CN115434038B - High-softening-point asphalt-based microporous activated carbon fiber and preparation method thereof - Google Patents

Abstract

The invention discloses a pitch-based microporous activated carbon fiber with a high softening point and a preparation method thereof, belonging to the technical field of activated carbon fiber preparation. The invention uses coal direct liquefaction residue as a raw material and prepares a pitch-based activated carbon fiber through a continuous method of pre-oxidation, carbonization and activation. Microporous activated carbon fibers. The invention proposes a high value-added utilization method of coal direct liquefaction residue, and the process is simple, time-consuming and low energy consumption, and the pitch-based microporous activated carbon fiber prepared by the invention is evenly activated, has excellent adsorption performance, large specific surface area, micro The porosity is as high as 98.71%.

Description

A kind of pitch-based microporous activated carbon fiber with high softening point and preparation method thereof

technical field

The invention belongs to the technical field of active carbon fiber preparation, and in particular relates to a pitch-based microporous active carbon fiber with a high softening point and a preparation method thereof.

Background technique

Activated carbon fiber is a new type of material after granular and powdered activated carbon. It is a new type of high-efficiency adsorption material with excellent pore structure and specific surface area in the form of fibers. The remarkable feature of activated carbon fiber is that it has a high specific surface area (1000-3000m ² /g) and abundant micropores. The volume of micropores reaches more than 90% of the total pore volume. Therefore, activated carbon fibers are considered to be very promising adsorbents. . According to different preparation raw materials, activated carbon fibers can be divided into pitch-based activated carbon fibers, phenolic-based activated carbon fibers, viscose-based activated carbon fibers, and polyacrylonitrile-based activated carbon fibers. Among them, pitch-based fibers are developing rapidly due to the characteristics of low raw material, high carbonization yield, and large specific surface area of products. However, phenolic-based and polyacrylonitrile-based activated carbon fibers are generally prepared so far, and there are still technical shortcomings in the production and preparation process of pitch-based activated carbon fibers.

A large amount of coal liquefaction residue will be produced in the process of direct coal liquefaction, accounting for about 30% of the total coal input. The efficient, reasonable and high value-added utilization of coal liquefaction residue is of great significance to the development and application of coal direct liquefaction technology. The preparation of carbon fiber is a way of high value-added utilization of coal direct liquefaction residue developed in recent years.

Literature "Li Ji. Preparation of activated carbon fiber and its performance of adsorption of volatile organic compounds and CO ₂ [D]. Dalian University of Technology, 2020." Using phenolic fiber as raw material, copper chloride as activator, by adjusting copper chloride phenolic-based activated carbon fibers with different specific surface area and pore size distribution; but the raw material of this method is fiber felt, and the microporosity of the prepared activated carbon fibers is only more than 90%. Literature "Luo Jingyuan, Qiu Weihua, Mei Yongzhan, Yu Zongsen. Preparation and Adsorption of Activated Carbon Fibers [J]. Journal of University of Science and Technology Beijing, 1989(05): 481-485." Taking pre-oxidized pitch-based fibers as The raw material is impregnated in ZnCl ₂ and heated up to 350°C under air atmosphere to oxidize the surface, and then heated up to the activation temperature under nitrogen atmosphere to carbonize, and CO ₂ is used as the activator to obtain pitch-based carbon fiber; the raw material of this method is pitch-based fiber , the raw material needs to be further oxidized, the treatment process is complicated, and the specific surface area of activated carbon fiber can only reach 900m ² /g. Literature "Yun Qingyue. Preparation, modification and performance research of phenolic-based activated carbon fiber [D]. Taiyuan University of Technology, 2018." Using novolac resin as raw material, phenolic fiber precursor was prepared by melt spinning, and then processed Phenolic-based activated carbon fibers with high specific surface area are prepared by curing, carbonization and activation; the raw material of this method is phenolic-based activated carbon fibers, and the curing, carbonization and activation processes are not continuous, and there are disadvantages of cumbersome preparation process, long time-consuming and high energy consumption.

