Preparation method of bio-based carbon fiber
Through the wet spinning technology of modifying lignin to form a covalent cross-linked network with cellulose, the problems of uniformity and stability of high-performance carbon fibers prepared from lignin are solved, and the preparation of bio-based carbon fibers with high carbon yield and low cost is achieved, which is suitable for industrial production.
Patent Information
- Application Number
- CN202511075501.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-08-01
- Publication Date
- 2025-10-14
AI Technical Summary
In the existing technology, the preparation of high-performance carbon fibers from lignin has problems such as unstable raw yarn quality, poor fiber diameter uniformity, and spinning nozzle clogging during the spinning process. In addition, the carbon yield of commercial bio-based carbon fibers is low, the preparation cost is high, and it is difficult to achieve large-scale production.
The method of amino-modified lignin and oxidatively modified cellulose is adopted to form lignin-cellulose composite precursor fibers by wet spinning, and then pre-oxidation and carbonization treatment are carried out. The covalent cross-linked network is formed by the synergistic effect of multiple hydrogen bonds and Schiff base condensation reaction, avoiding the use of highly corrosive solvents and adopting ionic solvents to dissolve the precursors.
The uniformity and stability of carbon fibers are improved, production costs are reduced, carbon yield is increased, the process is suitable for industrial production, and is environmentally friendly and efficient.
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Figure CN120776485A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of carbon fiber preparation, and particularly relates to a method for preparing bio-based carbon fiber. Background Art
[0002] The overexploitation of fossil resources and the resulting environmental impacts (such as greenhouse gas emissions and ecological degradation) have become global challenges, drawing significant attention from academia and international organizations. Against this backdrop, the development and utilization value of renewable biomass resources, as a key source of sustainable energy, advanced functional materials, and green chemicals, is becoming increasingly prominent.
[0003] Lignocellulose (mainly including cellulose, hemicellulose and lignin) is the most abundant renewable biomass resource on Earth. Among them, lignin, as the only renewable aromatic polymer existing in nature, shows great potential in the preparation of high-value-added chemicals and functional materials due to its unique phenylpropane structural unit and rich functional groups (such as phenolic hydroxyl and methoxy groups).
[0004] Currently, approximately 90% of isolated lignin (especially industrial alkaline lignin) is directly burned or disposed of as a low-value byproduct, and lignin components have yet to be efficiently and effectively utilized. In a biomass refining system, efficient conversion and utilization of lignin is not only key to improving overall process economics, but also a core link in achieving full utilization of biomass components and reducing environmental impact.
[0005] After separation, lignin can be used directly as a macromolecular material or depolymerized to produce aromatic platform chemicals. Its physical and chemical properties depend on the separation and purification process and subsequent chemical modification methods. Notably, lignin, due to its high carbon content and rich aromatic structure, is considered a highly promising bio-based carbon fiber precursor, with the potential to replace traditional petroleum-based raw materials (such as polyacrylonitrile).
[0006] However, the use of lignin to prepare high-performance carbon fibers faces significant challenges. For example, the inherent heterogeneous structure and wide molecular weight distribution of lignin lead to problems such as unstable raw yarn quality, poor fiber diameter uniformity, and clogging of the spinning nozzle during the spinning process. In addition, the commercial bio-based carbon fibers currently on the market mainly use regenerated cellulose fibers as precursors. Despite their renewable advantages, their carbon yields are generally low (only 10-30% after carbonization), and they rely on high-temperature hot stretching processes to improve mechanical strength, which significantly increases the preparation cost and process complexity. These technical bottlenecks have seriously restricted the large-scale production and market competitiveness of bio-based carbon fibers. Therefore, the development of new, homogenized, high-performance bio-based precursor materials and the optimization of their preparation processes for conversion to carbon fibers are key technical directions that urgently need breakthroughs in this field. Summary of the Invention
[0007] In order to solve the above technical problems, the present invention proposes a method for preparing bio-based carbon fibers.
[0008] The method of the present invention specifically is:
[0009] (1) Aminated lignin is modified to obtain ammoniated lignin;
[0010] (2) Oxidative modification of cellulose to obtain dialdehyde cellulose;
[0011] (3) mixing and dissolving the ammoniated lignin and dialdehyde cellulose in an ionic solvent, and obtaining lignin-cellulose composite precursor fibers by wet spinning;
[0012] (4) The precursor fiber is subjected to pre-oxidation and carbonization treatment in sequence to obtain bio-based carbon fiber.
