CN105780198B - A kind of preparation method of order mesoporous carbon nano-fiber - Google Patents

Abstract

The invention relates to a preparation method of nanometer carbon fiber with ordered mesopore structure and its products. The preparation method comprises steps: (1) preparing a solution according to a certain ratio of phenolic resin, polyvinylpyrrolidone, amphiphilic copolymer, inorganic salt, and ethanol; (2) preparing nano-carbon fiber precursors by electrospinning; (3) nano-carbon fiber precursors (4) carbonization and pickling to obtain carbon nanofibers. The method has simple process and low cost, and is suitable for large-scale continuous production. The prepared carbon nanofibers are rich in ordered mesopores, the pores are parallel to the fiber axis, the fiber diameter is 300-900nm, the pore diameter can be adjusted at 3-20nm, the mesoporosity is 80-97%, and the specific surface area is 100-900nm. 1000m ² /g, it has potential applications in capacitors, lithium batteries, catalyst carriers, drug carriers, adsorbents, etc.

Description

A kind of preparation method of ordered mesoporous nano carbon fiber

Technical field:

The invention belongs to the technical field of nanoporous carbon fiber preparation, and relates to a preparation method of nanoporous carbon fiber with ordered mesopores and a product thereof.

Background technique

Porous carbon materials are widely used in water and air due to their high specific surface area and developed porosity, good chemical stability, excellent high temperature stability, high electrical conductivity, long cycle life and environmental friendliness. purification, gas separation, catalysis, chromatography, energy storage and other fields. As a new type of porous carbon material, nanoporous carbon fiber has a higher outer surface, shorter pore depth, more uniform pore size distribution, and higher molding and weaving properties unique to fiber materials. It has great potential in the field of adsorption and separation. Significantly enhanced mass transfer rate, higher energy storage density and higher rate performance in the field of energy storage, and higher loading rate and catalytic effect in the field of catalysis.

According to the classification of pore size by the International Union of Pure and Applied Chemistry (IUPAC), the pores of porous carbon materials can be divided into micropores (pore diameter less than 2nm), mesopores (pore diameter between 2nm and 50nm) and macropores (pore diameter greater than 50nm). A large number of studies have shown that the mesopores in carbon materials can not only adsorb organic macromolecules (such as vitamins, dyes, humic acid, dextrin, etc.), so that they can be used in fields involving macromolecules such as sewage treatment, chemical products, and food decolorization. , and its wide pore channel and high specific surface area can realize high-efficiency loading of the catalyst, and can play a shape-selective catalytic role as a catalyst carrier. In recent years, carbon materials with mesoporous structure have received more and more attention and applications in new application fields such as electric double layer capacitors, fuel storage, sensors, lithium batteries, nano-micro reactors, and even as bacteria and drug carriers. . Therefore, carbon nanofibers with mesoporous structure will have broader application prospects.

