Method for preparing carbon fibers from bamboo fibers

Abstract

The invention discloses a method for preparing carbon fiber from bamboo fiber, which comprises the following steps: extracting bamboo fiber as a raw material, and carrying out catalytic dipping pretreatment, activating treatment and carbonization treatment to obtain the carbon fiber. According to the method, the bamboo fibers are used as the raw material, the interaction between the catalyst and the bamboo fibers is increased through the effect of shortening the carbonization time through dipping catalysis treatment, the carbonization efficiency is improved, resources are saved, and the original fiber network morphology can be maintained in the carbonization process. According to the method, green, low-cost and continuous preparation of the carbon fiber material can be realized, the energy consumption and the production cost are greatly reduced, and the problems that the treatment temperature is high, the treatment time is long, the performance of the carbon fiber cannot meet the requirements and the like when the carbon fiber is prepared by carbonizing the bamboo fiber are solved.

Description

Technical Field

[0001] The invention belongs to the technical field of carbon fibers, and more specifically, relates to a method for preparing carbon fibers from bamboo fibers. Background Art

[0002] Carbon fiber composite materials have many advantages such as high specific strength, high specific modulus, low density, high temperature resistance, corrosion resistance, etc., and are widely used in various fields such as aerospace, transportation, and medical equipment due to their many advantages such as anti-fatigue. At present, the main raw materials for the production of carbon fiber are polyacrylonitrile (PAN), asphalt and viscose fiber. Among them, viscose fiber is rarely used to produce carbon fiber except as ablation materials and other special performance products due to its complex graphitization and low carbonization yield; impurities in asphalt raw materials are difficult to completely remove, and the cost of converting it into mesophase asphalt to prepare high-performance carbon fibers is high.

[0003] The highly porous microstructure of bamboo fiber can greatly reduce the production cost by using renewable bamboo resources to prepare carbon materials. At the same time, compared with petroleum-based products, the preparation using bamboo resources is green and environmentally friendly. Carbonization of bamboo fiber to prepare carbon materials has attracted widespread attention, making it a potential candidate for carbon fiber production. In CN202211475001.2, a method for preparing self-supporting biomass porous carbon is disclosed, which uses natural wood or bamboo as raw materials, removes lignin and hemicellulose by chemical methods, and then undergoes pre-compression and high-temperature carbonization treatment to obtain a self-supporting biomass porous carbon skeleton with anti-compression properties. Although the patent retains the good pore structure and structural integrity of natural wood or bamboo itself, the powdering of the material is avoided during the carbonization process, and the porous carbon obtained has a certain mechanical strength. However, the patent has a high temperature and a long time for its carbonization, and the direct carbonization used may cause the prepared carbonized fiber to fail to meet the ideal performance requirements due to insufficient temperature. Summary of the invention

[0004] The invention provides a method for preparing carbon fiber from bamboo fiber in order to overcome the problems of high processing temperature, long processing time, and performance failing to meet requirements in the existing carbonization of bamboo fiber for preparing carbon fiber.

[0005] The present invention is achieved through the following technical solutions:

[0006] A method for preparing carbon fiber from bamboo fiber, comprising the following steps:

[0007] S1. Bamboo fiber extraction: Bamboo strips are boiled with alkali, neutralized, stripped and dried to obtain bamboo raw fibers;

[0008] S2. Catalyst pretreatment: The bamboo fibers are immersed in a catalyst mixed aqueous solution for catalysis;

[0009] S3. Activation treatment: placing the catalyzed bamboo fiber into an alkaline solution for activation;

[0010] S4. Pre-oxidation treatment: The activated bamboo fiber is heated from room temperature to 400°C under a protective gas atmosphere for 0.5 to 1 hour;

[0011] S5. Carbonization: The pre-oxidized bamboo fiber is heated from 400°C to 1000°C to obtain carbonized fiber.

[0012] Furthermore, the alkaline solution used in the alkali boiling includes 30-50 g / L of NaOH, 25-50 g / L of Na2SO4, and 3-5 g / L of high-temperature penetrant.

[0013] Furthermore, the catalyst content in the catalyst mixed aqueous solution is 1 to 10 wt%.