[0013] Beneficial effects of the present invention:
[0014] (1) This invention innovatively adopts the strategy of grafting dialdehyde cellulose with ammoniated lignin to construct a carbon fiber precursor with excellent performance. The core of this strategy is to utilize the synergistic effect of multiple hydrogen bonds and the efficient Schiff base condensation reaction mechanism to form a covalent cross-linked network between the lignin amino group and the cellulose aldehyde group. This covalent bonding method significantly reduces the grafting electrostatic repulsion caused by charge repulsion in traditional physical mixing or simple grafting processes, effectively improves the intermolecular interaction force and compatibility, and is conducive to obtaining a homogeneous and stable lignin / cellulose precursor solution.
[0015] (2) The present invention utilizes ionic solvents to efficiently dissolve pretreated lignin and cellulose, forming a uniform, stable, and highly spinnable spinning solution. This system avoids the use of highly corrosive and toxic solvents, resulting in a more environmentally friendly process with reduced energy consumption, while also ensuring the high quality and processing stability of the precursor solution.
[0016] (3) Based on innovative precursor design and dissolution spinning technology, the present invention successfully prepared high-quality lignin-cellulose composite precursors, which were ultimately converted into high-performance lignin-based carbon fibers through pre-oxidation and carbonization. Thanks to the structural stability of the strong covalent cross-linked network in the precursor and the excellent homogenization effect brought by the solvent system, the resulting carbon fibers exhibit excellent mechanical strength. Furthermore, by utilizing abundant renewable biomass resources in nature as carbon fiber precursors, the carbon yield is high, which greatly reduces production costs, improves economic benefits, and is suitable for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS
[0017] Figure 1a This is a scanning electron microscope image of the surface of the bio-based carbon fiber prepared in Example 1;
[0018] Figure 1b This is a scanning electron microscope image of the surface of the bio-based carbon fiber prepared in Example 1 after being magnified twice;
[0019] Figure 1c This is a scanning electron microscope image of the surface of the bio-based carbon fiber prepared in Example 1 after ten times magnification. DETAILED DESCRIPTION
[0020] In the following description, different "one embodiment" or "embodiment" do not necessarily refer to the same embodiment. In addition, the specific features, structures or characteristics of one or more embodiments may be combined in any suitable form.
[0021] Unless otherwise defined, technical or scientific terms used herein shall have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.
[0022] The methods in the following examples, unless otherwise specified, are conventional methods; the materials or reagents in the following examples, unless otherwise specified, are commercially available.
[0023] The present invention is further described below with reference to specific embodiments, which are not intended to limit the present invention. Based on the described embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.
[0024] The present application provides a method for preparing carbon fibers based on wet spinning of modified lignin grafted cellulose, comprising the following steps:
[0025] (1) Aminated lignin is modified to obtain ammoniated lignin;
[0026] Specifically, industrial alkali lignin is dissolved in an appropriate amount of anhydrous ethanol by magnetic stirring at room temperature; then, the mixed solution is centrifuged to remove insoluble by-products, and the supernatant is concentrated using a rotary evaporator to obtain a viscous lignin solution, which is then vacuum dried to obtain an ethanol-soluble fraction of lignin powder.
[0027] Under nitrogen protection, the obtained ethanol-soluble fraction lignin powder is added to tetrahydrofuran solvent and mixed evenly. Then, a functional amination reagent is added to the mixed solution and the mixture is continuously stirred and mixed. After the reaction is completed, the reaction product is extracted and separated by n-hexane, and purified ammoniated lignin is obtained after centrifugation, washing, and drying.
[0028] (2) Oxidative modification of cellulose to obtain dialdehyde cellulose;
[0029] Specifically, the dissolving pulp is placed in a round-bottom flask, deionized water and a strong oxidant are added, and the reaction is carried out under light-proof conditions. After the reaction is completed, the dialdehyde cellulose is obtained by filtering, washing and freeze-drying in sequence.
