CN111072014B - Preparation method of graphene - Google Patents
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- CN111072014B CN111072014B CN201911363875.7A CN201911363875A CN111072014B CN 111072014 B CN111072014 B CN 111072014B CN 201911363875 A CN201911363875 A CN 201911363875A CN 111072014 B CN111072014 B CN 111072014B
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Abstract
The invention discloses a preparation method of graphene, which takes lignin-like substances as raw materials, tetrahydrofuran as a modifier and ferric nitrate nonahydrate as a catalyst, wherein the lignin-like substances are subjected to water bath treatment by the modifier and the ferric nitrate nonahydrate and then calcined to obtain the graphene, and the lignin-like substances are residues of straw fermentation biogas residues or straw acid hydrolysis.
Description
Technical Field
The invention relates to the technical field of carbon material manufacturing processes, in particular to a preparation method of graphene.
Background
The energy source is the cornerstone of human survival and development. At present, in the global energy system, the energy on which human beings mainly depend is still mineral energy (coal, petroleum and the like). However, the use of these fossil energy resources in large quantities results in the production of greenhouse gases and high molecular wastes that are difficult to degrade, which have an effect on the environment that is difficult to recover. Meanwhile, the reserves of the energy sources on the earth are limited, and from the long-term perspective, mankind is bound to face the energy crisis, so that the task of seeking renewable energy sources capable of replacing petrochemical energy sources is urgent. Among various renewable energy sources, biomass is a unique and unique renewable carbon source, has the characteristics of being renewable, large in reserve, low in sulfur and nitrogen, and zero in carbon dioxide emission, and has a significance for relieving petroleum crisis and environmental pollution, wherein according to statistics, the annual output of the biomass energy sources is 20 times of that of current human mineral energy sources.
The lignin in the biomass energy is the only non-petroleum resource capable of providing renewable aryl compounds in nature, accounts for 20-30% of the total mass of plants, and is the second most natural high polymer material. But mainly exists as a byproduct in the paper making and biofuel industries, most of the lignin is usually directly incinerated, the efficiency is low, and the energy is wasted and the environment is polluted. Therefore, increasing the added value of lignin is a problem to be solved urgently at present. At present, a great deal of straw waste is generated in agricultural production, and the traditional treatment is to treat the waste by adopting an incineration mode, but the mode generates a great deal of smoke to cause serious air pollution. At present, cellulose and hemicellulose in straws are converted into soluble sugar through a fermentation process or an acid hydrolysis process, but both processes can generate a large amount of waste residues and generate a new solid waste problem. The main component of these waste residues is lignin, and therefore these waste residues can be referred to as lignin-like.
Graphene, as a research hotspot in recent years, is currently the thinnest and most rigid nanomaterial, and has fascinating mechanical, thermal and electrical properties in a hexagonal honeycomb stacked structure. The composite material is applied to the field of wave absorption, and can enhance the wave absorption performance of the material on the basis of reducing the density. Methods for large scale preparation of graphene are redox and Chemical Vapor Deposition (CVD). Many strong oxidizing and reducing agents are used in redox processes; such agents are toxic and harmful to the environment and human health. In addition, the product quality is poor due to defects and residual functional groups introduced during severe oxidation. Chemical vapor deposition meets large-scale, high-quality requirements. The micro-mechanical stripping method has poor controllability, the prepared graphene has small size and great uncertainty, and meanwhile, the efficiency is low, the cost is high, and the micro-mechanical stripping method is not suitable for large-scale production. The waste residue generated by removing cellulose and hemicellulose from the straws by acid hydrolysis or fermentation process contains a large amount of lignin, and the lignin is destroyed to a certain extent by fermentation or acid hydrolysis, so that the chemical activity of the lignin is enhanced. The lignin contains about 55-65% of carbon, can be used as a carbon source for preparing carbon materials such as graphene and the like, and has great potential in the aspect of preparing carbon materials. Therefore, the method for preparing the graphene by taking the straw waste lignin as the raw material is developed, and the application prospect of the graphene is explored, so that the method has important significance.