At present, mesoporous carbon nanofibers generally adopt nano-molding-post-activation method, template-nano-molding method, and polymer-mixed-nano-molding method. The nano molding-post-activation method is to obtain nano-carbon fibers first, and then perform post-activation to obtain porous nano-carbon fibers. Ji Hyun Kim et al. used K ₂ CO ₃ to activate polyacrylonitrile-based carbon nanofibers, and the obtained porous nanocarbon fibers had mesopore distribution between 2-7nm and a specific surface area of 187-704m ² /g (Journal of Industrial and Engineering Chemistry, 25, (2015) 192-198). The patent (200580045720.9) introduces a method of etching carbon fibers using a metal atmosphere to form mesopores, and the obtained carbon nanofibers have mesopores of 20-30 nm on the outer periphery. . In the template-nano forming method, a template agent has been added to the raw material precursor to form fibers, and the template is washed with a solvent to obtain mesoporous carbon nanofibers. Template agents include metal organic or inorganic salts, metal oxides and silicon oxides and compounds. Ji Sun Im et al added nano-silica to polyacrylonitrile solution for electrospinning, pre-oxidation, high-temperature carbonization and washing to obtain mesoporous nano-carbon fibers with a specific surface area of 90-207m ² /g (Journal of Industrialand Engineering Chemistry, 15, (2009) 914-918). The organic blending-nanometer forming method is to form the fiber by blending other organic polymers, and remove the added polymers at high temperature to obtain mesoporous nano-carbon fibers. Zeng Yue et al. blended copolymerized polymer nanoparticles into polyacrylonitrile solution for electrospinning, and obtained carbon nanofibers with mesopore distribution at 3-6nm after pre-oxidation and carbonization, with a fiber diameter of 100-400nm and a ratio of The surface area is 104-535m ² /g, and the mesoporosity is 38-84% (Materials Letters, 161, (2015) 587-590). The patent (application number: 200610052381.3) introduces a method of blending other polymer copolymers in polyacrylonitrile, and then using electrospinning technology to prepare mesopore and macroporous nano-carbon fibers. The patent (201210168735.6) incorporates N-myristoyl L-glutamic acid assemblies into polypyrrole nanofibers, and direct high-temperature treatment to obtain chiral mesoporous carbon nanofibers with a specific surface area of 38-277m2/g. It is easier to form micropores in the later stage of activation, the pore size is not easy to control, and the pore distribution is wider. The specific surface area of carbon nanofibers obtained by organic blending-nanometer molding method is often low. In contrast, the idea of template-nanoforming method is easy to obtain carbon nanofibers with small pores, medium pores and high mesoporosity, and has certain controllability to the pore size. However, the generally obtained pores are disordered pores, and the use of silicon-based templates requires the use of dangerous reagents such as hydrofluoric acid.

Invention content:

The invention provides a method for preparing porous nano-carbon fibers with an ordered mesopore structure using metal inorganic salts and block copolymers as synergistic templates and phenolic resins as carbon precursors and its products. The method is simple in process, the template can be washed away with common dilute acid, and the cost is low. The prepared nanoporous carbon fiber contains abundant ordered mesopores, the pores are parallel to the direction of the fiber axis, the average fiber diameter is 300-700nm, the pore diameter is uniform and adjustable, and the specific surface area is 100-1000m ² /g. The pore structure and pore size distribution are regulated by adjusting the ratio of metal inorganic salt/block copolymer/phenolic resin in the spinning solution and the spinning process parameters.

A method for preparing ordered mesoporous carbon nanofibers provided by the invention comprises the following steps:

(1) Preparation of ethanol solution of phenolic resin/polyvinylpyrrolidone/triblock copolymer/inorganic salt

First, the block copolymer is dissolved in absolute ethanol, and stirred at 10-60° C. to obtain a uniform solution. After 10 minutes, add metal inorganic salt and continue to stir until completely dissolved. Then add ethanol solution of phenolic resin and continue to stir for 2-5h. Finally, polyvinylpyrrolidone was added and stirred for 10-20 hours to obtain a homogeneous solution. The mixed solution is subjected to defoaming treatment, and then sealed and allowed to stand at room temperature for 1-3 days to obtain a spinning solution.

(2) Preparation of carbon nanofiber precursors by electrospinning;

Put the obtained spinning solution into the injection device for electrospinning, the propulsion speed is 5-10uL/min, the voltage is 10-35kV, the distance between two stages is 10-25cm, the spinning environment temperature is 20-35℃, and the humidity is 20 %-50%.

(3) solidification of carbon nanofiber precursor;

The as-spun fiber is cured under 100-180°C flowing air for 1-24h, and the heating rate is 1-5°C/min.

(4) carbonization and pickling to obtain carbon nanofibers.

The carbonization of the precursor is carried out in an inert atmosphere (nitrogen, argon) at a rate of 1-3°C/min to 700-1100°C for 1-5 hours at a constant temperature, and then the samples are taken out after natural cooling. Afterwards, impregnate and stir for 1-3 days with hydrochloric acid, nitric acid, oxalic acid and sulfuric acid with a concentration of 2-10wt.%, and then repeatedly wash with water until the filtrate is neutral. Dry to obtain porous nano-carbon fibers.

