KR20090095699A - Manufacturing method of Fibrous Adsorbent by blend electrospinning for VOC absorbent - Google Patents

Abstract

A manufacturing method of a fibrous adsorbent for VOC absorption is provided to absorb volatile organic compounds effectively and easily such as Benzene, Toluene, Xylene etc. A manufacturing method of a fibrous adsorbent for VOC absorption includes the following steps of: producing a fiber precursor compound by dissolving polyacrylo nitrile resin and cellulose based resin with a weight ratio of 70 ~ 90:10 ~ 30; producing the fiber through electrospinning by adding voltage of 20 ~ 30kV to the fiber precursor compound; stabilizing the fiber for 0.5 ~ 3 hours; carbonizing the stabilized fiber in inert atmosphere or a vacuum condition at the temperature of 800 ~ 1000°C; and activating the carbonized fiber in the temperature of 800 ~ 1000°C.

Description

Manufacturing method of fibrous adsorbent for adsorption of volatile organic compounds by mixed electrospinning {Manufacturing method of Fibrous Adsorbent by blend electrospinning for VOC absorbent}

The present invention relates to an adsorbent for volatile organic compounds using a mixed polymer solution of polyacrylonitrile and a cellulose resin.

Volatile organic compounds are classified as specific atmospheric harmful substances due to their great effect on human body and ecosystem, and also produce photochemical oxides, which are secondary pollutants such as ozone, through photochemical reactions. Such volatile organic compounds are toxic to the human body because they contain a number of chemicals known to be highly carcinogenic and cause problems such as ozone layer destruction, global warming, photochemical smog and odor.

The direct effects of volatile organic compounds on the human body are known to cause leukemia and central nervous system disorders in benzene among aromatic volatile organic compounds, and chromosomal abnormalities are often found in people exposed to very low concentrations of benzene. Is being reported. On the other hand, organic solvents are problematic because they are toxic in their own right or those substances contained therein are highly toxic. Representative organic solvents include aromatic hydrocarbons such as benzene, toluene and xylene, which are emitted from various sources. Korea's volatile organic compound emissions account for 55% of the paint industry's emissions. Back transportation is followed by 28%.

Activated carbon is the most widely used adsorbent to remove volatile organic compounds. Silica gel, alumina and zeolite are used as adsorbents other than activated carbon. Raw materials for activated carbon use carbon-containing materials such as wood, coal and coconut fruit, and the types include powdered coal, granular carbon and fibrous activated carbon.

Double granular activated carbon is the most widely used because it has a sufficiently large surface area, a low pressure drop, and relatively easily recovers the adsorbed volatile organic compounds. On the other hand, fibrous activated carbon is an adsorbent that has received much attention recently because the pore size of fibrous activated carbon is composed of only micropores, and the adsorption portion is directly connected to micropores from the fiber surface, which has the advantage of fast adsorption and desorption rate. . In addition, it can be made in a variety of shapes, such as honeycomb structure or plate shape has the advantage that the surface can be used to the maximum.

An object of the present invention is to provide an adsorbent having a very good adsorption capacity of a volatile organic compound and a method for producing the same.

Specifically, the present invention aims to provide a fibrous adsorbent having an average diameter of 150 to 500 nm, a specific surface area of 1403 to 1566 m 2 / g, a pore diameter of 6.0 to 6.8 mm 3 and a mesopore diameter of 40 to 65 mm 2. .

In addition, the present invention is to provide a fibrous adsorbent having a very high adsorption capacity of volatile organic compounds compared to the conventional granular activated carbon.

In order to solve the problems of the conventional granular activated carbon used as the adsorbent of the volatile organic compounds as described above, extensive research has been conducted. As a result, when using the fibrous adsorbent according to the present invention, the adsorption capacity of toluene is higher than that of the conventional granular activated carbon. The present invention was completed by recognizing the doubling point.

