CN112619599B - Active carbon fiber and preparation method thereof - Google Patents

Abstract

The application provides an activated carbon fiber and a preparation method thereof. The ash content of the activated carbon fiber is 0.8wt% -3wt%, and the specific surface area is 1000m ² /g‑2200m ² The total pore volume is 0.4120cc/g-0.8370cc/g, the 1-2nm pore volume ratio is 28% -75%,200mg/m ³ The xylene adsorption capacity is 20-45%. The preparation method of the activated carbon fiber comprises the following steps: impregnating the raw material with a phosphoric acid aqueous solution, drying, carbonizing, cooling, washing and drying to obtain the activated carbon fiber; the mass fraction of the phosphoric acid aqueous solution is 5-13%. According to the activated carbon fiber and the preparation method thereof, phosphoric acid can repeatedly permeate into the fiber, the adhesion phenomenon cannot occur, the production process is continuously carried out, the production efficiency is high, the production cost is low, and the performance of the obtained activated carbon fiber is excellent.

Description

Activated carbon fiber and its preparation method

technical field

The invention relates to the field of activated carbon fibers, in particular to an activated carbon fiber and a preparation method thereof.

Background technique

In the prior art, the method of phosphate catalysis and high-temperature carbonization is generally used in the manufacture of activated carbon fibers. This method has the following problems: first, the phosphate remaining on the fiber surface increases the ash content of the product; second, the pyrolyzed phosphate will cause great corrosion damage to the equipment, and the maintenance cost of the equipment is high, resulting in an increase in production cost; The 3rd, usually need to use activator, but activator can cause the ablation of charcoal, has greatly reduced the yield of product (generally only 18-23%), causes raw material great waste, further increases production cost; 4th, The ablation in the activation stage causes a great loss of carbon material (the loss is 30%-50% of the carbonized fiber), which makes the activated carbon fiber structure loose, and its bulk density is generally 60-150Kg/m ³ , the use of this type of activated carbon Fibers are not conducive to the preparation of miniaturized filter components. In addition, due to a large amount of ablation of carbon materials, the strength of activated carbon fibers deteriorates, resulting in a reduction in the service life of gas filter components made of activated carbon fibers; fifth, the product pore size is small, and the proportion of pores less than 1nm is high, and the pore size distribution range is narrow. The regeneration effect of activated carbon fibers after adsorption is poor.

In view of this, the present invention is proposed.

Contents of the invention

The first object of the present invention is to provide an activated carbon fiber with large specific surface area, high strength, no sticking problem, low ash content, and excellent adsorption and desorption properties.

The second object of the present invention is to provide a method for preparing activated carbon fibers with low cost, high product yield and excellent performance.

In order to realize the above-mentioned purpose of the present invention, special adopt following technical scheme:

An activated carbon fiber, the ash content of the activated carbon fiber is 0.8wt%-3wt%, the specific surface area is 1000m ² /g-2200m ² /g, the total pore volume is 0.4120cc/g-0.8370cc/g, and the pores are 1-2nm The volume ratio is 28%-75%, and the adsorption capacity of 200mg/m ³ xylene is 20%-45%.

A preparation method of activated carbon fiber, comprising:

impregnating raw materials with phosphoric acid aqueous solution, carbonizing after drying, cooling, washing with water, and drying to obtain the activated carbon fibers;

The raw material is man-made fibers and/or natural fibers;

The mass fraction of the phosphoric acid aqueous solution is 5%-13%.