As a preferred technical solution:

A method for preparing carbon nanofibers with an ordered mesoporous structure as described above is characterized in that the phenolic resin is a thermosetting resin with an average molecular weight of 500-2500 g/mol.

A method for preparing carbon nanofibers with an ordered mesoporous structure as described above is characterized in that the amphiphilic copolymer is a triblock copolymer, mainly referring to EO, PO, EO including P103, P85, F127, P123, type copolymer.

A method for preparing carbon nanofibers with an ordered mesoporous structure as described above is characterized in that the ratio of the phenolic resin to the block copolymer is 2:1-1:5.

A method for preparing carbon nanofibers with an ordered mesoporous structure as described above is characterized in that the mass fraction of polyvinylpyrrolidone is 3%-6%.

A method for preparing carbon nanofibers with an ordered mesoporous structure as described above, characterized in that the inorganic salts are magnesium nitrate, magnesium acetate, magnesium chloride, nickel nitrate, cobalt nitrate, aluminum nitrate, iron nitrate, iron acetate, chloride At least one of iron, nickel chloride, and copper nitrate.

A method for preparing carbon nanofibers with an ordered mesoporous structure as described above is characterized in that the ratio of the inorganic salt to the phenolic resin is 1:2-5:1.

The above-mentioned electrospun porous carbon fiber product is characterized in that the obtained product is a mesoporous carbon fiber with a diameter of 300-700 nm, the carbon fiber contains mesoporous pores arranged in an orderly manner, and the channels are parallel to the fiber axis direction, and the pore diameter can be between 3-700 nm. The 20nm is adjustable, the mesoporosity is 80-97%, and the specific surface area is 100-1000m ² /g.

The advantages of the present invention are as follows:

Using phenolic resin as carbon precursor, metal inorganic salt, and block copolymer as synergistic template through electrospinning technology combined with high-temperature carbonization and washing process is a new method for preparing nano-carbon fibers with ordered mesoporous structure. Simple, low cost, high carbon yield, less pollution, based on industrial production, provides a simple process route for large-scale production of high-quality porous carbon fibers. The carbon nanofiber prepared by the above method has abundant mesopores, high mesoporosity, orderly arrangement of channels along the fiber axis, high specific surface area, good chemical stability, and is suitable for large-scale continuous production.

Description of drawings

Fig. 1 is the photo of carbon nanofiber SEN obtained in Example 2

Fig. 2 is the pore size distribution diagram of the carbon nanofiber obtained in Example 2.

Fig. 3 is the TEM photograph of nano carbon fiber obtained in Example 2.

detailed description

The present invention will be further described below in conjunction with specific embodiments. It should be understood that these examples are only used to illustrate the present invention and not limit the scope of the present invention. In addition, it should be understood that after reading the teachings of the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of the present application.

Example 1:

A method for preparing ordered mesoporous carbon nanofibers, comprising the following steps:

(1) Preparation of ethanol solution of phenolic resin/polyvinylpyrrolidone/triblock copolymer/inorganic salt

First dissolve the block copolymer F127 in absolute ethanol, and stir at -10°C to obtain a homogeneous solution. After 10 minutes, magnesium nitrate was added, and the mass ratio of inorganic salt to phenolic resin was 1:2. Continue stirring until completely dissolved. Then add phenolic resin ethanol solution (average molecular weight is 500), the ratio of phenolic resin and block copolymer is 1:2. Stirring was continued for 2h. Finally, polyvinylpyrrolidone was added, and the mass fraction of polyvinylpyrrolidone was 3%. After stirring for 10 h, a homogeneous solution was obtained. The mixed solution was subjected to defoaming treatment, and then sealed and stood at room temperature for 1 day to obtain a spinning solution.

(2) Preparation of carbon nanofiber precursors by electrospinning;

The resulting spinning solution was put into an injection device for electrospinning, the propulsion speed was 5uL/min, the voltage was 10kV, the distance between two stages was 10cm, the spinning ambient temperature was 20°C, and the humidity was 50%.