Therefore, there is an urgent need for a method for preparing activated carbon fibers using coal liquefaction residue as a raw material through a continuous process to achieve continuous industrial production of coal liquefaction residue-based activated carbon fibers with excellent performance.

Contents of the invention

In order to solve the above-mentioned problems in the prior art, the present invention provides a pitch-based microporous activated carbon fiber with a high softening point and a preparation method thereof.

To achieve the above object, the present invention provides the following technical solutions:

One of the technical solutions of the present invention: a method for preparing high softening point pitch-based microporous activated carbon fibers, comprising the following steps:

(1) Dissolving the coal direct liquefaction residue in tetrahydrofuran, extracting organic matter and preheating, then heating, polymerizing, and cooling to obtain a pitch precursor;

(2) placing the asphalt precursor obtained in step (1) in a vacuum condition and heating and polymerizing again to obtain a high softening point asphalt precursor;

(3) Grinding the high softening point pitch precursor obtained in step (2) into powder, and performing melt spinning to obtain high softening point pitch fiber precursors;

(4) Pre-oxidizing and carbonizing the high softening point pitch fiber precursors obtained in step (3) to obtain high softening point pitch-based carbon fibers;

(5) activating the pitch-based carbon fiber with high softening point obtained in step (4) to obtain the pitch-based microporous activated carbon fiber with high softening point.

Further, in step (1), the preheating, heating polymerization, and cooling are all carried out in an inert atmosphere; the preheating is carried out until the organic matter of the coal direct liquefaction residue can be stirred at a speed of 30 to 60 rpm; the heating polymerization is carried out under stirring The specific steps are: first raise the temperature to 220-300°C, keep it warm for 1h, then raise the temperature to 350-400°C, and keep it warm for 2.5h; the specific steps of the cooling are: first cool to 150°C under stirring conditions, and then stop stirring , naturally cooled to room temperature.

Furthermore, the inert atmosphere is argon, and the flow rate of the inert atmosphere is 100-200ml/min.

Furthermore, the stirring speeds of the heating polymerization stirring and cooling stirring are both 40-100 rpm.

Furthermore, the temperature increase rate of the temperature increase is 5-10° C./min.

Further, in step (2), the vacuum degree of the vacuum condition is below 1000 Pa, the temperature of the reheating polymerization is 270-350° C., and the holding time is 30-60 min.

Furthermore, the temperature increase rate of the temperature increase is 5-10° C./min.

Further, in step (3), the particle size of the powdery high softening point pitch precursor is 0.074-0.178 mm (sieved with 80-200 mesh).

Further, in step (3), nitrogen is used as the extruding gas in the melt spinning, the temperature of the melt spinning is 200° C. to 350° C., and the spinning speed of the spinning tube is 500 to 1000 m/min.

Further, in step (4), the gas atmosphere of the pre-oxidation is oxygen; the temperature of the pre-oxidation is the softening point of the high softening point pitch precursor obtained in step (2), and the holding time is 0-1 h.

Furthermore, the flow rate of the oxygen is 50-100ml/min.

Furthermore, the heating rate is 0.5-1° C./min.

Further, in step (4), the carbonization is carried out in a nitrogen atmosphere, specifically: firstly, the temperature is raised to 700-800°C, and the temperature is kept for 15-30 minutes, and then the temperature is raised to 800-1000°C, and the temperature is kept for 15-30 minutes.

Furthermore, the temperature increase rate of the temperature increase is 5-10° C./min.

Furthermore, the flow rate of the nitrogen gas is 100-200ml/min.

Further, in step (5), the activated gas atmosphere is carbon dioxide, the activation temperature is 850-950° C., and the holding time is 2-4 hours.

Furthermore, the temperature increase rate of the temperature increase is 5-10° C./min.

Furthermore, the flow rate of the carbon dioxide is 100-200ml/min.

Further, in step (5), cooling to room temperature under a carbon dioxide atmosphere is required after the activation.

The second technical solution of the present invention: the high softening point pitch based microporous activated carbon fiber prepared by the method for preparing the high softening point pitch based microporous activated carbon fiber.