Using phosphoric acid as the impregnation solution has the following advantages: 1. It can effectively improve the impregnation process. By controlling the concentration of the phosphoric acid aqueous solution, phosphoric acid can fully penetrate into the fiber during the impregnation process and fully exert its catalytic dehydration effect; 2. .Inhibit the production of tar, so that more carbon materials can be retained, and the yield of the final product can be increased; 3. Phosphoric acid also has a swelling effect, which can penetrate into the fiber at a temperature lower than 200 ° C, dissolving the cellulose and thus Form voids; 4. Accelerate carbonization, change the pyrolysis process of raw materials, reduce the activation temperature, and the fiber product impregnated with superphosphoric acid will heat up quickly and evenly, without local overheating, so the activation time is short; 5. Pore-forming effect, after phosphoric acid is removed by water washing , the original phosphoric acid sites generate corresponding pores; 6. Promote aromatization. After phosphoric acid is loaded, the size of condensed aromatic hydrocarbons in fiber raw materials increases significantly, and the dehydrogenation temperature decreases and the amount of dehydrogenation increases; 7. The hydroxyl group in phosphoric acid and polymer Dehydration and cross-linking, and the generation of phosphate bonds, improve the thermal dimensional stability of cellulose, so that the pores that have been formed are retained. After the temperature rises, the phosphate bonds are destroyed, and the shrinkage of the pores will occur, reducing the specific surface and pore volume. After that, the temperature continues to rise, and the phosphorus oxide produced by the decomposition of phosphoric acid has the ability to oxidize, so that the pores continue to increase.

It should be noted that if the concentration of phosphoric acid is too low, it cannot play an effective role, and the amount of phosphoric acid solution used will be too large, resulting in a longer drying time, which is not conducive to continuous production, and at the same time increases energy consumption and cost; if the concentration of phosphoric acid is too high , Phosphoric acid cannot be repeatedly penetrated into the fiber during the impregnation process, which will cause serious sticking and silk problems of activated carbon fibers. The water consumption in the washing process increases, and the energy consumption and difficulty of the phosphoric acid concentration and reuse process increase. Therefore, the use of phosphoric acid with an appropriate concentration in the impregnation stage can also reduce the energy consumption of the activated carbon fiber washing and recovery of phosphoric acid refining process, and reduce production costs.

Preferably, the raw material is paper, felt or cloth processed from artificial fibers and/or natural fibers and their respective raw materials, and the artificial fibers include one of viscose fiber, solvent-process cellulose fiber and cupro ammonia fiber or more; the natural fiber includes one or more of hemp fiber, cotton fiber and silk fiber.

Various forms of raw materials can be used to obtain various forms of products, effectively meeting the purpose of mass production.

Preferably, the mass ratio of phosphoric acid in the phosphoric acid aqueous solution to the raw material is 0.2-0.8:1.

Preferably, the impregnation time is 10-600min, and the impregnation temperature is 10-65°C, preferably 40-65°C; after the impregnation is completed, the mass ratio of the raw material, the phosphoric acid, and the water is 1:(0.2- 0.8): (1.8-9.2).

The impregnation process can be further optimized by controlling the impregnation ratio, impregnation time, and impregnation temperature. The degree of impregnation can be controlled by controlling the proportion of materials after impregnation.

Preferably, the drying method is air drying or hot air drying, the temperature of the drying air is 20-50° C., and the mass ratio of the man-made fibers or natural fibers, the phosphoric acid, and water after drying is 1:(0.2- 0.8): (0-1).

Preferably, the carbonization is carried out in an air atmosphere or an inert gas atmosphere, using a gradient temperature rise method:

The temperature of the first gradient is 50-80°C and the time is 10-30min; the temperature of the second gradient is 90-110°C and the time is 15-32min; the temperature of the third gradient is 120-160°C and the time is 15-40min ; The temperature of the fourth gradient is 200-250°C, and the time is 10-20min; the temperature of the fifth gradient is 280-300°C, and the time is 0-20min; the temperature of the sixth gradient is 300-450°C, and the time is 10- 90min.

Gradient heating can optimize the carbonization process and ensure the carbonization effect. Gradient heating can make the heating equipment work intermittently, which usually only accounts for about 30% of the total power, and the power consumption per hour is greatly reduced, saving energy consumption and reducing costs.

Preferably, the end point of the cooling is room temperature.

Preferably, the water washing adopts a multi-stage countercurrent washing mode, the temperature of the water washing is 65-95°C, and the quality of the water used in the water washing is 1-12 times the mass of the activated carbon fiber; the number of stages is 3- 5 levels, each level washing residence time is 5-20min.

Multi-stage countercurrent washing can effectively clean the carbonized fibers, reduce the ash content and ensure the specific surface area.