(3) solidification of carbon nanofiber precursor;

The as-spun fibers were cured in flowing air at 100°C for 21 h with a heating rate of 1°C/min.

(1) Carbonization and pickling to obtain carbon nanofibers.

The carbonization of the original silk was carried out in a nitrogen atmosphere at a rate of 1 °C/min to 700 °C for 1 hour, and then the samples were taken out after natural cooling. After that, impregnate and stir with 2wt.% hydrochloric acid for 3 days, and then repeatedly wash with water until the filtrate is neutral. Dry to obtain porous nano-carbon fibers.

The diameter of the obtained electrospun porous carbon fiber is 300-500nm, the mesopores are concentrated at 10nm, the pores are arranged in order along the fiber axis, the mesoporosity is 87%, and the specific surface area is 103m ² /g.

Example 2:

A method for preparing ordered mesoporous carbon nanofibers, comprising the following steps:

(1) Preparation of ethanol solution of phenolic resin/polyvinylpyrrolidone/triblock copolymer/inorganic salt

First dissolve the block copolymer P123 in absolute ethanol and stir at 45°C to obtain a homogeneous solution. After 10 minutes, ferric chloride was added, and the mass ratio of inorganic salt to phenolic resin was 2:1. Continue stirring until completely dissolved. Then add phenolic resin ethanol solution (average molecular weight is 1000), the ratio of phenolic resin and block copolymer is 2:3. Stirring was continued for 3h. Finally, polyvinylpyrrolidone was added, and the mass fraction of polyvinylpyrrolidone was 4%. After stirring for 13h, a homogeneous solution was obtained. The mixed solution was subjected to defoaming treatment, and then sealed and stood at room temperature for 1.5 days to obtain a spinning solution.

(2) Preparation of carbon nanofiber precursors by electrospinning;

The resulting spinning solution was put into an injection device for electrospinning, the propulsion speed was 10uL/min, the voltage was 15kV, the distance between two stages was 12cm, the spinning ambient temperature was 25°C, and the humidity was 40%.

(3) solidification of carbon nanofiber precursor;

The as-spun fibers were cured in flowing air at 120°C for 16 hours with a heating rate of 2°C/min.

(4) carbonization and pickling to obtain carbon nanofibers.

The carbonization of the original silk is carried out in an argon atmosphere at a rate of 2 °C/min to 800 °C for 2 hours, and then the samples are taken out after cooling naturally. Afterwards, impregnate and stir with 4wt.% nitric acid for 2 days, and then wash repeatedly until the filtrate is neutral. Dry to obtain porous nano-carbon fibers.

The diameter of the obtained electrospun porous carbon fiber is 100-600nm, the mesopores are concentrated at 5nm, the pores are arranged in order along the fiber axis, the mesoporosity is 90%, and the specific surface area is 488m ² /g.

Example 3:

A method for preparing ordered mesoporous carbon nanofibers, comprising the following steps:

(1) Preparation of ethanol solution of phenolic resin/polyvinylpyrrolidone/triblock copolymer/inorganic salt.

First dissolve the block copolymer F127 in absolute ethanol, and stir at 50°C to obtain a uniform solution. After 10 minutes, add magnesium chloride, and the mass ratio of inorganic salt to phenolic resin is 3:1. Continue stirring until completely dissolved. Then add phenolic resin ethanol solution (average molecular weight is 1500), the ratio of phenolic resin and block copolymer is 1:2. Stirring was continued for 4h. Finally, polyvinylpyrrolidone was added, and the mass fraction of polyvinylpyrrolidone was 5%. After stirring for 16h, a homogeneous solution was obtained. The mixed solution was subjected to defoaming treatment, and then sealed and allowed to stand at room temperature for (2) days to obtain a spinning solution.

(2) Preparation of carbon nanofiber precursors by electrospinning;

The obtained spinning solution was filled into an injection device for electrospinning, the propulsion speed was 20 μL/min, the voltage was 20 kV, the distance between the two stages was 15 cm, the spinning ambient temperature was 28° C., and the humidity was 20%.