Referring to the method for producing the fibrous adsorbent of the present invention in detail,

a) polyacrylonitrile resin: dissolving a cellulose resin in a solvent in a weight ratio of 70 to 90: 10 to 30 to prepare a fiber precursor composition;

b) preparing the fiber by inserting the fiber precursor composition into a syringe with a needle and electrospinning a voltage of 20 to 30 kV;

c) heating the fiber to 250 to 300 ° C., and oxidatively stabilizing for 0.5 to 3 hours in an air atmosphere;

d) carbonizing the oxidative stabilized fiber at 800 to 1000 ° C. in an inert atmosphere or in a vacuum state;

e) activating the carbonized fiber in 800 ~ 1000 ℃, steam atmosphere;

It includes.

The fiber precursor composition is preferably prepared in a solid content of 10 to 30% by weight. The most important factor in the preparation of nanofibers using electrospinning is the proper viscosity of the composition, which is not suitable for spinning because of the low viscosity of the composition when prepared in less than 10% by weight, and the high viscosity in excess of 30% by weight.

Hereinafter, the present invention will be described in more detail.

The fiber precursor composition, which is a starting material of the present invention, is prepared by dissolving a polyacrylonitrile resin: cellulose-based resin in a weight ratio of 70 to 90:10 to 30 to dissolve in a solvent.

The weight average molecular weight of the polyacrylonitrile resin is preferably used in the range of 50,000 to 500,000, and may be any conventional synthetic polymer. If it is less than 50,000, the viscosity of the fiber precursor composition is low, and if it exceeds 500,000, the viscosity is high, which is not preferable.

In addition, the cellulose resin may be any one or more selected from cellulose acetate, cellulose, cellulose acetate butyrate, cellulose acetate petalate, cellulose acetate propionate, more preferably using cellulose acetate, It may be a conventional synthetic polymer. It is preferable to use the weight average molecular weights 30,000-500,000. If it is less than 30,000, the viscosity of the fiber precursor composition is lowered, and if it exceeds 500,000, the viscosity is excessively increased, which is not preferable. The reason for using the cellulose resin in the present invention is because of the hydrogen bonding ability of the hydroxy group and the carboxyl group unique to the ester group. In addition, it is inexpensive and easy to change into the annular structure excellent in the specific surface area and pore development required for the adsorbent due to the annular structure of the cellulose acetate itself.

The mixing ratio of the cellulose-based resin was found to have the best specific surface area when mixed in the range of 10 to 30% by weight, and excessive mixing of cellulose acetate is not preferable because it reduces the specific surface area by increasing the medium pores. not.

The solvent may be any one or more selected from dimethylformamide (DMF), dimethylacetamide (DMAc) and tetrahydrofuran (THF).

More specifically, a solution obtained by dissolving a polyacrylonitrile polymer in 10% by weight in a dimethylformamide solvent and a solution in which cellulose acetate is dissolved in 10% by weight in a dimethylformamide solution are mixed in a ratio of 90 to 70:10 to 30 by weight. A fiber precursor composition is prepared.

After homogenizing the composition thus prepared, it is placed in a syringe with a needle, and electrospun by applying a voltage of 20 to 30 kV to prepare a fiber, and the fiber prepared in the above manner is heated to 250 to 300 ° C., Oxidative stabilization under 0.5 to 3 hours.

In general, thermoplastic resins are melted when carbonized and activated at high temperatures, or fusion between fibers occurs. To prevent this, the thermoplastic resin is converted into a thermosetting resin through an oxidative stabilization process. That is, the oxidation stabilization process is a process of oxidizing fibers from the surface to prevent the fusion and thermal melting of the fibers in the subsequent high temperature carbonization, activation process by converting the thermoplastic resin into a thermosetting resin. If carbonization or activation is performed directly without performing an oxidative stabilization process, exothermic reactions such as ring opening and dehydrogenation proceed rapidly and are burned rather than carbonized. In the present invention, the oxidative stabilization process forms a crosslinking of oxygen or a strong hydrogen bond, thereby reducing volatile matter in the subsequent high temperature carbonization or activation process, resulting in a solid phase carbonization reaction and maintaining the dimensions and structure of the fiber even during the carbonization process.