Optionally, the drying temperature is 90-120° C.; preferably, blast drying is used for the drying, and the hot air circulation volume is 300-900 m ³ /kg of the activated carbon fiber.

An activated carbon fiber is prepared by using the preparation method of the activated carbon fiber.

Compared with prior art, the beneficial effect of the present invention is:

(1) The activated carbon fiber provided by the application has large specific surface area, low ash content, high strength, and good adsorption and desorption properties;

(2) The preparation method of activated carbon fibers provided by the application has low cost, high production efficiency, high yield, and no sticking problem.

Description of drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art.

Fig. 1 is the schematic diagram of the carbonization equipment that the embodiment of the present application uses;

Fig. 2 is the partial process flow diagram of the embodiment of the present application;

Fig. 3 is the comparative figure of the pore size distribution interval of the activated carbon fiber obtained in Example 5 of the present application and commercially available products;

Figure 4 is a comparison chart of the volatile content of activated carbon fibers obtained in Example 5 of the present application and commercially available products.

detailed description

Embodiments of the present invention will be described in detail below in conjunction with examples, but those skilled in the art will understand that the following examples are only for illustrating the present invention, and should not be considered as limiting the scope of the present invention. Those who do not indicate the specific conditions in the examples are carried out according to the conventional conditions or the conditions suggested by the manufacturer. The reagents or instruments used were not indicated by the manufacturer, and they were all conventional products that could be purchased from the market.

Example 1

The viscose fiber felt is soaked in 65°C, 5% phosphoric acid solution for 10min, the mass ratio of phosphoric acid in the phosphoric acid aqueous solution to viscose fiber is 0.2:1, and dried with hot air at 50°C until the material is composed of viscose fiber: phosphoric acid: water = 1 :0.2:0.3. Then use the carbonization equipment shown in Figure 1 to carry out carbonization. The carbonization process selects a gradient temperature rise: the temperature of the first gradient is 70°C and the time is 18min; the temperature of the second gradient is 96°C and the time is 20min; the temperature of the third gradient The temperature of the fourth gradient is 280°C and the time is 8 minutes; the temperature of the sixth gradient is 450°C and the time is 90 minutes. As shown in Figure 2, cool to room temperature after carbonization, and then use 3 stages of countercurrent water washing, the temperature of water washing is 75 ° C, the quality of water used for water washing is 12 times the quality of the activated carbon fiber, and the residence time of each stage of water washing 15min. Then carry out blast drying, the drying temperature is 90°C, and the hot air circulation volume is 900m ³ /kgACF to obtain activated carbon fibers.

Measured: activated carbon fiber (ACF) yield 44%, ash content 1.3%, ACF specific surface area 1374m ² /g, total pore volume 0.4750cc/g, 1-2nm pore volume accounts for 30.52% of the total pore volume, non-sticky The fiber mat is soft, and the dynamic adsorption capacity of 200mg/m ³ xylene is 25%.

Example 2

Solvent method cellulose fiber paper is immersed in 45°C, 8% phosphoric acid solution for 540min, the mass ratio of phosphoric acid in phosphoric acid aqueous solution to solvent method cellulose fiber is 0.3:1, and dried with hot air at 40°C until the material is composed of solvent method cellulose fiber : phosphoric acid: water = 1:0.3:1. Then carbonization is carried out, and the carbonization process selects a gradient temperature rise: the temperature of the first gradient is 80°C, and the time is 10min; the temperature of the second gradient is 96°C, and the time is 15min; the temperature of the third gradient is 160°C, and the time is 15min; The temperature of the fourth gradient is 200° C. and the time is 20 minutes; the temperature of the fifth gradient is 300° C. and the time is 20 minutes; the temperature of the sixth gradient is 400° C. and the time is 30 minutes. Cool to room temperature after carbonization, and then adopt 4 stages of countercurrent washing, the temperature of water washing is 95°C, the quality of water used for water washing is 1 times the mass of the activated carbon fiber, and the residence time of each stage of water washing is 5min. Then carry out blast drying, the drying temperature is 120°C, the hot air circulation volume is 300m ³ /kgACF, and activated carbon fibers are obtained.