Compared with the prior art, the present invention has the following beneficial effects:

(1) The present invention uses coal direct liquefaction residues as raw materials, and prepares pitch-based activated carbon fibers through pre-oxidation, carbonization, and activation continuous methods. The process is simple, time-consuming, and energy-consuming;

(2) The pitch-based microporous activated carbon fiber prepared by the present invention has uniform activation, excellent adsorption performance, large specific surface area, and a microporosity as high as 98.71%.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the accompanying drawings required in the embodiments. Obviously, the accompanying drawings in the following description are only some of the present invention. Embodiments, for those of ordinary skill in the art, other drawings can also be obtained based on these drawings without any creative effort.

Fig. 1 is the scanning electron microscope picture of the pitch-based microporous activated carbon fiber prepared in Example 1 of the present invention;

Fig. 2 is a pore size distribution diagram of pitch-based microporous activated carbon fibers prepared in Example 1 of the present invention.

Detailed ways

Various exemplary embodiments of the present invention will now be described in detail. The detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features and embodiments of the present invention. It should be understood that the terminology described in the present invention is only used to describe specific embodiments, and is not used to limit the present invention.

In addition, regarding the numerical ranges in the present invention, it should be understood that each intermediate value between the upper limit and the lower limit of the range is also specifically disclosed. Each smaller range between any stated value or intervening value in a stated range and any other stated value or intervening value in a stated range is encompassed within the invention. The upper and lower limits of these smaller ranges may independently be included or excluded from the range.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although only the preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and/or materials in connection with which the documents are described. In case of conflict with any incorporated document, the contents of this specification control.

It will be apparent to those skilled in the art that various modifications and changes can be made in the specific embodiments of the present invention described herein without departing from the scope or spirit of the present invention. Other embodiments will be apparent to the skilled person from the description of the present invention. The description and examples of the invention are illustrative only.

As used herein, "comprising", "comprising", "having", "comprising" and so on are all open terms, meaning including but not limited to.

A kind of preparation method of pitch-based microporous activated carbon fiber with high softening point disclosed by the invention comprises the following steps:

(1) Dissolving the coal direct liquefaction residue in tetrahydrofuran, extracting organic matter and preheating, then heating, polymerizing, and cooling to obtain a pitch precursor;

(2) placing the asphalt precursor obtained in step (1) in a vacuum condition and heating and polymerizing again to obtain a high softening point asphalt precursor;

(3) Grinding the high softening point pitch precursor obtained in step (2) into powder, and performing melt spinning to obtain high softening point pitch fiber precursors;

(4) Pre-oxidizing and carbonizing the high softening point pitch fiber precursors obtained in step (3) to obtain high softening point pitch-based carbon fibers;

(5) activating the pitch-based carbon fiber with high softening point obtained in step (4) to obtain the pitch-based microporous activated carbon fiber with high softening point.

Further, in step (1), the preheating, heating polymerization, and cooling are all carried out in an inert atmosphere; the preheating is carried out until the organic matter of the coal direct liquefaction residue can be stirred at a speed of 30 to 60 rpm; the heating polymerization is carried out under stirring The specific steps are: first raise the temperature to 220-300°C, keep it warm for 1h, then raise the temperature to 350-400°C, and keep it warm for 2.5h; the specific steps of the cooling are: first cool to 150°C under stirring conditions, and then stop stirring , naturally cooled to room temperature.

Furthermore, the inert atmosphere is argon, and the flow rate of the inert atmosphere is 100-200ml/min.

Furthermore, the stirring speeds of the heating polymerization stirring and cooling stirring are both 40-100 rpm.

Furthermore, the temperature increase rate of the temperature increase is 5-10° C./min.

Further, in step (2), the vacuum degree of the vacuum condition is below 1000 Pa, the temperature of the reheating polymerization is 270-350° C., and the holding time is 30-60 min.

Furthermore, the temperature increase rate of the temperature increase is 5-10° C./min.

Further, in step (3), the particle size of the powdery high softening point pitch precursor is 0.074-0.178 mm (sieved with 80-200 mesh).

