Preparation method of cellulose-based graphitized material

Abstract

The invention belongs to the field of graphitized material preparation, and particularly relates to a cellulose-based graphitized material preparation method, which specifically comprises: 1, placing cellulose fibers in a sodium hydroxide solution, and treating for 50-70 min at a temperature of 80-100 DEG C to remove impurities existing in the cellulose fibers; 2, cellulose fibers are treated with a finishing agent solution for 25-35 min, and the finished cellulose fibers are subjected to heat preservation treatment for 45-70 min at the temperature of 280-320 DEG C; 3, the cellulose fibers treated in the step 2 are soaked in a treatment solution for 25-35 s, and then drying treatment is conducted for 90-120 s at the temperature of 180-200 DEG C; step 4, carrying out carbonization treatment on the cellulose fibers treated in the step 3; and step 5, heating and graphitizing the carbonized cellulose fibers in the presence of inert gas, and carrying out heat preservation treatment at 1700-2000 DEG C for 50-70 minutes to obtain the cellulose-based graphitized material. According to the process, the cellulose can be subjected to graphitization conversion at the temperature of 1700-2000 DEG C, and the temperature is greatly lower than the temperature required by traditional graphitization; and the graphitization degree of the obtained product can exceed 95%.

Description

Technical Field

[0001] The present invention belongs to the field of preparation of graphitized materials, and particularly relates to a method for preparing a cellulose-based graphitized material. Background Art

[0002] Graphitized carbon materials have important applications in the fields of lithium / sodium ion battery electrodes, supercapacitors, pollutant adsorption, etc. due to their high conductivity, high specific surface area, chemical stability, and adjustable pore structure. However, traditional graphite materials mainly rely on fossil energy for preparation, and there are problems such as non-renewable resources, high energy consumption, and process pollution. Therefore, the development of low-cost and green graphitized materials based on renewable biomass has become a key research direction in academia and industry. Cellulose is the most abundant renewable polymer material in nature, with advantages such as wide sources, low cost, and degradability, and is an ideal carbon source to replace fossil raw materials.

[0003] Currently, the commonly used methods for preparing cellulose graphitized materials include catalytic graphitization method, high-temperature graphitization method, etc. However, due to the diverse sources of cellulose, there are large differences in its degree of polymerization and crystallinity, resulting in difficult control of the graphitization degree, and structural defects are easily generated during the graphitization process, affecting the material properties, and there is an urgent need for improvement. Summary of the Invention

[0004] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a method for preparing a cellulose-based graphitized material.

[0005] The present invention adopts the following technical scheme: A method for preparing a cellulose-based graphitized material specifically includes the following steps: Step 1, place cellulose fibers in a sodium hydroxide solution with a mass concentration of 4-6%, treat at 80-100 °C for 50-70 min, and then repeatedly wash with deionized water and dry to remove impurities existing in the cellulose fibers; Step 2, treat the cellulose fibers with a finishing agent solution for 25-35 min, dry the treated cellulose fibers and place them in a nitrogen atmosphere, and carry out heat preservation treatment at 280-320 °C for 45-70 min; Step 3, immerse the cellulose fibers treated in Step 2 in the treatment solution for 25-35 s, and then carry out drying treatment at 180-200 °C for 90-120 s; Step 4, carry out carbonization treatment on the cellulose fibers treated in Step 3, adopting a staged carbonization process: Primary carbonization stage: Feed the cellulose fibers obtained in Step 3 into a carbonization furnace, and carry out heat preservation treatment at 550-650 °C for 20-30 min. Among them, the carbonization atmosphere in the carbonization furnace is as follows: under a nitrogen atmosphere, the hydrogen content is 4-6%; Deep carbonization stage: Heat the temperature in the carbonization furnace to 800 - 1000 °C and keep it warm for 25 - 35 min. Among them, the carbonization atmosphere in the carbonization furnace is as follows: under a nitrogen atmosphere, the hydrogen content is 2 - 3%. Step 5: Heat and graphitize the carbonized cellulose fiber under an inert gas. At 1700 - 2000 °C, keep it warm for 50 - 70 min to obtain the cellulose-based graphitized material.