Measured: activated carbon fiber (ACF) yield 43%, ash 0.93%, ACF specific surface 1892m ² /g, total pore volume 0.6483cc/g, 1-2nm pore volume accounts for 60.14% of the total pore volume, non-stick The fiber mat is soft, and the dynamic adsorption capacity of 200mg/m ³ xylene is 36%.

Example 3

The copper ammonia fiber mat is immersed in 10% phosphoric acid solution at 30°C for 30 minutes, the mass ratio of phosphoric acid in the phosphoric acid aqueous solution to cupro fiber is 0.5:1, and dried with hot air at 50°C until the material is composed of cupro ammonia fiber: phosphoric acid: water = 1 :0.5:0.6. Then carbonization is carried out, and the carbonization process selects a gradient temperature rise: the temperature of the first gradient is 60°C, and the time is 15min; the temperature of the second gradient is 110°C, and the time is 20min; the temperature of the third gradient is 150°C, and the time is 40min; The temperature of the fourth gradient is 250° C., and the time is 10 minutes; the time of the fifth gradient is 0; the temperature of the sixth gradient is 400° C., and the time is 60 minutes. Cool to room temperature after carbonization, and then use 5 stages of countercurrent washing, the temperature of water washing is 80 ° C, the quality of water used for water washing is 6 times the mass of the activated carbon fiber, and the residence time of each stage of water washing is 20min. Then carry out blast drying, the drying temperature is 100°C, the hot air circulation volume is 600m ³ /kgACF, and activated carbon fibers are obtained.

Measured: activated carbon fiber (ACF) yield 43%, ash content 1.28%, ACF specific surface 1963m ² /g, total pore volume 0.6954cc/g, 1-2nm pore volume accounts for 63.29% of the total pore volume, non-sticky The fiber mat is soft, and the dynamic adsorption capacity of 200mg/m ³ xylene is 39%.

Example 4

The viscose fiber cloth is soaked in 25 ℃, 5% phosphoric acid solution for 200min, the mass ratio of the phosphoric acid in the phosphoric acid aqueous solution and the viscose fiber cloth is 0.4:1, dry naturally until the material is composed of viscose fiber cloth: phosphoric acid: water = 1:0.4:0.8. Then carbonization is carried out, and the carbonization process selects a gradient temperature rise: the temperature of the first gradient is 60°C, and the time is 20min; the temperature of the second gradient is 90°C, and the time is 30min; the temperature of the third gradient is 150°C, and the time is 15min; The temperature of the fourth gradient is 250° C., and the time is 15 minutes; the time of the fifth gradient is 0; the temperature of the sixth gradient is 350° C., and the time is 60 minutes. Cool to room temperature after carbonization, and then use 3-stage countercurrent washing, the temperature of water washing is 90 ° C, the quality of water used for water washing is 10 times the mass of the activated carbon fiber, and the residence time of each stage of water washing is 15min. Then carry out blast drying, the drying temperature is 110°C, the hot air circulation volume is 800m ³ /kgACF, and activated carbon fibers are obtained.

Measured: activated carbon fiber (ACF) yield 44%, ash 0.86%, ACF specific surface 1298m ² /g, total pore volume 0.4472cc/g, 1-2nm pore volume accounts for 28.47% of the total pore volume, non-sticky The fiber mat is soft, and the dynamic adsorption capacity of 200mg/m ³ xylene is 20%.

Example 5

Solvent method cellulose fiber mat is immersed in 13% phosphoric acid solution at 20°C for 600min, the mass ratio of phosphoric acid in phosphoric acid aqueous solution to solvent method cellulose fiber mat is 0.5:1, and dried with hot air at 50°C until the material is composed of solvent method fiber Vegan fiber mat: phosphoric acid: water=1:0.5:0.5. Then carbonization is carried out, and the carbonization process selects a gradient temperature rise: the temperature of the first gradient is 50°C, and the time is 30min; the temperature of the second gradient is 90°C, and the time is 32min; the temperature of the third gradient is 120°C, and the time is 15min; The temperature of the fourth gradient is 250° C., and the time is 20 minutes; the time of the fifth gradient is 0; the temperature of the sixth gradient is 300° C., and the time is 90 minutes. After carbonization, cool to room temperature, and then use 3-stage countercurrent washing, the temperature of water washing is 70 °C, the quality of water used for washing is 3 times the mass of activated carbon fiber, and the residence time of each stage of washing is 10min. Then carry out blast drying, the drying temperature is 100°C, the hot air circulation volume is 400m ³ /kgACF, and activated carbon fibers are obtained.