Disclosure of Invention
In order to solve the problem of preparing graphene by lignin-like substances, the invention adopts the following technical scheme.
A preparation method of graphene takes lignin-like substances as raw materials, tetrahydrofuran as a modifier and ferric nitrate nonahydrate as a catalyst, the lignin-like substances are subjected to water bath treatment by the modifier and the ferric nitrate nonahydrate and then calcined to obtain the graphene, and the lignin-like substances are residues of straw fermentation biogas residues or straw acid hydrolysis.
(1) Adding lignin-like substance, ferric nitrate nonahydrate, and tetrahydrofuran into water to form mixed solution, and maintaining in water bath at 60-100 deg.C for 2-24 hr.
(2) And (2) drying the heated mixed solution in the step (1) to obtain a precursor.
(3) And (3) placing the precursor in the step (2) in a tubular furnace, heating to 150-200 ℃ from normal temperature, keeping the temperature for 0.5-2h, continuing to heat to 700-1000 ℃ and keeping the temperature for 1-5 h, and then cooling to normal temperature to obtain the graphene precursor.
(4) And (3) placing the graphene precursor obtained in the step (3) in a hydrochloric acid solution, cleaning until no bubbles are generated, standing for 2-24 hours, filtering out insoluble substances, placing the insoluble substances in the hydrochloric acid solution, keeping the temperature in a water bath at 50-80 ℃ for 2-3 hours, cooling, performing ultrasonic treatment for 1-2 hours, centrifuging, performing suction filtration, washing and drying to obtain the graphene.
Preferably, in the step (1), the lignin is 3-6g, the ferric nitrate nonahydrate is 1-4g, the tetrahydrofuran is 3-10mL, and the water is 50-300 mL.
Preferably, the temperature of the water bath in step (1) is maintained at 60-80 ℃.
Preferably, the mixed solution in the step (2) is dried in a forced air drying oven.
Preferably, the temperature range of the second temperature rise in the step (3) is 800-.
Preferably, the temperature rising process and the temperature reduction process in the step (3) are carried out at the speed of 2-6 ℃/min.
Preferably, inert gas is introduced into the tube furnace at a rate of 40-60mL/min during the step (3).
Preferably, the inert gas in step (3) is nitrogen.
Preferably, the concentration of the hydrochloric acid solution used in step (4) is 0.5 to 2 mol/L.
Straw fermentation is the prior art, and is not described herein any more, and can effectively reduce the cellulose and hemicellulose content in the straw through fermentation, so that the lignin accounts for a very high proportion in the finally formed biogas residues. The acid hydrolysis process is also a highly efficient technique for industrially treating the straws, and is not described herein. The acid hydrolysis process mainly degrades cellulose and hemicellulose in the straws into soluble sugar through acid hydrolysis. Therefore, the residue of the straw after the acid hydrolysis process mainly contains lignin.
The graphene prepared by the preparation method disclosed by the invention is used for electrochemical performance tests, and the performance of the graphene as a good electrode material of a super capacitor is found.
Compared with the traditional methods for preparing graphene, such as a mechanical stripping method, a redox method, a chemical vapor deposition method, an organic synthesis method and the like, the method for preparing graphene disclosed by the invention is simple in process, the prepared graphene shows good electrochemical performance, the conversion from low-added-value biomass waste lignin to high-added-value product graphene is realized, the academic value is high, and meanwhile, the method provides good reference significance for the conversion of renewable biomass resources.
Drawings
Fig. 1 is an XRD pattern of graphene prepared in example 1.
Fig. 2 is an SEM image of the graphene prepared in example 1.
Fig. 3 is an infrared spectrum of graphene prepared in example 1.
Fig. 4 is an XRD spectrum of the sample prepared in comparative example 1.