[0006] Preferably, the treatment solution uses water as a solvent and includes 6 - 8 g / L of sodium borohydride.

[0007] Preferably, the finishing agent uses water as a solvent and includes 8 - 12 g / L of ammonium sulfate, 5 - 8 g / L of caprolactam, and 3 - 5 g / L of ammonium polyphosphate.

[0008] Preferably, in step 4, during the primary carbonization stage, the draft ratio is 3.2 - 3.6%, and during the deep carbonization stage, the draft ratio is 1.1 - 1.3%.

[0009] Preferably, in step 2, during the heat preservation treatment, the draft ratio is 2 - 3%.

[0010] Preferably, in the preliminary carbonization stage, the temperature of the carbonization furnace is raised to 550 - 650 °C at a rate of 1.5 °C / min; in the deep carbonization stage, the temperature of the carbonization furnace is raised to 800 - 1000 °C at a rate of 2 °C / min.

[0011] Preferably, in step 5, the inert gas is argon.

[0012] Preferably, in step 5, during the graphitization treatment, the temperature is raised to 1700 - 2000 °C at a rate of 10 - 20 °C / min.

[0013] Preferably, the cellulose fiber is made of viscose fiber, lyocell fiber and cellulose industrial yarn. As can be seen from the above description of the present invention, compared with the prior art, the beneficial effects of the present invention are as follows: In view of the problems existing in the preparation of existing cellulose graphitized materials, by innovating the pre-oxidation process, carbonization process and graphitization process of cellulose fiber, the preparation bottleneck and structural defects of cellulose graphitized materials are solved, providing high-performance and sustainable cellulose-based graphitized materials for the new energy and environmental protection fields; this process can cause the graphitization transformation of biomass cellulose at a temperature of 1700 °C - 2000 °C, which is much lower than the 2800 °C required for traditional graphitization; and the graphitization degree of the obtained product can exceed 95%, and can reach the crystallinity of natural graphite, and can be further developed for battery materials, wave-absorbing materials and adsorption materials; among them, a pretreatment process is added between the pre-oxidation process and the carbonization process, and the pre-oxidized cellulose fiber is impregnated in the treatment solution. During the impregnation process, sodium borohydride can penetrate into the viscose fiber, and at the same time cause moderate cross-linking of the cellulose fiber macromolecules, and specifically limit the carbonization atmosphere. Under a nitrogen atmosphere, a small amount of hydrogen is added, and hydrogen can remove oxygen in the pre-oxidized fiber at a low temperature, reducing the generation of carbon monoxide and carbon dioxide, and improving the stretchability of cellulose fiber during carbonization, so as to reduce the temperature and time of the carbonization process. Detailed implementation mode

[0014] The present invention will be further described below through specific implementation modes.

[0015] A preparation method of a cellulose-based graphitized material specifically includes the following steps: Step 1: Place the cellulose fiber in a sodium hydroxide solution with a mass concentration of 4 - 6%, treat it at 80 - 100 °C for 50 - 70 min, and then repeatedly wash it with deionized water and dry it to remove impurities existing in the cellulose fiber; Step 2: Treat the cellulose fiber with a finishing agent solution for 25 - 35 min, dry the treated cellulose fiber and place it in a nitrogen atmosphere, and keep it at 280 - 320 °C for 45 - 70 min, wherein the draw ratio is 2 - 3%; Step 3: Immerse the cellulose fiber treated in Step 2 in the treatment solution for 25 - 35 s, and then dry it at 180 - 200 °C for 90 - 120 s; Step 4: Carbonize the cellulose fiber treated in Step 3, adopting a staged carbonization process: Primary carbonization stage: Feed the cellulose fiber obtained in Step 3 into a carbonization furnace, heat it to 550 - 650 °C at a rate of 1.5 °C / min, and keep it at 550 - 650 °C for 20 - 30 min, wherein the draw ratio is 3.2 - 3.6%, and the carbonization atmosphere in the carbonization furnace is as follows: under a nitrogen atmosphere, the hydrogen content is 4 - 6%; Deep carbonization stage: Heat the temperature in the carbonization furnace at a rate of 2 °C / min to 800 - 1000 °C, and keep it warm for 25 - 35 min. Among them, the draw ratio is 1.1 - 1.3%. The carbonization atmosphere in the carbonization furnace is as follows: under a nitrogen atmosphere, the hydrogen content is 2 - 3%. Step 5: Heat and graphitize the carbonized cellulose fiber in an argon atmosphere, heat it at a rate of 10 - 20 °C / min to 1700 - 2000 °C, and keep it warm at 1700 - 2000 °C for 50 - 70 min to obtain the cellulose-based graphitized material.