[0030] (3) mixing and dissolving the ammoniated lignin and dialdehyde cellulose in an ionic solvent, and obtaining lignin-cellulose composite precursor fibers by wet spinning;
[0031] Specifically, the ammoniated lignin and dialdehyde cellulose obtained in steps (1) and (2) are added to an ionic solvent in a certain ratio, and mixed and dissolved by magnetic stirring at a certain temperature to obtain a homogeneous solution. The solution is extruded into a coagulation bath through a wet spinning machine spinneret, and then subjected to processes such as drawing, washing, oil immersion, drying, and winding to obtain a lignin / cellulose-based carbon fiber precursor.
[0032] (4) pre-oxidizing and carbonizing the precursor fibers in sequence to obtain bio-based carbon fibers;
[0033] Specifically, the lignin / cellulose-based carbon fiber precursor spun in step (3) is subjected to a slow and controllable heat treatment in an air atmosphere to pre-oxidize the fiber; then, the fully stabilized fiber is placed in a high-purity nitrogen atmosphere for high-temperature heat treatment, and after a carbonization stage, a bio-based carbon fiber material is obtained.
[0034] Preferably, in step (1), the ethanol-soluble fraction lignin powder has a hydroxyl content of 5.03 mmol / g, a number average molecular weight of 1157 g / mol, and a polydispersity index of 1.56.
[0035] Preferably, in step (1), the functional amination reagent is 3-aminopropyltriethoxysilane, and the mass ratio of 3-aminopropyltriethoxysilane to the ethanol-soluble fraction lignin is 0.05-0.15:1.0; the stirring speed of the continuous stirring and mixing is 300-500 rpm, and the reaction time at room temperature is 5-6 h.
[0036] Preferably, in step (2), the dissolving pulp is wood pulp or bamboo pulp dissolving pulp with a degree of polymerization of 500-600; the strong oxidant is sodium periodate, and the mass ratio of sodium periodate to dissolving pulp is 0.8-1.0:1.0; and the reaction process lasts for at least 3 hours.
[0037] Preferably, in step (2), the dialdehyde cellulose has an aldehyde content of 1.60-1.67 mmol / g.
[0038] Preferably, in step (3), the mass ratio of the ammoniated lignin and the dialdehyde cellulose is 1-3:1; the ionic solvent is at least one of 1,8-diazabicycloundec-7-ene methoxyacetate, 1,5-diazabicyclo[4.3.0]non-5-ene acetate, and 1-allyl-3-methylimidazolium chloride; the temperature for mixing and dissolving is 75-85°C, and the concentration of the homogeneous solution is 4-8 wt%.
[0039] Preferably, in step (4), the slow and controllable heat treatment is performed at a temperature range of 200-300°C, a heating rate of 0.5-1.0°C / min, and a holding time of 2-3 h, which enables the fibers to maintain the fiber morphology and not to be adhered in the high-temperature carbonization; the high-temperature heat treatment is performed at a temperature of 600-1500°C, a heating rate of 10°C / min, and a holding time of 1-2 h.
[0040] Example 1
[0041] 10 parts of industrial alkali lignin was weighed out and dissolved in 300 parts of anhydrous ethanol at room temperature by magnetic stirring, then the mixed solution was centrifuged to remove the insoluble by-products, and the supernatant was concentrated by a rotary evaporator to obtain a viscous lignin solution, which was then placed in a vacuum drying oven at 60°C for 24 h to obtain an ethanol-soluble fraction lignin powder.
[0042] 10 parts of the ethanol-soluble fraction lignin powder was weighed out and added to 200 parts of tetrahydrofuran solvent and mixed uniformly, then 1 part of 3-aminopropyltriethoxysilane was added to the mixed solution, and the mixture was continuously stirred at 400 rpm for 5 h. After the reaction was completed, the reaction product was separated by n-hexane extraction, and then purified by centrifugation, washing, and drying to obtain purified ammoniated lignin.
[0043] 10 parts of dissolving pulp was weighed out and placed in a round-bottom flask, 200 parts of deionized water and 8 parts of sodium periodate were added, and the reaction was carried out in the dark for 4 h. After the reaction was completed, the dialdehyde cellulose was obtained by filtration, washing, and freeze-drying in sequence.
[0044] 4 parts of ammoniated lignin and 4 parts of dialdehyde cellulose were added to 92 parts of 1,8-diazabicycloundec-7-ene methoxyacetate, and the mixture was mixed and dissolved by magnetic stirring at 80°C to obtain a homogeneous solution. The solution was extruded through the spinneret of a wet spinning machine into a coagulation bath, and then subjected to processes such as drawing, washing, oil immersion, drying, and winding to obtain a lignin / cellulose-based carbon fiber precursor.