Measured: activated carbon fiber (ACF) yield 42%, ash content 1.09%, ACF specific surface area 2059m ² /g, total pore volume 0.7162cc/g, 1-2nm pore volume accounts for 72.51% of the total pore volume, non-sticky The fiber mat is soft, and the dynamic adsorption capacity of xylene at 200 mg/m ³ is 41%.

Example 6

The hemp fiber cloth is immersed in 35°C and 7% phosphoric acid solution for 300min, the mass ratio of phosphoric acid in the phosphoric acid aqueous solution to the hemp fiber cloth is 0.8:1, and it is naturally dried until the material is composed of hemp fiber cloth: phosphoric acid: water = 1:0.8 :0.7. Then carbonization is carried out, and the carbonization process selects a gradient temperature rise: the temperature of the first gradient is 65°C, and the time is 25min; the temperature of the second gradient is 110°C, and the time is 20min; the temperature of the third gradient is 150°C, and the time is 35min; The temperature of the fourth gradient is 230° C., and the time is 15 minutes; the temperature of the fifth gradient is 280° C., and the time is 10 minutes; the temperature of the sixth gradient is 450° C., and the time is 60 minutes. Cool to room temperature after carbonization, and then use 4 stages of countercurrent washing, the temperature of water washing is 85 °C, the quality of water used for washing is 8 times the mass of activated carbon fiber, and the residence time of each level of water washing is 15min. Then carry out blast drying, the drying temperature is 110°C, the hot air circulation volume is 600m ³ /kgACF, and activated carbon fibers are obtained.

Measured: activated carbon fiber (ACF) yield 40%, ash content 1.29%, ACF specific surface area 1536m ² /g, total pore volume 0.5628cc/g, 1-2nm pore volume accounted for 49.28% of the total pore volume, non-sticky The fiber felt is soft, and the dynamic adsorption capacity of xylene at 200 mg/m ³ is 31%.

It can be seen that the preparation method of activated carbon fibers provided by the application avoids the problem of sticking and threading of activated carbon fibers during the carbonization process, improves the yield of activated carbon fibers, increases the strength of activated carbon fibers, reduces the ash content, and improves the performance of activated carbon fibers. The specific surface of activated carbon fiber, the prepared activated carbon fiber is softer and has better performance.

Comparative example 1

The viscose fiber cloth is soaked in 20% phosphoric acid solution at room temperature for 16 hours, the mass ratio of phosphoric acid aqueous solution to viscose fiber is 1:10, take out the fiber raw material and fully dry it with a centrifugal dryer, then dry it in the sun, and then carbonize it. Process Nitrogen atmosphere, carbonization activation temperature is 450°C, and total carbonization activation time is 2h. After carbonization, cool to room temperature, wash with water to remove residual phosphoric acid, and dry at 110°C to obtain activated carbon fibers.

Measured to get: activated carbon fiber (ACF) yield 38%, ACF specific surface 702m ² /g, ash content 1.5%, fiber mat soft, poor strength.

Comparative example 2

The viscose fiber silk is soaked in 35% phosphoric acid solution at room temperature for 12 hours. The mass ratio of phosphoric acid solution to viscose fiber is 1:10. Take out the fiber raw material and fully dry it with a centrifugal dryer, then dry it in the sun, and then carbonize it. Process Nitrogen atmosphere, carbonization activation temperature is 400°C, and total carbonization activation time is 2h. After carbonization, cool to room temperature, wash with water to remove residual phosphoric acid, and dry at 110°C to obtain activated carbon fibers.

Measured to obtain: activated carbon fiber (ACF) yield 40%, ACF specific surface 1117m ² /g, ash content 1.8%, fiber felt soft, poor strength.