Fig. 5 is a raman spectrum of the graphene prepared in example 1 and the sample prepared in comparative example 2.
Detailed Description
The apparatus used in the present invention comprises: digital display constant temperature water bath (W-201B type), JintanCity medical instrument factory; forced air drying cabinets (DGX-9143B), Shanghai Nanrong laboratory facilities, Inc.; vacuum drying oven (DZF-6020), Shanghai Soxhlet area test Equipment, Inc.; x-ray diffractometer (XRD, ESCALAB 250Xi model), thermo fisher Scientific, usa; raman spectroscopy (Raman Spectra, inVia model), Renishaw corporation, uk; a Fourier Infrared Spectroscopy (LIDA-20); SEM Electron microscope (FlexSEM 1000) Hitachi, Japan.
Example 1, 6g of lignin-like substances, 2.5g of ferric nitrate nonahydrate and 6ml of tetrahydrofuran were added to 100ml of deionized water at room temperature, heated in a water bath at 80 ℃ for 8 hours, and then dried in a forced air drying oven until all was converted into a precursor. And transferring the obtained precursor into a porcelain sample boat, putting the porcelain sample boat into a solid tube furnace, heating the porcelain sample boat to 180 ℃ from the normal temperature at a speed of 5 ℃/min, keeping the temperature for 1 hour, continuing heating the porcelain sample boat to 900 ℃ and keeping the temperature for 3 hours, then cooling the porcelain sample boat to the normal temperature at a speed of 5 ℃/min, and introducing nitrogen at a constant speed for protection in the calcining process at a speed of 60 ml/min. And taking out the calcined sample, continuously washing with 1mol/L dilute hydrochloric acid until no bubbles are generated, clarifying the supernatant, standing for 24 hours, changing the hydrochloric acid, carrying out 80-degree water bath heat preservation for 3 hours, carrying out ultrasonic treatment for 2 hours after cooling, centrifuging to obtain a solid, carrying out vacuum filtration on the solid, washing with deionized water, and carrying out vacuum drying at 80 ℃ for 10 hours to obtain the graphene. Fig. 1 shows an XRD spectrum of the graphene prepared in example 1, which shows that the graphene sample has a sharp characteristic peak at the peak of the graphene standard, indicating that the graphene prepared by the method exhibits a good graphene structure. Fig. 2 is an SEM image of the prepared graphene, and it can be seen from the image that there are thin layers, and a lamellar structure of the graphene. FIG. 3 is an IR spectrum of graphene obtained, wherein a is an IR spectrum of graphene, b is an IR spectrum of a sample obtained by directly calcining lignin-like substance (i.e., no ferric nitrate and tetrahydrofuran are added during the preparation process, and other steps are as described in example 1), and c is an IR spectrum of lignin-like substance per se, as can be seen from the figure, the IR spectrum of graphene is 1461cm for lignin-like substance-1、1517 cm-1And 1610 cm-1The characteristic peak at (A) disappeared at 1629 cm-1A characteristic peak appears, which is a characteristic peak of the vibration of the C = C skeleton of the graphene sheet, i.e. it is proved that the product of the present embodiment has a typical graphene structure.
