KR20100023946A - Fibrous adsorbent and manufacturing method for voc absorbent - Google Patents

Abstract

PURPOSE: A fibrous adsorbent for adsorbing a volatile organic compound and a method for manufacturing the adsorbent are provided to appropriately control a pore of fiber and adsorption quantity of the volatile organic compound. CONSTITUTION: A fibrous adsorbent for adsorbing a volatile organic compound comprises: a step of manufacturing a fiber precursor composition by adding 0.1 ~ 5 weight% of manganese precursor after dissolve polyacrylo nitrile resin into a solvent; a step of manufacturing the fiber through an electric radiation by adding 20 ~ 30kV voltage using the fiber precursor composition; a step of increasing a temperature of the fiber to 250 ~ 300°C and oxidation-stabilizing the fiber under air atmosphere for 0.5 ~ 3 hours; a step of carbonizing the oxidation-stabilized fiber to 800 ~ 1000°C in inert atmosphere or a vacuum condition; and a step of activating the carbonized fiber at 600 ~ 800°C and steam atmosphere.

Description

Fibrous adsorbent for volatile organic compound adsorption and its manufacturing method {Fibrous Adsorbent and manufacturing method for VOC absorbent}

The present invention relates to an adsorbent for volatile organic compounds using a fiber precursor composition in which polyacrylonitrile and a manganese precursor are mixed, and a method for preparing the same.

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 provides a fibrous adsorbent having an average diameter of 200 to 400 nm, specific surface area of 853 to 1300 m 2 / g, pore diameter of 5.6 to 6.0 mm 3 and mesopores of 59 to 91 mm 2. .

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 the fibrous adsorbent according to the present invention is used, 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 of producing the fibrous adsorbent of the present invention in detail,

a) preparing a fiber precursor composition by dissolving polyacrylonitrile resin in a solvent and then adding manganese precursor in an amount of 0.1 to 5% by weight based on the total solid content;

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 at 600 ~ 800 ℃, 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 the starting material of the present invention, may be dissolved in a solvent after the polyacrylonitrile resin is added, and then mixed with the manganese precursor, but the polyacrylonitrile resin and the manganese precursor are respectively dissolved in the solvent, and then It can be prepared by adjusting the mixing ratio of the two solutions so that the solids content of the manganese precursor in the solids content is 0.1 to 5% by weight.

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.

The manganese precursor may be any one or more selected from manganese acetate, manganese acetate tetrahydrate, manganese acetate dihydrate, manganese acetacetonate, and manganese chlorite. The content of the manganese precursor was found to have the best specific surface area when mixed in the range of 0.1 to 5% by weight, more preferably 0.5 to 1.5% by weight of the total solid content of the fiber precursor composition, excessive mixing On the contrary, it is not preferable because the specific surface area is decreased by increasing the mesopores.

The present invention is to prepare a fiber precursor composition by mixing polyacrylonitrile and manganese precursor, and then using the same to prepare a fiber adsorbent through electrospinning, oxidative stabilization, carbonization, activation step, the inside of the fiber in the activation process Through the catalytic activity of the manganese precursors present in the outside and physical movement by heat, the pores of the activated carbon fibers can be increased, as well as the manufacturing process is simple and the specific surface area can be increased.

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

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 600 to 800 ° 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 are mainly gas activation and chemical activation. Gas activation is a fine porous adsorbed coal by contact reaction at around 1000 ° C with carbonized raw materials in the state of mixing water vapor, carbon dioxide, and oxygen. How to make it. However, in the present invention, activated using steam in the temperature range (600 ~ 800 ℃) lower than the carbonization temperature. The stabilization temperature and time may be given under any conditions, but it is preferable to select a temperature lower than the carbonization temperature so that catalysis of the metal is not induced. When activated at high temperatures above 900 ° C., it can be burned off with little left over in the final product.

 The resulting fibrous adsorbent for adsorption of volatile organic compounds according to the present invention has a fiber diameter of 200 to 400 nm, an average diameter of 250 nm, a specific surface area of 853 to 1300 m 2 / g, and a diameter of micropores of 5.6 To 6.0 kPa, medium and large pore diameters of 59 to 91 kPa, excellent adsorption of 40 to 68 g / 100 g of the adsorption force of the volatile organic compounds 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 flowed per minute, and then the amount of toluene adsorption is gas chromatography. 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, since the process is simpler and easier to handle than the case of using a particulate form, the expected effect is very high as the volatile organic compound adsorbent.