[0016] Among them, the cellulose fiber uses viscose fiber, lyocell fiber, and cellulose industrial yarn; the finishing agent uses water as a solvent, including 8 - 12 g / L of ammonium sulfate, 5 - 8 g / L of caprolactam, and 3 - 5 g / L of ammonium polyphosphate; the treatment solution uses water as a solvent, including 6 - 8 g / L of sodium borohydride. Example 1

[0017] A preparation method of a cellulose-based graphitized material specifically includes the following steps: Step 1: Place the cellulose fiber in a sodium hydroxide solution with a mass concentration of 4%, treat it at 80 °C for 70 min, then repeatedly wash it with deionized water and dry it to remove the impurities existing in the cellulose fiber. Step 2: Treat the cellulose fiber with the finishing agent solution for 25 min, dry the treated cellulose fiber and place it in a nitrogen atmosphere, keep it warm at 280 °C for 70 min. Among them, the draw ratio is 2%. Step 3: Immerse the cellulose fiber treated in Step 2 in the treatment solution for 25 s, and then dry it at 180 °C for 120 s. Step 4: Perform carbonization treatment on the cellulose fiber treated in Step 3, adopting a staged carbonization process: Primary carbonization stage: Feed the cellulose fiber obtained in Step 3 into the carbonization furnace, heat it at a rate of 1.5 °C / min to 550 °C, and keep it warm at 550 °C for 30 min. Among them, the draw ratio is 3.2%. The carbonization atmosphere in the carbonization furnace is as follows: under a nitrogen atmosphere, the hydrogen content is 6%. Deep carbonization stage: Heat the temperature in the carbonization furnace at a rate of 2 °C / min to 800 °C, and keep it warm for 35 min. Among them, the draw ratio is 1.1%. The carbonization atmosphere in the carbonization furnace is as follows: under a nitrogen atmosphere, the hydrogen content is 2%. Step 5: Heat and graphitize the carbonized cellulose fiber in an argon atmosphere, heat it at a rate of 10 °C / min to 1700 °C, and keep it warm at 1700 °C for 70 min to obtain the cellulose-based graphitized material.

[0018] Among them, the cellulose fiber is viscose fiber; the finishing agent uses water as the solvent and includes 8 g / L of ammonium sulfate, 8 g / L of caprolactam, and 3 g / L of ammonium polyphosphate; the treatment solution uses water as the solvent and includes 6 g / L of sodium borohydride.

[0019] The obtained cellulose graphitized material was detected, and its graphitization degree was 93%. Example 2