[0014] Furthermore, the catalyst includes a mixed solution of sulfuric acid and urea, and a CaCl2 solution.

[0015] Furthermore, the mixing ratio of the sulfuric acid and urea is 1:1.

[0016] Furthermore, the pretreatment further comprises heating the impregnated bamboo fibers to 150° C. at 3-5° C. / min, keeping the temperature for 0.5-1 hour for roasting, and then cooling to room temperature.

[0017] The cellulose in natural bamboo fiber contains some free hydroxyl groups, and hydroxyl groups are polar groups that easily adsorb polar water molecules and metal ions. The present invention uses an impregnation process. On the one hand, the solid is in contact with the liquid, and the capillary generates pressure due to the surface tension of the device, so that the liquid penetrates into the capillary; on the other hand, the active component is adsorbed on the surface of the carrier. After drying and roasting, the water evaporates and escapes, forming a high-efficiency catalyst that can be left on the inner surface of the carrier, thereby shortening the carbonization time.

[0018] Furthermore, the alkaline solution includes one or more of a NaOH solution and a KOH solution.

[0019] Furthermore, the activation is that the bamboo fibers are immersed in an aqueous alkaline solution with a concentration of 1 to 5 wt% for 2 to 3 hours, which can accelerate the reaction of the pyrolysis pathway and decompose more cellulose into low molecular weight fragments rather than levoglucosan. At the same time, the presence of alkali elements can improve the shape retention and thermal stability of the fibers.

[0020] Furthermore, the heating rate during the pre-oxidation process is 2-5°C / min.

[0021] Furthermore, the heating rate during the carbonization process is 2-5°C / min. Secondly, too high or too fast a heating reaction rate will cause a slow or excessive reaction during the carbonization process. Different temperature gradients will lead to different results, which will have more or less impact on the quality and performance of the product.

[0022] Too low a carbonization temperature will result in insufficient carbonization of the fiber, and non-carbon elements cannot be completely removed, which will affect the performance and quality of the final product; too high a temperature will lead to severe carbonization, resulting in the formation of defects, small cracks on the surface of the fiber or an uneven and rough fiber surface, which will cause great damage to the strength and modulus of the carbonized fiber.

[0023] Compared with the prior art, the beneficial effects are:

[0024] The present invention uses bamboo fiber as raw material, and shortens the carbonization time through impregnation catalytic treatment, increases the interaction between the catalyst and the bamboo fiber, can effectively shorten the carbonization time and reduce the carbonization temperature, accelerate the carbonization efficiency, and enable it to maintain the original fiber network morphology during the carbonization process. The method of the present invention can realize the preparation of green, low-cost and continuous carbon fiber materials, can achieve the same carbonized fiber at a relatively low temperature, obtain relatively good effects at a low cost, and greatly reduce energy consumption and production costs. DETAILED DESCRIPTION

[0025] The following is further explained and illustrated in conjunction with the examples, but the specific examples do not limit the present invention in any form. If not specifically stated, the methods and equipment used in the examples are conventional methods and equipment in the art, and the raw materials used are all conventional commercially available raw materials.

[0026] Example 1

[0027] This embodiment provides a method for preparing carbon fiber from bamboo fiber, the steps comprising:

[0028] S1. Extraction of bamboo fiber: Select fresh mature bamboo, make it into 10×4cm bamboo strips, put it into alkali solution prepared by 50g / L NaOH, 50g / L Na2SO4, and 5g / L JFC-M mixed solution for cooking, keep alkali boiling at 60℃ for 6h, and after alkali boiling, let it stand, neutralize, strip and dry to obtain single bamboo fiber.

[0029] S2. Catalyst pretreatment: The extracted bamboo fibers are washed with water, washed with deionized water to improve the purity of the raw fibers, and then the bamboo fibers are treated by excessive impregnation with a mixed aqueous solution of 2wt% sulfuric acid and urea (1:1). After the impregnation equilibrium, the impregnated bamboo fibers are heated to 150°C at 3°C / min, kept warm for 0.5-1h for roasting, and then cooled to room temperature.