After stabilization to maintain the fiber's dimensions and structure, it is carbonized and activated by heating the raw material at high temperatures under special conditions to remove volatile non-carbon components or increase its surface area. At this time, the stabilization temperature and time may be given under any conditions. Specifically, the stabilized fibers were carbonized at 800 to 1000 ° C. in an inert atmosphere or vacuum state, and then activated at 800 to 1000 ° C. and a steam atmosphere to prepare a fibrous adsorbent. The activation process plays a very important role in controlling the pore structure. Conventional activation methods mainly include gas activation and chemical activation. Gas activation is a fine porous adsorbed coal obtained by contacting and reacting carbonized raw materials at around 1000 ° C with water vapor, carbon dioxide, and oxygen mixed. How to make it. In the present invention, activated using steam in the same temperature range as the carbonization temperature. The steam activation method according to the present invention is very simple in the process and prevents the generation of excessive pores.

 In addition, the resulting fibrous adsorbent for volatile organic compound adsorption according to the present invention has a fiber diameter of 150 to 500 nm, an average diameter of 200 nm, a specific surface area of 1403 to 1566 m 2 / g, and a diameter of micropores. 6.0-6.8 kPa, medium-to-pore diameter of 40-65 kPa, excellent adsorption of volatile organic compounds of 65-80g / 100g can be prepared.

In the present invention, the adsorption power of the volatile organic compound is filled into a 6 mm diameter and 15 mm length adsorption cell optionally prepared with the fibrous adsorbent, and 180 ml of nitrogen gas containing 200 ppmv of toluene is flown per minute, and then the amount of toluene adsorption is gas chromatography. Adsorption amount was calculated using.

The present invention can properly control the pores of the fiber, it was possible to adjust the amount of adsorption of volatile organic compounds.

The fibrous adsorbent according to the present invention was found to have a very high adsorption characteristics of volatile organic compounds as compared to the conventional granular activated carbon.

In addition, the expected effect is very high as the volatile organic compound adsorbent because the process is simpler and easier to handle than the case of using the particulate form.

The following will be described by way of example for a detailed description of the invention. However, the present invention is not limited to the following examples.

Physical property measurement method used in the following Examples are as follows.

Diameter distribution and surface images were measured using a scanning microscope (FE-SEM, Hitachi, S-4700).

Specific surface area and pore distribution were obtained by adsorption isotherm of nitrogen gas (N ₂ ). Nitrogen adsorption and desorption experiments were carried out using ASAP2020, USA of Micromeritics, and the samples were pre-treated at 300 ° C. for 24 hours and measured while changing the pressure of nitrogen under isothermal conditions of 77K.

Toluene adsorption experiment was carried out for the adsorption amount of volatile compounds, and the adsorption amount was determined from the breakdown curve which is the concentration change of adsorption gas at the inlet and outlet of the adsorbent.

A fibrous adsorbent prepared according to the embodiment was packed into a 6 mm diameter and 15 mm length adsorption cell arbitrarily prepared at 0.05 to 0.06 g, and 180 ml of nitrogen gas containing 200 ppmv of toluene was flowed per minute, and then the amount of toluene adsorbed was gas chromatographed. The amount of adsorption was calculated using chromatography. In the present invention, the experiment was performed at room temperature.

Example 1

A polyacrylonitrile resin having a weight average molecular weight of 86,200 was added to dimethylformamide (N, N-dimethylforamide) as a solid content of 10% by weight, and then dissolved at 60 ° C. for 24 hours to prepare a polymer solution (A). In addition, a cellulose acetate having a weight average molecular weight of 30,000 was added to 10% by weight of solids in dimethylformamide (N, N-dimethylforamide) solvent and dissolved at 60 ° C. for 24 hours to prepare a polymer solution (B).

