Preparation method of lignin and silk fibroin carbon fiber

Abstract

The invention discloses a preparation method of lignin and silk fibroin carbon fibers. The preparation method comprises the following steps: S1, extracting graded lignin; s2, extraction of silk fibroin; s3, grading lignin and silk fibroin in-situ synthesis; mixing the ethanol graded lignin solution and the silk fibroin solution, adding horse radish peroxidase with the mass fraction of 1%, and uniformly mixing to obtain an electrostatic spinning solution; s4, preparing continuous nitrogen-doped lignin and silk fibroin fibers through electrostatic spinning; s5, carrying out continuous nitrogen-doped lignin and silk fibroin fiber pre-oxidation to obtain a trapezoidal polymer structure; then carrying out carbonization treatment to obtain nitrogen-doped lignin and silk fibroin carbon fibers; according to the invention, a nitrogen doping technology is combined with the preparation of lignin and silk fibroin carbon fibers, so that not only can the sustainability and economic benefits of the pulping and papermaking industry be improved, but also new performance characteristics such as better biocompatibility and degradability can be injected into the carbon fiber material.

Description

Technical Field

[0001] The invention relates to the technical field of lignin and silk fibroin carbon fibers, in particular to a preparation method of lignin and silk fibroin carbon fibers. Background Art

[0002] With the increasing global attention to environmental protection and sustainable development, traditional non-renewable resources are gradually being replaced by renewable resources. Lignin, as the second largest renewable resource in nature after cellulose, can produce about 70 million tons in the pulp and paper industry each year. Unfortunately, however, only about 2% of lignin is effectively utilized, and most of it is directly burned as fuel or discharged with wastewater, which not only causes a huge waste of resources, but also brings serious environmental pollution. Therefore, how to efficiently utilize lignin has become an urgent problem to be solved. In addition, the heterogeneity and high polydispersity of lignin limit its direct application, resulting in most lignin resources being wasted or inefficiently utilized. Summary of the invention

[0003] The purpose of the present invention is to provide a method for preparing lignin and silk fibroin carbon fibers to solve the problem that most of the lignin mentioned in the background technology is directly burned as fuel or discharged with wastewater, resulting in a huge waste of resources.

[0004] To achieve the above object, the present invention provides the following technical solution: a method for preparing lignin and silk fibroin carbon fibers, comprising the following steps:

[0005] S1. Extraction of fractionated lignin;

[0006] Firstly, industrial lignin and ethanol are placed in a shaker at a rotation speed of 200 r / min, and the supernatant is separated after centrifugation to obtain an ethanol-graded lignin solution;

[0007] S2, extraction of silk fibroin;

[0008] First, cut the cocoons into 4cm 2 The silk was cut into small pieces, and then boiled in 0.10 mol / L NaHCO3 boiling water for 3 times, each time for 30 min, and the boiled silk was dissolved in 10 mol / L lithium bromide solution for 4 h to obtain silk fibroin solution;

[0009] S3: in situ synthesis of graded lignin and silk fibroin;

[0010] The ethanol graded lignin solution in step S1 and the silk fibroin solution in step S2 are mixed, and 1% horseradish peroxidase is added thereto. After the mixture is evenly mixed, the graded lignin and the silk fibroin are self-crosslinked to obtain an electrospinning solution;

[0011] S4: electrospinning;

[0012] Electrospinning the electrospinning solution obtained in step S3 to prepare continuous nitrogen-doped lignin and silk fibroin fibers;

[0013] S5: pre-oxidation and carbonization;

[0014] The continuous nitrogen-doped lignin and silk fibroin fibers obtained in step S4 are pre-oxidized at 200° C. in an air atmosphere for 30 min to obtain a ladder-shaped polymer structure;

[0015] The pre-oxidized fibers are then carbonized; carbonization is the process of causing the organic matter in the fibers to undergo pyrolysis and polycondensation reactions at high temperatures to obtain nitrogen-doped lignin and silk fibroin carbon fibers.

[0016] Preferably, the mass ratio of industrial lignin to ethanol in step S1 is 1:4.

[0017] Preferably, the standing time in step S1 is 3 hours.