[0045] The spun lignin / cellulose-based carbon fiber precursor was pre-oxidized at 300 °C with a heating rate of 1.0 °C / min and kept warm for 2 h. Then, the fully stabilized fiber was placed in a high-purity nitrogen atmosphere and carbonized at 1500 °C with a heating rate of 10.0 °C / min for 1 h to obtain a bio-based carbon fiber material, the surface of which was as follows. Figure 1a 、 1b and 1c. The carbon yield is 31.7% and the carbon fiber tensile strength is 1.21 GPa.
[0046] Example 2
[0047] The same method as Example 1 was used, except that 5 parts of ammoniated lignin and 3 parts of dialdehyde cellulose were weighed. The carbon yield was 32.3%, and the tensile strength of the carbon fiber was 1.16 GPa.
[0048] Example 3
[0049] The same method as Example 1 was used, except that 6 parts of ammoniated lignin and 2 parts of dialdehyde fiber were weighed. The carbon yield was 33.0%, and the tensile strength of the carbon fiber was 0.92 GPa.
[0050] Example 4
[0051] The same method as Example 1 was used, except that 1-allyl-3-methylimidazolium chloride was used as the ionic solvent. The carbon yield was 31.1%, and the tensile strength of the carbon fiber was 0.97 GPa.
[0052] Comparative Example 1
[0053] The same method as Example 1, except that unfractionated industrial alkali lignin was used to graft dialdehyde cellulose. The carbon yield was 23.9%, and the tensile strength of the carbon fiber was 0.33 GPa.
[0054] The present invention is not limited to the above-mentioned embodiments, and all equivalent changes and modifications made within the scope of application of the present invention should fall within the scope of the present invention.
Claims
1. A method for preparing bio-based carbon fiber, characterized in that: The following steps are involved: (1) Aminated lignin is modified to obtain ammoniated lignin; (2) Oxidative modification of cellulose to obtain dialdehyde cellulose; (3) mixing and dissolving the ammoniated lignin and dialdehyde cellulose in an ionic solvent, and obtaining lignin-cellulose composite precursor fibers by wet spinning; (4) The precursor fiber is subjected to pre-oxidation and carbonization treatment in sequence to obtain bio-based carbon fiber.
2. The method according to claim 1, wherein: The lignin is alkali lignin fractionated by ethanol, and has a hydroxyl content of 5.03 mmol / g, a number average molecular weight of 1157 g / mol, and a polydispersity index of 1.
56.
3. The method according to claim 1 or 2, characterized in that The amination modification uses 3-aminopropyltriethoxysilane as a modifier, the mass ratio of 3-aminopropyltriethoxysilane to lignin is 0.05-0.15:1.0, and the reaction time is 5-6 hours.
4. The method according to claim 1, wherein The cellulose is wood pulp or bamboo pulp dissolving pulp with a polymerization degree of 500-600, and is oxidatively modified using sodium periodate, with a mass ratio of sodium periodate to cellulose of 0.8-1.0:1.
0.
5. The method according to claim 1 or 4, characterized in that The aldehyde content of the dialdehyde cellulose is 1.60-1.67 mmol / g.
6. The method according to claim 1, characterized in that The mass ratio of the ammoniated lignin to the dialdehyde cellulose is 1-3:
1.
7. The method according to claim 6, characterized in that The ionic solvent is at least one of 1,8-diazabicycloundec-7-ene methoxyacetate, 1,5-diazabicyclo[4.3.0]non-5-ene acetate or 1-allyl-3-methylimidazolium chloride.
8. The method according to claim 1 or 7, characterized in that The temperature of the mixed dissolution is 75-85° C., and the concentration of the obtained homogeneous solution is 4-8 wt %.
9. The method according to claim 1, characterized in that The pre-oxidation is carried out in an air atmosphere at a temperature of 200-300° C., a heating rate of 0.5-1.0° C. / min, and a holding time of 2-3 hours.
10. The method according to claim 1 or 9, characterized in that The carbonization is carried out in an inert gas at a temperature of 600-1500° C., a heating rate of 10° C. / min, and a holding time of 1-2 hours.