Further, in step (3), nitrogen is used as the extruding gas in the melt spinning, the temperature of the melt spinning is 200° C. to 350° C., and the spinning speed of the spinning tube is 500 to 1000 m/min.

Further, in step (4), the gas atmosphere of the pre-oxidation is oxygen; the temperature of the pre-oxidation is the softening point of the high softening point pitch precursor obtained in step (2), and the holding time is 0-1 h.

Furthermore, the flow rate of the oxygen is 50-100ml/min.

Furthermore, the heating rate is 0.5-1° C./min.

Further, in step (4), the carbonization is carried out in a nitrogen atmosphere, specifically: firstly, the temperature is raised to 700-800°C, and the temperature is kept for 15-30 minutes, and then the temperature is raised to 800-1000°C, and the temperature is kept for 15-30 minutes.

Furthermore, the temperature increase rate of the temperature increase is 5-10° C./min.

Furthermore, the flow rate of the nitrogen gas is 100-200ml/min.

Further, in step (5), the activated gas atmosphere is carbon dioxide, the activation temperature is 850-950° C., and the holding time is 2-4 hours.

Furthermore, the temperature increase rate of the temperature increase is 5-10° C./min.

Furthermore, the flow rate of the carbon dioxide is 100-200ml/min.

Further, in step (5), cooling to room temperature under a carbon dioxide atmosphere is required after the activation.

In the following examples, the coal direct liquefaction residue comes from the National Energy Group, and the tetrahydrofuran soluble organic matter of the coal direct liquefaction residue is obtained after tetrahydrofuran solvent extraction.

Example 1

(1) Weigh 100g of the THF soluble organic matter of the coal direct liquefaction residue, preheat it to 100°C under an argon atmosphere with an argon flow rate of 200ml/min, and wait until the sample melts until the fluidity reaches a stirring speed of 30rpm Finally, start the stirring paddle, heat up to 260°C at a heating rate of 10°C/min for polymerization, keep warm for 1h, then raise the temperature to 360°C at a heating rate of 5°C, and keep warm for 2.5h, during which the stirring paddle maintains a stirring speed of 50rpm;

(2) After the reaction in step (1), cool to 150°C under an argon atmosphere with an argon flow rate of 200ml/min, then stop stirring, then cool naturally to room temperature to obtain a pitch precursor, and measure its softening point, Its softening point is 160°C;

(3) Put the asphalt precursor obtained in step (2) in a vacuum container with a vacuum degree of 800Pa, raise the temperature to 270°C at a heating rate of 5°C, and keep it for 30 minutes to obtain a high softening point asphalt precursor, and measure its softening point, its softening point is 240°C;

(4) Grinding the high softening point asphalt precursor obtained in step (3) to a powdery high softening point asphalt precursor with a particle size of 0.074 mm (200 mesh);

(5) Weigh 20g of the powdery high softening point pitch precursor obtained in step (4) and heat it up to 320°C in a melt spinning machine, keep the temperature at a constant temperature for 30min, spin at a spinning pressure of 0.2MPa, and the spinning drum at a speed of 1000m/min , melt-spinning under the condition of nitrogen as the extrusion gas to obtain high softening point pitch fiber precursors;

(6) Weigh 1.25 g of the high softening point pitch fiber precursor obtained in step (5) and place it in a tube furnace, and raise the temperature to 240 ° C at a heating rate of 0.5 ° C / min under an oxygen atmosphere with an oxygen flow rate of 50 ml / min , pre-oxidized for 30min;

(7) After the pre-oxidation in step (6) is completed, the high softening point pitch fiber precursor is heated to 800°C at 5°C/min under the _N2 atmosphere with a _N2 flow rate of 100ml/min, kept for 15min, and the first step is carried out. Stage carbonization, then raise the temperature to 950°C at 10°C/min under _N2 atmosphere with _N2 flow rate of 100ml/min, keep it warm for 15min, and carry out the second stage carbonization to obtain high softening point pitch-based carbon fibers;

(8) Keep the high softening point pitch-based carbon fiber obtained in step (7) at 950°C for 3 hours in a _CO atmosphere with a _CO flow rate of 100ml/min, and cool to room temperature under a _CO atmosphere to obtain a high softening point pitch based microporous activated carbon fibers.