[0018] Preferably, the mixing ratio of the ethanol graded lignin solution and the silk fibroin solution in step S3 is 1:1.

[0019] Preferably, the injection flow rate in step S4 is 1 mL / h, the electrospinning voltage is 15 kV, the receiving distance is 20 cm, and the time is 6 h.

[0020] Preferably, the carbonization heating rate in step S5 is 5° C. / s, the carbonization temperature is raised to 800° C., and the holding time is 30 min.

[0021] Compared with the prior art, the present invention provides a method for preparing lignin and silk fibroin carbon fibers, which has the following beneficial effects: first, nitrogen doping, as an effective modification method, is widely used to improve the electrochemical properties, conductivity and thermal stability of carbon materials; the introduction of nitrogen atoms can not only change the electronic structure of the carbon material, but also provide it with more active sites, thereby giving the material more superior performance; therefore, combining nitrogen doping technology with the preparation of lignin and silk fibroin carbon fibers can not only improve the sustainability and economic benefits of the pulp and paper industry, but also inject new performance characteristics into carbon fiber materials, such as better biocompatibility and degradability. DETAILED DESCRIPTION

[0022] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] The present invention provides a technical solution: a method for preparing lignin and silk fibroin carbon fibers, comprising the following steps:

[0024] S1. Extraction of fractionated lignin;

[0025] Firstly, industrial lignin and ethanol are placed in a shaker at a rotation speed of 200 r / min, and the supernatant is separated after centrifugation to obtain an ethanol-graded lignin solution;

[0026] S2, extraction of silk fibroin;

[0027] First, cut the cocoons into 4cm 2 The silk was cut into small pieces, and then boiled in 0.10 mol / L NaHCO3 boiling water for 3 times, each time for 30 min, and the boiled silk was dissolved in 10 mol / L lithium bromide solution for 4 h to obtain silk fibroin solution;

[0028] S3: in situ synthesis of graded lignin and silk fibroin;

[0029] The ethanol graded lignin solution in step S1 and the silk fibroin solution in step S2 are mixed, and 1% horseradish peroxidase is added thereto. After the mixture is evenly mixed, the graded lignin and the silk fibroin are self-crosslinked to obtain an electrospinning solution;

[0030] S4: electrospinning;

[0031] Electrospinning the electrospinning solution obtained in step S3 to prepare continuous nitrogen-doped lignin and silk fibroin fibers;

[0032] S5: pre-oxidation and carbonization;

[0033] The continuous nitrogen-doped lignin and silk fibroin fibers obtained in step S4 are pre-oxidized at 200° C. in an air atmosphere for 30 min to obtain a ladder-shaped polymer structure;

[0034] The pre-oxidized fibers are then carbonized; carbonization is the process of causing the organic matter in the fibers to undergo pyrolysis and polycondensation reactions at high temperatures to obtain nitrogen-doped lignin and silk fibroin carbon fibers.

[0035] Preferably, the mass ratio of industrial lignin to ethanol in step S1 is 1:4.

[0036] Preferably, the standing time in step S1 is 3 hours.

[0037] Preferably, the mixing ratio of the ethanol graded lignin solution and the silk fibroin solution in step S3 is 1:1.

[0038] Preferably, the injection flow rate in step S4 is 1 mL / h, the electrospinning voltage is 15 kV, the receiving distance is 20 cm, and the time is 6 h.

[0039] Preferably, the carbonization heating rate in step S5 is 5° C. / s, the carbonization temperature is raised to 800° C., and the holding time is 30 min.

[0040] Example 1: First, industrial lignin and ethanol were placed in a shaker at a speed of 200 r / min, and the supernatant was separated after centrifugation to obtain an ethanol graded lignin solution; the silkworm cocoons were cut into 4 cm 2 The silk was cut into small pieces and then boiled in 0.10 mol / L NaHCO3 boiling water for 3 times, each time for 30 min. The boiled silk was dissolved in 10 mol / L lithium bromide solution for 4 h to obtain silk fibroin solution.