[0030] S3. Activation treatment: The catalytically pretreated bamboo fibers were activated using a 2 wt % NaOH solution for 2 h, thereby improving the shape retention and thermal stability of the fibers.

[0031] S4. Pre-oxidation treatment: The activated bamboo fiber was placed in a tubular furnace for pre-oxidation. The temperature was raised from room temperature to 400°C at a heating rate of 2°C / min in an argon atmosphere at 100 ml / min and kept at this temperature for 1 hour.

[0032] S5. Carbonization: Continue to maintain the argon atmosphere and increase the temperature from 400 to 1000°C within 5°C / min to carbonize the bamboo fiber mainly through deep dehydration, pyrolysis and aromatization to remove non-carbon elements and form a turbostratic graphite structure, the strength of which usually increases with the increase of graphite plane stacking.

[0033] The carbon fiber was obtained by keeping the mixture warm for 0.5 h in an argon atmosphere, cooling it to room temperature, washing it with deionized water to remove metal elements, and drying it at 105° C. for 0.5 h.

[0034] Example 2

[0035] This embodiment provides a method for preparing carbon fiber from bamboo fiber, the steps comprising:

[0036] S1. Extraction of bamboo fiber: Select fresh mature bamboo, make it into 10×4cm bamboo strips, put it into alkali solution prepared by 50g / L NaOH, 50g / L Na2SO4, and 5g / L JFC-M mixed solution for cooking, keep alkali boiling at 60℃ for 6h, and after alkali boiling, let it stand, neutralize, strip and dry to obtain single bamboo fiber.

[0037] S2. Catalyst pretreatment: The extracted bamboo fibers are washed with water, washed with deionized water to improve the purity of the raw fibers, and then the bamboo fibers are treated by excessive impregnation with a mixed solution of 4wt% sulfuric acid and urea (1:1). After the impregnation equilibrium, the impregnated bamboo fibers are heated to 150°C at 3°C / min, kept warm for 0.5-1h for roasting, and then cooled to room temperature.

[0038] S3. Activation treatment: The catalytically pretreated bamboo fibers were activated using a 2 wt % NaOH solution for 2 h, thereby improving the shape retention and thermal stability of the fibers.

[0039] S4. Pre-oxidation treatment: The activated bamboo fiber was placed in a tubular furnace for pre-oxidation. The temperature was raised from room temperature to 400°C at a heating rate of 2°C / min in an argon atmosphere at 100 ml / min and kept at this temperature for 1 hour.

[0040] S5. Carbonization: Continue to maintain the argon atmosphere and increase the temperature from 400 to 1000°C within 5°C / min to carbonize the bamboo fiber mainly through deep dehydration, pyrolysis and aromatization to remove non-carbon elements and form a turbostratic graphite structure, the strength of which usually increases with the increase of graphite plane stacking.

[0041] The carbon fiber was obtained by keeping the mixture warm for 0.5 h in an argon atmosphere, cooling it to room temperature, washing it with deionized water to remove metal elements, and drying it at 105° C. for 0.5 h.

[0042] Example 3

[0043] This embodiment provides a method for preparing carbon fiber from bamboo fiber, the steps comprising:

[0044] S1. Extraction of bamboo fiber: Select fresh mature bamboo, make it into 10×4cm bamboo strips, put it into alkali solution prepared by 50g / L NaOH, 50g / L Na2SO4, and 5g / L JFC-M mixed solution for cooking, keep alkali boiling at 60℃ for 6h, and after alkali boiling, let it stand, neutralize, strip and dry to obtain single bamboo fiber.

[0045] S2. Catalyst pretreatment: The extracted bamboo fibers are washed with water, washed with deionized water to improve the purity of the raw fibers, and then the bamboo fibers are treated by excessive impregnation with a mixed solution of 6wt% sulfuric acid and urea (1:1). After the impregnation equilibrium, the impregnated bamboo fibers are heated to 150°C at 3°C / min, kept warm for 0.5-1h for roasting, and then cooled to room temperature.

[0046] S3. Activation treatment: The catalytically pretreated bamboo fibers were activated using a 2 wt % NaOH solution for 2 h, thereby improving the shape retention and thermal stability of the fibers.