Comparative example 3

Collect solvent method cellulose fiber sample A (Hua Shijie-A900) and viscose fiber sample B (Hua Shijie-B1200) on the market at present, compare with the activated carbon fiber sample prepared in Example 5, determine its specific surface area and pore size distribution, the results are shown in Table 1 below, the pore size distribution range is shown in Figure 3, and the volatile content comparison is shown in Figure 4.

Table 1 Comparison of performance parameters

It can be seen from the above table 1 that the specific surface area, total pore volume, volatile matter content, and xylene dynamic adsorption capacity of the activated carbon fiber obtained in the present application are better than those of commercially available products, and the pore size distribution is more reasonable.

In order to further illustrate the composition of the activated carbon fiber prepared by the present application and compare it with commercially available products, collect activated carbon fiber samples currently on the market, compare them with the samples prepared in Example 4, and determine the difference in their elemental composition. The results are shown in Table 2 below:

Table 2 Element content

As can be seen from Table 2, the oxygen content of the activated carbon fibers obtained by the present application is higher than that of commercially available products, and the nitrogen content is lower than that of commercially available products.

The preparation method of activated carbon fiber provided by this application has low cost, high production efficiency, high yield, and no sticking problem; the activated carbon fiber provided by this application has large specific surface area, low ash content, high strength, and excellent adsorption and desorption properties. it is good.

For those skilled in the art, various modifications and changes may occur in this application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of this application shall be included within the protection scope of this application. While particular embodiments of the invention have been illustrated and described, it should be appreciated that various other changes and modifications can be made without departing from the spirit and scope of the invention. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this invention.

Claims (5)

1. A preparation method of activated carbon fiber, characterized in that, comprising: Using a phosphoric acid aqueous solution with a mass fraction of 5%-13% to impregnate raw man-made fibers and/or natural fibers, carbonize after drying, cool, wash, and dry to obtain the activated carbon fibers, the ash content of the activated carbon fibers is 0.8wt%-3wt %, the specific surface area is 1000m ² /g-2200m ² /g, the total pore volume is 0.4120 cc/g-0.8370cc/g, the proportion of 1-2nm pore volume is 28%-75%, 200mg/m ³ xylene adsorption The capacity is 20%-45%; The immersion temperature is 10-65°C; the drying method before carbonization is air drying or 20-50°C hot air drying, and the mass ratio of the artificial fiber or natural fiber, the phosphoric acid, and water after drying is 1:( 0.2-0.8): (0-1); the carbonization is carried out in an air atmosphere or an inert gas atmosphere, using a gradient temperature rise method, the temperature of the first gradient is 50-80°C, and the time is 10-30min; the second gradient The temperature is 90-110°C and the time is 15-32min; the temperature of the third gradient is 120-160°C and the time is 15-40min; the temperature of the fourth gradient is 200-250°C and the time is 10-20min; the fifth gradient The temperature of the gradient is 280-300°C, and the time is 0-20min; the temperature of the sixth gradient is 300-450°C, and the time is 10-90min; the washing adopts a multi-stage countercurrent washing mode, and the washing temperature is 65-95 °C, the mass of water used for the washing is 1-12 times the mass of the activated carbon fiber; the number of stages is 3-5, and the residence time of each stage of washing is 5-20min. 2. preparation method according to claim 1, is characterized in that, described raw material is the paper, felt or cloth that its raw material processing forms with man-made fiber and/or natural fiber, and described man-made fiber comprises viscose fiber, One or more of solvent-processed cellulose fibers and cupro fibers; the natural fibers include one or more of hemp fibers, cotton fibers, and silk fibers. 3. The preparation method according to claim 1, characterized in that, the soaking time is 10-600min, and the soaking temperature is 40-65°C; after the soaking is completed, the raw material man-made fiber or natural fiber, the phosphoric acid, The mass ratio of water is 1:(0.2-0.8):(1.8-9.2). 4. preparation method according to claim 1 is characterized in that, the end point of described cooling is room temperature. 5. The preparation method according to any one of claims 1-4, characterized in that the drying temperature after carbonization is 90-120°C; the drying adopts blast drying, and the hot air circulation volume is 300-900m ³ /kg. Activated carbon fiber.

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