Example 2

Same as Example 1, the difference is that step (7) is to heat up the high softening point pitch fiber precursors at ₅ ° C./min under _N atmosphere with N flow rate of 100 ml/min after the pre-oxidation of step (6) is completed. To 800°C, hold for 15 minutes, carry out the first stage of carbonization, then raise the _temperature to 920°C at 10°C/min under _N2 atmosphere with a flow rate of N2 of 100ml/min, hold for 15 minutes, carry out the second stage of carbonization, and obtain a high softening point Pitch-based carbon fibers;

Step (8) is to heat the high softening point pitch-based carbon fiber obtained in step (7) at 920°C for 3 hours under a _CO atmosphere with a _CO flow rate of 100ml/min, and cool it to room temperature under a _CO atmosphere to obtain a high softening point Dot pitch-based microporous activated carbon fibers.

Comparative example 1

The same as in Example 1, the difference is that step (1) is to weigh 100 g of THF soluble organic matter from coal direct liquefaction residue, preheat to 100 ° C under an argon atmosphere with an argon flow rate of 200 ml/min, and wait for the sample to melt to After the fluidity reaches a stirring speed of 30rpm, start the stirring paddle, heat up to 360°C at a heating rate of 10°C, and keep the temperature for 3.5 hours, during which the stirring paddle maintains a stirring speed of 50rpm.

Comparative example 2

Same as Embodiment 1, the difference is that step (3) is omitted.

Comparative example 3

Same as Example 1, the difference is that step (7) is to heat up the high softening point pitch fiber precursors at ₁₀ ° C./min under _N atmosphere with N flow rate of 100 ml/min after step (6) pre-oxidation is completed. To 950 ℃, heat preservation for 15 minutes, carbonization, to obtain high softening point pitch-based carbon fiber.

Comparative example 4

Same as Example 1, the difference is that step (7) is to cool the high softening point pitch fiber precursors naturally to room temperature after the pre-oxidation of step (6) is completed, and then in _{the N2} atmosphere with a flow rate of 100ml/min The temperature was raised to 800°C at 5°C/ _min and kept at 15min for the first stage of carbonization, and then the temperature was raised to 950°C at 10°C/min at a _N2 flow rate of 100ml/min and kept at 30min for the second stage of carbonization. Stage carbonization to obtain high softening point pitch-based carbon fibers.

Effect example:

The high softening point pitch-based microporous activated carbon fiber prepared in Example 1 is scanned by a scanning electron microscope, and the results are as shown in Figure 1;

It can be seen from the results of the scanning electron microscope that the fibers still maintain a good fiber shape after activation, and obvious etching marks appear on the surface of the fibers, which has a relatively uniform activation effect.

The high softening point pitch-based microporous activated carbon fiber prepared in Example 1 is tested for pore size distribution, and the specific test method is nitrogen adsorption/desorption test, and the results are as shown in Figure 2;

It can be seen from the pore size distribution diagram that the peak value of the pore size distribution curve is below 2nm, further indicating that the prepared activated carbon fiber is a kind of microporous material.

The activated carbon fiber that embodiment 1-2 and comparative example 1-5 prepare carries out pore size distribution test, and concrete test method is nitrogen adsorption/desorption test, and its result is as shown in table 1:

Table 1 Pore structure differences of activated carbon fibers

sample yield Specific surface area m ² /g Total pore volume cm ³ /g Pore volume cm ³ /g Micropores % Example 1 60% 912 0.232 0.229 98.71 Example 2 50% 798 0.250 0.238 95.20 Comparative example 1 15% 1408 0.594 0.563 94.78 Comparative example 2 42% 1224 0.420 0.390 92.86 Comparative example 3 64% 705 0.222 0.198 89.19 Comparative example 4 47% 1046 0.465 0.403 86.67

The nitrogen adsorption/desorption test results show that pitch-based microporous activated carbon fibers with excellent adsorption performance and a microporosity as high as 98.71% are successfully prepared by the preparation method of the present invention.