[0047] S4. Pre-oxidation treatment: The activated bamboo fiber was placed in a tubular furnace for pre-oxidation. The temperature was raised from room temperature to 400°C at a heating rate of 2°C / min in an argon atmosphere at 100 ml / min and kept at this temperature for 1 hour.

[0048] S5. Carbonization: Continue to maintain the argon atmosphere and increase the temperature from 400 to 1000°C within 5°C / min to carbonize the bamboo fiber mainly through deep dehydration, pyrolysis and aromatization to remove non-carbon elements and form a turbostratic graphite structure, the strength of which usually increases with the increase of graphite plane stacking.

[0049] The carbon fiber was obtained by keeping the mixture warm for 0.5 h in an argon atmosphere, cooling it to room temperature, washing it with deionized water to remove metal elements, and drying it at 105° C. for 0.5 h.

[0050] Example 4

[0051] This embodiment provides a method for preparing carbon fiber from bamboo fiber, the steps comprising:

[0052] S1. Extraction of bamboo fiber: Select fresh mature bamboo, make it into 10×4cm bamboo strips, put it into alkali solution prepared by 50g / L NaOH, 50g / L Na2SO4, and 5g / L JFC-M mixed solution for cooking, keep alkali boiling at 60℃ for 6h, and after alkali boiling, let it stand, neutralize, strip and dry to obtain single bamboo fiber.

[0053] S2. Catalyst pretreatment: The extracted bamboo fibers are washed with water, washed with deionized water to improve the purity of the raw fibers, and then the bamboo fibers are treated by excessive impregnation with a mixed solution of 8wt% sulfuric acid and urea (1:1). After the impregnation equilibrium, the impregnated bamboo fibers are heated to 150°C at 3°C / min, kept warm for 0.5-1h for roasting, and then cooled to room temperature.

[0054] S3. Activation treatment: The catalytically pretreated bamboo fibers were activated using a 2 wt % NaOH solution for 2 h, thereby improving the shape retention and thermal stability of the fibers.

[0055] S4. Pre-oxidation treatment: The activated bamboo fiber was placed in a tubular furnace for pre-oxidation. The temperature was raised from room temperature to 400°C at a heating rate of 2°C / min in an argon atmosphere at 100 ml / min and kept at this temperature for 1 hour.

[0056] S5. Carbonization: Continue to maintain the argon atmosphere and increase the temperature from 400 to 1000°C within 5°C / min to carbonize the bamboo fiber mainly through deep dehydration, pyrolysis and aromatization to remove non-carbon elements and form a turbostratic graphite structure, the strength of which usually increases with the increase of graphite plane stacking.

[0057] The carbon fiber was obtained by keeping the mixture warm for 0.5 h in an argon atmosphere, cooling it to room temperature, washing it with deionized water to remove metal elements, and drying it at 105° C. for 0.5 h.

[0058] Example 5

[0059] This embodiment provides a method for preparing carbon fiber from bamboo fiber, the steps comprising:

[0060] S1. Extraction of bamboo fiber: Select fresh mature bamboo, make it into 10×4cm bamboo strips, put it into alkali solution prepared by 50g / L NaOH, 50g / L Na2SO4, and 5g / L JFC-M mixed solution for cooking, keep alkali boiling at 60℃ for 6h, and after alkali boiling, let it stand, neutralize, strip and dry to obtain single bamboo fiber.

[0061] S2. Catalyst pretreatment: The extracted bamboo fibers are washed with water, washed with deionized water to improve the purity of the raw fibers, and then the bamboo fibers are treated by excessive impregnation with a 1%wt CaCl2 solution. After the impregnation equilibrium, the impregnated bamboo fibers are heated to 150°C at 3°C / min, kept warm for 0.5-1h for roasting, and then cooled to room temperature.

[0062] S3. Activation treatment: The catalytically pretreated bamboo fibers were activated using a 2 wt % NaOH solution for 2 h, thereby improving the shape retention and thermal stability of the fibers.

