5.

Busy by-products for tofu production provide relatively uniform raw materials for the production of plant-based activated carbon, and are composed of high molecular weight cellulose, making it possible to produce activated carbon of higher purity and higher yield than wood-based or waste-based. Therefore, according to the method for producing busy activated carbon of the present invention, it is possible to obtain special purpose activated carbon having a specific surface area of 2000 to 4000 m 2 per unit weight and an average pore diameter in the range of 2 to 3.5 nm.

Hereinafter, the production method of busy activated carbon of the present invention will be described in more detail.

1. First, vacuum and dry the busy paper to completely remove residual moisture, and then grind and classify it, and then increase the fixed carbon by primary carbonization treatment in the temperature range of 500 ~ 1000 ℃ under inert atmosphere such as nitrogen gas or argon gas. . In this case, the carbonization method is a conventionally used method, but since the degree of crystallinity is increased by increasing the heat treatment temperature, it affects the activation degree. In the present invention, the activated raw material is carbonized at about 600 ° C. for about 60 minutes. Used as.

2. Potassium hydroxide (KOH) is mixed at a weight ratio of 1: 2 to 1: 6 with respect to the carbonized sample and activated while maintaining the temperature in a temperature range of 500 to 1000 ° C. under an inert atmosphere. The carbide thus obtained was repeatedly washed several times with an acidic aqueous solution and distilled water to obtain a hydrogen ion concentration (pH) of about 6 to 9, which was dried at 120 ° C. for 24 hours using a vacuum dryer, and then classified and treated. Prepare activated carbon. In addition to potassium hydroxide (KOH) used at this time, salts such as sodium hydroxide (NaOH), zinc chloride (ZnCl ₂ ), phosphoric acid (H ₃ PO ₄ ) may be used.

3. In another method, the carbonized sample is mixed with a mixture of potassium hydroxide (KOH) and sodium hydroxide (NaOH), activated in an inert atmosphere in the range of 600 to 1000 ° C., and then repeated with an acid solution and distilled water. It can be washed with water and dried to produce busy activated carbon. In the case of the busy activated carbon produced in this way, while the ash content is less than 0.0001%, the specific surface area is 2000 m 2 / g or more, and the average pore diameter can be prepared for special purpose activated carbon.

The ultra high specific surface area activated carbon produced by the present invention can be applied to various industrial fields such as various odor removal, water and air purification, natural gas adsorption, electric double layer supercapacitor, catalyst carrier or molecular sieve. .

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the examples described below are for illustrating the present invention, whereby the scope of the present invention is not limited.

Example 1 Preparation of Busy Activated Carbon

After grinding and classifying busy paper dried at 120 ° C. for 24 hours, using a tubular electric furnace, the temperature was increased by 5 ° C. per minute under nitrogen gas and carbonized at 600 ° C. for 1 hour. The carbonized sample was mixed with potassium hydroxide (KOH) in a weight ratio of 1: 4 and divided into three parts. The first sample was 700 ° C., the second sample was 800 ° C., and the third sample was 900 ° C. using a tubular electric furnace. Activation treatment for 1 hour at. The activated sample was washed with 1 M aqueous nitric acid solution (HNO ₃ ) and distilled water at 80 ° C. until the hydrogen ion concentration (pH) was about 6 to 8. After washing with water, a vacuum oven was used to dry at 120 ° C. for 24 hours to obtain busy activated carbon.

A scanning electron micrograph of the activated carbon prepared above is shown in FIG. 1, and FIG. 2 shows a 77K nitrogen gas adsorption isotherm curve of non-activated carbon activated at 700, 800, and 900 ° C. for 1 hour using potassium hydroxide, respectively. Table 1 shows the change of specific surface area and pore structure with activation temperature.

Activation temperature (℃) ^a Activation Yield (%) BET SSA (m ² / g) ^{b c} TPV (cm ³ / g) Pore Volume Fraction (%) ^d APS (nm) Micro Meso 700 47.7 2700 1.72 63.9 36.1 2.12 800 41.6 3500 2.17 36.4 63.6 2.78 900 39.9 3700 2.56 27.6 72.4 3.04

(Ratio of carbide / activator (KOH): 1: 4)

^a Activation yield = (weight of carbonized sample / weight of activated sample after activation) × 100 (%),

^b BET specific surface area (BET SSA): BET specific surface area,

^c TPV (Total pore volume, P / P ₀ = 0.990): total pore volume

^d Average pore size (diameter): average pore diameter

As shown in Table 1, all of the activated carbons prepared in Example 1 are composed of special purpose activated carbons having a specific surface area of 2500 m 2 / g or more and at the boundary between micropores and mesopores having an average pore size of 2 to 3.5 nm. It was. As a result of elemental analysis, more than 98.5% is composed of carbon, and the content of oxygen and nitrogen is 1.45% respectively. It was 0.049% of ash and 0.001% of ash of high purity activated carbon.