The polymer solution (A) and the polymer solution (B) were mixed and homogenized in a 90:10 weight ratio.

The homogenized fiber precursor solution was electrospun using an electrospinner. At this time, the spinning condition was put into the 30ml syringe attached to a 0.5mm needle and the fiber precursor solution was electrospun by applying a voltage of 20 kV. In this case, the distance between the needle and the current collector was maintained at 18 cm, and the dissolution rate of the fiber precursor solution was 1 ml / h. When the fibers were accumulated in the current collector, the nonwoven fabric was separated and separated.

The fibrous web composed of the separated polyacrylonitrile and cellulose acetate was oxidatively stabilized at 280 ° C. for 1 hour in an air atmosphere. At this time, it heated up at 1 degree-C / min, and maintained at 280 degreeC for about 1 hour.

After sufficient oxidation stabilization, the carbonization process was performed at 1000 ° C. for about 1 hour, and then activated at 1000 ° C. for 30 minutes using 30% by volume steam (H ₂ O / N ₂ ). The temperature increase rate was 5 degrees C / min.

Scanning micrographs of the fibrous adsorbent thus prepared are shown in FIG. 1. In addition, the nitrogen adsorption desorption isotherm is shown in Figure 5, the pore distribution of the fiber is shown in Figure 6, the breakthrough curve of toluene adsorption (Breakthrough) is shown in Figure 7.

Example 2

A polymer solution (A) and a polymer solution (B) were prepared in the same manner as in Example 1, except that 80:20 was added in a weight ratio.

Scanning micrographs of the fibrous adsorbent thus prepared are shown in FIG. 2. In addition, the nitrogen adsorption desorption isotherm is shown in Figure 5, the pore distribution of the fiber is shown in Figure 6, the breakthrough curve of toluene adsorption (Breakthrough) is shown in Figure 7.

Example 3

A polymer solution (A) and a polymer solution (B) were prepared in the same manner as in Example 1 except that the polymer solution was mixed in a weight ratio of 70:30.

Scanning micrographs of the fibrous adsorbent thus prepared are shown in FIG. 3. In addition, the nitrogen adsorption desorption isotherm is shown in Figure 5, the pore distribution of the fiber is shown in Figure 6, the breakthrough curve of toluene adsorption (Breakthrough) is shown in Figure 7.

Comparative Example 1

Except for using only the polymer solution (A) was prepared in the same manner as in Example 1.

Scanning micrographs of the fibrous adsorbent thus prepared are shown in FIG. 4. In addition, the nitrogen adsorption desorption isotherm is shown in Figure 5, the pore distribution of the fiber is shown in Figure 6, the breakthrough curve of toluene adsorption (Breakthrough) is shown in Figure 7.

As shown in Figures 1 to 4, it can be seen that due to the difference in the thermal properties of cellulose acetate and polyacrylonitrile, it has a non-uniform surface compared to Figure 4 using polyacrylonitrile alone. This is because the final activated carbon nanofibers have a change in morphological and pore properties because the chain structure of the two polymer materials is different and the thermal stability and other physical properties are different.

The average diameter of the activated carbon nanofibers prepared by the manufacturing method was about 200 nm, and the fiber diameter ranged from 150 to 400 nm. This fiber is 10 microns in diameter, which is made from melt spinning, solution spinning, and gel spinning, which is a common fiber manufacturing method, and is about 50 times thinner and finer than the carbon nanofibers activated by polyacrylonitrile alone. It can be seen that manufactured.