It can be seen from Comparative Example 1 that during the polymerization reaction, since molecular polymerization is a slow process, if the temperature is directly raised to 360°C, some molecules in the THF-soluble organic matter of the coal direct liquefaction residue will be evaporated, and cannot occur. The polymerization reaction, therefore, the yield will be greatly reduced, and it will also have a large impact on the number of micropores.

It can be seen from Comparative Example 2 that if vacuum polymerization is not used, the softening point of the pitch precursor is lower, which will have a certain impact on the number of micropores.

It can be known from Comparative Example 3 that if the two-stage carbonization is not adopted, the carbonization and subsequent activation of the activated carbon fiber, the specific surface area of the product and the number of micropores will be affected to a certain extent.

As can be seen from Comparative Example 4, the activated carbon fiber prepared by the continuous method of preoxidation, carbonization and activation of the present invention is better than the number of micropores of the activated carbon fiber prepared by traditional preoxidation, cooling, carbonization, cooling and activation.

The above is only a preferred specific embodiment of the present invention, and the scope of protection of the present invention is not limited thereto. Anyone familiar with the technical field within the technical scope disclosed in the present invention, according to the technical solutions of the present invention and Any equivalent replacement or change of the inventive concepts shall fall within the protection scope of the present invention.

Claims (2)

1. a preparation method of high softening point pitch base microporous activated carbon fiber, is characterized in that, comprises the following steps: (1) Dissolving the coal direct liquefaction residue in tetrahydrofuran, extracting organic matter and preheating, then heating, polymerizing, and cooling to obtain a pitch precursor; (2) placing the asphalt precursor obtained in step (1) in a vacuum condition and heating and polymerizing again to obtain a high softening point asphalt precursor; (3) Grinding the high softening point pitch precursor obtained in step (2) into powder, and performing melt spinning to obtain high softening point pitch fiber precursors; (4) Pre-oxidizing and carbonizing the high softening point pitch fiber precursors obtained in step (3) to obtain high softening point pitch-based carbon fibers; (5) activating the high softening point pitch-based carbon fiber obtained in step (4) to obtain the high softening point pitch-based microporous activated carbon fiber; In step (1), the preheating, heating polymerization, and cooling are all carried out in an inert atmosphere; the preheating is carried out until the organic matter of the coal direct liquefaction residue can be stirred at a speed of 30 to 60 rpm; the heating polymerization is carried out under stirring, Specifically: first heat to 220-300°C, keep warm for 1 hour, then raise the temperature to 350-400°C, keep warm for 2.5 hours; the specific steps for cooling are: first cool to 150°C under stirring conditions, then stop stirring, and cool naturally to room temperature; In step (2), the vacuum degree of the vacuum condition is below 1000Pa, the temperature of the reheating polymerization is 270-350°C, and the holding time is 30-60min; In step (3), the melt spinning uses nitrogen as the extruding gas, the temperature of the melt spinning is 200°C-350°C, and the spinning speed of the spinning tube is 500-1000m/min; In step (4), the gas atmosphere of the pre-oxidation is oxygen; the temperature of the pre-oxidation is the softening point of the high softening point pitch precursor obtained in step (2), and the holding time is 0 to 1 h; In step (4), the carbonization is carried out in a nitrogen atmosphere, specifically: firstly, the temperature is raised to 700-800°C, and the temperature is kept for 15-30min, and then the temperature is raised to 800-1000°C, and the temperature is kept for 15-30min; In step (5), the activated gas atmosphere is carbon dioxide, the activation temperature is 850-950°C, and the holding time is 2-4 hours; In step (5), cooling to room temperature under a carbon dioxide atmosphere is required after the activation. 2. A high softening point pitch-based microporous activated carbon fiber prepared according to the preparation method of the high softening point pitch-based microporous activated carbon fiber according to claim 1.

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