1 is a scanning micrograph and a transmission micrograph according to Example 1 containing 0.5% by weight of manganese. The picture above is 30,000 times magnified. The picture below is 300,000 times magnified.
2 is a scanning micrograph and a transmission micrograph according to Example 2 containing 1.0% by weight of manganese. The picture above is 30,000 times magnified. The picture below is 300,000 times magnified.
3 is a scanning micrograph and a transmission micrograph according to Example 3 containing 1.5% by weight of manganese. The picture above is 30,000 times magnified. The picture below is 300,000 times magnified.
4 shows nitrogen adsorption and desorption isotherms of carbon nanofibers according to manganese content.
Figure 5 shows the pore distribution of activated carbon nanofibers according to the manganese content.
6 shows a breakthrough graph of toluene adsorption.

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.

The fibrous adsorbent prepared according to the embodiment was packed with a diameter of 6 mm and a length of 15 mm adsorbed cells at 0.05 to 0.06 g, and 180 ml of nitrogen gas containing 200 ppmv of toluene was poured per minute. Calculations were performed using chromatography. In the present invention, the experiment was performed at room temperature.

Example 1

A polyacrylonitrile resin (weight average molecular weight 86,200) was added to a solid content of 10% by weight in a dimethylformamide (N, N-dimethylforamide) solvent and dissolved at 60 ° C. for 24 hours to prepare a polymer solution. 0.5% by weight of manganese acetate was added to the polymer solution, and homogenized.

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 separated fibrous web 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 sufficiently oxidative stabilization, the carbonization process was performed at 1000 ° C. for about 1 hour and then activated at 800 ° 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 and transmission micrographs of the fibrous adsorbent thus prepared are shown in FIG. 1. In addition, the nitrogen adsorption and desorption isotherm is shown in FIG. 4, the pore distribution of the fiber is shown in FIG. 5, and the breakthrough curve of toluene adsorption is shown in FIG. 6.

Example 2

Except for mixing 1.0% by weight of manganese acetate in the polymer solution was prepared in the same manner as in Example 1.

Scanning micrographs and transmission micrographs of the fibrous adsorbent thus prepared are shown in FIG. 2. In addition, the nitrogen adsorption and desorption isotherm is shown in FIG. 4, the pore distribution of the fiber is shown in FIG. 5, and the breakthrough curve of toluene adsorption is shown in FIG. 6.

Example 3

Except for mixing the manganese acetate 1.5% by weight in the polymer solution was prepared in the same manner as in Example 1.

Scanning micrographs and transmission micrographs of the fibrous adsorbent thus prepared are shown in FIG. 3. In addition, the nitrogen adsorption and desorption isotherm is shown in FIG. 4, the pore distribution of the fiber is shown in FIG. 5, and the breakthrough curve of toluene adsorption is shown in FIG. 6.

1, 2, and 3 show scanning micrographs and transmission micrographs of fibrous adsorbents prepared by a steam activation method at 800 ° C. for 30 minutes. When activated at a temperature higher than 900 ℃, the final product was burned off with almost no remaining product. This is because the diameter of the fiber produced by electrospinning was very small and the catalytic activity was increased by the mixed manganese. In the present invention, it was activated at 800 ℃.

The average diameter of the activated carbon nanofibers prepared by the manufacturing method was about 250 nm, which is much thinner than the fiber diameter made from melt spinning, solution spinning, and gel spinning, which is a general fiber manufacturing method. It can be seen that manufactured. Also, the surface of the fiber showed that the mesopores increased as the content of manganese increased.

Hereinafter, the results of transmission micrographs will be described in detail.

The white lumps of the transmission micrographs are considered to be manganese element aggregates, and the black pore channels appearing in front and back of the manganese aggregates appear to be made along the migration path of manganese particles. In Example 1 containing 0.5% by weight of manganese, pore channels were observed along several manganese element aggregates and their migration paths. In Example 2 containing 1.0 wt% manganese, the aggregate of manganese elements of the same size as in Example 1 and the resulting pore channel number were much higher than 0.5 wt%. The formation of such pore channels is due to the thermal movement of manganese particles during the activation process. The size of the manganese particles was about 5 to 10 nm, which was much smaller than the 10 to 40 nm shown in the metal-containing activated carbon fibers produced by other methods, and their distribution was evenly distributed. Activated carbon fiber containing 1.5 wt% manganese was found to have a much shorter pore channel length of about 50 nm. This is due to the increase in the content of manganese increases the coalescing of the manganese elements, and the increased manganese element aggregates are relatively large volume and weight compared to the case of low content, it is determined that the formation of pore channels is not easy. Therefore, it can be seen that the method for preparing activated carbon nanofibers containing the pore channel using the electrospinning method according to the present invention can produce nano-sized uniform carbon fibers, and it is possible to maintain the dimensions and structure of the fibers well to stabilize and It was found that the activation conditions were appropriate.

 4 is a chart showing nitrogen adsorption and desorption isotherms of activated carbon nanofibers according to the content of manganese, and FIG. 5 is a chart showing pore distribution of activated carbon nanofibers having different manganese contents.