[0041] Embodiment 2: The ethanol graded lignin solution in step S1 and the silk fibroin solution in step S2 are mixed, and horseradish peroxidase with a mass fraction of 1% is added. After mixing them evenly, the graded lignin and silk fibroin are self-crosslinked to obtain an electrospinning solution; the electrospinning solution obtained in step S3 is electrospun to prepare continuous nitrogen-doped lignin and silk fibroin fibers; the continuous nitrogen-doped lignin and silk fibroin fibers obtained in step S4 are pre-oxidized at a temperature of 200° C. in an air atmosphere for 30 minutes to obtain a ladder-shaped polymer structure; the pre-oxidized fibers are then carbonized; carbonization is to cause the organic matter in the fibers to undergo pyrolysis and polycondensation reactions at high temperatures to obtain nitrogen-doped lignin and silk fibroin carbon fibers.

[0042] Lignin fractionation to recover polymer fractions with clear molecular weight and low dispersity is an important way to increase the value of lignin and develop new applications; on the other hand, silk fibroin, as a natural high molecular fibrous protein extracted from silk, has excellent biocompatibility, degradability and diverse processability, and has shown great application potential in the field of biomedical materials; it is also known as silk protein, which is a natural high molecular fibrous protein extracted from silk; it is mainly composed of heavy chains, light chains and glycoproteins, and is a nitrogen-containing high molecular compound; the present application aims to prepare nitrogen-doped lignin and silk fibroin carbon fibers by in situ synthesis, electrospinning, pre-oxidation and carbonization of fractionated lignin and silk fibroin.

[0043] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, rather than to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions of the technical solution of the present invention by ordinary technicians in this field do not deviate from the essence and scope of the technical solution of the present invention.

Claims

1. A method for preparing lignin and silk fibroin carbon fiber, characterized in that: The steps include: S1. Extraction of fractionated lignin; Firstly, industrial lignin and ethanol are placed in a shaker at a rotation speed of 200 r / min, and the supernatant is separated after centrifugation to obtain an ethanol-graded lignin solution; S2, extraction of silk fibroin; First, cut the cocoons into 4cm 2 The silk was cut into small pieces, and then boiled in 0.10 mol / L NaHCO3 boiling water for 3 times, each time for 30 min, and the boiled silk was dissolved in 10 mol / L lithium bromide solution for 4 h to obtain silk fibroin solution; S3: in situ synthesis of graded lignin and silk fibroin; The ethanol graded lignin solution in step S1 and the silk fibroin solution in step S2 are mixed, and 1% horseradish peroxidase is added thereto. After the mixture is evenly mixed, the graded lignin and the silk fibroin are self-crosslinked to obtain an electrospinning solution; S4: electrospinning; Electrospinning the electrospinning solution obtained in step S3 to prepare continuous nitrogen-doped lignin and silk fibroin fibers; S5: pre-oxidation and carbonization; The continuous nitrogen-doped lignin and silk fibroin fibers obtained in step S4 are pre-oxidized at 200° C. in an air atmosphere for 30 min to obtain a ladder-shaped polymer structure; The pre-oxidized fibers are then carbonized; Carbonization is the process of causing the organic matter in the fiber to undergo pyrolysis and polycondensation at high temperature to obtain nitrogen-doped lignin and silk fibroin carbon fibers.

2. The method for preparing lignin and silk fibroin carbon fibers according to claim 1, characterized in that: The mass ratio of industrial lignin to ethanol described in step S1 is 1:

4.

3. The method for preparing lignin and silk fibroin carbon fibers according to claim 1, characterized in that: The standing time described in step S1 is 3 hours.

4. The method for preparing lignin and silk fibroin carbon fiber according to claim 1, characterized in that: The mixing ratio of the ethanol-fractionated lignin solution and the silk fibroin solution described in step S3 is 1:

1.

5. The method for preparing lignin and silk fibroin carbon fiber according to claim 1, characterized in that: The injection flow rate described in step S4 is 1 mL / h, the electrospinning voltage is 15 kV, the receiving distance is 20 cm, and the time is 6 h.

6. The method for preparing lignin and silk fibroin carbon fiber according to claim 1, characterized in that: The carbonization heating rate in step S5 is 5°C / s, the carbonization temperature is raised to 800°C, and the holding time is 30 minutes.