[0020] A preparation method of a cellulose-based graphitized material specifically includes the following steps: Step 1: Place the cellulose fiber in a sodium hydroxide solution with a mass concentration of 6%, treat it at 100 °C for 50 min, then repeatedly wash it with deionized water and dry it to remove the impurities existing in the cellulose fiber. Step 2: Treat the cellulose fiber with the finishing agent solution for 35 min. After drying the treated cellulose fiber, place it in a nitrogen atmosphere and keep it at 320 °C for 45 min. Among them, the draw ratio is 3%. Step 3: Immerse the cellulose fiber treated in Step 2 in the treatment solution for 35 s, and then dry it at 200 °C for 90 s. Step 4: Perform carbonization treatment on the cellulose fiber treated in Step 3, adopting a staged carbonization process: Primary carbonization stage: Send the cellulose fiber obtained in Step 3 into a carbonization furnace, heat it to 650 °C at a rate of 1.5 °C / min, and keep it at 650 °C for 20 min. Among them, the draw ratio is 3.6%, and the carbonization atmosphere in the carbonization furnace is as follows: under a nitrogen atmosphere, the hydrogen content is 4%. Deep carbonization stage: Raise the temperature in the carbonization furnace to 1000 °C at a rate of 2 °C / min, and keep it at 1000 °C for 25 min. Among them, the draw ratio is 1.3%, and the carbonization atmosphere in the carbonization furnace is as follows: under a nitrogen atmosphere, the hydrogen content is 3%. Step 5: Heat and graphitize the carbonized cellulose fiber in an argon atmosphere, heat it to 2000 °C at a rate of 20 °C / min, and keep it at 2000 °C for 50 min to obtain the cellulose-based graphitized material.

[0021] Among them, the cellulose fiber is lyocell fiber; the finishing agent uses water as the solvent and includes 12 g / L of ammonium sulfate, 5 g / L of caprolactam, and 5 g / L of ammonium polyphosphate; the treatment solution uses water as the solvent and includes 8 g / L of sodium borohydride.

[0022] The obtained cellulose graphitized material was detected, and its graphitization degree was 92%. Example 3

[0023] A preparation method of a cellulose-based graphitized material specifically includes the following steps: Step 1: Place the cellulose fiber in a sodium hydroxide solution with a mass concentration of 5%, treat it at 90 °C for 60 min, then repeatedly wash it with deionized water and dry it to remove the impurities present in the cellulose fiber; Step 2: Treat the cellulose fiber with the finishing agent solution for 30 min, dry the treated cellulose fiber and place it in a nitrogen atmosphere, and keep it at 300 °C for 60 min. Among them, the draw ratio is 2.4%; Step 3: Immerse the cellulose fiber treated in Step 2 in the treatment solution for 30 s, and then dry it at 190 °C for 110 s; Step 4: Carbonize the cellulose fiber treated in Step 3, adopting a staged carbonization process: Primary carbonization stage: Feed the cellulose fiber obtained in Step 3 into a carbonization furnace, heat it to 600 °C at a rate of 1.5 °C / min, and keep it at 600 °C for 25 min. Among them, the draw ratio is 3.5%. The carbonization atmosphere in the carbonization furnace is as follows: under a nitrogen atmosphere, the hydrogen content is 5%; Deep carbonization stage: Raise the temperature in the carbonization furnace to 900 °C at a rate of 2 °C / min, and keep it at 900 °C for 30 min. Among them, the draw ratio is 1.2%. The carbonization atmosphere in the carbonization furnace is as follows: under a nitrogen atmosphere, the hydrogen content is 2.5%; Step 5: Heat and graphitize the carbonized cellulose fiber in an argon atmosphere, heat it to 1800 °C at a rate of 15 °C / min, and keep it at 1800 °C for 60 min to obtain the cellulose-based graphitized material.

[0024] Among them, the cellulose fiber uses cellulose industrial yarn; the finishing agent uses water as a solvent and includes 10 g / L of ammonium sulfate, 6 g / L of caprolactam, and 4 g / L of ammonium polyphosphate; the treatment solution uses water as a solvent and includes 7 g / L of sodium borohydride.

[0025] Detect the obtained cellulose graphitized material, and its graphitization degree is 95%.