(3) solidification of carbon nanofiber precursor;

The as-spun fibers were cured in flowing air at 140°C for 10 h with a heating rate of 3°C/min.

(1) Carbonization and pickling to obtain carbon nanofibers.

The carbonization of the original silk was carried out in an argon atmosphere, and the temperature was raised to 900°C at a rate of 3°C/min for 3 hours, and then the samples were taken out after natural cooling. Then impregnate and stir with oxalic acid with a concentration of 6wt.% for 1 day, and then wash with water repeatedly until the filtrate is neutral. Dry to obtain porous nano-carbon fibers.

The diameter of the obtained electrospun porous carbon fiber is 500-650nm, the mesopores are concentrated at 4nm, the pores are arranged in order along the fiber axis, the mesoporosity is 80%, and the specific surface area is 989m ² /g.

Example 4:

A method for preparing ordered mesoporous carbon nanofibers, comprising the following steps:

(1) Preparation of ethanol solution of phenolic resin/polyvinylpyrrolidone/triblock copolymer/inorganic salt

First dissolve the block copolymer F127 in absolute ethanol and stir at 55°C to obtain a homogeneous solution. After 10 minutes, aluminum nitrate was added, and the mass ratio of inorganic salt to phenolic resin was 3:1. Continue stirring until completely dissolved and then add phenolic resin ethanol solution (average molecular weight is 2000), the ratio of phenolic resin to block copolymer is 2:5. Stirring was continued for 5h. Finally, polyvinylpyrrolidone was added, and the mass fraction of polyvinylpyrrolidone was 5%. Stir for 18 hours to obtain a homogeneous solution. The mixed solution is subjected to defoaming treatment, and then sealed and allowed to stand at room temperature for 2.5 days to obtain a spinning solution.

(2) Preparation of carbon nanofiber precursors by electrospinning;

The resulting spinning solution was put into an injection device for electrospinning, the propulsion speed was 30uL/min, the voltage was 30kV, the distance between two stages was 18cm, the spinning ambient temperature was 30°C, and the humidity was 30%.

(3) solidification of carbon nanofiber precursor;

The as-spun fibers were cured in flowing air at 160°C for 5 hours, and the heating rate was 4°C/min.

(1) Carbonization and pickling to obtain carbon nanofibers.

The carbonization of the original silk was carried out in an argon atmosphere at a rate of 2 °C/min to 1000 °C for 4 hours, and then the samples were taken out after natural cooling. After that, impregnate and stir with 8wt.% hydrochloric acid for 3 days, and then repeatedly wash with water until the filtrate is neutral. Dry to obtain porous nano-carbon fibers.

The diameter of the obtained electrospun porous carbon fiber is 500-700, the mesopores are concentrated at 3nm and 15nm, the channels are arranged orderly along the fiber axis, the mesoporosity is 95%, and the specific surface area is 840m ² /g.

Example 5:

A method for preparing ordered mesoporous carbon nanofibers, comprising the following steps:

(1) Preparation of ethanol solution of phenolic resin/polyvinylpyrrolidone/triblock copolymer/inorganic salt.

First dissolve the block copolymer P123 in absolute ethanol, and stir at 60°C to obtain a homogeneous solution. After 10 minutes, magnesium acetate was added, and the mass ratio of inorganic salt to phenolic resin was 5:1. Continue stirring until completely dissolved. Then add phenolic resin ethanol solution (average molecular weight is 2500), the ratio of phenolic resin and block copolymer is 1:3. Stirring was continued for 6h. Finally, polyvinylpyrrolidone was added, and the mass fraction of polyvinylpyrrolidone was 6%. After stirring for 20 h, a homogeneous solution was obtained. The mixed solution was subjected to defoaming treatment, and then sealed and stood at room temperature for 3 days to obtain a spinning solution.

(2) Preparation of carbon nanofiber precursors by electrospinning;

The resulting spinning solution was put into an injection device for electrospinning, the propulsion speed was 10uL/min, the voltage was 35kV, the distance between two stages was 20cm, the spinning ambient temperature was 35°C, and the humidity was 35%.