Example 2, 6g of lignin-like substances, 2.5g of ferric nitrate nonahydrate and 6ml of tetrahydrofuran were added to 100ml of deionized water at room temperature, heated in a water bath at 80 ℃ for 8 hours, and then dried in a forced air drying oven until all was converted into a precursor. And transferring the obtained precursor into a porcelain sample boat, putting the porcelain sample boat into a solid tube furnace, heating the porcelain sample boat to 180 ℃ from the normal temperature at a speed of 5 ℃/min, keeping the temperature for 1 hour, continuing heating the porcelain sample boat to 800 ℃ for 3 hours, cooling the porcelain sample boat to the normal temperature at a speed of 5 ℃/min, and introducing nitrogen at a constant speed for protection in the calcining process at a speed of 60 ml/min. And taking out the calcined sample, continuously washing with 1mol/L dilute hydrochloric acid until no bubbles are generated, clarifying the supernatant, standing for 24 hours, changing the hydrochloric acid, carrying out 80-degree water bath heat preservation for 3 hours, carrying out ultrasonic treatment for 2 hours after cooling, centrifuging to obtain a solid, carrying out vacuum filtration on the solid, washing with deionized water, and carrying out vacuum drying at 80 ℃ for 10 hours to obtain the graphene. In addition, through other tests, better graphene can be obtained within the calcination range of 700-1000 ℃, and the performance of the obtained graphene is optimal within the range of 800-900 ℃, so that the graphene has higher electrical performance. When the calcination temperature is lower than 700 ℃, the prepared sample is detected by XRD to find that the content of graphene is lower.
Comparative example 1, 6g of lignin-like, 2.5g of ferric nitrate nonahydrate and 6ml of tetrahydrofuran were added to 100ml of deionized water at room temperature, left for 8 hours, and dried in an air-blast drying oven until all was converted into a precursor. And transferring the obtained precursor into a porcelain sample boat, putting the porcelain sample boat into a solid tube furnace, heating the porcelain sample boat to 180 ℃ from the normal temperature at a speed of 5 ℃/min, keeping the temperature for 1 hour, continuing heating the porcelain sample boat to 900 ℃ and keeping the temperature for 3 hours, then cooling the porcelain sample boat to the normal temperature at a speed of 5 ℃/min, and introducing nitrogen at a constant speed for protection in the calcining process at a speed of 60 ml/min. Taking out the calcined sample, continuously washing with 1mol/L dilute hydrochloric acid until no bubbles are generated, clarifying the supernatant, standing for 24 hours, changing hydrochloric acid, carrying out 80-degree water bath heat preservation for 3 hours, carrying out ultrasound treatment for 2 hours after cooling, carrying out centrifugation operation to obtain a solid, carrying out vacuum filtration on the solid, washing with deionized water, carrying out vacuum drying for 10 hours at 80 degrees to obtain a corresponding sample, carrying out XRD detection on the sample, wherein the XRD pattern of the sample shows that the prepared sample does not show an obvious graphene XRD characteristic peak, as shown in figure 4. Research shows that the added modifier tetrahydrofuran does not participate in the reaction on lignin-like substances because water bath treatment is not carried out in the preparation process of the precursor, namely, the modification effect on the lignin-like substances is not realized, so that the prepared sample only contains few graphene structures. Through further research, the water bath temperature is controlled to be 60-100 ℃, so that the lignin can be effectively modified by tetrahydrofuran, and graphene can be prepared in the subsequent steps.
Comparative example 2, 6g of lignin-like substance and 2.5g of iron nitrate nonahydrate were added to 100ml of deionized water at room temperature, heated in a water bath at 80 ℃ for 8 hours, and then dried in an air-blast drying oven until all was converted into a precursor. And transferring the obtained precursor into a porcelain sample boat, putting the porcelain sample boat into a solid tube furnace, heating the porcelain sample boat to 180 ℃ from the normal temperature at a speed of 5 ℃/min, keeping the temperature for 1 hour, continuing heating the porcelain sample boat to 900 ℃ and keeping the temperature for 3 hours, then cooling the porcelain sample boat to the normal temperature at a speed of 5 ℃/min, and introducing nitrogen at a constant speed for protection in the calcining process at a speed of 60 ml/min. Taking out the calcined sample, continuously washing with 1mol/L dilute hydrochloric acid until no