[0026] Comparative Example 1 A preparation method of a cellulose-based graphitized material specifically includes the following steps: Step 1: Place the cellulose fiber in a sodium hydroxide solution with a mass concentration of 5%, treat it at 90 °C for 60 min, then repeatedly wash it with deionized water and dry it to remove the impurities present in the cellulose fiber; Step 2: Treat the cellulose fiber with the finishing agent solution for 30 min, dry the treated cellulose fiber and place it in a nitrogen atmosphere, and keep it at 300 °C for 60 min. Among them, the draw ratio is 2.4%; Step 3: Carbonize the post-treated cellulose fibers from Step 2 using a staged carbonization process: Primary carbonization stage: Feed the cellulose fibers obtained in Step 3 into a carbonization furnace, heat it to 600 °C at a rate of 1.5 °C / min, and hold for 8 min at 600 °C. Among them, the draw ratio is 3.5%. The carbonization atmosphere in the carbonization furnace is as follows: under a nitrogen atmosphere, the hydrogen content is 5%; Deep carbonization stage: Raise the temperature in the carbonization furnace to 900 °C at a rate of 2 °C / min, and hold for 10 min. Among them, the draw ratio is 1.2%. The carbonization atmosphere in the carbonization furnace is as follows: under a nitrogen atmosphere, the hydrogen content is 2.5%; Step 4: Heat and graphitize the carbonized cellulose fibers under an argon atmosphere, heat it to 1800 °C at a rate of 15 °C / min, and hold for 60 min at 1800 °C to obtain the cellulose-based graphitized material.

[0027] Among them, the cellulose fibers use cellulose industrial yarns; the finishing agent uses water as a solvent and includes 10 g / L of ammonium sulfate, 6 g / L of caprolactam, and 4 g / L of ammonium polyphosphate.

[0028] Test the obtained cellulose graphitized material, and its graphitization degree is 83%.

[0029] Comparative Example 2 A preparation method of a cellulose-based graphitized material specifically includes the following steps: Step 1: Place the cellulose fibers in a sodium hydroxide solution with a mass concentration of 5%, treat at 90 °C for 60 min, then repeatedly wash with deionized water and dry to remove impurities existing in the cellulose fibers; Step 2: Treat the cellulose fibers with a finishing agent solution for 30 min, dry the treated cellulose fibers and place them under a nitrogen atmosphere, hold for 60 min at 300 °C. Among them, the draw ratio is 2.4%; Step 3: Carbonize the post-treated cellulose fibers from Step 2 using a staged carbonization process: Primary carbonization stage: Feed the cellulose fibers obtained in Step 3 into a carbonization furnace, heat it to 800 °C at a rate of 1.5 °C / min, and hold for 60 min at 800 °C. Among them, the draw ratio is 3.5%. The carbonization atmosphere in the carbonization furnace is as follows: under a nitrogen atmosphere, the hydrogen content is 5%; Deep carbonization stage: Raise the temperature in the carbonization furnace to 1200 °C at a rate of 2 °C / min, and hold for 60 min. Among them, the draw ratio is 1.2%. The carbonization atmosphere in the carbonization furnace is as follows: under a nitrogen atmosphere, the hydrogen content is 2.5%; Step 4: Heat the carbonized cellulose fibers to graphitize them under an argon atmosphere. Heat them at a rate of 15 °C / min to 1800 °C, and hold them at 1800 °C for 60 min to obtain the cellulose-based graphitized material.

[0030] Among them, the cellulose fibers are cellulose industrial yarns; the finishing agent uses water as a solvent and includes 10 g / L of ammonium sulfate, 6 g / L of caprolactam, and 4 g / L of ammonium polyphosphate.

[0031] The obtained cellulose graphitized material is tested, and its graphitization degree is 92%.

[0032] It can be seen from the comparison between Comparative Example 1, Comparative Example 2 and Example 3 that adding a pretreatment process between the pre-oxidation process and the carbonization process can reduce the temperature and time of the carbonization process.

[0033] In response to the problems existing in the preparation of existing cellulose graphitized materials, this application solves the preparation bottleneck and structural defects of cellulose graphitized materials by innovating the pre-oxidation process, carbonization process and graphitization process of cellulose fibers, and provides high-performance and sustainable cellulose-based graphitized materials for the new energy and environmental protection fields; this process can graphitize biomass cellulose at a temperature of 1700 °C - 2000 °C, which is much lower than the 2800 °C required for traditional graphitization; and the graphitization degree of the obtained product can exceed 95%, and it can reach the crystallinity of natural graphite, and it can be further developed for battery materials, wave-absorbing materials and adsorption materials; among them, a pretreatment process is added between the pre-oxidation process and the carbonization process, and the pre-oxidized cellulose fibers are impregnated in the treatment solution. During the impregnation process, sodium borohydride can penetrate into the viscose fiber, and at the same time, the macromolecules of the cellulose fiber are moderately crosslinked, and the carbonization atmosphere is specifically defined. Under a nitrogen atmosphere, a small amount of hydrogen is added. Hydrogen can remove the oxygen in the pre-oxidized fiber at a low temperature, reducing the generation of carbon monoxide and carbon dioxide, and improving the stretchability of the cellulose fiber during carbonization, so as to reduce the temperature and time of the carbonization process.