Also, as the content of cellulose acetate increased, the roughness of the fiber surface increased. This is primarily because the polyacrylonitrile chains and cellulose acetate chains in the mixed fibers have physically different expansion, shrinkage, and torsional properties. This may be due to chemical changes in the fiber due to thermal stability differences between nitrile and cellulose acetate. Activated carbon nanofibers having a thinner fiber diameter according to the present invention are expected to exhibit rapid adsorption and desorption characteristics when used in the adsorption field. As a result, cellulose acetate, which is less thermally stable in the mixture, is first decomposed and burned off during the heat treatment, so that small holes, layers, and fibers are cracked, thereby changing the characteristics of the fiber surface.

 5 is a graph showing nitrogen adsorption and desorption isotherms of activated carbon nanofibers according to the content of cellulose acetate, and FIG. 6 is a chart showing pore distribution of activated carbon nanofibers according to the content of cellulose acetate. In case of preparing nanofibers by spinning a solution prepared by mixing polyacrylonitrile and cellulose acetate, and preparing activated carbon nanofibers using the same, the surface area of Comparative Example 1 prepared by spinning only polyacrylonitrile 1403 m 2 / g, while the surface area tended to be relatively large. The highest surface area was found at 1443 m 2 / g when the content of cellulose acetate was 10% by weight, and 1566 m 2 / g at 20% by weight, and 30% by weight. In the case of 1452 m 2 / g, the surface area tended to decrease.

Therefore, it can be seen that the surface area can be adjusted by controlling the content of cellulose acetate. This increases the specific surface area up to a certain level of cellulose acetate mixing ratio, but it is believed that excessive mixing of cellulose acetate reduces specific surface area by increasing mesopores.

In addition, the pore size also tended to increase as the cellulose acetate increased. In Comparative Example 1, in which polyacrylonitrile was spun alone, the micropores were 6.0 Å and the medium pores were 40,. In Example 1, the micropores were 6.6. Å, the medium pore is 45Å, the fine pores are 6.6Å, the medium pores are 51Å, and the medium pores are 6.8Å, the medium pores are 6.8Å, and the medium pores are 61Å, respectively. It was found that the diameter and the diameter of the coarse holes increased.

 Therefore, the present invention discloses that the control of the content of cellulose acetate can play an important role in controlling the surface area and pore size.

7 is a graph showing toluene adsorptive properties of carbon nanofibers according to respective cellulose acetate contents. The breakthrough time of the activated carbon nanofibers was 4.08 hours in Comparative Example 1, 4.16 hours in Example 1, 4.50 hours in Example 2, 4.16 hours in Example 3, and the final adsorption amount in Comparative Example 1 65 / 100g, 66g / 100g in Example 1, 72g / 100g in Example 2, 67g / 100g in Example 3, the longest breakthrough in Example 2 having a cellulose acetate content of 20% Time and highest adsorption amount were shown. As a result, it was found that the adsorption amount of volatile organic compounds was higher when cellulose acetate was mixed as compared with the case where polyacrylamide was spun alone.

As a result, the present invention was able to appropriately control the pores of the fiber, it was possible to adjust the amount of adsorption of volatile organic compounds.

Example 4

While preparing in the same manner as in Example 1, carbonization was performed at 800 ° C., 900 ° C., and 1000 ° C., respectively, to compare the adsorption amount according to the carbonization temperature.

As a result, the toluene adsorption properties of carbon nanofibers activated at high temperature tended to be higher, and the toluene adsorption amount of toluene was 57g / adsorbent 100g at 800 ° C, 60g / 100g at 900 ° C and 66g / 100g at 1000 ° C. It was.

As such, as the carbonization temperature increases, the adsorption amount tends to increase, and when activated at 1000 ° C, the adsorption amount is 1.2 times higher than when activated at 800 ° C.

This is because carbonization at high temperature increases the surface area of the fiber and also increases the pore diameter, which means that the activated carbon nanofibers carbonized at 1000 ° C have the most effective pore distribution that can be adsorbed when activated at 1000 ° C. The longest breakthrough time and the most adsorption amount were found.