Carbon nanofibers prepared by mixing a manganese acetate precursor with a polyacrylonitrile solution showed a relatively large surface area, whereas the surface area of carbon nanofibers prepared by spun with polyacrylonitrile alone was 853 m 2 / g. When the content of 0.5% by weight 1053㎡ / g, 1.0% by weight was 1229㎡ / g showed the highest surface area, 1.5% by weight was 918㎡ / g tended to decrease the surface area.

Therefore, it can be seen that the surface area can be controlled by controlling the content of manganese. In addition, the pore size also tended to increase as manganese increased, showing the highest surface area with 5.7Å for 0.5% by weight and 5.8Å for 1.0% by weight, and 5.6Å for 1.5% by weight. Seemed. That is, the manganese precursor plays a good role in increasing the specific surface area and pore size when a certain amount is added, but when it is added above a certain amount, the surface area and the pore size are judged to be reduced. Therefore, it is disclosed through the present invention that the control of the manganese precursor can play an important role in controlling the surface area and pore size.

Adsorption experiments of activated carbon nanofibers in which the pore channel is completed by the carbonization and activation process were carried out by calculating the amount of adsorption from a breakthrough curve, which is a change in concentration of adsorption gas at the inlet and outlet of the adsorbent. Adsorption experiments were carried out by filling the adsorption cells of about 15 mm in length and about 6 mm in diameter by filling stainless steel with about 0.05 to 0.06 g of the adsorption sample. Adsorption experiment in the present invention was performed at room temperature.

7 is a graph showing toluene adsorption properties of each manganese-containing carbon nanofibers. Breakthrough time of activated carbon nanofibers according to manganese content is 1.5 hours for activated carbon nanofibers using polyacrylonitrile-only spun fiber, and when the contents of manganese are 0.5, 1.0, 1.5 wt%, 2.3, 3.3, It was 2.0 hours and the final adsorption amount was 40 / 100g, 50g / 100g, 68g / 100g, 47g / 100g. When 1.0 wt% was contained, the longest breakthrough time and the highest adsorption amount were obtained.

This result shows that the adsorption amount of the activated carbon nanofibers prepared by the manganese mixture is higher than that of the activated carbon nanofibers prepared by spinning the polyacrylonitrile alone. This is related to the specific surface area, pore size, and pore volume. It is believed that the carbon nanofibers containing 1.0 wt% of manganese have a specific surface area and pore size that are optimal for toluene adsorption.

Accordingly, the activated carbon nanofibers prepared after the mixed electrospinning of manganese precursor and polyacrylonitrile according to the present invention were able to form pore channels well, and the pore channels of appropriate size were easier to adsorb toluene. .

Example 4

While preparing in the same manner as in Example 1, carbonization was carried out 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. Toluene adsorption of toluene 42g / adsorbent 100g at 800 ℃, 55g / 100g at 900 ℃, 68g / 100g at 1000 ℃, Indicated.

As such, as the carbonization temperature increases, the adsorption amount tends to increase, and when activated at 1000 ° C, the adsorption amount is 1.6 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, granular activated carbon was purchased from Union Carbon Co., Ltd. (Naju), and the adsorption characteristics were investigated by filling a certain amount into the adsorption cell.

As a result, Example 1 was 50g / 100g, Example 2 was 68g / 100g, Example 3 was 47g / 100g, and the particulate activated carbon was 24g / 100g. Therefore, in Examples 1 to 3 according to the present invention, the adsorption capacity was two times higher than that of the conventional granular activated carbon, and it was judged to have a large ripple effect such that the replacement of the granular activated carbon mainly used as the volatile organic compound adsorbent. do.

Claims (9)

a) preparing a fiber precursor composition by dissolving polyacrylonitrile resin in a solvent and then adding manganese precursor in an amount of 0.1 to 5% by weight based on the total solid content;
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 at 600 ~ 800 ℃, 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 manganese precursor is a manganese acetate, manganese acetate tetrahydrate, manganese acetate dihydrate, manganese acethiaacetonate, manganese chlorite, characterized in that any one or more selected from the fibrous adsorbent for adsorbing volatile organic compounds. The method of claim 1,
The polyacrylonitrile resin is a method of producing a fibrous adsorbent for adsorbing volatile organic compounds, characterized in that the weight average molecular weight is 50,000 ~ 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 the volatile organic compound is 40 ~ 68g / 100g. The method of claim 7, wherein
The fibrous adsorbent is a fibrous adsorbent, characterized in that the average diameter of the fiber 200 ~ 400 nm. The method of claim 8,
The fibrous adsorbent has a specific surface area of 853 to 1300 m 2 / g, the diameter of the fine pores is 5.6 to 6.0 mm 3, the diameter of the medium and large pores is 59 to 91 mm 3.

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