[0063] S4. Pre-oxidation treatment: The activated bamboo fiber was placed in a tubular furnace for pre-oxidation. The temperature was raised from room temperature to 400°C at a heating rate of 2°C / min in an argon atmosphere at 100 ml / min and kept at this temperature for 1 hour.

[0064] S5. Carbonization: Continue to maintain the argon atmosphere and increase the temperature from 400 to 1000°C within 5°C / min to carbonize the bamboo fiber mainly through deep dehydration, pyrolysis and aromatization to remove non-carbon elements and form a turbostratic graphite structure, the strength of which usually increases with the increase of graphite plane stacking.

[0065] The carbon fiber was obtained by keeping the mixture warm for 0.5 h in an argon atmosphere, cooling it to room temperature, washing it with deionized water to remove metal elements, and drying it at 105° C. for 0.5 h.

[0066] Example 6

[0067] This embodiment provides a method for preparing carbon fiber from bamboo fiber, the steps comprising:

[0068] S1. Extraction of bamboo fiber: Select fresh mature bamboo, make it into 10×4cm bamboo strips, put it into alkali solution prepared by 50g / L NaOH, 50g / L Na2SO4, and 5g / L JFC-M mixed solution for cooking, keep alkali boiling at 60℃ for 6h, and after alkali boiling, let it stand, neutralize, strip and dry to obtain single bamboo fiber.

[0069] S2. Catalyst pretreatment: The extracted bamboo fibers are washed with water, washed with deionized water to improve the purity of the raw fibers, and then the bamboo fibers are treated by excessive impregnation with a 5wt% CaCl2 solution. After the impregnation equilibrium, the impregnated bamboo fibers are heated to 150°C at 3°C / min, kept warm for 0.5 to 1h for roasting, and then cooled to room temperature.

[0070] S3. Activation treatment: The catalytically pretreated bamboo fibers were activated using a 2 wt % NaOH solution for 2 h, thereby improving the shape retention and thermal stability of the fibers.

[0071] S4. Pre-oxidation treatment: The activated bamboo fiber was placed in a tubular furnace for pre-oxidation. The temperature was raised from room temperature to 400°C at a heating rate of 2°C / min in an argon atmosphere at 100 ml / min and kept at this temperature for 1 hour.

[0072] S5. Carbonization: Continue to maintain the argon atmosphere and increase the temperature from 400 to 1000°C within 5°C / min to carbonize the bamboo fiber mainly through deep dehydration, pyrolysis and aromatization to remove non-carbon elements and form a turbostratic graphite structure, the strength of which usually increases with the increase of graphite plane stacking.

[0073] The carbon fiber was obtained by keeping the mixture warm for 0.5 h in an argon atmosphere, cooling it to room temperature, washing it with deionized water to remove metal elements, and drying it at 105° C. for 0.5 h.

[0074] Example 7

[0075] This embodiment provides a method for preparing carbon fiber from bamboo fiber, the steps comprising:

[0076] S1. Extraction of bamboo fiber: Select fresh mature bamboo, make it into 10×4cm bamboo strips, put it into alkali solution prepared by 50g / L NaOH, 50g / L Na2SO4, and 5g / L JFC-M mixed solution for cooking, keep alkali boiling at 60℃ for 6h, and after alkali boiling, let it stand, neutralize, strip and dry to obtain single bamboo fiber.

[0077] S2. Catalyst pretreatment: The extracted bamboo fibers are washed with water, washed with deionized water to improve the purity of the raw fibers, and then the bamboo fibers are treated by excessive impregnation with a 10wt% CaCl2 solution. After the impregnation equilibrium, the impregnated bamboo fibers are heated to 150°C at 3°C / min, kept warm for 0.5 to 1h, and then cooled to room temperature.

[0078] S3. Activation treatment: The catalytically pretreated bamboo fibers were activated using a 2 wt % NaOH solution for 2 h, thereby improving the shape retention and thermal stability of the fibers.

[0079] S4. Pre-oxidation treatment: The activated bamboo fiber was placed in a tubular furnace for pre-oxidation. The temperature was raised from room temperature to 400°C at a heating rate of 2°C / min in an argon atmosphere at 100 ml / min and kept at this temperature for 1 hour.