(3) solidification of carbon nanofiber precursor;

The as-spun fibers were cured in flowing air at 180°C for 1 h with a heating rate of 5°C/min.

(1) Carbonization and pickling to obtain carbon nanofibers.

The carbonization of the original silk was carried out in a nitrogen atmosphere at a rate of 3 °C/min to 1100 °C for 5 hours, and then the samples were taken out after natural cooling. Afterwards, it was impregnated and stirred with 10wt.% nitric acid for 2 days, and then washed repeatedly until the filtrate was neutral. Dry to obtain porous nano-carbon fibers.

The diameter of the obtained electrospun porous carbon fiber is 500-900nm, the mesopores are concentrated at 20nm and 5nm, the pores are arranged in order along the fiber axis, the mesoporosity is 97%, and the specific surface area is 604m ² /g.

Claims (9)

1. a kind of preparation method of the carbon nano-fiber with ordered mesopore structure, it is characterised in that its preparation method includes following Several steps：

(1) phenolic resin, polyvinylpyrrolidone, parents notion, inorganic salts, ethanol are configured to according to a certain percentage molten Liquid；

(2) electrostatic spinning prepares carbon nano-fiber precursor；

(3) solidification of carbon nano-fiber precursor；

(4) carbonization, pickling obtain carbon nano-fiber.

2. a kind of preparation method of carbon nano-fiber with ordered mesopore structure according to claim 1, its feature exist In phenolic resin be thermosetting resin, mean molecule quantity 500-2500.

3. a kind of preparation method of carbon nano-fiber with ordered mesopore structure according to claim 1, its feature exist It is triblock copolymer in parents notion, the triblock copolymer is selected from P103, P85, F127, P123.

4. a kind of preparation method of carbon nano-fiber with ordered mesopore structure according to claim 1, its feature exist It is 2: 1-1: 5 in the ratio of phenolic resin and parents notion, the mass fraction of polyvinylpyrrolidone is 3%-6%.

5. a kind of preparation method of carbon nano-fiber with ordered mesopore structure according to claim 1, its feature exist In inorganic salts be magnesium nitrate, magnesium acetate, magnesium chloride, nickel nitrate, cobalt nitrate, aluminum nitrate, ferric nitrate, ferric acetate, iron chloride, chlorination At least one of nickel, copper nitrate.

6. a kind of preparation method of carbon nano-fiber with ordered mesopore structure according to claim 1, its feature exist In the ratio of inorganic salts and phenolic resin be 1: 1-1: 5.

7. a kind of preparation method of carbon nano-fiber with ordered mesopore structure according to claim 1, its feature exist It is in the electrostatic spinning process parameter：Fltting speed is 5-10 μ L/min, and voltage 10-35kV, two-stage spacing is 10- 25cm, spinning environment temperature are 20-35 DEG C, humidity 20%-50%.

8. a kind of preparation method of carbon nano-fiber with ordered mesopore structure according to claim 1, its feature exist In：Described solidification is to rise to 100-180 DEG C of constant temperature 1-24 hour with 1-5 DEG C/min, carbonization be in an inert atmosphere, wherein, Inert atmosphere is nitrogen atmosphere or argon gas atmosphere, and 700-1100 DEG C of constant temperature 1-5 hour is risen to 1-3 DEG C/min, treats it certainly afterwards Sample is so taken out after cooling, described pickling uses concentration to stir dipping for 2-10wt.% hydrochloric acid, nitric acid, oxalic acid or sulfuric acid 1-3 days, filtrate is then washed to repeatedly as neutrality, drying obtains carbon nano-fiber.

9. a kind of carbon nano-fiber with ordered mesopore structure, it is characterised in that the carbon nano-fiber is by claim 1 Prepared by described preparation method, the carbon nano-fiber is mesoporous carbon fiber of the diameter in 300-700nm, and the carbon fiber contains Ordered arrangement it is mesoporous, and duct is parallel to fiber direction of principal axis, aperture 3-20nm, mesoporous 80-97%, specific surface area 100-1000m²/g。