Example 2

Samples carbonized at 600 ° C. by the method of Example 1, and potassium hydroxide (KOH) and sodium hydroxide (NaOH), respectively, at a ratio of 0/100, 30/70, 50/50, 70/30, 100/0. (Carbide / activator = 1/4) was mixed and activated for 1 hour at 800 ° C. using a tubular electric furnace. The activated sample was repeated using a 1M aqueous solution of nitric acid and distilled water at 80 ° C until the hydrogen ion concentration (pH) was about 6-8. After washing with water, a vacuum oven was used to dry at 120 ° C. for 24 hours to prepare busy activated carbon using a composite activator.

Figure 3 shows the 77K nitrogen gas adsorption isotherm curve of the busy activated carbon activated by 1 hour at 800 ℃ by mixing the complex activator of potassium hydroxide and sodium hydroxide by ratio, Table 2 shows the specific surface area according to the activator mixing ratio and The pore structure was shown to change.

KOH / NaOH ratio (wt.%) BET SSA (m ² / g) ^{b c} TPV (cm ³ / g) Pore Volume Fraction (%) ^d APS (nm) Micro Meso 0/100 2670 1.92 83 17 2.87 30/70 2560 1.62 87 13 2.49 50/50 2600 1.64 87 13 2.49 30/70 2660 1.77 87 13 2.66 100/0 3500 2.17 36 64 2.78

(Activation temperature 800 ° C)

As shown in Table 2, all of the activated carbons prepared in Example 2 are composed of special purpose activated carbons composed of a micropore and a mesopore having a specific surface area of 2500 m 2 / g or more and an average pore size of 2 to 3 nm. It was. As a result of elemental analysis, more than 98% is composed of carbon, and the content of oxygen and nitrogen is 1.5%. It was 0.4% of ash and 0.1% of ash with high purity activated carbon.

Example 3

By using the busy activated carbon prepared in Example 1, the busy activated carbon, PTFE binder, and carbon black were mixed in a ratio of 8: 1: 1, respectively, to prepare a slurry, and then cut into 1.5 × 1.5 cm to form a nickel. Electrode was prepared by placing on a foam (Ni-form) and pressure molding.

As an electrolyte, the performance of the supercapacitor was evaluated by measuring constant current charge / discharge, CV (cyclic voltammogram), and AC-impedance using 6M KOH aqueous solution. 4 and 5 show the CV graph according to the scanning speed of the supercapacitor in aqueous solution electrolyte using busy activated carbon, and the capacitance per unit weight.

Example 4

The electrode was prepared by the method of Example 3 using the busy activated carbon prepared in Example 1, and then the performance of the capacitor was evaluated using the organic electrolyte 1M tetraethylammonium tetrafluor borate (Et ₄ NBF ₄ ) as an electrolyte. It was.

6 shows the CV graph, FIG. 7 shows the charge and discharge curve, FIG. 8 shows the capacitance according to the discharge current, and FIG. 9 shows the result of the AC impedance. As a result of the charge and discharge, it was confirmed that the high output characteristics according to the discharge current were excellent.

The present invention provides a low cost, high purity novel busy carbon activated carbon manufacturing method capable of controlling the specific surface area and the average pore diameter, and a busy activated carbon produced thereby, and also has excellent high output characteristics produced using the busy activated carbon. An electrode material for an electric double layer super capacitor is provided.

The activated carbon produced by the present invention can also be used as a high-performance, high-functional activated carbon such as various odor removal, water and air purification, natural gas adsorption, catalyst carrier or molecular sieve.

Claims (11)

Drying the busy paper to remove moisture; A carbonization step of carbonizing at 500 to 1000 ° C. under a vacuum or inert atmosphere to increase the content of fixed carbon; Mixing the carbide produced in the carbonization step with potassium hydroxide (KOH) in a weight ratio of 1: 2 to 1: 6 to activate the drug at 500 to 1000 ° C; And Method of producing busy activated carbon comprising the step of high purity by removing the residual ash using an acidic aqueous solution and water. delete delete delete The method of claim 1, wherein in the high purity step, the acidic aqueous solution is at least one selected from the group consisting of aqueous nitric acid solution (HNO ₃ ), aqueous sulfuric acid solution (H 2 SO 4), and aqueous hydrochloric acid solution (HCl). . The method of claim 1, wherein the residual ash content in the high purity step is 0.0001% or less, pH of 6 to 9 characterized in that the manufacturing method of activated carbon activated carbon. delete The busy activated carbon produced by the method of any one of claims 1, 5, and 6, having a specific surface area of 3000 to 4000 m 2 / g and an average pore diameter of 2 to 3.5 nm. The busy activated carbon according to claim 8, which is used for removing odors, for purifying water and air, for absorbing natural gas, and as a catalyst carrier or a molecular sieve. An electrode material for an electric double layer supercapacitor comprising a busy activated carbon of claim 8, a PTFE binder, and carbon black. The electrode material for an electric double layer supercapacitor according to claim 10, wherein the biji activated carbon, PTFE binder, and carbon black are included in a weight ratio of 7-9: 0.5-1.5: 0.5-1.5.

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