[0080] S5. Carbonization: Continue to maintain the argon atmosphere and increase the temperature from 400 to 1000°C within 5°C / min to carbonize the bamboo fiber mainly through deep dehydration, pyrolysis and aromatization to remove non-carbon elements and form a turbostratic graphite structure, the strength of which usually increases with the increase of graphite plane stacking.

[0081] The carbon fiber was obtained by keeping the mixture warm for 0.5 h in an argon atmosphere, cooling it to room temperature, washing it with deionized water to remove metal elements, and drying it at 105° C. for 0.5 h.

[0082] The strength of the carbon fibers prepared in Examples 1 to 7 was tested, and the test results are shown in the following table:

[0083]

[0084] In implementation cases 1-4, carbon fibers were prepared using different catalyst contents. Four groups were compared and it was found that when the catalyst content was 6%, the strength and modulus of the generated carbon fibers were the best, with a tensile strength of 0.94 GPa and a Young's modulus of 82.1 GPa. At the same time, it can effectively shorten the carbon fiber molding cycle, reduce the loss of high temperature and high heat during the molding process, save resources and avoid waste.

[0085] In implementation cases 5-7, the impregnated catalyst was replaced, and the optimal solution was obtained through repeated tests and comparisons. When the content of CaCl2 was 5%, the prepared carbon fiber reached a tensile strength of 1.08GPa and a Young's modulus of up to 91.6GPa, and as the concentration of CaCl2 increased, the residual amount of the final product gradually increased, and the weight loss rate also decreased. Compared with implementation case 3, the obtained carbon fiber is more ideal.

[0086] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A method for preparing carbon fiber from bamboo fiber, characterized in that the steps include: S1. Bamboo fiber extraction: Bamboo strips are boiled with alkali, neutralized, stripped and dried to obtain bamboo raw fibers; S2. Catalyst pretreatment: The bamboo fibers are immersed in a catalyst mixed aqueous solution for catalysis; S3. Activation treatment: placing the catalyzed bamboo fiber into an alkaline solution for activation; S4. Pre-oxidation treatment: The activated bamboo fiber is heated from room temperature to 400°C under a protective gas atmosphere for 0.5 to 1 hour; S5. Carbonization: The pre-oxidized bamboo fiber is heated from 400°C to 1000°C to obtain carbonized fiber.

2. The method for preparing carbon fiber from bamboo fiber according to claim 1, characterized in that: The alkaline solution used in the alkaline boiling includes 30-50 g / L of NaOH, 25-50 g / L of Na2SO4, and 3-5 g / L of high-temperature penetrant.

3. The method for preparing carbon fiber from bamboo fiber according to claim 1, characterized in that: The catalyst content in the catalyst mixed aqueous solution is 1-10 wt %.

4. The method for preparing carbon fiber from bamboo fiber according to claim 1 or 3, characterized in that: The catalyst includes a mixed solution of sulfuric acid and urea and a CaCl2 solution.

5. The method for preparing carbon fiber from bamboo fiber according to claim 4, characterized in that: The mixing ratio of the sulfuric acid and urea is 1:

1.

6. The method for preparing carbon fiber from bamboo fiber according to claim 1, characterized in that: The pretreatment further comprises heating the impregnated bamboo fibers to 150° C. at a rate of 3 to 5° C. / min, maintaining the temperature for 0.5 to 1 hour for roasting, and then cooling to room temperature.

7. The method for preparing carbon fiber from bamboo fiber according to claim 1, characterized in that: The alkaline solution includes one or more of a NaOH solution and a KOH solution.

8. The method for preparing carbon fiber from bamboo fiber according to claim 1, characterized in that: The activation is that the bamboo fibers are soaked in an aqueous alkali solution with a concentration of 1 to 5 wt% for 2 to 3 hours.

9. The method for preparing carbon fiber from bamboo fiber according to claim 1, characterized in that: The heating rate during the pre-oxidation process is 2-5°C / min.

10. The method for preparing carbon fiber from bamboo fiber according to claim 1, characterized in that: The heating rate during the carbonization process is 2-5°C / min.

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