Example 5

The adsorption capacities of the fibrous adsorbents prepared in Examples 1 to 3 of the present invention and the particulate activated carbon, which were previously used as adsorbents of volatile organic compounds, were compared. At this time, the granular activated carbon was purchased from Union Carbon (Naju, Korea), and the adsorption characteristics were investigated by filling a predetermined amount in the adsorption cell.

As a result, Example 1 was 66g / 100g, Example 2 was 72g / 100g, Example 3 was 67g / 100g, and the particulate activated carbon was 24 / 100g. Therefore, Examples 1 to 3 according to the present invention showed more than three times higher adsorption capacity than conventional particulate activated carbon, and had a large ripple effect such that the replacement of granular activated carbon mainly used as a volatile organic compound adsorbent. Judging.

1 is a 30,000-fold magnified image of the scanning micrograph of Example 1 containing 10 wt% cellulose acetate precursor.

FIG. 2 is a magnified 30,000-fold image of the scanning micrograph of Example 2 containing 20 wt% cellulose acetate precursor. FIG.

FIG. 3 is a magnified 30,000-fold image of the scanning micrograph of Example 3 including 30 wt% cellulose acetate precursor. FIG.

FIG. 4 is a magnified 30,000-fold image of a scanning microscope photograph of Comparative Example 1 without cellulose acetate. FIG.

Figure 5 shows the nitrogen adsorption and desorption isotherm of carbon nanofibers according to the content of cellulose acetate.

Figure 6 shows the diameter distribution of activated carbon nanofibers according to the content of cellulose acetate.

7 shows a breakthrough graph of toluene adsorption.

Claims (9)

a) polyacrylonitrile resin: dissolving a cellulose resin in a solvent in a weight ratio of 70 to 90: 10 to 30 to prepare a fiber precursor composition; b) producing a fiber by applying a voltage of 20 ~ 30kV and electrospinning using the fiber precursor composition; c) heating the fiber to 250 to 300 ° C., and oxidatively stabilizing for 0.5 to 3 hours in an air atmosphere; d) carbonizing the oxidative stabilized fiber at 800 to 1000 ° C. in an inert atmosphere or in a vacuum state; e) activating the carbonized fiber in 800 ~ 1000 ℃, steam atmosphere; Method for producing a fibrous adsorbent for volatile organic compound adsorption comprising a. The method of claim 1, The fiber precursor composition is a method for producing a fibrous adsorbent for adsorbing volatile organic compounds, characterized in that the solid content of 10 to 30% by weight. The method of claim 1, The cellulose-based resin is a cellulose acetate, cellulose acetate, cellulose, cellulose acetate butyrate, cellulose acetate petalate, cellulose acetate propionate manufacturing method of the fibrous adsorbent for adsorbing volatile organic compounds, characterized in that at least one selected from. . The method of claim 1, The polyacrylonitrile resin has a weight average molecular weight of 50,000 to 500,000, and the cellulose-based resin has a weight average molecular weight of 30,000 to 500,000. The method of claim 1, The solvent is any one or more selected from dimethylformamide (DMF), dimethylacetamide (DMAc), tetrahydrofuran (THF), the method of producing a fibrous adsorbent for adsorption of volatile organic compounds. Fibrous adsorbent prepared by the manufacturing method according to any one of claims 1 to 5. The method of claim 6, The fibrous adsorbent is a fibrous adsorbent, characterized in that the adsorption amount of volatile organic compounds is 65 ~ 80g / 100g. The method of claim 7, wherein The fibrous adsorbent is a fibrous adsorbent, characterized in that the diameter of the fiber 150 ~ 500 nm. The method of claim 8, The fibrous adsorbent has a specific surface area of 1403 to 1566 m 2 / g, the diameter of the micropores of 6.0 to 6.8 Å, the diameter of the mesopores of 40 to 65 Å, characterized in that the fibrous adsorbent.

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