bubbles are generated, clarifying the supernatant, standing for 24 hours, changing hydrochloric acid, carrying out 80-degree water bath heat preservation for 3 hours, carrying out ultrasound treatment for 2 hours after cooling, carrying out centrifugation operation to obtain a solid, carrying out vacuum filtration on the solid, washing with deionized water, carrying out vacuum drying at 80 degrees for 10 hours to obtain a corresponding sample, and carrying out Raman spectrum detection on the sample. Fig. 5 is a raman spectrum of graphene in example 1 (curve a) and sample (b) prepared in this comparative example 2. The Raman spectra of the graphene and the massive graphite formed by stacking a large amount of graphene show two strong peaks which are respectively located at a frequency shift of about 1580cm-1And 2700cm-1G peak and G' peak (also referred to as 2D peak). Analyzing the position, shape and strength of the 2D peak can determine the number of graphene layers of the constituent graphene sheets. For the graphene with defects, the third characteristic peak is located at 1350cm-1. As can be seen from fig. 5, the 2D peak in curve a shows the 2D peak of 2-layer graphene requiring 4 lorentzian peaks to fit, while the 2D peak exhibited in curve b is more depressed, showing more layers of graphene, indicating a comparative exampleThe sample prepared in 2 tended to be more graphitic. Lignin has a large number of oxygen-containing functional groups, such as hydroxyl, carboxylate, carbon group, ester, bond, etc., which make the lignin structure very chemically stable. Tetrahydrofuran is used as a modifier, and can react with functional groups in lignin to cause some bond breaking reaction of the lignin, which is more beneficial to improving the solubility of the lignin and further promoting the subsequent carbonization process of the lignin.
The above description is only a preferred embodiment of the present invention, and these embodiments are based on different implementations of the present invention, and the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.
Claims (7)
1. The preparation method of the graphene is characterized in that lignin-like substances are used as raw materials, tetrahydrofuran is used as a modifier, ferric nitrate nonahydrate is used as a catalyst, the lignin-like substances are subjected to water bath treatment by the modifier and the ferric nitrate nonahydrate and then calcined to obtain the graphene, and the lignin-like substances are residues of straw fermentation biogas residues or straw acid hydrolysis;
the method comprises the following steps:
(1) adding lignin-like substances, ferric nitrate nonahydrate and tetrahydrofuran into water to form a mixed solution, and keeping the mixed solution in a water bath at the temperature of 60-100 ℃ for 2-24 hours;
(2) drying the heated mixed solution in the step (1) to obtain a precursor;
(3) placing the precursor in the step (2) in a tubular furnace, introducing inert gas into the tubular furnace at the rate of 40-60mL/min for protection, heating to the temperature of 150-;
(4) and (3) placing the graphene precursor obtained in the step (3) in a hydrochloric acid solution, cleaning until no bubbles are generated, standing for 2-24 hours, filtering out insoluble substances, placing the insoluble substances in the hydrochloric acid solution, keeping the temperature in a water bath at 50-80 ℃ for 2-3 hours, cooling, performing ultrasonic treatment for 1-2 hours, centrifuging, performing suction filtration, washing and drying to obtain the graphene.
2. The method for preparing graphene according to claim 1, wherein the temperature of the water bath in the step (1) is maintained at 60-80 ℃.
3. The preparation method of graphene according to claim 1, wherein in the step (1), the lignin-like substance is 3-6g, the ferric nitrate nonahydrate is 1-4g, the tetrahydrofuran is 3-10mL, and the water is 50-300 mL.
4. The method for preparing graphene according to claim 1, wherein the mixed solution in the step (2) is dried in a forced air drying oven.
5. The method for preparing graphene according to claim 1, wherein the temperature rising process and the temperature lowering process in the step (3) are performed at a rate of 2-6 ℃/min.
6. The method according to claim 1, wherein the inert gas in step (3) is nitrogen.
7. The method for preparing graphene according to claim 1, wherein the hydrochloric acid solution used in the step (4) has a concentration of 0.5-2 mol/L.
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| CN103935986B (en) * | 2014-02-28 | 2016-03-30 | 中国科学院宁波材料技术与工程研究所 | A kind of method preparing Graphene with biological carbon source material high yield |
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