[0034] The above is only a preferred embodiment of the present invention, so the scope of implementation of the present invention cannot be limited thereby. That is, equivalent changes and modifications made according to the scope of the patent application of the present invention and the content of the specification should still fall within the scope covered by the patent of the present invention.

Claims

1. A method for preparing a cellulose-based graphitized material, characterized in that: The specific steps include: Step 1, placing the cellulose fibers in a sodium hydroxide solution with a mass concentration of 4-6%, treating at 80-100° C. for 50-70 minutes, then repeatedly washing with deionized water and drying to remove impurities in the cellulose fibers; Step 2, treating the cellulose fibers with a finishing agent solution for 25-35 minutes, drying the finished cellulose fibers, placing them in a nitrogen atmosphere, and heat-treating them at 280-320° C. for 45-70 minutes; Step 3, immersing the cellulose fibers treated in step 2 in the treatment solution for 25-35 seconds, and then drying at 180-200° C. for 90-120 seconds; Step 4, carbonizing the cellulose fibers treated in step 3, using a staged carbonization process: Primary carbonization stage: the cellulose fibers obtained in step 3 are fed into a carbonization furnace and heat treated at 550-650°C for 20-30 minutes, wherein the carbonization atmosphere in the carbonization furnace is as follows: nitrogen atmosphere with a hydrogen content of 4-6%; Deep carbonization stage: the temperature in the carbonization furnace is raised to 800-1000°C and kept warm for 25-35 minutes. The carbonization atmosphere in the carbonization furnace is as follows: under nitrogen atmosphere, the hydrogen content is 2-3%; Step 5, heating the carbonized cellulose fibers under inert gas for graphitization at 1700-2000° C. for 50-70 minutes to obtain the cellulose-based graphitized material.

2. The method for preparing a cellulose-based graphitized material according to claim 1, characterized in that: The treatment solution uses water as solvent and includes 6-8 g / L of sodium borohydride.

3. The method for preparing a cellulose-based graphitized material according to claim 1, characterized in that: The finishing agent uses water as solvent and includes 8-12 g / L of ammonium sulfate, 5-8 g / L of caprolactam, and 3-5 g / L of ammonium polyphosphate.

4. The method for preparing a cellulose-based graphitized material according to claim 1, characterized in that: In step 4, in the primary carbonization stage, the draft ratio is 3.2-3.6%, and in the deep carbonization stage, the draft ratio is 1.1-1.3%.

5. The method for preparing a cellulose-based graphitized material according to claim 1, characterized in that: In step 2, during the heat preservation treatment, the draft ratio is 2-3%.

6. The method for preparing a cellulose-based graphitized material according to claim 1, characterized in that: In the preliminary carbonization stage, the temperature of the carbonization furnace is increased to 550-650° C. at a rate of 1.5° C. / min; in the deep carbonization stage, the temperature of the carbonization furnace is increased to 800-1000° C. at a rate of 2° C. / min.

7. The method for preparing a cellulose-based graphitized material according to claim 1, characterized in that: In step 5, argon is used as the inert gas.

8. The method for preparing a cellulose-based graphitized material according to claim 1, characterized in that: In step 5, during the graphitization treatment, the temperature is raised to 1700-2000° C. at a rate of 10-20° C. / min.

9. The method for preparing a cellulose-based graphitized material according to claim 1, characterized in that: The cellulose fibers include viscose fibers, lyocell fibers and cellulose industrial fibers.